Towards Sustainable Pavement Systems:

A Reference Document

FHWA-HIF-15-002
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Technical Report Documentation Page

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

FHWA-HIF-15-002

4. Title and Subtitle 5. Report Date

January 2015

6. Performing Organization Code

8. Performing Organization Report No.

7. Author(s)

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTFH61-10-D-00042-T-12001

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address

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15. Supplementary Notes

16. Abstract

17. Key Words 18. Distribution Statement

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Unclassified Unclassified 456

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

 FHWA Contracting Officer’s Representative: Gina Ahlstrom

Thomas J. Van Dam, John T. Harvey, Stephen T. Muench, Kurt D.

Smith, Mark B. Snyder, Imad L. Al-Qadi, Hasan Ozer, Joep Meijer,

Prashant V. Ram, Jeffery R. Roesler, and Alissa Kendall

Towards Sustainable Pavement Systems:

A Reference Document

All stakeholders in the pavement community—from owner/agencies to designers, and from material suppliers to 

contractors and consultants—are embracing the need to adopt more sustainable practices in all aspects of their 

work, and are continually seeking the latest technical information and guidance available to help improve those 

practices. This reference document has been prepared to provide guidance to the pavement community on 

sustainability considerations in pavement systems, drawing from and synthesizing the large and diverse body of 

knowledge that exists on pavement sustainability. As such, it provides the currently available knowledge and 

information for designing, constructing, and maintaining pavement structures more sustainably, and has been 

structured so that it can adapt to new findings and new information as sustainability considerations continue to 

develop and evolve. Key information is presented on pavement sustainability concepts, sustainable materials 

for paving applications, design of sustainable pavements, sustainable pavement construction practices, use 

phase considerations, sustainable maintenance and preservation practices, sustainable end-of-life 

considerations, pavement sustainability and livable communities, and assessment of pavement sustainability.

It is important to recognize that there is no universal definition of a “sustainable” pavement. Sustainability is 

very much context sensitive in that each project is unique, with specific needs depending on the location, 

climate, available materials, facility type, and required level of service, as well as on the overall goals of the 

organization. In essence, sustainability is very much a system characteristic, and pavements represent but one 

small part of the transportation infrastructure system; consequently, any improvements to the sustainability 

characteristics of pavement systems cannot be done in isolation from the transportation infrastructure system or 

from other systems with which pavements interact.

Final

 Federal Highway Administration May 2012 – January 2015

 1200 New Jersey Avenue, SE

 Washington, DC 20590

Applied Pavement Technology, Inc.

115 West Main Street, Suite 400

Urbana, IL 61801

Sustainability, sustainable pavements, 

environment, society, economics, asphalt, 

concrete, materials, design, construction, use 

phase, maintenance, rehabilitation, recycling, life 

cycle assessment, life cycle costing, rating 

systems

No restrictions. This document is available to the 

public through the National Technical Information 

Service, Springfield, VA 22161.
ii 

SI* (MODERN METRIC) CONVERSION FACTORS

APPROXIMATE CONVERSIONS TO SI UNITS

Symbol When You Know Multiply By To Find Symbol 

LENGTH

in inches 25.4 millimeters mm 

ft feet 0.305 meters m 

yd yards 0.914 meters m 

mi miles 1.61 kilometers km

AREA

in2 square inches 645.2 square millimeters mm2 

ft2 square feet 0.093 square meters m2 

yd2 square yard 0.836 square meters m2 

ac acres 0.405 hectares ha 

mi2 square miles 2.59 square kilometers km2

VOLUME

fl oz fluid ounces 29.57 milliliters mL 

gal gallons 3.785 liters L 

ft3 cubic feet 0.028 cubic meters m3 

yd3 cubic yards 0.765 cubic meters m3

NOTE: volumes greater than 1000 L shall be shown in m3

MASS oz ounces 28.35 grams g 

lb pounds 0.454 kilograms kg 

T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t") 

TEMPERATURE (exact degrees)

°F Fahrenheit 5 (F-32)/9 Celsius °C 

or (F-32)/1.8

ILLUMINATION 

fc foot-candles 10.76 lux lx 

fl foot-Lamberts 3.426 candela/m2 cd/m2

FORCE and PRESSURE or STRESS 

lbf poundforce 4.45 newtons N 

lbf/in2 poundforce per square inch 6.89 kilopascals kPa 

APPROXIMATE CONVERSIONS FROM SI UNITS

Symbol When You Know Multiply By To Find Symbol

LENGTH mm millimeters 0.039 inches in 

m meters 3.28 feet ft 

m meters 1.09 yards yd 

km kilometers 0.621 miles mi 

AREA mm2 square millimeters 0.0016 square inches in2

m2 square meters 10.764 square feet ft2

m2 square meters 1.195 square yards yd2 

ha hectares 2.47 acres ac 

km2 square kilometers 0.386 square miles mi2 

VOLUME

mL milliliters 0.034 fluid ounces fl oz 

L liters 0.264 gallons gal 

m3 cubic meters 35.314 cubic feet ft3

m3 cubic meters 1.307 cubic yards yd3 

MASS

g grams 0.035 ounces oz 

kg kilograms 2.202 pounds lb 

Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T 

TEMPERATURE (exact degrees)

°C Celsius 1.8C+32 Fahrenheit °F 

ILLUMINATION

lx lux 0.0929 foot-candles fc 

cd/m2 candela/m2 0.2919 foot-Lamberts fl 

FORCE and PRESSURE or STRESS

N newtons 0.225 poundforce lbf 

kPa kilopascals 0.145 poundforce per square inch lbf/in2

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of 

ASTM E380.

Front Matter Towards Sustainable Pavement Systems
Towards Sustainable Pavement Systems Front Matter

TABLE OF CONTENTS

EXECUTIVE SUMMARY.................................................................................... ES-1 

CHAPTER 1. INTRODUCTION.......................................................................... 1-1

Background........................................................................................................... 1-1

What is Sustainability?......................................................................................... 1-2

Importance of Sustainability in Pavement Engineering .................................... 1-3

About This Document........................................................................................... 1-4

Scope ................................................................................................................ 1-5 

Target Audience ................................................................................................ 1-6 

Document Overview .......................................................................................... 1-6 

References ............................................................................................................ 1-7

CHAPTER 2. CONCEPTS OF PAVEMENT SUSTAINABILITY................. 2-1 

Sustainability Defined .......................................................................................... 2-1 

The Sustainability Continuum............................................................................ 2-2 

Sustainable Best Practices................................................................................ 2-2 

Sustainability is Context Sensitive..................................................................... 2-2 

Importance of a Sustainability Definition ........................................................... 2-3 

Integrating Sustainability into a System............................................................. 2-3 

Context: The Role of Pavements in Sustainability............................................. 2-3 

Beyond Greenhouse Gas .................................................................................. 2-4 

The Role of Pavements ..................................................................................... 2-5 

The Pavement Life Cycle...................................................................................... 2-5 

Materials Production.......................................................................................... 2-7 

Pavement Design .............................................................................................. 2-7 

Construction ...................................................................................................... 2-7 

Use .................................................................................................................... 2-8 

Maintenance and Preservation.......................................................................... 2-8 

End-of-Life......................................................................................................... 2-8 

Measuring Sustainability...................................................................................... 2-8 

Performance Assessment ................................................................................. 2-8 

Life-Cycle Cost Analysis.................................................................................... 2-9 

Life-Cycle Assessment ...................................................................................... 2-9 

Rating Systems ............................................................................................... 2-10

Integrating Measurement Systems .................................................................. 2-10

Reasons to Measure Sustainability ................................................................. 2-11

Trade-off Considerations ................................................................................... 2-12

Priorities and Values of the Organization or Project ........................................ 2-13

Risk ................................................................................................................. 2-13

Summary ............................................................................................................. 2-14 

References .......................................................................................................... 2-14 

CHAPTER 3. MATERIALS CONSIDERATIONS TO IMPROVE 

PAVEMENT SUSTAINABILITY .......................................................................... 3-1 

Introduction...................................................................................................... 3-1 

Materials and Consideration of the Life Cycle......................................... 3-1 

Chapter Overview ................................................................................... 3-2 

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Front Matter Towards Sustainable Pavement Systems

Aggregate Materials ........................................................................................ 3-3 

Introduction............................................................................................. 3-3 

Strategies for Improving Sustainability.................................................... 3-9 

Issues/Future Directions/Emerging Technologies................................. 3-14 

Asphalt Materials and Mixtures.................................................................... 3-15 

Introduction........................................................................................... 3-15 

Strategies for Improving Sustainability.................................................. 3-32

Future Directions/Emerging Technologies ............................................ 3-35 

Hydraulic Cement Materials.......................................................................... 3-35 

Introduction........................................................................................... 3-36 

Strategies for Improving Sustainability.................................................. 3-57 

Future Issues/Emerging Technologies.................................................. 3-62

Other Concrete Mixtures....................................................................... 3-63 

Other Materials .............................................................................................. 3-64 

Steel...................................................................................................... 3-64 

Reinforcing Fibers................................................................................. 3-65

Interlocking Concrete Pavers................................................................ 3-65 

Geosynthetics ....................................................................................... 3-66 

Soil Modifiers/Stabilizers....................................................................... 3-66 

Major Issues ......................................................................................... 3-67 

Strategies for Improving Sustainability.................................................. 3-68 

Concluding Remarks..................................................................................... 3-69 

References ..................................................................................................... 3-70

CHAPTER 4. PAVEMENT AND REHABILITATION DESIGN TO 

IMPROVE SUSTAINABILITY .............................................................................. 4-1 

Introduction...................................................................................................... 4-1 

Pavement Design Considerations........................................................... 4-2 

Consideration of Payback Time .............................................................. 4-5 

Mechanistic-Empirical Design Methods .................................................. 4-6 

Process for Consideration of Sustainability in Pavement Design .............. 4-7 

Design Objectives................................................................................... 4-7 

Alternative Pavement or Rehabilitation Types ........................................ 4-9 

Layer and Material Type Selection ....................................................... 4-20

Drainage ............................................................................................... 4-21 

Construction Quality Specifications ...................................................... 4-21 

Construction Process and Traffic Management .................................... 4-23 

Consideration of Future Maintenance and Rehabilitation ..................... 4-23 

Sample Sustainable Design Strategies ....................................................... 4-23 

Longer Life Pavement........................................................................... 4-23 

Design for Local Materials or Low Impact Transportation..................... 4-26 

Accelerated Construction...................................................................... 4-26 

Single-Lane Rehabilitation.................................................................... 4-26 

Consideration of Use Phase in Design ................................................. 4-27 

Major Issues and Trade-offs in Designing More Sustainable Pavements 4-27 

Future Directions and Emerging Technologies.......................................... 4-27

Concluding Remarks..................................................................................... 4-32 

References ..................................................................................................... 4-32 

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Towards Sustainable Pavement Systems Front Matter

CHAPTER 5. CONSTRUCTION CONSIDERATIONS TO IMPROVE 

PAVEMENT SUSTAINABILITY .......................................................................... 5-1 

Introduction...................................................................................................... 5-1 

Sustainability of Pavement Construction Operations: General Issues ...... 5-1 

Construction-Related Energy Consumption and Emissions.................... 5-1 

Impact of Construction on Surrounding Areas ........................................ 5-3 

Economics of Construction Practices, Including User Costs................... 5-6 

Quality and Performance of Constructed Pavement System.................. 5-9 

Strategies to Improve Sustainability of General Pavement Construction 

Operations........................................................................................................ 5-9 

Strategies to Reduce Construction-Related Energy Consumption and 

Emissions ............................................................................................. 5-11

Strategies to Reduce Impact of Construction on Surrounding Area...... 5-14 

Evaluation of Sustainable Contracting Alternatives for Environmental 

Considerations...................................................................................... 5-18

Strategies for Improving Sustainability of Asphalt Pavement Construction 

Practices ........................................................................................................ 5-18

Placement and Laydown....................................................................... 5-20 

Construction Quality Assurance............................................................ 5-25

Improving Sustainability through the Use of Innovative and Emerging 

Technologies ........................................................................................ 5-26

Strategies for Improving the Sustainability of Concrete Pavement 

Construction Practices ................................................................................. 5-28

Site Prep Work...................................................................................... 5-29

Proportioning Concrete Mixtures – Impacts on Sustainable 

Construction Practices.......................................................................... 5-31 

Concrete Hauling and Placement ......................................................... 5-32

Finishing, Texturing, Jointing, and Curing............................................. 5-34

Improving Sustainability through the Use of Innovative and Emerging 

Technologies ........................................................................................ 5-36

Concluding Remarks..................................................................................... 5-38 

References ..................................................................................................... 5-38 

CHAPTER 6. USE-PHASE CONSIDERATIONS........................................... 6-1 

Introduction...................................................................................................... 6-1 

Vehicle Fuel Consumption and Pavement Characteristics.......................... 6-3

Background............................................................................................. 6-3

Strategies for Improving Sustainability.................................................. 6-17 

Future Directions and Emerging Trends ............................................... 6-18 

Tire-Pavement Noise ..................................................................................... 6-19 

Background........................................................................................... 6-19 

Strategies for Improving Sustainability.................................................. 6-31

Future Directions and Emerging Trends ............................................... 6-31

Addressing Stormwater Runoff through Pavement Permeable Surfaces 6-32

Background........................................................................................... 6-32

Strategies for Improving Sustainability.................................................. 6-37 

Future Directions and Emerging Trends ............................................... 6-38 

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Front Matter Towards Sustainable Pavement Systems

Pavement Thermal Performance and Contribution to Urban 

and Global Climate ........................................................................................ 6-38 

Pavement Properties Affecting Thermal Performance.......................... 6-38 

Urban and Global Warming Effects ...................................................... 6-40

Pavement Type and Thermal Performance .......................................... 6-47 

Other Strategies to Reduce Pavement Temperatures .......................... 6-54

Strategies for Improving Sustainability.................................................. 6-54 

Future Directions and Emerging Trends ............................................... 6-54 

Artificial Lighting........................................................................................... 6-58 

Background........................................................................................... 6-58 

Future Directions and Emerging Trends ............................................... 6-60

Strategies for Improving Sustainability.................................................. 6-60

Safety.............................................................................................................. 6-62

Concluding Remarks..................................................................................... 6-64

References ..................................................................................................... 6-67 

CHAPTER 7. MAINTENANCE AND PRESERVATION TREATMENTS 

TO IMPROVE SUSTAINABILITY ....................................................................... 7-1 

Introduction...................................................................................................... 7-1 

Pavement Preservation and Sustainability ................................................... 7-2 

Pavement Management Systems and Pavement Preservation.............. 7-2 

Integrating PMS and Pavement Preservation......................................... 7-2 

General Pavement Preservation Strategies for Improving Sustainability 7-3 

Preservation Treatment Selection........................................................... 7-5 

Asphalt-Surfaced Pavement Maintenance and Preservation Treatments .. 7-9 

Introduction............................................................................................. 7-9 

Crack Filling/Sealing ............................................................................... 7-9 

Asphalt Patching................................................................................... 7-14

Fog Seals/Rejuvenators........................................................................ 7-15 

Chip Seals ............................................................................................ 7-16 

Slurry Seals .......................................................................................... 7-17 

Microsurfacing ...................................................................................... 7-17

Ultra-Thin and Thin Asphalt Concrete Overlays.................................... 7-19 

Hot In-Place Recycling (HIR)................................................................ 7-20

Cold In-Place Recycling (CIR) .............................................................. 7-22 

Ultra-Thin Bonded Wearing Course...................................................... 7-23 

Bonded Concrete Overlays................................................................... 7-24 

Energy Use and Emissions for Asphalt-Surfaced Pavement Treatments . 7-25 

Strategies for Improving Sustainability.................................................. 7-27

Future Opportunities ............................................................................. 7-28 

Concrete-Surfaced Pavement Maintenance and Preservation Treatments 7-28 

Introduction........................................................................................... 7-28 

Joint Resealing/Crack Sealing .............................................................. 7-31

Slab Stabilization/Slab Jacking............................................................. 7-33

Diamond Grinding/Grooving ................................................................. 7-34 

Partial-Depth Repairs............................................................................ 7-36 

Full-Depth Repairs................................................................................ 7-37 

Dowel Bar Retrofitting........................................................................... 7-38 

Cross Stitching...................................................................................... 7-39 

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Towards Sustainable Pavement Systems Front Matter

Retrofitted Edge Drains......................................................................... 7-39 

Ultra-Thin Wearing Course ................................................................... 7-40

Bonded Concrete Overlays................................................................... 7-40

Energy Use and Emissions for Concrete-Surfaced Pavement Treatments . 7-41

Strategies for Improving Sustainability.................................................. 7-43 

Future Opportunities ............................................................................. 7-43 

Concluding Remarks..................................................................................... 7-44 

References ..................................................................................................... 7-45 

CHAPTER 8. END-OF-LIFE CONSIDERATIONS......................................... 8-1 

Introduction...................................................................................................... 8-1 

Recycling and Reuse Statistics of Pavements........................................ 8-1 

Economic and Environmental Considerations of EOL Options ............... 8-2 

Closed-Loop or Zero-Waste Thinking for Pavement Systems ................ 8-4 

EOL Considerations for Asphalt Pavements ................................................ 8-7 

Central Plant Recycling........................................................................... 8-8 

Full-Depth Reclamation (FDR).............................................................. 8-10

Strategies for Improving Sustainability.................................................. 8-15

Future Directions and Emerging Technologies ..................................... 8-17

EOL Considerations for Concrete Pavements............................................ 8-17

Introduction........................................................................................... 8-17

Concrete Recycling............................................................................... 8-20

Concrete Pavement Reuse................................................................... 8-24

Strategies for Improving Sustainability.................................................. 8-25

Future Directions/Emerging Technologies ............................................ 8-30

Concluding Remarks..................................................................................... 8-32

References ..................................................................................................... 8-32

CHAPTER 9. PAVEMENT SUSTAINABILITY WITHIN LARGER 

SYSTEMS................................................................................................................. 9-1 

Introduction...................................................................................................... 9-1 

Larger System Goals and Metrics.................................................................. 9-1 

Sustainable Communities ....................................................................... 9-1 

Ecosystems ............................................................................................ 9-3 

Strategies for Improving Sustainability......................................................... 9-4 

Aesthetics ............................................................................................... 9-4 

Historical and Cultural Identity ................................................................ 9-6 

Utility Cuts............................................................................................... 9-8 

Odor, Soot, and Particulate Matter ....................................................... 9-11 

Allowable Hours of Construction........................................................... 9-11 

Strategies for Improving Sustainability.................................................. 9-12 

Future Directions/Emerging Technologies ................................................. 9-12 

Concluding Remarks..................................................................................... 9-13 

References ..................................................................................................... 9-14 

CHAPTER 10. ASSESSING PAVEMENT SUSTAINABILITY................... 10-1 

Introduction.................................................................................................... 10-1 

Life-Cycle Cost Analysis (LCCA) ................................................................. 10-1 

Background........................................................................................... 10-1 

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Front Matter Towards Sustainable Pavement Systems

Key Issues in LCCA.............................................................................. 10-2 

Use of LCCA in Various Pavement Delivery Approaches..................... 10-6 

Available LCCA Tools........................................................................... 10-7 

Examples .............................................................................................. 10-8 

Life-Cycle Assessment (LCA)....................................................................... 10-8 

Purpose of an LCA ............................................................................... 10-8 

The LCA Process.................................................................................. 10-9 

Types of LCA Studies ......................................................................... 10-12 

Most Pavement LCAs are Process Based and “Attributional”............. 10-12

Available Tools ................................................................................... 10-12

Key Issues .......................................................................................... 10-13

Example Studies................................................................................. 10-14 

Methodological Framework in Greater Detail...................................... 10-15 

What Lies Ahead: Environmental Product Declarations...................... 10-15

An Example of an Important Methodological Element: Allocation...... 10-16

Sustainability Rating Systems ................................................................... 10-20

Background......................................................................................... 10-20

Rating Systems in Context.................................................................. 10-21 

Potential Industry Impacts of Rating Systems..................................... 10-21 

Rating Systems Relevant to Pavements ................................................... 10-21 

INVEST (Infrastructure Voluntary Evaluation Sustainability Tool)....... 10-22 

Greenroads® ...................................................................................... 10-22 

EnvisionTM........................................................................................... 10-23 

GreenLITES........................................................................................ 10-23 

Leadership in Energy and Environmental Design (LEED®)................ 10-23 

Use of Assessment Methods...................................................................... 10-34

Use Depends on Owner/Agency and Project Priorities....................... 10-34

Application at Various Levels.............................................................. 10-34

Level of Standardization ..................................................................... 10-35 

Concluding Remarks................................................................................... 10-35 

References ................................................................................................... 10-36 

CHAPTER 11. CONCLUDING REMARKS ................................................... 11-1 

Review of Technologies, Innovations, and Trends .................................... 11-1 

Implementation: The Next Step.................................................................... 11-3 

GLOSSARY

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Towards Sustainable Pavement Systems Front Matter

LIST OF FIGURES

Figure 1-1. GHG emissions by economic sector in the U.S. (EPA 2013) .............................. 1-1 

Figure 1-2. Basic components of a typical pavement system ................................................. 1-5 

Figure 2-1. Pavement life-cycle phases (UCPRC 2010) ........................................................ 2-6 

Figure 3-1. Typical volumes of aggregate in dense-graded asphalt concrete and in densegraded hydraulic cement concrete (asphalt concrete: summary of mixture 

designs by authors; concrete: Tayabji, Smith, and Van Dam 2010) .................... 3-5 

Figure 3-2. Coarse aggregates: rounded gravel (left) and crushed stone (right) 

(Kosmatka and Wilson 2011) .............................................................................. 3-5 

Figure 3-3. Primary energy and global warming potential from aggregate production per 

kg, at quarry (adapted from Wang et al. 2012) .................................................... 3-7 

Figure 3-4. Schematics illustrating straight-run distillation of asphalt within a complex 

refinery (Asphalt Institute and Eurobitume 2011) ............................................. 3-17 

Figure 3-5. Estimated tons of WMA usage by industry sector 2009-2011 (Hansen and 

Copeland 2013). ................................................................................................. 3-24 

Figure 3-6. RAP use in the U.S., 2009 through 2011 (adapted from Hansen and 

Copeland 2013) .................................................................................................. 3-26 

Figure 3-7. Typical volumetric distribution of hydraulic paste (cement, water, air) and 

aggregates in paving concrete (Taylor et al. 2006) ............................................ 3-36 

Figure 3-8. Steps in the modern dry-process manufacture of portland cement (Kosmatka 

and Wilson 2011) ............................................................................................... 3-39 

Figure 3-9. U.S. fly ash production, use (U.S. short tons), and utilization rate from 1966 

to 2011 (ACAA 2013b) ..................................................................................... 3-44 

Figure 3-10. U.S. slag cement shipments from 1996 to 2007 (adapted from SCA 2007) ...... 3-46 

Figure 3-11. Schematic of mixer truck washout water recycling for concrete batch plant 

mix water (Taylor et al. 2006) ........................................................................... 3-51 

Figure 3-12. Polished slab of concrete viewed through stereomicroscope. Dark circles are 

entrained air voids distributed throughout the grey hydrated cement paste 

(Courtesy of Karl Peterson, University of Toronto). ......................................... 3-53 

Figure 4-1. Example of payback time analysis considering only the material production 

and construction phases of three different pavement design lives (Santero, 

Harvey, and Horvath 2011) .................................................................................. 4-5 

Figure 4-2. Overall process for considering sustainability in pavement design ..................... 4-8 

Figure 4-3. Cross sections of various asphalt pavement types (not to scale) ....................... 4-10 

Figure 4-4. Cross sections of rehabilitated asphalt pavement structures (not to scale) ........ 4-12 

Figure 4-5. Cross sections of concrete pavement structure types (not to scale) ................... 4-13 

Figure 4-6. Cross sections of rehabilitated concrete pavement structures (not to scale) ...... 4-15 

Figure 4-7. Cross section of asphalt-surfaced composite pavement ..................................... 4-16 

Figure 4-8. Cross section of two-lift concrete pavement ...................................................... 4-17 

Figure 4-9. Cross section of semi-rigid pavement ................................................................ 4-18 

Figure 4-10. Cross sections of pervious concrete pavement, porous asphalt pavement, 

and permeable interlocking concrete pavement ................................................. 4-19 

Figure 4-11. Perpetual pavement cross section ...................................................................... 4-25 

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Front Matter Towards Sustainable Pavement Systems

Figure 4-12. Example of CRCP longer life design ................................................................. 4-26 

Figure 5-1. EPA non-road diesel engine limits for construction vehicles with two 

different ranges of rated power illustrating tightening of the emission limits 

(adapted from EPA 2013a) .................................................................................. 5-4 

Figure 5-2. Impact of construction-related traffic delay: (a) addition emissions, (b) 

additional energy consumption for normal traffic and traffic delay scenarios 

for work zone lengths of 1.9 mi (four 8-hr nighttime closures avoiding 

morning and evening peak hours), 3.8 mi (two 16-hr night and daytime 

closures avoiding evening peak hours), and 7.6 mi (32-hr closure) ................. 5-8 

Figure 5-3. Generalized asphalt pavement construction processes and associated fuel 

factors (fuel factor source: Skolnik, Brooks, and Oman 2013) ......................... 5-19 

Figure 5-4. Effect of compaction on predicted bottom-up fatigue life for two-layer beam 

specimens in mixture using a AR4000c binder (binder type used in several 

western highway agencies prior to Superpave) and at different air void and 

binder content levels (after Harvey et al. 2004) ................................................. 5-23 

Figure 5-5. Bulk specific gravity profile of one test lane (Leng 2011) ................................ 5-26 

Figure 5-6. Spray paver on the left and material transfer device on the right used in the 

overlay construction in Illinois (Al-Qadi et al. 2012) ........................................ 5-28 

Figure 5-7. Generalized concrete pavement construction processes and associated fuel 

factors (fuel factor source: Skolnik, Brooks, and Oman 2013) ......................... 5-29 

Figure 6-1. Pavement characteristics and influences on use-phase objectives ....................... 6-1 

Figure 6-2. Pavement texture and wavelength (Sandberg 1997) ............................................ 6-7 

Figure 6-3. Energy savings in MJ and equivalent gallons of gasoline for a medium-to-highvolume route over 10-year analysis period for preservation treatment versus 

leaving the pavement rough (Wang et al. 2012) .................................................. 6-8 

Figure 6-4. Estimate of light vehicle noise due to tire-pavement noise, powertrain noise, 

and aerodynamic noise at cruise speed (Rasmussen et al. 2008) ....................... 6-22 

Figure 6-5. Close Proximity (CPX) test trailer (Bendtsen and Thomsen 2008) ................... 6-23 

Figure 6-6. On-Board Sound Intensity (OBSI) setup (photo courtesy of John Harvey). ..... 6-23 

Figure 6-7. Controlled vehicle pass-by levels at 25 ft (7.6 m) versus OBSI level for the 

SRTT at all test sites and speeds—normalized data (Donavan and Lodico 2009) . 6-24 

Figure 6-8. Noise-generation mechanisms on dry pavement (Olek, Weiss, and GarciaVillarreal 2004) ................................................................................................... 6-26 

Figure 6-9. Example plot of one-third octave frequency content for several asphalt mixtures 

and influence of tire-pavement noise mechanisms (Ongel et al. 2008) ............. 6-26 

Figure 6-10. Normalized distributions of OBSI noise levels for conventional concrete 

pavement textures (Rasmussen et al. 2012) ....................................................... 6-28 

Figure 6-11a. Frequency content of OBSI measured at 60 mi/hr (97 km/hr) for pretreatment 

(PreCDG), conventional diamond grinding (CDG) and NGCS (GnG in the figure) 

for a California test section, Yolo 113–PM R0.5/R2.5 (Guada et al. 2013) ........ 6-29 

Figure 6.11b. Conventional diamond-ground surface showing “fins” that are eventually 

removed by traffic (Guada et al. 2013) ............................................................. 6-29 

Figure 6.11c. Conventional diamond-ground surface with the Next Generation Concrete 

Surface showing definition of “land area” between grooves (Guada et al. 2013) .. 6-29 

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Towards Sustainable Pavement Systems Front Matter

Figure 6-12a. Frequency content of OBSI measured at 35 mi/hr (56 km/hr) for Caltrans 

open-graded asphalt mixtures with typical 0.375 inch (9.5 mm) and #4 

(4.75 mm) maximum aggregate sizes (Wu et al. 2013) ..................................... 6-30 

Figure 6.12b. Examples of residual specimens after Cantabro testing for raveling of the 

same OGFC mixtures (Wu et al. 2013). (Each original specimen had a 

diameter of 4 inches (100 mm) .......................................................................... 6-30 

Figure 6-13. Pervious concrete (left, courtesy John Kevern) and porous asphalt (right, 

courtesy National Asphalt Pavement Association) ............................................ 6-33 

Figure 6-14. Permeable interlocking concrete pavers (courtesy Interlocking Concrete 

Pavement Institute) ............................................................................................ 6-34 

Figure 6-15. Vegetated pavement.(photo courtesy of Tom Van Dam) .................................. 6-34 

Figure 6-16. Heat flow and the basic thermal model for day and night (NCPTC/ 

NCAT 2013) ...................................................................................................... 6-39 

Figure 6-17. Heat islands for various areas of development (EPA 2003) .............................. 6-40 

Figure 6-18. Average June horizontal flat plate solar radiation map of the U.S. (NREL 2012) . 6-42 

Figure 6-19. Illustration of the main drivers of climate change (Cubasch et al. 2013) .......... 6-45 

Figure 6-20. Surface temperature and albedo for selected types of pavements in Phoenix, 

Arizona (Cambridge Systematics 2005) ............................................................ 6-47 

Figure 6-21. Effect of albedo on pavement surface temperature in Davis, California 

(16:00 9 July 2012) (Li et al. 2013) ................................................................... 6-48 

Figure 6-22. Near-surface air temperatures of different pavements measured 2 inches 

(50 mm) above the surface (Li 2012) ................................................................ 6-49 

Figure 6-23. Heat flux from pavement surfaces for 1 full day during July 2012 (Li et al. 2013) .. 6-50 

Figure 6-24. Typical pavement solar reflectance of conventional asphalt and concrete 

pavements over time (EPA 2008) ...................................................................... 6-52 

Figure 6-25. Diamond ground concrete pavement surface ..................................................... 6-53 

Figure 6-26. Pavement reflective differences (FHWA 2012) ................................................ 6-59 

Figure 6-27. Fatality and fatality rates, 2002 – 2011 (NHTSA 2013) .................................... 6-62 

Figure 6-28. Crash costs by crash factor (Miller and Zaloshnja 2009) .................................. 6-63 

Figure 7-1. Illustration of the impact of pavement preservation. ........................................... 7-2 

Figure 7-2. Steps in integrating PMS and pavement preservation (adapted from 

Zimmerman and Peshkin 2003) ........................................................................... 7-3 

Figure 7-3. Effect of overlay interval on agency, user and total GHG (CO2e) emissions 

(Lidicker et al. 2012) ............................................................................................ 7-4 

Figure 7-4. Process of selecting the preferred preservation treatment (adapted from 

Peshkin et al. 2011) .............................................................................................. 7-6 

Figure 7-5. Installation of hot-applied sealant ........................................................................ 7-9 

Figure 7-6. Full-depth asphalt patch ..................................................................................... 7-14 

Figure 7-7. Fog seal application ........................................................................................... 7-15 

Figure 7-8. Chip seal construction ........................................................................................ 7-16 

Figure 7-9. Slurry seal application........................................................................................ 7-17 

Figure 7-10. Ultra-thin asphalt overlay .................................................................................. 7-19 

Figure 7-11. Hot in-place recycling with application of overlay (Kandhal and Mallick 1997) .. 7-21 

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Front Matter Towards Sustainable Pavement Systems

Figure 7-12. Cold in-place recycling (photo courtesy of D. Matthews) ................................. 7-22 

Figure 7-13. Short panels for bonded concrete overlay .......................................................... 7-24 

Figure 7-14. Typical sequence of concrete-surfaced pavement treatments as part of CPR 

(ACPA 2006) ..................................................................................................... 7-31 

Figure 7-15. Joint sealing ....................................................................................................... 7-32 

Figure 7-16. Surface texture produced by diamond grinding (courtesy ACPA) .................... 7-34 

Figure 7-17. Diamond grooving operation ............................................................................. 7-35 

Figure 7-18. Partial-depth repair ............................................................................................. 7-36 

Figure 7-19. Full-depth repair................................................................................................. 7-37 

Figure 7-20. Placement of dowel bars in a dowel bar retrofitting operation .......................... 7-38 

Figure 7-21. Bonded concrete overlay construction (courtesy ACPA) .................................. 7-40 

Figure 7-22. Details for the high-traffic case study of the material production phase showing 

the energy consumption for different LCI data sets (Wang et al. 2012) ............ 7-42 

Figure 8-1. Recycling and reuse statistics of asphalt and concrete materials (data 

compiled from Hansen and Copeland (2013) for RAP and Wilburn and 

Goonan (1998) and USGS (2000) for RCA) ....................................................... 8-2 

Figure 8.2. Environmental cost determinants for pavement EOL considerations (adapted 

from Horvath 2004) ............................................................................................. 8-3 

Figure 8-3. An illustration of EOL allocation rules potentially applicable for pavements 

(cut-off method, 50/50 method, and substitution method) .................................. 8-7 

Figure 8-4. Optimal performance levels based on (a) total cost and (b) GHG emissions 

(Aurangzeb and Al-Qadi 2014) ........................................................................... 8-9 

Figure 8-5. Full depth reclamation train (courtesy of John Harvey) .................................... 8-11 

Figure 8-6. Example effect of type of crusher on RCA particle size distribution. ................... 8-28 

Figure 8-7. Carbon sequestration by fine RCA in laboratory column studies (Gardner, 

Leipold, and Peyranere 2006) ............................................................................ 8-29 

Figure 8-8. On-site concrete recycling operation ................................................................. 8-30 

Figure 8-9 Recycling existing concrete pavement in place (photo courtesy of 

Jim Grove) ......................................................................................................... 8-31 

Figure 9-1. Zion Park Blvd. in Utah (SR 9) with a chip seal surfacing that uses local red 

volcanic cinders to match the aesthetics of the surrounding environment and to 

be consistent with historical road surfacing (photo courtesy of Steve Muench) .... 9-5 

Figure 9-2. Brick crosswalk in Charlotte, NC implemented as part of an intersection 

improvement (Hughes, Chappell, and Chen 2006) .............................................. 9-5 

Figure 9-3. Vehicular interlocking concrete pavers being placed in a pedestrian-friendly 

downtown area in Houghton, MI. Note the use of colored concrete for the 

pavers to provide a visual offset for the cross walk (photo courtesy of 

Thomas Van Dam) ............................................................................................... 9-6 

Figure 9-4. Old cobblestone pavement preserved and still in use on East Republican St., 

Seattle, WA (photo courtesy of Steve Muench) .................................................. 9-7 

Figure 9-5. Lombard Street in San Francisco during construction in 1922 (FoundSF 2013) ... 9-7 

Figure 9-6. Lombard Street as it looks today with its brick pavement, kept for historical 

and cultural reasons (Wikipedia, public domain) ................................................ 9-8 

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Towards Sustainable Pavement Systems Front Matter

Figure 9-7. Poor quality patch in an existing concrete pavement (photo courtesy of Steve 

Muench) ............................................................................................................... 9-8 

Figure 9-8. Illustration of how existing concrete pavers can be removed to repair a gas line 

(a), and then the bedding recompacted (b), joint sand reapplied (c), and the 

final product which shows little sign of disturbance (d) (ICPI 2009) .................. 9-9 

Figure 9-9. Removal of French hexagonal modular pavement to access utility (Larrod, 

Sedran, and Balay 2012) .................................................................................... 9-10 

Figure 9-10. A utility cut in Rome, Italy shown with the excavation open and sampietrini 

(individual rounded black basalt stones) removed. Upon completion the cut 

is filled and sampietrini reinstalled (photo courtesy of Steve Muench) ............ 9-10 

Figure 10-1. Example projected life-cycle cost stream diagram (FHWA 2002) .................... 10-2 

Figure 10-2. Probabilistic analysis of two design alternatives (Walls and Smith 1998) ........ 10-5 

Figure 10-3. Life-cycle assessment framework (ISO 2006a) ............................................... 10-10 

Figure 10-4. Data types relevant to a typical LCA ............................................................... 10-10 

Figure 10-5. Sample EPD for a concrete mix design (courtesy of Central Concrete 

Supply Company) ............................................................................................ 10-16 

Figure 10-6. Example of economic allocation for a multi-output process ........................... 10-18 

Figure 10-7. Assessing sustainabilty with LCCA, LCA, and rating systems on different 

levels ................................................................................................................ 10-34 

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Front Matter Towards Sustainable Pavement Systems

LIST OF TABLES

Table 3-1. Summary of estimated national average freight movement fuel efficiency (diesel) 

of freight transportation modes (2009 data) (Kruse, Protopapas, and Olson 2012). .. 3-8 

Table 3-2. Approaches for improving aggregate production for pavement sustainability. .. 3-10 

Table 3-3. Approaches for improving pavement sustainability with regard to asphalt 

materials production ............................................................................................ 3-33 

Table 3-4. Annual energy and CO2 emissions associated with U.S. cement 

manufacturing and concrete production (Choate 2003) ...................................... 3-37 

Table 3-5. Chemical composition and select properties of common SCMs (Taylor et al. 

2006; Kosmatka, Kerkoff, and Panarese 2002) ................................................... 3-42 

Table 3-6. Effects of SCMs on the properties of fresh concrete (Taylor et al. 2006)........... 3-42 

Table 3-7. Effects of SCMs on the properties of hardened concrete (Taylor et al. 2006) .... 3-43 

Table 3-8. Harmful contaminants, tests methods and limits for grey water to be used in 

concrete mixtures (Taylor et al. 2006) ................................................................ 3-51 

Table 3-9. Effect of recycled water on concrete properties (Taylor et al. 2006) .................. 3-52 

Table 3-10. Common chemical admixtures used in paving concrete (Taylor et al. 2006) ..... 3-52 

Table 3-11. Approaches for improving pavement sustainability with regard to concrete 

materials production ............................................................................................ 3-58 

Table 4-1. Division of scope between design, maintenance and preservation, and 

end-of-life chapters ................................................................................................ 4-2 

Table 4-2. Summary of major issues and trade-offs for improving pavement 

sustainability through design ............................................................................... 4-28 

Table 5-1. Thresholds of significance for construction operations (AEP 2012) .................... 5-4 

Table 5-2. Approaches for improving general sustainability of pavement construction 

operations ............................................................................................................ 5-10 

Table 5-3. GHG emissions reduction scenarios from fossil fuel use (EPA 2009). .............. 5-11 

Table 5-4. Operational strategies to reduce emissions incurred due to construction 

activities (EPA 2007) .......................................................................................... 5-12 

Table 5-5. Alternative fuel use strategies to reduce emissions (EPA 2007) ......................... 5-13 

Table 5-6. Energy efficiency and CO2 emissions for common equipment used in 

asphalt pavement construction (compiled from Santero and Horvath [2009a]; 

Skolnik, Brooks, and Oman [2013]) ................................................................... 5-19 

Table 5-7. Approaches for improving sustainability of asphalt pavement construction 

operations. ........................................................................................................... 5-21 

Table 5-8. Best practices to control fumes, emissions, and odors from asphalt mixture 

plant and paving operations ................................................................................. 5-22 

Table 5-9. Typical minimum requirements for laydown temperatures as a function of 

base temperature and lift thicknesses (NCDOT 2012) ........................................ 5-24 

Table 5-10. General approaches for improving the sustainability of concrete pavement 

construction ......................................................................................................... 5-30 

Table 5-11. Energy efficiency and CO2 emissions for typical equipment used for concrete 

pavement construction (compiled from Santero and Horvath 2009a and 

Skolnik, Brooks, and Oman 2013) ...................................................................... 5-32 

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Towards Sustainable Pavement Systems Front Matter

Table 6-1. Summary of strategies for improving vehicle use phase fuel consumption 

and potential trade-offs ........................................................................................ 6-17 

Table 6-2. Decibel changes, energy loss, and loudness (FHWA 2011b) ............................. 6-20 

Table 6-3. FHWA noise abatement criteria in dBA (hourly A-weighted sound level) 

(FHWA 2011b) .................................................................................................... 6-21 

Table 6-4. Summary of strategies for improving tire-pavement noise and potential 

trade-offs ............................................................................................................. 6-31 

Table 6-5. Summary of strategies to address stormwater runoff issues and potential 

trade-offs. ............................................................................................................ 6-37 

Table 6-6. Summary of considerations to address UHIE issues and potential trade-offs .... 6-56 

Table 6-7. Summary of strategies to address lighting issues and potential trade-offs .......... 6-61 

Table 7-1. Pavement maintenance and preservation techniques. ........................................... 7-7 

Table 7-2. Potential use of non-traditional materials and techniques with potential 

pavement maintenance and preservation application (TRB 2012) ....................... 7-8 

Table 7-3. Evaluation of sustainability impacts of treatments for asphalt-surfaced pavements ... 7-10 

Table 7-4. Energy consumption and GHG emissions data for some typical asphaltsurfaced pavement preservation treatments (Chehovits and Galehouse 2010) ... 7-26 

Table 7-5. Energy consumption and GHG emissions data for new construction and 

major rehabilitation activities (Chehovits and Galehouse 2010) ........................ 7-27 

Table 7-6. Comparison between microsurfacing and other treatment alternatives for 

asphalt-surfaced pavement (Chan et al. 2011) .................................................... 7-27 

Table 7-7. Evaluation of sustainability impacts of treatments for concrete-surfaced 

pavements. ........................................................................................................... 7-29 

Table 8-1. Summary of FDR advantages, candidate pavements, and limitations ................ 8-12 

Table 8-2. Commonly used test methods in the mixture design of FDR projects ................ 8-14 

Table 8-3. Common additives used in FDR projects (recommended additive percentages 

from ARRA 2001a) ............................................................................................. 8-14 

Table 8-4 Approaches for improving sustainability of asphalt pavement recycling for 

pavement sustainability ....................................................................................... 8-16 

Table 8-5. Design recommendations for RCA concrete pavements (ACPA 2009) ............. 8-24 

Table 8-6. Approaches for improving sustainability of concrete pavement recycling ......... 8-26 

Table 8-7. Recommended RCA subbase quality tests and threshold values for various 

applications (Saeed and Hammons 2008) ........................................................... 8-27 

Table 9-1. General strategies to improve pavement sustainability within larger systems. ... 9-12 

Table 10-1. Typical LCA impact categories ......................................................................... 10-11 

Table 10-2. Summary of INVEST sustainability criteria and scoring (FHWA 2011) ......... 10-24 

Table 10-3. Summary of Greenroads credit categories and scoring (Muench et al. 2011) .. 10-26 

Table 10-4. Summary of ENVISION sustainability criteria and scoring (ISI and 

Zofnass 2012) .................................................................................................... 10-27 

Table 10-5. Summary of GreenLITES sustainability criteria and scoring (NYSDOT 2010) ... 10-29 

Table 10-6. Summary of LEED-ND sustainability criteria and scoring (USGBC 2012; 2013) .. 10-33 

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Front Matter Towards Sustainable Pavement Systems

ACRONYMS

AADT Average Annual Daily Traffic 

AAR Alkali-Aggregate Reactivity 

AASHTO American Association of State Highway and Transportation Officials

AC Asphalt Concrete 

ACAA American Coal Ash Association

ACBFS Air-Cooled Blast Furnace Slag 

ACEC American Council of Engineering Companies 

ACI American Concrete Institute

ACPA American Concrete Pavement Association

ACR Alkali-Carbonate Reactivity

AEAs Air-Entraining Admixtures 

AEP Association of Environmental Professionals 

AI Asphalt Institute

AISC American Institute of Steel Construction

APT Accelerated Pavement Testing 

APWA American Public Works Association

ARRA Asphalt Recycling and Reclaiming Association 

ASR Alkali-Silica Reactivity 

ASCE American Society of Civil Engineers 

ASTM American Society for Testing and Materials

ATB Asphalt Stabilized Bases

BCA Benefit-Cost Analysis 

BMP Best Management Practice

BTS Bureau of Transportation Statistics

CA4PRS Construction Analysis for Pavement Rehabilitation Strategies 

CAC Cement Association of Canada 

Caltrans California Department of Transportation

CaCO3 Calcium Carbonate/Limestone 

CaO Lime 

CARB California Air Resources Board

CCPR Cold Central Plant Recycling

CDG Conventional Diamond Grinding 

CEQ Council on Environmental Quality 

CEQA California Environmental Quality Act

CGS California Geological Society 

CH4 Methane

CI Compression Ignition 

CIR Cold In-place Recycling 

CKD Cement-Kiln Dust

CKRC Cement Kiln Recycling Coalition

CNG Compressed Natural Gas

CO Carbon Monoxide 

CO2 Carbon Dioxide 

CO2e Carbon Dioxide Equivalent 

CP Road Map Long-Term Plan for Concrete Pavement Research and Technology

CPB Controlled Pass By 

CPR Concrete Pavement Restoration

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Towards Sustainable Pavement Systems Front Matter

CPX Close Proximity 

CRCP Continually Reinforced Concrete Pavements

CRM Crumb Rubber Modifier

CSD Context-Sensitive Design

C-S-H Calcium Silicate Hydrate

CTB Cement Treated Base

CTE Coefficient of Thermal Expansion and Contraction

dB Decibels

dBA Adjusted Decibels

DBB Design-Bid-Build

DB Design-Build

DBM Design-Build-Maintain

DLM Dynamic Lane Merge

DOT Department of Transportation

EAPA European Asphalt Pavement Association

EDC Every Day Counts

EIO Economic Input-Output 

EIR Environmental Impact Review

EO Executive Order 

EOL End-of-Life

EPA Environmental Protection Agency

EPD Environmental Product Declaration

ESAL Equivalent Single-Axle Load

EUAC Equivalent Uniform Annual Cost

FDR Full-Depth Reclamation

FDR-FA Full-Depth Reclamation using Foamed Asphalt

FEMA Federal Emergency Management Agency

FHWA Federal Highway Administration

GDP Gross Domestic Product

GGBFS Ground Granulated Blast Furnace Slag

GHG Greenhouse Gas

GPR Ground Penetrating Radar

GreenLITES Green Leadership in Transportation and Environmental Sustainability

GSI Gomaco Smoothness Indicator

GSSI Geophysical Survey Systems, Inc.

GWP Global Warming Potential

H3PO4 Orthophosphoric Acid

HC Hydrocarbons

HCC Hydraulic Cement Concrete

HFCs Hydrofluorocarbons

HIPERPAV HIgh PERformance Concrete PAVing

HIR Hot In-place Recycling

HMA Hot-Mix Asphalt

HOV High-Occupancy Vehicle

HRWRA High-Range Water-Reducing Admixtures

HSIP Highway Safety Improvement Program

IC Intelligent compaction

ICPI Interlocking Concrete Pavement Institute

IEA International Energy Agency

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Front Matter Towards Sustainable Pavement Systems

INVEST Infrastructure Voluntary Evaluation Sustainability Tool

IPCC Intergovernmental Panel on Climate Change

IRI International Roughness Index

IRT Infrared Thermography

ISI Institute for Sustainable Infrastructure

ISO International Organization for Standardization

ITS Intelligent Transportation Systems

JPCP Jointed Plain Concrete Pavement

JRCP Jointed Reinforced Concrete Pavement

KDOT Kansas Department of Transportation

LAB Los Angeles Abrasion

LCA Life Cycle Assessment

LCB Lean Concrete Base

LCCA Life-Cycle Cost Analysis

LCI Life-Cycle Inventory

LCIA Life-Cycle Impact Assessment

LED Light-Emitting Diode

LEED® Leadership in Energy and Environmental Design

LFATB Lime and Fly Ash Binder

LNG Liquefied Natural Gas

LWA Light Weight Aggregate

MAP-21 Moving Ahead for Progress in the 21st Century Act

MDPDG AASHTO DARWin-METM Mechanistic-Empirical Design Guide

ME Mechanistic-Empirical

MEPDG Mechanistic-Empirical Pavement Design Guide

MGGRA Midwest Greenhouse Gas Reduction Accord

MoDOT Missouri Department of Transportation

MOVES Motor Vehicle Emission Simulator

MPD Mean Profile Depth

MPO Metropolitan Planning Organizations

MRD Material-Related Distress

MRWRA Mid-Range Water Reducing Admixture 

MTD Mean Texture Depth

MTV Material Transfer Vehicle

NAPA National Asphalt Pavement Association

NCAT National Center for Asphalt Technology

NCDOT North Carolina Department of Transportation

NCHRP National Cooperative Highway Research Program

NCPTC National Concrete Pavement Technology Center

NDT Nondestructive Testing

NEPA National Environmental Policy Act

NGCS Next Generation Concrete Surface

NHPP National Highway Performance Program

NHS National Highway System

NHTSA National Highway Traffic Safety Administration

NLA National Lime Association

NMAS Nominal Maximum Aggregate Size

NMHC Non-Methane Hydrocarbons

NOx Nitrogen Oxides

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Towards Sustainable Pavement Systems Front Matter

NPC Net Present Cost

NPS National Park Service

NPV Net Present Value

NRCS Natural Resources Conservation Service

NRMCA National Ready-Mix Concrete Association

NYSDOT New York State Department of Transportation

OBSI On-Board Sound Intensity

OGFC Open-Graded Friction Course

PAPA Pennsylvania Asphalt Pavement Association

PCA Portland Cement Association

PCC Portland Cement Concrete

PCR Pavement Condition Rating

PDC Positive Dust Control

PE-2 Project Emissions Estimator

PFCs Perfluorocarbons

PG Performance Grade

PI Profile Index

PLC Portland Limestone Cement

PM Particulate Matter

PM10 Fugitive Particulate Matter/Fugitive Dust

PMA Polymer-Modified Asphalt

PMS Pavement Management Systems

PPA Polyphosphoric Acid

PPCPS Precast Pre-Stressed Concrete Pavement Systems

PWL Percent within Limits

QA Quality Assurance

QC Quality Control

QPPP Quiet Pavement Pilot Program

QPR Quieter Pavement Research 

RAP Recycled Asphalt Pavement

RAS Recycled Asphalt Shingles

RCA Recycled Concrete Aggregate

RCC Roller Compacted Concrete

RCC Roller-Compacted Concrete

RCWM Recycled, Co-product, or Waste Material

RGGI Regional Greenhouse Gas Initiative 

ROW Right of Way

RTP Real-Time Profiler

SAEFL Swiss Agency for the Environment, Forests and Landscape

SCA Slag Cement Association

SCM Supplementary Cementitious Material

SEAM Sulfur Extended Asphalt Modifier

SETAC Society of Environmental Toxicology and Chemistry

SF6 Sulfur Hexafluoride

SFS Steel Furnace Slag

SHAs State Highway Agencies

SHRP Strategic Highway Research Program

SIT State Inventory Tool

SLWA Saturated Lightweight Aggregate 

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Front Matter Towards Sustainable Pavement Systems

SMA Stone Mastic Asphalt

SOx Sulfur Oxides

SPB Statistical Pass By Method

SPL Sound Pressure Levels

SRI Surface Reflectivity Index

SRTT Standard Reference Test Tire

TCP Thin Concrete Pavement

TEA-21 Transportation Equity Act for the 21st Century 

TiO2 Titanium Dioxide

TNM Traffic Noise Model

TRB Transportation Research Board

TWh Terawatt Hours

UCPRC University of California Pavement Research Center

UHI Urban Heat Island

UHPC Ultra-High-Performance Concrete

ULSD Ultra Low Sulfur Diesel

UNFCCC United Nations Framework Convention on Climate Change

US DOE U.S. Department of Energy

USGBC U.S. Green Building Council

USGS U.S. Geological Survey

UTW Ultra-Thin Whitetopping

VMT Vehicle-Miles Traveled

VOC Volatile Organic Carbon

WCED World Commission on Environment and Development

WCI Western Climate Initiative

WHO World Health Organization

WMA Warm-Mix Asphalt

WRAs Water-Reducing Admixtures

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Towards Sustainable Pavement Systems Executive Summary

EXECUTIVE SUMMARY

This document has been prepared to provide guidance to the pavement community on 

sustainability considerations in pavement systems, drawing from and synthesizing the large and 

diverse body of technical information that exists on the subject. Sustainability considerations 

throughout the entire pavement life cycle are examined (from material extraction and processing 

through the design, construction, use, maintenance/rehabilitation, and end-of-life phases) and the 

importance of recognizing context sensitivity and assessing trade-offs in developing sustainable 

solutions are emphasized. Key points from each of the eleven chapters contained in the 

document are summarized in the following sections. 

Chapter 1. Introduction

Chapter 1 provides a broad introduction to sustainability and its importance in pavement 

engineering. It also describes the overall scope and target audience for the document. 

• What is sustainability? Most definitions of sustainability begin with that issued by the

World Commission on Environment and Development (WCED, often referred to as the

Brundtland Commission) in 1987: “Sustainable development is development that meets

the needs of the present without compromising the ability of future generations to meet

their own needs.” Moreover, sustainability is often described as a quality that reflects the

balance of three primary components: economic, environmental, and social impacts,

which are often collectively referred to as the “triple-bottom line.” A focus on

sustainability can be interpreted as a recognition of the importance of all three triplebottom line components. However, the relative importance and consideration of each of

these factors are context sensitive and very much driven by the goals, demands,

characteristics, location, materials, and constraints of a given project, as well as the

overarching goals of the sponsoring agency.

• Systems approach to sustainability. In this context, more sustainable pavement

systems are achieved through the balanced consideration of a number of trade-offs and

competing priorities for a given project. It is important to recognize that, in some cases,

it may not be productive (and it may even be counterproductive) to introduce certain

features that are thought to be sustainable. For example, the use of recycled materials

may not improve project sustainability when the economic and environmental costs of

transporting the material over a great distance outweigh the benefits of using that

material. This is the type of trade-off that must be continually assessed as the pavement

industry moves towards more sustainable solutions.

• Scope of the document. This document focuses exclusively on the sustainability

considerations associated with the pavement structure and pavement materials, and only

those pavements constructed with a semi-permanent surface.

• Target audience. The primary audience for this document are practitioners doing work

within and for state Departments of Transportation (DOTs), and it is intended for

designers, maintenance, material and construction engineers, inspectors, and planners

who are responsible for the design, construction, and preservation of the nation’s

highway network.

ES-1 
Executive Summary Towards Sustainable Pavement Systems

Chapter 2. Concepts of Pavement Sustainability

This chapter presents the basic concepts of pavement sustainability, and includes definitions, an 

overview of the pavement life cycle, an outline of sustainability issues and trade-offs, and an 

overview of how sustainability can be measured. 

• Sustainable pavements defined. “Sustainable” in the context of pavements refers to 

system characteristics that encompasses a pavement’s ability to (1) achieve the 

engineering goals for which it was constructed, (2) preserve and (ideally) restore 

surrounding ecosystems, (3) use financial, human, and environmental resources 

economically, and (4) meet basic human needs such as health, safety, equity, 

employment, comfort, and happiness. 

• Sustainability is an aspirational goal. It is unlikely a truly “sustainable” pavement will 

be constructed in the near future so pursuit of sustainability should be viewed as a 

process of continual improvement towards an ultimate goal. This document, therefore, 

highlights “sustainability best practices,” which are processes, actions, and features that 

advance the state of the practice towards more sustainable pavements.

• Sustainability is context sensitive. There needs to be a full accounting of surrounding 

systems and a pavement’s influence on them in order to define the most appropriate 

sustainability practices associated with a particular pavement system. Furthermore, the 

approach must be tailored to fit into the overall goals and objectives of the agency. 

• Pavement sustainability includes a large range of issues. Among other items, this can 

include such things as greenhouse gas (GHG) emissions, energy consumption, impacts on 

habitat, water quality, changes in the hydrologic cycle, air quality, mobility, access, 

freight, community, depletion of non-renewable resources, and economic development. 

Again, these must be considered within the confines of the particular project and the 

goals of the agency. 

• Sustainability measurement is an evolving field. The “measurement” of sustainability 

is the first step in being able to establish benchmarks and assess progress. Currently, four 

general measurement tools, or methods, can be used to quantify sustainability: 

performance assessment, life-cycle cost analysis (LCCA), life-cycle assessment (LCA), 

and sustainability rating systems. These methods can be used alone or in concert to 

measure sustainability. Using them in concert provides a more holistic assessment of 

sustainability since each system tends to either address one specific component of 

sustainability in detail or address all components in less detail. Considerable work 

remains on establishing the framework and boundaries for pavement LCA, and outside of 

some treatment by rating systems, metrics to measure equity/social impacts associated 

with pavement systems do not currently exist. 

• Considerations of trade-offs is important. The considerations of trade-offs is 

essentially a benefit/cost analysis performed in a more holistic sense (i.e., considering 

more than just economics). Even if benefits and costs are difficult to quantify, it is 

important to use a consistent approach in analyzing trade-offs to avoid introducing 

unintended bias. In general, these considerations should include the priorities and values 

of the organization or project, costs, impact magnitude and duration, and risk. 

ES-2 
Towards Sustainable Pavement Systems Executive Summary

Chapter 3. Materials Considerations to Improve Pavement Sustainability

Chapter 3 reviews the materials commonly used in paving applications—including aggregate, 

asphalt, and cementitious materials—and describes how the production and use of those 

materials affect the overall sustainability of the pavement system. The scope is from the 

production or manufacture of materials to the point where the materials arrive at the construction 

site, either on grade or before leaving the plant. Sustainability impacts of other materials 

commonly used in pavements (such as steel, reinforcing fibers, interlocking concrete pavers, soil 

modifiers and stabilizers, and geosynthetics) are also discussed.

• Consideration of life-cycle impacts of materials is important. Impacts from material 

acquisition through processing, construction, use, and ultimately to the end of life need to 

be considered. Discussions are presented concerning the decision-making process 

inherent in material selection, the use of recycled, co-product, and waste materials 

(RCWMs), overall constructability considerations, trade-offs between higher quality 

materials and transportation costs/impacts, and the unintended consequences of restrictive 

specifications.

• Sustainability impacts of aggregates. Specific strategies are presented to improve the 

sustainability of aggregate production. In general, reducing the use of virgin materials 

and increasing the use of locally available materials and the use of durable RCWMs 

improves overall sustainability. Future challenges include more widespread use of 

RCWMs as aggregate, the ability to successfully incorporate “marginal” aggregates into 

pavement systems, and more sustainable transportation of aggregate over greater 

distances. 

• Sustainability impacts of asphalt materials. Asphalt-based materials have evolved 

significantly in recent years, with increased amounts of reclaimed asphalt pavement 

(RAP) and recycled asphalt shingles (RAS) being used to replace virgin binder. 

Moreover, increased levels of polymerization and the addition of rubber are being used to 

develop binders that are better suited to modern paving and preservation needs, to create 

specialized mixtures to provide improved structural support, and to enhance safety and 

reduce noise. Multiple approaches for improving sustainability with regards to asphalt 

materials are presented, including reducing virgin binder and virgin aggregate content in 

hot-mix asphalt (HMA) and warm-mix asphalt (WMA) mixtures, reducing energy 

consumed and emissions generated in mixture production, use of alternative binders, 

extending the life of asphalt mixtures, reducing materials transportation impacts, 

extending lives of seal coats, reducing the need for new materials, and increasing surface 

reflectivity (where warranted).

• Sustainability impacts of concrete materials. The major challenge facing cementitious 

materials is that the production of the primary binder (portland cement), is energy- and 

GHG-emission intensive. Reductions in those energy and emission levels is best met by 

expanding efforts to reduce the amount of portland cement used in paving mixtures. 

Several strategies are presented to achieve this, including the use of improved aggregate 

gradations, the use of portland limestone and blended cements, and the increased use of 

supplementary cementitious materials (SCMs) added at the concrete plant. Other 

approaches for improving the sustainability of concrete materials includes reducing water 

use in concrete production, increasing the use of RCWMs and marginal aggregates, and 

improving the durability of paving concrete. 

ES-3 
Executive Summary Towards Sustainable Pavement Systems

Chapter 4. Pavement and Rehabilitation Design to Improve Sustainability

This chapter describes sustainability considerations through the design process for both asphalt 

and concrete pavements. The focus is on new pavement design and structural rehabilitation, 

including reconstruction and structural overlays. Pavement design considerations are described, 

as is the concept of “payback time,” which is useful when evaluating the sustainability of design 

approaches that incur a larger initial economic or environmental impact as compared to standard 

practices. 

• Improved pavement design procedures. Mechanistic-empirical pavement design 

procedures offer the promise of more efficient pavement designs for the prevailing 

traffic, climatic, and locational design conditions, which contributes to the overall 

sustainability of the resultant design.

• Optimized use of materials. Innovative pavement designs that incorporate the 

optimized use of materials and cross sections are an attractive means of meeting 

performance requirements while achieving environmental and economic benefits. 

• Evaluation of pavement designs. Pavement designs can be evaluated by using LCA, 

LCCA, and rating systems to assess their environmental and societal impacts so that they 

can be improved. Moreover, several key use-phase issues, such as smoothness, noise, 

and stormwater management, can be considered in the design stage to help control later 

use-phase impacts.

• Sample design strategies. Some sample design strategies that may address sustainability 

issues for given projects are described, including long-life asphalt and concrete 

pavements, use of inlays, structural designs using local materials/low-impact 

transportation, accelerated construction, noise-reducing surfaces, modular pavement 

systems (including concrete pavers), pavement strategies for stormwater management, 

and consideration of use-phase impacts in the design phase. 

• Emerging trends in pavement design. Among the emerging trends in the pavement 

design area are ongoing improvement to mechanistic-empirical pavement design 

procedures, the integration of design and environmental impact analyses, the 

consideration of emerging materials and future maintenance and rehabilitation in design, 

the possible integration of performance-related specifications, and improved smoothness 

prediction models. 

Chapter 5. Construction Considerations to Improve Pavement Sustainability

This chapter briefly reviews the key elements to be considered to enhance the sustainability of 

construction for both asphalt and concrete pavements. This includes discussions on 

specifications, construction setup and operations, reduction of construction equipment fuel and 

emissions, management and handling of construction materials, construction quality assurance, 

and effective lane closures. 

• Pavement construction affects sustainability. Pavement construction has an effect on 

the overall sustainability of a project. For example, construction-related fuel 

consumption, exhaust emissions, particulate generation, noise generation, and traffic 

delays and congestion are typical construction-related impacts. Furthermore, the area 

surrounding the construction site is also impacted by the pavement construction due to 

possible effects on residents, businesses, and local ecosystems.

ES-4 
Towards Sustainable Pavement Systems Executive Summary

• Improving sustainability of pavement construction operations. Sustainability 

improvements in the pavement construction process can be gained through the 

optimization of construction planning and sequencing, the control of erosion and 

sedimentation, the management of construction-related traffic delays, the control of onsite equipment- and construction-related noise, and the management of construction 

waste. At the same time, regulations continue to require improvements in the operation 

efficiency of construction equipment, lowering combustion emissions such as VOC and 

NOx, diesel particulates, and fugitive particulate matter. Quality assurance is an essential 

element in constructing a durable pavement and, consequently, is essential in improving 

the overall sustainability. 

• Emerging technologies and construction techniques. A number of innovative 

technologies are being adopted to improve construction efficiency, quality, and 

monitoring, including techniques such as intelligent compaction, stringless paving, 

infrared thermographic scanning, and real-time smoothness measurement. At the same 

time, new construction techniques, such as two-lift concrete paving and the use of cold 

plant asphalt mixes, have the potential to revolutionize construction, minimizing the use 

of non-renewable virgin materials and maximizing the use of RCWMs.

Chapter 6. Use-Phase Considerations

Chapter 6 identifies the critical sustainability impacts associated with pavement structures while 

they are in service, commonly referred to as the use phase. This chapter includes discussions of 

rolling resistance and fuel consumption, tire-pavement noise, stormwater management, pavement 

thermal performance, lighting, and safety, all of which, in turn, can also affect water quality, air 

quality, and, ultimately, human health. 

• Achieving and maintaining smoothness. Achieving the highest level of smoothness 

during initial construction and maintaining that level throughout the service life is a key 

factor in improving fuel economy and reducing vehicle emissions, especially for heavily 

trafficked pavements. 

• Utility cuts. In urban areas, pavement roughness is often affected by the quantity of 

utility cuts and the quality of the repairs. The smoothness of pavements in locations 

where there are utilities should be preserved by avoiding utility cuts where possible, and 

by obtaining the best possible repairs to cuts where they must be performed. An 

alternative for new pavement construction is to place utilities in locations on the right of 

way outside of heavily trafficked portions of the paved areas. 

• Structural responsiveness and vehicle fuel economy. Several mathematical models 

have been developed and a number of field studies have been performed to assess fuel 

economy on different pavement structures. These provide indications that under various 

conditions the structural responsiveness of different pavements to vehicle loading can 

have a measureable effect. However, unlike roughness, this effect is highly dependent on 

pavement temperatures and is much more sensitive to vehicle type and speed. The 

calibration of models that will allow definitive conclusions to be drawn based on general 

application of the models to a wide range of pavements under a broad range of traffic and 

climatic conditions in various locations has not yet been completed. 

• Noise emissions. Although other factors are typically more important than the pavement 

in determining noise levels, noise attributable to the pavement surface characteristics can 

ES-5 
Executive Summary Towards Sustainable Pavement Systems

be detrimental to surrounding communities and habitat. Tire-pavement noise emissions 

can be partly addressed through the selection of appropriate paving materials and/or 

surface textures. 

• Stormwater management. Permeable pavements are an effective means of providing 

stormwater management by capturing and storing runoff, reducing contaminants in 

waterways, and recharging groundwater supplies. They also make for more efficient land 

use by eliminating the need for retention ponds and swales. These pavements are 

currently limited to low-volume roadways and parking lots. 

• Urban Heat Island Effect (UHIE). Relationships between the pavement surface 

reflectivity and the UHIE are very complex; influencing factors include such items as the 

size of urban area, the pavement density, solar reflectance, tree canopy, building patterns, 

and the climate. In certain cases, surface reflectivity may be significant and thus should 

be evaluated within the specific context of a given project. At this time, it is unclear to 

what degree pavement solar reflectance impacts the development of the UHIE for 

different urban architectures, climate regions, and other variables. Research is underway 

to provide a more comprehensive understanding of the UHI phenomenon. 

• Lighting. The high energy demand of current lighting systems has a significant 

economic and environmental footprint. Pavement surface luminance is known to 

influence the amount of artificial lighting required, but practical application of this 

knowledge is currently unclear as surface luminance changes with time. Development 

and implementation of new adaptive lighting systems, which provide lighting only when 

it is needed, is currently underway and has the strong potential to significantly lower 

economic, environmental, and societal costs associated with artificial lighting.

• Safety. Pavement characteristics that impact safety include smoothness, friction, cross 

slopes, porosity, and constructed features such as rumble strips. Smoother pavements 

provide a comfortable riding surface and cause less distractions for the driver, high 

friction levels are especially important in specific cases such as ramps and curves, 

adequate cross slope is required to promote surface drainage and prevent hydroplaning, 

porous pavements minimize splash and spray (thereby improving visibility in wet 

weather conditions), and rumble strips alert drivers of changing conditions. 

Chapter 7. Maintenance and Preservation Treatments to Improve Sustainability

This chapter presents the maintenance and preservation treatments most commonly used on 

asphalt and concrete pavements. Currently there is limited information available on quantifying 

the sustainability of pavement maintenance and preservation practices, so much of the current 

analysis is subjective. Still, opportunities exist for enhancing pavement system sustainability 

through careful treatment selection, materials considerations, treatment timing and application, 

and treatment design and construction. 

• Linking pavement management systems and pavement preservation. The need for 

the further integration of various asset management systems and overall pavement 

sustainability considerations is stressed, including the consideration of environmental 

factors in the analysis of pavement performance. 

• Effect of traffic volumes. On higher traffic routes, the higher economic cost of more 

frequent treatments (including lane closures/traffic disruptions) may be offset by large 

reductions in environmental impacts due to vehicle operations on smoother pavements. 

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Towards Sustainable Pavement Systems Executive Summary

For lower traffic routes, the minimization of agency life-cycle cost through proper timing 

of the right treatment also generally improves sustainability. 

• Treatment selection factors. Critical factors for consideration in selecting a suitable 

maintenance or preservation treatment includes performance history of the treatments, 

overall performance needs or requirements, construction constraints, LCCA, and LCA.

• Favorable factors for sustainable treatments. The sustainability value of any given 

treatment is difficult to judge as there are multiple factors at work; however, in general, 

treatments that use the least amount of material to maintain smoothness over the longest 

period of time have the greatest positive effect. Moreover, understanding the complete 

life-cycle impacts is an essential element in establishing the advantages and 

disadvantages of any given treatment. Unfortunately, available data are currently 

insufficient to support detailed environmental analyses to characterize maintenance and 

preservation treatments.

Chapter 8. End-of-Life Considerations

Chapter 8 discusses the impacts of the end-of-life phase on the sustainability of both asphalt and 

concrete pavements. Critical end-of-life issues and strategies for improving pavement system 

sustainability are presented. 

• Increase use of RCWMs. These materials can be incorporated in virtually every layer 

of the pavement structure and are effective means of increasing the sustainability of 

pavements. Recycling processes can be conducted off site (e.g., in central plants) or on

site, using various technologies. 

• “Highest use” of recycled materials. The “highest use” refers to the preferred use of a 

recycled material in order to extract the greatest payback in terms of sustainability. This 

requires the consideration of all of the costs involved in recycling and using a particular 

material. Under such an approach, a material such as RAP, for example, would find its 

highest use as a replacement for both binder and aggregate in a new asphalt mixture 

instead of being used as an aggregate base. This approach also considers the costs of 

transporting materials and landfilling to ensure that materials are employed according to 

their highest value. 

• Specific end-of-life strategies. Multiple end-of-life strategies are discussed for both 

asphalt and concrete pavements, including central plant recycling and full-depth 

reclamation for asphalt pavements and the use of recycled concrete as base material or as 

aggregate in new concrete or asphalt. The specific incorporation of these strategies on a 

given project is based on the project needs, context sensitivity, and agency goals. 

Landfilling as an end-of-use option is becoming less attractive because of dwindling 

landfill space and the value associated with recycling and reusing pavement demolition 

products. 

Chapter 9. Pavement Sustainability within Larger Systems

This chapter presents various sustainability considerations that are not addressed elsewhere in the 

manual. These impacts can influence decisions even though they are often not easily 

quantifiable. 

ES-7 
Executive Summary Towards Sustainable Pavement Systems

• Systems approach required. When evaluating and incorporating other aspects, an 

overall “systems” approach is required to consider the entire reach and totality of the 

pavement and roadway setup. 

• Role of pavements. The role of pavements in a larger system is discussed in terms of 

aesthetics, historical and cultural identity, the impact of utility cuts, and the impact of 

odor, soot, and particulate matter. An example of aesthetics impacting pavement design 

is documented along State Road 9 in Utah, in which a chip seal surfacing that uses local 

red volcanic cinders was placed to ensure that the pavement surface matched the 

aesthetics of the surroundings. 

• Emerging technologies. A number of technologies are emerging in this area, with 

examples including the use of photocatalytic pavement, the ongoing evolution of modular 

pavement systems, and the development of pavements that produce energy. 

Chapter 10. Assessing Pavement Sustainability

This chapter provides information on measuring pavement sustainability and why it is important. 

An overview of sustainability rating systems is provided, along with a summary of LCCA and 

LCA procedures. 

• Need for measuring sustainability. In order to move forward with sustainability 

considerations in pavements, it is important that there be ways to measure it so that 

baseline levels can be established and future progress can be assessed. Together, LCCA, 

LCA, and sustainability rating systems provide a means of quantifying economic, 

environmental, and societal factors in pavement sustainability. 

• LCCA. LCCA is a widely accepted technique for evaluating the economic impacts of 

pavement systems. At its very core, it is a process for evaluating the total economic 

worth of a usable project segment by analyzing initial costs and discounted future costs, 

such as maintenance, user costs, reconstruction, rehabilitation, restoring, and resurfacing 

costs, over the life of the project segment. The most widely accepted and adopted LCCA 

tool for pavement applications in the U.S. is the FHWA’s RealCost Software. 

• LCA. LCA is an emerging technology that works to quantify environmental impacts 

over the entire life cycle of the pavement system; results are expressed, in terms of a 

number of key environmental factors (commonly energy usage and greenhouse gas 

emissions, but there are many others). Pavement-specific LCA tools are not available 

yet, but several software programs can be used with customization to assess pavement 

environmental impacts. 

• Sustainability rating systems. A sustainability rating system is essentially a list of 

sustainability best practices with an associated common metric (commonly expressed as 

“points”). In this way, the diverse measurement units of sustainability best practices 

(e.g., pollutant loading in stormwater runoff, pavement design life, tons of recycled 

materials, energy consumed/saved, pedestrian accessibility, ecosystem connectivity, and 

even the value of art) can all be compared using a common unit (points). A number of 

rating systems relevant to pavements are described (e.g., Greenroads®, INVEST, 

EnvisionTM, GreenLITES). 

• Integration of assessment methods. LCA, LCCA, and rating systems can be used 

independently or in concert to quantify various aspects of sustainability, but ultimately 

ES-8 
Towards Sustainable Pavement Systems Executive Summary

the priorities of the owner/agency and the characteristics of the project, as well as the 

desired outcomes viewed within the context of larger systems, will determine which 

approach (or set of approaches) is most appropriate. 

Chapter 11. Concluding Remarks

This chapter summarizes several of the technologies and innovations that are contributing to 

sustainability initiatives along with recommended implementation activities for helping to move 

the process forward. 

• Technologies and innovations. A number of technologies and innovations are being 

used to improve pavement sustainability, including, among others, the increased use of 

recycled materials, adoption of WMA technologies as a standard practice, reduction of 

portland cement and increased use of SCMs and RCWMs in concrete, optimization of 

materials and cross sections, and the expanded use of preservation treatments.

• Sustainability trends. Several trends emerging in the area of pavement sustainability 

include a growing understanding of the importance of the use phase, a recognition that 

pavement systems are a small part of much larger systems, and the 

development/enhancement of sustainability tools. 

• Sustainability is context sensitive. Sustainability is very much context sensitive, and 

that sustainable strategies will depend on the characteristics of the project, the materials 

and technologies that are readily available, and the specific economic, environmental, and 

societal goals of the agency. 

• Implementation of sustainability. Key factors essential to the implementation of 

sustainability considerations within the pavement community include leadership at the 

national and state levels, partnerships between key stakeholders, effective education and 

outreach, identification of knowledge gaps, development of focused research strategies, 

and the development and application of useful LCA tools. 

ES-9 
Executive Summary Towards Sustainable Pavement Systems

ES-10
Towards Sustainable Pavement Systems Chapter 1. Introduction

CHAPTER 1. INTRODUCTION

Background 

An ever-growing number of agencies, companies, organizations, institutes, and governing bodies 

are embracing principles of sustainability in managing their activities and conducting business. 

This approach focuses on the overarching goal of emphasizing key environmental, social, and 

economic factors in the decision-making process. In many ways, sustainability considerations 

are not new, since they were often considered indirectly or informally in the past, but recent 

years have seen increased efforts to quantify their effects and to incorporate them in a more 

systematic and organized fashion. 

There are many reasons for this emphasis on applying sustainability, among which are a growing 

recognition of how human activity affects the environment (e.g., climate change, ecosystem 

changes, non-renewable resource depletion) and a better appreciation for considering key 

societal factors (e.g., land use, access, aesthetics) and economic considerations (net benefits, lifecycle costs) in decision making. Thus, a focus on sustainability reflects a commitment to address 

the entirety of impacts associated with human existence, not only in monetary terms but also in 

terms of environmental and social impacts. 

The criticality of implementing sustainability has become more acute in light of growing 

evidence suggesting that human activities are jeopardizing the health of the planet at a global 

scale and, by extension, the welfare and prosperity of future generations (IPCC 2007; IPCC 

2014). For example, greenhouse gas (GHG) emissions, a commonly used surrogate for assessing 

environmental sustainability, are known to trap heat in the atmosphere and contribute to climate 

change (see call-out box on next page). The burning of fossil fuels (in manufacturing, electricity

production, and transportation) is the largest contributor of GHG emissions, the most prevalent 

of which is carbon dioxide (CO2). According to the Environmental Protection Administration 

(EPA 2013), and using 2011 data as the basis, the transportation industry (including cars, trucks, 

aircraft, rail, ships, and pipelines) accounts for over 27 percent of all human-caused GHG 

emissions in the U.S. (see figure 1-1); this is second only to the amount of GHG emissions 

attributed to the electric 

power industry. In 

addition, the 

construction of 

transportation facilities 

also contributes to GHG 

emissions, which are 

represented as part of the 

industry section. As a 

result, any significant 

reductions in GHG 

emissions made in the 

transportation sector will 

have an effect on the 

total amount of GHG 

emissions in the U.S. Figure 1-1. GHG emissions by economic sector in the U.S. 

(EPA 2013).

Transportation

27.3%

(Cars: 62.2%

Med/Heavy 

Trucks 21.9%

Aircraft 8.2%

Other: 7.8%)

Industry, 

19.9%

Residential, 5.3% Commercial, 5.6%

Agriculture, 

8.2%

US 

Territories, 

0.9%

Electric Power 

Industry, 32.8%

GHG Allocations by Sector

1-1 
Chapter 1. Introduction Towards Sustainable Pavement Systems

What is Sustainability? 

Most definitions of sustainability 

begin with that issued by the World 

Commission on Environment and 

Development (WCED), often referred 

to as the Brundtland Commission 

Report (WCED 1987): 

Sustainable development is 

development that meets the needs 

of the present without 

compromising the ability of future 

generations to meet their own 

needs. 

This definition is focused on the 

concept of “needs” and the idea of 

limitations imposed by the state of 

technology and social organization on 

the environment’s ability to meet 

present and future needs. In a shorter 

version of this, sustainability is often 

described as being made up of the 

three components of environmental, 

social, and economic needs, 

collectively referred to as the “triplebottom line.” 

For many years, the economic 

component has been the dominant 

decision factor, but more recent years 

have seen the growing emergence of 

both the environmental and social 

components (even though there are 

some current limitations associated 

with their measurement and 

assessment). A focus on 

sustainability can then be interpreted 

in such a way that all triple-bottom 

line components are considered

important, but the relative importance 

of these factors (and how each are 

considered) are case sensitive, very 

much driven by the goals, demands, 

characteristics, and constraints of a 

given project. Chapter 2 provides a 

more detailed discussion on this 

topic. 

GHGs, GWP, and CO2 e

Gases that trap infrared radiations (heat) in the Earth’s 

atmosphere are referred to as greenhouse gases 

(GHGs). Once present in the atmosphere, most of these 

gases do not break down very quickly and thus can 

contribute to planetary warming over an extended period. 

Although the presence of GHGs makes our planet 

livable, excess GHGs produced due to human activity 

are believed to be contributing to global warming.

GHGs are generated by a variety of agricultural and 

industrial processes including raising livestock, burning 

of fossil fuels, solid waste, wood products, and 

production of portland cement and asphalt. GHGs of 

greatest concern are carbon dioxide (CO2), methane 

(CH4), nitrous oxide (N2O), and fluorinated gases, with 

each exhibiting differences in their atmospheric 

concentration, the amount of time they remain in the 

atmosphere, and their ability to trap radiation. 

Because each individual GHG has a different impact on 

global warming, it is useful to express them in a single 

equivalent unit so they can be compared. Global 

Warming Potential (GWP) is a measure of the total 

energy that a gas absorbs over a period of time (typically 

100 years) using CO2 as the base unit. By definition, 

CO2, which accounts for over 80 percent of all U.S. GHG 

emissions, has a 100-year GWP of 1. For comparison, 

according to the IPCC (2013): 

– Methane, which accounts for about 10 percent of all 

U.S. GHG emissions, has a 100-year GWP of 34.

– Nitrous oxide, which accounts for approximately 5 

percent of all U.S. GHG emissions, has a 100-year 

GWP of 298.

– Fluorinated gases [hydrofluorocarbons (HFCs), 

perfluorocarbons (PFCs), and sulfur hexafluoride(SF6)] 

are synthetic GHGs that are typically emitted in smaller 

amounts; however, they are potent and sometimes 

referred to as High GWP Gases. The 100-year GWP 

of these materials is 140 to 11,700 for HFCs, 6,500 to 

9,200 for PFCs, and 23,900 for SF6.

Carbon Dioxide Equivalent (CO2e) is the metric used to 

compare emissions from various GHGs based on their 

GWP. The CO2e is computed by multiplying the amount 

of the GHG (usually mass) by its GWP. The GWP 

values are dependent on the time period considered, 

with 100-year GWP values commonly used for 

comparison.

Additional information on GHGs is available on the EPA 

website: 

http://www.epa.gov/climatechange/ghgemissions/gases.

html

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Towards Sustainable Pavement Systems	 Chapter 1. Introduction 

Importance of Sustainability in Pavement Engineering 

The nation’s roadway system is one part of a transportation network that provides mobility and 

access to a range of users. The roadway network is not only important to the nation’s overall 

economic vitality by providing for the movement of freight and commodities, but it also provides 

societal benefits as well (e.g., access to schools, services, and work; leisure travel; and general 

mobility). There are more than 4 million miles of public roads in the United States, which 

includes 1 million miles of Federal-Aid roadways (FHWA 2013). In 2010, nearly 3 trillion 

vehicle miles traveled (VMT) were logged over those roadways, consuming more than 169 

billion gallons of fuel in the process (FHWA 2010). And, based on 2008 data (the most recent 

available), the total expenditures for highways in the U.S. was $182.1 billion (FHWA 2010). 

Taken together, these numbers are staggering and demonstrate the magnitude of the investment 

in public roadways and the positive impacts of the system in providing movement, access, and 

mobility. 

Pavements are an integral part of this roadway network. Pavements provide a smooth and 

durable all-weather traveling surface that benefits a range of vehicles (cars, trucks, buses, 

bicycles) and users (commuters, commercial motor carriers, delivery and service providers, local 

users, leisure travelers). Given their key role and widespread use, there is a unique opportunity 

to improve the sustainability of pavement structures with the potential to deliver tremendous 

environmental, social, and economic benefits. With regard to those components, listed below are 

just a few examples of how pavements can impact sustainability: 

•	 Environmental component: energy consumption; GHG emissions; noise; air quality; 

stormwater treatment. 

•	 Social component: safety (fatalities, injuries, property damage); smoothness; vehicle 

operating costs; GHG emissions; access, mobility; aesthetics. 

•	 Economic: construction, maintenance, and rehabilitation costs; vehicle operating costs; 

crash costs. 

Moreover, the current timing is such that transportation agencies and the general public alike are 

demanding increased consideration of sustainability principles and practices. This evolution in 

the role that transportation plays in society is well summarized as follows (AASHTO 2009): 

Transportation’s mission is no longer about just moving people and goods. It’s much 

broader. Transportation fundamentally allows us to achieve economic, social, and 

environmental sustainability. Transportation supports and enhances our quality of life. 

As state transportation professionals, we need to model the way toward achieving a 

sustainable future...Sustainable transportation requires innovative approaches and 

partnerships like never before. 

Transportation and highway agencies are already making advancements to improve and enhance 

overall sustainability. Recent years have seen significant strides being made to better align 

current practices and technologies with more long-term sustainable strategies. In fact, the 

pavement engineering community has adopted a number of technologies as a way of improving 

sustainability, such as the increased use of recycled materials in pavement structures, the 

incorporation of modified binders to increase pavement performance, and the development of 

rating systems to measure sustainability. At the same time, there is considerable research being 

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Chapter 1. Introduction	 Towards Sustainable Pavement Systems 

conducted on energy use, GHG emissions, and other impacts associated with pavement materials 

and construction activities to support the development of life-cycle assessment tools. 

Nevertheless, there are no universal characteristics or design features that describe a sustainable 

pavement. Although a general sustainability framework for pavement can be defined, it is 

context sensitive in that each situation is unique, with specific needs depending on the location, 

climate, available materials, facility type, required level of service, and so on, as well as on the 

overall goals of the organization. Furthermore, it is important to recognize that, in some cases, it 

may even be counterproductive to try to introduce certain features that are thought to be 

sustainable without a complete assessment; for example, trucking in recycled materials from a 

great distance when an acceptable local aggregate is readily available could actually have 

negative environmental consequences. 

About This Document 

Although significant progress has been made in advancing the sustainability of pavements and 

pavement systems, there remain a number of complex issues and difficult challenges; a few of 

these are listed below: 

•	 What are the appropriate sustainability factors to be considered over the life cycle of a 

pavement (from material extraction to the end-of-life)? 

•	 How do the various materials used in paving applications impact the overall sustainability 

of the pavement system? 

•	 How can pavements be effectively designed and constructed to meet the specific 

sustainability needs of a given project?
 

•	 How can the pavement community make more sustainable choices, given different 

facility types (interstates, state highways, local roads/streets), locations (climatic regions, 

urban vs. rural settings), and paving situations (new alignment, overlays, varying project 

sizes)? How does one consider trade-offs in the process? 

•	 What methods are available to assess the sustainability of pavement systems? 

•	 What implementation strategies are available for highway agencies to adopt more
 

sustainable pavement practices?
 

All stakeholders in the pavement community—including owner agencies, designers, material 

producers and suppliers, contractors, consultants, and the traveling public—are embracing the 

need to adopt more sustainable practices in all aspects of their work, and are continually seeking 

the latest technical information and guidance available to help improve those practices. This 

document has been prepared to provide guidance to the pavement community on sustainability 

considerations in pavement systems, drawing from and synthesizing the large and diverse body 

of knowledge that currently exists on pavement sustainability. As such, it provides the currently 

available knowledge and information for designing, constructing, and maintaining pavement 

structures more sustainably, and has been structured so that it can adapt to new findings and new 

information as sustainability considerations continue to develop and evolve. 

1-4
 
Towards Sustainable Pavement Systems Chapter 1. Introduction

Scope

It is recognized that sustainability is a system characteristic, and pavements are but one part of 

the transportation system. It is the scope of this document to focus on pavements and describe 

how more sustainable pavement systems can be designed and constructed, but this cannot be 

done in total isolation from the transportation infrastructure system or from other systems in 

which pavements interact. Moreover, as described in chapter 2, the entire pavement life cycle is 

covered, from materials to design, from construction through the use phase, and from 

maintenance/rehabilitation to the end-of-life. 

In this document, the pavement is defined as the structure constructed above the native subgrade 

soil, typically constructed in distinct layers and including compacted or stabilized subgrade, a 

bound or unbound subbase/base, and the riding surface (see figure 1-2). Broadly, this 

encompasses pavement structures in a number of different facility types, such as highways, 

streets, roads, shoulders, and parking areas, but the focus of this document is on pavement 

structures used in mainline paving and shoulders of highways/roadways. Furthermore, only 

paved roadways consisting of a semi-permanent surface are considered; this includes asphalt 

concrete (AC) pavements, which may be constructed with hot-mix asphalt (HMA) or warm-mix 

asphalt (WMA) technologies, and hydraulic cement concrete (HCC) pavements, which includes 

portland cement concrete (PCC). For the purposes of this document, all permanent surfaces 

constructed with asphalt materials are generically referred to as “asphalt” pavements, whereas all 

permanent surfaces constructed with hydraulic cement materials are generically referred to as 

“concrete” pavements.

Figure 1-2. Basic components of a typical pavement system.

Surface Course

Base Course

Subbase Course

Compacted/Natural Subgrade

Embankment/Natural Soil

As a point of clarification, it is noted that there are a number of items related to a highway or 

roadway that are not included or considered in this document; examples include: 

• Planning. 

• Capacity. 

• Roadway striping. 

• Roadway signage and message boards. 

• Barriers and other safety appurtenances. 

• Ice and snow management. 

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Chapter 1. Introduction	 Towards Sustainable Pavement Systems 

•	 Roadside management. 

•	 Drainage structures. 

•	 Bridges and other structures. 

Thus, it is reiterated that this document focuses exclusively on the sustainability considerations 

associated with the pavement structure and pavement materials, and only on those pavements 

constructed with a semi-permanent surface. 

Target Audience 

The primary audience for this document is state Department of Transportation (DOT) 

practitioners, and it is intended for designers, maintenance, material and construction engineers, 

inspectors, and planners who are responsible for the design, construction, and preservation of the 

nation’s highway network. The overarching goal is to provide state DOT practitioners 

information to help design, specify, and construct a more sustainable pavement. However, other 

key stakeholders in the pavement community are also expected to benefit from the information 

contained in this document, including local roadway agencies, industry (suppliers, producers, 

contractors, and consultants), academia, and various public interest groups. 

Document Overview 

This document consists of eleven chapters, including this introductory chapter. The chapters 

closely mirror the critical phases in the pavement life cycle, allowing users to quickly and easily 

locate desired information. Each chapter generally follows the same layout, first providing 

general background information on the topic, then describing sustainability-related issues 

associated with the topic, followed by strategies or methodologies to address the issues 

identified, including the consideration of trade-offs. The chapter then concludes with a brief 

look at future directions and emerging technologies. 

A description of the primary chapters in this document is provided below: 

•	 Chapter 2. Concepts of Pavement Sustainability. This chapter presents the basic 

concepts of pavement sustainability and includes definitions, an overview of the 

pavement life cycle, a framework for considering sustainability issues and trade-offs, and 

an overview of how sustainability can be quantified and measured. 

•	 Chapter 3. Materials Considerations to Improve Pavement Sustainability. Chapter 

3 reviews the common materials used in paving applications—including aggregate, 

asphalt, and cementitious materials—and describes how these materials affect the overall 

sustainability of the pavement system. The scope is from the materials acquisition until 

the materials arrive at the construction site, either on grade or at the plant. 

•	 Chapter 4. Pavement and Rehabilitation Design to Improve Sustainability. This 

chapter addresses techniques for improving the sustainability of pavements during the 

design process, for both asphalt and concrete pavement structures. The focus is on new 

pavement design and structural rehabilitation, including reconstruction and overlays. 

•	 Chapter 5. Construction Considerations to Improve Pavement Sustainability. This 

chapter briefly reviews the key elements to be considered to enhance the sustainability of 

construction for both asphalt and concrete pavements. The chapter includes discussions 

on specifications, construction setup and operations, construction equipment fuel and 

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Towards Sustainable Pavement Systems Chapter 1. Introduction

emission reduction, management and handling of construction materials, construction 

quality assurance, and effective lane closures.

• Chapter 6. Use-Phase Considerations. Chapter 6 identifies the critical sustainability 

impacts associated with pavement structures while they are in service, and includes 

discussions on rolling resistance, safety, noise, heat island effects, lighting, and 

stormwater management.

• Chapter 7. Maintenance and Preservation Treatments to Improve Sustainability. 

This chapter presents common maintenance and preservation treatments used for asphalt 

and concrete pavements and describes opportunities for enhancing their sustainability 

through careful treatment selection, material considerations, treatment timing and 

application, and treatment design and construction. 

• Chapter 8. End-of-Life Considerations. Chapter 8 discusses the impacts of the end-oflife (EOL) phase on the sustainability of both asphalt and concrete pavements. Critical 

issues and strategies for improving the sustainability of this phase of the pavement life 

cycle are presented. 

• Chapter 9. Pavement Sustainability within Larger Systems. This chapter presents 

various sustainability impacts that are not addressed elsewhere in the manual, including 

such items as aesthetics, historic and cultural identity, multi-modal design, and local 

ecosystems. These impacts can influence decisions even though they are often not easily 

quantifiable. 

• Chapter 10. Assessing Pavement Sustainability. Chapter 10 provides information on 

measuring pavement sustainability and why it is important. An overview of 

sustainability rating systems is provided, along with a summary of life-cycle assessment 

(LCA) and life-cycle cost analysis (LCCA) procedures.

• Chapter 11. Concluding Remarks. This chapter offers some concluding remarks by 

briefly summarizing some of the technologies, innovations, and trends in pavement 

sustainability and by providing a listing of recommended implementation activities for 

moving forward. 

An appendix is included that presents a glossary of terms used throughout the document. In 

addition, a stand-alone executive summary has been prepared that summarizes the contents of 

each chapter and captures the main points and primary considerations.

References

American Association of State Highway and Transportation Officials (AASHTO). 2009. 

“Transportation and Sustainability Best Practices Background.” Sustainability Peer Exchange – 

Center for Environmental Excellence. American Association of State Highway and 

Transportation Officials, Washington, DC. 

Environmental Protection Agency (EPA). 2013. Inventory of U.S. Greenhouse Gas Emissions 

and Sinks, 1990–2011. EPA 430-R-13-001. Environmental Protection Agency, Washington, 

DC. (Web Link). 

Federal Highway Administration (FHWA). 2010. Highway Statistics 2010. Federal Highway 

Administration, Washington, DC. (Web Link). 

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Chapter 1. Introduction Towards Sustainable Pavement Systems

Federal Highway Administration (FHWA). 2013. 2013 Pocket Guide to Transportation. 

Federal Highway Administration, Washington, DC. (Web Link). 

Intergovernmental Panel on Climate Change (IPCC). 2007. Climate Change 2007: Synthesis 

Report. Intergovernmental Panel on Climate Change, Geneva, Switzerland. (Web Link). 

Intergovernmental Panel on Climate Change (IPCC). 2013. Climate Change 2013: The 

Physical Science Basis. Fifth Assessment Report. Intergovernmental Panel on Climate Change, 

Geneva, Switzerland. (Web Link). 

Intergovernmental Panel on Climate Change (IPCC). 2014. Climate Change 2014: Synthesis 

Report. Intergovernmental Panel on Climate Change, Geneva, Switzerland. (Web Link). 

World Commission on Environment and Development (WCED). 1987. Our Common Future: 

the Report of the World Commission on Environment and Development. Document A/42/427. 

Oxford University Press, University of Oxford, United Kingdom 

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Towards Sustainable Pavement Systems Chapter 2. Concepts of Pavement Sustainability 

CHAPTER 2. CONCEPTS OF PAVEMENT SUSTAINABILITY 

This chapter introduces the basic concepts of sustainability as they relate to pavements. It 

includes discussions on (1) the definition of sustainability and its implications, (2) the role of 

pavements in sustainability, (3) the pavement life cycle, (4) different ways of measuring 

sustainability, and (5) an introduction to the framework used in this document for considering 

potential sustainability trade-offs. 

Sustainability Defined 

In a broad sense, the “sustainability” of a human-devised system refers to its ability to (1) exist 

and function within a larger system without degrading it, and (2) provide for and meet the human 

needs for which the system was developed. There are a number of popular definitions of 

sustainability, but as described in chapter 1 these often start with the short definition issued by 

the World Commission on Environment and Development (WCED 1987): 

Sustainable development is development that meets the needs of the present without 

compromising the ability of future generations to meet their own needs. 

And, as also noted in chapter 1, most sustainability definitions also reference three discrete 

components (environmental, social, and economic) that are to be considered; however, they 

usually do not direct how those components are to be prioritized beyond generally stating that 

they should be “balanced” without offering much direction on the definition of “balanced” or 

how such balancing is to occur. 

This document uses a sustainability definition that 

is consistent with and complementary to the 

approach described in the National Cooperative 

Highway Research Program (NCHRP) Report 

708: A Guidebook for Sustainability Performance 

Measurement for Transportation Agencies 

(Zietsman et al. 2011).

This approach has also been adopted by other highway sustainability efforts, including NCHRP Project 20-83(07), 

Sustainable Transportation Systems and Sustainability as an Organizing Principle in Transportation Agencies. It 

is also complimentary to the FHWA’s Infrastructure Voluntary Evaluation Sustainability Tool (INVEST). 

1 This approach emphasizes 

the underlying sustainability principles as the basis 

for guidance, with the actual definition being of 

secondary importance. Thus, “sustainable” in the 

context of pavements refers to system 

characteristics that encompasses a pavement’s 

ability to (1) achieve the engineering goals for 

which it was constructed, (2) preserve and (ideally) 

restore surrounding ecosystems, (3) use financial, 

human, and environmental resources economically, and (4) meet basic human needs such as 

health, safety, equity, employment, comfort, and happiness. 

Sustainable Pavements Should: 

 Achieve the engineering goals for 

which they were constructed. 

 Preserve and (ideally) restore 

surrounding ecosystems. 

 Use financial, human, and 

environmental resources 

economically. 

 Meet human needs such as health, 

safety, equity, employment, comfort, 

and happiness. 

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Chapter 2. Concepts of Pavement Sustainability Towards Sustainable Pavement Systems 

Sustainability Direction at the 

Federal Level: Executive Order 

13514 

Presidential Executive Order (EO) 

13514, "Federal Leadership in 

Environmental, Energy, and Economic 

Performance” expands on EO 13423, 

“Strengthening Federal Environmental, 

Energy, and Transportation 

Management” in order to, “...establish 

an integrated strategy towards 

sustainability in the Federal 

Government and to make reduction of 

GHG a priority for Federal agencies.” 

EO 13514 states, “‘sustainability’ and 

‘sustainable’ mean to create and 

maintain conditions, under which 

humans and nature can exist in 

productive harmony, that permit fulfilling 

the social, economic, and other 

requirements of present and future 

generation...” (Bush 2007; Obama 

2009). This executive order constitutes 

direction from the President to various 

Federal Agencies on how they are to be 

“sustainable.” While its specific 

definition of “sustainability” is important, 

it is most significant because it sets 

specific targeted requirements for 

Federal agencies including reductions 

in GHG emissions, petroleum 

consumption, water use, and waste. 

EO 13514’s definition of “sustainability” 

is a paraphrasing of the United Nations 

1987 Report of the World Commission 

on Environment and Development 

(commonly called the Brundtland 

Commission Report), in which 

sustainable development is defined as 

“...meeting the needs of the present 

without compromising the ability of 

future generations to meet their own 

needs...” (WCED 1987). 

The Sustainability Continuum 

As defined here, a “sustainable pavement” is, at present, 

an aspirational goal. That is, it is unlikely any 

pavement system based on current knowledge and 

technology could satisfy all or even most of the 

characteristics in the previous sustainability definition. 

However, continual improvement with an emphasis on 

each of these characteristics leads to more sustainable 

pavements, and, ultimately, to pavements that actually 

meet the rather demanding standards of sustainability. 

Progress towards sustainability may at first mean 

reducing bad outcomes (e.g., less pollution, reduced 

extraction of non-renewable resources, less waste). 

Further progress would transition to achieving a 

pavement system that is essentially a neutral player in 

the larger and surrounding systems (i.e., it does no 

harm). Importantly, however, progress should continue 

so that the pavements could ultimately produce positive 

outcomes (e.g., pavements that produce more energy 

than they consume, construction that restores more land 

than it uses). Current efforts at reducing the impact or 

amount of bad outcome and improving efficiency 

should be viewed as good transitional strategies on the 

long path towards the ultimate goal of producing only 

positive outcomes. This interpretation of sustainability 

is substantially different, and ultimately more positive, 

than one limited to reducing negative outcomes. 

Sustainable Best Practices 

Recognizing the aspirational nature of a truly 

“sustainable pavement,” this document highlights 

processes, actions, and features that advance the state of 

the practice towards more sustainable pavements rather 

than those that actually achieve the definition. 

Specifically, “sustainable best practices” are those 

practices that work to either (1) go above and beyond 

required regulatory minimums or standard practice, or 

(2) show innovation in meeting these minimums and 

standards. 

Sustainability is Context Sensitive 

Because a pavement must exist and function within larger systems, practices that support 

sustainability must contribute to more sustainable systems and thus depend on context. As a 

result, a full accounting of surrounding systems and a pavement’s influence on them is necessary 

in order to define the most appropriate sustainability practices associated with a particular 

pavement system. 

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Towards Sustainable Pavement Systems Chapter 2. Concepts of Pavement Sustainability 

Importance of a Sustainability Definition 

The specific definition of sustainability is considered to be of secondary importance to 

understanding the basic principles of sustainability; this is because a definition typically 

addresses what should be considered but does not give direction on how those considerations are 

to be prioritized or implemented. This is especially relevant because sustainability often requires 

the consideration of trade-offs in the decision-making process. For example, should a pavement 

use locally available extracted materials or make use of recycled materials that require long 

distance hauling? Should the benefit of a quieter surface course be selected over a pavement 

with a longer service life? Often, both alternatives have legitimate sustainability arguments, but 

the option that is ultimately selected (in other words, how sustainability is actually implemented) 

reflects agency, stakeholder, and project priorities and limitations. These priorities and 

limitations are the appropriate focal point in approaching sustainability. 

Integrating Sustainability into a System 

As a system characteristic that encompasses environmental, social, and economic dimensions, 

sustainability is necessarily the highest-level strategy or goal of an organization. In short, 

sustainability tends to mean “consider everything.” Other organizational strategies and goals 

(e.g., safety, conservation, ecosystem health, education, open space, and so on) are an expression 

of (1) which sustainability components an organization particularly values, (2) the order of 

precedence for these values, and (3) a plan to operationalize those values and precedence. This 

is why Amekudzi et al. (2011) and others have been able to identify many sustainability 

components that are already present in current transportation organization mission statements. 

Consequently, incorporating sustainability into an organization or into a particular system (such 

as pavement infrastructure) is not adding a separate value to the system but instead is assessing 

the current prioritization of values within that system and making changes as needed. The 

outcome is an alignment of the system’s goals and the organization’s sustainability goals. In 

many cases, the results of sustainability efforts are that an organization or project elevates the 

priorities of environmental and social issues above the levels where they were previously. 

However, in the strictest sense, these are only part of the overall sustainability principles 

discussed previously. Thus, sustainability considerations for a particular system (like pavement 

structures) can often be reduced to understanding how each system component affects 

sustainability (this is often broken down into how each component affects environmental, social, 

and economic outcomes) and which outcomes are most desirable given the (1) priorities of the 

organization, and (2) the outcomes within larger systems. 

Context: The Role of Pavements in Sustainability 

While it may not be possible to quantify the “sustainability” of the planet as a whole, a few 

useful proxy measurements are often used as an indication of the role and relative impact of 

transportation and roads. As described in chapter 1, human-caused GHG emissions are often 

used as a simple proxy to quantify the impact of human activity on the planet. This metric can 

be further broken down to quantify and understand the relative contributions made by various 

countries, industry sectors and practices. While GHG emissions do not account for all pavement 

sustainability impacts, they are a useful starting point. 

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Chapter 2. Concepts of Pavement Sustainability Towards Sustainable Pavement Systems 

Beyond Greenhouse Gas 

Chapter 1 presented a brief discussion on the human-caused GHG emissions by economic 

sectors in the U.S. It is important to recognize that roads have sustainability impacts beyond just 

GHG emissions. Some of these major impacts (both positive and negative) include: 

•	 Energy consumption. Roads take energy to construct, maintain, rehabilitate, and 

recycle. Furthermore, and often of much greater impact, roads affect the energy 

consumption of the vehicles using them through their interaction with those vehicles to 

include such properties as geometric design, surface roughness, and rolling resistance. 

Since the consumption of energy also tends to produce GHG, the emission of GHG is 

also affected by these features. 

•	 Habitat loss, fragmentation, and change. Roads cause direct habitat loss over their 

footprint and diminish adjacent habitat, impede wildlife movement, and can change 

wildlife distribution in an area based on their barrier effects, roadkill, and dispersal 

function (Bissonette and Cramer 2008). 

•	 Water quality. Pavement surfaces generally collect significant pollutants from the vehicles 

that use the facility, and rainwater can carry those pollutants into nearby bodies of water 

unless properly managed. Runoff from pavements is also often warmed, thereby affecting 

the temperature of streams and potentially the suitability of the habitat for some species. 

•	 Hydrologic cycle changes. Pavements represent significant amounts of impervious 

surface and, as such, can alter the natural hydrological cycle resulting in greater 

stormwater runoff (and less evapotranspiration and infiltration) when compared to the 

same area before development. 

•	 Air quality. Vehicles that use a pavement facility, as well as the equipment used to process 

the necessary raw materials and construct the roads, degrade overall air quality. This 

degradation includes not only emission from the combustion of fuel but also fine airborne 

particulate (less than 0.01 mm [10 micron or < PM10] in size). 

•	 Mobility. Roads can contribute to a population’s mobility by providing greater capacity 

and desirability of all transportation modes: pedestrian, bicycle, car, and transit. 

•	 Access. Roads can provide greater modal access to locations. This could be vehicular 

access to a rural area, or it could be pedestrian, bicycle, or transit access in urban areas. 

•	 Freight. Roads carry a significant amount of commercial freight across the U.S. In fact, 

trucking constitutes the largest share of the U.S. commercial freight industry based on value 

(71.3 percent) and weight (70.0 percent) (USDOT/USDOC 2010). In 2007, over $8.3 

trillion worth of freight was moved via the trucking industry (USDOT/USDOC 2010). 

•	 Community. Roads are long, linear forms of infrastructure exhibiting many access 

points and providing access and mobility. As such, they can have large community 

impact both positive (e.g., gathering area, sense of place, modal access, mobility) and 

negative (e.g., fragmentation, health issues, safety). 

•	 Depletion of non-renewable resources. Roads, in their current state, require the use of 

a significant amount of nonrenewable natural resources (e.g., aggregate, petroleum, 

limestone) to construct, maintain, and rehabilitate. 

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Towards Sustainable Pavement Systems Chapter 2. Concepts of Pavement Sustainability 

•	 Economic development. Road construction and maintenance can create local 

employment opportunities and contribute to the ability of other businesses to function 

(e.g., freight transport, workers getting to/from work). 

The Role of Pavements 

Within the transportation sector, GHG emissions associated with pavement construction are 

significant, but they are generally much less than GHG emissions associated with vehicle 

operations. Although there are no official statistics to quantify the magnitude of GHG emissions 

due solely to pavement construction, a reasonable estimate can be made using available data. First, 

based on a seasonally adjusted activity of $80.85 billion of highway and street construction work 

done in 2012 (U.S. Census Bureau 2012), and using the Economic Input-Output Life Cycle 

Assessment (EIO-LCA) online calculator2 

Using the 1997 Industry Benchmark U.S. Department of Commerce EIO dataset and selecting the “construction” 

industry with a “highway, street, bridge, and tunnel construction” sector. 

available from Carnegie Mellon University (2008), the 

total GHG emissions due to all highway and street construction is estimated at 117 million tons 

(106 million mt) CO2e, or about 7 percent of the U.S. transportation total. Then, given that 

pavements account for about 70 percent of the highway and street construction expenditures 

(USDOT 2010), it can be roughly estimated that pavement construction, maintenance, and 

rehabilitation in the U.S. produces about 83 million tons (75 million mt) CO2e of GHG emissions, 

which, for comparison, is about 5 percent of the U.S. transportation GHG emission total and about 

1.4 percent of the total U.S. GHG emission amount.3 

The emissions associated with pavement construction span at least three of EPA’s five defined major fuel 

consuming sectors: electricity generation, transportation, industrial, residential, and commercial. In a strict sense, 

using the EPA’s sector definitions pavement construction is not an exclusive subcategory of transportation. 

According to the EPA (2013), about 80 

percent of the total emissions from the transportation sector come from cars and truck fuel 

combustion. Pavements also have significant potential to influence these emissions based on their 

design and surface characteristics largely because these can influence vehicle fuel efficiency. 

This overview provides a rather crude estimate while ignoring many other important impacts, but 

it nonetheless gives an idea of the role of pavements in contributing to the larger GHG emissions 

picture. In terms of impacts beyond GHG, pavements also play a significant role but are likely 

secondary to roadway planning, design, and operation. 

The Pavement Life Cycle 

In order to better understand the effects of pavements on sustainability, it is useful to divide a 

pavement’s life cycle into several significant phases (see figure 2-1). This document uses the 

following phases: 

•	 Materials production. 

•	 Pavement design. 

•	 Construction. 

•	 Use. 

•	 Maintenance and preservation. 

•	 End-of-life. 

2 

3 

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Chapter 2. Concepts of Pavement Sustainability Towards Sustainable Pavement Systems 

Figure 2-1. Pavement life-cycle phases (UCPRC 2010). 

This section introduces each phase, how they are related, and how this document associates 

pavement-related processes with each of these phases. Most processes are interrelated and can 

conceivably be included in several different phases. However, this discussion addresses each 

process primarily within one particular phase. If the process is relevant to other phases, the 

reader is referred to the primary phase location for its discussion. 

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Towards Sustainable Pavement Systems Chapter 2. Concepts of Pavement Sustainability 

Materials Production 

Pavement materials production refers to all processes involved in pavement materials acquisition 

(e.g., mining, crude oil extraction) and processing (e.g., refining, manufacturing, mixing). This 

document includes plant processes (e.g., production of AC by mixing aggregate, asphalt cement 

and additives; production of concrete by mixing aggregate, cementitious materials and additives) 

used in the materials production phase. Materials production affects such sustainability factors 

as air/water quality, ecosystem health, human health and safety, depletion of non-renewable 

resources, and life-cycle costs. Chapter 3 addresses materials production and includes 

discussions on aggregates, asphalt binder, and hydraulic cements, as well as some other common 

construction materials used in pavement applications. 

Pavement Design 

Pavement design refers to the process of identifying the structural and functional requirements of 

a pavement for given site conditions (subgrade, climate, existing pavement structure, traffic 

loadings) and then determining the pavement structural composition and accompanying 

materials. Included in this phase are the design processes for not only new pavement design, but 

also those processes associated with pavement rehabilitation (e.g., structural overlays, 

bonded/unbonded concrete overlays, crack-and-seat, rubblization). Structural design affects such 

sustainability factors as performance life, durability, life-cycle costs, construction (e.g., 

constructability, sequencing, schedule), and materials use. Chapter 4 addresses structural design 

considerations in detail for: 

•	 Asphalt pavements. Asphalt pavements (constructed with AC) that may or may not 

incorporate underlying layers of stabilized or unstabilized granular materials on a prepared 

subgrade. These types of pavements are sometimes referred to as “flexible” pavements since 

the total pavement structure bends (or flexes) to accommodate traffic loadings. 

•	 Concrete pavements. Concrete pavements (constructed with HCC) that may or may not 

incorporate underlying layers of stabilized or unstabilized granular materials. These 

types of pavements are sometimes called “rigid” pavements. 

Designs that are primarily used as maintenance and preservation treatments are addressed in 

chapter 7, while those that are done at the end-of-life are addressed in chapter 8. Structural 

designs for gravel and dirt roads are outside of the scope of this document. 

Construction 

Pavement construction refers to all processes and equipment associated with the construction of 

pavement systems. Generally, construction activities are associated with initial construction as 

well as subsequent maintenance and rehabilitation efforts. For the purposes of this document, 

construction activities are confined to actions and equipment within the project limits as well as 

materials transported to the project site. Production of mixtures (most notably AC and HCC) is 

addressed in the materials production phase. Construction activities affect such sustainability 

factors as air and water quality, human health and safety, durability, and work zone traffic delay, 

as well as project costs and time. Chapter 5 addresses construction activities in detail and 

includes equipment, construction sequencing, work zone traffic delay, and construction 

processes. 

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Chapter 2. Concepts of Pavement Sustainability Towards Sustainable Pavement Systems 

Use 

Pavement use refers to interactions with vehicle operations and the environment. A number of 

key pavement factors (e.g., roughness, viscoelastic energy dissipation, deflection, macrotexture) 

can have large effects on most sustainability metrics, including fuel economy, vehicle operating 

costs, and associated GHG emissions and energy use. Environmental interactions (e.g., 

stormwater disposition, heat capacity/conductivity, and reflectivity) can also impact other 

sustainability factors such as human health and safety, the urban heat island effect, and radiative 

forcing on a global scale. Chapter 6 addresses use factors in detail, including rolling resistance 

and vehicle fuel consumption, safety, noise, heat island effect, lighting, and stormwater. 

Maintenance and Preservation 

Pavement maintenance and preservation refer to actions that help slow the rate of deterioration of 

a pavement by identifying and addressing specific pavement deficiencies that contribute to 

overall deterioration. This document classifies the following as maintenance and preservation: 

sealing, patching, seal coats, chip seals, thin overlays, in-place recycling of pavement surfaces, 

diamond grinding, load transfer restoration, and concrete pavement repairs. Maintenance and 

preservation impacts sustainability factors such as performance life, durability, life-cycle costs, 

construction (e.g., constructability, sequencing, schedule), and materials use. Chapter 7 

addresses maintenance and preservation treatments. 

End-of-Life 

Pavement end-of-life refers to the final disposition and subsequent reuse, processing, or 

recycling of any portion of a pavement system that has reached the end of its useful life. This 

document classifies the following as end-of-life considerations: full-depth reclamation, recycled 

materials including reclaimed asphalt pavement (RAP) and recycled concrete aggregate (RCA), 

and landfilling. Specific materials, designs, and construction techniques associated with end-oflife treatments are covered in other chapters, whereas the treatment and disposition of the 

material itself is addressed by chapter 8. End-of-life considerations impact sustainability factors 

such as waste generation and disposition, air and water quality, and materials use. 

Measuring Sustainability 

Sustainability measurement is an evolving area of research within both the pavement and 

transportation fields, as it is in other areas as well (e.g., consumer products). Inconsistencies 

associated with definitions, system boundaries, and valuations generally make it difficult to 

compare the few measurement efforts that have been done to date with pavements. Currently, 

four general measurement tools, or methods, tend to be used either in isolation or in concert to 

quantify various aspects of sustainability: performance assessment, LCCA, LCA, and 

sustainability rating systems. Notably, there are few, if any, generally accepted metrics able to 

measure equity/social impacts associated with pavement systems. All the above mentioned 

approaches are introduced in this chapter. Chapter 10 describes in more detail the approaches 

and methods used for measuring and assessing pavement sustainability. 

Performance Assessment 

Performance assessment involves evaluating pavement performance in relation to its intended 

function and specified physical attributes deemed necessary to meet that function. Metrics that 

provide information for performance assessment vary but include traditional condition and 

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Towards Sustainable Pavement Systems Chapter 2. Concepts of Pavement Sustainability 

distress ratings (e.g., roughness, rutting, cracking, faulting), composite condition rating systems, 

pavement structural capacity, material design attributes (e.g., thickness, asphalt content, 

compressive strength, gradation), as well as mechanisms to compare these attributes to expected 

or design parameters. Most often, performance is addressed in relation to the current standard 

practice; for instance, if the current standard asphalt pavement surfacing is expected to last 15 

years, the value of alternative surfacings (e.g., open-graded, stone matrix, rubber asphalt) are 

determined based on how their projected service life compares to the standard 15 years. While it 

may be a narrow view (since it does not consider added benefits), the most common sentiment is 

that alternatives must perform equal to or better than the current standard practice. 

Because performance assessment is a longstanding method of evaluation and is essentially built 

into current standards, it is not addressed in detail as a measurement tool in this document. 

However, this document makes frequent reference to pavement performance as a critical 

consideration in choosing between alternatives. 

Life-Cycle Cost Analysis 

LCCA is an analysis technique that uses economic analysis to evaluate the total cost of an 

investment option over an analysis period. As such, it is principally used to address the 

economic component of sustainability. The underlying assumption is that the benefits of 

considered alternatives are equal, and thus only costs (or differential costs) must be considered. 

LCCA does not address equity or environmental issues (e.g., environmental justice, clean 

air/water, habitat impacts) unless such issues can be monetized and treated purely as costs. 

Guidance for using LCCA as a decision-support tool was promulgated in the National Highway 

System (NHS) Designation Act of 1995 for large NHS projects (those greater than $25 million) 

but later rescinded in the 1998 Transportation Equity Act for the 21st Century (TEA-21) (Walls 

and Smith 1998) based on a perceived lack of guidance. Nevertheless, many government 

documents and agencies recognize the utility of LCCA and related financial analyses (e.g., 

Executive Order 13123, OMB Circular No. A-94) and most highway agencies practice LCCA 

(largely guided by Walls and Smith, 1998) to some degree in selecting pavement type for major 

projects (Rangaraju, Amirkhanian, and Guven 2008). The most prevalent LCCA software tool is 

the FHWA’s RealCost program (FHWA 2011). 

Life-Cycle Assessment 

LCA is a technique that can be used for analyzing and quantifying the environmental impacts of 

a product, system, or process. The International Organization for Standardization (ISO 2006) 

states that LCA is a process that “addresses the environmental aspects and potential 

environmental impacts (e.g., use of resources and the environmental consequences of releases) 

throughout a product’s life cycle from raw material acquisition, through production, use, end-oflife treatment, recycling, and final disposal (i.e., cradle to grave).” 

LCA is a field of science that is still very much evolving, yet it has demonstrated real-world 

value over the last two decades by helping manufacturers, companies, governments, and other 

groups identify what is environmentally important to them and then to define needed action to 

lower those environmental impacts. It is widely used for material profiling and is increasingly 

being looked at for use in a number of applications, one of them being pavements. LCA is very 

powerful in that it relates environmental impacts to the overall performance of a system (such as 

a pavement) over the lifespan of the application and over a wide set of environmental 

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Chapter 2. Concepts of Pavement Sustainability Towards Sustainable Pavement Systems 

performance indicators. This systematic approach identifies where the most relevant impacts 

occur and where the most relevant improvements can be made while identifying potential tradeoffs to other life-cycle phases or impact categories. 

Rating Systems 

A sustainability rating system is essentially a list of sustainability best practices with an 

associated common metric. This metric, usually expressed in terms of points, quantifies each 

best practice in a common unit. In this way, the diverse measurement units of sustainability best 

practices (e.g., pollutant loading in stormwater runoff, pavement design life, tons of recycled 

materials, energy consumed/saved, pedestrian accessibility, ecosystem connectivity, and even the 

value of art) can all be compared using a common unit (points). In its simplest form, a rating 

system can count every best practice equally (e.g., all worth one point), in which case the rating 

system amounts to a tally of the number of best practices used. In more complex forms, rating 

systems weight best practices (usually in relation to their impact on sustainability or priority), 

which can assist in choosing the most impactful best practices to use given a limited scope or 

budget. Currently, there are a number of national and international rating systems available in 

the transportation community. 

Integrating Measurement Systems 

The previously discussed methods can be used alone or in concert to measure sustainability. 

Using them in concert provides a more holistic assessment of sustainability since each system 

tends to either address one specific component of sustainability in detail or address all 

components in less detail. For instance, performance assessment can provide a quantitative 

assessment of fitness for use, but does not address cost or environmental impact. LCCA and 

LCA could supplement a performance assessment by providing quantitative assessments of cost 

and environmental impact. Using performance assessment, LCCA, and LCA in concert can 

provide a good, yet still incomplete, picture of the overall sustainability impact of a pavement 

system. It is incomplete because (1) there are no common existing systems that provide 

quantitative assessments of social issues associated with pavements, and (2) it can be unclear 

how to relate the values obtained from performance assessment, LCCA, and LCA (i.e., which is 

most important and to what degree?). Rating systems can address these issues to some extent in 

that they attempt to incorporate all components of sustainability and usually relate them to one 

another using a common point system. However, in order to do this, they tend to sacrifice detail, 

and the inclusion/exclusion of sustainability best practices and their relative weighting within a 

rating system is somewhat subjective. 

Ultimately, the sustainability measurement systems used depend upon the priorities and 

limitations of the agency and the characteristics of the project, as well as the desired outcomes 

viewed within the context of larger systems. For instance, a statewide GHG reduction goal lends 

itself to using LCA as a pavement system metric both for accounting and process improvement 

purposes. Or, a strategic DOT goal to improve or communicate sustainability (however, the 

DOT chooses to define it) may favor the use of a rating system that takes a broad view of 

sustainability. Furthermore, it is also possible to target certain credits within a rating system for 

accomplishment based on agency or project goals (Muench, Armstrong, Allen 2012). In other 

words, rather than creating a new rating system from scratch to be used as an internal 

performance metric, an agency could use an existing one and target those credits that are 

consistent with its strategic sustainability goals. 

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Towards Sustainable Pavement Systems Chapter 2. Concepts of Pavement Sustainability 

Reasons to Measure Sustainability 

The reasons to measure sustainability can be placed in three broad categories: accounting, 

decision support, and process improvement. Each of these is described in more detail below. 

Accounting 

“Accounting” refers to measurement for the sole purpose of quantifying. Usually this is in 

response to a reporting requirement, most often associated with GHG reporting and reduction 

limits. While initial cost has long been measured, there are currently no broad regulations within 

the U.S. to quantify sustainability. In Europe, quantification is more advanced with some owners 

requiring GHG or energy assessments, even for competing alternatives considered in design. In 

the U.S., it is likely that any future initiatives or mandates involving GHG emissions inventories 

will require measurement of GHG emissions at the national, state, agency, or project level. 

These initiatives/mandates can be broadly classified as: 

•	 National Environmental Policy Act (NEPA) requirements for large GHG emitters. 

The draft guidance from the Council on Environmental Quality (CEQ) states: “...if a 

proposed action would be reasonably anticipated to cause direct emissions of 27,500 tons 

(25,000 mt) or more of CO2e GHG emissions on an annual basis, agencies should 

consider this an indicator that a quantitative and qualitative assessment may be 

meaningful to decision makers and the public” (Sutley 2010). Generally, 27,500 tons 

(25,000 mt) is beyond what even a large paving project would generate. However, 

paving may play a smaller role in projects that meet or exceed the 27,500 tons (25,000 

mt) criterion (Sutley 2010). 

•	 State GHG reduction mandates and reporting registries. At least thirty states have 

some sort of official GHG reduction mandate, while forty-two have some form of 

reporting registry (i.e., they report GHG totals but not all are mandated to reduce them) 

(Center for Climate and Energy Solutions 2012). As state governments continue to flesh 

out these mandates and reporting requirements, they will have to take inventory of their 

GHG emissions at some level. While this may not initially involve pavements, their 

eventual inclusion cannot be discounted. 

•	 Cap-and-trade. Various cap-and-trade initiatives are predicated on the ability to 

inventory GHG emissions. While a federal cap-and-trade program is not likely to be 

implemented in the near future, many agencies have entered into various cap-and-trade 

programs including the Western Climate Initiative (WCI), the Midwest Greenhouse Gas 

Reduction Accord (MGGRA), and Regional Greenhouse Gas Initiative (RGGI). 

In general, these initiatives are at a high level, and it remains to be seen how their requirements 

will be interpreted to apply to pavement systems and the traffic which they support. 

Decision Support 

“Decision support” refers to measurement done to obtain quantities or qualities that can help in 

making organizational or project decisions. Results of multiple alternatives are often compared 

but may not be used to improve individual alternatives or processes. Decision-support tools can 

be mandated (e.g., many states require LCCA for pavement projects above a certain size) but 

many are not. Based on the language of the current U.S. transportation bill (Senate and House of 

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Chapter 2. Concepts of Pavement Sustainability Towards Sustainable Pavement Systems 

Representatives 2012), the use of LCCA may become even more prominent in the future. 

Pavement management systems (PMS) are an example of a decision-support tool that most states 

and large owner agencies possess. They measure pavement condition and track new 

construction, rehabilitation, preservation, and (in some cases) maintenance actions in an effort to 

identify appropriate rehabilitation/preservation/maintenance treatments and their timing in order 

to optimize pavement network condition. Decision support using LCA and sustainability rating 

systems is in its infancy in the U.S. transportation industry; there are a few systems publically 

available but their current use is, generally, experimental. However, it should be noted that the 

use of LCA (and its predecessors) for decision support in other industries has a history dating 

back to at least the 1960s. 

Process Improvement 

“Process improvement” refers to measurements that provide feedback data in support of refining 

and updating the overall methodology. Measurements can be compared to benchmarks or other 

indicators and then processes can be altered or modified to produce better results. Process 

improvement is one of the stated purposes of the FHWA’s Infrastructure Voluntary Evaluation 

Sustainability Tool (INVEST) sustainability self-assessment tool (FHWA 2012) and the New 

York State DOT’s Green Leadership in Transportation Environmental Sustainability 

(GreenLITES) program (NYSDOT 2012). Currently, process improvement as it relates to 

sustainability is not mandated and the use of measurement tools is minimal, but such use may be 

increasing. 

Trade-off Considerations 

Since sustainability is a broad systems characteristic encompassing virtually every impact a 

system has, most pavement features and qualities can be argued to support sustainability goals in 

one way or another. However, it is unlikely that all such features can be included in a pavement, 

either because some features support one sustainability objective but are in opposition to another, 

or because some features are mutually exclusive. For instance, an open-graded friction course 

(OGFC) may be desirable because it reduces tire-pavement noise and provides health benefits to 

the surrounding area (supports the social/equity component), but the same surface may also have 

a much shorter performance life (especially in the presence of studded tire wear), which would 

make its life-cycle cost substantially higher than a more traditional dense-graded AC surface (in 

opposition to the financial portion of the economy component). As another example, it may be 

desired to incorporate recycled materials in a rural paving project, but the nearest source of 

recycled material is 100 mi (161 km) away while an acceptable local extracted material is only 5 

mi (8 km) away. In these instances, it is necessary to analyze the available options within the 

context of sustainability in order to make the best choice. 

