Low-CO2 Binders for restoring a Pb-contaminated Soil: Improvements and Drawbacks with respect to Ordinary Portland Cement

The remediation of heavy metal contaminated soils is usually approached with binder-based techniques, like solidification/stabilization (S/S), and ordinary Portland cement (OPC) as the main binding agent. This paper reports our preliminary attempts of substituting traditional OPC with more environmentally sustainable alkali-activated cements, in the S/S of a Pb-contaminated soil. The treatment of Pb contamination is complicated by the amphoteric behavior of Pb, whose mobility is increased at high pH values, which are characteristic of cementitious systems. The use of alkali-activated cements proved to be suitable for soil remediation, with different performances depending on the formulation studied. These preliminary findings may be further enhanced by long-term investigations and further optimization of the alkaline activating solution, as first steps towards the improvement of the environmental impact of soil remediation technologies.