CalAPACalAPACalAPACalAPA 2016 Spring Conference2016 Spring Conference2016 Spring Conference2016 Spring Conference

Asphalt Institute’s recommendations for

Mix Design Using RAP / RAS

Robert P. Humer, PE.

Sr. Regional Engineer (for CA, AZ, NV, OR, WA and HI)

Asphalt Institute

3625 Thousand Oaks Blvd., Suite 278

Westlake Village, CA 91362

cell phone: 805-402-1211

e-mail: rhumer@asphaltinstitute.org

Old Mix Design Manuals, SP-2 and MS-2

2

Combined into newly revised MS-2

Covers;

• Marshall

• Hveem

3

• Hveem

• Superpave

Chapter 11;

Mix Designs using

RAP/RAS

Properties to Consider

Mixes using Recycled materials should meet the same specifications as for mixes using only virgin materials

There are Binder and Aggregate sides to consider:

• Binder: After blending, the RAP binder and virgin binder, the binder • Binder: After blending, the RAP binder and virgin binder, the binder blend should meet the PG grade for the project’s climatic conditions

• Aggregates: After blending, the Aggregates should meet both the “Consensus” and the “Source” properties as specified

• Volumetrics: After blending, the volumetric properties shall meet the requirements as specified for virgin mixes.

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Aggregate Properties

Aggregates need to meet:

• Consensus Properties:

• Course aggregate angularity (CAA)

• Fine aggregate angularity (FAA)

• Sand Equivalent (SE) [not for the RAP Aggregates]

• Flat and Elongated (F&E)

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• Flat and Elongated (F&E)

• Source Properties:

• Toughness (LA Abrasion)

• Soundness

• Deleterious materials

VMA

Va

Vbe

VFA

Mass air = 0

Mb

Analyzed byAnalyzed byAnalyzed byAnalyzed by

VOLUMEVOLUMEVOLUMEVOLUME

Measured byMeasured byMeasured byMeasured by

MASSMASSMASSMASS

Total

Air

Asphalt

Abs. AsphaltV

Mbe

Volumetrics

6

Vmb

(Total

Unit

Volume)Vsb

Gsb

Ms

Total

Mass

Aggregate

Abs. Asphalt

Vse

Gse

Vba

Specific Gravity bridges the gapVbinder = Vbe + Vba

See MS-2

Figure 5.3

See MS-2

Figure 5.3

NCHRP 9-12

Recommended Use of Reclaimed Asphalt Pavement (RAP) in the Superpave Mix Design Method.

National Guidelines

AASHTO M323 Table 2

Binder Selection Guidelines for

RAP Mixtures

NCHRP 9-12 Recommendations

• RAP mixtures should be able to perform at least as well as virgin mixes

• RAP aggregates need to be included in consensus properties and gradations. Watch changes in aggregates due to changes in aggregates due to extraction/ignition

—Exception: sand equivalent value

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Recommended Virgin Asphalt Binder Grade RAP Percentage

No change in binder selection < 15

Select virgin binder one grade softer than

Binder Selection Guidelines for RAP Mixtures

AASHTO M323 Table 2

Select virgin binder one grade softer than normal (e.g., select a PG 58-28 if a PG 64-22 would

normally be used.

15 to 25

Follow recommendations from blending charts > 25

The limits may vary per agency. Example: Some

agencies allow 30% RAP with no grade adjustment.

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MS-2

Section 11.3.4.1

MS-2

Section 11.3.4.1

RAP Considerations

• > 15% RAP requires Lab work (at a minimum for gradation and RAP binder content

• Fractionated RAP (FRAP) allows for better control

• RAP Pavement Binder Ratio (RPBR) is replacing • RAP Pavement Binder Ratio (RPBR) is replacing %RAP, especially when RAS is involved.

• For important paving projects, use binder blending charts for > 15% RAP, and consider using Performance Tests (such as HWT)

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MS-2

Section 11.1 & 11.3

MS-2

Section 11.1 & 11.3

AASHTO M320 (PG-grading)

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Example

Desired Final Binder Grade: PG 64-22

RAP Percentage: 30%

Blending Charts (example)

Tc(need)

NCHRP 752

changes to

RAP Binder

Ratio (RAPBR) Ratio (RAPBR)

or Total Binder

Replacement

12

76

82

88

, C

Blending Charts (example)

DSR High Temperature (same method is used

for Low and Intermediate Temperatures)

52

58

64

70

0% 20% 40% 60% 80% 100%

Percentage of RAP

T crit

ica

l, C

54.3

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The RAP / Black Rock Question

• Does RAP act Like a Black Rock in the Mixture?

