Solidification/stabilization of Pb-contaminated soil by using low-carbon binder derived from dehydrated waste concrete powders and GGBS

The low reactivity and high stability of waste concrete powder (WCP) hinder the promotion of recycled binder applications with WCP addition. This study provides an innovative utilization strategy for thermal-modified WCP (TMWCP) recycling as an environmentally friendly solidification/stabilization (S/S) binder material for Pb-contaminated soil by adding ground granulated blast furnace slag (GGBS). The S/S treated soils underwent performance evaluations including unconfined compressive strength and leaching tests. Furthermore, the X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry tests were conducted to elucidate the underlying mechanisms. The results show that at an optimal heat treatment temperature of 600 °C for WCP, the S/S treated soil achieved a compressive strength of 4.2 MPa after 28 d of curing. Additionally, the optimum mixture ratio of TMWCP and GGBS was 9:1. It was found that the novel binder was much superior to OPC in terms of Pb immobilization and carbon emission reduction. When the dosage of the formed binder is twice that of OPC, it can compensate for the lack of strength in S/S treated Pb-contaminated soil.