Abstract
The usage of Ground Tire Rubber (GTR) in asphalt pavements has gained renewed interest due to its potential sustainability, economic, and performance benefits. This study focuses on asphalt mixtures designed with three different rubber modifier products including (1) a terminal-blend GTR, (2) a dry-process, chemically processed rubber product, and (3) a terminal-blend rubber-polymer hybrid product. The modifications were incorporated into Illinois Tollway’s approved Stone Matrix Asphalt (SMA) designs using (1) a base binder (PG 58-28), (2) a softer binder (PG 46-34), and (3) a softer binder with higher recycled content. Disk-shaped Compact Tension (DC(T)) test, Hamburg Wheel Tracking Test (HWTT) and Acoustic Emission (AE) tests were performed to characterize the mixtures. The fracture energy for most mixtures met the stringent criteria of 690 J/m2 and the rut depths measured were less than 6 mm at 20,000 wheel passes. A Hamburg-DC(T) plot suggests that higher amounts of RAP/RAS (RAP: Reclaimed Asphalt Pavement; RAS: Reusable Asphalt Shingles) can be successfully used if a suitably soft base binder is employed.
Highlights
More than 90% of roads in the United States are surfaced with asphalt
This study describes a detailed laboratory study involving a suite of mixture performance tests performed on mixture composed of three ground tire rubber (GTR) products used on the Illinois Tollway, namely: (1) Terminal-Blend GTR; referred to as TB-GTR-1, (2) a Dry-Process, chemically-treated rubber product; referred to as DP-GTR-1, and, (3) a second Terminal-Blend modified asphalt product composed of a hybrid GTR and styrene-butadiene-styrene (SBS) pellet blend, referred to as TB-GTR-2
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Summary
There are approximately 3500 asphalt plants in the US that produce roughly 400 million tons of asphalt mixtures annually [1,2]. The industry has been steadily moving towards adopting more sustainable practices. Prime examples of this have been the incorporation of recycled materials such as recycled asphalt pavement (RAP), recycled asphalt shingles (RAS), and ground tire rubber (GTR) in asphalt mixtures. Using recycled content in asphalt mixtures has economic and environmental benefits by reducing the production of new asphalt and aggregates, and by preventing the recycled material from being placed in landfills. Recycled materials can be used in high-performing asphalt mixtures [4,5,6,7,8,9,10,11,12,13,14], if carefully designed
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