Recycled Concrete Aggregates:

Current Practice,

Implementation Challenges 

and New Guidance

Tara L. Cavalline, PhD, PE

University of North Carolina at Charlotte

Presented at NIST Workshop:

Fostering a Circular Economy and 

Carbon Sequestration for Construction Materials

June 8, 2022
RCA Increases Pavement Sustainability 

● RCA can be used in bound and unbound applications in concrete paving projects

● Increased use of RCA will address several challenges:

○ dwindling landfill space and increased disposal costs

○ increased demand for aggregates

○ reduced availability and longer hauls for virgin aggregates

● Use of RCA provides reduced environmental impacts due to:

○ conservation of materials

○ reduced emissions associated with production of virgin aggregates and hauling

○ reduced construction traffic

● Use of RCA can reduce project cost and schedule

● RCA can potentially improved pavement performance

Source: Phillip Lamoureux, 

FHWA Western Federal Lands
Production and Reuse of RCA
National production and reuse (annual, unless noted)

Construction Byproduct Production Beneficial Reuse Disposal

Recycled asphalt 

pavement (RAP)

107 million tons 102.1 million tons 4.9 million tons

(EPA 2020)

Recycled concrete 

aggregates (RCA)

405.2 million tons 

24.2 (6%) – construction waste

381.0 (94%) – demolition waste

334.0 million tons 71.2 million tons

(EPA 2020)

Quarry fines

484 million tons N/A N/A

(Willet 2021a and 2021b)

RCA fines 101.3 million tons N/A N/A

(EPA 2018 data @ 25% fines production estimate)

Solids recovered from 

diamond grinding

0.284 million tons 0.10 million tons 0.184 million tons

(IGGA 2021 and Dufalla et al. 2015, IGGA 2020 annual grinding estimate @ 100 tons fines/lane mi 

with 35% beneficial reuse rate)

Solids recovered from 

diamond grooving

0.006 million tons 0.002 million tons 0.004 million tons

(IGGA 2021 and Dufalla et al. 2015)

Hydrodemolition

materials

36 million square feet of deck area 

hydrodemolished per state since 

practices began

N/A N/A

(Simmons et al. 2020)
National production and reuse

107

24.2

381

101.3

484

Million Tons of Material Produced

RAP

RCA from construction waste

RCA from demolition waste

RCA fines

Quarry fines

Diamond grinding solids

Diamond grooving solids
End uses for crushed concrete

Used as 

aggregate 

base 

Used as high- Other uses

value rip rap

Used as fill

Used in new 

concrete mixtures

Used in asphalt 

concrete

After Van Dam et al. 2015, 

from USGS 2000 after T.A. 

Deal 1997
Characteristics of RCA

and RCA Concrete
Properties of RCA

Property Virgin Aggregate RCA

Shape and Texture Well–rounded; smooth to 

angular/rough

Angular with rough surface

Absorption Capacity 0.8% – 3.7% 3.7% – 8.7%

Specific Gravity 2.4 – 2.9 2.1 – 2.4

L.A Abrasion 15% – 30% 20% – 45%

Sodium Sulfate 7% – 21% 18% – 59%

Magnesium Sulfate 4% – 7% 1% – 9%

Chloride Content 0 – 2 lb/yd3 1 – 12 lb/yd3
Properties of Concrete with RCA

MN 4-1 (Recycled) MN 4-2 (Control)

Photos from Mark Snyder, PERC
Fresh Properties of Concrete Containing RCA

Property Coarse RCA Coarse and Fine RCA

Workability Similar to slightly lower Slightly to significantly lower

Finishability Similar to more difficult More difficult

Water bleeding Slightly less Less

Water demand Greater Much greater

Air content Slightly higher Slightly higher
Influence of RCA on Hardened Properties of Concrete

Property RCA used as Coarse 

Aggregate

RCA used as Coarse and Fine 

Aggregate Potential Adjustments

Compressive 

strength 0% to 24% less 15% to 40% less Reduce w/cm ratio

Tensile strength 0% to 10% less 10% to 20% less Reduce w/cm ratio

Strength 

variation Slightly greater Slightly greater Increase average strength compared to specified strength

