Evaluating the Effect of Coarse Rubber Particles on Asphalt Concrete Mixtures James K. Laicovsky Laura C. Miller Amanda R. Zimmerman The 18 th International Conference on Solid Waste Technology and Management Philadelphia, PA March 25, 2003

Outline of Presentation  The Tire Problem  Superpave  Project Scope  Results

Waste Tires Total ~ 300 Million Tires ~2.5 Million Tons

Solid Waste in the U.S. Scrap Tires = 1.5% Commercial & Industrial Residential

Solution

Recent Projects 85% of scrap tires are located in -- Connecticut, New York, Pennsylvania, Ohio, Michigan, Colorado, Virginia, Texas, and Alabama.

Superpave SUperior PERforming Asphalt PAVEments Strategic Highway Research Program New techniques to specify, test, and design

Project Scope §Rubber Analysis §Gradation Manipulation §Rubber Substitution §Specimen Fabrication §Specimen Testing §Fine-Tune Rubber Substitution

Gradation Manipulation Desired Superpave Gradation Curve Sieve Size.45 Percent Passing Bad Mix Good Mix Bad Mix

Rubber Analysis ¾” Rubber Particles #4 Rubber Particles #12 Rubber Particles

Rubber Substitution §Substituted Rubber into Original Superpave Gradation §0.5% - 5.0% Rubber Particles

Specimen Fabrication

 Gyratory Compactor 1.25°

GC Data Compaction Height, cm Gyration, N

GC Data Analysis Log (Number of Gyrations) H1 H2 Area = ½(H1-H2)(log100-log1) k 1 Slope = k Air voids at 100 gyrations Lower the number, softer mix

GC Data Plot Log (Number of gyrations), N Compaction Height, cm

Results Area Under “k” Curve vs. Rubber Substitution Area Under “k” Curve Rubber Substitution, %

Analysis  4% rubber substitution uses:  60 tons of GTR ~ 7,600 tires/lane mile  Rubber cost ~ $10,000/lane mile

Analysis  4% rubber substitution reduces:  780 tons of aggregates ~ $156,000 savings/lane mile Savings of $146,000/lane mile

Conclusions  Improved rutting performance.  Potentially useful with NJ aggregates.  Continued investigation to determine optimal substitution percentage.

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