—When a chunk of RAP is added to the mix does the RAP asphalt binder actually interact (blend) with the virgin AC?

Answer to this question determines the need for *blending charts.

*Blending charts: Require recovered asphalt testing to better understand the potential asphalt grade.

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MS-2

Section 11.4

MS-2

Section 11.4

Mix Tests to check blending

• High Temperature— Superpave Shear Test: Repeated

Shear at Constant Height (RSCH)

— Shear Modulus

— Accelerated Mixture Performance Test (AMPT) Flow Number

• Intermediate Temperature• Intermediate Temperature— Modulus

— Fatigue

— Accelerated Mixture Performance Test (AMPT) Dynamic Modulus

• Low Temperature— Indirect Tensile Creep and Strength

We evaluated RAP using the tests that are red.

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0.020

0.025

0.030

0.035

Pla

stic

Sh

ea

r S

tra

in

(ru

ttin

g p

ote

nti

al)

RSCH Test @58C, PG 64-22 CT 10% RAP

AAAA

BBBB

CCCC

�Case A represents “black rock”

�Case B represents standard practice

�Case C represents total blending

0.000

0.005

0.010

0.015

0.020

0 1000 2000 3000 4000 5000 6000

Pla

stic

Sh

ea

r S

tra

in

(ru

ttin

g p

ote

nti

al)

Cycles

Higher strain is more potential rutting

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0.025

0.030

0.035

0.040

Pla

stic

Sh

ea

r S

tra

in

(ru

ttin

g p

ote

nti

al)

RSCH Test @58C, PG 64-22 CT, 40% RAP

�Case A represents “black rock”

�Case B represents standard practice

�Case C represents total blending

A

B

0.000

0.005

0.010

0.015

0.020

0 1000 2000 3000 4000 5000 6000

Pla

stic

Sh

ea

r S

tra

in

(ru

ttin

g p

ote

nti

al)

Cycles

BC

Higher strain is more potential rutting

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Indirect Tensile Testing (IDT)Indirect Tensile Testing (IDT)Indirect Tensile Testing (IDT)Indirect Tensile Testing (IDT)Indirect Tensile Testing (IDT)Indirect Tensile Testing (IDT)Indirect Tensile Testing (IDT)Indirect Tensile Testing (IDT)

IDT measures the critical low-temperature cracking properties of a mixture by testing how the mixture relaxes (creep compliance).relaxes (creep compliance).

MS-2

Section 10.5.1

MS-2

Section 10.5.118

15,000

20,000

25,000

Sti

ffn

ess

, M

Pa

Higher stiffness means more potential for cracking

Creep Stiffness at -20°C, 40% RAP

0

5,000

10,000

Case A Case B Case C

Sti

ffn

ess

, M

Pa

PG

52

-34

PG

52

-34

PG

52

-34

PG

64

-22

PG

64

-22

PG

64

-22

�Case A represents “black rock”

�Case B represents standard practice

�Case C represents total blending

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Conclusion

• Blending does occur to an appreciable extent at higher %RAP

• Therefore…

Using blending charts is reasonable for Using blending charts is reasonable for higher RAP contents!

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NCHRP 9-12 Recommendations

• Blending occurs at higher RAP contents. At low RAP contents, effects are not significant.

• Results from all phases of the NCHRP research support concept of a tiered system for selecting the support concept of a tiered system for selecting the virgin binder grade for use with RAP.

• Mix ETG recommendations were largely confirmed!

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MS-2

Section 11.3.4

MS-2

Section 11.3.4

Effects when using WMA Technology

• In order to bring the RAP up to the required mixing temperature

(approx. 320 F), the virgin aggregate needs to be “super-heated”.

• Over-heating (> 400 F) the virgin aggregate may cause aggregate

break down.

• This limits the %RAP that can be used in the mix

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• This limits the %RAP that can be used in the mix

• By using WMA Technology you can lower the required mix

temperature, and use a higher %RAP.

• However blending of the RAP binder and virgin binder may happen

to a lesser extent.

MS-2

Section 11.2

MS-2

Section 11.2

RAS Properties

• RAS binder is very different from paving grade binders, and may not blend sufficiently.

• Shingles are made using “air-blown” asphalt.

• RAS binder compares with approx. a PG 142 or • RAS binder compares with approx. a PG 142 or higher, with a softening point above 120 °C, and can not be tested with normal PG test protocols.

• If using RAS, study up on the most recent research and National recommendations.

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MS-2

Section 11.2

MS-2

Section 11.2

Questions

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