Modulus of 

elasticity 10% to 33% less 25% to 40% less This may be considered a benefit with 

regard to cracking of slabs on grade

Specific gravity 0% to 10% lower 5% to 15% lower None recommended

CTE 0% to 30% greater 0% to 30% greater Reduce panel sizes

Drying shrinkage 20% to 50% greater 70% to 100% greater Reduce panel sizes

Creep 30% to 60% greater 30% to 60% greater Typically not an issue in pavement 

applications

Bond strength Similar to conventional concrete, or slightly less None recommended

Permeability 0% to 500% greater 0% to 500% greater Reduce w/cm ratio
Bound and Unbound Uses of RCA
Uses of Recycled Concrete Aggregate

in Pavement Applications

• PCC pavement

• Single and Two-Lift 

• HMA pavement

• Subbase

• Unbound

• Stabilized

• Fill material

• Filter material

• Drainage layer
Unstabilized Subbases/Backfill

● Most common application for RCA in U.S.

● Application used by 38+ of 44 states using RCA in U.S.

○ Some believe it outperforms virgin aggregate as an unstabilized subbase!

● Some level of contaminants 

is tolerable.

Photo: Gary Fick, Transtec

• On-grade recycling reduces 

time, cost, and hauling 

impacts (fuel, traffic)
Cement-stabilized and Lean Concrete Subbases

● Stabilization helps to prevent 

migration of crusher fines, mitigates 

high pH runoff

● Physical and mechanical properties of 

the RCA must be considered in the 

design and production of cementstabilized subbases
Use of RCA in Lean Concrete Bases

● Caltrans - use of all old pavement resulted in a “Zero Concrete Waste” project

● Completed in 2020

● Constructed over 55 hours of extended weekend closures

● Demonstrated that RCA mixtures can be used in projects with short timeframes

Source: Caltrans
Concrete Mixtures

● RCA can be (and has been) incorporated as the 

primary or sole aggregate source in new concrete 

pavements.

● Used in the U.S. concrete mixtures since the 1940s

○ Roadway surfaces, shoulders, median barriers, 

sidewalks, curbs and gutters, building/bridge 

foundations 

and even structural concrete.

● Common in the lower lift of 

two-lift concrete pavements in Europe. 

Photos: Andy Naranjo, TxDOT (top), CP Tech Center (bottom)
RCA in Two-Lift Construction

● Iowa US 75 Reconstruction (1976)

○ 60-40 RCA and RAP in 7-in lower lift; 23 ft wide

○ All virgin in 4-in top lift; 24 ft wide

○ Provided more than 40 years of service!

● Austrian Standard Practice since late 1980s

○ A-1 (Vienna-Salzburg)

○ 19-cm (7.5-in) lower lift (RCA and RAP), 3-cm (1.5-in) upper 

lift fines to stabilize foundation (100 percent PCC recycled) 

○ Overall project savings >10 percent

○ Using recycled materials, particularly in lower lift, is 

now standard
Use of RCA in Concrete Pavement

● Colorado State Highway 470 (C-470) – SW portion of Denver’s beltway

● 100,000 vehicles per day expected to increase 40% by 2035

● 12.5 miles – addition of 3 express 

lanes + full reconstruction of 

existing pavement 

● All existing pavement removed 

used to produce RCA on-site

● 86,000 tons of 11⁄2 inch nominal 

max coarse RCA used in concrete 

mixture for 926,000 SY of 

pavement

Source: Castle Rock Construction Company 
Conclusions of 2006 Field Study of RCA Pavements in Service

• Need to treat RCA as “engineered material” and modify mix and 

structural designs accordingly

• Reduce w/c

• ASR mitigation

• Reduced panel lengths

• Other modifications as needed

• Mortar contents are generally higher for RCA

• Varied with aggregate type, crushing process

• Higher mortar contents often had more distress – may need to control 

reclaimed mortar content
Paving with RCA Concrete Mixtures 

● Batching, mixing, delivery, placement and finishing techniques can be 

similar to those used for virgin aggregate concrete mixtures.

