Stabilization of Cobalt By Using Blended Cement Pastes

Stabilization of Cobalt Chloride, a representative of soluble cobalt compounds, with five cements pastes based on either Ordinary Portland Cement (OPC) or blended Portland cement with Granulated Blast Furnace Slag (GBFS) or Metakaolin (MK) were studied. Various mixtures were prepared by using a water/solid ratio (W/S) of 0.28 (by weight). Two ratios of Co ions (2.0 and 3.0% by weight of the solid binder) were used by adding to the mixing water. Hydration characteristics of the different cement pastes were investigated via the examination of chemically combined water content, compressive strength, X-ray diffraction analysis and thermal analysis (DTA/TGA). Leaching of cobalt ions from various hardened cement pastes was examined. The results showed that cobalt chloride retards cement hydration through the formation of plumbate salt. The obtained results of leaching showed a high degree of immobilization of Co ions in the various cement pastes. Moreover, partial replacement of OPC by MK is more efficient than GBFS.