Rheological benchmarking of GTR-modified asphalt binder as a sustainable alternative to SBS modification

Styrene-butadiene-styrene (SBS)-modified binder is engineered for improved performance. However, as a proprietary product, its high-cost limits widespread use. Meanwhile, ground tyre rubber (GTR)-modified binder also has several performance benefits. Regardless, GTR-modified binder has not received widespread application in some regions despite availability of waste tyres. One reason could be a limited empirical understanding of the comparative differences in the performance characteristics of GTR- and SBS-modified binders. Therefore, the objective of this study was to determine GTR dosage of an AC-20 binder that would yield comparable rheological characteristics as a commercial SBS-modified binder. A six-year-old scrap tyre was processed into GTR particles and blended with an AC-20 graded bitumen at dosages ranging from 2% to 12%. Commercial SBS-modified binders containing 1%, 2%, and 3% SBS—corresponding to Superpave binder grades PG 70 − 22, PG 76 − 22, and PG 82 − 22, respectively—served as control. The GTR-modified binder containing 10% GTR content yielded similar or better fatigue cracking, thermal cracking and rutting performance characteristics than the 1% SBS-modified binder (PG 70 − 22). FTIR analysis revealed no detectable chemical alterations in the GTR-modified binder, indicating that the performance improvements observed were due to physical interaction of the GTR and AC-20 binder. Overall, the GTR dosage of 10% yielded rheological characteristics that benchmarked it against 1% SBS-modified binder (PG 70 − 22). This study shows the feasibility of utilizing GTR modification as a sustainable alternative to SBS binder modification.