Effect of styrene-butadiene-styrene on the properties of asphalt and stone-matrix-asphalt mixture

This study investigates the benefits of modifying asphalt and stone-matrix-asphalt (SMA) mixtures in flexible pavement. 70/100-penetration-grade asphalt cement and 5% styrene-butadiene-styrene (SBS) triblock copolymer were selected. Unmodified and modified asphalt binders were subjected to physical and compatibility tests. Performance tests, including Marshall stability, static indirect tensile strength and static compressive strength at 25 and 60°C, tensile strength ratio, index of retained strength, rutting resistance, low-temperature cracking, and resilient modulus, were conducted on unmodified and SBS-modified SMA mixtures. The regression relationships between the performance tests were obtained. A mechanistic-empirical design approach was used to estimate the improvement in service life of the pavement or the reduction in thickness of the SMA and base layer for the same service life caused by modifying the SMA mixtures. The test results show that SBS-modified asphalt mixtures perform better than control mixtures. Temperature susceptibility can be reduced by including SBS in the asphalt mixture. The results of multilayer elastic analysis indicate that using SBS-modified SMA as surface layer in pavements reduces the number of construction materials used. Actual savings would depend on the designer's decision in reducing the thickness of an individual layer.