Essentially, this choice between multiple alternatives represents a consideration of “opportunity 

cost,” the cost of an alternative that must be foregone in order to pursue a certain action 

(Investopedia 2012). In the previous example, if the local extracted material is selected in favor 

of the non-local recycled material, the difference in value between the two represents an 

opportunity cost. The difficulty is in determining the value of the alternatives in a sustainability 

context. In classic economics, value is usually expressed in monetary units (i.e., dollars). 

However, value in a sustainability context can have many different metrics expressed in many 

different units, some of which may be controversial or difficult to quantify. Some examples of 

sustainability value include life-cycle cost, GHG emissions, energy use, water/air quality, waste 

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Towards Sustainable Pavement Systems Chapter 2. Concepts of Pavement Sustainability 

generation, scenic views quality, art, community context, history, habitat continuity, and 

performance life. Historically, the value of alternative pavement features has been 

overwhelmingly based on economics, often being based on initial construction cost alone. While 

important, initial cost represents an incomplete view of the overall costs and benefits of a 

particular feature. Even standard LCCA procedures tend to ignore benefits and costs that are not 

easily monetized. 

Ultimately, this consideration of trade-offs is essentially a benefit/cost analysis done in a more 

holistic sense (i.e., considering more than just economics). This section describes considerations 

when contemplating trade-offs for pavement sustainability best practices. Or, put differently, 

this section describes a few key items to be considered when conducting a benefit/cost analysis 

of sustainable pavement features. Even if benefits and costs are difficult to quantify, it is 

important to use a consistent approach in analyzing trade-offs to avoid introducing unintended 

bias. In general, these considerations involve the following: priorities and values of the 

organization or project, performance, cost, impact magnitude and duration, and risk. None of 

these considerations is new, so this section amounts to a formal articulation of what they are. 

These basic trade-off considerations are referenced throughout this document. 

Priorities and Values of the Organization or Project 

Since sustainability is such a broad system concept, most pavement features support some 

component goals and may be in opposition to others. Thus, judgment on the sustainability value 

of a pavement feature depends on the relative value of sustainability components. Therefore, 

organization or project goals and priorities should be considered in evaluating trade-offs. Ideally 

these goals and priorities should indicate (1) which sustainability components an organization or 

project particularly values, (2) an order of precedence for these values, and (3) a plan to 

operationalize those values and precedence. If sustainability goals and priorities exist and are 

clearly articulated, the first order trade-off consideration is to favor the feature that best supports 

those values. 

In some cases, LCA can be used to quantify and compare environmental impacts, while in other 

cases quantification is difficult, if not impossible. In these cases, it may be enough to determine 

the general duration of impact (that is, does it occur just during construction or is it over the 

entire life of the pavement) in order to make a decision. 

Risk 

All pavement sustainability choices involve an amount of risk. Generally, “risk” means that 

there is some uncertainty regarding the impact and cost of a selected alternative and such 

uncertainty leaves open the possibility of less desirable outcomes than predicted on average. For 

instance, a composite pavement may be selected as the preferred alternative because it results in 

the lowest life-cycle cost among alternatives considered. However, if inadequate bonding is 

developed between the surface and underlying layers, it may be that performance life is 

substantially reduced, resulting in a much higher life-cycle cost. Metrics that provide a 

probabilistic-based analysis (e.g., RealCost [FHWA 2011], Construction Analysis for Pavement 

Rehabilitation Strategies—CA4PRS [Caltrans 2008]) can help quantify risk due to uncertainty. 

Some metrics, like LCA, are only now beginning to incorporate uncertainty into their analysis. 

2-13
 
Chapter 2. Concepts of Pavement Sustainability Towards Sustainable Pavement Systems

Summary

This chapter provides a general overview of sustainability concepts and describes how they 

relate to pavements. This includes a basic definition of sustainability and a discussion of why 

sustainability essentially means “consider everything,” yet also explains how its application must 

fall within the priorities and goals established by the organization. The role that pavements play 

in sustainability is described in terms of a common proxy (GHG emissions), and the key 

components of the pavement life cycle (materials production, pavement design, construction, 

use, maintenance and rehabilitation, and end-of-life) are also presented. The chapter concludes 

with summary of current methods for assessing sustainability and a general framework for 

considering potential issues and trade-offs.

References

Amekudzi, A., M. Meyer, C. Ross, and E. Barrella. 2011. Transportation Planning and 

Sustainability Guidebook. Federal Highway Administration, Washington, DC. 

Bissonette, J. A. and P. C. Cramer. 2008. Evaluation of the Use and Effectiveness of Wildlife 

Crossings. NCHRP Report 615. Transportation Research Board, Washington, DC. 

Bush, G. W. 2007. Executive Order 13423: Strengthening Federal Environmental Energy, and 

Transportation Management. The White House, Washington, DC. 

California Department of Transportation (Caltrans). 2008. Construction Analysis for Pavement 

Rehabilitation Strategies (CA4PRS) Caltrans ‘Rapid Rehab’ Software. California Department of 

Transportation, Sacramento, CA. (Web Link). 

Carnegie Mellon University. 2008. Economic Input-Output Life Cycle Assessment (EIO-LCA), 

US 1997 Industry Benchmark Mode. Carnegie Mellon University, Green Design Institute, 

Pittsburgh, PA. (Web Link). 

Center for Climate and Energy Solutions. 2012. Greenhouse Gas Reporting and Registries. 

Center for Climate and Energy Solutions, Arlington, VA. (Web Link).

Environmental Protection Agency (EPA). 2013. Inventory of U.S. Greenhouse Gas Emissions 

and Sinks, 1990–2011. EPA 430-R-13-001. Environmental Protection Agency, Washington, 

DC. (Web Link). 

Federal Highway Administration (FHWA). 2011. Life-Cycle Cost Analysis Software. Federal 

Highway Administration, Washington, DC. (Web Link). 

Federal Highway Administration (FHWA). 2012. INVEST. Federal Highway Administration, 

Washington, DC. (Web Link).

International Organization for Standardization (ISO). 2006. ISO 14040:2006 Environmental 

Management – Life Cycle Assessment – Principles and Framework. International Organization 

for Standardization, Geneva, Switzerland. 

Investopedia. 2012. Opportunity Cost. Investopedia, New York, NY. (Web Link).

2-14
Towards Sustainable Pavement Systems Chapter 2. Concepts of Pavement Sustainability

Muench, S. T., A. Armstrong, and B. Allen. 2012. “Sustainable Roadway Design and 

Construction in the Federal Lands Highway Program.” Transportation Research Record 2171. 

Transportation Research Board, Washington, DC.

New York State Department of Transportation (NYSDOT). 2012. GreenLITES. New York 

State Department of Transportation, Albany, NY. (Web Link).

Obama, B. H. 2009. Executive Order 13514: Federal Leadership in Environmental, Energy, 

and Economic Performance. The White House, Washington, DC.

Rangaraju, P. R, S. Amirkhanian, and Z. Guven. 2008. Life Cycle Cost Analysis for Pavement 

Type Selection. FHWA-SC-08-01. South Carolina Department of Transportation, Columbia, SC. 

Senate and House of Representatives of the United States of America. 2012. Moving Ahead for 

Progress in the 21st Century Act, S. 1813. 112th Congress, Washington, DC.

Sutley, N. H. 2010. Memorandum for Heads of Federal Departments and Agencies: Draft 

NEPA Guidance on Consideration of the Effects of Climate Change and Greenhouse Gas 

Emissions. White House Council on Environmental Quality, Washington, DC. 

University of California Pavement Research Center (UCPRC). 2010. Pavement Life Cycle 

Assessment Workshop. UCPRC-TM-2010-03. University of California Pavement Research Center, 

Davis, CA. (Web Link).

U.S. Census Bureau. 2012. Construction Spending. U.S. Census Bureau, Washington, DC. 

(Web Link).

U.S. Department of Transportation (USDOT). 2010. Transportation Statistics Annual Report 

2008. U.S. Department of Transportation, Washington, DC. (Web Link). 

U.S. Department of Transportation and U.S. Department of Commerce (USDOT/USDOC). 

2010. 2007 Economic Census: Transportation, 2007 Commodity Flow Survey. U.S. Department 

of Transportation and U.S. Department of Commerce, Washington, DC. (Web Link). 

Walls, J. and M. R. Smith. 1998. Life-Cycle Cost Analysis in Pavement Design. Interim Technical 

Bulletin. FHWA-SA-98-079. Federal Highway Administration, Washington, DC. (Web Link).

World Commission on Environment and Development (WCED). 1987. Our Common Future: 

the Report of the World Commission on Environment and Development. Document A/42/427. 

Oxford University Press, University of Oxford, United Kingdom.

Zietsman, J., T. Ramani, J. Potter, V. Reeder, and J. DeFlorio. 2011. A Guidebook for 

Sustainability Performance Measurement for Transportation Agencies. NCHRP Report 708. 

Transportation Research Board, Washington, DC. 

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Chapter 2. Concepts of Pavement Sustainability Towards Sustainable Pavement Systems 

2-16
 
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

CHAPTER 3. MATERIALS CONSIDERATIONS TO IMPROVE 

PAVEMENT SUSTAINABILITY

Introduction

This chapter reviews materials used for paving applications, and how these materials affect the 

overall sustainability of the pavement system. Included in this review are aggregates, asphalt

materials, cementitious materials, and other materials that are commonly used in pavement 

construction. Recycled materials are introduced, with more detailed information provided in 

chapter 8. Some construction quality considerations are also introduced, but these are discussed 

in more detail in chapter 5.

The impacts of material acquisition, processing, and transportation are discussed and presented 

in the context of how they influence pavement life. The scope of this chapter is from the 

extraction of materials to the point where materials begin final transportation to the construction 

site, either from the final processing plant (e.g., the stockpile for aggregates being used for base 

or subbase construction) or from the exit gate of the mixing plant (in the case of asphalt or 

hydraulic cement concrete production). In the latter case, it includes the mixture design and 

proportioning, as well as the plant operations to the point where the material is placed in trucks 

for transportation to the pavement grade. The disposition of the materials once they leave the 

plant is considered in chapter 5. 

Materials and Consideration of the Life Cycle 

Pavement materials should be assessed from a life-cycle perspective to determine the role they 

play in contributing to the sustainability of a pavement system. A life-cycle perspective allows 

decision makers to examine potential economic, environmental, and social impacts that may 

occur throughout the life cycle, and also to evaluate potential trade-offs. Some typical questions 

that arise with regards to pavement materials and overall decision making include: 

• What are the sustainability goals of the organization specifying the materials, and are 

they compatible such that a clear set of criteria can be used when making materials 

decisions? 

• For a selected life-cycle time period, what is the total life-cycle impact resulting from 

using a paving material only once versus using it multiple times? 

• If a recycled, co-product, or waste material (RCWM) is used in a pavement construction 

project: 

– Does the RCWM result in equivalent structural or durability behavior as the material 

being replaced such that performance is not compromised? Does sufficient 

knowledge regarding performance exist that this question can be answered with 

confidence? 

– Does the RCWM have to be processed or transported long distances such that the 

impact on sustainability of the processing or transportation is greater than the benefits 

to sustainability of using it?

– Does the inclusion of the RCWM make the resulting material difficult to recycle in 

the future? 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

• Does the constructability of a particular material 

increase the variability of performance in the field 

and, if so, does it increase the risk that it must be 

replaced more frequently? 

• Does specifying a longer lasting material offset 

the impact of longer transportation distances or 

higher production-related impacts?

• Are specifications that limit the use of lower 

impact materials effective in reducing the risk of 

poor performance, or do they prevent the 

opportunity to improve the overall sustainability 

of a pavement project? 

• Is the pavement designed to make the best use of 

lower impact materials without compromising 

performance?

• Can the impacts of transporting materials be 

reduced by improving logistics and through 

greater permitting of local materials? Can 

transportation impacts also be reduced by 

targeting the use of higher grade materials in the 

wearing course and lower quality local materials 

in the other layers? 

These are just a few of the questions that 

transportation professionals often face when making 

material choices to improve the overall sustainability 

of a pavement over the life cycle. Others will be 

apparent in the discussions presented in this chapter.

Chapter Overview

The primary materials used in pavement applications 

include aggregates, asphalt materials and mixtures, 

hydraulic cement materials, and other assorted 

materials (e.g., steel, fibers). Each of these materials 

is addressed in this chapter as a separate section, with 

parallel sections introducing the material, describing 

the issues associated with its use, outlining strategies 

for improving its sustainability, and describing future 

directions and emerging technologies. Again, the 

focus is on aspects of the material processing and 

production, and includes consideration of RCWM

materials.

Recycled, Co-Product, or Waste 

Materials – What’s the 

Difference?

– Recycled materials are obtained from 

an old pavement and are included in 

materials to be used in the new 

pavement. Common recycled materials 

include reclaimed asphalt pavement or 

recycled concrete pavement. 

Depending on the regional market, 

these materials would be “waste” if not 

recycled, ending up in a landfill. 

Allocation of environmental impact 

between the manufacture of the original 

material and its reuse in the new 

material is based on the processing 

needed to make this material suitable 

for use in the new pavement. The 

demolition of the existing pavement and 

its transportation to a processing plant 

is allocated to the old pavement. 

– Co-products are derived as part of 

another process—often industrial but 

possibly agricultural—that brings value 

to the overall process. For pavement 

applications, some of the most common 

co-products result from the production 

of pig iron for steel making, including 

slag cement and air-cooled iron blast 

furnace slag aggregate. Allocation for 

co-products is based on some agreed 

upon approach, but most often is based 

on economic worth of the various coproducts. 

– Wastes are materials that normally 

would be sent to a landfill, for which the 

cost of transport and processing is the 

only source of economic value. If the 

material has value beyond this, it is no 

longer considered a waste, but instead 

a co-product. Recycled asphalt 

shingles is an example of one such 

waste material as long as the 

economics stay consistent with the 

above definition. The classification of fly 

ash is more complex, as in some 

regional markets it would fit the 

definition of waste whereas in other 

markets it is clearly a co-product 

because it has economic value beyond 

the cost of transport and disposal. 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Aggregate Materials

Introduction

Aggregates make up the largest share of the mass and 

volume in a pavement structure, whether used without 

a binding material (e.g., unbound subbase or base 

material), or as part of an asphalt or hydraulic 

cementitious bound layer. Although aggregates are 

relatively low cost and have a low environmental 

impact per unit mass relative to other materials that 

are used in pavements, they can have a significant 

impact on pavement sustainability because they are 

consumed in such large quantities. The U.S. 

Geological Survey (USGS 2013a) terminologies for 

different sources of aggregates used in pavements are 

crushed stone and construction sands and gravels. 

The majority of crushed stone and construction sands and gravels produced in the U.S. are used 

for roads. Crushed stone is defined as aggregate taken from hard rock quarries (often by 

blasting) and then processed through crushing to desired sizes. Groundwater may need to be 

pumped off depending on the depth of the quarry and the level of the water table, which can 

affect water tables in the surrounding areas. The biodiversity of a quarry site can be improved 

from pre-quarry to after-quarry use when proper remediation or restoration efforts are put in 

place. 

Construction sands and gravels are predominantly mined from alluvial sources, usually by 

scraping or bucketing directly from the deposits. Some alluvial sources are in existing 

waterways, such as rivers and lakes, in which case removal of the sand and gravel can affect 

water quality and change stream flow patterns (speed, volume, and connectedness of channels). 

This, in turn, can affect aquatic habitat and can also change scour and the sediment-carrying 

capacity of streams. Other alluvial sources are from historical flood plains that do not currently 

hold water. In either case, large quantities of material are permanently removed, leaving deep 

pits across large areas of land that require remediation either to restore stream flow 

characteristics or to make dry land pits suitable for other purposes. Sands and gravels are often, 

but not always, processed through crushing to obtain the desired sizes and surface textures for 

road base and for mixing with asphalt or hydraulic cement. 

Aggregates from both sources (hard rock quarries and alluvial deposits) must also be transported 

within the site and mechanically sorted by particle size by sieving, both of which are processes 

that consume energy. Aggregates are categorized by particle size as being coarse or fine. 

Typically, coarse aggregates are those retained on the No. 4 (4.26 mm) sieve, and fine aggregates 

are those that pass that same sieve. For unbound bases and subbases, material passing the No. 

200 (0.075 mm) sieve is often referred to as fines whereas in asphalt mixture production those 

materials are most commonly referred to as dust or as filler. For concrete production, it is 

desirable to eliminate aggregates smaller than sand size from the gradation. This often requires 

washing the aggregates, which can consume significant quantities of water and affect water 

quality. 

Major Issues: 

 Environmental and social 

implications of aggregate 

acquisition and transportation.

 Special concerns regarding 

aggregate processing.

 Implications of aggregate durability.

 The utilization and performance of 

RCWMs as aggregates.

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

As shown in figure 3-1, aggregates account for 80 to 85 

percent by volume of typical asphalt concrete and 62 to 

68 percent by volume of hydraulic cement concrete 

(Tayabji, Smith, and Van Dam 2010). 

About 42 percent of the aggregates consumed by 

weight in the U.S. have been processed through 

crushing (Moray et al. 2006). These are mainly used in 

highway applications. As shown in figure 3-2, crushed 

aggregates, whether from crushed stone (hard rock 

mining) or construction sand and gravel (alluvial 

mining), are more angular than aggregates obtained 

from natural sand and gravel deposits. Crushed faces 

on aggregates are required for use in unbound 

aggregate base courses and asphalt mixtures as they 

interlock and provide stability to the layer under 

loading. They are also used for higher strength 

concrete mixtures as the increased roughened surface 

area provides enhanced bonding of the hydrated cement 

paste to the aggregate. In concrete mixtures, uncrushed 

rounded sand and gravel often provides better mixture 

workability, and is acceptable for use in concrete 

provided that the required strength and other specified 

property requirements are met. 

In general, processing to achieve crushed aggregates 

consumes more energy and releases more GHGs during 

extraction and production than unprocessed sand and 

gravel aggregates. This is because manufacturing 

crushed stone requires drilling, blasting, and crushing, 

while production of unprocessed sands and gravels 

does not. Energy consumption and the release of 

GHGs for construction sands and gravels that are 

processed through crushing falls between that for 

crushed stone and unprocessed construction sands and 

gravels.

Aggregate Usage and 

Economics

In the U.S. in 2012, approximately 

1,324 million tons (1,200 million mt) of 

crushed stone worth approximately 

$12 billion was produced by 1,550 

companies operating 4,000 quarries, 

91 underground mines, and 210 

sales/distribution yards in all 50 

states. Of the total crushed stone 

produced in 2012, about 69 percent 

was limestone and dolomite, 14 

percent granite, 7 percent traprock, 5 

percent miscellaneous stone, and 4 

percent sandstone and quartzite 

(USGS 2013a). Limestone is also 

used in the manufacture of most 

hydraulic cements including portland 

cement as well as being used as the 

aggregate in concrete and asphalt 

mixtures and for base and subbase 

layers. Granite and traprock (such as 

basalt) are used extensively as 

aggregate in both concrete and 

asphalt mixtures. Of the portion of 

total crushed stone production 

reported by use in 2012, 82 percent 

was used as a construction material, 

mostly for road construction and 

maintenance and 10 percent, for 

cement manufacturing (USGS 

2013a).

In the U.S., approximately 927 million 

tons (840 million mt) of construction 

sand and gravel worth $6.4 billion 

was produced in 2012 by an 

estimated 4,000 companies from 

about 6,400 operations in 50 states 

(USGS 2013a). It is estimated that 

about 43 percent of construction sand 

and gravel was used as concrete 

aggregates, 26 percent for road base

and coverings and road stabilization; 

12 percent as construction fill; and 12 

percent as asphalt concrete 

aggregates and in other asphaltaggregate products (USGS 2013a).

3-4 
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

 

Figure 3-1. Typical volumes of aggregate in dense-graded asphalt concrete and in dense-graded 

hydraulic cement concrete (asphalt concrete: summary of mixture designs by authors; concrete: 

Tayabji, Smith, and Van Dam 2010). (Note: Aggregate for dense-graded asphalt concrete 

includes all sizes, whereas aggregate for concrete typically excludes sizes smaller than sand.) 

Figure 3-2. Coarse aggregates: rounded gravel (left) and crushed stone (right) 

(Kosmatka and Wilson 2011).

Another group of aggregates that are used in highway construction are manufactured aggregates. 

Manufactured aggregates are those that are created specifically to possess a unique property 

(such as expanded shale and clay to create lightweight aggregates), or are a co-product of another 

process (such as crusher fines, foundry sands, or slag aggregates). Manufactured lightweight 

aggregates are rarely used in pavements, but are occasionally used in bridge structures. An 

emerging application of lightweight aggregates is to provide a source of internal moisture for 

curing concrete (ACI 2013). In that application, part of the natural sand is replaced with fine 

saturated lightweight aggregate (SLWA) to enhance strength gain and minimize early-age 

cracking of concrete (Bentz and Snyder 1999; Henkensiefken et al. 2009). 

10 to 12%

80 to 85%

2 to 3%

3 to 8%

Percentage of Volume of Typical 

Asphalt Concrete

Asphalt Binder Aggregate Filler Air

10 to 14%

62 to 68%

14 to 18%

4 to 8%

Percentage of Volume of Typical 

Concrete

Cementitious Aggregate Water Air

1 inch

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

From a sustainability perspective, it is convenient to combine manufactured aggregates with 

recycled materials into the RCWMs category that was defined earlier. Thus, the following 

aggregates are classified as RCWMs:

• Reclaimed asphalt pavement (RAP) – RAP is most often produced when existing asphalt 

concrete layers are cold milled from an existing asphalt pavement as part of a 

rehabilitation or maintenance overlay, and the removed materials stockpiled for use in a 

new asphalt pavement, base, or subbase. While the predominant use is in new asphalt 

pavement, RAP is commonly used in aggregate bases, and coarse fractionated RAP is 

being used as aggregate in new concrete. More details on the use of RAP are provided 

later in this chapter and in chapter 8. 

• Recycled concrete aggregate (RCA) – RCA is created when concrete is purposefully 

crushed to create aggregates for use in subbase, base, or paving (asphalt or concrete) 

applications. RCA often contains previously unhydrated cement that produces increased 

stiffness in bases/subbases when mixed with compaction water, creating a material with 

superior properties compared with virgin aggregates (Chai, Monismith, and Harvey 

2009). When used as base or subbase, both the coarse and fine RCA are often used. In

new concrete, it is most common to use only the coarse fraction of the RCA as the fines 

significantly increase water demand and also have a disproportionately high 

concentration of chlorides if recycled from pavements subjected to chemical deicing. 

RCA is discussed in greater detail in chapter 8. 

• Recycled asphalt shingles (RAS) – Although predominately used as a source of reclaimed 

binder, RAS also provides fine aggregate for use in new asphalt concrete mixtures. RAS 

is discussed in detail later in this chapter. 

• Air-cooled blast furnace slag (ACBFS) – ACBFS is an industrial co-product from iron 

blast furnaces in which pig iron is extracted from iron ore and the remaining molten 

material (slag) is directed into pits where it is allowed to cool in air. Once cooled, this 

material is crushed and can be used as aggregate for subbase and base applications, in 

asphalt concrete, and in concrete. Two recent publications provide more details on the 

use of ACBFS as an aggregate material in concrete (Morian, Van Dam, and Perera 2012; 

Smith, Morian, and Van Dam 2012). 

• Steel furnace slag (SFS) – SFS is a co-product of the manufacturing of steel. The 

properties of the SFS, and thus the suitability for it to be used in pavement applications, 

are largely controlled by the method of processing. While most SFS can readily be used 

in asphalt pavements, some SFS is not considered suitable for use in concrete as it may 

lead to undesirable expansion and deterioration. Further, the expansion potential of some 

SFS has resulted in damaging expansion of unbound base or subbase material. As a 

result, SFS must be tested and its properties understood prior to use in a pavement 

structure to ensure that damaging expansion will not occur (Chesner, Collins, and 

MacKay 1998). 

• Foundry sand – Waste foundry sand is generated by the ferrous and nonferrous metal 

casting industries. It can be used as a partial replacement of fine aggregate in concrete, in 

asphalt concrete mixtures, and as engineered fill material. As a waste material generated 

through an industrial process, the impact on mixture performance must be fully studied, 

as must the potential for leaching of heavy metals. 

3-6 
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Regardless of the aggregate grouping, the extraction (e.g., mining, dredging, milling), processing 

(crushing and sieving), and transport of aggregates consumes energy and generates emissions 

from the fuel consumed by equipment and vehicles, and often from the electrical grid. 

Furthermore, fugitive dust is produced and water resources are utilized and impacted. Figure 3-3 

summarizes the environmental burdens of mining and processing crushed aggregates and natural 

aggregates from a number of cited sources. Energy consumption and GHG emissions (in terms 

of Global Warming Potential [GWP]) included in the figure are calculated based on the lower 

heating values of consumed fuels and the electrical grid mix of the specified region (CA – 

Canada; SE – Sweden; CH – Switzerland; FI – Finland, US – United States) as identified by 

different life cycle inventories (Ecoinvent 2011; Stripple 1998; Häkkinen and Mäkelä 1996; 

Athena 2006; Marceau, Nisbet, and VanGeem 2007). An examination of each inventory data 

source indicates that the production of crushed stone consumes more primary energy (meaning 

the total energy burden including the production of energy resources) than the production of 

gravels and sands. That energy use will increase as the amount of crushing of the alluvial 

gravels and sands is increased to meet tighter material specifications for crushed faces on the 

aggregate, which improves the performance of asphalt materials and aggregate base materials. 

Figure 3-3. Primary energy and global warming potential from aggregate production per kg, at 

quarry (adapted from Wang et al. 2012). (Notes: 1. Energy consumption shown here excludes 

the production of capital goods such as construction of dams, power plants and transmission 

lines; 2. CO2e per MJ is different for each case, depending on the electrical power production 

mix and fuels consumed). 

0.000

0.003

0.006

0.009

0.012

0.015

0.00

0.03

0.06

0.09

0.12

0.15

Crushed,

CH, Eco

Gravel,

CH, Eco

Sand,

CH, Eco

Crushed,

SE, Stripple

Gravel/Sand,

SE, Stripple

Crushed,

FI, Hakkinen

Gravel,

FI, Hakkinen

Fine,

CA, Athena

Coarse,

CA, Athena

Crushed,

US, PCA

Sand and

Gravel,

US, PCA

Global Warming Potential (CO2-e kg)

Energy Consumption (MJ)

Total Primary Energy Total GWP

3-7 

The environmental burden of energy consumption depends largely on the source of the energy 

(e.g., coal, oil, gas, hydro, nuclear, renewables). Energy consumed in the production of 

aggregates includes transportation within the quarry and processing plant using earth moving 

equipment and trucks that are primarily powered by petroleum products, and conveyors powered 

by electricity. Another major component is the crushing and sorting equipment, which are 
Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

typically powered by electricity. Electricity is usually drawn from the regional grid although in 

some cases the electricity may be produced on site through fossil fuel powered generators. As 

fuels that power electrical grids vary considerably by region and country, energy intensity, 

environmental emissions, and water use will vary as well. The regional electricity grid can affect 

the life-cycle impacts of aggregate production, or any other product, and must be considered 

when calculating or interpreting life-cycle impacts or comparing sources of materials. 

Accounting for water consumption for electricity generation is an important topic and not always 

a straightforward issue. Energy produced in power plants by thermoelectric systems evaporate 

water during the cooling of the condenser water and hydroelectric plants evaporate water off the 

surface of the reservoirs (Torcellini, Long, and Judkoff 2003). There are differences in modeling 

storage water for hydroelectric facilities, turbine, and cooling water; a specific example is the net 

water consumption at hydroelectric facilities. This consumption is primarily related to the 

evaporation rate from the associated reservoir. This rate, which is a function of surface area, 

local climate, and other factors, is a challenging value to ascertain. Not only is the science 

complex and evolving, but is also highly variable between locations. These complexities are 

apparent when comparing different life-cycle inventory (LCI) datasets for hydropower (e.g., 

Ecoinvent, GaBi).

Another major source of environmental burden associated with aggregate is transportation. 

Aggregate must be transported from the source to the job site for unbound bases and subbases, 

and transported to the mixing plant for asphalt bound materials and hydraulic cement concrete (if 

the plant is not located at the quarry) and then to the project site. Transport-related impacts 

primarily involve the burning of petroleum-based fuels in trucks or other transport vehicles. The 

energy use and GHG emissions from transport can be larger than those from mining and 

processing, especially if trucks are used instead of more fuel efficient transportation modes such 

as rail or barges. Table 3-1 shows the relative fuel efficiency for the three primary modes of 

aggregate transport: truck, rail and barge. The values shown in the table are gross estimates that 

provide a first order comparison; actual fuel use will vary based on the specific mode technology 

used, load magnitude, percent of empty back haul, and topography. 

Table 3-1. Summary of estimated national average freight movement fuel efficiency1 (diesel) of 

freight transportation modes (2009 data) (Kruse, Protopapas, and Olson 2012).

Mode Ton-Miles/Gallon

Trucks2 150

Rail 478

Inland towing 616

Notes: 

1. This is gross fuel use, not life-cycle fuel use. 

2. Truck load assumed to be 25 tons (22.6 mt) on a 40 ton (36.28 mt) 

gross vehicle weight truck, loaded one way.

3-8 
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Other environmental issues arising from aggregate mining, processing, and transportation 

include dust pollution, groundwater use, noise, pavement damage and traffic safety issues on 

roads leading to and from the source, and quality of life issues for residents and plant/wildlife 

subjected to those impacts. For these reasons, it can be a long and difficult process to obtain 

permits for aggregate quarries and pits, sometimes taking 10 years or more. 

Because of these challenges, new aggregate quarries in some areas are located further away from 

the urbanized areas where aggregates are most often needed, increasing the environmental 

burden of aggregate transport to the main locations of consumption. In some areas, suburban 

sprawl has occurred on prime aggregate sources making it even more difficult to get permits, or 

the encroaching development results in reduced operating hours and other restrictions on existing 

quarry operations. For example, the California Geological Society (CGS 2012) has documented 

the anticipated scarcity of aggregate supplies in California over the next 50 years. Some urban 

areas that have river, lake, or sea access (such as Detroit, the San Francisco Bay Area, Chicago, 

Los Angeles) overcome this problem by importing aggregate to urban processing plants using 

low-impact marine transportation, sometimes from foreign countries over very long distances. 

Strategies for Improving Sustainability

Some general approaches to improving pavement sustainability with regard to aggregate 

production, and the trade-offs that should be considered are summarized in table 3-2. A brief 

discussion of some of the major strategies to address these issues is summarized next. 

Strategy: Reduce the Amount of Virgin Aggregate Used

There are two approaches that can be utilized to achieve Strategy No.1. The first is to increase 

the volume of recycled material used as aggregate. Pavement recycling is discussed in detail in

chapter 8, but it is noted again here that a wide variety of RCWMs (e.g., RAP and RCA) can be 

effectively used as aggregate in pavements. The use of these materials often requires additional 

knowledge and care in processing, handling, and proportioning of the aggregate to ensure 

performance. Although it is attractive to introduce RCWMs into a paving project as a 

“sustainable” aggregate solution, this may lead to reduced sustainability if done without 

consideration of the effects that those materials have on the performance of the pavement. Thus, 

the use of a given RCWM for a given application must be carefully considered to achieve a 

balance between the following: 

• Availability – Is the RCWM locally available compared to the natural aggregate being 

replaced? In many cases suitable RCWMs are readily available and are less expensive 

or similarly priced. But in those cases where a local source of the RCWM is not 

available, it may require long distance transportation that may result in increased cost and 

environmental damage. Thus, local availability must be considered before requiring the 

use of a certain percentage of RCWMs.

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Table 3-2. Approaches for improving aggregate production for pavement sustainability.

Aggregate 

Materials 

Objective

Sustainability 

Improving Approach Economic Impact Environmental Impact Societal Impact 

Reduce the 

Amount of Virgin 

Aggregate Used

Use more aggregates 

derived from RCWM 

sources.

Can potentially reduce 

cost, and preserve scarce or 

difficult to permit virgin 

sources. May increase cost 

depending upon 

availability, transportation, 

or processing required; 

reduce ability to recycle in 

the future; durability; 

special pollution problems 

(pH, toxicity, 

contaminants). 

Dependent on 

characteristics of 

RCWM, considering 

transportation, 

processing, ability to 

recycle multiple times, 

special pollution 

problems. 

Preserves virgin 

sources. Can reduce 

need for new sources 

and associated 

impacts. Reduces 

need for new landfills. 

Potential for negative 

impacts depending 

upon transportation, 

processing 

requirements. 

Use more durable 

aggregate, maximizing 

pavement life.

May increase initial cost, 

decrease life cycle cost.

Dependent upon 

transportation distance if 

not locally available.

Primarily dependent 

upon transportation.

Reduce the Impact 

of Virgin 

Aggregate 

Acquisition and 

Processing

Review environmental 

impact and remediation 

plans of different 

aggregate sources when 

permitting (handled via 

the NEPA guidelines or 

equivalent environmental 

impact review [EIR] and 

permit process in many 

states).

Dependent upon 

requirements imposed by 

permit. Most permit 

processes do not consider 

impacts of locating 

quarries outside of the 

jurisdictional area and 

importing the aggregate 

(transfer of impacts).

More sustainable 

features for quarry may 

come from permitting 

process.

More sustainable 

features for quarry 

may come from 

permitting process.

Implement processing and 

mining operations using 

less or lower impact 

energy sources and less 

water.

Will often result in initial 

cost increase due to 

changeover and life cycle 

cost decrease due to greater 

energy efficiency.

Will generally reduce 

environmental impact.

Will often reduce 

societal impact.

Use locally available 

materials or those using a 

low impact mode for 

transportation (next item).

Will often reduce initial 

cost, may increase life 

cycle cost if there are 

significant differences in 

durability.

Will often reduce 

environmental impact.

May increase impact 

for those near local 

source production and 

transportation 

locations.

Reduce the Impact 

of Aggregate 

Transportation 

Minimize transportation 

impact by maximizing 

use of marine/barge and 

rail transport and 

minimizing truck 

transport. 

Will often reduce cost. Will usually reduce 

environmental impact.

Will usually reduce 

societal impact, 

focusing it on marine 

and rail routes 

reducing noise, safety 

issues compared with 

road transport.

Facilitate permitting of 

aggregate sources and 

processing sites near 

major use areas.

Will generally reduce cost 

due to reduced 

transportation cost.

Will usually reduce 

environmental burden 

due to reduction in truck 

transportation. 

Will increase impact 

on those living near 

mining or processing 

sites.

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

• Experience – Is the local contracting 

community experienced in using RCWMs in 

the application and volumes that are being 

considered? It is well known that many 

RCWMs act differently during construction 

than natural aggregates, depending on the use 

and application. For example, if coarse 

aggregate RCA is to be used as a replacement 

for natural coarse aggregate in concrete, the 

RCA stockpile must be kept wet during mixture 

batching (ACPA 2009). This is not a common 

practice in some locales and omission of this 

important step can lead to mixing problems and 

performance issues. Similarly, RAP can be 

added to asphalt concrete mixtures at much 

higher levels than most current practices allow, 

but additional care must be taken throughout 

the entire mixture design and construction 

process to minimize durability and workability 

difficulties, such as processing to reduce 

variability within the stockpile, and screening 

into separate size graded or “fractionated” 

stockpiles. Providing additional information, 

training, and support to the contracting 

community may be required to develop local 

expertise on the use of RCWMs for different 

applications. 

• Performance – Although the potential exists for 

the volume of RCWMs in a given application 

to be increased, there is also an increased risk 

that pavement performance will suffer if care is 

not taken to understand the impacts of 

increased RCWM aggregate volume on mixture 

performance. For example, in recent years as 

technology and understanding have improved, 

the maximum amount of RAP used in asphalt 

concrete mixtures has increased well beyond 

what had traditionally been specified. Yet 

there is a point beyond which increased RAP 

volume may have a negative impact on the 

long-term performance of the pavement, 

perhaps stiffening the mixture and adding a source of variability that can be difficult to 

manage. A good understanding of the material and the use of mechanistic-empirical

design and appropriate laboratory testing and specifications is needed to design pavement 

structures without increasing risk. In addition, the use and application must also be 

considered, as “too much” RAP may create a mixture that is too stiff and brittle for a thin 

overlay surface mix, yet the same percentage of RAP might be much less than can be 

used for thick structural layers located below the surface where the increased stiffness is 

needed to reduce bottom-up tensile stresses (see chapter 4 for more information). 

Illinois Tollway’s Experience with 

RCWMs

The Illinois Tollway System is 

comprised of four toll roads including 

the Tri-State (I-94/I-294/I-80), Jane 

Addams Memorial (I-90/I-39), Reagan 

Memorial (I-88), and Veterans 

Memorial (I-355), collectively routes

carrying more than 1.4 million vehicles 

per day and connecting Northern 

Illinois, Wisconsin, and Indiana. The 

Tollway has been enhancing the 

transportation infrastructure of Chicago 

Metropolitan area through major 

programs such as Congestion Relief 

(2004-2016) and Move Illinois (2012-

2026). The major objectives of these 

programs are to enhance regional 

mobility, save drivers’ time and money, 

and create jobs while adopting 

materials and construction 

sustainability plans. The Tollway 

requires 100 percent recycling of 

concrete and asphalt pavements to be 

reused in new pavements. The levels 

of asphalt binder replacement (ABR) in 

asphalt mixtures are typically 40-60

percent. High levels of ABR are 

achieved by Tollway contractors due to 

good construction practices such as 

RAP fractionation, inclusion of RAS, 

and utilization of the fine portion of 

fractionated RAP. WMA has been used 

in all large volume asphalt paving and 

overlay applications including warm mix 

stone matrix asphalt (WMSMA). The 

Tollway has recently implemented twolift or composite concrete pavements. 

Large volumes of two-lift concrete, as 

high as 3,000,000 yd2, are expected to 

be used on I-90 reconstruction over the 

next 4 years starting from 2014, which 

will allow for high levels of RCWM use 

in the non-exposed lower lift.

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Improvements in understanding and technology continue to push the limit on RAP 

replacement levels, but additional research is required to provide better design and 

construction information for wide-scale adoption of elevated RCWM replacement levels.

The increased use of RCWMs as aggregate for bases and subbases and in asphalt concrete and 

concrete mixtures offers a significant opportunity to increase the overall sustainability of 

pavements. The key to effectively implementing this approach is increased understanding and 

improved technology. Understanding is needed to appreciate how the inclusion of higher 

volumes of RCWMs will impact constructability and long-term performance. Improvements in 

technology will help address current limitations as well as provide better understanding of how 

these materials perform.

A second approach that can be employed to reduce the amount of aggregate used over the life 

cycle is to improve aggregate durability. Durability is not an intrinsic material property of the 

aggregate, but instead reflects the ability of the material to maintain its integrity when exposed to 

service conditions. Aggregates can degrade due to physical processes (e.g., wetting and drying, 

freezing and thawing) or chemical processes (e.g., alkali-silica reactivity [ASR] in cementitious 

materials) or may just interact poorly with the binding agent (e.g., moisture susceptibility in 

asphalt mixtures). Premature pavement failure due to durability issues can have significant 

environmental, economic, and social costs.

A suite of laboratory tests are used to assess the durability of aggregates for various applications. 

Some common tests include:

• AASHTO T 104/ASTM C88, Standard Test Method for Soundness of Aggregates by Use 

of Sodium Sulfate or Magnesium Sulfate – This test is a surrogate for general aggregate 

soundness. 

• AASHTO T 161/ASTM C666, Standard Test Method for Resistance of Concrete to 

Rapid Freezing and Thawing – This test assesses the aggregates’ resistance to freezing 

and thawing. 

• AASHTO T 303/ASTM C1260, Standard Test Method for Potential Alkali Reactivity of 

Aggregates (Mortar Bar Method) – This test, along with ASTM C1293, Standard Test 

Method for Determination of Length Change of Concrete Due to Alkali-Silica Reaction, 

assesses the aggregates resistance to ASR.

• ASTM D4792, Standard Test Method for Potential Expansion of Aggregates from 

Hydration Reactions - This test is used as a measurement of durability for steel slag.

• AASHTO T 283/ASTM D4867, Standard Test Method for Effect of Moisture on Asphalt 

Concrete Paving Mixtures – This test method evaluates an asphalt mixture’s 

susceptibility to moisture damage. 

There are many other tests for various applications. Some are used exclusively by a local or 

statewide transportation agency whereas others are documented in national standards. The key is 

recognizing that the durability of the aggregate has a big impact on the future performance of the 

pavement and that adequate testing of aggregates is needed in order to avoid unanticipated 

failures. 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

In addition, there are standard practice documents to help guide pavement practitioners through 

the process of selecting durable aggregates. For example, AASHTP PP 65-11, Standard 

Practice for Determining the Reactivity of Concrete Aggregates and Selecting Appropriate 

Measures for Preventing Deleterious Expansion in New Concrete Construction, can be used to 

guide a practitioner through the recommended testing sequence and to develop a reasonable ASR 

mitigation strategy for a given pavement project. 

As high-quality, durable aggregates become increasingly scarce, it is important to require only 

that level of durability that is needed for the specific application. Requiring “premium” 

aggregates for every application is not prudent, but instead is wasteful and contributes to the 

scarcity of those durable aggregates that are needed for the most severe environment, 

contributing to associated high economic and environmental costs. With the use of appropriate 

specifications, pavement durability can be ensured in a cost effective and more sustainable 

manner. 

Strategy: Reduce Impact of Virgin Aggregate Acquisition and Processing 

The first step in reducing the impact of virgin aggregate acquisition is to review environmental 

impact and remediation plans of different aggregate sources when issuing permits. This is 

typically conducted under NEPA guidelines or equivalent environmental impact review (EIR) 

and permit process conducted in many states. Most permit processes do not consider the 

potential for increasing the environmental impacts of locating quarries outside of the 

jurisdictional area caused by the need to transport aggregate over longer distances. A permitting 

process that establishes a broader analysis has the potential to reduce the likelihood of 

unintended consequences of transferring impact and therefore may improve the overall 

sustainability of aggregate acquisition. 

Aggregates must uniformly possess the size and properties needed to ensure performance within 

the pavement structure. Uniformity is controlled by the parent material, the extraction operation, 

transportation, and handling during construction. Other attributes of the aggregate can impact 

the required processing energy and emissions, including the type of equipment used and 

aggregate hardness. In particular, the type and size of the crusher has a large impact on the size 

and shape of the aggregate particles. Efforts must be exerted to optimize the crushing operations 

to create aggregates possessing the size and shape needed for the application while minimizing 

waste by avoiding the production of an inordinate amount of fines (known as crusher fines). 

Many aggregate sources require washing to be suitable for use in some applications and thus 

issues of water use, reuse, and quality must be addressed. Noise and dust from aggregate 

processing also have environmental and social impacts. 

Strategy No: Reduce Impact of Aggregate Transportation

High-quality aggregates often must be transported over long distances to meet localized 

demands. In some cases, these aggregates are being imported hundreds and even thousands of 

miles from other states and even from other countries (e.g., Mexico and Canada on the west 

coast, Bermuda on the east coast, Central America in the Gulf region). This can have a 

significant economic and environmental impact, especially if the major mode of transportation is 

by truck. Additionally, as previously mentioned, the expansion of existing aggregate pits and 

quarries and the development of new ones are becoming increasingly difficult, particularly in 

environmentally sensitive areas or in the vicinity of human habitation. Priorities for protecting 

local habitats and local communities must be weighed against the disruption of habitat and 

3-13
Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

communities elsewhere, along with increased environmental impacts associated with longdistance transport.

Approaches to reduce the impact of aggregate transportation include increased use of locally 

available materials. This includes both natural sources of aggregates as well as the use of locally 

available RCWMs including RCA, RAP, and ACBFS. A key element of this approach is to 

ensure that the aggregate meets the durability requirements specifically for the application. For 

example, aggregates used in lower layers of a pavement—whether an asphalt mixture (e.g., base 

and binder layers) or concrete (the lower lift in a two-lift concrete pavement)—do not need to 

possess the same resistance to wear and polishing as those used in the surface layer. This 

consideration can be used to reduce the need to import wear resistant aggregates from greater 

distances at a higher cost. 

Another approach is to minimize transportation impact by maximizing the use of marine/barge 

and rail transport and minimizing truck transport. As indicated previously in table 3-1, truck 

transport is significantly less efficient compared to marine/barge and rail transport. Facilities 

have been established in a number of urban centers that have marine access to specifically handle 

and stockpile aggregates, thus supplying the urban market. Further, continued growth in rail 

facilities will result in increased efficiency and reduced cost and environmental burden.

The final approach listed is to facilitate permitting of new aggregate sources and processing sites 

near major use areas. This approach will result in lowering the impact of aggregate transport, 

with the trade-off of potentially operating aggregate sources within more populated areas thus 

increasing negative social impact. The use of advanced aggregate acquisition and processing 

strategies can minimize this impact, but cannot completely alleviate it.

Issues/Future Directions/Emerging Technologies

Issues, future directions, and emerging technologies for enhanced sustainability of aggregates in 

transportation include:

• Increased shipping of aggregates by truck from long distances increases emissions, 

energy use, and noise, whereas local quarrying of aggregates has implications for land 

use, noise, dust, and other factors. As local aggregate sources are exhausted and the 

development of new sources stymied by community opposition, pressure will be exerted 

to use aggregates with less desirable characteristics. This could affect the long-term 

performance of pavements. 

• Increasing pressure to use higher volumes of RCWMs will likely renew pressure to make 

complete use of all materials from a construction site (e.g., current practice often is to 

waste crushed concrete fines, but their use may be highly encouraged in the future). 

Further, pressure to use non-conventional RCWMs (such as steel slag aggregate or 

recycled glass, for example) may also increase. If done without sufficient research, the 

increased use of RCWMs may compromise pavement performance unless it is 

accommodated in the design stage and utilizes effective construction practices. 

• As readily available sources of aggregates of the highest quality become exhausted, the 

use of “marginal” aggregates will increase. In many cases, these aggregates can be used 

without negatively affecting pavement life. Yet if such aggregates are used 

inappropriately, premature pavement failures will likely occur. 

3-14
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

• Specialty aggregates are at times needed to fulfill a specific need driven by a 

sustainability goal. For example, highly durable aggregates will be needed on an exposed 

aggregate surface, or a light-colored aggregate may be specified to increase surface 

reflectivity to reduce lighting requirements. In addition, other aggregates might be 

sought to improve the quality of the pavement material such as saturated, lightweight fine 

aggregate added to cementitious mixtures to enhance curing. 

Asphalt Materials and Mixtures

This section reviews the manufacture and 

transportation of asphalt materials. It summarizes 

generic asphalt mixture types and provides a brief 

overview of their uses, design, and plant operations. 

Sources of environmental impact are identified in 

the exploration, extraction, and transport of 

petroleum, the refining of petroleum into asphalt 

binder, the modification of the binder, the transport 

of all materials to the plant, and the combining of 

the materials at the plant where asphalt mixtures are 

made. Discussions of mixture design, 

proportioning, and plant operations are also 

included, while specific construction considerations 

are presented in chapter 5 (except as it is affected by 

materials selection and mixture proportions). 

Long-term binder availability and sources of cost 

variability are also discussed in this section. 

Introduction of recent innovations that are changing 

the face of the asphalt paving industry are presented, 

including WMA and high binder replacement 

mixtures using RAP and RAS.

Introduction

Asphalt materials, are sticky, black, highly viscous liquids or semisolids that consist of the 

heavier and more polar molecules that are present in many crude petroleum sources (AI 2007). 

Asphalt materials may be found in natural deposits where geological conditions have left 

primarily asphalt-type material mixed with fine dust material, such as Trinidad Lake (Trinidad, 

West Indies) and La Brea (Los Angeles), or distributed in rock formations, such as in west 

Texas. Some forms of these natural asphalt material deposits may be used directly in pavement 

construction and maintenance. 

However, the vast majority of asphalt material used for pavement comes from petroleum 

refineries that produce gasoline, kerosene, diesel, and lubricating oils, among other products. 

Petroleum residues from the distillation of crude oils are the starting materials for asphalt 

material production. Of the multitude of crude oils commercially available, only a limited 

number are considered suitable for producing asphalt materials of the required quality in 

commercial quantities. In general, heavy (specific gravity >0.9) crude oils are used to produce 

asphalt materials of the required quality. These types of crude oil tend to contain high sulfur 

contents (>1 percent by mass). Asphalt residues, as a fraction of suitable crude oils, typically 

range between 20 to 50 percent by mass, and a smaller percentage by volume because of the 

Asphalt Materials Usage and 

Economics

The U.S. used approximately 130 million 

barrels (23 million tons [21 million mt]) of 

asphalt binder and road oil in 2011, worth 

$7.7 billion, according to the US Energy 

Information Administration. In the recent 

peak years of 1999 and 2005, nearly 200 

million barrels were consumed (EIA 2011). 

According to the Asphalt Institute, 

approximately 83 percent of asphalt binder 

used in the U.S. in 2011 was used for 

paving purposes (Grass 2012). In the 

U.S., more than 92 percent of all paved 

roads and highways are surfaced with 

asphalt products. The U.S. has about 

4,000 plants producing asphalt mixtures 

with total production of about 452 million 

tons (410 million mt) in 2007 (NAPA/EAPA

2012) and about 396 million tons (359 

million mt) in 2010 (Hansen and Newcomb 

2011). The value of asphalt paving 

mixtures produced in the U.S. was 

estimated at $11.5 billion in 2007 (U.S. 

Census Bureau 2007a).

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

heavier specific gravity of asphalt materials

compared to other materials made from 

crude oil (Asphalt Institute and Eurobitume 

2011). 

Asphalt material is typically produced by 

removing the lighter hydrocarbon molecules 

through a combination of vacuum and heat, 

or by mixing with a solvent such as 

propane. The source of crude oil can have a 

significant effect on the energy and 

environmental impact of a specific asphalt 

material as the processes needed to extract, 

process, transport, and refine it to produce 

asphalt material and other products will 

vary with the source. 

Confusion sometimes arises in the 

terminology used to describe asphalt paving 

products. In North America, asphalt is 

taken to be the material refined from petroleum that is then combined with other materials to 

create products having a variety of names (e.g., asphalt concrete, hot-mix asphalt, warm-mix 

asphalt). In other countries, the petroleum-derived product is referred to as bitumen, and the 

term asphalt refers specifically to certain types of mixtures of bitumen and aggregate. 

Additionally, the word tar is sometimes incorrectly used as a colloquialism to refer to asphalt. 

Actually, tar is a specific material made from destructive heating of organic materials in a 

process called pyrolysis, and when produced from pyrolysis of coal or petroleum the resulting tar 

may have negative environmental impacts associated with its use (Mahler and Metre 2011; EPA 

2008). Tar mixtures were used for a small portion of the paving done in the United States up 

until the 1970s and in other countries (NAPA/ EAPA 2012). Tar was attractive as a paving 

material because it is not soluble in petroleum-derived fuels or lubricants and thus will not 

degrade in parking or service areas where it may be exposed to fuel or lubricant leaks or spills. 

As a result, it is still sometimes used as a surface sealant for asphalt parking lots and driveways, 

even though there are environmental and human health concerns associated with its use because 

of the carcinogenic nature of coal-derived tars. 

Asphalt Binders

In a complex refinery, a broad range of petroleum products is produced, with asphalt material

being a minor product compared to the more valuable transport fuels (Bernard, Blomberg, and 

Southern 2012). Plant design and operations vary for each refinery based on the markets for 

each product, the characteristics of the crude sources, and prevailing environmental and other 

regulations. Different processes, such as vacuum/steam or solvent deasphalting, can be used to 

break the hydrocarbons in crude oil into different products, with each having different 

environmental and energy impacts. Crude sources can have different composition depending on 

their location and to a lesser extent on the method of retrieval; this determines which crudes can 

be recovered economically (e.g., primary, secondary or tertiary recovery from wells, surface 

deposits, oil sands, hydraulic fracturing), but can also vary with time, depending on market 

prices for products and the availability and cost of different types of crudes. “Light” and “sweet” 

crudes, meaning respectively those with less asphalt material and less sulfur, command higher 

Major Issues: 

 Continued increase in price of petroleum, and 

thus asphalt, which is a finite resource.

 Appropriate use of polymer, rubber, and other 

types of binder modifiers.

 Depletion of high-quality aggregates needed 

for some type of mixtures.

 Specialization of mixtures for safety, noise, 

and structural considerations and their 

environmental and cost implications.

 Use of RAP and other RCWMs including 

asphalt shingles, recycled tire rubber, and 

sulfur.

 Environmental, social, and cost implications 

of mixture design and durability.

 Future binder availability and alternatives.

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

prices because they produce more transport fuels and are generally less costly to refine. In 

assessing the contribution of refinery operations to the energy and emission of asphalt 

production, storage of asphalt should also be considered, since asphalt must often be kept at a 

constant high temperature by heating to pump it through the refinery, in and out of storage tanks, 

and while in truck or rail transport. This is particularly important in cold climates. Blending of 

different grades of asphalt to meet specifications, and the production, milling, and blending of 

polymers, rubber, and other asphalt modifiers also consume energy and produce emissions. 

Not all petroleum refineries produce asphalt. Since 1980, the refining industry’s emphasis has 

shifted from growth of operable crude oil distillation capacity to investment in downstream 

(secondary) processing units, thereby increasing the overall level of refinery complexity 

(Lidderdale, Masterson and Dazzo 1995). Secondary processing units, such as use of delayed 

cokers, catalytic crackers, and hydrocrackers, are used to break the portion of the oil that would 

otherwise be used for asphalt to improve the yields of lighter products. As of January 2013, 56 

of 131 oil refineries in the U.S. produced asphalt (EIA 2013). 

Asphalt Paving Materials

Asphalt is produced in different forms for use in pavements, which mostly have to do with how 

the viscosity of the asphalt is reduced (i.e., made more flowable) for construction so that it can 

coat aggregates or be sprayed onto the surface before reverting to a more viscous or semisolid 

state prior to opening to traffic. A schematic illustrating the production of asphalt cement is

shown in figure 3-4. 

Figure 3-4. Schematics illustrating straight-run distillation of asphalt within a complex refinery 

(Asphalt Institute and Eurobitume 2011). 

The following defines some basic terminology as applies to asphalt paving materials (note that 

most asphalt and asphalt-aggregate materials have a number of nearly synonymous terms and 

nomenclatures, varying by specifying agency and sometimes changing over time) (AI 2007): 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

• Asphalt cement, also referred to as neat asphalt, asphalt, or asphalt binder, is the portion 

of the crude oil that is used directly in paving. In this form, it is made flowable by 

heating and then reverts to a semisolid state as it cools. Asphalt cement is used as the 

binder in hot-mix asphalt, warm-mix asphalt, open-graded asphalt, stone mastic asphalt, 

chip seals and as a tack coat. It is the asphalt material used to produce asphalt emulsion, 

polymer-modified asphalt, rubberized asphalt, and asphalt cutback. 

• Asphalt emulsion is made by shearing asphalt into microscopic droplets (0.5 to 10 

microns) which are mixed with water (typically in ratios between 40:60 and 60:40 

asphalt:water) and an emulsifying agent (very small percentages) that keeps the drops in 

suspension in the water. The asphalt reverts to the semisolid state when the emulsifying 

agent is neutralized or “breaks,” allowing the particles to join together, which is followed 

by evaporation of the water. Asphalt emulsions are used extensively for surface 

treatments such as fog seals (emulsion and other hydrocarbons), sand seals (emulsion and 

fine aggregate), microsurfacings (emulsion, water, fine aggregate, mineral filler, other 

additives) and slurry seals (emulsion, fine aggregate and cement). Polymer-modified 

asphalt and rubberized asphalt emulsions are also used for these and other applications. 

Asphalt emulsion can be mixed with aggregate at an asphalt mixing plant to create coldmix asphalt or in situ for cold in-place recycling (CIR).

• Asphalt cutback is made when asphalt cement is dissolved in a petroleum-based solvent. 

Solvents include gasoline or naphtha (rapid curing cutback), kerosene (medium curing 

cutback) or low-volatility oils (slow curing cutback). These materials are liquid at 

ambient temperatures with the asphalt cement being reconstituted as the solvent 

volatilizes after the cutback is spray applied or mixed with aggregates. The modern use 

of asphalt cutbacks has been curtailed as they produce significant volatile organic carbon 

(VOC) air emissions, but they are still used in some locales, especially during cooler 

temperatures or in wetter climates when asphalt emulsions become ineffective. Asphalt 

cutback can be mixed with aggregate at an asphalt mixing plant to create cold-mix 

asphalt or in situ for CIR.

• Hot-mix asphalt is produced when heated asphalt cement is mixed with heated, densegraded aggregates in a plant to achieve a mixture at temperatures of approximately 275 

°F to 329 °F (135 °C to 165 °C). HMA is often used as the main structural layer as well 

as the surface layer in many kinds of asphalt, composite, and semi-rigid pavements. 

• Warm-mix asphalt represents a broad range of technologies used with asphalt concrete

that allow the mixture to stay workable and compactable at lower temperatures. WMA 

can be used to reduce the mixing temperature and facilitates paving in cooler weather, 

and also allows longer transportation distances. Utilization of WMA technology can 

reduce compaction temperatures by approximately 25 to 80 °F (14 to 25 °C) (PAPA 

2011). The amount of reduction depends on the WMA technology used and the 

characteristics of the mix, plant, climate, lift thicknesses, and hauling distance. 

• Open-graded asphalt is made when asphalt cement is mixed in a plant with the aggregate 

gradation missing portions of the smaller-sized particles. Open-graded asphalt placed as 

a thin surface course on top of a traditional asphalt concrete improves surface friction and 

reduces tire-pavement noise. Open-graded asphalt can also be used to create a permeable 

base if used below an impervious surface layer or it can be used as the full depth of the 

paved surface as part of a pervious pavement system. 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

• Stone mastic asphalt (SMA) is created when 

asphalt cement is mixed with gap-graded 

aggregates. SMAs are used almost 

exclusively as surface courses as they are 

highly resistance to pavement deformation 

(rutting) in the wheelpaths and top-down 

cracking. 

• A tack coat is an asphalt cement, asphalt 

emulsion, or asphalt cutback sprayed onto a 

paved surface to assist in bonding asphalt 

concrete layers together during construction. 

• A prime coat is used to waterproof and bind 

together aggregate base surfaces. 

Sometimes prime coats are made with 

asphalt emulsions having up to 30 percent 

slow curing solvent to keep the asphalt 

liquid longer. Slow curing cutbacks are also 

used as prime coats. 

• Chip seals are created when an asphalt 

cement, asphalt emulsion, or asphalt cutback 

is sprayed onto a granular base or onto an 

existing pavement surface and followed 

with the application and embedment of 

single-size aggregate “chips.” Rubberized 

asphalt is also used for chip seals. 

• Crumb rubber modifier (CRM) is created by 

grinding recycled tire rubber after stripping 

out steel reinforcement. CRM can be mixed 

with asphalt cement, natural rubber, and 

other ingredients to produce rubberized 

asphalt (ASTM specifies that rubberized 

asphalt has a minimum 15 percent recycled 

rubber by mass; AASHTO does not 

currently have a specification but is working 

on developing one [RAF 2013]). 

Rubberized asphalt is used in different types 

of asphalt-aggregate mixtures for structural 

and surface layers, and for chip seals. CRM 

is also used with polymers in terminal blend 

rubberized asphalt, although with no 

required minimum CRM content and more 

finely ground particles (Hicks, Cheng, and 

Duffy 2010). 

• Polymer-modified asphalt (PMA) is created 

when, asphalt cement is mixed with a 

number of different polymers to produce a binder with the properties needed for different 

applications, most typically with enhanced high temperature performance characteristics. 

Co-Product Treatment for Asphalt 

Materials

Asphalt is one of many co-products 

produced in oil refineries. Because of the 

importance of refinery products on the 

environment and economy, many of 

these products have been studied using 

LCA. Each study has had to select a coproduct treatment approach. Nearly all 

rely on allocation, although some have 

combined subdivision methods with 

allocation by distinguishing processes 

within the refinery that can be attributed 

to particular products while relying on 

allocation by energy or mass to partition 

oil extraction and transport impacts and 

other processes that cannot be 

reasonably partitioned. Since different 

refinery products have different fuel 

contents, weights, or economic values, 

the method of allocation can have a 

significant effect on the calculated impact. 

Different allocations can be applied to 

different steps in the asphalt production. 

The extraction and transport of the crude 

to the refinery is similar for all the 

products obtained from the crude. At the 

refinery level, depending on the refinery 

setup, some processes may be common 

to some products while other processes 

are unique to a single product. 

Most LCA studies use mass allocation. 

To help understand the impact, sensitivity 

analyses are often performed in LCA 

using alternative allocation methods.

Wang, Lee, and Molburg (2004) suggest 

that the different approaches for 

allocation for different refinery products 

can lead to differences in assigned 

environmental impacts of up to 25 

percent. A more recent LCI considering a 

typical set of crude sources in Northern 

European refineries has been prepared 

by Eurobitume for conventional asphalt 

binders. A hybrid approach using 

allocation based on mass for parts of the 

process and economic value for other 

parts was used to determine the 

environmental impacts for the cradle-togate inventory (Eurobitume 2012; 

Bernard, Blomberg, and Southern 2012).

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Polymer-modified asphalt are used in different types of asphalt-aggregate mixtures for 

structural and surface layers, and for chip seals. As mentioned, CRM is also used with 

polymers in terminal blend rubberized asphalt (Hicks, Cheng, and Duffy 2010). 

• Cold-mix asphalt used as a storable patching material most often uses cutback asphalt 

and/or asphalt emulsion mixed with aggregate and/or RAP. 

• Cold in-place recycling and full-depth reclamation produce materials that involve mixing 

RAP that is created in-place with various materials, including asphalt emulsion, foamed 

asphalt, cement, lime, and other cementitious materials. These treatments are discussed 

in more detail in chapters 7 and 8. 

Mixture Design of Asphalt Concrete

Mixture design for asphalt concrete generally requires the following steps: 

• Identification of the function of the pavement layer (e.g., surface drainage layer, surface 

layer, structural layer, fatigue resistant bottom layer, subsurface drainage layer, base for 

concrete or asphalt pavement), and selection of appropriate mixture type (e.g., densegraded asphalt concrete, SMA, open-graded asphalt concrete, rich-bottom asphalt 

concrete). A decision on whether to use a WMA technology is often also made at this 

juncture. Open-graded asphalt mixtures used for thin permeable layers on pavement for 

high-speed traffic are also used as the surface layers for fully permeable asphalt 

pavements (NAPA 2008). 

• Identification of the asphalt material to be used appropriate to the mixture type 

(conventional, polymer-modified, rubberized, terminal blend rubberized) and the 

selection of the grade of asphalt. Most paving asphalt used in the U.S. is specified in 

terms of its Performance Grade (PG), which considers workability, the high-temperature 

properties important for rutting, and the low-temperature properties important for lowtemperature cracking as the binder ages.

• Identification of the aggregate sources having specified properties for the application and 

testing of volumetric properties to determine the aggregate gradation. 

• Selection of the final binder content based on relationships between the binder content 

and other mixture proportions. These include the risks of too much binder, such as 

rutting and shoving, which are predominately an issue in the first few years of service 

before the asphalt stiffens as it ages. Also considered are the risks of too little binder, 

which include early cracking, raveling, water damage, and inadequate compaction, all of 

which have additional negative impacts that affect the long-term performance of the 

mixture. 

• Consideration of the amount of RAP or RAS included in the mixture, as these affect the 

properties of the blended asphalt binder (composed of virgin and recycled binder), the 

aggregate characteristics and gradation, and the volumetric proportions associated with 

performance. 

• On some projects where the risks warrant additional cost and time, advanced materials 

characterization is performed on the draft final mixture design to help determine whether 

it meets the requirements for the project (called performance-related testing). The 

properties measured in many of these tests, such as the complex modulus, can also be 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

used as inputs to mechanistic-empirical pavement design methods, which are discussed in 

more detail in chapter 4. 

Two strategies for reducing the environmental impacts of asphalt mixtures are to:

1. Increase their performance and therefore increase the time between future maintenance 

and rehabilitation treatments. 

2. Decrease the negative impact of materials in the mixture by reducing the amount of 

virgin asphalt binder and aggregate through the use of recycled materials such as RAP, 

RAS, and recycled tire rubber, by minimizing or eliminating those additives that may 

increase the impact of material production (polymers, virgin rubber, or chemical WMA

additives1

1 Note that there are a number of WMA technologies that have very different environmental impacts. Those based on 

chemical additives often have a greater benefit in maintaining compactability at lower temperatures than those based on 

mechanical water foaming, but chemical additives may also have a higher environmental impact during their production. 

However, most chemical WMA additives are used in very small amounts, typically 1 percent by weight of asphalt cement 

(~0.24 gal/yd3 [1.2 l/m3]), and thus the overall environmental impact is thought to be small. 

, for example), and by changing specifications to permit increased use of 

locally available but lower quality aggregates. Inherent in the use of these approaches is 

that overall pavement performance is not reduced or compromised. 

These two strategies may contradict each other, with one calling for enhanced durability and the 

other for the use of potentially less durable materials, and therefore must be balanced. Solutions 

that are able to achieve both longer life and a reduction in the amount of virgin materials offer 

the most promise for improving sustainability. 

One type of distress that can substantially shorten the life of asphalt pavements is moisture 

damage, which is amplified when water is able to penetrate the asphalt pavement matrix. Certain 

types of aggregates carry a much greater risk of moisture damage than others. Lime and liquid 

anti-strip chemicals are two additives that can reduce the susceptibility of mixtures to moisture 

damage. Lime is typically added at about 1 percent by weight of mixture (~37.3 lb/yd3 [22 

kg/m3]), whereas liquid anti-strip agents are typically added at about 1 percent by weight of 

asphalt cement (~0.24 gal/yd3 [1.2 l/m3]). Each additive has its own particular economic and 

environmental impacts. Lime, for example, has a relatively high GHG emissions footprint as its 

production requires calcination of calcium carbonate, which uses heat to liberate fossil carbon 

dioxide, leaving calcium oxide. Liquid anti-strip additives are made from a variety of chemicals, 

each of which has its own impact on the environmental impact of the mixture. 

Mixture Design of Other Asphalt Road Materials

The design of materials for full-depth reclamation (FDR, as well as other forms of in-place 

recycling), chip seals, and other road materials containing asphalt follow a similar process as that 

described for asphalt concrete above: identification of the function of the material; review of 

alternative aggregates, asphalt binder, and other materials to be included in the mixture; selection 

of final materials based on the existing structure, climate, traffic, and applicable specifications; 

and optimization of the proportions. For example, chip seals will include consideration of 

aggregate size, shape, gradation and mechanical durability, determination of whether to use 

sprayed asphalt or an emulsion and whether it will include polymers or rubber, and selection of 

the final application rates for the asphalt and aggregate. For full-depth reclamation, the mixture

design will include characterization of the in-place materials, selection of stabilization materials 

3-21

 
Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

(as appropriate), such as cement, foamed 

asphalt (typically with a small amount of 

cement as well) or asphalt emulsion 

(conventional and fast curing), and final 

proportions to achieve desired properties that 

can be tested in the laboratory. FDR is most 

commonly used on low- to medium-volume 

routes, but has been used on some high-volume 

routes such as I-80 in California (over a 

cement-treated base) and I-81 in Virginia. 

The same approach should be used when 

designing these materials, attempting to find the 

balance between specifying the use of higher

quality materials (which often have higher initial 

cost and environmental impact) and the use of 

lower quality, lower cost materials (with a lower 

environmental impact but potential performance 

reductions). Thus, the entire life cycle must be 

considered, not only from an economic 

perspective but also from an environmental 

perspective. The ideal solution will be a 

function of the materials, traffic, climate, and 

construction processes. 

Mechanistic-empirical (ME) design procedures 

can be used to calculate the anticipated effects 

of material choices on pavement performance, 

given detailed material properties, pavement 

structure information, traffic loadings, and 

climatic factors. It can therefore be used to 

investigate the trade-offs due to changes in 

material that affect the material properties and 

to see how those changes affect the structural 

capacity of the pavement over time. If LCA is 

combined with ME design, together they can 

be used to calculate the net environmental 

impact of changing materials properties and 

performance over the life cycle. Chapter 4 

includes more discussion on the use of ME 

design, and how materials properties are 

considered in the structural design of 

pavements. 

Warm-Mix Asphalt Technologies

Almost without exception, increasing the density 

and decreasing the variability of asphalt materials 

will improve performance. WMA is a relatively 

new technology being used to increase overall 

Full-Depth Reclamation with Foamed 

Asphalt

The process of full-depth reclamation (FDR) 

involves the pulverization of the existing 

asphalt surface and the recyclable (unbound 

or chemically stabilized aggregate) 

underlying materials, to a maximum depth of 

12 to 18 in (305 to 457 mm) depending on 

available compaction equipment and 

subgrade support, while simultaneously 

mixing it with a binding material, or less 

frequently compacting it without stabilization 

as aggregate base. Binding materials can 

include a combination of foamed asphalt, 

cement filler, and water, cement and water, 

emulsified asphalt, or other cementitious 

materials. The mixture is graded, 

compacted, and overlaid after recycling. 

One type of full-depth reclamation is with 

foamed asphalt (FDR-FA), which is created 

when cold water, along with compressed air, 

is injected into hot asphalt in a specially 

designed chamber. The water becomes 

steam when it undergoes the sudden 

increase in temperature, which becomes 

trapped in tiny asphalt binder bubbles. This 

results in a thin-film, high-volume asphalt 

foam with reduced viscosity and increased 

coating potential. The foaming state is 

temporary, and within a few minutes the 

asphalt binder will assume its original 

properties. Foamed asphalt has been used 

effectively as a stabilizing agent in full-depth 

reclamation (source: 

http://www.pavementinteractive.org/). 

FDR-FA has sustainability benefits for lower 

volume roads (AADT <20,000) including

(Caltrans 2012; Fu 2010):

- Reduced life-cycle costs due to longer 

service life. 

- Lower environmental impact due to 

reduced use of virgin aggregates and 

reduced landfill usage. 

- Increased structural capacity. 

- Reduced use-phase costs through 

expedited construction and simplified 

staging. 

Caltrans (2012) and Jones, Harvey, and 

Halles (2008) provide further details on this 

topic.

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

density and lower variability of density, and offering the possibility of lower production temperatures 

and less initial environmental impact of materials production and construction. 

As discussed in chapter 5, increased asphalt concrete density is a result of good specifications and 

the effective quality assurance (QA) practices regarding compaction that are well known in the 

industry. This requires attention from both the owner and the contractor. Improved compaction 

requires no additional materials, and usually requires no additional equipment usage, but rather 

careful attention to details and effective management of the factors controlling success. Unlike 

changing mixture design parameters (e.g., changing the binder content in an asphalt concrete

material, using a softer binder to improve reflection cracking resistance in an asphalt concrete

material, or increasing the cement content of a FDR material), increasing the density of a material by 

compaction will improve both the rutting and cracking resistance. Further discussion of compaction 

and other construction operations is included in chapter 5. 

As previously described, WMA technologies are used with asphalt concrete to allow the mixture 

to stay workable/compactable at lower temperatures. WMA may be used for a number of 

reasons, including reducing mixing temperature, facilitating paving in cooler weather, or 

allowing longer transportation distances (or combinations of all three). 

Most asphalt mixing plants in the U.S. have shifted from diesel or other fuel oil and are now 

fueled by natural gas, which is primarily used for heating aggregate and asphalt for mixing, and 

secondarily for drying aggregate (EPA 2000; Cleaver 2011; Carbon Trust 2010). In recent years, 

a number of asphalt mixing plants have begun burning recycled motor oil as a fuel for mixing 

and drying, which disposes of this otherwise hazardous material in a safe manner while at the 

same time offsetting the use of other fossil fuels (EPA 2012). WMA can be used to significantly 

reduce mixing temperatures, with the amount of reduction depending on the WMA technology 

used and the characteristics of the mixture, plant, climate, lift thicknesses, and hauling distance 

(D’Angelo et al. 2008). WMA technologies will reduce the environmental impact of asphalt 

mixture preparation and paving if they are used to reduce mixing temperature, thus decreasing 

the fuel consumed to heat the asphalt mixture. The total environmental impact of the use of 

WMA will depend on the technology used as technologies that use waxes or polymers have 

associated environmental impact of the additive itself that must be considered, but are also 

generally more effective than mechanical foaming WMA technologies. Keeping aggregate and 

RAP sources dry also helps to reduce the energy needed to dry aggregates (Cleaver 2011; 

Carbon Trust 2010). 

The estimated total amount of WMA in the U.S. has grown rapidly over the past several years as

shown in figure 3-5. This increase in use reflects the key advantages of using WMA: reducing 

the fuel used to heat the mixture at the plant, improved mixture compactability, and increased 

flexibility during the construction phase allowing longer haul distances and extending the paving 

temperature range. 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Figure 3-5. Estimated tons of WMA usage by industry sector 2009-2011 (Hansen and 

Copeland 2013). 

3-24

WMA technologies are generally grouped into three families: chemical admixtures, chemical 

foaming agents, and mechanical foaming, the latter of which is most commonly used in the U.S. 

(Hansen and Newcomb 2011). Chemical admixtures can further be divided into those that 

change the melting point of asphalt and those that change the coating characteristic of the 

asphalt. Chemical foaming agents add a chemical that does not change volume as it releases 

water into the mix. Mechanical foaming of the asphalt cement is accomplished either before the 

cement is added to the aggregate in a special foaming chamber or after by introducing moisture 

in the fine aggregates. All of these technologies allow the aggregate particles to orient 

themselves at lower than normal temperatures while being compacted. The reduction in mixing 

temperature at the plant depends on the WMA technology used, the materials, the haul distance, 

and the weather. Current research suggests that WMA does not significantly affect the long-term 

performance of the pavement, provided all other aspects of mixing and compaction are done 

appropriately. If asphalt mixing plants are adjusted to use WMA technologies by reducing 

mixing temperatures, then WMA can potentially reduce energy use. Because good asphalt 

compaction has such a significant effect on performance, it is possible that the major benefit of 

WMA is as a compaction aid resulting in increased pavement longevity with longer times 

between maintenance and rehabilitation activities. 

Research regarding environmental benefits for different situations is ongoing. LCIs of WMA 

chemicals, which would permit consideration of the environmental impacts of their production in 

an LCA, have not been published to date. Mechanical foaming only uses relatively small 

amounts of water and involves the initial installation of foaming equipment, which should have 

minimal environmental impact.
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Over the years, there have been a number of studies 

looking at air emissions and exposure of 

construction workers to asphalt concrete materials

(see, for example, NAPA/EAPA 2012). While

WMA technologies are used to reduce the mixing 

and compaction temperatures of asphalt mixtures, 

they can also reduce the emissions associated with

the hot material that sometimes cause short-term 

worker irritation during mixing and laydown (there 

are very few emissions released after initial 

compaction) (Farshidi et al. 2011). This is 

especially helpful for rubberized mixtures that 

otherwise can sometimes generate enough fumes 

that workers require respirators when paving

(Farshidi et al. 2011). Worker exposure and 

leachate into water are issues to consider when 

adding any material other than conventionally 

refined asphalt and aggregate to asphalt concrete. 

Although it is far more difficult to document, and 

less conspicuous than introducing a new material, 

increasing the density and decreasing the variability 

of asphalt concrete offers opportunities for 

significant improvements in performance and 

consequent environmental benefits. The benefits 

include less use of currently used materials, which 

may be amplified in high-traffic situations. 

Implementation of good QA practices requires 

investments in human capital and organization, 

which may pose a particular challenge for smaller 

contractors and local governments where 

specialized pavement expertise for effective QA is 

less available. Moreover, the benefits that come 

from these investments may be difficult to 

communicate.

Recycling and Asphalt Road Materials

RAP is an important source of aggregate and asphalt 

binder for asphalt paving projects. RAP can be used 

as a replacement for virgin aggregate base, which 

does not take full advantage of the potential 

contribution of the asphalt coating the aggregate as 

a binder. In general, recycled materials should be 

used for the “highest use,” which would be first as 

replacement for virgin asphalt and aggregate in new 

asphalt concrete, followed by use in recycled cold-mix materials, followed by use as aggregate 

base or aggregate in concrete. The asphalt binder in asphalt concrete carries much of the total 

environmental impact of the mixture because of the impact of petroleum acquisition and refining. 

Use of RAP in asphalt concrete replaces not only virgin aggregate, but the RAP binder is reused 

Highest Use for Recycled 

Materials: Core Concepts

Recycling of used materials can be a 

good strategy to reduce the need for new 

materials. Examples are the use of RAP 

in new asphalt pavement or RCA in new 

concrete pavement. But it extends 

beyond aggregates. Depending on the 

material, secondary uses can include the 

use as fuel (for example rubber tires), 

feedstock (for example RAS to displace 

asphalt binder), or material resource (for 

example RAP or RCA). In addition to 

that, the material can be used in the 

original function (aggregate in asphalt 

mixture), or in a different function 

(aggregate in the base). When 

considering sustainability, the question 

comes up: what is the highest use for 

recycled material? 

The first step to realize is that defining 

the highest use is a project-based (or at 

most a regional) decision. The second 

step is to make sure that whatever use is 

intended, it has to perform from a 

technical perspective. If adjustments 

need to be made, for example to a mix 

design, then those adjustments need to 

be taken into account when making this

decision. The next step is to look at other 

relevant sustainability parameters 

through an LCCA approach, an LCA 

approach, and a rating systems 

approach. The highest use can be 

synergetic between these three systems, 

but sometimes it is not. This is what is 

referred to as trade-offs. Another 

consideration in defining the highest use 

is the starting point at which whatever 

decision is made, and that it should 

always be made with a life cycle 

perspective. Not setting appropriate 

systems boundaries and leaving out lifecycle phases can lead to missing 

important trade-offs. The implementation 

approach is presented in a sidebar 

discussion in chapter 8.

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

as binder, at least in part, thereby reducing the amount of virgin binder needed in the new asphalt 

concrete. Thus, RAP use in new asphalt concrete reduces the need for virgin asphalt and 

aggregate, both non-renewable and finite materials, making asphalt concrete the highest use (i.e., 

its use displaces consumption of high impact and non-renewable materials) for this material. 

The amount of RAP used in asphalt mixtures was 66.7 million tons (60.5 million mt) in 2011, a 

19 percent increase over 2009 (56 million tons [50.1 million mt]) and about a 7 percent increase 

over 2010 (62.1 million tons [56.3 million mt]). Assuming 5 percent liquid asphalt in RAP, this 

represents approximately 3.6 million tons (3.3 million mt), of virgin asphalt binder conserved, or 

about 12 percent of the total binder used in 2011 (Hansen and Copeland 2013). 

Looking at U.S. data from 2011 (see figure 3-6), approximately 87 million tons (79 million mt) 

of RAP that was milled from existing pavements was run through asphalt mixing plants that 

year, with approximately 74 million tons (67 million mt) of the 81 million tons (73 million mt) of 

RAP (92 percent) recycled into new asphalt concrete materials. For the years 2009 through 

2011, RAP that was not recycled into asphalt concrete was used for aggregate base (less than 10 

percent annually) and cold mix (less than 3 percent annually). Less than 0.1 percent landfilled

(Hansen and Copeland 2013). These figures do not consider asphalt pavement recycled in place. 

Figure 3-6. RAP use in the U.S., 2009 through 2011 (adapted from Hansen and 

Copeland 2013). 

The characteristics and quality of the aggregate and asphalt in the RAP are dependent on the 

quality of the original materials, any additional patching or other maintenance materials 

recovered during milling, and any additional processing that occurs during and after milling and 

reuse. The effects of moisture-sensitive aggregate, rubber, polymers, or other ingredients in the 

milled material have not been the subject of intensive research. The variability of the 

characteristics and quality are dependent on the variability in the milled material, and the amount 

of crushing, sizing, and reblending that is done to homogenize the material at the plant. 

56.0

6.2

1.5 0.7 0.1

62.1

7.3

1.6 0.8 0.0

66.7

4.9

0.2 0.7 0.3

0

10

20

30

40

50

60

70

80

Tons Used in

HMA/WMA

Tons Used in

Aggregate

Tons Used in

Cold Mix

Tons Used in

Other

Tons Landfilled

2009 2010 2011

3-26
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

The asphalt binder in RAP, called the residual binder, is generally stiffer and more brittle than 

virgin asphalt because it has been oxidized through previous heating in the mixer and its 

atmospheric exposure during service. The latter is particularly true for RAP recovered from 

older pavements, for RAP in hotter climates, and for RAP obtained from layers near the surface 

where some of the lighter molecules may have volatilized. The aged residual asphalt binder will 

stiffen the new mixture, generally improving rutting resistance but potentially increasing the 

tendency for top-down cracking when used in surface mixtures unless it is well managed through 

specifications. The stiffer, aged residual binder in RAP can help reduce bending and tensile 

strains that contribute to bottom-up cracking when used in thicker layers below the surface. 

The degree to which the residual binder on the RAP particles blends with virgin asphalt has an 

important effect on the properties of the new mixture and its performance. The amount of 

blending is dependent on the properties of the new asphalt, how long and at what temperatures 

the RAP is heated during its processing, the mixing time, and whether softening agents are 

added. For example, there is very little blending in cold-mix recycling technologies. The 

amount of blending that actually occurs in asphalt concrete, its effect on the mixture properties, 

and how much of the asphalt in the RAP can be considered as replacement of virgin asphalt is a 

subject of research at this time.

The ability to control particle size and avoid segregation during mixing with virgin materials in 

an asphalt plant is largely dependent on whether the RAP is sized, or fractionated, and binned

into different consistent size gradations (Bonaquist 2011; Christensen and Bonaquist 2006). 

Controlling particle size is more difficult during in-place mixing processes. 

RAP has been used for up to 50 percent replacement of virgin materials in dense-graded asphalt 

concrete. However, where mixture performance is most critical, such as in asphalt surface 

layers, the level of replacement is often lower. Many agencies place limits on how much RAP 

can be used for different applications, depending on their assessment of risk. In general, 

replacement at up to 15 percent is considered to have minimal effects on properties. Most state 

highway agencies allow up to 15 or 30 percent replacement for structural layers, and some also 

allow those amounts for surface layers. The average RAP content in asphalt concrete mixtures in 

the U.S. in 2009/10 was about 13 percent for state DOT mixtures, 15 percent for other agency 

mixtures, and 18 percent for commercial and residential paving mixtures (Hansen and Newcomb

2011). Since most asphalt used in asphalt concrete is specified in terms of its PG grade (which 

accounts for the binder’s contribution to rutting, thermal cracking, and fatigue cracking), the 

method of estimating these properties for the blended (or partially blended) residual and virgin 

binder is critical. 

Increasing the amount of virgin binder replaced through mobilization of the residual binder as 

part of the new blended binder greatly reduces the environmental impact of the mixture. These 

benefits are offset somewhat by the additional energy needed to heat the virgin aggregate in the 

blended mixture to higher than normal temperatures for mixing, because the RAP cannot be 

heated to normal mixing temperatures without burning the residual asphalt. Instead, for RAP 

contents up to about 35 percent, the virgin aggregate must be heated to temperatures of 420 °F to 

500 °F (215 °C to 260 °C) compared to 275 °F to 330 °F (135 °C to 165 °C) for a mixture made 

entirely with virgin materials (Kandhal and Mallick 1997; AI 2013). For higher RAP contents it 

is necessary to ensure that the RAP is dry (stockpiles should be covered) to avoid heat loss in 

removing water from RAP. Transportation of RAP for use in locations where it is not readily 

available must also be considered when evaluating energy and environmental impacts because 

long haul distances by truck have significant cost and environmental impacts. 

3-27
Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

As is discussed in more detail in chapter 7, most 

in-place recycling is done “cold” or “warm.” 

CIR consists of milling the top 3 inches (76 mm) 

of the existing pavement, mixing with asphalt 

emulsion or cutback and asphalt cement, 

placement and compaction of the mix, followed 

by a thin asphalt overlay or surface treatment. It 

is used in lieu of milling and replacement with 

asphalt concrete. CIR reduces the thickness of 

the asphalt concrete overlay needed (or may 

eliminate it altogether) to obtain the desired life. 

Full-depth reclamation, which is discussed in 

detail in chapter 8, is used for badly cracked 

asphalt pavement where overlays and surface 

treatments will not provide much additional life. 

It consists of pulverizing all of the existing 

asphalt and part of the aggregate or treated base 

and subbase beneath it up to depths of 

approximately 18 inches (457 mm), compaction, 

and then the placement of an asphalt overlay. 

FDR can use the pulverized material as an 

untreated aggregate base, or more commonly, a 

stabilizer (e.g., small amounts of cement, asphalt 

emulsion with some cement, or foamed asphalt 

with some cement) is introduced during the 

pulverization process. The stabilized FDR 

eliminates reflection cracking, reducing the 

thickness of the asphalt overlay needed, and can 

potentially provide a long life stabilized base 

with no need for new aggregate (see chapter 8 

for more details on FDR). 

Hot in-place recycling (HIR) is sometimes 

performed on existing asphalt pavements, where 

about 2 inches (51 mm) of the existing pavement 

is heated, milled, mixed with virgin materials, 

placed and compacted, all in one pass of an 

equipment train. Chapter 7 provides more 

information on HIR. 

Use of CRM in Asphalt Binders

The inclusion of CRM from recycled tires in 

asphalt binders, primarily as rubberized 

asphalt, has been the subject of extensive 

research starting in the 1980s. It is used 

extensively by a few states, primarily in gapgraded and open-graded asphalt concrete

and rubberized chip seals. Rubberized 

asphalt includes at least 15 percent recycled 

tire rubber. Accelerated pavement testing 

has demonstrated that a rubber-modified 

asphalt mix on top of a dense-graded mix 

can delay or arrest further propagation of 

bottom up cracks through the rubber 

modified mix to the surface (Gibson et al. 

2012; Jones, Harvey, and Monismith 2008). 

Field studies in California indicate that 

rubberized open-graded asphalt mixtures 

have superior performance to open-graded 

mixtures with conventional binders in terms 

of raveling, cracking, and noise (Rezaie, 

Harvey, and Lu 2012). These mixtures have 

higher binder contents and are mixed at 

temperatures that are approximately 18 to 36 

°F (10 to 20 °C) higher than conventional 

binders, both of which increase their 

environmental impact per unit volume 

(Bearden and Le 2011). The net effect with 

the thickness reduction and performance can 

be calculated through an LCA. An LCA that 

considered GHG and energy use in one case 

study demonstrated that full thickness of 

asphalt concrete and half thickness of gapgraded rubberized asphalt concrete in a thin 

overlay with similar expected performance 

had nearly the same materials production 

impacts, but the half thickness rubberized 

mix had a lower construction phase impact 

due to the reduced mass of material that had 

to be transported to the site (Wang et al. 

2012). Similar calculations can be made for 

terminal blended rubberized asphalt, which is 

used in some asphalt concrete mixtures and 

in chip seals. The future effects of increasing 

quantities of rubberized asphalt in RAP 

stockpiles on mixture design and 

performance have not yet been investigated 

by researchers. Methods need to be 

developed to determine how much 

rubberized material exists in a given RAP 

stockpile as well as understanding of how 

this material will affect the properties of the 

new asphalt mixture.

3-28

RAS, obtained from the roofing industry, is 

another source of recycled asphalt for asphalt 

concrete. On average, RAS contains about 20 

percent asphalt binder by mass compared with 

about 5 percent for RAP, along with aggregates, 

mineral filler, and fibers. Approximately 1.3 

million tons (1.2 million mt) of RAS were used 

in asphalt concrete in 2011 (Hansen and 
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Newcomb 2011), with RAS usage in 2011 replacing about 0.42 million tons (0.38 million mt) of 

asphalt. To create RAS, shingles are shredded and sorted for use. If shingles were obtained 

postconsumer (i.e., as part of a roof tear off and replacement), additional sorting is necessary to 

remove nails and other impurities. Typical use is limited to about 5 percent by mass of the total 

mixture because of potential for variability, the higher stiffness of roofing asphalt compared to 

asphalt used for pavements, and the degree to which RAS blends with virgin and residual RAP 

asphalt. A number of high profile projects have been constructed with mixtures containing both 

RAS and RAP, including an overlay of Michigan Avenue in Chicago (Illinois Interchange 2012). 

RAS/RAP mixtures are also being used by the Illinois Tollway to lower costs and reduce the 

environmental impacts of pavement materials. The EPA (2013a) recently performed a limited

LCI and LCA on the use of RAS, evaluating only GHG emissions, and concluded that there are 

environmental benefits to the use of recycled asphalt shingles in asphalt production for use in 

road construction, and that the addition of RAS to pavement mixtures containing RAP helps 

further increase environmental reductions relative to the baseline of using virgin asphalt. 

Various polymers are used to improve the viscoelastic properties of asphalt binders, improving 

the rutting and cracking performance of pavements. Polymer addition is typically 3 percent by 

weight of asphalt cement (about 0.70 gal/yd3 [3.5 l/m3]). Polymers used to modify asphalt are 

primarily derived from petroleum, and there are a number of different polymers each used for 

specific purposes. The use of polymer-modified asphalt can improve the performance of 

pavements, but the manufacturing of these polymers can also increase the environmental impact 

of the asphalt binder in the mixture, a fact that must be considered when evaluating 

environmental impacts. 

Polyphosphoric acid (PPA) is a polymer of orthophosphoric acid (H3PO4). Experience has 

shown that PPA increases the high temperature stiffness of an asphalt binder to reduce rutting 

with only minor effects on the intermediate and low temperature properties, and it is typically 

used as an alternative to polymers for this purpose. Some highway agencies have no restrictions 

on the use of PPA as an asphalt modifier, while others have restrictions on its use. Work by the 

FHWA has clearly demonstrated that the increase in binder stiffness from the addition of PPA is

crude-source dependent, with anywhere from 0.5 to over 3 percent needed to increase the high 

temperature binder grade (FHWA 2012a). Other laboratory testing has indicated that there may 

be some interactions with hydrated lime and an increased potential for moisture damage when 

more than 1 to 1.5 percent by mass of binder is used. LCI data are available for PPA to evaluate 

its environmental impact when included in asphalt materials (FHWA 2012a). 

In addition to tire rubber (see CRM sidebar), other RCWMs have been recycled into asphalt 

concrete mixtures, including glass as a replacement for aggregate, slag from metallurgical 

processing, foundry sands, and recovered sulfur as an asphalt binder modifier. Before utilizing 

these or other RCWMs, a thorough review of the available information on the RCWM in 

question should be performed, and an LCI should be used to evaluate potential environmental 

impacts over the life cycle (this should include an assessment of leachate and volatilization 

potential as well as worker health and safety). Furthermore, the impact of RCWM use on 

pavement performance must be considered. One particular issue that should be considered is 

whether the inclusion of the RCWM places any constraints on the future recycling of the 

mixture. Even if an RCWM is used in a mixture, aggregate and asphalt will still be the primary 

materials, and the influence of the additional materials on their repeated recyclability may not be 

considered in the literature and can only be considered in an LCI if the information is available. 

3-29
Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Assessment and Minimization of Environmental Impacts of Asphalt Road Materials

As previously indicated, different asphalt materials and mixtures have different environmental 

impacts. With regards to binders, the crude source, refining, transport, and the type of binder 

(asphalt cement, cutbacks, emulsions) all influence the environmental impacts (energy, GHG, air 

pollution, and so on). The amounts and methods of inclusion of rubber, polymers, PPA, 

solvents, emulsifying agents, and other binder modify agents will also change the impacts, 

generally increasing the impact in the materials production stage of the life cycle on a per mass 

basis. 

The type of mixture (e.g., HMA or WMA, dense graded or open graded) and how it is placed 

(e.g., with a paver or applied as a surface treatment) also affect its environmental impact. 

Additionally, the type and amount of RCWM that is used, whether RAP, CRM, RAS, or any 

number of other materials, will likely influence the environmental impact either adversely or 

positively. An overriding concern is how the performance of the pavement is influenced by 

changes in the mixture, because a reduction in pavement performance can counteract any 

environmental benefit that was gained during the materials selection and construction phases. 

Thus, the overall pavement life cycle must be considered in order to help resolve some of the 

complexity in the decision-making process. 

Other Asphalt Road Material Considerations

Where local or area urban heat islands are an issue (see chapter 6 for details), the solar 

reflectivity, heat capacity, heat conductivity, and permeability of the pavement may play a role. 

Ongoing research is being conducted to determine the importance of these characteristics and 

this phenomenon in different contexts. New asphalt concrete typically has low solar reflectivity, 

or albedo, on the order of about 5 percent, which means 95 percent of the incident solar radiation 

is absorbed. However, it tends to become more reflective over time as the asphalt oxidizes and 

as traffic or other abrasive actions wear the asphalt film off of the surface aggregates, at which 

point the reflectivity becomes more a function of the color of the aggregate. 

Slurry seals are expected to exhibit reflectivity levels similar to the asphalt binder used, although 

there are little data available. The reflectivity of chip seals is largely dependent on the 

reflectivity of the aggregate used for the chips. Chips that are precoated with asphalt will have 

reflectivity similar to that of asphalt concrete materials, with the same type of increase in 

reflectivity occurring over time. Fog seals and other treatments that place fresh asphalt on the 

surface will tend to reduce reflectivity for a short period of time. The aggregate mineralogy, and 

the permeability of the pavement material, will affect the heat capacity and thermal conductivity 

that can have a significant effect on pavement temperatures, although less so than reflectivity (Li 

et al. 2013; Stempihar et al. 2012). 

Treatments are available for asphalt concrete that can make it more reflective to solar radiation

(Tran et al. 2009). Information regarding the environmental impacts of producing those 

treatments, and their potential effects on performance and future recycling, is not available in the 

literature. However, if the temperatures in the upper 4 inches (102 mm) of asphalt concrete

layers is reduced, the risk of rutting is also reduced, particularly where heavy trucks move at 

slow speeds in hot climates. Light colored chip seals or other surface treatments that can reduce 

pavement temperature may help reduce that risk (Pomerantz, Akbari, and Harvey 2000). 

3-30
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Photocatalytic coatings primarily based on titanium dioxide have been developed for asphalt 

pavements to react with chemicals in the ambient air contributing to air pollution (Dylla et al. 

2013; Brovelli and Crispino 2013). 

Most pavement materials, including rubberized and polymer-modified asphalt mixtures, have 

been found to produce no leaching of pollutants into water that exceeds regulatory requirements, 

even when used with open-graded mixtures and after simulated aging (Kayhanian et al. 2009). 

Open-graded asphalt materials can potentially be used on pavement surfaces to trap pollutants 

from vehicles and airborne deposition that might otherwise be carried off the roadway into 

receiving waters or stormwater systems by rainfall.

Substitutes for Petroleum Asphalt

Petroleum typically contains between 0 and 3 percent sulfur, with the sulfur being removed 

during processing of “sour” crudes, resulting in an abundance of sulfur. The last decade has also 

seen a rise in the available sulfur on the market due to the increased use of acid gas wells to 

produce liquefied natural gas (LNG); sulfur levels can be as high as 35 percent (weight of 

material) taken from these natural gas wells. Because of this abundance of elemental sulfur, 

there has been considerable interest in using sulfur as a binder extender. Work on this was first 

performed in the late 1970s and early 1980s, but interest dropped due to cost and technical/safety 

reasons (FHWA 2012b). More recently, a new technology, known as Sulfur Extended Asphalt 

Modifier (SEAM) and recently renamed Shell Thiopave®, has been developed that is intended to 

function as both a binder extender and an asphalt mixture modifier (Tayabji, Smith, and Van 

Dam 2010). However, even though Thiopave pellets contain some additives designed to reduce 

odor and fumes during mixing, temperature control of the mixture and good ventilation practices 

are still required. Asphalt concrete mixtures produced with Thiopave must be mixed above a 

temperature of 248 °F (120 °C) for the sulfur pellets to melt and be dispersed throughout the 

asphalt mixture, but the temperature must remain below 293 °F (145 °C) to avoid the potential 

for emission generation that can be harmful to both workers and equipment. Furthermore, the 

location of Thiopave mixtures must be tracked in the field so that it can be properly handled and 

engineered if it is recycled as RAP into new asphalt concrete materials because of possible 

worker safety and equipment damage issues. 

Research work is underway in the U.S. and other countries evaluating the replacement of 

petroleum-based asphalt with “bio-binders,” which are made from biomass such as tree, plant, 

and animal waste (TRB 2012). Bio-binders exhibit similar properties to asphalt, such as the 

ability to flow when heated so they can coat aggregate or be sprayed, and the ability to withstand 

large strains without cracking. Examples include binders derived from corn stover, the non-food 

portion of corn (Metwally 2010), swine waste (Fini et al. 2011), algae (TRB 2012), and 

vegetable oil. One issue is the desire not to use biomass that would otherwise be useful as 

human or animal food. 

Land-produced plant biomass is typically 80 percent cellulose and 20 percent lignin, and lignin 

can be a source of polymers for use in asphalt. Cellulose is a dense polymer chain of sugar 

molecules, and lignin is composed primarily of phenolic compounds in a hard, polymer-like 

structure. Three different types of processes are being evaluated to convert cellulose containing 

biomass to liquid fuels (King and King 2009): 

3-31
Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

• Fermentation, in which enzymes convert the biomass to energy, leaving lignins that

would need to be further modified to function as paving binder. 

• Fast pyrolysis, in which biomass is heated to very high temperatures in the absence of 

oxygen, breaking down the cellulose and lignin into smaller molecules that might then be 

processed into liquid fuels and possibly asphalt. 

• Gasification, in which biomass is converted to combustible gases using newly developed 

processes similar to coal gasification technology. 

Currently, there are some bio-binder products available on the market, although none have 

replaced a significant amount of paving asphalt in pavements built for state DOTs. No LCA 

publication was found in the literature on any of these bio-binders that considers the net lifecycle effects of the materials production, construction, use, and end-of-life phases.

Strategies for Improving Sustainability

Some general approaches to improve sustainability with regard to asphalt materials (and the 

trade-offs that should be considered) are summarized in table 3-3. It is noted that very little 

quantitative analysis of the net effects of these possible sustainability-improving practices has 

been evaluated using LCA procedures that would consider the materials production, 

construction, use, and end-of-life phases. A brief discussion of the identified strategies is 

provided below, and it is noted that many of these strategies reduce life-cycle costs as well as 

environmental impacts while enhancing overall social good. 

Strategy: Reduce Amount of Virgin Asphalt Binder and Virgin Aggregate in Asphalt 

Concrete by Plant Recycling

The extraction and production of virgin asphalt binder from petroleum, a finite resource, is one 

of the major sources of environmental impact for asphalt concrete. The technology for 

performing mixture designs with increased percentages of reclaimed asphalt materials, such as 

RAP and RAS, and the use of binders modified with CRM from waste tires, is rapidly improving 

as is the design technology for using these mixtures in a manner that does not compromise the 

performance of the pavement. 

Strategy: Reduce Energy Needed and Emissions from Mixing Asphalt Concrete

Use of warm-mix technology can potentially reduce the energy needed to produce asphalt 

concrete, and can also reduce the emissions. However, this does depend on the type of WMA 

technology employed and how it is used. The environmental impact of producing alternative 

WMA technologies has not been clearly established. Changing the fuel used in production (e.g., 

from diesel to natural gas) will reduce emissions, but with the potential for slight additional cost. 

The use of newer, more efficient asphalt mixing plants will reduce energy consumption and 

emissions, allow a greater percent incorporation of RAP and RAS, and many newer plants are 

equipped with WMA foaming technologies. This will result in overall cost and emission 

reductions, although requiring additional capital investment. 

3-32
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Table 3-3. Approaches for improving pavement sustainability with regard to asphalt 

materials production. 

Asphalt Materials 

Objective

Sustainability Improving 

Approach

Economic Impact Environmental Impact Societal Impact

Use greater quantities of 

RAP if same or better 

performance can be realized.

Reduces cost of asphalt 

concrete if RAP available.

Dependent on performance, 

energy costs of mixing, 

transportation. 

Extends life of 

petroleum resources. 

Reduced need for 

landfill.

Reduce Virgin Binder 

Content in Asphalt 

Concrete

Use rubberized asphalt for 

asphalt concrete. 

Some increase in initial cost, 

impact of mixture design 

higher, potential payback in 

less material for thin overlays, 

increased life.

Reduces impacts by 

decreasing amount of 

materials needed over time 

horizon. 

Reduced exposure of 

public to accidents in 

work zones. 

Use RAS as partial 

replacement for asphalt 

binder if same or better 

performance can be realized.

Reduces cost of asphalt 

concrete if RAS available.

Extends life of 

petroleum resources. 

Reduced need for 

landfill.

Use bio-binders. Impacts and trade-offs 

unknown.

Impacts and trade-offs 

unknown.

Impacts and trade-offs 

unknown.

Use sulfur-modified asphalt. Not well quantified. Potential difficulty in future 

recycling.

Risks for worker health.

Reduce Virgin Aggregate 

Content in Asphalt 

Concrete 

Use greater quantities of 

RAP if the same or better 

performance can be realized.

Reduced cost of asphalt 

concrete if RAP available.

Dependent on performance, 

energy costs of mixing, 

transportation. 

Extends life of 

aggregate resources. 

Reduced need for 

landfill.

Reduce Energy

Consumed and Emissions 

Generated to Produce

Asphalt Concrete

Use WMA to reduce mixing 

temperatures. 

Zero to small increase in cost. Reduced energy and GHG to 

make asphalt concrete. 

Impact of producing WMA 

additives needs to be 

considered.

Reduced worker

exposure to fumes.

Change fuel used for heating 

to reduce emissions, such as 

natural gas. 

May increase cost. Reduced emissions to make 

asphalt concrete. 

Reduced worker 

exposure to fumes.

Reduce Energy

Consumed and 

Emissions Generated to 

Produce Asphalt 

Concrete 

Employ new, more 

efficient plant designs to 

reduce energy consumption 

and increase the percent 

RAP and RAS used

Increased capital cost to 

upgrade existing facilities. 

Reduced operating cost due 

to decreased energy 

consumption as well as 

increased use of RAP and 

RAS.

Reduce emissions to make 

asphalt concrete through 

reduced fuel consumption 

and higher percentage use 

of RAP and RAS

More efficient 

utilization of 

recovered materials 

such as RAP and RAS

Increase compaction 

specifications, no tradeoffs.

Some increase in initial cost 

for extra contractor effort 

and inspection, large 

payback in increased life.

Reduces impacts by 

decreasing amount of 

materials needed over time 

horizon.

Reduced exposure of 

public to accidents in 

work zones. 

Use WMA to obtain better 

compaction. 

Zero to small increase in 

cost, payback in increased 

life. 

Reduces impacts by 

decreasing amount of 

materials needed over 

pavement life cycle. WMA 

additives needs to be 

considered.

Reduced exposure of 

public to accidents in 

work zones

Extend Lives of Asphalt 

Concrete Materials 

Improved mixture designs. Some cost for new 

equipment, training, payback 

from longer lives.

Reduces impacts by 

decreasing amount of 

materials needed over life 

cycle.

Reduced exposure of 

public to accidents in 

work zones.

Use polymers. Some increase in initial cost, 

impact of polymer 

production, potential 

payback in increased life.

Reduces impacts by 

decreasing amount of 

materials needed over life 

cycle. Impact of producing 

polymer additives needs to 

be considered.

Reduced exposure of 

public to accidents in 

work zones. Increased 

exposure of workers 

to fumes.

Use rubberized asphalt. Some increase in initial cost, 

impact of mixture design 

higher, potential payback in 

less material for thin 

overlays, increased life.

Reduces impacts by 

decreasing amount of 

materials needed over time 

horizon. 

Reduced exposure of 

public to accidents in 

work zones. 

Increased exposure of 

workers to fumes.

3-33
Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Table 3-3. Approaches for improving pavement sustainability with regard to asphalt 

materials production (continued). 

Asphalt Materials 

Objective

Sustainability Improving 

Approach

Economic Impact Environmental Impact Societal Impact

Extend Lives of Asphalt 

Concrete Materials 

Use lime or liquid anti-strip to 

decrease risk of early failure 

due to moisture damage. 

Slight increase in initial cost, 

payback from extended life 

where warranted.

Initial impact from 

manufacture of materials, 

potential payback if life 

would otherwise be 

shortened.

Increased worker 

exposure to lime or 

chemicals. 

Reduce Materials 

Transportation Impacts

Use more locally available 

materials. 

Lower initial cost. Potential 

for greater life cycle cost if 

perform is compromised. 

May have shorter lives if 

performance-related 

properties are poorer.

Reduces impacts of 

transportation of materials, 

particularly important if 

trucks would be used. May 

have shorter lives if 

performance-related 

properties are poorer.

Reduced exposure of 

public to trucking.

Extend Lives of Seal 

Coats 

Use rubber or polymer 

binders.

Some increase in initial cost, 

impact of binder production 

higher, potential payback 

from increased life.

Increased impact due to 

production of polymers. 

Potential payback from 

improved life.

Polymers made from 

finite petroleum 

resources. 

Reduce Need for Virgin 

Materials and 

Transportation 

Use in-place recycling (fulldepth reclamation, partialdepth recycling). May have 

high construction variability.

Can potentially reduce initial 

cost by reducing 

transportation of virgin 

materials and permitting 

thinner overlays, and may 

extend life where 

appropriately selected and 

designed. May have high 

construction variability.

Can reduce use of virgin 

materials depending on life. 

Can reduce transportation of 

materials. Energy savings 

dependent on technology and 

life. May have high 

construction variability.

Fewer heavy trucks on 

the road hauling 

materials. 

Increase Pavement 

Albedo where Warranted

(See Chapter 6)

Use lighter colored 

aggregates, place light colored 

chip seals, other reflective 

surface treatments. 

Cost may be greater if 

reflective treatment not 

otherwise needed. Can 

potentially reduce risk of 

rutting of asphalt concrete. 

More materials used if 

additional coating applied 

that is not otherwise needed. 

Needs to be evaluated on a 

case by case basis (see 

Chapter 6). If warranted, 

specific impacts that are 

positively impacted must be 

noted. Unintended 

consequences should also be 

examined. 

Needs to be evaluated 

on a case by case basis 

(see Chapter 6). If 

warranted, specific 

impacts that are 

positively impacted 

must be noted. 

Unintended 

consequences should 

also be examined.

Strategy: Extend Life of Asphalt Concrete Materials

All things being equal, extending the life of asphalt concrete and seal coats reduces 

environmental impacts over the pavement life cycle. Effective mixture design and a high degree 

of construction compaction are strategies that are known to extend life, typically with few tradeoffs. Dense-graded asphalt concrete can usually be compacted to 2 percent air voids without risk 

of rutting, and good compaction can be made easier to achieve with the aid of warm-mix 

technology. Rubber and polymers can be used in mixture designs for specific applications to 

increase life, but these may potentially carry some additional environmental impact from a 

materials production standpoint. They also typically have additional initial cost, which can be 

offset if they permit a reduction in pavement thickness. They may also negatively affect the 

ability to fully utilize RAP containing the additives in future asphalt concrete. As such, these 

materials should be used where they provide significant increases in performance. Reducing the 

risk of moisture damage in asphalt concrete through additives can also increase life, although the 

net environmental impacts of the additives have not been investigated through an LCA.

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Strategy: Reduce Need for Virgin Materials and Transportation through In-Place 

Recycling 

Recycling and reclamation can result in substantial cost savings and environmental impact 

reductions over the use of new materials when the technology (partial-depth recycling, full-depth 

reclamation) is properly selected, designed, and constructed. The cost and impact reductions can 

come from less use of new materials and reduced haulage. The life of the material must be 

considered when selecting strategies, since improvements in manufacture and construction can 

be offset by reduced life. Recycled materials have proven to be at least equal to new materials in 

quality, when properly engineered. FDR can be used to improve pavement cross-sectional 

geometrics and in some cases the traffic disruption is lessened compared to other rehabilitation 

techniques. Kandhal and Mallick (1997) provide additional information on recycling. 

Strategy: Develop Alternatives to Petroleum-Based Binders

Work is under way to develop alternative binders, particularly bio-binders that have reduced 

environmental impacts compared to those derived from petroleum. However, the environmental 

impacts of these materials have not yet been evaluated using LCA, nor have their long-term 

performance capabilities been demonstrated. 

Future Directions/Emerging Technologies

A number of strategies for reducing impacts from asphalt binders, modifiers, additives, and 

aggregate have been presented. Some future directions and emerging technologies that should be 

monitored and implemented, when and where beneficial, are: 

• A reduction in material quantities through improvements in mixture design, construction 

practices, and, in some cases, new materials such as WMA or, where traffic, climate and 

existing condition warrant, inclusion of polymers, rubber, and other modifiers.

• Greater use of RCWMs, including RAP, RAS, and others, to reduce the mining, 

extraction, manufacture, and transport of non-renewable virgin materials, provided that 

performance is not compromised. For individual projects, this requires analysis of 

whether suitable RCWMs are locally available because long transportation distances may 

reduce the energy and environmental benefits of using RCWMs.

• Greater use of locally available pavement materials provided that those benefits are not 

offset by reduced performance. For asphalt materials, locally available aggregates are the 

primary consideration. 

• Development of alternatives, namely bio-based alternatives, to nonrenewable feedstocks 

such as petroleum. The environmental, economic, and societal impacts of producing 

these alternatives will need to be evaluated to determine their overall feasibility.

Hydraulic Cement Materials

This section reviews the manufacture of HCC mixtures, including material acquisition, 

processing, transportation, and processing at a concrete plant. As aggregates were discussed at 

the beginning of this chapter, the focus of this section is on cementitious binders and additives, 

and how these combined with aggregates can be used to improve the sustainability of pavements. 

Economic and environmental impacts occur throughout all life-cycle phases, with this section 

focused on those directly related to the materials including cementitious materials, mixture 

design, proportioning, and mixing. Topics include energy consumption, emissions, calcination, 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

resource consumption, and water use. 

Recent innovations are discussed including 

mixtures with high contents of 

supplementary cementitious materials

(SCMs), portland limestone and other 

blended cements, high-efficiency cement 

manufacturing plants, and concrete plant 

operations. Materials transport from the 

plant and construction are discussed 

separately in chapter 5. 

Introduction

In its simplest form, HCC is a mixture of 

coarse and fine aggregate bound together 

with “glue” that is created when water is 

mixed with hydraulic cement. Air is present in the mixture, either being entrapped or 

purposefully entrained as microscopic air bubbles. Figure 3-7 presents the components and their 

typical volumetric distribution in dense-graded HCC.

Major Issues: 

 The relatively high non-renewable energy 

consumption and GHG emissions inherent in 

the portland cement manufacturing.

 The non-renewable energy consumption and 

GHG emissions associated with the 

production of traditional paving concrete. 

 Water use associated with concrete 

production.

 Increasing the use of RCWMs as aggregates 

without compromising performance.

 Ensuring concrete durability.

3-36

Figure 3-7. Typical volumetric distribution of hydraulic paste (cement, water, air) and 

aggregates in paving concrete (Taylor et al. 2006). 

The hydraulic cement used today is most commonly a blend of portland cement (AASHTO M 

85/ASTM C150), SCMs, and ground limestone. Furthermore, chemical admixtures are almost 

always employed to modify the behavior of the fresh and hardened HCC, making it easier to 

place, enhancing its strength, and making it more durable. In addition, the aggregates are often 

graded to possess a more optimized size distribution to create a mixture with a reduced 

cementitious content, improved workability, and enhanced long-term performance.
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Portland Cement

Following water, HCC is humankind’s most commonly used material, with roughly 1 yd3 (0.76 

m3) of it produced annually for every person on the planet. As such, the economic, 

environmental, and societal impacts of HCC are huge. Furthermore, the cost and environmental 

impact of HCC is largely dependent on the cement (much of this section will generally refer to 

portland cement instead of hydraulic cement since it is by far the mostly commonly used type). 

This is illustrated in table 3-4, which shows that the production of portland cement consumes 74 

percent of the energy and produces 81 percent of the GHG emissions associated with the cement 

and concrete industry in the U.S. (Choate 2003). 

Table 3-4. Annual energy and CO2 emissions associated with U.S. cement manufacturing 

and concrete production (Choate 2003). 

On-site 

Energy

106 kJoules

On-site 

Energy

%

CO2

Emissions

106 tonne

CO2

Emissions

%

Raw Materials – Quarrying and Crushing

Cement Materials 3,817 0.7% 0.36 0.3%

Concrete Materials 14,287 2.6% 1.28 1.2%

Cement Manufacturing

Raw Grinding 8,346 1.5% 1.50 1.4%

Kiln: fuels 410,464 74.0% 38.47 36.8%

Reactions 48.35 46.3%

Finish Milling 24,057 4.3% 4.32 4.1%

Concrete Production

Blending, Mixing 31,444 5.7% 5.65 5.4%

Transportation 61,933 11.2% 4.53 4.3%

Total 554,409 100% 104.50 100%

Source: Energy and Emission Reduction Opportunities from the Cement Industry, U.S. Department of Energy.

Portland cement is manufactured by pyroprocessing raw materials, dominated by limestone, in a 

rotary cement kiln at high temperatures (2460 to 2640 o

F [1348 to 1448 oC]). This alters the 

mineralogy of the raw materials, creating small, dark nodules referred to as cement “clinker” 

composed of reactive cementitious phases (Kosmatka and Wilson 2011). Although the 

consumption of fuel (which will differ regionally, consisting of pulverized coal, natural gas, used 

tires, waste industrial oils and solvents, and, in some cases, biomass) is responsible for a portion 

of the GHG emissions, over half of the GHG emissions in clinker production are released due to 

the decomposition of limestone (CaCO3) into lime (CaO) and carbon dioxide (CO2) (EPA 2013b; 

Van Dam et al. 2012). 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Even though cement kiln efficiency has improved 

markedly over the last two decades—significantly 

reducing the energy needed for pyroprocessing and 

the associated emissions—the calcination reaction is 

an unavoidable occurrence in creating portland 

cement and thus the CO2 liberated from this reaction 

cannot be eliminated. Approximately 0.8 to 1.0 tons 

(0.7 to 0.9 mt) of CO2 are produced per ton of 

cement manufactured in the U.S. (Van Dam et al. 

2012). Furthermore, cement production is

responsible for approximately 31.6 Tg CO2e, or just 

under 0.5 percent of the U.S. total GHG emissions of 

6,702 Tg CO2e in 2011 (EPA 2013b). This is a 

dramatic reduction in GHG emissions from the peak 

that occurred in 2005 when 45.2 Tg CO2e were 

associated with cement production, largely due to 

the economic downturn and resultant reduction in 

demand for cement that began in 2008. 

As previously described, portland cement clinker is 

manufactured through pyroprocessing in large rotary 

kilns. Older technology is referred to as “wet

process” in which the raw materials were ground 

wet, and then stored, proportioned, and fed into the 

kiln as a slurry. Modern cement kiln technology has 

reduced the energy needed to evaporate the water 

used in grinding through dry-process grinding and 

material handling. A schematic of a modern dryprocess plant is shown in figure 3-8. This figure shows a general process design, but in truth 

every plant is unique, with modern plants incorporating new technologies to increase efficiency 

and reduce waste/emissions. A modern cement plant can take over a decade to permit and build 

at a cost of over $1 billion, and is much more efficient than plants that were prevalent two 

decades ago. Prior to the economic downturn in 2008, the U.S. cement industry continued to use 

a number of the wet-process plants, but today these are no longer operational. The following 

discussion focuses on the production of cement and enhancements that have occurred over time. 

The first step in manufacturing cement is to mine and process the raw materials necessary. The 

single largest need is for calcium, which is predominately obtained from limestone (calcium 

carbonate). As a result, cement plants are often located near an abundant source of limestone. Silica 

and alumina are most often provided by natural materials such as clay or shale, although to create the 

desired proportions of calcium, silica, alumina, and iron, other materials are often blended in 

including fly ash or iron blast-furnace slag. This basic process has not changed much over the 

decades, although more efficient mining equipment and crushers have been employed.

Hydraulic Cement Materials Usage 

and Economics

The U.S. used approximately 79 million 

tons (72 million mt) of hydraulic cement in 

2011, worth about $6.5 billion, according to 

the U.S. Geological Survey (USGS 

2013b). In the recent peak year of 2005, 

approximately 111 million tons (122 million 

mt) of cement were consumed (USGS 

2013b). Calcium sulfoaluminate and other 

non-portland hydraulic cements used are 

included in these figures, but only account 

for about 0.03 percent of cement used. 

According to the USGS, approximately 5 

percent of cement used in the U.S. in 2011 

was used for road paving purposes 

(USGS 2013b). In the U.S., about 8 

percent of all paved roads and highways 

are surfaced with concrete. The U.S. has 

about 5,500 ready mixed concrete plants 

in 2011 (U.S. Census Bureau 2013), many 

of which produce concrete for paving. The 

value of ready mixed concrete produced in 

the U.S. was estimated at $34.7 billion in 

2007 (U.S. Census Bureau 2007b), which 

suggests that the value of concrete used 

for road paving was about $1.7 billion 

based on 5 percent of cement used.

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Figure 3-8. Steps in the modern dry-process manufacture of portland cement 

(Kosmatka and Wilson 2011). 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

As illustrated in figure 3-8, these mined raw materials are sized (crushed if needed) and stored, 

then finely ground prior to burning in a rotary kiln. Improvements in technology at this stage 

have resulted in significant increases in processing efficiency over the last few decades, with the 

biggest change occurring by moving from wet processing to dry processing. As the name 

implies, in wet processing water is used in a grinding mill to create slurry that is then fed into the 

rotary kiln. This requires a very long kiln, as the first stage in the burning process is to dry the 

slurried kiln feed, a process that is very energy (and therefore emissions) intensive. In older dry 

process facilities, grinding mills and air separators are used to create powder that is then fed into 

a shorter kiln. Although grinding energy is increased, the net energy savings relative to wet 

process technology is significant. In modern cement plants, as illustrated in figure 3-8, the older 

grinding mills and air separators are replaced with much more efficient roller mills that combine 

crushing, grinding, drying, and classifying into a single vertical unit. 

Additional efficiencies have been incorporated into the burning process, most focusing on 

recirculating hot exhaust gases and using them to dry, heat, and initiate the calcination of raw 

materials before they enter the kiln. As shown in figure 3-8, hot gases from the kiln already begin 

the drying process in the vertical roller mills. The raw materials in a modern plant are then fed 

through a series of vertical heat exchange devices known as preheater cyclones and precalciner 

vessels. The most modern cement plants will have flash furnaces installed at which point 85 to 95 

percent of the calcination occurs before the raw feed even enters the kiln (Kosmatka and Wilson 

2011). Such cement plants have very short kilns, further improving efficiency.

In the kiln, the raw materials are heated until “clinkering” occurs in which the primary cement 

phases are formed. Upon cooling, the greyish black pellets that emerge are called clinker. As 

shown in figure 3-8, the cooled clinker is combined with calcium sulfate (gypsum), which is 

added to control the time of setting, and is then ground in a grinding mill. Many improvements 

in efficiency have occurred during this step as well, including the use of more efficient grinding 

mills, high efficiency separators, and high efficiency dust collection. After grinding, the grey 

powder is now “portland” cement, which will be stored for shipping in bulk or bagged form. 

Today, portland cement sold in the U.S. under AASHTO M 85 almost always contains 

ingredients beyond ground clinker and gypsum. For one, the specification allows up to 5 percent 

limestone to be interground with the clinker, although the practical limit is somewhere around 

3.5 percent in order to meet other specification requirements. Furthermore, up to 5 percent 

inorganic processing additions may also be added, the most common being slag cement. And 

finally, 1 percent organic processing addition may also be added. As these additions have a 

lower environmental impact (e.g., lower GHG emissions, embodied energy) than portland 

cement, the addition of each has the potential to lower the energy consumed and emissions 

generated to manufacture a unit mass of portland cement.

Innovations at cement plants continue to improve efficiency and thus lower energy consumption 

and emissions. Some plants rely on renewable energy to provide their electrical needs, including 

electricity produced by wind and solar. Additionally, coal is increasingly being replaced as a 

fuel, with some plants switching to natural gas or a combination of biomass fuel and waste fuels, 

such as worn-out tires, solvents, and waste oil (Kosmatka and Wilson 2011). Many plants also 

use highly efficient modes of transportation, shipping cement in bulk either by rail or barge. The 

main driver for most of these changes is economics, but regulatory changes and the need to be 

more “sustainable” has motivated the cement manufacturing industry to minimize waste and 

reduce emissions, with the overall effect being an increase in efficiency. 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Nevertheless, increasing levels of efficiency do 

not reduce the CO2 released in the calcination 

process, which as shown in table 3-4 is 

roughly 46 percent of all CO2 released in the 

production of concrete (Choate 2003). As 

mentioned earlier, this CO2 cannot be reduced 

through improved efficiency or renewable 

fuels. The only solution for reducing 

calcination CO2 is to reduce the amount of 

portland cement clinker consumed over the life 

cycle of the pavement. A recent LCI on the 

manufacturing of portland cement in the U.S. 

is available (Marceau, Nisbet, and VanGeem 

2007). 

Supplementary Cementitious Materials

SCMs are materials that when blended with 

portland cement contribute to the properties of 

concrete through hydraulic or pozzolanic 

activity, or both (Kosmatka and Wilson 2011). 

Hydraulic activity occurs when the material 

chemically reacts with water, forming 

cementitious hydration products. Pozzolanic 

activity occurs in the presence of water when 

reactive siliceous or aluminosiliceous material 

reacts with calcium hydroxide (a reaction 

product from the hydration of portland cement) 

forming calcium silicate hydrate and other 

cementitious compounds. Calcium silicate 

hydrate is a more desirable hydration product 

than calcium hydroxide and the pozzolanic 

reaction is considered to have a positive 

impact on the long-term properties of the 

hardened concrete.

SCMs can be mixed into the cement by the 

cement manufacturer and sold as blended 

cement under AASHTO M 240 or added at the 

concrete plant by the concrete producer. 

SCMs that are commonly used in paving 

concrete include fly ash (specified under 

AASHTO M 295) and slag cement (specified 

under AASHTO M 302). Far less commonly 

used SCMs are natural pozzolans (also 

specified under AASHTO M 295) and possibly 

small amounts of silica fume (specified under 

AASHTO M 307). 

Alternative Fuels for Cement Kilns

As part of their effort to reduce their GHG 

footprint, the cement industry continues to seek 

alternative fuels to burn in cement kilns as an 

alternative to the use of fossil fuels such as 

coal, petroleum coke (produced when asphalt 

is processed to make lighter products), and 

natural gas. The most common alternative fuel 

is derived from waste tires, which pound for 

pound have more fuel value than coal, and can 

also result in lower emissions (PCA 2011). 

Other waste-derived alternative fuels include 

paper, packaging, plastics, saw dust, and 

solvents that, because of the extremely high 

temperatures that exist in a cement kiln (well 

above 3000 °F [1650 °C]), burn quickly and 

with extreme efficiency (PCA 2011). This 

perspective is echoed by the Cement Kiln 

Recycling Coalition (CKRC 2013), which states 

that alternative fuels for cement kilns can be 

produced from paint solvents, discarded paints 

and coatings, inks and ink solvents, various 

resins and organic sludges, petroleum refining 

by-products, as well as scrap tires and many 

other materials. In 2010, over 68 percent of 

U.S. and Canadian cement plants reported 

using one or more waste fuels, providing 13 

percent of the energy demand at cement plants 

(PCA 2011).

The sustainability benefits of using these types 

of alternative fuels are great as materials that 

would otherwise need to be treated as 

hazardous waste are handled and used in a 

safe and beneficial manner. This reduces the 

need for landfills for hazardous waste as well 

as the amount of fossil fuel consumed in 

cement production, thus conserving fossil fuel 

and reducing GHG emissions. In addition to 

waste-derived alternative fuels, considerable 

interest exists to utilize biofuels in cement 

production. In one investigation, the main 

biofuel used was sorghum, which was 

complemented by maize (varieties of corn that 

don't go to seed), perl millet, switchgrass and 

oat hulls (Norris 2011). The investigation 

showed enough promise that it was thought 

that biofuels could be used to completely 

replace coal by 2020. In another investigation, 

a cement plant has employed a novel approach 

to use the carbon dioxide-rich exhaust gases 

from the cement kiln to accelerate the growth 

of algae, which in turn is dewatered and burned 

as fuel in the kiln (Tree Hugger 2013). 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Table 3-5 summarizes properties of these common SCMs, noting that calcined clay, shale, and 

metakaolin are classified as natural pozzolans. Tables 3-6 and 3-7 summarize how each SCM 

impacts the behavior of fresh and hardened concrete, respectively. Brief descriptions of some of 

the primary SCMs are provided in the following sections. 

Table 3-5. Chemical composition and select properties of common SCMs (Taylor et al. 

2006; Kosmatka, Kerkoff, and Panarese 2002). 

