Waste tire rubber recycling for developing a high viscosity-elasticity composite modified asphalt

Abstract

Non-biodegradable waste tire rubber poses serious environmental and public health risks. Thus, waste tires recycling has become a critical global issue. In this study, crumb rubber (CR) derived from waste tires was recycled to synthesize a new type of high viscosity-elasticity composite modified asphalt (RSTMA) with styrene-butadiene block copolymer (SBS), and terpene resin (T105). Three major indicators, dynamic viscosity, elastic recovery rate, and softening point difference after segregation were used to determine the optimal formula of RSTMA. Dynamic shear rheometer (DSR) tests were employed to systematically evaluate the rheological properties of RSTMA. The individual contributions of the three modifiers to RSTMA performance improvement were quantified via the Entropy Weight Method (EWM). Experimental results show that compared with base asphalt, the elastic recovery rate of RSTMA with the optimal formulation increases by 71%, while the non-recoverable creep compliance decreases by 98.56%. The segregation index (SI) of this optimal RSTMA reaches 0.87, and its fatigue life at a 35% damage degree exceeds 8000 loading cycles. It was also found that CR significantly increases the viscosity upper limit of RSTMA, CR and T105 jointly elevate its elasticity upper limit, while SBS improves both viscosity and elasticity. Overall, under the synergistic modification of CR-SBS-T105, the performance of RSTMA is significantly enhanced, with CR content reaching up to 15% (by asphalt mass). This study provides a pathway for the high-value, low-carbon recycling of crumb rubber, promoting sustainable development in the solid waste management.