● Concerns with water demand and premature stiffening:

○ Limiting or eliminate fine RCA

○ Presoak RCA

○ Chemical and mineral admixtures

● Contaminants can lead to air entrainment problems.

● Fresh and hardened properties of RCA PCC might be different 

from virgin aggregate PCC. 

User must understand the 

RCA that will be used.... 

Characterization is key!
Guidance for Use of RCA
Guidance on Use of RCA

prepared as part of Concrete Recycling 

Initiative (2018)

Ch. 1: Introduction to Concrete Pavement Recycling

Ch. 2: Economics and Sustainability

Ch. 3: Project Selection and Scoping

Ch. 4: Using RCA in Pavement Base Products

Ch. 5: Using RCA in Unbound Aggregate Shoulders

Ch. 6: Using RCA in Concrete Paving Mixtures

Ch. 7: Mitigating Environmental Concerns
Tech Brief: Use of RCA in 

Concrete Paving Mixtures

● Prepared as part of FHWA Cooperative Agreement 

with CP Tech Center

● Updated guidance to build upon 2018 Practitioner’s 

Reference Guide

● Guidance for:

○ Characterizing RCA

○ Influence of RCA on concrete properties

○ Mixture design approaches

○ Production and use considerations

○ Example projects 
Tech Brief

● Characteristics of byproducts

● Provides information on handling and processing 

needed for reuse

● Recommends how to evaluate construction byproducts 

for reuse in bound and unbound applications

● Describes potential impacts of reusing each byproduct 

in specific applications

● Presents a protocol for characterizing and assessing 

byproducts for reuse

● Provides recommendations for qualification-, 

preconstruction- and construction-phase tests for the 

byproduct materials and applications (bound/unbound 

bases, fills, concrete mixtures)

● Describes design and construction considerations and 

ways to protect the environment
Planning, Scoping, 

and Construction Considerations
Project Selection and Scoping

● Includes checklist of considerations for use of 

RCA in different applications

○ Materials considerations

○ Production considerations

○ Other considerations

Structured around a flowchart showing typical 

project selection and scoping process

Characterization of the 

Source Concrete

Production Options for 

RCA

Economics

Other Factors

Potential Recycling 

Project Identified 

Project Scoping 

Completed 
Project Selection and Scoping

Checklist of considerations for use of RCA in different applications

RCA use Materials 

considerations

Production 

Considerations

Other 

considerations

New RCA concrete and 

stabilized base materials

• Sources

• Specifications

• Processing options

• Hauling

• Crusher types

• Production 

rates/storage

• QA/QC

• Residuals 

management

• Project staging

• Costs

• Environmental 

considerations

• Permitting

• Public perception

Unbound bases and drainage 

layers

Filter material around 

drainage structures

Fill (beneficial reuse of fines) 

not in pavement structure

! Highly simplified table shown here ! 

See Reference Guide for all details...
Mitigating Environmental Concerns

● Legislative and regulatory considerations

● Overview of potential environmental 

concerns

○ water quality

○ air quality

○ noise/local impacts

○ waste generation 

Mitigating environmental concerns during project planning and design

• Focus on water quality issues 

Mitigating environmental concerns during construction

• Strategies for mitigating issues on-site

Photo: Dwayne Stenlund, MnDOT
Evaluation for Use
Practical considerations

● Availability

○ Project-specific (project-produced byproducts)

○ Proximity to a producer (e.g. quarry, C&D waste recycling facility)

○ Phasing should be considered

■ Immediate need, handling/storage capacity, ways to maximize use

● Consistency

○ Function of quality of the source material, processing/handling techniques

○ Characterization of materials is essential to understand properties and 

consistency

● Economic factors

○ Difference in cost between using byproduct vs. using virgin material
Recent Advancements in RCA Characterization

● ACI CRC 2019 P0027: 

