Investigation on microstructure characteristics of crumb rubber compound modified asphalt at preparation process

This study presented the investigation on the microstructure characteristics and the interaction among asphalt, crumb rubber (CR) and modifiers (softener, activator, and cross-linking agent) of crumb rubber compound modified asphalt (CRCMA) at process phases by microscopic testing techniques. The results showed that CRCMA had excellent rheological properties at high or low-temperature. The softener was only physically mixed with asphalt and did not change the microscopic morphology of the asphalt. The activator can break some of the chemical bonds of CR and promote the desulphurization degradation reaction which makes the asphalt show a large number of small-body type mesh structures and a small amount of chains in microscopic morphology. The crosslinking agent provided a source of sulphur to induce the crosslinking reaction which resulted in an increase in the reticulation of CRCMA. Finally, a modification mechanism model and the evolution mechanisms based on the microstructure characteristics at preparation phases of CRCMA were proposed.