Compatibility and low-temperature performance evaluation of asphalt modified with untreated and KH-151-treated crumb rubber

A common challenge in asphalt is low-temperature hardening due to wax crystallization, causing cracking and elevated internal stress-induced fractures. The asphalt binder modification with crumb rubber (CR) has been extensively studied to improve asphalt pavement performance and sustainability. However, conflicting findings have been reported regarding the impact of CR on the ductility of asphalt binder, specifically at low temperatures. This study investigates the low-temperature performance of rubberized asphalt modified with CR treated using the KH-151 coupling agent. Conventional, untreated CR modified, and KH-151-treated CR modified asphalt samples were evaluated through force ductility tests at 5 ℃ and bending beam rheometer (BBR) tests. The asphalt binders were modified using 25% CR by weight of asphalt, with CR treated at KH-151 concentrations ranging from 1% to 2%. KH-151 treatment improved compatibility, reducing the softening point difference from 12.7 ℃ for untreated to 1.8 ℃ for 1.6% KH-151-treated CR modified asphalt, ensuring even CR particle distribution in asphalt. The viscosity reduced from 5.1 Pa⋅s for untreated CR modified asphalt to 2.6 Pa⋅s for 1.6% KH-151-treated CR modified asphalt, improving workability. Force ductility tests at 5 ℃ showed superior flexibility for 1.6% KH-151-treated CR modified asphalt, with elongation reaching 17.2 cm before aging and 12.2 cm after short-term aging. BBR tests at -24 ℃ showed creep stiffness reduced from 298 MPa for untreated CR modified asphalt to 221 MPa for 1.6% KH-151-treated CR modified asphalt, and m -values increased from 0.238 to 0.305. Correlation analysis confirmed strong relationships between BBR m -values and force ductility parameters ( R 2 > 0.8).