Effective Characterization of RCA for Concrete Applications 

(PI – Jiong Hu, UNL, Co-PI Tara Cavalline, UNC Charlotte)

● Improved existing tests and developed new tests:

○ Modified residual mortar content (RMC) test 

■ improved thermal shock method

○ Modified Aggregate crushing value (ACV) test 

■ strength characterization

○ Aggregate freeze-thaw test 

■ able to differentiate the air-entrainment level of parent concrete

○ Portable handheld XRF 

■ can be used for chemical characterization and residual mortar 

determination
Mixture Proportioning Using RCA 

● Proportioning does not differ significantly from procedures from conventional 

concrete

● ACI 211 and similar approaches have been successfully used for decades

○ Adequate characterization of RCA is key

○ Trial batching and testing is a must

● Lower w/cm is often needed to meet concrete property targets

● Use of SCMs improves performance of RCA concrete by supporting enhanced 

hydration → helps compensate for relatively weak interfacial transition zone (ITZ) 

of RCA

● Use of Class F fly ash, slag, or lithium nitrate admixtures should also be used if 

the potential for ASR exists.
Recent Developments in RCA Mixture Proportioning

● NJIT Method (Adams and Jayasuriya 2019)

○ Statistical study using data from more 

than 100 peer-reviewed studies of RCA 

concrete

○ Linked RCA properties and mixture 

characteristics to RCA concrete 

mechanical properties 

(compressive/flexural strength, elastic 

modulus)

○ Developed a new RCA concrete mixture 

design procedure based on models 

developed as part of this study, along with 

recommendations from ACI 302.

Overview of NJIT 

RCA Mixture Proportioning Method

● Step 1 – Approximate effective w/cm ratio

● Step 2 – Approximate RCA replacement level

● Step 3 – Determine aggregate-to-cement 

ratio

● Step 4 – Finalize material ratios

● Step 5 – Select aggregate size

● Step 6 – Select minimum requirements for 

cement contents

● Step 7 – Determine mixture proportions for 

concrete materials
Recent Developments in RCA Mixture Proportioning

● UN-L Method 

○ Mamirov 2021, and Hu et al. 2022

○ Based on particle packing and excess paste theory

○ ACI CRC Project 2019 P0027: Effective 

Characterization of RCA for Concrete Applications
Considerations for Pavement Design Using RCA Concrete

Input Type Input RCA used as Coarse Aggregate RCA used as Coarse and Fine 

Aggregate

Recommended Test 

Protocol and/or 

Additional Guidance

PCC

Poisson’s ratio Similar to mixture with virgin aggregates ASTM C469

Thickness Select based on user preferences

Unit weight 0% to 10% lower 5% to 15% lower AASHTO T 121

PCC 

Thermal

CTE 0% to 30% greater 0% to 30% greater AASHTO T 336

Thermal conductivity 0% to 40% lower (Bravo et al. 2017) ASTM E1952

Heat capacity Somewhat higher (Damdelen et al. 2014) ASTM D2766

PCC Mixture

Aggregate type Select based on actual or expected aggregate source

Cementitious material 

content

Select based on actual or expected concrete mixture design

Cement type Select based on actual or expected cement source

w/cm ratio Select based on actual or expected concrete mixture design

Curing method Select based on agency recommendations and practices

Reversible shrinkage (%) Estimate using agency historical data or select M-EPDG defaults

Time to develop 50% of 

ultimate shrinkage

Estimate using agency historical data or select M-EPDG defaults

Strength and 

Modulus

Elastic modulus 10% to 33% lower than mixture 

with virgin aggregates

25% to 40% less than mixture 

with virgin aggregates

ASTM C469

Flexural strength Mixture can be designed to meet 

specified strength with reduced 

w/cm ratio

AASHTO T 97

Indirect tensile strength 

(CRCP only)

