Zinc and total organic carbon leachability from hydrometallurgical treated end-of-life tyre rubber in rubberised asphalt concrete

While most research focused on the effects of end-of-life tire (ELT) rubber on the engineering performance of rubberized asphalt concrete (RAC), fewer studies have considered environmental aspects. This study investigates whether asphalt binder can immobilize leachable zinc and total organic carbon (TOC) content from ELT rubber. The authors used ELT rubber before and after the zinc-recovery process to replace 20 % sand in asphalt concrete through dry mixing. Indirect tensile, cracking, asphalt pavement analyzer rutting, and dynamic modulus tests were conducted along with environmental tests. While untreated ELT rubber reduced tensile strength and cracking tolerance index, it improved the rutting resistance and the dynamic modulus at high-temperatures. However, the treated ELT rubber had minimal effect on the tensile strength. Zinc leaching remained significant in RAC with both untreated and treated ELT rubber while no TOC leaching was observed in the leachate, indicating effective TOC immobilization by the asphalt binder.