Evaluation of heavy metal leachability of incinerating recycled aggregate and solidification/stabilization products for construction reuse using TCLP, multi-final pH and EDTA-mediated TCLP leaching tests

Abstract

Incinerating recycled aggregate (IRA) produced using bottom ash generated from the incineration of municipal solid wastes can be reused as construction materials and cement-based solidification/stabilization (S/S) can be employed to improve their environmental compatibility. Toxicity characteristic leaching procedure (TCLP) is commonly used to evaluate heavy metal leachability before reuse. However, the applicability of TCLP to IRA and their S/S products can be limited because of their alkaline nature which may cause underestimation of metal release. In this study, the leaching of heavy metals from an IRA and two S/S products, low-strength material (CLSM) and multi-functional regenerated concrete (MRC), were evaluated using TCLP, multi-final pH leaching test and EDTA-mediated TCLP. The results showed that TCLP results generally met the reuse standards. However, the results obtained from multi-final pH leaching test and EDTA-mediated TCLP showed exceedances of reuse standards for Pb and Cu when the final pH was < 5 or in the presence of> 7 mM EDTA. The results suggested that the reuse of IRA or S/S products requires further evaluation of their metal leachability in more harsh environmental conditions. Considering its simplicity, it is suggested that EDTA-mediated TCLP could be used for this purpose.

Keywords: EDTA; Heavy metal; Incinerating recycled aggregate; Solidification/stabilization; TCLP.