effectof crumb rubber on rheological properties of asphalt ... 2015...–crumb rubber size, rubber...

Effect of Crumb Rubber on RheologicalProperties of Asphalt Binder and Aggregate

Packing of Asphalt Mixtures

Tirupan Mandal and Hussain BahiaUniversity of Wisconsin-Madison, USA

Hypothesis and Objective

•Hypothesis:– Crumb rubber size, rubber concentration, and reaction

time plays an important role in the rheologicalproperties of rubber modified binders and aggregatepacking of rubberized asphalt mixtures

•Objective:– Evaluate the effect of crumb rubber particles on the

rheological properties of asphalt binders and theaggregate packing of the rubber modified asphaltmixtures

Rubber Modified Binder Preparation

Factor Levels DescriptionBase Binder 1 PG 64-22

Crumb Rubber Size 2 0.595 mm (Coarse) and0.075 mm (Fine)

Crumb RubberConcentration 3 10%, 15%, and 20%

Blending Duration(or Reaction Time) 2 Green and Reacted

Selection of Reaction Times- Using Hand-held Viscometer @ 180±5 °C

0100020003000400050006000700080009000

10000

0 1 2 3 4 5 6 7 8

Visc

osity

(cP)

Time (hr)

Fine Rubber 15% 0.075-mm Rubber20% 0.075-mm Rubber10% 0.075-mm Rubber

0

500

1000

1500

2000

2500

3000

0 1 2 3 4 5 6 7 8

Visc

osity

(cP)

Time (hr)

Coarse Rubber 15% 0.595-mm Rubber10% 0.595-mm Rubber20% 0.595-mm Rubber

Green and Reacted times selected from these graphs!

Rubberized Asphalt Mixture Preparation

Size (mm)% Passing

Coarse Gradation Fine Gradation37.5 100.00 100.0025 100.00 100.0019 99.73 100.00

12.5 78.64 94.259.5 64.47 80.40

4.75 41.12 63.702.36 27.37 43.901.18 18.73 28.720.6 12.90 19.180.3 7.82 11.86

0.15 4.87 7.750.075 3.24 5.98

CompactionTemperature (CT):

155°C

MixingTemperature (MT):

145°C

From Viscosity-Temperature Profile

AC: 5.4% AC: 4.8%

Binder Testing Methods

Test Method Binder Type EvaluationParameters/Response Testing Standard

Cup and Bob Original Viscosity -NA-

Multiple Stress CreepRecovery (MSCR) RTFO Jnr

Stress Sensitivity AASHTO TP70

High Temperature(HT) Performance

Grading

Original andRTFO G*/sinδ AASHTO T315

Elastic Recovery (ER)-DSR RTFO Elastic Recovery AASHTO T XXX-13

Linear AmplitudeSweep (LAS) PAV Fatigue

AASHTO TP 101-12

Binder Testing Methods- Bob and Cup

Output: Viscosity

Binder Testing Methods- MSCR

• Creep stress:0.1kPa, 3.2 kPa

• 10 cycles– 1 sec constant creep

stress– 9 sec zero stress

• Output: Creepcompliance (Jnr)and PercentRecovery (%R) at 0.1kPa, and 3.2 kPa

MSCR B5 46ºC

0.001

0.01

0.1

1

10

0 25 50 75 100 125 150 175 200time (s)

g

DataModel PredictionStress: 0.1 kPa

Stress: 3.2 kPaStra

in

Binder Testing Methods- ER-DSR

Typical strain curve for elastic recovery test inthe DSR

- Temperature: 25°C- Conditioning Time: 20

minutes- Constant strain rate of

0.02315 1/s is applied for 2minutes.

- This step is run in straincontrolled mode and thenfollowed by a constant zeroshear stress for a period of30 minutes.

- This step is run in stresscontrolled mode andcorresponds to the recoverypart of the test.

Binder Testing Methods- LAS

The test involves two steps:- An initial 100 cycles applied

at 0.1% strain to determineundamaged linearviscoelastic properties, and

- A final step that consists oframping strain amplitude,beginning at 0.1% andending at 30% appliedstrain, over 3100 cycles ofloading at 10 Hz.

Fatigue law on log-scale (Hintz 2012)

Aggregate Packing Analysis- iPas2

Cutting Sections(Roohi et al. 2012)

Microstructural parameters

10% FineRubber - 2 h






1 rpm 3.8 3.0 10.8 8.3 28.1 12.010 rpm 2.2 1.8 4.3 3.9 10.6 6.6100 rpm 1.8 1.5 2.8 2.8 6.4 4.6

0.0

5.0

10.0

15.0

20.0

25.0

30.0

Visc

osity

(Pa.

s)

Viscosity @ 135°C

Fine Rubber

Binder Test Results - Viscosity

10% CoarseRubber - 2 h






1 rpm 1.9 2.0 4.1 4.5 18.1 17.010 rpm 1.5 1.6 2.6 2.9 7.9 7.9100 rpm 1.2 1.2 1.6 1.9 3.7 4.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

Visc

osity

(Pa.

s)

Viscosity @ 135°C

Coarse Rubber

- Viscosity increases with increase in crumb rubber concentration, and decrease withincrease in shear rate

