New ternary blend limestone calcined clay cement for solidification/stabilization of zinc contaminated soil.

This study evaluates the potential use of a new limestone calcined clay cement (LC) for stabilization/solidification of zinc contaminated soil. LC is a new ternary blend manufactured by the replacement of 50% cement clinker by locally available two supplementary cementitious materials (SCMs) - limestone and calcined clay. The incorporation of LC is evaluated on the soil spiked with 0.5% and 1% of Zinc (Zn) at curing times of 3, 7, 14, 28 and 56 days. pH, strength and leachability properties of the solidified/stabilised soil are measured for both mechanical and environmental conditions. Additionally, sequential extraction procedure (SEP), X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) analysis are performed to elucidate the mechanisms of Zn immobilization in the soil. The results show that the leachable Zn concentrations in the stabilised soil are well below the corresponding hazardous waste management regulatory limit after the curing time of 14 days. The soil pH and unconfined compressive strength of the stabilised soil increase with curing time. The SEP results confirm that LC considerably reduces the acid soluble fraction (F1) and increase the residual fraction (F4). The XRD and SEM results indicate that formation of Tri-calcium Silicate 3CaO·SiO, Portlandite Ca(OH), Ettringite CaAl(SO)(OH).26 HO and Wulfingite Zn(OH) are the primary mechanisms for the immobilization of Zn in the LC stabilised soil.