RECLAIMED MATERIALS 

AND THEIR APPLICATIONS 

IN ROAD CONSTRUCTION: 

A CONDENSED GUIDE FOR 

ROAD MANAGERS

United States Department of Agriculture

Forest Service

Cover photo by Al Watson, Sequoia National Forest

National Technology & Development Program • 7700 Travel Management • 1277 1807—SDTDC • December 2013
Non-Discrimination Policy

The U.S. Department of Agriculture (USDA) prohibits discrimination against its customers, employees, and applicants for employment on the 

bases of race, color, national origin, age, disability, sex, gender identity, religion, reprisal, and where applicable, political beliefs, marital status, 

familial or parental status, sexual orientation, or all or part of an individual’s income is derived from any public assistance program, or protected 

genetic information in employment or in any program or activity conducted or funded by the Department. (Not all prohibited bases will apply to 

all programs and/or employment activities.)

To File an Employment Complaint

If you wish to file an employment complaint, you must contact your agency’s EEO Counselor (click the hyperlink for list of EEO Counselors) 

within 45 days of the date of the alleged discriminatory act, event, or in the case of a personnel action. Additional information can be found 

online at http://www.ascr.usda.gov/complaint_filing_file.html.

To File a Program Complaint

If you wish to file a Civil Rights program complaint of discrimination, complete the USDA Program Discrimination form, found online at http://

www.ascr.usda.gov/complaint_filing_cust.html, or at any USDA office, or call (866) 632-9992 to request the form. You may also write a letter 

containing all of the information requested in the form. Send your completed complaint form or letter to us by mail at U.S. Department of 

Agriculture, Director, Office of Adjudication, 1400 Independence avenue, S.W., Washington, D.C. 20250-9410, by fax (202) 690-7442 or email 

at program.intake@usda.gov.

Persons with Disabilities

Individuals who are deaf, hard of hearing or have speech disabilities and you wish to file either an EEO or program complaint please contact 

USDA through the Federal Relay Service at (800) 877-8339 or (800) 845-6136 (in Spanish).

Persons with disabilities who wish to file a program complaint, please see information above on how to contact us by mail directly or by email. 

If you require alternative means of communication for program information (e.g., Braille, large print, audiotape, etc.) please contact USDA’s 

TARGET Center at (202) 720-2600 (voice and TDD).

Forest Service Disclaimer

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, 

age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, 

political beliefs, reprisal, or because all or part of an individual’s income is derived from any public assistance program. (Not all prohibited 

bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large 

print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write 

USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410, or call (800) 795-3272 (voice) or 

(202) 720-6382 (TDD). USDA is an equal opportunity provider and employer.

Keywords:

Recycled asphalt, recycled asphalt pavement, reclaimed asphalt pavement, RAP, full depth reclamation, stabilization, reclaimed concrete 

aggregate, glass cullet, roofing shingles, wood chips, scrap tires, coal fly ash, blast furnace slag

Abstract

Federal land management agencies recently received instruction and direction through Executive Order 13423 “Strengthening Federal 

Environmental, Energy, and Transportation Management” that required Federal agencies to reduce greenhouse gas emissions and develop 

programs to become more sustainable. Executive Order 13423 identified six areas for lessening environmental impacts; one was waste 

prevention and recycling of materials. In an attempt to address this Executive order, this document provides a variety of tables, references, 

links, and case studies to assist in developing a program to recycle industrial byproduct materials, such as crushed concrete, asphalt, and 

shingles. 

Currently, information is available regarding the use of industrial byproduct materials in construction applications, particularly pavement 

construction and maintenance. This document provides road managers with an easy-to-use toolbox with the basics on using recycled 

materials in construction projects, particularly road construction and maintenance. Also, it provides information on where to find guidance to 

verify that recycled materials are used correctly.

This document provides information on materials if you have a recycling application, or provides information on applications if you have a 

material to use. Table 1-3 provides additional information (references, links, and case studies) for materials or applications. 

The primary audience is road managers for the Forest Service, an agency of the U.S. Department of Agriculture, and other Federal land 

management agencies. The document may be applicable to counties and towns or any agency that manages rural and low-volume roads. 

This publication is the result of a partnership between the Forest Service, National Technology 

and Development Program and the U.S. Department of Transportation, Federal Highway 

Administration, Coordinated Federal Lands Highway Technology Improvement Program.
Reclaimed Materials 

and Their Applications 

in Road Construction: 

A Condensed Guide 

for Road Managers

December 2013

By

Jeffery S. Melton

AECOM, Boston, MA

Maureen A. Kestler

National Technology & Development Center 

San Dimas, CA

v

Introduction

Scope......................................................................................................................................... vii

Outline of the Guide .................................................................................................................. viii

How To Use This Guide ............................................................................................................ viii

Materials and Applications Covered in This Guide.................................................................... viii

Chapter 1–Initial Survey and Introduction of Full Depth Reclamation

Combinations of Applications and Materials .............................................................................. 1

Matrices ...................................................................................................................................... 4

Chapter 2–Recycled Material Applications 

Hot-Mix Asphalt Pavement.........................................................................................................11

Concrete Construction .............................................................................................................. 12

Structural Fills and Embankments ............................................................................................ 13

Road Base and Subbase Layers .............................................................................................. 15

Stabilized Road Base and Subbase Layers.............................................................................. 16

Erosion Control ......................................................................................................................... 17

Full Depth Reclamation (with Stabilization) .............................................................................. 18

Chapter 3–Descriptions of Recycled Materials with Potential Use to Federal Land Management Agencies

Reclaimed (or recycled) Asphalt Pavement .............................................................................. 19

Reclaimed Concrete Aggregate (RCA)..................................................................................... 24

Glass Cullet (Waste Glass)....................................................................................................... 26

Roofing Shingles....................................................................................................................... 27

Wood Chips............................................................................................................................... 29

Scrap Tires................................................................................................................................ 30

Coal Fly Ash.............................................................................................................................. 31

Blast Furnace Slag.................................................................................................................... 34

Conclusions.......................................................................................................................................... 37

Acknowledgments ................................................................................................................................ 37

Appendixes

A–Survey Responses ............................................................................................................... 39

B–Glossary ............................................................................................................................... 40

C–Web sites, References, Specifications ................................................................................. 45

D–Case Studies ........................................................................................................................ 49

Table of Contents

vii

Introduction

Introduction

Executive Order 13423 “Strengthening Federal 

Environmental, Energy, and Transportation 

Management” requires Federal agencies to 

reduce greenhouse gas emissions and develop 

programs to become more sustainable. The 

subsequent Executive Order 13514 “Federal 

Leadership in Environmental, Energy and 

Economic Performance” also requires agencies 

to reduce waste, conserve water and fuel, and to 

develop a greenhouse gas emissions reduction 

target for 2020. 

Executive Order 13423 identified six areas for 

lessening environmental impacts. One area 

was waste prevention and recycling. Federal 

land management agencies and other agencies 

that manage low-volume roads have already 

made strides in waste prevention and recycling 

of paper, plastic, glass, and aluminum. The 

focus of this project is to provide information 

on developing a program to recycle industrial 

byproduct materials, such as crushed concrete, 

asphalt, and shingles. 

Considering that the Federal land management 

agencies own and manage hundreds of 

thousands of miles of roads and tens of 

thousands of buildings, the maintenance and 

decommissioning of these assets will produce 

a significant volume of material, much of it 

recyclable or reusable. Using recycled materials 

in road construction and maintenance is important 

because the agencies have an extensive road 

network to manage, and road construction and 

maintenance require significant volumes of 

construction materials.

Much information is available regarding the use 

of industrial byproduct materials in construction 

applications, particularly pertaining to pavement 

construction and maintenance. This project 

developed a very basic, easy-to-use toolbox 

that provides road managers with the basics of 

recycled materials used in construction projects, 

particularly road construction and maintenance. 

While geared toward the Forest Service and 

the other Federal land management agencies, 

it also is applicable to counties, towns, and any 

agencies that manage rural and low-volume 

roads. 

Scope

At least 20 industrial byproduct material streams 

are used or have been used as material for 

road construction projects. Discussing all of the 

byproduct material streams and all of the possible 

applications is beyond the scope of this project, 

so only those materials that might reasonably 

be used by Federal land management agency 

personnel will be discussed. Also, this is not a 

design manual. The design of roadways and 

other infrastructure is very site specific, and it is 

beyond the scope of this project. Ultimately, it is 

the responsibility of the road manger to ensure 

that the design is done correctly. Therefore, this 

toolbox only provides information on where to 

get guidance to verify that recycled materials are 

used correctly.

INTRODUCTION
viii

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Outline of the Guide

❏ Introduction. 

❏ Chapter 1 discusses combinations of 

materials and applications. 

❏ Chapter 2 provides information and tables 

from an applications perspective. 

❏ Chapter 3 provides information and tables 

from a materials perspective. 

❏ Conclusions.

❏ Appendixes

t Survey responses.

t Glossary of recycled material terms.

t References and links.

t Selected case studies.

Much of the documentation in this report was 

drawn from public domain materials developed 

by the U.S. Department of Transportation, 

Federal Highway Administration (FHWA); the 

Recycled Materials Resource Center (a partner 

laboratory of FHWA); and the U.S. Environmental 

Protection Agency (EPA). The information can be 

downloaded and distributed. Care has been taken 

to limit the use of documents that are not in the 

public domain to encourage the dissemination of 

information.

How To Use This Guide

If you know the material or the application you 

want to use, refer to the tables and figures in 

chapter 1 (figure 1-3 and table 1-3 focus on 

Federal land management agencies). After you 

select the material or application from table 

1-3, go to chapters 2 and 3 to obtain details on 

the materials or applications. Web sites and 

references are provided for further guidance. 

Case studies are provided in the appendixes.

Materials and Applications Covered In 

This Guide

This section describes the process to select the 

recycled materials and applications for inclusion 

in the guide, based on potential use by Federal 

land management agency personnel. The 

selection process was based on the assumption 

that Federal lands generally are farther from 

urban centers and heavy industry, or at least far 

enough that the transportation of materials from 

those locations would be cost prohibitive. 
1

Chapter 1—Initial Survey and Introduction of Full Depth Reclamation

Initial Survey and Introduction 

of Full-Depth Reclamation

During the summer of 2010, the National 

Technology and Development Center of 

the Forest Service, an agency of the U.S. 

Department of Agriculture, distributed an informal 

survey on recycled materials to Forest Service 

representatives. The survey had three goals:

1. To determine what byproduct materials Forest Service representatives were aware of, 

or at least thinking about.

2. To determine how they wanted to use the 

materials.

3. To provide a minimum list of questions and 

issues that could be covered if possible in 

this publication. 

Specific survey responses are available in 

appendix A. Most responses referenced reuse 

of hot-mix asphalt and the use of in-place 

recycling through full-depth reclamation. While 

individual materials and applications for fulldepth reclamation will be addressed, it should 

be noted that in 2005, the U.S. Department of 

Transportation, Federal Highways Administration, 

Federal Lands Highway Division published 

the “Context Sensitive Roadway Surfacing 

Selection Guide” <http://www.cflhd.gov/programs/

techDevelopment/pavement/context-roadwaysurfacing/>, which includes detailed information 

about full-depth reclamation applications on 

Federal lands. A summary is included in chapter 3 

with links to relevant document sections. 

Combinations of Applications and 

Materials

Table 1-1 provides a general list of potential 

applications for recycled materials. While it is 

easy to come up with more than 40 specific 

applications, table 1-1 is limited to only 10 

applications that provide value in terms of 

sustainable practices.

