High Reclaimed Asphalt Pavement Use in Asphalt Mixtures

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U.S. Department of TransportationFederal Highway Administration

High Reclaimed Asphalt Pavement Use in Asphalt Mixtures

Canadian User/Producer Group for AsphaltMoncton, Canada

November 15, 2009

Audrey Copeland and Gerry HuberFHWA and Heritage Research


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

• State of the Practice

• Primary Barriers and Remaining Challenges for Increased RAP Use

• National Efforts to Overcome Challenges

U.S. Department of TransportationFederal Highway Administration 4

States that Permit more than 25% RAP


States that Use More than 20% RAP in HMA Layers

CA

AZ

CO

NM

TX

OK AR

LA

MO KY

AL GA

FL

VA

OH

MI

VTAK

MT

NV

MEWA

OR

UTKS

IDWY

ND

SD

MN

NE

WI

IAIL IN

MS

TNSC

NC

WV

PA

NY

CTNJDEMD

DC

MANH

PR

HI

RI

All layers (20% or more)Base and Intermediate layers onlyBase layer onlyDo not use more than 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.

6


Other “Roadblocks”

• Presence of dust

• Consistency/variability of RAP

• Lack of Quality Control (QC) by contractor

• Durability, especially in the surface layers– Raveling

7


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


HMA Asphalt Pavement Recycling Expert Task Group

Advance the use of RAP in asphalt paving applications by providing highway agencies with critical information regarding the use of RAP, technical guidance on high-RAP projects, and direction on research activities.

The members consist of representatives from highway agencies, industry, and academia.

Website: www.moreRAP.us


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!

Recommended Virgin Asphalt Binder Grade Percent (%) RAPNo change in binder selection < 15Select virgin binder grade one grade softer than normal 15 – 25

Follow recommendations from blending charts > 25


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


• Mill Intelligently

• Processing RAP

• Stockpile Management

Processing and Quality Control


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


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

https://engineering.purdue.edu/NCSC/index.htm


EXPERIMENTAL DESIGN

Reclaimed Asphalt Pavement

Binder Grade 0% 15% 25% 40%

PG 58-28 X XPG 64-22 X X X X


0.0001

0.0010

0.0100

0.1000

1.0000

10.0000

100.0000

1000.0000

10000.0000

0.001 0.010 0.100 1.000 10.000 100.000 1000.000 10000.000

Log Reduced Frequency, Hz

Log

Mod

ulus

, MPa

mix |E*| |G*|b,rec |G*|b,rap PG64

Phase I, PG64-22, 40% RAP



0.0001

0.0010

0.0100

0.1000

1.0000

10.0000

100.0000

1000.0000

10000.0000

0.001 0.010 0.100 1.000 10.000 100.000 1000.000 10000.000


Log

Mod

ulus

, MPa

mix |E*| |G*|b,rec |G*|b,rap PG58

Phase I, PG58-28, 40% RAP



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

• 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



Phase 2 Contractor A, PG 64-22 Mixes

100

1000

10000

100000

1.E-04 1.E-02 1.E+00 1.E+02 1.E+04 1.E+06

Log

|E*|,

MPa


PG64-22

MixA (0%0 RAP)

MixB (15% RAP)

MixC (25% RAP)

MixD (40% RAP)



Contractor A, 64-22 vs 58-28

100

1000

10000

100000

1.E-04 1.E-02 1.E+00 1.E+02 1.E+04

Log

|E*|,

MPa


PG64-22 versus PG58-28

MixC (25% RAP)

MixE (25% RAP)

MixD (40% RAP)

MixF (40% RAP)



Contractor B, PG64-22 Mixes

100

1000

10000

100000

1.E-04 1.E-02 1.E+00 1.E+02 1.E+04 1.E+06

Log

|E*|,

MPa


PG64-22

MixA (0%0 RAP)

MixB (15% RAP)

MixC (25% RAP)

MixD (40% RAP)



Contractor B, PG64-22 vs 58-28



Contractor C, PG64-22 Mixes

100

1000

10000

100000

1.E-04 1.E-02 1.E+00 1.E+02 1.E+04 1.E+06

Log

|E*|,

MPa


PG64-22

MixA (0%0 RAP)

MixB (15% RAP)

MixC (25% RAP)

MixD (40% RAP)