Component Type I 

Cement

Class F

Fly Ash

Class C

Fly Ash

Slag

Cement

Silica

Fume Metakaolin

Silica (SiO2),% 22.00 52.00 35.00 35.00 90.00 53.00

Alumina (AI2O2),% 5.00 23.00 18.00 12.00 0.40 43.00

Iron oxide (Fe2O2)% 3.50 11.00 6.00 1.00 0.40 0.50

Calcium oxide (CaO),% 65.00 5.00 21.00 40.00 1.60 0.10

Sulfate (SO4),% 1.00 0.80 4.10 9.00 0.40 0.10

Sodium oxide (Na2O),% 0.20 1.00 5.80 0.30 0.50 0.05

Potassium oxide (K2O),% 1.00 2.00 0.70 0.40 2.20 0.40

Total eq. alkali 

(as Na20),% 0.77 2.20 6.30 0.60 1.90 0.30

Loss on ignition,% 0.20 2.80 0.50 1.00 3.00 0.70

Blaine fineness, m2/kg 350.00 420.00 420.00 400.00 20,000.00 19,000.00

Relative density 3.15 2.38 2.65 2.94 2.40 2.50

Table 3-6. Effects of SCMs on the properties of fresh concrete (Taylor et al. 2006).

Property Class F

Fly Ash

Class C

Fly Ash

Slag 

Cement

Silica 

Fume

Calcined 

Shale

Calcined 

Clay Metakaolin

Water Requirements ↓ ↓ ↓ ↓ ↓ ↑ ↑ ↔ ↔ ↑

Workability ↑ ↑ ↑ ↓ ↓ ↑ ↑ ↓

Bleeding and segregation ↓ ↓ ↕ ↓ ↓ ↔ ↔ ↓

Air Content ↓ ↓ ↓ ↓ ↓ ↓ ↔ ↔ ↓

Heat of Hydration ↓ ↕ ↓ ↔ ↓ ↓ ↓

Setting Time ↑ ↕ ↑ ↔ ↑ ↑ ↔

Finishability ↑ ↑ ↑ ↔ ↑ ↑ ↑

Pumpability ↑ ↑ ↑ ↑ ↑ ↑ ↑

Plastic Shrinkage 

Cracking ↔ ↔ ↔ ↑ ↔ ↔ ↔

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Table 3-7. Effects of SCMs on the properties of hardened concrete (Taylor et al. 2006). 

Property Class F

Fly Ash

Class C

Fly Ash

Slag 

Cement

Silica 

Fume

Calcined 

Shale

Calcined 

Clay Metakaolin

Early strength ↓ ↔ ↓ ↓ ↓

Long-term strength ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑

Permeability ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓

Chloride ingress ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓

ASR ↓ ↓ ↕ ↓ ↓ ↓ ↓ ↓ ↓

Sulfate resistance ↑ ↑ ↕ ↑ ↑ ↑ ↑ ↑ ↑

Freezing and thawing ↔ ↔ ↔ ↔ ↔ ↔ ↔

Abrasion resistance ↔ ↔ ↔ ↔ ↔ ↔ ↔

Drying shrinkage ↔ ↔ ↔ ↔ ↔ ↔ ↔

Sources: Thomas and Wilson (2002); Kosmatka, Kerkoff, and Panarese (2002) 

Key: ↓ reduced ↑ ↑ significantly increased

↓ ↓ significantly reduced ↔ no significant change

 ↑ increased ↕ effect varies

Fly ash is collected from the flue gases of coal-fired power plants. As pulverized coal is 

combusted, mineral impurities are carried away in the flue gases, solidifying into spherical 

glassy particles as they cool. These are collected by electrostatic precipitators or bag filters as 

particles roughly the same size as cement. In 2011, approximately 59 million tons (54 million 

mt) of fly ash were produced in the U.S., of which 38 percent was beneficially used with 13 

million tons (12 million mt) used in concrete/concrete products or in blended cement/raw feed 

for clinker (ACAA 2013a). As shown in figure 3-9, this is a decrease in both peak fly ash 

production (which was approximately 78 million tons [71 million mt] in 2002) and utilization 

rate (approximately 45 percent in 2006) (ACAA 2013b). The main reason for the decrease in fly 

ash production and utilization was the economic slowdown in the U.S. beginning in 2006. Other 

pressures exist that may reduce fly ash availability in the future, including increased reliance on 

natural gas instead of coal for electrical production as well as increasing environmental pressures 

to reduce emissions from power plants. 

Fly ash varies in composition and mineralogy as a result of the source of coal, how it is burned, 

and how the ash cools. Under AASHTO M 295, it is classified as either a Class C fly ash or a 

Class F fly ash. A summary of how the different fly ashes behave in concrete, based on tables 3-

6 and 3-7, is as follows: 

• As seen in table 3-5, in general, Class C fly ash has higher calcium oxide content than 

Class F fly ash and thus has both hydraulic cementitious and pozzolanic characteristics; 

Class F fly ash, on the other hand, has less calcium oxide and is therefore more 

pozzolanic. 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Figure 3-9. U.S. fly ash production, use (U.S. short tons), and utilization rate from 1966 to 2013 

(ACAA 2013b). (Note: 1 short ton = 0.907 metric ton) 

3-44

• Class C fly ash is typically dosed at 15 to 40 percent by mass of the total cementitious 

materials used whereas Class F fly ash is typically dosed at 15 to 25 percent for pavement 

applications (Taylor et al. 2006).

• The spherical nature of the fly ash particles improves the workability and cohesiveness of 

concrete paving mixtures while reducing water demand. Furthermore, the lower density 

of fly ash versus portland cement means that for a given mass there is more volume in the 

paste. This improves cohesiveness and workability and also reduces bleeding. 

• The presence of fly ash can negatively impact the ability to entrain air in the concrete, 

primarily due to carbon impurities that may be present. The limits on loss on ignition is 

an attempt to control the amount of carbon. A newly released NCHRP study provides 

methods to evaluate a given fly ash’s impact on air entrainment (Sutter, Hooton, and 

Schlorholtz 2013).

• Class C fly ash may affect early setting and the heat of hydration whereas Class F fly ash 

almost always delays setting while reducing the heat of hydration. In concrete made with 

Class F fly ash, the delay in setting and early strength gain increase with increasing 

dosage and may impact the constructability of the pavement, especially in cooler weather.

• Early strength gain is rarely affected by Class C fly ash but almost always slowed when 

Class F fly ash is used. On the other hand, all fly ash tends to improve long-term strength

and reduce permeability (which increases durability). 
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

• The pozzolanic reaction helps mitigate 

ASR and sulfate attack. Thus, in 

general, concrete made with Class F fly 

ash will have improved chemical 

durability over concrete made with pure 

portland cement or Class C fly ash. In 

some cases and in some dosages, 

concrete containing Class C fly ash can 

actually have poorer durability than 

would be incurred in concrete made with 

a pure portland cement. 

As an industrial co-product or waste material, 

the composition, reactivity, and properties of fly 

ash are highly variable. This variability can be 

extreme for fly ashes from different sources, but 

is also true for fly ash produced at the same 

electrical plant because coal sources, burning 

techniques, and environmental technologies are 

changing rapidly. As a result, rigorous testing 

of fly ash must be conducted on a frequent basis 

to ensure its continued suitability for use in 

concrete. NCHRP Report 749 provides 

guidance on the testing of fly ash for highway 

structures (Sutter, Hooton, and Schlorholtz 

2013). 

Slag cement is an industrial co-product from 

iron blast furnaces in which pig iron is extracted 

from iron ore. The remaining molten material 

(slag) is directed into a granulator that quenches 

the material using water to form glassy, sandlike particles. These are then ground to similar 

size, or slightly finer, than portland cement. 

Although the chemical composition is identical 

to that of air-cooled blast furnace slag, the rapid 

cooling through quenching does not allow 

chemically stable crystalline minerals to form. 

Instead, the amorphous oxides of calcium, 

aluminum, magnesium, and iron (the typical 

composition is shown in table 3-5) are reactive, 

either slowly in the presence of water alone or 

more vigorously when activated in water in the 

presence of sodium hydroxide or calcium 

hydroxide. The latter is the condition present in 

the pore solution of hydrating portland cement, 

and thus the two react in a complementary 

manner. 

Co-Product Treatment for SCMs

There is debate on how to allocate 

environmental impacts for high value SCMs, 

such as fly ash and slag cement. In the past 

these materials were considered wastes from 

industrial processes (coal-powered electricity 

generating fly ash, and steel production 

generating blast furnace slag). The current 

practice in the U.S. is to consider fly ash a 

waste material diverted from a landfill for 

beneficial use, meaning that none of the 

environmental impact associated with 

electricity generation is typically assigned to 

the fly ash. As long as the cost of transport 

and processing of the fly ash is the only 

source of economic value, a waste 

classification is appropriate. However, once

the fly ash has value beyond this, it should no 

longer be considered waste, but instead a coproduct. Already in some markets fly ashes 

are in high demand and economically 

valuable, meaning they are no longer waste 

flows. In these cases, it is appropriate to 

allocate some of the environmental burden 

associated with coal-fired power plants to fly 

ash. The most common means to accomplish 

this is through economic worth of the coproducts. LCAs in some regions (e.g., 

Europe) show that the economic worth of fly 

ash compared to electricity generation is small 

and hence the assigned environmental 

impacts are also small. The same practices 

can be applied to slag cement as a co-product 

in steel production. It is noted that different 

allocation methods can lead to differences in 

assigned environmental impacts. There are 

also other motivations for industries to seek 

classification as waste or co-product. For 

example, in Europe fly ash producers often do

not want classification as “waste” because 

that requires a much more difficult regulatory 

environment for handling, storing, and 

transporting the material. Chen et al. (2010) 

considered different allocation methods for 

slag cement and fly ash used in Europe, 

arguing that demand for these products 

outpaced production and thus their 

designation as a waste may not be 

appropriate. Allocation based on economic 

value as compared to allocation by mass 

leads to significantly lower environmental 

flows attributable to both SCMs, and seems to 

better reflect the purpose of the industries that 

produce the SCMs – production of steel or 

electricity. 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

As shown in figure 3-10, slag cement use dropped with the economic downturn beginning in 

2007. The Slag Cement Association (SCA) reported an 11 percent drop in 2009, although there 

was an even greater drop in the use of portland cement suggesting that slag cement was gaining 

popularity even as portland cement use fell. Overall trends appear to show some increases in 

slag production as the economy improves, but a long-term trend of decreased availability due to 

the closure of a number of U.S. blast furnaces and a lack of construction of new furnaces is 

expected. As of 2011, there were only four granulators installed at active blast furnaces in the 

U.S. (USGS 2013a).

Figure 3-10. U.S. slag cement shipments from 1996 to 2007 (adapted from SCA 2007). 

3-46

Slag cement is an attractive SCM for a number of reasons. For one, the typical dosage of slag 

cement is usually in the range of 25 to 35 percent of the total cementitious materials for paving 

concrete, although it can be used in even higher amounts (ACPA 2003). Furthermore, slag

cement creates very light colored concrete that some find aesthetically pleasing and has a high 

albedo that may help reduce the urban heat island effect where this is important (this is discussed 

in chapter 6). Some additional commentary on slag cement and paving concrete constructed 

with it include:

• Although slag cement particles are angular, it has a lower specific gravity than portland 

cement, meaning that a greater volume of slag cement is used to replace the same mass of 

portland cement; this results in reduced water demand and improved workability. 

• Slag cement can reduce air entraining efficiency so this must be carefully controlled.

• Slag cement can reduce the heat of hydration, which can be effectively used to reduce 

built-in curl and cracking if the specific concrete heat of hydration is measured. On the 

other hand, the lower heat of hydration can result in increased setting times, particularly 
Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

during cold weather placements. A rule of thumb is that the set time is delayed 30 

minutes for every 10 percent slag cement replacement of portland cement (ACPA 2003). 

• Early strength gain is generally retarded when slag cement is used, but the long-term 

strength is increased. 

• Permeability and chloride ion ingress are reduced when slag cement is used, and slag 

cement can be used to effectively mitigate ASR and sulfate attack.

As an industrial co-product material, slag cement will vary from source to source, but variability 

within a given source is usually very low. Often the properties of the slag cement are altered 

slightly depending on the fineness of the grind, with more finely ground slag cement being more 

reactive. An LCI for slag cement has been published (Prusinski, Marceau, VanGeem 2004). 

Other SCMs, including silica fume and natural pozzolans, are rarely used in concrete paving. 

Silica fume, an ultrafine non-crystalline silica co-product of the production of silicon metals and 

ferrosilicon alloys, is a highly reactive pozzolan often used in high-performance and ultra-highperformance concrete (UHPC). It is difficult to work with and is significantly higher in cost than 

portland cement and thus its use is often restricted to applications such as bridge decks that 

demand high strengths and a highly impervious matrix. 

Natural pozzolans represent a family of SCMs produced from natural mineral deposits or 

biomass. Some of these minerals, such as volcanic ash, are similar to what were used in ancient 

Rome to construct the Pantheon and aqueducts and can be used with only minimal processing, 

whereas others require calcination through heat treatment. More recently, there have been 

efforts to derive commercially viable natural pozzolans from biomass such as rice husks, but this 

effort has not yet been commercially successful in the U.S., primarily because of difficulties in 

controlling burning processes to produce consistently high quality pozzolans. Abundant supplies 

of natural pozzolans are available in many parts of the world where volcanic activity is common, 

including parts of Europe, Central America, and Africa. In the U.S., interest in natural pozzolans 

is increasing due to some rising uncertainty regarding the supplies of fly ash and slag cement. 

Blended Cements

Blended cement is produced and sold by cement manufacturers that intergrind or blend portland 

cement with fly ash, natural pozzolans, slag cement, limestone, or a combination. The blended 

cement can be a binary system, made with portland cement and one other material, or a ternary 

combination of portland cement and two other materials as specified under AASHTO M 240, 

Standard Specification for Blended Hydraulic Cements. These materials are classified as follows:

• Type IP(X) – The “P” indicates that this is portland-pozzolan cement in which “X” 

denotes the targeted percentage of pozzolan expressed as a whole number by mass of the 

final blended cement. Thus, a Type IP(20) is a blended portland-pozzolan cement that 

contains 20 percent pozzolan. The range of X allowed is up to 40 percent by mass of the 

blended cement. 

• Type IS(X) – The “S” indicates that this is portland-slag cement in which “X” denotes 

the targeted percentage of slag cement expressed as a whole number by mass of the final

blended cement. Thus, a Type IS(35) is blended portland-slag cement that contains 35 

percent slag cement. The range of X allowed is up to 95 percent by mass of the blended 

cement.

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

• Type IL(X) – The “L” indicates that this is portland-limestone cement in which “X” 

denotes the targeted percentage of limestone expressed as a whole number by mass of the 

final blended cement. The limestone can constitute up to 15 percent by mass of the 

blended cement. 

• Type IT(AX)(BY) – The “T” indicates that this is ternary blended cement in which the 

“A” refers to the type of pozzolan, slag, or limestone (either “P” for pozzolan, “S” for 

slag cement, or “L” for limestone) that is present in the larger amount by mass and the 

“B” refers to the additional material, either “P” for pozzolan, “S” for slag cement, or “L” 

for limestone that is present in the lesser amount. The “X” and “Y” refer to targeted 

percentage of mass for constituent “A” and “B” respectively. For example, a material 

designated as Type IT(S25)(P15) contains 60 percent portland cement, 25 percent slag 

cement, and 15 percent pozzolan. Two different pozzolans can also be blended together 

to create a Type IT(PX)(PY).

Typical portland cement replacement rates for blended cements are 10 to 12 percent for Type IL, 

15 to 25 percent for Type IP, and 30 to 50 percent for Type IS (based on Van Dam and Smith 

2011). The composition of a Type IT can vary significantly depending on the characteristics of 

the specific SCMs. 

In addition to the above designations, blended cements can be further labeled with the following 

suffixes:

• “A” to indicate air-entrained material.

• “MS” or “HS” to indicate moderate or high sulfate resistance.

• “MH” or “LH” to indicate moderate or low heat of hydration. 

• “R” to indicate resistance to alkali-silica reactivity (note this was added in 2014). 

The most recent addition to AASHTO M 240 is the Type IL portland-limestone cements that

were added in 2012. This followed the allowance of intergrinding portland cement clinker with 

up to 5 percent limestone that has been allowed in AASHTO M 85 since 2007. Portlandlimestone cements have been used in Europe for over 25 years (with the most popular type of 

cement used in Europe containing up to 20 percent limestone), and Canada approved the use of 

portland-limestone cements containing up to 15 percent limestone in 2009. In the latter case, the 

15 percent limit is in place to ensure the portland-limestone cement performs similarly to 

conventional portland cement and blended cements. At that replacement level, it is estimated 

that the use of a portland-limestone cement reduces CO2 emissions by up to 10 percent compared 

to conventional portland cement (CAC 2009). 

Although it is more common in the U.S. for the concrete supplier to blend portland cement with 

SCMs at the concrete plant, when the pozzolan, slag cement, or limestone are interground or 

blended by the cement supplier under AASHTO M 240 there is a greater level of quality 

assurance over the final product with less potential for unforeseen interactions and 

incompatibilities (Taylor et al. 2006). In addition, the use of AASHTO M 240 blended cements 

helps to avoid the potential for proportioning mistakes that can occur in the field. One drawback, 

however, is the use of a blended cement limits the concrete supplier’s ability to adjust the SCM 

content in response to changing conditions (e.g., cooler weather). 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Although all of these blended cements have been extensively evaluated in the laboratory, and 

early performance has also been assessed, continued monitoring and assessment of their longterm performance and characteristics for consideration in pavement design is needed. 

Aggregates in Hydraulic Cement Concrete

Aggregates have been discussed earlier in this chapter, including the environmental impacts of 

mining and processing them for use in pavements. This section addresses attributes of 

aggregates as they have a direct impact on the sustainability of hydraulic cement paving 

concrete. These attributes include aggregate grading, durability, and the use of RCWMs.

Aggregate coefficient of thermal expansion (CTE) is an important property that is defined as 

the change in unit length per degree of temperature change. Since coarse aggregate makes up the 

bulk of the volume of concrete, the CTE of the coarse aggregate is the most influential factor in 

the CTE of the concrete. Aggregates with very high CTE require special consideration when

used in concrete paving mixtures, particularly in climates with large diurnal and seasonal 

temperature changes. High CTE in concrete results in greater curling of the concrete under a 

thermal gradient, when the top and bottom of the slab are at different temperatures. This results 

in the development of higher tensile stresses that increase the potential for cracking in both 

jointed plain concrete pavement (JPCP) and continuously reinforced concrete pavement (CRCP), 

and provides an increased potential for faulting and roughness in jointed designs that must be 

handled in the pavement structural design and construction specifications. AASHTO T 336 is 

the recommended test method for CTE of the concrete mixture (FHWA 2011). Greater 

discussion of the effects of concrete CTE is included in chapter 4. 

Aggregate grading is an important step in establishing concrete mixture proportions as it has a 

profound effect on the amount of cementitious material needed to obtain the desired fresh and 

hardened properties for paving concrete. There are multiple approaches used to establish mixture 

proportions to achieve the proper balance of workability, strength, volumetric stability, and 

durability in the most cost effective and environmentally benign manner possible. Trade-offs often 

exist when attempting to optimize any one or two of these criteria at the expense of another. For 

example, reductions in the water-cementitious materials ratio (w/cm) generally decreases paste 

permeability and increases paste density, thereby increasing both strength and durability; however, 

workability will likely suffer if other adjustments are not made at the same time (e.g., changes in 

aggregate gradation or particle shape or the inclusion of chemical or mineral admixtures). 

A properly proportioned concrete paving mixture will often have an “optimized” aggregate 

grading (sometimes referred to as a well-graded mixture), in which multiple aggregate particle 

sizes are represented. This allows for a reduction in cementitious material content (making good 

use of fly ash, slag cement, and limestone replacement of portland cement) while achieving the 

required fresh (workability, finishability, and so on) and hardened (strength and durability) 

properties. Aggregate grading optimization has many different forms and there is not a single 

method that must be followed to achieve it. Pioneering work by Shilstone (1990), modified by 

others, provides good guidance but other approaches exist that work equally well. At its core, 

aggregate optimization is an empirical exercise that not only is affected by the aggregate particle 

sizes, but also the particle shape, texture, and specific gravities. When done correctly, aggregate 

grading optimization maximizes the aggregate volume through careful consideration of the 

particle size distribution. Today it is common to find highly workable, strong, and durable 

concrete paving mixtures with total cementitious materials contents of 540 lbs/yd3

 (320 kg/m3) 

or less, resulting in both economic and environmental savings compared to previous practices. 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Aggregate durability has been discussed earlier in this chapter, but its importance to the overall 

durability of concrete and on the longevity of the pavement cannot be overemphasized. 

Fundamentally, durability reflects the ability of a material to maintain its integrity in the 

environment it serves, and a concrete pavement that fails prematurely due to poor durability is 

not considered sustainable. It is therefore critical that aggregates used in concrete meet all the 

requirements of AASHTO M 6, Standard Specification for Fine Aggregate for Portland Cement 

Concrete and M 80, Standard Specification for Coarse Aggregate for Portland Cement 

Concrete. In addition, the aggregate should meet the following durability requirements:

• Freeze-thaw durability – Certain coarse aggregates are susceptible to damage if subjected 

to cyclic freezing and thawing in a saturated state. Aggregates are most often tested for 

freeze-thaw durability using ASTM C666. 

• ASR – ASR has affected countless pavements throughout the U.S. resulting in early loss 

of service life. The FHWA maintains a web-based ASR reference center 

(http://www.fhwa.dot.gov/pavement/concrete/asr.cfm) to provide the latest information 

on ASR to the pavement community and AASHTO recently published a provisional 

protocol PP65-11, Standard Practice for Determining the Reactivity of Concrete 

Aggregates and Selecting Appropriate Measures for Preventing Deleterious Expansion in 

New Concrete Construction that should be used to screen aggregates to be used in paving 

concrete. The use of SCMs such as Class F fly ash or slag cement are the most common 

mitigation strategies employed if susceptible aggregates are to be used. 

As discussed previously under the aggregates section of this chapter, the use of RCWMs

continues to increase for economic and environmental reasons. Specific issues regarding the use 

of RCWMs as aggregate in paving concrete are as follows:

• Recycled concrete aggregate – Specific caution needs to be exercised when using RCA as 

aggregate in new concrete. For one, it is most common to use only the coarse fraction of 

the RCA because the fine fraction has high water demand that affects workability and 

may have high chloride contents if deicers have been used. Furthermore, it is critical that 

the aggregate stockpile is watered prior to batching. There are several recent publications 

that provide excellent guidance on the use of RCA as aggregate in paving concrete 

(ACPA 2009; Van Dam et al. 2011).

• Reclaimed asphalt pavement – RAP is a commonly recycled material produced when an 

existing asphalt concrete pavement is cold milled as part of a pavement rehabilitation or 

reconstruction. The preferred higher use of RAP is in new asphalt concrete as it makes 

maximum use of the binder as well as the aggregate. In some markets, such as the 

Chicago area, there is a large surplus of coarse “fractionated” (material retained on larger 

sized sieves) RAP and it is being used as aggregate in new paving concrete by some 

entities such as the Illinois Tollway Authority. In these instances, care should be 

exercised to ensure the presence of the RAP will not negatively impact the fresh and 

hardened properties of the concrete. 

• Air-cooled blast furnace slag – ACBFS continues to be used as a coarse aggregate in 

paving concrete. However, there are pavement design, concrete mixture, and 

construction considerations that must be followed in order for the material to be used 

most effectively in this application (Morian, Van Dam, and Perera 2012; Smith, Morian, 

and Van Dam 2012). 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Water Sources

Water is used in the concrete production process not only in the preparation of the concrete 

mixtures, but also in the cleaning of trucks and equipment. Decisions regarding concrete mixing 

water must consider three criteria (Van Dam et al. 2012): 

1. Quality (e.g., the water must be free of organic materials that may adversely affect 

strength and durability of the concrete); 

2. Impact on the environment (e.g., depletion of local water resources, such as wells, 

streams and ponds, or energy required for potable water distribution systems and the 

infrastructure required for delivery of that water); and 

3. Economic factors. 

Technologies for using increasing amounts of “grey water” (that obtained from washing concrete 

production equipment and trucks) are rapidly becoming more common and accepted. Figure 3-

11 presents a schematic for recycling concrete wash water into concrete mixture water, while 

table 3-8 presents typical limits on chlorides, solids, and other potentially harmful contaminants 

in recycled water. Table 3-9 shows some of the impacts the use of recycled water can have on 

concrete properties, with the primary concern being high solids content. 

Figure 3-11. Schematic of mixer truck washout water recycling for concrete batch plant mix 

water (Taylor et al. 2006). 

Table 3-8. Harmful contaminants, tests methods and limits for grey water to be used in 

concrete mixtures (Taylor et al. 2006). 

Maximum Conc. In Combined Water Limits, ppm Test Method

Chloride as Cl-

 Prestressed

 Other Reinforced Concrete

500

1000

ASTM C 114

Sulfate as SO4 3000 ASTM C 114

Alkalis as (Na2O +0.658 K2O) 600 ASTM C 114

Total Solids by Mass 50,000 ASTM C 1603

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Table 3-9. Effect of recycled water on concrete properties (Taylor et al. 2006). 

Recycled Water with Water 

Demand

Setting 

Time

Compressive 

Strength Permeability Freeze-thaw Resistance

Solid contents within 

ASTM C94 limits 

(< 8.9 kg/m3 or <15 lb/yd3)

↔ ↔ ↔ ↔ ↔

High solid contents 

(> 8.9 kg/m3 or >15 lb/yd3) ↑ ↓ ↓** ↑** ↔

High solid contents and 

treated with hydration 

stabilizing admixture

↔ ↔ ↔ no data no data

Source: After Lobo and Mullings (2003)

* Compared to reference concrete with tap water.

** Strength and permeability effects were related to increased mixing water content.

Key: ↓ decreased

 ↑ increased

↔ no trend

Chemical Admixtures

Chemical admixtures are added during batching to modify the fresh or hardened properties of 

concrete. These modifications can enhance sustainability by improving the workability of the 

concrete, reducing water demand, and improving durability. Modern paving concrete makes 

extensive use of chemical admixtures with the most common admixtures listed in table 3-10. An 

excellent description of the various chemical admixtures can be found in Kosmatka and Wilson 

(2011). A summary of the three most common classes of chemical admixtures used in 

pavements follows. 

Table 3-10. Common chemical admixtures used in paving concrete (Taylor et al. 2006). 

Class Function

Air-entraining admixture (AEA)

To stabilize microscopic bubbles in concrete, 

which can provide freeze-thaw resistance and 

improve resistance to deicer salt scaling.

Water-reducing admixture (WRA) 

To reduce the water demand by 5 to 10

percent, while maintaining slump 

characteristics.

Mid-range water reducing admixture

(MRWRA) 

To reduce the water demand by 6 to 12

percent, while maintaining slump and 

avoiding retardation.

High-range water reducing admixture

(HRWRA)

To reduce the water demand by 12 to 30

percent, while maintaining slump.

Retarder To decrease the rate of hydration of cement.

Accelerator To increase the rate of hydration of cement.

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Air entraining admixtures (AEAs), specified in accordance with AASHTO M 154, are used 

almost universally in modern paving concrete to enhance the freeze-thaw durability of the 

hydrated paste, but they also improve the workability of the concrete and reduce water demand, 

mixture segregation, and bleeding (Taylor et al. 2006). AEAs form microscopic spherical 

bubbles that should remain stable as the concrete hardens. It is essential that the bubbles are 

uniformly spaced and sufficiently close to protect the paste from damage during freezing and 

thawing. Figure 3-12 shows the air voids in a polished concrete sample viewed through a 

stereomicroscope.

Traditionally, AEAs were predominately based on salts of wood resins (Vinsol® resin) but 

modern AEAs are often derived from varied natural and synthetic sources. Because the 

chemistry of the AEA and interactions with other mixture constituents can impact its 

effectiveness, it is important to test the concrete during laboratory mixture proportioning through 

construction using the job mix formula (Taylor et al. 2006). 

Figure 3-12. Polished slab of concrete viewed through stereomicroscope. Dark circles are 

entrained air voids distributed throughout the grey hydrated cement paste. 

3-53

For the most part, testing of fresh concrete measures only the total air content in the concrete, but 

ideally what is desired is an indication of the size and distribution of those air voids in the 

concrete. The air-void analyzer (AVA) showed early promise in measuring the air-void system 

parameters in fresh concrete but it has not been found to be as effective when used with stiff, low 

slump paving concrete. Currently, the only way to ensure that the air-void system parameters 

meet the criteria for resistance to freeze-thaw damage is to cut and polish the hardened concrete 

and examine it with a stereomicroscope in accordance with ASTM C457. Automated methods 

based on digital image analysis are in use and being refined to make this process less onerous.
Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Water-reducing admixtures are divided into two classes, according to ASTM C494: waterreducing admixtures (WRA) and high-range water-reducing admixtures (HRWRA), although it 

is common to also include a mid-range water-reducing admixture (MRWRA) as previously listed

in table 3-10. These admixtures function at the surface of the cement grains, causing grains to 

disperse and minimizing cement particle agglomeration. This makes the available water much 

more effective, and therefore reduces water demand. 

For paving, it was very common in the past to use standard WRAs (based primarily on 

lignosulfonate chemistry) but this practice is slowly giving way to the increasing use of 

MRWRA based on the newer polycarboxylate chemistry. This chemistry is highly advantageous 

as it maintains its effectiveness for longer periods of time, but polycarboxylates are also known 

to entrain air and thus must be formulated for the application and tested for compatibility with 

the AEA to ensure that the entrained air-void system has the desired properties. 

From a sustainability perspective, water-reducing admixtures have revolutionized concrete 

technology including concrete paving. A WRA will permit up to 12 percent water reduction 

while maintaining the desired level of workability (slump, cohesiveness, compactability, 

finishability). This allows for the mixing water to be reduced while holding the cementitious 

content constant, thus reducing the w/cm. All things equal, lowering the w/cm reduces the 

volume of pores in the hardened concrete, which in turn results in higher strength and lower 

permeability. Thus, water-reducing admixtures are considered an essential constituent in 

improving the sustainability of paving concrete as they increase concrete longevity, reduce water 

use, and allow for a reduction in cementitious materials. 

Set-Modifying Admixtures are used to either accelerate (accelerators) or retard (retarders) the 

set time and early strength gain of concrete. Cement hydration is a chemical reaction that is 

sensitive to many factors, some of which are inherent in the mixture and others external to it. 

Externally, the biggest factor affecting set time is temperature, with cold temperatures slowing 

down the hydration process. To address this, accelerators are sometimes used during cold 

weather placements to “kick-start” the reactions so that the heat of hydration can be engaged to 

support continued reaction. This is especially true for high SCM mixtures that often have a 

lower heat of hydration. Accelerators are also often used in accelerated construction in which 

the pavement needs to be opened to traffic as soon as possible. 

At the other extreme, higher temperatures may accelerate the hydration process, and the use of 

retarders may then be needed during hot weather conditions in an attempt to delay hydration. In 

addition, a long hauling distance may require that the concrete set be retarded to accommodate 

the time of transport. 

In the long term, accelerated mixtures rarely achieve the same strength or as low a permeability 

as mixtures that were retarded. Thus, the need for early strength in some applications needs to 

be balanced against the potential for lower long-term strength and reduced durability over the life 

cycle. 

Alternatively, proprietary non-portland cement-based systems are available that can achieve 

high-early strength and reportedly long-term performance, but these materials are more costly 

than portland cement-based systems and are often more difficult to work with. This restricts 

their use primarily to maintenance and rehabilitation applications. The environmental impacts of 

non-portland cements depend on the raw materials and processes used to produce them. For 

example, the GHG emissions from calcium sulfoaluminate (CSA) cement production can be 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

significantly lower than for portland cement. This is true even though the mining of the primary 

raw ingredient in CSA, bauxite, produces more GHG than does the raw materials extraction for 

portland cement, because the bauxite does not undergo calcination (Quillen 2007). Other 

emissions may be higher for CSA than portland cement. 

The environmental impact of admixtures must consider the impacts incurred in the production 

and transportation of the admixture to the concrete plant site. In general, the amount of 

admixture used is quite small, usually on the order of less than 0.25 gal of liquid admixture per 

yd3 (1.23 l per m3) of concrete. As a result, it is common for the environmental impact of 

chemical admixtures to not be included in an LCA as the impact of such small dosages of these 

admixtures was found to be insignificant in previous LCA studies. However, there are some 

types of admixtures that are rarely used in paving concrete, such as HRWRA, that when added at 

a much higher dose may contribute significantly to the environmental impact of the concrete 

mixture. For example, at least one study on concrete bridge decks has shown that admixtures 

can contribute a non-negligible fraction of material production energy and emissions when 

heavily dosed (Keoleian et al. 2005). 

Mixture Proportioning and Plant Production

For slipform paving concrete, the general approach to mixture design is to economically create 

relatively stiff concrete mixtures (slumps typically in a range of 0.5 to 1.5 inches [13 to 38 mm]) 

with good cohesiveness and finishability. The specified air content will vary with the type of 

exposure the pavement will have to freeze-thaw cycling and deicers, but generally will lie in a 

specified range between 5.0 and 7.5 percent. The concrete strength is often assessed based on 

flexural strength, most often measured in third-point loading in accordance with AASHTO T 97, 

and exhibiting typical values between 600 and 800 lb/in2

 (4.2 and 5.5 MPa) at 28 days. There 

are many other factors that can be considered, any of which contribute to the overall 

sustainability of the concrete. Detailed information on concrete mixture design and 

proportioning for pavements can be found in Taylor et al. (2006). Other plant-prepared concrete 

mixtures that might be used on a pavement project include roller compacted concrete (RCC), 

cement-stabilized or cement-treated bases, or pervious concrete. Regardless of the mixture type, 

a similar approach is used for proportioning and production. 

Mixture proportions are selected prior to construction to meet the various mixture design 

objectives, which may include economy, workability, strength, durability, and sustainability. 

There are many approaches to establishing the required proportions, but all involve working in 

the laboratory with the anticipated concrete constituents and batching and testing mixtures until 

the desired mixture design objectives are met in the laboratory. It is then essential that the 

concrete is tested in the field prior to full-scale production to ensure that the laboratory-derived 

proportions can be produced under field conditions using the assigned concrete plant and will 

yield the desired fresh and hardened properties. 

Batching is the process of measuring quantities of concrete mixture ingredients, based on the 

proportions developed previously, and then introducing them into the mixer. Central batching of 

the mixture must be executed under tight control because the consistency of the mixture from 

batch-to-batch and day-to-day significantly affects the workability and finishability of the fresh 

concrete as well as the hardened concrete properties (strength and durability). Batch-to-batch 

consistency is absolutely essential to creating a good performing concrete pavement as nonuniform concrete can lead to variable quality that can adversely affect initial ride quality, surface 

texture, and ultimately performance and life. 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Once the concrete is batched into the mixer, it must be thoroughly mixed to a uniform 

consistency. Not only must the mixing process thoroughly combine the cementitious materials, 

aggregates, and water, it is also an essential step in creating the entrained air-void system that 

protects the concrete paste against freeze-thaw damage. Properly mixed concrete should have 

essentially the same fresh and hardened properties throughout the entire batch, allowing for 

variability in the testing itself. This can be evaluated using AASHTO M 157. 

Most concrete used in paving projects will be produced by a stationary central mixer, whether a 

permanent plant or a portable plant erected on site. There are many different types of stationary 

concrete mixers, with a tilt rotating drum mixer being the most common for paving concrete 

although non-tilting type, reversing drum, or horizontal shaft mixers are also used. Quality 

concrete can only be produced in a well-maintained plant, and thus worn, damaged, or coated 

blades must be replaced, repaired, or corrected. For a given concrete plant, the three most 

important factors are:

• Batch Size – Mixers should not be loaded above their rated mixing capacities. 

• Sequencing – Mixture constituents must be added in a given sequence that must not vary 

batch to batch. In general, some of the water is added first, followed by coarse aggregate, 

sand, and then the cementitious materials. Approximately 10 percent of the water is held 

back to be added after all other materials are in the mixer. Admixtures in particular must 

be added in the same sequence each time.

• Mixing Time – The time of mixing is critical as inadequate mixing will result in nonuniformity and over mixing can negatively impact the entrained air-void system. Many 

specifications require a minimum mixing time of 1 minute plus 15 seconds for every 

cubic yard of concrete unless performance testing is conducted that demonstrates 

uniformity in a shorter period of time.

Once concrete is mixed in a stationary mixer, it is deposited in non-agitating trucks or into truck 

mixers that operate at “agitating speed” of 2 to 6 rpm to maintain homogeneity (Kosmatka and 

Wilson 2011). Truck mixers can also be used to finish the mixing process that was begun in the 

stationary mixer (referred to as shrink-mixed concrete). 

In some cases, typically for smaller projects, when high-early-strength materials are being used 

in maintenance or rehabilitation, or when exceptionally long transit times exist, concrete 

constituent materials are batched dry and mixed in truck mixers. Typically 70 to 100 revolutions 

of the drum or blades at mixing speed (12 to 18 rpm) are used to produce the uniformity 

required, after which the speed is reduce to 2 to 6 rpm (agitating speed) to maintain homogeneity 

in transit and during delivery (Kosmatka and Wilson 2011). Overmixing can have negative 

effects on the fresh and hardened concrete properties and thus AASHTO M 157 limits the 

number of drum revolutions to 300 after water is added to the dry constituents.

There are also specialized mobile volumetric mixers that batch concrete by volume and 

continuously mix it using an auger system (Kosmatka and Wilson 2011). These types of mixers 

are typically used for small batches or with rapid-setting proprietary materials during concrete 

pavement maintenance and rehabilitation. 

Factors that impact the quality assurance of mixture production include material handling and 

stockpiling operations (especially the use of techniques that prevent aggregate segregation and 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

ensure consistent aggregate moisture conditions), the calibration and accuracy of batch scales 

and weigh hoppers, and ensuring adequate mixing time. It is particularly important that 

aggregate moisture contents be measured frequently and that mixture proportions are adjusted 

accordingly. In addition, mixer uniformity testing should be performed in accordance with 

ASTM C94 for each concrete plant/mixture combination to determine the minimum mixing time 

required to achieve uniform concrete. Taylor et al. (2006) and Kosmatka and Wilson (2011) 

provide excellent guidance on the required concrete plant operations necessary to produce 

consistent concrete for a paving operation. 

Durability

A number of properties of the hardened concrete influence durability, including permeability, 

strength, air-void system characteristics, resistance to external chemical attack, and the physical 

and chemical stability of the aggregates. ACI 201.2R (ACI 2008) provides an excellent 

summary of physical and chemical mechanisms that can impact the durability of concrete and 

describes strategies to improve durability. 

Sustainability dictates that the concrete used in paving be durable in the environment in which it 

serves. Concrete has a reputation as a long-lasting paving material, and there are many examples 

of concrete pavements remaining in service for 40 years or more (Tayabji and Lim 2006). As a 

result, it has become common practice for some highway agencies to design high-traffic-volume 

concrete pavements for services lives of 40 to 50 years. But for this practice to be sustainable, 

the concrete must possess the durability to withstand the environmental loading it will be 

subjected to over many decades of service. During laboratory mixture proportioning, testing 

must be conducted confirming that the proposed concrete mixture meets or exceeds the design 

requirements, and rigorous testing must be conducted during production to make sure that 

concrete as produced possesses the attributes to create a long-lasting concrete pavement.

The concrete design, proportioning, and production process must create a concrete paving 

mixture that economically meets all design strength, durability, and sustainability requirements 

over the pavement life cycle. Concrete with a low cementitious materials content (540 lbs/yd3

[320 kg/m3

]), a high replacement of portland cement with high-quality SCMs (30 percent or 

greater), durable aggregates, a properly entrained air-void system, and a relatively low w/cm

(based on mass, 0.40 to 0.45 is considered good for most applications) will have a relatively low 

GHG emissions footprint at production and is expected to have good long-term physical 

properties to provide excellent economic, environmental, and societal performance. However, 

there is no one “recipe” that will create “sustainable” paving concrete. Instead, the concrete 

technologist/producer needs to work within project constraints and the available materials to 

balance a number of discrete and competing variables to enhance sustainability moving forward. 

Strategies for Improving Sustainability

Some general strategies for addressing the major issues described above are summarized in table 

3-11, with greater elaboration provided below. Although some quantitative analysis of the net 

impacts of these practices to improve sustainability have been evaluated using LCA (particularly 

as relating to the use of SCMs to replace portland cement in concrete), more work needs to be 

done to consider the full materials production phase. 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Table 3-11. Approaches for improving pavement sustainability with regard to concrete 

materials production. 

Concrete Materials 

Objective

Sustainability Improving 

Approach

Economic Impact Environmental Impact Societal Impact

Improved cement plant 

efficiency through better energy 

harvesting and improved 

grinding

High capital cost but lower 

cost of manufacturing

Reduced energy 

consumption and GHG 

emissions

Less fuel consumed

and emissions 

generated 

Utilization of renewable energy

including wind and solar

High capital cost but lower 

cost of manufacturing

Reduced non-renewable 

energy consumption and 

GHG emissions

Less non-renewable 

fuel consumed and 

GHG generated

Reduce Non-Renewable 

Energy Consumption

Utilization of more efficient 

fossil fuels

Lowers manufacturing 

costs

Reduces emissions per 

unit of energy used

Cleaner burning fuel

and GHG Emissions in 

Cement Manufacturing

Utilization of waste fuels Lowers manufacturing 

costs

Beneficial use of waste

material

Reduces materials in 

landfills

Utilization of biofuels Reduces cost to cost 

neutral

Reduces GHG emissions Reduces dependency 

on fossil fuels

Minimize clinker content in 

portland cement through 

allowable limestone additions 

and inorganic processing 

additions

Reduces cost to cost 

neutral 

Reduces GHG emissions 

and consumption on fuel

Reduces dependency 

on fossil fuels and 

lowers emissions

Increase production of blended 

cements containing limestone or 

SCMs

Reduces cost Significant reduction in 

energy consumption and 

GHG emissions. 

Redirects RCWMs from 

landfill

Reduces dependency 

on fossil fuels and 

less material sent to 

landfill

Increase concrete mixing plant 

efficiency and reduce emissions

Increased capital cost but 

decrease production costs

Reduced emissions Reduced local 

emissions including 

noise and particulate

Utilization of renewable energy Cost neutral to increase 

cost

Reduced emissions Reduced emissions

Use electrical energy from the 

grid

Depends on proximity to 

grid – should save cost

Reduced emission, better 

emission controls

Reduced local 

emissions

Reduce Energy 

Consumption and 

Emission in Concrete 

Production

Use less cement in concrete 

mixtures without compromising 

performance 

Reduce cost of concrete Reduced emissions and 

energy 

Longer lasting 

pavements – less 

delays 

Use more blended cements 

without compromising 

performance

No impact on cost Reduced emissions and 

energy 

Longer lasting 

pavements – less 

delays

Increase addition rate of SCMs 

at concrete plant without 

compromising performance

Reduce cost of concrete Reduced emissions and 

energy 

Longer lasting 

pavements – less 

delays

Reduce Water Use in

Recycle washout water Cost neutral to slightly 

added cost

Use less water resources Improved water 

quality

HCC Production Recycle water used to process 

aggregates

Cost neutral to slightly 

added cost

Use less water resources Improved water 

quality

Increase Use of 

RCWMS and Marginal

Change specifications to allow 

greater amounts of RCWMs to 

be used in concrete without 

compromising performance

Reduced cost Less landfill material, 

less transportation

Materials as Aggregate 

in Concrete

Use RCWMs and marginal 

aggregates in lower-lift of twolift pavement

Cost neutral to slightly 

added initial cost; potential 

for reduced life cycle costs

Less landfill material, 

less transportation

Lower w/cm through admixture 

use

Cost neutral to slightly 

added cost

Longer lasting pavements Less delays over life 

cycle

Improve the Durability 

of Concrete

Utilize an effective QA program 

throughout material production 

phase

Slightly added initial cost 

– save cost on litigations

Longer lasting pavements Less delays over life 

cycle 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Strategy: Reduce Non-Renewable Energy Consumption and GHG Emissions in Cement 

Manufacturing 

There are two major approaches to implementing this strategy: reduce consumption of nonrenewable energy in the manufacturing process and reduce the clinker content of the cement that 

is shipped. Regarding the first approach, the main obstacle to implementation is the need to 

invest capital to improve existing cement plants or construct new ones. Retrofitting new 

technology on older plants is not always possible and it can take over a decade and $1 billion to 

permit and construct a new cement plant. Yet innovations can result in significant improvement 

to existing plants, including increasing the use of renewable energy (e.g., wind, solar) to generate 

electricity and switching to alternative fuels in the kiln (such as natural gas, waste fuels such as 

used tires and solvents, and increased use of biofuels). Nevertheless, the “low hanging fruit” 

regarding improvements to existing facilities have already been picked and future enhancements 

will take greater investment. The capital to invest in such improvements will remain tight until 

the world market for cement improves. 

The second approach to this strategy is to focus on diluting the clinker content of the cement that 

is shipped from the plant. The largest contributor to GHG emissions is tied to calcination of 

calcium carbonate, an inherent process essential to the manufacturing of portland cement. From 

a cement manufacturer’s perspective, major reductions in GHG emissions can only occur by 

reducing the clinker content in the cement sold, both by increasing the percent of limestone and 

inorganic processing aids in AASHTO M 85 portland cement and through increased production 

of AASHTO M 240 blended cements containing limestone or SCMs (i.e., Type IL, Type IP, 

Type IS, and Type IT). As manufactured products, the quality assurance on blended cements is 

higher than what occurs when SCMs are added to the concrete mixture at the plant. However, 

the trade-off is reduced flexibility during concrete production that may require capital investment 

by the concrete producer to add one or more additional cement silos. Furthermore, stable 

sources of high quality SCMs are uncertain, which may result in shortages in the future. 

Strategy: Reduce Energy Consumption and Emissions in Concrete Production

The concrete production process is complex, but efficiencies can be realized at almost every step. 

To help evaluate the overall efficiency of concrete production, the National Ready Mix Concrete 

Association (NRMCA) offers a Sustainable Concrete Plant Certification2

2 http://www.nrmca.org/sustainability/Certification/PlantCertification.asp

 that provides a 

quantitative, performance-based metric for concrete suppliers to demonstrate excellence in 

sustainable development. This certification includes reduced energy consumption, particulate

and GHG emissions, water use, and groundwater and surface water contamination.

The efficiencies of concrete plants continue to improve, resulting in economic, environmental, 

and societal savings. The utilization of renewable energy, whether produced on site or purchased 

off the grid, will result in reduced consumption of energy produced by fossil fuels and a 

reduction in emissions. If electricity is not produced on site using renewable means (e.g., wind, 

solar), the concrete plant should draw from the electrical power grid if at all possible because this 

is more efficient than producing power with on-site generators. On-site production of power is 

the least attractive alternative as it is not only inefficient, but can have major local impacts 

regarding emissions and noise generation. 

Although the strategies cited to reduce energy consumption in concrete production also reduce 

GHG emissions, additional strategies can be employed to further reduce GHG emissions 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

associated with the production of concrete. These are centered on using less portland cement 

clinker per cubic yard of concrete, which can be accomplished through the following means: 

• Use an optimized aggregate gradation. This is commonly the most effective way to 

reduce the required total cementitious materials content, but often requires one or more 

additional aggregate bins be added to a concrete plant that was originally set up to handle 

only coarse and fine aggregate. The concrete properly produced with an optimized 

gradation will have good uniformity, resist segregation, be readily consolidated and 

finished, and have excellent strength, shrinkage, and permeability characteristics. 

• Use blended cements. Blended cements provide a means to significantly reduce GHG 

emissions by reducing the content of GHG-intensive portland cement used in the mixture. 

However, the use of blended cements will require concrete suppliers to have at least three 

cement silos: one for portland cement, one for blended cement, and one for an SCM. In 

this scenario, many suppliers would have to add an additional silo that would represent a 

significant capital investment. 

• Increase the addition rate of SCMs at the concrete plant. SCMs added at the concrete 

plant can be used in lieu of blended cement or can be used in addition to a blended 

cement in a complementary fashion. There is a practical limitation to how much total 

replacement of portland cement with SCMs can be used, and depends on the required 

early strength, type of SCM, and ambient climatic conditions, among other factors. The 

importance of good mixture proportioning and testing, as well as good quality assurance

during production, cannot be overemphasized; otherwise, pavement performance may be 

compromised. 

Strategy: Reduce Water Use in HCC Production

Water is used in the production of concrete to support the chemical reactions that cause cement 

to harden and gain strength. A typical concrete made with 564 lbs of cement per yd3

 (335 kg of 

cement per m3) of concrete and a w/cm of 0.50 will require 282 lbs of water per yd3 (167 kg of 

water per m3) of concrete. Through good mixture proportioning and the use of water-reducing 

admixtures, the cement content could easily be reduced to 520 lbs/yd3

 (308 kg/ m3) and the w/cm

could be reduced to 0.42, saving 64 lbs of water per yd3

 (38 kg of water per m3) of concrete. Not 

only is water saved, but the GHG emissions are also reduced through the reduced quantities of 

cement.

Water consumption can also be reduced by recycling water used to process aggregates, including 

the water used for aggregate washing and for maintaining aggregate moisture, and in washing 

out trucks and equipment as illustrated previously in figure 3-11. This requires capital 

investment and space to establish an area to recycle water.

Strategy: Increase Use of RCWMs and Marginal Materials as Aggregate in Concrete

Of all the various strategies, this one requires the greatest care during mixture proportioning and 

production to ensure pavement performance is not compromised. RCA and ACBFS have both 

been successfully used as coarse aggregates in concrete pavement, yet both have also resulted in 

some notable failures. One problem is that concrete made with RCWM coarse aggregates often 

exhibits hardened properties that differ from concrete made with virgin aggregates and these 

differences may not be accounted for in the structural design of the pavement. Another potential 

issue is that RCA and ACBFS coarse aggregate must be kept wet when stockpiled prior to 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

batching due to their high absorptivity. If batched dry, they will absorb a significant amount of 

the mixing water, which not only negatively affects workability but can also lead to early 

cracking. Guidance on using RCWMs as aggregates in paving concrete is available from several 

sources (e.g., ACPA 2009; Van Dam et al. 2011; Smith, Morian, and Van Dam 2012).

The use of “marginal” aggregates is something that is becoming a necessity as sources of good 

quality aggregates become exhausted. Many factors can make an aggregate marginal, including 

issues with cleanliness, freeze-thaw durability, wear resistance, or susceptibility to ASR, among 

other items. The key to the effective utilization of marginal aggregates is to understand what 

properties of the aggregate are in question and then implementing strategies to address those 

limitations, primarily through consideration of these properties in design. For example, if it is a 

matter of cleanliness, washing the aggregates may be all that is needed. If freeze-thaw durability 

is an issue and it is related to the size of the aggregate (larger sized aggregate particles are more 

susceptible to freeze-thaw damage, all other things equal), then the aggregate can be crushed 

more thoroughly to a smaller size and then blended with a larger-sized stone that possesses the

required freeze-thaw durability. Aggregates that are susceptible to ASR can be used if an 

effective mitigation strategy is employed, such as the use of an appropriate SCM. Wear 

resistance can be addressed by using susceptible aggregates in lower depths within the concrete 

slab through the use of two-lift construction. In fact, two-lift construction is a very effective 

design that can be used to accommodate increasing levels of RCWMs in the lower lift and thus 

reduce the overall environmental impact of the pavement. 

Overall, the success in using marginal aggregates depends on having the knowledge to mitigate 

the weakness in the aggregate and then employing the appropriate mitigation strategy is 

employed during production.

Strategy: Improve the Durability of Concrete

There are many examples around the U.S. where concrete roads built in the early 1900s are still 

in service today, and other examples of concrete roads that carried traffic for 30 to 40 years with 

little need of maintenance. At the same time, there are also many examples of concrete roads 

that have suffered serious damage within a decade of construction due to durability issues such 

as freeze-thaw damage or ASR. For example, a current issue in several Midwestern States is 

joint deterioration that is the result of freeze-thaw damage, apparently amplified by the use of 

liquid brine deicing agents (Taylor 2011). Since durability is not an intrinsic property of 

concrete, but instead reflects the concrete’s ability to resist the environment in which it serves, 

there is no way to directly measure it. ACI 201.2R (ACI 2008) provides a good description of 

mechanisms that can affect concrete durability and how durability can be enhanced. In general, 

depending on the environment, durable concrete possesses the following characteristics:

• A relatively low w/cm, typically in a range of 0.40 to 0.45. This will reduce the 

permeability and increase the strength of the hardened concrete.

• A high quality SCM in sufficient quantity to reduce permeability and increase long-term 

strength. An SCM can also be used to mitigate ASR and sulfate attack, but its ability to 

do so must be verified through testing. 

• An effective air-void system comprised of closely spaced, spherical microscopic air 

bubbles. These are essential to relieve pressure generated as the water freezes in the 

concrete pores, and are particularly critical in freeze-thaw environments where deicing 

chemicals are used. 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

• Aggregates that are both physically and 

chemical stable, and will not degrade or 

crack under service conditions. If ASR 

susceptible aggregates must be used, 

mitigation strategies in accordance with 

AASHTO PP 65-11 should be employed to 

minimize the risk of damage. 

Additional features may be needed to ensure 

durability for a given situation. It is essential that 

an effective QA program be rigorously adhered to 

throughout concrete production and construction.

Future Issues/Emerging Technologies

There are a number of issues and emerging 

technologies that have the potential to affect the 

production and use of concrete materials in the 

near future. These include: 

• The EPA released an amended air toxics 

rule for portland cement manufacturing 

that significantly restricts emissions 

(especially of mercury which comes from 

both the burning of coal and calcination of 

the calcium carbonate) by U.S. cement 

plants by September 20153

3 http://www.epa.gov/airquality/cement/pdfs/20121220_port_cement_fin_fs.pdf

. The impact of 

this new rule is uncertain, but it is clear 

that it will result in lowering the 

environmental impact of cement 

production. Switching to alternative fuel 

sources can address some of the issues 

related to mercury released during coal

combustion, but mercury released during 

calcination of the calcium carbonate will 

result in increased capital cost for some 

cement plants to install mercury capture 

equipment and the likely closing of others 

where it is not economically viable. 

• If fly ash becomes scarce, the market share 

of slag cement would be expected to 

increase. As U.S. slag production is 

expected to remain relatively constant, the 

long-term growth in the supply of slag 

cement is likely to hinge on imports, either 

of ground or unground material (USGS 

2013b). The environmental impact of 

 

Portland Limestone Cements (PLC)

One way to reduce the environmental 

footprint of cementitious binders is through 

the use of AASHTO M240 (ASTM C595) 

Type IL portland-limestone cements, which 

allows up to 15 percent limestone to be 

interground with portland cement clinker. 

The 15 percent limit is in place to ensure 

the PLC performs similarly to conventional 

portland cement and blended cements. At 

this replacement level, it is estimated that 

the use of portland-limestone cement 

reduces CO2 emissions by up to 10 

percent compared to conventional portland 

cement (CAC 2009).

Although the major motivation to use Type 

IL cement is to reduce CO2 emissions, 

there are other advantages. Limestone is 

softer than clinker and thus when the two 

are interground the limestone particles are 

finer than the clinker particles resulting in 

improved particle packing. The fine 

limestone particles act as dispersed 

nucleation sites for the formation of 

hydration products that result in a dense 

microstructure as hydration proceeds. And 

finally, the limestone reacts with the 

aluminate phases present in portland 

cement and many SCMs to create 

carboaluminate phases (Matschei, 

Lothenbach, and Glasser 2007). Further 

advantages can be achieved when an 

SCM (e.g., fly ash, slag cement) is 

combined with a Type IL cement. Thus, in 

an AASHTO M240 Type IT blended ternary 

cement, cement manufacturers can 

optimize the chemical and physical 

properties of the portland cement, 

limestone, and the SCM to achieve 

equivalent or even improved performance 

to that obtained using conventional 

portland cement. Several North American 

field studies have demonstrated that Type 

IL cements can be used similarly to 

AASHTO M85 and other M240 cements in 

the construction of concrete pavements 

(Thomas et al. 2010; Van Dam, Smartz, 

and Laker 2010). It is cautioned that longterm pavement performance data are not 

yet available for concrete pavements made 

with Type IL cements.

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

importation will be closely linked to the mode of transportation, with transport by 

barge/ship having significantly lower impact than by truck (see table 3-1). 

• One innovation is the high-volume SCM/portland limestone cement mixtures that are 

becoming more common. As state highway agencies accept this technology, it has the 

potential to significantly lower the GHG emissions associated with paving concrete. 

• Photocatalytic cement is another innovation that potentially offers an opportunity to 

create a highly reflective surface that remains clean while treating air pollution through a 

photocatalytic reaction involving nanoparticles of titanium dioxide (TiO2). The reactions 

result in a chemical reduction of nitrous oxides (NOx), which prevents the formation of 

ozone and associated smog. In addition to this pollution-reducing quality, these cements 

are often very lightly colored and have very high albedo (reflectance) properties, which 

can result in a lowering of pavement and near surface temperatures (see chapter 6) while 

providing an aesthetically pleasing appearance due to their self-cleaning properties. The 

environmental benefits of photocatalytic cements have been documented in laboratories 

and on paving projects throughout Europe (Guerrini et al. 2012; Beeldens 2012), where 

more than 2.4 million yd2 (2 million m2

) of photocatalytic surfaces have been 

constructed, with horizontal surface applications like pavements (including both paving 

block and single-lift concrete pavement) comprising about half of that total. Reductions 

in NOx have been reported to be as high as 60 percent, depending upon local 

environmental conditions and the technique for dispersing the TiO2 in the concrete 

(Beeldens 2012). Pavement uses of photocatalytic cements in the U.S. have included 

paving blocks, porous concrete, and slurry-infiltrated asphalt pavement (Guerrini et al. 

2012). One acclaimed project is the reconstruction of Cermak Road in Chicago, where 

pervious pavers with a photocatalytic surface have been employed (Oberman 2013). An 

effort to implement this technology featuring its use in the top layer of a two-lift concrete 

pavement project constructed on Route 141 near St. Louis, Missouri in 2010 was not as 

successful as hoped, demonstrating the need for continued research on this technology to 

determine the best avenue for implementation. 

• Low carbon and carbon sequestering cementitious systems are emerging including 

geopolymers (Van Dam 2010) and alkali-activated fly ash (Hicks, Cheng, and Duffy 

2010). Work continues on a number of other cementitious systems that have the potential 

to actually sequester carbon dioxide as they harden, lowering the carbon footprint of 

concrete mixtures. However, at the current time none of these systems is currently 

viewed as economically viable for large-scale adoption.

Other Concrete Mixtures 

The preceding discussion focused almost exclusively on paving grade concrete, which is most 

often placed with a slipform paver or in fixed-form construction. Other types of plant-mixed 

concrete used in pavement applications include: 

• Roller-compacted concrete (RCC) – RCC consists of the same basic ingredients as 

conventional paving grade concrete and obtains the same basic strength properties, but is 

a much stiffer mixture that is placed and compacted similar to asphalt concrete. The 

biggest difference is in the mixture proportions, in which RCC has a higher percentage of 

fine aggregate allowing tight packing and consolidation. For pavements, RCC has 

traditionally been used for industrial and heavy-duty parking and storage applications, but 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

lately it is seeing more use for streets and highway shoulders. Detailed information on 

RCC for pavement applications is available from Harrington et al. (2010).

• Lean concrete and cement-treated base (CTB) course – There are multiple variations of 

cement-stabilized and cement-treated base courses consisting of aggregate, cement (also 

made with SCMs), and water. They can be made in a concrete plant or mixed on grade.

A lean concrete base is, as the name implies, similar to a traditional concrete but has less 

total cementitious materials content (typically between 200 and 350 lbs/yd3 [99 and 174 

kg/m3]) and develops 28-day compressive strengths between 750 and 1500 lbf/in2 (5.2 

and 10.3 MPa). If still less cementitious materials are used, the material is referred to as 

cement-treated, which typically achieves a 28-day compressive strength of just around 

750 lbf/in2 (5.2 MPa) (Smith and Hall 2001). CTBs can be made to be permeable, 

allowing infiltrating water to flow through the base to the drainage system.

• Pervious concrete – Pervious concrete pavements have a high degree of porosity allowing

precipitation to flow through the voids in the concrete surface, helping to recharge 

groundwater while reducing stormwater runoff. Pervious concrete mixtures are carefully 

controlled, containing little to no sand that results in the inherent porosity (15 to 25 

percent) needed to allow moisture flow through the material. Some pervious concrete 

mixtures being used have much smaller maximum aggregates sizes, but have similar 

permeability to that of “traditional” pervious concrete mixtures. Pervious concrete is 

most often used in parking areas, shoulders, or for low-volume roads. Information on 

pervious concrete can be found in a recent FHWA Tech Brief (Smith and Krstulovich 

2012).

Other Materials 

This section briefly reviews the manufacture of other common materials used in pavements, 

including steel, soil stabilizers and geosynthetic materials. Sources of environmental impact are 

identified in the acquisition, manufacturing, and transport of these materials to the site. Topics 

include energy and emissions generated. 

Steel

Most concrete pavements constructed today are either JPCP or CRCP. JPCP is the most 

common type, and are built without steel reinforcement in the central portions of the slab, but 

may contain embedded steel in the form of smooth, round dowel bars at the transverse joints or 

deformed tie bars at the longitudinal joints. CRCP designs are constructed by several highway 

agencies, often in high-volume urban corridors. These designs contain a significant amount of 

continuous longitudinal steel, perhaps up to 100 to 120 tons (90.7 to 108.8 mt) per lane-mile 

(Tayabji, Smith, and Van Dam 2010). 

Traditional steel manufacturing is a high environmental impact activity, involving the extraction 

of iron ore, limestone, and coal; making of coke; smelting the ore to create pig iron in a blast 

furnace; and then making steel through alloying with carbon and other elements in a steel 

furnace. Improvements in technology have increased the efficiency of the process, but there are 

still unavoidable impacts from the production system, which requires high temperatures and thus 

combustion of fuels, and the release of additional CO2 emissions as the limestone undergoes 

calcination during the reduction of iron ore to pig iron. Secondary (recycled) steel production in 

electric arc furnaces has fewer environmental impacts; this is important because structural steel 

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

is estimated to have a recycled content of greater than 90 percent, and much of the reinforcing 

steel used in the U.S. is recycled (AISC 2013). 

Reinforcing Fibers

It is becoming more common for fibers to be used in concrete in certain pavement applications

(most notably thin overlays) to overcome the quasi-brittle nature of concrete and its relative 

weakness in tension/flexure. Common fibers are composed of various materials including organic 

matter (i.e., cellulose), polymers (i.e., polypropylene, polyester, nylon), glass, and steel. The 

ability to modify the behavior of concrete is heavily influenced by the fiber material, shape, and 

volume fraction. In general, low-strength, low-modulus fibers such as polypropylene microfibers

added in low volume show some ability to reduce plastic shrinkage cracking in concrete but little 

ability to affect the mechanical properties of hardened concrete. On the other hand, the use of 

high-strength, high-modulus fibers at relatively high volumes significantly increases the modulus 

of rupture, fracture toughness, and impact resistance of the hardened concrete. 

The addition of fibers to concrete changes its workability, and as the fiber stiffness, length, 

thickness, and volume fraction increase, so do difficulties in placing and finishing. The trade-off 

is to find a fiber type (material and size) and volume that provides the desired enhancement to 

the concrete’s mechanical properties without compromising workability beyond the point where 

the pavement cannot be placed and finished. Today, synthetic macrofibers (1.5 to 2 inches [38 to 

51 mm] long with an aspect ratio of 75) are filling this niche for pavement applications, typically 

being composed of high-strength, high-modulus polymers and dosed at a rate between 3 to 7.5 

lbs/yd3

 (1.8 to 4.5 kg/m3).

The sustainability benefits derived from fiber reinforcement can be ascertained by considering 

the environmental impact of fiber production and balancing it with anticipated improvements in 

pavement performance or reductions in slab thickness. As with many additives, the mass of 

fibers added to concrete is relatively small (around 0.1 percent by mass) and thus the impact is 

likely below the cutoff for consideration in an LCA. Nevertheless, this should be demonstrated 

by considering the manufacturing process for the particular fiber under consideration and the 

anticipated dosage.

Interlocking Concrete Pavers

Interlocking concrete pavers are precast concrete manufactured in central plants. They can be 

used to create both impermeable and permeable pavements, typically where vehicles are 

traveling at lower speeds. Permeable pavers have laying patterns that create gaps between them

that are filled with permeable aggregate that allows water to pass through the surface (Smith 

2011). Concrete grid pavements consist of larger units with surface openings typically filled 

with soil and grass (ICPI 2013). Interlocking concrete pavers can be manufactured with two 

layers of concrete where the top layer is made with photocatalytic cement. Pavers are often used 

in urban areas for traffic calming and aesthetics, and their easy removal and reinstatement 

provides ready utility access. Pavers have also been used extensively in port areas carrying 

extremely heavy wheel loads. 

Sustainability issues for the production of pavers are similar to those for other concrete materials, 

since they share many of the same mixture ingredients and processes. But they provide aesthetic 

appeal, are readily repairable, can be used to create permeable surfaces, and can be highly 

reflective, all features that give them strong applicability to urban markets. 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

Geosynthetics

Geosynthetic materials take many forms that are used for a number of pavement applications, 

primarily with asphalt-surfaced structures. These include: 

• Non-woven geotextiles or geosynthetic fabrics are used to reduce infiltration of fine and 

plastic soils particles from the subgrade into non-plastic base and subbase layers. This is 

particularly critical when the base or subbase layer is being used as a drainage layer, in 

which case the drainage pipes/trenches are often also wrapped in the fabric.

• Woven geotextiles and polymeric geogrids are used as reinforcement to improve the 

stiffness and shear strength of granular soils layers by providing confinement and 

bridging support near the bottom of the granular layer, particularly when placed over soft 

subgrades. 

• A number of geosynthetic products, often different types paired in layers, have been used 

to retard the propagation of reflection cracking; applications include asphalt layers placed 

over existing cracked asphalt layers, asphalt layers placed over existing jointed concrete 

pavement, or asphalt layers placed over cement- or lime-stabilized soils or base layers 

that may have the possibility of shrinkage cracking. 

Geosynthetics are primarily made of polymers derived from petroleum or fiberglass. Each has 

their own inherent environmental impacts that have not been assessed in the current literature, 

but can be roughly quantified by considering the mass of the materials. The additional 

environmental impacts of using geosynthetics should be considered relative to their contributions 

to extended pavement life. 

The potential constraints on the future recycling of pavements that incorporate geosynthetic 

systems should also be considered. These constraints occur if the materials make it difficult for 

recycling machinery to operate (such as milling and pulverization equipment) or if the materials 

will interfere with mixing and other construction processes.

Soil Modifiers/Stabilizers

There are various materials that can be used to modify or stabilize soils to improve their behavior 

during and after pavement construction. These include some previously discussed materials such as: 

• Portland cement – Portland cement can be used to stabilize both fine-grained plastic, nonplastic, and granular materials (see http://www.cement.org/pavements/pv_sc.asp). 

Depending on the application, the dose of portland cement can be relatively small (to 

improve the mechanical properties of a problem soil) to relatively high (for binding 

aggregates together to form a solid base). The environmental impact of portland cement 

stabilization largely rests with the amount of cement that is used in the application.

• Fly ash – Fly ash is a commonly used soil stabilizer. It can be used alone if the fly ash is 

“self-cementing,” which is characteristic of many Class C fly ashes. Class F fly ashes are 

also used for soil stabilization if combined with a source of reactive calcium such as lime, 

cement kiln dust (CKD), lime kiln dust (LKD), or cement. When using fly ash for soil 

stabilization, care must be exercised to avoid swelling resulting from the expansion of 

sulfate minerals. Additional information on the use of fly ash for soil stabilization can be 

found at: http://www.fhwa.dot.gov/pavement/recycling/fach07.cfm

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

• Asphalt stabilizers – Asphalt can be used as a stabilizer of non-plastic granular materials. 

The most common asphalt stabilizers are emulsions or foamed asphalt, which are often 

used as part of a full-depth reclamation. Additional information on asphalt stabilizers is 

found at: http://ict.illinois.edu/publications/report%20files/FHWA-ICT-09-036.pdf 

In addition to the materials listed above, lime is one of the most common soil modifiers/ 

stabilizers used in pavement construction (NLA 2013). Lime reduces the plasticity of highly 

plastic soils, making them more compactable and significantly reducing differential soil 

expansion under wetting and drying cycles, which can be critical to the functionality of the 

pavement. Where siliceous components are part of the soil chemistry, lime provides calcium and 

thus can also lead to pozzolanic reactions creating soil cementing in addition to soil 

modification. In soils that do not have a reactive form of silica present, lime can be combined 

with fly ash to achieve soil stabilization. More information on lime for stabilization can be 

found at: (http://www.lime.org/index/). Similar to lime, CKD and LKD can be used to treat 

plastic soils if they possess sufficient free lime to chemically react with siliceous components in 

the soil; they also have the added advantage of being waste products that have the potential for 

beneficial use.

Care must be taken in applying soil stabilizers that chemically react with the soil (e.g., portland 

cement, lime, fly ash, CKD, or LKD) to be certain that they will gain expected strength with a 

particular soil, and not produce undesirable unintended effects such as high levels of expansion 

due to unwanted chemical reactions. This is particularly true if lime stabilizers are being used 

and if sulfates are present in the soil (or if fly ash, CKD, or LKD are used that contain sulfates). 

It is therefore necessary to conduct a thorough laboratory investigation with the proposed 

stabilizing agent and actual soils from the project prior to using them in a full-scale field 

application. 

The environmental impacts of portland cement, fly ash, and asphalt have already been discussed 

previously. Lime is produced by calcining limestone, and thus considerable CO2 is liberated in 

the conversion of calcium carbonate to calcium oxide (quick lime) as well as from the burning of 

fuel. This must be considered when evaluating the benefits of stabilization through the use of 

lime. CKD and LKD are waste products, and therefore allocation is based on transporting the 

materials from the source (cement or lime kiln) to the project site. If the local market for CKD 

or LKD becomes such that they obtain economic value beyond the cost of transportation and 

disposal, they then need to be treated as a co-product.

Soil stabilization has the potential to substantially reduce the thickness of the pavement structure 

and to increase the life, both of which can reduce environmental impact. Moreover, they can be 

used to provide an effective working platform, greatly expediting the construction process and 

making it more efficient. Consideration of alternative pavement structures including those with 

soil stabilization should consider the life cycle to obtain an understanding of the trade-offs 

between materials production impacts and life increases or pavement structure reductions.

Major Issues

• Fibers may improve the mechanical properties of concrete such that the thickness of the 

pavement structure may be reduced or its life extended, but those benefits must be 

balanced with the increased difficulty in handling fresh concrete and increased 

environmental impacts and increased costs of using the fibers. 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

• Geosynthetics represents a broad range of products, most based on polymers derived 

from petroleum and fiberglass that can be used to reinforce soil, aggregates, and even 

asphalt surfaces. Again, the benefits of extended life should be considered in terms of 

their environmental impacts and costs.

• A number of different soil modifiers are available to improve a range of soil conditions. 

As with the other items, the benefits of reduced structural thicknesses or extended life 

must be balanced with the increased environmental impacts and costs.

Strategies for Improving Sustainability

• Fibers are being used as reinforcement to improve the mechanical properties of concrete 

used in thin bonded overlays. They can potentially reduce the thicknesses of the concrete 

slab by making the concrete more ductile and less susceptible to cracking.

– Some fibers may be used to extend joint spacing without increasing the risk of 

cracking.

– Some fibers can be used to reduce the risk of plastic shrinkage cracking.

– Macrofibers of sufficient volume can reduce the amount of cracking and severity of 

cracking that does occur.

• Geosynthetics are often used to stabilize areas where conventional techniques fail, 

contributing to the pavement structure while expediting construction. They can 

potentially reduce the thicknesses needed for other pavement materials.

– Geosynthetics can reinforce soil and unstabilized subbase and base materials.

– Geosynthetics can be used to reinforce asphalt pavements.

– Geosynthetics can be used to minimize or control the development of reflection 

cracking.

• Soil modifiers are typically based either on cementitious systems or asphalt and thus 

suffer many of the issues previously described.

– Some soil stabilizers, such as lime, have a high carbon footprint due to calcination of 

the limestone.

– Others stabilizers, such as fly ash, CKD, and LKD, are RCWMs and thus may have a 

low carbon footprint if locally available and if acceptable performance can be 

achieved.

• Potential issues and trade-offs.

– There are various fibers on the market and it requires knowledge to select the proper 

fiber for a given application. At the high-volume fractions needed to modify the 

hardened properties of concrete, fibers will negatively impact mixture workability 

and potentially affect the environmental impact of the concrete.

– Geosynthetics must be carefully designed and placed to be certain that they provide 

sufficient desired benefits (e.g., reflection crack control, longer life) for their cost

(Koerner 2005). 

– Some soil modifiers/stabilizers derived from RCWMs can have chemistries that result 

in soil heaving, resulting in poor pavement performance.

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

– Other modifiers, such as lime, are made by calcining limestone and thus have a high 

carbon footprint. Lime can also negatively interact with some soil types resulting in 

heaving.

Concluding Remarks

This chapter reviews the range of materials that can be used for paving applications, primarily 

including aggregates, asphalt materials, and cementitious materials. The way that each of these 

materials affects the overall sustainability of the pavement system is described, along with strategies 

that can be used to improve that sustainability. The scope of the chapter is from the extraction of 

materials to the point where materials begin final transportation to the construction site.

Some of the major issues regarding aggregate production and use are:

• Environmental and social implications of aggregate acquisition and transportation.

• Special concerns regarding aggregate processing.

• Implications of aggregate durability.

• The utilization and performance of RCWMs as aggregates.

Some of the major issues regarding asphalt materials used for pavement are:

• Continued increases in the price of petroleum, and thus asphalt, which is a finite resource.

• Appropriate use of polymer, rubber, and other types of binder modifiers.

• Depletion of high-quality aggregates needed for some type of mixtures.

• Specialization of mixtures for safety, noise, and structural considerations and their 

environmental and cost implications.

• Use of RAP and other RCWMs including asphalt shingles, recycled tire rubber, and sulfur.

• Environmental, social, and cost implications of mixture design and durability.

• Future binder availability and alternatives.

• Ensuring asphalt material durability.

A summary of some of the major issues confronting the acquisition and production of concrete 

materials used for paving are as follows:

• The relatively high non-renewable energy consumption and GHG emissions inherent in 

the portland cement manufacturing.

• The relatively high GHG emissions associated with the production of traditional portland 

cement, and its impact on portland cement concrete mixtures with high cement contents. 

• Water use associated with concrete production.

• Reducing the amount of cement used in concrete mixtures through improved gradations 

and increased use of SCMs.

• Increasing the use of RCWMs as aggregates without compromising performance.

• Ensuring concrete durability.

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

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Highway Concrete. NCHRP Report 749. Transportation Research Board, Washington, DC. 

Tayabji, S. and S. Lim. 2006. Long-Life Concrete Pavements: Best Practices and Directions 

from the States. Federal Highway Administration, Washington, DC. (Web Link).

Tayabji, S., K. D. Smith, and T. Van Dam. 2010. Advanced High-Performance Materials for 

Highway Applications: A Report on the State of the Technology. FHWA-HIF-10-002. Federal 

Highway Administration, Washington, DC. (Web Link).

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Towards Sustainable Pavement Systems Chapter 3. Materials Considerations

Taylor, P. C. 2011. Preventing Joint Durability in Concrete Pavements – A Summary of 

Current Knowledge. Map Brief 6-1. April. National Concrete Pavement Technology Center, 

Iowa State University, Ames, IA. (Web Link).

Taylor, P. C., S. H. Kosmatka, G. F. Voigt, M. E. Ayers, A. Davis, G. J. Fick, J. Grove, D. 

Harrington, B. Kerkhoff, H. C. Ozyildirim, J. M. Shilstone, K. Smith, S. Tarr, P. D. Tennis, T. J. 

Van Dam, and S. Waalkes. 2006. Integrated Materials and Construction Practices for Concrete 

Pavements: A State-of-the-Practice Manual. FHWA-HIF-07-004. Federal Highway 

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Thomas, M. D. A., D. Hooton, K. Cail, B. A. Smith, J. De Wal, and K. G. Kazanis. 2010. 

“Concrete Produced with Portland Limestone Cement.” Concrete International. Vol. 32, No. 1. 

American Concrete Institute, Farmington Hills, MI.

Thomas, M. D. A. and M. L. Wilson. 2002. Admixtures for Use in Concrete. CD-ROM CD039. 

Portland Cement Association, Skokie, IL. 

Torcellini, P., N. Long, and R. Judkoff. 2003. Consumptive Water Use for U.S. Power Production. 

NREL/TP-550-33905. National Renewable Energy Laboratory, Golden, CO. (Web Link).

Tran, N., B. Powell, H. Marks, R. West, and A. Kvasnak. 2009. “Strategies for Design and 

Construction of High-Reflectance Asphalt Pavements.” Transportation Research Record 2098. 

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Chapter 3. Materials Considerations Towards Sustainable Pavement Systems

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

CHAPTER 4. PAVEMENT AND REHABILITATION DESIGN TO 

IMPROVE SUSTAINABILITY

Introduction

This chapter describes sustainability considerations in the design of both new and rehabilitated 

pavement structures, with the latter including structural overlays and reconstruction. The first 

step in pavement design is to define the objectives based on the goals and policies of the 

owner/agency, which should include sustainability objectives. The design process results in the 

development of alternative pavement structures (including structural layers and thicknesses), 

specifications for materials that meet the performance objectives of the individual layers as well 

as the system as a whole, considerations for subsurface drainage (as appropriate), and governing 

construction specifications needed for the pavement to perform as intended. 

As described in chapter 2, all pavement types can be designed to be more sustainable by 

considering costs, environmental impacts, and social needs together. This is true even for 

pavements built with relatively conventional materials and construction techniques, but as noted 

in chapter 2 it is up to the owner/agency to set the goals and establish the considerations that will 

receive greater emphasis in the development of “more sustainable” pavement designs. 

In particular, this chapter reviews the decisions made in the design process (e.g., layer type 

options, materials, thicknesses, appropriate layer combinations, and geometric features) that can 

affect the overall sustainability of the resulting pavement, with a focus on pavement types, 

specific materials, and structural design considerations. The objective of the chapter is not to 

present innovative pavement designs but rather to communicate the need to critically evaluate 

the entire design process in order to make the pavement that is ultimately designed the most 

sustainable option for the stated design objectives and constraints. 

The scope of this chapter, relative to several other related chapters, is shown in table 4-1. It is 

observed that, in addition to new and reconstruction design, this chapter includes structural 

overlays (both asphalt and concrete) as they require a design component (considering the 

existing pavement condition and future traffic levels) that leads to the provision of additional 

load-carrying capacity. Nonstructural overlays and pavement maintenance and preservation 

treatments are covered in chapter 7, and specific end-of-life strategies (e.g., full-depth 

reclamation, recycling) are covered in chapter 8. 

The selection of alternate routes or alternative modes of transportation are outside the scope of 

this document. The design and construction of new geometry for roads, including consideration 

of the impacts of horizontal and geometric alignment on construction activities (e.g., excavation, 

material movement, tunneling, balancing of cut and fill) and vehicle operations (e.g., effects of 

vertical and horizontal curves on fuel economy, other vehicle operating costs and safety) are also 

outside the scope of this document. Research by various organizations over a number of years 

has identified the effects of road geometry on vehicle fuel consumption, other vehicle operating 

costs, and safety (see, for example, Claffey 1971; Watanatada et al. 1987, and Ko, Lord, and 

Zietsman 2013, among others). The net effects of environmental impacts considering earthworks 

and materials to construct different geometric designs, as well as the benefits from improved 

vehicle operating cost in the use phase, can be evaluated through LCA. 

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

Table 4-1. Division of scope between design, maintenance and preservation, and end-of-life 

chapters.

Pavement 

Type

Chapter 4.

Pavement and Rehabilitation 

Design to Improve 

Sustainability

Chapter 7.

Maintenance and Preservation 

Treatments to Improve 

Sustainability

Chapter 8.

End-of-Life 

Considerations

Asphalt 

Pavements 

• New Asphalt Pavement 

Design or Reconstruction

• Structural Asphalt Overlay

• Bonded Concrete Overlay 

• Unbonded Concrete 

Overlay 

• Crack Filling/Sealing

• Asphalt Patching 

• Fog Seals/Rejuvenators

• Chip Seals

• Slurry Seals

• Microsurfacing 

• Ultra-thin and Thin Asphalt 

Overlays 

• Hot In-Place Recycling

• Cold In-Place Recycling

• Ultra-thin Bonded Wearing 

Course

• Bonded Concrete Overlays

• Central Plant 

Recycling

• Full-Depth 

Reclamation

Concrete 

Pavements 

• New Concrete Pavement 

Design or Reconstruction

• Bonded Concrete Overlay

• Unbonded Concrete 

Overlay 

• Structural Asphalt Overlay

− Conventional

− Crack/Break Seat

− Rubblization

• Joint/Crack Sealing

• Slab Stabilization/Slab Jacking

• Diamond Grinding/Grooving

• Partial-Depth Repairs

• Full-Depth Repairs

• Dowel Bar Retrofit

• Slot/Cross Stitching

• Ultra-thin Bonded Wearing 

Course

• Bonded Concrete Overlays

• Concrete Recycling

− In Place

− Off site

Other 

Pavement

Types

• New Composite or Semirigid Concrete

• Pavement Design or 

Reconstruction

• New Drainable Pavement 

Design or Reconstruction

• New Modular Pavement 

Design or Reconstruction

Pavement Design Considerations

Pavement design for a new or rehabilitation construction project is the process of:

1. Identifying the functional and structural requirements of the pavement including the 

design life and constraints. 

2. Gathering key design inputs such as material properties, traffic loadings, and climatic 

factors.

3. Selecting the pavement type and associated materials, layer placement and thicknesses, 

and construction specifications to achieve the desired performance. 

4. Considering design alternatives for all of the above to determine the preferred solution in

terms of life-cycle cost, environmental impacts, and societal needs. 

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

The identification of sustainability goals should be considered the first step in the process shown 

above. However, as described in chapter 2, although sustainability and life-cycle assessment are 

growing in importance, most highway agencies still primarily consider costs (either the lowest 

initial cost or the lowest life-cycle cost) in the pavement design process (GAO 2013). As will be 

seen in many cases in this chapter, pavement designs that improve environmental sustainability 

can often reduce life-cycle costs, largely as the result of reductions in natural resource 

requirements and energy consumption. 

The following are items that may be included in project-specific requirements for the design of a 

particular pavement: 

• Expected design life. 

• Smoothness. 

• Surface texture as it impacts friction and noise. 

• Splash/spray. 

• Stormwater runoff. 

• Traffic delay associated with future maintenance. 

• Reliability considering cost and level of interruption of service for maintenance and 

future rehabilitation. 

• Ability to accommodate utility installation and maintenance. 

• Potential for future obsolescence (the pavement will need to be replaced or removed 

before its design life is reached).

• Local thermal environment as influenced by pavement. 

• Aesthetics. 

Each of these considerations can have an impact on the sustainability of the pavement, but their 

relative importance will depend on the context of the design as well as the overall sustainability 

goals of the owner/agency and the specific project objectives. Each requirement should be 

assessed by the designer based on how the pavement will interact over its entire life cycle with 

users (both for passenger mobility and freight movement, where applicable, and primarily in 

terms of safety and efficiency), the surrounding community, and the environment (both local and 

global effects). The requirements of the users and community will also depend on the functional 

class of the roadway, and may also vary with time. Similarly, the overall benefits of different 

design approaches to improving sustainability will depend on the context of the design (such as 

location, traffic volumes and characteristics, support conditions, climatic conditions, and so on) 

and will also likely vary with time (Santero and Harvey 2010). 

Some considerations and general guidance regarding the inclusion of sustainability as part of 

pavement design include the following: 

• Surface performance. 

– Smoothness is often considered the most important surface characteristic; texture and 

deflection may also be considerations (see chapter 6 for details). 

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

– The pavement surface affects vehicle fuel consumption (see chapter 6 for details), 

vehicle life, and freight damage costs. 

– The consideration of future maintenance and rehabilitation and their effects on 

smoothness are important components to be considered in evaluating sustainability 

impacts.

– Surface performance is context sensitive in that it is very critical to pavements 

exposed to higher traffic volumes and less important to pavements carrying lower 

traffic volumes. For pavements carrying heavy traffic volumes, the environmental 

benefits of keeping the pavement smoother can far outweigh the negative 

environmental impacts of materials production and construction. 

• Design life selection. 

– The functional and structural life of the pavement is influenced by both traffic and 

environmental factors. 

– The selection of the design life should include the consideration of higher initial 

economic costs and environmental impacts associated with longer life designs versus 

higher future costs and environmental impacts associated with shorter life designs 

(due to the need for additional maintenance and rehabilitation activities). 

– The selection of the design life should include consideration of end-of-life 

alternatives (see chapter 8). 

• Pavement type selection. 

– The pavement type selection impacts every phase of the pavement life cycle, 

including the selection of initial materials and construction as well as the future 

maintenance and rehabilitation, use phase, and end of life. 

– The relative sustainability impacts of different pavement types depend on location, 

design traffic, and available materials. 

• Construction and materials selection. 

– The impacts of materials selection on sustainability depend on the local sources of 

materials and the transportation alternatives available (see chapter 3 for details). 

– The ability to achieve quality construction with available materials and construction 

equipment and expertise impacts the sustainability of the pavement (see chapter 5 for 

details). 

– Traffic delays in construction work zones may result in negative sustainability

impacts where traffic volumes are high and traffic management plans (TMP) cannot 

mitigate delay; slowing traffic down may lead to small improvements in the 

sustainability impact. 

• Construction quality requirements (see chapter 5 for details). 

• Recycling strategies (see chapters 3 and 8 for details). 

The impact on pavement sustainability that results from these types of decisions can be assessed 

through LCA and through sustainability ratings systems as part of an overall assessment process 

(see chapter 10 for details on these processes).

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

Consideration of Payback Time

One approach to evaluating whether sustainability goals are being met is the concept of “payback 

time.” Payback time is defined as the period between the initial environmental impact and the 

time to achieve a zero difference compared to the standard approach, after which there is a net 

reduction in environmental impact; more simply, it is the time required to recoup the benefits (be 

they cost, environmental, or social) associated with a pavement design investment. This concept 

is useful when evaluating design approaches that require a larger initial cost or environmental 

impact as compared with standard practice, but which provide significant impact reductions over 

the rest of the pavement life cycle. Some typical examples involve long-life pavement designs, 

which increase the time (years) before the first rehabilitation or reconstruction, reduce the level 

and frequency of maintenance during the life, and keep a pavement smoother over its life, but 

will likely have a higher initial impact on cost and the environment because of the use of 

premium or unique materials or increased layer thicknesses. A payback analysis provides an 

indication of the uncertainty of achieving a reduction in environmental impact over the life cycle 

due to a design decision, with longer payback times have greater uncertainty regarding the ability 

of the assessment to accurately quantify them and whether they will actually occur.

An example of the payback time for a specific case study is provided in figure 4-1, which shows 

a comparison of the GWP of the materials production and construction phases for pavements 

with 20-, 40- and 100-year design lives (all using the same materials). It can be seen that the 40-

year pavement initially has more GWP than the 20-year pavement, primarily due to a thicker 

structure, but that the difference is made up after 29 years; furthermore, over a 100-year analysis 

period the 40-year pavement has approximately half the GWP of the 20-year pavement. 

Figure 4-1. Example of payback time analysis considering only the material production 

and construction phases of three different pavement design lives (modified from Santero, 

2009). 

4-5 

As noted previously, longer payback times indicate greater uncertainty in the final difference 

between alternatives. For example, it can be seen in figure 4-1 that the payback time (cross-over 

point) is 93 years between the 40- and 100-year design lives, and that the actual difference in 

initial GWP between those two alternatives is small. Longer payback periods also mean that the 
Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

planet and humans are exposed to the environmental 

impact for an extended period before any 

environmental benefit is realized, although societal and 

economic impacts may occur. The example shown in 

figure 4-1 only considers the impacts of material 

production and construction, and consideration of use 

phase impacts will likely change the cross-over point. 

Approaches for considering the time dependency of 

impacts in LCA and carbon footprints are being 

developed (Kendall, Harvey, and Lee 2009: Harvey et 

al. 2010; Kendall 2012). 

Mechanistic-Empirical Design Methods

Empirical pavement design methods, which are based 

on observations of the performance of in-service 

pavements without consideration of theoretical 

concepts of pavement behavior, can only consider how 

pavements perform within the narrow realm of the 

prevailing conditions (e.g., fixed material types, fixed 

pavement types and design features, fixed 

environmental conditions and traffic loadings). This 

design framework makes it more difficult to introduce 

innovative materials, designs, and specifications 

without constructing full-scale test sections and 

observing performance. 

Mechanistic-empirical (ME) design methods offer 

much greater opportunity to consider alternative 

materials, pavement structures, and construction 

procedures. For both conventional and new paving 

materials, ME design directly considers key material

properties (such as stiffness, fatigue resistance, lowtemperature cracking properties, permanent 

deformation resistance, and thermal expansion) and is 

able to relate those properties directly to pavement 

performance through available response and 

performance models. ME design allows the 

development of designs even for new materials that have not been used before, based on their 

predicted mechanistic (the “M” in ME) response to traffic loads, temperatures, and moisture 

condition. The performance predictions can be improved as more empirical (the “E” in ME) 

performance data become available. Similarly, ME design permits the evaluation of changing 

construction specifications through consideration of their effect on input materials properties. 

ME design can estimate key asphalt or concrete pavement distresses (such as cracking, rutting, 

faulting) and roughness (e.g., International Roughness Index [IRI]) versus time, which allows the 

designer to consider alternative trigger levels for maintenance and rehabilitation. ME design 

tools also allow the designer to analyze alternative decisions that will affect many of the factors 

in the pavement life cycle that are shown in figure 2-1 in chapter 2. 

AASHTOWare Pavement ME 

Design Software

The AASHTO mechanistic pavement 

design procedure (AASHTO 2008) 

and the accompanying AASHTOWare 

Pavement ME Design software 

(AASHTO 2012) are based on 

mechanistic-empirical design 

principles and provide a powerful tool 

for pavement engineers to predict 

pavement performance. Pavement 

ME considers different pavement 

types, layer types and thicknesses, 

material properties, traffic projections, 

and climatic data. It allows users the 

ability to evaluate multiple pavement 

designs over a specified analysis 

period and match future maintenance 

and rehabilitation needs with the 

predicted distresses. From the user 

defined layer types, properties, and 

general inputs, the software 

determines the minimum pavement 

surface thickness based on project 

and agency objectives and selected 

failure criteria. The Pavement ME 

software can also be used for forensic 

investigations to study the 

deficiencies associated with existing 

pavements. 

The AASHTO Pavement ME is 

calibrated at the national level, and 

thus local calibration of the distress 

models may need to be completed; 

furthermore, particular scrutiny may 

need to be given to designs utilizing 

innovative designs, materials, and 

construction not part of the distress 

model calibration.

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

The AASHTOWare Pavement ME Design Software (see sidebar) uses an iterative process, with 

the designer calculating the expected performance of a proposed structure, and then changing 

aspects of the design to move towards design objectives, such as structural and functional 

performance levels, cost stipulations, and geometric constraints, but these objectives can also 

include environmental and societal impacts. The AASHTO Pavement ME is a tool for 

determining the pavement type and corresponding layer types and thicknesses for a wide range 

of new and rehabilitated pavement structures. Some state DOTs have developed and are using 

other ME design procedures and software tools (e.g., California, Minnesota, Texas) for different 

types of pavements and some states are using Pavement ME or other ME tools in combination 

with empirical procedures. There are also ME design tools available from industries, 

organizations, universities, and other countries that are too numerous to provide a comprehensive 

list of citations. All ME procedures including the AASHTO Pavement ME Design have various 

advantages and limitations in terms of models, extent of calibration, local applicability with 

regards to materials and environment, availability of input data, and ability to consider new 

pavement and rehabilitation alternatives such as many of those discussed in this document. Any 

ME procedure should be evaluated before it is used, and the results used with care by an 

experienced pavement designer. 

Process for Consideration of Sustainability in Pavement Design

An example of an overall process for considering sustainability in pavement design is shown in 

figure 4-2. The process shown in the figure is particularly oriented towards the design-bid-build

(i.e., low-bid) project delivery process. 

There are numerous alternative pavement solutions that can be proposed for any set of design 

requirements. The pavement design process, whether asphalt, concrete, modular, or composite, 

must begin by defining the owner/agency design and policy objectives as well as any 

sustainability objectives. Once various pavement design alternatives have been developed, 

LCCA, LCA, and pavement rating tools can be applied to assess economic, environmental, and 

societal impacts to varying degrees as a way of improving the sustainability aspects of the 

proposed pavement designs. Chapter 10 provides additional information on those assessment 

tools. 

Design Objectives

An owner/agency has a number of different objectives to consider when developing a pavement 

design. These may be explicit objectives included in policy, may be implicit to the local agency, 

or may be just emerging. 

Performance Objectives

The overall performance objectives used in the design process will depend on agency policies. 

These polices are typically developed based on a number of items, such as acceptable distress 

and ride quality levels and economic analyses of agency initial and life cycle costs, and may also 

include some types of road user costs and funding agency guidelines. 

In a design-bid-build (DBB) or design-build (DB) project delivery environment, it is assumed 

that the design methodology will adequately predict the ability of the constructed pavement to 

meet the performance objectives. Some examples of performance objectives in the DBB or DB 

delivery environment include: 

4-7 
Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

Figure 4-2. Overall process for considering sustainability in pavement design. 

Inputs:

- Project performance, cost, and sustainability objectives

- Project traffic, climate, available materials, and construction processes

- Agency design, LCCA, sustainability practices and policies

Step 1: Develop generalized pavement type 

or rehabilitation approach alternatives 

Step 2: Develop pavement designs using 

ME or agency design procedures 

Step 3: Consider future maintenance and 

rehabilitation (chapters 4 & 7)

Step 4: Calculate and Evaluate:

- Performance

- Cost

- Environmental Impact

- Societal Impact

Step 5: Modify initial design using LCCA, 

LCA, and rating systems

(to reduce cost and minimize

environmental and societal impact while 

still meeting performance and agency 

objectives and policies)

Modified 

Alternative 1

Modified 

Alternative 2

Modified 

Alternative 3

Modified 

Alternative n

Step 6: Select preferred design alternative 

based on agency goals and policies.

Materials

(chapter 3)

Construction 

Specifications

Layer 

Combinations

Integration of 

Construction and Traffic

Construction 

Methods (chapter 5)

4-8 
Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

• Design life, or the number of years it takes to reach the defined end of life based on the 

effects of the predicted traffic loading and climatic impacts on the assumed pavement 

structure.

• Reliability, or the probability of reaching the design life before exceeding established 

distress or ride quality thresholds. 

In a design-build-maintain (DBM) project delivery environment, performance objectives are 

explicitly written as contractual performance requirements that the contractor must deliver 

during the contract performance period. Some examples of performance requirements for DBM

include: 

• Maximum allowable IRI. 

• Maximum amount of cracking or other indicators of structural deterioration. 

Cost Objectives

It is common for an agency’s cost objective to be to minimize the overall life-cycle cost of the 

pavement over a defined analysis period, or it may be to minimize the life-cycle cost while also 

operating within an initial cost constraint. Additional guidance on LCCA is found in chapter 10, 

with detailed information available from the FHWA (Walls and Smith 1998). The General 

Accounting Office has recently reviewed a sample of state LCCA practices and provided 

recommendations for improvements (GAO 2013). 

Sustainability Objectives

Chapter 2 lists in detail the potential sustainability goals and objectives that are inherent as part 

of the pavement design process. This includes not only meeting the performance goals and cost 

requirements, but also minimizing environment impacts and meeting key societal needs. 

Alternative Pavement or Rehabilitation Types 

After the goals and policy objectives of the owner/agency have been defined, the project traffic 

and climate data have been compiled, and available materials and construction processes have 

been determined, the next step is the development of various pavement design alternatives. 

There are a variety of new and rehabilitated pavement structures that can be considered, broadly 

grouped into the following categories: asphalt pavements (including asphalt overlays), concrete 

pavements (including concrete overlays), composite pavements (asphalt over concrete and twolift concrete on concrete), modular pavements, and fully permeable pavements. These are 

described in the following sections. 

Asphalt Pavement Types

New or Reconstructed Asphalt Pavement Structures

As described in chapter 1, asphalt pavements are those with an asphalt surface layer of any 

thickness (even including only a chip seal), and may include various asphalt stabilized structural 

layers. They may also include granular support layers (bases and subbases) below the asphalt 

bound layers and above the subgrade. Full-depth asphalt pavements include only an asphalt 

surface and binder course layers paved on treated or compacted subgrade, as illustrated in figure 

4-3. 

4-9 
Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

Figure 4-3. Cross sections of various asphalt pavement types (not to scale).

Full-depth Asphalt Pavement Conventional Asphalt Pavement

Granular Subbase Layer

Asphalt Layers Asphalt Layers

Asphalt Pavement with 

Stabilized Subbase or Subgrade Inverted Pavement

Stabilized Granular Base Layer Granular Base Layer

Cement Bound Subbase Layer

Stabilized Granular Subbase Layer

Compacted Subgrade Compacted treated Subgrade

Asphalt Surface Asphalt Layers

Asphalt base Layers Granular Base Layer

Compacted Subgrade Compacted Subgrade

In some cases, granular layers may be used between the asphalt stabilized surface layers and a 

cement-stabilized subbase, a design referred to as an “inverted” pavement. The “inverted” 

nature of the design provides strong structural support for the pavement while eliminating the 

reflection of shrinkage cracks in the cement-stabilized subbase into the asphalt layers. A typical 

rehabilitation for asphalt pavements is the placement of a structural asphalt overlay, generally 

defined as having a thickness greater than 2 inches (51 mm). When the slabs in concrete 

pavements are “rubblized” and then paved with an asphalt overlay, the rubblized concrete 

effectively serves as an aggregate base.

A detailed description of the various materials used in asphalt pavements are discussed in chapter 

3. In general, opportunities for using recycled materials exist in all layers of an asphalt

pavement, including the use of RCA and RAP in the granular layers and rubber, RAP, and RAS 

in the asphalt-stabilized layers. Furthermore, asphalt concrete technology can be used to batch 

and construct the various asphalt layers. Effective compaction of all pavement layers is critical

for improving the performance of all asphalt and granular layers as well as the subgrade, and 

achievable compaction specifications that maximize overall compaction and minimize the 

variability of compacted density will improve pavement performance without imposing any 

significant environmental impact from construction. 

Open-graded drainage layers below the asphalt layers may be considered to help handle 

stormwater. Care must be taken to ensure that drainage layers below the surface have adequate 

cross-slope and will be maintained to provide free drainage for the life of the pavement and 

future rehabilitations. This includes providing filters to keep these layers from becoming 

4-10
Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

clogged, and maintaining free flow from these 

layers away from the pavement either through 

“daylighting” to the shoulder or by maintaining 

shoulder drains. 

Various types of interlayers may be considered to 

improve the performance of granular layers by 

providing confinement and tensile stress handling 

capability. Interlayers are designed to allow water 

to pass through but filter out soil particles, thereby 

preventing fine subgrade materials from moving 

into and contaminating granular base, subbase, and 

drainage layers under hydraulic pressures caused 

by traffic loadings. 

Reconstruction of asphalt pavements consists of 

removing some or all of the existing structural 

layers and replacing them, substantially

constructing a new pavement structure. There are 

often many alternatives for recycling materials 

removed from the existing structure in the new 

structure. The decision to reconstruct is based on 

comparison of rehabilitation alternatives 

considering the condition of the existing pavement 

and the overall objectives of the owner/agency for 

the project.

Asphalt Pavement Surface Types

Asphalt pavement surface layers may be selected to 

achieve certain functional and structural objectives. Examples of asphalt surface types are: 

• Dense-graded asphalt concrete. 

• High-friction materials (such as chip seals and microsurfacings). 

• SMA for noise, durability, and friction. 

• Open-graded asphalt courses for noise, splash/spray, and friction. 

In addition to noise benefits, thin open-graded asphalt surfaces transmit stormwater below the 

surface of the permeable pavement laterally to the shoulder of the road where it is discharged. 

This causes a slowing of the rate of runoff, which reduces the peak flow of stormwater discharge

and also results in pollutants being captured in the open-graded layer (Grant et al. 2003). All 

these surface layer types can include options for recycling. Additional details regarding tirepavement noise and various asphalt surface types are provided in chapter 6. 

For asphalt overlays, rubberized (using recycled tires) or polymer-modified overlays will often 

provide improved resistance to bottom-up reflection of existing cracking and top-down cracking. 

Stress absorbing membrane interlayers of various types are also sometimes used to slow 

reflection cracking.

Open Graded Asphalt Surfaces

Open-graded asphalt surfaces are thin 

asphalt concrete layers (typically 0.5 to 2 

inches [13 to 51 mm]) that are constructed 

with an air void content in the range of 15 

to 25 percent of the total mixture volume. 

The porosity of the surface layer provides 

a number of potential benefits, including:

- High surface friction.

- Reduced hydroplaning potential.

- Reduction in and splash and spray.

- Improved visibility.

- Reduced noise levels.

- Reduction in urban heat island effects.

These benefits are highly dependent on 

mix characteristics of the asphalt layer, 

traffic levels (including the use of studded 

tires), climatic factors, and maintenance.

Various options exist for open-graded 

asphalt mix design to obtain these 

benefits for the longest period possible, 

while balancing performance with cost and 

environmental impact. Open-graded 

asphalt surfaces may be incorporated into

a fully permeable pavement system, as 

discussed in chapter 6.

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

Asphalt Pavement Rehabilitation Options

Structural rehabilitation strategies for asphaltsurfaced pavements include asphalt and concrete 

(bonded and unbonded) overlays, both of which 

provide additional load-carrying capacity to the

existing pavement. Schematic cross sections of 

these various overlay types are provided in figure 

4-4. Non-structural overlays, either asphalt or 

concrete overlays of thickness less than about 2 

inches (51 mm), do not add significant structural 

load-carrying capacity and would be used to 

address functional pavement issues. Those nonstructural overlays are discussed in more detail in 

chapter 7 (preservation and maintenance). 

Figure 4-4. Cross sections of rehabilitated asphalt pavement structures (not to scale).

Structural Asphalt Concrete 

Overlay

Structural (Bonded/Unbonded) 

Concrete Overlay

Structural Asphalt Overlay Bonded or Unbonded

Concrete Overlay

Existing Asphalt Pavement Layers Existing Asphalt Pavement Layers

Granular Base Layer Granular Base Layer

Granular Subbase Layer Granular Subbase Layer

Compacted Subgrade Compacted Subgrade

Structural asphalt overlays consist of placement of thicker new asphalt layers (typically more 

than 2 inches [51 mm]) on the existing surface to increase or restore the pavement’s structural 

capacity as well as improve functional characteristics. Structural asphalt overlays commonly use 

conventional dense-graded asphalt concrete. For a structural asphalt overlay of an existing 

asphalt pavement, some or all of the existing asphalt surface layers may be milled in order to 

improve bonding to the existing surface, eliminate surface rutting, establish the desired surface 

elevation, and for removal of top-down cracking, old sealants, patching material, and oxidized 

asphalt materials. These millings are a source of RAP, and could be recycled into the same 

project or stockpiled for future use. 

An alternative to milling is to recycle in place the upper 2 to 4 inches (51 to 102 mm) of the 

existing asphalt layers with either cold in-place recycling followed by an overlay or with hot inplace recycling (see chapter 7). However, full-depth reclamation (see chapter 8), with no 

stabilization or stabilized with cement, cement/foamed asphalt, asphalt emulsions or other 

stabilizers, may be a better selection if all of the existing asphalt layers are heavily cracked, if 

there is significant delamination between asphalt layers, if the asphalt layers have moisture 

Overlays for Asphalt-Surfaced 

Pavements

 Structural asphalt overlays: Thicker, 

new dense-graded asphalt layers 

placed on existing surface to improve 

structural capacity. 

 Structural concrete overlays: Bonded 

overlays rely significantly on the 

thickness and stiffness of the existing 

asphalt pavement in the structural 

design whereas in an unbonded 

overlay the existing asphalt pavement 

functions as a base layer. 

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

damage at various depths, or if there are unbound base layers that will provide inadequate 

structural support to the asphalt layers. 

Structural concrete overlays over existing asphalt surfaced pavements are classified as either 

unbonded or bonded based on the interface condition between the existing asphalt pavement and 

the new concrete overlay (Harrington 2008; Harrington and Fick 2014; Torres et al. 2012). 

Unbonded concrete overlays are placed over existing asphalt, composite, or semi-rigid pavement, 

with the existing pavement essentially functioning as the base and subbase layers. The unbonded 

concrete overlay (of thickness 7 to 10 inches [178 to 254 mm]) is typically designed as a new 

concrete pavement, either a JPCP or as a CRCP, with the existing asphalt pavement acting as a 

base. If the existing asphalt surface is highly distressed, a thin asphalt interlayer (typically less 

than 2 inches [51 mm]) may be placed on top to provide a smooth and durable layer beneath the 

concrete overlay. Part of an existing asphalt surface may also be milled and removed prior to 

placing the concrete overlay for the same reasons as for structural asphalt overlays on asphalt

pavement. 

Bonded concrete overlays of asphalt pavement consist of placement of a 3 to 6 inches (76 to 152 

mm) thick layer of concrete bonded to an existing asphalt or semi-rigid pavement. The existing 

asphalt or semi-rigid pavement structure has a larger impact on the design of bonded concrete 

overlays and thus must be in relatively good structural condition. Slab sizes are much shorter, 

typically 4 to 6 ft (1.2 to 1.8 m), compared with unbonded concrete overlays that commonly (but 

not always) have more conventional joint spacing (typically about 15 ft [4.6 m]). 

Concrete Pavement Types

New or Reconstructed Concrete Pavement Structures 

Concrete pavements are constructed or reconstructed with a concrete surface layer resting on a 

base and possibly a subbase layer, depending on the traffic, climate, and foundation support 

conditions. As described previously, JPCP and CRCP designs are the most common types of 

concrete pavements, with typical cross sections of each depicted in figure 4-5. 

Figure 4-5. Cross sections of concrete pavement structure types (not to scale). 

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

Noted characteristics of JPCP and CRCP designs 

are as follows:

• JPCP has transverse joints spaced typically 

about 15 ft (4.6 m) apart and contains no 

reinforcing steel distributed throughout the 

slab. Steel dowel bars across transverse 

joints provide effective load transfer at the 

transverse joints and significantly reduce 

joint faulting, pumping, and corner breaks, 

while JPCP without dowels will tend to 

have reduced load transfer when slabs 

contract under colder temperatures. Steel 

tie bars across longitudinal contraction and 

construction joints keep these joints tight 

and in alignment. 

• CRCP has no regularly spaced transverse 

joints but typically contains 0.6 to 0.8 

percent longitudinal steel reinforcement 

(expressed as a percentage of the crosssectional area of the slab). The higher

steel content both influences the 

development of transverse cracks within a 

desired spacing (about 3 to 6 ft [0.9 to 1.8 

m]) and serves to hold them tightly 

together. Transverse reinforcing steel may 

also be used, primarily to support the 

longitudinal steel. 

These traditional concrete pavement sections 

include opportunities for use of recycled materials 

in the base and subbase layers as well as various 

recycled materials in the concrete surface as 

described in chapter 3. 

As with asphalt pavements, reconstruction of 

concrete pavements consists of removing some or 

all of the existing structural layers and replacing 

them with a substantially new pavement structure. 

There are often many alternatives for recycling 

materials removed from the existing structure in the 

new structure. Once again, the decision to 

reconstruct is based on comparison of rehabilitation alternatives considering the condition of the 

existing pavement and the overall objective of the owner/agency for the project.

Concrete Pavement Surface Options

Concrete pavements have a number of surface textures that can be constructed to provide 

different functionality for friction and noise. Transverse tining has commonly been used to 

provide surface friction, but has been found to be a noisier surface (Rasmussen et al. 2008). 

Concrete Pavement Thermal 

Characteristics

Most materials expand when they are 

heated and contract when cooled. The 

degree to which this occurs is measured by 

the coefficient of thermal expansion (CTE), 

which is presented in terms of the change 

in unit length of a material as a function of 

an associated change in temperature. This 

behavior is important for concrete 

pavement design, as higher CTE values 

result in higher stress development due to 

temperature differences that exist between 

the top and bottom of the concrete slab. 

These temperature differences are affected 

by the albedo (solar reflectivity) of the 

surface and the conductivity and heat 

capacity of the concrete and other

pavement layers.

CTE is a direct user input in the 

AASHTOWare Pavement ME Design 

procedure for concrete pavements. Higher 

CTE values result in higher predicted levels 

of slab cracking and joint faulting for JPCP 

(Hall and Tayabji 2011), and a greater 

incidence of punchouts and associated 

roughness on CRCP (Roesler and Hiller 

2013). 

The CTE of concrete depends primarily on 

the coarse aggregate used in the mixture. 

CTE values can range from around 4 x 10-6

in/in/oF (7 x 10-6 mm/mm/oC) for concrete 

containing limestone aggregate to a value 

of about 6.6 x 10-6 in/in/oF (11 x 10-6

mm/mm/oC) for concrete containing quartz

aggregate. 

Given the importance of the CTE in new 

ME design procedures, many highway 

agencies are working to characterize the 

CTE properties of their concrete mixtures. 

A test protocol for CTE testing has been 

standardized by AASHTO under T 336 

(Hall and Tayabji 2011).

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

Other surface textures include longitudinal tining, diamond ground, diamond grooved, and 

various turf drags. Joint design and construction can affect also affect noise levels. More 

information on these surface textures is provided in chapter 5, and information on noise studies 

related to concrete pavement surface textures is provided in chapter 6. 

Concrete Pavement Rehabilitation Options

Rehabilitation strategies for concrete surfaced pavements include structural asphalt overlays and 

structural bonded and unbonded concrete overlays (non-structural asphalt overlays are 

considered in chapter 7). Concrete overlays of existing concrete pavements are either unbonded 

or bonded (Harrington 2008; Harrington and Fick 2014; Torres et al. 2012). An unbonded 

concrete overlay utilizes a separation layer between the concrete pavement and the new concrete 

overlay (Smith, Yu, and Peshkin 2002). This has typically been a 1 to 2 inches [25 to 51 mm] 

thick asphalt material, although some agencies are now using non-woven geotextile materials as 

a separator layer (Harrington and Fick 2014). This separation layer is placed to ensure 

independent behavior between the two slabs, thereby minimizing the potential for reflection 

cracking. Unbonded concrete overlays are typically constructed between about 6 to 12 inches

(152 to 305 mm) thick, with the structural requirements based on support conditions and 

projected traffic loadings. Unbonded concrete overlays are used when the existing pavement 

deterioration is so advanced that it cannot be effectively corrected prior to overlaying. Figure 4-

6 shows the cross sections of rehabilitated concrete pavement structures.

Figure 4-6. Cross sections of rehabilitated concrete pavement structures (not to scale).

Structural Asphalt Concrete 

Overlay

Structural (Bonded/Unbonded) 

Concrete Overlay

Structural Asphalt Overlay Bonded or Unbonded

Concrete Overlay

Intact Distressed Concrete 

Pavement or 

Rubblized Concrete Pavement

Existing Concrete Pavement 

Asphalt, Cement Treated or

Granular Base Layer

Asphalt, Cement Treated or

Granular Base Layer

Granular Subbase Layer Granular Subbase Layer

Compacted Subgrade Compacted Subgrade

Bonded concrete overlays consist of a thin layer of concrete (typically 3 to 4 inches [76 to 102 

mm] thick) that is bonded to the existing concrete pavement (Smith, Yu, and Peshkin 2002). 

These are used to increase the structural capacity of an existing concrete pavement or to improve 

its overall ride quality. A critical construction and performance aspect of bonded concrete 

overlays is the achievement of an effective bond between the overlay and the existing concrete 

pavement in order to create a monolithic pavement system. Bonded concrete overlays of 

existing concrete pavement are not used frequently and require the existing pavement to be in 

good to excellent structural condition prior to placement (Harrington 2008; Harrington and Fick 

2014). 

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

For structural asphalt overlays of concrete

pavements, the overlay is typically placed directly 

on the existing concrete pavement using a tack 

coat. The existing concrete pavement may be 

broken into smaller-sized pieces using crack and 

seat or rubblization procedures as a means of 

slowing or minimizing the development of 

reflection cracking (Thompson 1989; NAPA 1994; 

Hoerner et al. 2001; TRB 2006). When the 

concrete pavement is in poor condition with 

extensive patches or materials problems, 

rubblization will reduce the concrete to a state 

similar to aggregate base. However, rubblization 

may not be appropriate if the subgrade is too soft to 

support the rubblizing process, or if the pavement 

does not exhibit distresses for which rubblizing is 

the best alternative (Heckel 2002). 

Composite Pavement Types

Asphalt-Surfaced Composite Pavement

Asphalt-surfaced composite pavements refer to asphalt layers placed on a concrete pavement, 

either as part of new pavement construction or as part of a rehabilitation project. This type of 

design takes advantage of both paving material types, and may be used for a number of reasons, 

including reduced noise, increased friction, improved smoothness and rideability, and utilization 

of higher volumes of recycled materials in the concrete layer (if part of a new pavement 

construction). A thin asphalt layer with low noise emissions and high frictional properties can be 

placed over a durable and fatigue resistant concrete layer to achieve a quiet, safe, and potentially 

long-lasting structure. The asphalt layer may also help reduce negative temperature gradients 

(cold on top), reducing excessive tensile stresses that can lead to cracking (Rao et al. 2013a; Rao 

et al. 2013b). A typical cross section of an asphalt-surfaced composite pavement is shown in 

figure 4-7. 

Figure 4-7. Cross section of asphalt-surfaced composite pavement. 

Asphalt Layers 2 to 3 in 

(51 to 76 mm)

Jointed Plain or Continuously 

Reinforced Concrete

Base Layers

Compacted Subgrade

Overlays for Concrete-Surfaced 

Pavements:

 Structural asphalt overlays: Overlay 

is placed on intact, distressed 

concrete using tack coat; if existing 

concrete is in poor condition, then 

crack and seat or rubblization 

procedures may be used.

 Structural concrete overlays: 

Bonded or unbonded. Unbonded 

overlays contain an interlayer 

between the existing and new 

concrete to provide separation; 

bonded overlays consist of a thin, 

concrete layer bonded to existing 

concrete pavement to produce a 

monolithic structure.

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

Two-Lift Composite Concrete

Another type of composite pavement is constructed using two independent lifts of concrete that 

are placed “wet on wet” so that an effective bond develops between them. The properties of the 

two layers are designed for the specific application. The upper lift may consist of abrasion 

resistant and more durable materials optimized for surface characteristics such as noise and 

texture while the lower lift utilizes recycled materials or aggregates of lesser quality (Darter 

1992; Hall et al. 2007; Van Dam et al. 2012; Rao et al. 2013b). This optimized approach serves 

to not only lower costs, but also reduces environmental impacts as well. A typical cross section 

of a two-lift concrete pavement is shown in figure 4-8. 

Figure 4-8. Cross section of two-lift concrete pavement.

Concrete Surface Layer 2 to 4 in

(51 to 102 mm)

Concrete Lower Layer

Base and Subbase Layers

Compacted Subgrade

Over the years, a number of projects featuring two-lift concrete have been constructed (Sommer 

1994; Smiley 1995; Wojakowski 1998; NCPTC 2008; Tompkins, Khazanovich, and Darter 

2010; Brand et al. 2012). Two recent examples of two-lift concrete pavements include: 

• A composite pavement constructed by the Missouri DOT in 2011 consisted of an 8-in

(203-mm) bottom lift of conventional concrete and a top lift of 2 inches (51 mm) of 

concrete containing photocatalytic cement on Route 141 in St. Louis County (Cackler et 

al. 2012; Sikkema 2013). 

• A composite pavement on the I-88 Illinois Tollway consisted of an 8-in (203-mm)

ternary concrete bottom lift containing 20 percent fractionated coarse RAP and a 3.5-in

(89-mm) top lift of conventional concrete pavement materials (Brand and Roesler 2013). 

Semi-Rigid Pavement

Semi-rigid composite pavements are composed of an asphalt surface course placed on a 

cementitious layer (e.g., CTB, LCB, or RCC). Semi-rigid pavements are often used where highquality aggregate is not readily available. However, the reflection of shrinkage cracks from the 

cementitious layer into the asphalt surface may need to be addressed. One approach to minimize 

reflection cracking is to “microcrack” the cementitious layer with impact rollers as it is curing, 

which produces well-distributed, fine cracks that exhibit little movement (Sebesta 2004). 

Another approach is to saw narrow joints in the cementitious layer to more uniformly distribute 

crack movements and thereby slow the rate of reflection cracking. A final way to establish a 

tight cracking pattern is to introduce discrete cracks with an impact device (Cockerell 2007). 

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

There are a number of potential opportunities for using large quantities of recycled materials in 

semi-rigid pavements. For example, the cementitious base layers can be produced either using 

plant-mixed materials, or through full-depth reclamation with cement stabilization (as described 

in chapter 8). A typical cross section of a semi-rigid pavement is shown in figure 4-9. 

Figure 4-9. Cross section of semi-rigid pavement. 

Asphalt Layers

Cement Treated or Lean Concrete 

or Roller Compacted Concrete

Granular Subbase

Compacted Subgrade

Rehabilitation of Composite Pavement

Rehabilitation alternatives for composite pavement types are the same as for other types of 

asphalt- and concrete-surfaced pavement. 

Modular Pavement Systems

Modular pavement systems are composed of a wide 

variety of precast components in order to either 

rapidly construct or repair a section of roadway or to 

provide an aesthetically pleasing design. One type of 

modular pavement is precast concrete slabs, of which 

a number of different technologies have become 

available over the past 15 years (Tayabji, Ye, and 

Buch 2012). They are typically used for very short 

construction windows to minimize user delays and to 

provide better performance than might be obtained 

using rapid-setting concrete materials with cast-inplace construction. Better performance is expected 

because the precast concrete is cast and cured under 

controlled conditions, and is therefore not exposed to 

potentially poor field curing conditions and 

trafficking while curing. In addition, effective joint 

load transfer can be built into the slab either through 

unique doweling configurations or, for some 

systems, through post-tensioning (Merritt, 

McCullough and Burns 2003; Smith 2008; Smith 

2012). Grinding is performed after some 

installations to improve smoothness. 

Modular Pavement System Types

Intermittent Systems: These are 

isolated pavement repairs conducted 

using precast concrete slabs and 

typically include full-depth repairs of 

deteriorated joints and cracks and fullpanel replacement of severely 

deteriorated slabs. Several different 

systems are available, with successful 

installations in New York, New Jersey, 

and Michigan, among others locations.

Continuous Systems: These involve 

full-scale rehabilitation of asphalt and 

concrete pavements. Common systems 

that have been used in the U.S. include 

jointed precast concrete pavement 

systems with dowel bars and precast, 

prestressed concrete pavement systems 

formed by post-tensioning together a 

series of panels. These continuous 

systems have been constructed in a 

number of states, including California, 

Delaware, Texas, Missouri, New Jersey,

New York, and Virginia.

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

Another example of a modular pavement system is interlocking concrete pavements. These are 

often used on low speed facilities or in urban areas to provide aesthetically pleasing roadways 

(ASCE 2010; Smith 2011). 

Modular pavements potentially permit thinner and longer lasting structures that could reduce 

environmental impacts over the life cycle. Modular pavement systems also allow easy access for 

utility cut repairs to reduce repair costs and minimize user delays.

Pavements and Stormwater Management

Pavements can be constructed using permeable materials to innovatively control, manage, and 

treat stormwater runoff. Permeable pavements can capture and store stormwater runoff, allowing 

it to percolate into the ground and thereby recharge groundwater supplies while also controlling 

outflow. Fully permeable pavements, shown in figure 4-10, are defined as those in which all 

layers are intended to be permeable and the pavement structure serves as a reservoir to store 

water during storm periods in order to minimize the adverse effects of stormwater runoff.

Figure 4-10. Cross sections of pervious concrete pavement, porous asphalt pavement, and 

permeable interlocking concrete pavement. 

Pervious Concrete Pavement Porous Asphalt Pavement

Pervious Concrete (various mix 

designs)

Porous Asphalt (various mix 

designs)

Small Stone Open Graded 

Granular Base

Small Stone Open Graded 

Granular Base

Large Stone Open-Graded 

Granular Base

Large Stone Open-Graded 

Granular Base

Compacted or Lightly Compacted 

Subgrade

Compacted or Lightly Compacted 

Subgrade

Permeable Interlocking 

Concrete Pavement

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

Most applications of fully permeable pavements in North America have not been subjected to 

high-speed traffic or heavy trucks, which reflects concerns about durability. Structural design 

methods are empirical in nature, and are available from the National Asphalt Pavement 

Association (Hansen 2008), the American Concrete Pavement Association (ACPA 2009), and 

the Interlocking Concrete Pavement Institute (Smith 2011) for design of porous asphalt, pervious 

concrete pavements, and permeable interlocking concrete pavements, respectively.

For state highway agencies, fully permeable pavements are being considered as a shoulder 

retrofit adjacent to conventional impermeable pavement with geofabric barriers to limit water 

affecting the layers in the impermeable pavement, and for some low-speed applications carrying 

trucks. An ME design approach and a preliminary LCCA have been produced for fully 

permeable pavements to carry trucks (considering both structural and hydraulic capacity) for 

California conditions (Jones et al. 2010; Li, Jones, and Harvey 2012a; Li, Jones, and Harvey 

2012b). More information regarding fully permeable pavements is included in chapter 6. 

Layer and Material Type Selection

The pavement type alternative determines what layer combinations and materials (virgin, 

recycled, or co-product) can be used. For the type of facilities considered here, all pavement 

types will have a permanent surface layer (asphalt or concrete), a higher quality base layer that 

may or may not be stabilized, and perhaps even a subbase layer to provide for added subgrade 

protection from moisture, frost, and repeated traffic loading. Base and subbase material 

properties and combinations are chosen for multiple reasons including transmitting and 

spreading the load-induced stresses to the subgrade, providing uniformity of support to the 

surface layer, providing subsurface drainage, protecting lower layers from frost penetration, and 

providing a working platform for surface course construction. Base and subbase material layers 

can often make use of more recycled and lower quality aggregates to reduce construction costs 

and emissions while still achieving the structural goals of the layer. To improve pavement 

performance and potentially reduce the thickness of the surface layer, these layers can be 

stabilized if desired. Trade-offs between the impacts of reduced surface layer thicknesses versus 

the impacts of foundation layers stabilization can be considered with LCA (see chapter 10), as 

can trade-offs between the impacts of increased thickness versus materials of lower quality but

with reduced environmental impact. 

Subgrades should always be compacted to improve stiffness and shear strength and to reduce 

permeability. Subgrades may also be treated or stabilized to further improve stiffness and shear 

strength. The improvement of these properties may permit thinner pavement structures above 

the subgrade to carry the same traffic. Treatment and stabilization materials can include cement, 

lime, asphalt emulsions, fly ash, kiln dust, or other cementitious materials. Guidance on 

stabilization selection, mixture design, and construction are available from the FHWA 

(Carpenter et al. 1992a; Carpenter et al. 1992b). These two volumes represent the revisions to 

original manuals prepared in 1980 (Terrel et al. 1980). 

Clay subgrades may also be treated with lime to reduce plasticity and improve compaction, 

although care must be taken to check that a given subgrade soil will not be susceptible to 

swelling due to unwanted chemical reactions, such as certain expansive lime-clay reactions

(Mitchell 1986). Trade-offs between the impacts of reduced surface layer thicknesses versus the 

impacts of subgrade stabilization can be considered with LCA (see chapter 10).

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

Chapter 3 provides an overview of the various virgin, recycled, co-product, and waste materials 

that are currently being used in pavements. The availability of recycled (e.g., RCA, RAP, RAS, 

rubber) and co-product (e.g., slag, fly ash, limestone dust) materials must be thoroughly explored 

as part of the design process since they may have a significant impact on the LCA in terms of 

cost, energy, and emissions. To effectively, efficiently, and safely use all available resources 

(virgin, recycled, and co-product materials), existing agency guidelines and specifications should 

be reviewed or new ones created to ensure the selected pavement sustainability strategies will 

provide the desired pavement performance. 

One potential strategy for reducing the energy, emissions, and overall environmental impact of 

transporting pavement materials (see chapter 3 for details of minimizing material transportation)

is to reduce the cross section of the new pavement or rehabilitation structure by using higher 

quality materials or by balancing the use of locally available materials with higher quality 

materials in critical pavement layer locations. ME design procedures, with appropriate material 

characterization, can be used to identify the required change in the cross section to ensure that 

performance requirements are still met even when sub-optimal recycled or local materials are 

employed. 

As described in chapters 3, and 5, the main contributors to energy consumption, GHG emissions, 

and other environmental impacts in the paving materials production phase are cement, asphalt 

binder, and aggregate production, and the asphalt and concrete mixing plant operations. The 

production of polymers, crumb rubber, and other additives in asphalt mixtures and chemical 

admixtures for concrete pavements can potentially improve pavement performance or permit 

thinner structures, but may also result in increased energy and emissions. A full LCA analysis 

will assist in the selection of materials for use in the design (see chapter 3). 

