RAS Research Update

Dr. Richard WillisNational Center for Asphalt Technology at Auburn University

March 11, 2014

1

Background

• Mix design considerations– Binder

Quantity and quality

– AggregateQuantity and quality

– VolumetricsAir voidsVoids in mineral aggregateVoids filled with asphaltDust

2

Things to Consider

RAP• 3 – 6 % asphalt binder• 94 – 97% stone

RAS• 19 – 36% asphalt• 2 – 15% fibers• 20 – 38% mineral aggregate• 8 – 40% mineral filler

3

What Affects Mix Design and Mixture Quality?

• Shingle type• Shingle gradation• Shingle quantity• Deleterious materials

4

Shingle Type

Manufacturer’s Waste• New shingles with less

oxidation• No contaminants• No asbestos

Post-Consumer• Commonly 20-40 years

old• Oxidized asphalt• Nails and other

deleterious materials• Might contain asbestos

– Must conform to EPA’s NESHAP and other local requirements

5

Shingle Gradation• Oversized shingles affect

– Asphalt mobilized– Mixture consistency

6

State Percent Passing½” 3/8” #4 No. 100 No. 200

Texas 100% 95% -- -- --Missouri -- 100% -- -- --GA/VA/AASHTO 100% -- -- -- --Iowa 100% 98% 90% -- --Oregon 100% 90% -- -- --South Carolina 100% -- 70.0 – 95.0% 15% Max 7% Max

Minnesota 100% -- 90% -- --

Shingle Aggregate Gradation

Sieve Size % Passing3/8 in (9.5 mm) 100No. 4 (4.75 mm) 95No. 8 (2.36 mm) 85No. 16 (1.18 mm) 70No. 30 (600 μm) 50No. 50 (300 μm) 45No. 100 (150 μm) 35No. 200 (75 μm) 25

• RAS Aggregate must be accounted for in new mix design

• AASHTO – Assumes gradation

• Does it matter if your RAS has a different gradation?

7

RAS Quantity

• Most states use between 3 – 5 percent RAS• AASHTO Recommendations

– If greater than 30 percent is shingle binder, must evaluate the blended binder to ensure performance grade (MP 15-09)

– Possibly effected by grind size

8

Deleterious Materials

• Material retained on #4 sieve

• AASHTO – Total deleterious < 3%– Lightweight < 1.5%

• Some states < 0.5%• Cleaner stockpiles =

better mixtures

9

Deleterious Materials

• Example specification (TEX-217-F Part III)– Oven dry sample– Sample 1000 g = WT

– Weigh Pan and pour sample over pan

– Magnet on pan catches metal pieces in shingle

– Weigh metal pieces = M

Deleterious Materials

• Sieves Used: 3/8”, No. 4, No. 8, No. 30• Shake sample for 10 minutes• Discard – No. 30 material• Test material retained on each sieve for deleterious

materials (wood, paper, plastic, felt paper)– Manual separation

• Weigh material removed from RAS for each sieve– Deleterious materials on 3/8” sieve =N3/8

Deleterious Materials

• P = percent of deleterious matter by weight• M = weight of material retained by magnet, g• N# = weight of deleterious substance on sieve, g

Design Considerations

• How do I determine the specific gravity of the RAS?

• How much binder is in the RAS?• How much of that binder am I actually

getting?

13

Shingle Specific Gravity

14

Peregrine et al., 2011

How Much Binder is in the RAS?

• Chemical extraction vs. Ignition Oven– Chemical Extraction:

Do I get all of the RAS?

– Ignition oven:Do I burn off other organic matter?

• AASHTO – Must use chemical extraction• Virginia – Developed ignition oven correction

factor

15

16

Shingle Binder Contribution

17

Organization How Much RAS Binder Is Available for Mix?

AASHTO Shingle Binder AvailabilityAlabama Department of Transportation 100 of RAS binderIowa Department of Transportation 66.7 percent of RAS binderMissouri Department of Transportation 100 Percent of RAS BinderTexas Department of Transportation 100 Percent of RAS BinderOregon Department of Transportation 100 Percent of RAS Binder

What’s the truth?

What Can Affect Binder Availability?

• Size of RAS• Where is the RAS

introduced• Aggregate temperature

• Binder temperature• Mixing time• Moisture content!

