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High Reclaimed Asphalt Pavement Use in Asphalt Mixtures. Canadian User/Producer Group for Asphalt Moncton, Canada November 15, 2009 Audrey Copeland and Gerry Huber FHWA and Heritage Research. Defining High RAP. R eclaimed A sphalt P avement Removed and/or reprocessed pavement

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high reclaimed asphalt pavement use in asphalt mixtures

High Reclaimed Asphalt Pavement Use in Asphalt Mixtures

Canadian User/Producer Group for Asphalt

Moncton, Canada

November 15, 2009

Audrey Copeland and Gerry Huber

FHWA and Heritage Research

defining high rap
Defining High RAP
  • Reclaimed Asphalt Pavement
  • Removed and/or

reprocessed pavement

materials containing:

~ binder (5%)

~ aggregates (95%)

High RAP is defined as more than

25% RAP by weight of mix.

rap efforts
RAP Efforts
  • State of the Practice
  • Primary Barriers and Remaining Challenges for Increased RAP Use
  • National Efforts to Overcome Challenges
slide5

AK

WA

VT

ME

MT

ND

OR

MN

NH

WI

MA

NY

ID

SD

RI

WY

MI

PA

CT

NJ

DE

MD

DC

NE

IA

NV

OH

IL

IN

UT

WV

CO

KS

MO

VA

CA

KY

NC

TN

OK

AZ

AR

NM

SC

GA

MS

AL

TX

LA

HI

FL

PR

States that Use More than 20% RAP in HMA Layers

All layers (20% or more)

Base and Intermediate layers only

Base layer only

Do not use more than 20% RAP

so why does half of the nation use 20 rap
So, why does < half of the nation use < 20% RAP?
  • Blended virgin and RAP binder qualities especially for high RAP mixes and polymer modified binders
  • Stiffening of the mix from high RAP quantities and resulting cracking performance.
other roadblocks
Other “Roadblocks”
  • Presence of dust
  • Consistency/variability

of RAP

  • Lack of Quality Control (QC) by contractor
  • Durability, especially in the surface layers
    • Raveling
things are improving
Things are improving…

Since 2007:

21 States have increased amount of RAP permitted

23 States now have experience with high RAP mixes

11 States have experience with high RAP and Warm Mix Asphalt mixes

current guidelines
Current Guidelines

AASHTO M 323 Standard Specification

for SuperpaveTM Volumetric Mix Design

Based on significant blending between virgin and RAP binder

Effects of plant production unknown

Calls for virgin binders that may be more expensive, hard to get

Blending chart analysis is time-consuming!

10

issues to consider when increasing rap
Issues to Consider when Increasing RAP
  • Additional Processing & Quality Control (QC)
  • Characterizing RAP
  • Changing Binder Grade
  • Mix Design
  • Blending/Co-mingling of Virgin and RAP Binder
  • Performance
processing and quality control
Processing and Quality Control
  • Mill Intelligently
  • Processing RAP
  • Stockpile Management
characterizing rap for high rap use
Characterizing RAP for High RAP Use
  • Asphalt Content
    • RAP binder contribution, reduce virgin binder required
    • Ignition oven or solvent extraction
  • Performance Grade of RAP binder
    • Estimate blended binder properties
    • Evaluate stiffness of RAP
    • Recovered Binder is unaged
  • RAP Aggregate Gradation
    • Ensure quality material
    • Determining Gsb, Gse of RAP aggregate – significant effect on VMA and asphalt content
    • Combined aggregate properties must meet consensus requirements
slide14

Investigation of Properties of Plant

Produced RAP Mixtures

Assess current guidelines for RAP usage by determining low and high temperature properties of plant-produced HMA with varying RAP contents and virgin binder grades

Investigate virgin and RAP binder blending during plant production

14

14

phase i conclusions
Phase I Conclusions
  • RAP has less impact than expected.
  • Higher RAP contents not significantly stiffer than virgin mix.
  • Binder did not stiffen linearly with increasing RAP content.
  • Dropping grade to PG58-28 not necessary.
phase ii mixture test methods
Phase II – Mixture Test Methods
  • Dynamic Modulus, E*
    • Master Curves
  • Indirect Tensile Test (IDT) Creep & Compliance
    • Critical Cracking Temperature
  • IDT at high temperatures
    • Relaxation Modulus
  • Complex Modulus, G* and d, of Recovered Binder
indirect tensile test
Indirect Tensile Test

Low temperature creep compliance test

0, -10, -20C

Low temperature strength test -10°C

Determine stiffness, strength, and critical cracking temperature, Tc

contractor a idt strength
Contractor A - IDT Strength

0% 15% 25% 40% 25% 40%

PG64-22 PG58-28

contractor a idt stiffness
Contractor A - IDT Stiffness

0% 15% 25% 40% 25% 40%

PG64-22 PG58-28

contractor b idt strength
Contractor B - IDT Strength

0% 15% 25% 40% 25% 40%

PG64-22 PG58-28

contractor b idt stiffness
Contractor B - IDT Stiffness

0% 15% 25% 40% 25% 40%

PG64-22 PG58-28

contractor c idt stiffness
Contractor C - IDT Stiffness

0% 15% 25% 40% 25% 40%

PG64-22 PG58-28

contractor d idt strength
Contractor D - IDT Strength

0% 15% 25% 40% 25% 40%

PG64-22 PG58-28

contractor d idt stiffness
Contractor D - IDT Stiffness

0% 15% 25% 40% 25% 40%

PG64-22 PG58-28

phase ii summary
Phase II Summary
  • Dynamic Modulus results seem to agree with Phase I results
    • RAP has less impact than expected.
    • Higher RAP contents not significantly stiffer than virgin mix.
    • Dropping grade to PG58-28 may not be necessary.
  • Critical cracking temperatures are mixed bag, but also indicate that binder grade changes may not be necessary.
slide37
NCHRP 9-46 Mix Design and Evaluation Procedure for High Reclaimed Asphalt Pavement Content in Hot Mix Asphalt

High RAP Mix Design

  • Objective: Develop mix design method and specification for HMA containing up to50% RAP.

37

37

evaluating rap performance
Evaluating RAP Performance

at Auburn University

  • Long Term Pavement Performance SPS-5 sections
    • Virgin
    • 30% RAP
    • Milled and non-milled surface
    • 50 and 125 mm thick
    • Oldest is over 17 years
sps 5 project locations
SPS-5 Project Locations

at Auburn University

so what s the take away
Experience and data supports the proper use of high RAP can provide similar or better performance than virgin mixes, but available plant and field data is sporadic.

On-going research results indicate high RAP use is possible without adversely affecting performance.

More studies are needed with emphasis on plant mixtures and field performance.

So….What’s The Take-away?