Consideration of energy dissipation due to structural responsiveness is an area of current 

research and validation, and contributions to energy use and GHG emissions may be a 

consideration in the structural design (see chapter 6). 

Drainage

Poor drainage conditions can contribute to early failures and reduced pavement life, and 

therefore can significantly increase the environmental and cost impacts of the original pavement 

because of early and more frequent maintenance and rehabilitation activities. It is essential that 

the need for drainage be reviewed for all new and rehabilitation projects. Failing to remediate 

poor drainage, even where it affects a relatively small percentage of the project length, will lead 

to increased life cycle costs and higher environmental impacts. 

Construction Quality Specifications

The sustainability of a pavement structure can be improved through any increases in pavement 

performance (e.g., longer service life, higher and maintained levels of smoothness and frictional 

properties). In many cases, this can be achieved with small increases in construction quality and 

concomitant reductions in overall variability. Because the development of effective construction 

quality specifications is part of the design process, a careful review of construction specifications 

is appropriate to see where increased levels of quality could be achieved and impact 

performance. Moreover, the implementation of an effective quality assurance plan promotes 

higher levels of quality should be part of the effort to improve pavement sustainability through 

design. More details regarding construction quality are presented in chapter 5. 

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

Material Trade-Offs

As has been discussed previously, there are a number of trade-offs that can be evaluated

regarding the use of materials in a pavement design; for example, trade-offs between the 

desirable characteristics of a material and the distance from which it must transported, or tradeoffs in the thickness requirements of the material for it perform adequately versus the benefits of 

treating or stabilizing the material to reduce thickness. Materials specifications should be 

reviewed to determine whether they impose any restrictions on using materials that have lower 

life-cycle environmental impact but produce the same performance when used in a given 

structure. In some cases, the use of thicker layers of less desirable recycled or local material may 

still provide acceptable performance but with lower economic and environmental impacts. 

It may be that some outdated specifications require virgin materials because the technology for 

effectively using recycled materials was not fully developed at the time the specifications were 

written. The use of empirical design methods requires that performance be observed for 

sufficient time to assess the risk of failure, which for many materials requires years of

monitoring before considered acceptable for inclusion in routine designs. In other cases, there 

may be an assumption that virgin materials inherently possess superior properties compared with 

recycled materials. The more widespread use of ME design methods should speed the 

implementation of new and innovative materials through effective laboratory characterization. 

Compaction

As described in chapter 5, more stringent compaction specifications for subgrade, unbound 

granular, cement-treated, and asphalt materials can result in increased pavement life. Increased 

levels of compaction improve the density, stiffness, and strength of unbound and cement-treated 

materials, and increase the stiffness, durability, rutting, and fatigue performance of asphaltbound materials. Many agencies use a standard specification of 90 to 95 percent of standard 

AASHTO T 99 compaction for subgrades and granular materials. Increasing compaction to 95 

to 100 percent for granular materials will result in increased pavement life with the increase in 

environmental impact primarily coming from the increased use of construction equipment. 

Airfield pavements use 100 percent of modified AASHTO compaction (AASHTO T 180) for 

aggregate bases with similar gradations to those used for highways. The use of 95 percent of 

standard AASHTO T 99 compaction for subgrades instead of 90 percent, or even 95 percent, of 

modified AASHTO T 180 compaction should improve pavement performance with minimal 

environmental impact. The primary trade-offs are increases in construction cost, potentially an 

extension to the construction schedule, increased quality assurance testing by the owner/agency

for verification, and potentially some increase in construction equipment emissions. However, 

increases in pavement life and extension of the time that the pavement is smooth will often have 

a much larger positive impact than the additional equipment emissions required to achieve those 

higher levels of compaction. Verification testing should be performed to ensure that more 

stringent compaction specifications can be achieved for the given material. An example is given 

in chapter 5 regarding the benefits of increased life from improved asphalt compaction. 

Smoothness

Obtaining good initial smoothness levels during construction of new or rehabilitated high traffic 

volume roadways, and designing the pavement to maintain those levels of smoothness 

throughout its life, can result in a large reduction of use-phase energy/emissions compared to 

impacts associated with materials production and construction. However, the impacts associated 

with the materials production and construction phases will likely be more important for lower

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

volume routes (see chapter 6). Smoothness acceptance levels should be part of the construction 

specifications developed for the design (preferably in terms of IRI), with high-volume traffic 

facilities deriving greater benefits from higher levels of initial smoothness. 

Construction Process and Traffic Management

One sustainability aspect that can be considered during the pavement design and construction 

process is the integration of traffic management plans in order to adequately consider and possibly 

minimize user delays. For example, more rapid means of pavement construction or rehabilitation 

can help reduce user delays. Construction analysis programs for pavements, such as CA4PRS 

(Lee, Harvey, and Samadian 2005; Lee and Sivaneswaran 2007; Lee at al. 2009; FHWA 2008; 

Caltrans 2013), can be used to analyze the effects of pavement design on traffic delays and 

construction window policies. The impact of traffic delays on vehicle GHG emissions and energy 

consumption relative to the impacts of materials production, construction, and the use phase will 

depend on the types of delay and the number and types of vehicles affected. It is possible that 

traffic slowing in a construction zone could conceivably have a beneficial effect on sustainability; 

for example, if traffic speed in a work zone is reduced from 65 mi/hr (104 km/hr) to 45 mi/hr (72 

km/hr), the overall vehicle fuel economy is expected to improve. 

Consideration of Future Maintenance and Rehabilitation

The design of new pavements and rehabilitation projects should include consideration of future 

maintenance and rehabilitation that will be required based on the design decisions. These future 

decisions should include consideration of maintaining the overall structural capacity of the 

pavements, its overall functional capabilities (e.g., smoothness, friction), and future roadway 

recycling and reuse (see chapter 8 on end-of-life strategies).

Sample Sustainable Design Strategies

Longer Life Pavement

Longer life pavements can be achieved as a policy objective in new, rehabilitated, and 

reconstructed pavements and are generally justified for higher volume facilities. Design lives 

may range from 30 to more than 60 years and can be accomplished using both asphalt and 

concrete designs. Longer life design options should be considered for new corridors and 

rehabilitation of existing pavements that are severely distressed and may also possess geometric 

deficiencies, and may afford the opportunity to reduce life-cycle costs, user delays, and 

environmental impacts as compared to a standard, 20-year pavement design. 

A general rule for load-related cracking is that as critical tensile strains or stresses decrease (for 

either concrete or asphalt pavements), the overall structural capacity of the pavement (i.e., the 

number of truck loads it can carry) increases logarithmically. Therefore, when there are heavy 

volumes of traffic, higher structural capacity can be achieved by increasing the bending 

resistance of the pavement; this can be accomplished by increasing the thickness or by increasing 

the material stiffness (or both). Longer life designs can select innovative combinations of layer 

thicknesses and materials to achieve this, including the use of recycled materials in the lower 

layers. However, effective material and construction specifications are essential in order to 

reduce variability and maximize the performance of the selected materials. Because of the 

increased thicknesses or increased material stiffnesses, longer life designs may increase initial 

costs and possibly initial environmental impacts, but the overall life-cycle costs and 

environmental impacts over the life cycle are expected to be less. 

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

Longer Life Asphalt Pavement

Longer life asphalt pavement designs can be developed to provide a number of sustainability 

benefits, including: 

• Reduction in the amount of asphalt mixture through the selection of materials and 

construction requirements for better compaction that produce greater bending resistance 

than conventional materials; this reduces the cross-sectional area compared with what 

would be required with conventionally designed and compacted asphalt mixtures. 

• Incorporation of higher quantities of RAP combined with stiffer and less viscoelastic 

asphalt binders in the middle layer; this reduces the amount of new asphalt binder used 

(and its commensurate environmental burden) and provides increased stiffness and 

reduced viscoelastic energy dissipation. 

• Use of modified open-graded surfaces to reduce noise, slow stormwater runoff, and trap 

pollutants, and provide a sacrificial layer for top-down cracking. 

• Use of recycled concrete pavement or building waste as the granular base layer. 

If the longer life pavement is designed so that the tensile strain at the bottom of the asphalt layers 

is below the limit at which the potential for cracking begins, it is often referred to as a perpetual 

pavement (see figure 4-11). The composition of each of the layers in a perpetual pavement is 

described below (starting from the bottom of the pavement system and working to the surface): 

• A fatigue-resistant bottom layer is provided that resists damage under tensile strains 

caused by traffic, and thus stops cracks from forming in the bottom of the pavement. 

This bottom-up fatigue cracking resistance can come from increasing the total pavement 

thickness such that the tensile strain at the bottom of the base layer is insignificant (which

requires more asphalt), or by specifying air voids to between 0 and 3 percent and slightly 

increasing the asphalt content to achieve this high level of compaction (referred to as a 

“rich-bottom” layer). 

• The next layer is designed specifically to increase the bending stiffness through the use of 

stiffer conventional asphalt and potentially higher RAP contents. This layer can also 

have an increased compaction requirement to increase the stiffness and fatigue resistance

of the section. 

• The third layer from the bottom is designed specifically to resist surface-initiated 

distresses such as top-down cracking, rutting, and low-temperature cracking (where 

applicable). Some typical mixtures used for the surface layer are polymer-modified 

asphalt concrete and SMA. ME pavement design procedures can be used to design the 

structure considering the different pavement materials (Timm and Newcomb 2006; 

Buncher and Newcomb 2000; Newcomb, Willis, and Timm 2010; Harm 2001). 

• A fourth layer—typically either a high-quality polymer- or rubber-modified, open-graded or 

gap-graded mixture or a 1 to 2 inches (25 to 51 mm) SMA—can be placed on top of the rut 

resistant layer and is designed for abrasion resistance and vehicle safety. This layer is 

considered to be a sacrificial layer in a 30- to 50-year long-life asphalt pavement. Once its 

effectiveness is diminished (approximately every 10 to 15 years), it can be removed, 

recycled, and replaced. Many open-graded and SMA mixtures used for this layer can 

provide tire-pavement noise reductions when compared to dense graded materials (Rezaie, 

Harvey, and Lu 2012). 

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

Figure 4-11. Perpetual pavement cross section. 

Optional Wearing Surface 1 to 2 in (25 to 51 mm)

Rut and Top-Down Crack Resistant Asphalt or SMA Layer 1.5 to 4 in (38 to 102 mm)

High Modulus Asphalt Layer Thickness dependent on 

structural design requirement

Fatigue and Bending Resistant Asphalt Layer 2 to 3 in (51 to 76 mm)

Optional Granular Base as a Working Platform 

for Asphalt Layers

Compacted or Lightly Compacted Subgrade

For longer life structural overlays, the prudent use of polymer-modified asphalt materials may

also be a way to achieve longer life (as compared to conventional materials). Polymer-modified 

asphalt can extend the life of the surface by increasing rutting resistance and decreasing 

susceptibility to top-down cracking. It can also be used to decrease reflection cracking in an 

overlay application. The increased life can help decrease the frequency of maintenance and 

rehabilitation, thus reducing some environmental impact. However, polymer modification 

should be used where its benefits are of most value, because polymer modification may increase 

overall GHG emissions of the asphalt pavement design due to the manufacture and production of 

the polymer itself (Bernard, Blomberg, and Southern 2012). 

Longer Life Concrete Pavement

Longer life concrete pavements (either JPCP or CRCP), with anywhere from 35- to 60-year 

design lives, are designed to maintain structural integrity and require only periodic retexturing of 

the surface to restore smoothness, friction, and noise performance. Longer life concrete

pavements are designed to resist the heavy truck traffic that will cause repeated load distresses 

such as fatigue cracking, faulting, and punchouts. These design objectives are achieved by using 

durable concrete mixtures, adopting slightly thicker concrete slabs placed on non-erodible bases, 

including properly designed and corrosion-resistant dowel bars or reinforcing steel, and 

incorporating stress-relieving design features such as tied concrete shoulders or widened slabs.

Figure 4-12 shows an example of a longer life CRCP designed for fatigue resistance and low 

maintenance requirements. The life-cycle environmental benefits of the longer life CRCP have 

to be evaluated using LCA and compared to the environmental impacts associated with the 

inclusion of the steel reinforcement.

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

Figure 4-12. Example of CRCP longer life design. 

0.7 to 0.8 %

epoxy coated 

steel

12 to 13 in

(305 to 330 mm)

Asphalt Concrete Base 4 to 6 in

(102 to 152 mm)

Aggregate Working Platform 12 in

(305 mm)

Compacted Subgrade

Recycled concrete aggregate can be used in all layers of concrete pavements with the majority of 

the recycled concrete placed in the granular base or subbase layer to reduce subgrade stresses, 

protect against frost action, and to enhance subsurface drainage. Recycled concrete or coarse 

RAP can be used in the concrete mixture as long as the mixture design is adjusted for the 

expected changes to the fresh and hardened concrete properties (Snyder et al. 1994; Sturtevant 

2007; Roesler, Huntley, and Amirkhanian 2011; Brand et al. 2012; Brand and Roesler 2013). 

Co-product materials such as fly ash and slag cement are commonly used in all types of concrete 

pavements including longer life designs, as these significantly improve the durability of the 

concrete (see chapter 3 for more information).

Design for Local Materials or Low Impact Transportation

Designing for the incorporation of local materials to reduce transportation costs should be 

considered for all aggregate materials, whether they are used in asphalt, concrete, or unbound 

layers. Minimization of earthwork hauling for the roadway foundation is also another 

consideration. Alternatives can be analyzed to minimize both costs and environmental impacts. 

Accelerated Construction

Accelerated construction can be employed that minimizes the duration of construction and 

associated lane closure times. Construction processes and materials such as rapid-setting or 

high-early-strength concrete, modular concrete, or rubblization/asphalt overlays are examples of 

accelerated construction. Each of these options will expedite the construction process, thus 

reducing user delays, reducing emissions, and improving safety (by reducing the risk of crashes). 

Single-Lane Rehabilitation

In many situations involving multi-lane highways, the outer (truck) lanes may be in need of a 

structural rehabilitation or reconstruction, while the inner lanes are still in relatively good 

condition. If a thick overlay (concrete or asphalt) is needed on the truck lanes, the inner lanes must 

receive the same treatment in order to maintain elevations. In these cases, consideration could be

given to the reconstruction of the outer lane, with the new pavement structure either matching the 

surface elevation of the inner lanes, or perhaps slightly higher to accommodate the placement of a 

thin overlay on the inner lanes to restore functional performance. Computations can be made for 

the environmental impact of each scenario (complete overlay vs. outer lane reconstruction), 

including consideration of the recycling of the existing pavement and associated traffic delays. 

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

Local reconstruction of the outer traffic lane can also be considered on corridors with mixed 

pavement types (i.e., different pavement types in adjacent lanes), provided that this does not 

impose any major maintenance issues. Existing asphalt pavements can receive either an inlaid 

reconstructed asphalt or concrete outer lane, and existing concrete pavements can receive new 

inlaid concrete truck lanes and an asphalt overlay on the passenger lanes that matches the 

elevation of the outer lanes. There are also opportunities for inlaid reconstruction with semirigid pavements in the truck lanes. The pavement materials that are removed can be recycled 

next to the construction site into the new truck lanes.

Consideration of Use Phase in Design

The main design factors that have the most significant effects on the use phase are:

1. Smoothness over the design life of the pavement. High levels of smoothness maintained 

throughout the life of the pavement will incur reduced environmental impacts. 

2. Overall pavement longevity. This serves to not only decrease the life-cycle costs, but 

also reduces the environmental and social impacts associated with materials production, 

construction, and periodic maintenance and rehabilitation. 

Which of these factors is most important depends on the context of a particular project. The 

importance of both depends, in large part, on the traffic volumes using the facility. Where there 

are heavy traffic volumes, the benefits of smoothness over the design life can be much larger than 

material production and construction impacts. Conversely, for low-volume roads and highways, 

material production and construction will often tend to dominate the net calculation of 

environmental impacts. Additional details on use-phase considerations are discussed in chapter 6. 

Major Issues and Trade-offs in Designing More Sustainable Pavements

Based on the discussions presented in this chapter, the major design and policy objectives, 

associated approaches to providing sustainability improvements, and potential trade-offs with 

regard to economic, environmental, and societal impacts are summarized in table 4-2. 

Future Directions and Emerging Technologies

There are a number of potential future directions and emerging technologies in the pavement 

design arena that may have a significant effect on improving overall pavement sustainability. 

These include:

• Improvements in ME design: testing, models, validation. Further improvements in the 

ability of laboratory testing to characterize materials properties that control performance, 

and in models that use those properties to predict pavement performance, will permit 

improved and more rapid consideration of new materials in pavement design. There are a 

number of accelerated pavement testing (APT) facilities around the world that can be 

used to provide more rapid feedback on the performance of full-scale constructed 

pavements to help validate new models, materials, and structures. This should result in a 

shorter time for their implementation. Balancing the risk versus reward in the use of new 

materials and structures, incorporating them into new testing and design procedures, and 

providing training of engineers to use them, are all significant challenges. ME design 

procedures will need to see more widespread use in order to provide more precise 

performance estimates with consideration for construction variability.

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

Table 4-2. Summary of major issues and trade-offs for improving pavement sustainability 

through design. 

Design/Policy 

Objective

Sustainability Improving 

Approach

Economic 

Impact Environmental Impact Societal Impact

Achieve 

Longer Life

Use ME design to be able 

to consider alternative 

materials, construction 

specifications and 

structures to increase life 

for same pavement 

thickness1, 2. Use selected 

recycled materials to 

improve structural 

characteristics. Require 

higher construction quality. 

Virgin materials 

may increase cost; 

increased 

construction quality 

may increase cost; 

reduced frequency 

of maintenance and 

postponement of 

rehabilitation may 

decrease cost. 

Virgin materials may 

have higher 

environmental impact 

during production; 

decreased maintenance 

frequency may decrease 

emissions; increased 

pavement quality may 

decrease user emissions. 

Stays smoother 

longer; less delay 

associated with 

maintenance. 

Achieve 

Longer Life Use of higher quality 

materials. 

Increased cost of 

materials; decreased 

cost of maintenance. 

Potential for increased 

emissions due to 

production and 

transportation of higher 

quality materials if not 

locally available; higher 

quality pavement may 

result in lower user and 

maintenance emissions.

Higher quality 

pavement; less 

delay associated 

with maintenance. 

Achieve 

Longer Life

Improved construction 

specifications (less 

variability, greater density, 

stiffness, strength, 

durability depending on 

material)2

. 

Somewhat increased 

initial cost; could 

decrease 

maintenance cost or 

upfront cost if 

reduced thickness is 

used. 

Less frequent 

maintenance or reduced 

thickness will reduce 

environmental effects of 

construction and 

materials use; additional 

initial construction work 

may have minor impact.

Less delay 

associated with 

decreased 

maintenance. 

Consider 

Inlaying New 

Truck Lane 

Pavements (vs.

Multi-lane 

Overlay)

Minimize total material 

used for rehabilitation by 

not overlaying lanes to 

match grade that do not 

have structural needs. 

Can reduce cost; 

may cause some 

additional traffic

delay.

May reduce total 

amount of new materials 

needed; can consider 

recycling materials 

removed from old truck 

lanes.

May cause more 

initial traffic delay 

due to closure for 

reconstruction. 

Obtain Same 

Life for 

Reduced 

Thickness

Use ME design to consider 

new materials, 

construction specifications, 

pavement structure 

types1,2. 

Virgin materials 

may have higher 

cost; increased 

construction quality 

may increase cost. 

Potential increase due to 

production of virgin 

material; less material 

use lowers 

environmental impact 

due to reduction in 

production, 

transportation and 

construction.

May reduce traffic 

delay due to more 

rapid construction. 

Reduce Noise 

Emissions

Use of noise reducing 

asphalt (open-graded) or 

concrete (new generation 

concrete surfaces) 

surfaces.

3

Increased cost; more 

frequent 

replacement for the 

asphalt surface. 

Minor impact of 

additional 

grinding/grooving for 

concrete; more materials 

use and construction.

Reduction of noise 

in surrounding 

areas. 

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

Table 4-2. Summary of major issues and trade-offs for improving pavement sustainability 

through design (continued). 

Design/Policy 

Objective

Sustainability Improving 

Approach

Economic 

Impact Environmental Impact Societal Impact

Achieve/ 

Maintain

Pavement 

Smoothness

 

Consider smoothness over 

the pavement life as a key 

design parameter, 

especially for high traffic 

volume routes. Include 

construction specifications 

for smoothness, design 

features to maintain 

smoothness, and costing of 

maintenance to keep 

surface smooth.

Potential for small to 

moderate increases 

in initial costs but 

reduced life-cycle 

costs due to longer 

pavement lives. 

Reduced vehicle 

operating costs for 

road users.

Reduced environmental 

impact due to less fuel 

use, particularly on high 

traffic volume routes.

Improved economic 

efficiency.

Maximize Use 

of Recycled

and Local

Materials 

Use recycled pavement 

materials to replace virgin 

materials and minimize 

transportation distances for 

materials.1

Higher variability in 

recycled material 

quality may increase 

maintenance 

frequency and lifecycle cost; generally 

reduces initial cost. 

Reduced impact of 

materials production and 

transportation; less use 

of scarce materials; use 

of stabilizers have an 

impact and can be 

compared with benefits 

of reduced need for 

resurfacing layers, 

transportation of 

materials, etc.

May increase 

maintenance delay 

if materials do not 

perform as 

expected in design; 

reduced landfill 

disposals. 

Maximize Use 

of Recycled 

Material

Use recycled materials 

from other industries to 

replace virgin materials.1

Use where 

transportation cost

feasible if not 

locally available; 

Evaluate variability 

in material quality to 

avoid increase 

maintenance and 

rehabilitation; 

generally reduces 

initial cost; 

additional processing 

or construction 

issues may increase 

initial cost.

Use where

transportation and 

processing are 

environmentally 

beneficial; may reduce 

future recycling if 

inclusion of recycled 

materials makes future 

recycling too costly, 

unpredictable or 

difficult; reduced impact 

of virgin materials 

production; less use of 

scarce materials. 

May increase 

maintenance delay 

if materials do not 

perform as 

expected in design; 

reduced landfill 

disposals. 

Minimize 

Impact of 

Utility 

Construction

Eliminate or minimize 

utility cuts in pavement, or 

use pavement systems that 

allow easy restoration of 

pavement structure after 

utility work (utility 

corridors in pavement).

Higher initial cost; 

reduced life-cycle 

costs due to less 

frequent 

maintenance and 

rehabilitation; 

reduced cost of 

maintenance and 

rehabilitation with 

no manhole covers; 

reduced life-cycle 

cost if longer life 

designs are used.

Potential increased 

initial materials and 

construction impacts of 

utility corridor; reduced 

impacts due to longer 

pavement life, less 

frequent maintenance 

and rehabilitation. 

Keeping utilities out of 

pavement improves 

ability to do in-place 

recycling strategies.

Smoother pavement 

over life cycle; 

increased pavement 

life resulting from 

less frequent repairs 

and patching. 

Keeping utilities 

out of pavement 

improves ability to 

do in-place 

recycling strategies.

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

Table 4-2. Summary of major issues and trade-offs for improving pavement sustainability 

through design (continued). 

Design/Policy 

Objective

Sustainability 

Improving 

Approach

Economic 

Impact Environmental Impact Societal Impact

Minimize 

Impact of 

Construction

Accelerated

construction. 

Often reduces initial user 

costs but increases agency 

costs; must maintain 

quality standards. 

Difficulty with shorter 

construction may 

influence quality and 

functional life; 

accelerated materials

may have a shorter 

performance life.

Reduced traffic 

delay. 

Use Pavement 

to Capture 

Runoff 

Pollutants and

Reduce 

Hydraulic 

Requirements 

from Storms3

Use partially 

permeable pavement 

(e.g., open-graded 

asphalt). 

Increased cost; need for 

more frequent resurfacing.

Increased 

environmental impact 

of materials and 

construction for opengraded layers; reduced

pollutants in water. 

Cleaner water for 

surrounding area. 

Use Pavement 

to Capture 

Runoff

Pollutants and

Reduce 

Hydraulic 

Requirements 

from Storms3

Use fully permeable 

concrete or asphalt 

pavement (very little 

application to date, 

only for highway 

shoulders). 

Largely unknown; 

increased cost, need for 

more resurfacing; 

potential to reduce 

stormwater conveyance. 

Requires more 

materials, thicker layers 

than conventional 

shoulders; reduced 

pollutants in water; 

groundwater recharge. 

Cleaner water for 

surrounding area. 

Use and 

Maintain 

Pavements that 

Reduce Urban 

Heat Island 

Effects and 

Reduce 

Lighting Costs

where 

Warranted by 

Net Benefits

Where it is 

determined to be 

beneficial based on 

assessment of the life 

cycle for specific 

project type and 

climate region, 

engineer pavement to 

reduce heat island 

effects.3

Range of potential costs 

from net reduction to 

neutral to net increase if 

energy savings from air 

conditioning and lighting 

are less than pavement 

alternative life-cycle cost 

differences. 

Increased impact of 

thickness and materials 

if not warranted by 

climate, urban 

environment, lighting 

requirements; potential 

for increased 

environmental impact 

of materials designed 

for thermal 

characteristics; reduced 

energy use due to less 

required lighting.

Less energy use 

from air 

conditioning in 

locations where 

pavements make 

substantial 

contribution to 

increased urban 

temperatures in late 

afternoon and 

evening. 

Consider Fuel 

Use Due to 

Structural 

Responsiveness 

to Vehicle 

Loading (Once 

Research is 

Completed) 

Once calibrated 

models are available, 

consider using them 

to determine where 

structural 

responsiveness is 

significant and 

develop appropriate 

strategies based on 

those results.3

Calibrated models will 

permit evaluation of 

alternative structures 

considering traffic, 

climate and other 

variables which will allow 

consideration of both road 

user and agency costs 

versus environmental 

benefits for designs.

Optimization may 

reduce environmental 

impact due to less fuel 

use, particularly on high 

truck traffic volume 

routes.

Optimization may 

improve economic 

efficiency 

particularly on high 

truck traffic 

volume routes.

Note: For more details on: 1Materials, including recycled materials, see chapter 3 2Construction quality, see chapter 5 3Use-phase considerations, see chapter 6 4Maintenance and preservation, see chapter 7 5Interaction of cost and sustainability, see chapter 10

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

• Improvements in ME design: reliability. Data and methods for incorporating withinproject and between-project as-built variability into design methods will need to be 

developed. Better consideration of reliability will be needed to consider the effects of 

increased use of recycled materials, to provide fair comparisons between alternative 

designs, and to better estimate future maintenance and rehabilitation activities. 

• Integration of design and environmental impact analyses. As the pressure for 

consideration of environmental impacts in the pavement design decision-making process, 

there will likely be more integration of design, LCCA, and LCA in routine project 

development. There will be difficulties in balancing multiple design alternatives and 

selecting the optimal design based on costs (both agency costs and sometimes user costs), 

sustainability, and constructability. The process laid out in this chapter provides a 

starting point for agencies to identify major sustainability goals and then develop their 

own procedures for optimizing alternative design types based on sustainability 

considerations important to them. Methods for multi-criteria decision making will need 

to be developed, and this includes the selection of the best design approach for different 

project delivery environments (DBB with alternative designs, DB, and DBM).

• Development of new materials. Economic, environmental, and political pressures are 

resulting in much more competition between materials production industries, and 

potential creation of new industries that reduce the environmental impact of pavements. 

Increased recycling of pavement materials (such as RAP, RAS and RCA), and the 

inclusion of co-product materials (such as fly ash and slag cement) will drive much of the 

competition. Designers will need to consider new laboratory tests, models, and 

validation studies for newly developed materials as they are introduced by the industry at 

a faster pace. Specifications will need to be evaluated to ensure that they provide the 

contractor and materials supplier the flexibility to achieve the desired pavement 

performance while also maintaining owner/agency costs and risks at an acceptable level.

• Consideration of future maintenance and rehabilitation in design. There will be increased 

demand to accurately consider future maintenance and rehabilitation as part of the design 

process in order to provide better inputs to LCC and LCA analyses for both new 

pavement and major rehabilitation projects. Validated models will be needed for 

rehabilitation alternatives so that they can be compared on an equal basis. This is 

essential for DBM projects in order to estimate bid price and risk, but will also be 

increasingly used for other types of project delivery as well. 

• Performance-related construction specifications. It is likely that there will be increased 

use of performance-related tests for pavement materials and requirements for contractors 

and materials producers to provide products meeting the properties assumed by the 

designer using ME design methods. Approaches for developing materials and 

construction quality specifications that lead to improvements in performance, while still 

being achievable with available materials and equipment, will be a challenge.

• Better models for smoothness performance. Designers will need to have and use better 

models for smoothness prediction, particularly as technology for real-time measurement 

of smoothness at construction is now practical and there is a growing recognition of the 

importance of smoothness on use-phase environmental impacts (see chapter 6).

• Approaches for designing better performing fully permeable pavements. The technology 

will likely improve for designing fully permeable pavements that can carry heavier loads 

and handle stormwater with less space, cost, and difficulty than many current stormwater 

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Chapter 4. Pavement and Rehabilitation Design Towards Sustainable Pavement Systems

management practices. Designers will likely be faced with more opportunities and 

challenges in using these pavements.

Concluding Remarks

This chapter describes sustainability considerations through the design process for both new and 

rehabilitated pavement structures, including structural overlays and reconstruction. It 

specifically reviews the entire design process and identifies key areas that affect the overall 

sustainability of the resulting pavement. As noted in previous chapters, there are a number of 

trade-offs that must be considered, as improvements in one area might be detrimental to another, 

with the ultimate goals of the owner/agency ultimately determining which approach may be most 

suitable for a particular project. 

The major issues for improving the sustainability of pavements through design decisions are 

summarized as follows:

• Achieve longer pavement life with the same quantity of materials, or achieve the same 

pavement life using thinner structures and less materials through design and construction 

specification decisions. 

• Use design and construction specifications to maximize smoothness over the life cycle of 

the pavement to reduce environmental, economic, and social impacts related to vehicle 

operations, taking into consideration materials production and construction impacts. 

• Consider maximizing the use of recycled materials and minimization of materials 

transportation where they can produce positive environmental and cost benefits, while not 

compromising pavement performance. 

• Seek to integrate construction and traffic management into design decisions to minimize 

cost, materials use, and construction-related traffic delay. 

• Consider use-phase impacts throughout the life cycle in design, including not only 

smoothness but other factors as well such as deflection, noise, and stormwater 

management. 

References

American Association of State Highway and Transportation Officials (AASHTO). 2008. 

Mechanistic-Empirical Pavement Design Guide, Manual of Practice. American Association of 

State Highway and Transportation Officials, Washington, DC. 

American Association of State Highway and Transportation Officials (AASHTO). 2012. 

AASHTOWare Pavement ME Design Guide Software. American Association of State Highway 

and Transportation Officials, Washington, DC. 

American Concrete Pavement Association (ACPA). 2009. Stormwater Management with 

Pervious Concrete Pavement. American Concrete Pavement Association, Skokie, IL. 

American Society of Civil Engineers (ASCE). 2010. Structural Design of Interlocking Concrete 

Pavement for Municipal Streets and Roadways. ASCE Standard 58-10. American Society of 

Civil Engineers, Reston, VA. 

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Towards Sustainable Pavement Systems Chapter 4. Pavement and Rehabilitation Design

Bernard, F., T. Blomberg, and M. Southern. 2012. “Life Cycle Inventory: Bitumen.” 

International Symposium on Life Cycle Assessment and Construction July 10-12. CSTB, Nantes, 

France. 

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4-38
Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

CHAPTER 5. CONSTRUCTION CONSIDERATIONS TO IMPROVE 

PAVEMENT SUSTAINABILITY 

Introduction

Pavement construction practices have changed significantly over the last several decades, 

utilizing new technologies that have significantly improved pavement quality and construction 

efficiency while decreasing environmental impacts. These construction practices, in concert 

with an appropriate pavement structural design (chapter 4) that uses appropriate materials 

(chapter 3), can provide significant improvements to the overall sustainability of a pavement 

system. Critical areas of pavement construction that can have a significant effect on the overall 

sustainability of a paving project include:

• Fuel consumption (during material transport from the site and between the plant and the 

site and the construction operations themselves).

• Exhaust and particulate emissions. 

• Traffic delays, congestion, and noise emissions generated during construction. 

• Constructed characteristics of the pavement surface, which impacts surface friction

(safety), noise, and possibly fuel efficiency during the use phase. 

• Pavement performance and overall life (as a result of construction quality).

This chapter summarizes various approaches for improving the sustainability of pavement 

construction. It first begins with a discussion of general sustainability issues that are common to 

all types of pavement construction (such as energy consumption and effects on localized or 

surrounding areas), and includes a summary of specific strategies that can be used to address 

those issues. This is followed by separate sections that are devoted to strategies and approaches 

that can be used to improve the sustainability of both asphalt and concrete pavement 

construction. Note that material production (discussed under chapter 3) includes plant mixing, 

and thus construction starts “at the gate” with respect to asphalt and concrete mixtures.

Sustainability of Pavement Construction Operations: General Issues

The following are the general pavement construction factors that impact pavement system 

sustainability over the life cycle:

• Construction-related energy consumption.

• Effect on the surrounding area (including particulate and gas emissions, noise, effects on 

residents and businesses, and effects on wetlands and streams).

• Economics of construction practices, including user costs (due to construction-related 

traffic delays or normal operations).

An introduction to these factors is presented next, followed by a section on potential strategies 

for addressing them. 

Construction-Related Energy Consumption and Emissions

In general, pavement construction is an energy-intensive process that involves excavation, 

earthwork movement, material processing and placement, and compaction/consolidation of the 

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

paving layers. Pavement construction equipment includes excavators and haul equipment, 

crushers, asphalt and concrete mixing plants (discussed as part of materials in chapter 3), 

graders, pavers, rollers, and more. The associated energy consumption of equipment is a 

function of the equipment/vehicle operation energy efficiency, which in turn is a function of the 

operation of that equipment within ideal power bands and minimization of idle time and engine 

speed during idle time. External factors (independent of equipment efficiency) that influence 

construction fuel consumption include site operations (e.g., haul distances, construction staging, 

and the need for multi-pass operations) and specific site-related conditions (e.g., quality and 

maintenance of haul road surfaces). Other factors that can affect energy consumption include 

fuel types (including the use of alternative fuels such as biodiesel and compressed natural gas) 

and the type of power source for stationary construction equipment (i.e., generator driven vs. grid 

powered). 

The use of RAP and RCA in the base or subbase offers a strong potential for sustainable 

construction, particularly when the source materials are available and processed on site. In 

addition to offering the potential for reductions in construction-related fuel consumption and 

emissions, recycling (particularly on-site recycling) reduces the costs, fuel consumption, 

emissions, and land use associated with excavating, processing, and hauling virgin materials, as 

well as the economic and environmental costs of disposing of the old materials. Actual savings 

of fuel, emissions, and costs vary widely for a particular recycling project, depending on such 

things as the abundance of suitable local virgin aggregate sources, haul distances, crushing costs, 

and the potential for use of the recycled material in a higher type application (e.g., in new asphalt 

or concrete surface layers), which depends upon the quality of the source material. There may 

even be savings in surface material costs if the increased stiffness of a recycled base (due, for 

example, to the rough-textured, angular nature and secondary cementing action of RCA) 

provides additional structural capacity to allow a reduction in surface layer thickness. Additional 

guidance on the cost and energy savings and structural benefits associated with recycling asphalt 

and concrete pavements is available from ARRA (2001) and ACPA (2009), respectively. 

Construction emissions are those generated from the operation of the various constructionrelated equipment due to direct construction activities, and also include the emissions that result 

from indirect construction activities (including vehicles using a roadway that experience 

construction-related delays). The emissions emanate from equipment powered by fossil fuels 

(using diesel, gasoline, or coal to heat or run equipment) and from electricity obtained from the 

grid used as part of the construction. Waste disposal should also be considered in order to 

account for a comprehensive measure of sustainability. 

Emission categories for mobile sources used during construction activities usually include the 

following exhaust pollutants: 

• Hydrocarbons (HC) or non-methane hydrocarbons (NMHC).

• Nitrogen oxides (NOx). 

• Carbon monoxide (CO). 

• Carbon dioxide (CO2).

• Sulfur oxides (SOx). 

• Volatile organic compound (VOC) (replaced all HCs by EPA [2005]). 

• Particulate matter (PM).

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

There have been numerous studies estimating the contribution of roadway construction projects 

to the overall life-cycle energy consumption and emissions of a pavement system. As described 

in chapter 2, pavement construction activities are estimated to be responsible for 70 percent of 

the highway and street construction expenditures (USDOT 2010). Total GHG emissions due to 

all highway and street construction is estimated to be around 117 million tons (106 million mt), 

which is approximately 7 percent of the U.S. transportation total. Currently, a national effort is 

underway to develop a guidebook for selecting and implementing sustainable highway 

construction practices (under NCHRP Project 10-91, Guidebook for Selecting and Implementing 

Sustainable Highway Construction Practices). 

With respect to the total life cycle of a pavement system, the construction stage constitutes 

approximately 5 percent of the total pavement production cycle, including plant production, 

transportation, and construction activities. In an overall roadway life cycle, which commonly 

may be 40 to 50 years, the total energy consumed can be 18 to 20 times that for pavement 

production, which includes plant production, transportation, and construction (Muench 2010). 

The total energy and associated emissions during the life cycle of a pavement include pavement 

production, use phase related to the operation of roadway (e.g., fuel consumption by vehicles, 

lighting, traffic signals, urban heat island), maintenance, and end-of-life strategies. A detailed 

discussion of the pavement life cycle is presented in chapter 2. 

The EPA (2009) has introduced the concept of emission intensity to provide a means for 

comparing the relative emissions of GHGs between various industries or economic sectors while 

taking into account their economic output. Emission intensity is typically calculated as the ratio 

of the GHG emissions produced per dollar of gross domestic product (GDP). Within the 

construction sector, the highway construction subsector had the highest emission intensity at 0.54 

tons (0.49 mt) of CO2e emissions per thousand dollars of GDP (in 2002 dollars), with total 

annual emissions of 19.5 million tons (17.6 million mt) CO2e. 

Impact of Construction on Surrounding Areas

Emissions from Equipment Exhaust

The use of heavy equipment for earth moving and construction operations generates engine 

combustion emissions that may have significant impact on local air quality in surrounding areas, 

as well as on climate change. Heavy duty construction equipment is usually diesel powered, 

which yields NOx, GHG, and diesel PM as significant emissions. The particulate fraction of 

diesel exhaust emissions is reported as a toxic air contaminant posing chronic and carcinogenic 

public health risks (AEP 2012). 

The EPA regulates the emissions from all mobile sources including on-road and non-road 

vehicles and engines. Non-road vehicles and engines include a category called compressionignition (CI) engines covering equipment used in various construction activities. The EPA has 

established stringent standards for carbon monoxide, volatile organic carbon, nitrogen oxides, 

and particulate matter that a vehicle and engine may emit, and manufacturers, refineries, and 

mixing plants are responsible for meeting those standards. A tiered approach was put forward by 

EPA depending on the vehicle’s engine rated power and age. Figure 5-1 illustrates the limits 

proposed by EPA (EPA 2013a), and it is noted that the band of restrictions will become much 

tighter after 2015. 

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

Figure 5-1. EPA non-road diesel engine limits for construction vehicles with two different 

ranges of rated power illustrating tightening of the emission limits (adapted from EPA 2013a).

0

0.25

0.5

0.75

1

0 5 10 15

PM (g/kW-hr)

NMHC + NOx (g/KW-hr)

75 ≤ kW < 130 450 ≤ kW < 560

Tier 2 (early 2000s)

Tier 3 (late 2000s) Tier 1 (late 1990s)

Tier 4 (late 2015s)

Construction emissions can be calculated for all projects that are expected to exceed a certain 

threshold defined by the construction significance criteria (AEP 2012). Emissions can be 

calculated using the available databases, EPA sources, or commercial software using the 

construction activities and productivity of the equipment and use. For those projects exceeding 

the significance criteria, short- and long-term mitigation strategies can be applied, as described 

later in this chapter. An example of the construction emissions thresholds proposed by the 

California Environmental Quality Act (CEQA) is given in table 5-1. 

Table 5-1. Thresholds of significance for construction operations (SLO county APCD 2012). 

Pollutant Daily

Threshold

Quarterly Tier 1

Threshold

Quarterly Tier 2

Threshold

VOC + NOx (combined) 137 lbs 2.5 tons 6.3 tons

Diesel PM 7 lbs 0.13 tons 0.32 tons

Fugitive PM (PM10), Dust 2.5 tons

GHG * * *

1 lb = 0.45 kg; 1 ton = 0.91 metric ton

* GHG emissions need to be combined with other life-cycle emissions and amortized over the life of the project.

In order to estimate GHG emissions, the information related to equipment productivity is needed. 

Hourly equipment emission rates can be calculated using the following formula (Tang, Cass, and 

Mukherjee 2013): 

5-4 
Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

HHHHHHHHHHHH EEEEHHEEEEEEEEEEEE GGHHGG EEEEEEEEEEEEHHEE RRRREEEE = OOtt ∗ LLff ∗ HHHH ∗ CCff ∗ εε (Equation 5-1) 

where: 

OOtt = Operating time factor (usually taken as 45 min per hr) 

LLff = Average load factor corresponding to actual operating horsepower 

HP = Average horsepower 

CCff = Fuel consumption rate (Gal/(HP*hr))

εε = Emission rate (i.e., 22 lbs CO2/Gal (2.6 kg/l) for burning conventional diesel)

Airborne Particulates from Construction Operations

In addition to the generation of particulates and pollutants from vehicle exhaust, pavement 

construction activities commonly generate dust, fine soil, and other airborne particulates from 

normal operations, particularly when construction takes place in dry or windy conditions. This is 

sometimes referred to as fugitive dust, and is primarily particulate matter that is less than ten 

microns in size (PM10) (AEP 2012). There are a number of sources of fugitive dust, including

the following: 

• Haul vehicle traffic on dry, unstabilized surfaces (including haul roads, pavement 

foundation layers). 

• Wind erosion of exposed unstabilized materials. 

• Stockpiling, hauling, and placement of unstabilized materials. 

• Tracking and subsequent breakdown of soils and construction materials on local roads 

near site and plant entrances. 

The distribution of particulates can vary constantly with wind speed and patterns, precipitation 

events, and other factors. However, it can be controlled and mitigated through good construction 

practices.

Noise Generated from Construction Operations

Pavement construction generates noise from the excavation, movement, processing, and 

placement of large volumes of material using large, powerful machinery. The resulting noise 

from exhaust stacks, plant site operations, earthwork construction, material hauling, and so on 

can be irritating at best, and potentially hazardous to the health of workers or area residents in the 

worst cases. High noise levels contribute to many health problems, including hearing loss, sleep 

disturbance, interference with communication, and physical health issues typically associated 

with stress (e.g., cardio-vascular problems) (Hygge 1998; Berglund and Lindvall 1995). Similar 

to airborne particulates, construction noise problems can be affected by wind patterns and other 

weather conditions. 

Construction Impacts on Local Traffic, Residences, and Business Operations

In addition to pollution, particulate, and noise concerns, construction activities can also impact local 

residents, businesses, and visitors by temporarily preventing or restricting access to residential and 

commercial buildings, creating congestion and contributing to significant travel delays, and generally 

making an area undesirable to visit. Congestion-related impacts can spread well beyond the 

immediate limits of the construction area, depending upon local traffic patterns and route capacities 

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

and the availability of alternate modes of transportation. Significant and prolonged access problems 

to commercial areas may cause financial hardship to business owners and, in some cases, may result 

in business failures, having financial impacts on both the business owners and the community in 

general.

Public safety, both on the road and in areas adjacent to the construction site, is also a concern, 

particularly in high business zones and residential areas. The use of private property for 

construction activities (whether through rental, purchase, or condemnation) is another social 

impact of construction activities.

Construction Near Streams, Wetlands, and Environmentally Sensitive Areas

The potential for soil erosion in construction zones is increased by the removal of vegetation 

during earthwork and grading operations, allowing for more rapid concentration of precipitation 

and subsequent higher flow rates and increased potential for erosion. In addition, surface water 

runoff from construction zones can carry potentially hazardous materials into local waterways. 

The failure to control erosion and surface runoff during construction can cause both on-site and 

off-site impacts (NRCS 2000). On-site impacts include the loss of topsoil resulting in 

elimination of the soil’s natural ability to provide nutrients to plants. Off-site impacts are related 

to the erosion from construction sites resulting in water quality problems through excess 

nutrients transported via eroded soil and excess sediment. Excess nutrients impact water quality 

through eutrophication, a process in which excess nitrogen and phosphorus transported into 

surface waters causes unwanted biological growth, raising the level of lake or river beds which 

can eventually convert the area to dry land (Lawrence, Jackson, and Jackson 1998). Transported 

sediments can also be detrimental to aquatic life by interfering with photosynthesis, respiration, 

growth, reproduction, and oxygen exchange in waterways (Waters 1995; Newcombe and 

MacDonald 1991; Illinois Tollway 2013).

Economics of Construction Practices, Including User Costs

The adopted or specified construction practices for any given pavement construction project have 

direct bearing on both the initial construction costs and the long-term life-cycle costs of the 

project. Changes in construction practices to enhance the sustainability of the project (such as 

noise and pollution reduction procedures, controlling erosion and stormwater runoff, and 

providing better local access) are expected to incur increased costs, which must be considered 

and weighed against expected benefits over the life cycle of the pavement to determine its 

effective impact. Changes that incur unacceptable economic expense may not be easily adopted 

in spite of potential environmental or societal benefits.

In addition, construction work often results in reductions in roadway capacity and throughput 

due to geometric restrictions, reduced speed limits, temporary closures, detours, and other 

congestion-inducing activities. Significant costs are associated with construction-related traffic 

delays and congestion, including lost time and decreased productivity for users, wasted fuel, and 

economic loss due to the inefficient movement of goods and services. Highway construction 

work zones account for nearly 24 percent of nonrecurring congestion in the U.S. (other sources 

include vehicle crashes and breakdowns, and weather conditions), which translates to 482 

million vehicle hours of delay per year (USDOT 2006). Highway construction work zones are 

estimated to be responsible for 10 percent of all highway congestion in the U.S., which translates 

to an annual fuel loss of $700 million (Antonucci et al. 2005). 

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

According to recent congestion reports, while the magnitude of these emissions varies widely, 

Chan (2007) has reported an increase in emissions related to traffic delay as traffic volume

increases, but generally less than the emissions associated with material production. In another 

study, Häkkinen and Mäkelä (1996) reported that fuel consumption and corresponding emissions 

due to the disruption of normal traffic flow by construction and maintenance activities are in the 

range of 1 percent of the total life-cycle emissions of asphalt and concrete pavements. These 

numbers may vary depending on the type of the pavement and sequence of construction activities 

and the assumptions of use-phase traffic related emissions. 

In order to calculate emissions from traffic delays during construction and maintenance activities, 

the modeling effort must consider the stop and go nature of traffic flow as it approaches, passes 

through, and leaves the construction zone. For example, consider a typical vehicle traveling at 55 

mi/hr (89 km/hr) that stops as it approaches a construction zone and remains stopped for 10 

minutes; it then proceeds through the construction zone at a constant speed of 45 mi/hr (73 km/hr) 

and at the end of the construction zone accelerates to once again reach the posted speed limit 

(Mukherjee, Stawowy, and Cass 2013). This travel schedule can be modeled in various available 

programs to calculate emission factors for the given traffic and project construction data. The final 

outcomes of this analysis are the emissions and fuel usage from traffic delays triggered by highway 

construction activities. The EPA’s Motor Vehicle Emission Simulator (MOVES) software is one 

program that can be used to calculate emissions due to construction and maintenance activities (see 

http://www.epa.gov/otaq/models/moves/). 

Different road closure strategies and their impacts on the pavement construction energy 

consumption and GHG emissions were calculated by Kang et al. (2014). Three hypothetical 

scenarios were generated for a reconstruction project on the I-90 highway corridor around the 

Chicago area. The Kentucky Highway User Costs Program (KYUCP) model, developed by the 

University of Kentucky, was used to estimate driving schedules due to road closure scenarios. 

The emissions associated with changing driving schedules were predicted using EPA’s MOVES 

software. The following scenarios for work zone closures and construction schedules were 

considered in the traffic and emissions simulations for a 7.6 mi (12.2 km) work zone: 

• The first case assumed that the 7.6 mi (12.2 km) work zone was divided equally into four 

1.9 mi (3 km) work zones. For the construction of each 1.9 mi (3 km) work zone, a 

nighttime closure strategy was assumed between 9 p.m. and 5 a.m. in order to minimize 

additional emissions from traffic delay by avoiding the time period when peak traffic 

volumes would be experienced. 

• The second case assumed that the 7.6 mi (12.2 km) work zone was divided in half. For 

the construction of each of the two 3.8 mi (6.1 km) work zones, a 16-hour closure 

between 10 p.m. and 2 p.m. (following day) was assumed to avoid the time period when 

peak traffic volumes would be experienced. 

• The third case was based on the construction of the entire 7.6 mi (12.2 km) in a single 

stage. A 32-hour closure was assumed for this scenario from 9 p.m. to 5 a.m. (2 days 

later). 

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

The simulation results for energy consumption and CO2e emissions are provided in figure 5-2. 

Total emission and energy during construction activities were compared in the figure to the 

baseline case assuming traffic flow at the posted speed limits. The additional emissions and 

energy from work zone traffic delay increased slightly as the length of the work zone doubled 

from 1.9 mi (3 km) to 3.8 mi (6.1 km) because no traffic queue was developed during the 

nighttime closure. The emissions and energy consumption drastically increased in the third case 

when the entire 7.6-mi (12.2-km) work zone was assumed to be closed for 32 hours. Total 

energy and emissions were converted to the functional unit of LCA to evaluate the impact of 

traffic delay on pavement construction and material acquisition phase. Global warming potential 

due to traffic delay was reported to be 1.3 percent (best case scenario) to 2.7 percent (worst case 

scenario) of the total GWP including material and construction phases. 

Figure 5-2. Impact of construction-related traffic delay: (a) addition emissions, (b) additional 

energy consumption for normal traffic and traffic delay scenarios for work zone lengths of 1.9 

mi (four 8-hr nighttime closures avoiding morning and evening peak hours), 3.8 mi (two 16-hr 

night and daytime closures avoiding evening peak hours), and 7.6 mi (32-hr closure). (Traffic 

delay case indicates the case in which traffic delay due to work zone construction is developed; 

normal case indicates the traffic when all lanes are open with no work zone construction 

activity) (Kang et al. 2014). 

(a) 

(b) 

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Quality and Performance of Constructed Pavement System 

Even with the most durable materials and the most effective pavement designs, the overall 

pavement performance expectations will go unrealized if poor construction practices or 

inadequate quality assurance are performed. The quality of constructed roads becomes even 

more critical as transportation agencies need to maintain the facilities with limited resources. 

Performance specifications have been recently accepted as a way to improve the quality of 

construction and also to encourage contractors to develop innovative solutions that save time, 

minimize traffic delays, and enhance durability. SHRP 2 project R07 was charged to develop 

such performance specifications (Scott et al. 2014). The implementation of performance 

specifications are discussed in the context of various contract delivery methods including designbuild, design-bid-build, and other innovative contracting variations. The findings of the study 

support the use of performance specifications. 

Providing an effective working platform to facilitate construction activities is critical in ensuring 

adequate pavement performance. The load bearing capacity of native subgrade soil is generally 

improved through soil stabilization. Several techniques can be used to stabilize subgrade soils 

depending on site-specific characteristics and the predominant soil type; these include 

pulverization and homogenization using existing materials (without additives); stabilization 

using a single additive such as lime, cement, or asphalt binder (or less commonly, fly ash or 

other mineral fillers); and stabilization using multiple additives such as lime-fly ash (LF) or limecement-fly ash (LCF) combinations. These materials and technologies were introduced in 

chapters 3 and 4. 

One of the primary factors that control the sustainability of a pavement system through the use 

phase of its life cycle is the durability and longevity of the pavement. Pavements that deteriorate 

quickly and require frequent repairs and rehabilitation result in greater agency and user costs, 

greater environmental impacts (i.e., fuel consumption and emissions), and undesired levels of 

service to the users. 

The overall quality of the pavement must be reflected in both its structural and functional 

characteristics. For example, even a strong and durable pavement that has poor ride quality will 

result in relatively higher levels of user fuel consumption (and resulting vehicle emissions), 

lower levels of service, and may even increase average vehicle maintenance costs and damage to 

transported goods (or increases in required packaging costs). Specific issues and strategies for 

improving the quality of construction for asphalt and concrete pavements will be discussed later 

in this chapter.

Strategies to Improve Sustainability of General Pavement Construction 

Operations 

Table 5-2 summarizes several different strategies for improving the sustainability of construction 

operations that are applicable to all highway construction projects, regardless of pavement type. 

These strategies revolve around four major objectives (reduce fuel consumption and emissions, 

reduce noise, accelerate construction, and control runoff, erosion, and sedimentation), and the 

economic and environmental impact and trade-offs associated with each strategy are described. 

Additional discussion on these strategies is provided in the following sections. 

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

Table 5-2. Approaches for improving general sustainability of pavement construction 

operations. 

Objectives Sustainability 

Improving Approach Economic Impact Environmental Impact Societal Impact

Minimize haul distances Reduced fuel costs Reduced GHG emissions 

and air pollutants

Select appropriate 

equipment type and size 

for the job

Reduced fuel costs but may 

require capital investment

Reduced GHG emissions 

and air pollutants

Reduce Fuel 

Consumption 

and Emission

Idling reduction Reduced fuel costs; may 

require some capital 

investment to minimize 

idling

Reduced GHG emissions 

and air pollutants

Improved air 

quality

Use alternative fuels Varies Reduced emission Improved air 

quality

Retrofit construction 

equipment, use hybrid 

equipment, or both.

Will increase costs due to 

initial capital investment

Reduced GHG emissions 

and air pollutants

Improved air 

quality and may 

decrease 

construction related 

noise

Construction time 

restrictions

It may lead to reduction in 

construction productivity

May increase emissions if 

construction is prolonged

Less noise and may 

affect air quality 

Reduce Noise Equipment maintenance 

or modification

Increased capital 

investment 

No environmental impact Less noise

Effective traffic control 

and lane closure strategies

Reduced fuel costs for 

users and agency

May reduce traffic delays 

and associated emissions

Less traffic 

disturbance

Establish performance 

goals and measures for 

work zones

Reduced fuel costs for 

users and agency costs

May reduce traffic delays 

and associated emissions

Less traffic 

disturbance 

Accelerate 

Construction

Use project management 

software for construction 

sequencing and managing 

traffic delays

Reduced fuel costs for 

users and agency; extra 

effort for agency/contractor

May reduce traffic delays 

and associated emissions

Less traffic 

disturbance 

Implement intelligent 

transportation warning 

systems

Increased agency costs May reduce traffic delays 

and associated emissions

Less traffic 

disturbance and 

improve work zone 

safety

Use perimeter control 

barriers (fences, straw 

bales, etc.)

May result in increased 

project costs

Reduced sedimentation, 

prevent degradation of 

water quality

No direct impact on 

society

Control 

Erosion, 

Water 

Minimize the extent of 

disturbed areas

May result in increased 

project costs

Reduce disturbed areas May reduce impact 

on surrounding 

residential areas

Runoff, and 

Sedimentation

Apply erosion control 

matting or blankets

May result in increased 

project costs

Reduced sedimentation May reduce impact 

on surrounding 

residential areas

Store/stockpile away from 

watercourse

No significant economic 

impact

May reduce potential 

water pollution

May reduce 

potential impact on 

area water

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Strategies to Reduce Construction-Related Energy Consumption and Emissions

Opportunities to Reduce Energy Consumption and Emissions

There are a number of opportunities in the pavement construction process where energy and 

GHG emissions can be reduced. These opportunities can be grouped into three major categories: 

1. Fuel use (moderate to major effect).

2. Electricity conservation (moderate to major effect).

3. Selection of construction materials (no to minor effect). 

This section focuses on activities that contractors can control or influence to reduce energy and 

GHG emissions. Often, steps taken to reduce these parameters can provide a number of 

auxiliary benefits, such as increased equipment life and improved working conditions. 

Fuel Use 

According to the estimates reported by EPA (2009), nearly three-quarters of the GHG emissions

in various industrial processes are due to fossil fuel combustion. This is true for pavement 

construction, where fuel type and its efficient use can play a major role in the reduction of GHG 

emissions. Table 5-3 presents the emission factors for commonly used fossil fuels, that is, the

emissions generated (in terms of lbs of CO2) per gallon of fuel used. It also shows the potential 

reduction in GHG emissions for two assumed levels of increased fuel efficiency resulting in 

either a 3 percent or a 10 percent reduction in fuel consumption for highway construction 

activities. Clearly, even a modest reduction in fuel usage can have a significant effect on GHG 

emissions.

Table 5-3. GHG emissions reduction scenarios from fossil fuel use (EPA 2009). 

Fuel

Type 

Emissions, lbs CO2 per 

unit material1

Estimated GHG2

Reduction 

Using 3% less fuel

Estimated GHG2

Reduction

Using 10% less fuel

Diesel 22.37 lbs CO2/gallon 600 million lbs CO2 2000 million lbs CO2

Gasoline 19.54 lbs CO2/gallon 186 million lbs CO2 621 million lbs CO2

Natural Gas 11.7 lbs CO2/1,000 ft3 106 million lbs CO2 353 million lbs CO2

1 Emission factors are taken from EPA (2009). 

2 GHG reduction is calculated using the data provided in EPA (2009) and percentage of highway construction sector (13.4

percent) in total GHG of entire construction sector. The reduction in GHG is derived from the total construction sector 

emissions reported in EPA (2009). For example, using 3 percent less fuel may reduce CO2 emissions by 4,455 million lbs 

(2,022 million kg) as an estimate of sector-wide emissions, with highway construction responsible for approximately 13.4

percent of total emissions. Therefore, such reduction in fuel use may contribute to an emission reduction of 600 million 

lbs (272 million kg). 

The EPA (2007) recommends several low-cost strategies to reduce construction equipment 

emissions, including improved operating strategies, fuel strategies, and equipment strategies. 

Additional details on these strategies are provided below.

Operation Strategies for Fuel Reduction 

Equipment idle control, engine preventive maintenance, and operator training are some of the 

primary strategies for reducing fuel consumption and resultant emissions. For example, a typical 

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

Class 8 diesel engine at high idle may consume 1.2 gal (4.5 L) of fuel per hour, a value that 

translates to the release of 26.1 lbs (11.8 kg) of CO2 emissions per hour (EPA 2009). At low 

idle, the fuel consumption can be cut by one-half to 0.6 gal (2.3 L) of fuel per hour. For many 

contractors, fuel reduction simply involves changing work practices or investing in low-cost 

equipment. A summary of some of the recommended strategies for reducing fuel consumption, 

along with anticipated costs and benefits, is presented in table 5-4 (EPA 2007). In addition, 

carefully selecting material sites and plant locations for a specific job, as well as maintaining a 

stable haul road, can contribute to reduced fuel consumption. 

Table 5-4. Operational strategies to reduce emissions incurred due to construction 

activities (EPA 2007). 

Operation Strategy Costs Benefits

Equipment idle reduction and 

control

Low administrative costs for 

training and tracking of idling

Upfront investment if on-board 

idle reduction equipment1 is 

used (cost varying $500-$9000)2 

Reduced PM, NOx, CO, and HC 

emissions

Significant fuel savings

Longer engine life and reduced 

maintenance costs

Engine preventive maintenance

Low administrative costs for 

tracking equipment maintenance 

needs

Reduced PM, NOx, CO, and HC 

emissions

Significant fuel savings

Longer engine life and reduced 

maintenance costs

Equipment operator training

Upfront investment for training 

programs

Reduced PM, NOx, CO, and HC 

emissions

Significant fuel savings

Improved operator efficiency

Construct choose and maintain 

stable haul roads

Upfront investment may be 

required to construct and 

maintain haul roads

Smooth haul roads improve fuel 

consumption

Longer engine life and reduced 

maintenance costs

Select proper size and type of 

equipment depending on the 

production rate and road 

conditions

No investment is required Reduction fuel consumption

Longer engine life and reduced 

maintenance costs

Minimize haul distances by 

optimizing the plant and 

materials storage site location

No investment is required Reduction fuel consumption

1 Idle reduction technologies recommended by EPA’s SmartWay Technology Program can be found at 

the following web address: http://www.epa.gov/smartway/

2 The benefits of idling can be calculated using the worksheets developed by Argonne National 

Laboratory for heavy-duty and light-duty vehicles (Argonne 2011).

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Fuel Use Strategies

Ultra low sulfur diesel (ULSD), biodiesel fuels, and compressed natural gas (CNG) are examples 

of alternative fuels that are being used in construction equipment to help reduce emissions. 

ULSD is a diesel fuel that has gone through additional processing to remove sulfur, and hence is 

a cleaner-burning fuel that can be used in any diesel engine. For example, regular non-road 

diesel has a sulfur content of 3,000 to 5,000 parts per million (ppm), whereas ULSD has a sulfur 

content of 15 ppm or less. Biodiesel is a renewable fuel made from domestically grown crops 

such as soybeans, cottonseed, peanuts, and canola. Biodiesel is usually available at the pumps 

blended with conventional petroleum diesel (e.g., B5, 5 percent biodiesel; B20, 20 percent 

biodiesel). CNG is made by compressing natural gas (which is mainly composed of methane, 

CH4) to less than 1 percent of its volume and storing it in special containers under high pressure 

(up to 3,600 lb/in2 [25 MPa]). Table 5-5 summarizes some of the alternative fuel strategies with 

associated benefits and trade-offs. 

Table 5-5. Alternative fuel use strategies to reduce emissions (EPA 2007). 

Operation Strategy Costs Benefits

Ultra-low sulfur diesel 

(ULSD)

Higher price at the pump 

Lower energy content

Reduce PM and SOx 

emissions

Reduce engine wear

Increase oil change interval

Biodiesel (B5 and B20)

Higher price at the pump

Increase NOx emissions

Power loss and decreased fuel 

economy

Degradation and wear in 

engine hoses or gaskets

Reduce PM, CO, and HC 

emissions

Improve lubricity and reduce 

engine wear

Compressed natural gas 

(CNG)

Retrofit from gasoline and 

diesel vehicles is required

Limited vehicle availability

Lower price at the pump

Reduction in PM and 

greenhouse gas emissions

Equipment Optimization Strategies

Modifying and retrofitting existing construction equipment is another way to reduce emissions 

during construction activities. The initial investment required for this strategy is relatively high

compared to the aforementioned strategies. Major equipment modification approaches include 

repowering or upgrading older diesel engines and using grid electricity or hybrid equipment 

(EPA 2007). 

Diesel retrofitted devices can be installed on new or existing equipment as a post-treatment 

pollution control to reduce PM, NOx, HC, and CO. Diesel oxidation catalysts, diesel particulate 

filters, selective catalytic reductions, and exhaust gas recirculation are some of the retrofit 

technologies available in the market (EPA 2013b). 

Switching to dual-fuel generators or grid electricity, when it is available, can provide modest 

emissions benefits. On average, an approximate reduction of 15 percent can be achieved using 

grid electricity over the use of diesel generators, although this can be much higher depending on 

the source of the grid electricity. 

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

Other equipment optimization strategies may include 

selecting haul equipment (type, size, and quantity) 

based on production rates, haul route conditions, and 

maneuverability requirements; matching plant 

production, hauling needs, and paving operations; and 

avoiding extended time of heavy equipment idling. 

Strategies to Reduce Impact of Construction on 

Surrounding Area

Air Quality Assurance Practices during 

Construction (Other than Vehicle Emissions) 

There are a number of practices that can be adopted to 

improve air quality issues associated with pavement 

construction, other than those that result from vehicle 

emissions. Some of these strategies include water 

sprinkling and other dust control techniques, regular 

maintenance of dust collectors at concrete and asphalt 

plants, and consideration of the proximity of 

residential and light commercial areas in the selection 

of plant and materials storage locations. 

Construction Noise Control

Among the potential activities that could be considered 

to help control pavement construction noise are 

selecting plant and material storage locations away 

from residential and light commercial areas, limiting 

and mitigating excessive noise from haul vehicles 

(e.g., loud exhaust, banging tailgates), employing 

noise-reducing equipment modifications, and applying 

time-of-day construction restrictions. 

Effective Traffic Control, Lane Closures, and 

Work Zone Safety

Establishing work zones imparts restrictions on the 

highway driving space, and can result in traffic 

congestion with a number of detrimental impacts, 

including lost time, increased fuel consumption and air 

pollution, inefficient movement of goods, decreased 

productivity, and potentially compromised roadway 

safety. The contribution of emissions from 

construction-related traffic delays to total life-cycle 

emissions varies with construction schedule and 

duration, roadway capacity, and traffic volume and 

control. A wide range of emissions and additional fuel 

consumption has been associated with traffic delays 

(Chan 2007). Based on several construction and 

reconstruction projects studied in Michigan, the 

contribution of traffic delays to overall pavement service life emissions was comparable to 

Transportation GHG Analysis 

Tools

A number of tools are available for use 

in analyzing GHG emissions on 

construction projects. 

State Inventory Tool (SIT): This tool 

from the EPA consists of eleven 

modules for applying top-down 

approach to calculate GHG emissions 

and provides an aggregated total for 

each sector (industrial, commercial, 

residential, and transportation) at the 

state level. Emissions for specific 

construction activities are not included.

NONROAD: This tool from the EPA 

helps to estimate emission factors 

from all non-road vehicles (except 

locomotives, aircrafts, and commercial 

marines). This tool can differentiate 

equipment type and other 

characteristics and can be used to 

calculate emissions from specific 

construction activities.

MOVES: This is a comprehensive tool 

from the EPA for all on-road vehicles 

providing detailed reports on vehicle 

emissions. Vehicle operation 

characteristics, fuel type, geographic 

location, vehicle miles traveled, and 

other factors that may contribute to 

emissions are considered. However, 

since non-road vehicles are not 

considered, this model cannot be used 

alone to estimate construction related 

emissions.

PE-2: This is a web-based pavement 

LCA tool applying a project based 

approach. The focus of the tool is 

estimating emissions associated with 

highway transportation projects over 

their life cycle, including production, 

construction, maintenance, and use 

phase.

GreenDOT: This is an Excel-based 

greenhouse calculator from the 

operations, construction, and 

maintenance activities of state DOTs. 

It was developed under NCHRP 

Project 25-25 Task 58.

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

production stage emissions for high-volume roads; however, projects with Average Annual Daily 

Traffic (AADT) less than 20,000 vehicles per day (vpd) did not show a significant contribution 

to pavement total emissions and fuel use (Chan 2007). 

An FHWA study reported on the analysis of 3,110 work zones on the National Highway System, 

covering thirteen states (Wunderlich and Hardesty 2003). Analysis of the collected data shows 

that the work zone closures resulted in a loss of 60 million vehicles of capacity per day. Among 

the work zones examined, 58 percent of them had lane closures primarily during the daylight 

hours, 33 percent had closures primarily during the nighttime hours, and 9 percent had

continuous, 24-hour closures. The average work zone had lane closures for 11 hours a day and 

occupied 6.8 mi (10.9 km) of roadway for an average of 125 days (Wunderlich and Hardesty 

2003). 

Several strategies can be considered to reduce the impact of work zone delays, including the 

following (FHWA 2007):

• Implementing effective road and lane closure strategies – Effective traffic control 

strategies should reduce the period of time that work zones are active. This minimizes 

traffic delays and resultant emissions while keeping the motorists and construction 

workers safe. Some of the specific work zone strategies include using narrower lanes or 

shoulders, applying weekend lane or road closures, and charging lane rental, where 

contractors are charged for closing down lanes with an incentive to accelerate the time of 

construction. 

• Establishing performance goals and measures for work zones – Highway agencies can set 

goals to help manage their work zones, and could target such items as reducing work 

zone delays, reducing queue length, and minimizing GHG emissions. This strategy has 

been implemented by some DOTs and by some European countries, including Germany 

and the Netherlands. For example, in the Netherlands the target work zone delay is 6

percent of all traffic delays. This number in the U.S. has been reported as 10 percent, 

based on national averages (Cambridge Systematics 2005). 

• Incorporating lane/road closure analysis strategies during project planning – Different 

project management software programs can be incorporated into the planning and design 

phase to predict the impact of various lane or road closure strategies on traffic delays and 

emissions, and can also be used during construction to obtain feedback and monitor 

progress. This type of analysis in the planning stage can help sequence the schedule of 

activities while optimizing the process to reduce the impact on the users and the 

environment. Examples of the tools that can be used for this purpose include QuickZone, 

CA4PRS, and Dynasmart-P. CA4PRS is available free of charge to all highway agencies 

and is available at: http://www.fhwa.dot.gov/research/deployment/ca4prs.cfm.

• Implementation of intelligent transportation systems (ITS) – ITS technologies measure, 

analyze, and regulate traffic speed and volume and can help reduce traffic congestion in 

work zones by advising drivers of downstream traffic conditions. Components of an ITS 

may include dynamic message signs, a highway advisory radio, a citizen band radio 

channel, portable signs, a portable trailer, variable work zone speed limits, speed warning 

systems, and web cameras (Antonucci et al. 2005). Providing alternate routes or modes 

to drivers can also significantly reduce traffic demand in the work zone (Lee, Choi, and 

Lim 2008). A case study in Michigan that adopted ITS technology and a dynamic lane 

merge (DLM) system (which encourages motorists to merge lanes well before reaching 

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

the work zone) found that the DLM can increase safety while reducing the delay in lane 

closure area in work zone (Paniati 2004). Monitoring and optimizing the entrance and 

exit of operation equipment to the construction site is also an important activity to reduce 

delays in the work zone. 

Erosion/Stormwater Runoff and Sedimentation Control

Generally, highway construction projects that involve earthwork removal require a plan for 

erosion and sedimentation control. Temporary erosion and sedimentation control plans or 

stormwater pollution prevention plans may be needed for the highway project that includes 

earthwork removal. In addition to conventional approaches, a number of innovative methods are 

being used in this regard, such as harvesting the existing vegetation mat and then reinstating it 

after the earthwork has been completed, and performing only a partial cleaning of the bottom of 

the ditch so that the upper part of the vegetation remains in place. However, even on project 

sites where recommended practices or innovative procedures are employed, sediment can 

continue to be discharged at concentrations dangerous to aquatic life. For example, in one 

construction project, it was reported that suspended solid concentrations increased by 500 

percent on the downstream side of the construction site (City of Toronto 2006). Hence, effective 

best management practices to prevent erosion and to reduce the risk of costly sedimentation 

control measures and environmental damage are part of sustainable pavement construction. 

The unique characteristics of each pavement construction project challenges contractors to meet 

the governing regulatory agency requirements (conservation authorities, municipal, provincial, 

and federal). Therefore, it is critical to have an environmental assessment to determine the 

extent of environmental constraints to ensure implementing sustainable construction practices. 

The control plan should include a multi-barrier approach to control erosion during construction 

and sediment transport from the construction site. In addition, timely consideration of 

environmental constraints is critical to reduce delays and undesired environmental implications. 

The suggested plan for erosion control may include the following (City of Toronto 2006): 

• Minimize the extent of disturbed areas by construction sequencing, preserving and 

protecting natural cover, and immediately stabilizing disturbed areas. 

• Establish erosion control protocols for the site considering topography, site conditions, 

and infiltration rates; these protocols may include vegetation (e.g., mechanical seeding, 

terraseeding, hydroseeding, sodding, tree and shrub planting), erosion control matting or 

blankets, and scarification of disturbed surfaces. 

• Apply sediment transport control measures when vegetation practices could not be 

implemented. This includes perimeter controls, settling controls, and filtration controls. 

• Limit duration of soil exposure and phase construction when possible. 

• Minimize slope length and gradient. 

• Store/stockpile away from watercourse (e.g., greater than 40 ft [12.2 m]).

• Ensure inspection and maintenance of the implemented sediment and erosion control 

practices. 

• Perform revegetation of plant and construction sites as soon as is practical. 

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Construction Sequencing and Planning

Knowledge-based construction and scheduling analysis 

tools can be used to estimate optimum rehabilitation 

schedules, balance pavement design requirements, and 

develop effective traffic management plans. With a 

strong need to maintain traffic while rehabilitating or 

reconstructing a deteriorated pavement, accelerating the 

overall construction process becomes the key to reducing 

problems with congestion, safety, and user delays, 

particularly in heavily traveled urban areas. The 

CA4PRS software, mentioned earlier, is one tool that can 

help planners and engineers select economical 

rehabilitation strategies while minimizing disruption to 

drivers and the surrounding community (Lee, Harvey, 

and Samadian 2005). Several demonstration projects 

illustrated that the tool was beneficial in increasing 

productivity and reducing work zone related traffic 

delays. For example, the concept of a 55-hour, extended 

weekend closure was first validated on the I-10 Pomona 

project in California, achieving a 40 percent increase in

production when compared to traditional nighttime 

closures (Lee, Harvey, and Thomas 2005). Other 

construction planning tools available include QuickZone 

and Dynasmart-P.

Construction Materials Storage and Waste 

Management

Management of construction materials and waste can be 

critical in controlling stormwater pollution. Best 

practice management plans should be prepared for dealing with contaminated soils; vegetative 

waste and excess paving materials; materials removed from ditches, drains, and culverts; waste 

piles; and other material that can affect stormwater quality (ICF 2006). In addition, plans for 

hazardous waste management should be developed during construction when applicable, and 

may include critical recommendations such as:

• Groundwater resources should be protected from leaching by placing an impervious 

material on areas where toxic liquids are to be stored.

• During rain events, stockpiles of cold-mix asphalt should be covered.

• During rain events, stockpiles of soil should be covered or protected with a temporary 

sediment barrier.

• During rain events, stockpiles of hydraulic cement concrete and asphalt concrete rubbles 

should be covered or protected with a temporary sediment barrier. 

• Aggregate segregation during storage and handling should be avoided. 

Software Tools to Support 

Construction Practices

CA4PRS is a software tool 

supporting the analysis of project 

alternatives for different pavement 

design, construction logistics, and 

traffic operation options and is 

designed to help highway agencies 

and contractors develop 

construction schedules to minimize 

traffic delay and reduce agency 

costs.

QuickZone is a software tool for 

traffic analysis that compares traffic 

impacts for work zone mitigation 

strategies and estimates traffic 

delays and cost.

Dynasmart-P is a dynamic traffic 

assignment analysis tool used in 

decision making for regional work 

zone management. It models the 

evolution of traffic flows resulting 

from travel decisions of the 

individual travelers. It can be used 

to evaluate traffic management 

strategies for highway construction 

projects, and can also help assess 

the impacts of ITS technologies.

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

Evaluation of Sustainable Contracting Alternatives for Environmental Considerations

The level of emissions associated with construction operations is considerable and thus effective 

mitigation strategies are needed. For example, contract specifications may require contractors to 

use construction equipment certified by EPA, or may require that diesel retrofit devices be 

installed to reduce emissions. Some examples of such contract specifications used in public 

projects include the Central Artery project by Massachusetts Highway Department, the Dan 

Ryan Expressway construction by Illinois Department of Transportation, and in every recent 

contract by the New York Metropolitan Transportation Agency (Ahn 2012). The primary intent 

of these specifications is mainly to reduce critical air pollutants rather than GHG emissions. 

There are currently only a few agencies (e.g., Metropolitan Transportation Commission in San 

Francisco area and the Capital District Transportation Committee in Albany) attempting to 

quantify GHG emissions associated with construction and maintenance activities (ICF 2008). 

Innovative and alternative contracting and bidding methods may also be considered as a means of 

reducing the environmental burden of construction activities; otherwise, contractors may not 

voluntarily take the necessary steps to reduce GHG emissions or critical air pollutants. As one 

example, in 1994, the New York State DOT introduced “A+B” bidding (also referred to as cost plus 

time bidding) to encourage contractors to more actively manage their work schedules and adopt 

innovative and aggressive scheduling and construction management processes to accelerate 

construction completion. The “A” in the term refers to the cost associated with the amount of work 

to be completed, while the “B” refers to the calendar days proposed by the bidder to complete work 

multiplied by a daily user costs. The success of the A+B bidding method laid the groundwork to 

introduce environmental costs in the bidding process; for example, Ahn (2012) proposed “A+C” and 

“A+B+C” bidding methods, in which “C” refers to an environmental component. Environmental 

costs are defined based on the concept of the eco-costs (Vogtländer, Brezet, and Hendriks 2001; Ahn 

2012). However, emission estimates, eco-cost of emissions, fossil fuel use, and eco-cost of natural 

material depletion need to be known to calculate the “C” component, and thus bidders are required to 

use LCA to estimate emission and energy consumption values. 

Strategies for Improving Sustainability of Asphalt Pavement Construction Practices

Asphalt pavement construction generally entails the preparation and compaction of the subgrade, 

granular or treated subbase and base layers, and asphalt mixture layers, as described below:

• The construction activities for unbound and treated layers (subgrade and subbase/base 

layers) may include excavation, leveling, hauling of excavated or borrow materials, and 

layer compaction to design density levels. Locally available crushed aggregates are 

usually used for layer construction. 

• Construction of asphalt mixture layers usually involves asphalt mixture preparation, 

transportation, material placement, and compaction. Asphalt mixture preparation 

involves the mixing of multiple aggregate stockpiles at predetermined ratios, heating the 

combined aggregate, and mixing it with hot asphalt binder at a specific temperature, as 

described in chapter 3. The resulting asphalt mixture is transported directly to the project 

site or stored for later transport. The asphalt mixture is placed utilizing a paver and then 

compacted at predetermined temperature using appropriate rollers of defined types and 

with specified loading magnitude and frequency. A schematic of the overall asphalt 

pavement construction process is presented in figure 5-3. 

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Figure 5-3. Generalized asphalt pavement construction processes and associated fuel factors

(fuel factor source: Skolnik, Brooks, and Oman 2013). 

Major equipment used in asphalt pavement construction and their contribution to energy use and 

emissions should also be noted. Approximate levels of energy use and GHG emissions 

associated with the construction and equipment used in various asphalt pavement construction 

activities are presented in table 5-6. 

Table 5-6. Energy efficiency and CO2 emissions for common equipment used in asphalt pavement 

construction (compiled from Santero and Horvath [2009a]; Skolnik, Brooks, and Oman [2013]). 

Construction 

Activity Equipment Horsepower Range

Fuel Consumption 

Range (gal/hr)

CO2 Emissions 

Range (lb/hr)

Paver 125-225 35-50 90-136

Asphalt Paving Pneumatic Roller 100-135 6-12 45-136

Vibratory Roller 100-135 4-6 226-1130

Milling Milling Machine 400-875 2-6 113-339

Excavator 100-320 10-50 136-226

Excavation and 

Placing

Vibratory soil 

compactor 100-180 5-15 271-361

Bulldozer 250-500 6-10 90-136

1 gal = 3.8 l; 1 lb = 0.45 kg

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

General approaches to improving pavement sustainability with regard to the construction of 

asphalt pavements are summarized in table 5-7. It is recommended that a comprehensive LCA

be used to verify the precise environmental benefits or trade-offs that may result from employing 

any of these specific strategies. The following sections describe these strategies in more detail.

Placement and Laydown

Every year 500 million tons (453 million mt) of new asphalt pavement material is produced in the 

U.S. at approximately 4000 asphalt mixing plants (NAPA 2013). Because of the widespread use 

of asphalt mixtures, even small changes in asphalt pavement technology can lead to significant 

savings in fuel and energy consumption and reductions in GHG emissions. In addition, 

opportunities exist to reduce exposure to asphalt fumes and other potential hazards associated with 

asphalt mixture production and placement. Table 5-8 presents some of the best practices that can 

be implemented at the plant and paving site to reduce fumes, emissions, and odors. 

Asphalt pavement system layers must be placed in accordance with prevailing standards and 

specifications. The effective placement and compaction of bound and unbound subbase and base 

layers ensures the needed foundation for the surface layers, while the placement and compaction of 

asphalt concrete layers are elements critical to long-term performance. The proper placement and 

compaction of asphalt concrete layers prevents the development of segregation and longitudinal 

joint deterioration, ensures that the proper grade and cross slope of the pavement are met, and 

achieves the specified density and smoothness requirements. Recommended practices for asphalt 

concrete placement and compaction are summarized below. 

Segregation Control

Asphalt concrete may undergo aggregate or temperature segregation, which can occur during any 

stage of production, transportation, or placement due to improper mixing or handling. Hence, 

addressing segregation usually involves troubleshooting different stages of production and 

placement. At the asphalt plant, production must be monitored carefully to avoid segregation 

(checking aggregate stockpiles, storage silos, and loading of the hauling trucks). In the 

production stage, modifying the mixture design, correcting improper material transfer from the 

stockpiles to the bins and from the bins to mixers, and improving handling and movement of 

mixtures in the storage are some of the key items to be considered. During the paving operation, 

paver hopper and auger are the two key areas that need to be monitored to prevent segregation. 

The use of a material transfer vehicle (MTV), a transfer vehicle positioned between the truck and 

the paver, helps minimize segregation since it serves to remix the asphalt and makes the 

temperature of the asphalt more uniform. 

Proper Construction of Longitudinal Joints

Improperly constructed longitudinal joints in asphalt concrete surface layers result in an overall 

reduction of pavement service life and ride quality due to potential density variations. Joint 

failures can be due to a combination of low density, segregation, and lack of adhesion between two 

adjacent lanes. Minimum density requirements at the longitudinal joints are usually specified, 

being no more than 2 percent less than the mat density and with no density measurement being less 

than 90 percent of the theoretical maximum density, although some agencies accept densities as 

low as 88 percent (Buncher 2012). A notched wedge joint is recommended when the lift thickness 

is between 1.5 and 3 inches (38 and 76 mm). Joint adhesives (overbanding with sealants) or 

tacking the existing face of joint with emulsion or asphalt binder can also be considered. 

Recommended practices must be followed to avoid mixture segregation.

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Table 5-7. Approaches for improving sustainability of asphalt pavement construction operations.

Objectives Sustainability 

Improving Approach Economic Impact Environmental Impact Societal Impact

Increase thickness to 

nominal maximum 

aggregate size ratio

Potentially reduce costs 

since it can reduce 

number of lifts 

constructed

Reduce environmental 

impact through less 

hauling trips

Increased pavement life 

due to better compaction

Better resistance to topdown cracking 

Longer life and less 

frequent interventions

Achieve 

Target 

Density 

Requirements

Use warm-mix 

technologies 

Potentially increase costs 

due to additives and 

capital investment

Reduce environmental 

impact by lowering 

compaction temperature

Reduce construction 

related air pollution 

and potential for 

irritation for sensitive 

workers

Follow laydown 

temperature 

requirements 

No change in cost Accelerate construction 

due to achieving required 

mat thickness and density 

at a faster rate 

Less exposure to 

traffic delays

Select proper equipment 

for placement and 

compaction equipped 

with smart technology

Need capital investment 

and increased agency

costs but has long-term 

benefits to contractors 

and agencies

Reduce environmental 

impact through good 

quality materials and 

longer life pavements

Longer pavement life

Less intervention

Use thermal cameras to 

avoid erratic mat 

temperatures and 

temperature related 

segregation

May increase contract 

costs due to capital 

investment 

Reduce environmental 

impact through good 

quality materials and 

longer life pavements

No direct impact 

Prevent 

Segregation

Use of material transfer 

vehicles 

May increase contract 

costs

Reduce environmental 

impact through good 

quality materials and 

longer life pavements

Longer pavement life

Less intervention

Proper handling of 

materials during 

transportation, 

placement, compaction

No cost associated with 

this approach 

Reduce environmental 

impact through good 

quality materials and 

longer life pavements

Longer pavement life

Less intervention

Avoid segregation 

during transportation and 

placement

No cost associated with 

this approach

Reduce environmental 

impact through good 

quality materials and 

longer life pavements

Improve ride quality

Longer pavement life

Less intervention 

Construct 

Effective 

Longitudinal 

Joints

Use of adhesives or 

sealants overbanding the 

joint 

May increase contract 

costs

Reduce environmental 

impact through good 

quality materials and 

longer life pavements

Improve ride quality 

Longer pavement life

Less intervention

Proper compaction to 

achieve joint density

No cost associated with 

this approach

Reduce environmental 

impact through good 

quality materials and 

longer life pavements

Improved ride quality

Longer pavement life

Less intervention 

Achieve 

Target 

Smoothness 

Requirements

Proper placement and 

compaction techniques

No cost associated with 

this approach

Reduce environmental 

impact through reduced 

fuel consumption

Improve ride quality 

Longer pavement life

Less intervention

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

Table 5-7. Approaches for improving sustainability of asphalt pavement construction operations

(continued). 

Objectives Sustainability 

Improving Approach Economic Impact Environmental Impact Societal Impact

Use 

Innovative 

Implement multiparameter bidding 

systems (i.e., A+B+C)

May increase contract 

budgets due to 

consideration of time to 

complete projects and 

environmental damage

Reduce environmental 

impact since lowest 

bidder will win and 

accelerate construction

Less exposure to 

traffic delays

Contracting 

Alternatives

Incentivize equipment 

retrofits

No additional agency 

costs if federal grants or 

tax reduction incentives 

are in place

Reduce air pollutants and 

greenhouse gas 

Reduce impact on 

local air quality

Table 5-8. Best practices to control fumes, emissions, and odors from asphalt mixture 

plant and paving operations. 

Location Best Practices1

Plant Select plant mixing temperature by consulting asphalt supplier

Plant Read the material data safety sheet for all materials

Plant Regularly calibrate thermocouples

Plant Collect continuous data on aggregate moisture and fuel/energy usage

Plant Have stack gases tested to check limits

Plant Keep a record of fuel usage over time

Plant Do not use diesel fuel and kerosene as release agents

Paving Site Keep paving temperatures as low as possible (blue smoke indicates overheating)

consistent with achieving adequate compaction of the mat

Paving Site Check paver ventilations systems regularly

Paving Site Ensure that tail pipe and ventilation stacks exhaust above the height of the paver 

operator

Paving Site Consider increasing mat thickness prior to an increase in plant temperature

1 Compiled from APEC (2000) and NYSDOT (2003). 

Meeting In-Place Density Requirement

The two main objectives of compaction are achieving prescribed layer densities and meeting 

smoothness requirements. Most minimum density requirements are in the range of 92 to 93 

percent of the theoretical maximum density. A strong correlation between service life and inplace density of asphalt concrete layers is reported in the literature (Puangchit et al. 1983; 

Christensen 2006; Buncher 2012). For example, figure 5-4 shows the estimated impact on 

pavement life by improving the density of the asphalt concrete (expressed in terms of a reduction 

of the air voids from 8 to 5 percent) and thus reducing bottom-up fatigue cracking. An optimized 

mixture density reduces rutting and cracking potential (Harvey et al. 2004). 

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Figure 5-4. Effect of compaction on predicted bottom-up fatigue life for two-layer beam

specimens in mixture using a AR4000c binder (binder type used in several western highway 

agencies prior to Superpave) and at different air void and binder content levels (after Harvey et 

al. 2004). 

Effect of AV, AC on fatigue life

1.00E+06

1.00E+07

1.00E+08

1.00E+09

1.00E+10

1.00E+11

200 250 300 350 400 450 500

Total AC thickness(mm)

Fatigue Life 

AR4000c (8% av, 5% ac), AR4000c (8% av, 5% ac)

AR4000c(5% av, 5% ac), AR4000c (5% av, 5% ac)

AR4000c (5% av, 5% ac), AR4000c (2%av, 5% ac)

AR4000c (5% av, 5% ac), AR4000c (2% av, 5.5% ac)

Traffic Index 15

Traffic Index 17

5-23

Improved compaction requires no additional materials, and usually requires no new equipment, 

but does demand strong attention to details, effective temperature monitoring and control, and 

management of the factors controlling the compaction process. Unlike changing mixture design 

parameters (e.g., changing the binder content in an asphalt concrete material, using a softer 

binder to improve reflection cracking resistance in an asphalt concrete material, or increasing the 

cement content of an FDR material), increasing the density of a material by compaction will 

improve both the rutting and cracking resistance. Overall, the factors affecting asphalt concrete 

compaction can be categorized into five classes:

1. Mixture properties (aggregate, binder, and mixture design) – The pavement construction

stage has little to no influence on the selection of mixture properties. Selecting the

materials and design of pavements with proper materials is discussed in chapters 3 and 4.

2. Environmental conditions – Most highway agencies follow standard specifications that

address air and surface temperature requirements, seasonal limitations, and weather

requirements. In general, asphalt concrete shall not be produced and placed in rainy

weather and when ambient temperatures are less than 35 to 60 °F (2 to 16 °C) (based on

the mixture type).

3. Laydown temperatures – The temperature of the mixture is one of the main factors

affecting compaction. The lower and upper temperature limits at which compaction is

effective is approximately in a range of 185 to 350 °F (85 to 176 °C) (NCDOT 2012). At
Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

the time of placement, the temperature can be considered uniform in the mat; however, 

the mixture quickly starts cooling down and at a higher rate on the surface resulting in a 

temperature gradient through the mat. The rate of cooling is a function of the mixture

type, design, base temperature, air temperature, and layer thickness. The allowable time 

recommended for compaction as a function of these variables is summarized in table 5-9. 

Table 5-9. Typical minimum requirements for laydown temperatures as a function of base 

temperature and lift thicknesses (NCDOT 2012).

Lift thickness 1⁄2 in 3⁄4 in 1 in 1-

1

/2 in 2 in +3 in

Base 

Temperature

Mixture 

Temp (°F)

Mixture 

Temp (°F)

Mixture 

Temp (°F)

Mixture 

Temp (°F)

Mixture 

Temp (°F)

Mixture 

Temp (°F)

20-32 NA NA NA NA NA 285

32-40 NA NA NA 305 295 280

40-50 NA NA 310 300 285 275

50-60 NA 310 300 295 280 270

60-70 310 300 290 285 275 265

70-80 300 290 285 280 270 265

80-90 290 280 275 270 265 260

+90 280 275 270 265 260 255

Rolling Time 

(min) 4 6 8 12 15 15 

oC = 5/9 (oF – 32); 1 in = 25.4 mm

4. Lift thickness – Lift thicknesses are commonly selected based on the nominal maximum 

aggregate size (NMAS) in the mixture and the mixture type (leveling or surface course). 

The thickness may vary from 0.38 to 3 inches (9.5 to 76 mm) from smaller to larger 

aggregate size, respectively. The rule of thumb for the ratio of lift thickness to NMAS is 

at least 3:1 for fine-graded mixtures and 4:1 for coarse-graded mixtures (Brown et al. 

2004). Fine graded and coarse graded refer to the ratio between the coarse aggregate in a 

mixture (create voids) and the fine aggregate (fill voids) relative to the control sieve for a 

particular mixture. The lift thickness is one of the factors governing in-place density as it 

influences the cooling rate and provides space for aggregate movements. As the lift 

thickness increases, the lift can retain the heat for longer time periods thereby increasing 

the compaction time and allowing desirable density levels to be more easily achieved 

(Brown et al. 2004). The lift thickness has an impact on the environment as well, since it 

influences compaction productivity due to cooling time. 

5. Compaction equipment and procedures – Compaction is done using several types of 

compactors including vibratory, static steel, static pneumatic rubber, and oscillatory 

rollers. The compactor type and applied loading amplitude and frequency are selected 

based on the layer characteristics. In recent years, rollers are equipped with intelligent 

compaction systems to ensure the pavement material is appropriately compacted. 

Additional details on intelligent compactors are provided later in this chapter. 

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Achieving Smoothness

There are numerous benefits of achieving specified initial pavement smoothness. Some of these 

benefits are reduction in dynamic loads on pavements, enhanced rideability over a longer period 

of time, reduced fuel consumption, and reduced vehicle wear and tear in the use phase. In 

addition, studies have shown that pavements constructed smoother initially stay smoother longer, 

all other things considered equal (Smith et al. 1997). 

Most highway agencies have adopted smoothness specifications, along with incentive and 

disincentive provisions, to encourage the construction of smooth pavements. At the same time, 

recent years have seen a number of agencies move to the use of lightweight inertial profilers to 

assess initial smoothness, although a few agencies still use profilographs. During placement and 

compaction of asphalt concrete layers, pavement smoothness can be adversely affected by lack 

of uniformity in paving operations, variations in mixture temperature, variations in paver speed, 

segregation, and improper rolling. Critical items to help ensure that high levels of initial 

smoothness are achieved include (NCDOT 2012):

1. Maintain continuous operation of the paving train and minimize paver stops. 

2. Correct irregularities in lower courses by adding or removing materials.

3. Leave adequate amount of material in the paver hopper between loads to prevent rough 

texture due to end of the load segregation. 

Construction Quality Assurance

Quality assurance (QA) activities performed during pavement construction are necessary to 

ensure that the material and workmanship meet the project specifications. This includes proper 

placement and compaction of all pavement layers and ensuring that specified smoothness criteria

are met. Pavements constructed in accordance with specifications and meeting all quality 

standards are likely to achieve their design life and exhibit lower maintenance costs and 

corresponding lower use phase and maintenance-related environmental burdens. 

Effective specifications and adherence to rigorous construction inspection procedures play a 

significant role in achieving the expected quality of pavements. QA plans have been 

implemented by contractors and agencies to improve the quality of materials and processes used 

in the construction of highway projects and to reduce life-cycle costs. The QA plan often covers 

all phases of asphalt concrete construction, including production, placement, and compaction. In 

many highway agencies, asphalt concrete acceptance and payments are based on contractor’s 

fulfillment of inspection, sampling and testing, resident engineer’s inspection, and statistical 

evaluation of specified quality characteristics (Caltrans 2009). Important pavement quality 

characteristics during asphalt concrete placement may include subgrade density, ambient and 

mixture temperature, layer thicknesses, joint construction, segregation, in-place density, and 

smoothness. 

Many highway agencies are using percent within limits (PWL) statistical methods as part of their 

acceptance criteria. The PWL method is used to assess the “quality” of the constructed 

pavement by estimating the percentage of the quality characteristic population that falls within 

the specification limit; the results can be used to determine pay factors (incentives or 

disincentives) based on the anticipated effects of the quality characteristic on pavement 

performance (Hand and Epps 2006). 

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

Some of the common quality characteristics used to determine PWL (and pay factors) for asphalt 

pavements are in-place density or air voids and initial smoothness. This framework is designed 

with an assumption that there is a relationship between these quality characteristics and the longterm performance of the pavement. There is clearly a need for developing advanced methods 

and procedures for performing real-time monitoring and measurement of some of these key 

quality characteristics, and some advancements are being made in the use of ground penetrating 

radar (GPR), intelligent compaction (IC) technology, and infrared thermography (IRT) for this 

purpose. 

The quality assurance of as-constructed pavement smoothness is performed by profile testing. 

Smoothness is one of the most critical pay items in most asphalt pavement contracts, and 

pavements that do not meet specification requirements can be subjected to expensive corrective 

actions and significant price adjustments. There is a strong correlation between in-service 

pavement smoothness and fuel consumption by vehicles using the pavement, as discussed in 

chapter 6. 

Improving Sustainability through the Use of Innovative and Emerging Technologies

Traditionally, various field and laboratory tests using field-extracted cores have been used for 

asphalt pavement density measurements. However, these conventional methods have several 

shortcomings. For example, in situ field tests (such as nuclear density gauge measurements) 

provide data from only a limited number of test locations. Similarly, extracted cores provide 

data from only a few locations on the pavement, in addition to being a destructive test (Al-Qadi 

et al. 2010; Leng 2011; Leng, Al-Qadi, and Lahouar 2011; Leng et al. 2012; Shangguan, AlQadi, and Leng 2012; Shangguan et al. 2013). 

The application of nondestructive testing (NDT) methods, such as GPR and IRT, can overcome 

some of the shortcomings of the conventional QA methods. For example, figure 5-5 shows 

continuous density measurements of an asphalt pavement using the GPR technique. This method 

is rapid, provides greater coverage area, allows real-time monitoring of compaction efforts, 

provides near real-time density data, and, when calibrated for the specific aggregate used, 

provides greater accuracy than nuclear gauges (Leng 2011). 

Figure 5-5. Bulk specific gravity profile of one test lane (Leng 2011). 

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Infrared thermographic scanning carried out immediately behind the paver screed can be used to 

monitor asphalt concrete materials and pavement surface temperatures. When temperature 

differentials exist in an asphalt pavement, the degree of compaction varies due to the viscoelastic 

material response to loading. The ability to detect and address thermal segregation during 

construction reduces potential pavement irregularities and, hence, improves the rideability and 

durability of asphalt pavements (Mahoney et al. 2003). 

Another innovative construction QA method that can 

be used to optimize the compaction and desired density 

of unbound materials is intelligent compaction. The IC 

system uses a double-drum vibratory roller equipped 

with a measurement/control system. Unlike 

conventional asphalt pavement compaction equipment, 

IC rollers are equipped with technology such as a GPSbased system, color-coded display, and a temperature 

measurement system that can help monitor pavement 

construction data in real time, including the number of 

roller passes, roller speeds, and asphalt pavement 

surface temperatures, and can store these data for later 

evaluation (Horan et al. 2012). 

It is noted that the application of IC for asphalt 

materials is limited to compaction process monitoring 

at this time. Measurements are affected by the material 

temperature and the stiffness of the supporting layers. 

During the asphalt paving process, the use of spray 

pavers and MTVs can also be beneficial. A spray 

paver includes the functions of both a conventional 

paver and tack coat distributor (see figure 5-6). Thus, 

a tack coat can be placed immediately before the 

asphalt concrete layer is placed. This approach saves 

time, reduces the use of a distributer vehicle, and 

prevents contamination from the passage of paver 

treads over the tack coat thereby enhancing bond 

potential. And, as previously described, the use of an 

MTV is also expected to improve pavement 

sustainability by reducing potential segregation and 

temperature variation and maintain material 

consistency and uniformity.

Intelligent Compaction 

Since 2008, the FHWA has been 

leading a national effort to advance 

the implementation of intelligent 

compaction (IC) technology to improve 

compaction of materials that include 

granular and cohesive soils, stabilized 

bases, and asphalt pavements. One 

of the emphasis areas in its Every Day 

Counts (EDC) initiative, the FHWA 

defines IC as a process that includes 

vibratory rollers equipped with a 

measurement and control system that 

can automatically control compaction 

parameters in response to materials 

stiffness measured during the 

compaction process. The roller must 

be equipped with GPS measurements 

and a documentation system that 

allows for continuous measurements 

of the roller location and the 

corresponding stiffness-related output. 

Through this process, improvements 

in the quality and uniformity of 

constructed pavements are achieved, 

resulting in better performing, longer

lasting pavements. Moreover, IC 

efficiencies also produce significant 

time, cost, and fuel savings. 

Additional information on IC is found at 

http://www.intelligentcompaction.com/. 

5-27
Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

Figure 5-6. Spray paver on the left and material transfer device on the right used in the overlay 

construction in Illinois (Al-Qadi et al. 2012). 

5-28

Strategies for Improving the Sustainability of Concrete Pavement Construction 

Practices

Concrete pavement construction generally consists of the following activities: 

• Preparation of the subgrade (including any required excavation, hauling, borrow,

leveling, and compaction of multiple lifts of material).

• Hauling, placement, trimming, and compaction of subbase and base layers, which may

also include curing.

• Proportioning and mixing of the concrete materials (see chapter 3).

• Hauling and placing of the concrete materials.

• Finishing, texturing, and curing of the concrete pavement.

This general process is depicted in figure 5-7. Throughout every stage of this construction 

process, there are numerous opportunities for improving the environmental, economic, and 

societal impacts (i.e., the sustainability of the process).

Long service life is one of the primary drivers of pavement sustainability. The ability to achieve 

that long service life is strongly impacted by the quality of construction. In fact, the potential 

gains in sustainability afforded by the optimization of structural design, the use of highly durable 

or recycled materials, and the improved efficiencies in the production of cement and other 

materials can be completely negated by poor construction quality and improper construction 

techniques. The following subsections describe the various impacts of construction quality on 

pavement service life and sustainability and provide strategies and techniques for improving the 

same.

Previous portions of this chapter describe many of the strategies that can be considered for 

pavement construction processes in general, and those are not repeated here. Furthermore, 

chapter 3 describes techniques for improving the sustainability of the production of concrete 

materials, including the production of cement and the operation of concrete batch plants, and 

those topics are generally not repeated here other than to discuss how they impact the 

sustainability of concrete pavement construction operations. 
Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Figure 5-7. Generalized concrete pavement construction processes and associated fuel factors

(fuel factor source: Skolnik, Brooks, and Oman 2013).

5-29

General approaches to improving the sustainability of concrete pavement construction 

operations, along with a qualitative assessment of the interactions and trade-offs between their 

economic, environmental and societal impacts, are summarized in table 5-10. A comprehensive 

LCA must be considered to provide quantitative estimates of the benefits and impacts that result 

from any proposed sustainability-improving action. 

Site Prep Work

Preparation of Support Layers

The accurate grading and uniform compaction of foundation layers are essential for ensuring the 

economy and long-term performance of all pavement types. These are accomplished by 1) 

providing a solid and accurate paving platform that allows the construction of the pavement 

surface (usually the highest quality and most expensive material in the structure) to the proper 

grade and cross slope without using unnecessary material; and 2) providing uniform as-designed 

support to ensure long-term ride quality and resistance to distress. The latter item is particularly 

true and important for concrete pavements because the rigidity of the pavement surface resists 

deformation due to movement in the underlying layers. Studies have also shown that, all things 

being equal, improvements in initial ride quality translate directly into longer pavement service 

life (when structural or material durability problems are not present) (Smith et al. 1997). Care 

must also be taken that any required interlayer materials are properly installed to ensure isolation 

of the surface (i.e., over cement-treated or lean-concrete base layers, where required). 
Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

Table 5-10. General approaches for improving the sustainability of concrete pavement 

construction. 

Objectives Sustainability Improving 

Approach Economic Impact Environmental Impact Societal Impact

Protect Water 

Resources 

Concrete wash water 

collection and reuse

Increased cost for collection 

and removal, but reduced costs 

of remediation and clearing 

drains.

Positive impact by eliminating 

localized vegetation kills and 

pH impact on local surface 

waters.

Negligible to slightly 

positive impact.

On-Site Recycling Reduced haul costs, reduced 

material costs.

Reduced fuel consumption, 

reduced GHGs, reduced 

consumption of resources.

Negligible to slightly 

positive impact.

Reduce Use of 

Virgin 

Materials Two-Lift Paving Negligible to slightly higher 

construction costs.

More energy consumed in 

construction, improved use of 

local and recycled materials, 

potential reductions in usephase fuel consumption and 

GHGs.

Negligible to slightly 

positive impact.

Improve 

Initial Ride 

Quality 

(Minimize 

Use- Phase 

Two-Lift Paving Negligible to slightly higher 

construction costs.

More energy consumed in 

construction, improved use of 

local and recycled materials, 

potential reductions in usephase fuel consumption and 

GHGs.

Positive impact of 

improved ride quality, 

reduced use-phase costs for 

vehicles. 

Fuel 

Consumption 

and 

Emissions)

Real-Time Profile 

Measurement Capital cost of equipment.

Potential reductions in usephase fuel consumption and 

GHGs.

Positive impact of 

improved ride quality, 

reduced use-phase costs for

vehicles.

Increase 

Pavement 

Service Life

Improved Construction QA

(including Dowel 

Alignment Measures)

Good Curing Materials and 

Practices

Additional testing costs.

Negligible to modest increase 

in construction costs.

Potential for longer life cycle. 

Potential for extended time 

between maintenance 

activities, longer life cycle, 

and lower user costs.

Balance 

Surface 

Friction and 

TirePavement 

Noise

Selection and Design of 

Surface Texture

Negligible to modest increase 

in construction costs 

(depending upon surface 

texture selected).

Potential to reduce tirepavement noise inside and 

outside of vehicles.

Potential for improvements 

in friction, safety.

On-Site Recycling 

(Foundation Layers)

Reduced haul costs, reduced 

material costs.

Reduced fuel consumption, 

reduced GHGs, reduced 

consumption of resources.

Negligible to slightly 

positive impact.

Match Construction 

Equipment and Production 

Capacities

Cost savings

Reduced fuel consumption 

and GHGs, less wasted 

material.

Minor impact.

Minimize

Construction 

Fuel Use and 

Emissions

Single-Lift Construction Cost savings over multi-lift 

construction processes 

Lower fuel consumption and 

GHG emissions.

Negligible to favorable 

impact, depending upon 

time savings.

Use Roller-Compacted 

Concrete 

Significant construction cost 

savings (mainly due to 

materials)

Lower fuel consumption and 

GHG emissions in 

construction 

Minimal impact for lowspeed pavements; generally 

inadequate ride quality 

(without overlay or 

diamond grinding) for highspeed roadways

Use Early Entry Saws Reduced cost

Reduced construction fuel 

consumption and GHG 

emissions.

Negligible. 

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Installation of Dowels, Tie Bars and Slab Reinforcement

Dowels, tie bars, and slab reinforcement are essential structural elements of concrete pavement 

systems. As with any structure, these elements can only perform their intended functions 

properly if they are installed at the correct locations, at the proper elevations, and in the correct 

alignment or orientation. For example, reinforcing steel that is placed too close to the pavement 

surface may cause surface distresses that require costly and disruptive repair activities. Dowels, 

an essential element for the performance of heavy-duty concrete pavements, may be misaligned 

or mislocated in one or more of five different ways (three translational modes, two rotational 

modes), each of which has a different potential impact on pavement performance. Mislocated tie 

bars may cause surface spalls, may fail to hold joints tightly together and in alignment, or may 

improperly interfere with the function of other joints. 

Ensuring the proper location and alignment of dowels, tiebars, and slab reinforcing can require 

maintenance and calibration of insertion equipment, proper location of baskets and support 

systems, proper anchoring of basket and support systems (to prevent shifting and overturning 

during paving), and adequate joint marking and sawing practices (to ensure that joints are sawed 

over properly located dowels and tie bars). The specification and use of corrosion resistant (or 

corrosion proof) dowels, tiebars, and reinforcing is a design issue, but is worth mentioning again as 

an important component in the context of the construction of long-life, durable concrete pavement 

systems.

After the concrete has been placed, the measurement of in situ dowel alignment can be 

performed nondestructively using one of several relatively new devices. The MIT-SCAN2-BT, 

which uses magnetic tomography to determine dowel alignment, was first introduced to the 

market in 2001, and is probably the most widely adopted dowel alignment measurement device 

in the U.S. Additional information on this device can be found at the websites of the 

manufacturer1

1 http://www.mit-dresden.de/en/produkte/duebelmessgeraet/kurzbeschreibung1.html

 and the FHWA.

2

http://www.fhwa.dot.gov/pavement/concrete/mitreport/mits03.cfm

 GPR-based devices for measuring dowel alignment include the 

GSSI StructureScanTM Mini HR3

http://www.geophysical.com/

 and the Hilti PS 1000.4

http://www.hilti.com/holcom/page/module/product/prca_rangedetail.jsf?&nodeId=-450121&selProdOid=1107542

 An additional device, the MIRA 

Tomographer, uses ultrasonic tomography to measure dowel alignment. More information on 

this device can be found at the manufacturer’s website.

5

http://www.germann.org/Brochures/Catalog-NDT-2010.pdf

 Overall guidance concerning dowel 

alignment tolerances is available in several recent publications (Snyder 2011; ACPA 2013). 

Proportioning Concrete Mixtures – Impacts on Sustainable Construction Practices

Strategies for developing and producing durable, economical, and sustainable concrete mixtures 

are covered in chapter 3. However, one key point worth repeating is concrete mixture 

proportioning, largely because of its impact on concrete pavement constructability and paving 

operations, as well as its effect on pavement longevity. 

Mixture proportions must be developed to achieve the proper balance of economy, strength, 

durability, and workability (defined as the property of fresh concrete that determines the ease 

with which it can be mixed, transported, placed, consolidated, and finished to a homogenous 

condition). Improvements in any two or three of these criteria are generally achieved at the 

expense of the others. For example, reductions in the water-cementitious materials ratio 

 

2

3

4

5

5-31

 
Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

generally increase both strength and durability, but may adversely affect concrete workability 

and finishing characteristics if other mixture adjustments are not made as well (e.g., changes in 

aggregate gradation or the use of chemical or mineral admixtures). A mixture with poor 

workability and finishing characteristics may require additional energy for mixing, placing, 

strike off, vibration, screeding, and finishing. Furthermore, paving production rates may be 

lower and construction-related energy and labor costs may also increase. 

Concrete Hauling and Placement

The best concrete hauling, placement, and finishing operations cannot add to the quality and 

longevity of a concrete pavement; they can only serve to achieve the potential intended by the 

design and materials engineers. Substandard operations can, however, negatively affect concrete 

pavement and material properties, thereby adversely affecting long-term pavement performance 

and sustainability. 

One way in which the sustainability of the pavement construction process can be improved is by 

maximizing the efficiency of the overall operation. This requires that the most efficient 

equipment be selected for the critical operation (typically, the paving operation) and that the 

production capacities of other operations be matched to that efficiency. For example, the type 

and size of equipment to be used for hauling operations must be selected with consideration of 

the project haul routes and maneuverability requirements, and the number of units must be 

chosen to allow continuous operation of the paver at its most efficient speed. Table 5-11 

presents typical ranges of fuel consumption and emissions for concrete mixing, paving, and 

texturing activities and illustrates the potential impact of “right-sizing” equipment to minimize 

fuel consumption and emissions. It should be noted that the ranges presented also reflect 

potential variations in operational efficiencies, which are affected by the stiffness, workability, 

and finishing characteristics of the paving mixtures. 

Table 5-11. Energy efficiency and CO2 emissions for typical equipment used for 

concrete pavement construction (compiled from Santero and Horvath 2009a and Skolnik, 

Brooks, and Oman 2013).

Construction 

Activity Equipment Horsepower Range 

Fuel 

Consumption 

Range (gal/hr)

CO2 Emissions 

Range (lb/hr)

Concrete mixing

in truck Mixing truck -- 6-10 136-226 

Slipform paver 100-250 5-13 113-294

Concrete Paving Texture/curing

machine 70 5 113 

Concrete saw 10-40 0.5-1 11-23

Competing sustainability measures involving economics (initial and life-cycle costs) and 

environmental impacts (fuel consumption and emissions) must be weighed and balanced in 

considering the construction of single-lift pavement surfaces versus multi-lift pavement 

structures (including two-lift concrete paving [discussed at the end of this chapter], typical 

asphalt pavement construction, composite pavement construction, and even “staged 

construction”). Single-lift construction offers clear benefits in terms of reducing the number of 

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

paving passes (and rolling and compacting passes for asphalt and RCC pavements), and may 

even result in the operation of fewer pieces of construction equipment for a given project (e.g., 

two paving machines and two batch plants are often employed for two-lift concrete paving 

versus one of each for single-lift paving). In addition, the placement of a single lift of paving 

may expedite project completion. However, the construction of multi-layer pavement structures, 

whether concrete or asphalt, generally results in better initial pavement smoothness, which can 

extend pavement maintenance cycle times and service life. Multi-layer paving also facilitates the 

use of different types of materials in the various paving layers (e.g., in two-lift concrete 

pavement, recycled concrete aggregate in the lower lift and hard, angular rock in the top lift). 

Skolnik, Brooks, and Oman (2013) recently compiled updated typical fuel usage factors for 

many aspects of pavement construction; these values can be used to compare the relative fuel 

consumptions associated with single-lift versus multi-lift construction activities. This 

information can then be weighed against the other benefits and costs of each construction 

technique while keeping in mind the overall sustainability goals and objectives of the agency. 

There are many aspects of concrete pavement construction for which QA is essential in order to 

achieve the full potential longevity (and, therefore, sustainability) of concrete pavements. These 

include (but are not limited to): stringline setup and maintenance, plant certification, proper 

equipment setup and hauling (including haul time restrictions in normal and hot weather), proper 

placement of the concrete (to minimize segregation and maintain a constant load ahead of the 

paver), control of water use at the job site, proper materials quality assurance (e.g., monitoring 

mixture consistency through air, slump and unit weight testing, as well as thickness control and 

strength or maturity testing), proper concrete consolidation of concrete without overvibration 

(through the use of vibratory frequency monitors and their adjustment with variations in the 

concrete mixture), and proper selection and use of curing materials, among others. Best 

practices for all of these aspects of concrete paving are described in detail in several key 

references (ACPA 2008; ACPA 2010). 

All hauling, paving, and finishing equipment must be maintained in a way that prevents the 

buildup of hardened concrete. This is particularly true for haul trucks, where old concrete 

material can become a “contaminant” and cause finishing or performance problems in future 

loads. 

Haul trucks and other equipment must be washed out frequently, but concrete wash water is toxic 

to fish and aquatic life and can contaminate drinking water supplies. In addition, washout 

sediment can clog pavement drain systems. Therefore, concrete wash water must be prevented 

from entering waterways, drainage systems, and groundwater. Best management practices 

include the return of all concrete waste and wash water with each concrete truck for disposal at 

the concrete batch plant. If this is not possible, an on-site, concrete washout area should be 

established to collect washout water.

There are several options for on-site, concrete washout water collection, including prefabricated 

containers (for which some supply companies offer maintenance and disposal services) and selfinstalled, above-ground or below-ground containers (which may be less reliable and more prone 

to leaks than the prefabricated containers) (Ecology 2012). Any on-site containers should be 

placed 50 ft (15.3 m) or more from drains, ditches, and surface waters, and must be properly 

sized. Ecology (2012) provides good guidance on the design of on-site, washout watercollection facilities.

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

Technologies for using increasing amounts of 

“grey water” (from washing concrete 

production equipment and trucks) are rapidly 

becoming more common and accepted. 

Chapter 3 presents a schematic illustration for 

recycling concrete wash water into batch plant 

mixture water and also summarizes typical 

limits on chlorides, solids, and other 

potentially harmful contaminants in recycled 

water. 

Finishing, Texturing, Jointing, and Curing

Finishing, texturing, jointing, and curing have 

the potential to impact pavement service life 

(which affects maintenance activities and lifecycle costs) and initial smoothness (which 

impacts fuel efficiency and vehicle wear and 

tear in the use phase). The following 

subsections briefly describe sustainable 

practices these aspects of concrete pavement 

construction. 

Finishing

If good mixture proportioning, hauling, and 

placement practices are followed and if the 

paving equipment is properly set up and well 

maintained, very little hand finishing is

needed. Hand finishing should be used 

sparingly and only as necessary to correct 

significant pavement surface flaws and profile 

defects. Overfinishing and the use of water 

added to the surface as a finishing aid must be 

avoided because loss of surface durability may 

result. ACPA (2010) provides additional 

details concerning best practices for concrete 

pavement finishing. 

Texturing 

Concrete pavement surface texture must be 

constructed to provide both adequate surface 

friction (sustainability through safety and 

reduced crash rates, particularly in wet 

weather) while also minimizing the generation 

of noise through tire-pavement interaction. 

There are many concrete pavement surface 

texture options, including transversely oriented 

textures (e.g., transverse tining, brooming and 

grooving), longitudinal textures (e.g., longitudinal tining, brooming, grooving, turf drag and 

5-34
Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

diamond grinding), and textures with no 

particular orientation (e.g., porous concrete, and 

exposed aggregate finishes). Details 

concerning the tire-pavement noise and friction 

characteristics of each of these surface types 

throughout the use phase of the pavement life 

cycle are presented in chapter 6. 

The success of some of these types of texture 

require specific mixture design characteristics 

(e.g., the inclusion of siliceous fine aggregate 

for microtexture, specifically graded and 

shaped coarse aggregate particles for exposed 

aggregate finishes, and low water-cementitious 

ratios for durable turf drag finishes) and 

construction techniques to achieve proper 

texture depth and pattern spacing. 

Jointing Considerations

All concrete pavement contraction joints must 

be sawed in a timely manner to prevent the 

development of uncontrolled cracking. 

Successful joint cutting requires that the 

contractor accurately determines the window of 

sawing opportunity: too early and the concrete 

will ravel and be damaged by the sawing 

operation, too late and the pavement may crack 

randomly and not at the planned joint locations. 

Contractor experience can play a major role in 

the timing of joint saw cuts, but tools such as 

the HIPERPAV program (which considers 

factors such as mixture components, 

proportions, and temperature in the context of 

ambient environmental conditions) can also be 

used to determine appropriate sawing times. 

HIPERPAV can be downloaded free of charge 

at http://www.hiperpav.com/. 

Early entry saws, which can be used to make a 

shallower joint sawcut at an earlier age, 

typically require less operational energy and 

can be used to improve the sustainability of the 

joint sawing operation (although extra care 

must be taken to avoid damaging the young concrete with the early sawing operation). 

It is very important that the joint locations be accurately established prior to sawing and that the 

saw operators take care to cut the joints precisely. Failure to do so may result in an effective 

longitudinal translation of any dowel load transfer devices, even if the basket placements or 

insertion processes were accurate. Significant longitudinal translations can result in poor joint 

5-35
Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

behavior and premature failures. ACPA (2010) provides 

guidance on joint sawing operations and ACPA (2013) 

provides guidance on limitations for dowel longitudinal 

translation (and, therefore, accuracy of joint saw cutting). 

Curing

Good curing practices are essential to the control of 

early-age pavement temperatures and the prevention of 

moisture loss, which can result in decreased concrete 

strength, shrinkage cracking, slab warp and curl (and 

their associated stresses), loss of concrete durability, and 

other problems that can reduce concrete pavement 

performance life and, therefore, sustainability. The use 

of effective curing materials (applied at the proper time 

and (for liquid curing compounds) at the proper rates of 

application is essential. Research suggests that there is a 

wide range of effectiveness in moisture retention among 

commonly accepted curing techniques (Whiting and 

Snyder 2003; Vandenbossche 1999). 

Improving Sustainability through the Use of 

Innovative and Emerging Technologies

Two-Lift Concrete Paving

Two-lift concrete paving involves the placement of the 

concrete in two layers (wet-on-wet) rather than the 

single-lift paving that is typically used. Two-lift paving 

can provide improved ride characteristics, facilitate the 

effective use of local, recycled, or marginal quality 

aggregates (in the lower layer), increase the use of SCMs 

(in the lower lift), and reduce overall material costs 

without sacrificing pavement quality and service life 

(Fick 2010). Environmental impacts are expected to be 

less because of the use of SCMs and RCWMs, and 

construction costs may also be reduced, although this 

will be project specific.

Two-lift concrete pavements have been constructed in 

the United States since 1891, when the first U.S. concrete 

pavement was constructed in Bellefontaine, Ohio as a 

“two-course” pavement. Two-lift construction was 

widely used to facilitate the placement of mesh 

reinforcing in jointed reinforced concrete pavement 

(JRCP) designs that were widely used in the 1960s and 1970s, but fell from common practice 

when short-panel, unreinforced slab construction became the norm. Only a handful of two-lift 

concrete pavements were constructed in the U.S. in the 1980s and 1990s, but two-lift paving 

technology was identified as a high-priority implementation technology as a result of the May 

2006 FHWA SCAN tour of European concrete pavements. The strong potential for improved 

sustainability in this type of construction has been demonstrated in several countries, including 

Two-Lift Paving

Kansas Demonstration:

In October 2008, the Kansas DOT 

(KDOT) constructed a two-lift paving 

demonstration project on I-70 in 

Saline County, Kansas. Dense, 

wear-resistant rhyolite aggregate 

was imported for the top lift, while a 

more porous local limestone was 

used for the lower course. A Class 

F fly ash-gypsum combination was 

substituted for 20 percent of the 

cement in the top lift to reduce 

permeability and assist in mitigating 

any possible ASR. In addition, 

cement-treated recycled concrete 

aggregate from the original 

pavement was used as a base layer. 

Several different surface textures 

were used in various sections to 

evaluate their effects on tirepavement noise.

Missouri Demonstration:

In September 2010, a portion of 

Route 141 in St. Louis County was 

reconstructed with an innovative 

section of two-lift concrete paving 

that was highlighted by the use of 

photocatalytic cement in the top lift, 

along with pervious concrete 

pavement in the shoulders. 

Open Houses were held for both of 

these demonstration projects, and 

the presentations and other reports 

and handout materials from the 

open houses are available through

the National Concrete Pavement 

Technology Center at: 

http://www.cptechcenter.org/researc

h/research-initiatives/two-lift/

http://www.cptechcenter.org/events/

archive/2lift-StL-page.cfm

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

Austria, where 100 percent of the old concrete pavement is recycled into a bound subbase and 

the lower lift of a two-lift concrete pavement (Hall et al. 2007). 

Between 2008 and 2010, two major two-lift PCCP demonstration projects were constructed in 

the U.S. (in Kansas and Missouri – see sidebar for additional information) in order to 

demonstrate the technology and assess the potential economic and environmental benefits of 

two-lift concrete paving. Moving from demonstration to routine practice, the Illinois Tollway 

made two-lift concrete paving (using reclaimed asphalt pavement and crushed concrete in the 

lower lift) a major component of the 2012-2016 reconstruction and widening program of more 

than 180 lane miles of Interstate 90 between Elgin and Rockford. 

Roller Compacted Concrete (RCC) Paving 

RCC is a no-slump concrete mixture that is initially compacted using the paver screeds and 

tamping bars of a traditional asphalt paving machine or high-density paver, followed by the use 

of heavy vibratory and rubber-tired rollers—much like conventional hot-mixed asphalt concrete. 

RCC consists of the same basic ingredients as conventional concrete, but has different mixture

proportions, and has similar strength properties. The most significant difference between RCC 

mixtures and conventional concrete pavement mixtures is that RCC has a higher percentage of 

fine aggregates, a lower cement content, and a very low water-cementitious material ratio (hence 

the very low slump). Load transfer dowels are not used with stiff, dense RCC mixtures, and 

transverse joints are either not sawed or are sawed at greater-than-usual spacing (due to the 

reduced shrinkage potential of the mixtures) mainly for aesthetics. Load transfer across 

transverse cracks and joints is provided mainly by aggregate interlock. 

The initial compaction of the RCC allows for almost immediate use of the pavement by light 

vehicles (support is provided through particle-to-particle contact), with cement hydration 

providing excellent, long-term strength and durability (without the use of air-entraining 

admixtures). The resulting ride quality is generally adequate for lower-speed traffic, but 

diamond grinding and overlays are often used to provide an improved surface profile for higher 

speed traffic.

RCC offers the superior load-carrying capacity and longevity of concrete pavements while 

having reduced material costs (due to lower cement contents and fewer admixture requirements), 

reduced construction costs (due to the use of lower-cost paving equipment and often no sawing 

of contraction joints), and lower local impact to traffic because of the ability to allow limited 

traffic access within just a few hours of placement.

A comprehensive review of the design and construction of roller-compacted concrete pavements 

is available from the Portland Cement Association (Harrington et al. 2010). 

Real-Time Smoothness Measurements

The measurement of concrete pavement profiles (useful in computing indicators of pavement 

ride quality and smoothness, like IRI and various forms of the Profile Index [PI]) has historically 

(and necessarily) been performed after the pavement has hardened and can be subjected to foot 

or light vehicle traffic. Two major disadvantages of this approach to profile measurement are: 1) 

pavement texturing and joint forming operations can affect profile measurements (usually 

adversely), and 2) corrective measures (to address existing profile problems and to prevent 

problems with further paving) are limited.

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Chapter 5. Construction Considerations Towards Sustainable Pavement Systems

Non-contact surface profilers are now available to provide real-time measures of pavement 

profile directly behind the paving machine, thereby eliminating the effects of measuring texture 

and pavement joints while allowing for construction process corrections that will prevent 

continuing and recurring profile problems (Rasmussen et al. 2013). The data collected can still 

be used to produce IRI or PI values, and are also useful in establishing baseline profiles for 

pavement curing or curling/warping studies. Some real-time profile measurement devices can 

also be used for prepaving checks of stringline setup and subgrade/subbase profile (to maximize 

paving yields). 

Real-time profile measurement of concrete pavements offers potential sustainability advantages 

in improving initial pavement smoothness, which should produce corresponding increases in 

vehicle mileage in the use phase and may also result in deferment of ride-related maintenance 

and rehabilitation actions, as well as extended overall pavement service life.

Available real-time profiling equipment comes in different options for mounting directly on the 

paver, on a work bridge, or on a separate piece of specially designed and dedicated profile 

measurement equipment. More information on two of the available systems can be found at

http://www.gomaco.com/Resources/gsi.html (for the Gomaco Smoothness Indicator [GSI] 

system) and at http://www.amesengineering.com/RealTimeProfiler.html (for the Ames 

Engineering SmoothPave RTP [Real-Time Profiler]).

Concluding Remarks

Pavement construction activities offer many opportunities to adopt practices that improve the 

sustainability of the pavement system. Obvious and highly visible example practices include the 

use of on-site recycling to produce pavement foundation layers and the protection of 

groundwater and local fauna by collecting and removing (for recycling) concrete waste water. 

Less obvious are the impacts that good construction practices can have on fuel consumption and 

user vehicle expenses and agency repair costs during the use phase.

The potential impacts of the construction phase (i.e., construction equipment and activities) on 

overall life cycle assessment for a given roadway may be relatively small, particularly when 

compared to the impact of the materials phase and the use phase (Santero and Horvath 2009b). 

For example, Zapata and Gambatese (2005) indicate that the “placement phase” consumes only 

about 3 percent of the total energy in the pavement life cycle. However, the construction phase 

is a phase over which engineers and contractors have a great deal of influence. Therefore, it is 

important to be cognizant of the many ways that construction phase activities can influence 

overall pavement sustainability. This chapter provides a good perspective of the many 

opportunities for improving (or maintaining) pavement sustainability during the construction 

phase of the overall pavement life cycle.

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Towards Sustainable Pavement Systems Chapter 5. Construction Considerations

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

CHAPTER 6. USE-PHASE CONSIDERATIONS

Introduction

This chapter reviews environmental and social impacts of pavements in the use phase, which 

includes the influence of the pavement on vehicle operations and the interaction between the 

pavement, the environment, and humans. This chapter identifies use-phase impacts and 

considerations, provides current information regarding their effects, and describes current efforts 

to better quantify them in order to improve pavement sustainability. Figure 6-1 indicates various 

pavement characteristics and their potential impacts on the use phase.

Figure 6-1. Pavement characteristics and influences on use-phase objectives. 

6-1 

As shown in figure 6-1, pavement roughness (or smoothness), structural responsiveness (related 

to stiffness, damping, and deflection under traffic), and macrotexture have all been identified as 

affecting vehicle fuel consumption, and as a result can have significant economic and ecological 

implications on vehicle operating costs and emissions. In addition, those same factors may 

contribute to freight damage while impacting the safety and comfort of road users. Moreover, 

pavement surface texture, permeability, and other pavement surface characteristics can impact 

the noise generated by the tire-pavement interaction, which can affect humans both in vehicles 

and within the acoustical range of the vehicles operating on the pavement; they also have 

important safety considerations with regards to surface friction, hydroplaning, and wet-weather 

crashes. 
Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

The permeability of the pavement system can influence stormwater runoff and surface friction, 

and potentially the costs associated with stormwater treatment. Pavements that are partially or 

fully permeable can flatten flow-duration curves to reduce the peak flow rate and can also affect 

pollution flow into receiving water bodies and their water temperatures.1

 

1Permeable pavements can refer to pavements constructed with permeable pavers, porous asphalt, or pervious 

concrete, but the terms “permeable,” “pervious,” and “porous” are used interchangeably in this chapter. 

The albedo (reflectivity), heat capacity, and 

thermal conductivity of the pavement all affect 

the absorption of energy from the sun and the 

emission of reflected and thermal energy from 

the pavement, which can potentially affect 

energy consumption of building cooling and 

lighting systems, vehicle cooling systems, air 

quality, and human health (depending on a 

number of factors). The global balance of 

energy (radiative forcing) is also influenced by 

surface albedo. For some applications, the 

luminance of the pavement may also have an 

effect on the energy needed for roadway 

lighting for nighttime safety, visibility of 

objects, and the ability for drivers to see 

pavement markings and obstacles. Some of the 

decisions regarding use-phase effects that can 

affect sustainability are made at the network 

level and can be implemented through effective pavement management systems (PMS), while 

others can only be implemented at the project level through design and construction decisions. 

There are trade-offs that may be considered within many of these decisions, including important 

safety issues. As is discussed in this chapter, many of these trade-offs are sensitive to project 

context, particularly traffic levels and climate. Project context also often has a large influence on 

the relative importance of environmental impacts of different phases of the pavement life cycle; 

for example, use-phase impacts on routes with heavy traffic are often much greater than material 

production and construction phase impacts, while the opposite may be true for low-traffic routes. 

Only those use-phase effects that can be changed by pavement decisions are considered in this 

chapter, and it must be recognized that many of these effects are not currently well quantified. 

Other impacts that occur from the use of the pavement but are outside the control of pavement 

engineers, managers, and decision makers—such as the addition of new lanes to existing roads, 

the selection of new road locations and alignments, and the impacts of vehicle operation that are 

not influenced by pavement decisions—are also not considered in this chapter. In addition, 

safety is a critical concern and is addressed in this chapter where decisions regarding pavementrelated environmental impacts also have safety implications. However, this chapter is not 

intended to be comprehensive in its treatment of safety issues, and the reader is referred to a 

series of highway safety reports available from NCHRP for additional information.

2

2 NCHRP Report 500, Guidance for Implementation of the AASHTO Strategic Highway Safety Plan. 

(http://www.trb.org/main/blurbs/152868.aspx) 

Major Issues: 

 Trade-offs between negative effects of 

material production and construction 

activities during maintenance and 

rehabilitation versus use-phase benefits.

 Consideration of smoothness over the 

entire life cycle and achieving highest 

level of smoothness possible during initial 

construction and subsequent 

maintenance and rehabilitation activities.

 Consideration of pavement structural 

responsiveness to loading

 Preserving smoothness in locations with 

utilities (avoiding utility cuts when 

possible)

6-2 

 
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Vehicle Fuel Consumption and Pavement Characteristics

Background

Vehicle fuel consumption and associated emissions from combustion are influenced by a large 

number of factors including vehicle and cargo mass, engine size and type, fuel type, tire type and 

inflation, driving behavior, vehicle maintenance, grades and curves, traffic congestion, traffic 

control, wind, and several other factors, as well as the number of miles traveled. In fact, many of 

these have a greater influence on fuel economy than pavement characteristics. However, 

pavements can influence the fuel efficiency of vehicles—and therefore the associated GHG and 

air pollution emissions as well—through three mechanisms that together are called pavementrelated rolling resistance. A discussion of the basic concepts of rolling resistance considering 

the total system of the vehicle components, pavement and road geometry, and measurement 

techniques is included in a report edited by Sandberg (2011). Another report (Jackson et al. 

2011) also includes a summary of the principles of rolling resistance and its measurement. The 

pavement influences on these rolling resistance mechanisms are summarized as follows: 

1. Roughness—consumption of vehicle energy through the working of shock absorbers and 

drive train components, and deformation of tire sidewalls as the wheels pass over 

deviations from a flat surface in the wheelpath with wavelengths greater than 1.6 ft (0.5 

m) and less than 164 ft (50 m). The working of these vehicle components converts 

mechanical energy into heat that is then dissipated into the air, requiring greater work by 

the engine than would be necessary to propel it along a flat surface. Roughness is both 

built into the pavement during construction and materializes over time as the pavement 

ages and distresses develop, and is further influenced by subsequent maintenance and 

rehabilitation treatment applications and timing. Roughness on some pavement types can 

undergo relatively small changes with daily temperature fluctuations. For a given 

roughness condition, this rolling resistance mechanism affects all vehicles all the time. 

2. Macrotexture—consumption of vehicle energy through the viscoelastic working of the 

deformable tire tread rubber in the tire-pavement contact patch as it passes over positive 

surface macrotexture and converts it into heat dissipated into the rest of the tire and into 

the air. Positive macrotexture is produced by stones or other texture protruding above the 

average plane of the pavement surface with wavelengths of 0.2 to 2 inches (5 to 51 mm). 

It is the primary pavement characteristic controlling surface friction at high speeds under 

wet conditions and the associated potential for hydroplaning (Anderson et al. 1998; 

Panagouli and Kokkalis 1998; Flintsch et al. 2002). Pavements serving high-speed 

vehicles must have a minimum amount of surface macrotexture and/or sufficient 

permeability to remove water films from the pavement surface so that frictional 

resistance is maintained for steering and braking. Macrotexture is provided by the 

characteristics of the surfacing materials (primarily relevant to asphalt surfaces) and 

texturing (primarily relevant to concrete surfaces), as well as subsequent maintenance and

rehabilitation timing and treatment type. Macrotexture does not change due to daily or 

seasonal temperature and moisture conditions, although it can increase or decrease with 

age depending on the pavement surface materials, texture type, traffic, climate and use of 

chains or studded tires. For a given macrotexture, this rolling resistance mechanism 

affects all vehicles all the time.

3. Structural Responsiveness—consumption of vehicle energy in the pavement itself 

through deformation of pavement materials under passing vehicles, including delayed

deformation of viscoelastic materials and other damping effects that consume energy in 

6-3 
Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

the pavement and subgrade. This mechanism has also been characterized in terms of the 

delayed deformation of the pavement under the wheel such that the moving wheel is 

continually on a slope (Flugge 1975; Chupin, Piau, and Chabot 2013). Pavement 

structural responsiveness to loading is determined by layer thicknesses, stiffnesses and 

material types that determine viscoelastic and elastic pavement response under different 

conditions of wheel loading and vehicle speed, and temperature and moisture conditions. 

For a given pavement structure, the effect of this mechanism on viscoelastic materials 

such as asphalt can be highly dependent on daily and seasonal changes in pavement 

temperatures (particularly near the surface), and is more sensitive to vehicle speeds and 

loading than are roughness and macrotexture. Structural responsiveness can change with 

time. 

As noted above, roughness, macrotexture, and structural responsiveness can change over the life 

of the pavement surface. In addition, roughness and structural responsiveness can change under 

daily and seasonal temperature and moisture conditions depending on pavement type and other 

conditions. The effects of these mechanisms over the life cycle are controlled by decisions 

regarding design, construction, and maintenance and rehabilitation applications. 

High levels of roughness can be built into the pavement during construction because of poor 

practices and lack of specifications controlling constructed roughness. Roughness typically 

increases after construction due to the development of pavement distresses, such as rutting and 

cracking on asphalt surfaces and faulting and cracking on concrete surfaces. Smoothness can be 

improved with some maintenance and rehabilitation treatments and through greater attention to 

achieving smoothness during construction. 

Initial macrotexture depends on the surface texture created during construction of the new 

pavement or later maintenance or rehabilitation treatments. Some surface types, such as some 

open-graded asphalt mixtures, chip seals with large aggregates, and improperly textured 

concrete, can exhibit high positive macrotexture from the time of construction. Positive 

macrotexture can increase over time due to raveling of asphalt surfaces or where concrete 

surfaces lose the paste around the large aggregates. Studded tires and chain wear can rapidly 

increase the macrotexture of both asphalt and concrete surfaces. Positive macrotexture can be 

reduced with time if the aggregate is susceptible to polishing under traffic, sometimes even to 

unsafe levels such that surface friction under wet weather conditions is compromised. 

Macrotexture can be changed through replacement of the surface materials for asphalt or 

concrete pavements, and through grinding or grooving for concrete surfaces.

The pavement structural responsiveness at the time of construction under different conditions of 

temperatures, traffic speeds, and wheel loadings is determined by the pavement type, the 

materials used, and the design of the structural section. The overall deformation of the pavement 

structure is controlled by the stiffness and thickness of the layers, and the extent of viscoelastic 

(delayed elastic) stiffness behavior that the layer materials exhibit under different temperatures 

and at specific times of loading. Together, these factors determine the energy dissipated in the 

pavement and the effect on vehicle fuel economy. Thicker and stiffer layers reduce the 

deformation response of the pavement, with a given percent change of thickness generally 

having a greater effect than the same percent change in stiffness. 

6-4 
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Most concrete and cement-stabilized materials demonstrate elastic response and do not change 

stiffness under the range of temperature and traffic loading conditions typically experienced by 

in-service pavements. Concrete generally exhibits stiffness values in the range of about 4.3 to 

7.3 million lb/in2

 (30,000 to 50,000 MPa). Fatigue damage in concrete is generally localized and 

does not decrease the stiffness much, if at all. Somewhat higher deflections occur at concrete 

pavement joints with poor load transfer under cold temperatures when the joints are open 

(Snyder 2011; Harvey et al. 2003). 

For asphalt layers and asphalt-stabilized layers, the stiffness and extent of delayed elastic response 

is dependent on the type of asphalt binder, the temperature, and the traffic speed, with stiffness 

decreasing under hotter temperatures and slower moving wheel loads, and increasing under colder 

temperatures and faster moving wheel loads. The stiffness of new asphalt concrete under these 

conditions can vary between about 43,000 and 4.3 million lb/in2 (300 and 30,000 MPa), 

corresponding to hottest temperatures/slowest moving loads and coldest temperatures/fastest

moving loads, respectively. The interaction of variations in temperature profiles through the 

asphalt layers and variations in traffic loading and speeds with the materials properties determines 

the structural responsiveness of the asphalt layers throughout the year. Because temperatures 

change more at the surface, these effects are most important near the surface. Asphalt materials 

tend to “age” over time, increasing in stiffness and having less viscoelastic and more elastic 

response, which reduces deflections but is also associated with increased risk of top-down 

cracking. Aging occurs most rapidly over the first 5 years after placement, and is also greater near 

the surface due to increased exposure to heat, UV light from the sun, and atmospheric oxygen. 

The stiffness of asphalt layers in the wheelpaths can be reduced towards the end of their structural 

life as a result of fatigue damage caused by repeated loading.

The stiffness of unbound granular layers depends on the applied stress (both magnitude and 

duration) and the saturation of the material. Subgrade materials can also be a source of damping. 

High moisture contents in the subgrade and granular pavement layers, due to unsealed surface 

cracking or poor drainage, can cause significant reductions in their stiffness. 

The additional fuel use for on-road vehicles caused by different levels of roughness, macrotexture, 

and structural responsiveness can have an environmental impact. From a life cycle perspective, 

these impacts must be balanced with consideration of the environmental impacts of building, 

maintaining, and rehabilitating pavements in order to maintain a smooth condition, minimize 

excessive positive macrotexture, and elicit lower levels of structural responsiveness. For example, 

as can be seen in figure 1-1 for sources of GHG emissions in the U.S., the transportation sector is a 

leading source of emissions, but it must be remembered that the production and transportation of 

pavement materials such as asphalt, cement, steel, lime and aggregate, as well as the consumption

of fuel by construction equipment, also produce emissions. The construction of longer life 

pavements and the application of more frequent pavement maintenance and rehabilitation 

treatments can reduce pavement roughness, provide positive surface texture, and therefore reduce 

vehicle fuel consumption and GHG emissions over the life cycle. At the same time, constructing 

longer life pavements and applying more frequent maintenance and rehabilitation treatments also 

requires additional energy and produces additional emissions. Maintenance and rehabilitation 

treatments can also influence structural response depending on changes in thickness, stiffness, and 

properties of the treatment. Optimization of the longevity of the pavement design and of the 

maintenance/rehabilitation treatment type and frequency must take into consideration all of the 

life-cycle phases (materials production, construction, use and end-of-life), but is also highly 

dependent on the level of traffic using the pavement.

6-5 
Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

The relative impact of pavement-related rolling resistance on fuel economy and vehicle 

emissions depends primarily on the level of roughness, surface texture, and structural 

responsiveness. Vehicle types, traffic volumes and speeds, and climatic conditions also play an 

important role. For two pavements sharing similar characteristics, the total impact of the 

pavement on energy use and vehicle emissions then depends on the number and type of vehicles 

using it. If there are relatively few vehicles using the pavement, then all of these mechanisms 

(i.e. roughness, macrotexture, and structural responsiveness) will produce fewer emissions and 

other environmental impacts (resulting from materials production, construction, and maintenance 

and rehabilitation of the pavement) will play a larger role. For very heavily trafficked 

pavements, the cumulative effects of roughness, macrotexture, and structural responsiveness can 

become much greater than those produced by materials production and construction. 

The relative impact of changing an agency’s practices regarding different elements of pavementrelated rolling resistance depends on the starting points for roughness, macrotexture, and 

structural responsiveness for the network and the individual pavement sections in the network. 

For example, if the network is already particularly smooth, then those practices should be 

continued, and additional changes in practice to further improve smoothness will likely have a 

small effect. On the other hand, if the network has high roughness, particularly on high-volume 

routes, then improvements in smoothness may result in high returns in reduced environmental 

impacts. Similar analyses can be applied to the other factors influencing pavement-related 

rolling resistance. 

Roughness and Macrotexture Effects

There are four components of pavement texture defined based on the maximum dimension of 

their deviation (wavelength) from a true planar surface: roughness (also called unevenness, with 

wavelengths of 1.6 to 164 ft [0.5 to 50 m]), megatexture, macrotexture (wavelengths of 0.02 to 2 

inches [0.5 to 51 mm]), and microtexture. The relative scale between each component is shown 

in figure 6-2 (Sandberg 1997). As part of network-level pavement management, agencies 

routinely collect profile data in the wheelpaths on a regular cycle (typically annually or biannually) using high-speed vehicles equipped with laser profilers (different laser technologies 

need to be used for asphalt and concrete pavements to avoid an upward bias in IRI caused by 

directionally textured concrete surfaces). A roughness index, the most common being the IRI, is 

calculated from the collected profile data. The IRI is one parameter for characterizing roughness 

and was primarily developed to consider the riding comfort of vehicle occupants. Although IRI 

was not primarily developed to capture the effects of pavement roughness on fuel 

consumption—and there are likely better parameters for that purpose—IRI does correlate with 

vehicle fuel use for all vehicle types, and is used by most highway agencies.

Macrotexture can be measured on asphalt-surfaced pavements and concrete pavements that do 

not have directional textures (tining, grooving, grinding) using the same profiler vehicles when 

equipped with high-speed profilers, and can be measured for directionally textured concrete 

pavements using other measurement techniques. The relationships between different types of 

concrete directional textures and vehicle fuel economy are not as clear as it is for asphaltsurfaced pavements. 

6-6 
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Figure 6-2. Pavement texture and wavelength (Sandberg 1997). 

 Megatexture 

Macrotexture

Microtexture

Tire

Tire/road

Contact 

Patch

Single 

Aggregate

Roughness (unevenness) Short 

Stretch 

of 

Road

6-7 

A recent evaluation/calibration of the World Bank’s HDM-4 model (PIARC 2002) for vehicle 

operating costs, using measurements made with a fleet of representative North American 

vehicles, found the following when comparing roughness and macrotexture without 

consideration of the structural response (Chatti and Zaabar 2012):

For fuel consumption, the most important factor is surface roughness (measured using 

IRI). An increase in IRI of 1 m/km (63.4 in/mi) will increase the fuel consumption of 

passenger cars by about 2% irrespective of speed. For heavy trucks, this increase is 

about 1% at normal highway speed (96 km/hr or 60 mph) and about 2% at low speed (56 

km/hr or 35 mph). 

In another study of fuel consumption, measurements were made at WesTrack using two 

automated heavily loaded articulated trucks traveling around a closed circuit track for many 

hours a day over a 7-week period both before and after rehabilitation on a set of test sections 

(Sime and Ashmore 2000). The results showed that the fuel efficiency was about 4.5 percent 

higher when trucks traveled on a smoother pavement (the IRI was reduced from 150 in/mi [2.3 

m/km] to 75 in/mi [1.2 m/km] through the placement of an overlay). The winds and 

temperatures were similar during the two periods, and the grade was controlled. This is the most 

extensive testing regarding the effect of IRI that has been documented. Most other recent 

experimental results are based on less than 10 replicate runs, possibly repeated several times over 

a year. 

Regarding surface texture, the effect is generally less than that of roughness for typical ranges of 

roughness and macrotexture in the U.S., with Chatti and Zaabar (2012) reporting that:
Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

...the effect of surface texture is statistically significant at [the] 95 percent confidence 

interval only for heavier trucks and at low speed. An explanation of this observation is 

that at higher speeds, air drag becomes the largely predominant factor in fuel 

consumption. The increase in rolling resistance (i.e., fuel consumption) due to texture is 

masked by the increase in air drag due to speed. 

Chatti and Zaabar (2012) include coefficients for surface texture, measured by mean profile 

depth (MPD), in the recommended model and found that for heavy trucks “an increase in MPD 

of 1 mm (0.039 in) will increase fuel consumption by about 2% at 56 km/hr (35 mi/hr),” with no 

statistically significant effect for other vehicles or for heavy trucks at highway speeds. Positive 

macrotexture (stones and texture protruding up from the average surface elevation of the 

pavement) is expected to have a much greater effect on fuel economy than negative texture 

(downward gaps below the average surface elevation of the pavement). 

On pavements carrying high volumes of traffic, the effects of pavement smoothness on fuel 

economy and the resulting impacts on energy use and GHG emissions in the use phase can be 

much greater than any differences caused by different materials or construction techniques

during the material production and construction phases. This can be seen in figure 6-3 (Wang et 

al. 2012), which shows for an example segment of highway the relative effects on energy use (in 

terms of MJ and equivalent million gallons of gasoline) of applying a pavement preservation 

treatment (materials and construction), and the resulting savings from vehicle use on the 

smoothened pavement compared to letting the pavement remain rough. 

Figure 6-3. Energy savings in MJ and equivalent gallons of gasoline for a medium-to-highvolume route over 10-year analysis period for preservation treatment versus leaving the 

pavement rough (Wang et al. 2012). (Note: material production values calculated using three 

alternative sources of information shown [PCA, Stripple, EcoInvent] in order to test sensitivity 

of results to data source). 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

The example shown in figure 6-3 is for one direction of a 5-mi (8-km) segment of a medium-tohigh-volume two-lane highway carrying 5,600 vpd with about 29 percent trucks. The current IRI 

is about 190 inches/mi (3 m/km), and the average (Medium Smooth Rehab) reduction in the IRI

to about 105 inches/mi (1.7 m/km) was simulated by typical results achieved at initial

construction consisting of grinding and some slab replacements followed by increases in IRI 

under traffic over the 10-year period. The results were calculated using the HDM-4 models

calibrated by Chatti and Zaabar (2012) and coupled with emissions models in the EPA’s 

MOVES software (EPA 2010a). Similar simulations were analyzed for asphalt overlays on 

asphalt pavement in the same study. Models for changes in macrotexture (measured as mean 

texture depth [MTD] for concrete) caused by the treatment and later traffic and their effect on 

fuel consumption are included in the simulation shown in figure 6-3 and in other simulations in 

the study, but had a much smaller effect than the change in IRI for both the concrete and asphalt 

cases. The structural responsiveness to vehicle loading was assumed to not change with the 

treatments because the pavement structures did not change much. Additional benefits of the 

preservation-type treatments simulated in the study due to extension of the life of the underlying 

pavement were not considered in the analyses. 

The sensitivity analysis shown in figure 6-3 indicates that the smoothness achieved by the 

contractor has a major impact on the benefits. The figure shows analysis results for high-quality 

(Smooth Rehab = mean IRI minus two standard deviations, 57 to 72 inches/mi [0.9 to 1.2 

m/km]), and low-quality (Less Smooth Rehab = mean IRI plus two standard deviations, 140 to 

144 in/mi [2.2 to 2.3 m/km]) smoothness from construction of the treatment based on historical 

data from similar projects, in addition to the average (Medium Smooth Rehab) result. These 

results indicate that a strong construction smoothness quality assurance program can have a 

significant effect on vehicle fuel use for high-volume routes with high roughness. The changes 

in IRI over the life of the pavement after construction also significantly affect the net impact of 

the preservation treatment. Also shown in the figure are scenarios for 0 and 3 percent growth in 

total traffic over the 10-year analysis period. It can be seen that the construction smoothness had 

a much larger effect than the differences in the traffic growth rate and, paradoxically, there are 

greater relative savings when more traffic uses the smoother pavement, although the overall 

impact is greater for the higher traffic growth. Again, in terms of optimizing fuel economy on a 

network, construction smoothness is most important on higher volume routes and is not as 

important on lower volume routes (of course, smoothness is still important to the users of those 

lower volume routes). 

The effects of vehicle speed have some interaction with roughness, but it does not change the 

overall trends or have much effect on the sensitivities of fuel economy to roughness (Chatti and 

Zaabar 2012). Modeling results also indicate that the effects of pavement roughness on fuel 

economy under stop-and-start congested traffic are similar to those under steady-state traffic, 

even including stop-and-start traffic in congested areas (Wang, Harvey, and Kendall 2013). 

Since fuel economy goes down as driving speeds increase above 45 mi/hr (72 km/hr), one 

question that arises in discussions regarding the effectiveness of keeping pavements smooth is 

whether improving smoothness results in faster driving speeds under free-flow conditions that 

can reduce the fuel economy benefits of smoothness. Modeling by Hammarström et al. (2012), 

using driver speed behavior measurements from Sweden (Ihs and Velin 2002), indicated that 

increased driver speeds essentially cancel out the benefits of improved smoothness. On the other 

hand, a recently completed study in California (Wang, Harvey, and Lea 2013), using a large 

number of traffic speed measurements before and after pavement maintenance (on the same 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

concrete sections with grinding plus slab replacements or asphalt overlays, and on the same 

asphalt sections with asphalt overlays), indicated that a reduction of IRI of 63 inches/mi (1 

m/km) leads to only about a 0.3 to 0.4 mi/hr (0.48 to 0.64 km/hr) change in free-flow speed on 

freeways, which has a negligible effect on vehicle emissions or energy consumption. 

In urban areas, pavement roughness is often affected by the quantity of utility cuts and the 

quality of the repairs. Poorly constructed utility cuts can immediately cause large increases in 

roughness in an otherwise smooth pavement. Even if utility cuts are initially constructed with a 

smooth surface, they can adversely affect the pavement smoothness if they are not well 

compacted or well bonded to the existing pavement, leading to an increase in vehicle fuel use. 

An alternative for new pavement construction is to place utilities in locations on the right of way 

outside of heavily trafficked portions of the paved areas. The timing of utility upgrades should 

be scheduled before maintenance or rehabilitation, as it will otherwise affect the pavement life. 

Utility cuts causing roughness are of greatest concern on higher volume routes. 

With respect to the costs of timely application of maintenance and rehabilitation treatments, 

research has shown for asphalt pavements that applying a pavement maintenance treatment 

before a pavement reaches an advanced level of cracking can potentially reduce the life-cycle 

cost compared with waiting until the pavement damage reaches a critical level that a major

rehabilitation is required (Lee, Rezaie, and Harvey 2012). 

Pavement Structural Responsiveness to Loading Effects

Pavement structural response to loading, the third mechanism of rolling resistance that can affect 

fuel consumption, has been modeled as two phenomena: 

1. Dissipation of energy in the pavement due to the pavements structural response under 

traffic loading.

2. Pavement surface structural responsiveness modeled as a change in geometry between 

the tire and the surface.

For both phenomena, larger deflections and greater delayed elasticity (more viscous damping as 

opposed to elastic behavior) will increase the pavement rolling resistance. The first pavement 

structural responsiveness phenomenon, dissipation of energy in the pavement structure due to the 

viscoelastic nature of asphalt materials, has been the subject of recent model development by the 

LUNAM University/IFSTTAR (Chupin, Piau, and Chabot 2013), the University of Lyon, France 

(Pouget et al. 2012), and by the University of Nottingham (Thom, Lu, and Parry 2010). There 

have also been a number of previous studies employing various approaches to model structural 

responsiveness (e.g., Kelly 1962; Perloff and Moavenzadeh 1967; Huang 1967; Hopman 1993; 

Hajj, Sebaaly, and Siddharthan 2006) that consider viscoelastic properties for some or all layers. 

The second phenomenon is the subject of recent and ongoing model development at the 

Massachusetts Institute of Technology (Akbarian et al. 2012). Flugge (1975), Chupin, Piau, and 

Chabot (2013), and Loughalam, Akbarian, and Ulm (2013) have derived or reviewed 

relationships between the energy needed to move vehicles forward based on the position of the 

wheel in the deflection basin as it is affected by the delayed elasticity of viscoelastic deflections 

(the second structural responsiveness phenomenon described above) and the energy dissipated in 

the pavement (the first phenomenon). 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

It is interesting to note that the work by Akbarian et al. (2012), Chupin, Piau, and Chabot (2013), 

Pouget et al. (2012), and Thom, Lu, and Parry (2010) produce somewhat similar results for 

energy consumption for the distinct pavement structure, traffic speed, and temperature conditions 

that come from their modeling, yet draw opposite conclusions as to the overall importance of 

energy dissipation due to structural response under loading. This is because the researchers have 

not applied their results for the combined effects of traffic speed, temperature, structure and 

hourly traffic volumes as they occur together over a year for a given pavement, or for a range of 

different pavement structures. For example, Pouget et al. (2012) modeled an 8.7-inch (220-mm) 

thick asphalt structure with a 2.4-inch (60-mm) polymer-modified asphalt surface (and the rest 

conventional asphalt) as it was subjected to uniform temperatures throughout the asphalt; the 

results of the model (which was not calibrated with field data) indicated that, for a 7,300 lb (32 

kN) truck wheel loading condition, reductions in fuel economy occur when the speed is reduced 

from 60 mi/hr (100 mi/hr) to 30 mi/hr (50 km/hr). The estimated reductions in fuel efficiency 

were approximately 0.1 percent at an asphalt temperature of 50 oF (10 oC), 1 percent at 95 oF (35 o

C), 3 percent at 122 oF (50 oC) and 5.5 percent at 140 oF (60 oC) (Pouget et al. 2012). It is 

emphasized that this result is for one structure, one type of heavy truck, one truck wheel load, 

and for the two vehicle speeds over the described range of temperatures. The net result for a 

road section would depend on the joint occurrences of vehicle travel and pavement temperatures 

across each day and night and across all the seasons of the year.

A number of field studies have also been performed to measure the effects of pavement type on 

vehicle fuel economy, including those by Zaniewski et al. (1982), Taylor and Patten (2006), 

Ardekani and Sumitsawan (2010), Bienvenu and Jiao (2013), and Hultqvist (2013). For 

automobile traffic, the study by Zaniewski et al. (1982) showed no measureable difference in 

fuel economy between asphalt and concrete pavement. The study by Taylor and Patten (2006) 

had limited results for an automobile driven over 11 test sections that included concrete, asphalt, 

and composite (asphalt surface over concrete) paved roads in Ontario and Quebec; two seasons 

(winter and summer) and two travel speeds (37 and 62 mi/hr [60 and 100 km/h]) were included. 

All of the pavement sections had IRI values less than 126 inches/mi (2 m/km) and the IRI was 

considered directly in the results, but the study did not control for or measure pavement surface 

texture. Of the statistically significant results, the study showed a small increase in fuel use for 

asphalt pavement compared to concrete pavement for one season, and a small increase in fuel use 

for concrete pavement compared to composite for one season (the opposite was observed for the 

other season). The pavements considered by Ardekani and Sumitsawan (2010) consisted of four 

rough to extremely rough urban streets (IRI values of 170 to 325 inches/mi [2.7 to 5.2 m/km]) 

tested using a Chevy Astro van with a relatively small number of replicate runs and no 

consideration of texture or roughness. The study by Hultqvist (2013) showed about a 1 percent 

difference in fuel economy for cars when tested on one asphalt and one concrete pavement on the 

same route in the Swedish summer. However, the authors concluded that these results were 

primarily due to the higher macrotexture from studded tire use on the asphalt pavement based on 

modeling results. The pavement structures were not characterized for their stiffnesses.

Noting possible problems with measurements in two earlier phases of their work, Taylor and 

Patten (2006) performed a Phase III study on the Canadian pavements listed above using a heavy 

articulated truck outfitted with different weights and running at two travel speeds (37 and 62 

mi/hr [60 and 100 km/h]) to establish if loading was a contributing factor to truck fuel 

consumption differences among the three different pavement types (concrete, asphalt, and 

composite). Testing was performed under different seasonal conditions in eastern Canada. The 

study found statistically significant fuel use savings for trucks traveling on concrete pavements 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

for most of the five seasons and day/night conditions across the range of vehicle loadings, with 

greater differences noted at 37 mi/hr (60 km/hr) (1.3 to 3.9 percent) than at 62 mi/hr (100 km/hr) 

(0.8 to 1.8 percent). The study also found statistically significant fuel saving results for most of 

the seasonal and day/night conditions for concrete pavements compared to composite pavements, 

again with larger differences at 37 mi/hr (60 km/hr) (1.9 to 6.0 percent) than at 62 mi/hr (100 

km/hr) (0.8 to 3.1 percent). Interestingly, statistically significant results under the hottest 

conditions on summer days found the opposite result, with the trucks consuming less fuel on 

composite pavements than on concrete pavements, with larger differences at 37 mi/hr (60 km/hr) 

(2.4 to 3.0 percent) than at 62 mi/hr (100 km/hr) (about 1.4 percent). The models developed in 

the Phase III study also noted that “The insensitivity of the fuel consumption differences to 

temperature, load and speed is somewhat counterintuitive to the engineering physical models”; 

however, no explanation for this lack of sensitivity was identified in the study. Thicknesses of 

the pavement structures were noted, but no structural evaluation or characterization of the 

pavements (other than being classified as asphalt, concrete or composite) was included in the 

analyses of the fuel consumption results. Texture was not measured or considered. 

Coast-down measurements were also performed as part of the Taylor and Patten (2006) study on 

the asphalt and concrete sections to measure rolling resistance. Coast-down tests consist of 

measuring how far a vehicle (the loaded truck in this case) will roll without braking and after 

shutting off the engine and putting the transmission in neutral. The results showed no significant 

differences between the asphalt and concrete structures included in the fuel economy studies. 

The truck results from the study by Hultqvist (2013) showed up to a 5 to 7 percent difference in 

fuel efficiency for heavy vehicles operating on hot days on one concrete and one asphalt 

pavement. The differences were attributed to a combination of structural responsiveness and 

macrotexture, with macrotexture levels higher on the asphalt pavement while the IRI was slightly 

higher on the concrete pavement. The effects of texture and structural responsiveness were not 

separated for the truck measurements, and the authors expressed concern about the presence of 

relatively strong winds during testing. As noted previously, the pavement structures were not 

characterized for their stiffnesses. The Swedish study is unique in that the sections were used to 

check a mechanistic model of pavement energy consumption from vehicles called VETO 

(Hammarström et al. 2012), which showed results similar to the measurements for the test 

sections. Many of the models in VETO are similar to those in HDM-4. 

A field study by Bienvenu and Jiao (2013) along 28 mi (45 km) of Interstate 95 in Florida

indicated that passenger vehicles on a concrete pavement use 3.2 percent less fuel compared to 

asphalt pavement. The study also showed that, along the same corridor, loaded tractor trailers 

traveling on the concrete pavement experienced 4.5 percent better fuel economy than on the 

asphalt pavement. The asphalt pavement consisted of 9.25 inches (235 mm) of asphalt 

(including an open-graded friction course) on 5 inches (125 mm) aggregate base and 12 inches 

(300 mm) of treated subgrade. The concrete pavement consisted of a 13-inch (330 mm) JPCP 

resting on a 1-inch (25 mm) asphalt-treated permeable base and 4-inch (100 mm) asphalt base. 

The pavement structures were not characterized for their structural responsiveness nor were the 

surface textures measured or considered. 

The previously cited study by Chatti and Zaabar (2012) had as a secondary objective the 

evaluation of fuel economy for vehicles traveling on asphalt and concrete pavements. It included 

11 pavement sections in Michigan divided between asphalt and concrete, five types of vehicles 

operating at different speeds, daytime winter and summer measurements (for most vehicles), and 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

ranges of roughness and texture levels. As with the other studies cited, there was very little 

characterization of the pavement structure besides being noted as being either asphalt or 

concrete. The results of the study indicated that “pavement type [does] not affect the fuel 

consumption of any vehicle class except for heavy trucks.” More detailed analysis of the same 

data indicated that articulated (heavy) trucks and light trucks had statistically significant higher 

fuel consumption, with about a 4 percent difference for the heavy trucks when operated on 

asphalt pavements included in the study at 35 mi/hr (56 km/hr) in the daytime in the summer, but 

there no statistically significant difference at speeds of 45 or 55 mi/hr (72 or 88 km/hr) or when 

the trucks operated during the winter. As noted there was no characterization of the pavement 

structures in terms of the structural responsiveness to vehicle operating conditions and 

temperature that would permit generalized application to other structures and other temperature 

and loading conditions. 

From the review of the various studies noted here, it can be said with reasonable certainty that 

the influence of structural responsiveness on fuel economy and associated environmental impacts

has not been comprehensively validated with an experiment that has accounted for the broad 

range of environmental conditions or the various types of pavement structures used in the 

nation’s highway network (e.g., composite pavements, semi-rigid pavements, rubberized and 

polymer modified mixtures, doweled and nondoweled JPCP, and CRCP). The field studies 

conducted to date to measure the effects of dissipated energy on vehicle fuel efficiency suffer 

from a serious lack of characterization of the pavement structures in terms of their structural 

responsiveness to loading as a function of the stiffness and thickness of the pavement layers or 

the viscoelastic nature of the materials under different conditions of temperature and traffic 

speed. Without consideration of those variables, it is difficult to use the results for model 

validation, and, without validated models, it is difficult to calculate the net results of all of the 

variables affecting this mechanism. The structural responsiveness to vehicle loading of 

pavements depends on subgrade, subbase, and base support conditions, and, particularly for 

asphalt pavements, the temperature and time of loading. To complicate matters, these responses 

change as the pavement materials age and deteriorate. Therefore, consideration of pavement 

structural responsiveness effects must be analyzed separately for each project considering the 

intersection of structural responsiveness, traffic levels, traffic speeds and pavement temperatures, 

and the moisture conditions in the underlying unbound layers, which may vary widely with daily 

and seasonal climatic fluctuations. 

Although deflection testing using a falling weight deflectometer (FWD) does not replicate the 

effects of a vehicle moving across the pavement, deflection testing has been used to help 

understand the effects of structural response and energy consumption. Studies that considered 

FWD testing include those performed by Ullidtz et al. (2010) and by Faldner and Lenngren (2012). 

While it is known that water, snow, and ice on the pavement will also impact rolling resistance, 

the fuel economy studies cited above were all carried out under dry pavement conditions 

(Karlsson, Carlson, and Dolk 2012). Modeling results from Sweden (Hammarström and 

Karlsson 1987) indicate that water depths of 0.039, 0.078, and 0.156 inches (1, 2 and 4 mm) can 

increase vehicle fuel use by 30 percent, 90 percent, and nearly 80 percent, respectively, 

compared to dry pavement (Karlsson, Carlson, and Dolk 2012). These results indicate that 

pavement designs and materials that can remove water from the pavement surface quickly may 

contribute to substantial reductions in fuel use and environmental impact, particularly in areas 

with high rainfall; they will also contribute positively to overall safety. In general, open-graded 

friction courses and directional texturing are used on asphalt and concrete surfaces, respectively, 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

to reduce water depths under tires. Some of these textures also tend to increase macrotexture and 

might slightly reduce fuel consumption. It should be noted that these modelling results are also 

not yet validated. 

It must be again emphasized that none of the effects on vehicle fuel consumption and pavement 

characteristics matter much if only a few vehicles are using the pavement, and that these effects 

should only be considered for higher traffic volume locations from the standpoint of 

environmental impact on the network. This is borne out for the case of IRI as described in the 

next section of this chapter. 

Network-Level Considerations 

As has been noted previously, the effects of a pavement on vehicle fuel economy and the 

associated energy and environmental impacts are controlled by the number of vehicles using the 

pavement. The previously cited study by Wang et al. (2012) analyzed the net effects of several 

pavement preservation treatments on the GHG emissions and energy use as a function of traffic 

level, with the materials production and construction effects being the same and the reductions in 

GHG emissions and energy use depending on traffic flow during the use phase. The study 

included consideration of pavement deterioration after the treatment, and showed that the net 

effect can be positive or negative, depending on the traffic level and the constructed smoothness. 

Furthering this concept, another study by Wang, Harvey, and Kendall (2013) determined trigger 

levels for the same typical California preservation treatments (5- to 10-year design lives) on 

asphalt and concrete roads optimized to reduce GHG emissions as a function of traffic level. 

The modeling in the study did not consider changes in structural responsiveness of treatments in 

the use phase because the treatments did not change the pavement type (asphalt surfaces 

remained asphalt and concrete surfaces remained concrete) and the treatments did not 

significantly change the structural responsiveness of the typical existing pavement. The results 

indicated that optimized IRI trigger values for different traffic flows, in terms of daily passengercar equivalent (trucks count as 1.5 cars) per direction, were on the order of (Wang, Harvey, and 

Kendall 2013): 

• 101 inches/mi (1.6 m/km) for the highest traffic levels (directional daily traffic above 

34,000 passenger-car equivalents). 

• 127 inches/mi (2 m/km) for directional daily traffic levels between about 12,000 and 

34,000 passenger-car equivalents. 

• 177 inches/mi (2.8 m/km) for directional daily traffic flows between 2,500 and 12,000 

passenger-car equivalents. 

• Use-phase savings from treatments to reduce roughness were generally less than the 

GHG emissions from materials production and construction regardless of IRI for 

directional daily traffic flows below about 2,500 passenger-car equivalents. 

As can be seen from these values, the optimum IRI trigger level decreases as the traffic level 

increases, and emissions from construction and materials used in the treatment could not be 

recovered in the use phase for low traffic flows. Although specific trigger values would be expected 

for different agencies and treatments (preservation, rehabilitation, reconstruction), the overall trends 

are expected to be the same. 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Summary

A general summary of the effects of pavement characteristics on vehicle fuel economy, and the 

resulting environmental impacts of fuel economy changes, is presented below: 

• Roughness as measured by IRI generally has the greatest effect on fuel economy for 

typical ranges of IRI on U.S. highway networks, compared with structural responsiveness

and macrotexture. The effect is essentially linear, with sensitivity depending on the 

vehicle type. According to recently calibrated models (Chatti and Zaabar 2012), an 

increase in IRI from 63 inches/mi (1 m/km) to 190 inches/mi (3 m/km) increases 

passenger car fuel consumption by 4.8 percent at 86 oF (30 oC), 55 mph (88 km/hr) with 

zero grade, and an MPD (macrotexture) value of 0.04 inches (1 mm). For heavy 

articulated trucks the same change in IRI increases fuel consumption by 2.9 percent under 

the same conditions. SUVs show a change of 4.1 percent, and light trucks and vans show 

changes of 1.6 and 1.8 percent, respectively Although the effects of roughness vary 

somewhat with temperature and vehicle speed (Chatti and Zaabar 2012), it has an effect 

on fuel economy for every vehicle throughout the year. Given its impact, pavement 

roughness can be controlled by three methods:

– Consideration of smoothness performance (smoothness over time) and having 

smoothness over the life cycle as a key parameter in the pavement design process.

– The implementation of effective smoothness specifications, since pavements “born 

rough” will start rough and only get rougher with time. 

– The timely application of maintenance and rehabilitation strategies that restore and 

promote smoothness before the pavement gets too rough, including consideration of 

traffic volume when determining IRI trigger values for treatment.

• Macrotexture as measured by MPD on asphalt and MTD on concrete (MPD and MTD are 

generally considered interchangeable in terms of values for fuel economy models) has a 

linear effect on vehicle fuel economy. The effect of macrotexture is generally much 

smaller than that of IRI, to the point that it is statistically insignificant for all but heavy 

trucks at slow speeds for typical ranges of well-maintained pavement occurring on state 

highway networks in the U.S. According to the recently calibrated models (Chatti and 

Zaabar 2012) an increase in MPD or MTD of 0.04 inches (1 mm) will increase heavy 

truck fuel consumption by about 2 percent at 35 mi/hr (56 km/hr), when IRI is held 

constant at 63 inches/mi (1 m/km), while for other vehicles and heavy trucks at highway 

speeds the effect was statistically insignificant. Macrotexture is controlled by pavement 

surface type selection (minimizing positive texture for both concrete and asphalt) and 

timely maintenance (e.g., repairing raveled asphalt surfaces, degraded concrete surfaces, 

chain wear). However, sufficient macrotexture must be maintained to provide a 

pavement with adequate surface friction. Macrotexture improves wet-pavement surface 

friction by providing drainage between the tire and the pavement; this reduces the risk of 

hydroplaning, which is the phenomenon in which a film of water develops between the 

moving tire and the pavement surface leading to the tire losing contact with the 

pavement. The risk of hydroplaning increases as vehicle speed increases. Increased

macrotexture may help with wet-weather fuel economy by reducing water film 

thicknesses, which for some pavement textures could otherwise consume vehicle energy 

by increasing rolling resistance (particularly in wet climates). Macrotexture is primarily 

controlled by surface materials selection and maintenance practices.

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

• Structural responsiveness and its effect on vehicle fuel economy is the subject of several 

models that have been developed, and a number of field studies have been performed 

measuring vehicle fuel economy on different pavement structures under different 

conditions. These studies provide indications that under certain conditions the structural 

responsiveness of different pavements to vehicle loading can have a measureable effect, 

which like that of roughness and macrotexture, is variable depending on vehicle type and 

operating conditions. Unlike roughness and macrotexture, the effect of structural 

responsiveness is highly variable, depending on temperature and the underlying support 

conditions which undergo daily and seasonal fluctuations. In general, the effects of 

different pavement structures range from approximately no difference under some 

conditions of vehicle type/operation and climate conditions to effects of the same order of 

magnitude as high levels of highway roughness under the most extreme temperature and 

loading conditions at certain times of the year. This effect also depends on the 

viscoelastic properties of the pavement materials, primarily the type and age of asphalt 

materials located near the surface. 

In general, modeling and measurements to date indicate that lighter and faster vehicles, as 

well as colder conditions, result in the least differences in rolling resistance between 

different pavements whereas heavier and slower vehicles under hotter conditions result in 

larger differences. The frequencies at which these conditions occur in combination with 

traffic patterns control the net effect on fuel economy of structural responsiveness for a 

given structure. 

However, the influence of structural responsiveness on vehicle fuel economy has not yet 

been comprehensively validated with any experiment that has characterized the pavement 

structures in terms of their responsiveness under different conditions. As a result, the 

available models have not been calibrated with the type of data that allows the general 

application of the models to evaluate in-service pavements under the range of traffic and 

climatic conditions that occur daily, seasonally, and from location to location. Research 

is needed that uses field measurements of fuel economy for a range of vehicles, climates, 

and pavement structural responses, controlling for roughness and macrotexture, to 

complete calibration and validation of models that can be used to make design and 

management decisions. 

• Environmental impacts and energy use from all three rolling resistance mechanisms are a 

function of the number of vehicles using the pavement in the use phase. Beneficial 

environmental impacts from managing roughness, macrotexture, or structural 

responsiveness decrease as the number of vehicles using the pavement decrease.

• The relative impact of decisions affecting the different vehicle use phase mechanisms 

discussed in this section are highly context sensitive, with the benefits from changing 

existing practices dependent on the baseline conditions in terms of existing roughness, 

macrotexture conditions, and pavement structures. For example, a network with 

generally low roughness on high traffic routes will not see much improvement in 

emissions from focusing on improving roughness, although keeping the pavement 

smooth to avoid increasing emissions will be important. The relative effects of the 

different mechanisms also depend on vehicle types, loads, and speeds, daily and seasonal 

pavement temperature fluctuations, and interaction with the distributions of vehicle 

variables listed above across the years. 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Strategies for Improving Sustainability

Practices that are available to pavement managers, designers, and specification developers that 

might be optimized to help meet GHG emission, energy use, and other environmental objectives 

associated with the influence of pavement characteristics on vehicle fuel economy are 

summarized in table 6-1. 

Table 6-1. Summary of strategies for improving vehicle use phase fuel consumption and 

potential trade-offs.

Vehicle Fuel 

Consumption 

and Pavement 

Objective

Vehicle Fuel 

Consumption 

Sustainability 

Improving Strategy

Economic Impact Environmental 

Impact

Societal

Impact

Implement pavement 

design process that 

considers smoothness 

over the pavement life 

as a key design 

parameter, especially 

for high traffic volume 

routes.

Potential for small to 

moderate increases in 

initial costs but reduced 

life-cycle costs due to 

longer pavement lives. 

Reduced vehicle operating 

costs for road users.

Reduced 

environmental 

impact due to less 

fuel use, particularly 

on high traffic 

volume routes.

Improved economic 

efficiency.

Implement 

construction 

specifications to 

incentivize maximum 

possible smoothness, 

especially for high 

traffic volume routes. 

Potential for small 

increases in construction 

costs, reduced life-cycle 

costs due to longer 

treatment lives from 

reduction in dynamic 

loading. Reduced vehicle 

operating costs for road 

users.

Reduced 

environmental 

impact due to less 

fuel use, particularly 

on high traffic 

volume routes.

Improved economic 

efficiency.

Reduce Fuel Use 

Due to 

Roughness

Optimize timing of 

maintenance and 

rehabilitation based on 

IRI trigger value and 

traffic volume. 

Potentially increased 

agency initial costs if 

results in earlier treatment 

than current practice. 

Potentially reduced agency 

life-cycle cost from 

pavement preservation. 

Reduced vehicle operating 

costs for road users as 

pavements are kept in 

smoother condition. 

Increased 

environmental 

impact of materials 

production and 

construction when 

treatments are more 

frequent; reduced 

environmental 

impact due to less 

fuel use. Benefit 

can be offset if 

vehicle speeds 

increase because of 

improved 

smoothness.

Emphasis on 

maintaining highvolume routes in 

smoother condition 

may improve 

economic efficiency 

and average road 

user cost, but may 

result in neglect of 

lower volume routes 

depending on 

funding levels. 

Minimize pavement 

roughness due to 

utility cuts through 

regulation, 

construction practice 

enforcement and better 

planning.

Reduced pavement 

maintenance costs. 

Increased enforcement

costs. Reduced vehicle 

operating costs for road 

users.

Reduced 

environmental 

impact due to less 

fuel use when poorly 

repaired utility cuts 

cause roughness, 

particularly on high 

traffic volume 

routes.

Improved economic 

efficiency. 

Improved urban 

aesthetics. 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Table 6-1. Summary of strategies for improving vehicle use phase fuel consumption and 

potential trade-offs (continued). 

Vehicle Fuel 

Consumption 

and Pavement 

Objective

Vehicle Fuel 

Consumption 

Sustainability 

Improving Strategy

Economic Impact Environmental 

Impact

Societal

Impact

Reduce Fuel Use 

Due to 

Macrotexture

(where impact is 

significant)

Avoid high positive 

macrotexture on routes 

with high heavy truck 

traffic volumes at slow 

speeds while 

maintaining safety. 

May result in less use of 

some low-cost 

maintenance treatments 

with high positive 

macrotexture over the life 

cycle on high-volume 

heavy truck routes.

Reduced 

environmental 

impact due to less 

fuel use on high 

traffic volume heavy 

truck routes. 

Improved economic 

efficiency, reduced 

tire wear. Potential 

for increased 

crashes due to 

reduced surface 

friction if also high 

speed traffic.

Calibrate and 

Validate Models 

for Fuel Use Due 

to Structural 

Responsiveness 

to Vehicle 

Loading (use 

them once 

research is 

completed) 

Perform research to 

calibrate and validate 

models for vehicle fuel 

use as a function of 

pavement structural 

responsiveness to 

vehicle loading. 

Calibration requires

experiments that 

characterize 

responsiveness of 

pavement sections and 

then measure fuel use

on same sections. 

Calibrated models can 

be used to determine 

where structural 

responsiveness is 

significant and develop 

appropriate strategies 

based on those results.

Calibrated models will 

permit evaluation of 

alternative structures 

considering traffic, climate 

and other variables which 

will allow consideration of 

both road user and agency 

costs versus environmental 

benefits for designs.

Optimization may 

reduce

environmental 

impact due to less 

fuel use, particularly 

on high truck traffic 

volume routes in

certain climates. 

Optimization may 

improve economic 

efficiency 

particularly on high 

truck traffic volume 

routes.

Future Directions and Emerging Trends

Highway agencies are moving towards construction smoothness specifications based on IRI for 

new pavement construction and rehabilitation and maintenance activities. The implementation 

of improved methods for quality assurance for as-built smoothness will have a great impact not 

only on pavement serviceability but also on fuel consumption. These improvements and the 

potential for maximizing the specified smoothness on high-traffic volume routes should result in 

decreases in fuel use and decreases in its associated environmental impacts.

As pavement management systems become more sophisticated, they can be used for explicit 

consideration of the timing of maintenance, rehabilitation, and reconstruction treatments to 

optimize net reductions in energy use and environmental impacts considering the pavement life 

cycle (materials production, construction, use, and end-of-life phases). Improvements in lifecycle inventories (LCI) for each of these phases are needed to improve the ability to optimize. 

Requirements in the federal transportation legislation (MAP-21) for pavement management 

systems to track the performance of pavement management decisions may help push 

implementation of this type of approach. 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Improved mechanistic-empirical models for predicting pavement smoothness over the life cycle 

of the pavement will aid in making design decisions that result in reduced vehicle fuel use. At 

the same time, improved models that consider the effects of pavement structural responsiveness 

on vehicle fuel use, and the calibration/validation of those models with experimental data, will 

provide pavement designers with better information for selecting pavement structures that reduce 

vehicle fuel use. 

Improvements in pavement deflection measurement technologies, such as rolling wheel 

deflectometers that measure deflections at highway speeds, will likely result in greater 

consideration of structural responsiveness as part of network-level monitoring. Measurement 

methods for texture using high-speed lasers (for pavements that do not have directional texture) 

and deflection using rolling wheel deflectometers (FHWA 2011a) have been developed and are 

being evaluated by a number of different state agencies. Methods for directly measuring 

pavement rolling resistance due to texture and structural responsiveness are also being developed 

(Bergiers et al. 2011; FHWA 2011a).

Tire-Pavement Noise

Background

Noise can be defined as unwanted or unpleasant 

sound. All sound is produced by vibrating objects 

and transmitted by pressure waves in a compressible 

medium such as air. Sound waves are often 

characterized in terms of amplitude (strength of the 

wave) and frequency (speed of their variation) 

(Snyder 2006). Sound pressure or sound intensity 

levels are used to quantify the loudness of an ambient 

sound. The frequencies of sound audible to humans 

range from 20 to 20,000 Hz, and sound pressures 

range from 20 micropascals (μPa), the threshold of 

hearing, to 120 pascals (Pa), the threshold of pain 

(Norton 1989). 

The broad range of sound pressures important to human noise perception (seven orders of 

magnitude) has led to the common use of a logarithmic scale for sound pressure levels (SPL), 

which is normalized to a reference standard of 2 x 10-5 Pa and has units of decibels (dB). Sound 

intensity, which is a measure of energy flow through a unit area, is also typically discussed using 

a logarithmic scale with units of Watts/m2, normalized to a reference standard of 10-12 W/m2. 

The unit of the linear sound intensity scale is also the decibel. The reference standards for SPL 

and sound intensity have been chosen to obtain the same reading in decibels regardless of 

whether SPL or sound intensity is used to define the sound wave, and irrespective of whether 

pressure or intensity in an acoustic free field is measured. Because of the logarithmic scale for 

noise, the emissions from multiple noise sources cannot be added linearly. For example, two 

noise sources, each emitting at 70 dB, produce a noise level of 73 dB, not 140 dB (Ongel et al. 

2008). Noise is usually adjusted to reflect human sensitivity, the units of which are expressed in 

terms of adjusted decibels (dBA). 

Major Issues: 

 Noise effects on humans and 

wildlife.

 Noise is partly controlled by 

pavement surface characteristics, 

but tire characteristics are typically 

more important.

 Methods available to measure tirepavement noise.

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Human perception of changes in sound energy is also non-linear. Most observers perceive an 

increase or decrease of 10 dB in the sound pressure level as doubling or halving of the sound, as 

shown in table 6-2 (FHWA 2011b). It can also be seen in the table that a change of 3 dBA is 

barely perceptible to most people. For this reason, changes in highway noise of less than 3 dBA 

are generally considered to be relatively insignificant. However, the information shown in table

6-2 is based on laboratory studies of humans listening to pure tones in a laboratory setting, such 

as in a common hearing test. Many people can hear differences in tire-pavement noise less than 

3 dBA and can perceive differences in the frequency content of two tire-pavement noise sources 

that have the same sound intensity as measured in dBA, with different sound patterns and 

frequencies of sound being more irritating than others. 

Table 6-2. Decibel changes, energy loss, and loudness (FHWA 2011b). 

Sound Level 

Change (dBA)

Change in 

Sound Energy (%)

Human 

Perception

0 0 No change

-3 50 Barely perceptible

-5 67 Readily perceptible

-10 90 50% as loud

-20 99 25% as loud

-30 99.99 12% as loud

Noise levels are also affected by the distance from the source, with near-ground sources 

spreading out over a hemispherical volume. Noise wave energy is conserved with the result that 

sound intensity variation is proportional to the square of the distance from the source as it is 

spread over a wider surface. Therefore, the sound intensity level is decreased by a factor of four 

when the distance from the source is doubled. 

Noise pollution has become an increasing concern in the U.S. and worldwide. Highway noise 

affects people in adjacent residences and businesses as well as people in vehicles; road noise 

effects on wildlife have also been identified (Clevenger et al. 2002). Various health and quality 

of life effects on humans from noise pollution have been identified by the World Health 

Organization (WHO 2013). Although somewhat controversial, attempts have been made to 

calculate the economic consequences of noise (Berglund, Lindvall, and Schvela 2000). 

Public awareness of road noise has increased over the past 40 years and most industrialized 

countries have introduced noise emission regulations. In the U.S., regulations have been 

developed by the FHWA and other agencies for dealing with highway noise. For example, as 

required by the Federal-Aid Highway Act of 1970, the FHWA developed Regulation 23 CFR 

772, Procedures for Abatement of Highway Traffic Noise and Construction Noise, which applies 

to highway construction projects where a DOT has requested federal funding for participation in 

the project. The regulation requires the highway agency to investigate traffic noise impacts in 

areas adjacent to federal-aid highways for proposed construction of a highway on a new location 

or for the reconstruction of an existing highway to either significantly change the horizontal or 

vertical alignment or increase the number of through-traffic lanes (FHWA 2013). 

The FHWA states that effective control of undesirable highway traffic noise requires a three-part 

approach: noise compatible planning, source control, and highway project noise mitigation 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

(FHWA 2013). If the highway agency identifies impacts, it must consider abatement and must 

incorporate all feasible and reasonable noise abatement measures into the project design. FHWA 

cannot approve the plans and specifications for a federal-aid highway project unless the project 

includes adequate noise abatement measures to comply with the standards (FHWA 2013). 

Modeling of noise level contours around a highway project is performed using the FHWA 

Traffic Noise Model (TNM) (see www.fhwa.dot.gov/environment/noise/traffic_noise_model/). 

The TNM has the capability to consider different pavement types when modeling noise, although 

an assumed pavement type has typically been used in practice. 

The regulations contain noise abatement criteria, which represent the upper limit of acceptable 

highway traffic noise for different types of land uses and human activities, as presented in table

6-3 (FHWA 2011b). The regulations do not require meeting the abatement criteria in every 

instance, but instead require the agency to make every reasonable and feasible effort to provide 

noise mitigation when the criteria are approached or exceeded. Abatement typically consists of 

noise barriers (sound walls), although other measures are also included. Quieter pavement 

surfaces are not considered adequate for abatement because the long-term performance of many

of those surfaces has not yet been fully demonstrated, and there is the possibility that surfaces 

will not retain their low-noise characteristics if they are not sufficiently maintained. 

Table 6-3. FHWA noise abatement criteria in dBA (hourly A-weighted sound level)

(FHWA 2011b). 

Activity Category NAC, Leq(h)* Description of Activity Category

A 57 (exterior) Lands on which serenity and quiet are of extraordinary 

significance and serve an important public need and where 

the preservation of those qualities is essential if the area is to 

continue to serve its intended purpose.

B 67 (exterior) Residential

C 67 (exterior) Active sport areas, amphitheaters, auditoriums, campgrounds, 

cemeteries, day care centers, hospitals, libraries, medical 

facilities, parks, picnic areas, places of worship, playgrounds, 

public meeting rooms, public or nonprofit institutional 

structures, radio studios, recording studios, recreation areas, 

Section 4(f) sites, schools, television studios, trails, and trail 

crossings

D 52 (interior) Auditoriums, day care centers, hospitals, libraries, medical 

facilities, places of worship, public meeting rooms, public or 

nonprofit institutional structures, radio studios, recording 

studios, schools, and television studios

E 72 (exterior) Hotels, motels, offices, restaurants/bars, and other developed 

lands, properties or activities not included in A-D or F.

F - Agriculture, airports, bus yards, emergency services, 

industrial, logging, maintenance facilities, manufacturing, 

mining, rail yards, retail facilities, shipyards, utilities (water 

resources, water treatment, electrical), and warehousing

G - Undeveloped lands that are not permitted for development

* Leq(h) is the sound pressure averaged over 1 hour.

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Highway noise generated by passing vehicles comes from three sources: air passing over and 

around the vehicle (aerodynamic noise); the operation of the engine, exhaust, and drive train 

system (propulsion noise); and several mechanisms occurring as the tire passes over the 

pavement (tire-pavement noise) (Nelson and Phillips 1997; Sandberg 2001). As shown in figure 

6-4, for passenger cars the tire-pavement noise dominates over propulsion noise at speeds above 

20 to 30 mi/hr (30 to 50 km/hr), while at lower speeds the propulsion predominates. For heavyduty trucks, it was found that propulsion noise dominates during acceleration from 0 to 50 mi/hr 

(0 to 80 km/hr), but tire-pavement noise dominates for all driving conditions above 50 mi/hr (80 

km/hr) (Rasmussen et al. 2008). Tire-pavement noise depends on pavement surface 

characteristics, vehicle speed, environmental conditions, type of tire, and the dynamics of the 

rolling process (McDaniel and Thornton 2005). The tire-pavement noise level increases 

logarithmically with increasing speed (Sandberg 2001). 

Figure 6-4. Estimate of light vehicle noise due to tire-pavement noise, powertrain noise, and 

aerodynamic noise at cruise speed (Rasmussen et al. 2008). 

6-22

Noise at the side of the road from all of these sources is primarily measured via pass-by methods. 

Pass-by measurements can either be made with individual vehicles, which is referred to as the 

Controlled-Pass-By (CPB) method, or by measuring the total noise from all of the vehicles in 

mixed flow, which is referred to as the Statistical-Pass-By method (SPB) (ISO 1997). Noise

measured using pass-by methods is the parameter of concern for modeling and decision making 

regarding the need for noise mitigation. However, such testing requires one or more days to 

conduct, is difficult and expensive to perform because it requires placement of microphones at 

different heights and at different distances from the edge of the road, and only provides 

measurements for small numbers of locations where this detailed arrangement can be installed. 

Two test methods have been developed that permit continuous noise measurements along a 

roadway at highway speeds and also focus on the tire-pavement noise alone (which can be 

addressed through pavement design and management). The first method is called the Close 

Proximity method (CPX), which uses the equipment shown in figure 6-5. The CPX method 

involves the use of directional microphones inside of an acoustically insulated enclosed space 

built on a trailer that is towed behind the vehicle. This device is primarily used in Europe. 
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Figure 6-5. Close Proximity (CPX) test trailer (Bendtsen and Thomsen 2008). 

The second method is called the On-Board Sound Intensity (OBSI) method, and is illustrated in 

figure 6-6. This method was developed in the U.S. based on technology originally developed by 

General Motors Corporation and recently introduced into the pavement community (Donavan 

and Lodico 2009). OBSI measurement involves the use of directional microphones placed at the 

leading and trailing edges of the tire-pavement contact patch, just above the pavement, and is 

performed in accordance with AASHTO TP-76-09. Comparisons between the OBSI and CPX 

methods have been performed, and show that they have similar sensitivity to pavement 

characteristics (Donavan 2006). The OBSI is primarily used in the U.S. because the equipment 

is mounted on the vehicle and it does not require the use of a trailer as does the CPX method. 

Figure 6-6. On-Board Sound Intensity (OBSI) setup (photo courtesy of John Harvey). 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Tire tread characteristics are major determiners of tire-pavement noise, and standard tirepavement noise testing should include careful control of tire type and condition (Donavan and 

Lodico 2009; Lu, Wu, and Harvey 2011). A special type of test tire has been developed for 

pavement testing and other purposes called the Standard Reference Test Tire (SRTT). 

Comparisons have been made between OBSI and CPB noise levels (with the CPB testing 

performed using automobiles equipped with the SRTT), and the resulting correlations have been 

good, as shown in figure 6-7 (Donavan and Lodico 2009). 

Figure 6-7. Controlled vehicle pass-by levels at 25 ft (7.6 m) versus OBSI level for the SRTT at 

all test sites and speeds—normalized data (Donavan and Lodico 2009). 

6-24

Nelson and Phillips (1997) have further separated the phenomenon of tire-pavement noise into 

different mechanisms, as summarized below by Ongel et al. (2008): 

• Tire tread/road surface impacts. This component of tire-pavement noise results from 

vibrations that occur as the tire tread initially contacts the pavement surface, and again as 

the tire tread breaks contact with the pavement surface and returns to its normal radius, 

which is referred to as “block snap out” (Bergmann 1980). These vibrations are 

transmitted through the tire, and from the tire to the air, creating noise. The flattening of 

the tire in the contact patch is resisted by friction between the tire and the pavement, 

which can also vibrate the tire when there is slip. The generation of vibrations on a 

rolling tire is dependent on the design of the tire tread, the macrotexture of the pavement 

(see figure 6-2, usually expressed in terms of MPD), and frictional adhesion between the 

tire and the pavement surface (Sandberg and Descornet 1980; Kropp 1992). In addition, 

Sandberg and Descornet (1980) suggested that stiffer pavements (concrete or asphalt) 

may generate more noise, which has also been advanced by Biligiri and Kaloush (2010). 

However, Beckenbauer and Kuijpers (2001) did not find that to be true, and Ongel et al. 

(2008) also disputed that hypothesis after accounting for other explanatory factors when 

comparing softer rubberized and stiffer conventional asphalt mixtures. 
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

The noise generated due to the vibration of the tire tends to occur at frequencies up to 

1,000 Hz (Nelson and Phillips 1997; Morgan, Nelson, and Steven 2003; Van Keulen and 

Duškov 2005), with the frequency of vibrations increasing as the tire rotation speed or the 

block tread length decreases. This phenomenon occurs because the tire acts as a lowfrequency band-pass filter, attenuating the noise radiation at higher frequencies. Tire 

vibration is also increased as the tire tread pattern becomes more aggressive with deeper 

channels and larger lugs (or blocks) that are further apart. 

• Aerodynamic processes between the tire and the road surface. Noise is generated by 

various mechanisms that occur as air moves in the contact patch. The most important of 

these mechanisms is called “air pumping,” which is the sudden expelling of air that is 

trapped in the tread grooves or pavement texture due to the reduced groove volume when 

the tire makes contact with the road surface, and the sudden suction of air when the tire 

leaves the contact patch (Hayden 1971). The air-pumping mechanism may cause 

significant levels of noise in the frequency range above 1,000 Hz. Noise due to air 

pumping can be reduced by providing the air with more and larger pathways to move 

under the tire and through the pavement (Sandberg and Descornet 1980; Petterson 1988; 

Kropp 1992). These pathways can be provided by space between the stones due to 

macrotexture from stones on the surface, texturing of the surface (particularly concrete), 

and increasing the air permeability of the surface (particularly asphalt). 

• Adhesion mechanisms. These mechanisms are caused by tire vibrations associated with 

the frictional forces that develop at the contact patch between the tire and the pavement 

surface (Nelson and Phillips 1997). The tire flattens at the contact path, causing 

tangential forces due to the changing radial deflections. These forces are resisted by the 

friction between the pavement surface and the stiffness of the tire, and the remaining 

forces are dissipated by the slip of the tread over the pavement surface. Friction between 

the tread and the pavement has two components: adhesion and hysteresis. The adhesion 

component is governed by microtexture of the surface, and the hysteresis component is 

largely controlled by macrotexture. Adhesion involves the formation and breaking of 

bonds at the contact patch followed by the hysteresis component of friction. This 

process, known as slip/stick, occurs at the contact patch and excites the tire vibration. 

Noise-generation mechanisms are illustrated in figure 6-8. These general effects of the tire 

vibration and air pumping mechanisms are shown in figure 6-9 on a plot of OBSI measurements 

from a set of asphalt sections with the frequencies divided into 1/3 octave bands. 

The mechanisms discussed above all assume that the pavement is dry. Phillips (2002) measured 

noise on wet surfaces and found an increase in the noise levels and also that the noise is 

dominated by the tire and pavement interacting with the water under wet conditions. 

Macrotexture can be divided into two types: negative and positive texture. Positive 

macrotexture occurs when the texture is dominated by protrusions above the mean surface, while 

negative macrotexture occurs when the texture is dominated by indentations below the mean 

surface. From this discussion, it can be seen that positive macrotexture increases surface impact 

(tire vibration) mechanisms while at the same time increasing the air passages that reduces the 

noise at higher frequencies caused by aerodynamic processes (air pumping). Negative texture 

does not necessarily produce tire vibration. 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Figure 6-8. Noise-generation mechanisms on dry pavement (Olek, Weiss, and Garcia-Villarreal 2004).

Figure 6-9. Example plot of one-third octave frequency content for several asphalt mixtures and 

influence of tire-pavement noise mechanisms (Ongel et al. 2008). 

6-26

Asphalt pavements that have higher positive macrotexture include open-graded mixtures

(especially those with larger maximum stone sizes), raveled dense-graded mixtures, and chip 

seals (again, particularly those with larger stones) (Rezaei, Harvey, and Lu 2012). The surface 

labeled “older than 4 years OGAC” in figure 6-9 is an open-graded asphalt concrete mixture that 

has raveling. 

Pavement surfaces that can provide and maintain both negative macrotexture and air 

permeability are likely to reduce tire-pavement noise at the lower and higher frequencies, 
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

respectively (Bendtsen and Thomsen 2008; Lu and Harvey 2011; Ongel et al. 2008). Some 

asphalt surface examples include open-graded friction courses that have good raveling resistance 

(such as the rubberized open-graded asphalt concrete labeled “1-4 years old RAC-O” in figure 

6-9) and some SMA mixtures (Donavan 2006). In addition to raveling resistance, open-graded 

asphalt surfaces also need to maintain surface air permeability to exhibit their high frequency 

noise reducing properties. Surface air permeability is more important than average air void 

content in noise-reducing asphalt mixtures (Reyes and Harvey 2011; Ongel et al. 2008). Surface 

permeability in the wheelpaths tends to diminish with time because of filling of the surface with 

mineral particles, oil, and tire rubber, as well as the additional compaction caused by trafficking. 

The durability of noise benefits for asphalt surface mixtures will depend on their raveling and air 

permeability performance. As an example, the average life of noise benefits (defined as a 2 dBA 

or greater overall OBSI reduction compared to a standard, dense-graded asphalt) for rubberized 

open-graded asphalt concrete in California is about 10 years over a range of traffic levels and 

climate regions, which was found to be longer than for conventional open-graded mixes which 

raveled at a faster rate (Lu and Harvey 2011). The Arizona DOT has reported noise benefits for 

high-binder content rubberized open-graded mixtures lasting approximately 8 years on freeways 

in the Phoenix area (Scofield and Donovan 2003). 

As previously described, new concrete pavements can be constructed with a number of different 

surface textures, including transverse tining, longitudinal tining, broom drag, burlap drag, and 

turf drag. Diamond grinding or diamond grooving can also be performed at the time of 

construction or as a later rehabilitation or preservation measure. Of these surfaces, diamond 

grinding and diamond grooving have been found to be the quietest, followed by longitudinal 

tining. Transverse tining is generally the noisiest type of texture, as shown in figure 6-10, 

although there can be a fairly wide tire-pavement noise distributions within each texture type 

(Rasmussen et al. 2012; Rezaei and Harvey 2012). Transverse tining can produce a “whine” 

(tonal spike) in the middle of the frequency spectrum, at about 1000 to 1500 Hz, with the 

frequency at which the spike occurs being a function of both the tine spacing and the speed at 

which the vehicle tires are passing over them (ACPA 2006). 

Longitudinal tining of concrete pavement surfaces is being more commonly used by highway 

agencies. The noise levels of longitudinal tining and other texture types depends in part on the 

amount of positive texture that they produce, and the shape and depth of the negative texture that 

allows air to escape from under the tire. If there is loss of mortar around the coarse aggregates in 

the concrete pavement surface, it can create positive macrotexture similar to that caused by 

raveling of asphalt surfaces, with associated increases in noise. 

In addition to surface texture, other factors can also make major contributions to tire-pavement 

noise. For asphalt pavements, weathering/raveling of the surface increases noise levels through 

the creation of positive macrotexture. For concrete pavements, wide, deep sawed joints (those 

with high cross-sectional area) increase noise levels due to a “flute” effect (Donavan 2009), 

while transverse joint faulting causes a thumping noise as the tire passes over the joint (Kohler

and Harvey 2010). Transverse cracks due to low temperatures or shrinkage due to aging 

(sometimes showing as block cracking) cause similar thumping in asphalt pavements, especially 

when there is collapse of the edges of the crack, or when the edges of the crack are “tented” up. 

For both asphalt and concrete pavement, overbanding of sealant over joints or cracks produces 

positive texture that can increase noise. 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

 

Figure 6-10. Normalized distributions of OBSI noise levels for conventional concrete 

pavement textures (Rasmussen et al. 2012).

The combined effects of faulting, sealing, and joint cross-sectional area can increase overall tirepavement noise levels, and together are referred to as “joint slap” on concrete pavement (IGGA 

2011). The magnitude of noise generated by joint slap can be estimated using a web tool (ACPA 

2013) that considers joint geometry, existing pavement texture noise level, and vehicle speed 

using data from the Purdue University Tire Pavement Test Apparatus in the laboratory with some 

field validation at the MnROAD test track in Minnesota (ACPA 2007). Spalling of joints and 

cracks in all pavement types is also expected to increase noise levels. 

Narrow joints and control of faulting in concrete pavement, good sealing practice (no 

overbanding), and good pavement preservation practices that minimize the extent and severity of 

cracking for both asphalt and concrete pavement will help maintain quieter pavements. Diamond 

grinding for concrete pavement and thin overlays (using durable polymer-modified or rubberized 

open-graded asphalt or SMA) for asphalt pavement are preservation treatments particularly 

suited to maintaining quiet pavements. 

Innovative pavement surfaces are being developed based on studies indicating that negative 

macrotexture and paths that allow air to escape result in quieter pavements. For concrete 

pavement, laboratory investigations led to the development of the Next Generation Concrete 

Surface (NGCS), which features flush grinding (to minimize positive texture and remove

faulting and old texture) and grooving (to provide passages for air and water) (Dare et al. 2009). 

These surfaces are under investigation in several states (Wilde and Izevbekhai 2010; Guada et al. 

2013) and show some promise based on early performance, with noise levels below those of 

conventional diamond grinding. It has been observed that the NGCS is susceptible to 

accelerated wear under the action of studded tires/chains and therefore should not be used under 

such conditions (Anderson et al. 2014). 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Figure 6-11a shows the frequency content of an example test section in three conditions: before 

treatment (designated as PreCDG [pre-conventional diamond grinding]), after treatment 

(designated as CDG [conventional diamond grinding]), and after flush grinding and grooving 

(designated as GnG (grinding and grooving, an NGCS texture). Figures 6-11b and 6-11c 

illustrate the surface textures corresponding to the CDG and NGCS treatments, respectively. 

Figure 6-11 (a). Frequency content of OBSI measured at 60 mi/hr (97 km/hr) for pretreatment 

(PreCDG), conventional diamond grinding (CDG), and NGCS (GnG in the figure) for a 

California test section, Yolo 113– PM R0.5/R2.5 (Guada et al. 2013). 

Figure 6.11 (b). Conventional diamond-ground surface showing “fins” that are eventually removed 

by traffic (Guada et al. 2013) (c). Conventional diamond-ground surface with the Next Generation 

Concrete Surface showing definition of “land area” between grooves (Guada et al. 2013). 

6-29

Field measurements and laboratory work have led to the development of asphalt mixtures with 

smaller maximum aggregate sizes (passing # 4 [4.25 mm] sieve) and open gradations and air-void 

contents of 15 percent or more to provide air permeability. Although these have not been tested 

under high-speed traffic, preliminary laboratory testing (Lu and Harvey 2011; Wu et al. 2013) 

indicates improved raveling performance and high frequency tire-pavement noise performance 

compared with larger stone size mixtures (see figure 6-12a) and low-speed OBSI results on a test 

section indicate improved initial noise performance (see figure 6-12b). 
Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Figure 6-12 (a). Examples of residual specimens after Cantabro testing for raveling of the same 

OGFC mixtures (Wu et al. 2013). Each original specimen had a diameter of 4 inches (100 mm). 

Figure 6-12 (b). Frequency content of OBSI measured at 35 mi/hr (56 km/hr) for Caltrans opengraded asphalt mixtures with typical 0.375 inch (9.5 mm) and #4 (4.75 mm) maximum aggregate 

sizes (Wu et al. 2013).

The Arizona DOT is currently involved in a Quiet Pavement Pilot Program (QPPP) in 

partnership with the FHWA. Several other states have Quieter Pavement Research (QPR) efforts 

underway that are producing research results such as those shown in this chapter, including 

California, Colorado, Florida, Texas, Virginia, and Washington (FHWA 2011c). 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Strategies for Improving Sustainability

Practices that are available to pavement managers, designers, and specification developers that 

might be used to address tire-pavement noise are summarized in table 6-4. 

Table 6-4. Summary of strategies for improving tire-pavement noise and potential trade-offs.

Tire-Pavement 

Noise Objective

Tire-Pavement Noise 

Improving Strategy Economic Impact Environmental Impact Societal Impact

Reduce Noise on 

New and Existing 

Asphalt 

Pavements

Use durable open-graded 

or SMA mixtures

Open-graded mixtures

generally have shorter 

lives than dense graded 

mixtures. SMA 

mixtures are more 

expensive than dense 

graded. Life-cycle cost 

analysis can be 

performed.

Quieter pavement 

benefit. Trade-offs 

depend on surface 

mixture impact and 

longevity. Can be 

calculated with 

LCA.

Quieter pavement 

improves the 

livability of 

neighborhoods near 

highways. Can 

potentially reduce 

stress on wildlife.

Reduce Noise on 

New Concrete 

Pavement

Eliminate transverse 

tining by using 

longitudinal textures; use 

quieter textures; use 

narrow (single-saw cut 

width) joints with 

recessed sealant if 

sealant is used.

Depends on alternative 

texture used. Generally 

very small cost 

compared to 

construction cost.

Quieter pavement 

benefit. Trade-offs 

depend on surface 

texture and 

longevity. Texturing 

generally low 

impact. Can be

calculated with 

LCA. 

Quieter pavement 

improves the 

livability of 

neighborhoods near 

highways. Can 

potentially reduce 

stress on wildlife. 

Must have adequate 

surface friction.

Reduce Noise on 

Existing Concrete 

Pavement

Retexture with 

conventional diamond 

grinding or NGCS

Relatively low cost 

treatment that also 

improves smoothness

and removes faulting. 

Increased cost 

compared to Do 

Nothing.

Quieter pavement 

benefit. Trade-offs 

depend on surface 

texture and 

longevity. Texturing 

generally low 

impact. Can be 

calculated with 

LCA. 

Quieter pavement 

improves the 

livability of 

neighborhoods near 

highways. Can 

potentially reduce 

stress on wildlife. 

Must have adequate 

surface friction.

Minimize Noise on 

Existing Pavement

Perform pavement 

preservation to minimize 

cracking, faulting and 

other surface 

imperfections that 

contribute to noise; use 

good practice for sealing 

to prevent overbanding

Can also reduce lifecycle costQuieter pavement 

benefit. Impact 

depends on traffic 

and interaction of

smoothness and 

vehicle use. Can be 

calculated with 

LCA. 

Quieter pavement 

improves the 

livability of 

neighborhoods near 

highways. Can 

potentially reduce 

stress on wildlife. 

Must have adequate 

surface friction.

Future Directions and Emerging Trends

The most important emerging trend in this area is the greater attention being paid to tirepavement noise, and the increased consideration of pavement effects on highway noise in 

planning, traffic noise modeling, and pavement maintenance and rehabilitation design decisions. 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Important future directions include the development of new materials and surface textures for 

concrete and asphalt that reduce noise while maintaining adequate surface friction, and the 

potential to set performance requirements for tire-pavement noise measured with OBSI for new 

construction and during long-term maintenance contracts.

Addressing Stormwater Runoff through Pavement Permeable Surfaces 

Background

Conventional paved pavement surfaces are 

relatively impermeable, allowing precipitation to 

run off much faster than it does from vegetated or 

undeveloped surfaces. In addition, runoff from 

impermeable surfaces is often directed to 

stormwater collection systems and thus is not 

absorbed into the nearby soil. That runoff, because 

it does not benefit from being naturally filtered 

through the soil, can pollute and raise the 

temperature of the nearby surface waters and 

streams to which it is being diverted. Furthermore, 

the collection of runoff in this manner during high 

precipitation events can cause stormwater collection 

systems to overflow, potentially resulting in

flooding and erosion because of the speed with 

which the runoff leaves the paved surface. In cases where the stormwater collection system is 

combined with the sanitary sewage system, the release of raw sewage may occur as the result of 

the system being overwhelmed during high precipitation events, causing significant 

environmental and economic impact for treatment and clean up. Finally, typical stormwater 

management solutions, including the reliance on retention ponds, are difficult to accommodate in 

areas with space constraints (such as built-up urban areas); consequently, innovative solutions to 

reducing road surface runoff are needed. 

Research has shown that pavement materials themselves do not significantly contribute 

pollutants to stormwater runoff. Laboratory experiments on a range of concrete and asphalt 

pavements, including open- and dense-graded materials and different cement- and asphalt-binder 

sources (including asphalt rubber and aged specimens), showed that pollutant contributions to 

runoff were generally extremely low (Kayhanian et al. 2009; Kayhanian et al. 2010). From the 

laboratory study performed by Kayhanian et al. (2010) it was concluded that the major sources of 

pollutants measured from road surface runoff are mostly associated with vehicles and airborne 

deposition. One pollutant of concern in runoff is polyaromatic hydrocarbons (PAHs). These 

toxic compounds, which are primarily related to the combustion of transportation fuels and are 

deposited on the pavement surface through vehicle exhaust, are present at low concentrations in 

urban and highway runoff (Lau, Kayhanian, and Stenstrom 2005; Kang et al. 2009). It is 

important to note that large concentration of PAHs are reported in coal tar sealant and if these are 

used on a pavement then high PAH concentrations in the surface runoff would be expected (Van 

Metre and Mahler 2010; USGS 2011). However, the use of coal tar pitch or tar sealant are 

mostly isolated to residential driveways and parking lots in some regions of the U.S. and are 

rarely used on pavements for urban roads or highways. 

Major Issues: 

 Permeable surfaces may help 

economically handle stormwater 

quality and runoff rates.

 Currently best suited for low-speed, 

low-volume roadways and parking 

areas.

 Requires more frequent cleaning and 

maintenance.

 Due to runoff drained through 

permeable surfaces, groundwater 

sources may be contaminated.

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Another pollutant of concern is metals. The laboratory study by Kayhanian et al. (2009; 2010) 

found amounts of toxic metal above the reporting limits in simulated runoff on a few of the 

concrete mixtures tested, which was attributed to the cement sources used. Additional 

information related to the type and concentration of different organic and inorganic pollutants 

observed from highway runoff can be obtained from a recent review article prepared by 

Kayhanian et al. (2012b). 

Thin open-graded surfaces placed on otherwise impermeable pavements, such as thin opengraded asphalt surfacing, can help slow runoff and capture solids and pollutants, improving the 

quality of stormwater runoff (Pagotto, Legret, and Le Cloirec 2000; Barrett and Shaw 2007). 

An innovative solution to actually reducing or eliminating runoff is through the use of fully 

permeable pavements, which were introduced in chapter 3. As described in chapter 3, permeable 

pavements can be constructed using pervious concrete, porous asphalt, or permeable interlocking 

pavers. Vegetated pavements have also been used effectively for low-volume traffic 

applications, most prominently as parking lots. All of these pavements types allow major 

portions of the stormwater runoff to pass through the surface and be absorbed into the underlying 

ground. This has the advantages of minimizing or eliminating the need for a stormwater 

collection system, recharging the groundwater table, filtering the runoff naturally through the 

soil, and reducing the direct discharge of runoff and any contaminants associated with them into 

nearby surface water. These applications can potentially be applied to the traveled way of the 

pavement, to the shoulders or strips of pavement outside the traveled way, or to parking areas. 

Pervious concrete and porous asphalt pavements (see figure 6-13) are created by greatly reducing 

the fine aggregate fraction in a mixture, increasing the percentage of void space. In the case of 

interlocking permeable pavers (figure 6-14), void space is often created at the gaps between the 

pavers, and these voids are filled with permeable aggregate. For porous asphalt, the same 

mixtures used for thin surface open-graded layers can also be used for fully permeable 

pavements. With the increase in void space, rainwater can drain through the surface into a 

base/storage layer designed for hydraulic performance to retain the design rainfall, from where it 

seeps into the ground reducing the amount of runoff while recharging the groundwater. The 

natural filtering that occurs in the soil removes the majority of particle-bound inorganic and 

organic contaminates, but there may be an increased risk of groundwater contamination from 

regulated dissolved pollutants and thus it is not recommended to construct permeable pavements 

in locations near drinking groundwater supplies (EPA 1999). 

Figure 6-13. Pervious concrete (left, courtesy John Kevern) and porous asphalt (right, courtesy 

National Asphalt Pavement Association).

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Figure 6-14. Permeable interlocking concrete pavers (courtesy Interlocking Concrete Pavement 

Institute).

Another permeable pavement solution is the use of vegetated pavement. Vegetated pavements, an 

example of which is shown in figure 6-15, use a lattice of concrete, plastic, or metal to provide 

stability while vegetation is encouraged to grow between the lattices. The vegetation allows for a 

more natural infiltration of stormwater runoff and also can provide a more visually appealing 

surface compared to hard surfaces. Vegetated pavements can have comparable load-carrying 

capacity to conventional pavements, but are typically used in low-traffic conditions such as alleys, 

parking lots, residential streets, and trails in order to minimize damage to the vegetation. Also, 

they are best suited to climates with adequate summer moisture to keep the vegetation alive (EPA 

2008). 

Figure 6-15. Vegetated pavement (photo courtesy of Soil Retention Products, Inc.). 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Water that passes through the pavement surface and is stored below the surface can also reduce 

pavement temperatures by means of evapotranspiration, where the heat that is stored in the 

pavement is released through the conversion of the stored water into water vapor. There is also 

significantly more surface area associated with the increased void space and thus the increased 

exposure to air increases the heat conductivity of the pavement. Consequently, permeable 

pavements (whether pervious concrete, porous asphalt, permeable interlocking pavers, or 

vegetated pavements) can be used in urban areas to help alleviate the need for other stormwater

management devices such as retention ponds, sand filters, and swales (PCA 2011). 

At the present time, the EPA (2010b) cites the use of pervious concrete and porous asphalt 

pavements as a Best Management Practice (BMP) for handling stormwater runoff on a local and 

regional basis. The majority of current pervious concrete and porous asphalt pavements are used 

as BMP in low-traffic, low-speed applications, such as shoulders or parking lots. When using 

these types of pavements, they need to be regularly maintained (typically using vacuum cleaning 

machines with no sweeping) in order to ensure continuous infiltration with no or minimum 

surface overflow. Surface infiltration can be measured through permeability measurements. In 

one recent study, the surface permeability of 20 pervious concrete and porous asphalt parking 

lots were measured in California and the results showed a large variability within each parking 

lot and among all parking lots, although localized impermeability did not affect the overall 

drainage of the facilities (Kayhanian et al. 2012a). The permeability value was directly related to 

the age of pavement as the older pavements had lower infiltration rates. The lower permeability 

in older permeable pavements was suspected to be impacted by particles from atmospheric 

deposition or from surrounding area soil erosion. Some densification under truck loads at hot 

temperatures may have contributed to reduced permeability in the porous asphalt materials in 

addition to clogging. 

A similar study was performed on 40 permeable pavement sites in North Carolina, Maryland, 

Virginia, and Delaware (Bean et al. 2007). Again, localized low permeability was observed but 

often it did not hinder the overall performance of the facility as long as there was also localized 

areas with high permeability. In another study on open-graded asphalt under accelerated 

pavement testing, the addition of particles on the pavement surface was found to be partially 

responsible for surface void and permeability reductions; however, most of the void and 

permeability reduction was due to densification and rutting under loading (Coleri et al. 2013). 

The use of permeable pavement for stormwater runoff management may not necessarily be 

limited to parking lots and other low-traffic or low-speed facilities. Preliminary research, 

although not yet validated by field sections or accelerated pavement testing, indicates that it may 

be possible to design and construct permeable pavements for the highway environment. For 

example, one innovative approach on a high-speed or high-volume roadway is to retrofit the 

shoulders of the impermeable pavement with a permeable pavement to capture the runoff from 

the impermeable mainline pavement. The technical feasibility of this design concept was 

recently simulated by researchers and the results of both structural and hydraulic performance 

simulations are reported by Li, Harvey, and Jones (2012) and by Chai et al. (2012), respectively. 

Extended periods of saturation of moisture-sensitive subgrade soils is a major concern for the 

design of permeable pavements to carry heavy loads. The simulation results indicated that thick 

layers of crushed permeable aggregate are needed to reduce shear stresses to acceptable levels at 

the surface of saturated clay subgrades.

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

One critical design consideration is that care must be taken to prevent water stored in the fully 

permeable shoulder from infiltrating back into the pavement layers and the subgrade of the 

adjacent impermeable pavement. Several example designs of permeable pavements for highway 

shoulder retrofits were proposed and simulated (and not yet validated by field or accelerated 

pavement testing sections) under heavy truck traffic at low to medium speeds and found to be 

technically feasible (Li, Harvey and Jones 2012). The study recommends that test sections be 

evaluated using APT or in actual field trials. The use of a full-depth permeable shoulder retrofit 

for highways was also recently investigated as part of an NCHRP project (Hein et al. 2013). As 

part of that study, several conceptual designs are proposed (not validated) and recommended for 

further investigation and verification under pilot and field conditions. 

In addition to the benefit gained for stormwater management, other added benefits regarding the 

use of both porous asphalt surfaces and fully permeable asphalt, concrete, and paver pavements 

are improved surface friction and safety during rainstorms due to the open-graded surface. There 

may be noise benefits as well, although only open-graded asphalt materials have been evaluated 

for noise performance and the noise performance of pervious concrete and permeable 

interlocking pavers has not been evaluated. There are also reported water quality benefits from 

the use of various kinds of permeable pavements (Barrett, Kearfott, and Malina 2006; Bean, 

Hunt, and Bidelspach 2007; Brattebo and Booth 2003; Roseen et al. 2012; Sansalone, Kuang, 

and Ranieri 2008). In addition, Roseen et al. (2012) reported that lower salt application is 

required for the porous asphalt pavements investigated and no adverse freeze-thaw effects were

observed in cold climates; for that reason, the life span of porous asphalt is expected to exceed 

that of typical pavement applications in cold climates. The concern about freeze-thaw resistance 

is also often raised for permeable concrete pavements, but testing and performance has shown 

mixtures with good freeze-thaw performance can be achieved through the proper fine aggregate 

grading, coarse aggregate absorptivity, and possible use of fibers (Kevern et al. 2008; Kevern et 

al. 2010). Freeze-thaw deterioration would generally not be expected to be a concern for 

permeable paver pavements unless the pavers themselves have high permeability.

There are a number of trade-offs to evaluate when considering the use of permeable pavements, 

including the potential for clogging, the additional cost of construction and cleaning, and 

potential moisture damage. The cost consideration is related to the underlying permeable 

aggregate layer used as the reservoir that causes the pavements to be more expensive than 

conventional pavement construction. This increased cost can often be overcome when 

considering the value of the land that would be needed for use as a retention basin (or other 

stormwater management requirements) (NAPA 2008). Another consideration is the maintenance 

of the permeable surface, which typically consists of vacuum sweeping and is essential to 

prevent dust and other particle matter from clogging the surface and rendering the pavement 

ineffective (Levine 2011). However, a preliminary analysis of life-cycle costs indicated that a 

full-depth permeable shoulder retrofit for highways is economically justifiable for stormwater 

management compared to conventional BMPs (Jones et al. 2010). In addition, a study performed 

by Houle et al. (2013) concluded that low impact development (LID) systems (including 

permeable pavements) generally have lower marginal maintenance burdens as measured by cost 

and personnel hours when compared to conventional treatment systems. 

Care must be taken in the design of permeable pavements, particularly asphalt pavements, to 

minimize long-term saturation that would otherwise weaken the surface layers; however, water 

draining through these layers should not cause problems. Therefore, hydraulic design should 

aim to keep the water level in the pavement below the surface layers most of the time. The use 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

of rubber-modified or polymer-modified binders and anti-stripping additives may help extend the 

life of open-graded asphalt mixtures. A study performed by Liu and Cao (2009) demonstrated 

that permeable pavement mixtures with typical neat asphalt were prone to be seriously damaged 

by water, whereas high-viscosity binders demonstrated better resistance to moisture damage, 

rutting, and raveling. 

Strategies for Improving Sustainability

Practices available to pavement managers, designers, and specification developers that can be 

used to address stormwater runoff issues are provided in table 6-5. 

Table 6-5. Summary of strategies to address stormwater runoff issues and potential trade-offs.

Stormwater Runoff 

Objective

Stormwater 

Runoff Improving 

Practices

Economic Impact Environmental 

Impact Societal Impact

Increase Structural 

Capacity for 

Application in 

Pervious concrete.

Porous asphalt. 

Increased initial cost 

over comparable 

impermeable concrete 

and asphalt. Cost of 

handling and treating 

stormwater may be less 

than other BMP.

Improved 

stormwater quality. 

Impact on other 

impact categories 

has not been 

evaluated.

Uncertain.

High-Speed, HighLoad Areas. Permeable pavers. Not applicable for highspeed applications.Not applicable for 

high-speed 

applications.

Not applicable for 

high-speed 

applications.

Vegetated 

pavement.

Not applicable for highspeed applications.

Not applicable for 

high-speed 

applications.

Not applicable for 

high-speed 

applications.

Create Lower 

Maintenance 

Permeable 

Pavement Surfaces.

Pervious concrete. 

Porous asphalt.

Permeable pavers.

Research is still 

underway to develop 

improved durability 

without sacrificing 

hydraulic performance, 

and to develop better 

structural designs. 

Trade-offs between 

initial and life-cycle 

costs to be determined.

Longer life 

pavement designs 

should reduce 

environmental 

impact of materials 

production and 

construction.

Longer life 

pavement designs 

should improve 

societal impact of 

repeated 

construction.

Vegetated 

pavement.

Improved designs for 

vegetation selection and 

management should 

reduce economic, 

environmental (water 

use) and societal 

impacts.

Improved designs 

for vegetation 

selection and 

management should 

reduce economic, 

environmental 

(water use) and 

societal impacts.

Improved designs 

for vegetation 

selection and 

management should 

reduce economic, 

environmental 

(water use) and 

societal impacts.

Understand the 

Potential for 

Ground-water 

Contamination.

All permeable 

pavement types.

Investment required in 

research to determine 

level of risk and 

mitigation approaches, 

although initial results 

positive.

Uncertain. Once 

the level of risk is 

fully assessed it can 

be weighed against 

alternatives, as 

needed.

Uncertain. Once 

the level of risk is 

fully assessed it can 

be weighed against 

alternatives, as 

needed.

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Future Directions and Emerging Trends

One major initiative in the stormwater management area is integrating permeable pavements into 

urban designs, with benefits including reduced runoff, improved water quality, and the potential 

to reduce the localized urban heat island (UHI) effect through evaporative cooling. This is still 

under investigation. In addition, coupling permeable pavement surfaces with photocatalytic 

additives and/or coatings is also being studied, particularly with pervious concrete pavement and 

permeable interlocking concrete pavers. The presence of voids inherent in these surfaces 

increases the photocatalytic area exposed to the atmosphere, thus increasing the photocatalytic 

efficiency per unit of pavement surface area.

There is strong interest in using permeable pavement surfaces as part of mainline pavement 

construction. The initial effort thus far has been in parking areas and on mainline pavement 

shoulders, but work continues on evaluating designs that can perform well under heavier traffic 

loadings. 

Scholz and Grabowiecki (2007), among others, have introduced the idea of developing a 

heating/cooling system that can be installed within the subbase of modern permeable pavement 

systems in urban areas. The energy gained from the below-ground pump can be used as a 

substitute for energy derived from fossil fuel and hence has the potential for reducing CO2

emissions. The research suggests that the development of a combined geothermal heating and 

cooling, water treatment, and recycling pavement system is promising (Scholz and Grabowiecki 

2007). 

Pavement Thermal Performance and Contribution to Urban and Global Climate

Pavement Properties Affecting Thermal Performance

The thermal performance of a pavement is defined as the change in its temperature (most often 

surface temperature) over time as influenced by properties of the paving materials (e.g. albedo, 

thermal emittance, thermal conductivity, specific heat, and surface convection) and by the 

ambient environmental conditions (sunlight, wind, air temperature). It can also be influenced by 

evaporative cooling, which is related to ambient conditions, permeability, and the availability of 

near surface water (most often a factor if fully pervious pavement systems are used).

Albedo (or solar reflectance) is a measure of the ability of a surface to reflect solar radiation. 

Solar reflectance values range from 0 (no sunlight reflected) to 1 (all sunlight reflected). Lightcolored materials generally have higher solar reflectance values than dark-colored materials, 

although color alone is not the only indicator of solar reflectance (NCPTC/NCAT 2013). 

Emittance is the efficiency with which a surface emits radiant energy, and is defined as the ratio 

of energy radiated by the surface to the energy radiated by a black body (a perfect absorber and 

emitter) at the same temperature. Emittance ranges from 0 (no emission) to 1 (perfect emission). 

Thermal emittance is the emittance of a surface near 300 K (81 oF or 27 oC). Most nonmetallic 

surfaces have thermal emittances in the range of 0.80 to 0.95. The thermal emittances of densegraded concrete and asphalt are similar, being in the range of 0.90 to 0.95. 

Thermal conductivity is a measure of the ability of a material to conduct or transmit heat. It is 

the ratio of heat flux (power per unit area) to temperature gradient, and is expressed in units of 

W/m•K. A material with a high thermal conductivity will transfer heat at a higher rate than a 

material having a low thermal conductivity. The thermal conductivity of pavement materials 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

varies widely in the reported literature from 0.8 W/m•K to 2.0 W/m•K or greater, with similar 

values reported for dense-graded asphalt and concrete. 

Specific heat is the energy needed to raise a unit mass of a substance by one unit of temperature, 

typically expressed in units of J/kg•K. The specific heat of dense-graded asphalt and concrete 

are very similar, being about 900 J/kg•K. 

Of these material properties, albedo is the most important with regards to how pavements 

interact thermally with the environment when exposed to sunlight. Thermal emittance, thermal 

conductivity, and specific heat capacity of the materials are second order factors (Li et al. 2013). 

However, as will be discussed, understanding the thermal characteristics of the pavement 

materials alone is insufficient to fully understand how pavements thermally interact with the 

urban and global environments. 

The means by which solar radiation warms a pavement surface, the underlying layers, and the 

surrounding atmosphere during the day and then releases the absorbed energy as heat at night is 

illustrated in figure 6-16 (NCPTC/NCAT 2013). During the day, the pavement’s surface will 

reflect some of the incident sunlight and absorb the rest. The absorbed solar energy is emitted as 

long-wave radiation from the pavement, convected to the air moving over the pavement, 

conducted into the pavement and ground below, and/or dissipated by evaporation of water. 

Some of the solar energy stored in the pavement during the day is released at night through 

emitted long-wave radiation and convection, and some is released laterally to cooler zones 

through conduction. 

Figure 6-16. Heat flow and the basic thermal model for day and night (NCPTC/NCAT 2013). 

6-39

The thermal emittance, thermal conductivity, and specific heat of common paving materials are 

influenced by their density (which is largely controlled by mixture porosity and aggregate type 

and gradation), the amount of binder (cement, asphalt or other materials) if they are present, and 

the moisture content (Li et al. 2013). As discussed, the thermal emittance, thermal conductivity, 

and specific heat of common dense-graded paving materials are similar and therefore differences 

in the thermal performance of pavements are largely the result of differences in albedo. It is 
Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

noted that many additional factors contribute to how pavements interact thermally with their 

surroundings, which is the focus of the remaining discussion of this section. 

Urban and Global Warming Effects

The Urban Heat Island Effect

On a summer afternoon, urban areas are generally warmer than surrounding rural locations 

(Jones et al. 1990), as illustrated in figure 6-17 (EPA 2003). This urban–rural air temperature 

difference, known as the urban heat island effect (UHIE), is driven by a variety of factors 

including the prevalence of dark, dry surfaces in cities and heavily urbanized locations. 

Figure 6-17. Heat islands for various areas of development (EPA 2003). 

6-40

Although urban heat islands (UHIs) are most often thought of as existing in the atmosphere 

above the city, they actually exist at many different levels, including at the ground/pavement 

surface, in the air just above the surface (near-surface), and in the ambient air temperatures well 

above street level, as well as in the atmosphere above the city. In many cases, it is convenient to 

consider near-surface heat islands, which are characterized by increased ambient air temperature 

just above the ground/pavement surface, typically at 3 to 6 feet (1 to 2 m) where human outdoor 

activities occur (Li et al. 2013). Surface and near-surface heat islands can potentially affect 

human thermal comfort, air quality, and energy use of buildings and vehicles. Atmospheric heat 

islands can affect communities by increasing summertime peak energy demand, electrical grid 

reliability, air conditioning costs, air pollution and GHG emissions, heat-related illness and 

death, and water quality. 

As illustrated in figure 6-17, the rise in the temperature of man-made urban areas is quite noticeable 

compared with the other land uses. Although heat islands may form on any rural or urban area, and 

at any spatial scale, cities are favored since their surfaces are dark and dry, which increases solar heat 

gain and reduces evaporative cooling. 

The increased air temperatures associated with UHIs can contribute to greater energy demands 

(and the associated environmental impacts of increased electrical energy production) when and 

where increases in air temperatures result in greater use of air conditioning to cool buildings. In 
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

places that are already burdened with high temperatures, the UHIE can make cities warmer, more 

uncomfortable, and occasionally more life threatening (FEMA 2007). Furthermore, increases in 

temperature increase the probability of formation of ground-level ozone (commonly called 

smog), which exacerbates certain respiratory conditions such as asthma. Thus, it is believed that 

in most urban environments any potential benefits that might be derived from the UHIE (such as 

reduced winter heating requirements) are outweighed by their otherwise negative effects of 

extreme summer temperatures that can lead to increased air pollution, increased energy use for 

air conditioning, increased CO2 emissions, and adverse health and economic impacts (Navigant 

Consulting 2010). 

It is estimated that paved surfaces for travel, parking, and pedestrian use can account for around 

one-third of the land surface area in urban areas. Multiple studies have concluded, through 

simulation modeling, that low solar reflectance of paving materials can contribute to the 

formation of urban heat islands (Akbari, Rose, and Taha 1999; Taha, Konopacki, and Gabersek 

1999; Rose, Akbari, and Taha 2003; Rosenzweig et al. 2006; Millstein 2013; Li et al. 2013; 

Santamouris 2013). Although research has demonstrated through the evaluation of satellite 

imagery the efficacy of using reflective roofs to lower urban temperatures in a city such as 

Chicago (Mackey, Lee, and Smith 2012), field data demonstrating the extent that pavement 

surface albedo contributes to the UHIE have not been found in the literature. This is partly 

because the relationships between the contribution of pavement surface albedo and the UHIE are 

complex and as of yet not fully defined due to urban areas having differing sizes, pavement 

densities, tree canopies, building patterns, latitudes, and climates (Navigant 2010). Furthermore, 

factors such as building ordering and heights create three-dimensional “urban canyons” that 

impact the flow of air through the urban environment and appear to have a significant effect on 

urban warming (Sobstyl 2013). And as pavements are for the most part at ground level, they are 

often shaded by buildings and trees in an urban environment. 

To address these shortcomings, many simulation efforts have incorporated urban canopy models 

(UCMs) that accommodate the effects of urban canyons and complex urban morphology (Taha 

2008a; Taha 2008b; Chen et al. 2011; Li and Bou-Zeid 2014; Li, Bou-Zeid, and Oppenheimer 

2014). The most sophisticated models recognize the three-dimensional nature of urban surfaces, 

taking into account the impacts of vertical surfaces (walls) and horizontal surfaces (roofs and 

pavements) and considering shadowing, reflections, and radiation trapping in urban canyons 

(Chen et al. 2011). The exchange of energy between building interiors and the outside 

atmosphere can also be modeled to evaluate this important interaction. The model sophistication 

is such that calculations can be made on overall building energy consumption due to air 

conditioning and interior artificial lighting needs. These simulation efforts will continue to 

improve in complexity through better resolution and incorporation of even more sophisticated 

models, likely resulting in more definitive results focused exclusively on the impact of pavement 

albedo on the UHIE. 

Published studies have evaluated the effect of changing both the albedo of roofs and pavements 

together, and as a result the impact of changing pavement albedo alone cannot be easily 

interpreted (Taha 2008a; Taha 2008b; Li et al. 2013). However, at least one study has been 

published that included the modeling of the urban canyon in which only the pavement albedo has 

been altered. In that study, Hamdi and Schayes (2008), when simulating the city of Basel, 

Switzerland, found that a mid-day summer temperature reduction of 1.1 o

F (0.6 °C) could be 

obtained when the albedos of the road surfaces in the city were increased from 0.08 to 0.30. The 

effect of the urban canyon was investigated, showing that narrower streets with higher buildings 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

resulted in a decrease in UHIE due to shadowing. Still, much more work is needed to determine 

to what degree pavement albedo alone has on the UHIE in typical North American cities. Efforts 

employing these sophisticated models to solely evaluate the effect of pavement albedo within a 

realistic range (0.05 to 0.50) are currently underway in California (CARB 2013). 

With regards to the effects of pavements being shaded, pavement albedo is most relevant with 

regards to warming the pavement if the surface is exposed to direct solar radiation. Thus, not 

only is shading from buildings and trees relevant, but so is cloud cover and latitude. Figure 6-18 

shows the average June flat plate solar radiation map of the U.S. illustrating that the 

southwestern U.S. has some of the highest annual levels of solar radiation nationally (as well as 

worldwide), whereas other areas of the country have far less (NREL 2012). June was chosen in 

this figure as it is the month where solar radiation is most direct, and is also a month where the 

UHIE becomes most relevant in many North American cities. Similar solar radiation trends exist 

monthly throughout the year. 

Figure 6-18. Average June horizontal flat plate solar radiation map of the U.S. (NREL 2012).

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Figure 6-18 illustrates why the impacts of pavement albedo (with all other factors held constant) 

would be far greater in Phoenix compared to cities such as Chicago or New York. To some 

degree, this is reflected in the literature as a number of papers on the UHIE have been published 

focusing on Phoenix and on cities in California. On the other hand, there are also papers 

discussing the effectiveness of cool roof and pavements in Chicago (Mackey, Lee, and Smith 
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

2012), New York City (Rosenzweig et al. 2006), and for many other regions in the U.S. (Taha, 

Konopacki, and Gabersek 1999), all of which demonstrated a reduction in their UHIE through 

the use of reflective surfaces. As another example, Li, Bou-Zeid, and Oppenheimer (2014) 

modeled a heat wave that occurred in the Washington-Baltimore metropolitan area in June 2008 

showing that more reflective roofs and pavements could have helped mitigate some of the UHIE. 

This illustrates the importance of considering location and local climatic conditions, including 

singular events such as heat waves, when evaluating the impact of pavement albedo on the 

UHIE. 

It is also apparent in the literature that simply reflecting more light off of paved surfaces in an 

urban environment may have unintended negative impacts. For example, a study modeling the 

impact of increasing the albedo of impermeable surfaces from 0.15 to 0.5 found that although 

this strategy was the most effective at reducing urban surface and near surface air temperatures, 

at periods of high sun (noon) it had a negative impact on modeled human comfort (Lynn et al. 

2009). This is because although the pedestrian on a higher albedo surface experiences a 

reduction in thermal radiation due to the reduced pavement and near surface air temperatures of 

the high albedo surface, the increase in reflected solar flux is greater resulting in an increase in 

the effective temperature experienced.

In another example, a modeling study investigating reflective pavements (albedo of 0.5) found 

that although a small decrease in urban air temperature could be realized, high pavement 

reflectivity actually contributed to increased building energy use for summer cooling, especially 

for pre-1980 buildings constructed in Phoenix in areas having certain urban configurations 

(Yaghoobian and Kleissl 2012). In an associated press release, the authors state that the biggest 

increase in cooling energy use would be incurred in office park settings with older mid-rise 

office buildings that have large expanses of windows and do not have solar-control coatings 

(UCSD 2012). The press release also stated that this additional cooling energy could potentially 

be offset by utilizing the additional natural reflected lighting as one watt of daylight replaces up 

to two watts of fluorescent lighting, which could reducing electrical energy consumption and 

also cooling needs by reducing interior heating from the artificial lights. The authors concluded 

by stating further study is needed to quantify these potential savings (UCSD 2012). 

Experimental results from Li (2012) conducted on a paved test site in Davis, California found 

that a more reflective surface reduced the paved surface temperature by 27 °F (15 °C) as 

compared to a less reflective surface on a hot summer day; however, it was also observed that the 

temperature of an adjacent painted wall (albedo around 0.3) was actually 5 °F (3 °C) warmer for 

the reflective versus the non-reflective pavement surface. The basis of these observations is 

found in the heat flow schematic presented in figure 6-16. Raising pavement albedo increases 

the short-wave flux incident on a nearby vertical surface, such as a wall or vehicle, but decreases 

the long-wave flux incident on the surface. The change in the surface’s overall radiative heat 

gain will depend on the albedo and thermal emittance of the vertical surface. 

In this context, some recent studies have questioned the overall regional and global climate 

impact of using highly reflective surfaces in urban areas, including roofs and pavements. 

Although these studies universally acknowledge that increasing the average urban albedo will 

reduce local air temperatures, the broader regional and global climate impacts are less clear. For 

example, Jacobson and Ten Hoeve (2011) used global climate simulations to conclude that white 

roofs would be expected to reduce local urban temperatures, but may result in a “net effect on 

globally-averaged temperatures that may be warming,” although it is stated that a great amount 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

of uncertainty still exists regarding this conclusion. The biggest effects were due to a decrease in 

cloud cover resulting from the stabilization of air masses over the city, which in turn reduced 

cloud cover and precipitation away from the urban areas. This had the net result of increasing 

the incidence of solar radiation in the affected regions and decreasing soil moisture. 

In another paper, Millstein and Menon (2011) used a fully coupled regional climatic model and 

compared the results to previous work conducted at the Lawrence Berkeley National Laboratory 

(LBNL) that did not include coupling of the land-surface model to the atmospheric circulation 

scheme. The results found increased regional variability, characterized by a general cooling of the 

urban areas investigated but with some regional warming influences in rural areas that in some 

cases were significant. Even with the increased variability, the researchers concluded that the 

improved modeling showed greater normalized temperature reductions overall compared to past 

studies, although broader climatic effects were acknowledged. As climatic models continue to 

improve, the potential trade-offs between urban and surround rural areas, as well as broader 

regional and global effects, will be better understood and improved decisions can be made 

regarding the circumstances (e.g., climate, location, surface hydrology, emission profiles, 

chemistry transport) in which increasing the surface albedo of a city can have a net positive impact.

The majority of the analyses of the UHIE and the role of pavements has focused primarily on 

pavements with high albedo. To fully understand the impact of pavement strategies to address 

the UHIE, all pavement life-cycle phases must be considered, including material acquisition and 

pavement construction, while factoring in the longevity of the pavement treatments specifically 

directed at increasing albedo. A research project is currently underway, funded by the California 

Air Resources Board and the California Department of Transportation, to perform an LCA for 

implementation of high albedo pavement strategies in different cities and climate regions 

compared to normal practices (CARB 2013). 

In summary, the degree to which pavement albedo contributes to the UHIE depends on a variety 

of local variables. All things equal, the surface of pavements with lower solar reflectivity 

(albedo) will become hotter when exposed to solar radiation. But the complexity of the urban 

fabric and local conditions make it difficult to ascertain what the overall impact of pavement 

albedo is on the development of the atmospheric UHIE. Further, the impact of reflective 

pavements on the overall energy balance of nearby buildings is yet to be resolved. Research 

strongly suggests that localized cooling can be achieved in certain urban areas by increasing 

average albedo of roofs and pavements, but the broader regional and global climatic impacts of 

uniformly increasing urban albedo are unclear. The variation in cooling potential will depend on 

local urban properties such as pavement area, shading, and building height, as well as on regional 

weather patterns. 

As a result, cooling potential may be negated in locations where complex interactions exist 

between urban heating and cloud formation, which leads to decreased cloud formation as urban 

albedo increases. This effect could also result in some downwind rural areas experiencing low 

levels of surface warming due to increases in urban albedo. Climatic modeling efforts are being 

directed at developing a better understanding of the context in which the application of cool 

pavement strategies is justified for specific urban areas. 

Radiative Forcing

In addition to UHIEs, there is a growing body of knowledge that relates planetary solar 

reflectance to global warming as a result of changes in radiative forcing. The concept of 

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radiative forcing is fairly straightforward, but in practice it is a very complex phenomenon. A 

complex and complete definition of radiative forcing was presented by the Intergovernmental 

Panel on Climate Change (IPCC 1996), stating that radiative forcing is “the change in net (down 

minus up) irradiance (solar plus irradiance long-wave; in W•m-2) at the tropopause after allowing 

for stratospheric temperatures to readjust to radiative equilibrium, but with surface and 

tropospheric temperatures and state held fixed at the unperturbed values.” A common and more 

accessible definition is that radiative forcing is the difference between the radiant energy 

received by the earth and the energy radiated back into space (Wikipedia 2014). 

Basically, solar energy is constantly flowing into the atmosphere on half of the Earth’s surface. 

Some of this sunlight (about 30 percent) is reflected back to space and the rest is absorbed by the 

planet. Like any warm object in cold surroundings, some of the absorbed energy is radiated from 

the Earth back into space as long-wave (thermal infrared) radiation. A positive forcing (more 

incoming energy than outgoing) warms the system, while negative forcing (more outgoing 

energy than incoming) cools it. The factors contributing to radiative forcing are many, complex, 

and often interact with each other. They including the natural incoming solar irradiance (which 

changes with solar activity), atmospheric aerosols, GHGs, cloud microphysics, and changes to 

the land surface (Cubasch et al. 2013). The latter two categories (changes to the atmosphere and 

land surface) are influenced by both natural processes and human activities. The contribution of 

pavements to radiative forcing lies primarily in changes to the land surface by changing surface 

albedo, as illustrated in figure 6-19 (Cubasch et al. 2013). 

Figure 6-19. Illustration of the main drivers of climate change (Cubasch et al. 2013). 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Although much of the work conducted on the contribution of pavements to radiative forcing has 

focused on urban areas (since those are most affected by human development), radiative forcing 

is considered in addition to the UHIE because it is a factor wherever the land surface albedo has 

been changed through human activity. Multiple studies have used modeling to demonstrate how 

increasing roof and pavement albedo (increasing reflection of sunlight to space) can reduce 

urban solar heat gain, lower urban surface temperatures, and thereby decrease both convection 

and thermal radiation of heat into the atmosphere (Akbari, Menon, and Rosenfeld 2009; 

Millstein and Menon 2011; Akbari and Matthews 2012). Related work concluded that the global 

warming mitigation effect of increasing the average albedo of urban environments worldwide by 

0.1 could be on the order of 49 billion short tons (44 Gt) of CO2 (Menon et al. 2010). Roughly 

55 percent of this benefit (27 billion short tons [24 Gt]) would result from increasing the albedo 

of roofs by at least 0.25, whereas the remainder would derive from increasing the albedo of 

pavements by at least 0.15 for roadway and parking surfaces. These prospective savings equate 

to almost an entire year’s estimated anthropogenic CO2e emissions (roughly 50 billion short tons 

[45 Gt] CO2e). Follow-up work, focusing on the continental U.S. and using a fully coupled 

regional climatic model joining the land-surface model to the atmospheric circulation scheme, 

found increased regional variability but concluded that overall even greater impacts could be 

achieved by increasing the average urban albedo of horizontal surfaces (Millstein and Menon 

2011). 

On the other hand, conclusions drawn in another paper found that an increase in average surface 

albedo will result in less local cloud cover, thus actually increasing local incident solar radiation 

and potentially contributing to global warming (Jacobson and Ten Hoeve 2011). Further, that 

study suggested that reflected short-wave solar radiation from higher albedos for white roofs 

(changes in pavement albedo were not considered) will result in additional heating of black and 

brown soot particles in the atmosphere resulting in increased localized atmospheric warming, 

although this effect was considered minimal and thus requires additional investigation to 

determine if it is of significance. 

In closing, the use of high albedo pavements to provide global cooling through radiative forcing 

is uncertain. If there is no interaction with clouds, more reflective pavements could provide 

important global cooling benefits. However, once feedback to cloud formation is accounted for, 

the answer is not definitive and may depend on whether pavement albedo is universally 

increased in all locations, or whether high albedo pavements are constructed in select locations 

where effectiveness is demonstrated. The question of whether global changes in pavement 

albedo can provide global cooling benefits remains an active area of research.

Stormwater Warming

Hotter, impermeable pavements also hold the potential to warm stormwater, which may affect 

sensitive biological communities (e.g., trout) in the receiving waters if their thermal regimes are 

altered by the stormwater runoff (NRDC 1999; OEC 2007; Jones and Hunt 2007). This is a 

particular issue in locations that receive significant rainfall during hot seasons and where heated 

stormwater is not cooled before entering the sensitive area, but should not be an issue in climate 

regions that have little or no summer rainfall. Fully permeable pavements (discussed earlier) can 

be used to mitigate stormwater heating if designed to retain water before releasing it into the 

environment. 

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Pavement Type and Thermal Performance

From the preceding discussion. it is clear that the solar reflectance of paved surfaces can be a 

strong contributor to pavement warming and that this warming has the potential to impact the 

UHIE in those built environments that experience hot weather and are large enough to generate a 

heat island. Furthermore, pavement reflectance may also contribute to overall global warming 

through radiative forcing although, as noted, additional research is needed to more clearly 

demonstrate that effect. In this section, studies specifically focused on various pavement types 

are reviewed.

Typical albedo values range from 0.04 to 0.16 for asphalt pavements and from 0.18 to 0.35 for 

concrete pavements (Pomerantz et al. 2003), although the albedo of new concrete can be as high 

as 0.69 (Marceau and VanGeem 2007). These albedo values are correlated to the color of the 

pavement whether it is asphalt (black) or concrete (grey or white), but the exposure of aggregates 

at the surface also plays a role in determining albedo. New asphalt pavements are quite black 

and have little exposed aggregate and thus have low albedos (less than 0.10). This will result in 

high pavement surface temperatures during hot, sunny periods when not shaded by trees or 

buildings (Li et al. 2013). With pavement albedo values around 0.10, extreme high pavement 

surface temperatures of 158 to 176 °F (70 to 80 °C) have been measured on hot summer days in 

mid-afternoon in Phoenix, Arizona, and up to 158 °F (70 °C) for similar pavements in Davis, 

California (Li et al. 2013). Figures 6-20 and 6-21 illustrate how pavement surface temperatures 

were greatly affected by pavement albedo both in Phoenix (Cambridge Systematics 2005) and in 

Davis (Li et al. 2013), respectively. 

Figure 6-20. Surface temperature and albedo for selected types of pavements in Phoenix, 

Arizona (note: UTW = ultra-thin whitetopping) (Cambridge Systematics 2005). 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Figure 6-21. Effect of albedo on pavement surface temperature in Davis, California

(16:00 9 July 2012) (Li et al. 2013). 

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New concrete pavements are typically light in color as long as no pigments are added. Even 

though over 90 percent of all paved surfaces in the U.S. are asphalt (NAPA 2013), in urban areas 

it is not uncommon to find a higher level of concrete in use as a paving material (14 to 20 percent 

of all paved surfaces including sidewalks [Levinson and Akbari 2001]). Work by Levinson and 

Akbari (2001) characterized the albedo of various concrete constituents (cement, sand, and 

coarse aggregate) and of the concrete produced from combinations of those constituents, and 

found that the albedo of unworn/unsoiled concrete was largely controlled by the albedo of the 

cement and sand, with cement albedo having a disproportionately strong influence on the albedo 

of concrete. Similar conclusions were made by Marceau and VanGeem (2007), who found that 

the solar reflectance of the cement has the largest single effect on concrete albedo compared to 

other constituent materials. Since the color of cement is largely affected by the iron content, 

cements being low in iron generally are lighter in color. For example, cement with a reported 

iron oxide content of 3.5 percent had a measured albedo of 0.32, whereas the albedo of a white 

cement with a reported iron oxide content of 0.2 percent had an albedo of 0.87 (Levinson and 

Akbari 2001). 

The reflectance of concrete can be either enhanced or diminished depending on the type and 

color of SCMs or pigments added to the concrete. Marceau and VanGeem (2007) studied this in 

detail and found that fly ash can have an albedo either less than or greater than cement, and thus 

can darken or lighten the concrete. Slag cement on the other hand has a solar reflectance that is 

much higher than ordinary portland cement or fly ash and thus its use results in higher albedo 

concrete. The white cement included in the study had the highest albedo of any of the 

cementitious materials and thus could be used to create concrete with an albedo of 0.69. Further, 

it is not uncommon that pigments are added to concrete to change its color for aesthetic affect, 

almost always resulting in a decrease in albedo. For example, it is known that “lamp black” is

routinely added to municipal concrete in areas of California to darken it (significantly reducing 

its albedo) so it will better match the color of existing concrete that may be several decades old. 
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Interlocking concrete pavers can also be manufactured to have high albedo. For example, the 

City of Chicago used highly reflective permeable concrete pavers featuring a photocatalytic 

surface to keep the pavers clean on the Cermak Road reconstruction project, a high-profile 

“green” pavement (CDOT 2013). 

A recent study evaluated a number of different pavement types to investigate their thermal 

performance and how they interact with the surrounding environment (Li 2012; Li et al. 2013). 

A total of nine 13.1 ft (4 m) square instrumented asphalt, concrete, and interlocking concrete 

paver pavement sections were constructed and monitored for over a year. Climate and pavement 

temperature monitoring over the course of the year clearly showed that peak pavement 

temperature was strongly correlated to albedo, as shown previously in figure 6-21. Furthermore, 

the near-surface air temperature measured 2 inches (50 mm) above the surface was higher for the 

dark asphalt pavement compared to the conventional concrete pavement and conventional 

concrete pavers. As stated by Li et al. (2013), this increase in near-surface air temperature is 

thought to decrease the comfort level of human beings (especially the young) and contribute to 

the formation of ground-level ozone. Typical near-surface air temperatures for the four seasons 

in Davis, California are shown in figure 6-22. 

Figure 6-22. Near-surface air temperatures of different pavements measured 2 inches

(50 mm) above the surface (Li 2012). 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

These results clearly demonstrate the effect of convection, in which heat from the pavement 

surface warms the air at the boundary. Based on this alone, it is understood why the use of 

highly reflective pavements exposed to sunlight will reduce pavement temperatures and lessen 

the temperature of the air immediately above them compared to lower albedo pavements. 

Nevertheless, as discussed previously, the effect of albedo on the urban environment is more 

complex. This is partly explained by figure 6-23, where q_ref is reflected short-wave solar 

radiation; q_em is emitted long-wave radiation; q_radio is radiosity which is equal to q_ref + 

q_em; and q_conv is convective heat. 

Figure 6-23. Heat flux from pavement surfaces for 1 full day during July 2012 (Li et al. 2013). 

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As shown in figure 6-23, the convective heat and emitted long-wave radiation is highest for 

pavements with the lowest albedo (B1, B3). Pavements with high albedo (C1, C3) will absorb 

the least solar radiation and thus have the highest reflected short-wave solar radiation. This 

results in higher pavement and near-surface air temperatures in the low albedo pavements, but in 

some cases the total radiosity is higher with the high albedo pavements. This is reflected in 
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

figure 6-23 where the conventional concrete (C1) has the highest radiosity of the four sections. 

Reflected short-wave solar radiation transmitted into space contributes to negative radiative 

forcing. However, if it is absorbed by nearby buildings or cars it can result in increased cooling 

energy needs or if by humans it can increase discomfort, modeling of which has not been 

validated. Research is currently underway modeling the effects of light and energy reflected 

from pavements on the energy use for interior lighting of nearby buildings, in addition to energy 

use for cooling and heating. 

But the broader impacts of this are far less clear. For instance, 33 feet (10 m) of air will absorb 

only 1.6 percent of reflected short wavelength sunlight, but will absorb 22 percent of emitted 

long wavelength thermal radiation. Thus, at a path length of 0.6 miles (1 km), absorption is 9 

percent and 61 percent, respectively. Hence, emitted long wavelength thermal radiation heats the 

air much more effectively than reflected short wavelength radiation. Further, the albedo of the 

surface of a wall, vehicle, or even the clothing worn by a person has a large impact on the 

radiative heat gain from reflected light. Radiosity is thus not equivalent to radiative heat gain, 

and thus all these factors have to be accounted for when considering increased cooling needs for 

buildings or human comfort. Consequently, the overall influence of reflected solar radiation is 

uncertain and needs further evaluation. 