Mixture can be designed to meet 

specified strength with reduced 

w/cm ratio

AASHTO T 198
Resources

● CP Tech Center has a concrete 

recycling website with links to many 

resources

● https://cptechcenter.org/concreterecycling/
Acknowledgements

● Peter Taylor – Director, CP Tech Center at Iowa State University

● Mark Snyder – PERC 

● Gary Fick - Transtec

● Jiong Hu and Miras Mamirov – University of Nebraska-Lincoln

● Arindam Dey – UNC Charlotte

● Castle Rock Construction – Amy Brooks and Matt Fonte

● Georgene Geary – GGfGA

● Caltrans – Dulce Rufino Feldman

● Flatiron – Michael Roe 

● Southwest ACPA – Charles Stewart
Extra slides
Using RCA in Pavement Base Products

Bound (stabilized) base applications 

○ Lean concrete subbase and cementstabilized subbase

○ Asphalt concrete and asphalt-stabilized 

subbase Includes example projects for 

each application

Unbound aggregate base 

applications

– Performance concerns

• Structural issues

• Drainage issues

– Qualification testing

• General

• Gradation

• Other tests (abrasion, soundness, 

etc.) 

– Subbase design and construction 

considerations

– Concrete pavement design considerations

– Environmental considerations
Using RCA in Unbound Aggregate Shoulders

• Constructability considerations

• particle degradation during roll-down

• moisture-density control

• other concerns

• Qualification testing 

• gradation

• Absorption

• LA abrasion/MicroDeval

• unconfined compression

• other tests

• Examples and Case Studies
Using RCA in Paving Mixtures

● Constructability considerations 

○ Fresh properties

● Pavement design considerations 

○ Hardened properties 

● Developing concrete mixture designs using RCA

○ Qualification Testing

○ Proportioning

● Examples and Case Studies

○ D-cracking aggregate

○ ASR

○ Continuously reinforced concrete pavement
Mixture Design Using RCA 

● Qualification testing

○ Agencies report success when ensuring RCA meets same requirements as 

virgin aggregates

○ Contaminant limits (ACPA 2009):

■ Asphalt concrete: < 1% by volume (although 30% or more ahs been 

successfully used in lower lift of 2-lift paving applications)

■ Gypsum: < 0.5% by weight 

■ Glass: 0%

■ Chlorides 0.6 lb/cy

○ Waive magnesium and sodium sulfate soundness tests since RCA results 

are unreliable - reaction between cement paste and test solutions
Use of RCA in Concrete Pavement

● Coarse RCA used as 38% replacement for natural aggregate

● Other RCA used in unbound base for the pavement

● Benefits

○ Cost savings to owner on price of 

material

○ Reduced hauling of existing material offsite and hauling new material on-site

● Contractor’s experience:

○ Make sure material is prewetted before 

adding to the mixer

○ Log washers have been successfully 

used to prewet RCA prior to mixing

Source: Castle Rock Construction Company 
Log Washer

Source: Matt Fonte, Castle Rock Construction Company 

Developed in 1890s –

Used in the mining industry 

to remove clay from gravel, 

ores, crushed stone to 

improve the quality of the 

material feed
Use of RCA in Interstate Concrete Shoulders

● Georgia DOT I-16 project – 56 miles 

● Truck lane replacement plus new inside and outside shoulder construction

● Existing 10-inch slab crushed at nearby stationary facility

● Trial batches used 100% RCA as fine and coarse aggregate but were too sticky

● Final mixture blended some natural sand to improve workability

● Final mixture 81.1% RCA and 

18.9% natural sand

● Approach allowed recycling of 

100% of removed concrete

● GDOT gained confidence in 

use of RCA for shoulders

Source: Georgene Geary, GGfGA
Use of RCA in Lean Concrete Bases

● Caltrans I-710 project in Los Angeles

● Rehabilitation of 3.5-mile stretch with 5 lanes in each direction

● Existing JPCP removed and mostly replaced with rapid strength JPCP, 

700 foot section of rapid strength CRCP constructed, weekend-closure schedule

● Existing pavement crushed and combined with existing aggregate base

○ 75-80% RCA plus 20-25% original aggregate base

● This blend was used as 100% of the 

coarse and fine aggregate in the new 

lean concrete base mixture

● Also used in new permeable base

Source: Caltrans
Factors to consider when comparing costs

Cost of the Virgin Material Cost of the Construction Byproduct

• Material costs (either virgin aggregate or binder)