Contractor C, PG64-22 vs 58-28

100

1000

10000

100000

1.E-04 1.E-02 1.E+00 1.E+02 1.E+04 1.E+06

Log

|E*|,

MPa



MixC (25% RAP)

MixE (25% RAP)

MixD (40% RAP)

MixF (40% RAP)



Contractor D, PG64-22 Mixes

100

1000

10000

100000

1.E-04 1.E-02 1.E+00 1.E+02 1.E+04

Log

|E*|,

MPa


PG64-22

MixA (0%0 RAP)

MixB (15% RAP)

MixC (25% RAP)

MixD (40% RAP)



Contractor D, PG64-22 vs 58-28

100

1000

10000

100000

1.E-04 1.E-02 1.E+00 1.E+02 1.E+04

Log

|E*|,

MPa



MixC (25% RAP)

MixE (25% RAP)

MixD (40% RAP)

MixF (40% RAP)



Indirect Tensile Test

Low temperature creep compliance test 0, -10, -20C

Low temperature strength test -10°C

Determine stiffness, strength, and critical cracking temperature, Tc


Contractor A - IDT Strength

RR-A RR-B RR-C RR-D RR-E RR-F2000

2400

2800

3200

3600

4000

-44

-38

-32

-26

-20

Strength

Temperature

Mixes

Stre

ngth

, kPa

Pvmt. C

racking Tem

perature, °C

0% 15% 25% 40% 25% 40% PG64-22 PG58-28


Contractor A - IDT Stiffness

RR-A RR-B RR-C RR-D RR-E RR-F10

14

18

22

26

30

-44

-38

-32

-26

-20Stiffness

Temperature

Mixes

Stiff

ness

, GPa

Pvmt. C

racking Tem

perature, °C

0% 15% 25% 40% 25% 40% PG64-22 PG58-28


Contractor B - IDT Strength

JH-A JH-B JH-C JH-D JH-E JH-F2000

2500

3000

3500

-26

-20

-14

Strength

Temperature

Mixes

Stre

ngth

, kPa

Pvmt. C

racking Tem

perature, °C

0% 15% 25% 40% 25% 40% PG64-22 PG58-28


Contractor B - IDT Stiffness

JH-A JH-B JH-C JH-D JH-E JH-F10

14

18

22

26

30

-44

-38

-32

-26

-20Stiffness

Temperature

Mixes

Stiff

ness

, GPa

Pvmt. C

racking Tem

perature, °C

0% 15% 25% 40% 25% 40% PG64-22 PG58-28


Contractor C - IDT Stiffness

EB-A EB-B EB-C EB-D EB-E EB-F20

30

40

-20

-14

Stiffness

Temperature

Mixes

Stiff

ness

, GPa

Pvmt. C

racking Tem

perature, °C

0% 15% 25% 40% 25% 40% PG64-22 PG58-28


Contractor D - IDT Strength

PB-A PB-B PB-C PB-D PB-E PB-F2500

3000

3500

4000

-26

-20

-14

Strength

Temperature

Mixes

Stre

ngth

, kPa

Pvmt. C

racking Tem

perature, °C

0% 15% 25% 40% 25% 40% PG64-22 PG58-28


Contractor D - IDT Stiffness

PB-A PB-B PB-C PB-D PB-E PB-F10

15

20

25

-26

-20

-14

Stiffness

Temperature

Mixes

Stiff

ness

, GPa

Pvmt. C

racking Tem

perature, °C

0% 15% 25% 40% 25% 40% PG64-22 PG58-28


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.



High RAP Mix Design

• NCHRP 9-46 Mix Design and Evaluation Procedure for High Reclaimed Asphalt Pavement Content in Hot Mix Asphalt

• Objective: Develop mix design method and specification for HMA containing up to 50% RAP.


Evaluating RAP Performance

• 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

at Auburn University


SPS-5 Project Locationsat Auburn University


40

Fatigue Cracking

29%

10%61%

Virgin performedsignificantly betterthan RAP

RAP performedsignificantly betterthan Virgin

Differencebetween Virginand RAPinsignificant



41

Longitudinal Cracking

15%

10%

75%






42

Block Cracking

3% 1%

96%






43

Raveling7%

15%

78%






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.


Thank you!

Documents

High Reclaimed Asphalt Pavement Use in Asphalt Mixtures