Potential applications for composite utilization of rubber and plastic in asphalt pavements: A critical review

Waste plastics and rubber have always posed a threat to the environment and a great challenge for disposal. The use of these two waste materials as modifiers for road asphalt provides new road asphalt binders and at the same time provides a new way for waste material resource treatment. Rubber-modified asphalt and plastic-modified asphalt have received widespread attention due to their green and low-carbon characteristics and some performance advantages, but there are still some performance shortcomings that hinder their promotion and application. In order to continue to explore the application of waste materials in the field of road engineering, combined with the performance advantages of both, many scholars began to study the rubber-plastic composite modified asphalt (RPCMA). Therefore, this paper reviewed the different types of waste rubber and plastic, the comprehensive performance of different types of asphalt and its mixture performance, analyzed the modification mechanism of rubber-plastic composite modified asphalt and its performance changes. The results show that rubber-plastic composite modified asphalt is mostly prepared by directly adding modified materials. However, the pretreatment or melt granulation of rubber and plastic will make the performance of rubber-plastic modified asphalt has improved. There is a mutual promotion mechanism between rubber and plastic in asphalt, which makes the performance of rubber-plastic modified asphalt better than that of asphalt obtained by a single modification method (rubber modified asphalt or plastic modified asphalt). In some properties, it can be close to the commercial SBS modified asphalt. The performance of rubber and plastic composite modified asphalt at high temperature has been generally recognized by researchers, but its low-temperature performance is still controversial. Therefore, it is recommended to apply in high-temperature areas. Future work should focus on the development of composite modifiers with stable performance, low cost and ease of use, standardization of modification processes, improvement of low-temperature performance, and monitoring of road performance and environmental impact.