CHAPTER 1
2

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Table 1-1. Basic list of potential uses for recycled industrial materials. Where possible, the materials are linked to 

the “Recycled Materials Resource Center Beneficial User Guidelines” or other sources for application descriptions

Application Links

Bituminous asphalt pavement http://www.recycledmaterials.org/tools/uguidelines/app.

asp#asp

Portland cement concrete pavement http://www.recycledmaterials.org/tools/uguidelines/

app2.asp

Portland cement concrete products http://www.industrialresourcescouncil.org/Applications/

PortlandCementConcrete/tabid/381/Default.aspx

Portland cement manufacturing/

additives

http://www.industrialresourcescouncil.org/Applications/

PortlandCementManufacturing/tabid/384/Default.aspx

Granular base/subbase http://www.recycledmaterials.org/tools/uguidelines/

app3.asp

Embankment or fill http://www.recycledmaterials.org/tools/uguidelines/

app4.asp

Stabilized base/subbase http://www.recycledmaterials.org/tools/uguidelines/

app5.asp

Flowable fill http://www.recycledmaterials.org/tools/uguidelines/

app6.asp

Erosion control http://www.caes.uga.edu/publications/pubDetail.

cfm?pk_id=6296

Agricultural land application http://www.industrialresourcescouncil.org/Applications/

AgriculturalLandApplication/tabid/421/Default.aspx

Table 1-2 lists 20 common industrial byproduct and coproduct materials that have been used in 

construction projects. 
3

Chapter 1—Initial Survey and Introduction of Full Depth Reclamation

Table 1-2. Industrial byproduct and coproduct materials that have been used in construction projects. Where 

possible, the materials are linked to the “Recycled Materials Resource Center Beneficial User Guidelines” or other 

sources for material properties

Materials Links

Reclaimed asphalt pavement http://www.recycledmaterials.org/tools/uguidelines/rap131.asp

Reclaimed concrete aggregate http://www.recycledmaterials.org/tools/uguidelines/rcc1.asp

Waste glass http://www.recycledmaterials.org/tools/uguidelines/wg1.asp

Roofing shingles http://www.recycledmaterials.org/tools/uguidelines/rss1.asp

Compost/wood chips

Scrap tires http://www.recycledmaterials.org/tools/uguidelines/st1.asp

Blast-furnace slag http://www.recycledmaterials.org/tools/uguidelines/bfs1.asp

Coal-fly ash http://www.recycledmaterials.org/tools/uguidelines/cfa51.asp

Coal-bottom ash/boiler slag http://www.recycledmaterials.org/tools/uguidelines/cbabs1.asp

Foundry sand http://www.recycledmaterials.org/tools/uguidelines/fs1.asp

Steel slag http://www.recycledmaterials.org/tools/uguidelines/ssa1.asp

Kiln dusts http://www.recycledmaterials.org/tools/uguidelines/kd1.asp

Flue gas desulfurization material http://www.recycledmaterials.org/tools/uguidelines/fgd1.asp

Baghouse fines http://www.recycledmaterials.org/tools/uguidelines/bd.asp

Mineral processing byproducts http://www.recycledmaterials.org/tools/uguidelines/mwst1.asp

Quarry byproducts http://www.recycledmaterials.org/tools/uguidelines/qbp121.asp

Wastewater treatment plant 

residuals (paper sludge)

http://www.industrialresourcescouncil.org/Materials/

PulpandPaperIndustryMaterials/tabid/368/Default.aspx

Solid waste combustor ash http://www.recycledmaterials.org/tools/uguidelines/mswca1.asp

Sewage sludge ash http://www.recycledmaterials.org/tools/uguidelines/ss1.asp

Nonferrous slags http://www.recycledmaterials.org/tools/uguidelines/nfs1.asp
4

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Matrices

Figure 1-1 shows a basic application/material matrix from the “Recycled Materials Resource Center 

Beneficial User Guidelines” <http://www.recycledmaterials.org/tools/uguidelines/index.asp> (Used with 

permission of the Recycled Materials Resource Center). Figure 1-2 shows a similar matrix developed 

by the Industrial Resources Council <http://www.industrialresourcescouncil.org> that contains additional 

materials and applications. Potential applications are listed across the top, while potential materials are 

listed down the left-hand side. The basic idea is that someone with surplus asphalt or crushed concrete 

could read across to see how this material could be used, or someone looking for sustainable fill 

material could read down and see what materials could be used. 

Asphalt 

concrete 

pavement

Portland 

cement 

concrete 

pavement

Granular 

base

Embankment 

or fill

Stabilized 

base

Flowable 

fill

Baghouse 

fines

x

Blast furnace 

slag

x x x x

Coal bottom 

ash/boiler slag

x x x x

Coal fly ash x x x x x

Flue gas 

desulfurization 

scrubber 

material

x x

Foundry sand x x x x

Kiln dusts x x

Mineral 

processing 

wastes

x x x

Municipal 

solid waste 

combustor ash

x x

Nonferrous 

slags

x x x
5

Chapter 1—Initial Survey and Introduction of Full Depth Reclamation

Asphalt 

concrete 

pavement

Portland 

cement 

concrete 

pavement

Granular 

base

Embankment 

or fill

Stabilized 

base

Flowable 

fill

Quarry 

byproducts

x

Reclaimed 

asphalt 

pavement

x (hot and 

cold)

x x

Reclaimed 

concrete 

material

x x

Roofing 

shingle scrap

x

Scrap tires x (wet 

and dry)

x

Sewage 

sludge ash

x

Steel slag x x

Sulfate wastes x

Waste glass x x

Figure 1-1. Matrix of recycled materials and their potential uses. The x represents a potentially successful 

material/application combination. This matrix is hyperlinked to the original matrix on the Recycled Materials 

Resource Center Web site at <http://www.recycledmaterials.org/tools/uguidelines/index.asp#matrix>. (Used with 

permission of the Recycled Materials Resource Center.) 
6

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers Figure 1-2. A matrix by the Industrial Resources Council <http://www.industrialresourcescouncil.org> that shows additional materials and applications. The colors indicate materials that are produced by different industries. Used with permission of Elizabeth Olenbush of the Industrial Resources Council. The original matrix can be found at: <http://www.industrialresourcescouncil.org/Applications/

IndustrialMaterialsMatrix/EMatrix/tabid/409/Default.aspx>.

Fly ash X X

FDG gypsum x

Bottom ash x

Foundry sands x x x x

Iron foundary slags

Blast furnace slag

x

Slag cement x x x

Steel furnace slag

Reclaimed concrete aggregate

x x

Other

Mine reclaimation

Brownfield remediation

Landfill cover/construction

Soils-based applications, other

Manufactured soils

Agricultural land applications

Building products

Soil stabilization

PCC products

Portland cement manufacturing

Flowable fill

Hot mix asphalt

PCC pavement

Stabilizaed base/subbase

Granular base/subbase

Embankments

Structural fill

APPLICATIONMATERIAL
7

Chapter 1—Initial Survey and Introduction of Full Depth Reclamation

Figure 1-2. A matrix by the Industrial Resources Council <http://www.industrialresourcescouncil.org> that shows additional materials and applications. The colors indicate materials that are produced by different industries. Used with permission of Elizabeth Olenbush of the Industrial Resources Council. The original matrix can be found at: <http://www.industrialresourcescouncil.org/Applications/IndustrialMaterialsMatrix/EMatrix/tabid/409/Default.aspx>. continued

Scrap wood

Dry wall

Asphalt shingles x

Tire derived fuel x

Ground rubber

Waste water treatment residual

x x

Causticizing residues

x

Boiler ash

Other

Mine reclaimation

Brownfield remediation

Landfill cover/construction

Soils-based applications, other

Manufactured soils

Agricultural land applications

Building products

Soil stabilization

PCC products

Portland cement manufacturing

Flowable fill

Hot mix asphalt

PCC pavement

Stabilizaed base/subbase

Granular base/subbase

Embankments

Structural fill

APPLICATION MATERIAL
8

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

The challenge is to reduce these matrices to just 

applications and materials of interest to the Forest 

Service and other Federal land management 

agencies.

To arrive at such a matrix, first consider the 

potential applications based on Federal land 

management agencies’ activities. This thought 

process reduces the list of potential applications 

to: 

❏ Hot-mix asphalt. 

❏ Structural fill/embankments. 

❏ Granular base/subbase layers, stabilized 

base/subbase layers. 

❏ Portland cement concrete. 

❏ Full-depth reclamation. 

In addition, erosion control is not shown in figures 

1-1 or 1-2, but is a growing application and might 

be of interest to road managers who need to 

protect new slopes from erosion.

A similar thought experiment can be applied to 

the recycled materials. Realistically, the materials 

most likely to be generated by Federal land 

management agency activities are reduced to:

❏ Reclaimed hot-mix asphalt. 

❏ Reclaimed concrete. 

❏ Shingles.

❏ Tires.

❏ Scrap wood and brush. 

❏ Waste glass. 

Slag cement is not generated by these agencies, 

but it could be used in new concrete construction 

as part of their sustainability program. Slag 

cement has a fraction (or all) of the Portland 

cement replaced by ground granulated blastfurnace slag. This cement is supported by 

the Environmental Protection Agency as a 

sustainable building material.

Table 1-3 presents a simplified applications/

materials matrix specific to Federal land 

management agency needs. Table 1-3 is the 

basis on which the recycled materials toolbox is 

built.
9

Chapter 1—Initial Survey and Introduction of Full Depth Reclamation

Table 1-3. Applications and recycled materials matrix for use by Federal land management agencies. These materials and applications were chosen based on activities most pertinent to the agencies

Hot-mix 

asphalt

Concrete 

construction

Structural fill /

embankments

Granular 

base /

subbase

Stabilized 

base /

subbase

Full-depth 

reclamation

Erosion 

control

Reclaimed asphalt pavement

• • • • •

Reclaimed concrete

• • • •

Reclaimed shingles

• • • •

Scrap tires •Scrap wood/brush

•

Waste glass • •Slag cement •

With the information obtained from table 1-3, the user can proceed to chapters 2 and 3 for general information about material descriptions and properties, environmental and safety issues, case studies, and references and Web sites with further details and guidance. 

APPLICATIONS

MATERIALS

11

Chapter 2—Recycled Material Applications

Recycled Material Applications

Each application has a separate table. The applications are described, and the materials used for each 

application are discussed.

Table 2-1. Hot-mix asphalt pavement

Description

The Forest Service and other Federal land management agencies tend to use flexible pavement 

designs, which usually include an asphalt surface layer constructed over a compacted granular base 

and subbase. The subbase sits on top of the subgrade, the native soil of the area. Asphalt pavements 

can be constructed using hot-mix or cold-mix asphalt. This summary however focuses on hot-mix 

placement.

Hot-mix asphalt is a mixture of fine and coarse aggregate with asphalt cement binder that is mixed, 

placed, and compacted in a heated condition. The components are heated and mixed at a central 

plant and placed on the road using an asphalt spreader. After placement, it is compacted using rollers 

or similar equipment.

Materials in Hot-Mix Asphalt

The use of recycled asphalt products (RAP) in hot-mix asphalt is a generally accepted practice, with 

roughly 90 percent of the hot-mix asphalt placed in the United States containing some amount of 

RAP. Using RAP in new hot-mix asphalt takes advantage of the aggregate and bituminous binder 

already in the RAP, reducing the need for new asphalt binder and aggregates. The challenge for 

many Federal land management agencies would seem to be finding hot-mix plants near enough to 

units to make hot-mix asphalt recycling cost effective. If asphalt pavement is being milled as part of 

rehabilitation effort, then the milled asphalt can go back to the plant in the trucks that brought the new 

hot-mix asphalt, and it is straightforward to add the millings into new asphalt. It is more challenging to 

use stockpiled RAP sections. The RAP must be free of soil and debris, and then it must be crushed 

and screened before being added to new hot mix. All of these extra steps add to the cost of reusing 

the RAP, and if the hot-mix plant is far away, the transportation costs, fuel burned, and emissions 

produced offset the sustainable benefits of reusing the RAP in hot-mix asphalt. However, if there 

is a hot-mix plant nearby, then putting the old RAP into new hot-mix asphalt is the best use of the 

material.

Much of the same reasoning applies to shingles from decommissioned buildings or roof repairs. Like 

RAP stockpiles, the shingles need to be free of nails, tar paper, wood, and other debris. The shingles 

then need to be ground small enough (0.5 inches or less) to be used in new hot-mix asphalt. Again, 

these steps add cost to reusing the shingles in asphalt, and if the processor and hot-mix plant are 

far away, the environmental benefit is reduced as well. However, if a processer and hot-mix plant are 

nearby, then using shingles in new hot-mix asphalt is the best reuse option.

