Treatment of recycled rubber crumb to reduce content of hazardous elements

Abstract

One of the major trends in material science consists of the reuse of various waste and by-products in order to reduce the environmental load associated with extensive landfilling and other waste disposal scenarios. Specifically, disposal of end-of-life tires and related reuse of this durable material represents a major issue for modern society. In this regard, various attempts can be recognized in the available literature. However, the production of tires is related to the use of various hazardous compounds such as heavy metals and polycyclic aromatic hydrocarbons in particular. These pollutants have an adverse effect not only on the natural environment but also on human health. On this account, the present paper deals with the treatment of rubber crumb as a possible way how to mitigate the environmental and health risk. Methods including the acid washing and hot-air scrubbing are employed with different duration to access the efficiency of the procedure. Presented results based on acid washing and hot-air treatment show a significant reduction below 10 mg/kg in polycyclic aromatic hydrocarbons content compared to untreated material (57 mg/kg). Consequent utilization of treated rubber crumb in the concrete as the aggregate replacement is not accompanied with increased reduction of mechanical properties compared to conventional rubber crumb. Namely, the reduction in strength was linear up to 30 wt% replacement of natural aggregate and further increase in the replacement ratio did not result in substantial deterioration in strength. Based on the obtained results, the described treatment procedure should be more broadly employed to avoid undesired consequences on human health as well as natural environment.