Permeable surfaces (porous asphalt, pervious concrete, and permeable pavers) show trends 

similar to impermeable surfaces regarding the impact of albedo on pavement surface temperature 

and near-surface air temperature when the pavement is dry. The addition of surface voids in 

permeable surfaces decreases albedo as well as thermal conductivity and specific heat capacity, 

and thus it is common for the peak surface temperature of pervious pavement alternatives to be 

higher than those of comparable impervious pavements if the pavement is dry (Li, Harvey, and 

Jones 2013). Independent of albedo, the effects of the lower thermal conductivity and lower 

specific heat are to trap heat nearer the surface and resulting in more rapid heating. For the same 

reasons, once solar radiation diminishes at the end of the day, permeable surfaces also cool more 

rapidly and have less heat energy to emit than impermeable surfaces (Li, Harvey, and Jones 

2013). 

If there is a source of near surface water, permeable pavements will undergo evaporative cooling 

that has been found to significantly reduce peak surface temperatures. Under these conditions, 

even though comparable permeable surfaces would have a lower albedo, the peak surface 

pavement temperature and near-surface air temperature is lower than the conventional 

impermeable pavement counterparts (Li, Harvey, and Jones 2013). 

An additional complicating factor is that the solar reflectance of both asphalt and concrete 

pavements changes over time. For example, at the time of initial construction, a dense-graded 

asphalt pavement will have a very low albedo (typically below 0.05), but over time that asphalt 

surface oxidizes and becomes lighter, increasing the albedo. In addition, the asphalt film on the 

surface of the pavement wears away under traffic, exposing the underlying coarse aggregate and 

potentially increasing the solar reflectance, particularly if a light-colored aggregate was used in 

the mixture. 

Similarly, as concrete is abraded under the action of traffic, the albedo of the coarse aggregate 

becomes more important; if the aggregate is light in color, the albedo may not be negatively 

impacted and may even increase, but if a dark coarse aggregate is used, the surface will become 

less reflective. Additionally, even the lightest colored concrete pavement will become soiled 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

over time from road grime, oil, and tire rubber, reducing the albedo. Figure 6-24 illustrates this 

concept, qualitatively showing the change in solar reflectance (albedo expressed as a percentage) 

of typical concrete and asphalt pavements over time. This figure shows that the reflectance of 

the two surfaces gradually begin to approach one another. There is a study underway to better 

characterize changes in pavement albedo over time (NCPTC/NCAT 2013).

Figure 6-24. Typical pavement solar reflectance of conventional asphalt and concrete pavements 

over time (EPA 2008). 

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Another factor to consider regarding albedo is the application of pavement maintenance and 

rehabilitation treatments. In general, any treatment that changes the color of the pavement 

surface will impact the albedo. With regards to asphalt pavements, surface treatments can either 

decrease or increase the albedo, depending on the nature of the treatment. Those that leave a lot 

of asphalt binder exposed, such as conventional fog seals, slurry seals, sand seals, and 

microsurfacing, will have a tendency to darken the surface and reduce the solar reflectance. 

These treatments are a common application to “weathered” asphalt surfaces, the very surface that 

has increased solar reflectance due to oxidation. It is the tendency of many maintenance 

engineers to “restore” a weathered asphalt surface through these treatments that yields a “like 

new” surface that may adversely affect solar reflectance if the project is located in an area where 

UHIEs are a concern.

Decreasing the reflectivity of existing asphalt pavements with maintenance treatments such as 

fog seals can potentially increase the risk of rutting because of increased pavement temperatures, 

particularly in those locations with hot climates and heavy, slow-moving truck traffic. Reducing 

the near surface temperatures in asphalt pavements through the use of higher albedo surface 

materials—such as chip seals with more reflective aggregate or highly reflective surface 

coatings—can potentially reduce the risk of rutting by lowering peak pavement temperatures. 
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Such reflective coating may also help reduce aging in the asphalt binder, which in turn can 

reduce the probability of top-down cracking and thermal cracking in the winter months 

(Pomerantz, Akbari, and Harvey 2000). It is noted that the stiffening of an asphalt binder that 

occurs as it ages helps resist rutting, so a balance between reducing the risk of rutting and 

increased risk of cracking needs to be struck. 

Where solar reflectance is important, treatments that can lighten the surface, such as chip seals 

using light-colored aggregate or pigmented/colored surface seals, should be favored (Nichols 

Consulting Engineers 2012). Regarding the latter, pigmented/colored surface seals continue to 

evolve with a number of proprietary materials becoming available for coating pavement surfaces 

that are designed specifically to reduce the pavement surface temperature not only through using 

a lighter color, but actually preferentially reflecting infrared radiation through the use of infrared 

reflective pigments (Wan et al. 2009; Synnefa et al. 2011; Santamouris et al. 2012). The longterm durability of pavement coatings and the environmental impacts of their manufacture have 

not yet been fully documented and are currently being evaluated. 

The albedo of concrete pavement can be changed by diamond grinding, which removes a thin 

layer of the surface to restore ride quality, while also removing tire rubber, oil drippings, and 

other deposited materials that may have darkened the pavement surface. Figure 6-25 shows a 

typical diamond ground surface in which the coarse aggregates have been exposed. If the coarse 

aggregate is light colored, diamond grinding will likely increase the solar reflectance. On the 

other hand, grinding a concrete pavement made with dark coarse aggregates may reduce albedo. 

For both asphalt and concrete pavements, rehabilitation featuring the use of overlays will have 

obvious impacts on the solar reflectance of the resulting surfaces. All the same considerations 

exist for asphalt and concrete overlays as exists for newly constructed asphalt and concrete 

pavements. 

Figure 6-25. Diamond ground concrete pavement surface. 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Other Strategies to Reduce Pavement Temperatures

In addition to solar reflectance, there are other pavement factors that contribute to reducing the 

temperature of pavement surfaces. A few of these are highlighted below: 

• Permeable pavements (discussed previously), in addition to their capability of providing a 

mechanism for stormwater management, are known to contribute positively to a 

reduction of the peak pavement temperature if near surface water is available for 

evapotranspiration (Tran et al. 2009). This is well documented in a recent study showing 

that permeable pavements (including concrete, asphalt, and concrete pavers) under wet 

conditions have reduced surface temperatures compared to impermeable pavements of 

similar solar reflectance (Li et al. 2013). This was largely the result of evaporative 

cooling, which is dependent on the availability of near surface water and a high rate of 

evaporation. The benefit disappears once the pavement dries out. Combining high 

reflectance with a permeable surface was found to be especially effective.

• There are coatings that can be applied to a pavement surface that do not actually change 

the visible color of the pavement, but instead only increase the reflectance of the near 

infrared spectrum (Kinouchi et al. 2004; Wan et al. 2009). These can create a dark 

pavement with a relatively high albedo, thus reducing the pavement surface temperature. 

These are still experimental in nature and their effectiveness and durability have not been 

fully established.

• Strategies that use shade to minimize exposing pavements to direct sunlight, particularly 

through vegetation, is a well-practiced strategy employed in many urban environments to 

mitigate the UHIE (McPherson 1994; Akabari, Pomerantz, and Taha 2001; EPA 2003; 

Nichols Consulting Engineers 2012). Solar panels have also been used to provide shade 

to pavements (particularly in parking lots) while also providing a renewable source of

electrical energy.

• As described earlier, the use of vegetated permeable pavers in parking and low-volume 

traffic areas is an innovative approach to addressing both stormwater management and 

the UHI effect (EPA 2008; Nichols Consulting Engineers 2012). These pavers are made 

of plastic, metal, or concrete lattices that provide support to traffic while allowing grass 

or other vegetation to grow in the substantial voids space. 

Strategies for Improving Sustainability

Practices available to pavement managers, designers, and specification developers that can be 

used to reduce peak pavement temperatures and might be used to address UHI issues are 

provided in table 6-6. 

Future Directions and Emerging Trends

A number of pavement technologies continue to emerge that have the potential to address or 

reduce the UHIE, as listed below:

• Photocatalytic cements and coatings. Certain forms of titanium dioxide are known to be 

photocatalysts, using solar energy to accelerate chemical reactions without being 

consumed in the process. In the presence of sunlight, organic materials such as dirt 

components (soot, grime, oil, and particulates), biological organisms (mold, algae, 

bacteria, and allergens), airborne pollutants (VOCs, NOx and SOx), and chemicals that 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

cause odors are all decomposed by the photocatalytic effect (Burton 2011). Not only 

does titanium dioxide help to reduce air pollution, but it can help maintain a high albedo 

for pavements by removing surface contaminants that typically darken the concrete 

surface (PCA 2013). This technology is in the earliest phases of implementation, being 

employed both in white cements and in concrete pavers, as well as in coatings for asphalt 

pavements. Its long-term effectiveness and the environmental footprint of producing 

these materials are still being investigated. 

• Alternative binders. Resin‐based binders (such as clear tree resins) are being used in place 

of the typical black petroleum‐derived asphalt binder, which allows the pavement to have 

the natural appearance of the aggregates used in the mixture. Resin‐based binders have 

been used to construct pavements for hiking and biking trials, but have not been used for 

highway applications. Aside from resin‐based binder, a variety of colorless and reflective 

synthetic polymer binders are available that have been used with light-colored aggregates, 

typically for surface courses for sports and leisure areas (Tran et al. 2009).

• Reflective chip seals. The development of exposed aggregate surfaces for asphalt 

pavements with light-colored aggregates that are more suitable to urban environments 

than current chip seal technologies hold promise and should be further investigated. 

• Coatings and pigments. There are a number of coatings that increase the solar reflectance 

of an asphalt surface, either by changing the color of the surface through the addition of a 

thin layer and/or by preferentially increasing the reflectivity of the surface in the near 

infrared spectrum (Kinouchi et al. 2004; Wan et al. 2009). The long-term effectiveness 

of such coatings on high-traffic facilities has not been demonstrated. Similarly, there 

have been studies investigating the use of pigments to lighten the asphalt binder and thus 

increasing solar reflectance, but these have only been used on a limited basis and their 

long-term effectiveness has not been established.

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Table 6-6. Summary of considerations to address UHIE issues and potential trade-offs.

UHIE 

Objective

Sustainable Approach 

and Trade-offs

Economic

Impact

Environmental 

Impact

Societal 

Impact

Improve 

Understanding of 

Systematically collect 

data on the solar 

reflectance of various 

pavement types at various 

ages

Initial cost for 

conducting data 

collection and research 

effort

Better information will 

support better decision 

making improving the 

environmental and 

societal impacts

Improve 

understanding of 

pavement solar 

reflectance and the 

UHIE

Pavement Solar 

Reflectance and the 

UHIE

Improved modeling of 

pavement solar 

reflectance and the impact 

on the surface, near 

surface, and atmospheric 

UHIE

Initial cost for 

conducting research and 

modeling effort

Better modeling 

capabilities will 

support better decision 

making improving the 

environmental and 

societal impacts

Wise use of 

available funding for 

global warming 

solutions requires 

informed decisions

Utilize a Robust, 

Repeatable 

Methodology to 

Assess Pavement 

Solar Reflectance

Requires a concerted 

effort by the pavement 

community to establish 

standards for specifying 

and assessing pavement 

solar reflectance

Initially high, but over 

time low once 

procedures are 

established 

Improved as a standard 

approach for assessing 

solar reflectance will 

increase 

implementation 

Improved as a 

standard approach 

for assessing solar 

reflectance will 

increase 

implementation

For concrete pavement, 

use light colored cement

White cement is more 

costly than typical grey 

portland cement

Can be negative if 

using white cement as 

it has a higher 

production 

environmental 

footprint

Improved human 

comfort

For concrete pavement, 

use light colored SCMs

Generally less 

expensive or cost 

neutral

Improved as reduced 

need to landfill 

industrial waste

Improved as a 

potential waste is 

beneficially used

For asphalt pavement, 

apply high albedo 

coatings, such as exposed 

light colored aggregate 

treatments such as chip 

seals or specialized 

coatings

Initial and long-term 

costs dependent on cost 

of material and 

frequency of 

applications required

Specialized coatings 

may have high 

environmental 

footprint 

Improved through 

reduced UHIE

Increase the Albedo 

of New Pavement 

Surfaces (where it is 

determined to be 

beneficial)

Employ permeable 

pavement technologies 

where applicable (water 

must be available during 

critical UHIE periods)

Permeable pavement 

technologies can be cost 

neutral to slightly 

increased cost

Reduced 

environmental 

footprint and improved 

social benefit through 

reduced UHIE and 

improved stormwater 

management 

Reduced 

environmental 

footprint and 

improved social 

benefit through 

reduced UHIE and 

improved 

stormwater 

management

Use high albedo 

interlocking concrete 

pavers where applicable

Typically more costly 

than conventional 

pavement alternatives

Reduced 

environmental 

footprint and improved 

social benefit through 

reduced UHIE

Reduced 

environmental 

footprint and 

improved social 

benefit through 

reduced UHIE

Use vegetated pavers in 

low-volume traffic and 

parking areas

Less expensive than 

conventional pavement 

alternatives

Reduced 

environmental 

footprint and improved 

social benefit through 

reduced UHIE and 

improved stormwater 

management 

Reduced 

environmental 

footprint and 

improved social 

benefit through 

reduced UHIE and 

improved 

stormwater 

management

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Table 6-6. Summary of considerations to address UHIE issues and potential trade-offs (continued).

UHIE

Objective

Sustainable Approach 

and Trade-offs

Economic 

Impact

Environmental and 

Societal Impact

Use light colored 

aggregates in concrete 

and asphalt mixtures 

Cost neutral to 

increased cost 

depending on local 

availability

Lower UHIE over time but may have 

increased environmental and societal 

impact if aggregate not locally available

Use high albedo

surfaces, including 

reflective coatings, thin 

overlays and light 

colored chip seals, to 

maintain asphalt 

pavements

Cost neutral to 

significantly increased 

cost depending on 

local availability of 

reflective aggregates 

and proprietary nature 

of coating

Lower UHIE over time but may have 

increased environmental and societal 

impact if aggregate not locally available or 

if proprietary coatings contain 

environmentally damaging constituents 

Maintain High 

Albedo Over Time

(where it is 

determined to be 

beneficial)

Use diamond grinding to 

expose light colored 

aggregates if present for 

concrete pavements

High initial cost if not 

done to also improve 

ride quality

Lower UHIE, while also improving ride 

quality and reducing tire-pavement noise 

provides environmental and societal 

benefits

Use photocatalytic 

surface on concrete 

pavement to reduce 

soiling

High initial cost

Lower UHIE over time but may have 

increased environmental and societal 

impact if the photocatalyst has large 

environmental footprint

Use cleaning program to 

maintain high solar 

reflectance of high 

albedo surfaces

Increased maintenance 

cost

Trade-off between improved UHIE and 

energy and water use for cleaning

Lower societal impacts through reduced 

UHIE

Concrete overlays on 

concrete and asphalt 

pavements

High initial cost, but 

potentially reduced 

long-term expenses 

depending on design 

and application, and 

also depends on cost 

of cleaning to maintain 

albedo

Lower UHIE and improved structural 

capacity over time but may have increased 

environmental and societal impact due to 

materials production and construction 

environmental impacts, traffic delays and

materials cost.

Employ Systemwide Strategies to 

Reduce Pavement 

Temperatures Where 

it is Determined to 

be Beneficial

Use vegetation, trees 

and solar panels to shade 

pavements as

appropriate

Slightly higher initial 

cost

Lower UHIE plus the multiple 

environmental and social impacts of 

increasing plant density or low impact 

energy production in an urban 

environment

• Enhanced data and thermal modeling. A number of efforts are underway to better 

characterize the contribution of pavements to the UHIE, as well as the broader issue of 

radiative forcing (e.g., NCPTC/NCAT 2013 and initiatives undertaken by the Heat Island 

Group at Lawrence Berkeley National Laboratory and by the Global Institute of 

Sustainability at Arizona State University). 

The UHIE has emerged as a statewide issue in California with the passage of Assembly Bill No. 

296 in the 2011-2012 session (see http://leginfo.legislature.ca.gov/faces/billSearchClient.xhtml). 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

Among other things, that legislation requires the California DOT to develop a standard 

specification for sustainable pavements that can be used to reduce or minimize the UHIE. The 

research currently underway to support implementation of that legislation includes modeling of 

the effects of changing pavement albedo in cities in California using a statewide WRF climate 

model similar to that used by Chen et al. (2011), and initial life cycle assessment modeling of the 

net effects on GHG, energy use, and emissions affecting air pollution of changing pavement 

albedo on material production, construction, and the use phases (building energy use for cooling, 

heating, and lighting). 

Artificial Lighting

Background

Roadway lighting is an often overlooked 

component in roadway and pavement design, even 

though it can have a large impact on safety, energy 

consumption, and generation of emissions. As a 

means of perspective, it was estimated that 131 

million luminaires were used in the U.S. in 2007 

for street and area lighting, consuming 178.3 

terawatt hours (TWh) of electricity each year 

(Navigant Consulting 2008). This lighting was 

predominately provided by high pressure sodium 

lamps (39 percent), with metal halide (27 percent), 

mercury vapor (13 percent), fluorescent (6 percent), halogen quartz (8 percent), and incandescent 

(2 percent) lamps also being used. 

Solid-state lighting, using light-emitting diode (LED) technology, is an energy efficient option in 

roadway lighting. LEDs produce light by moving electrons through a semiconductor compared 

to traditional light bulbs that use a filament that heats up and ultimately burns out. LED lighting 

can reduce energy consumption by up to 75 percent compared to the mercury lamps that are in 

common use today for street lighting (Wu et al. 2008). On top of comparative energy savings, 

LED lighting can be better positioned to direct most of the light directly on to the roadway where 

it is needed. This requires less light or energy to sufficiently and safely light the roadway and 

also reduces light pollution, which affects both people and wildlife, especially migrating birds 

(Rich and Longcore 2005). Furthermore, the characteristics of the light provided by an LED 

(color rendering, lighting distribution, and enhanced nighttime lighting conditions) may permit a 

reduction in total lumen output from an LED light source relative to the most common highpressure sodium light source, resulting in further savings (Cook, Shackelford, and Pang 2008). 

Solid-state LED lighting technology is fully embraced by the U.S. Department of Energy 

(DOE).3

http://www1.eere.energy.gov/buildings/ssl/index.html

 It is estimated that a 100 percent market penetration by more efficient solid-state LED 

technologies could save 44.7 TWh/yr, which is equivalent to the electrical consumption of 3.7 

million residential households (Navigant Consulting 2008). The U.S. DOE has participated in 

the GATEWAY Demonstrations4

http://www1.eere.energy.gov/buildings/ssl/gatewaydemos.html

in which the effectiveness of high-performance LED lighting 

products have been demonstrated on real world projects in multiple cities and also established 

3

4

Major Issues: 

 High energy demand of current 

lighting has high economic and 

environmental impact.

 Providing appropriate amount of 

artificial lighting for driver safety

 Reducing amount of light pollution

 Understanding impact of pavement 

reflectivity/luminosity on nighttime and

daytime safety.

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

the Municipal Solid-State Street Lighting Consortium5

http://www1.eere.energy.gov/buildings/ssl/consortium.html

 to further promote that technology (U.S. 

DOE 2013). The City of Boston, for example, began installing LED street lighting in 2010 and 

has seen up to a 60 percent decrease in energy use and carbon emissions (City of Boston 2013). 

The City expects the LED lamps to last up to three times longer than conventional lamps and, 

although the initial cost is higher, it is expected that the payback period is 2 to 3 years. 

In addition to energy conservation, light pollution from roadway lighting, which results in 

“skyglow,” “light trespass,” and “glare,” has become a major social concern in many urban areas 

(AASHTO 2008). Sky glow is a brightening of the night sky caused by natural and human-made 

factors, while glare is an objectionable brightness or reflection of light and a driving hazard 

especially bothersome to older drivers. Light trespass is the actual light that falls off the right-ofway and can be measured and quantified. Although safety is of paramount concern, there are 

ways to reduce the amount of light pollution while still providing a completely safe amount of 

light. Positioning the light to be directed at the roadway surface and reducing the amount that is 

projected elsewhere is important regardless of the light sources. Also, reducing the amount of 

light that is being used (i.e., maintaining safe levels without overdesign) is another part of the 

solution. Finally, as previously mentioned, using more efficient solid-state LED lighting with 

high light quality can provide the same level of safety at lower lumens, thus contributing less 

light pollution.

From a pavement perspective, the color and texture of the pavement can also aid in reducing the 

amount of lighting needed (Gajda and VanGeem 2001; Adrian and Jobanputra 2005; MnDOT 

2010; FHWA 2012). Lighter, more reflective pavement surfaces, or those with less texture, can 

provide the same level of luminance (the intensity of light emitted from the surface) at reduced

illuminance (the amount of luminous flux per unit area) values. This can result in energy savings 

either by increasing the spacing between luminaries or by reducing the required lumens per 

luminary to achieve similar illumination. This is illustrated in figure 6-26, which shows that for 

the same illuminance values (e.g. lighting energy) across the two lanes, the lane on the right has 

twice the luminance value due to reflective differences in the pavement surfaces due to color and 

texture (FHWA 2012). 

Figure 6-26. Pavement reflective differences (FHWA 2012).

5

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

This concept of illumination is standardized in the pavement reflectivity classification numbers 

(R-numbers) used in IESNA RP-8 (IESNA 2000) to compute the required pavement illumination 

based on pavement surface luminance and roadway classification. A higher pavement luminance 

(e.g., R1) requires less illumination than pavements having less luminance (e.g., R3). This 

standard is used in the Minnesota DOT roadway lighting manual that prescribes more 

illumination for darker and more textured pavement surfaces (R2 and R3 which are 

asphalt/gravel and asphalt/rough texture) than for lighter, smoother textured pavement surfaces 

(R1 which is cement/concrete, and to a lesser degree R4 which is smooth textured asphalt); this 

standard is applied for all paved surfaces (including sidewalks) other than interstates (MnDOT 

2010). 

Many state DOTs (for example, California, Florida, and Texas) do not differentiate between 

surface types, partially because it is unknown what the long-term color and texture of the 

pavement will be. Thus, they are designed for a reduced luminance condition even though the 

newly constructed pavement may have a high luminance value, which results initially in 

overdesign. Although it is recognized that reductions in illumination can be warranted due to 

initial pavement surface luminance, reducing energy costs, and environmental impacts, it is

difficult to design long-term lighting systems with the assumption that the pavement surface will 

always retain a given reflectance. The use of adaptive lighting, in which occupancy sensors, 

ambient light sensors, and adjustable lighting are employed, could address this limitation as the 

lighting level (and thus energy consumption) can be automatically adjusted as pavement 

luminance changes over time (FHWA 2014). 

In addition to stationary roadway lighting, there are questions regarding the impact of pavement 

luminance on the effectiveness of vehicle headlights. Although lighter pavements may increase 

the efficiency of vehicle headlights, little documentation is available in terms of how they affect 

safety, and what was found reveals that this issue is unresolved. The problem is more complex 

than it may at first appear, as the contrast between an obstacle and the background is extremely 

important, as is the glare generated by oncoming traffic (Mace et al. 2001). Thus, in some 

scenarios, darker pavements may provide enhanced nighttime obstacle recognition for light 

colored obstacles, but further work needs to be done to better understand this issue (Dumont et 

al. 2009). 

Future Directions and Emerging Trends

The impact of roadway lighting practices on the surrounding environment is of increasing 

concern to the public and highway agencies out of concern for impacts on wildlife and on energy 

efficiency and costs (AASHTO 2008). Overall, there is a general trend to reduce light pollution 

and unneeded lighting and its associated cost and environmental impact. As of about 2005, cities 

and states have responded with lighting ordinances and requirements regarding certain types of 

fixtures, minimum and maximum lighting levels, lumen/acre limits, and lighting elimination in 

some cases. Legislation has been adopted in Arizona, California, Connecticut, Colorado, Maine, 

New Mexico, Texas, Georgia, and New Jersey and has also been introduced in other states 

(AASHTO 2008). 

Strategies for Improving Sustainability

Practices available to pavement managers, designers, and specification developers that might be 

used to address lighting issues are provided in table 6-7. 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Table 6-7. Summary of strategies to address lighting issues and potential trade-offs.

Lighting Objective Sustainable Approach and 

Trade-offs Economic Impact Environmental Impact

Societal 

Impact

Increase Energy 

Savings

Use of LED technology 

coupled with adaptive 

lighting.

High initial costs but 

with high energy 

savings, payback 

period is around 3 

years. 

Significant reduction 

in energy 

consumption and 

reduced emissions. 

Downward 

directionality helps 

migrating birds.

Provides clear, 

consistent, and 

more natural 

light and less 

lighting when 

not needed.

Provide Appropriate 

Amount of Artificial 

Lighting

Better design that accounts 

for the long-term pavement 

reflectivity. Adaptive 

lighting to only provide 

illumination when needed.

Lower economic 

costs for lighting

Reduced 

environmental 

impact due to reduce 

lighting. 

Less light 

pollution.

Reduce Light Pollution

Better design of luminaries, 

consideration of lighting 

needs, and implementation 

of new technologies

Increase in cost due 

to investment in new 

luminaries and 

lighting technologies

Reduction in light 

pollution

Reduction in 

light pollution

Provide Better 

Understanding of the 

Impact of Pavement 

Reflectivity/Luminosity 

on Safety

Conduct research to 

determine what effect, if 

any, pavement reflectivity/ 

luminosity have on night

and daytime safety 

Investment is 

required to conduct 

research to 

determine 

significance

Unknown

Positive if 

safety can be 

enhanced

As an example of addressing the effects of light pollution on wildlife, the Florida Department of 

Transportation (FDOT) performed lighting research primarily because the state’s beaches serve 

as important nesting habitat for several species of threatened and endangered sea turtles. 

Artificial light on or near nesting beaches can negatively affect the nesting process by interfering 

with normal nocturnal behaviors and spatial orientation of sea turtles, a problem to which 

streetlights contribute. Consequently, FDOT contributed to the development of the Florida 

Power and Light Company’s Coastal Roadway Lighting Manual (AASHTO 2008; Ecological 

Associates 1998; Salmon, Wyneken, and Foote 2003). 

The need to reduce electrical energy consumption has stimulated significant research and product 

development in the field of roadway lighting, the most relevant being the coupling of LED lights 

with adaptive lighting technology. Research is underway considering lighting types, 

directionality, placement, and warrants for placing lighting and adaptive lighting controls. 

Adaptive lighting controls allow lighting levels to be reduced during off-peak periods and to 

adjust to ambient lighting conditions (FHWA 2012). Simply put, a significant amount of power 

can be saved by varying the levels of lighting between peak and off-peak periods and as lighting 

needs change due to changes in ambient light conditions and pavement luminance over time. 

Adaptive lighting can be even more responsive to demand using tools such as occupancy sensors 

and multilevel lighting (FHWA 2014). For example, a new project on the campus of the 

University of California–Davis wirelessly connects more than 1,400 energy efficient lights along 

pathways and roadways to a main control area, so that lights that once operated in solitude are 

now “talking” to each other as part of a seamless web. The lighting can be scheduled and 

adjusted for increased or decreased levels of activity, such as during sporting events, or to guide 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

pedestrians along preferred routes. The system senses occupants, whether on foot, bicycle or 

automobile, predicts their direction of travel, and lights the path ahead. The smart network also 

senses when areas are vacant, then dims lights enough to save energy and reduce light pollution, 

without compromising safety. This system has an approximate 10-year payback period 

($950,000 investment and $100,000 per year in energy savings). These types of controls are 

currently being piloted on a city street (CLTC 2012). Similar systems will likely become more 

widely available for street and highway lighting, and can be tuned to consider pavement 

luminance (FHWA 2014). 

Safety

Safety is a key part of a sustainable transportation system. Figure 6-27 shows the trends in 

fatalities and fatality rates from 2002 to 2011 in the U.S., where it is observed that the number of 

fatalities has decreased by almost 25 percent since 2002 and the fatality rate per 100 million vmt 

(161 million vkt) has declined from 1.51 to 1.10 (NHTSA 2013). This is the result of the 

continuous improvements in transportation safety. One of the goals of the Federal Surface 

Transportation Policy and Planning Act of 2009 is to reduce the motor-vehicle related fatalities 

by 50 percent by 2030. 

Figure 6-27. Fatality and fatality rates, 2002 – 2011 (NHTSA 2013). 

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Fatality Rate

Fatalities

Year

Fatalities Fatality Rate per 100 Million VMT

6-62

A study conducted by Miller and Zaloshnja (2009) found that the roadway condition is a key 

contributing factor in vehicle crashes and that roadway-condition related crash costs are over 

$215 billion dollars annually (see figure 6-28). In order to have a sustainable and safe 

transportation system, keeping roadways in good condition is one of the most important factors. 

The MAP-21 Act signed into law in July 2013 supports FHWA’s aggressive transportation 

safety goals. The Highway Safety Improvement Program (HSIP) is highlighted as one of the key 

programs in the MAP-21 act. The HSIP emphasizes a data-driven approach with each state 

required to identify key safety problems, establish a relative severity, and then adopt 

performance-based objectives to maximize transportation safety.
Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

Figure 6-28. Crash costs by crash factor (Miller and Zaloshnja 2009). 

From a pavement perspective, there are a number of major pavement-related factors that can 

influence safety, including the following: 

• Traffic work zones. It is well documented that the number of crashes increases in work 

zones (Walls and Smith 1998). The utilization of pavement systems that minimize the 

number and duration of work zones over the life cycle reduce exposure to the increased 

crashes that occur in work zones. 

• Surface friction. Adequate surface friction is critical to provide safe stopping distances. 

Friction levels should be based on friction demand, i.e., higher levels of friction required 

where there is a distinct need, such as on curves, ramps, and signalized intersections

(Larson et al. 2008). 

• Pavement macrotexture. Longitudinally grooved or tined concrete surfaces can add 

directional stability, reduce splash and spray, and provide drainage channels for surface 

water to reduce hydroplaning. Open-graded friction courses are effective at minimizing 

splash and spray from adjacent vehicles, which increases visibility while also reducing 

hydroplaning. Porous pavements also remove water from the surface, although they are 

generally not used on high-speed routes. 

• Cross slopes. The pavement must have an adequate cross slope (typically a minimum of 

2 percent) to promote surface drainage and help prevent hydroplaning. This includes 

maintenance of a continuous slope to the outside edge of the shoulder by avoiding 

wheelpath ruts and other transverse profile changes that can allow water to pond on the 

pavement surface. 

• Rumble strips. These undulations that are paved, cast, or retrofitted into pavements emit 

a loud and abrupt noise when traversed, and have proven effective in shoulders 

(preventing roadway departure accidents by alerting wayward drivers to return to the 

roadway), at approaches to intersections and stop lights (preparing the driver to slow 

down or stop), and along the centerlines of two-lane roadways (helping to prevent headon collisions). 

$59.6

$97.1

$129.7

$217.5

Seat Belt Non-Use

Speeding-Related

Alcohol-Related

Roadway ConditionRelated

Crash Cost (Billion Dollars, annually)

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

• Pavement smoothness. Smoother pavements are comfortable and help reduce driver 

fatigue and minimize the potential for the driver to make unsafe maneuvers. 

Obviously, there are a number of other roadway factors that also affect safety (e.g., geometrics, 

pavement markings, signage, shoulder condition/dropoff, ditch and roadway side slopes, rightof-way and clear zones, etc.), but these are not considered as part of the pavement decision. 

Concluding Remarks

This chapter reviews important sustainability impacts of pavements in the use phase, including 

key factors related to rolling resistance and fuel consumption, tire-pavement noise, stormwater 

runoff, pavement thermal performance, lighting, and safety. For each of these factors, 

information is provided on their importance, quantification of their impact where available, 

current limitations, and trade-offs that must be considered. Only those use-phase effects that are 

influenced by pavement decisions are included. 

The major highlights with regard to pavement characteristics and vehicle fuel use (and associated 

environmental benefits) are the following:

• Significant environmental benefits from reduced fuel consumption can be achieved by 

keeping high traffic pavements in smooth condition. There are trade-offs between 

negative effects of materials production and construction that occur when maintaining 

pavements in good condition versus benefits that may be realized in the use phase. 

Therefore, little or no environmental benefits from fuel economy improvements may be 

achieved from maintaining low-traffic pavements in smooth condition even though there 

are other reasons for doing so. Considering social aspects, roads should be kept in a 

functional condition to maintain access to the transportation system for efficient 

movement of people and goods by protecting pavement structures with appropriate 

preservation treatments.

• A high level of pavement smoothness should be sought whenever a pavement is built, 

rehabilitated, or maintained, particularly on high-volume routes. This can be 

accomplished by instituting rigorous smoothness specifications for new construction and 

rehabilitation, and by requiring that high-volume pavements are maintained at a high 

level of smoothness throughout their life. 

• Structural responsiveness and its effect on vehicle fuel economy is the subject of several 

models that have been developed, and a number of field studies have been performed 

measuring vehicle fuel economy on different pavement structures under different 

conditions. These provide indications that under various conditions the structural 

responsiveness of different pavements to vehicle loading can have a measureable effect. 

However, unlike roughness, this effect is highly dependent on pavement temperatures 

and is much more sensitive to vehicle type and speed than roughness. The calibration of 

models that will allow definitive conclusions to be drawn based on general application of 

the models to a wide range of pavements under a broad range of traffic and climatic

conditions in various locations has not yet been completed. 

• The smoothness of pavements in locations where there are utilities should be preserved 

by avoiding utility cuts where possible, and by obtaining the best possible repairs to cuts 

where they must be performed. 

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Towards Sustainable Pavement Systems Chapter 6. Use-Phase Considerations

The major conclusions with regard to pavement characteristics and tire-pavement noise are the 

following: 

• Noise can have adverse effects on humans and wildlife. Although other factors are 

typically more important than the pavement in determining noise levels, noise attributable 

to the pavement surface characteristics should be controlled if it is determined to be 

detrimental to surrounding communities and habitat. 

• Methods are available to measure tire-pavement noise. Research performed to date offers 

information regarding the noise benefits of different pavement surface types and textures, 

and initial indications of their long-term performance. For example, thin rubberized 

asphalt overlays have been found to be effective at mitigating pavement-generated noise 

in some locations such as Phoenix, Arizona. Diamond grinding is another strategy that 

has noticeably reduced noise emissions from some concrete pavement surfaces. The 

longevity of these noise mitigation strategies is still under investigation.

• New materials for asphalt surfaces and new textures for concrete surfaces have been 

developed to reduce noise and are being evaluated. 

The major conclusions regarding the use of permeable pavements and stormwater management 

are:

• There are many options to construct permeable pavements including porous asphalt, 

pervious concrete, and permeable paver systems. Regardless of the pavement type, 

permeable pavements are currently better suited for low-speed, low-volume roadways 

and parking areas. Ongoing research is being done to investigate the applicability of 

permeable pavements to more heavily loaded facilities.

• Permeable pavement systems require more frequent cleaning and maintenance than do 

conventional pavements in order to maintain adequate permeability. This often requires 

the need to purchase specialized cleaning equipment and to schedule more frequent 

cleanings.

• Although rare, the runoff drained through permeable pavement surfaces may contain 

pollutants that could potentially contaminate groundwater sources. This must be 

evaluated for each specific application.

The major conclusions of the discussion on the thermal performance of pavements and their 

potential contribution to the UHIE are as follows:

• Methods are available to measure solar reflectance, but quality assurance and control 

procedures need to be more fully developed (NCPTC/NCAT 2013). Typically, concrete 

pavements have higher reflectivity than asphalt pavements but it is recognized that age 

and weathering generally result in asphalt pavements becoming more reflective over time 

(increasing albedo) whereas concrete pavements become less reflective over time

(decreasing albedo). Application of preservation and rehabilitation treatments can alter 

the reflectivity of the pavement surface. These changes in pavement solar reflectance 

over time are not well understood and research is underway to better quantify them 

(NCPTC/NCAT 2013). 

• In general, in locations where it is deemed important, high solar reflectance should be 

maintained over time, which may become a consideration for maintenance and 

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Chapter 6. Use-Phase Considerations Towards Sustainable Pavement Systems

rehabilitation activities. For example, the frequent use of some asphalt surface treatments 

(e.g., slurry seals, microsurfacing) has a tendency to keep albedo low. Diamond grinding 

of concrete may also change the surface reflectivity, either increasing it or decreasing it 

depending on the color of the aggregate. 

• Some materials used to create the most highly reflective surfaces, particularly highly 

reflective photocatalytic materials and some proprietary coatings, may have a high 

environmental footprint during manufacturing compared to conventional materials. Their 

use in pavements should be considered on a case-by-case basis. An LCA study can help 

to evaluate the net environmental effects of implementing more reflective surfaces for 

different applications. 

• Pavement strategies that reduce pavement surface temperatures consist of more than just 

using pavements with high solar reflectance, and instead require a systems approach. 

The use of pervious pavements and shading should also be considered. 

• At this time, it is unclear to what degree pavement solar reflectance impacts the 

development of the UHIE for different urban architectures, climate regions, and other 

variables. Research is underway to provide a more comprehensive understanding of the 

UHI phenomenon. Similarly, the overall impact of reflective surfaces and regional and 

global climate is a subject of current research, which is needed to provide a more 

complete understanding of the potential positive and negative impacts of increased 

pavement reflectivity.

Some of the major conclusions surrounding roadway lighting and pavement are as follows: 

• The high energy demand of current lighting systems has a significant economic and 

environmental footprint. Thus, the goal is to provide an appropriate amount of artificial 

lighting for driver safety that is not excessive or wasteful. This will not only result in 

economic and environmental savings, but will also help reduce the amount of light 

pollution produced. 

• Pavement surface luminance is known to influence the amount of artificial lighting 

required, but practical application of this knowledge is currently unclear as surface 

luminance changes with time. Adaptive lighting technologies featuring the use of LEDs 

offers an opportunity to account for pavement luminance by adjusting illuminance in 

response to changing ambient conditions. 

• Understanding of the impact of pavement luminance on nighttime and daytime safety is 

still unclear, as trade-offs exist with respect to the improved lane demarcation that can 

exist between light-colored line markings and a dark pavement surface, with light colored 

pavement and dark backgrounds beyond the pavement edge, and with the increased 

efficiency of artificial lighting (such as headlights) on pavement surfaces with higher 

luminance. 

• Development and implementation of new adaptive lighting systems, which provide 

lighting only when it is needed, is currently underway and has the strong potential to 

significantly lower economic, environmental, and societal costs associated with artificial 

lighting. 

Finally, regarding safety, it is emphasized that adequate surface friction should be made 

available on all pavement facilities to ensure that safe stopping distances are achievable. Friction 

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levels should be based on the demands of the facility or location, in that higher levels should be 

targeted where there is a distinct need, such as at curves, ramps, and intersections. Smoothness 

levels of pavements should also be maintained as it contributes to safer traveling conditions. 

Open-graded friction courses or porous pavements are effective at minimizing splash and spray 

from adjacent vehicles, which increases visibility. Similarly, grooved concrete surfaces can add 

directional stability, reduce splash and spray, and provide drainage channels for surface water to 

reduce hydroplaning. 

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Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

CHAPTER 7. MAINTENANCE AND PRESERVATION TREATMENTS TO 

IMPROVE SUSTAINABILITY

Introduction

Diminishing budgets and the recent recognition of the benefits of considering life-cycle costs have 

motivated changes in agency policies that advocate environmental and financial sustainability 

through the practice of pavement preservation. This is in stark contrast to the “worst-first” approach

that was commonly practiced in the past, in which pavements were allowed to deteriorate to a highly 

distressed condition before performing major (and more intrusive) rehabilitation. In fact, the FHWA 

has been a strong proponent and supporter of the concept of cost effectively preserving the nation’s 

pavement network. This has helped to spur a nationwide movement of pavement preservation and 

preventive maintenance programs, with an overall goal of improving safety and mobility, reducing 

congestion, and providing smoother, longer lasting pavements (Geiger 2005). 

Pavement preservation is inherently a sustainable 

activity. It often employs low-cost, lowenvironmental-impact treatments to prolong or extend 

the life of the pavement by delaying major 

rehabilitation activities. This conserves energy and 

virgin materials while reducing GHG emissions over 

the life cycle. Furthermore, as mentioned above, wellmaintained pavements provide smoother, safer, and 

quieter riding surfaces over a significant portion of 

their lives, resulting in higher vehicle fuel efficiencies, 

reduced crash rates, and lower noise impacts on 

surrounding communities, which positively contributes 

to their overall sustainability. The philosophy of 

pavement preservation is often succinctly captured in 

terms of “applying the right treatment to the right 

pavement at the right time.” 

This chapter describes the impact that maintenance 

and preservation treatments have on the 

sustainability of pavement systems. It first describes 

the role that pavement management systems play in 

the pavement planning and decision making of 

highway agencies, and how they can incorporate 

preservation programs. This is followed by a review 

of common maintenance and preservation treatments 

for both asphalt and concrete pavements, and an 

assessment of how these various treatments impact 

sustainability. It is important to point out that only 

limited information exists in this regard, so much of 

the information is conjectural at this stage. This 

chapter does not delve into the details of the 

materials or the specific construction details of the 

various treatments, as there are a number of manuals 

and documents covering those aspects. 

Incorporating Pavement 

Preservation into the 

AASHTOWare Pavement ME 

Design Software 

A recently completed study for the 

National Cooperative Highway Research 

Program (Project 1-48) investigated 

different approaches for incorporating 

pavement preservation into the 

pavement design process, and 

specifically into the AASHTOWare 

Pavement ME Design software. The 

project identified several procedures and 

approaches for designing asphalt and 

concrete pavement structures so that 

they account for the effects of future 

scheduled preservation treatments (e.g., 

chip seals, thin overlays, diamond 

grinding, partial-depth repair) on 

pavement life. By designing a pavement 

to include preservation at key points in 

its life and carrying through with the

application of those treatments once the 

pavement has been put into service, the 

pavement can be kept in better overall 

condition with less disruption to traffic 

because of delayed and less frequent 

rehabilitation treatments. This 

preservation-based design philosophy 

represents a sustainable approach to 

building and maintaining highway 

infrastructure, as it optimizes the use of 

pavement materials and minimizes the 

amount of energy and resources used in 

keeping the infrastructure in good 

condition.

7-1 
Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Pavement Preservation and Sustainability

Pavement Management Systems and Pavement Preservation

Since their conceptualization in the late 1960s and initial implementation by state highway 

agencies beginning in the late 1970s, the use of pavement management systems (PMS) has 

grown considerably. The benefits of pavement management are well documented, and include: 

• Enhanced planning ability at all levels, including strategic, network, and project. 

• Decision making based on observed and forecasted conditions rather than opinions. 

• The ability to generate alternate scenarios for future pavement conditions based on 

different budget scenarios or management approaches.

Many state highway agencies have been using pavement management systems to demonstrate to 

legislators the benefits of pavement preservation in maintaining or improving the overall 

condition of the pavement network (Zimmerman and Peshkin 2003). Figure 7-1 shows a 

schematic that illustrates how pavement preservation can help extend the life of the pavement, 

delaying the need for major (and more costly) rehabilitation activities.

Figure 7-1. Illustration of the impact of pavement preservation. 

7-2 

Integrating PMS and Pavement Preservation

The integration of pavement preservation into pavement management requires a deliberate effort 

on the part of transportation agencies to reevaluate their existing data collection activities, to 

revise and update performance modeling approaches, and to improve overall program 

development activities. The desired outcome (and ultimate goal) is that the need for pavement 

preservation treatments, and their timing of application, can be identified within the pavement 

management system, and that the benefits realized from the application of the treatments can be 

accounted for in the system’s optimization analysis. The critical steps involved in the integration 

of PMS and pavement preservation are summarized in figure 7-2. 
Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

Figure 7-2. Steps in integrating PMS and pavement preservation (adapted from 

Zimmerman and Peshkin 2003). 

Pavement Condition Assessment

- Evaluate pavement condition using accepted agency standards at 

a set inspection frequency

- Document conditions that can be beneficially addressed through 

preservation in the PMS

Pavement Performance Models

- Develop pavement performance models to forecast future 

performance with and without the application of preservation 

treatments and integrate them into the PMS

Pavement Treatment Rules and Treatment Impact Rules

- Develop rules under which preservation treatments are feasible 

within the PMS

- After treatments are placed, monitor performance to develop 

and refine treatment treatment impact rules and performance 

models

Major Issues: 

 Lack of life cycle inventories specific 

to maintenance and preservation 

activities. 

 Cost effectiveness has been 

investigated and widely accepted. 

 Impact of traffic. 

 Treatment and material selection. 

 Construction quality.

7-3 

General Pavement Preservation Strategies for Improving Sustainability

Pavement preservation is primarily concerned with 

minimizing the project-level life-cycle cost of the 

agency. To minimize the agency life-cycle cost, 

only the materials and construction phases of the 

pavement life cycle are considered, since use-phase 

costs (primarily vehicle operating costs) are mostly 

borne by pavement users and not by the agency. 

For low-volume roads, where the environmental 

impact of vehicle operations is small, improvements 

in the agency life-cycle cost and improvements in 

sustainability are generally compatible, since the 

objective for both is to minimize the frequency of 

treatment applications and the amount of material 

used for each treatment. Assuming that preservation treatments all generally use combinations 

of aggregate, water, cement, and asphalt as construction materials and that internal combustion 

engines are used in their placement (e.g., the transport, removal, and application of the treatment 

and associated waste), the environmental impact of pavement treatments is roughly linearly 

proportional to the total thickness of the treatment, whether it is a milling/grinding activity, a 

surface treatment, or an overlay. Therefore, for low-volume routes, the general strategy for 

improving sustainability is to minimize the amount of materials used and the number of 

construction cycles over the life cycle by optimizing the treatment selection and timing to avoid 

major structural damage while minimizing costs. 
Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

For higher traffic volume roadways, the environmental impact of the use phase becomes more 

important, often to the point that, for very high-volume routes, the materials and construction 

phase impacts of maintenance and preservation become very small relative to the influence of the 

pavement smoothness, deflection, and macrotexture on vehicle operations (primarily in terms of 

fuel economy). Depending on the route, the optimization of the environmental benefit will 

require balancing the impacts incurred to keep the pavement in good condition (in order to 

reduce vehicle operating costs) with the impacts resulting from materials production and 

construction of the treatment. An example of this is provided in chapter 6, in which the 

optimization of ride quality (in terms of IRI) to minimize CO2 emissions is presented for routes 

with different levels of traffic and considering materials, construction, and vehicle use. The 

optimization of environmental benefits for high-volume routes is, therefore, much more complex 

than it is for low-volume routes because it may increase agency economic life-cycle cost as the 

need for more frequent treatment is increased to maintain good condition to reduce road user 

costs and vehicle-produced emissions. 

An example of this situation for high-volume routes is illustrated in figure 7-3 for asphalt concrete

overlays placed at different recurring intervals on a high-volume interstate highway. The 

placement of the asphalt concrete overlays at different recurring intervals results in varying 

amounts of cumulative agency GHG emissions (expressed in terms of CO2e). In the figure, it can 

be seen that the cumulative agency GHG emissions from materials production and construction 

decrease as the overlay interval increases from 10 years (when the IRI is expected to be 136 in/mi 

[2.2 m/km]) to 30 years (when the IRI is expected to be 273 in/mi [4.4 m/km]), while the 

cumulative user GHG emissions increase from vehicles operating on a rougher pavement. For this 

example, it is also observed that the net emissions are minimized at an overlay interval of 22 years; 

however, the IRI is 211 in/mi (3.4 m/km) at this age interval and the GHG emissions due to 

increased roughness may potentially offset any benefits obtained. This is but one example and the 

results change considerably depending on the expected overlay performance, the traffic levels, and 

the emissions from materials, construction, and end-of-life scenarios. Nevertheless, the application 

of such multi-criteria decision-making tools and approaches can be used as a way of balancing 

trade-offs between environmental goals and life-cycle cost goals.

Figure 7-3. Effect of overlay interval on agency, user and total 

GHG (CO2e) emissions (Lidicker et al. 2013*).

*With permission from ASCE. This material may be downloaded for personal use only. Any other use requires 

prior permission of the American Society of Civil Engineers. This material may be found 

at http://cedb.asce.org/cgi/WWWdisplay.cgi?302677

7-4 
Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

To summarize, the selection of the right treatment 

for existing conditions is always important to 

improve sustainability. Most agencies are focused 

on minimizing agency economic life-cycle cost 

while preserving the pavement structure. For lowtraffic-volume routes, minimization of agency 

life-cycle cost through the right timing of the right 

treatment also generally improves sustainability. 

The selection of the right treatment for existing 

conditions is also important for reducing agency 

life-cycle costs for higher traffic volume routes. 

However, as traffic levels increase, more frequent 

maintenance and preservation treatments can 

further reduce environmental impacts (in terms of 

its effect on the use phase), albeit at a higher 

agency cost. 

Preservation Treatment Selection

The selection of appropriate preservation

treatments must consider the variables that are 

most important in the decision-making process. 

These variables may include factors that differ 

from those considered in identifying and selecting 

rehabilitation activities. The literature suggests 

that the following factors be considered in 

selecting appropriate pavement preservation

treatments (Hicks, Seeds, and Peshkin 2000):

• Existing pavement type. 

• Type and extent of distress. 

• Climate.

• Cost of treatment.

• Availability of qualified contractors.

• Time of year of placement.

• Duration of lane closures. 

• Traffic loading and expected life. 

• Availability of quality materials.

• Pavement noise and surface friction. 

A sequential approach for evaluating possible 

preservation treatments for an existing pavement 

and identifying the preferred alternative is 

provided in figure 7-4. *http://wwwcf.fhwa.dot.gov/exit.cfm?link=http://cedb.asce.org/cgi/WWWdis

play.cgi?302677

7-5 
Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Figure 7-4. Process of selecting the preferred preservation treatment (adapted from 

Peshkin et al. 2011). 

7-6 
Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

The rest of this chapter discusses various pavement maintenance and preservation techniques for 

asphalt and concrete pavements, particularly in terms of their associated benefits or costs with 

regards to enhancing sustainability. These benefits and costs are expressed in terms of the level 

of performance, performance longevity, congestion, lane closure durations, fuel consumption, as 

well as many others. Table 7-1 lists the maintenance and preservation treatments included in this 

discussion. 

Table 7-1. Pavement maintenance and preservation techniques.

Asphalt Concrete

Crack Filling/Sealing

Asphalt Patching 

Fog Seals/Rejuvenators 

Chip Seals 

Slurry Seals

Microsurfacing

Ultra-thin and Thin Asphalt 

Overlays 

Hot In-Place Recycling

Cold In-Place Recycling

Ultra-thin Bonded Wearing Course 

Bonded Concrete Overlays 

Joint/Crack Sealing

Slab Stabilization/Slab Jacking

Diamond Grinding/Grooving

Partial-Depth Repairs

Full-Depth Repairs

Dowel Bar Retrofit

Slot/Cross Stitching

Retrofitted Edge Drains

Ultra-thin Bonded Wearing Course 

Bonded Concrete Overlays 

Whereas there is abundant literature available on the topics of how pavement materials, design, 

and construction influence sustainability, far less information is available on how pavement 

maintenance and preservation treatments and practices impact sustainability. One recent project 

(TRB 2012) concluded that environmental sustainability research related specifically to postconstruction operations is an emerging field and that the consideration and quantification of the 

sustainability associated with pavement maintenance and preservation programs is not 

commonly practiced in the United States. 

A concise summary of the potential applicability of RCWMs and other emerging 

techniques/materials for use in pavement maintenance and preservation treatments is shown in 

table 7-2 (TRB 2012). Although it is generally simply assumed that maintenance and 

preservation is inherently sustainable, the details of treatment type, placement frequency, and 

functional condition levels (especially roughness) affecting environmental impacts are not 

necessarily addressed.

7-7 
Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Table 7-2. Potential use of non-traditional materials and techniques with potential pavement 

maintenance and preservation application (TRB 2012). 

Material/ 

Technique Literature Cited Possible Preservation Uses

Possible 

Maintenance Uses Remarks

Bio-Fluxing 

Agent

Denevillers 

(2010)

• Prime Coat

• Chip Seal

• Microsurfacing

• Overlay tack coat

• Cold mix

• Warm mix Trade name is Vegeflux®

Bio Binder Denevillers 

(2010)

• Chip Seal

• Microsurfacing

• Cold in-place 

recycling

• Chip seals

• Road marking Trade name is Vegecol®

Recycled 

Concrete 

Aggregate (RCA)

Gardner and 

Greenwood 

(2008)

• Bonded Concrete 

Overlay

• Full-depth patching

• Partial-depth 

patching

RCA acts to sequester CO2

in addition to recycling

Recycled Glass 

Gravel

Melton and 

Morgan (1996) • Untried • Unbound base 

courses

Potential use on gravel 

roads

Fly Ash MnDOT (2005)

• Microsurfacing 

mineral filler

• Slurry seal mineral 

filler

• Concrete Overlays

• Concrete 

maintenance 

mixtures

• Microsurfacing Widely used in a variety of 

products

Bottom Ash Carpenter and 

Gardner (2007)

• Microsurfacing 

mineral filler

• Subbase under 

gravel surfaces

Flue Gas 

Desulfurization 

Gypsum

Benson and Edil 

(2009)

• Microsurfacing 

mineral filler

• Slurry seal mineral 

filler

• Concrete 

maintenance 

mixtures

Kiln Dust MnDOT (2005) • Prime coat

• Microsurfacing

• Prime coat

• Microsurfacing

Baghouse Fines Denevillers 

(2010)

• Microsurfacing 

mineral filler

• Slurry seal mineral 

filler

• Untried

Crushed Slag Chappat and Bilal 

(2003)

• Chip seal 

aggregate

• Special binder road 

mixture

Ultra-High 

Pressure Water 

Cutter

Pidwerbesky and 

Waters (2007)

• Restore 

macrotexture on 

chip seals

• Retexture chipsealed roads prior to 

resealing

Uses no virgin material and 

the sludge can be recycled 

as precoating for chip seal 

aggregates

Shotblasting Gransberg (2009) 

• Restore 

microtexture on 

polished HMA and 

PCC pavements

• Restore skid 

resistance on 

resealed PCC 

bridge decks

Uses no virgin material and 

the steel shot is recycled 

for reuse in the process

Recycled Motor 

Oil Waters (2009) • Dust palliative

• Otta Seals

• Otta seal as surface 

course

Motor oil is refined before 

use

Recycled Tire 

Rubber

Beatty et al. 

(2002)

• Chip seals

• Thin overlay

• Chip seals

• Thin overlays

Also found to reduce road 

noise

7-8 
Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

Asphalt-Surfaced Pavement Maintenance and Preservation Treatments

Introduction

Asphalt-surfaced pavements include any pavement surfaced with an asphalt material, whether 

asphalt concrete (i.e., HMA, WMA) or an asphalt surface treatment of some type. Although this 

represents a large family of different pavement types, the maintenance and preservation activities 

are identical. 

Table 7-3 presents an overall summary of various maintenance and preservation treatments 

applicable to asphalt-surfaced pavements. First, it provides a brief description of the technique 

and then indicates its effect on a number of preventive and restorative benefits (“↑” indicates

positive impact, “↓” indicates negative impact, and “↔” indicates both positive and negative 

impacts). This is followed by a general assignment of the relative life expectancy and cost, and 

the relative environmental and social impacts. It is noted that these relative comparisons are 

inherently non-specific, by definition, due to the general lack of available information and the 

broad number of variables that affect the performance, costs, life-cycle environmental impacts, 

and social impacts of each treatment. The relative comparisons will also vary depending on the 

traffic levels, climate region, and a host of other variables.

Various resources are available that discuss each treatment type, including the type of pavement 

conditions addressed, how each should be constructed, and their cost effectiveness. These 

include a series of three courses offered by the National Highway Institute (NHI Course Nos. 

131115, 131103, and 131116), a series of webinars on key concepts and guidelines related to 

asphalt pavement maintenance, preservation, and recycling developed by the Asphalt Institute 

(http://www.asphaltinstitute.org/public/asphalt_academy/webinars/index.dot), and a manual on 

basic asphalt recycling and reclaiming concepts published by the Asphalt Recycling and 

Reclaiming Association (ARRA) and the FHWA, among others. As considerable information is 

readily available regarding the proper timing, cost effectiveness, and construction of the various 

treatments, the following sections specifically address the sustainability aspects of each 

treatment, focusing on the environmental and social impacts. 

Crack Filling/Sealing

Crack filling (see figure 7-5) involves the 

process of placing an adhesive material 

(generally a lower quality, non-polymerized or 

polymerized cold-pour emulsion asphalt binder) 

into or over non-working cracks (cracks that are 

not expected to open and close with temperature 

changes) to reduce the infiltration of moisture 

and incompressible materials into the pavement 

structure (FHWA 1999; Peshkin et al. 2011). 

Typically very little preparation of the crack is 

performed prior to the installation of the filler 

material.

Figure 7-5. Installation of hot-applied sealant.

7-9 
Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems Table 7-3. Evaluation of sustainability impacts of treatments for asphalt-surfaced pavements. Seal Pavement Rejuvenate Surface Addresses Surface Distress Eliminate Stable Ruts Improves Texture for Friction Improves Ride Quality and Surface Profile Improve Texture for Noise Relative Treatment Life 

( to )

Relative 

Cost 

($ to $$$$)

Crack Filling

Placement of adhesive material into and/over non-working cracks, minimal crack preparation, lower-quality materials used

↑

↑

Cracking 

only

↓

Longitudinal 

overbanding 

can 

negatively 

impact friction

Overbanding may 

increase 

roughness; 

sealing cracks 

may slow 

development of 

roughness

↔

Overbanding 

increases 

noise

 $ Low

Reduced traffic delays, less pleasing aesthetics, potential roughness and noise issues

Crack Sealing

Placement of adhesive material into and/over working cracks, good crack preparation, high-quality materials used

↑

↑

Cracking 

only

↓

Longitudinal 

overbanding 

can 

negatively 

impact friction

↔

Overbanding 

increases 

noise, filling 

can reduce 

noise

 $ Low

Reduced traffic delays, less pleasing aesthetics, potential roughness issues

Asphalt Patching

Used to treat localized distresses; partial-depth patches address surface distresses and full-depth patches address structural distresses 

↑ ↑ ↑  $$

Variable

Depends on amount of patching 

and improvement gained in 

structural life and ride quality

Reduced traffic delays compared to other treatments; negative impact on ride quality and noise, poor aesthetics (if patching is substantial)

Fog Seal/Rejuvenators

Very light application of asphalt emulsion on pavement surface to seal the existing asphalt surface

↑ ↑

↓

(May 

negatively 

impact skid 

resistance)

 $ Medium Depends in part on materials Reduced traffic delays; improves aesthetics

Chip Seals

Sprayed application of asphalt (usually emulsion, heated asphalt cement and cutbacks also used) followed by aggregate chips roller to achieve 50 to 70% embedment. Cost and performance depends on whether it is single or multi-course, as well as binder type and aggregate quality

↑ ↑ ↑

↑

Depends largely 

on number of 

courses placed

↓

Depends on 

chip size

 $$

Medium to High

Depends on number of courses 

and binder type

Increases safety by improving friction, reduced traffic delays due to faster construction and opening to traffic; reduced ride quality due to rough surface, potential vehicle damage due to loose aggregate chips

Slurry Seals

Mix of well-graded aggregate (fine sand and mineral filler) and asphalt emulsion spread over entire pavement surface

↑ ↑

↑  $$ Medium

Increases safety by improving friction, reduced traffic delays due to faster construction and opening to traffic; improves aesthetics. Lower albedo may negatively impact UHI effect

Societal Impact

Preventive

Treatment Description

Relative Environmental 

Impact based on life cycle 

energy use and GHG 

emissions, materials

(Low, Medium, High, Variable)

Restorative Performance and Cost

7-10
Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments Table 7-3. Evaluation of sustainability impacts of treatments for asphalt-surfaced pavements (continued). Seal Pavement Rejuvenate Surface Addresses Surface Distress Eliminate Stable Ruts Improves Texture for Friction Improves Ride Quality and Surface Profile Improve Texture for Noise Relative Treatment Life 

( to )

Relative 

Cost 

($ to $$$$)

Microsurfacing

Mix of crushed, well-graded aggregate, mineral filler, and latex-modified emulsified asphalt spread over entire pavement surface. Cost and performance depends on whether single, double, or multiple-course

↑ ↑ ↑ ↑ ↑ ↑

↑

Depends on 

system

 $$

Variable

Highly dependent on system 

and materials used, longevity of 

treatment, and improvements 

gained in ride quality

Increases safety by improving friction and eliminating stable ruts; reduced traffic delays due to faster construction and opening to traffic; improves aesthetics. Lower albedo may negatively impact UHI effect

Ultra-thin and Thin HMA Overlay: DenseGraded

Asphalt binder (may be polymerized) and dense-graded aggregate combined in central mixing placement and placed with paver in thickness ranging from 0.625 to 0.75 in. for ultra-thin and 0.75 to 1.5 in. for thin overlays. Cost and performance depends on binder type and whether milling is performed prior to treatment placement

↑ ↑ ↑ ↑ ↑ ↑  $$$

High

Use of WMA may reduce 

construction impact (see 

Chapter 3)

Improved ride quality; improved safety through improved friction and drainage; improved aesthetics. Lower albedo may negatively impact UHI effect

Ultra-thin and Thin HMA Overlay: Open-Graded

Asphalt binder (often polymerized or rubberized) and open-graded aggregate combined in central mixing placement and placed with paver in thickness ranging from 0.625 to 0.75 in. for ultrathin and 0.75 to 1.5 in. for thin overlays. Cost and performance depends on binder type and whether milling is performed prior to treatment placement

↑ ↑ ↑ ↑ ↑  $$$

High

Use of WMA may reduce 

construction impact (see 

Chapter 3)

Improved ride quality; improved safety through improved friction and drainage; reduces splash and spray; noise; improved aesthetics. Lower albedo may negatively impact UHI effect

Ultra-thin and Thin HMA Overlay: Gap-Graded

Asphalt binder and gap-graded aggregate, usually made with polymerized or rubberized binder and/or fibers, combined in central mixing placement and placed with paver in thickness ranging from 0.625 to 0.75 in. for ultra-thin and 0.75 to 1.5 in. for thin overlays. Cost and performance depends on binder type and whether milling is performed prior to treatment placement

↑ ↑ ↑ ↑ ↑ ↑  $$$

High

Use of WMA may reduce 

construction impact (see 

Chapter 3)

Improved ride quality; improved safety through improved friction and drainage; highly rut resistant; improved aesthetics. Lower albedo may negatively impact UHI effect

Societal Impact

Preventive

Treatment Description

Relative Environmental 

Impact based on life cycle 

energy use and GHG 

emissions, materials

(Low, Medium, High, Variable)

Restorative Performance and Cost

7-11
Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems Table 7-3. Evaluation of sustainability impacts of treatments for asphalt-surfaced pavements (continued). Seal Pavement Rejuvenate Surface Addresses Surface Distress Eliminate Stable Ruts Improves Texture for Friction Improves Ride Quality and Surface Profile Improve Texture for Noise Relative Treatment Life 

( to )

Relative 

Cost 

($ to $$$$)

Hot In-Place Recycling

Corrects surface distresses within top 2 in. of existing asphalt pavement by softening surface material through heat, mechanically loosening it, mixing with recycling agent, aggregate, rejuvenators, and/or virgin asphalt

↑ ↑ ↑ ↑ ↑  $$$

Medium to High

Re-use of existing materials 

reduces impact. Impact 

depends on whether it involves 

surface recycling, remixing, or 

repaving

Improved ride quality; improved safety through improved friction and drainage; improved aesthetics. Lower albedo may negatively impact UHI effect

Cold In-Place Recycling

Milling and sizing reclaimed asphalt pavement (RAP) and mixing in-place with recycling additive and new aggregate which is then relaid and compacted as new base course. CIR requires that a new surface be placed over it, usually an asphalt overlay or other surface treatment

↑ ↑ ↑ ↑ 

↑  $$

Variable

Depends on additives used and 

type of surface applied; re-use 

of existing materials reduces 

impact

Increases safety through improved friction and drainage; improved ride quality; improved aesthetics. Lower albedo may negatively impact UHI effect

Ultra-thin Bonded Wearing Course

May be used as an alternative to chipseals, microsurfacing, or thin overlays. Consists of a open-graded or gapgraded, polymer-or rubber-modified asphalt layer (0.4 to 0.8 in. thick) placed on a heavy tack coat

↑ ↑ ↑ ↑ ↑  $$$

Medium

Partly dependent on use of 

proprietary additives

Improved ride quality; improved safety through improved friction and drainage; improved aesthetics. Lower albedo may negatively impact UHI effect

Bonded Concrete Overlay

Placement of a thin (2 to 4 in.) PCC layer, with slab dimensions between 2 and 6 ft. over an existing asphaltsurfaced pavement

*

Existing 

surface 

supports 

new 

concrete 

surface

*

Existing 

surface 

supports 

new 

concrete 

surface

↑

↑

Also 

addresses 

unstable 

rutting

↑ ↑

↔

Depends on 

surface 

texture and 

joint 

condition

 $$$$

Medium

Virgin materials and concrete 

materials increase impact, 

thinner cross section reduces 

impact

Increases safety through improved friction and drainage; improved ride quality; improved aesthetics. Increase in albedo may positively impact the UHI effect

Societal Impact

Preventive

Treatment Description

Relative Environmental 

Impact based on life cycle 

energy use and GHG 

emissions, materials

(Low, Medium, High, Variable)

Restorative Performance and Cost

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7-12
Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

In applications where significant crack movement is expected, crack filling is not expected to 

perform particularly well and crack sealing should be considered. Crack sealing is a more 

rigorous process than crack filling, and thus is more energy and emission intensive than crack 

filling. It begins with more preparation of the crack (e.g., routing, cleaning) before the 

placement of a higher quality adhesive and elastic material (typically polymerized or rubberized 

hot-poured asphalt materials) into or over prepared working cracks to minimize the infiltration of 

moisture and incompressible materials into the pavement structure. 

Crack filling and crack sealing do not add any structural benefit to the pavement, but they do 

slow the rate of moisture ingress, which will slow the rate of pavement deterioration by 

preventing moisture from infiltrating and degrading the pavement layers (FHWA 1999; Peshkin 

et al. 2011). 

Positive Sustainability Attributes of Crack Filling/Sealing

• Crack filling/sealing is expected to extend the life of the pavement by keeping the 

pavement sealed against water infiltration. 

• Crack filling/sealing uses relatively small material quantities and thus does not have large 

material-related environmental impacts (but LCAs are not readily available).

• Crack filling/sealing generates little construction waste.

• Crack filling/sealing construction operations use relatively little energy. 

• Crack filling/sealing can be conducted using moving traffic control operations, thus 

minimizing traffic disruptions and delays.

Potential Negative Sustainability Attributes of Crack Filling/Sealing 

• Crack filling/sealing has a relatively short life compared to the pavement and thus must 

be repeated multiple times over the pavement life cycle. 

• Crack filling/sealing configurations that apply material on the surface of the pavement on 

either side of the crack (i.e., overband configurations) can negatively impact ride quality 

and tire-pavement noise. 

• Crack filling/sealing can negatively impact the pavement aesthetics.

• Overutilization of filling/sealing of longitudinal cracks using an overband configuration 

can negatively impact surface friction, especially for motorcycles.

• Construction operations (specifically the crack routing and cleaning processes) are 

typically noisy and produce particulates that can be a potential issue in a community 

setting. 

7-13
Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Asphalt Patching 

The placement of an asphalt patch (see 

figure 7-6) is a common maintenance 

procedure used to treat localized 

distresses. Patching can be performed 

with limited preparation and using a 

cold-mix material (such as under winter 

conditions) or may employ a more 

rigorous approach consisting of milling

or saw cutting, application of a tack coat, 

and placement of a high-quality asphalt 

concrete patching material. Patching 

may be partial depth or full depth, 

depending on the type and severity of the 

distresses being addressed. Patching is 

typically used to fix potholes and 

severely cracked areas. Patching is also 

commonly done in preparation for (or in 

conjunction with) other forms of maintenance activities or preservation treatments, or as a pretreatment for an asphalt overlay. The primary materials used for patching are asphalt concrete, 

cold-mix asphalt, aggregate/asphalt emulsions, and various proprietary patching mixtures. 

Positive Sustainability Attributes of Asphalt Patching 

• The replacement of localized pavement failures restores structural integrity and ride 

quality. If done correctly, this is a long-term repair that should last for the life of the 

pavement.

• For isolated repairs, patching uses relatively little material and thus does not have large 

material-related impacts.

• Construction operations associated with patching use relatively little energy (when 

compared to a more substantial treatment like asphalt overlays). 

• Although some construction waste is generated from the removed material, it can be 

recycled as RAP.

• Patching can be completed in a relatively short period of time, thus minimizing traffic 

disruptions and delays. 

Potential Negative Sustainability Attributes of Asphalt Patching

• Poorly constructed asphalt patching can negatively impact ride quality and tire-pavement 

noise. 

• Patching becomes costly with increasing environmental impact as the density of patching 

increases.

• Large quantities of asphalt patching can negatively impact the overall aesthetics of the 

pavement. 

7-14

Figure 7-6. Full-depth asphalt patch.
Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

Fog Seals/Rejuvenators 

Fog seals or rejuvenators (see figure 7-7) 

are treatments used to add fresh asphalt 

binder or more volatile asphalt constituents 

to the surface of an existing pavement to 

seal the pavement surface, prevent or slow 

oxidation, and prevent further loss of 

aggregates from the pavement surface. Fog 

seals/rejuvenators are not effective in

treating cracking or other surface distresses 

that may compromise the structural integrity 

of the pavement. 

Positive Sustainability Attributes of Fog 

Seals/Rejuvenators 

• Fog seals/rejuvenators restore the 

pavement surface with minimal 

application of material, effectively 

sealing it and preventing further loss of aggregate.

• Fog seals/rejuvenators improve pavement aesthetics creating the impression of a new 

pavement.

• Construction operations associated with the placement of fog seals/rejuvenators use 

relatively little energy. 

• The application of fog seals/rejuvenators can be completed in a relatively short period of 

time, thus minimizing traffic disruptions and delays. 

Potential Negative Sustainability Attributes of Fog Seals/Rejuvenators 

• Poorly constructed fog seals/rejuvenators can negatively impact surface friction and 

safety.

• Some non-emulsion-based rejuvenators contain volatiles that can negatively impact the 

local community.

• The application of asphalt binder over the entire surface results in moderate overall 

environmental impact, especially due to the relatively short performance period of the 

treatment (which, therefore, would require the application of multiple treatments over the 

life of the pavement). 

• Fog seals/rejuvenators will typically darken the surface, and will likely decrease the 

pavement albedo. 

Figure 7-7. Fog seal application. 

7-15
Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Chip Seals 

Chip seals are typically used to seal the 

pavement, address minor, nonstructural 

surface distresses, and improve the friction of 

the wearing course. The construction of a 

chip seal (see figure 7-8) uses a nonpolymerized, polymerized, or rubberized 

asphalt material as a binder, most commonly 

in emulsion form, but heated asphalt and 

cutbacks may also be used. The binder is 

applied to the pavement surface (typical 

application rates are between 0.35 and 0.50 

gal/yd2 [1.58 and 2.26 l/m2]) followed by the 

application of aggregate chips (generally one 

stone thick; typical application rates are 

between 15 and 50 lb/yd2 [27 kg/m2]), and 

these are then rolled into the asphalt binder 

to achieve 50 to 70 percent embedment. Chip seals can be applied in single or multiple layers and 

in combination with other surface treatments (such as microsurfacing, which yields a “cape seal”) 

to reduce concerns associated with loose aggregate chips and to improve ride quality. In many 

cases, chip seals can significantly extend pavement life at relatively low costs. Guidelines for 

constructing effective chip seal treatments are documented in an NCHRP synthesis document 

(Gransberg and James 2005).

Positive Sustainability Attributes of Chip Seals

• Chip seals renew the pavement surface, effectively sealing and addressing minor surface 

defects.

• Chip seals restore surface friction.

• When multiple courses are used, chip seals can improve ride quality and surface profile.

• Chip seals improve pavement aesthetics by creating the impression of a new pavement.

• The use of light-colored aggregates in chip seals can increase surface albedo. 

• The construction of chip seals can be completed in a relatively short period of time, thus 

minimizing traffic disruptions and delays.

• Chip seals have a much lower initial cost than thin asphalt overlays.

Potential Negative Sustainability Attributes of Chip Seals 

• Poorly constructed chip seals can result in vehicle damage due to loose chips and can 

result in wasted aggregate resources when excessively applied or poorly bound. 

• Chip seals can exhibit a rough ride and high noise levels at high speeds, particularly if large 

size stone is used or if there is non-uniform stone loss due to poor application of the binder. 

• The application of asphalt binder and aggregate over the entire pavement surface results 

in a moderate overall environmental impact, especially where traffic and climate 

Figure 7-8. Chip seal construction. 

7-16
Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

conditions result in a relatively short performance period of the treatment (requiring 

multiple applications over the life of the pavement). 

Slurry Seals 

Slurry seals (see figure 7-9) consist of 

a mixture of well-graded aggregate 

(fine sand and mineral filler) and 

asphalt emulsion that is spread over the 

surface of the pavement using a 

squeegee or a spreader box fixed to the 

back of the truck that is depositing the 

mixture. Slurry seals are generally 

used to seal the pavement surface, 

address low-severity cracking on the 

pavement surface, or improve the 

friction of the pavement surface. 

Slurry seals can also help reduce noise 

due to tire-pavement interaction to an 

extent (Peshkin et al. 2011). Slurries 

typically have a short service life on high 

speed routes due to abrasion loss. 

Positive Sustainability Attributes of Slurry Seals

• Slurry seals help keep water out of the pavement structure, potentially extending 

pavement life.

• Slurry seals can improve the surface friction of the pavement, thereby enhancing safety.

• Slurry seals improve pavement aesthetics by creating the impression of a new pavement.

• Slurry seal construction can be completed in a relatively short period of time, thus 

minimizing traffic disruptions and delays.

Potential Negative Sustainability Attributes of Slurry Seals

• The application of asphalt binder and aggregate over the entire pavement surface results 

in a moderate overall environmental impact, especially due to the relatively short 

performance period associated with slurry seals (requiring multiple applications over the 

life of the pavement). 

• Improperly constructed slurry seals can adversely affect surface friction.

• Slurry seals are often dark in color and will likely decrease pavement albedo. 

Microsurfacing

Typical microsurfacing consists of a mixture of crushed, well-graded aggregate, mineral filler, 

and polymer-modified emulsified asphalt spread over the entire pavement surface. This 

represents a broad category of different treatments, many of which are proprietary. The primary 

use of microsurfacing is to seal surface cracks, inhibit raveling and oxidation of the existing 

asphalt surface, address minor surface irregularities and rutting, and improve surface friction. 

Microsurfacing may be applied in a single or double course, depending upon project 

Figure 7-9. Slurry seal application. 

7-17
Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

requirements. A double course usually involves a rutfill application followed by another course to cover the 

entire pavement surface (Peshkin et al. 2011). 

The cost, performance, and environmental impacts of 

microsurfacing depend on whether single, double, or 

multiple courses are used and the nature of the binder 

(i.e., binder type and level of polymerization). Many 

studies have specifically identified microsurfacing as a 

very sustainable treatment with relatively low lifecycle economic and environmental impacts (Chehovits 

and Galehouse 2010; Kazmierowski 2012; Uhlman 

2012). 

Positive Sustainability Attributes of Microsurfacing

• Microsurfacing renews and seals the pavement 

surface.

• Microsurfacing can restore surface friction and 

fills ruts, thereby improving safety.

• Microsurfacing improves pavement aesthetics

by creating the impression of a new pavement.

• Although new material is used in 

microsurfacing projects, it is often of less 

quantity than that used in asphalt concrete

paving options.

• Microsurfacing has a relatively long life when 

compared to other preservation treatments, 

reducing material consumption and 

construction impacts that are associated with 

frequent and repeated applications of other 

treatments.

• Microsurfacing construction can be completed 

in a relatively short period of time, thus 

minimizing traffic disruptions and delays.

Potential Negative Sustainability Attributes of 

Microsurfacing

• Some of the polymerized materials used in 

microsurfacing projects may have a relatively 

high environmental impact and this should be 

considered when determining life-cycle 

impacts. 

• Microsurfacing is often dark in color and will 

likely decrease pavement albedo (although 

some microsurfacing techniques actually are designed to increase albedo). 

Environmental Impact of 

Preservation Treatments 

The environmental impacts of two 

pavement preservation treatment 

scenarios were evaluated by Uhlman 

(2012). The first scenario compared a 

polymer-modified emulsion 

microsurfacing to a 2-inch (51-mm) 

mill and replacement with a polymermodified HMA overlay. The overall 

environmental impact of the 

microsurfacing was determined to be 

significantly lower because of specific 

aspects of the HMA alternative, 

namely its elevated production and 

application temperatures, the milling 

operation performed prior to HMA 

placement, and the increased fuel 

requirements. In a second scenario, 

various chip seal options (including a 

hot-applied chip seal incorporating 

ground tire rubber [GTR] and two 

different polymer-modified coldapplied emulsion chip seals with and 

without fibers) were compared. The 

chip seal made with GTR had the 

lowest impact for solid waste 

emissions due to the diversion of tires 

from landfill, yet it also exhibited the 

greatest environmental impact in all 

categories considered except toxicity 

potential. This was because of the 

extra requirements for precoating the 

aggregates, the higher manufacturing 

and application temperatures for the 

GTR chip seal, and the production 

and storage requirements for the GTR 

binder. Thus, although at face value 

the use of recycled products appears 

to be a “sustainable” practice, the 

results in this case indicate that the 

use of cold-applied polymer-modified 

emulsions provided lower 

environmental impacts over the life

cycle. However, it is important to 

recognize that the findings from this 

study are not absolute, as different 

results might be obtained for projects 

constructed under different situations 

(e.g., traffic, climate, pavement 

condition, material sources, system 

boundaries for analysis). 

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Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

Ultra-Thin and Thin Asphalt Concrete Overlays 

This is a very broad category of overlays made 

with asphalt concrete in a central mixing plant 

and placed with a paver in thicknesses ranging 

from 0.625 to 0.75 inches (16 to 19 mm) for 

ultra-thin and 0.75 to 1.50 inches (19 to 38 mm) 

for thin overlays (see figure 7-10). Life-cycle 

cost, performance, and environmental impacts 

depend on traffic, binder type, bonding to the 

existing surface, the extent of cracking in the 

existing surface, and whether milling is 

performed prior to treatment placement. 

Ultra-thin and thin overlays are effective in 

sealing the pavement, addressing minor surface 

cracking and rutting, and improving surface 

friction. They will generally be quieter and 

smoother than chip seals, but will have higher 

initial costs. The incorporation of polymermodified binders may improve overall 

performance. These overlays may be constructed 

using dense-graded, open-graded, or gap-graded mixtures:

• Dense-graded—A well-graded, relatively impermeable mixture, for general application. 

• Open-graded—An open-graded, permeable mixture containing crushed aggregate and a 

small fraction of manufactured sand. Open-graded mixtures are effective in addressing 

splash/spray issues and also in reducing noise due to tire-pavement interaction. Polymer 

and rubberized binders can extend pavement life in terms of cracking and raveling. 

• Gap-graded—A gap-graded mixture with either rubberized gap-graded mixtures or 

stone matrix asphalt (SMA) containing polymerized binder and fibers. These mixtures 

are designed to maximize cracking and rutting resistance and durability through stone-onstone contact and high binder film thicknesses. Rubberized gap-graded mixtures are 

specifically designed to be highly resistant to reflection cracking.

Positive Sustainability Attributes of Ultra-Thin and Thin Asphalt Concrete Overlays

• Ultra-thin and thin overlays address minor surface distress, restore surface friction, fill 

ruts, improve ride quality, and improve texture that results in improved safety. Opengraded overlays can reduce both splash/spray (thus improving safety in wet-weather 

conditions) and noise emissions.

• Ultra-thin and thin dense-graded overlays improve pavement aesthetics by providing a 

new pavement surface.

• Ultra-thin and thin dense-graded overlays exhibit a relatively long life if placed on a 

pavement that is not significantly cracked and if good bonding is achieved with the 

existing surface, which reduces material consumption and construction impacts due to 

repeated applications.

Figure 7-10. Ultra-thin asphalt overlay. 

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

• Construction of ultra-thin and thin overlays can be completed in a relatively short time

period, thus minimizing traffic disruptions and delays.

• Ultra-thin and thin overlays are generally quieter and smoother than chip seals.

Potential Negative Sustainability Attributes of Ultra-thin and Thin Overlays 

• Ultra-thin and thin overlays require acquisition, processing, and transporting of material 

from central mixing facilities. 

• Poor construction of ultra-thin and thin overlays, or their misapplication on badly 

deteriorated pavements, can result in early failures that negatively impact economic and 

environmental performance. 

• Ultra-thin and thin overlays are initially dark in color and will likely decrease pavement 

albedo. 

• In some cases, open-graded ultra-thin and thin overlays with conventional binders have 

exhibited notably shorter lives due to raveling. 

Hot In-Place Recycling (HIR)

HIR is used to correct surface distresses limited to the top 2 inches (51 mm) of the existing 

asphalt surface by softening the binder using heat treatment, mechanically loosening it, and 

mixing it with recycling additives, rejuvenators, or virgin asphalt binder before placing and 

compacting the modified mixture. The National Highway Institute offers a training course 

(Course No. 131050) on asphalt pavement in-place recycling techniques where this topic is 

covered in further detail (see https://www.nhi.fhwa.dot.gov). 

HIR includes three different techniques (Peshkin et al. 2011): 

• Surface recycling—The wearing surface (typically 0.50 to 1.50 inches [13 to 38 mm]) is 

heated, loosened, and mixed with new asphalt binder and relaid and compacted. For lowvolume roadways, a single-pass recycling operation is used where the recycled mixture is 

relaid and compacted and serves as the wearing surface. For high-volume roads, the 

recycled and relaid mixture serves as the base course on top of which an asphalt overlay 

or surface treatment may be placed.

• Remixing—The wearing surface is heated, loosened, and mixed with virgin aggregates 

and new asphalt binder and relaid and compacted for significant improvement and minor 

pavement strengthening. The recycled surface may serve as the wearing course (for lowvolume roads) or as the base layer for a subsequent asphalt overlay or a surface treatment 

(for higher volume roads). 

• Repaving—This technique essentially involves surface recycling followed by the 

placement of a thermally bonded asphalt overlay (see figure 7-11) in order to strengthen 

the pavement and restore the surface profile.

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Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

Figure 7-11. Hot in-place recycling with application of overlay (Kandhal and Mallick 1997). 

Positive Sustainability Attributes of Hot In-Place Recycling

• HIR seals and restores the pavement surface.

• HIR addresses minor surface distress, restores surface friction, removes rutting, improves 

ride quality, and improves texture, all contributing to improved safety.

• HIR improves pavement aesthetics by providing a new pavement surface.

• If not resurfaced with an asphalt overlay, HIR requires very little use of virgin materials, 

thus reducing transportation of materials to the site.

• HIR exhibits a relatively long life, reducing material consumption and construction 

impacts.

• The construction of HIR can be completed in a relatively short time period, thus 

minimizing traffic disruptions and delays.

• HIR followed by an asphalt overlay can have a positive impact on tire-pavement noise

emissions.

Potential Negative Sustainability Attributes of Hot In-Place Recycling

• The use of heat in the HIR process to soften the existing pavement surface and 

subsequently to combine with new material is energy and emission intensive. 

• The HIR operation can generate fumes that can be objectionable in a community setting. 

• The new surface produced by the HIR is initially dark in color and will likely have a 

lower albedo.

• A chip seal or asphalt overlay is often required as part of the HIR treatment, adding cost 

and environmental burden. 

• The improper application of HIR can result in early failures that negatively impact 

economic and environmental performance. 

• HIR followed by a chip seal can have a negative impact on tire-pavement noise 

emissions. 

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Cold In-Place Recycling (CIR)

CIR is primarily used to restore the profile/cross slope and address other minor surface 

distresses. CIR consists of cold milling, sizing the RAP, and mixing the RAP with asphalt 

emulsion, recycling additives, and new aggregate to produce a recycled cold mix; this cold mix 

is relaid and compacted to serve as the base course for a new surface (see figure 7-12). For lowvolume roads, the surface resulting from the recycled cold mix is typically treated with a fog 

seal/rejuvenator to delay surface raveling. On higher volume roads, the recycled cold mix is 

treated with a more substantial treatment such as a chip seal or a thin asphalt overlay. The 

National Highway Institute offers a training course (Course No. 131050) on asphalt pavement inplace recycling techniques where this topic is covered in greater detail

(see https://www.nhi.fhwa.dot.gov).

Figure 7-12. Cold in-place recycling (photo courtesy of D. Matthews). 

Positive Sustainability Attributes of Cold In-Place Recycling

• CIR seals and restores the pavement surface.

• CIR addresses surface distress, removes rutting, and corrects minor profile deficiencies.

• Depending on the final surface, CIR can restore surface friction, improve ride quality, 

and improve surface texture, all contributing to improved safety.

• CIR improves pavement aesthetics by providing a new pavement surface.

• CIR uses existing materials in place, thus reducing the impacts of procuring and 

transporting new materials.

• CIR offers the potential for a relatively long life, thereby reducing material consumption 

and construction impacts due to repeated applications.

• CIR followed by an asphalt overlay can have a positive impact on tire-pavement noise

levels.

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Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

Potential Negative Sustainability Attributes of Cold In-Place Recycling

• The sustainability of CIR is heavily dependent on the type of surface material applied on 

top of it. 

• The new surface on a CIR project is often dark in color and will likely have a lower 

albedo. 

• The construction of CIR projects is often performed in stages, which can result in traffic 

disruptions and delays.

• The improper application of CIR can result in early failures that negatively impact 

economic and environmental performance. 

• CIR followed by a chip seal can have a negative impact on tire-pavement noise levels.

Ultra-Thin Bonded Wearing Course

This treatment is effective in addressing minor surface distresses and improving the frictional 

characteristics of the riding surface. It consists of a gap-graded or open-graded polymer- or 

rubber-modified asphalt layer (typically 0.4 to 0.8 inches [10 to 20 mm] thick) placed on a thick 

tack coat or membrane, and is commonly used as an alternative to chip seals, microsurfacing, or 

thin asphalt overlays. 

Positive Sustainability Attributes of Ultra-Thin and Thin Bonded Wearing Course 

• An ultra-thin bonded wearing course effectively seals the pavement surface.

• An ultra-thin bonded wearing course addresses minor surface distress, restores surface 

friction, improves ride quality, and improves texture, all contributing to improved safety.

• An ultra-thin bonded wearing course improves pavement aesthetics by providing a new 

pavement surface.

• An ultra-thin bonded wearing course can reduce noise generated through tire-pavement 

interaction.

• Ultra-thin bonded wearing courses can exhibit relatively long life, thereby reducing 

material consumption and construction impacts otherwise associated with repeated 

applications of other treatments.

• The construction of an ultra-thin bonded wearing course can be completed in a relatively 

short time period, thus minimizing traffic disruptions and delays.

Potential Negative Sustainability Attributes of Ultra-Thin Bonded Wearing Course 

• An ultra-thin bonded wearing course requires the use of new material transported from a 

central mixing facility.

• The improper application of an ultra-thin bonded wearing course can result in early 

failures that negatively impact economic and environmental performance. 

• An ultra-thin bonded wearing course is initially dark in color and will likely decrease 

pavement albedo. 

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Bonded Concrete Overlays 

Bonded concrete overlays (sometimes referred to as thin or ultra-thin whitetopping) are placed 

on existing asphalt pavements to eliminate surface distresses and correct pavement deformations 

(rutting, corrugation, and shoving). This treatment is characterized by the placement of a thin (2- 

to 6-inch [51 to 152 mm] thick) concrete (sometimes fiber reinforced) layer onto a cold-milled 

asphalt pavement (Harrington and Fick 2014). The cold milling is necessary to establish a strong 

bond between the two materials. Typical slab dimensions range from about 2 to 6 ft (0.61 to 1.8 

m) for thinner overlays to about 6 to 12 ft (1.8 to 3.6 m) for thicker (6-inch [152-mm]) slabs. 

Figure 7-13 shows the short panels associated with many thin overlays. A comprehensive 

document describing the use, application, and construction of bonded concrete overlays is 

available (Harrington and Fick 2014). 

Figure 7-13. Short panels for bonded concrete overlay. 

Positive Sustainability Attributes of Bonded Concrete Overlays

• A completely new concrete surface is bonded onto the existing asphalt pavement, 

effectively sealing it while addressing minor surface distress, rutting, and continued 

instability in the asphalt layer.

• The concrete surface can be shaped and textured as desired, restoring surface friction, 

eliminating profile deficiencies, and reducing tire-pavement noise. 

• Bonded concrete overlays improve pavement aesthetics by providing a new pavement surface.

• The pavement can be easily colored or textured to enhance aesthetics.

• Bonded concrete overlays typically are initially light in color and will likely increase 

pavement albedo.

• Bonded concrete overlays exhibit relatively long life, reducing material consumption and 

construction impacts that would be otherwise caused by repeated applications of other 

treatments.

Potential Negative Sustainability Attributes of Bonded Concrete Overlays 

• Bonded concrete overlays require the use of new material transported from a central 

mixing facility, so the environmental impact of those materials must be considered. 

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Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

• The improper construction of bonded concrete overlays (primarily through poor joint 

layout, construction and sealing practices or poor bonding) can result in early failures that 

negatively impact economic and environmental performance.

• The construction of bonded concrete overlays may require a longer period of time, 

leading to the development of traffic disruptions and delays. 

Energy Use and Emissions for Asphalt-Surfaced Pavement Treatments

Limited information is available on the life-cycle energy consumption and emissions generated 

by asphalt-surfaced pavement maintenance and preservation treatments. This is partly because 

the diversity of these treatments is such that they are not easily categorized for analysis. In 

addition, most of the early focus in investigating environmental impacts has been on new 

construction and major rehabilitation. It has not been until fairly recently that the life-cycle 

impacts of preservation have been investigated by the pavement community. 

For example, table 7-4 presents energy consumption and GHG emissions data for some typical 

asphalt-surfaced pavement preservation treatments, along with assumptions related to the 

extension of service life (Chehovits and Galehouse 2010). Table 7-5, which is from the same 

study, presents similar data for typical new construction and major rehabilitation. In developing 

the values shown in tables 7-4 and 7-5, energy use and GHG emissions were calculated for each 

treatment on the basis of the unit area of the pavement surface being treated and using typical 

quantities of raw materials for each treatment (agency costs only, no user costs). Those values 

were then divided by the pavement life extensions for each treatment to produce annualized 

results to allow more meaningful comparisons of the energy use and GHG emissions associated 

with the different treatments. In this context, relative comparisons can be made between the 

different treatments. 

What is evident from these data is that the energy consumption and GHG emissions per year are

considerably lower for many of the preservation and maintenance treatments compared to new 

construction or major rehabilitation, although not universally so. For instance, thin HMA 

overlays and hot in-place recycling both exhibit energy and GHG emissions that are similar to 

those of new construction. This suggests that these alternatives are similar for the factors 

considered, but other environmental and social factors not included in the analysis (e.g., solid 

waste generation, noise, safety, particulate matter) could also impact the results. Furthermore, 

the boundary conditions for the analysis were quite limited, and did not include such items as 

traffic delays resulting from construction operations and improved vehicle fuel efficiencies

associated with smoother pavements. Regardless of the limitations associated with the data, it 

clearly demonstrates the reduced energy consumption and GHG emissions associated with many 

preservation and maintenance treatments.

A study conducted in Ontario (Chan et al. 2011) on various asphalt pavement treatment 

alternatives found that microsurfacing had the lowest annualized energy consumption and emission

levels when compared to the other treatment alternatives (see table 7-6). However, that study 

suffers from some simplifications in the analysis. For one, it assumes that all of the treatments 

exhibit similar benefits over their entire life. In addition, it does not consider the broader impact of 

creating additional traffic disruptions for short-lived treatments. Still, it illustrates that less 

material-intensive preservation treatments have positive environmental impacts than more 

material-intensive options, reinforcing the concept that the environmental impact of materials 

production and construction is generally well correlated with the thickness of the treatment. 

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Table 7-4. Energy consumption and GHG emissions data for some typical asphalt-surfaced 

pavement preservation treatments (Chehovits and Galehouse 2010). 

Treatment Details

Pavement 

Life 

Extension 

(Years)

Energy Use per 

Year

BTU/yd2 

Energy Use 

per Year

MJ/M2

GHG 

Emissions 

per Year

lb/yd2

GHG 

Emissions 

per Year

kg/m2

Hot-Mix 

Asphalt

Thickness 

1.5 in (3.8 cm) 5-10 4,660 – 9,320 5.9 – 11.8 0.9 – 1.8 0.5 – 1.0

Hot-Mix 

Asphalt

Thickness 

2.0 in (5.0 cm) 5-10 6,080 – 12,160 7.7 – 15.4 1.2 – 2.4 0.7 – 1.3

 Hot In-Place 

Recycling

Thickness 

1.5 in (3.8 cm) 

50/50 Recycle/New

5-10 3,870 – 7,740 4.9 – 9.8 0.7 – 1.4 0.4 – 0.80

Hot In-Place 

Recycling

Thickness 

2.0 in (5 cm) 

50/50 Recycle/New

5-10 5,130– 10,260 6.5 – 13.0 0.9 – 1.5 0.5 – 1.0

 Chip Seal

Emulsion 

0.44 g/yd2 (2.0 L/m2)

Aggregate

38 lb/yd2 (21 kg/m2)

3-6 1,170 -2,340 1.5 – 3.0 0.15 – 0.3 0.08 – 0.10

Chip Seal

Emulsion 

0.35 g/yd2 (1.6 L/m2)

Aggregate

28 lb/yd2 (15 kg/m2) 

2-5 1,026 – 2,565 1.3 – 3.3 0.14 – 0.35 0.08 – 0.20

Slurry Seal/ 

Microsurfacing

Type III

12% Emulsion,

24 lb/yd2 (13 kg/m2)

3-5 1,026 – 1,710 1.3 – 3.3 0.12 – 0.2 0.06 – 0.10

Slurry Seal/ 

Microsurfacing

Type II

14% Emulsion,

16 lb/yd2 (8.7 kg/m2)

2-4 968 – 1,935 1.2 – 2.4 0.10 – 0.2f0 0.05 – 0.10

Crack Seal

1 lin ft/yd2

(0.37 m/m2),

0.25 lb/ft

(0.37 kg/m2)

1-3 290 - 870 .05 – .14 0.05 – 0.14 0.03 – 0.08

Crack Fill

2 lin ft/yd2

(0.74 m/m2),

0.50 lb/ft

(0.74 kg/m2)

1-2 930 – 1,860 1.0 – 2.0 0.13 – 0.25 0.07 – 0.14

Fog Seal

0.05 gal/yd2

(0.23 L/m2)

50/50 Diluted

Emulsion

1 250 0.4 0.04 0.02

Fog Seal

0.10 gal/yd2

(0.46 L/m2)

50/50 Diluted

Emulsion

1 500 0.8 0.07 1.04

Fog Seal

0.15 gal/yd2

(0.69 L/m2)

50/50 Diluted

Emulsion

1 750 1.2 0.12 0.07

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Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

Table 7-5. Energy consumption and GHG emissions data for new construction and major 

rehabilitation activities (Chehovits and Galehouse 2010). 

Treatment Details 

Pavement 

Life or Life

Extension 

(Years)

Energy 

Use per 

Year

BTU/yd2

Energy 

Use per 

Year

MJ/M2

GHG 

Emissions 

per Year

lb/yd2

GHG 

Emissions 

per Year

kg/m2

New 

Construction 

4 in (102 mm)

HMA over

6 in (152 mm)

Aggregate Base

20 7840 9.9 1.2 0.7

Major Rehab HotMix Asphalt 4 in (102 mm)

Overlay 15 7500 9.4 1.3 .08

Major Rehab HotMix Asphalt3 in (76 mm)

Overlay 12 7050 8.9 1.3 0.7

Major Rehab 

Warm-Mix 

Asphalt

4 in (102 mm)

Overlay 15 7210 9.2 1.3 .08

Major Rehab 

Warm-Mix 

Asphalt

3 in (76 mm)

Overlay 17 6780 8.5 1.3 0.7

Table 7-6. Comparison between microsurfacing and other treatment alternatives for asphaltsurfaced pavement (Chan et al. 2011). 

Treatments Service 

Life Energy CO2 NOx SOx

Mill 1.95 in (50 mm)

Pave 1.95 in (50 mm) 10 Yrs 65 million BTU(67,493 MJ)

3.9 ton

(3.5 mt)

67.6 lbs

(30.7 kg)

2110 lbs

(958 kg)

Mill 1.95 in (50 mm)

Pave 1.95 in (50 mm) WMA 10 Yrs 45 million BTU(47,782 MJ)

2.2 ton

(2.0 mt)

35.5 lbs

(16.1 kg)

1478 lbs

(671 kg)

1.95 in (50 mm) HIR 10 Yrs 54 million BTU

(56,694 MJ)

3.0 ton

(2.7 mt)

52.6 lbs

(23.9 kg)

1645 lbs

(747 kg)

0.39 in (10 mm)

Microsurfacing 7 Yrs 7.6 million BTU (8,064 MJ)

0.33 ton

(0.3 mt)

14.1 lbs

(6.4 kg)

619 lbs

(281 kg)

Strategies for Improving Sustainability

The general strategies for improving sustainability discussed at the beginning of this chapter are 

applicable, namely that thinner cross sections, the use of local or in-place materials, maintaining 

high levels of smoothness, and increased construction quality all reduce environmental burden 

and contribute to more sustainable treatments. It is emphasized that significant differences may 

exist in the approaches that are used to reduce environmental impacts, depending on a number of 

project-specific characteristics (perhaps most notably the traffic volumes and associated burdens 

created in the use phase).

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Future Opportunities

As interest in improving the sustainability of asphalt-surfaced pavement maintenance and 

preservations techniques continues to evolve and move forward, future opportunities exist in the 

following areas: 

• Improved maintenance materials that require the use of less material or last longer. 

However, some of the materials now being developed and marketed are proprietary and 

the environmental impacts of the component materials used is not known. 

• Improved approaches for optimizing treatment selection and timing through the use of 

more sophisticated pavement management systems and more proactive “leading” 

indicators of performance. 

• Improved construction, particularly improvements in paving machines that place the tack 

coat just ahead of the laydown of the hot mix, and improved compaction from the use of 

warm mix.

• Other improvements identified in chapter 3 on materials.

Concrete-Surfaced Pavement Maintenance and Preservation Treatments

Introduction

Concrete-surfaced pavements are any pavement structures surfaced with concrete, including 

JPCP, CRCP, and older jointed reinforced concrete pavement (JRCP) designs. In general, these 

pavements consist of a concrete surface on one or more granular or bound layers, but concretesurfaced pavement also includes various concrete overlays that can be placed on existing 

concrete pavements (unbonded and bonded concrete overlays) or on existing asphalt pavements 

(again, either bonded or unbonded). Although this represents a range of different pavement 

types, the maintenance and preservation activities are largely identical (although there are some 

variations in how the treatments are executed). 

Table 7-7 presents an overall summary of various maintenance and preservation treatments 

applicable to concrete-surfaced pavements. First, it provides a brief description of the technique 

and then indicates its effect on a number of preventive and restorative benefits (“↑” indicates 

positive impact, “↓” indicates negative impact, and “↔” indicates both positive and negative 

impact). This is followed by a general assignment of the relative life expectancy and cost, and 

the relative environmental and social impacts. 

As noted before in the discussions of the treatments for asphalt-surfaced pavements, these 

relative comparisons are inherently non-specific, which is due to the general lack of available 

information and the large number of variables that affect the performance, cost, life-cycle 

environmental impact, and social impact of each treatment. The relative comparisons will also 

vary depending on the traffic levels, climate region, and a host of other variables. In general, 

treatments that require more material or materials that have higher environmental impacts will 

have higher environmental impacts through construction. Those that last longer and have the 

greatest impact on preserving functional surface characteristics (e.g., ride quality, surface 

friction, and high albedo) will have reduced environmental impacts over the life cycle, especially 

in high-traffic applications where the economic and environmental impacts of vehicles are the 

greatest.

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Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments Table 7-7. Evaluation of sustainability impacts of treatments for concrete-surfaced pavements. Seal Pavement Prevent Intrusion of Incompressibles Eliminate/ Control Faulting Improve Texture for Friction Improves Ride Quality and Surface Profile Improve Texture for Noise Relative Treatment Life 

( to  )

Relative 

Cost 

($ to $$$$)

Joint Resealing/Crack Sealing

Joint resealing consists of removing existing longitudinal/transverse joint sealants, preparing and installing new sealant material.Crack Sealing consists of cleaning, preparing and sealing longitudinal/transverse cracks

↑ ↑

↓

Longitudinal 

overbanding 

can negatively 

impact friction

↔

Overbanding 

increases 

noise, filling 

can reduce 

noise

 $ Low

Reduced traffic delays; less pleasing aesthetics and potential roughness issues with crack sealing

Slab Stabilization/Slab Jacking

Slab stabilization involves the restoration of support to slabs by filling voids, thereby reducing deflections.Slab jacking involves raising slabs to their desired elevation by pressure inserting material beneath settled slabs

↑

In 

combination 

with other 

CPR 

treatments

↑

In combination 

with other 

CPR 

treatments

 $$$

Low to Medium

Depends on amount of slab 

stabilization required

When combined with other treatments, results in longterm Improvement in ride quality

Diamond Grinding

Removal of thin concrete layer (0.12 to 0.25 in.) from pavement surface using special equipment.

↑ ↑

↑

Significant 

improvements 

on faulted pavement

↑  $$

Medium to High

Depends on how much surface is 

being removed, hardness of the 

aggregate, level of smoothness 

obtained, and traffic level

Increases safety by improving friction, reduces noise from tire-pavement interaction

Diamond Grooving

Cutting narrow, discrete grooves (typically longitudinal) into pavement surface to increase friction and reduce noise

↑  $$ Low

Improved wet weather safety and reduced noise. Some issues regarding negative impact on vehicle tracking (particularly motorcycles) have been cited

Partial-Depth Repairs

Localized removal and replacement of deteriorated concrete, most often in vicinity of joints) in the upper third of the slab using approved repair materials

↑

In combination 

with other CPR 

treatments

↑

In combination 

with other CPR 

treatments

↑  $$$

Variable

Depends on type of material used 

and amount of patching required

Rapid-setting repair materials used for partial-depth patching reduce traffic delays. Restoration of ride quality is significant for badly damaged pavement if slabs are ground. Aesthetics can be negatively affectively if repair material does not match existing pavement

Societal Impact

Preventive

Treatment Description

Relative Environmental Impact 

based on life cycle energy use 

and GHG emissions, materials

(Low, Medium, High, Variable)

Restorative Performance and Cost

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems Table 7-7. Evaluation of sustainability impacts of treatments for concrete-surfaced pavements (continued). Seal Pavement Prevent Intrusion of Incompressibles Eliminate/ Control Faulting Improve Texture for Friction Improves Ride Quality and Surface Profile Improve Texture for Noise Relative Treatment Life 

( to  )

Relative 

Cost 

($ to $$$$)

Full-Depth Repairs

Removal and replacement of deteriorated concrete through the full depth of the slab using approved repair materials; may be cast inplace of precast

↑

In combination 

with other CPR 

treatments

↑

In combination 

with other CPR 

treatments

↑

At affected 

joint(s)

↑  $$$$

Medium to High

Depends on amount of patching 

and type of material used; also 

depends on whether repairs are 

cast in-place or pre-cast

Pre-cast panels reduce traffic delays. Aesthetics can be negatively affectively if repair material does not match existing pavement

Dowel Bar Retrofit

Placement of dowel bars across joints or cracks in existing jointed concrete pavement

↑

In 

combination 

with other 

CPR 

treatments

↑

In combination 

with other 

CPR 

treatments

 $$$

Variable

If globally applied, high initial 

negative impact but restoration of 

load transfer, in combination with 

diamond grinding, will make the 

smoothness last longer and have 

positive impact throughout the life 

cycle.

Improves ride quality by controlling faulting, which is eliminated when combined with diamond grinding. Aesthetics can be negatively affectively if repair material does not match existing pavement

Cross Stitching

Technique used to maintain load transfer across non-working longitudinal cracks that are in relatively good condition

↑ $$$ Low

Improves long-term performance by keeping longitudinal cracks tight. Eliminates the need for slab removal and replacement

Retrofitted Edge Drains

Technique used to collect water that has infiltrated into the pavement structure and discharges it to the ditches through regularly spaced outlet drains. Can have negative impact if creates "bathtub" through poor design or construction

↑  $$$$

Variable

Can have a large impact if poor 

drainage is primarily responsible 

for poor performance, but must be 

properly designed, constructed 

and maintained or can trap water 

in the pavement

Can improve long-term performance by reducing moisture induced distress 

Ultra-Thin Wearing Course, typically open-graded with rubberized or polymerized binders

Used to improve the functional surface characteristics of the concrete pavement including enhancing friction and reducing noise. Consists of open or gapgraded aggregates and rubberized or polymer-modified asphalt layer (0.4 to 0.8 in. thick) well bonded to the concrete surface

↑ ↑ ↑ ↑ ↑  $$$

Variable

Depends on type of material used 

and life of treatment

Primarily used to enhance functional surface characteristics of the pavement, most notably noise reduction and improved friction

Bonded Concrete Overlay

Placement of a relatively thin (2 to 6 in.) concrete layer, with slab over an existing concrete-surfaced pavement

↑ ↑ ↑ ↑  $$$

Medium

Virgin materials and concrete 

materials increase impact, thinner 

cross section reduces impact

Increases safety through improved friction and drainage; improved ride quality; improved aesthetics. Increase in albedo may positively impact the UHI effect

Societal Impact

Preventive

Treatment Description

Relative Environmental Impact 

based on life cycle energy use 

and GHG emissions, materials

(Low, Medium, High, Variable)

Restorative Performance and Cost

Note: Relative Environmental Impacts discussed in tale 7-3 provide rough comparisons; reliable estimates will be available only after new assessments are conducted.

Key: ↓ decreased

↑ increased↔ no trend

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Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

Various resources are available that discuss concrete pavement preservation/maintenance 

strategies as well as each treatment type, including the types of pavement conditions addressed, 

how each treatment should be constructed, and their cost effectiveness. These include a webbased training series developed by the National Concrete Pavement Technology Center and 

offered by the National Highway Institute (NHI Course No. 131126) and a number of treatmentspecific references available from the American Concrete Pavement Association, the FHWA, 

and others. As considerable information is readily available regarding the application, cost

effectiveness, and construction of the various treatments, the following sections specifically 

address the sustainability aspects of each treatment, focusing on the environmental and social 

impacts.

Although any given concrete-surfaced pavement treatment can be applied alone (for example 

full-depth patching can be used to repair a localized slab failure), it is far more common to use 

several treatments together in an approach often referred to as concrete pavement restoration 

(CPR) to restore a structurally sound but distressed concrete pavement to a higher level of 

serviceability. Thus the sustainability impact of any one treatment is very difficult to assess, as 

ultimately the economic, environmental, and social impacts of the entire strategy should be 

assessed together. A recommended sequence for the placement of various treatments during a 

CPR project is illustrated in figure 7-14 (ACPA 2006). In the following discussion, each 

treatment is considered individually with the linkage to other treatments established in the 

narrative.

Figure 7-14. Typical sequence of concrete-surfaced pavement treatments as part of CPR 

(ACPA 2006).

Joint Resealing/Crack Sealing

Joint and crack sealing is a commonly performed pavement maintenance activity that serves two 

purposes: reduce the amount of moisture infiltration into the pavement structure, thereby 

reducing moisture-related distresses such as pumping, joint faulting, base and subbase erosion, 

and corner breaks; and prevent the intrusion of incompressibles to prevent pressure-related 

distresses such as spalling, blowups, buckling, and shattered slabs (Smith et al. 2014). 

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Joint resealing involves the removal of 

existing deteriorated sealant material (if 

present), preparation of the joint 

sidewalls, and installation of the new 

sealant material (see figure 7-15). Crack 

sealing is typically done only on 

longitudinal and transverse cracks and 

corner break cracks that are wider than 

0.125 inch (3 mm) and involves routing, 

cleaning, and sealing cracks using a highquality sealant material (Peshkin et al. 

2011). 

Joint resealing and crack sealing should 

be the last activities in the sequence of 

treatments performed on a given 

restoration project. Intended for 

pavements in relatively good condition, 

joint resealing can also be performed 

independently on a project with an 

original sealant that has failed or become 

ineffective.

Positive Sustainability Attributes of Joint Resealing and Crack Sealing 

• Joint/crack sealing helps minimize the amount of moisture infiltrating the pavement, 

potentially extending the life. 

• Joint/crack sealing uses relatively little material and, thus, does not have large materialrelated environmental impacts.

• Joint/crack sealing generates little construction waste.

• Joint/crack sealing operations use relatively little energy. 

• Joint/crack sealing can be performed using a moving traffic control operation, thus 

minimizing traffic disruptions and delays.

Potential Negative Sustainability Attributes of Joint Resealing and Crack Sealing 

• Joint/crack sealing can have a relatively short life when compared to that of the concrete 

pavement and thus must be repeated multiple times over the life cycle (with associated 

more frequent disruptions to traffic). 

• Multiple joint resealing operations widen the joint reservoir and can negatively impact 

ride quality and increase tire-pavement noise emissions. 

• Crack sealing can negatively impact pavement aesthetics over time. 

• The sealant removal and cleaning portions of joint/crack sealing operations are typically 

noisy and can produce particulate that may be problematic in a community setting. 

Figure 7-15. Joint sealing. 

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Slab Stabilization/Slab Jacking

Slab stabilization is a technique used to restore support beneath the concrete pavement by filling 

voids that developed under service, thereby reducing deflections (Smith et al. 2014). Slab 

stabilization should be performed in areas where loss of support is known to exist. For optimum 

performance, it is critical that this technique be used prior to the onset of damage caused by loss 

of support (ACPA 1994).

Slab jacking involves the injection of a cement grout or expansive polyurethane material beneath 

the slab to gradually elevate a settled slab back to its original profile. This technique is used to 

correct localized areas of settlement or depression, and not to address common transverse joint 

faulting (Smith et al. 2014).

Slab stabilization is rarely used alone, instead often being the first step in a restoration project. 

Slab jacking, on the other hand, can be applied independently of other treatments as its sole 

purpose is to elevate a slab that has settled due to underlying conditions (such as often occurs at 

bridge approach slabs or over culverts). 

Positive Sustainability Attributes of Slab Stabilization/Slab Jacking 

• Slab stabilization restores slab support, thereby reducing deflections and reducing the 

likelihood of corner breaking. However, in order for slab stabilization to be effective in 

the long term, the underlying causes of pumping and loss of support (such as poor 

drainage and poor load transfer) must be addressed. 

• Slab stabilization and slab jacking use relatively little material and, thus, do not have 

large material-related environmental impacts.

• Slab stabilization and slab jacking generate little construction waste.

• The construction operations associated with slab stabilization and slab jacking use 

relatively little energy. 

• Slab stabilization and slab jacking are expected to provide long-term positive impacts if 

the voids are filled and the root causes of the loss of support are addressed. 

Potential Negative Sustainability Attributes of Slab Stabilization/Slab Jacking 

• Slab stabilization must be appropriately applied to slabs in which loss of support has 

occurred. The inappropriate application of this treatment can result in waste and early 

pavement failure. 

• Slab stabilization and slab jacking can be labor-intensive operations that may result in 

traffic disruptions and delays, but innovative construction practices and materials can be 

used to minimize that impact.

• Although material usage is low, the environmental impact of the materials (cement grout, 

polyurethane) must be evaluated. 

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Diamond Grinding/Grooving

Diamond Grinding involves the removal 

of a thin (0.12 to 0.25 inch [3 to 6 mm]) 

layer of material from the concrete surface 

using special grinding equipment equipped 

with gang-mounted, closely-spaced 

diamond saw blades. This technique has 

traditionally been used to address faulting 

and other surface irregularities (Peshkin et 

al. 2011). Diamond grinding contributes to 

improved sustainability by providing a 

smooth riding surface (which increases 

vehicle fuel efficiency) and also by 

providing a safe pavement surface (through 

increased surface friction) (Smith et al. 

2014). Diamond grinding has also been 

used on new pavements and older 

pavements with no apparent distress simply to improve ride quality, provide frictional 

characteristics, and reduce tire-pavement noise emissions. Diamond grinding also creates an 

aesthetically pleasing surface that exposes the underlying aggregates (see figure 7-16). 

Positive Sustainability Attributes of Diamond Grinding 

• Diamond grinding renews the pavement surface without the need for additional material 

other than the water used in the grinding operation and the wear of the diamond blades. 

This provides a significant sustainability advantage over treatments that rely on the 

application of new material.

• Diamond grinding produces a riding surface that is functionally (ride quality, surface 

friction, noise) as good, or better, than what was originally constructed. This 

significantly reduces user impacts as long as the high level of functionality is maintained.

• Diamond grinding generates little construction waste, although the disposal of the slurry 

that is produced during the operation must be addressed.

• Diamond grinding can be conducted under a moving traffic control operation, thus 

minimizing traffic disruptions and delays.

• Diamond grinding is expected to provide a long-term, positive impact if the pavement is 

structurally sound and the root causes of the roughness issues (i.e., faulting) are 

addressed. 

Potential Negative Sustainability Attributes of Diamond Grinding 

• The effectiveness of diamond grinding to restore surface friction is largely a function of 

the polishing susceptibility of the coarse aggregate. If the aggregate is susceptible to 

polishing, the positive effects of diamond grinding on surface friction will be short lived. 

• Although material usage is low, the environmental impact of disposal of the slurry must 

be considered. 

Figure 7-16. Surface texture produced by 

diamond grinding (courtesy ACPA)

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Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

• If the coarse aggregates are dark in color, diamond grinding will result in a darker surface 

color, likely reducing the pavement albedo. 

• Diamond grinding operations are typically noisy, which may be a potential issue in a 

community setting. 

Diamond Grooving (see figure 7-17) 

involves cutting narrow, discrete 

grooves (longitudinal or transverse) 

to help improve safety by reducing 

hydroplaning potential, splash and 

spray, and wet-weather-related 

crashes. Transverse grooving, which 

is common on bridges, may have an 

adverse impact on tire-pavement 

noise, which is why longitudinal 

grooving is more commonly used on 

highways as it reduces tire-pavement 

noise while still reducing 

hydroplaning potential. A hybrid 

surface texture, called the Next 

Generation Concrete Surface, 

employs a combination of diamond 

grinding and diamond grooving and has demonstrated excellent restoration of the pavement 

functional characteristics (ride quality, friction, and noise reduction) (IGGA 2011).

Positive Sustainability Attributes of Diamond Grooving 

• Diamond grooving is specifically applied to reduce hydroplaning potential and the noise 

emissions associated with tire-pavement interaction. There is no need for additional 

material other than the water used in the grooving operation and the wear of the diamond 

blades. This provides a significant sustainability advantage over treatments that rely on 

the application of new material. 

• Diamond grooving generates little construction waste, although the disposal of the slurry 

that is produced must be addressed.

• Diamond grooving can be conducted under a moving traffic control operation, thus 

minimizing traffic disruptions and delays.

Potential Negative Sustainability Attributes of Diamond Grooving 

• Although material usage is low, the environmental impact of disposal of the slurry 

created by diamond grooving must be considered. 

• Diamond grooving operations are typically noisy, which may be a potential issue in a 

community setting. 

Figure 7-17. Diamond grooving operation.

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Partial-Depth Repairs

Partial-depth repairs (see figure 7-18) are used 

to address joint spalling and other surface 

distresses that are limited to the top third to 

top half of the slab through the use of 

approved repair materials. This treatment is 

effective in restoring the ride quality and 

structural integrity of localized areas while 

allowing joints to be effectively sealed. 

Improper repair finishing can result in poor 

ride quality, so diamond grinding is typically 

recommended to blend the repaired surface 

with the adjoining pavement (Smith et al. 

2014). 

Although they can be used alone to repair 

isolated damaged joints, partial-depth repairs 

are most typically conducted before full-depth repairs are completed and after slab stabilization

is performed. 

Positive Sustainability Attributes of Partial-Depth Repairs 

• Partial-depth repairs use relatively little material and, thus, do not have large materialrelated environmental impacts.

• Partial-depth repairs generate a small amount of construction waste.

• Partial-depth repairs are expected to have long-term positive impacts if properly 

constructed in conjunction with other needed treatments. 

Potential Negative Sustainability Attributes of Partial-Depth Repairs 

• Partial-depth repairs must be appropriately applied to appropriate distresses and on slabs 

in which the limits of the damaged area are correctly identified and removed. The 

inappropriate application of partial-depth repairs can result in waste and early pavement 

failure.

• The construction of partial-depth repairs has historically been a labor-intensive, timeconsuming operation with a high potential for traffic disruptions and delays; however, 

newer construction processes (including milling) and rapid-setting materials are being 

used to reduce these impacts. 

• Partial-depth repairs can compromise pavement aesthetics if the repair material does not 

match the existing pavement material or if installed at a high density. 

• The installation of partial-depth repairs is typically noisy and produces particulates, 

which may be problematic in a community setting. 

Figure 7-18. Partial-depth repair.

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Full-Depth Repairs

Full-depth repairs (see figure 7-19) are 

effective in addressing structural 

distresses that extend through more 

than one-half of the slab thickness. 

Full-depth repairs extend through the 

entire thickness of the existing slab 

and involve the removal and 

replacement of full lane-width areas

with cast-in-place or precast concrete. 

The additional joints created through 

full-depth repairs have the potential to 

decrease the ride quality. Hence, 

diamond grinding should be 

considered after full-depth repair 

installation to blend the repairs with 

the adjoining pavement and provide a 

smooth-riding surface (Smith et al. 2014). These repairs may not be a sustainable solution from 

an environmental and societal standpoint if they are performed over a large area of the project. 

Positive Sustainability Attributes of Full-Depth Repairs

• Full-depth repairs are most often used to replace deteriorated joints or entire slabs, 

thereby restoring ride quality and pavement structural integrity.

• Full-depth repairs applied on a moderate scale have less environmental impact and lower 

costs than more extensive alternatives such as overlays or reconstruction.

• Full-depth repairs are expected to have a long-term positive impact on pavement 

longevity if properly constructed in conjunction with other needed treatments. 

Potential Negative Sustainability Attributes of Full-Depth Repairs 

• The installation of full-depth repairs is a labor-intensive operation that can result in 

significant traffic disruptions and delays. Various innovative construction practices and 

materials can be used to minimize this impact, but these are sometimes at a greater cost 

and a higher risk of early failure. Full-depth repair using precast concrete panels is an 

innovative option that can result in a reduction in environmental impact through reduced 

material-related impacts and expedited construction to minimize traffic delays. 

• Full-depth repairs can compromise pavement aesthetics if the repair material does not 

match the existing pavement material or if installed at a high density. 

• The installation of full-depth repairs is typically noisy and produces particulates, which 

may be an issue in a community setting. 

Figure 7-19. Full-depth repair.

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Dowel Bar Retrofitting

Dowel bar retrofitting (also called load 

transfer restoration) involves the placement 

of dowel bars across joints or cracks with 

poor load transfer (see figure 7-20). The 

operation involves cutting slots, removing the 

existing concrete and preparing the slots, 

installing the dowels in the slot seated on a 

small chair, and backfilling the slot with 

repair grout. This technique helps reduce 

deflections by improving the load transfer 

across joints and cracks, thereby reducing the 

potential for the development of pumping, 

faulting, void formation, and corner breaks. 

This treatment is often performed along with 

diamond grinding, which removes faulting and reduces noise levels. It is a common practice to 

use dowel bar retrofit to provide load transfer in jointed pavements that were originally 

constructed without dowels, or to provide improved transfer at mid-panel cracks.

Positive Sustainability Attributes of Dowel Bar Retrofitting

• Dowel bar retrofitting is used to provide/restore joint load transfer and reduce loadrelated stresses and deflections at joints and cracks, thereby helping to control the 

development of faulting and corner breaks.

• Dowel bar retrofitting uses relatively little material and thus does not have large materialrelated environmental impact. The use of dowels with a high recycled steel content 

provides further sustainability benefits.

• A relatively small amount of construction waste is generated by the dowel bar retrofitting 

operation.

• Dowel bar retrofit is expected to have a long-term positive impact if properly constructed 

in conjunction with other needed treatments. 

Potential Negative Sustainability Attributes of Dowel Bar Retrofitting

• Dowel bar retrofitting must be appropriately applied to slabs; the inappropriate 

application or poor construction can result in early pavement failure at a high cost. 

• Dowel bar retrofitting is a labor-intensive operation that can result in traffic disruptions 

and delays. The process can be expedited to some degree through the use of innovative 

construction practices and materials to minimize this impact, but at a greater cost and a 

higher risk of early failure.

• Dowel bar retrofitting can compromise pavement aesthetics if the repair material does not 

match the existing pavement material.

• The construction operations associated with dowel bar retrofitting are typically noisy and 

produce particulates, which may be problematic in a community setting. 

Figure 7-20. Placement of dowel bars in a 

dowel bar retrofitting operation. 

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Cross Stitching

Cross stitching is a technique used to maintain load transfer across non-working longitudinal cracks 

that are in relatively good condition (Smith et al. 2014). This treatment helps keep the cracks tight 

(or keeps them from opening further) by preventing vertical and horizontal movement, thereby 

maintaining adequate load transfer and reducing the rate of deterioration. 

Positive Sustainability Attributes of Cross Stitching

• If done correctly, cross stitching provides a good long-term alternative to full-depth 

replacement of the affected slabs. This results in significant economic and environmental 

savings.

• Cross stitching uses relatively little material and thus has a small material-related 

environmental impact, made even less impactful if the steel has a high recycled content.

• Cross stitching generates little construction waste. 

Potential Negative Sustainability Attributes of Cross Stitching

• Cross stitching must be appropriately applied to non-working cracks. Inappropriate 

application or poor construction can result in early pavement failure at a high cost. 

Retrofitted Edge Drains

Retrofitted edge drains are sometimes used on concrete pavements that exhibit early indications 

of moisture-related distresses such as pumping and joint faulting. This technique involves the 

excavation of narrow trenches longitudinally at the outside edge of the pavement, the placement 

of a pipe or “fin” drain in the trench, and backfilling with drainable material to collect water that 

has infiltrated into the pavement structure and discharge it into the ditches through regularly 

spaced outlet drains (Smith et al. 2014). In some regions, retrofitted edge drains have been 

successful in slowing pavement degradation. 

Retrofitting of edge drains is done near the beginning of the pavement restoration process, 

usually after slab stabilization has been completed. 

Positive Sustainability Attributes of Retrofitted Edge Drains

• Retrofitted edge drains are intended to extend pavement life by removing excess moisture 

beneath the pavement. 

• The installation of retrofitted edge drains can be completed in a relatively short time period 

and with relatively short work zones, thus minimizing traffic disruptions and delays. 

• Retrofitted edge drains use no new paving materials, but do incorporate polyethylene or 

polyvinyl chloride piping materials whose environmental impacts must be assessed.

Potential Negative Sustainability Attributes Retrofitted Edge Drains

• Retrofitted edge drains must be appropriately installed, as the inappropriate application or 

poor construction can result in early pavement failure. 

• The installation of retrofitted edge drains is a labor-intensive operation that can result in 

traffic disruptions and delays. 

• Continued maintenance of the edge drain system is essential to its long-term effectiveness. 

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Ultra-Thin Wearing Course

This type of treatment on concrete pavement is used exclusively to improve the functional 

surface characteristics (friction and noise) of an existing pavement. These are very similar to the 

treatment of the same name discussed under asphalt-surfaced pavements, consisting of specially

graded aggregates and a polymer-modified asphalt layer (0.4 to 0.8 inch [10 to 20 mm] thick) 

placed on a polymer-modified asphalt membrane. The life expectancy for ultra-thin wearing 

courses on jointed concrete pavements is shorter than when used on asphalt pavements due to the 

occurrence of joint reflection cracking in the wearing course (Tayabji, Smith, and Van Dam 

2010). Ultra-thin wearing courses are applied to concrete pavements to achieve improved 

surface friction or to reduce noise emissions (or both). 

Positive Sustainability Attributes of Ultra-Thin Bonded Wearing Course 

• Ultra-thin wearing courses effectively seals the pavement, including joints and cracks.

• Ultra-thin wearing courses improve wet-weather safety by increasing texture and 

reducing splash and spray.

• Ultra-thin wearing courses improve pavement aesthetics by providing a new pavement

surface.

• Ultra-thin wearing courses reduce noise generated through tire-pavement interaction.

• The construction of ultra-thin wearing courses can be completed in a relatively short time 

period, thus minimizing traffic disruptions and delays.

Potential Negative Sustainability Attributes of Ultra-Thin Bonded Wearing Course 

• Ultra-thin wearing courses are dark in color and will likely decrease pavement albedo.

• Ultra-thin wearing courses require the use of new material transported from a central 

mixing facility.

• The life of ultra-thin wearing courses is relatively short when compared to the underlying 

concrete pavement, and thus will need to be reapplied multiple times during the pavement life.

Bonded Concrete Overlays

Bonded concrete overlays (see figure 7-21) 

are characterized by the placement of a 

relatively thin (2 to 4 inch [51 to 102 mm] 

thick) concrete layer over an existing concrete 

pavement after isolated areas of deterioration 

on the existing pavement have been repaired 

and proper surface preparation practices have 

been followed to ensure adequate bonding. 