CHAPTER 2
12

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Table 2-2. Concrete construction

Description

Concrete is almost ubiquitous in modern life, found in everything from sidewalks and post anchors to 

bridges to building foundations. Concrete is made by combining coarse and fine aggregates, water, 

and a cement binder. The water hydrates the cement to form a gel that holds the aggregate together. 

The most common type of cement is Portland cement, which is made by mixing lime with silica, iron, 

and aluminum minerals in a very hot kiln. Most of the lime comes from calcination of limestone, which 

involves applying tremendous heat to the limestone to convert it from calcium carbonate (CaCO3) to 

lime (CaO). The calcination process is very energy intensive and produces about one ton of calcium 

dioxide (CaO2) gas for each ton of cement produced. Concrete can be made more sustainable by 

using recycled materials, such as aggregate, or by using non-Portland type cements as a binder.

Materials in Concrete Construction

The Forest Service does not produce many materials that would be good aggregate for new concrete 

construction. However, there is growing experience showing that old concrete can be crushed and 

reused in new concrete. The old crushed concrete must be free of soil and debris, and also be free of 

distress from alkali-silica reactions to prevent premature failure of the concrete. The crushed concrete 

also has a higher water demand than regular aggregates, so the mix design must be changed 

accordingly. The biggest challenge would seem to be getting the concrete crushed and screened so 

that it meets the size requirements for new concrete aggregate.

Another option for more sustainable concrete is to use slag cement. Slag cement uses ground blastfurnace slag as a substitute for Portland cement, reducing the carbon footprint of the new concrete 

structure. Assuming the agency does not produce slag or slag cement, it could put a notice about the 

use of slag cement in bid documents.
13

Chapter 2—Recycled Material Applications

Table 2-3. Structural fills and embankments

Description

Structural fills and embankments often are used interchangeably. Typically, a structural fill describes 

the use of quality granular materials to fill in a hole or depression to raise the grade, or to create 

a strong, stable base. Structural fills also include backfill behind retaining walls. An embankment 

usually refers to an earthen structure that is used to raise the elevation of a roadway or railway 

above the surrounding area. An example of an embankment is the approach to a bridge, where 

the embankment raises the road to the level of the bridge deck. The structures are usually built by 

compacting sand, gravel, or other earthen materials to some unit weight near the maximum dry unit 

weight in order to achieve certain levels of compressibility and shear strength. An increase in unit 

weight and loss of shear strength due to saturation also are important considerations, so structural 

fills and embankments usually are built with materials that have good drainage properties.

Materials in Structural Fills and Embankments

Structural fills and embankments are good applications for the materials generated by the Forest 

Service and other Federal land management agencies, especially when taking cost and equipment 

requirements into account. Generally, it is argued that placing crushed concrete in embankments and 

fills is not the best use of the material and that it should be used for higher-value applications, such 

as granular-base aggregate. While this is a reasonable argument, it does not take into account the 

specific issues faced by the Federal land management agencies. Aggregate for base layers needs to 

meet specific gradation requirements, so the concrete would need to be crushed and screened. For 

many sites, this would entail transporting crushing and screening equipment some distance to the 

site at significant cost or perhaps transporting the concrete to a crusher and then to the construction 

site at significant cost. In the end, the transportation and processing costs would make using the 

crushed concrete in base applications unfeasible. However, crushed concrete makes a good 

embankment and fill material. Generally, the gradation requirements for these applications are better 

suited for larger aggregate, so the concrete can be crushed with regular construction equipment and 

used without expensive processing. 

A similar situation exists for recycled asphalt products and shingles. Using RAP and shingles in 

embankment and fill applications does not make use of the asphalt binder in these materials. 

However, the cost incurred, energy used, and greenhouse gases produced by transporting RAP 

and shingles from a remote site often outweigh the benefits of processing it and reusing it in hot-mix 

asphalt. In general, the RAP and shingles are broken up and mixed with aggregate and soil to meet 

the gradation requirements of the project. The mixture behaves like a natural granular material with 

the same gradation.

Crushed glass also is an excellent aggregate. It has excellent permeability and has been used as 

aggregate where drainage is very important, such as stormwater control structures. While crushed 

glass can be used by itself as aggregate, it often is difficult to get sufficient volumes of the material, 

so usually it is mixed with other aggregate.

Table 2-3 continued on next page
14

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Old tires can be used in fill and embankments either as whole tires or tire shreds. Tire shreds provide 

an excellent low-density material, typically one-third the weight of gravel, and provide good drainage. 

Usually, the tire shreds are mixed with other materials, or placed in layers separated by aggregate to 

prevent self-ignition of the rubber. It may be difficult and expensive for Forest Service sites to obtain 

a tire shredder, so using whole tires is another option. Typically, the tires are placed on their side in 

flat layers, or tied together in columns, and then filled with compacted soil.

In general, the use of recycled materials for structural fill for embankments is relatively 

straightforward from an engineering point of view, and some materials have guidance documents 

and best practices for their use. However, different sites will have different issues (seismic activity, 

fire danger, nearby surface water, and so forth), and the individual properties of the respective 

recycled materials must be taken into consideration.

Table 2-3 continued from previous page
15

Chapter 2—Recycled Material Applications

Table 2-4. Road base and subbase layers

Description

The Forest Service and other Federal land management agencies typically use flexible pavement 

structures composed of a layer or layers of hot-mix asphalt over unbound layers of granular material. 

The base layer is the load-bearing layer immediately below the asphalt layers and provides strength 

and support to the overlying pavement. The subbase serves as the foundation for the overall 

pavement structure, transmitting traffic loads to the subgrade while providing drainage and frost 

protection. The base and subbase layers are formed by spreading relatively thin layers (about 1-foot 

thick) of aggregate and then compacting it with heavy equipment until the material forms a dense 

layer of interlocking aggregate. Typically, base and subbase materials should last for 20 years or 

more, so they must be strong and durable, and must meet specific gradation requirements.

Base and subbase materials traditionally are sand, gravel, crushed rock, quarry stone, and other 

natural mineral materials that provide the necessary strength and durability. Some areas of the 

country are beginning to suffer from aggregate shortages, or sources of aggregate are now so far 

from construction sites that hauling costs are becoming a significant expense. These factors are 

causing many transportation agencies to use recycled materials as a source of quality aggregate 

while reducing costs. This application deals with stockpiles of RECYCLED ASPHALT PRODUCTS, 

concrete, and other materials that are crushed, screened, and used as aggregate. This is a different 

approach than in situ recycling of an asphalt pavement through full-depth reclamation, which is 

discussed in a following section.

Materials in Road Base and Subbase Layers

While plenty of materials would serve as suitable aggregate for base and subbase layers, the 

increased processing costs may make this application unsuitable except for specific situations. 

The costs of crushing and screening stockpiles of material to obtain the required gradation must be 

balanced against using the materials as structural fill. When the economics work, concrete, recycled 

asphalt products, shingle, and glass stockpiles can be used in base and subbase layers.

When stockpiles of old concrete are crushed, a range of material sizes is produced, which allows 

the concrete to be used as coarse and fine aggregate in base and subbase layers. In general, the 

crushed concrete is mixed with natural aggregates, and is not used as the sole aggregate source. In 

some areas, the best aggregate was used in making old concrete, so recycling the concrete has the 

added benefit of keeping high-quality natural aggregates in use. Similarly, recycled asphalt products 

and shingles contain high-quality aggregates. Recycled asphalt product millings, the small pieces 

of asphalt pavement ground up during resurfacing, can be mixed with natural aggregates and used 

as base material as long as the gradation is met. Shingles and chunks of recycled asphalt products 

must be ground or crushed first, and then mixed with other aggregates to meet the gradation 

requirements.

Table 2-4 continued on next page
16

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Crushed glass also has been used in subbase applications, mixed with natural aggregates. 

One issue with crushed glass is that it can be difficult to obtain enough material to meet the job 

requirements, so glass is often used on small projects.

In general, the construction practices are the same when using recycled materials in base and 

subbase applications, though adjustments may be needed. For instance, the presence of crushed 

concrete will usually increase the amount of water needed to compact the aggregate. However, a 

number of guidance documents are available that discuss these issues.

Table 2-5. Stabilized road base and subbase layers

Description

Usually, the base and subbase layers of flexible pavement systems the Forest Service uses are 

made of compacted granular material. However, the properties of these pavement layers can be 

improved by adding a binder, such as lime, cement, Class C coal fly ash, or Class F coal fly ash and 

lime. The increased construction cost from using the binder is offset by reduced maintenance costs, 

and possibly a reduced need for hot-mix asphalt. Stabilized layers describe layers built during new 

construction or complete reconstruction. In such cases the materials are mixed with the binder (and 

water if needed) and then placed, graded, and compacted. Stabilized base layers also can be formed 

through full-depth reclamation when binder is added to the reclaimed pavement material; however 

this technique is described in a later section. Stabilizing the base and subbase layers is not an 

inherently sustainable practice, but there are methods that can be used to improve its sustainability.

Materials in Stabilized Road Base and Subbase Layers

Recycled asphalt pavement (RAP), concrete, and shingles can be used for regular granular base 

and subbase layers, though this is not really an improvement over the unbound layers in terms of 

sustainability. However, some sites may be near a coal burning power plant, then use coal-fly ash 

as a binder. Class C coal-fly ash, typically found in the Western United States, can be used by itself 

as the binder because of its cementitious properties. Class F coal-fly ash (typically Eastern United 

States) can be used as a pozzolanic admixture in combination with lime or with cement as the binder. 

Using coal-fly ash in this way has fairly broad support as a beneficial use of the material and it does 

not seem that it will be affected by upcoming changes in Environmental Protection Agency (EPA) 

policy. In addition, slag cement can be used as the binder for stabilized base and subbase layers. 

Slag cement substitutes some or all of the Portland cement with blast-furnace slag. The use of slag 

cement is supported by the EPA as a way to reduce greenhouse gas levels. Again, using fly ash or 

slag cement is very site specific, and lands far from sources of ash and slag cement will not see a 

benefit from using them because of the transportation costs and emissions.

Table 2-4 continued from previous page
17

Chapter 2—Recycled Material Applications

Table 2-6. Erosion control

Description

Road construction or rehabilitation often can result in the creation of new earthen slopes on the 

construction site. Typically, these slopes are seeded to promote plant growth, which stabilizes the 

slope and prevents erosion during rain events. However, seeding often is one of the last things done 

during construction, so until seeding, the new slopes are at risk of erosion. One successful technique 

for preventing erosion during construction is to use shredded brush and trees as mulch on the slope. 

This mulch is not meant to be a decorative final product, like uniform colored bark mulch, but is 

rather simply an erosion control treatment. It is spread on the slope to protect the slope from rain 

and to minimize the formation of preferential flow pathways across the slope. As the project finishes 

up, the shredded brush is mixed into the slope soil as an organic amendment, and the final seeding 

takes place.

Materials in Erosion Control

As a result of maintenance operations, the Forest Service and other Federal land management 

agencies have access to brush, limbs, trees, and other woody material. Shredding woody material 

and using it for erosion and sedimentation control is a very sustainable practice because it prevents 

erosion of earthen structures and adverse impacts on surface waters due to sedimentation, and it is 

a source of nutrients for newly seeded areas.
18

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Table 2-7. Full-depth reclamation (with stabilization)

General Information

Full-depth reclamation (FDR) is a rehabilitation technique in which the full thickness of the asphalt 

pavement and predetermined portion of the underlying materials (base and, sometimes, subbase) 

are uniformly pulverized and blended to provide an upgraded, homogenous base material. The 

reclaimed layer is then compacted to provide a uniform platform for the asphalt base course or 

surface course. FDR is an in situ process without heat. Stabilizing additives can be applied to 

enhance the properties of the reclaimed layer.

Three different types of stabilization can be used: bituminous (using emulsified asphalt or foamed 

asphalt); chemical (using Portland cement, hydrated lime, cement kiln dust, or lime kiln dust); and 

mechanical (using new granular material, recycled asphalt pavement, or crushed Portland cement 

concrete). FDR with mechanical, bituminous, and foamed asphalt stabilizations are covered in detail 

in separate product summaries.

Full-depth stabilized layers commonly are overlaid with hot asphalt concrete pavement or covered 

with chip seals.

FDR material has been used as a temporary road surfacing, but generally is not used as a 

permanent surfacing.

NOTE: This text was modified from the section on FDR in the Federal Highways Administration 

Federal Lands Highway Division publication “Context Sensitive Roadway Surfacing Selection 

Guide” <http://www.cflhd.gov/programs/techDevelopment/pavement/context-roadway-surfacing/>. 

The section on FDR can be found at <http://www.cflhd.gov/programs/techDevelopment/pavement/

context-roadway-surfacing/documents/context5-append-a8.pdf>. 

Modified and used with permission of Mike Voth, pavement and materials technical leader, Federal 

Lands Highway Division.

Materials in Full-Depth Reclamation

Many of the survey responses were related to the reuse of old asphalt pavement in base and 

subbase applications. FDR is a potentially cost-effective way to reuse asphalt pavement. Recycled 

asphalt pavement is often taken back to a central hot-mix asphalt plant where it is added in to new 

hot-mix asphalt. However, the hot-mix plant has to be relatively close to make the process cost 

effective. The Forest Service has the challenge of its units often being at some distance from a hotmix plant, so trucking old recycled asphalt products back and forth becomes expensive. The same 

may apply for other Federal land management agencies. When using FDR, the old asphalt is put 

directly into the base, reducing the need for new aggregate while at the same time providing a good 

foundation for the new hot-mix asphalt. In addition, using an asphalt emulsion as the binder will 

take advantage of the binder in the recycled asphalt pavement to provide better performance. It can 

be expensive to mobilize an FDR train if the unit is remote, so the technology is best used on big 

projects, on the order of miles, to make it cost effective.
19

Chapter 3—Descriptions of Recycled Materials with Potential Use to Federal Land Management Agencies

Descriptions of Recycled Materials with Potential Use to Federal 

Land Management Agencies 

A separate table is provided for each material. Materials are described and applications are discussed.

Table 3-1. Reclaimed (or recycled) asphalt pavement

General Information

Material Name(s): Reclaimed Asphalt Pavement (RAP), Recycled Asphalt Pavement, Recycled 

Asphalt Concrete

Description: Reclaimed asphalt pavement (RAP) is the material removed from bound bituminous 

pavement layers. RAP is generated when asphalt pavements are removed for reconstruction, 

resurfacing, or utility work. Asphalt pavement generally is removed either by milling or full-depth 

removal. Milling uses grinders to remove the upper layers of the asphalt pavement and typically is 

done prior to rehabilitation work on the asphalt part of the pavement structure. Full-depth removal 

describes removal of the whole asphalt pavement down to the base course. Bulldozers or front-end 

loaders break the pavement structure into manageable slabs and then load them into trucks, which 

transport the pavement to a reprocessing site for crushing and sizing.

RAP may be stockpiled by millings or slabs, or may be stockpiled by project. Large quantities of RAP 

from single projects are kept separate because once the RAP is processed it will provide consistent 

stone gradation, quality, asphalt content, and asphalt characteristics. However, it is more common 

that smaller amounts of RAP from various sites are stored in common piles before crushing and 

blending. The RAP is then crushed down to the largest aggregate size. This allows for the creation of 

a consistent product from various sources. Experience has demonstrated that with thorough blending 

and crushing, RAP with a consistent stone gradation and asphalt content can be manufactured from 

multiple-source stockpiles. Care should be taken when stockpiling RAP as it can “reaggomerate,” 

forming large chunks that are hard to process.

Although the majority of old asphalt pavements are recycled at central processing plants, asphalt 

pavements may be pulverized in place using a self-propelled pulverizing machine. This is known 

as full-depth reclamation. The pulverized material can be compacted as is, or it can be mixed with 

cement, lime, or asphalt emulsions as a stabilization agent prior to compaction.

National Asphalt Pavement Association Asphalt Recycling and Reclaiming Association

5100 Forbes Boulevard # 3 Church Circle, Suite 250

Lanham, MD 20706-4413 Annapolis, MD 21401

<http://www.hotmix.org/> <http://www.arra.org/>

CHAPTER 3

Table 3-1 continued on next page
20

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Applications

Milled or crushed RAP can be used in many highway construction applications. These include its 

use as an aggregate substitute and asphalt cement supplement in recycled asphalt paving (hot-mix 

recycling), as a granular base or subbase, stabilized base aggregate, or as an embankment or fill 

material.

Hot-Mix Asphalt Aggregate and Asphalt Cement Supplement

Recycled asphalt pavement can be used as an aggregate substitute material in new hot-mix asphalt. 

However, in this application it provides an additional asphalt cement binder, thereby reducing 

the demand for asphalt binder in the mix. In hot-mix recycling, the RAP usually is processed at a 

central facility where crushers, screening units, conveyors, and stackers produce and stockpile a 

finished granular RAP product processed to the desired gradation. This product is then added to 

hot-mix asphalt paving mixtures as an aggregate substitute. Batch plants and drum-mix plants can 

incorporate RAP into hot-mix asphalt and deliver it to the site.

Granular Base Aggregate

To produce a granular base or subbase aggregate, RAP must be crushed, screened, and blended 

with conventional granular aggregate, or reclaimed concrete material. Blending granular RAP

is necessary to attain the bearing strengths needed for most load-bearing unbound granular 

applications. RAP by itself may exhibit a somewhat lower bearing capacity than conventional 

granular aggregate bases.

Embankment or Fill

Stockpiled RAP material (figure 3-1) also may be used as a granular fill or base for embankment 

or backfill construction, although it is not the most suitable use. However, it may be an alternative 

for material that has been stockpiled for a considerable time period, or commingled from several 

different project sources, or used as an embankment base or fill material within the same right of 

way.

Table 3-1 continued from previous page
21

Chapter 3—Descriptions of Recycled Materials with Potential Use to Federal Land Management Agencies

\

Figure 3-1. Ripped-up asphalt stockpiled in a quarry (Al Watson, Sequoia National Forest).
22

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Stabilized Base Aggregate

To produce a stabilized base or subbase aggregate, RAP also must be crushed and screened, then 

blended with one or more stabilization reagents so that the blended material, when compacted, will gain 

strength.

Relevant Physical Properties

Type of Property RAP Property Typical Range of Values

Physical properties Unit weight 1,940-2,300 kg/m3 

(120-140 lb/ft3)

Moisture content Normal: up to 5% 

Maximum: 7-8%

Asphalt content Normal: 4.5-6% 

Maximum Range: 3-7% 

Asphalt penetration Normal: 10-80 at 25 °C (77 °F) 

Absolute viscosity or recovered 

asphalt cement

Normal: 4,000-25,000 poises at 

60 °C (140 °F) 

Mechanical properties Compacted unit weight 1,600-2,000 kg/m3 

(100-125 lb/ft3 )

California bearing ratio (CBR) 100% RAP: 20-25% 

40% RAP and 60% Natural 

Aggregate: 150% or higher 
23

Chapter 3—Descriptions of Recycled Materials with Potential Use to Federal Land Management Agencies

Environmental and Safety Information

Asphalt pavement consists of aggregate- and petroleum-derived asphalt binder containing volatile 

and semivolatile constituents (e.g., polycyclic aromatic hydrocarbons (PAHs)). Additionally, the 

asphalt pavement roadway may contain surface treatments, rubberized materials, or contaminants 

from vehicles or other emissions (e.g., historically lead). The environmental issues are different for 

RAP based upon various beneficial uses. For bound applications, such as RAP in hot-mix asphalt, 

research into the difference in emissions has not been conducted. For unbound applications, 

leachability from the RAP also may be a concern. This same leachability would be a concern if 

RAP was stockpiled or stored and exposed to precipitation. A project in Florida tested the leaching 

volatile organic compounds (VOCs), PAHs, and heavy metals; results were below the detection 

limit and below the applicable State regulatory groundwater guidance concentrations. This indicates 

that all RAP samples tested pose minimal risk under current waste policy in Florida. Other batch 

and column leaching tests were completed on RAP, which also found constituents leached were 

low and generally below European drinking water standards (The Drinking Water Directive, Council 

Directive 98/83/EC) (14). Additionally, the University of Minnesota completed a review of current 

literature on PAHs in asphalt pavement concluding that PAH concentrations depend on the type of 

pavement (coal-tar versus petroleum based). Petroleum-based asphalt pavement contained PAHs at 

concentrations below Minnesota Pollution Control Agency human health risk clean-up levels (15). The 

only exceedance was when PAHs were converted to benzo(a)pyrene equivalents, they could exceed 

the lowest limit (Tier I). The report further concluded that when RAP is used as subbase aggregate, 

it is mixed with soils or other aggregates that do not contain PAH, so this mixture would not likely 

exceed applicable limits.
24

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Table 3-2. Reclaimed concrete aggregate (RCA)

General Information

Material Name(s): Reclaimed Concrete Aggregate, Recycled Concrete Aggregate (RCA)

Description: RCA is generated through the demolition of concrete elements, such as roads, 

runways, and structures during road reconstruction, utility excavations, or demolition operations. The 

Forest Service does not have many concrete roads and runways, but concrete also can come from 

foundations, footings, sidewalks, curbing, and so forth. Concrete sidewalks and driveway sections 

may have steel reinforcements, while heavy concrete elements like roads or foundations usually 

will have steel. Usually, the RCA is removed with a backhoe or payloader and is loaded into dump 

trucks for removal. The concrete may need to be broken into manageable sizes with a hammer 

before loading. The RCM excavation may include 10 to 30 percent subbase soil material and asphalt 

pavement. Therefore, the RCA is not concrete, but a mixture of concrete, soil, rock, and perhaps brick 

and bituminous concrete.

The excavated concrete that will be recycled may be hauled to a central facility for stockpiling and 

processing or processed onsite using a mobile plant. During crushing and screening, ferrous metal 

recovery operations occur. Present crushing systems, with magnetic separators, are capable of 

removing reinforcing steel without much difficulty. However, welded wire mesh reinforcement may be 

difficult to remove.

Construction Materials Recycling Association

P.O. Box 122

Eola, IL 60519

<http://www.cdrecycling.org>.

<http://www.concreterecycling.org>.

Applications

The use of RCM as an aggregate substitute in pavement construction is well established and 

includes its use in granular and stabilized base, engineered fill, and Portland cement concrete 

pavement applications. Since the volume of material is expected to be somewhat limited, it most 

likely that Forest Service concrete will be used in fill applications.

Although the use of RCA in embankments or fills may not make the best use of the high-quality 

aggregates associated with RCA, where no other applications are readily available, RCA can be 

used satisfactorily. RCA aggregates are considered by many specifying agencies to be conventional 

aggregate. It requires minimal processing to satisfy the conventional soil and aggregate physical 

requirements for embankment or fill material. The lower compacted unit weight of RCA aggregates 

compared with conventional mineral aggregates results in higher yield (greater volume for the same 

weight), and is therefore economically attractive to contractors. In addition, for large reconstruction 

projects, onsite processing and recycling of RCA is likely to result in economic benefits through 

reduced aggregate hauling costs.
25

Chapter 3—Descriptions of Recycled Materials with Potential Use to Federal Land Management Agencies

Physical and Mechanical Properties

Property Value

Los Angeles abrasion loss (ASTM C131), (%) 

— Coarse particles 20-45 (6,1)

Magnesium sulfate soundness loss ASTM C88), (%) 

— Coarse particles 

— Fine particles

4 or less (6,1,8) 

less than 9 (9)

California bearing ratio (CBR), (%)* 94 to 148 (1,8)

 * Typical CBR value for crushed limestone is 100 percent.

