Comparing Ground Tire Rubber, Styrene-Butadyene-Styrene, and GTR-SBS Hybrids as Asphalt Binder Modifiers

Abstract

This technical note evaluated hybrid asphalt binders modified with a combination of styrene-butadyene-styrene (SBS) and postconsumer ground tire rubber (GTR). These hybrid blends were evaluated in laboratory mixture experiments against more traditionally modified binder using either SBS or GTR. Mechanical properties measured during laboratory experiments were supplemented with a literature review, followed by a discussion of trade-offs between these modification options within the context of a sustainability triple bottom line of environment, economics, and social well-being. This technical note also discussed test sections containing hybrid binders and how some state departments of transportation have incorporated hybrid binders into their specifications. Overall, this work suggests that performance leans toward SBS, sustainability leans toward GTR, economics sometimes leans toward GTR, and social well-being benefits from consideration of all these factors simultaneously. A hybrid binder containing 1%–2% SBS and 3%–8% GTR should allow for high-temperature grading increases and the use of GTR in a wider range of mix types than have historical approaches.