Internal de-crosslinking of scrap tire crumb rubber to improve compatibility of rubberized asphalt

Currently, the use of Crumb Rubber (CR) derived from scrap tires for paving asphalt modification has been regarded as an effective and sustainable approach, while the end product, namely rubberized asphalt, severely suffered from poor compatibility. One solution to this incompatibility problem was the internal de-crosslinking pretreatment of CR, also known as devulcanization. The internal de-crosslinking was referred to as the selective cleavage of crosslinking bonds (mainly CS and SS bonds) in the vulcanized CR without affecting the main backbone chains. Firstly, the compatibility evaluation methods of rubberized asphalt were summarized in this paper, including morphology observation, segregation test, rheological test, and interaction measurement. Secondly, the state-of-art internal de-crosslinking technologies of CR for compatibility improvement of rubberized asphalt were summarized and compared, involving the physical radiation, mechanochemical extrusion, and microbial metabolism. Finally, concerning the limitations of present technologies, recommendations for future studies focusing on this issue were also provided.