Environmental and Safety Information

For RCA, environmental considerations have focused on the leaching of high pH changes from 

porewater from concrete. Ohio Department of Transportation research concluded that using RCA 

as an aggregate base in low lying or wet areas where alkaline runoff likely would occur could have 

an adverse effect on the environment (1). An Iowa report found that the high pH of the drainage 

water from RCA use can kill or impede grass growth at a drain outlet (2). Texas also has completed 

research in using RCA in mechanically stabilized earth (MSE) berms that involved thorough material 

characterization, pH measurements, and an evaluation of use (3,4). They concluded that pH and 

resistivity specifications for MSE wall backfill materials should be waived for crushed concrete, 

concrete structures that have suffered sulfate attack should not be crushed and used as backfill in 

MSE walls, and MSE walls with crushed concrete backfill should include adequate drains and high 

permittivity filter fabrics behind the wall to avoid drainage problems (4). The potential for pH and 

drainage issues leads some jurisdictions to require that RCA stockpiles be separated (a minimum 

distance) from water courses.

References

1. Ohio Department of Transportation. Recycled materials report, box test. <http://www.dot.state.

oh.us/testlab/In-House-Research/boxtest1.pdf>.

2. Steffes, R. 1999. Laboratory study of the leachate from crushed Portland cement concrete base 

material. Des Moines, IA: Iowa Department of Transportation. <http://www.operationsresearch.dot.

state.ia.us/reports/reports_pdf/mlr/reports/mlr9604.pdf>.

3. Rathje, E.M.; Rauch, A.F.; Folliard, K.J.; Trejo, D.; Little, D.; Viyanant, C.; Ogalla, M.; Esfelle, 

M. 2001. Recycled asphalt pavement and crushed concrete backfill: state-of-the-art review and 

material characterization. Austin, TX: Texas Department of Transportation, Center for Transportation 

Research, University of Texas, Austin. <http://www.utexas.edu/research/ctr/pdf_reports/4177_1.pdf>

4. Rathje, E.; Rauch, A.; Trejo, D.; Folliard, K.; Viyanant, C.; Esfellar, M.; Jain, A.; Ogalla, M. 2006. 

Evaluation of crushed concrete and recycled asphalt pavement as backfill for mechanically stabilized 

earth walls. Austin, TX: Texas Department of Transportation, Center for Transportation Research, 

University of Texas, Austin. <http://www.utexas.edu/research/ctr/pdf_reports/0_4177_3.pdf>.
26

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Table 3-3. Glass cullet (waste glass)

General Information

Material Name(s): Glass Cullet, Cullet, Waste Glass, Glass Sand, Glass Gravel

Description: Glass is a product of the supercooling of a melted liquid mixture of sand (silicon 

dioxide) and soda ash (sodium carbonate) to a rigid condition in which the supercooled material does 

not crystallize and retains the organization and internal structure of the melted liquid. When waste 

glass is crushed to sand-like particle sizes, similar to those of natural sand, it exhibits properties of 

an aggregate material.

In many localities, it is not cost effective to separate glass containers by color to make new glass, so 

all of the glass is stockpiled together. Furthermore, the glass usually contains plastic, metal, paper, 

and dirt contaminants. Crushing and screening the stockpiled glass removes many contaminants and 

provides a useful construction material. Glass gradation can vary widely depending on the crushing 

and screening process. It ranges in size from fine sand to inches. It is often difficult to get enough 

crushed glass to use as aggregate in a fill application, so it is usually mixed with natural aggregates 

to meet the gradation and volume requirements of the project.

Applications

Glass containers collected from Forest Service visitor centers or administrative buildings could 

be stockpiled until the volume is large enough to justify hiring a contractor to crush and screen 

the material. Once the material is crushed, it could be used as fill material, or mixed with natural 

aggregate and used as base-course material. See American Association of State Highway and 

Transportation Officials M318 for guidance on using glass in base applications.

Environmental and Safety Information

Most hazards arising from the use of glass result from what was in the container, not the glass itself. 

Clean crushed glass is essentially colored sand and is safe.

References

1. American Association of State Highway and Transportation Officials. 2009. Standard specification 

for materials: M 318-01, “Standard specification for glass cullet use for soil-aggregate base course.” 

(2002), Part 2 Specifications, 14th Edition. Washington, DC: American Association of State Highway 

and Transportation Officials.
27

Chapter 3—Descriptions of Recycled Materials with Potential Use to Federal Land Management Agencies

Table 3-4. Roofing shingles

General Information

Material Name(s): Scrap Shingles, Post-Consumer Shingles, Torn-Off Scrap Shingles (TOSS), 

Recycled Asphalt Shingles (RAS)

Description: Approximately 11 million tons of asphalt roofing shingle scrap is generated each year 

in the United States. The scrap shingle can be divided into two groups: tear-off roofing shingles 

(TOSS) and roofing shingle tabs, also called manufacturer shingle scrap. TOSS is generated during 

the demolition or replacement of existing roofs, while roofing shingle tabs are generated when new 

asphalt shingles fail quality control specifications. 

Because Forest Service units are far from most shingle manufacturers, it would not be cost effective 

to use manufacturer-scrap shingles. However, shingles could be collected from Forest Service 

buildings that are being reroofed or decommissioned. The quality of tear-off roofing shingles can 

vary. Tear-off roofing shingles may contain debris, such as nails, wood, paper, and plastic, that is 

removed through processing. The aggregate in scrap shingles can be lost in the weathering process 

that occurs during the service period. As a result, tear-off scrap may contain more than 30 percent 

asphalt by weight. The aged binder in tear-off roofing scrap also may be hard or even brittle, but a 

tear-off shingle is easier to shred than factory scrap. Shingles can be recycled in hot-mix asphalt 

because of the asphalt binder; the shingles also can be used as fill material.

Construction Materials Recycling Association

P.O. Box 122

Eola, IL 60519

<http://www.shinglerecycling.org>.

Applications

The best use of old shingles is to mix them into new hot-mix asphalt (figure 3-2). In many ways, 

shingles have the same effect on hot-mix asphalt as RAP. The use of recycled shingles in hot-mix 

asphalt typically will improve rutting resistance, but may cause lower fatigue resistance and a lower 

low-temperature cracking resistance. Using a softer virgin binder, the fatigue and low-temperature 

performance challenges of the mix can be improved.

TOSS is easier to shred than factory scrap because the binder has aged and become brittle. Early 

recyclers used wood chippers to shred the shingles, but the hard aggregate quickly wore out the 

teeth. However, there are now a number of specialized shingle shredders that will quickly break 

up the shingles into a useful size. Also, because the TOSS has hardened with age, it is unlikely to 

agglomerate during processing. The debris that contaminates tear-off roofing shingle scrap can be 

removed effectively. Nails are removed with magnets; paper and other lightweight contaminants 

are removed with blowers or vacuums. The shingle chips can then be added to hot-mix asphalt. 

However, the Forest Service unit should consider whether grinding the shingles and sending them to 

a hot-mix plant is the most cost-effective option.

Table 3-4 continued on next page
28

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

The cost of transporting and processing shingles can be prohibitive, so there is an increasing amount 

of work focusing on shingles as fill material. In this application, it is treated much like RAP, breaking 

it down to a manageable size and mixing it with natural materials to form a fill material with the 

appropriate gradation.

Environmental and Safety Concerns

Asbestos content in tear-off roofing shingles continues to be a concern for regulators. The California 

Integrated Waste Management Board reported that the total asbestos content in asphalt shingles 

manufactured in 1963 was 0.02 percent and in 1977 it had dropped to 0.00016 percent. However, the 

Georgia Department of Transportation reported that asbestos was used in roofing shingles as late as 

the 1980s. The Iowa Department of Transportation states that the use of asbestos in roofing shingles 

was discontinued after 1973. The Iowa Department of Transportation also conducted a study on 

the asbestos content of roofing shingles. From 368 shingle samples analyzed, only 3 contained 

asbestos, 0.8 percent.

One issue often overlooked with grinding the shingles is that the aggregate dust also can be harmful, 

even without the asbestos, so workers need to use appropriate safety equipment to avoid silicosis. 

1. Receiving

We receive tear-off shingle material from roofers and contractors. Asphalt shingle waste contains 

roughly 20% - 30% asphalt cement (asphalt binder). The material must be free of contaminants 

such as flashing, wood and plastic wrappers to ensure a high quality end product. For an additional 

charge, we will clean up any contaminated loads on site to ensure everything we receive will be 

recycled.

2. Processing

With the exclusive rights to the most technologically advanced shingle grinding equipment available, 

we have the ability to grind shingles faster and cleaner, without any waste byproduct. This means 

that unlike every other processor, 100% of the shingle material that we receive will be recycled. The 

nails are also automatically removed utilizing a built in magnetized separator. The nails collected are 

also recycled. We have the ability to process at rates exceeding 60 metric tons per hour.

3. Raw Product

Shingle waste is ground into clean 1/2” minus crumble ready for recycling. We adhere to strict 

guidelines for cleanliness to ensure a superior product to the end user. The clean crumble is then 

shipped to asphalt manufacturers to be used in their hot mix production.

4. End Result

Clean crumble is added to the asphalt hot mix which is used in paving roads. As much as 5% can 

be used to produce high quality asphalt for highways and high-traffic public roadways. Higher 

percentages can be used for private paving projects such as parking lots or driveways. Utilizing 

asphalt crumble not only reduces production costs, but also reduces the quantity of virgin resources 

that would otherwise be used in the production process. Adding crumble to the asphalt creates a 

superior product that is more durable and has a longer lifespan.

Figure 3-2. Recycled shingles. (Shane Ducholke, Environmental Processors) <http://www.

environmentalprocessors.com>.

Table 3-4 continued from previouspage
29

Chapter 3—Descriptions of Recycled Materials with Potential Use to Federal Land Management Agencies

Table 3-5. Wood chips

General Information

Material Name(s): wood chips, mulch, shredded brush

Description: Maintenance operations near roadways often result in brush being cut. Brush has to 

be kept clear of fire stands, signs, and stormwater structures. In addition, storms can bring down 

trees and tree limbs, which must be cleared. The brush and limbs are often fed through a chipper to 

make the material manageable. There is new interest in using shredded or chipped brush as erosion 

control.

To be clear, the shredded brush, sometime called mulch, is not the same as the decorative bark 

mulch used for landscaping. Shredded brush is not particularly attractive, and is not to be used as a 

permanent landscaping feature.

Applications

When a new soil slope is created, or a new cut is exposed, these structures are at risk for erosion 

until they can be seeded. One option for preventing erosion during construction is to use shredded 

brush and trees as mulch on the slope. The shredded brush is simply spread on the slope to protect 

it from rain and to minimize the formation of preferential flowpaths across the slope. When the project 

is finished, the shredded brush is mixed into the slope soil as an organic amendment, and the final 

seeding takes place. So the wood chips serve two purposes, erosion control and nutrition for future 

plants.

Environmental and Safety Concerns

Studies have found no adverse effects on the soil or subsequent plants when the wood chips are 

tilled into the ground.
30

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Table 3-6. Scrap tires

General Information

Material Name(s): Chipped Tires, Shredded Tires, Ground Tire Rubber, Crumb Tire Rubber, TireDerived Aggregate (TDA)

Description: A typical scrapped automobile tire weighs 9.1 kilograms (kg) (20 pounds (lb)). Roughly 

5.4 kg (12 lb) to 5.9 kg (13 lb) consists of recoverable rubber, composed of 35 percent natural rubber 

and 65 percent synthetic rubber. A typical truck tire weighs 18.2 kg (40 lb) and contains from 60 to 70 

percent recoverable rubber. Rubber, and rubber tires, have very unique civil engineering properties 

and can be used safely in civil engineering applications. The tires can be utilized whole, slit in half, 

shredded, or reduced to a powder as crumb rubber. Given the number of tires generated by the 

Forest Service, it is likely that whole tires would be the most practical.

Rubber Manufacturers Association

1400 K Street, NW, Suite 900 

Washington, DC 20005

<http://www.rma.org/scrap_tires/>

Applications

Whole tires have been used to construct retaining walls. They also have been used to stabilize 

roadside shoulder areas and provide channel slope protection. For each application, whole tires are 

stacked vertically. Adjacent tires are then clipped together horizontally, and metal posts are driven 

vertically through the tire openings and anchored into the underlying earth as necessary to provide 

lateral support and prevent later displacement. Each tire layer is filled with compacted earth backfill. 

This construction technique was first used in California.

Environmental and Safety Information

Early on, there were some instances where buried shredded tires caught fire. This was due to selfignition because of the thickness of the layer. Another fire was caused by spilled fuel on the tires. 

Spreading the tires out and filling them with soil will prevent self-ignition.
31

Chapter 3—Descriptions of Recycled Materials with Potential Use to Federal Land Management Agencies

Table 3-7. Coal fly ash

General Information

Material Name(s): Coal Fly Ash (CFA)

Description: Usually, fly ash is derived from burning pulverized coal in a coal-fired boiler to generate 

electricity. It gets its name from the fact that it is a powdery ash that “flies away” in the exhaust gases, 

where it is captured using electrostatic precipitators, baghouses, or mechanical collection devices, 

such as cyclones.

Fly ash that is produced from burning older, harder anthracite or bituminous coal typically is 

pozzolanic and is referred to as a Class F fly ash if the ash meets the chemical composition and 

physical requirements specified in American Society for Testing and Materials C618 (1, 2). Class F 

fly ash generally contains less than 10 percent material reported as lime (CaO). Although possessing 

pozzolanic properties, the glassy silica and alumina of Class F fly ash require a cementing agent, 

such as Portland cement, quicklime, or hydrated lime, with the presence of water to react and 

produce calcium silicate hydrates (cementitious compounds).

Fly ash that is produced from the burning of younger lignite or subbituminous coal, in addition to 

having pozzolanic properties, also has self-cementing properties (ability to harden and gain strength 

in the presence of water) (2). When this fly ash meets the chemical composition and physical 

requirements outlined in ASTM C618, it is referred to as a Class C fly ash. Class C fly ash typically 

contains between 15 and 35 percent material reported as lime (CaO) (1). Most Class C fly ashes 

have self-cementing properties.

American Coal Ash Association (ACAA)

15200 E. Girard Avenue, Suite 3050

Aurora, CO 80014-3955

<http://www.acaa-usa.org/>

Coal Combustion Products Partnership (C2P2)

Office of Solid Waste (5305P)

1200 Pennsylvania Avenue, NW

Washington, DC 20460

http://www.epa.gov/epaoswer/osw/conserve/c2p2/

index.asp>

AASHTO Center for Environmental Excellence

444 North Capitol Street, Suite 249, NW

Washington, DC 20001

202-624-5800

<http://environment.transportation.org/>

Electric Power Research Institute (EPRI)

3412 Hillview Road

Palo Alto, CA 94304

<http://my.epri.com/>

Table 3-7 continued on next page
32

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Applications

It is unlikely that a Forest Service unit will be sufficiently close to a coal-burning power plant that 

produces enough CFA to justify transporting the material and using it as bulk fill. However, lesser 

quantities of CFA can be used as a soil stabilizer or as an amendment for Portland cement.

Fly ash has been used as a cement and mineral admixture in Portland cement concrete (PCC) for 

nearly 70 years. Approximately 50 percent of recycled fly ash is used in the production of concrete 

and concrete products, making it the largest single use of fly ash (3). Adding CFA to cement 

generally results in a denser, more durable concrete, and the pozzolanic effect leads to enhanced 

long-term strength. In addition, like blast-furnace slag, using CFA as a cement admixture reduces the 

carbon footprint of the project.

Note: It is important to know which class of CFA is available, since Class C and Class F have very 

different properties. See FHWA’s booklet “Fly Ash Facts for Highway Engineers” at <http://www.fhwa.

dot.gov/PAVEMENT/recycling/fatoc.cfm>. (2)

Stabilized bases or subbases are mixtures of aggregates and binders, such as Portland cement, 

which increase the strength, bearing capacity, and durability of a pavement substructure. Because fly 

ash may exhibit pozzolanic properties or self-cementing properties; fly ash can be part of the binder 

in stabilized base construction applications. Results from laboratory and field studies have shown 

that fly ash can be used in stabilized bases or subbases, and those stabilized layers can be included 

in flexible pavement designs. Again, it is important to know what type of CFA is being used, since 

Class F CFA requires the addition of lime for the solidification process to take place.

Environmental and Safety Information

A concern with fly-ash use is the possibility of groundwater contamination by trace elements that 

are associated with coal-combustion byproducts. The possibility for trace elements to dissolve 

in rainwater that percolates through fly ash has caused restrictions on fly ash use by State 

environmental regulations.

When fly ash is used in concrete, the potential for leaching of trace elements is very low. This is 

due to the constituents of fly ash being encapsulated in the matrix of the concrete. It is less clear 

about CFA used for stabilization. While soil stabilization is a bound application, it also is subjected 

to rainwater and occasional flooding, which is a concern for leaching. The Environmental Protection 

Agency is currently reworking their rule on the use of CFA in different applications, which should 

provide more guidance on the use of CFA for soil stabilization.

Fly ash can cause a dust problem during placement. Workers involved with dry-ash handling should 

take precautions by wearing safety goggles to protect their eyes from dust, and by wearing a suitable 

particulate respirator (i.e., approved by the National Institute for Occupational Safety and Health for 

particulates). Dust problems can be partially alleviated by compaction and covering of the fly ash, 

moistening fly ash during placement, and using mechanical ventilation or extraction in areas where 

dust could escape into the workplace. Special lay-down trucks exist that reduce dusting issues.

Table 3-7 continued from previous page

Table 3-7 continued on next page
33

Chapter 3—Descriptions of Recycled Materials with Potential Use to Federal Land Management Agencies

References

1. ASTM C618-05. 2005. Standard specification for fly ash and raw or calcined natural pozzolan for 

use as mineral admixture in Portland cement concrete. In: Annual book of ASTM standards. West 

Conshohocken, PA: ASTM.

2. U.S. Department of Transportation, Federal Highway Administration. 2003. Fly ash facts for 

highway engineers. FHWA-IF-03-019. Washington, DC: U.S. Department of Transportation, Federal 

Highway Administration.

3. American Coal Ash Association. 2007. Coal combustion product (CCP) production and use. 

Aurora, CO: American Coal Ash Association.

Table 3-7 continued from previous page
34

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Table 3-8. Blast furnace slag

General Information

Material Name(s): Blast-Furnace Slag (BFS), Ground Granulated Blast-Furnace Slag (GGBFS)

Description: Blast-furnace slag is a coproduct from the blast-furnace production of iron. A coproduct 

is a material that is required for the production of another material (iron), while having its own intrinsic 

values. This is different than a byproduct material, which is an undesirable material with no intrinsic 

value. Iron is produced by heating iron, iron ore, iron scrap, and fluxes (limestone and/or dolomite) in 

a blast furnace along with coke for fuel. The coke is combusted to produce carbon monoxide, which 

reduces the iron ore to a molten-iron product. This molten-iron product can be cast into iron products, 

but is most often used as a feedstock for steel production. The fluxes capture noniron components of 

the feedstock, resulting in blast-furnace slag. The slag consists primarily of silicates, aluminosilicates, 

and calcium-alumina-silicates.

Different forms of slag product are produced depending on the method used to cool the molten slag. 

If the liquid slag is poured into beds and slowly cooled under ambient conditions, a hard, durable 

crystalline material called air-cooled blast-furnace slag (ACBFS) is formed. This slag can be crushed, 

screened, and used as a mineral aggregate.

If the molten slag is cooled and solidified by rapid water quenching to a glassy state, little or no 

crystallization occurs. This is called granulated blast-furnace slag. When crushed or milled to very 

fine cement-sized particles, ground granulated blast-furnace slag (GGBFS) has cementitious 

properties, which make a suitable partial replacement for or additive to Portland cement.

National Slag Association

P.O. Box 1197

Pleasant Grove, UT 84062

<http://www.nationalslag.org/>

Table 3-8 continued on next page
35

Chapter 3—Descriptions of Recycled Materials with Potential Use to Federal Land Management Agencies

Applications

Conceivably, the Forest Service could use ACBFS as an aggregate substitute. State transportation 

agencies have standards which consider ACBFS to be a conventional aggregate. It is used 

extensively in granular base, hot-mix asphalt, Portland cement concrete, and embankments or fill 

applications. The material can be crushed and screened to meet specified gradation requirements 

using conventional aggregate-processing equipment. Realistically however, most Forest Service 

units will be located at a significant distance from an iron foundry, and it is unlikely that transporting 

ACBFS to a Forest Service site would be cost effective.

On the other hand, GGBFS is increasingly being used in the production of blended hydraulic cements 

(AASHTO M240) (1). When used in blended cements, granulated blast-furnace slag is too fine a 

particle size in accordance with AASHTO M302 (2) requirements. The ground slag can be introduced 

and milled with the cement feedstock or blended separately after the cement is ground to its required 

fineness. 

The Environmental Protection Agency has recommended that effective May 1, 1995, procuring 

agencies specifically include provision in all construction contracts for the use of GGBFS in Portland 

cement concrete contracts (3). Cements containing GGBFS are now available from many producers 

of Portland cement, so the Forest Service can use slag cements or blended slag/Portland cements to 

lower their carbon footprint.

Environmental and Safety Information

Blast-furnace slag is primarily composed of calcium oxide, silicon dioxide, aluminum oxide, and 

magnesium oxide. It is not inherently dangerous, though the slag often contains some sulfur, which 

can leach out in certain conditions. In slag cement applications, the slag cement is handled and 

treated like Portland cement.

References

1. American Association of State Highway and Transportation Officials (AASHTO). 1986. Standard 

Specification for Materials, “Blended Hydraulic Cements.” AASHTO Designation: M240-85, Part I 

Specifications, 14th Edition. Washington, DC: AASHTO.

2. AASHTO. 1986. Standard Specification for Materials, “Ground Iron Blast-Furnace Slag for 

Use in Concrete and Mortars.” AASHTO Designation: M302-86, Part I Specification, 14th Edition. 

Washington, DC: AASHTO.

3. U.S. Environmental Protection Agency. 1995. Recovered Materials Advisory Notice. 

Environmental Protection Agency. Federal Register; May 1, 1995.

Table 3-8 continued from previous page

37

Conclusions/Acknowledgements

CONCLUSIONS / ACKNOWLEDGEMENTS

Conclusions

Federal land management agencies have long 

been sensitive to the need for sustainable 

practices in order to maintain the forests and 

grasslands for future generations, while also 

providing recreation opportunities to the public. 

However, Federal agencies have been tasked to 

show more leadership in sustainable practices 

by reducing energy and water usage, reducing 

waste, and reducing greenhouse gas emissions. 

All of this is occurring at a time when agencies 

are being asked to conserve. One way for these 

agencies to show leadership in sustainable 

practices while reducing costs is to incorporate 

more recycled industrial byproduct materials into 

their construction and maintenance activities, 

particularly road construction and maintenance. 

Road construction and maintenance was targeted 

in this project because the activities require 

significant volumes of fine and course aggregate, 

hot-mix asphalt, and possibly Portland cement. 

Mining and transporting the aggregates disrupts 

the environment around the mine, burns fuel, and 

releases greenhouse gases into the air. Asphalt 

binder is expensive; the cement in concrete 

requires significant energy during its production; 

and calcining the limestone releases carbon 

dioxide (CO2) into the atmosphere (calcining uses 

high heat to convert limestone (CaCO3) to lime 

(CaO) with CO2 as a byproduct). The agencies 

need to address these issues in their respective 

sustainability plans.

However, using the materials in the applications 

shown in table 1-3 provides a way forward 

to reduce material and fuel demands while 

maintaining a satisfactory road system. Full 

depth reclamation provides a cost-effective way 

to recycle asphalt pavement and aggregates, 

reducing the demand for new materials. Using 

crushed concrete, asphalt, and glass as 

aggregate in fills and embankments also reduces 

the need for virgin aggregate. Shingles and old 

asphalt pavement also can be ground up and put 

back into new asphalt pavement, reducing the 

need for asphalt binder. And using slag cement 

instead of regular Portland cement reduces the 

carbon footprint of new concrete construction 

while providing a comparable product.

While this document provides only an introduction 

to recycling industrial materials, it provides 

the basis for road managers, engineers, and 

contractors to begin making more sustainable 

construction choices.

Acknowledgments

Thank you to the U.S. Department of 

Transportation, Federal Highway Administration 

(FHWA), Recycled Materials Resource Center; 

Alan Yamada (retired) and the National 

Technology and Development Center; Mike Voth 

(Central Federal Lands Highway Division FHWA); 

Elizabeth Olenbush and the Industrial Resources 

Council; Forest Service technical reviewers Rene 

Renteria (Pacific Northwest Region, Portland, 

OR), Leslie Boak (WO), and Kevin Contardi 

(Eastern Region, Milwaukee, WI); all those who 

provided input to the Forest Service’s recycledmaterials survey as well as photos; and the 

National Technology and Development Center’s 

editorial and publishing staff.

39

Appendixes

APPENDIX A

Survey responses

The National Technology and Development 

Center sent out an informal survey on recycled 

materials to Forest Service representatives. 

Forest Service representatives were queried as 

to what topics they would like to see covered. The 

survey had three goals:

1. To determine what byproduct materials 

Forest Service representatives were aware 

of, or at least thinking about.

2. To determine how they wanted to use the 

materials.

3. To provide a minimum list of questions and 

issues that could be covered if possible. 

The following is a list of excerpts from email 

responses from Forest Service personnel: 

1. A “how to” guide [on hot-mix asphalt] to 

identify methods to pick it up, mixing methods, laying it back down, how much and 

what kind of asphalt to add to reuse it, etc.

2. Contacts on forests, and possibly State 

highway departments, or local road agencies.

3. Can you recycle any asphalt material or 

does it get unusable over time?

4. What “admixtures” are popular and for what 

reason?

5. In an effort to promote reuse/recycle and 

sustainability, what options do we have?

6. Information on asphalt millings applications 

on forest roads.

7. What about using recycled pavement as an 

aggregate course. Have been seeing roads 

where we’ve pulled up the asphalt...are we 

using it for aggregate? I’ve also been reading about alternatives to aggregate in the 

asphalt. 

8. What about grinding up the existing asphalt 

pavement and reusing it in the sub-grade 

below the new asphalt?

9. Where is it appropriate to use recycled 

asphalt as “fill” material? The answer to this 

question probably varies by State. To be on 

the safe side, we’ve decided not to use the 

ground-up asphalt as fill in waterways or 

ditches that we’re filling as part of a restoration project, and we only use it in “dry sites.” 

This might be a point to cover: the appropriate use of recycled asphalt as fill in places 

other than road beds.

10.Where to place RAP so it is not an environmental hazard (i.e., roadway prism only)?

11. Maximum percent weight allowed in aggregate base or hot mix?

12.Size of the RAP in order to get a good compaction?

13.Where to place excess RAP (i.e., environmental issues)?

14.I would like to see some cost analysis...

when we do asphalt work we store the used 

asphalt in our quarries, hoping to one day 

use the material. So could you address the 

following concerns:

− What to do with wasted AC material?

− What options are there to use material that has been stockpiled over the 

years?

− Cost and value analysis. (Recycled 

product versus new.)

Out of the 14 responses received, 12 were 

specifically related to the reuse of hot-mix 

asphalt, primarily as fill material or as aggregate 

in base/subbase road construction. Question 

8 “What about grinding up the existing asphalt 

pavement and reusing it in the subgrade below 

the new asphalt?” and related questions are 

essentially asking about the use of in-place 

recycling through full-depth reclamation (FDR). 

There were a limited number of applications (fill 

and base/subbase uses) and no other recycled 

materials in the responses, though this is likely 

due to bias in the responses because of the 

survey format and who responded.

APPENDIXES
40

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

APPENDIX B

Glossary

Aggregate: Granular material that can be used 

in unbound applications, such as embankments 

and structural fill, or used in bound applications, 

such Portland cement and asphalt concretes. 

Aggregate materials include, but are not limited 

to, sand, gravel, crushed stone, rubber chips, 

crushed concrete, reclaimed asphalt pavement, 

foundry sand and slag, coal fly ash and bottom 

ash, blast-furnace slag and steel slag.

Aggregate gradation: See Gradation.

Agricultural land applications: Activities 

that focus on the application of materials on 

agricultural lands to modify soil conditions with 

the specific goal of improving crop health and 

yields. In this case, land application includes 

application directly to the surface as well as soil 

mixing. Agricultural land applications include the 

utilization of lime-bearing materials to change the 

soil pH; the utilization of materials to improve soil 

conditions, such as providing for better drainage 

or improved moisture retention, or the addition of 

mineral-bearing materials that provide nutrients to 

the soil.

Asphalt binder: A dark-brown to black 

cementitious material, in which the predominant 

constituents (+99 percent) are bitumens, which 

occur in nature or are obtained as residue in 

petroleum manufacturing, and are used as binder 

in asphalt-aggregate mixes.

Asphalt concrete: A mixture of asphalt binder 

and carefully graded coarse and fine aggregates.

Asphalt pavement: Pavement consisting of 

asphalt concrete layer(s) on supporting courses, 

such as concrete base, asphalt-treated base, 

cement-treated base, granular base, and/or 

granular subbase, placed over the subgrade.

Backfill: Material used to refill or backfill an 

excavated area. High quality, compacted backfill 

placed specifically to support a foundation or road 

is typically called structural fill.

Base: A layer of specified or selected material of 

planned thickness constructed on the subgrade or 

subbase to serve one or more functions, such as 

distributing load, providing drainage, minimizing 

frost action, and so forth. The base maybe placed 

in a granular or stabilized (bound) form.

Binder: A material or mixture of materials, which 

is primarily responsible for binding aggregate 

particles together in bound applications, such as 

Portland cement and asphalt concretes, as well 

as stabilized soils.

Bitumens: 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, and pitches are typical.

Bituminous: A material containing or treated with 

bitumen.

Blast-furnace slag: The nonmetallic components 

removed from iron ore during processing in a 

blast furnace. It consists essentially of silicates 

and aluminosilicates of calcium and other metals.
41

Appendixes

Boiler ash: General term to describe material 

produced by burning wood, coal, or other solid 

fuels to produce steam and electricity.

Byproduct: A secondary material that is 

produced as the result of some process. The 

production of the byproduct material is not the 

primary goal of the process. A byproduct also can 

be a product that has less value than the primary 

product. For instance, ash is a byproduct of the 

combustion process, though the primary product 

is heat.

Causticizing residues: Byproduct of the kraft 

pulping process, specifically from the recovery 

of energy and chemicals from spent pulping 

liquor. The most widely used of the causticizing 

residues is lime mud, which is essentially calcium 

carbonate (limestone) with a small amount of 

calcium hydroxide (lime).

Coal bottom ash: Granular, sandy residue 

generated by burning coal for electricity. 

The bottom ash falls out of the furnace into 

a collection hopper. Most bottom ash is 

predominantly silica, alumina, and iron.

Coal fly ash: A fine, powdery residue generated 

by burning coal used for electricity. The ash is 

captured from the flue gases using precipitators. 

Class F fly ash generally is generated by 

burning bituminous coal, while Class C fly ash is 

generated by burning lignite and subbituminous 

coal. Class F fly ash typically contains less lime 

than Class C ash and will act as a pozzolan in 

cementitous reactions, whereas Class C ash will 

form a cementitious compound when mixed with 

water.

Coarse aggregate: There is some variation 

in the definition of coarse aggregate between 

different industries, but it generally means the 

portion of aggregate retained on the No. 4 

(4.75mm) sieve.

Construction and demolition debris: An 

aggregate material composed of crushed 

concrete, brick, stone, and other materials 

derived from construction and demolition 

processes. It also may contain shingles, 

reclaimed asphalt pavement, wood, and drywall.

Coproduct: A coproduct is a material that is 

produced as part of a process. Coproducts have 

equal value to the other products of the process.

Crumb rubber: see ground rubber.

Embankment: An embankment is a “built up” 

earthen structure used to raise the surface 

level. An embankment in a road is the layer of 

engineered material that raises the pavement 

structure to the appropriate grade. Embankments 

also describe the raised approach to bridges. 

Some geotechnical sites also include dams as 

embankments. There is somewhat of an overlap 

with structural fill because that term is used 

sometimes to describe the material that is used to 

construct an embankment.

Fine aggregate: In the construction industry, it 

is aggregate passing the No. 4 (4.75mm) sieve 

and predominantly retained on the No. 200 sieve 

(0.075mm) sieve.

Fines: In a general sense, the fines are the 

fraction of a soil in a batch of aggregate. It is 

usually more specifically taken to mean the 

material finer than the No. 200 (0.075mm) sieve.
42

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Flowable fill: A self-compacting material 

typically composed of water, fine aggregate, a 

cementitious binder, and admixtures to control 

air and flowability. It is also called controlled 

low-strength material by the American Concrete 

Institute. Flowable fill is placed in a slurry form, 

usually to fill voids and trenches, after which it 

hardens into a strong, hard matrix. 

Foundry sand: Foundry sand is byproduct 

material generated from the metal casting 

processes at metal foundries. Metal casting is a 

metal-forming technique used to produce metal 

parts ranging from automobile engine blocks and 

pistons, to plumbing fixtures to precision aircraft 

parts. Foundry sands are high-quality silica sands 

used to make the molds for casting the parts. The 

sand is reused until it is physically degraded, at 

which point it is removed from the sand supply. 

Foundry slag: Foundry slag is similar to foundry 

sand. It is a byproduct material generated by 

metal casting processes at metal foundries. 

Foundry slag is composed of fluxing agents and 

impurities removed from the molten metal prior to 

casting. 

Gradation: Usually, granular materials and 

soils are composed of particles with a range of 

sizes. The gradation describes the distribution 

of particles sizes. It is expressed in terms of 

the mass retained on or passing different sized 

sieves.

Granular base: In pavement design, the base 

course is the layer directly below the surface 

layer. The function of the base course is to 

support the asphalt and transmit traffic loads 

to the underlying layers. A granular base is 

composed of select aggregate materials that are 

chosen for superior strength and durability. The 

base is placed in layers called lifts and densified 

using heavy compaction equipment.

Granular subbase: The subbase is the layer 

between base course and the subgrade, which is 

a prepared soil layer. The function of the subbase 

is to transfer and disseminate the loads from the 

base course into the underlying material. Like 

the granular base, the subbase is composed 

of compacted aggregate material. The main 

difference is that the subbase tends to have a 

coarser gradation.

Ground rubber: Also called crumb rubber, it is a 

fine granular material composed of small rubber 

particles obtained from old tires. It can be used as 

a solid or mixed with asphalt binder as a polymer 

modifier.

Hot-mix asphalt: A form of asphalt concrete. The 

hot-mix asphalt is made by mixing heated asphalt 

binder and aggregate, and then placed and 

compacted while the mixture is still hot.

Landfill applications: Activities that utilize 

material in the construction and maintenance 

of landfills. Typically, the focus is on drainage 

applications, liner construction, and capping of 

the landfill, though alternate daily cover also is 

included.

Lignite coal: Also called brown coal, it is a soft, 

brownish-black coal in which the alteration of 

vegetable matter has proceeded further than in 

peat but not as far as in bituminous coal.

Other concrete uses: Application that focuses 

on the utilization of materials in concrete 

blocks, masonry units, and other types of 

concrete construction products. This application 

complements the use of materials in Portland 

cement concrete pavement and other massive 

concrete structures that people are more familiar 

with.
43

Appendixes

Permeability: The rate of flow of a liquid or gas 

through a porous material.

pH: A measure of the acidity or alkalinity of 

a solution, numerically equal to 7 for neutral 

solutions, increasing with increasing alkalinity and 

decreasing with increasing acidity. The pH scale 

commonly in use ranges from 0 to 14.