• Cost to haul to site

• Cost to place and compact (for unbound uses)

• Cost to handle/store/manage (for bound uses)

• Cost to haul away existing or unsuitable materials

• Cost of existing or unsuitable material disposal

• Cost to take material to a crushing facility (if produced on site)

• Cost of hauling material to the site (if produced off site)

• Cost of blending material and hauling (if applicable)

• Cost of crushing and screening a material produced on site (if 

applicable)

• Cost of placement and compaction of the material (for 

unbound uses)

●Production costs for lower-grade applications (unbound base/fill) may be lower than 

production costs for higher-grade applications (bound bases/new concrete)

●Key to cost savings:

○ Consider use of byproducts early in project bidding or delivery phases 

■ Challenges can be addressed/cost savings potentially passed on

○ Allow contractor flexibility in establishing operations
Flowchart! Characterization and Assessment for Use

Tests to Support Use in 

Concrete

Tests to Support Use in

Base or Fill

Byproduct used as Aggregate Byproduct used as SCM

Tests to Support Use in 

Concrete

Tests to Support Use in 

Base or Fill

Tests of Byproduct Material

Recommended Tests for 

Qualification/Preconstruction Stage

 Contaminants (visual, or per 

AASHTO M 319)

 Uniformity should be 

evaluated by reviewing the 

variability of the 

characterization test results. 

The agency should 

determine the sampling 

frequency and allowable 

variability that provides 

confidence in the 

uniformity.

 Gradation (AASHTO T 27)

 Contaminants (visual, or per 

AASHTO M 319)

 Uniformity should be 

evaluated by reviewing the 

variability of the 

characterization test results. 

The agency should 

determine the sampling 

frequency and allowable 

variability that provides 

confidence in the 

uniformity.

 Optimum moisture and 

maximum dry density 

(AASHTO T 134)

 Gradation (AASHTO T 27)

 Contaminants (visual, or per 

AASHTO M 319)

 Uniformity should be 

evaluated by reviewing the 

variability of the 

characterization test results. 

The agency should 

determine the sampling 

frequency and allowable 

variability that provides 

confidence in the 

uniformity.

 Contaminants (visual, or per 

AASHTO M 319)

 Uniformity should be 

evaluated by reviewing the 

variability of the 

characterization test results. 

The agency should 

determine the sampling 

frequency and allowable 

variability that provides 

confidence in the 

uniformity.
Flowchart! Characterization and Assessment for Use

Tests to Support Use in 

Concrete

Tests to Support Use in

Base or Fill

Byproduct used as Aggregate Byproduct used as SCM

Tests to Support Use in 

Concrete

Tests to Support Use in 

Base or Fill

 Compressive strength

(ASTM C593 and/or 

 D1632)

 Freeze-thaw durability 

(ASTM C593 and/or D560)

 Maximum dry density and 

optimum moisture content 

(ASTM D698 or D1557)

 Compacted density 

(ASTM D1556 and/or 

 D3877)

 Volumetric stability 

(ASTM D3877)

 Resilient modulus 

(AASHTO T 307)

 Resilient modulus 

(AASHTO T 307)

 Shear strength (static triaxial 

and repeated triaxial 

loading, at optimal moisture 

content and saturated 

conditions)

 Assess the potential for 

Alkali-Aggregate Reactivity 

using AASHTO R 80

 Assess the susceptibility of 

the material to D-cracking 

using ASTM C666 (only if 

by-product material was not 

previously assessed using 

AASHTO T 103 or the 

hydraulic fracture test).

