Stabilisation/solidification of lead-contaminated soil using cementitious binders

Abstract

Reactive magnesia (MgO) has received lots of attention in geotechnical and construction areas due to MgO lower production temperature. To extend the application of MgO to geo-environmental area, this report investigated the potential of stabilising/solidifying Pb (lead)-contaminated soils using MgO. A series of laboratory tests were conducted to examine the properties of MgO treated Pb-contaminated soils, including unconfined compressive strength (UCS), leaching and X-ray diffraction (XRD) tests. For comparison purpose, lime (CaO) and cement were also used to treat the contaminated soil in this report. The results revealed the Pb-contaminated soil treated with MgO presented significantly lower UCS than that with cement but similar UCS with that with lime. However, MgO treatment produced much lower Pb leachability for Pb-contaminated soil comparing to cement and lime treatment. The presence of lead hydroxide (Pb(OH)2) and hydrocerussite in MgO treated soil was responsible for its lower Pb leachability than cement and lime treated soil. Although Pb(OH)2 and hydrocerussite were detected in cement treated soil, the pH range provided by cement (11.75-12.05) was so high that some of the precipitated Pb(OH)2 may become soluble, so cement treatment yielded higher Pb leachability than MgO treatment.