PC-based and MgO-based binders stabilised/solidified heavy metal-contaminated model soil: strength and heavy metal speciation in early stage

An investigation into using Portland cement (PC)-based and magnesia (MgO)-based binders for treating contaminated model soil was carried out to study the benefit of novel binders over conventional ones in stabilisation/solidification systems (S/S), as well as the binding mechanism involved. Binders used in this study include PC, ground granulated blast-furnace slag, pulverised fly ash and magnesia. The strength and the leaching properties of S/S treated samples by way of unconfined compressive strength and sequential extraction tests are presented. The results show that the early-age strength of these mixes is influenced by the reactivity of binders; heavy metals were principally distributed in the carbonate and the iron/manganese (Fe/Mn) oxide fractions in all mixes after 28 days of curing time; the speciation distribution characteristics are not the same among zinc (Zn), copper (Cu), nickel (Ni) and lead (Pb), and the stability of Zn, Cu, Ni and Pb benefits from a longer curing time and the use of magnesia.