 Strength development 

(AASHTO T 22 / T 97)

 Unrestrained volume change 

(AASHTO T 160 or T 334) 

or restrained volume change 

(AASHTO T 363) 

Tests of Application

Containing Byproduct Material

Recommended Tests for 

Qualification/Preconstruction Stage
Flowchart! Characterization and Assessment for Use

Tests to Support Use in 

Concrete

Tests to Support Use in

Base or Fill

Byproduct used as Aggregate Byproduct used as SCM

Tests to Support Use in 

Concrete

Tests to Support Use in 

Base or Fill

 Compressive strength

(ASTM C593 and/or 

 D1632)

 Freeze-thaw durability 

(ASTM C593 and/or D560)

 Maximum dry density and 

optimum moisture content 

(ASTM D698 or D1557)

 Compacted density 

(ASTM D1556 and/or 

 D3877)

 Volumetric stability 

(ASTM D3877)

 Resilient modulus 

(AASHTO T 307)

 Resilient modulus 

(AASHTO T 307)

 Shear strength (static triaxial 

and repeated triaxial 

loading, at optimal moisture 

content and saturated 

conditions)

 Assess the potential for 

Alkali-Aggregate Reactivity 

using AASHTO R 80

 Assess the susceptibility of 

the material to D-cracking 

using ASTM C666 (only if 

by-product material was not 

previously assessed using 

AASHTO T 103 or the 

hydraulic fracture test).

 Strength development 

(AASHTO T 22 / T 97)

 Unrestrained volume change 

(AASHTO T 160 or T 334) 

or restrained volume change 

(AASHTO T 363) 

Tests of

Byproduct Material

Recommended Tests for 

Delivery or Construction
Flowchart! Characterization and Assessment for Use

Tests to Support Use in 

Concrete

Tests to Support Use in

Base or Fill

Byproduct used as Aggregate Byproduct used as SCM

Tests to Support Use in 

Concrete

Tests to Support Use in 

Base or Fill

Tests of Application Containing

Byproduct Material

Recommended Tests for 

Delivery or Construction

 Workability 

 (AASHTO T 119 / TP 129 / 

 TP 137)

 Air content 

 (AASHTO T 152 or T 196)

 SAM number

 (AASHTO TP 118)

 Strength 

 (AASHTO T 22 / T97)

 Optimum moisture and 

maximum dry density 

(AASHTO T 134)

 Compacted density 

(AASHTO T 310, 

AASHTO T 191, 

ASTM D2167)

 Compacted density 

(AASHTO T 310, 

AASHTO T 191,

ASTM D2167)

 Workability 

(AASHTO T 119 / TP 129 / 

TP 137)

 Air content 

(AASHTO T 152 or T 196)

 SAM number

 (AASHTO TP 118)

 Strength 

(AASHTO T 22 / T97)
Environmental Impacts

● Consider during Qualification/Preconstruction

○ Review agency regulations, specifications, permitting

○ Identify and address any environmental considerations

● Many byproducts contain small amounts of heavy metals and contaminant materials

● Water quality should be protected on and near the site

● RAP and RCA can produce high-pH runoff, leachate with contaminants

● Although levels can be greater than those acceptable in drinking water, research has shown runoff 

or leachate can be readily diluted, mitigated, or captured in nearby environmental systems 

(bioswales) or typical stormwater BMPs

○ RAP - Cosentino et al. 2003, Townsend and Brantley 1998, Brantley and Townsend 1999

○ RCA - Snyder et al. 2018

Photo: Dwayne Stenlund, MnDOT
Processing, Handling, and Storage

● Typically use equipment and methods like (or the same as) conventional materials

● Stockpile management 

○ Appropriate stockpile management to ensure contaminants are not introduced

■ RCA - limiting stockpiles to a single source of material to support consistency 

● Guidance in Snyder et al. (2018)

■ RAP – processes and techniques exist to support blending of material from 

multiple sources to achieve uniform composition (Hoppe et al. 2015). 

● Sampling and testing of RAP in West (2015).

● Mitigate environmental impacts

○ Manage high pH runoff (BMPs, setbacks from receiving waters)

○ Snyder et al. (2018) provides strategies for protecting air, water 

quality, reducing noise Photo: Tom Cackler