Improving the properties of hot applied crack sealant by utilizing Pre-activated Crumb Rubber (PCR)

Crack sealing stands as a cost-effective pavement maintenance practice and has a typical life span of 1–3 years. To enhance sealants’ longevity and optimize their performance, evaluating potential material modification, particularly in hot and arid regions, is of interest. In this research study, a comprehensive testing protocol was designed to address prevalent failure modes observed in asphalt crack sealants such as adhesion, cohesion, pumping, and settlement failures. The primary modification involved the incorporation of Pre-activated Crumb Rubber (PCR) at varying concentrations (2.5%, 5%, and 7.5%) by weight of the sealant. Testing was conducted on both unaged and short-term aged sealant samples with different PCR contents. The findings revealed promising improvements associated with PCR concentrations up to 5%, manifesting as enhanced elasticity, toughness, tenacity, flexibility at low temperatures, and resistance to shear thinning at high temperatures. For a content of 5% PCR, the results show a decrease of the non-recoverable creep compliance (Jnr) of 60% for 0.1kPa and 81% for 3.2kPa loading conditions when compared to the control sealant. Furthermore, an increase in toughness and tenacity of 72% and 25% respectively was measured for the aged conditions. In terms of shear thinning resistance, the coefficient “P” increased from 0.75 to 0.83 indicating a greater resistance to tracking. The results indicated favorable trends with the addition of the modifier, yielding potential improved performance in the field.