Bonded concrete overlays can be placed on 

existing concrete pavements to eliminate 

surface distresses and improve surface 

friction, ride quality, and noise emissions. A 

strong bond between the new overlay and 

existing pavement is required so that the resultant pavement behaves as a monolithic structure. 

Bonded concrete overlays require that the existing pavement be in (or be restored to) good or 

Figure 7-21. Bonded concrete overlay 

construction (courtesy ACPA).

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Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

better structural condition. A comprehensive document on the use, application, and construction 

of concrete overlays is available from the National Concrete Pavement Technology Center 

(Harrington and Fick 2014). 

Positive Sustainability Attributes of Bonded Concrete Overlays

• The concrete surface can be shaped and textured as desired, restoring surface friction, 

eliminating profile deficiencies, and reducing tire-pavement noise.

• Bonded concrete overlays improve pavement aesthetics by providing a new pavement

surface.

• The pavement can be easily colored or textured to enhance aesthetics.

• Bonded concrete overlays are initially light in color and will likely increase pavement 

albedo.

• If properly designed and constructed, bonded concrete overlays exhibit relatively long 

life, reducing material consumption and construction impacts that would be otherwise 

caused by repeated applications of other treatments.

Potential Negative Sustainability Attributes of Bonded Concrete Overlays 

• Bonded concrete overlays require the use of new material transported from a central 

mixing facility, so the environmental impact of those materials must be considered.

• Bonded concrete overlays can be difficult to construct, and improper construction 

(particularly the failure to achieve good bond between the overlay and the original 

pavement) can result in early failures that negatively impact economic and environmental 

performance.

• The construction of bonded concrete overlays may require a longer period of time, 

leading to the development of traffic disruptions and delays. 

Energy Use and Emissions for Concrete-Surfaced Pavement Treatments

The information available regarding energy use and emissions for preservation and maintenance 

treatments placed on concrete-surfaced pavements is even more limited than that available for 

asphalt-surfaced pavements. Past studies of environmental impact have largely used LCI values 

for standard materials and computed hours of equipment use for a given treatment, assuming 

treatment life based on agency experience. Similar to asphalt-surfaced pavement treatments, the 

early focus has been on investigating the environmental impact of new construction and major 

rehabilitation. Only recently has the life-cycle value of preservation been investigated by the 

sector of the pavement community applying sustainability concepts. 

One recent study (Wang et al. 2012) evaluated a limited number of concrete-surfaced pavement 

maintenance treatments and concluded that pavement maintenance can produce important net 

reductions in GHG emissions and energy use for high-volume routes. For segments with lowtraffic volumes, the potential benefits take much longer to accrue, and payback may not occur 

before the end of the treatment life. 

To elaborate, the study by Wang et al. (2012) examined the impacts of different material types 

for early-opening-to-traffic full-depth repairs (i.e., a high-cementitious mixture comprising 

AASHTO M 85 Type III cement with a high dose of accelerator, compared to a standard 

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Caltrans-specified calcium-sulfo-aluminate cement [CSA] mixture) as well as the benefits of 

diamond grinding. The construction efforts and performance periods for the two materials were 

considered identical; thus, the differences in energy consumption and GHG emissions were

largely related to the material choices. As a result, the environmental impact of the more 

traditional Type III cement mixture was found to be significantly higher than that of the CSA 

mixture due to the following three factors: 

• The Type III mixture had a cement content of 801 lbs/yd3 (475 kg/m3

) versus 657 lbs/yd3

(380 kg/m3) for the CSA mixture.

• Although data on differences in embodied energy for the two cement types varies, the 

CSA cement is far less GHG intensive to produce than Type III cement as no calcination

of limestone takes place.

• The Type III mixture used a very high dosage of accelerator (63 lbs/yd3 [37 kg/m3]). At 

that dosage rate, the accelerator had a significant environmental impact.

Figure 7-22 illustrates the impact of the material choice on the calculated energy consumption 

for the high-traffic-volume case study. As can be seen, although the cementitious binder had the 

single largest impact on the energy consumption, the accelerating admixture had a very 

significant impact as well. The same trend was observed for GHG emissions, but to a slightly 

lesser degree. Aggregates and mixing plant effects are minimal. This illustrates the importance 

of using mixture-specific information in any environmental analysis. 

Figure 7-22. Details for the high-traffic case study of the material production phase showing the 

energy consumption for different LCI data sets (Wang et al. 2012). 

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In this same study, Wang et al. (2012) evaluated the use of diamond grinding to create three 

different levels of smoothness. It was concluded that the as-constructed pavement smoothness 

has an important effect on GHG emissions and energy use in the use phase and, therefore, on the 

total GHG emissions and energy use over the life cycle. It was also found that if the treatment

does not result in a smooth pavement, then the environmental benefit is greatly reduced. 

Furthermore, although the emphasis on most work to date has been on materials and 

construction, the differences in net energy consumption, GHG emissions, and payback time 

between materials for a given treatment (i.e., repairs constructed using CSA cement or Type III 

portland cement) were small compared with the effects of smoothness over the life of the 

treatment. The authors noted that the impact of materials was probably reduced due to the 

limited number of slabs being replaced (3 percent) in the case studies.

Considerable work remains to be done in order to document and validate the effects of 

preservation and maintenance with regards to life-cycle environmental impacts. Nevertheless, 

this early work on concrete-surfaced pavements suggests that treatments that use less material 

and create smooth pavements that remain smooth for long periods of time will have distinct 

environmental benefits, particularly on more heavily traveled routes.

Strategies for Improving Sustainability

The general strategies for improving sustainability of preservation and maintenance treatments 

for concrete-surfaced pavements discussed at the beginning of this chapter are applicable. Thus, 

factors such as limited new material use, thinner cross sections, maintaining high levels of 

smoothness, and increased construction quality all reduce environmental burden and contribute 

to more sustainable treatments. As noted before, significant differences may exist in the 

approaches that are used to reduce environmental impacts, depending on a number of projectspecific characteristics (perhaps most notably traffic volumes and associated burdens created in 

the use phase). As traffic volume increases, maintaining smooth surfaces becomes even more 

critical as the economic and environmental costs during the use phase begin to dominate the 

analysis. Although there is a clear distinction between agency costs and user costs with regards 

to economics, no such distinction exists when considering environmental impacts such as GHG 

and other emissions.

Future Opportunities

As interest in improving the sustainability of concrete-surfaced pavement maintenance and 

preservation techniques continues to evolve and move forward, future opportunities exist in the 

following areas:

• Improved materials that use less material and last longer. However, many of these 

innovative materials are (or will be) proprietary, so their environmental impacts are

unknown or difficult to determine.

• Improved approaches for optimizing treatment selection and timing through the use of 

more sophisticated pavement management systems and more proactive “leading” 

indicators of performance.

• Improved construction, particularly improvements in equipment that can expedite some 

of the more labor-intensive and time-consuming activities.

• The use of precast solutions to reduce traffic disruptions and lane closures.

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

• Increased emphasis and refinement of renewable surfaces (e.g., diamond grinding). 

• Alternative repair materials that can be opened to traffic more quickly without 

compromising future performance. 

• Alternative load transfer devices that expedite construction yet have exceptional longterm performance. 

• Increased sophistication of pavement evaluation equipment to determine suitability of 

various treatments.

• Other improvements as identified in chapter 3 for materials.

Concluding Remarks

This chapter reviews the effects of various maintenance and preservation treatments on the 

sustainability of pavement systems. There is a considerable lack of information on this topic, but 

clearly there are environmental and social impacts associated with the application of the broad 

range of preservation treatments on either asphalt-surfaced or concrete-surfaced pavements.

Although the cost effectiveness of these treatments has been investigated in recent years and they 

are widely accepted, the environmental and societal benefits still need to be explored. 

Specifically: 

• Life-cycle inventories have not generally been done for pavement maintenance/

preservation treatments. Although preliminary work has demonstrated significant 

environmental value for some techniques, considerably more work needs to be done. 

• Lower life-cycle costs are often highly correlated with lower environmental burden, with 

both being affected by: 

– Treatment selection.

– Materials selection.

– Timing of treatment.

• On higher-traffic routes, the higher economic cost of more frequent treatment may be offset 

by large reductions in environmental impact due to vehicle operation on smoother pavement.

• Treatment and materials selection.

– Treatments with thinner cross sections having the same service life result in reduced 

environmental impacts. 

– The use of local materials reduces transportation costs, but must be balanced with the 

need to meet performance requirements. 

– Reducing traffic delays on high-volume routes must be balanced with the need to 

maintain high levels of smoothness. 

– New materials that enhance performance or lower energy consumption and emissions 

should be investigated. 

– The environmental footprint during the manufacture of some materials may be high. 

The development and implementation of Environmental Product Declarations (EPD) 

(discussed in chapter 10) will help provide useful information to decision makers. 

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Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

• Construction quality. 

– Increased construction quality extends pavement life and reduces environmental burden.

– The additional effort required to achieve additional quality is generally very low.

– Pavements that are initially constructed smooth and that are maintained in a smooth 

condition over their life will result in reduced energy use and GHG emissions. 

References 

American Concrete Pavement Association (ACPA). 1994. Slab Stabilization Guidelines for 

Concrete Pavements. TB018P. American Concrete Pavement Association, Skokie, IL. 

American Concrete Pavement Association (ACPA). 2006. Concrete Pavement Field 

Reference—Preservation and Repair. EB239P. American Concrete Pavement Association, 

Skokie, IL. 

Beatty, T. L., D. C. Jackson, D. A. Dawood, R. A. Ford, J. S. Moulthrop, G. D. Taylor, F. L. 

Danchetz, D. A. Blanck, J. M. Fay, D. S. Keough, L. M. Rodriguez, M. D. Voth, and Z. L. 

Webb. 2002. Pavement Preservation Technology in France, South Africa, and Australia. 

FHWA-PL-3-001. Federal Highway Administration, Washington, DC. (Web Link).

Benson, C. and T. Edil. 2009. Quantifying the Benefits of Using Coal Combustion Products in 

Sustainable Construction. Electric Power Research Institute (EPRI), Palo Alto, CA. 

Carpenter, A. C. and K. H. Gardner. 2007. Recycled Material Highway Construction 

Environmental Assessment: Life Cycle Based Risk Assessment of Recycled Materials in Roadway 

Construction. Final Report. Research Project No. 43. Recycled Materials Resource Center, 

Durham, NH.

Chan, S., B. Lane, T. Kazmierowski, and W. Lee. 2011. “Pavement Preservation: A Solution 

for Sustainability.” Transportation Research Record 2235, Table 3, p. 38. Copyright, National 

Academy of Sciences, Washington, DC. Reproduced with permission of the Transportation 

Research Board.

Chappat, M. and J. Bilal. 2003. Sustainable Development: The Environmental Road of the 

Future, Life Cycle Analysis. The COLAS Group, France. 

Chehovits, J. and L. Galehouse. 2010. “Energy Usage and Greenhouse Gas Emissions of 

Pavement Preservation Processes for Asphalt Concrete Pavements.” Proceedings, First 

International Conference on Pavement Preservation, Paper 65. Newport Beach, CA.

Denevillers, C. 2010. “Renewable Carbon-Based Binders for Pavement Preservation.” 

Proceedings, ISSA Annual Conference. Sunny Isles, FL. 

Federal Highway Administration (FHWA). 1999. Manual of Practice: Materials and 

Procedures for Sealing and Filling Cracks in Asphalt-Surfaced Pavements. FHWA-RD-99-147. 

Federal Highway Administration, Washington, DC. 

Gardner, K. and S. Greenwood. 2008. Sustainable Highways Through the Use of Carbon 

Sequestering Construction Materials. Final Report. Research Project No. 35. Recycled 

Materials Resource Center, Durham, NH.

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Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

Geiger, D. R. 2005. Pavement Preservation Definitions. Technical Memorandum. Federal 

Highway Administration, Washington, DC. (Web Link).

Gransberg, D. 2009. “Life Cycle Cost Analysis of Surface Retexturing with Shotblasting as a 

Pavement Preservation Tool.” Transportation Research Record 2108. Transportation Research 

Board, Washington, DC. 

Gransberg, D. and D. M. B. James. 2005. Chip Seal Best Practices. NCHRP Synthesis 342. 

Transportation Research Board, Washington, DC. 

Harrington, D. and G. Fick. 2014. Guide to Concrete Overlays. Sustainable Solutions for 

Resurfacing and Rehabilitating Existing Pavements. Third Edition. National Concrete Pavement 

Technology Center, Ames, IA. (Web Link) 

Hicks, R. G., S. B. Seeds, and D. G. Peshkin. 2000. Selecting a Preventive Maintenance 

Treatment for Flexible Pavements. FHWA-IF-00-027. Federal Highway Administration, 

Washington, DC. (Web Link) 

International Grooving and Grinding Association (IGGA). 2011. Next Generation Concrete 

Surface. International Grooving and Grinding Association, West Coxsackie, NY. (Web Link). 

Kandhal, P. and R. Mallick. 1997. Pavement Recycling Guidelines for State and Local 

Governments, Participant's Reference Book. FHWA-SA-98-042. Federal Highway 

Administration, Washington, DC. (Web Link).

Kazmierowski, T. 2012. “Quantifying the Sustainable Benefits of Flexible Pavement 

Preservation Techniques in Canada.” Proceedings, National Pavement Preservation 

Conference. Nashville, TN. 

Lidicker, J., N. Sathaye, S. Madanat, and A. Horvath. 2013. “Pavement Resurfacing Policy for 

Minimization of Life-Cycle Costs and Greenhouse Gas Emissions.” Journal of Infrastructure 

Systems. Volume 19, No. 2. American Society of Civil Engineers, Reston, VA. 

Melton, J. S. and T. Morgan. 1996. Evaluation of Tests for Recycled Material Aggregates for 

Use in Unbound Application. Final Report. Project No. 6. Recycled Materials Resource Center, 

Durham, NH.

Minnesota Department of Transportation (MnDOT). 2005. Standard Specifications for 

Construction. Minnesota Department of Transportation, St. Paul, MN. 

Peshkin, D., K. L. Smith, A. Wolters, J. Krstulovich, J. Moulthrop, and C. Alvarado. 2011. 

Guidelines for the Preservation of High-Traffic-Volume Roadways. SHRP 2 Report S2-R26-RR2. Transportation Research Board, Washington, DC. (Web Link) 

Pidwerbesky, B. and J. Waters. 2007. “Sustainable Innovative Surfacing Treatments for Low 

Volume Roads.” Transportation Research Record 1989. Transportation Research Board, 

Washington, DC. 

7-46
Towards Sustainable Pavement Systems Chapter 7. Maintenance and Preservation Treatments

Smith, K. D., D. Harrington, L. Pierce, P. Ram, and K. L. Smith. 2014. Concrete Pavement 

Preservation Guide. Second Edition. FHWA-HIF-14-014. Federal Highway Administration, 

Washington, DC. 

Tayabji, S., K. D. Smith, and T. Van Dam. 2010. Advanced High-Performance Materials for 

Highway Applications: A Report on the State of the Technology. FHWA-HIF-10-002. Federal 

Highway Administration, Washington, DC. (Web Link).

Transportation Research Board (TRB). 2012. Sustainable Pavement Maintenance Practices. 

NCHRP Research Results Digest 365. Transportation Research Board, Washington, DC. 

Uhlman, B. 2012. “The Eco-Efficiency of Pavement Preservation Treatments.” Proceedings, 

National Pavement Preservation Conference. Nashville, TN. 

Wang, T., I. S. Lee, J. T. Harvey, A. Kendall, E. B. Lee, and C. Kim. 2012. UCPRC Life Cycle 

Assessment Methodology and Initial Case Studies on Energy Consumption and GHG Emissions 

for Pavement Preservation Treatments with Different Rolling Resistance. Research Report 

UCD-ITS-RR-12-36. Institute of Transportation Studies, University of California, Davis, CA. 

Waters, J. 2009. Long-Term Dust Suppression Using the Otta Seal Technique. Research Report 

368. New Zealand Transport Agency, Wellington. 

Zimmerman, K. A. and D. G. Peshkin. 2003. “Pavement Management Perspective on 

Integrating Preventive Maintenance into a Pavement Management System.” Transportation 

Research Record 1827, text, pp. 5-6. Copyright, National Academy of Sciences, Washington, 

DC. Reproduced with permission of the Transportation Research Board. 

7-47
Chapter 7. Maintenance and Preservation Treatments Towards Sustainable Pavement Systems

7-48
Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

CHAPTER 8. END-OF-LIFE CONSIDERATIONS

Introduction

Chapter 2 defines pavement end-of-life as the “final 

disposition and subsequent reuse, processing, or 

recycling of any portion of a pavement system that 

has reached the end of its useful life.” When the 

pavement reaches its end-of-life, it may: 1) remain 

in place and be reused as part of the supporting 

structure for a new pavement, 2) be recycled, or 3) 

be removed and landfilled. Each of these activities 

has economic and environmental costs that should 

be considered (e.g., consumption of raw materials, 

energy input, emissions), just as there are economic 

and environmental costs to the other more highly 

visible portions of the pavement life cycle (i.e., 

production of pavement materials, initial pavement 

construction, and the use phase). Therefore, end-oflife activities can impact sustainability factors such 

as waste generation and disposition, air and water quality, and materials use, and must be 

considered in a comprehensive LCA. 

This chapter introduces the methods and definitions associated with the EOL phase, drawing 

from ISO standards and practices and from case studies in the literature. Various EOL 

considerations for asphalt and concrete pavements and the associated challenges to quantify the 

EOL contribution in the pavement life cycle are also presented. 

Recycling and Reuse Statistics of Pavements

As quality aggregate sources are depleted, there is growing importance given to incorporating 

RCWMs even more aggressively in new and rehabilitated pavements. An ideal goal would be to 

use recycled materials to produce a long-lived, well-performing pavement, and then at the end of 

its life be able to use those materials again into a new pavement, effectively achieving a zero 

waste highway construction stream. This would not only produce distinct cost advantages, but it 

would also provide significant reductions in energy consumption and GHG emissions, 

eliminating the need for landfill disposal. 

Asphalt and concrete pavements are commonly recycled and reused construction materials (EPA

2009), with an overall description of reclaimed asphalt and concrete pavements and their reuse in 

highway applications provided by Chesner, Collins, and MacKay (1998). According to industry 

data, in 2012 less than 1 percent of RAP was sent to landfills, with 68.3 million tons (62.0 

million mt) of RAP being used in new asphalt concrete mixtures. This is a 22 percent increase in 

the use of RAP in 2012 compared to 2009 (Hansen and Copeland 2013). The total amount of 

recycled concrete used in the U.S. is estimated to be 140 million tons (127 million mt) in 2014, 

including materials recycled from both pavements and other sources (CDRA 2014). These 

recycled materials can be used back in new asphalt or concrete mixtures or used as aggregates in 

base layers, or even in a number of other uses such as fill, riprap, and ballast. A distribution of 

the use of recycled asphalt and concrete materials is shown in figure 8-1. 

Asphalt Pavement End-of-Life 

(EOL) Options:

 Central Plant Recycling (hot and 

cold)

 Full-Depth Reclamation

 Landfilling

Concrete Pavement End-of-Life

(EOL) Options:

 Recycling

 Reuse

 Landfilling

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

Figure 8-1. Recycling and reuse statistics of asphalt and concrete materials (data compiled from 

Hansen and Copeland (2013) for RAP and Wilburn and Goonan (1998) and USGS (2000) for 

RCA). 

Economic and Environmental Considerations of EOL Options

Using materials from a pavement at the end of its life is accepted as one of the most effective 

ways to improve pavement sustainability. However, a comprehensive economic and 

environmental analysis for recycling and reusing pavement materials must be done in order to 

fully quantify the effects of the various EOL options. For example, pavement recycling is highly 

affected by material transportation costs as compared to the cost of new virgin material delivered 

to the construction site (Horvath 2004). 

Different options are available for recycling asphalt and concrete pavement materials. However, 

in order to assess realistic benefits of recycling, all recycling options and their associated costs 

should be evaluated. Figure 8-2 illustrates a detailed characterization of the environmental cost 

determinants, including the potential factors contributing to the cost of pavement recycling and 

environmental implications. The important factors are technology (on site or off site), disposal 

costs (if the pavement is going to be landfilled), transportation, and the quality of the recycled 

material. These are expanded upon below: 

• Technology – This can be an important driving determinant for on-site and off-site 

recycling. This includes the construction equipment used for on-site recycling, such as 

cold in-place recycling, hot in-place recycling, and full-depth reclamation. On the other 

hand, if the pavement is recycled in a central plant, the environmental costs include 

demolition at the job site, crushing, screening, and stockpiling at the plant. 

• Disposal costs – If the recycled pavement materials are disposed of at a landfill, the total 

disposal costs include demolition, transportation, and landfill tipping fees. According to 

Horvath (2004), landfill tipping fees can be $10 to $70 per ton ($11 to $78 per mt) of 

material, varying widely even over relatively small distances. A very important 

consideration for landfill disposal is the diminishing number of landfills. 

8-2 
Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Figure 8-2. Environmental cost determinants for pavement EOL considerations (adapted 

from Horvath 2004). 

8-3 
Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

• Transportation – For recycled materials, 

transportation can have a major impact on the 

environmental burden. This results from 

transportation from job site to a landfill, from 

job site to a central plant for processing, or 

from the plant back to the job site. 

• Application – Recycled pavement can be 

reused in pavements as base layers or surface 

layers, in addition to embankments, fills, and 

scores of other potential uses. 

• Quality – The original quality of recycled 

pavement, its process, storage, and local 

specifications determine its final application. 

The quality requirements of using recycled 

pavement can be different for asphalt and 

concrete pavements, including surface and 

base layers. The potential contamination risk 

of recycled pavement can also limit its use and 

application. 

Closed-Loop or Zero-Waste Thinking for 

Pavement Systems

There is a growing interest among infrastructure 

professionals, such as urban planners, architects, and 

engineers, in the application of zero-waste or closedloop concepts. In closed-loop systems, a high 

proportion of energy and materials will need to be 

provided from reused waste and water from 

wastewater. This can be realized by transforming 

existing urban development design and construction 

philosophy to create or upgrade recycling 

infrastructure. Such thinking is encouraged for 

application at small scales of urban development such 

as planning for city districts. For instance, one of the 

critical planning considerations for more sustainable city districts is to have recycling facilities in 

close proximity to avoid transporting materials for longer distances. For pavements, closed-loop 

or zero-waste thinking will promote standardization of the recycling processes and improve the 

overall quality, the result of which will improve the overall sustainability of pavements. 

Closed-loop system thinking can deliver a series of advantages (compiled from Lehmann 2013): 

• Avoids waste being generated in the first place.

• Creates closed-loop economies with additional employment opportunities in recycling 

industries. 

• Transforms industries toward a better use of resources, cleaner production processes, and, 

importantly, extends the initial producer’s responsibility. 

A Strategy for Optimizing the 

Use of Recycled Materials 

Chapter 3 discusses approaches for 

highest use of recycled materials in 

pavements. While experience shows 

that using recycled aggregate in a base 

can be cost effective, other costs must 

be considered including material 

handling, preparation for reuse, and 

transportation. Transportation is 

usually a relevant aspect from both a 

cost and environmental perspective; in 

general, on-site recycling or 

transporting recycled materials within a 

small radius is feasible. However, it 

may not be optimal to transport 

recycled materials over a long distance 

when a local primary source or 

sometimes subprime materials are

available. An LCA provides the means 

to determine the optimized distance for 

transporting recycled materials 

compared to using local virgin 

materials to ensure efficiency and 

sustainability. Hence, applying all four 

concepts of sustainability assessment

(functional performance, LCCA, LCA 

and rating systems, as described in 

chapter 10) would provide a 

quantitative measure of the optimized 

use of recycled materials. It should be 

noted that the highest use is usually 

context defined, and may change over 

time as technologies continue to evolve 

and alternative recycling material 

implementation methods are 

developed. 

8-4 
Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

• Delivers economic benefits through more efficient use of resources. 

• Conserves landfill space and reduces the need for new landfill spaces. 

It is very important to place some level of responsibility of the pavement’s future on the initial 

producer (this can be the contractor or the owner/agency) instead of the last owner only. This 

will lead to practices where an increasing number of contractors or agencies consider future 

recovery and processing of the materials at the end of its useful life (Lehmann 2013). Economic 

incentives in the last decades have been the major driver of the increased use of recycled 

pavement and recycled materials or co-products (for example, shingles, slag, fly ash, tire rubber) 

from other industries. A detailed discussion of some of these materials is given in chapter 3. 

It is critical in a closed-loop pavement system to quantify and measure the benefits to incentivize 

contactors and owner/agencies. Some of the relevant questions that need to be addressed to 

generate robust, realistic, and scalable assessment of pavement recycling include (Horvath 

2004): 

• How much environmental “credit or burden” should be given to recycled materials (i.e., 

what is the environmental impact of recycled materials)? 

• Where should these credits be counted? 

• How should transportation be counted in the model? 

• Which life-cycle stage should it be assigned to? 

LCA deals with these issue through allocation rules. Allocation is defined by ISO 14044 (ISO 

2006) as the partitioning the input or output flows of a process or a product system between the 

product system and one or more product systems. Several allocation rules and procedures are 

applicable to reuse and recycling. 

ISO 14044 defines a closed loop as being when a material from a product is recycled into the 

same product system, while defining the open loop as being when a material from one product 

system is recycled in a different product system (ISO 2006). As far as the allocation procedures, 

similar categorization exists for both open- and closed-product systems. Closed-loop allocation 

procedures apply to materials from a product recycled into a material of the same product system 

(closed loop) or to a material in a different product system (open loop) without inherent property 

changes. On the other hand, open-loop allocation procedures apply to only open-loop product 

systems where the material is recycled into other product systems with substantial change in the 

inherent properties.

According to another definition of open- and closed-loop recycling and allocation procedures by 

Boguski, Hunt, and Franklin (1994), open-loop recycling can be defined as recycling of a postconsumer product into another useful product that will be disposed of or recycled only for 

limited number of cycles due to material degradation. An example for this is the recycling of old 

newspapers to the cereal box system where the cereal boxes are ultimately discarded. Boguski, 

Hunt, and Franklin (1994) go on to define closed-loop recycling as recycling of a material from a 

virgin product into another product that can be recycled over and over, theoretically endlessly. 

For example, used aluminum containers can be recycled into containers or other aluminum 

products virtually to no end. The key difference in the recycling definitions is the degradation of 

the recycled material, which can limit the number of recycling cycles. If the properties of the 

8-5 
Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

recycled product are not degrading, it can be 

recycled endlessly in the same or different product 

system (closed-loop recycling). 

There is no trivial answer to the question of 

allocation for pavement materials. When 

pavement materials (asphalt concrete and 

concrete) are recycled, they can be reused in 

another pavement application. The two critical 

questions that need to be answered to determine 

the type of recycling definition applies to RAP and 

RCA: Do the properties of pavement materials 

degrade, and is there infrastructure to collect RAP 

and RCA? The answer to both of these questions 

is generally yes. However, there is always some 

measurable value left in the recycled pavement 

that can make it reusable multiple times. 

Therefore, pavement recycling is more analogous 

to closed-loop recycling due to its potential for 

being reused many times. 

A comprehensive definition of a different class of 

allocation rules for different industrial products is

discussed by Boguski, Hunt, and Franklin (1994); 

Ekvall and Tillman (1997); Ekvall and Finnveden 

(2001); and Nicholson et al. (2009). A schematic 

description of the three allocation rules is shown in 

figure 8-3. 

The most commonly used allocation method is the 

cut-off and substitution method for pavements 

(Horvath 2004; Nicholson et al. 2009; Huang, 

Spray, and Parry 2013). According to the cut-off 

method, each product is assigned only the burdens 

directly associated with it; in other words, all 

benefits of recycling are given to using recycled 

materials. The cut-off method is usually applied 

when a “waste” material (negative economic 

value) turns into a product (positive economic 

value). The life of the recycled materials starts 

with its removal from the old pavement followed by transportation to a depository place for 

processing and transportation to a job site to be reused. All benefits are given to the pavement 

using the recycled materials by reduction in the use of virgin materials without any a priori

knowledge about the rate of recycling at the end of its life. 

Allocation Issues Related to 

Recycling at the End-of-Life of 

Pavements

Recycled materials can be produced 

during pavement rehabilitation (for 

example when a top layer of asphalt 

concrete is milled before adding a new 

layer). However, most recycled material is 

produced during a full pavement 

reconstruction or possibly from the 

demolition of some other civil structures

(e.g., recycled asphalt shingles and 

crushed concrete from buildings). When 

the material is recycled, a system 

boundary is crossed from one pavement 

life cycle to another. For example, RAP 

can be recycled back into new asphalt 

concrete where it can function as 

aggregate and also as a source of binder, 

reducing the need for virgin aggregate and

asphalt binder. Another example is 

recycling crushed concrete for use as 

aggregate in the base or as an aggregate 

in a new concrete pavement. Hence, it is 

important to determine the allocation of 

processing and handling to the producing 

and receiving life cycles. 

Several approaches have been and are 

being investigated to ensure that the 

“benefits” of using secondary materials or 

fuel resources are properly reflected in 

LCA for pavements. Most EPD 

approaches use a strict and conservative 

approach in that all processes and 

transportation needed to reuse or recycle 

the material are assigned to the product 

utilizing the recycled content. The 

allocation of environmental impact to the 

new application is cut off from the previous 

use at the start of the processes and 

transport to prepare it for use in the new 

application. 

8-6 
Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Figure 8-3. An illustration of EOL allocation rules potentially applicable for pavements (cut-off 

method, 50/50 method, and substitution method). 

The substitution method, on the other hand, gives new pavement full benefits of recycling at 

EOL. In other words, since the pavement is recyclable at the end of its life, it will replace the 

use of virgin material in another pavement. Therefore, the pavement under study can be 

rewarded a priori if the rate of recycling is known at present time. This approach requires 

appropriate accounting rules for the percentages of recycled content used in the pavement itself 

and the recycling at EOL. Double counting of benefits should be prevented. Another important 

consideration is the material to be substituted, whether it is virgin aggregate, binder, or a 

combination, and to what extent. 

The cut-off method and the substitution method are the two extremes of allocation rules. A third 

option is the 50/50 method in which one-half of the benefits of recycling are allocated to the 

pavement using recycled materials and the other half are allocated to the pavement producing the 

recyclable material. Some of the available strategies most applicable to pavement EOL scenarios 

are summarized by Santero, Masanet, and Horvath (2011). 

EOL Considerations for Asphalt Pavements

Asphalt pavement recycling has played a significant role in the pavement rehabilitation and 

preservation strategies employed by highway agencies since the energy crisis of the 1970s. With 

the more recent emphasis on sustainability considerations in pavement design and construction, 

8-7 
Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

effective pavement recycling strategies are sought even more by agencies interested in reducing 

energy usage, lowering material and transportation costs, and reducing GHG emissions. Asphalt 

pavement recycling can be done through central plant or in-place recycling techniques. Both of 

these EOL techniques are discussed in the following section along with best practices, 

procedures, and opportunities to improve sustainability at this stage of pavement life cycle. 

Central Plant Recycling

Central plant recycling (CPR) is the process of producing hot or cold asphalt mixtures in a 

central plant by combining virgin aggregates with new asphalt binder and recycling agents along 

with a certain amount of RAP. RAP is most commonly generated through cold milling or by 

ripping and crushing of existing pavements and then transported to asphalt plants. RAP from 

different source is usually kept in different stockpiles, and is usually screened into two, or 

sometimes three, different sizes at the asphalt plant. 

In hot central plant recycling (HCPR), heat transfer is used to soften RAP for mixing instead of 

direct heating. This means it is important that the moisture content of RAP be kept to a practical 

minimum as high moisture contents can significantly hamper the plant production as the heat 

will turn the moisture into steam instead of softening the RAP. Heat transfer is carried out by

overheating the virgin aggregates before introducing the RAP into the drum, and may lead to 

additional fuel and energy use, which may offset the economic and environmental benefits of 

using RAP. Heat radiation has also been used to heat RAP.

Cold central plant recycling (CCPR) combines RAP with emulsified asphalt/recycling agent 

without the use of heat; new aggregates can also be added if needed. Although not a common 

practice (Chesner, Collins, and Mackay 1998; Hansen and Copeland 2013), these mixtures can 

be used for surface, base, or subbase courses. Specifications for cold plant recycled mixtures are 

found in ASTM D4215. 

Best Practices for Construction of Asphalt Concrete with RAP

Processing and fractionating RAP at the central plant increases product uniformity and, 

consequently, produces more consistent asphalt concrete containing RAP. However, there are 

costs involved in processing and fractionating RAP, and greater stockpiling areas (multiple sizes 

vs. one) are required, which may present issues in some urban plant locations. Moreover, the 

amount of RAP that ends up in a given fractionated stockpile is usually a function of the parent 

material and the sizes chosen for fractionation. This, in turn, dictates how much each 

fractionated size is available for use in the new asphalt concrete. Thus, while processing helps 

improve consistency, the amount of RAP that ends up (on average) in each fractionated stockpile 

drives how much it can be used. Al-Qadi, Elseifi, and Carpenter (2007) provide a 

comprehensive review of RAP use in central plant recycling. 

Dust control is a critical issue with the use of RAP in a central plant facility. Plant production of 

mixtures with high RAP results in high dust contents and difficulties in meeting specifications 

(VMA and Dust/Effective Binder primarily). Very few plants are equipped to properly waste 

dust and even fewer have an outlet for that dust even if the plant is capable of wasting it. 

Without being able to address the increasing dusts, the use of a clean/washed aggregate material

becomes more important in order to achieve VMA. Unfortunately, this type of product is not 

readily available in many locations. 

8-8 
Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Environmental and Economic Impact of RAP 

The proponents of using high RAP contents in asphalt claim the benefit of resource conservation 

and waste reduction; however, it is necessary to corroborate such claims in a quantified way over 

the pavement life cycle. Horvath (2004), Ventura, Moneron, and Julien (2008), and, more 

recently, Aurangzeb and Al-Qadi (2014) and Aurangzeb et. al. (2014) discuss environmental 

benefits and trade-offs of using RAP in pavements from a pavement life-cycle perspective. 

Pavements incorporating RAP should be evaluated using LCCA and LCA and should include the 

materials production and maintenance stages. For example, when asphalt binder mixtures with 30

percent, 40 percent, and 50 percent RAP are used, LCCA showed a net savings up to $94,000/mi

($58,000/km), whereas LCA showed energy savings of 800 to 1400 MBTU and GHG reductions 

of 70 to 117 ton (64 to 106 mt) when 30 percent to 50 percent RAP was added to the asphalt 

mixtures (Aurangzeb and Al-Qadi 2014). However, when the loss of inherent properties of 

recycled pavement materials is considered, it can be argued that the pavement with recycled 

mixtures may deteriorate faster in the field than pavements with less (or without any) RAP. The 

possible substandard performance of recycled mixtures will necessitate more maintenance and 

rehabilitation activities, thereby offsetting the economic and environmental benefits of using RAP. 

Figure 8-4 illustrates the potential for increasing costs and emissions as the percentage of RAP 

increases in the pavement. An “optimum performance level” is defined where the economic and 

environmental benefits of using RAP are counterbalanced by the project costs and environmental 

burden incurred from increased frequency of maintenance and rehabilitation activities (Aurangzeb 

and Al-Qadi 2014). For example, based on the total cost, the mixture with 50 percent RAP can 

have a performance margin of 11.5 percent (100 − 88.5 = 11.5). 

Figure 8-4. Optimal performance levels based on (a) total cost and (b) GHG emissions 

(Aurangzeb and Al-Qadi 2014). 

8-9 

One environmental concern about the use of reclaimed pavement is associated with leachate 

when RAP is stockpiled, placed in a landfill, or used in a surface layer exposed to water 

infiltration. Brantley and Townsend (1999) investigated this issue of leachate produced by RAP, 

and concluded that RAP samples in the study were not hazardous waste and did not leach 

chemical greater than allowed by typical groundwater standards. Horvath (2003) reported 

average metal concentrations for various recycled and co-product materials used in construction 

including RAP. The hazardous limits were slightly exceeded only for two metals (barium and 

lead) out of fifteen metals examined. Legret et al. (2005) also concluded that insignificant 

leaching occurred from RAP. 
Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

Full-Depth Reclamation (FDR)

FDR is a technique in which the full thickness of the existing asphalt pavement and a 

predetermined portion of the underlying materials (base, subbase, and subgrade) are uniformly 

pulverized and blended to provide a homogeneous material. The pulverized material is mixed 

with or without additional binders, additives, or water, and is placed, graded, and compacted to 

provide an improved base layer before placement of the final surface layers. Full-depth 

reclamation can be performed through single-unit trains, two-unit trains, or multi-unit trains 

(Thompson, Garcia, and Carpenter 2009). The FDR trains may include combinations of a 

reclaimer (milling, reclaimer, and stabilizer), pugmill mixer/paver, or a portable crushing and 

screening unit. Figure 8-5 illustrates a full-depth reclamation train, with more detailed 

information provided elsewhere (ARRA 2001b; Wirtgen 2004; Asphalt Academy 2009). 

FDR is distinguished from other commonly used rehabilitation techniques, such as cold in-place 

recycling and hot-in place recycling, by its ability to recycle thicker pavement layers and to 

address specific problems rooted in different layers. FDR can recycle pavement depths up to 12 

inches (305 mm), with depths of 6 to 9 inches (152 to 229 mm) more common (ARRA 2001b; 

Stroup-Gardiner 2011). 

The FDR process varies between projects depending on needs of the owner/agency, the in situ 

material properties, and the required structural capacity after recycling. Three basic components 

of FDR processing are: 

• Pulverization – Pulverization is the first stage of the FDR process where existing HMA 

and part of the granular layers are transformed into uniform granular material with a 

target gradation that can be used as base layer. Once the layers are pulverized, a 

compacted base layer can be obtained by adding proper moisture. 

• Stabilization – Additives and stabilizers are commonly added to the pulverized materials 

to improve the strength and structural capacity of the compacted layers. Stabilization can 

be classified into four groups (ARRA 2001b). 

– Mechanical stabilization involves the incorporation of imported granular materials 

such as crushed aggregates, RAP, or RCA to achieve desired density and gradation 

and compaction. 

– Asphalt stabilization using asphalt emulsion or foamed asphalt binder (Wirtgen 2004; 

Jooste and Long 2007; Jones, Fu, and Harvey 2008; Fu, Jones, and Harvey 2011). 

– Chemical stabilization by adding additives such as fly ash, calcium chloride, 

magnesium chloride, lime, and portland cement. These additives can be added alone 

or in combination with other chemical additives. 

– Combination of asphalt and chemical additives is also a possibility to improve the 

properties of recycled layers. For example, Wirtgen (2004) indicates that cement is 

routinely used with emulsions to improve moisture resistance.

• Overlay or Surface Treatment – A structural asphalt concrete overlay is commonly used 

as the final wearing surface for a FDR project, although a number of surface treatments 

(chip seal, microsurfacing, slurry seal) may also be placed. These treatments are 

described in chapter 7. 

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Figure 8-5. Full-depth reclamation train (courtesy of John Harvey). 

HMA Overlay

Original HMA FDR + X

Original Granular Base  Remaining Original Granular Base

Other Pavement Layers Other Pavement Layers

X could be:

No stabilizer

Foamed asphalt + cement 

Cement

Asphalt emulsion

 Full Depth Reclamation (FDR)

Need to penetrate 

at least 50 mm into 

granular base

8-11

Project selection, using the proper stabilizing agent, mixture design, and curing considerations, 

are critical for the performance of any recycling project. Some of these considerations for 

improving quality of FDR mixture design and construction are discussed next. 
Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

There are several comprehensive references that document best practices for FDR construction 

(e.g., Stroup-Gardiner 2011; Wirtgen 2004; ARRA 2001b). At the same time, the successful 

installation and performance of FDR projects has been well documented in the literature, 

including in Minnesota (Dai et al. 2008), Canada (Berthelot et al. 2007); Georgia (Smith, Lewis, 

and Jared 2008); Nevada (Bemanian, Polish, and Maurer 2006); and Indiana (Nantung, Ji, and 

Shields 2011). A summary of advantages, limitations, and candidate pavements for FDR 

projects is presented in table 8-1. 

Table 8-1. Summary of FDR advantages, candidate pavements, and limitations. 

Summary Description

Advantages • Provides significant structural improvement.

• Can address most pavement distresses at different layers.

• Can improve ride quality.

• Minimizes hauling costs.

• Reduction in energy use and emissions in material production.

• Can correct smoothness deficiencies.

Candidates for FDR • Pavements with severe longitudinal and transverse cracking.

• Pavements with poor ride quality.

• Pavements with permanent deformation problems.

• Pavements with raveling problems and potholes.

• Inadequate structural capacity.

Limitations

• Not recommended for high-volume roads (i.e., > 20,000 ADT).

• Not recommended for roads with high percentage of trucks.

• Not suitable for areas with drainage problems.

• Soils with high plasticity can result in swelling.

Best Practices for FDR

Project selection, mixture design, the selection of appropriate additives for the project, and 

effective compaction are all critical to the effective construction of FDR. These are described in 

the following sections. 

• Project Selection – Understanding key project details such as traffic, roadway geometry 

and features, and the ability of the existing pavement structure to support the equipment 

recycling train are all critical in identifying suitable FDR projects. According to a recent 

survey done with contractors, the lack of project selection criteria was a strong factor 

limiting the use of in-place recycling techniques (Stroup-Gardiner 2011). Commonly 

used project selection criteria include pavement condition (distress type and severity, ride 

quality), pavement thickness, roadway geometry, and identification of the needed surface 

type for structural capacity, the prevention of moisture infiltration, and protection from 

thermal cracking. 

• Mixture Design – A mixture design is required for each FDR project. However, a unique 

mixture design could be impossible because the design depends on the properties of the 

in situ pulverized materials, which is often variable. The ultimate objective of mixture

design is to determine the quantity and type of additive, water, and compactive effort. A 

standard mixture design specification does not currently exist for FDR mixtures, but 

guidelines have been developed by some states and agencies to aid the development of 

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

good quality FDR layers (SEM Materials 2007; Caltrans 2012). Sieve analysis, 

extraction for binder content, soil plasticity, moisture susceptibility, critical low 

temperature cracking, resilient modulus, and triaxial compressive strength tests are 

usually conducted as part of the mixture design process. Material evaluation is primarily 

focused on the wet and dry strength of FDR mixtures and determination of the 

compaction curve for optimum moisture and additive content at a specified curing time. 

Compaction equipment and procedures and curing times can also vary depending on the 

additives and in situ climatic conditions. Table 8-2 summarizes the commonly used test 

methods used in the mixture design in addition to the standard ones. An on-going 

NCHRP study (Project 09-51) is currently studying the selection of material properties 

and the preparation of mixture designs for cold in-place recycling and full-depth 

reclamation of asphalt concrete for pavement design. 

• Additives – The cost effectiveness of additives can vary based on the characteristics of the 

project. However, one study demonstrated that emulsion, cement, or a combination of 

emulsion and lime improves moisture susceptibility of FDR mixtures (Mallick et al. 

2002). The same study indicated that emulsion-lime combination appears to be more 

cost-effective compared to water, emulsion, and cement stabilization. The critical issue 

for stabilized layers is the classification of the mixtures as “improved granular materials” 

(Anderson and Thompson 1995) or as bound materials such as HMA. The distinction 

between two material types governs the mixture design process as testing required will 

vary for each type of materials. Depending on the type and amount of additives, FDR 

mixtures can span a range of material behavior from very stiff (highly cemented) to very 

flexible (high emulsion content). The most commonly used additives are summarized in 

table 8-3 with their commonly reported and accepted advantages and limitations.

• Compaction – The importance of compaction and achieving target density is as critical as 

selecting the right amount and type of additive. Mallick et al. (2002) emphasize the 

selection of design number of gyrations and achieving the target density in the field. It

was reported that 97 percent of the laboratory density or 92 percent to 98 percent of the 

theoretical maximum specific gravity is suitable for wide range of FDR mixtures 

(Thompson, Garcia, and Carpenter 2009).

Economic and Environmental Impact 

A number of potential benefits can be listed for in-place recycling techniques that can be 

attributed to the increasing attention by agencies. Some of the major benefits are conservation of 

virgin materials; reduction in the cost of pavement preservation, maintenance, and rehabilitation; 

reduced lane closures; reduced fuel consumption; and reduced emissions. Of course, these are 

listed as potential benefits and they can only be realized when impacts over the complete life 

cycle of the pavement are considered.

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

Table 8-2. Commonly used test methods in the mixture design of FDR projects. 

Test Method Specification Purpose

Extraction of Binder Content ASTM D2172 Determine existing binder content in the 

HMA layers

Sieve Analysis ASTM C136 or AASHTO T27-11 Determine gradation of pulverized 

materials

Plasticity ASTM D4318 or AASHTO T90-00 Suitability for pavement layer and 

additive selection

Fines ASTM C117 or AASHTO T11-05 Determine materials finer than 75 μm in 

the granular layer

Wet and Dry Indirect Tensile 

Strength 

Similar to ASTM D4867 or AASHTO 

T283-07 (curing time may vary)

Moisture susceptibility of mixture

design

Resilient Modulus ASTM D4123 or AASHTO T307 Resilient modulus for thickness 

determination

Thermal Cracking AASHTO T322 Determine critical cracking temperature

Cohesiometer Test ASTM D1560 or AASHTO T246 Determine early mixture

Raveling Test ASTM D7196 Determine resistance to raveling

Confined and Unconfined 

Triaxial 

Similar to AASHTO T296 Determine cohesion and shear strength 

parameters

Table 8-3. Common additives used in FDR projects (recommended additive percentages 

from ARRA 2001a).

Additive Advantages Limitations

Liquid calcium chloride 

(1% by weight)

Improves freeze-thaw resistance

Portland cement 

(3 to 6% by weight)

Increases compressive strength, improves 

moisture resistance

Works best with soils plasticity index less 

than 10% (Thompson, Garcia, and 

Carpenter 2009), increases risk of 

shrinkage cracking

Lime 

(calcium hydroxide) 

(2 to 6% by weight)

Works best with reactive clay (plasticity 

index > 8) and fine content > 10% (Mathews 

2008; Franco et al. 2009); reduces plasticity 

of base material, improves moisture 

resistance

Too much lime can result in shrinkage 

cracking

Quicklime 

(calcium oxide)

Improves early strength Can result in shrinkage cracking

Fly ash 

(8 to 14% by weight)

Improves strength and moisture resistance 

Asphalt emulsions 

(1 to 4% by weight)

Improves strength and soften aged asphalt 

binder in RAP, reduce shrinkage cracking

Less resistance to permanent deformations, 

vulnerable to moisture related stripping

Foamed asphalt

(1 to 3% by weight)

Stockpile material for longer period (up to 1

month), deeper road stabilization (up to 14 

inches), open roads to traffic faster

Lime and cement Improves stiffness, moisture resistance, and 

strength (Naizi and Jalili 2009)

Fly ash and lime Improves strength Increased shrinkage cracking

Emulsion and lime 

slurry

Provides flexibility for low temperature 

cracking and shrinkage cracking

Cement and emulsion Improves strength, fatigue resistance, 

moisture resistance, accelerates curing time

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Strategies for Improving Sustainability

Some general approaches to improving sustainability with regard to pavement recycling at the 

end of its life along with associated environmental benefits and trade-offs are summarized in 

table 8-4. The specific strategies are discussed in the following sections.

Strategy No 1: Improve Plant Technology 

There exist few asphalt plants that are equipped with positive dust control (PDC) systems. The 

PDC system allows the producer to “waste dust” by returning less dust to the mixture than is 

being generated and the system is able to account for the aggregate weight change and translate 

that to adding the “correct” amount of virgin binder. Other energy efficient technologies should 

be explored. 

Strategy No 2: Increase Initial Quality of Pavement Materials and Construction

Improvement in the initial quality of paving materials and construction will increase the level of 

performance and the overall pavement life. The increase in pavement life will reduce the total 

cost of the pavement and the number of recycling phases, directly impacting the emission 

resulting from the total recycling process. 

Strategy No 3: Use Rejuvenators or Softening Agents

Recycled asphalt concrete materials, including plant and hot in-place recycling, have different 

characteristics than the original materials. The recycled materials usually have relatively high 

stiffness due to the aged binder. Effective rejuvenators are needed to reduce the brittleness of 

these materials, and these also affect the fatigue and thermal cracking of the new pavements with 

recycled materials. A suitable rejuvenator added at an optimized amount would increase the new 

pavement life, thereby reducing life-cycle costs, the impacts on the environment, and the number 

of recycling phases within a specific period of time. However, the upstream environmental 

impacts of any rejuvenator or softening agent must also be considered.

Strategy No 4: Maintain and Manage RAP Stockpiles Fractionated and Moisture Free 

It is important that the mixture design of asphalt concrete with RAP be developed to meet the 

design volumetrics. RAP fractionation is needed to accomplish that, which requires management 

of multiple stockpiles. This would allow achieving initial quality of the mixture that would 

result in extended performance. In addition, to reduce the cost of energy needed to process the 

RAP, the RAP stockpiles should be covered to protect them from exposure to moisture. 

Strategy No 5: Selection of Proper Type and Amount of Additives or Stabilizers

It is critical to use the proper type and amount of additives or stabilizers. The selection should be 

made on geotechnical inspection of in situ properties of the granular materials. This strategy 

may have minimal impact on the environmental burden of construction and material procurement 

phase; however, the expected improvement in performance and service life of the FDR can 

easily offset the initial environmental burdens and costs. 

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

Table 8-4. Approaches for improving sustainability of asphalt pavement recycling for 

pavement sustainability.

Asphalt

Pavement 

Recycling 

Objective

Sustainability 

Improving Approach Economic Impact Environmental Impact Societal Impact

Improve plant 

technology (including 

heating time, positive 

dust control, double 

barrel etc.)

Requires initial 

capital investment 

for the producer. 

Can potentially 

reduce pavement 

production costs.

Can reduce GHG 

emissions if 

transportation burden 

will not offset.

Preserves virgin 

natural sources. 

Reduces need 

for landfills. 

Increase Central 

Plant Recycling 

Rate of Pavements

Increase initial quality 

of pavement products 

and construction.

Can increase initial 

costs but may 

decrease life-cycle 

costs.

Can increase material 

production energy 

use but overall lifecycle energy and 

emissions may 

reduce.

Decline in 

natural 

resources. 

Use softening agents or 

rejuvenators

Can increase 

material production 

costs.

Can reduce GHG 

emission in overall 

life cycle if pavement 

quality is improved.

Preserves virgin 

natural sources. 

Reduces need 

for landfills. 

Maintain and manage 

RAP stockpiles (reduce 

moisture, fractionation) 

Can increase 

material production 

costs slightly but 

may decrease lifecycle costs.

Can increase material 

production energy 

use but overall lifecycle energy and 

emissions may 

reduce.

Preserves virgin 

natural sources. 

Reduces need 

for landfills. 

Use the proper type and 

amount of additive or 

stabilizers

Can increase 

material production 

costs but may 

decrease life-cycle 

costs.

Life-cycle energy and 

emissions may 

reduce.

Preserves virgin 

natural sources. 

Reduces need 

for landfills. 

Increase In-Place 

Recycling Rate of 

Pavements

Use structural asphalt 

overlays to improve 

weathering, cracking 

and fatigue resistance

Can increase 

material production 

costs but may 

decrease life-cycle 

costs.

Life-cycle energy and 

emissions may 

reduce.

Preserves virgin 

natural sources. 

Reduces need 

for landfills. 

Develop standards for 

mixture design and QA 

to improve quality

No costs. 

Life-cycle energy and 

emissions may reduce 

since the quality is 

improved.

Preserves virgin 

natural sources. 

Reduces need 

for landfills

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Strategy No 6: Structural Overlays

The type and thickness of an asphalt overlay can have considerable impact on the environmental 

burden of initial construction. However, their placement can protect the recycled layers from 

direct exposure to weathering and slow down the deterioration rate. LCCA and LCA can be 

used to demonstrate the potential benefits of different structural overlay alternatives.

Strategy No 7: Improve Construction Quality 

Similar to any other highway construction works, the quality of construction is also critical for 

the long-term performance of recycled pavements using FDR. Inexperienced contractors and the 

relative complexity of FDR jobs are some of the factors that may increase risks for quality 

construction. Stringent quality assurance protocols are critical to improve the long-term 

performance of pavements constructed with FDR. 

Future Directions and Emerging Technologies

Continued evaluation and eventual adoption of zero-waste strategy for all reconstruction projects

should be considered, providing the primary benefit that none of the existing pavement materials 

is ever wasted. This will require innovative equipment and approaches to make sure that all the 

materials can be recovered and effectively recycled. In addition, in order to minimize the 

recycled materials transportation cost and environmental impact, innovative equipment and 

processes that recycle the pavement completely in place should be considered. 

EOL Considerations for Concrete Pavements

Introduction

There are three primary end-of-life options for concrete pavement surfacing: reuse, recycling, 

and disposal. The sustainable aspects of each of these (and the impact that sustainable choices 

have on the necessary production and use processes of each) are introduced in this section and 

discussed in detail in following sections.

Recycling 

Natural aggregate resources are vast, but finite; many high-quality, conveniently located 

aggregate resources are being depleted rapidly. In addition, environmental regulations, land use 

policies, and urban/suburban construction and settlement are further limiting access to known 

aggregate resources. As a result, natural aggregate costs can be expected to rise with scarcity 

and increased haul distances. Concrete pavement recycling is a proven technology that offers an 

economical and sustainable solution to these problems.

Concrete recycling is a relatively simple process. It involves breaking, removing, and crushing 

hardened concrete from an acceptable source to produce RCA, which a granular material that can 

be produced for use as a substitute for natural aggregate in almost any application. 

Typical Uses of Recycled Concrete Products

Concrete recycling has been used extensively in Europe since the 1940s and in the U.S. since the 

1970s (NHI 1998), with one of the first U.S. applications of RCA in pavement construction 

taking place in the 1940s on U.S. Route 66 (Epps et al. 1980). Production of RCA in the U.S. 

currently averages about 140 million tons (127 million mt) per year from all sources (CDRA 

2014). USGS has reported that aggregate producers were responsible for approximately 100 

million tons of all crushed concrete production in 2000 (USGS 2000). The primary applications 

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

of RCA have been base and subbase materials, but it also has been used in both concrete and 

asphalt concrete paving layers, as well as in high-value riprap, general fill and embankment, and 

other applications.

The recycling of paving materials (including concrete pavement) into new paving applications is 

supported by the Federal Highway Administration, which states that “reusing the material used 

to build the original highway system makes sound economic, environmental, and engineering 

sense” (FHWA 2002; Hall et al. 2007). FHWA further states that “The engineering feasibility of 

using recycled materials has been demonstrated in research, field studies, experimental projects 

and long-term performance testing and analysis. When appropriately used, recycled materials 

can effectively and safely reduce cost, save time, offer equal or, in some cases, significant 

improvement to performance qualities, and provide long-term environmental benefits” (FHWA 

2002). 

The suitability of RCA products may be limited by the quality of the source concrete from which 

it is derived. For example, poorly controlled or highly variable sources (such as might be 

produced from building demolition stockpiles) or sources that include significant amounts of 

known materials-related distress (e.g., freeze-thaw durability cracking or alkali-aggregate 

reactivity [AAR] distress) will generally not be suitable for use in producing aggregate for new 

concrete mixtures; however, these products can often still be recycled into aggregate for subbase 

and backfill applications. 

Benefits of Concrete Recycling

One major incentive for concrete pavement recycling is economics. Aggregate costs (for fill, 

foundation and surface layers) constitute one of the greatest costs of highway construction, 

comprising between 20 and 30 percent of the cost of materials and supplies (Halm 1980). 

Concrete pavement recycling saves much of these costs. The cost of producing RCA can be 

considered to be limited to the costs of crushing the demolished concrete and screening and 

backhauling the RCA (along with quality assurance costs). The costs of concrete demolition, 

removal, and hauling are required whether the pavement is recycled or simply discarded. RCA 

production costs may be offset by savings in hauling and disposal costs, especially if the RCA is 

produced on site. 

The USGS reported that the average cost of RCA in 2005 was $6.93/ton ($7.62/mt), ranging 

from $3.41/ton ($3.75/mt) in New Jersey to more than $8.09/ton ($9/mt) in California, 

Louisiana, and Hawaii. Virgin aggregate was reported to cost an average of $6.52/ton 

($7.16/mt), ranging from $3.54/ton ($3.89/mt) in Michigan to more than $10.01/ton ($11/mt) in 

Mississippi and Hawaii (Kuennen 2007). In considering these numbers, it must be remembered 

that the volume of any given mass of RCA is 5 to 20 percent greater than the volume of natural 

aggregate, so a ton of RCA “goes farther” than a ton of virgin aggregate. Cost savings from 

concrete pavement recycling vary but have been reported to be as high as $5 million on a single 

project (CMRA 2008). 

In addition, concrete pavement recycling is a smart and environmentally sustainable choice that 

conserves aggregate and other resources, reduces unnecessary consumption of limited landfill 

space, saves energy, reduces greenhouse gas emissions, and captures CO2 from the atmosphere. 

Concrete recycling can eliminate the need for mining or extracting new virgin aggregates, and 

can reduce haul distances and fuel consumption associated with both aggregate supply and 

concrete slab disposal.

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Best practices for concrete pavement recycling and guide specifications for using RCA in new 

concrete and base materials can be found in many sources, including ACPA (2009). 

Reuse

The reuse of a material can be considered to include applications where the material is used in its 

current form, often in its current placement or location, with minimal (if any) processing. 

Typical Applications for Concrete Pavement Reuse

The most common example of reuse of concrete pavement is when it is used without significant 

processing as a base or subbase layer for an overlay or new pavement structure. Rubblization of 

concrete pavement in preparation for the placement of an asphalt overlay can be considered to be 

reuse of the concrete because the processing (rubblization) is not inherently necessary for the 

application but is one of several approaches for minimizing the potential for reflection cracking 

of concrete pavement joints and cracks in the asphalt (other options include the placement of 

various fabrics, membranes, and interlayer materials).

The suitability of a concrete pavement for reuse may be limited by the type, severity, and extent 

of the distresses that are present. Pavements that do not present relatively uniform quality (e.g., 

pavements with significant amounts of joint deterioration and other distresses that would result 

in “soft spots” or areas with significantly higher deflections) may require in-place processing 

(e.g., rubblization) in order to be reused successfully. Alternatively, such pavements may be 

better suited for recycling into an appropriate application or, in extreme cases, disposal.

Benefits of Concrete Pavement Reuse

The economic, environmental, and societal benefits of appropriately reusing the existing 

pavement structure are generally the highest of all end-of-life options for concrete pavements. 

There is great potential for material savings and conservation of resources, in terms of both the 

materials and energy required to produce and haul new materials, as well as reductions in the 

costs and energy associated with landfill disposal of old materials. In addition, construction 

duration is generally significantly shorter, resulting in reduced impacts to local users and 

businesses.

These benefits may be partially (or even wholly) offset by shorter performance life or more 

frequent maintenance requirements in some cases, particularly when a reconstruction alternative 

would address foundation or drainage deficiencies in the existing structure. LCA, LCCA, and 

pavement performance analyses are useful in determining whether reuse of the concrete 

pavement is appropriate for any given situation. 

Disposal

Disposal refers solely to the removal and hauling of a paving material to a landfill where it 

serves no purpose or value. As was noted earlier in this chapter, disposal costs are associated 

with demolition, transportation (which varies with haul distance), and landfill tipping fees, which 

vary widely, even over relatively short distances, and are increasing rapidly as available landfill 

space decreases. The National Solid Wastes Management Association reports that tipping fees 

increased from an average of $8/ton ($8.79/mt) in 1985 to $34.29/ton ($37.68/mt) in 2004, with 

averages as high as $70.53/ton ($77.51/mt) in the Northeast region (Kuennen 2007). One can 

also consider the potential value of RCA product (which can vary significantly with the quality 

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

of the source concrete and the availability of local natural aggregate) as a lost value or 

opportunity cost of disposal. 

Clearly, the economic and environmental costs of disposal are generally quite high and disposal 

is not an end-of-life option that will not often be preferred over the recycling and reuse options. 

Therefore, this option will not be discussed further in this chapter.

Concrete Recycling

RCA can be used as a replacement for natural aggregate in many situations and applications, but 

it is a composite material comprising natural aggregate and hardened mortar. As such, RCA can 

have significantly different physical, mechanical, and chemical properties than natural aggregate, 

and these differences must be addressed in the material processing, pavement design, and 

construction phases of road projects. Some of the most important issues to consider are 

highlighted below, along with strategies for improving the sustainability of concrete pavement 

recycling activities.

Source Material

The quality and overall properties of the source concrete must be evaluated to determine the 

potential uses of the RCA. High-quality, durable concrete may be suitable for producing RCA 

for use in structural concrete or pavement surface layers. Lower quality materials may be best 

suited for subbases, fill, or other applications. Additional factors, such as availability of local 

materials and haul distances, will also be necessary to determine the highest feasible use for the 

RCA. 

Original construction and mixture design records can be an excellent source of information 

concerning the component material sources and their qualities and proportions. If the pavement 

to be recycled is still in place, a condition survey should be performed to determine the type and 

extent of any distresses present and to retrieve samples for visual inspection and laboratory 

evaluation (FHWA 2007). If any material-related distresses (e.g., D-cracking or AAR) are 

observed in the source concrete, evaluations and tests should be conducted to ensure that 

mitigation measures will be effective in preventing recurrence of these distresses if the RCA is to 

be used in new concrete applications or the development of degradation-related problems in 

foundation or other applications. Techniques that may be effective in preventing recurrent ASR1

1

Note that there is no effective way to mitigate alkali-carbonate reactivity (ACR) and RCA obtained from a 

pavement affected by ACR must not be used as aggregate in new concrete.

for RCA to be used in new concrete applications include the introduction of lithium-based 

admixtures, the use of Class F fly ash or slag cement in place of a portion of the cement, a 

reduction in the total alkali loading in the concrete, or other ASR mitigation strategies applicable 

for virgin aggregate to be used in concrete. Recurrent D-cracking may be prevented by reducing 

the coarse RCA top size to 0.75 inches (19 mm) or less.

Stockpile Runoff and Drainage Effluent

The runoff from RCA stockpiles is initially highly alkaline, with one study finding median pH 

values of 9.3 and 9.8 for fine and coarse RCA stockpiles, respectively (Sadecki et al. 1996). The 

high alkalinity is the result of the leaching of calcium hydroxide from the freshly exposed mortar 

faces of the recycled aggregate. In addition, studies have shown the presence of trace amounts of 

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

heavy metals and other naturally occurring contaminants in RCA stockpile runoff, although 

generally not at levels considered hazardous (Sadecki et al. 1996). 

Similarly, the effluent from RCA foundation layers is initially highly alkaline (an effect that 

diminishes with time in service), and it is not uncommon to see very small regions of vegetation 

kill in the immediate area of associated pavement drain outlets for a short time after construction 

(Snyder 1995). Nevertheless, stockpile runoff and drainage effluent alkalinity usually decrease 

rapidly within a few weeks as the exposed calcium hydroxide is depleted through neutralization, 

dissolution, and reaction with carbon dioxide in the air; in addition, the concentrations of other 

contaminants in the runoff or effluent can also be expected to decrease rapidly with time (Snyder 

1995). 

Runoff and effluent alkalinity is generally not considered to be an environmental hazard because 

it is effectively diluted and partially neutralized at a very short distance from the stockpile or 

drain outlet with much greater quantities of rainwater runoff (Sadecki et al. 1996; Reiner 2008), 

which is typically slightly acidic (in the range of 5.2 to 5.4 inches some regions of the U.S). 

Furthermore, the effects of soil buffering and equilibration with atmospheric CO2 during 

transport from the RCA source to local surface waters may further reduce pH levels. Washing 

and selectively grading the RCA (as described in the next section) is also generally effective in 

reducing initial pH levels in RCA stockpile runoff and drainage effluent (Snyder and Bruinsma 

1996). 

The bottom line is that there appear to be no negative environmental effects from using RCA that

significantly offset the positive environmental effect of reduced use of virgin aggregate and 

landfills (Reiner 2008). 

Impact of RCA on Pavement Design and Construction

Because RCA typically has different physical, mechanical, and chemical properties than most 

natural aggregates, the properties and behavior of materials and layers comprising RCA can be 

significantly different from those of similar materials and layers comprising only natural 

aggregate. It is important to consider these differences in the design and construction of systems 

containing RCA components. Some of the key impacts of RCA on the design and construction 

of pavement foundation and concrete surface layers are described herein, along with generally 

accepted techniques for mitigating the effects.

Mitigation of Calcareous Tufa in RCA Base Materials

One major concern with using RCA in drained pavement layers is the potential for calcium 

carbonate precipitate in edge drainage structures and on associated filter fabrics. The mechanism 

of precipitate formation is presented completely in Bruinsma, Peterson, and Snyder (1997), 

where it is described as the dissolution of calcium hydroxide (an important cement hydration 

phase) into water from freshly exposed crushed mortar surfaces and the subsequent precipitation

of calcium carbonate as the dissolved calcium hydroxide reacts with atmospheric CO2. The

availability of calcium hydroxide increases with increasing surface area of recycled concrete 

(i.e., with finer particle sizes) and decreases over time as the available calcium hydroxide is 

depleted. 

Bruinsma (1995) and Tamarisa (1993) also determined that as much as 50 percent of the material

deposited in drainage structures and on associated filter fabrics may be dust and insoluble residue 

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

produced by the crushing operation. Bruinsma (1995) found that washing the product prior to 

use minimized the presence of this material. 

There have been many lab and field studies to characterize and identify solutions to this potential 

problem. The following conclusions, drawn from these reports, are useful in preventing 

problems with pavement drainage systems when using RCA in drained pavement layers: 

• Consider using “daylighted” subbase designs that provide broad paths for drainage 

(rather than concentrating all residue in outlet structures) (ACPA 2009).

• Unbound RCA layers that can pass water to pavement edge drainage systems or are 

“daylighted” should contain no more fine material than is necessary for stability. This 

will minimize the movement of dust and the formation of calcium carbonate precipitate. 

Blending with virgin aggregate will also reduce precipitate potential, but may not 

represent a best sustainable practice. Unstabilized fine RCA may be suitable for 

placement in layers below the pavement drainage system.

• Wash RCA prior to its use in a drained layer to minimize the contribution of “crusher 

dust” to drainage system problems. 

• Select filter fabrics with initial permittivity values that are at least double the minimum 

required so that adequate flow will be maintained even if some clogging takes place 

(Snyder 1995). 

• When filter fabrics are used in pipe drain trenches, leave the top of the trench unwrapped 

to reduce deposits of residue on the fabric. 

• Accumulations of precipitate and residue in drainage pipes can be significant and can 

reduce discharge capacity, but are rarely (if ever) observed to significantly impede 

drainage flow. 

• RCA intended for use in cement- or asphalt-stabilized layers require none of the special 

treatment or handling required for unstabilized RCA layers. 

Effects of Material Properties on Pavement Design and Construction

The use of RCA can significantly affect the properties and behavior of the materials and layers in 

which it is used. As a result, it may be necessary to modify certain pavement design and mixture 

proportions in order to obtain the desired behavior of the materials and performance of the 

pavement. Key considerations and possible design and construction modifications are provided 

below. 

• Effects of Unbound RCA Layers on Pavement Design. When unbound RCA is used in 

pavement subbase layers, it may initially behave similarly to layers comprising unbound 

natural aggregate (although studies suggest that the angular, rough-textured nature of the 

particles may provide modest increases in layer stiffness). However, after time, the 

hydration of freshly exposed and previously unhydrated cement grains (sometimes 

referred to as “secondary hydration”) can result in a layer that behaves like a stabilized 

layer. The increased stiffness of this layer may allow for a slight reduction in the 

thicknesses of surface layers. However, it may also result in increased slab curling and 

warping stresses and the need to reduce panel dimensions to mitigate the effect.

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

• Effects of RCA on PCC Mixture Properties. Fresh concrete mixtures containing RCA 

may exhibit higher water demand and have poorer workability or finishing 

characteristics, depending upon the amount and properties of RCA used. These 

difficulties are related to the inclusion of reclaimed mortar (which is generally angular 

and relatively porous) and can be especially acute for high replacement levels of fine 

natural aggregate with fine RCA. Mixture design and proportioning modifications (for 

example, using chemical and mineral admixtures or using lower levels of RCA 

substitution) can partially offset or eliminate many of these issues. ACPA (2009) and 

FHWA (2007) provide specific guidance on the proportioning of concrete mixtures 

containing RCA.

PCC mixtures comprising RCA may also be more susceptible to drying shrinkage 

problems due to the absorptive nature of the reclaimed mortar. These issues can be 

minimized with good RCA stockpile moisture management, mixture design 

modifications, and good construction and curing practices. 

• Effects of RCA on Hardened PCC Properties and Related PCCP Design Parameters. 

When all other factors are held constant (i.e., no compensating mixture adjustments are 

made), hardened RCA concrete can be expected to have somewhat lower (but still 

acceptable) strength and elastic modulus values, significantly more permeability, drying 

shrinkage and creep potential, slightly lower specific gravity, and somewhat higher CTE 

values (ACPA 2009). The physical and mechanical properties of RCA concrete must be 

determined and considered in the development of RCA concrete pavement design details. 

For example, increased shrinkage and thermal response of concrete containing RCA can 

cause larger joint movements, requiring different sealant materials and reduced panel 

dimensions. They also may increase slab curling and warping deformations. Strength 

and elastic modulus reductions can impact stress distributions and fatigue damage and 

may cause increases in required pavement thickness. Some of these effects can be offset 

with mixture proportioning modifications (e.g., lower w/cm) to reduce shrinkage and 

increase strength) or modifications in the properties of the RCA (e.g., reductions in the 

use of fine RCA and using impact crushing processes that remove most of the mortar 

from the reclaimed natural aggregate particles).

In some cases, the use of large amounts of coarse and fine RCA can have a beneficial 

effect on pavement behavior. Won (2007) describes the design and reconstruction of I-10 

near Houston, TX in 1995 using 100 percent recycled concrete aggregate in a CRCP. 

The resulting pavement had a 28-day compressive strength of 4600 lb/in2

 (32 MPa), but 

an elastic modulus of only 2.6 million lb/in2 (17,900 MPa); in other words, it was strong, 

but relatively compliant and not brittle, which is theorized to be at least partially 

responsible for the good behavior and excellent performance of the section to date. 

Table 8-5 summarizes pavement design modifications that should be considered when using 

RCA concrete in new pavement construction. 

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

Table 8-5. Design recommendations for RCA concrete pavements (ACPA 2009). 

Concrete Pavement 

Design Element Design Recommendations

Pavement Type

Use JPCP with panel length of 15 ft (4.6 m) or less to minimize potential for mid 

panel cracking.

JRCP and CRCP may be considered if aggregate interlock is enhanced with 

larger aggregate top size or blending virgin and recycled, coarse aggregate. 

Additional reinforcement may be desirable to ensure that cracks are held tight.

Slab Thickness

Generally the same as for conventional concrete pavement provided that the RCA 

concrete mixture design provides adequate strength.

For two-course construction using RCA concrete, the overall slab thickness might 

need to be greater than what is required for a conventional concrete pavement 

design, depending on the materials and mixture proportions used in each lift.

Joint Spacing Panel length should be selected to minimize the incidence of mid panel cracks in 

JPCP or to keep crack width to a minimum in JRCP.

Load Transfer

The criteria used for using dowels in RCA concrete pavements should be 

identical to those used for pavements constructed using virgin aggregate. 

Reinforcing steel recommendations for crack load transfer are presented below.

Joint Sealant 

Reservoir Design

Dimensions must consider both the selected sealant material and expected joint 

movements caused by temperature and shrinkage effects, which may be higher 

for RCA concrete.

Subbase Type

Subbase material should be selected in consideration of the structural 

requirements of the pavement type selected (as for conventional concrete 

designs). Free-draining subbase layers should be considered for RCA concrete 

pavements produced from D-cracked or ASR-damaged concrete.

Reinforcement 

Higher amounts of longitudinal steel reinforcing may be required in JRCP and 

CRCP to hold cracks tight so that aggregate interlock load transfer can be 

maintained.

Shoulder Type Same as for conventional concrete pavement.

Concrete Pavement Reuse

In some situations, concrete pavements can be reused (without recycling) at the end of their 

natural service lives by treating them as a base layer for a new pavement that is constructed 

directly over them (i.e., an overlay). Unbonded concrete overlays are prime examples of this 

end-of-life strategy because they are typically placed over concrete pavements that have no other 

options besides reconstruction. Asphalt overlays of badly distressed concrete pavements are 

another example, although it may be necessary to rubblize the concrete in situ (or provide an 

interlayer of some type) to provide a more uniform support condition for the asphalt pavement 

and to prevent joint/crack reflection. Some of the most important issues to consider in reusing 

concrete pavements are highlighted below. 

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Evaluation of Existing Pavement Structure

The in situ reuse of a concrete pavement may not be a sustainable end-of-life option if there are 

significant structural or drainage issues in the underlying foundation that must be addressed. 

Like any other pavement structure, the sustainability of a new pavement structure being built on 

a reused concrete pavement foundation will depend in part upon the quality, strength, and 

durability of that pavement foundation. Failing to correct known structural deficiencies may 

result in a shorter life cycle with higher economic and societal costs, and increased 

environmental impacts. In addition, the reuse of concrete pavements may require that additional 

geometric and safety considerations be addressed in the new pavement design due to the 

increased elevation of the new pavement surface (e.g., reductions in overhead clearances, 

changes in foreslope and ditch bottom location, adjustment of guardrail). 

Uniformity of Material

One of the most important aspects of concrete pavement reuse is the uniformity of support that the 

old pavement will provide to the new, particularly for new asphalt pavements, which are sensitive 

to foundation support. If the old pavement suffers from significant material-related distress (e.g., 

D-cracking, joint spalling), it may be necessary to construct or place interlayer materials (e.g., 

geotextile fabrics and constructed interlayers) or to rubblize the pavement (to reduce the stiffness 

of the entire pavement to levels comparable to those of the deteriorated areas). 

If non-uniform pavement conditions necessitate interlayer or rubblization treatments (or the 

construction of thicker pavement overlay structures), then reuse of the original pavement may 

not be the most sustainable approach. The sustainability assessment techniques described in 

chapter 10 are useful in making such determinations and decisions. 

Strategies for Improving Sustainability

The use of recycled concrete aggregate in lieu of natural aggregates is inherently sustainable 

when all other factors are equal. The following subsections describe strategies for improving the 

sustainability of concrete recycling by optimizing the production and use of the material, and 

these are also summarized in table 8-6. The ultimate goal for improving concrete pavement 

sustainability is the achievement of a zero-sized waste stream at the pavement end-of-life (as 

well as for rehabilitation operations). 

Strategy #1: Optimize Use of Recycled Materials through Testing and Characterization

As was noted previously, the quality and overall properties of the source concrete must be 

evaluated to determine how best to use the resulting RCA products as completely as possible and 

in the highest feasible applications. RCA particles tend to be highly angular and are comprised 

of reclaimed virgin aggregate and reclaimed mortar. Reclaimed mortar generally has higher 

absorption, lower strength, and lower abrasion resistance than most virgin aggregates. As a

result, RCA generally has lower specific gravity and higher absorption than virgin aggregate, 

particularly for smaller particle sizes, which tend to be comprised largely of mortar. The 

properties of a specific recycled concrete aggregate depend upon many factors, including the 

properties of the original concrete and the processes used to produce the RCA, particularly the 

crushing processes. Therefore, even when a preliminary assessment of product potential has 

been made, laboratory tests of product samples should be performed to further qualify the RCA 

for the selected applications, bearing in mind that higher type applications may require the use of 

higher test result thresholds. 

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

Table 8-6. Approaches for improving sustainability of concrete pavement recycling. 

Concrete 

Pavement 

Recycling 

Objective

Sustainability 

Improving 

Approach

Economic Impact Environmental 

Impact

Societal 

Impact

Optimize use of 

recycled materials 

through testing and 

characterization

Initial investments 

in research and 

development, will 

help understand 

material properties 

better

Optimized 

material usage 

will help reduce 

emissions and 

wastage

Preserves 

virgin natural 

sources. 

Reduces need 

for landfills

Increase Use of 

Recycled Materials 

and Minimize 

Wastage

Adjust RCA 

production 

operations

Initial investments 

to adjust production 

protocols

Reduced fuel 

consumption and 

minimizes 

wastage

Preserves virgin 

natural sources. 

Reduces need 

for landfills

Customize 

preparation and 

breaking of source 

concrete: removal of 

asphalt overlays and 

patches and 

pavement breaking

Potential increase in 

production costs, 

higher production 

rate may reduce 

overall material 

costs

Minimizes 

material wastage

Preserves virgin 

natural sources. 

Reduces need 

for landfills

Reduce CO2

Emissions over 

the Life Cycle 

Sequestration of 

CO2 by RCA

No economic 

impact.

Potential to offset 

CO2 emissions 

from the raw 

materials used in 

cement 

production (not 

including fuels 

used in 

production)

Reduced 

impact on 

climate 

change. 

Reduce Virgin 

Material Usage 

and Material 

Transportation 

needs

On-site recycling

Reduction in fuel 

and potentially labor 

costs, increased cost 

to setup up portable 

crusher at job site 

Reduced GHG 

emissions due to 

reduction in haul 

traffic 

Reduction in 

haul truck 

traffic and 

traffic 

congestions, 

reduces need 

for landfills

A good example of the use of several tests and varying criteria for use in different situations can 

be found in the final report for NCHRP Project 4-31 (Saeed 2008), which identifies several 

properties of recycled aggregate subbase materials that influence the performance of the 

overlying pavement, including aggregate toughness, frost susceptibility, shear strength, and 

stiffness. Table 8-7 is a matrix that was developed by Saeed (2008) to summarize their 

recommendations for critical test values to ensure good RCA subbase performance for specific

traffic, moisture, and temperature conditions.

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Table 8-7. Recommended RCA subbase quality tests and threshold values for various 

applications (Saeed and 2008). 

Tests and 

Test Parameters

Medium-High Traffic

Low or High Moisture

Freeze climate

Low, Medium or High Traffic

Low-High Moisture

Freeze or Non-freeze climate

Low-Medium Traffic

High Moisture

Non-freeze climate

Low Traffic

Low Moisture

Non-freeze climate

Micro-Deval test 

(percent loss) < 5 percent < 15 percent < 30 percent < 45 percent

Tube Suction test

(dielectric constant) ≤ 7 ≤ 10 ≤ 15 ≤ 20

Static Triaxial Test 

(Max. Deviator Stress)

OMC, sc = 5 psi

(35 kPa)

>100 psi

(0.7 MPa)

>60 psi

(0.4 MPa)

>25 psi

(170 kPa) Not required

Static Triaxial Test 

(Max. Deviator Stress)

Sat., sc = 15 psi

(103 kPa)

≥180 psi

(1.2 MPa)

≥135 psi

(0.9 MPa)

≥60 psi

(410 kPa) Not required

Repeated Load Test 

(Failure Deviator Stress)

OMC, sc = 15 psi

(103 kPa)

≥180 psi

(1.2 MPa)

≥160 psi

(1.1 MPa)

≥90 psi

(620 kPa) Not required 

Repeated Load Test 

(Failure Deviator Stress)

Sat., sc = 15 psi

(103 kPa)

≥180 psi

(1.2 MPa)

≥160 psi

(1.1 MPa)

≥60 psi

(410 kPa) Not required

Stiffness Test 

(Resilient Modulus)

≥60 ksi

(0.4 MPa)

≥40 ksi

(275 kPa)

≥25 ksi

(170 kPa) Not required

Note: Low traffic: < 100,000 ESALs/year, Medium traffic: 100,000 to 1,000,000 ESALs /year, High traffic: 1,000,000 ESALs/year

Strategy #2: Adjustment of RCA Production Operations

The intended use of the RCA products should drive production operations in ways that maximize 

production efficiency, which means maximizing product yield (i.e., producing as much of the 

desired particle sizes as possible and minimizing waste) and doing so with a minimum 

expenditure of effort and consumption of fuel). For example, the production of RCA for use in 

new concrete mixtures often requires additional care to prevent the inclusion of contaminants 

(e.g., joint sealant material, reinforcing steel, and perhaps asphalt materials) and should be 

produced using breaking and crushing equipment that maximizes the production of useful size 

fractions. Conversely, the use of RCA in base or backfill operations will be less sensitive to the 

inclusion of minor amounts of contaminants and may permit the use of different types of 

breaking and crushing equipment to produce properly graded materials. 

Strategy 2A: Customize Preparation and Breaking of Source Concrete

Removal of Asphalt Overlays and Patches – Concrete pavements with asphalt concrete patches

and overlays can be processed to produce RCA for use in new concrete mixtures or other 

applications. Historically, the asphalt and concrete components have been recycled separately in 

the U.S., but some European countries routinely recycle concrete with up to 30 percent coarse 

RAP into new concrete paving mixtures without any apparent detrimental effects (Hall et al. 

2007), and the Illinois Tollway has recently begun utilizing fractionated reclaimed asphalt 

pavement (FRAP) as a partial replacement for virgin coarse aggregate in the lower course of 

two-layer concrete pavement construction. The sustainability of these practices must be 

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

evaluated for any given situation to determine whether it is better to recycle the asphalt materials 

separately (thereby making high use of the RAP) or to simply recycle the asphalt and concrete 

together and save the costs of separate recycling.

Pavement Breaking – The main purpose of pavement breaking is to size the material for ease of 

handling and transport to the crushing plant. Slabs are typically broken into pieces small enough 

to be easily lifted, transported, and processed by the primary crusher (typically 18 to 24 inches

[457 to 610 mm] in diameter). Breaking processes that produce an excessive amount of fines 

(e.g., drop balls and vibrating beam breakers or resonant breakers) are not recommended for offsite processing operations because they tend to produce a greater amount of excessively small 

fragments that are not easily salvaged. Pavement breaking equipment and slab cracking patterns 

should be selected after considering the intended crushing operation and desired product yield 

and gradation. For example, impact crushers typically can handle larger broken concrete pieces 

than compression (jaw or cone) crushers, allowing the use of a larger crack pattern and often 

resulting in higher breaking production rates. 

Strategy 2B: Customize Crushing and Sizing Operations

The yield of coarse RCA from the recycling operation depends upon many factors, including the 

crushing processes used. Crushing for larger aggregate particles generally produces higher 

coarse RCA yields because less crushing is necessary and fewer fines are produced. For

example, 55 to 60 percent coarse RCA yield is common when crushing to 0.75 inches (19 mm)

top size, while 80 percent yield is common when crushing to 1.5 inches (38 mm) top size (NHI 

1998). 

Jaw crushers tend to produce fewer fines than impact or cone crushers, resulting in higher yields 

of coarse RCA, which often is more useful than fine RCA, particularly in new concrete mixtures.

Figure 8-6 shows the results of one study of the impact of crusher type on RCA particle size 

distribution for a particular concrete source. 

Figure 8-6. Example effect of type of crusher on RCA particle size distribution. 

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100

% Passing

Particle Size (mm)

Impact Crusher Jaw Crusher

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Impact and cone crushers often are more effective in removing most of the reclaimed mortar, 

producing RCA that looks and behaves similarly to the original virgin aggregate in the source 

concrete (although the yield of coarse RCA will be reduced). Impact crushers also can supply 

particle size distributions that are well suited for constructing unbound foundation layers (ACI 2001).

Strategy #3: Sequestration of CO2

Research has shown that RCA has significant value as a sink for CO2 when atmospheric CO2

reacts with calcium hydroxide (Ca(OH)2), one of the principal phases resulting from cement 

hydration that is present in the concrete mortar, to produce calcium carbonate (Gardner, Leipold, 

and Peyranere 2006). The potential for carbon dioxide sequestration is equal to all of the CO2

that was originally evolved from calcination of the raw materials used in the production of the 

cement (but not from the fuels used in production). Figure 8-7 shows an example of laboratory 

test results documenting CO2 removal over time for various moisture conditions. This study 

suggests that the use of RCA in unstabilized applications (e.g., unstabilized subbases, 

embankment stabilization) has the potential to “scrub” the local atmosphere of significant 

quantities of CO2. 

Figure 8-7. Carbon sequestration by fine RCA in laboratory column studies (Gardner, 

Leipold, and Peyranere 2006).

8-29

Strategy #4: On-Site vs. Off-Site Processing

When RCA is to be used in some component of the same project from which it was produced, 

substantial reductions in fuel consumption and emissions (as well as labor costs) can be achieved 

by processing the material at the construction site (as shown in figure 8-8) rather than by using 

an off-site facility. On-site processing also offers societal benefits (reductions in haul truck 

traffic and related traffic congestion and delays) and the potential for economic savings (which 

will be at least partially offset by the costs of setting up a portable crusher at the job site). 
Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

Figure 8-8. On-site concrete recycling operation. 

When the RCA will be used in a foundation layer of the reconstructed pavement, additional 

sustainability benefits can be achieved through the use of a mobile crusher (an in-place concrete 

recycling train) that includes primary and secondary crushers that have been specially adapted 

for in-place recycling and are mounted on crawler tracks. Figure 8-9 shows a concrete recycling 

train working on a pavement recycling project. 

Future Directions/Emerging Technologies

Current trends of increased and improved utilization of recycled concrete are expected to 

accelerate and continue for the foreseeable future, as highlighted in the following sections. 

Increased Recycling (Reduced Disposal in Landfills)

Recent statistics on concrete recycling are difficult to find, but Wilburn and Goonan (1998) 

indicated that, while it is accepted that concrete pavement is 100 percent recyclable, only 50 to 

60 percent of the 200 million tons (181 million mt) of concrete debris generated annually was 

being recycled in practice. This percentage has likely increased since 1998 due to national 

pushes by the FHWA and the development of a standard AASHTO specification for the use of 

RCA in new paving concrete. However, it is unlikely that 100 percent of all concrete paving 

demolition debris is currently being recycled or reused, so there is still room for concrete 

recycling initiatives to help in moving towards a zero-waste goal.

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Figure 8-9. Recycling existing concrete pavement in place (photo courtesy of Jim Grove). 

Improved Utilization of RCA Products

USGS (2000) reports that in 1997 only 15 percent of all recycled concrete aggregate were being 

used as aggregate in new concrete or asphalt concrete mixtures, which probably represents the 

highest type of application for recycled concrete aggregate. Seventy-eight percent was being 

used in base or landfill applications, which represents a relatively low value used for RCA. 

It is understandable that many engineers are not comfortable with using RCA in higher type 

applications because of the ramifications of premature failures in a surface layer are usually more 

critical than when defects develop in lower pavement layers. In addition, there has not been 

widely accepted guidance on the use of recycled concrete aggregate in new asphalt and concrete 

mixtures. However, guidance on the production, characterization and use of recycled concrete 

aggregate has recently been developed in several forms, including: 

• A technical bulletin from the American Concrete Pavement Association (ACPA 2009). 

• A technical report by the American Concrete Institute (ACI 2001). 

• Specifications from AASHTO. 

– AASHTO M319, “Reclaimed Concrete Aggregate for Unbound Soil-Aggregate Base 

Course.” 

– AASHTO MP16, “Reclaimed Concrete Aggregate for Use as Coarse Aggregate in 

Hydraulic Cement Concrete” 

• Newer policies and technical advisories from the U.S. Federal Highway Administration 

(FHWA 2002 and FHWA 2007). 

The advent of this level of technical support, combined with increased pressure for sustainable 

pavement construction, are certain to result in continued and improved high-type utilization of 

recycled concrete.

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

Concluding Remarks

This chapter describes the EOL phase of the pavement, particularly focusing on recycling, reuse, 

and disposal options for both asphalt and concrete pavements. Portions of the information 

presented in this chapter are also touched on in other chapters, including chapter 3 (materials), 

chapter 4 (design), chapter 5 (construction), and chapter 7 (maintenance and preservation). 

Major issues associated with asphalt pavement EOL considerations are listed below:

• According to a survey conducted as part of an NCHRP Synthesis 421 (Stroup-Gardiner 

2011), 33 out of 45 states have some experience with FDR. The implementation of inplace recycling—which includes cold in-place and hot in-place recycling in addition to 

FDR—is relatively low. Annual in-place recycling is less than 50 lane miles (80 lane

km) in most of the states. However, central plant recycling is very common. 

• Lack of mixture designs, specifications, and standards for project selection are some of 

the barriers for FDR applications. 

• Uncertainty of future EOL consideration in the life-cycle assessment of pavements is a 

barrier for LCA calculations. Because of this uncertainty, pavements are not usually 

given credits for producing recyclable materials at the end of their life time.

• The quality of the recycled material remains a challenge for the pavement using recycled 

materials. The major question with pavement recycling is, how many times can a 

pavement be recycled without loss in the inherent properties? 

Major issues associated with concrete pavement EOL considerations include: 

• Source material: quality and overall properties of the source concrete must be evaluated 

to determine the potential uses of the RCA. 

• Stockpile runoff and drainage effluent. 

• Impact of RCA on pavement design and construction. 

• Evaluation of existing pavement structure for concrete pavement reuse. 

References

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555R-01. American Concrete Institute, Farmington Hills, MI. 

Al-Qadi, I. L., M. Elseifi, and S. H. Carpenter. 2007. Reclaimed Asphalt Pavement—A 

Literature Review. FHWA-ICT-07-001. Illinois Department of Transportation, Springfield, IL. 

American Concrete Pavement Association (ACPA). 2009. Recycling Concrete Pavements. 

Engineering Bulletin 043P. American Concrete Pavement Association, Skokie, IL. 

Anderson, J. R. and M. R. Thompson. 1995. “Characterization of Emulsion Aggregate Mixtures.” 

Transportation Research Record 1492. Transportation Research Board, Washington, DC.

Asphalt Academy. 2009. “Technical Guidelines 2: A Guideline for the Design and Construction of 

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Towards Sustainable Pavement Systems Chapter 8. End-of-Life Considerations

Asphalt Recycling and Reclaiming Association (ARRA). 2001a. Full Depth Reclamation: A Century 

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MD.

Asphalt Recycling and Reclaiming Association (ARRA). 2001b. Basic Asphalt Recycling Manual.

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Boguski, T. K., R. G. Hunt, and W. E. Franklin. 1994. “General Mathematical Models for LCI 

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Philadelphia, PA. 

Bruinsma, J. E. 1995. Formation and Mitigation of Calcium Carbonate Precipitate and 

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Minnesota Department of Civil Engineering, St. Paul, MN. 

Bruinsma, J. E., K. R. Peterson, and M. B. Snyder. 1997. “A Chemical Approach to the 

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Transportation Research Record 1577. Transportation Research Board, Washington, DC. 

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Foamed Asphalt. California Department of Transportation, Sacramento, CA. 

Chesner, W., R. Collins, and M. MacKay. 1998. User Guidelines for Waste and By-Product 

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McLean, VA. (Web Link). 

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

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Aggregate in Hydraulic-Cement Concrete Pavement. Technical Advisory T 5040.37. Federal 

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Horvath, A. 2003. Life-Cycle Environmental and Economic Assessment of Using Recycled 

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Chapter 8. End-of-Life Considerations Towards Sustainable Pavement Systems

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Towards Sustainable Pavement Systems Chapter 9. Pavement Sustainability within Larger Systems

CHAPTER 9. PAVEMENT SUSTAINABILITY WITHIN LARGER SYSTEMS

Introduction 

Pavements can always be viewed as components of a larger system. Consider, for example, that 

transportation systems, highway corridors, neighborhoods, port terminals, pedestrian networks, 

stormwater treatment, and the local ecosystem are all larger systems that can influence or are 

influenced by a pavement system. The health, maintenance, improvement, restoration, or 

construction of these larger systems all have associated sustainability goals (which may or may 

not be explicitly stated) that will necessarily affect the sustainability goals of pavement 

subsystems. This could either encourage or exclude certain pavement sustainability practices. 

For instance, a larger corridor project may have a goal of minimizing GHG emissions from 

construction but may also specify a particular pavement type to match adjacent corridor sections 

for ease of maintenance and rehabilitation. In this case, recycled material use in pavements 

would be consistent with the project goals, but the pavement type with the lowest initial 

emissions may not be consistent with project goals. 

This chapter describes how pavement systems can interact with larger system sustainability goals 

by highlighting several larger system efforts and metrics. Specific sustainability considerations 

that can arise from these interactions and example treatments are also presented. 

Larger System Goals and Metrics

Larger systems within which pavements reside 

increasingly have sustainability goals and objectives 

to which the pavements subsystem contributes in 

some manner. This section provides examples to 

illustrate this concept and how it relates to the social 

and environmental components of sustainability, 

which are often undervalued or ignored when the 

focus is strictly on the pavement as the system in 

question. 

Sustainable Communities

Very generally, society is recognized by most as a 

large system that needs to function and grow in a 

sustainable manner. This includes how individuals, 

groups, industry, and infrastructure function 

together. This concept of an interacting population 

is often labeled “community.” There are a number of efforts nationwide aimed at strengthening 

the role of community (and community values) in the development, operation, and maintenance 

of infrastructure (including roads). An example effort at the federal government level is the 

Partnership for Sustainable Communities, which is a partnership between the U.S. Department of 

Housing and Urban Development (USHUD), U.S. Department of Transportation (USDOT), and 

the Environmental Protection Agency (EPA), that aims to “...coordinate federal housing, 

transportation, and other infrastructure investments to protect the environment, promote 

equitable development, and help to address the challenges of climate change” (EPA 2012). 

According to the partnership agreement, the HUD, USDOT, and EPA commit to coordinate and 

identify strategies that (USHUD, USDOT, and EPA 2009): 

Major Issues: 

 Inherent uncertainty in performance 

of materials specifically designed to 

meet aesthetic, environmental, or 

social criteria. 

 Higher cost of non-traditional 

approaches used to accommodate 

environmental and societal 

considerations.

 Quality and performance of utility 

cuts.

 Timing and quality of construction 

versus working in a prescribed 

window of operation.

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Chapter 9. Pavement Sustainability within Larger Systems Towards Sustainable Pavement Systems

• Provide more transportation choices. 

Develop safe, reliable and economical 

transportation choices in order to decrease 

household transportation costs, reduce the 

nation’s dependence on foreign oil, 

improve air quality, reduce GHG

emissions, and promote public health. 

• Promote equitable, affordable housing. 

Expand location and energy efficient 

housing choices for people of all ages, 

incomes, races, and ethnicities to increase 

mobility and lower the combined cost of 

housing and transportation.

• Increase economic competitiveness. 

Enhance economic competitiveness 

through reliable and timely access to 

employment centers, educational 

opportunities, services, and other basic 

needs by workers as well as through 

expanded business access to markets.

• Support existing communities. Target 

federal funding toward existing 

communities to increase community 

revitalization, to improve the efficiency of 

public works investments, and to 

safeguard rural landscapes.

• Leverage federal investment. 

Cooperatively align federal policies and 

funding to remove barriers, leverage 

funding, and increase the accountability 

and effectiveness of all levels of 

government to plan for future growth. 

• Value communities and neighborhoods. 

Enhance the unique characteristics of all 

communities by investing in healthy, safe, 

and walkable neighborhoods—rural, urban 

or suburban. 

Within this partnership context, pavements can 

play a significant role. Specifically, pavement 

construction, preservation, use, and reconstruction 

can be inferred to be a part of the strategies to (1) 

provide more transportation choices, (2) reduce 

GHG emissions, (3) increase mobility and lower the combined cost of housing and 

transportation, (4) expand business access to markets, (5) increase community revitalization, (6) 

increase the efficiency of public works investments, and (7) invest in walkable neighborhoods 

(USHUD, USDOT, and EPA 2009). These items also imply that pavement characteristics such 

Pavement Integrated into a 

Sustainable Street: City of 

Chicago’s Cermak/Blue Island 

Sustainable Streetscape.

The Chicago Department of Transportation 

(CDOT) advertises the first phase of a 2-

mile stretch of Blue Island Ave. and 

Cermak Rd. in the Pilsen neighborhood as 

the “greenest street in America.” It is a 

good example of how pavement is 

integrated into an overall approach to 

roadway sustainability. The $14 million 

project (completed in 2012) is helping to 

transform an industrial mixed-use stretch of 

street into one that can serve as a 

community focal point providing a sense of 

place, beautification, and ecological 

services. 

The overall drivers for the project involve 

more than just pavements, although 

pavement features play a significant role. 

Achievements of this project include:

- Reduced energy use by 42 percent. 

- Wind/solar powered pedestrian lights. 

- 76 percent local materials (manufactured 

within 500 mi (800 km) of the site). 

- 131 percent increase in tree canopy 

cover. 

- Education kiosks and an English/Spanish 

guidebook. 

- New bike lanes. 

Pavement contributions include:

- Warm-mix asphalt. 

- Photocatalytic cement, largely used for its 

self-cleaning properties. 

- Permeable pavements helping divert 80

percent of stormwater. 

- Use of RCWMs including slag, shingles, 

and ground tire rubber. 

More information is available at: 

http://www.cityofchicago.org/dam/city/depts

/cdot/CBISS_flier_2010.pdf

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Towards Sustainable Pavement Systems Chapter 9. Pavement Sustainability within Larger Systems

as materials, geometry, design, and location can be influenced or controlled by things like 

aesthetics, historical context, and cultural identity. Other examples of larger system efforts to 

which pavements may contribute are: 

• National Complete Streets Coalition. Part of Smart Growth America, the National 

Complete Streets Coalition is an advocacy group that assists organizations in creating and 

adopting policies that advocate for connected networks of multimodal access streets 

(Smart Growth America 2010) (http://www.smartgrowthamerica.org/complete-streets). 

• Walk Score. A private company that uses algorithms to provide scores related to the 

walkability, transit service, and bike friendliness. Among other things, scores are linked 

closely with apartment and home searches (http://www.walkscore.com/). 

• National Scenic Byways Program. This program, part of the FHWA, formally 

recognizes certain roads for their archeological, cultural, historic, natural, recreational, 

and scenic qualities (NSBP 2013) (http://byways.org/). 

• United States National Register of Historic Places. The official list of U.S. historic 

places worthy of preservation. Authorized by the National Historic Preservation Act of 

1966, the list is maintained by the National Park Service and contains over 6,800 

transportation-related listings among its over 80,000 properties. For instance, listings 

include the first concrete street in Bellefontaine, OH; a proprietary R.S. Blome Granitoid 

Pavement in Grand Forks, ND; a Hessler Court Wooden Pavement in Cleveland, OH; 

and on original brick portion of the 1913 “Yellowstone Road” (NPS 1974) that went from 

Boston to Seattle (http://www.nps.gov/nr/). 

Ecosystems 

Very generally, ecosystems are communities of living organisms interacting with their 

surrounding non-living environment. This interaction involves complex systems such as nutrient 

cycles, food chains, and energy flows. As the full impact of human development on these 

systems becomes better recognized, a large number of national and international efforts have 

been undertaken to better understand these impacts and preserve complex ecosystems. An 

example effort by the U.S. DOT, called “Eco-Logical,” defines what is called an “ecosystem 

approach to developing infrastructure projects” (Brown 2006). 

Eco-Logical provides guidance on an approach to mitigating the effects of infrastructure with the 

larger surrounding ecosystem as the focal point of the effort. Instead of regulatory driven 

individual mitigation efforts done within narrowly defined project boundaries, an ecosystems 

approach seeks to define and optimize solutions for the larger impacted ecosystem. Generally, 

this requires coordination among multiple agencies and can ultimately lead to more efficient and 

meaningful mitigation efforts. Goals that drive the Eco-Logical effort include (Brown 2006): 

• Conservation. Protect and even restore large-scale ecosystems.

• Connectivity. Reduce habitat fragmentation from infrastructure (including roads and 

their constituent pavements) projects. 

• Predictability. Commitments made by all participating agencies will be recognized and 

honored. 

• Transparency. Leverage better stakeholder (including the general public) involvement 

to improve public trust, credibility and streamline planning and development. 

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Chapter 9. Pavement Sustainability within Larger Systems Towards Sustainable Pavement Systems

An ecosystems approach to mitigating infrastructure impacts on ecosystems can create a set of 

goals and objectives for the ecosystem that has significant interplay with pavement systems. For 

instance, a particular area’s wildlife action plan can identify areas with high conservation needs, 

which may, in turn, influence the location of a temporary quarry for a roadway project. As a 

result, it may be that lesser quality aggregate is selected based on priorities of a wildlife action 

plan. 

Other examples of efforts with an ecosystem focus include those by the Federal Lands Highway 

(FLH) Program’s interaction with its partner agencies such as the National Park System, the U.S. 

Forest Service, and the U.S. Fish and Wildlife Service. These partner agencies are generally 

charged with the stewardship of larger ecosystems (e.g., Yosemite, Deschutes National Forest, 

Vieques Island National Wildlife Refuge) and tend to view roads and pavements within such 

ecosystems as secondary to the ecosystem itself. Consequently, when the FLH does work on 

roads and pavements with these partners, they frequently make design and construction decisions 

that conform to ecosystem goals and objectives that may not be optimized for pavements. For 

instance, many national parks and forests have aggressive invasive species programs that require 

imported aggregate be devoid of seeds from invasive weeds. This may require running the 

aggregate through the aggregate dryer portion of an asphalt plant to burn off weed seeds, 

resulting in a more energy-intensive pavement. Yet such a result is acceptable in light of the 

larger goal of controlling invasive species. 

Strategies for Improving Sustainability

This section identifies some specific pavement features that have not been described previously 

in other sections of this document yet may be influenced by larger system goals. These 

pavement features are often not quantifiable by LCCA or LCA and may or may not be explicitly 

recognized in sustainability rating systems. 

Aesthetics

“Aesthetics” refers to the nature and 

appreciation of beauty. In the context of 

infrastructure it refers to general appearance 

(typically meaning “visual appearance” but not 

necessarily excluding other senses) and usually 

implies a measure of beauty and harmony with 

the surrounding environment. There are limited 

opportunities to address the aesthetics of a 

pavement. To a large degree pavements are 

designed and materials selected for engineering 

reasons rather than artistic ones. However, 

there are situations where pavement aesthetics 

influence design; usually these influences are 

based on color or texture. 

Color can be controlled by choice of aggregate 

and binder materials, either alone or in 

combination with stains, dyes, or pigments. An

example of color-related aesthetics is the red 

cinder chip seal used in and around Zion 

National Park by the National Park Service and 

Pavement Aesthetics

The Eastern Federal Lands Highway Division 

(EFLHD) used a transparent, amber-colored 

synthetic binder combined with salmoncolored granite and pink quartzite aggregate 

to achieve desired aesthetics for paving the 

portion of Pennsylvania Avenue in front of 

the White House in 2004 (EFLHD 2004). 

Another example of aesthetics impacting 

pavement design is documented along the 

Gatlinburg Spur of the Great Smokey 

Mountains National Park Foothills Parkway. 

For this project, EFLHD was tasked with 

creating stabilized soil highway pull-offs for 

emergency use by motorists. Park 

aesthetics required that these pull-offs be 

grass surfaced (not paved) so EFLHD 

experimented with several different 

stabilization techniques that all proved 

successful (Hatcher 2004). 

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Towards Sustainable Pavement Systems Chapter 9. Pavement Sustainability within Larger Systems

Central Federal Lands Highway Division (CFLHD) (see figure 9-1). Pavement materials and 

type can also be changed in specific areas to create increased visibility, separating pedestrian and 

bicycle features based on color and texture (see figure 9-2). 

Figure 9-1. Zion Park Blvd. in Utah (SR 9) with a chip seal surfacing that uses local red 

volcanic cinders to match the aesthetics of the surrounding environment and to be consistent with 

historical road surfacing (photo courtesy of Steve Muench). 

Figure 9-2. Brick crosswalk in Charlotte, NC implemented as part of an intersection 

improvement (Hughes, Chappell, and Chen 2006). 

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Chapter 9. Pavement Sustainability within Larger Systems Towards Sustainable Pavement Systems

For concrete pavements, their normal grey color can be made nearly white through the use of 

white cement, slag cement, pigments, or stains. Projects have also been constructed where white 

cement is coupled with photocatalytic titanium dioxide to help keep the surface clean, thus 

maintaining the light color while also treating nitrous and sulfur oxides in air pollution. Concrete 

can also be patterned to add aesthetic appeal. A similar effect can also be achieved through the 

use of interlocking concrete pavers. Figure 9-3 shows how a combination of colored 

interlocking concrete pavers and colored concrete is being used to add aesthetic appeal on U.S. 

41 in a pedestrian-friendly historic downtown area of Houghton, Michigan. 

Figure 9-3. Vehicular interlocking concrete pavers being placed in a pedestrian-friendly 

downtown area in Houghton, MI. Note the use of colored concrete for the pavers to provide a 

visual offset for the cross walk (photo courtesy of Thomas Van Dam).

Historical and Cultural Identity

Historical and cultural identities are often closely associated with aesthetics since aesthetics can 

help create such identities, enhance feelings of community, or maintain ties to the past. Several 

of the examples previously given (paving of Pennsylvania Avenue in front of the White House 

[see sidebar in page 9-4], Zion Park Boulevard in Utah, and U.S. 41 in Houghton, Michigan) are 

all aesthetic treatments done for historical or cultural identity. Indeed, one of the most common 

ways pavement contributes to such identity is the preservation of an old pavement type or 

material in an historical area (see, for example, figures 9-4, 9-5 and 9-6). 

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Towards Sustainable Pavement Systems Chapter 9. Pavement Sustainability within Larger Systems

Figure 9-4. Old cobblestone pavement preserved and still in use on East Republican St., Seattle, 

WA (photo courtesy of Steve Muench). 

Figure 9-5. Lombard Street in San Francisco during construction in 1922 (FoundSF 2013). 

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Chapter 9. Pavement Sustainability within Larger Systems Towards Sustainable Pavement Systems

Figure 9-6. Lombard Street as it looks today with its brick pavement, kept for historical and 

cultural reasons (Wikipedia, public domain). 

Utility Cuts 

Utility cuts in pavements present a sustainability challenge because they breech the integrity of 

the pavement surface and their subsequent patches can result in weak points in the pavement 

structure through the existence of added joints, substandard pavement (figure 9-7), or inadequate 

subgrade repair. Some empirical work has been done to document these effects (e.g., City of 

Seattle 2000). 

Figure 9-7. Poor quality patch in an existing concrete pavement (photo courtesy of Steve Muench). 

Coordination Issues

In many instances paving and utility work schedules are not coordinated, which can result in 

utility cuts being made on newly paved surfaces. Many road owners have policies that forbid 

utility cuts for a specified time after paving (e.g., City of Spokane 2005; County of San Diego 

2008); however, coordination between street paving and utility work can be difficult. Generally, 

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Towards Sustainable Pavement Systems Chapter 9. Pavement Sustainability within Larger Systems

those jurisdictions that actively coordinate such work use some form of electronic database that 

registers all projects and checks for conflicts (Trombka and Rubin 2013). Some jurisdictions 

even charge a “pavement degradation fee” associated with utility cuts, which is intended to 

recover the cost of associated long-term pavement damage (Trombka and Rubin 2013). 

Repair Guidance

Most guidance on utility cut repair is directed at local agencies and focuses on traditional means 

including locating and marking existing utilities, traffic control, pavement cutting, excavation, 

backfill, surface restoration, and site cleanup (FHWA 1996). A key element to restoring longterm ride quality is to ensure that the backfill is adequately compacted. This is challenging in a 

long, narrow utility cut and thus the use of controlled low-strength materials (CLSM) to fill 

trenches is highly recommended. 

Ongoing work continues in the development of modular/precast pavements specifically designed 

to provide ready access to underground utilities, allowing panel removal and replacement after 

utility work is completed. Considerable work has been done showing how interlocking concrete 

pavers can be reused to create relatively seamless and repeatable repairs, as shown in figure 9-8 

(ICPI 2009). A French system using hexagonal panels is shown in figure 9-9 (Larrard, Sedran, 

and Balay 2012). While these methods are not new (see figure 9-10) they show promise in many 

instances.

Figure 9-8. Illustration of how existing concrete pavers can be removed to repair a gas line (a), 

and then the bedding recompacted (b), joint sand reapplied (c), and the final product which 

shows little sign of disturbance (d) (ICPI 2009). 

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Chapter 9. Pavement Sustainability within Larger Systems Towards Sustainable Pavement Systems

Figure 9-9. Removal of French hexagonal modular pavement to access utility (Larrard, Sedran, 

and Balay 2012). 

Figure 9-10. A utility cut in Rome, Italy shown with the excavation open and sampietrini 

(individual rounded black basalt stones) removed. Upon completion the cut is filled and 

sampietrini reinstalled (photo courtesy of Steve Muench). 

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Towards Sustainable Pavement Systems Chapter 9. Pavement Sustainability within Larger Systems

Odor, Soot, and Particulate Matter

Although of greatest concern to construction workers, odors, soot, and particulate matter (PM) 

generated during construction and shortly thereafter are also of concern to the adjacent 

communities. All paving construction operations have the potential to negatively impact worker 

health and local communities through plant and construction equipment emissions and PM 

generated from soil disturbance and demolition activity (SMAQMD 2013). For example, a 

recent study cited increased level of exposure to submicron PM for workers in both paving and 

milling operations, listing multiple strategies to improve worker safety including improved

maintenance of paver ventilation systems, diesel fume engineering controls, reduced idling, 

provision of cabs for the operators, and improved dust suppression systems on milling machines 

(Freund et al. 2012). Practices that can be used to help control construction generated emissions 

include (SMAQMD 2010):

• Fugitive dust can be controlled by watering all exposed unpaved surfaces twice daily, 

covering or maintain 2 ft (0.61 m) of free board space on haul trucks transporting loose 

material (all haul trucks using freeways or major roads should be covered), wet power 

vacuum paved surfaces daily, limiting vehicle speed on unpaved roads to 15 mi/hr (24 

km/hr), and paving surfaces as soon as possible.

• Soot and other emissions from diesel-powered fleets can be reduced by minimizing idle 

time and maintaining all construction equipment in proper working condition. 

In addition, as documented in chapter 3, the use of WMA technologies will reduce emissions and 

odors associated with the placement of asphalt materials.

Allowable Hours of Construction

It is very common in urban areas to have specified times in which delivery of materials and 

construction activities are allowed, being limited to certain times of the day, days of the week, or 

times of year. This is primarily to mitigate noise (e.g., in residential neighborhoods it is common 

for night construction to be prohibited) and minimize congestion during prime travel times. For 

example, in specifications used by the City of Azusa, California, construction is allowed between 

the hours of 7:00 a.m. to 6:00 p.m. Monday through Saturday and can be extended to 10:00 p.m. 

if approved by the City. For Sunday and national holidays, construction is only allowed if 

approved by the City, and is allowed only between the hours of 9:00 a.m. and 5:00 p.m.

Such restrictions are put in place to reduce the impact of construction on the community, yet they 

can impose difficult on contractors who often are working under tight schedules to complete the 

work as expeditiously as possible. Further, some construction activities are very sensitive to 

timing, and delays can cause serious damage and premature pavement failure. For example, 

concrete contraction joints must be sawed within a “sawing window” that is directly related to 

the properties of the mixture, the ambient temperature, and the length of time since mixing, 

among other factors. In general, joint sawing should be initiated within 4 hours and completed 

within 12 hours of paving, although specialized early-entry sawing equipment may allow sawing 

to begin within 1 to 2 hours of paving (Smith 2007). If paving is delayed and the sawing 

window falls at a time in which construction (e.g., sawing joints) is not allowed, the pavement 

can suffer random cracking and may require removal and replacement. 

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Chapter 9. Pavement Sustainability within Larger Systems Towards Sustainable Pavement Systems

Strategies for Improving Sustainability

Most important to this chapter is that larger system goals, and specifically sustainability goals, 

can drive pavement sustainability choices. Most prominently, social and environmental goals of 

larger systems contain elements to which pavements can contribute. In some instances, the more 

sustainable solution for the larger system requires pavement choices that are less than optimal 

when viewed from the perspective of pavement alone. Some general approaches to improving 

pavement sustainability within larger systems are summarized in table 9-1. 

Table 9-1. General strategies to improve pavement sustainability within larger systems.

Larger System 

Objective

Pavement 

Contribution Economic Impact Environmental Impact Societal Impact

Enhance Roadway 

Aesthetics

Color, texture, and 

historical materials

Increased cost, 

single-sourced or 

scarce materials 

Minimal Improved sense 

of place, beauty, 

and integration 

with 

surroundings

Minimize/Eliminate 

Impacts of Utility 

Cuts Through 

Coordination and 

Repair 

Better repair 

techniques, use of 

pavements that allow 

utility cuts without 

degrading pavement 

structure once 

repaired

Lower repair costs, 

less traffic 

disruption, longer 

pavement life

Reduction in 

needed material 

due to better 

repairs providing 

longer pavement 

life

Less disruption 

of transportation 

and services

Improve Worker and 

Community Health 

Through Reduction 

of Odors, Soot, and 

Particulate

Dust control, 

minimized idle time, 

warm-mix asphalt

Time and effort to 

train and implement 

new procedures

Less pollution that 

could adversely 

affect the 

environment

Improved 

worker and 

community 

health

Balance Approach to 

Allowable Hours of 

Construction

Faster construction 

and proper phasing 

of construction to 

conform to working 

hours

Increased 

construction costs 

(offset by impact 

savings) to 

accommodate 

community working 

hours

Improved 

environmental 

performance (e.g., 

reduced noise) 

during hours of 

non-work

Better 

accommodation 

of surrounding 

community 

needs and 

desires

Future Directions/Emerging Technologies

A few of the future directions and emerging technologies in this broad topic area are presented 

below: 

• Photocatalytic pavement. Photocatalytic pavement can be made using photocatalytic 

cement or through the use of photocatalytic coatings. This innovation potentially offers an 

opportunity to create a surface that remains clean while treating air pollution through a 

photocatalytic reaction involving nanoparticles of titanium dioxide (TiO2). In addition to 

its pollution-reducing quality, these materials are often lightly colored, having high albedo 

(reflectance). The technology has recently been implemented on a limited basis in the U.S. 

Additional information on photocatalytic cement can be found in chapters 3 and 6. 

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Towards Sustainable Pavement Systems Chapter 9. Pavement Sustainability within Larger Systems

However, titanium dioxide has recently been classified by the International Agency for 

Research on Cancer (IARC) as a possible carcinogen to humans (IARC 2006). The effects 

of nanostructured titanium dioxide on the environment are also not fully known; some 

initial studies show significant effects on microbial communities in surface waters (Battin 

et al. 2009). 

• Energy production. Pavements may provide a venue to produce electric power through 

use of pressure, vibration, embedded solar photovoltaic (PV) devices, or simply by 

harvesting heat from sun exposed surface with embedded tubing. Research is ongoing in 

this arena, with numerous promising ideas populating the worldwide web. No idea has 

yet taken root, but it is likely that at some point energy harvesting from pavement will 

become a reality. 

• Translucent concrete. Translucent concrete may be a viable material in urban 

environments for use in delineating crosswalks or bicycle crossings (PCA 2013). Made 

from orientated optical fibers, the concrete literally glows and if accompanied with 

sensors, can light up a crosswalk as a pedestrian approaches the intersection. The 

technology can be used to show predefined messages.

• Precast pavement systems. This technology continues to evolve, and new methods are 

being developed that offer the potential to allow ready removal and replacement of the 

surface to access underground utilities. This “snap in, snap out” approach is still in early 

stages of development, but if implemented, will provide an answer to municipal agencies 

that are confronted with seeing the integrity of newly placed pavement being 

compromised as it is cut into pieces for utility access. An overview of precast concrete 

pavement systems is provided by Tayabji, Ye, and Buch (2012). 

Concluding Remarks

This chapter describes how pavements interact with larger system sustainability goals and 

objectives, and highlights a number of key pavement-related sustainability considerations not 

directly covered elsewhere. There are a number of potential issues and trade-offs that are 

inherent when considering sustainable pavements within the context of these larger systems, 

including: 

• Uncertainty in performance of materials specifically designed to meet aesthetic, 

environmental, or social criteria.

• Cost is often higher for non-traditional approaches to pavement design, materials, and 

construction including meeting historical or cultural identity.

• Depending on local policy, utility cuts are often executed by utilities that are not focused 

on the quality or long-term performance of the repair. This will require education and 

accountability to improve the state-of-the-practice.

• Timing and quality of construction versus being allowed to work only within prescribed 

hours of operation. This is most acute in urban areas where construction often is 

prohibited during nighttime hours (e.g., 6:00 p.m. to 7:00 a.m.).

• Specific features designed to accommodate wildlife can be expensive, and their 

effectiveness not well demonstrated.

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Chapter 9. Pavement Sustainability within Larger Systems Towards Sustainable Pavement Systems

References

Brown, J. W. 2006. Eco-logical: An Ecosystem Approach to Developing Infrastructure 

Projects. FHWA-HEP-06-011. U.S. Department of Transportation, Research and Innovative 

Technology Administration, Volpe National Transportation Systems Center, Cambridge, MA. 

(Web Link). 

Battin, T. J., F. V. D. Kammer, A. Weilhartner, S. Ottofuelling, and T. Hofmann. 2009. 

“Nanostructured TiO2: Transport Behavior and Effects on Aquatic Microbial Communities 

Under Environmental Conditions.” Environmental Science & Technology. Vol. 43, No. 21. 

ACS Publications, Washington, DC. 

City of Seattle. 2000. Impact of Utility Cuts on Performance of Seattle Streets. 178.1.30. City 

of Seattle, Seattle Transportation, Seattle, WA. (Web Link). 

City of Spokane. 2005. Resolution No. 2005-0031. Resolution adopted by the Spokane City 

Council, 4 April 2005. City of Spokane, WA. (Web Link). 

County of San Diego. 2008. Pavement Cut Policy. POL-RO-7. County of San Diego 

Department of Public Works, San Diego, CA. (Web Link).

Eastern Federal Lands Highway Division (EFLHD). 2004. Federal Lands Highway Materials 

Technical Brief: Rustic Pavement. Eastern Federal Lands Highway Division, Sterling, VA. 

(Web Link). 

Environmental Protection Agency (EPA). 2012. HUD-DOT-EPA Partnership for Sustainable 

Communities. Environmental Protection Agency, Washington, DC. (Web Link). 

Federal Highway Administration (FHWA). 1996. Utility Cuts in Paved Road – Field Guide. 

FHWA Contract No. DTFH61-95-C-00069. U.S. Department of Transportation. Washington, 

DC. 

FoundSF. 2013. Lombard St 1922. FoundSF, San Francisco, CA. (Web Link). 

Freund, A., N. Zuckerman, L. Baum, and D. Milek. 2012. “Submicron Particle Monitoring of 

Paving and Related Road Construction Operations.” Journal of Occupational and 

Environmental Hygiene. Vol. 9, No. 5. Taylor & Francis, London. 

Hatcher, M. L. 2004. Construction of Stabilized Grass Pull-Offs Using Geo-Technology along 

the Gatlinburg Spur. Project PRA-FOOT 15A31. Federal Highway Administration, Eastern 

Federal Lands Highway Division, Sterling, VA. (Web Link).

U.S. Department of Housing and Urban Development (HUD), U.S. Department of 

Transportation (USDOT), and Environmental Protection Agency (EPA). 2009. HUD, DOT and 

EPA Partnership: Sustainable Communities. U.S. Department of Housing and Urban 

Development, U.S. Department of Transportation, and Environmental Protection Agency, 

Washington, DC. (Web Link). 

Hughes, W., D. Chappell, and S. R. Chen. 2006. Innovative Intersection Safety Improvement 

Strategies and Management Practices: A Domestic Scan. FHWA-SA-06-016. Federal Highway 

Administration, Washington, DC. (Web Link). 

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Towards Sustainable Pavement Systems Chapter 9. Pavement Sustainability within Larger Systems

International Agency for Research on Cancer (IARC). 2006. Titanium Dioxide. Monographs. 

Volume 93. International Agency for Research on Cancer, World Health Organization, France. 

Interlocking Concrete Paver Institute (ICPI). 2009. Repair of Utility Cuts Using Interlocking 

Concrete Pavers. ICPI Tech Spec No. 7. Originally published 1996, Revised August 2009. 

Interlocking Concrete Paver Institute, Herndon VA. 

Larrard, F., T. Sedran, and J. M. Balay. 2012. “Removable Urban Pavements: An Innovative, 

Sustainable Technology.” International Journal of Pavement Engineering. Volume 14, No. 1. 

Taylor and Francis, New York, NY. 

National Park Service (NPS). 1974. Yellowstone Road Nomination Form. U.S. National 

Register of Historic Places, National Park Service, U.S. Department of the Interior, Washington, 

DC. 

National Scenic Byways Program (NSBP). 2013. National Scenic Byways Program. National 

Scenic Byways Program, Federal Highway Administration, Washington, DC. (Web Link). 

Portland Cement Association (PCA). 2013. Light-Transmitting/Translucent Concrete. Portland 

Cement Association, Skokie, IL. (Web Link). 

Sacramento Metropolitan Air Quality Management District (SMAQMD). 2010. CEQA Guide – 

Basic Construction Emission Control Practices. December 2009, Revised September 2010. 

Sacramento Metropolitan Air Quality Management District, Sacramento, CA. (Web Link). 

Sacramento Metropolitan Air Quality Management District (SMAQMD). 2013. CEQA Guide – 

Chapter 3: Construction-Generated Criteria Air Pollutant and Precursor Emissions. December 

2009, Revised May 2011, Revised April 2013, Revised June 2013. Sacramento Metropolitan Air 

Quality Management District, Sacramento, CA. (Web Link). 

Smart Growth America. 2010. Elements of an Ideal Complete Streets Policy. National 

Complete Streets Coalition, Washington, DC. (Web Link). 

Smith, K. 2007. TechBrief: Early-Entry Sawing of Portland Cement Concrete Pavements. 

FHWA-HIF-07-031. Federal Highway Administration, Washington, DC. (Web Link).

Tayabji, S., D. Ye, and N. Buch. 2012. Precast Concrete Pavement Technology. Report S2-

R05-RR-1. Transportation Research Board, Washington, DC. (Web Link) 

Trombka, A. and L. Rubin. 2013. Coordinating Utility and Transportation Work in County 

Rights-of-Way. 2013-5. Office of Legislative Oversight (OLO), Montgomery County, MD. 

(Web Link).

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

CHAPTER 10. ASSESSING PAVEMENT SUSTAINABILITY 

Introduction

In general, there are four broadly categorized measurement tools, or methods, that are typically 

used either in isolation or in concert to quantify various aspects of sustainability: performance 

assessment, life-cycle cost analysis, life-cycle 

assessment, and sustainability rating systems. 

These methods were introduced in chapter 2 and 

are discussed in more detail here. Because 

performance assessment is a long-standing method 

of evaluation and is essentially built into current 

standards, it is not addressed in detail as a 

measurement tool. Notably, there are few, if any, 

generally accepted metrics able to measure 

equity/social impacts associated with pavement 

systems, although a few are recognized to some degree in sustainability rating systems. 

Life-Cycle Cost Analysis (LCCA)

Background

According to the Transportation Equity Act for the 21st Century (TEA-21), LCCA is “...a 

process for evaluating the total economic worth of a usable project segment by analyzing initial 

costs and discounted future costs, such as maintenance, user costs, reconstruction, rehabilitation, 

restoring, and resurfacing costs, over the life of the project segment.” Because LCCA is an 

essential component of most pavement type selection processes, many other definitions 

incorporate descriptions of typical LCCA applications (e.g., “LCCA is an analytical tool to 

provide a cost comparison between two or more competing design alternatives producing 

equivalent benefits for the project being analyzed” [NHI 2008]). However, whether used to 

compare competing alternatives or simply to assess the total expected cost of a single strategy, 

the basic analytical process remains the same. In simplest terms, LCCA can be considered to be 

a generally accepted accounting practice that “...offers sophisticated methods to determine and 

demonstrate the economic merits of the selected alternative in an analytical and fact-based 

manner” (FHWA 2013). 

The basic pavement LCCA process requires that the analyst define the schedule of initial and 

future activities involved in implementing a specific alternative (whether new construction or 

rehabilitation). Next, the costs of each of these activities are estimated. The predicted schedule 

of activities and their associated costs comprise the projected life-cycle cost stream, an example 

of which is depicted in figure 10-1. Using an economic analysis technique known as 

“discounting,” all projected costs are converted into present dollars and summed to produce a net 

present value (NPV) or net present cost (NPC). If multiple alternatives with similar benefits are 

being considered over identical analysis periods, the net present values or costs can be compared 

to determine which alternative is the most cost effective. More thorough descriptions of the 

LCCA process can be found in numerous publications (e.g., Walls and Smith 1998; Riggs and 

West 1986; FHWA 2002; FHWA 2004; NHI 2008; FHWA 2010; ACPA 2011).

Pavement Sustainability Aspects 

Can Be Evaluated Using: 

 Performance assessment. 

 Life-cycle cost analysis. 

 Life-cycle assessment. 

 Rating systems.

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

Figure 10-1. Example projected life-cycle cost stream diagram (FHWA 2002).