18Schroer 2009

AASHTO Methodology

1. Perform volumetric mix design on a mix which contains all components but RAS

2. Perform a second mix design on a RAS mixture1. RAS added at ambient temperature to aggregate

1. Should I heat the RAS overnight at 140F and then preheat for two hours at mix temp?

3. Determine the difference between the optimum asphalt content of virgin and RAS mixtures, Δ

19

AASHTO Methodology

4. If Δ is positive, RAS is contributing binder5. Multiply the percentage of shingle binder in

the RAS by the percent RAS in the mix = total available binder

6. Divide Δ by total binder available7. Correct shingle asphalt binder availability

factor

20

Limitations of Methodology

• Assumes– Differences in virgin and RAS mix is only due to

shingle binder and notFibersAggregate

21Townsend et al., 2007

Performance Grade

• When using high amounts of reclaimed binder, do I need to use a softer virgin binder?

• Blending charts

22

Performance Grade

• Challenge:– How do I determine the Performance Grade?– Too stiff for water controlled DSRs– BBRs can be difficult to make

23

Are Volumetrics Enough?

• Rutting– Flow number– Hamburg– Asphalt Pavement Analyzer

• Cracking– Energy ratio– Semi-circular bend (low and intermediate)– TSRST or IDT Creep Compliance– Overlay Tester– Beam fatigue or S-VECD

24

Research Plan Outline

• Phase I– Volumetrics of 5% RAS Mixture & Temperature

Study

• Phase II– Volumetrics of Alternate RAS Breakdown Mixtures– Investigation of results and additional testing

• Phase III – Performance testing of all mixtures

Phase I

• Lab mixed lab compacted 5% RAS Mixture– Based on Lee County Road Section 24– Volumetric samples mixed at:

350°F, 325°F, 300°F, 275°F, 250°F, & 225°F

– Aged and conditioned at 25 °F below mixing temperature

Aggregate StockpileBlend Percentages

L-24 5% RASCalera Limestone 820s 64% 63%Shorter Sand 30% 30%EAP Baghouse Fines 0% 1%Hydrated Lime 1% 1%Oxford PCRAS 5% 5%

Phase I - Results

Phase II

• Volumetrics of Alternate RAS Breakdown Mixtures– 5% RAS equivalent recovered shingle aggregate– 5% RAS equivalent recovered shingle binder– Control mixture matched to Lee County Road

159 Section 19 (L-19)

Phase II – 5% RAS Aggregate

• Mix design equivalent to original 5% RAS design BUT uses recovered shingle aggregate and fibers instead of whole shingles

Phase II – 5% RAS Binder

• Mix design similar to original 5% RAS design BUT no shingle aggregate or fibers were used– Other blend percentages were divided by 95% to

maintain aggregate structure

• Recovered RAS binder was added equivalent to the amount of binder from 5% RAS– 100% binder activation and blending assumed

Phase II – Control

• 0% RAS in Mix Design• Matched to Lee County Road 159 Section 19• Same aggregates and similar gradation to

the other mixtures

Stockpile Control (L-19) RAS Binder* RAS Aggregate 5% RASCalera Limestone 820s

74% 66.3% 63% 63%

Shorter Sand 25% 31.6% 30% 30%EAP Baghouse Fines 0% 1.1% 1% 1%Hydrated Lime 1% 1.1% 1% 1%Whole Oxford PCRAS 0% 0% 0% 5%Recovered RAS Agg. 0% 0% 5% 0%

Further Investigations

• Dry Mixing 5% RAS Samples– Three mixed for one minute

One washed and gradedOne aged for two hours

– One mixed for two minutes– Large Shingles still visible loosely coated with

fines– Color change between un-aged and aged sample

Further Investigations

• Shingles still visible and intact +#4 +#16

Further Investigations

• Fine aggregate color change Un-aged Aged

Conclusions• Temperature Study

– Temperature has a significant impact on volumetrics – The 5% RAS mixture has high variability due to either

the aggregate stockpiles, the inclusion of RAS, or both

• Alternate Mixtures– RAS aggregate and fibers had a slightly lower binder

content (6.2%)– Control mix, 5% RAS and RAS binder mixtures all had

approximately 6.4% optimum binder content

Conclusions

• Further investigations– Dry mixing experiment indicated that during

mixing little to no blending occurs– The color change may indicate that activation may

be more prevalent during the aging of the mixture

Thank you!

NCAT report 13-07: RAS Characterization: Best Practices

www.ncat.us

J. Richard Willis(334) 844-7301

willi59@auburn.edu37