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Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and...

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Background - Reclaimed Asphalt Pavement (RAP) ● Approx. 100 million tons of RAP produced each year and 80 million tons are reused ● Useful alternative to virgin aggregates in HMA:  Reduces cost  20% RAP with 5% binder  1% savings in new binder  Enables recycling  Conserves energy RAP Stockpile at Shilling Construction Co., Manhattan, KS
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Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain, Ph.D.,P.E. Department of Civil Engineering Kansas State University
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Page 1: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities

of RAP and Constituent Aggregates

Nassim SabahferMustaque Hossain, Ph.D.,P.E.

Department of Civil EngineeringKansas State University

Page 2: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Outline ● Background● Problem Statement ● Objective● Methodology● Laboratory Testing● Results● Conclusions & Recommendations● Acknowledgements

2

Page 3: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Background - Reclaimed Asphalt Pavement (RAP)

● Approx. 100 million tons of RAP produced each year and 80 million tons are reused

● Useful alternative to virgin aggregates in HMA:

Reduces cost 20% RAP with 5% binder 1% savings in new binder

Enables recycling Conserves energy RAP Stockpile at Shilling

Construction Co., Manhattan, KS

Page 4: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

RAP Usage in the US

Page 5: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Problem Statement● Superpave mix design is predominantly used now and

permits use of RAP

● Superpave volumetric mix design is highly dependent on properties like VMA, VFA, and Dust-to-Binder Ratio

● These parameters need blend bulk aggregate specific gravity in the calculation process

● RAP aggregate specific gravity is tricky

Page 6: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Objectives● Compare RAP aggregate bulk specific gravity (Gsb)

obtained from various methods

● Investigate influence of this Gsb on the calculated VMA

● Investigate effect of asphalt absorption assumption

● Study RAP maximum theoretical specific gravity (Gmm) as RAP Gsb

Page 7: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Methodology● Choose RAP sources (5)

● Run maximum specific gravity tests (Gmm) on two replicates of each RAP

● Obtain RAP aggregates via (a) extraction and (b) ignition oven burn off

● Sieve into coarse (plus #4) and fine (minus #4) fractions

● Run bulk specific gravity tests and compare

● Compute VMA and compare

Page 8: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

RAP Gradations (12.5 mm NMAS)

00

10

20

30

40

50

60

70

80

90

100

US 56

US 59

US 73

Konza

Shilling

0.075 0.15 0.3 0.6 1.18 2.36 4.75 9.5 12.5 19

Perc

ent P

assin

g

Page 9: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Measured RAP Properties

Source of RAP

Binder Content

(%)*Average Gmm

Asphalt Absorption (Initial Assumption)

(%)

US-56 5.18 2.424 1.5

US-59 6.86 2.470 1.5

US-73 5.77 2.342 1.5

Konza 4.20 2.477 1.5

Shilling 5.80 2.439 1.5

* Ignition oven

Page 10: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Gmm Test (KT-39)

Page 11: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Coarse and Fine Aggregates in RAP Materials

RAP Source Ignition Oven Solvent Extraction

% Coarse % Fine % Coarse % Fine

US-56 36 64 31 69

US-59 31 69 29 71

US-73 30 70 21 79

Konza 34 66 30 70

Shilling 28 72 25 75

Page 12: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

RAP Aggregate Bulk Specific Gravity

● Method #1 ● Split extracted aggregates into coarse and fine

fractions● Determine bulk specific gravity of each fraction

● Method #2● Same as #1; use burned off aggregates

Page 13: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

RAP Aggregate Bulk Specific Gravity

● Method #3 ● Determine RAP Gmm● Determine RAP binder content ● Calculate Gse of RAP:● Assume or know asphalt absorption, Pba● Calculate Gsb of RAP aggregate:

Page 14: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Aggregate Specific Gravity Test Results

US-56 US-59 US-73 Konza Shilling0

0.5

1

1.5

2

2.5

32.663 2.706

2.593 2.667 2.6912.557 2.471

2.319 2.3362.473

2.5672.436

2.244 2.3252.454

2.424 2.472.342

2.477 2.439

Gsb (Gse method)Gsb (Ignition oven)Gsb (Solvent extraction)RAP Gmm

Page 15: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Statistical Analysis

● Comparison of Gsb

Test method Compared to Reject H0

Gse Ignition oven Yes

Gse Solvent extraction Yes

Gse RAP Gmm Yes

Ignition oven Solvent extraction No

Ignition oven RAP Gmm No

Solvent extraction RAP Gmm No

Page 16: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Changes in Gsb as a function of asphalt absorption

1.2 1.5 1.82.5

2.55

2.6

2.65

2.7

2.75

2.671 2.663 2.655

2.713 2.706 2.697

2.6 2.593 2.585

2.675 2.667 2.659

2.699 2.691 2.683

US-56US-59US-73KonzaShilling

Asphalt Absorption (%)

Gsb

Page 17: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

VMA Obtained Using Gsb from Different Methods (Konza RAP)

20% RAP 30% RAP 40% RAP 30% FRAP 40% FRAP0

2

4

6

8

10

12

14

16

14 14.1 14 14 14

11.710.6

9.210.4

9.2

12.4 12.211.4

1211.4

9 GseGsb (Ignition)Gsb (Extract)Gmm RAP

VMA (%)

KDOT Require-ment

Page 18: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

VMA Obtained Using Gsb from Different Methods (Shilling RAP)

20% RAP 30% RAP 40% RAP 30% FRAP 40% FRAP0

2

4

6

8

10

12

14

16

14.1 14 14.2 14.1 14.312.6

11.811.3

11.9 11.412.511.5

1111.7

11.112.4

11.410.8

11.510.9

GseGsb (Ignition)Gsb (Extract)RAP Gmm

VMA (%)

KDOT Requirement

Page 19: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Statistical Analysis

VMA obtained from Compared to Reject H0

Gse Ignition oven Yes

Gse Solvent extraction Yes

Gse RAP Gmm Yes

Ignition oven Solvent extraction No

Ignition oven RAP Gmm No

Solvent extraction RAP Gmm No

Page 20: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Differences in calculated VMA as a function of RAP content

20 22 24 26 28 30 32 34 36 38 401

1.5

2

2.5

3

3.5

4

4.5

5

5.5

Gse and Ignition oven (Konza RAP)

Gse and Solvent extraction (Konza RAP)

Gse and Ignition oven (Shilling RAP)

Gse and Solvent extraction (Shilling RAP)

Percentage of RAP

Diff

eren

ce in

%V

MA

Page 21: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Conclusions● Gsbs obtained from the ignition oven and solvent

extraction methods are similar but both are different from that based on Gse

● Statistically RAP Gmm is not significantly different from Gsb obtained from the ignition oven or solvent extraction method

● VMA obtained from Gse-based Gsb is significantly different from the VMA’s obtained from other Gsbs

● Difference in VMA increases considerably as the RAP content increases

Page 22: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Recommendations

● RAP aggregate Gsb using either from the extraction or the ignition oven test method should be used in design of Superpave mixtures with RAP

Page 23: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Acknowledgements● This study has been sponsored by the Kansas

Department of Transportation (KDOT) ● Project Monitor: Brian Coree, Ph.D., P.E.

Page 24: Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates Nassim Sabahfer Mustaque Hossain,

Thank You


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