Characterization of Ground Tire Rubber Composites

Modifiers are used in asphalt binders to help create better mechanical and rheological properties. A common modifier is styrene-butadiene-styrene (SBS). The goal of this project is to replace SBS with ground tire rubber (GTR). Tires frequently end up in landfills and are not biodegradable. Incorporating GTR into asphalt would provide a way for the end-of-life tires to be recycled and allow for a reduction in landfill waste. This alternative will also reduce energy consumption and CO2 emission. Currently, GTR is not utilized because over time the GTR separates from the asphalt and creates stability issues. Finding a way to limit the separation of binder and GTR is key in creating a workable alternative to SBS. The addition of polymers to the GTR mitigates the separation. This project explored utilizing the polymers polybutadiene and polyisoprene with varying extruders. The polymers were extruded with a 15% polymer to GTR ratio. Two extruders were used for comparison of screw configuration, for a total of 4 GTR/polymer formulations. Asphalt blends are then prepared with the extruded product to create samples for testing. The tests that are run include DSR, SEM, Ball and Ring, and fluorescence microscopy to determine which combination produced the least amount of separation.