Rheological Interference of Amine and Silane–Based Antistripping Agents on Crumb Rubber–Modified Binder

Abstract

Liquid antistripping agents are added to asphalt binder to improve moisture resistance of the mixture. However, the chemical makeup and bonding mechanism of antistripping agents may cause significant effects on binder rheology. This paper investigates the effects of two different liquid antistripping agents, one amine based and another silane based, on the rheological properties of crumb rubber–modified binder CRMB60. Rheological properties determined included rotational viscosity, performance grade (PG), percent recovery, nonrecoverable creep compliance, creep stiffness, and rate of relaxation. The number of cycles to fatigue failure aided in evaluating the fatigue life. The results show that the addition of antistripping agents caused a decrease in rotational viscosity of CRMB60. Moreover, the silane antistripping agent was observed to cause a bump in high-temperature PG, whereas low-temperature PG remained unaffected by both antistripping agents. The multiple stress creep and recovery (MSCR) analysis exhibited that the silane antistripping agent increased the percent recovery and decreased the nonrecoverable creep compliance, whereas the contrary trend was observed with addition of the amine antistripping agent. Both the amine and silane antistripping agents caused a significant decrease in the fatigue life of CRMB60. Additionally, minor effect was observed on low-temperature cracking performance by both the amine and silane antistripping agents up to a certain temperature below which the cracking exacerbates. Overall, it was concluded that antistripping agents affect the rheology of CRMB60 and should be given due consideration prior to adopting a particular antistripping agent.