Terminal blended rubberized asphalt binder (TB) technology, which blends crumb tire rubber (CR) with asphalt under high interaction conditions, offers a promising waste tire recycling solution for pavement construction. By precisely controlling the degradation progress of CR, it is possible to prepare TB with specific property requirements. However, the degradation progress of CR and its impact on TB property during the TB preparation process remain ambiguous. This hinders the potential for efficient preparation of TB with specific property requirements. This study aims to understand the degradation progress of TB by analyzing binders, soluble fractions, and insoluble fractions obtained at various interaction durations. Microscopic analysis characterizes the chemical composition, morphology, and molecular weight distribution of insoluble and soluble fractions, while macroscopic analysis evaluates the solubility, viscosity, compatibility, and mechanical properties of binders. The results reveal that the degradation of CR during the preparation of TB consists of a desulfurization reaction, depolymerization reaction, and release behavior (carbon black and fillers). Depending on the degradation progress of CR, the interaction process can be classified into three stages: initial (desulfurization reaction dominant stage), middle (depolymerization reaction dominant stage), and last (release behavior dominant stage). The desulfurization reaction of CR is almost completed in the initial stage. The depolymerization reactions and release behavior occur throughout the process. The most pronounced depolymerization reactions occur in the initial stage for natural rubber and in the middle stage for synthetic rubber, while the most significant release behavior occurs in the last stage. Accordingly, in the initial stage, TB shows a rapid evolution in macro properties due to the significant development of degradation reactions, specifically, the notable improvement in viscosity, compatibility, and low-temperature properties, as well as the substantial deterioration in high-temperature properties. In the middle stage, the degradation reaction develops further but slower, with TB exhibits a further but slower evolution in macro properties. In the last stage, the degradation reaction is almost completed, and TB shows a gradual stabilization of macro properties. The findings are expected to achieve precise control of CR degradation progression, which offers the possibility of efficient preparation of TB with specific properties, thus advancing the application of CR in pavement engineering.

This study systematically investigated the potential of waste carbon fibers (WCFs) as a sustainable solution in enhancing the multiple induction heating healing of asphalt mixture, thereby tackling two major concerns: the environmental impact of WCFs and the durability of asphalt pavement. Firstly, four groups of asphalt binder samples with different WCFs contents were prepared. The viscosity and workability of WCFs modified asphalt binder were analyzed. Next, asphalt mixture containing 2% steel fibers was prepared at the optimal WCFs content, while control groups without WCFs were prepared with 2% and 4% steel fibers content. A comprehensive study was conducted on the induction heating rate, effective heating depth and surface temperature cooling rules of the asphalt mixture. Finally, by conducting multiple “fracture-healing” tests, the influence of WCFs on the healing efficiency of asphalt mixture was analyzed. The results revealed that WCFs increased the viscosity of the virgin asphalt, but excessive WCFs content hindered the workability. The optimal WCFs content was determined to be 1% (by weight of asphalt binder). WCFs enhanced the thermal conductivity of the asphalt mixture, accelerating heating and improving vertical heat transfer while reducing surface temperature decline. During multiple “fracture -healing” processes, the inclusion of WCFs enhanced the mechanical strength of the asphalt mixture, improved its healing efficiency, and increased the number of healings. Even after five cycles, the specimen with the most damage still showed a fracture energy recovery rate (FERR) of over 30%. In conclusion, WCFs significantly enhanced the multiple induction heating healing efficiency of the asphalt mixture.

Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges. In the past 10 years, the pavement infrastructure strongly supports the rapid development of the global social economy. New theories, new methods, new technologies and new materials related to pavement engineering are emerging. Deterioration of pavement infrastructure is a typical multi-physics problem. Because of actual coupled behaviors of traffic and environmental conditions, predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis. In order to summarize the current and determine the future research of pavement engineering, Journal of Traffic and Transportation Engineering (English Edition) has launched a review paper on the topic of “New innovations in pavement materials and engineering: A review on pavement engineering research 2021”. Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering, this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world. The content includes asphalt binder performance and modeling, mixture performance and modeling of pavement materials, multi-scale mechanics, green and sustainable pavement, and intelligent pavement. Overall, this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering.