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

Outline ● Background ● Problem Statement ● Objective ● Methodology ● Laboratory Testing ● Results ● Conclusions & Recommendations ● Acknowledgements 2

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

RAP Usage in the US

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

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

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

RAP Gradations (12.5 mm NMAS)

Measured RAP Properties Source of RAP Binder Content (%)* Average G mm Asphalt Absorption (Initial Assumption) (%) US US US Konza Shilling * Ignition oven

Gmm Test (KT-39)

Coarse and Fine Aggregates in RAP Materials RAP Source Ignition OvenSolvent Extraction % Coarse% Fine% Coarse% Fine US US US Konza Shilling

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

RAP Aggregate Bulk Specific Gravity

Aggregate Specific Gravity Test Results

Statistical Analysis ● Comparison of Gsb Test methodCompared toReject H 0 G se Ignition ovenYes G se Solvent extractionYes G se RAP G mm Yes Ignition ovenSolvent extractionNo Ignition ovenRAP G mm No Solvent extractionRAP G mm No

Changes in Gsb as a function of asphalt absorption

VMA Obtained Using Gsb from Different Methods (Konza RAP)

VMA Obtained Using Gsb from Different Methods (Shilling RAP)

Statistical Analysis VMA obtained fromCompared toReject H 0 G se Ignition ovenYes G se Solvent extractionYes G se RAP G mm Yes Ignition ovenSolvent extractionNo Ignition ovenRAP G mm No Solvent extractionRAP G mm No

Differences in calculated VMA as a function of RAP content

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

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

Acknowledgements ● This study has been sponsored by the Kansas Department of Transportation (KDOT) ● Project Monitor: Brian Coree, Ph.D., P.E.

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