MECHANISMS OF METAL STABILIZATION IN CEMENTITIOUS MATRIX - INTERACTION OF DICALCIUM SILICATE (C2S) PASTE AND COPPER-OXIDE

There are relatively few published studies describing the microstructu ral and microchemical interactions. of metal-containing wastes and sol idifying agents in solidification systems. An understanding of such in teractions would be useful to predict the ability of fixation systems to retard the solubility and/or mobilitty of the incorporated metal sp ecies. Thus, solidification systems could be designed to exert a minim al environmental impact. For the present study, the interactions betwe en dicalcium silicate (C2S) paste and CuO were characterized using X-r ay diffractometer (XRD) and scanning electron microscopy (SEM) equippe d with energy-dispersive X-ray analysis (EDAX). The results of XRD ana lysis indicated that the C2S paste/CuO fixation system provided a mild alkaline environment during hydration reaction. The interfacial micro analysis by SEM/EDAX of C2S paste and CuO showed a significant differe nce between hydrated beta- and non-hydrated gamma-C2S systems. The int erfacal zone is in about 1 mu m thickness and the concentration gradie nt of calcium and silicon observed in the CuO region is due to the int eraction of hydrated beta-C2S and CuO. It is suggested that the CuO wa s stabilized in the C2S paste by two major mechanisms; Ca and Si from hydrated beta-C2S diffuse and form a solid solution in the CuO region, and CuO is in well contact with C2S paste.