- Binder modified with fine crumb rubber is more viscous than coarse crumb rubber

Binder Test Results –High TemperatureTrue Grade (TG)

Binder10% -GreenBinder

10% -ReactedBinder

15% -GreenBinder

15% -ReactedBinder

20% -GreenBinder

20% -ReactedBinder

0.075-mm Fine RubberUnaged Binder 78.2 76.3 82 81.7 91.1 85.6

RTFO Aged Binder 78 73.6 78.7 78.8 89.8 83.20.595-mm Coarse Rubber

Unaged Binder 77.2 76.7 80.4 81 87.3 87.5RTFO Aged Binder 81 77.8 84.7 82.6 87.7 91.5

- No change in TG for different reaction times- TG increases with increase in crumb rubber concentration

- 4 times grade bump for 20% concentration

Binder Test Results - MSCR

10% FineRubber -2 Hours






%Recovery 12.55 5.79 20.17 20.41 54.62 33.49JnR 1.43 2.60 1.24 1.22 0.23 0.67

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.00

10.00

20.00

30.00

40.00

50.00

60.00

JnR

% R

ecov

ery

Fine Rubber - 3.2 kPa Stress Level

10%Coarse

Rubber -2 Hours

10%Coarse

Rubber -5 Hours

15%Coarse

Rubber -2 Hours

15%Coarse

Rubber -5 Hours

20%Coarse

Rubber -1 Hours

20%Coarse

Rubber -4 Hours

%Recovery 8.57 5.03 17.87 18.56 52.19 46.83JnR 1.02 1.59 0.69 0.78 0.14 0.23

0.000.200.400.600.801.001.201.401.601.80

0.00

10.00

20.00

30.00

40.00

50.00

60.00

JnR

% R

ecov

ery

Coarse Rubber - 3.2 kPa Stress Level

- The %Recovery was lower, and the Jnr was higher for all the reactedbinders

0

10

20

30

40

50

60

70

80

90

100

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

%Re

cove

ry

Jnr (kPa-1)

AASHTHO TP-70 Limit 10% Fine Rubber - 2 Hours10% Fine Rubber - 5 Hours 15% Fine Rubber - 2 Hours15% Fine Rubber - 5 Hours 20% Fine Rubber - 2 Hours20% Fine Rubber - 5 Hours 10% Coarse Rubber - 2 Hours10% Coarse Rubber - 5 Hours 15% Coarse Rubber - 2 Hours15% Coarse Rubber - 5 Hours 20% Coarse Rubber - 1 Hours20% Coarse Rubber - 4 Hours

Binder Test Results- Jnr vs. %Recovery at 3.2 kPa Stress Level

Only 20% Crumb Rubber Concentration Passes!

Passing %Recovery

Failing %Recovery

Binder Test Results – ER-DSR

10% Fine Rubber 15% Fine Rubber 20% Fine Rubber 10% CoareRubber

15% CoarseRubber

20% CoarseRubber

GreenBinder 57% 63% 72% 61% 73% 83%

ReactedBinder 50% 64% 65% 59% 73% 80%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Elas

tic R

ecov

ery (

%)

Green BinderReacted Binder

- 20% concentration has highest ER value!- ER value is less for reacted binder similar to MSCR results

Binder Test Results - LAS

0

5000

10000

15000

20000

25000

30000

35000

40000

Nf

Nf 2.5% Nf 5%

- Coarser rubber performs better in fatigue than finer!- Nf drops for reacted binder

Aggregate Packing Analysis– On Green Binders

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

10%

Fine

rRu

bber

Gree

nBi

nder

20%

Fine

rRu

bber

Gree

nBi

nder

20%

Coar

ser

Rubb

erGr

een

Bind

er

TPL (

mm

/100

cm2 )

Fine GradationTotal Proximity Length

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

10% Finer Rubber GreenBinder

20% Finer Rubber GreenBinder

20% Coarser RubberGreen Binder

TPL (

mm

/100

cm2 )

Coarse GradationTotal Proximity Length

Coarser rubber performs better!

Aggregate Packing Analysis– Green vs. Reacted Binders

0

1000

2000

3000

4000

5000

6000

7000

8000

20% Finer RubberGreen Binder

20% Finer RubberReacted Binder

20% Coarser RubberGreen Binder

20% Coarser RubberReacted Binder

TPL (

mm

/100

cm2 )

Total Proximity Length

Green binder performs better!

Conclusions

• Rubber size, rubber concentration, and reaction time play animportant role in the rheological properties of the rubbermodified binders

• Binders modified with coarser rubber (0.595-mm) has betterrheological properties compared to the finer rubber (0.075-mm)

• Binders modified with higher rubber concentration (20%)performs better for both the sizes of rubber than the lowerconcentration, and also passes the AASHTO TP-70 MSCRcriteria

• Green binders, for both the rubber sizes, show betterrheological properties than the reacted binders

Conclusions

• It is found that rubber size and reaction time could haveimportant effects on aggregate packing duringcompaction, and thus performance

• Green binders for both the size of rubber are found tohave better aggregate packing than the reacted rubbermodified binders.

Thank you!

Questions?

effectof crumb rubber on rheological properties of asphalt ... 2015...–crumb rubber size, rubber...

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