Effect of vulcanisation on the properties of natural rubber-modified asphalt

Natural rubber (NR), a bio-based polymer, has significant potential for economic and environmental sustainability when used as an asphalt modifier in flexible pavements. In this study, natural rubber-modified asphalt (NRMA) was produced and the effects of vulcanisation on NRMA were investigated. The results showed that vulcanisation can improve the stiffness and elasticity of NRMA, thereby strengthening its resistance to deformation at high loads and temperatures. Specifically, vulcanisation increased the rutting factor of NRMA by 1.5, increased the elastic recovery by 60%, and decreased the temperature-sensitivity factor by 6.75%. In addition, the softening-point difference (SPD) of vulcanised natural rubber-modified asphalt (VNRMA) was significantly reduced by 36.8%, and the thermal-storage stability was improved. The micromorphology and changes in chemical bonds that occurred in VNRMA revealed that vulcanisation not only deepened the level of crosslinking between NR and asphalt, but also refined the NR particles, making NR more uniformly dispersed within the asphalt phase. By creating new chemical bonds, vulcanisation reinforced the NR network structure and change the main modification method for asphalt using NR from physical to chemical modification. This improved the rheological and mechanical properties of NRMA. The results of this study provide new solutions for NRMA applications and help improve its performance and application scope.