Portland cement: Hydraulic cement comprised 

of very fine grains produced by pulverizing 

clinkers consisting essentially of hydraulic calcium 

silicates and calcium sulfate.

Portland cement concrete: The product of 

mixing Portland cement, mineral aggregates, 

water, and in some cases additives, such as an 

air-entering agent, which result in a hardened 

structural material after hydration.

Portland cement concrete pavement: Also 

called rigid pavements. They are pavement 

structures in which the top or surface layer is 

made from Portland cement concrete.

Portland cement manufacturing: This 

application is focused on materials that can be 

used as feedstock for cement manufacturing, or 

can be used as a cement amendment.

Pozzolanic: A siliceous volcanic ash used to 

produce hydraulic cement.

Prompt roofing shingle scrap (roofing shingle 

tabs): Asphalt roofing shingles that are generated 

from “out-of-spec” shingles or when new asphalt 

shingles are trimmed during production to the 

required physical dimensions.

Reclaimed asphalt pavement (RAP): Asphalt 

pavement or paving mixture removed from its 

original location for use in another application.

Reclaimed concrete aggregate: An aggregate 

material obtained from crushing concrete 

structures. Reclaimed concrete aggregate 

includes the original aggregate from the concrete 

as well as parts of the hardened cement.

Recycle: To use a waste or byproduct as an input 

material in the construction or manufacture of 

another product (replacing virgin material).

Soil stabilization: Application that refers to 

modifying soils to provide better engineering 

properties. This is different than stabilized base 

because soil stabilization considers true soils, 

while base stabilization is focused on binding 

aggregates. In addition, the application does 

not include dynamic stabilization or purely 

mechanical means of stabilization, but is focused 

on chemical soil stabilization to reduce the 

plasticity of clayey soils and to improve the shear 

strength. Materials that are high in lime or have 

pozzolanic properties would be candidates for 

soil stabilization. Sandy materials that improve 

drainage also would be considered.

Stabilized base: The function of the base layer 

is the same as described above. The major 

difference is that a binding agent is added to the 

aggregate to stiffen and strengthen the layer.

Stabilized subbase: The function of the subbase 

layer is the same as described above. The major 

difference is that a binding agent is added to the 

aggregate to stiffen and strengthen the layer.
44

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

Steel furnace slag: The nonmetallic product 

that is developed simultaneously with steel in 

basic oxygen, electric, or open-hearth furnaces. It 

consists of calcium silicates and ferrites combined 

with fused and mineralogically combined oxides 

of iron, aluminum, manganese, calcium, and 

magnesium

Stiffness: The physical property of being 

inflexible and hard to bend.

Strength: The ability of a material to resist 

deformation when a stress is applied to it.

Structural fill: This term can be confusing. It 

commonly is used to describe an application 

and the material that is used in that application. 

In general terms, the structural fill application is 

the filling in of a depression with a material that 

meets specific engineering requirements. For 

example, if a building is to be constructed at a 

particular site that has poor soil, the native soil 

will be excavated and replaced with high-quality 

material. The new body of material is called 

a structural fill. Another example is the use of 

material to fill in a trench in roadway.

Subbase: The layer of select compacted 

granular material placed on the subgrade, which 

is overlain by the base of a flexible pavement 

structure or the Portland cement concrete slab of 

a rigid pavement structure. The subbase can be 

placed in stabilized or granular forms.

Subbituminous: Coal of lower rank than 

bituminous coal but higher than lignite.

Subgrade: The soil prepared and compacted to 

support a pavement structure. The subgrade is 

the layer below the subbase.

Tear-off roofing shingles: Asphalt roofing 

shingles that are generated during the demolition 

or replacement of existing roofs. They also are 

referred to as post-consumer shingles.

Tire-derived aggregate: Coarse aggregate 

material obtained by shedding old tires.

Unconfined compression strength: The loadper-unit-area at which soil will fail in compression.

Virgin aggregate: Aggregate that has been 

mined and not used in any prior applications.

Wastewater treatment plant residuals:

Byproduct material of the pulp and paper industry 

composed of the solids removed from process 

water. They consist mostly of wood fibers and 

mineral materials, such as kaolin clay and 

calcium carbonate.
45

Appendixes

APPENDIX C

Web sites, References, Specifications

Toolbox

Table C-1. Primary recycled material tool box

NHI Module IV A - Recycling, February 25-27, 2009

1 DOCUMENTS Web Site PDF 

on CD

1.1 Level 1 Sources

1. Federal Highway Administration 

User Guidelines, April 1998

http://www.recycledmaterials.org/tools/

uguidelines/index.asp

2. National Cooperative Highway 

Research Program (NCHRP) 

4-21 Computerized Database, 

June 2000

http://www.recycledmaterials.org/

Resources/CD/NCHRP/NCHRP.zip

3 Federal Highway Administration 

Evaluation Framework, October 

2001

http://www.recycledmaterials.org/

Resources/CD/Framework/Start/start.htm

4. Recycled Materials Resource 

Center Project 23 PaLATE 

Life-Cycle Assessment Tool, 

December 2003

http://www.recycledmaterials.org/

Resources/CD/PaLATE/PaLATE.htm

1.2 Level 2 Sources

1. NCHRP 25-25(04) 

Compendium of Environmental 

Stewardship Practices in 

Construction and Maintenance 

http://environment.transportation.org/

environmental_issues/construct_maint_

prac/compendium/manual/

✔

2. NCHRP 25-09 Environmental 

Impacts of Construction and 

Repair Materials on Surface 

and Ground Waters 

http://onlinepubs.trb.org/Onlinepubs/nchrp/

nchrp_rpt_443.pdf

✔

3. Fly Ash Facts for Highway 

Engineers, 4th Edition, June 

2003

http://www.fhwa.dot.gov/Pavement/

recycling/fafacts.pdf

4. Foundry Sand Facts Handbook http://isddc.dot.gov/OLPFiles/

FHWA/011435.pdf
46

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

5. Asphalt Recycling and 

Reclaiming Association Basic 

Asphalt Recycling Manual

http://www.pavementpreservation.org/

library/getfile.php?journal_id=635

6. FHWA European Scanning Tour http://www.international.fhwa.dot.gov/Pdfs/

recycolor.pdf

✔

7. Association of State and 

Territorial Solid Waste 

Management Officials Beneficial 

Use Survey

http://www.astswmo.org/Publications/pdf/

Benfuserpt.pdf

✔

8. “Road to Reuse” article from 

Civil Engineering Magazine

✔

9. “An Integrated Framework for 

Evaluating Leaching in Waste 

Management and Utilization of 

Secondary Materials,” a journal 

article from Environmental 

Engineering Science by Dr. 

David Kosson and colleagues 

http://www.rmrc.unh.edu/Resources/

PandD/kosson/Kossonetal.pdf

✔

10. “Use of a New Leaching Test 

Framework for Evaluating 

Alternative Treatment Processes 

for Mercury-Contaminated 

Soils,” a journal article from 

Environmental Engineering 

Science by Dr. Florence 

Sanchez and colleagues

✔

11. “A Probabilistic Source 

Assessment Framework for 

Leaching from Secondary 

Materials in Highway 

Applications,” a journal article 

from Clean Technologies & 

Environmental Policy by Dr. 

Defne Apul and colleagues

✔

12. “Transportation Applications of 

Recycled Concrete Aggregate”

✔

13. Materials from Dr. Dana 

Humphrey

http://useit.umaine.edu/case_studies/tires/

case_studies.htm

1 DOCUMENTS Web Site PDF 

on CD

Table C-1. Primary recycled material tool box continued
47

Appendixes

2 WEB SITES

1. Recycled Materials Resource Center 

(RMRC)

http://www.recycledmaterials.org/

2. Turner Fairbanks Highway Research 

Center (TFHRC)

http://www.tfhrc.gov/hnr20/recycle/wrc.htm

3. Asphalt Recycling and Reclaiming 

Association (ARRA)

http://www.arra.org/

4. American Coal Ash Association 

(ACAA)

http://www.acaa-usa.org/

5. National Slag Association (NSA) http://www.nationalslagassoc.org/

6. Foundry Industry (AFS) http://www.foundryrecycling.org/whatis.html

7. Rubber Pavements Association http://www.rubberpavements.org/

8. Transportation Research Board 

– National Cooperative Highway 

Research Program 

http://www4.trb.org/trb/crp.nsf/reference/

appendices/NCHRP+Overview

9. U.S. Environmental Protection 

Agency – C&D Debris (USEPA C&D 

Debris)

http://www.epa.gov/epaoswer/non-hw/debris/

about.htm

10. Texas Department of Transportation 

(DOT) – Road to Recycling

http://www.dot.state.tx.us/gsd/recycle/mat.htm

11. Combustion Byproducts Recycling 

Consortium

http://wvwri.nrcce.wvu.edu/programs/cbrc/

index.cfm

12. State DOT Recycling Program 

Web Sites

12.1 California DOT (Caltrans) http://www.dot.ca.gov/hq/oppd/rescons/

rchomepg.htm

12.2 Massachusetts DOT (MassHighway) http://www.mass.gov/mhd/recycle/recycling.htm

12.3 North Carolina DOT (NCDOT) http://www.doh.dot.state.nc.us/preconstruct/

highway/dsn_srvc/value/recycle/default.html

12.4 Pennsylvania DOT (PennDOT) http://www.dot.state.pa.us/penndot/bureaus/

chiefeng.nsf/frmSEMPemsISO?openframes

et&frame=contents&src=/penndot/bureaus/

chiefeng.nsf/vSPL/inforecycling

12.5 Texas DOT (TXDOT) http://www.dot.state.tx.us/GSD/recycle/plan.htm

12.6 Virginia DOT (VDOT) http://www.virginiadot.org/infoservice/news/

HRO4232002-Recycled.asp

Table C-1. Primary recycled material tool box continued
48

Reclaimed Materials and Their Applications in Road Construction: A Condensed Guide for Road Managers

3 SPECIFICATIONS PDF on 

CD

3.1 Various American Association of State Highway Transportation Officials 

(AASHTO) Recycled Material Specification from RMRC Projects

1. Glass Cullet, Base Course Aggregate - AASHTO Designation: M 318-01 ✔

2. Reclaimed Concrete in Portland Cement - Draft ✔

3. Reclaimed Concrete in Granular Base - AASHTO Designation: M 319-02 ✔

4. Recycled Asphalt Shingle as an Additive in Hot Mix Asphalt – Draft ✔

5. Compost for Erosion Control (Compost Blanket) – AASHTO MP-10 ✔

6. Compost for Erosion Control (Filter Berms) – AASHTO MP-9 ✔

Table C-1. Primary recycled material tool box continued
49

Appendixes

APPENDIX D

Case study—Cold Recycling Foam. 

Recycling in Estes National Park, Colorado 

(taken with permission from Wirtgen)

A section of highway in Estes Park, Colorado, recently underwent rehabilitation and recycling, using 

foamed bitumen. Details outlining the pavement structure, mix design, and recycling process are 

provided at: <http://www.wirtgen.de/media/redaktion/pdf-dokumente/03_kaltrecycling_stabilisierung/_

allgemein_1/job-reports_kaltrecycling/jr_colorado_e.pdf>

Case study—Cold Recycling Foam. 

Recycling project, Canyon de Chelly, Arizona 

(taken with permission from Wirtgen)

Wirtgen and FHWA Central Federal Lands Highway Division recently rehabilitated 17.6 lane miles of 

road in Canyon De Chelly National Park using foam bitumen as the stabilization agent. The pavement 

sections that underwent rehabilitation consisted of a chip seal and bituminous base atop a sandy 

clay and silty sand subgrade. Details on the mix design, construction, and photos depicting the entire 

process are provided at:<http://www.wirtgen.de/media/redaktion/pdf-dokumente/03_kaltrecycling_

stabilisierung/_allgemein_1/job-reports_kaltrecycling/jr_arizona_e.pdf>