LCCA provides a means of measuring the economic consequences of design, materials, 

construction techniques, maintenance schemes, and end-of-life treatments. If the economic 

inputs for these are reasonable, LCCA is a tool that can account for their economic impact over 

the life cycle and is thus able to measure that component of sustainability.

Like most analytical tools, LCCA is not without limitations and, if used incorrectly, can provide 

false support for poor choices. While the accurate estimation of the timing and costs of lifecycle activities is the most important factor in conducting a good pavement LCCA (see Hallin et 

al. [2011] for guidance on developing reasonable maintenance and rehabilitation strategies), 

there are several additional considerations that are also important, as described in the next 

section. 

Key Issues in LCCA

As noted previously, LCCA is useful for determining the economic impact of potential changes 

in design, construction, materials, etc. that are intended to improve the environmental or societal 

impacts of a pavement project. NPV or NPC is also commonly used to select from among 

various design or rehabilitation alternatives that are believed to provide the same level of 

performance or benefits to the project’s users during normal operations over the same analysis 

period. 

If the benefits are the same but the analysis periods differ, then equivalent uniform annual cost 

(EUAC) analysis is useful in identifying the preferred alternative. Implicit in an EUAC analysis 

is the assumption that the strategies are repeated at the end of the analysis periods. An alternate 

approach (and the one that is recommended by FHWA) is to use the same analysis period 

(generally the shortest of those being considered) for all candidate alternatives and to include the 

remaining value of each alternative at the end of the analysis period (i.e., salvage value of 

materials or value of remaining service life) as a “benefit” or “negative cost” at the end of the 

analysis period. 

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

If the benefits vary among the candidate alternatives (e.g., if they provide different levels of 

service), then the alternatives cannot be compared solely on the basis of cost and, consequently, 

LCCA alone may not be an appropriate means of comparison. If all benefits can be expressed 

monetarily, then the benefits can be considered in the same analysis as the costs, discounted 

similarly, and a decision can still be made based on the results of the analysis and the overall 

objective (e.g., to maximize net benefits or minimize net costs). 

Another option for analyzing monetarily expressed costs and benefits that is sometimes favored 

by public agencies is benefit-cost analysis (BCA), in which the ratio of discounted benefits to 

discounted costs is computed. Unfortunately, simple BCA can lead to incorrect strategy 

selections in some cases, although incremental BCA, a more complex analysis, will yield 

consistently correct strategy selections (Riggs and West 1986). Because of its relative 

simplicity, NPV analysis is often preferred over BCA for economic analyses.

It must also be noted that, because there are usually other decision factors in the selection 

process that cannot be easily quantified monetarily (e.g., work zone safety, environmental 

impacts, impact of local development), LCCA alone is rarely sufficient for selecting from among 

competing alternatives. Utility theory and other forms of value engineering are sometimes useful 

in evaluating the preferred alternative when monetary and nonmonetary considerations must be 

balanced. In such cases, the option with the lowest LCC may not be implemented. Nevertheless, 

LCCA provides valuable information to the overall decision-making process. 

The following subsections briefly describe additional considerations in the proper conduct of 

LCCA.

Discount Rate

It is generally accepted that all future cost streams should be estimated in constant (current) 

dollars and discounted to present dollar values using a real discount rate, which represents the 

combined effects of interest and inflation rates. For pavement project LCCAs, the selected 

discount rate used should reflect both historical trends over long periods of time and near-term 

projections. The U.S. Office of Management and Budget (OMB) provides federal agencies with 

guidance concerning many of the technical aspects of conducting economic analyses, including 

the selection of a discount rate. FHWA recommends that highway agencies use OMB Circular 

A-94, Appendix C (OMB 2012) in selecting a discount rate, and many agencies use rates that are 

based on the “real interest rates on Treasury Notes and Bonds” found in that document, which is 

updated annually. 

The choice of discount rate is very important and thus it is useful to understand the impact of 

discount rate on LCCA. Higher discount rates reduce the present value of future costs by a 

greater amount than do lower discount rates; a zero discount rate values future costs the same as 

current costs; and negative discount rates increase the present value of future costs above those 

of current costs.

End-of-Analysis (Residual) Value: Salvage Value vs. Remaining Service Life Value

It is often necessary to assign a value (generally a benefit or negative cost) to the pavement at 

end of the LCC analysis period to capture either the value of the remaining pavement life 

(assuming that the pavement’s service life has not been fully consumed at the end of the analysis 

period) or the “salvage” value of the materials that will be derived from the pavement structure if 

it will have no remaining service life (e.g., if the pavement is to be removed and replaced at the 

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

end of the analysis period). Alternatively, the “salvage value” may be computed as the value of 

the existing pavement as a support layer for an overlay at the end of the analysis period (i.e., 

recycling or “repurposing” the pavement in place). 

These options are mutually exclusive for any given LCCA; that is, no analysis should include 

both a salvage value and a remaining service life value. Whichever end-of-analysis value is 

selected (if any), it should reflect what the agency realistically expects will be done with the 

pavement structure at the end of the analysis period. ACPA (2011) and West et al. (2012) 

provide summaries of U.S. state highway agency practices concerning the inclusion of salvage 

and remaining service life values in their LCCAs.

It should be noted that consideration must be given to the proper allocation of pavement salvage 

values to avoid “double counting” their contributions to the LCCA. For example, it may be 

appropriate to consider the value of salvaged materials as a positive cash flow at the end of the 

analysis period if the agency retains the ownership of the material for use on another project. In 

such cases, the salvage value might be considered to be equal to the cost savings associated with 

using the material on another project. On the other hand, if the contractor retains ownership of 

the material, then the agency receives no immediate benefit from the salvage operation and no 

benefit should be reflected at the end of the LCCA analysis period. However, it is reasonable to 

expect that the contractor will use the material on a different project and that the bid price for the 

material on that project will reflect the contractor’s low cost in obtaining the material. In this 

way, the agency benefit for the salvage value of the old pavement should be reflected (at least 

partially) in the lower initial costs of future projects. In any event, it is extremely important that 

the analyst place the salvage value benefit of any given material at the end of the analysis 

period or as a reduction in cost at the beginning of the next project, but not fully in both places. 

If different materials from the same project are used in different ways, then portions of the 

salvage value may be allocated to both places. 

User Cost Estimates

User costs originate primarily from vehicle operating costs (i.e., vehicle wear and tear, fuel 

consumption, repairs and maintenance), delay costs (e.g., from increases in time required to 

travel between two points as a result of work zones, congestion, etc.), and crash costs (which are 

often a result of driver error and other factors not related to the roadway conditions and, as a 

result, are generally not factored into LCCA) (Walls and Smith 1998). 

The value of road users’ time is a subject of great debate. User delay costs are generally 

computed in consideration of vehicle class, trip type (urban or rural), and trip purpose (business 

or personal). Details concerning the computation of user costs can be found in NCHRP (2004), 

and free software for computing these costs is a part of the FHWA RealCost LCCA program 

(FHWA 2010) or the CA4PRS software (Caltrans 2011). 

While there is no doubt that user costs should be considered in decision-making processes, it is 

widely recognized that these costs should not be included in the same LCCA cost stream as 

agency costs because: 1) although there is much literature on the topic, the quantification of user 

costs is subject to debate and uncertainty (FHWA 2002), 2) user costs “do not debit agency 

budgets as do agency costs” (FHWA 2002); and 3) computed user costs on some projects can be 

so large as to swamp the decision process or to drive it toward options that the agency cannot 

afford. Therefore, it is common for user costs to be weighted differently than agency costs in the 

decision process or (as current FHWA policy recommends) for user costs to be computed and 

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

analyzed separately from agency costs. The consideration of user costs in LCCA is described in 

more detail later in this chapter.

Deterministic LCCA vs. Probabilistic LCCA

The use of fixed values for all LCCA inputs (e.g., activity timing, costs, discount rate) to produce 

a single output value is referred to as the deterministic approach to LCCA. While this approach 

is relatively simple and requires few inputs, it fails to adequately account for either the variability 

in actual initial costs and discount rates over time or the uncertainty in the timing and costs of 

planned maintenance and rehabilitation activities. Furthermore, the output of a single value (i.e., 

NPV or NPC) without some statement to qualify that value may imply a degree of certainty in 

the conclusion that is inappropriate (FHWA 2010). Sensitivity analyses (i.e., varying input 

values, often one at a time, and rerunning the analysis to determine how sensitive the output 

value is to variations in specific inputs) can give the analyst a better sense of confidence in the 

accuracy of deterministic LCCA results.

The probabilistic approach to LCCA is more realistic in that it uses statistical descriptions of the 

probable distribution of values for each input (e.g., a mean and standard deviation for each 

normally distributed input value) to account for the input-associated variability that creates 

uncertainty in the outputs of the analysis, which helps quantify the risk in any decisions that are 

made on the basis of the outputs. A distribution of output values (often derived from numerical 

simulations involving input variables that have been randomly selected from populations of 

values that represent the input variable distributions) is produced to provide users with 

information for understanding the variability of the results and the confidence that can be placed 

in the analysis. Figure 10-2 provides an example illustration of the results of a probabilistic 

analysis.

Figure 10-2. Probabilistic analysis of two design alternatives (Walls and Smith 1998). 

0

0.1

0.2

0.3

0.4

0.5

0.6

18 23 28 33 38

Relative Probability

Net Present Value ($ Millions)

Alternative A Alternative B

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

The development of appropriate input-value distributions can be time-consuming, particularly if 

the data required to develop the input distributions are not routinely collected or available. The 

collection and use of good pavement cost, performance, and maintenance activity information is

essential for the conduct of a good LCCA. The probabilistic LCCA approach typically requires 

the use of sophisticated computer software (such as the FHWA’s RealCost tool), but is generally 

considered to have the potential for providing the most accurate “real-world” economic analysis 

and assessment of risk.

Use of LCCA in Various Pavement Delivery Approaches

LCCA can be used to improve decisions made in different types of pavement delivery 

approaches. For example, in traditional design-bid-build (DBB) programs, LCCA (along with 

other criteria) is typically used by the owner/agency to aid in determining the pavement type and 

principal design features (e.g., full-depth HMA vs. deep-strength HMA or JPCP vs. CRCP 

designs) based on very preliminary project assumptions and design inputs. Knowledge of the 

selected pavement type and principal design is used by planners, designers, right-of-way (ROW) 

acquisition teams, and others to develop the detailed designs, purchase ROW, and prepare bid 

documents that are specific to the project and the selected pavement type. 

As mentioned previously, user costs are commonly excluded from DBB project LCCA, but they 

may be recognized in the bidding process through “A + B” bidding. In this type of bidding, 

contractors submit both a bid price (A) and a number of days to complete the project 

construction (B), which is multiplied by some value that represents the impact on users caused 

by the duration of the construction activity and associated congestion and delays. Longer 

planned construction windows effectively increase the contractors’ bid prices, making them less 

competitive. There are typically substantial financial penalties for exceeding the contracted 

number of work days, and often incentives for completing the work early. 

“A + B” bidding recognizes only the impact of initial construction on user costs, and it is 

assumed that future agency maintenance costs and associated user costs (for work zone delays 

during future M&R activities) will be constant, regardless of which contractor builds the project. 

However, in “alternate design, alternate bid (ADAB)” projects, where the contractor can choose 

to bid on the construction of a specific design from among different design options, the future 

agency and user costs may differ significantly between the design options. In these cases, “A + 

B” bidding takes on a different meaning, where A is defined as the price of each contractor’s bid 

and B is the present value of future agency maintenance and rehabilitation costs for each 

alternative (note: B can also be computed as a difference in future costs between alternatives that 

is only applied to the alternatives with the higher NPV of future costs). Given the uncertainty in 

estimating future activity costs and timing, alternatives with NPVs that differ by less than 10 

percent are often considered to have similar costs to the agency. Since user costs are not 

considered directly in the analyses, the NPV of user costs for competing alternatives should be 

approximately equal for ADAB project alternatives. When the difference in NPV of user cost 

streams exceeds 20 percent, “the suitability of the project for (ADAB) should be carefully 

evaluated” (FHWA 2012). 

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

The use of LCCA in design-build (DB) 

contracting is similar to its use in DBB 

contracting in that the analysis can be used to 

estimate future agency (and user) costs for a 

particular type of pavement design. The 

owner/agency can then use this information in 

evaluating the preliminary designs and 

construction bid packages prepared by 

competing engineer-contractor consortiums to 

determine the overall best value to the agency 

(considering both the initial costs and the 

expected future costs).

In design-build-maintain (DBM) contracting, 

the successful contractor is responsible for 

designing, constructing, and maintaining the 

pavement at a specified level on behalf of the 

owner for a predetermined period of time that 

generally approaches the expected pavement 

life. The contractor bids typically reflect both a 

construction cost and an annual maintenance 

cost over the contract. The agency can use 

LCCA to determine the present value of these 

costs and can also factor in anticipated user 

costs (both during initial construction and 

future maintenance activities) to help in 

identifying the best value proposal (in 

consideration of other nonmonetary factors as 

well).

Available LCCA Tools

Since basic LCCA can be performed simply 

using pencil and paper, calculator, or 

spreadsheet programs, it is no surprise that 

there are probably many such tools available. 

In fact, many state highway agencies have 

developed and adopted their own software 

(generally computer-based spreadsheets) that 

incorporate their own predetermined unit costs, 

discount rates, assumed maintenance cycles, 

and other policy-based or standard parameters 

to facilitate uniform LCCAs by their staff and consultants. These LCCAs are usually 

deterministic and provide the users with relatively little flexibility in inputs.

The most widely accepted and adopted LCCA tool for pavement applications currently in use in 

the U.S. is the FHWA’s RealCost Software. Originally developed as a relatively simple proofof-concept, spreadsheet-based program for use in LCCA workshops in 1997, it has undergone 

numerous improvements and enhancements over the years and is routinely used by pavement 

design practitioners throughout the country. 

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

Examples

Numerous LCCA examples exist in agency and industry technical, reports, bulletins and training 

course materials (e.g., ACPA 2011; FHWA 2002; NHI 2008; West et al. 2012). For the most 

part, the examples included in those documents provide examples of LCCA for the purpose of 

pavement type selection and the selection of rehabilitation strategies. 

Documentation of the use of LCCA for applications more closely related to sustainability include 

the following: 

• Ram et al. (2011) studied a series of Michigan concrete pavement projects using both 

LCCA and LCA, concluding that higher levels of sustainability are achieved with 

increased pavement longevity. 

• Embacher and Snyder (2001) used LCCA to investigate actual maintenance and 

rehabilitation costs and strategies for concrete and asphalt pavements in two Minnesota 

counties, documenting the impact of differing maintenance strategies on the normalized 

costs (adjusted for varying traffic levels) of comparable pavements. 

• Hicks and Epps (1996) used LCCA to examine the cost effectiveness of using asphalt 

rubber as an alternative to traditional HMA. They concluded that, for the scenarios 

evaluated, asphalt rubber is a cost-effective alternative for many (but not all) highway 

pavement applications. When variability of the inputs was considered (e.g., cost, 

expected life), the asphalt rubber alternates were the best choices in most of the 

applications considered.

These three studies are presented as examples of the application of LCCA in making decisions 

that are related to pavement sustainability (beyond pure economics). The conclusions drawn 

from these studies are project specific and are not presented as universally applicable findings. It 

is important that the specific details of each analysis be considered in evaluating the conclusions 

drawn in these studies. 

Life-Cycle Assessment (LCA)

Awareness of the importance of environmental protection, and the possible impacts associated 

with the production, use, and retirement of products, has generated considerable interest in the 

use of assessment methods to better understand and address those impacts. Life-cycle 

assessment (LCA) is one of the techniques developed for this purpose. This section includes an 

introduction to the purpose, approach, intended outcomes, and limitations associated with the use 

of LCA. 

Purpose of an LCA

LCA is a structured evaluation methodology that quantifies the environmental impacts over the 

full life cycle of a product or system, including impacts that occur throughout the supply chain. 

LCA can be used for a variety of purposes, including: 

• Identifying opportunities to improve the environmental performance of products at 

various points in their life cycle.

• Informing and guiding decision makers in industry, government, and non-governmental

organizations for a number of purposes, including strategic planning, priority setting, 

product or process design selection, and redesign. 

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• Selecting relevant indicators of environmental performance from a system-wide 

perspective.

• Quantifying information on the environmental performance of a product or system (e.g., 

to implement an eco-labeling scheme, make an environmental claim, or produce an 

environmental product declaration statement).

Differences in results from an LCA can guide decision makers into making choices that have a 

lower or reduced environmental impacts. 

LCA is one of several environmental assessment techniques, and may not be the most 

appropriate technique for use in all situations. For example, environmental impact statement 

(EIS) or risk assessment may be more appropriate in some cases. An EIS is a detailed analysis 

that serves to ensure that the policies and goals defined in NEPA, the National Environmental 

Policy Act, are infused into the ongoing programs and actions of the federal agency. EISs are 

generally prepared for projects that the proposing agency views as having significant prospective 

environmental impacts. The EIS should provide a discussion of significant environmental 

impacts and reasonable alternatives that would avoid or minimize adverse impacts or enhance 

the quality of the human environment, whereas an LCA is focusing more on the environmental 

impacts associated with the material and energy flows throughout the pavement life cycle.

The LCA Process

LCA quantifies environmental flows that occur throughout a product’s life cycle, from raw 

material acquisition through production, use, end-of-life treatment, recycling, and final disposal 

(in other words, from cradle to grave). In LCA, these are referred to as life-cycle stages (or 

phases), and these were introduced in chapter 2 for pavement systems.

As shown in figure 10-3, there are four phases in an LCA study: 

1. The goal and scope definition phase. 

2. The inventory analysis phase. 

3. The impact assessment phase.

4. The interpretation phase. 

The first phase of an LCA determines key features of the analysis including the depth and the 

breadth of an LCA, which can differ considerably depending on the overall goal. The scope of 

an LCA defines the system boundary of analysis (essentially, what life-cycle stages and 

processes are included in the LCA), the geographic and temporal boundaries of analysis, the 

functional unit of analysis, and also determines the required quality of data. Again, all of these 

depend on the subject and the intended use of the LCA. 

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Figure 10-3. Life-cycle assessment framework (ISO 2006a). 

This figure is adapted from ISO 14040:2006, Figure 1 on page 8, with the permission of ANSI 

on behalf of ISO. (c) ISO 2013 - All rights reserved.

The second phase of an LCA, the life-cycle inventory analysis phase (LCI phase), is the 

accounting stage where environmental flows (inputs of material, energy, and resources, and 

outputs of waste, pollution, and co-products) are tracked for the system being studied. Figure 

10-4 illustrates the types of data that are collected. 

Figure 10-4. Data types relevant to a typical LCA (courtesy of theRightenvironment). 

The life-cycle impact assessment phase (LCIA) is the third phase of the LCA. The purpose of 

LCIA is to better understand the environmental significance of the LCI by translating 

environmental flows in to environmental impacts that are presented in different impact 

categories, typically:

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• Impacts to people (humans). 

• Impacts to nature (ecosystems).

• Depletion of resources. 

A list of typical impact categories is included in table 10-1. LCA studies usually include a 

selection of impact categories that are most relevant to the specific project goal and scope, and 

can range from narrowly focusing on energy and energy-related emissions to a full set of impact 

categories. The most commonly used impact categories in the U.S. are based on the TRACI 

impact assessment methodology developed by the EPA, the most recent version of which 

(TRACI v2.0) was released in 2012 (Bare 2011; EPA 2012b). The most widely used global 

impact assessment method is the CML methodology (Guinée et.al. 2002), with the most recent 

update from April 2013. 

Table 10-1. Typical LCA impact categories.

Group Impact

Category

Geographical 

scale

Comment on Available

Impact factors

Energy use

Fuel, non-renewable1

Resources, non-renewable

Resources, non-renewable, 

secondary

Fuel, renewable

Resource, renewable

Resource, renewable, 

secondary

Global

Small uncertainty, both energy use 

and feedstock energy should be 

quantified

Resource use Resource, renewable

Resources, non-renewable2 Global Small uncertainty

Climate Change1, 2 Global

Small uncertainty, typical 100 

year time horizon, biogenic CO2

requires special attention

Ozone layer depletion1, 2 Global Small uncertainty

Emissions Acidification1, 2 Regional Small uncertainty 

Tropospheric ozone1, 2 Local Medium uncertainty

Eutrophication1, 2 Local Small uncertainty, local

Toxicity

Human toxicity2, 

respiratory1

Human toxicity, 

carcinogenic1

Human toxicity, noncarcinogenic1

Ecotoxicity1

, fresh water2

Ecotoxicity, marine water2

Ecotoxicity, soil2

All scales High uncertainty, incomplete

Water Fresh water use Local Small uncertainty

Waste Hazardous

Non-hazardous Local Small uncertainty

1 part of TRACI

2 part of CML

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The life-cycle interpretation is the last phase of the LCA procedure, in which the results are 

summarized and discussed as a basis for conclusions, recommendations, and decision making in 

accordance with the goal and scope definition. 

Types of LCA Studies

There are cases where the goals of an LCA may be satisfied by performing only an inventory 

analysis and an interpretation. This is usually referred to as an LCI study. Generally, the 

information developed in an LCA or LCI study can be used as part of a much more 

comprehensive decision process. Comparing the results of different LCA or LCI studies is only 

possible if the assumptions and context of each study are equivalent. To address this, the ISO 

14044 standard contains several requirements and recommendations to ensure transparency on 

these issues (ISO 2006b).

Most Pavement LCAs are Process Based and “Attributional” 

Most pavement-oriented LCA studies are process based, meaning that data are collected for 

every process that is covered in the LCA. This is a bottom-up approach, and while data intensive 

it does allow for specific, regionalized, and representative results. Several commercial database 

and software tools are available that are based on this type of LCA. 

Other LCA studies are based on data generated from a top-down approach, called input-output 

LCA. These LCAs produce estimates of total supply chain impacts for economic sectors using 

economic input-output tables (which trace dollar flows across sectors) linked with resource use 

information and pollution flows for economic sectors. Products within a sector are assigned a 

portion of a sector’s supply chain impact based on their value. LCAs sometimes follow a hybrid 

approach where input-output data are used for secondary data and process LCI data are used for 

the primary processes, materials, and life-cycle phases that are under consideration. 

Regardless of whether the LCA is process based or input-output, pavement-oriented LCA studies 

most often are attributional, meaning they focus on describing the overall environmental 

properties of a life cycle and its subsystems. This is very useful in understanding the overall 

impact of a pavement project, for example. On the other hand, some pavement LCA studies that 

have been conducted are consequential, meaning that they aim to describe the environmental 

impacts of changes to an evaluated system. This can be useful in evaluating system wide 

impacts and is often used for studies that evaluate the impact of a proposed change in policy. 

Additionally, consequential LCA can be useful for infrastructure and traffic planning studies that 

evaluate decisions that have longer term and more far-reaching consequences.

Available Tools

Although there are no generally accepted LCA tools for pavements in the U.S., there are a 

number of LCA software programs (e.g., Athena, Gabi, SimaPro) that include relevant LCI 

datasets (many of which are proprietary) that can be used to develop LCA models. There are 

some pavement modeling tools available as well, such as PaLATE, which uses a hybrid LCA 

approach and considers energy use, air emissions, and leachate; information on this tool can be 

found at http://www.ce.berkeley.edu/~horvath/palate.html, but the tool is no longer maintained. 

This renders the database outdated and not fit-for-purpose. An update of the database would be 

required to make this a useful tool. This could leverage the results from LCI databases that rely 

less on input-output based LCI models. 

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More recently, the Project Emissions Estimator (PE-2) tool has been developed and provides a 

GHG emissions model for construction, maintenance, and use of pavements1

http://www.construction.mtu.edu/cass_reports/webpage/plca_estimator.php

 (Mukherjee, 

Stawowy, and Cass 2013). Additionally, AASHTO has also released a tool, GreenDOT, that 

estimates carbon dioxide emissions from the operations, construction, and maintenance activities 

of state highway agencies; it is designed to calculate emissions for geographical areas ranging 

from a single project to an entire state, and over time periods ranging from 1 day to several years 

(Gallivan, Ang-Olson, and Papson 2010). The two most likely uses of the GreenDOT tool are to 

calculate annual agency-wide emissions or to calculate emissions related to a specific project, 

covering a period of days or years2

http://onlinepubs.trb.org/onlinepubs/nchrp/docs/NCHRP25-25(58)_GreenDOTv1-5b.xls

. 

Most of these models rely on publicly available CO2 emissions factors such as those derived 

from MOVES, NONROAD and GREET. The EPA’s MOVES (Motor Vehicle Emission 

Simulator) (EPA 2012a) and NONROAD (EPA 2005) are air emissions inventory models and 

thus can be used to estimate on-road or non-road mobile source emissions (i.e., tailpipe 

emissions) associated with vehicles and equipment, but not life-cycle emissions. The GREET 

(The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation Model) model, 

developed by the Argonne National Laboratory, includes life-cycle emission and energy factors 

for different fuels, electricity, and other energy sources (ANL 2013). 

The Canadian Athena Institute released the most comprehensive North American LCA tool, a 

Highway Impact Estimator that relies on generic LCI data that the user cannot alter (Athena 

2013). There are many other examples of pavement LCA tools from Europe, including the 

decision-weighting model for roads, where the material life cycle of pavement can be modeled 

for environmental, economical, and user-defined project-specific sustainability aspects (Van 

Leest, Van Hartskamp, and Meijer 2008), and the RWS model DuboCalc3

http://www.rijkswaterstaat.nl/zakelijk/duurzaam/duurzaam_inkopen/duurzaamheid_bij_contracten_en_aanbestedin

gen/dubocalc/index.aspx

, which is an LCA 

model for the Dutch DOT that is mandated for use in all highway infrastructure. Other entities 

have developed their own models, often tailored for specific research projects or regional 

decision making including models developed at universities or by regional authorities. 

Key Issues

Pavement LCA methods and models continue to evolve. To illustrate some of the challenges 

that lie ahead, a short summary of the key issues that must be addressed to advance the use and 

implementation of LCA for pavements is provided below: 

• A general pavement LCA framework has not yet been agreed upon by practitioners. 

When pavement LCA studies are executed, LCA practitioners have to make many 

assumptions and make methodological choices that can lead to confusing and 

contradictory results among studies. The development of a generic pavement LCA 

framework could create a template that would define the most relevant starting points 

(i.e., for scope, goal, system boundaries, etc.) for any pavement LCA going forward. 

This would not only make LCAs easier to perform, but would also make them easier to 

interpret and compare.

• There is a need for a centralized database of non-proprietary LCIs for materials, 

equipment, vehicles, and other elements that can serve as a reference database for 

1

2

3

 

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

pavement LCA. This database would be used in conjunction with primary project data, 

and would include generic data covering all upstream data or “cradle-to-gate” data. A 

significant amount of data needs to be developed, preferably in a harmonized framework, 

such as an EPD framework for materials.

• A pavement life cycle can extend over a period of 60 to 75 years, and modeling a 

complete life cycle means making a number of assumptions based on design parameters, 

anticipated performance, maintenance and rehabilitation timing and frequency, and so on. 

It is extremely difficult to predict all these parameters today for the years to come. 

Transparently reporting the uncertainty in these assumptions is one step to improving 

LCAs.

• When the use phase is included, traffic-related impacts often dominate other life-cycle

stages. Some key traffic-related elements are traffic composition, volume, traffic delays, 

future traffic, vehicle fuel efficiency, rolling resistance, and pavement smoothness. The 

LCA models for these elements are still in development, and some still require basic 

research, especially with regards to vehicle and pavement interactions including the effect 

of pavement condition on vehicle fuel efficiency. 

Example Studies

A number of relevant pavement LCA studies have been performed in the last few years, with 

some of the significant findings and conclusions from selected studies summarized below. 

• Generally, most pavement LCA studies find that the materials for construction and 

overlays dominate the results when vehicle traffic is excluded from the analysis. This is 

true for both asphalt and concrete pavements. The combination of manufacturing the 

binder and producing the resultant mixture is a relevant contributor to the results for both 

pavement types. Aggregates constitute the majority of the mass of the pavement, making 

transportation and logistics particularly relevant for recycling and virgin aggregates. 

• The energy used and the emissions generated from the traffic that uses the pavement facility 

typically outweigh the emissions produced during the production of the materials and 

construction of the pavement. Steps towards cleaner fuels, higher fuel efficiency of the 

vehicles, and better traffic flow are relevant and potentially significant. This last point also 

favors nighttime work when traffic disruptions are minimized (Santero, Masanet, and 

Horvath 2010).

• Ram et.al. (2011) studied a series of concrete pavement projects in Michigan using 

LCCA and LCA tools, and concluded that increased pavement longevity was associated 

with reduced environmental impacts. Additionally, it was noted that if longevity is 

achieved, the use of SCM and RCA results in further improvements in both the economic 

and environmental life-cycle indicators.

• Wang et.al. (2012) applied LCA of pavement to research the impact of pavement 

smoothness over time and the relation between pavement maintenance and preservation 

on the fuel efficiency of vehicles for California state highways. The study found that the 

application of preservation treatments that enhance smoothness has a net positive effect 

on the overall energy and GHG emissions for facilities carrying high traffic volumes. 

• The time period that is covered by the LCA model is a very important factor. Typically, 

pavements are modeled using existing design criteria, construction practices and planned 

maintenance, rehabilitation, and replacement cycles, even though it is acknowledged that 

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these practices are constantly changing. Studies tend to use estimates for typical 

practices and use considerations such as traffic volume, traffic delays, and fuel efficiency 

over this long period of time, but these estimates become more and more uncertain as 

they are projected further into the future (Santero, Masanet and Horvath 2010). 

Methodological Framework in Greater Detail

The general framework for LCA is defined in the ISO 14040 series, with the most prominent one 

the ISO 14044 standard that defines the general requirements and guidelines (ISO 2006a). The 

standard provides a framework that encourages transparency and some consistency in 

approaches and reporting. However, because the ISO standard applies to LCAs for all products 

and systems, it does not prescribe an approach tailored to specific categories of analysis, such as 

for an LCA of pavements. Still, even though there is no generally accepted LCA framework for 

pavements, there are some important developments that should be noted. For example, a basic 

framework for pavement LCA was developed in 2010 that builds on the ISO guidelines and 

provides pavement-specific methodological guidelines (UCPRC 2010).

The European industry is organized in a technical working group that is defining pavement 

specific guidelines under the Construction Products Directive. It details the LCA process for 

products, buildings, and construction works. The CEN 15804 lays down a structure for product 

LCA and Environmental Product Declarations (CEN 2012). The focus of the CEN/TC 350/WG 

6 is to develop a framework for Civil Engineering Works, and it is estimated that a standard will 

be developed by 2016. 

ISO 14044 includes an important section that is meant to ensure that LCAs are methodologically 

sound and adhere to accepted practices. In section 6, rules and requirements are laid down for 

critical review, especially when comparisons are made with the aim of external publication. 

Depending on the goal and scope of the LCA, a critical review by an independent LCA expert is 

sufficient. For competitive LCAs, a critical review panel (consisting of at least three members, 

one of which needs to be an LCA expert and two that need to be independent industry experts) 

needs to be instituted. 

Although reviews are currently not common practice in pavement LCA, except when published 

as peer-reviewed articles, some recent studies have incorporated a review component. It is 

recommended that future work incorporate a critical review process and greater stakeholder 

involvement, which should lead to increased standardization and enhanced LCA practices. 

What Lies Ahead: Environmental Product Declarations

An EPD, as defined in the ISO 14025 standard (ISO 2006c), is a declared LCA for a product and 

is a form of certification. If all products had an EPD, a pavement LCA using those products 

would benefit tremendously in terms of quality and lower cost. EPDs can be issued on a specific 

product from a specific producer, but may also be issued for a generic product from a group of 

manufacturers (such as an association). Figure 10-5 shows a sample EPD for a concrete mix 

design. 

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Figure 10-5. Sample EPD for a concrete mix design (courtesy of 

Central Concrete Supply Company). 

The basis for an EPD is a Product Category Rule (PCR) document generated through a 

stakeholder procedure and including rules for specific product categories. Two recent examples 

of industry involvement in this area are: 1) the Product Category Rules Task Group produced a 

draft PCR for portland and blended cements in 2012 and is close to releasing a publication, and, 

2) the National Ready Mixed Concrete Association (NRMCA) is certifying EPDs for cement 

(Carbon Leadership Forum 2010) and concrete (Carbon Leadership Forum 2013) as a program 

operator. In addition, the National Asphalt Pavement Association (NAPA) has formed a task 

group to develop PCRs and EPDs for the asphalt 

pavement industry. 

An Example of an Important Methodological 

Element: Allocation

There are several important methodological elements to 

an LCA, but one that is keeping the LCA community 

engaged is the aspect of allocation. This topic is not 

limited to just pavement LCA, but is relevant to all LCA 

studies. This section is included to highlight some of the 

ongoing discussions that are relevant to pavement LCA. 

All elements of the pavement life cycle are germane to 

allocation, but this discussion on allocation is focused on 

material sources that are discussed in chapter 3 and on 

material recycling performed at the end of the life of the 

pavement that are discussed in chapter 8. Those chapters 

include several callout boxes that relate to allocation, and 

this section aims to tie it together.

Whenever a system of production yields multiple 

products or services, the environmental inputs and 

Product Category Rules

• The Product Category Rule (PCR)

document defines the rules for a 

product LCA, is industry accepted, 

and defines the Environmental 

Product Declaration (EPD) format. 

It is owned by a Program 

Operator.

• The LCA can be drafted against 

the PCR document. 

• The EPD follows the PCR 

requirements and uses the results 

from the LCA. 

• An independent third party 

performs a verification of the LCA 

and EPD against the PCR after 

which the Program Operator 

issues the EPD.

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outputs of the system have to be assigned to each product and service, referred to as co-products. 

The ISO 14040 standards for LCA prescribe a hierarchical preference for how to assign, or 

allocate, environmental flows that occur in the modeling of the LCA. These allocations must be 

assigned whenever a production system boundary is crossed. For example, when one pavement 

life cycle ends and another begins, allocation must be utilized when assigning environmental 

impact to the material that is recycled from the pavement.

A general consensus among LCA practitioners and those involved in evaluating products and 

systems is that allocation rules should be set up to:

• Incentivize practices that reduce environmental impact. 

• Prevent double counting of credits or the omission of important items.

• Provide fairness between industries by reflecting as closely as possible what is actually 

happening. 

• Be transparent so that all parties can understand how allocation is applied and how it 

influences the results. 

In addition, ISO standards, such as ISO 14044 for LCA, require sensitivity analysis to evaluate 

the impact of allocation rules to determine how they might change the final results of the 

assessment. According to ISO standards, the preference for treating co-products is to first try to 

avoid allocation by either 1) subdividing the production system into processes that can be 

assigned wholly to a single co-product, or 2) expanding the scope of interest to include the 

processes that seem to need allocation, thereby removing the need for allocation (this is referred 

to as system expansion). System expansion is more or less equivalent to displacement or 

substitution, where co-products are modeled as if they are displacing equivalent products in the 

marketplace. Thus, the system of production is credited with avoiding the need for producing 

these equivalent products. This approach is often used in consequential LCA approaches, as 

described earlier. 

In most pavement LCA studies, the boundaries for the system of production are crossed (and 

thus allocation is necessary) in three situations:

1. Multi-output situations like manufacturing processes with co-products (e.g., oil refineries). 

2. Reuse of components and recycling of materials after initial use, such as steel rebar, 

reclaimed asphalt pavement, coal combustion co-products from power generation, or use 

of discarded tires in asphalt binder. 

3. Multi-input situations like waste treatment processes, such as incineration and landfilling. 

All three situations are described below with examples of some actual processes and materials in 

pavement LCA. 

Manufacturing Processes with Co-Products

The preferred way to deal with assigning impacts to multi-outputs is to reflect the physical 

properties of the outgoing flows, such as mass or energy content. If a relationship can be 

established that is more suitable than mass, it should be used. This means that the physical basis 

for allocation can be different in different situations and for different materials. The economic 

value of co-products can also be used for allocation; however, Bernard, Blomberg, and Southern 

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(2012) suggest that allocation based on physicochemical properties (e.g., mass or energy content) 

is preferred to economic allocation. With that being said, Ayer et al. (2007), Basset-Mens and 

van der Werf (2005), and Guinee et al. (2002), among others, have stated a preference for 

economic allocation above other approaches, largely because economic value is typically the 

primary driver of business. 

Allocation requires a somewhat arbitrary partitioning of the co-producing processes without 

considering the interactions between subprocesses; thus, an objective justification is warranted 

between the chosen allocation parameter, such as mass or economic value, and the share of 

environmental loads (Weidema 2001). This makes co-product allocation sometimes contentious. 

Good LCA practice in this case requires justification of the grounds for allocation, transparency 

in reporting, showing the impact of allocation choices on the results, and performing sensitivity 

analyses to assess the significance of the allocation choice on the overall LCA conclusions. 

Some examples are provided in chapter 3 for specific materials (e.g., asphalt as a co-product 

from the petroleum refinery). An example of an economic allocation for a multi-output process 

is show in figure 10-6. 

Figure 10-6. Example of economic allocation for a multi-output process. 

Reuse of Components and Recycling of Materials after Initial Use 

When using a material from another product, pavement or system, several approaches for 

allocation have been and are being tried to ensure that the “benefits” of using secondary 

materials or fuel resources are properly reflected in an LCA. 

Most EPD approaches use a strict and conservative approach: all processes and transportation 

needed to reuse or recycle the material are assigned to the product utilizing the recycled content, 

but the production of the original product is assigned to the first product’s life cycle. The same 

is true of reused or recycled materials that are used in pavement projects, such as the secondary 

content in steel, recycled aggregate from building waste, rubberized asphalt binder containing 

recycled tires, recovered binder from asphalt shingles, and SCMs derived from other industrial 

processes. Furthermore, materials that become available for reuse or recycling at the end of the 

pavement life cycle, such as RAP, RCA, and reinforcing steel, are also allocated in this manner. 

An important element in this discussion is whether a material is defined as a waste or a product. 

If an economic approach is used to define a resource as a waste or a co-product, the following 

reasoning can be used: 

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• Where a waste flow material has value, it is considered a co-product and needs to have 

“production” processes allocated to it for the life cycle that is using the material. In 

essence, as soon as a waste flow has positive economic value, it is considered a coproduct and should be treated as such. 

• Where a waste flow material has a negative cost but becomes an economically valuable 

product through processing, the impact of processing and handling is allocated based on 

the difference between the cost (assigned to the producing life cycle where the waste 

occurred) and the positive value (assigned to the receiving life cycle where the coproduct is used). An example of this is concrete waste that requires an acceptance fee at 

a crushing facility where it is processed (crushed and sized), and then sold back to the 

market at a price. 

• Where the waste remains a cost regardless of processing, all environmental burdens of 

the processes are assigned to the producing life cycle; in this case, it essentially stays a 

waste and never becomes a co-product. The life cycle that uses materials like this are 

essentially part of the waste treatment process and receive the material “for free.” 

Other approaches assign a “value” to the recycled materials and include credits for preventing 

the need for new primary materials for the new application. This is referred to as substitution, 

and must be considered cautiously and aligned with the approach for the receiving product 

system. Double counting of credits should be prevented. 

One variation of assigning credits for recycling is the modeling of multiple life cycles to reflect 

repeated recycling benefits. This approach is typically used to assign future recycling credits to the 

current product. There are examples reported where an infinite number of life cycles are modeled 

to show the benefits of recycling, which can extend time periods that are irrelevant on a human 

scale. This is not considered good LCA practice, particularly given that modeling a pavement over 

a period in the range of 50 to 75 years is methodologically challenging enough as it is. 

Waste Treatment Processes

The preferred way to deal with assigning impacts to multi-input processes is to reflect the 

physical properties of the incoming flows. If a relationship can be established that is more 

suitable than mass, it should be used. An example is the relation between the chemical 

composition of a waste that is available for landfill and the associated emissions to air and water 

from the landfill. However, this is not very relevant for most pavement LCA materials since 

most of them are inert. Another example is the relation between the chemical composition of a 

waste that is available for incineration and the associated emissions to air and energy recovery as 

heat or electricity. Both situations occur in pavement LCA but are not very relevant to the 

outcome of most pavement LCA materials since most of them are inert or have little or no 

economic value as a combustion energy source.

Final Thoughts

Allocation is clearly a complex and contentious issue, and of particular importance to those 

conducting pavement LCAs given their wide range of processes and the significant amount of 

recycling that occurs. While it is expected that allocation will remain an ongoing topic of debate, 

it is recommended that the key goals for allocation should be to incentivize practices that reduce 

environmental impact, prevent double counting and omission of key inputs/outputs, provide 

fairness between industries, and be transparent about the procedure utilized.

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Sustainability Rating Systems

Transportation and associated industries offer a range of guidance on the sustainability of 

transportation infrastructure. This guidance ranges from generally advocated strategic directions, 

to more comprehensive guide documents, to rating systems that call out specific practices. Each 

level of guidance has value; the choice on which to use depends upon the goals and requirements 

of the governing agency or organization. 

Background

A sustainability rating system is essentially a list of sustainability best practices with an 

associated common metric. This metric, usually points, quantifies each best practice in a 

common unit. In this way the diverse measurement units of sustainability best practices (e.g., 

pollutant loading in stormwater runoff, pavement design life, tons of recycled materials, energy 

consumed/saved, pedestrian accessibility, ecosystem connectivity, and even the value of art) can 

all be compared. In its simplest form, a rating system can count every best practice equally (e.g., 

all worth one point), in which case the rating system amounts to a tally of the number of best 

practices used. In more complex forms, rating systems weight best practices (usually in relation 

to their impact on sustainability or priority), which can assist in choosing the most impactful best 

practices to use given a limited scope or budget. 

Currently there are a number of national and international rating system efforts within the 

transportation community. These systems vary in scope and complexity but are generally 

designed to provide guidance, scoring, and potential rewards for the use of sustainability best 

practices. Rating systems usually concentrate on practices that are compatible with current 

regulations but are above and beyond existing minimum regulatory requirements. Rating 

systems are particularly appealing because they: 

• Provide a common metric (points) for the entire range of sustainable solutions. 

• Measure sustainability and thus make it manageable. 

• Allow for straightforward communication of sustainability goals, efforts, and 

achievement.

• Provide a reasonable context within which designers, contractors, and material suppliers 

can be innovative in their solutions. 

While there has been and continues to be much debate over the scientific merit and basis for 

rating systems, such debate can miss the point. The essential purpose of most sustainability 

rating systems is not a scientifically defensible taxonomy of sustainability, but rather a tool to (1) 

encourage sustainability practices beyond the regulatory minimum, and (2) to communicate 

sustainability in a comprehensible manner. In particular, rating systems provide an 

understandable way to communicate sustainability whether it is within an agency or project, to 

design and construction professionals, or to the general public. Furthermore, rating systems are 

often turned to when other means of quantification (e.g., LCA) fail to capture the full range of 

sustainability best practice impacts. For instance, while LCA is capable of accounting for GHG 

emissions associated with pavement construction, it is not able to capture more abstract, yet 

important, sustainability features such as ecological connectivity and aesthetics. 

Rating systems are often criticized because (1) they tend to sacrifice detail for simplicity, (2) it is 

difficult to generate consensus on which items to include/exclude, (3) they do not capture the 

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

entire scope of sustainable solutions, and (4) their use in blindly pursuing points as part of a

rating system could trump good design/construction. However, a well-designed rating system 

used within a proper organizational approach to sustainability can overcome these issues and 

provide value to the agency or organization. 

Rating Systems in Context

It is important to view a rating system in the right context. For instance, project-based rating 

systems address sustainability within the context of an individual project. Therefore, they should 

be considered specialized tools that fit within a broader agency approach to sustainability but do 

not address all agency sustainability efforts. In this context, the adoption or use of a rating 

system does not supply sustainability but rather complements other agency-wide efforts. 

Potential Industry Impacts of Rating Systems

Beyond a single agency, well-designed and marketed rating systems can have broad-reaching 

sustainability impacts within an industry. For instance, the U.S. Green Building Council’s 

(USGBC) Leadership in Energy and Environmental Design (LEED®) rating system addressing 

building sustainability (often termed “green buildings”) has been in use since 1998 and is by far 

the most popular sustainability rating system worldwide. It can be argued that LEED has 

allowed sustainable infrastructure to gain a commercial foothold in the building industry because 

of its success. For instance, as of April 2013 there were 16,611 LEED certified projects, 39,712 

LEED registered projects, and the annual USGBC conference, GreenBuild®, attracts over 

30,000 attendees and 1,000 exhibitors (USGBC 2013). Growth of the green building industry is 

evidenced by Engineering News-Record’s (ENR’s) annual survey of green contractors, most of 

which are working on projects pursuing LEED certification. In September 2013, ENR’ s 

identified “Top 100 Green Contractors” in the U.S. received $42.75 billion in contracting 

revenue from green projects in 2012, which represented 34.4 percent of their total revenue 

(Tulacz 2013). They also identified 13,019 accredited staff in those 100 companies. While one 

might still argue the details of LEED rating systems, the number of certifications, registrations,

and conference attendees makes a strong case for the overwhelming success of the 

communication aspect of the USGBC’s suite of rating systems. 

Rating Systems Relevant to Pavements

While there are many rating system efforts that apply in some way to pavements worldwide, the 

following sections briefly outline those systems that are (1) the most prevalent on the national 

stage in the U.S., and (2) most relevant to pavements. Note that although all of these rating 

systems are relevant to pavements in some way, none of them are focused on pavements as the 

primary system under consideration. All focus on larger systems (e.g., road project, agency 

sustainability efforts, neighborhood design, infrastructure systems) and account for pavement as 

a contributing subsystem. Therefore, none of them should be used to rate or grade pavement 

sustainability in isolation because pavement tends to exist as a subsystem that contributes to 

larger systems (e.g., neighborhood, highway corridor, downtown street network, community, 

ecology). 

The following sections provide overviews of several sustainability rating systems that are 

reasonably well developed and are being used at the national level (either actively rating projects 

or engaged in a pilot phase). 

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

INVEST (Infrastructure Voluntary Evaluation Sustainability Tool)

INVEST (FHWA 2011; Bevan et al. 2012) is a sustainability rating system for roadways that 

encompasses planning and policy, project development, and operations and maintenance. It is

point based and voluntary and applicable to all U.S. road projects with a focus on state 

Departments of Transportation (DOTs) and Metropolitan Planning Organizations (MPOs). A 

summary of its characteristics is provided below. 

• Owner: FHWA. 

• Scope: Transportation system and project planning, design, construction, operations and 

maintenance. 

• Status: (as of April 2013): Version 1.0 is available at www.sustainablehighways.org. 

• Background: INVEST was created by the FHWA as a self-evaluation tool. There are 

no plans to make it required in any context. INVEST has three different subsystems that 

can be used independently: Systems Planning, Project Development, and Operations and 

Maintenance. INVEST is intended to function as a self-certification program (i.e., the 

project owner can also perform the review).

• Relevance to pavements: Systems Planning: no criteria are directly relevant to pavement 

sustainability concepts discussed in this document. Project Development: 14 criteria (48 

percent of the available points) are directly relevant to pavement sustainability concepts 

discussed in this document. Operations and Maintenance: 5 criteria (36 percent of the 

available points) are directly relevant to pavement sustainability concepts discussed in 

this document. 

Greenroads® 

Greenroads (Muench et al. 2011) is a sustainability rating system for roadway design and 

construction. It is point based and voluntary and applicable to all U.S. road projects. Relevant 

characteristics are given below.

• Owner: Greenroads Foundation (501 c3 non-profit organization). 

• Scope: Roadway design and construction. Does not directly address planning or 

operations and maintenance, although a number of credits influence those items. 

• Status: (as of April 2013): Version 1.5 is available to review projects 

at http://www.greenroads.org/. Six projects certified and 23 projects registered 

representing about $2.8 billion of construction value. 

• Background: Greenroads was originally created by the University of Washington and 

CH2M HILL in partnership, now independently owned and operated by the Greenroads 

Foundation, and also includes an individual accreditation program. Greenroads is a thirdparty certification program (i.e., the Greenroads Foundation functions as an independent 

third party review). 

• Relevance to pavements: 7 of 11 Project Requirements (64 percent) and 19 Voluntary 

Credits (49 percent of the available points) are directly relevant to pavement 

sustainability concepts discussed in this document. 

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

EnvisionTM 

Envision (ISI and Zofnass 2012) is a sustainability rating system for civil infrastructure. It is 

point based, voluntary, and applicable to all civil infrastructure. Important characteristics are 

listed below. 

• Owner: A joint collaboration between the Zofnass Program for Sustainable Infrastructure 

at the Harvard University Graduate School of Design and the Institute for Sustainable 

Infrastructure (ISI), a joint venture of the ASCE, American Council of Engineering 

Companies (ACEC), and the American Public Works Association (APWA). 

• Scope: All civil infrastructure (including roads). 

• Status: (as of February 2014): Version 2.0 manual is available to review projects at 

http://www.sustainableinfrastructure.org/. 

• Background: EnvisionTM has some features in common with CEEQUAL (a U.K.-based 

system). Also includes individual training and accreditation. 

• Relevance to pavements: 17 credits (31 percent of the available points) are directly 

relevant to pavement sustainability concepts discussed in this document. 

GreenLITES

GreenLITES (Leadership In Transportation and Environmental Sustainability) is a rating 

program for transportation infrastructure (NYSDOT 2010). It has the following key 

characteristics:

• Owner: NYSDOT. 

• Scope: NYSDOT project design and operations. There are two manuals, one for Project 

Design certification and one for Operations certification. 

• Status: (as of April 2013): Version 2.1.0 (April 2010) for the Project Design Certification 

Program, and a draft version for the Operations Certification Program are available.

• Background: The Project Design Certification Program is used as a design review for 

NYSDOT projects (NYSDOT 2012). The Operations Certification Program began 

piloting in 2009. Both are self-certification programs meaning the NSYDOT does the 

project work and the certification review.

• Relevance to pavements: 16 credits (10 percent of the available points) are directly 

relevant to pavement sustainability concepts discussed in this document. 

Leadership in Energy and Environmental Design (LEED®)

LEED is a series of rating systems (nine currently) focused on buildings. Characteristics of the 

system are provided below. 

• Owner: USGBC (501 c3 non-profit organization).

• Scope: Buildings, neighborhoods (there are nine separate rating systems). 

• Status: (as of April 2013): Fully deployed as LEED 2009 (this equates to Version 3) at 

http://www.usgbc.org/. Over 16,000 projects certified worldwide and 40,000 projects 

registered (USGBC 2013). The next full version, LEED v4, was launched in 2013. 

10-23
Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

• Background: LEED has been in existence since 1998. Claims over 12,000 member 

organizations, more than 160,000 accredited professionals and 491 government 

organizations with LEED legislation, executive orders, resolutions, ordinances, policies 

and incentives (USGBC 2012).

• Relevance to pavements: For LEED ND (LEED for Neighborhood Development) 

(USGBC 2012), 4 credits (6 percent of the available points) are directly relevant to 

pavement sustainability concepts discussed in this document. All 9 LEED rating systems 

are focused on buildings; only a small portion of each LEED rating system is relevant to 

pavements. Typically, this relevance is limited to credit for recycled content, high albedo 

surfaces, and porous pavement. 

Tables 10-2 through 10-6 show more detail about how INVEST version 1.0, Greenroads version 

1.5, GreenLITES Project Design version 2.1.0, Envision version 2.0, and LEED ND 2009, 

respectively, address and relate to the pavement sustainability concepts described in this 

reference document. 

Table 10-2. Summary of INVEST sustainability criteria and scoring (FHWA 2011).

Criterion

SYSTEM PLANNING CRITERIA

Title

Points

Possible

Pavement

Related

SP-1 Integrated Planning: Economic Development and Land Use 15

SP-2 Integrated Planning: Natural Environment 15

SP-3 Integrated Planning: Social 15

SP-4 Integrated Planning: Bonus 10

SP-5 Access and Affordability 15

SP-6 Safety Planning 15

SP-7 Multimodal Transportation and Public Health 15

SP-8 Freight and Goods Movement 15

SP-9 Travel Demand Management 15

SP-10 Air Quality 15

SP-11 Energy and Fuels 15

SP-12 Financial Sustainability 15

SP-13 Analysis Methods 15

SP-14 Transportation Systems Management and Operations 15

SP-15 Linking Asset Management and Planning 15

SP-16 Infrastructure Resiliency 15

SP-17 Linking Planning and NEPA 15

Total Points 250 0

Percentage of points directly relevant to pavement 0%

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

Table 10-2. Summary of INVEST sustainability criteria and scoring (FHWA 2011) (continued). 

Criterion

PROJECT DEVELOPMENT CRITERIA

Title

Points

Possible

Pavement

Related

PD-1 Economic Analysis 5

PD-2 Lifecycle Cost Analysis 3 

PD-3 Context Sensitive Project Development 5

PD-4 Highway and Traffic Safety 10 

PD-5 Educational Outreach 2

PD-6 Tracking Environmental Commitments 5 

PD-7 Habitat Restoration 3

PD-8 Stormwater 9

PD-9 Ecological Connectivity 3

PD-10 Pedestrian Access 2

PD-11 Bicycle Access 2

PD-12 Transit and HOV Access 5

PD-13 Freight Mobility 7

PD-14 ITS for System Operations 5

PD-15 Historical, Archaeological, and Cultural Preservation 3

PD-16 Scenic, Natural, or Recreational Qualities 3

PD-17 Energy Efficiency 8

PD-18 Site Vegetation 3

PD-19 Reduce and Reuse Materials 8 

PD-20 Recycle Materials 8 

PD-21 Earthwork Balance 3

PD-22 Long-Life Pavement Design 5 

PD-23 Reduced Energy and Emissions in Pavement Materials 3 

PD-24 Contractor Warranty 3 

PD-25 Construction Environmental Training 1 

PD-26 Construction Equipment Emission Reduction 2 

PD-27 Construction Noise Mitigation 2 

PD-28 Construction Quality Assurance Plan 5 

PD-29 Construction Waste Management 3 

Total Points 126 58

Percentage of points directly relevant to pavement 46%

Criterion

OPERATIONS AND MAINTENANCE CRITERIA

Title

Points

Possible

Pavement

Related

OM-1 Internal Sustainability Plan 15

OM-2 Electrical Energy Efficiency and Use 15

OM-3 Vehicle Fuel Efficiency and Use 15

OM-4 Reuse and Recycle 15 

OM-5 Safety Management 15

OM-6 Environmental Commitments Tracking System 15

OM-7 Pavement Management System 15 

OM-8 Bridge Management System 15

OM-9 Maintenance Management System 15 

OM-10 Highway Infrastructure Preservation and Maintenance 15 

OM-11 Traffic Control Infrastructure Maintenance 15

OM-12 Road Weather Management Program 15

OM-13 Transportation Management and Operations 15

OM-14 Work Zone Traffic Control 15 

Total Points 210 75

Percentage of points directly relevant to pavement 36%

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

Table 10-3. Summary of Greenroads credit categories and scoring (Muench et al. 2011). 

Credit Title Points

Possible

Pavement

Related

Project Requirements

PR-1 Environmental Review Process NA

PR-2 Lifecycle Cost Analysis NA 

PR-3 Lifecycle Inventory NA 

PR-4 Quality Assurance Plan NA 

PR-5 Noise Mitigation Plan NA 

PR-6 Waste Management Plan NA 

PR-7 Pollution Prevention Plan NA

PR-8 Low-Impact Development NA 

PR-9 Pavement Management System NA 

PR-10 Site Maintenance Plan NA

PR-11 Educational Outreach NA

Environment and Water

EW-1 Environmental Management System 2 

EW-2 Runoff Flow Control 3

EW-3 Runoff Quality 3

EW-4 Stormwater Cost Analysis 1

EW-5 Site Vegetation 3

EW-6 Habitat Restoration 3

EW-7 Ecological Connectivity 3

EW-8 Light Pollution 3

Access and Equity

AE-1 Safety Audit 2

AE-2 Intelligent Transportation Systems 5

AE-3 Context Sensitive Solutions 5

AE-4 Traffic Emissions Reduction 5

AE-5 Pedestrian Access 2

AE-6 Bicycle Access 2

AE-7 Transit & HOV Access 5

AE-8 Scenic Views 2

AE-9 Cultural Outreach 2

Construction Activities

CA-1 Quality Management System 2 

CA-2 Environmental Training 1 

CA-3 Site Recycling Plan 1 

CA-4 Fossil Fuel Reduction 2 

CA-5 Equipment Emission Reduction 2 

CA-6 Paving Emission Reduction 1 

CA-7 Water Use Tracking 2 

CA-8 Contractor Warranty 3 

Materials and Resources

MR-1 Lifecycle Assessment 2 

MR-2 Pavement Reuse 5 

MR-3 Earthwork Balance 1

MR-4 Recycled Materials 5 

MR-5 Regional Materials 5 

MR-6 Energy Efficiency 5

Pavement Technologies

PT-1 Long-Life Pavement 5 

PT-2 Permeable Pavement 3 

PT-3 Warm-Mix Asphalt 3 

PT-4 Cool Pavement 5 

PT-5 Quiet Pavement 3 

PT-6 Pavement Performance Tracking 1 

Total Points 108 53

Percentage of points directly relevant to pavement 49%

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

Table 10-4. Summary of ENVISION sustainability criteria and scoring (ISI and Zofnass 2012). 

Credit Title Points

Possible

Pavement

Related

Quality of Life

QL1.1 Improve Community Quality of Life 25

QL1.2 Stimulate Sustainable Growth and Development 16

QL1.3 Develop Local Skills and Capabilities 15 

QL2.1 Enhance Public Health and Safety 16 

QL2.2 Minimize Noise and Vibration 11 

QL2.3 Minimize Light Pollution 11

QL2.4 Improve Community Mobility and Access 14

QL2.5 Encourage Alternative Modes of Transportation 15

QL2.6 Improve Accessibility, Safety and Wayfinding 15

QL3.1 Preserve Historic and Cultural Resources 16

QL3.2 Preserve Views and Local Character 14

QL3.3 Enhance Public Space 13

Leadership

LD1.1 Provide Effective Leadership And Commitment 17

LD1.2 Establish A Sustainability Management System 14

LD1.3 Foster Collaboration And Teamwork 15

LD1.4 Provide for Stakeholder Involvement 14

LD2.1 Pursue By-Product Synergy Opportunities 15 

LD2.2 Improve Infrastructure Integration 16 

LD3.1 Plan for Long-Term Monitoring and Maintenance 10 

LD3.2 Address Conflicting Regulations and Policies 8

LD3.3 Extend Useful Life 12 

Resource Allocation

RA1.1 Reduce Net Embodied Energy 18 

RA1.2 Support Sustainable Procurement Practices 9

RA1.3 Use Recycled Materials 14 

RA1.4 Use Regional Materials 10 

RA1.5 Divert Waste from Landfills 11 

RA1.6 Reduce Excavated Materials Taken Off Site 6

RA1.7 Provide for Deconstruction and Recycling 12 

RA2.1 Reduce Energy Consumption 18

RA2.2 Use Renewable Energy 20

RA2.3 Commission and Monitor Energy Systems 11

RA3.1 Protect Fresh Water Availability 21

RA3.2 Reduce Potable Water Consumption 21

RA3.3 Monitor Water Systems 11

Natural World

NW1.1 Preserve Prime Habitat 18

NW1.2 Preserve Wetlands and Surface Water 18

NW1.3 Preserve Prime Farmland 15

NW1.4 Avoid Adverse Geology 5

NW1.5 Preserve Floodplain Functions 14

NW1.6 Avoid Unsuitable Development on Steep Slopes 6

NW1.7 Preserve Greenfields 23

NW2.1 Manage Stormwater 21 

NW2.2 Reduce Pesticides and Fertilizer Impacts 9

NW2.3 Prevent Surface and Groundwater Contamination 18

NW3.1 Preserve Species Biodiversity 16

NW3.2 Control Invasive Species 11

NW3.3 Restore Disturbed Soils 10

NW3.4 Maintain Wetland and Surface Water Functions 19

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

Table 10-4. Summary of ENVISION sustainability criteria and scoring (ISI and Zofnass 2012) 

(continued). 

Credit Title Points

Possible

Pavement

Related

Climate and Risk

CR1.1 Reduce Greenhouse Gas Emissions 25 

CR1.2 Reduce Air Pollutant Emissions 15 

CR2.1 Assess Climate Threat 15

CR2.2 Avoid Traps and Vulnerabilities 20

CR2.3 Prepare for Long-Term Adaptability 20 

CR2.4 Prepare for Short-Term Hazards 21

CR2.5 Management Heat Island Effects 6 

Total Points 809 247

Percentage of points directly relevant to pavement 31%

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

Table 10-5. Summary of GreenLITES sustainability criteria and scoring (NYSDOT 2010).

Credit Title Points

Possible

Pavement

Related

Alignment Selection

S-1a Avoidance of previously undeveloped lands (open spaces or “greenfields”) 2

S-1b Selecting an alignment that establishes a minimum 100-ft (30.5-m) buffer zone 2

S-1c Alignments which minimize overall construction “footprint” 2

S-1d Design vertical alignments which minimize total earthwork 1

S-1e Adjust alignment to avoid or minimize impacts to social/environmental 1

S-1f Alignments that optimize benefits among competing constraints 1

S-1g Micro-adjustments that do not compromise safety or operation 1

S-1h Clear zones seeded with seed mixtures that help to reduce maintenance 1

S-1i Provide a depressed roadway alignment 1

S-1j Use of launched soil nails as a more cost effective option to stabilize a slope 1

Context Sensitive Solutions

S-2a Adjust or incorporate highway features to respond to the unique character 2

S-2b Incorporate local or natural materials for substantial visual elements 2

S-2c Visual enhancements (screening objectionable views) 2

S-2d Period street furniture/lighting/appurtenances. 1

S-2e Inclusion of visually-contrasting (colored or textured) pedestrian 1

S-2g Incorporates guidance from Section 23 - Aesthetics of the NYS Bridge 1

S-2h Site materials selection & detailing to reduce overall urban “heat island” effect 1

S-2i Permanently protect viewsheds via environmental or conservation easements 1

S-2j Color anodizing of aluminum elements (ITS cabinets, non-decorative light 1

S-2k Decorative bridge fencing (in lieu of standard chain link). 1

S-2l Use of concrete form liners (for bridge approach barriers, parapet walls, etc.) 1

S-2m Imprinted concrete/asphalt mow strips, gores or snow storage areas 1 

Land Use/Community Planning

S-3a Use of more engaging public participation techniques (e.g., charette, task force) 2

S-3b Enhanced outreach efforts (e.g., newsletters, project-specific Web page 2

S-3c Projects better enabling use of public transit (e.g., bus shelters, 'Park &Ride') 2

S-3d Projects applying “Walkable Communities” or “Complete Streets” 2

S-3e Projects that increase transportation efficiencies for moving freight 2

S-3f Project-specific formal agreement with public or private entities 2

S-3g Project is consistent with local and regional plans 2

S-3h Project reports and community outreach materials available online 1

S-3j Establishment of a new recreational access facility (e.g., trailhead parking) 2

S-3k Establishment of a new recreational facility (pocket park, roadside overlook) 2

S-3l Enhancement of an existing recreational facility 1

Protect, Enhance or Restore Wildlife Habitat

S-4a Mitigation of habitat fragmentation 3

S-4b Providing for enhancements to existing wildlife habitat (e.g., bird/bat houses) 2

S-4c Partial mitigation of habitat fragmentation through techniques 2

S-4d Use of natural-bottomed culverts 2

S-4e Wildlife crossings that are structures that allow for safe passage of wildlife 2

S-4f Wetland restoration, enhancement, or establishment 2

S-4g Minimize use of lands that are part of a significant contiguous wildlife habitat 1

S-4h Use of wildlife mortality reduction measures 1

S-4k Stream restoration/enhancement 1

S-4l Installation of mowing markers to protect natural areas and wetlands 1

S-4m Inclusion of scheduling and logistic requirements to avoid disrupting wildlife 1

S-4n Permanently protects the new or expanded habitat 1

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

Table 10-5. Summary of GreenLITES sustainability criteria and scoring 

(NYSDOT 2010) (continued). 

Credit Title Points

Possible

Pavement

Related

Protect, Plant or Mitigate for Removal of Trees & Plant Communities

S-5a Avoidance/protection of established trees/veg communities 2

S-5b Designs that demonstrate a net increase in tree canopy 2

S-5c Re-establishment or expansion of native vegetation into reclaimed work areas 2

S-5d Use of trees, large shrubs or other suitable vegetation as living snow fences 2

S-5e Use of native species for seed mixtures and other plantings 1

S-5f Avoidance/protection of individual significant trees/desired vegetation 1

S-5g Designs that demonstrate no net loss of tree canopy or mitigation 1

S-5h Planting trees, shrubs or plant material in lieu of traditional turf grass 1

S-5i Removal of undesirable plant species 1

S-5j Preserving, replacing, or enhancing vegetation associated with historic property 1

W-1 Stormwater Management (Volume & Quality)

W-1a Improve water quality or nearby habitat 2

W-1b Detecting and eliminating any non-stormwater discharges 2

W-1c Demonstrate a reduction of pollutant loadings to adjacent water sources 2

W-1d Reduction in overall impervious area 2

W-1f Requirements for staged construction to minimize bare soil exposure 1

W-1g Detecting/documenting non-stormwater discharges from unpermitted sources 1

W-2 Best Management Practices (BMPs)

W-2a Design features that make use of highly permeable soils 2

W-2b Use of other structural BMPs (e.g., wet or dry swales, sand filters, filter bags) 2

W-2c Inclusion of “permeable pavement” such as grid pavers where practical 2 

W-2d Minimize the project's overall impervious surface area increase 1

W-2e Include grass channels, where appropriate 1

W-2f Designate qualified environmental construction monitor to provide oversight 2

M-1 Reuse of Materials

M-1a Specify that 75 percent or more of topsoil removed for grading is reused on site 2

M-1b Design the project so that “cut-and-fills” are balanced to within 10 percent 2

M-1c Reuse of excess fill (“spoil”) within the project corridor 2

M-1d Specify rubblizing or crack and seating of portland cement concrete 2 

M-1e Reuse of previous pavement as subbase during full-depth reconstruction 2 

M-1f Arranging for the reuse of excavated material, asphalt millings, old concrete 2 

M-1g Specify the processing of demolished concrete to reclaim scrap metals 2 

M-1h Salvaging removed trees for lumber or similar uses 2

M-1i Use surplus excavated material on nearby state highways for slope flattening 2

M-1j Use surplus excavated material, demolished concrete, or millings at nearby 

abandoned quarry

2 

M-1k Specify that 50 percent or more of topsoil removed for grading is reused on site 1

M-1l Design the project so that cut and fills are balanced to within 25 percent 1

M-1m Reuse (i.e., remove and reset versus remove and replace) of granite curbing 1

M-1n Reuse of elements of the previous structure (stone veneer, decorative railing) 1

M-1o Designing an on-site location for chipped wood waste disposal 1

M-1p Specifying the recycling of chipped untreated wood waste for use as mulch 1

M-1q Project documents make scrap metals available for reuse or recycling 1

M-1r Identify approved, environmentally acceptable and permitted sites for disposal 1

M-1s Obtain and implement a project specific DEC Beneficial Use Determination for

re-use of otherwise waster material from a location with New York State 1 

M-1t Specify the salvage/moving of houses rather than demo for disposal in landfill 1

M-1u Reuse of major structural elements such as bridge piers, bridge structure, etc. 2

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

Table 10-5. Summary of GreenLITES sustainability criteria and scoring 

(NYSDOT 2010) (continued). 

Credit Title Points

Possible

Pavement

Related

M-2 Recycled Content

M-2a Use tire shreds in embankments 2

M-2b Use recycled plastic extruded lumber or recycled tire rubber 2

M-2c Specify hot-in-place or cold-in-place recycling of hot-mix asphalt pavements 2 

M-2d Specify use of recycled glass in pavements and embankments 2 

M-2e Specify asphalt pavement mixtures containing recycled asphalt pavement 2 

M-2f Specify PCC pavement mixtures containing recycled concrete aggregate 2 

M-2g Use crumb rubber or recycled plastic for noise barrier material 2 

M-2h Use of porous pavement systems in light duty situations (e.g., sidewalks) 2 

M-3 Local Materials

M-3a Specify locally available natural light weight fill 2

M-3b Specify local seed stock and plants 2

M-4 Bio-engineering Techniques

M-4a Project designs that utilize soil bioengineering treatments 2

M-4b Project designs utilizing soil biotechnical engineering treatments 2

M-4c Projects using targeted biological control methods to reduce invasive species 2

M-4d Project designs utilizing soil biotechnical engineering treatments 1

M-4e Project designs that utilize soil bioengineering/soil biotechnical treatments 1

M-5 Hazardous Material Minimization

M-5a Project design substantially minimizes the need to use hazardous materials 2

M-5b Project design specifies less hazardous materials or avoids their generation 2

M-5c Removing and disposing of contaminated soils 2

E-1 Improved Traffic Flow

E-1a Special use lane (HOV/Reversible/Bus Express) 3

E-1b Innovative interchange design or elimination of freeway bottlenecks 3

E-1c Specify new roundabout(s) 3

E-1d Implementation of Traffic Management Center / Traveler Information System 3

E-1e Installation of a closed-loop coordinated signal system 2

E-1f Installation of a transit express system (queue jumper, pre-emptive signals, etc.) 2

E-1g Expansion of a Traffic Management Center / Traveler Information System 2

E-1h Implementation of a corridor-wide access management plan 2

E-1i Limiting/consolidating access points along highway 1

E-1j Improving a coordinated signal system and other signal timing and detection 1

E-1k Adding bus turnouts 1

E-1l Installing higher capacity controllers to improve flow/reduce delay 1

E-1m Infill or preparation for Traffic Management/Traveler Information System 1

E-1n Inclusion of integrated traffic/incident management/traveler information system 1

E-1o Installation of isolated systems to provide for spot warning 1

E-1p Road Diet (reduction in lanes to add turn lane & accommodate bike traffic) 2

E-2 Reduce Electrical Consumption

E-2a Solar/battery powered street lighting or warning signs 2

E-2b Replace overhead sign lighting with higher type retro-reflective sign panels 2

E-2c Use of LED street lighting 2

E-2d Solar bus stops 2

E-2e Use of LED warning signs/flashing beacons 1

E-2e Retrofit existing street/sign lighting with high efficiency types 1

E-3 Reduce Petroleum Consumption

E-3a Provide new Park & Ride lots 3

E-3b Provide new intermodal connections 3

E-3c Increase bicycle amenities at Park & Rides and transit stations 2

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

Table 10-5. Summary of GreenLITES sustainability criteria and scoring 

(NYSDOT 2010) (continued). 

Credit Title Points

Possible

Pavement

Related

E-3e Operational improvements of an existing Park & Ride lot 1

E-3f Improve an existing intermodal connection 1

E-3g Reduce mowing areas outside of the clear zone 1

E-3h Use of warm-mix asphalt 1 

E-3i Documented analysis proving the project design reduced carbon footprint 1 

E-3j Documented analysis proving the work zone requires the least fuel usage 1 

E-3k Improved shading through vegetation at Park & Ride lots to reduce UHI 1

E-4 Improve Bicycle & Pedestrian Facilities

E-4a New grade-separated (bridge or underpass) bike/pedestrian crossing structure 3

E-4b Separate bike lane at intersection 2

E-4c New separated bike path or shoulder widening to provide for on-road bike lane 2

E-4d Create new or extend existing sidewalks 2

E-4e New pedestrian signals 2

E-4f Align roadway and other highway features/structures within ROW for future 

development 2 

E-4g Work with local communities to create parallel bike routes 2

E-4h Sidewalk or bikeway rehabilitation, widening, realignment or repair 1

E-4i Upgrading pedestrian signals 1

E-4j Installation of bikeway signs, "Share the Road" signs, or shared lanes markings 1

E-4k Shoulder restoration for bicycling 1

E-4l Inclusion of five-rail bridge rail system for bicyclists 1

E-4m Installation of permanent bicycle racks 1

E-4n New crosswalks 1

E-4o New curb bulb-outs 1

E-4p New raised medians/pedestrian refuge islands 1

E-4q New speed hump/speed table/raised intersection 1

E-4r New curbing (where none previously existed), to better define the edge of road 1

E-4s New or relocated highway barrier or repeating vertical elements 1

E-4t Installation of bicycle detectors (quadrupoles) at signalized intersections 1

E-4u "All Stop" phase programmed into a traffic signal 1

E-4v Permanent digital "Your Speed is XX" radar speed reader signs 1

E-4w Overhead flashing beacon, lighted "Crosswalk" sign, or pedestrian signal 1

E-4x Advanced warning of crosswalk with signs and yield pavement markings 1

E-4y In street plastic pylon "State Law - Yield to Pedestrians within Crosswalk" sign 1

E-4z Use of durable cast iron detectible warning units embedded in concrete 1

E-4aa Add/replace crosswalks with high visibility cross walks 1

E-5 Noise Abatement

E-5a Construction of a new noise barrier 2

E-5b Incorporate traffic system management techniques to reduce prior noise 2

E-5c Provide a buffer zone for adjacent receptors 2

E-5d Provide sound insulation to public schools 2

E-5e Diamond grinding of existing portland cement concrete (PCC) pavement 1 

E-5f Rehabilitation of an existing noise wall 1

E-5g Berms designed to reduce noise 1

E-5h Provide planting to improve perceived noise impacts 1

E-6 Stray Light Reduction

E-6a Retrofit existing light heads with full cut-offs 2

E-6c Use cut-offs on new light heads 1

Total Points 271 27

Percentage of points directly relevant to pavement 10%

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

Table 10-6. Summary of LEED-ND sustainability criteria and scoring (USGBC 2012; 2013). 

Credit Title Points

Possible

Pavement

Related

Smart Location and Linkage

SLLp1 Smart Location NA

SLLp2 Imperiled Species and Ecological Communities NA

SLLp3 Wetland and Water Body Conservation NA

SLLp4 Agricultural Land Preservation NA

SLLp5 Floodplain Avoidance NA

SLLc1 Preferred Locations 10

SLLc2 Brownfield Development 2

SLLc3 Access to Quality Transit 7

SLLc4 Bicycle Facilities 2

SLLc5 Housing and Jobs Proximity 3

SLLc6 Steep Slope Protection 1

SLLc7 Site Design for Habitat or Wetland and Water Body Conservation 1

SLLc8 Restoration of Habitat or Wetlands and Water Bodies 1

SLLc9 Long-Term Conservation Management of Habitat or Wetlands and Water Bodies 1

Neighborhood Pattern and Design

NPDp1 Walkable Streets NA

NPDp2 Compact Development NA

NPDp3 Connected and Open Community NA

NPDc1 Walkable Streets 9

NPDc2 Compact Development 6

NPDc3 Mixed-Use Neighborhoods 4

NPDc4 Housing Types and Affordability 7

NPDc5 Reduced Parking Footprint 1

NPDc6 Connected Circulation Network 2

NPDc7 Transit Facilities 1

NPDc8 Transportation Demand Management 2

NPDc9 Access to Civic and Public Spaces 1

NPDc10 Access to Recreational Facilities 1

NPDc11 Visitability and Universal Design 1

NPDc12 Community Outreach and Involvement 2

NPDc13 Local Food Production 1

NPDc14 Tree-Lined and Shaded Streetscapes 2

NPDc15 Neighborhood Schools 1

Green Infrastructure and Buildings

GIBp1 Certified Green Building NA

GIBp2 Minimum Building Energy Performance NA

GIBp3 Indoor Water Use Reduction NA

GIBp4 Construction Activity Pollution Prevention NA 

GIBc1 Certified Green Buildings 5

GIBc2 Optimize Building Energy Performance 2

GIBc3 Indoor Water Use Reduction 1

GIBc4 Outdoor Water Use Reduction 2

GIBc5 Building Reuse 1

GIBc6 Historic Resource Preservation and Adaptive Use 2

GIBc7 Minimize Site Disturbance 1

GIBc8 Rainwater Management 4 

GIBc9 Heat Island Reduction 1 

GIBc10 Solar Orientation 1

GIBc11 Renewable Energy Production 3

GIBc12 District Heating and Cooling 2

GIBc13 Infrastructure Energy Efficiency 1

GIBc14 Wastewater Management 2

GIBc15 Recycled and Reused Infrastructure 1 

GIBc16 Solid Waste Management 1

GIBc17 Light Pollution Reduction 1

Total Points 100 6

Percentage of points directly relevant to pavement 6%

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

Use of Assessment Methods

Agencies that use the various assessment methods tend to do so by choice because they 

recognize a benefit in doing so. A general discussion on the use of these different methods is 

presented in the following sections. 

Use Depends on Owner/Agency and Project Priorities

LCCA, LCA, and rating systems can be used alone or in concert to measure sustainability. In 

general, using them in concert provides a more holistic assessment of sustainability since each 

system tends to either (1) address one specific component of sustainability in detail, or (2) 

address all components in less detail. Ultimately, the priorities of the owner/agency and the 

characteristics of the project, as well as the desired outcomes viewed within the context of larger 

systems, should determine what assessment methods are used and what priority is given to each. 

For instance, a desire to implement lowest life-cycle solutions has driven many state DOTs to 

use LCCA in their pavement type selection process for major projects. On the other hand, a 

statewide GHG reduction goal may make it sensible to use LCA as a pavement system metric 

both for accounting and process improvement purposes. Or, a strategic DOT goal to improve or 

communicate sustainability (however the DOT chooses to define it) may make it sensible to use 

a rating system that takes a broad view of sustainability. As a footnote to this, it is worth noting 

that some rating systems require the use of LCCA and LCA within their framework. 

Application at Various Levels

Goals for addressing sustainability can be defined on an agency level, on a pavement system 

level, and on a pavement project level. The types of sustainability performance tools described 

in this chapter can be used and tailored to address these different goals. Figure 10-7 provides a 

schematic of how LCCA, LCA, and rating systems can be applied at these different levels.

Figure 10-7. Assessing sustainabilty with LCCA, LCA, and rating systems on different levels. 

Rating 

System 

Societal Functions

Financial

Environmental

System LCA

System Performance

System LCCA

Societal Functions

Pavement LCA

Pavement 

Pavement LCCA

Societal Functions

Agency goals 

System goals 

Project goals 

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Towards Sustainable Pavement Systems Chapter 10. Assessing Pavement Sustainability

It can be seen in figure 10-7 that rating systems aim to be more comprehensive in terms of topics 

that are covered and they typically include requirements on all levels. It also shows that LCCA 

and LCA can be applied at different levels. Through all of this, it is important to understand that 

the LCCA and LCA applications at the different levels are different types of studies; that is, 

depending on the specific goals and questions to be addressed the right use can be defined. As a 

general rule of thumb, system LCAs tend to be more generic and pavement LCAs tend to be 

more specific.

Level of Standardization

Currently, LCCA is the most mature of the three assessment methods in the pavement industry. 

Guidance from Walls and Smith (1998) has been generally accepted by the industry and 

incorporated into numerous official methods and software, the most prominent of which is 

RealCost. 

LCA has a commonly accepted standard method (delineated by ISO 14040 and 14044); however, 

specifics within this method vary greatly from one application to another. Attempts at 

standardization within the pavement industry are underway (e.g., UCPRC 2010), but it may be 

some time before LCA reaches the same level of standardization that LCCA has in the pavement 

industry. 

Rating systems are relatively new to the pavement industry and are not subject to any standard 

method. The more mature ones that are beginning to be used in practice generally focus on 

transportation infrastructure as a whole rather than just specifically on pavements. These tend to 

address some of the same core pavement sustainability concepts; however, there are differences 

and exclusions that should be investigated. 

Concluding Remarks

Pavement sustainability can be evaluated using several different methods or tools, including 

performance assessment, life-cycle cost analysis, life-cycle assessment, and pavement rating 

systems. This chapter focuses on the latter three items, and describes the basis, inherent 

assumptions, and overall capabilities and limitations of each approach. Specifically:

• LCCA is an analysis technique that uses economic analysis to evaluate the total cost of an 

investment option over its entire life (Walls and Smith 1998). As such, it is principally 

used to address the economic component of sustainability. 

• LCA is a technique that can be used for analyzing and quantifying the environmental 

impacts of a product, system, or process. It focuses on the environmental impacts 

throughout the pavement life cycle (from raw material acquisition to final disposal).

• Sustainability rating systems are essentially a list of sustainability best practices with an 

associated common metric (typically points). Rating systems are one way of quantifying 

the diverse set of sustainability best practices. 

These methods can be used independently or in concert to quantify various aspects of 

sustainability, but ultimately, the priorities of the owner/agency and the characteristics of the 

project, as well as the desired outcomes viewed within the context of larger systems will 

determine which approach (or set of approaches) is most appropriate. It is important to note that 

there are currently few, if any, generally accepted metrics able to measure equity/social impacts 

associated with pavement systems.

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Chapter 10. Assessing Pavement Sustainability Towards Sustainable Pavement Systems

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Towards Sustainable Pavement Systems Chapter 11. Concluding Remarks

CHAPTER 11. CONCLUDING REMARKS

Sustainability is a journey, not a destination. This document provides guidance to the pavement 

community on how to begin this journey by incorporating sustainability considerations 

throughout the pavement life cycle. Even today there are a number of technologies and 

innovations that can be exploited to help facilitate that journey, and several of those key items 

are summarized in this chapter, along with the current and expected trends in each area. This is 

followed by a number of recommended implementation activities for helping to advance the 

adoption of more sustainable practices within the pavement community. 

Review of Technologies, Innovations, and Trends

Throughout this reference document, a number of technologies and innovations that hold the 

potential for improving some aspect of pavement sustainability are described; summarized below 

are just a few of the more prominent ones that are making significant contributions.

• Recycled material use at higher rates of replacement. While the standard use of 

recycled materials (e.g., RAP, RAS, RCA) has been a long-standing practice, the rates of 

use have often been limited by design procedures, technology, performance risk 

(perceived or real), and availability. Recent and likely continuing budget cuts associated 

with the general cost of construction have driven owners, designers, and contractors to 

explore ways of incorporating locally available recycled material at greater replacement 

levels. Rethinking mixture design processes, manufacturing requirements, specification 

limits, and construction practices from the ground up has already led to higher rates of 

use and better acceptance of recycled materials. As an added benefit, the reduced virgin 

material use and associated reductions in processing and transport can and has led to 

significant reductions in energy consumption and GHG emissions, which are now also 

becoming drivers for the greater use of recycled materials. 

• Adoption of WMA technologies as standard practice. For asphalt pavements, WMA 

has received much attention in both technology improvement and implementation. 

Documented benefits of reduced energy consumption, reduced emissions (GHG and 

others), and improved construction quality have been primary drivers in the expanded use 

of WMA. 

• Use of SCMs to reduce cement GHG emissions. The cement industry has put forth a 

substantial effort in reducing GHG emissions by reducing the cement content per unit 

volume while providing equal or better performance. Cement producers are producing a 

greater variety and amount of blended cements using SCMs or interground limestone to 

further reduce GHG emissions. Mixtures containing less than 50 percent cement of the 

total cementitious content are available and have shown good performance. As SCMs, 

limestone cements, and mixtures containing less cement per unit volume gain more 

acceptance by highway agencies, significant reductions in GHG emissions associated 

with concrete pavement construction will be realized. 

• Mechanistic based pavement design procedures. Improved pavement designs are 

being implemented as state transportation agencies adopt mechanistic-empirical 

pavement design methodologies, which are based on a better understanding of pavement 

responses to traffic and environmental loadings and how those responses are linked to 

pavement performance. 

11-1 
Chapter 11. Concluding Remarks Towards Sustainable Pavement Systems

• Optimization of use of materials. Two-lift concrete pavements and perpetual asphalt

pavements are examples of design approaches that optimize the use of paving materials

to meet specific needs. For example, two-lift pavements use higher recycled or marginal

aggregate content in a thicker bottom lift while reserving more durable material for the

thinner surface lift, thereby reducing the environmental impact of the overall structure

without compromising performance.

• Porous pavements for stormwater management. As concerns continue regarding the

volume and quality of stormwater runoff from paved surfaces, permeable asphalt (porous

asphalt) and concrete (pervious concrete) pavements are becoming more widely used.

These materials can not only be used to reduce stormwater runoff, but they can also be

effective in reducing contaminants in waterways and renewing groundwater supplies.

Other permeable pavement surfaces also exist, including those made with permeable

interlocking concrete pavers.

• Precast pavements and interlocking pavers. Precast pavement systems, either

intermittent or continuous, offer a unique solution to certain pavement challenges,

particularly where short work windows are demanded or when maintaining overall traffic

flow is critical. Interlocking concrete pavers provide an aesthetically pleasing appearance

while providing utility access without compromising the pavement structure, thereby

making them an attractive alternative in urban settings.

• Construction technologies. A number of emerging construction technologies are

resulting in the production of higher quality, longer lasting pavements that can have

significant environmental, economic, and social benefits. Intelligent compaction,

stringless paving, and real-time smoothness measurements are providing real-time data to

contractors. These data allow them to better control their processes to achieve improved

in-place material properties and higher levels of initial pavement smoothness.

• Expanded use of preservation treatments. Preservation treatments that use little

material yet maintain pavements in a smooth condition for longer periods of time have

great environmental benefit, especially on higher traffic volume roadways. This

realization is making the use of ultra-thin asphalt surfaces and diamond grinding of

concrete pavements particularly attractive.

In addition to these technologies, several trends are emerging within the sustainability arena that 

are expected to play a significant role in future activities and developments, including: 

• Recognition of the importance of the use phase. The use phase is beginning to be

recognized as having one of the most important impacts on pavement sustainability over

the life cycle. Vehicle fuel consumption, noise, safety, stormwater runoff, and urban

temperature can be impacted by pavement characteristics such as structural response,

macrotexture, roughness, permeability, and surface reflectivity. Studies are ongoing to

define the effects of these variables for possible inclusion in future pavement LCA tools,

potentially shifting the perspective to focus on pavement attributes that are most critical

to minimize environmental and social impacts over the pavement life cycle.

• Recognition that pavement systems are a small part of larger systems. Pavements do

not stand alone, but are part of larger systems that include both communities and

ecosystems possessing their own sustainability goals. Advances are occurring in the

development of pavement specific tools that integrate economic, environmental, and

11-2 
Towards Sustainable Pavement Systems Chapter 11. Concluding Remarks

societal impacts within the pavement system and in the broader context of these larger 

systems. 

• Development/enhancement of sustainability tools. Advances are occurring in the 

development of tools that integrate pavement LCCA, LCA, and elements of pavement 

sustainability rating systems. Considerable work remains on building a consensus LCA 

framework, populating the LCI database with accurate and regionalized data, and 

developing improved models that accurately reflect the contribution of the use phase. It 

is envisioned that the emergence of these tools will positively impact the paving 

community in the next decade. 

It is again emphasized that sustainability is context sensitive, and the development of sustainable 

strategies will depend on the characteristics of the specific project, the materials and technologies 

that are readily available, and the specific economic, environmental, and societal goals of the 

agency. Closely linked to this is that the selection of sustainable solutions often requires the 

consideration of trade-offs between several competing sustainability goals or objectives. The 

development of an LCA framework is one key area required to be able to assess relative 

environmental impacts and to monitor overall progress that is being made in the sustainability 

area.

Implementation: The Next Step

The information presented in this document forms the foundation for moving ahead in adopting 

sustainability principles in pavement systems. Key factors and activities that are essential to 

implement pavement sustainability best practices include: 

• Leadership at the national level. FHWA should work to make sustainability a strategic 

priority in all areas of pavement design, materials, and construction and in 

communicating the principles, strategies, and techniques outlined in this document. As 

part of this, the development of a sustainable pavements framework can help provide a 

measured, detailed approach on how to advance the concepts, provide the 

implementation, and promote the research of sustainable pavement systems. 

• Leadership at the state level. This is necessary to incorporate elements of pavement 

sustainability in the design and construction of state highway systems. This includes 

having strategic directions for sustainability established within an agency that include 

pavement systems. In addition, highway agencies can also contribute to the adoption of 

more sustainable practices by revisiting their design standards and material and 

construction specifications to ensure that they are not barriers to implementing more 

sustainable solutions. This can also have a positive “trickle down” effect to local 

governments that often rely on state design standards and material and construction 

specifications. Finally, agencies should identify a short list of items related to

sustainability that make sense to adopt or implement within their organization.

• Partnership between stakeholders. Collaborative relationships are needed in which 

industry, academia, and highway agencies work together to implement sustainability 

principles and address issues and problems that emerge during the ongoing sustainability 

journey. 

• Education and outreach. Educational materials and outreach programs must be 

developed to provide information on basic sustainability principles as well as on specific

examples of “low-hanging fruit” in which the implementation of innovative materials and 

11-3 
Chapter 11. Concluding Remarks Towards Sustainable Pavement Systems

technologies can have immediate economic, environmental, and societal benefits. Given 

that the available information is overwhelming, it must be simplified and properly 

directed as part of the implementation effort. The development of useful resources—

such as guide documents, technical briefs, case study examples, a user-friendly web page, 

simple computer-based tools, and mobile applications—are considered essential to this 

effort. Furthermore, sharing case studies, findings, and recommendations through 

workshops, webinars, and targeted conferences is also a fundamental part of that outreach 

effort.

• Identify knowledge gaps and develop a focused research map. The research should 

be fundamental and basic as well as practical. Broad stakeholder support is needed if 

research results are to be accepted and implemented. Potential topics requiring additional 

research include rolling resistance, urban heat island effects, maintenance and 

preservation impacts, and energy consumption and GHG emissions associated with a 

pavement over its entire life cycle.

• Educate, encourage, and implement LCA tools. Sustainable practices can only be 

implemented if the environmental impact of decisions over the pavement life cycle can 

be quantified to a high degree of certainty. The only tool capable of accomplishing this is 

LCA, and therefore the application of LCA principles are critical for evaluating many of 

the trade-offs encountered through the pavement life cycle. Efforts should be made to 

educate the pavement community on LCA concepts and tools, encourage the community 

to adopt changes in policy based on knowledge garnered from LCA studies, and 

ultimately implement pavement-based LCA tools developed and vetted through a peerreviewed process representing all stakeholders.

11-4
Towards Sustainable Pavement Systems Glossary

GLOSSARY OF TERMS

The following presents a summary of terms that are used in this document. Sources of 

information for this glossary include the Asphalt Institute1

1 Asphalt Institute (AI). n.d. Asphalt Industry Glossary of Terms. (Web Link

, the National Concrete Pavement 

Technology Center2

2 Taylor, P. C., S. H. Kosmatka, G. F. Voigt, M. E. Ayers, A. Davis, G. J. Fick, J. Grove, D. Harrington, B. 

Kerkhoff, H. C. Ozyildirim, J. M. Shilstone, K. Smith, S. Tarr, P. D. Tennis, T. J. Van Dam, and S. Waalkes. 2006. 

Integrated Materials and Construction Practices for Concrete Pavements: A State-of-the-Practice Manual. FHWAHIF-07-004. Federal Highway Administration, Washington, DC. 

, and the Transportation Research Board3

3 Transportation Research Board (TRB). 2013. Glossary of Transportation Construction Quality Assurance Terms: 

Sixth Edition. Transportation Research Circular E-C173. Transportation Research Board, Washington, DC. (Web 

Link

. 

AADT. The average annual daily traffic, expressed as the 24-hour traffic volume counts 

collected over a number of days greater than 1 day but less than 1 year, at a given location. 

AADT can also be approximated by adjusting the ADT count for daily (weekday versus 

weekend) and seasonal (summer versus winter) variations

Absorption. The amount of water absorbed under specific conditions, usually expressed as a 

percentage of the dry weight of the material; the process by which the water is absorbed. 

Accelerator. An admixture which, when added to concrete, mortar, or grout, increases the rate 

of hydration of hydraulic cement, shortens the time of set, or increases the rate of hardening or 

strength development. 

Admixture. A material other than water, aggregates, and portland cement (including airentraining portland cement, and portland blast furnace slag cement) that is used as an ingredient 

of concrete and is added to the batch before and during the mixing operation. 

Aggregate. Granular material, such as sand, gravel, or crushed stone used with a hydraulic 

cementing medium to produce either concrete or mortar; or used with asphalt cement to produce 

asphalt concrete; or used in the base and/or subbase layers of a pavement structure.

Aggregate Blending. The process of intermixing two or more aggregates to produce a 

different set of properties, generally, but not exclusively, to improve grading. 

Aggregate Gradation. The distribution of particles of granular material among various sizes, 

usually expressed in terms of cumulative percentages larger or smaller than each of a series of 

sizes (sieve openings) or the percentages between certain ranges of sizes (sieve openings). See 

also Grading. 

Agitation. The process of providing gentle motion in mixed concrete just sufficient to prevent 

segregation or loss of plasticity. 

Air Content. The amount of air in mortar or concrete, exclusive of pore space in the aggregate 

particles, usually expressed as a percentage of total volume of mortar or concrete.

Air-Entraining. The capabilities of a material or process to develop a system of minute bubbles 

of air in cement paste, mortar, or concrete during mixing. 

) 

) 

A-1 

 
Glossary Towards Sustainable Pavement Systems

Air Void. A space in cement paste, mortar, or concrete filled with air; an entrapped air void is 

characteristically 0.04 in (1 mm) or more in size and irregular in shape; an entrained air void is 

typically between 0.004 inches and 0.04 inches (10μm and 1 mm) in diameter and spherical (or 

nearly so).

Albedo. Solar reflectance.

Alkali-Silica Reaction. The reaction between the alkalis (sodium and potassium) in portland 

cement binder and certain siliceous rocks or minerals, such as opaline chert, strained quartz, and 

acidic volcanic glass, present in some aggregates; the products of the reaction may cause 

abnormal expansion and cracking of concrete in service. 

Allocate. Distribution of available resources among programs or geographic districts/regions. 

Alternatives. Available choices or courses of action that can be considered at each stage of 

resource allocation or utilization. 

Asphalt Cement. A bituminous material that, when used as a binder with aggregate, creates 

hot-mix asphalt. 

Asphalt Cutback. Asphalt cement that has been liquefied by blending with petroleum solvents 

(diluents). Upon exposure to atmospheric conditions the diluents evaporate, leaving the asphalt 

cement to perform its function.

Asphalt Emulsion. An emulsion of asphalt binder and water that contains a small amount of 

an emulsifying agent. Emulsified asphalt droplets may be of either the anionic (negative charge), 

cationic (positive charge) or nonionic (neutral).

Asphalt Rubber (AR). Conventional asphalt cement to which recycled ground tire rubber has 

been added, that when reacted with the hot asphalt cement causes a swelling and/or dispersion of 

the tire rubber particles.

Asset. The physical infrastructure (e.g., right-of-way, pavements, structures, roadside features). 

Assets can also include other agency resources capable of providing added value (e.g., human 

resources, real estate, equipment and materials).

Asset Management. Business processes for resource allocation and utilization with the 

objective of better decision-making based upon quality information and well-defined objectives.

Asset Management Plan. Tactical plan for managing an agency’s infrastructure (and/or other 

assets) to deliver an agreed upon level of service. Typically, the asset management plan 

encompasses more than one asset (e.g., a system approach). 

Base. The layer of material immediately beneath the pavement surface or binder course.

Base Course. A layer of specified select material of planned thickness constructed on the 

subgrade or subbase below a pavement to serve one or more functions such as distributing loads, 

providing drainage, minimizing frost action, or facilitating pavement construction. 

Batch Plant. Equipment used for batching concrete materials.

Batch Plant Mix Water. The mixing water added to a concrete or mortar mixture before or 

during the initial stages of mixing.

Benchmark. Process for comparing cost, performance life, productivity, or quality of a specific 

process or method to a standard or best practice. Benchmarking is used in strategic management

A-2 
Towards Sustainable Pavement Systems Glossary

to evaluate various process aspects in relation to best practice. Agencies then use the 

benchmarking results to develop plans for process improvement or adoption of best practices, 

usually with the aim of increasing performance. 

Benefit/Cost. A comparison analysis of the economic benefit of an investment to its cost. The 

benefit/cost analysis should include all costs and benefits to both the agency and the users of the 

facility over an appropriate life cycle period. In asset management, benefit/cost can be applied 

for prioritizing projects, evaluation of the benefits and costs for all projects in a program, and 

determination of program tradeoffs. 

Binder. An adhesive composition of asphalt cement, modified asphalt cement, or other 

bituminous materials which is primarily responsible for binding aggregate particles together. 

Also used to refer to the layer of asphalt directly below the surface course (i.e., binder course).

Bitumen. A class of black or dark-colored (solid, semisolid, or viscous) cementitious 

substances, natural or manufactured, composed principally of high molecular weight 

hydrocarbons, of which asphalts, tars, pitches, and asphaltites are typical. 

Bituminous. Any asphalt material used in the construction of maintenance of a roadway. 

Blast-Furnace Slag. The non-metallic byproduct, consisting essentially of silicates and 

aluminosilicates of lime and other bases, which is produced in a molten condition simultaneously 

with iron in a blast furnace.

Bleeding. The self-generated flow of mixing water within, or its emergence from, freshly 

placed concrete or mortar.

Blistering. The irregular rising of a thin layer of placed mortar or concrete at the surface during 

or soon after completion of the finished operation. 

Bond. The adhesion of concrete or mortar to reinforcement or other surfaces against which it is 

placed; the adhesion of cement paste to aggregate.

Bonded Concrete Overlay. Thin layer of new concrete 2 to 4 inches (51 to 102 mm) placed 

onto slightly deteriorated existing concrete pavement with steps taken to prepare the existing 

surface to promote adherence of new concrete.

Broom. The surface texture obtained by stroking a broom over freshly placed concrete. A sandy 

texture obtained by brushing the surface of freshly placed or slightly hardened concrete with a 

stiff broom. 

Capital. Type of investment that generally involves construction or major repair and can 

include: new construction, reconstruction, structural and functional improvements, and 

rehabilitation.

Cement, Blended. A hydraulic cement consisting essentially of an intimate and uniform blend 

of granulated blast-furnace slag and hydrated lime; or an intimate and uniform blend of portland 

cement and granulated blast-furnace slag cement and pozzolan, produced by intergrinding 

portland cement clinker with the other materials or by blending portland cement with the other 

materials, or a combination of intergrinding and blending. 

Cement, High-Early Strength. Cement characterized by producing earlier strength in mortar 

or concrete than regular cement, referred to in the United States as Type III.

Cement, Hydraulic. Cement that is capable of setting and hardening under water, such as 

normal portland cement. 

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Glossary Towards Sustainable Pavement Systems

Cementitious Materials. Substances that alone have hydraulic cementing properties (set and 

harden in the presence of water); includes ground, granulated blast-furnace slag, natural cement, 

hydraulic hydrated lime, and combinations of these and other materials. 

Chip Seal. A surface treatment in which a pavement surface is sprayed with asphalt (generally 

emulsified) and then immediately covered with aggregate and rolled. Chip seals are used 

primarily to seal the surface of a pavement with non-load-associated cracks and to improve 

surface friction (skid resistance). Also referred to as “seal coat.”

Clinker. A fused or partially fused by-product of the combustion of coal. Also includes lava and 

portland cement and partially vitrified slag and brick. 

Coal Tar. A dark brown to black cementitious material produced by the destructive distillation 

of bituminous coal. 

Cohesiveness. The property of a concrete mix which enables the aggregate particles and 

cement paste matrix therein to remain in contact with each other during mixing, handling, and 

placing operations; the “stick-togetherness” of the concrete at a given slump.

Cold In-Place Recycling (CIR). A process in which a portion of an existing bituminous 

pavement is pulverized or milled, the reclaimed material is mixed with new binder and new 

materials, and the resultant blend is placed as a base for a subsequent overlay. 

Cold Milling. A process of removing pavement material from the surface of the pavement 

either to prepare the surface to receive overlays (by removing rutting and surface irregularities), 

to restore pavement cross slopes and profile, or to re-establish the pavement’s surface friction 

characteristics.

Compaction. The process whereby the volume of asphalt, aggregate, soil, or freshly placed 

mortar or concrete is reduced to the minimum practical space, usually by vibration, 

centrifugation, tamping, or some combination of these; to mold it within forms or molds and 

around embedded parts and reinforcement, and to eliminate voids other than entrained air. See 

also Consolidation. 

Condition Index. A numeric score determined from pavement condition data and used to 

represent the performance of the pavement. 

Consistency. The degree of fluidity of asphalt cement at any particular temperature. The 

consistency of asphalt cement varies with its temperature; therefore, it is necessary to use a 

common or standard temperature when comparing the consistency of one asphalt cement with 

another. 

Consolidate. Compaction usually accomplished by vibration of newly placed concrete to 

minimum practical volume, to mold it within form shapes or around embedded parts and 

reinforcement, and to reduce void content to a practical minimum.

Consolidation. The process of inducing a closer arrangement of the solid particles in freshly 

mixed concrete or mortar during placement by the reduction of voids, usually by vibration, 

centrifugation, tamping, or some combination of these actions; also applicable to similar 

manipulation of other cementitious mixtures, soils, aggregates, or the like. See also Compaction. 

Continuously Reinforced Concrete Pavement (CRCP). A concrete pavement 

characterized by no regularly spaced transverse joints and continuous longitudinal reinforcement. 

A-4 
Towards Sustainable Pavement Systems Glossary

Cost Plus Time Bidding. Also called A+B Bidding. A bidding procedure that selects the 

low bidder based on a monetary combination of the traditional bid price (A) and the time (B) 

needed to complete the project or a critical portion of the project. A cost-plus-time contract can 

be devised to actually pay the contractor either only the A portion of the bid or the A portion plus 

or minus an agreed-upon incentive–disincentive amount for early or late completion; this latter 

form of the contract is sometimes referred to as a cost-plus-time with incentives or

disincentives (A + B + I/D) contract. [The intent of either form is to provide an incentive 

for the contractor to minimize delivery time for high-priority roadways.] 

Course. In pavement construction, a horizontal layer of asphalt, concrete, or aggregate, usually 

one of several making up a lift. See also Lift.

Crack and Seat. A fractured slab technique used in the rehabilitation of PCC pavements that 

minimizes slab action in a jointed concrete pavement (JCP) by fracturing the PCC layer into 

smaller segments. This reduction in slab length minimizes reflective cracking in new asphalt

overlays. 

Deflection Basin. The idealized shape of the deformed pavement surface as a result of a cyclic 

or impact load as depicted from the peak measurements of five or more deflection sensors.

Deformed Reinforcement. Metal bars, wire, or fabric with a manufactured pattern of surface 

ridges that provide a locking anchorage with surrounding concrete. 

Dense-Graded. Aggregates graded to produce low void content and maximum weight when 

compacted.

Design–Bid–Build (DBB). A project delivery system in which the design is completed either 

by in-house professional engineering staff or a design consultant before the construction contract 

is advertised. [The DBB method is sometimes referred to as the traditional method.]

Design–Build (DB). A project delivery system in which both the design and the construction 

of the project are simultaneously awarded to a single entity. [The main advantage of the DB 

method is that it can decrease project delivery time.]

Design–Build–Maintain (DBM). A project delivery system in which the design, construction, 

and maintenance of the project are awarded to a single entity. 

Diamond Grinding. The process used to remove the upper surface of a concrete pavement to 

remove bumps and restore pavement rideability; also, equipment using many diamondimpregnated saw blades on a shaft or arbor to shave the surface of concrete slabs.

Dolomite. A mineral having a specific crystal structure and consisting of calcium carbonate and 

magnesium carbonate in equivalent chemical amounts (54.27 and 45.73 percent by weight, 

respectively); a rock containing dolomite as the principal constituent.

Dowel. A device located across transverse joints at mid-depth of a PCC slab to provide load 

transfer from one slab to the adjoining slab. These are commonly smooth, round, and coated to 

resist corrosion.

Early-Entry Dry Saw. Lightweight saw equipped with a blade that does not require water for 

cooling and that allows sawing concrete sooner than with conventional wet-diamond sawing 

equipment. 

A-5 
Glossary Towards Sustainable Pavement Systems

Empirical model. A model developed from performance histories of pavements. [An empirical 

model is usually accurate only for the exact conditions and ranges of independent variables under 

which it was developed.] 

Emulsifying Agent or Emulsifier. The chemical added to the water and asphalt that keeps 

the asphalt in stable suspension in the water. The emulsifier determines the charge of the 

emulsion and controls the breaking rate. 

Entrained Air. Round, uniformly distributed, microscopic, non-coalescing air bubbles 

entrained by the use of air-entraining agents; usually less than 0.04 inches (1 mm) in size.

Entrapped Air. Air in concrete that is not purposely entrained. Entrapped air is generally 

considered to be large voids (larger than 0.04 inches [1 mm]).

Facility. A general term referring to a street, roadway, or highway. 

Fatigue Cracking. Cracking of a roadway surface (either asphalt or concrete) caused by 

repetitive loading. 

Faulting. Differential vertical displacement of abutting concrete pavement slabs at joints or 

cracks creating a step-like deformation in the pavement. 

Flexible Pavement. An asphalt pavement.

Flow. 1) Time dependent irrecoverable deformation. 2) A measure of the consistency of freshly 

mixed concrete, mortar, or cement paste in terms of the increase in diameter of a molded 

truncated cone specimen after jigging a specified number of times.

Fly Ash. The finely divided residue resulting from the combustion of ground or powdered coal 

and which is transported from the fire box through the boiler by flu gasses; used as mineral 

admixture in concrete mixtures.

Fog Seal. A light application of diluted asphalt emulsion. It is used to renew old asphalt 

surfaces, seal small cracks and surface voids, and inhibit raveling.

Full-Depth Asphalt Pavement. The term FULL-DEPTH (registered by the Asphalt Institute 

with the U.S. Patent Office) certifies that the pavement is one in which asphalt mixtures are 

employed for all courses above the subgrade or improved subgrade. A Full-Depth asphalt 

pavement is placed directly on the prepared subgrade.

Full-Depth Reclamation. A technique in which the full thickness of the existing asphalt 

pavement and a predetermined portion of the underlying materials (base, subbase, and/or 

subgrade) are uniformly pulverized and blended to provide a homogeneous material. 

Gap-graded. Aggregate so graded that certain intermediate sizes are substantially absent.

Grading. The distribution of particles of granular material among various sizes, usually 

expressed in terms of cumulative percentages larger or smaller than each of a series of sizes 

(sieve openings) or the percentages between certain ranges of sizes (sieve openings).

Heat of Hydration. Heat evolved by chemical reactions of a substance with water, such as that 

evolved during the setting and hardening of portland cement. 

Hot In-Place Recycling (HIPR). A process which consists of softening the existing 

bituminous surface with heat, mechanically removing the surface material, mixing the material 

A-6 
Towards Sustainable Pavement Systems Glossary

with a recycling agent, adding new asphalt or aggregate to the material (if required), and then 

replacing the material back on the roadway. 

Hot Mix Asphalt (HMA). A plant-produced, high-quality hot mixture of asphalt cement and 

well-graded, high-quality aggregate thoroughly compacted into a uniform dense mass. 

Incentive–Disincentive Provision (for quality). A pay adjustment schedule that functions to 

motivate the contractor to provide a high level of quality. [A pay adjustment schedule, even one 

that provides for pay increases, is not necessarily an incentive or disincentive provision, as

individual pay increases or decreases may not be of sufficient magnitude to motivate the

contractor toward high quality.] 

Inlay. A form of reconstruction where new concrete is placed into an area of removed pavement; 

the removal may be an individual lane, all lanes between the shoulders or only partly through a 

slab.

International Roughness Index (IRI). A measurement of the roughness of a pavement, 

expressed as the ratio of the accumulated suspension motion to the distance traveled obtained 

from a mathematical model of a standard quarter car traversing a measured profile at a speed of 

50 mi/hr (80 km/h). 

Jointed Plain Concrete Pavement (JPCP). A concrete pavement system characterized by 

short joint spacings and no reinforcement. Smooth dowels may be placed across the transverse 

joints to facilitate load transfer.

Jointed Reinforced Concrete Pavement (JRCP). A concrete pavement system 

characterized by longer joint spacings and containing steel mesh reinforcement distributed 

throughout the slab to hold any cracks tightly together. 

Level of Service (LOS). Measures related to the public’s perception of asset condition or of 

agency services; used to express current and target values for maintenance and operations 

activities.

Life Cycle. A length of time that spans the stages of asset construction, operation, maintenance, 

rehabilitation, and reconstruction or disposal/abandonment; when associated with analyses, 

refers to a length of time sufficient to span these several stages and to capture the costs, benefits, 

and long-term performance impacts of different investment options. 

Life Cycle Assessment (LCA). A technique that can be used for analyzing and quantifying 

the environmental impacts of a product, system, and/or process. 

Life Cycle Cost Analysis (LCCA). A method of reducing all of the significant costs of an 

asset over its lifetime to either a present worth (today’s cost) or equivalent uniform annual cost 

(annual cost). As such, LCCA accounts for initial (or in-place) costs, subsequent maintenance 

and rehabilitation costs, and salvage value. In addition to all of these costs, inputs to an LCCA 

include the analysis period and the discount rate (reflecting the time value of money. 

Life Cycle Inventory (LCI). LCI involves collecting, validating, and aggregating input and 

output data to quantify material use, energy use, environmental discharges, and waste associated 

with each life cycle stage.

Lift. The material placed between two consecutive horizontal placements, usually consisting of 

several layers or courses.

A-7 
Glossary Towards Sustainable Pavement Systems

Load Transfer Restoration (LTR). The placement of load transfer devices across joints or 

cracks in an existing jointed PCC pavement. 

Longitudinal Tining. Surface texture achieved by a hand held or mechanical device equipped 

with a rake-like tining head that moves in a line parallel to the pavement centerline.

Maintenance. Activities that enable a transportation system to continue to perform at its 

intended level; comprises a range of services in preservation, cleaning, replacing worn or failed 

components, periodic or unscheduled repairs and upkeep, motorist services (incident response, 

hazardous materials response), snow and ice control, and servicing of traffic devices and aids; 

does not add to structural or operational capacity of an existing facility.

Maintenance Mix. A mixture of asphalt emulsion and mineral aggregate for use in relatively 

small areas to patch holes, depressions, and distressed areas in existing pavements. Appropriate 

hand or mechanical methods are used in placing and compacting the mix. 

Mean Profile Depth (MPD). A measurement of pavement surface texture that strongly affects 

wet pavement friction. 

Mechanistic Model. A model developed from the laws of mechanics, in which the prescribed 

action of forces on bodies of material elements are related to the resulting stress, strain, 

deformation, and failure of the pavement. 

Mechanistic–Empirical Model. A model developed from a combination of mechanistic and 

empirical considerations. The basic advantage is that it provides more reliable performance 

predictions. 

Microsurfacing. A mixture of polymer modified asphalt emulsion, crushed dense graded 

aggregate, mineral filler, additives and water. It provides a thin resurfacing of 0.38 to 0.75 inches 

(10 to 19 mm) to the pavement. 

Mineral Filler. A finely divided mineral product, at least 70 percent of which will pass a 0.075 

mm (No. 200) sieve. Pulverized limestone is the most commonly manufactured filler, although 

other stone dust, hydrated lime, portland cement, and certain natural deposits of finely divided 

mineral matter are also used.

Multi-Parameter Bidding. Also called A + B + C bidding. A bidding procedure that selects 

the low bidder based on a monetary combination of the traditional bid price (A), the completion 

time (B), and other elements (C) such as construction quality, safety, and life-cycle costs. 

Quantification of the elements and bidder evaluation methodology are included in the procedure. 

Natural (Native) Asphalt. Asphalt occurring in nature, which has been derived from 

petroleum through natural processes of evaporation of volatile fractions, leaving the asphalt 

fractions. The native asphalt of most importance is found in the Trinidad and Bermudez Lake 

deposits. Asphalt from these sources is often called lake asphalt.

Network. System of assets to provide transportation services to customers.

Nominal Maximum Size. In specifications for and descriptions of aggregate, the smallest 

sieve opening through which the entire amount of the aggregate is permitted to pass; sometimes 

referred to as “maximum size (of aggregate).” 

Open-Graded. Aggregate in which the voids are relatively large when the aggregate is 

compacted.

A-8 
Towards Sustainable Pavement Systems Glossary

Open-Graded Friction Course (OGFC). A bituminous paving layer consisting of a mix of 

asphalt cement and open-graded (also called uniformly graded) aggregate. An open-graded 

aggregate consists of particles of predominantly a single-size aggregate.

Optimization. Process for determining the best available value (e.g., cost, performance life) 

within a given set of constraints.

Oven Dry. The condition resulting from having been dried to essentially constant weight, in an 

oven, at a temperature that has been fixed, usually between 221 and 239 oF (105 and 115 oC).

Oxidation. Chemical reaction between the asphalt in an asphalt pavement and air, causing the 

bituminous surface to become discolored and stiffer. 

Particle-Size Distribution. The division of particles of a graded material among various 

sizes; for concrete materials, usually expressed in terms of cumulative percentages larger or 

smaller than each of a series of diameters or the percentages within certain ranges of diameter, as 

determined by sieving. 

Pavement Maintenance. Work that is planned and performed on a routine basis to maintain 

and preserve the condition of the highway system or to respond to specific conditions and events 

that restore the highway system to an adequate level of service.

Pavement Management. All the activities involved in the planning, programming, design, 

construction, maintenance, and rehabilitation of the pavement portion of a public works program. 

A system which involves the identification of optimum strategies at various management levels 

and maintains pavements at an adequate level of serviceability. These include, but are not 

limited to, systematic procedures for scheduling maintenance and rehabilitation activities based 

on optimization of benefits and minimization of costs. 

Pavement Management System (PMS). A set of tools or methods that assists decisionmakers in finding optimum strategies for providing, evaluating, and maintaining pavements in a 

serviceable condition over a period of time. 

Pavement Preservation. A program employing a network-level, long-term strategy that 

enhances pavement performance by using an integrated, cost-effective set of practices that 

extend pavement life, improve safety and meet motorist expectations. 

Pavement Rehabilitation. Structural enhancements that extend the service life of an existing 

pavement and/or improve its load-carrying capacity. Rehabilitation techniques include 

restoration treatments and structural overlays.

Pay Factor. A multiplication factor, often expressed as a percentage, used to determine the 

contractor’s payment for a unit of work, based on the estimated quality of work. [Typically, the 

term “pay factor” applies to only one quality characteristic.] 

Performance-Based. Characteristic of an asset that reflects its functionality or its 

serviceability as perceived by transportation users; often related to condition. 

Placement. The process of placing and consolidating concrete; a quantity of concrete placed 

and finished during a continuous operation; also inappropriately referred to as “pouring.” 

Plastic. Condition of freshly mixed cement paste, mortar, or concrete such that deformation will 

be sustained continuously in any direction without rupture; in common usage, concrete with 

slump of 3 to 4 inches (76 to 102 mm).

A-9 
Glossary Towards Sustainable Pavement Systems

Pneumatic-Tire Roller. A compactor with a number of tires spaced so their tracks overlap 

delivering a kneading type of compaction. 

Polymer Modified Asphalt. Conventional asphalt cement to which one or more polymer 

compounds have been added to improve resistance to deformation at high pavement 

temperatures and often cracking resistance at low temperatures.

Porosity. The ratio, usually expressed as a percentage, of the volume of voids in a material to 

the total volume of the material, including voids.

Portland Cement Concrete. A composite material consisting of portland cement, coarse 

aggregate, fine aggregate, water, air, and possibly other additives that, when mixed together, 

hardens through a chemical reaction to form a hard solid mass. Physically, portland cement is a 

finely pulverized clinker produced by burning mixtures containing lime, iron, alumina, and silica 

at high temperature and in definite proportions, and then intergrinding gypsum to give the 

properties desired.

Pozzolan. A siliceous or siliceous and aluminous material, which in itself possesses little or no 

cementitious value but will, in finely divided form and in the presence of moisture, chemically 

react with calcium hydroxide at ordinary temperatures to form compounds possessing 

cementitious properties.

Preventive Maintenance. Proactive approach that applies maintenance treatments while the 

asset is still in good condition; extends asset life by preventing the onset or growth (propagation) 

of distress.

Profile Index. Smoothness qualifying factor determined from profilograph trace. Calculated by 

dividing the sum of the total counts above the blanking band for each segment by the sum of the 

segment length. 

Proportioning. Selection of proportions of ingredients for mortar or concrete to make the most 

economical use of available materials to produce mortar or concrete of the required properties. 

Pumping. The forceful displacement of a mixture of soil and water that occurs under slab 

joints, cracks and pavement edges which are depressed and released quickly by high-speed heavy 

vehicle loads; occurs when concrete pavements are placed directly on fine-grained, plastic soils 

or erodible subbase materials.

Punchout. In continuously reinforced concrete pavement, the area enclosed by two closely 

spaced transverse cracks, a short longitudinal crack, and the edge of the pavement or longitudinal 

joint, when exhibiting spalling, shattering, or faulting. Also, area between Y cracks exhibiting 

this same deterioration.

Quality Assurance. Planned and systematic actions by an owner or his representative to 

provide confidence that a product or facility meet applicable standards of good practice. This 

involves continued evaluation of design, plan and specification development, contract 

advertisement and award, construction, and maintenance, and the interactions of these activities. 

Quality Control. Actions taken by a producer or contractor to provide control over what is 

being done and what is being provided so that the applicable standards of good practice for the 

work are followed. 

Raveling. The wearing away of a bituminous pavement surface caused by the dislodging of 

aggregate particles and loss of asphalt binder.

A-10
Towards Sustainable Pavement Systems Glossary

Reclaimed Asphalt Pavement (RAP). Excavated asphalt pavement that has been 

pulverized, usually by milling, and is used like an aggregate in the recycling of asphalt 

pavements.

Recycled Asphalt. A mixture produced after processing existing asphalt pavement materials. 

The recycled mix may be produced by hot or cold mixing at a plant, or by processing the 

materials cold and in-place.

Recycled Concrete Aggregate. A granular material manufactured by removing, crushing, 

and processing hydraulic-cement concrete pavement for reuse with a hydraulic cementing 

medium to produce fresh paving concrete. 

Release Agent. Material used to prevent bonding of concrete to a surface. 

Reservoir. The part of a concrete joint that normally holds a sealant material. Usually a 

widening saw cut above the initial saw cut. 

Residual Asphalt. Amount of asphalt left in an emulsion after water has evaporated. 

Restoration. The process of reestablishing the materials, form, and appearance of a structure to 

those of a particular era of the structure. See also Pavement Preservation, Pavement 

Rehabilitation. 

Retardation. Reduction in the rate of hardening or strength development of fresh concrete, 

mortar, or grout; i.e., an increase in the time required to reach initial and final set.

Rigid Pavement. A pavement constructed with hydraulic cement concrete. 

Roughness. Distortions of the road surface that contribute to an undesirable, unsafe, 

uneconomical, or uncomfortable ride. 

Rubblization. The pulverization of a portland cement concrete pavement into smaller particles, 

reducing the existing pavement layer to a sound, structural base that will be compatible to an 

asphalt overlay. 

Rutting. A surface depression in the wheelpath caused by a permanent deformation in any of 

the pavement layers or subgrade. 

Sand Seal. An application of asphalt emulsion covered with fine aggregate. It may be used to 

improve the skid resistance of slippery pavements and to seal against air and water intrusion. 

Scaling. Flaking or peeling away of the near-surface portion of hydraulic cement concrete or 

mortar.

Screed. 1) To strike off concrete lying above the desired plane or shape. 2) A tool for striking 

off the concrete surface, sometimes referred to as a Strikeoff.

Separation. The tendency, as concrete is caused to pass from the unconfined ends of chutes or 

conveyor belts, for coarse aggregate to separate from the concrete and accumulate at one side; 

the tendency, as processed aggregate leaves the ends of conveyor belts, chutes, or similar devices 

with confining sides, for the larger aggregate to separate from the mass and accumulate at one 

side; the tendency for solids to separate from the water by gravitational settlement.

Set. The condition reached by a cement paste, mortar, or concrete when it has lost plasticity to 

an arbitrary degree, usually measured in terms of resistance to penetration or deformation. Initial 

set refers to first stiffening. Final set refers to attainment of significant rigidity.

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Glossary Towards Sustainable Pavement Systems

Skid Number (SN). A standard test measure of the friction between a braking tire and the 

pavement surface.

Slipform Paving. A type of concrete paving process that involves extruding the concrete 

through a machine to provide a uniform dimension of concrete paving. 

Slurry Seal. A mixture of quick- or slow-setting emulsified asphalt, well-graded fine aggregate, 

mineral filler, and water. It is used to fill cracks and seal areas of bituminous pavements, to 

restore a uniform surface texture, to seal the surface to prevent moisture and air intrusion into the 

pavement, and to provide skid resistance. 

Soundness. In the case of a cement, freedom from large expansion after setting. In the case of 

aggregate, the ability to withstand aggressive conditions to which concrete containing it might be 

exposed, particularly those due to weather. 

Spalling. The breakdown of the slab edges within 0.6 m (2 ft.) of the side of the joint caused by 

excessive stresses at the joint or crack or poor joint forming/sawing practices.

Specification Limit(s). The limiting value(s) placed on a quality characteristic, established

preferably by statistical analysis, for evaluating material or construction within the specification

requirements. The term can refer to either an individual USL or an LSL, called a single 

specification limit, or to USL and LSL together, called double specification limits.

Stakeholders. A person, group, or organization that affects or can be affected by an agencies 

actions.

Steel-Wheel Vibratory Rollers. A compaction device used to compress underlying asphalt 

layers. The amount of compactive force is adjusted by changing the frequency and amplitude of 

vibration. 

Stone Matrix Asphalt (SMA). A hot-mix asphalt consisting of a mix of asphalt cement, 

stabilizer material, mineral filler, and gap-graded aggregate. A gap-graded aggregate is similar to 

an open-graded material, but is not quite as open. 

Subbase. Layer of material immediately beneath the base course.

Subgrade Soil. The native soil prepared and compacted to support a pavement structure.

SuperpaveTM. Short for "Superior Performing Asphalt Pavement" a performance-based system 

for selecting and specifying asphalt binders and for designing asphalt mixtures. 

Supplementary Cementitious Material. Mineral admixtures consisting of powdered or 

pulverized materials, which are added to concrete before or during mixing to improve or change 

some of the plastic or hardened properties of Portland cement concrete. Materials are generally 

natural or by-products of other manufacturing processes.

Surface Friction. The retarding force developed at the tire-pavement interface that resists 

sliding when braking forces are applied to the vehicle tires. 

Surface Texture. The characteristics of the pavement surface that contribute to both surface 

fiction and noise. Surface texture is comprised of microtexture and macrotexture. 

Tamping. The operation of compacting freshly placed concrete by repeated blows or 

penetrations with a tamping device. 

A-12
Towards Sustainable Pavement Systems Glossary

Thin Asphalt Overlays. Plant-mixed combinations of asphalt cement and aggregate that are 

commonly placed in thicknesses between about 0.75 and 1.50 inches (19 and 38 mm).

Tradeoff Analysis. Comparisons of alternative solutions, particularly involving consequences 

of reallocating funds between programs. 

Transverse Crack. A crack in the pavement surface that is perpendicular to the direction of 

travel.

Transverse Tining. Surface texture achieved by a hand held or mechanical device equipped 

with a rake-like tining head that moves laterally across the width of the paving surface. 

Ultra-Thin Whitetopping (UTW). Thin concrete overlays of existing asphalt pavements that 

consist of very thin (2 to 4 inches [51 to 102 mm]) layers of concrete bonded to an existing 

asphalt pavement. 

Unbonded Concrete Overlay. Overlay of new concrete placed onto distressed existing 

concrete pavement with a layer of asphalt or other medium between the new and old concrete 

surface to separate them.

User Costs. Costs incurred by highway users traveling on the facility and the excess costs 

incurred by those who cannot use the facility because of either agency or self-imposed detour 

requirements. User costs typically are comprised of vehicle operating costs (VOC), crash costs, 

and user delay costs. 

Utilization. Process of applying labor, funds, information, and other resources to implement 

projects and services for the transportation system. 

Validation. (1) The process of confirming the soundness or effectiveness of a product (such as a 

model, a program, or specifications) thereby indicating official sanction; (2) The mathematical 

comparison of two independently obtained sets of data (e.g., agency acceptance data versus 

contractor data) to determine whether it can be assumed they came from the same population 

[The validation of a product often includes the verification of test results.]

Verification. The process of determining the accuracy of test results, by examining the data or 

providing objective evidence, or both. [Verification sampling and testing may be part of an

acceptance program (to verify contractor testing used in the agency’s acceptance decision).]

Vibration. Energetic agitation of concrete produced by a mechanical oscillating device at 

moderately high frequency to assist consolidation and compaction. 

Void. Gaps beneath pavements (usually concrete slabs) that lead to poor support conditions and 

high deflections. 

Warm Mix Asphalt (WMA). A general term for technologies that reduce the temperature 

needed to produce and compact asphalt mixtures for the construction of pavements. Utilization 

of WMA technology can reduce compaction temperatures by approximately 25 to 80 °F (14 to 

25 °C). 

Weathering. The hardening and aging of the asphalt binder. 

Well-Graded Aggregate. Aggregate having a particle size distribution that will produce 

maximum density; i.e., minimum void space. 

Whitetopping. Concrete overlay pavement placed on an existing asphalt pavement. 

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Glossary Towards Sustainable Pavement Systems

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