Optimization on Additives of SBS and CTR for Interlayer Asphalt in Rigid-Flexible Composite Pavement

Abstract This research was performed to improve the interlayer shear bond strength of rigid-flexible composite pavement. Based on the laboratory testing, three types of additive, which are listed as follows, were recommended and investigated to determine the optimum content of crumb tire rubber (CTR) and thermoplastic styrene-butadiene-styrene (SBS): 8 % CTR + 3.5 % SBS, 10 % CTR + 3 % SBS, and 12 % CTR + 2.5 % SBS. The high-temperature property and viscous nature of co-modified asphalts were studied by using a rotational rheometer. A temperature sweep and a shear fatigue test were performed to characterize the dynamic mechanical performance and fatigue property of asphalt materials. The results showed that the co-modified asphalt with 8 % CTR and 3.5 % SBS performed best in a viscosity test at 60°C. At 135°C and 165°C, it exhibited good viscous nature and had the desired workability of asphalt pumping and mixing. The high-temperature grade, the dynamic mechanical performance, and fatigue property of this co-modified asphalt were of great satisfaction as well. Therefore, 8 % CTR + 3.5 % SBS is recommended as a modifying material for construction and design purpose.