The preparation process, service performances and interaction mechanisms of crumb rubber modified asphalt (CRMA) by wet process: A comprehensive review

The application of end-of-life tires in asphalt pavement has benefits not only on reducing resource consumption but also on alleviating environmental pollution. The end-of-life tires are generally cut into crumb rubber (CR) and then blended with asphalt binder via wet process acting as polymer modifier to improve the rheological properties of asphalt binder. The objectives of this study are to review the related literature and delve into the inner connection among preparation process, service performances and interaction mechanisms of crumb rubber modified asphalt (CRMA). The characteristics of CR and mixing conditions with asphalt play important roles in the service properties of CRMA, including component, microstructure as well as mixing temperature, duration and shear speed. Different pretreatment technologies on CR particles, such as microwave, low temperature plasma, ultraviolet radiation and various chemical additives, have changed the microstructure and chemical bonds and differently affect the rheological responses of CRMA. The CR-asphalt interaction exhibits a process of light components penetration and followed a process of particle breakage, named CR swelling and degradation. The degree of swelling and degradation could be controlled by mixing conditions of CRMA and thus control the rheological properties. It is concluded that CRMA presents superior service performance when CR reaches swelling equilibrium in asphalt.