Effects of Amine and Silane Based Anti-Stripping Agents on the Performance Characteristics of Styrene-Butadiene-Styrene Polymer Modified Asphalt Binder

Anti-stripping agents (ASAs) have become a mandatory inclusion in bituminous mixtures containing hydrophilic aggregates and in regions experiencing extreme rainfall. Even with superior binders such as polymer-modified bitumen (PMB), ASAs are added to enhance moisture resistance in high-stress locations such as airfields, where significant pavement stresses and a strict zero-failure policy are critical for safety. This study deeply probes the rheological change in the behavior of PMB because of the addition of liquid ASAs: amine and silane. The performance of ASAs is analyzed from the perspective of cohesion, rutting, fatigue, and aggregate-bonding properties. Artificial aging of binders was performed to imitate short-term and long-term aging conditions using a rolling thin film oven and then a pressure aging vessel, respectively. A series of tests were conducted, which included FTIR (Fourier transform infrared spectroscopy), high performance grade temperature, Bitumen-Typisierungs-Schnell-Verfahren, rotational viscosity, force ductility, MSCR (multiple stress creep recovery), the BYET (binder yield energy test), and binder bond strength. FTIR tests evinced chemical rearrangement and polymer degradation because of the addition of ASAs in the PMB. MSCR analysis at multiple stress levels indicated a drop in rutting resistance with the presence of ASAs at high stresses and temperature, stipulating a loss of recovery property. The novel BYET measured the fatigue resistance of long-term aged binders and demonstrated that ASAs cause early yielding of binders. The addition of ASAs improved the bond strength of PMB with limestone, basalt, and quartzite aggregates. Comprehensively, this study concludes that ASAs have an impact on the rheology of PMB; however, there is a compromising of certain binder properties to attain the benefits of moisture resistance.