Immobilization of some heavy metals in cement pastes

The immobilization of some heavy metal salts such as CoCl2, CuCl2, NiCl2 and Pb(NO3)2 in various cement matrices is investigated using the solidification/stabilization (s/s) technique. The different cement pastes used in this study were neat Portland cement in absence and presence of water reducing- and water repelling-admixtures as well as blended cements with kaolin and metakaolin. The heavy metals were introduced to the cementitious materials in the form of soluble salts [CoCl2, CuCl2, NiCl2 and Pb(NO3)2] in two ratios (0.5 and 1.0% by weight of the solid binder). Then, the hydration characteristics of the used cement pastes is tested via the determination of the combined water content, phase composition and compressive strength at different time intervals from 1 up to 180 days.