MECHANISMS OF METAL STABILIZATION IN CEMENTITIOUS MATRIX - TRANSMISSION ELECTRON-MICROSCOPIC STUDY OF C3A CUO FIXATION SYSTEM/

A detailed understanding of the reaction mechanisms would be useful to predict and control the ability of fixation systems to retard the sol ubility and/or mobility of the incorporated metal species. For the pre sent study, the interactions between tricalcium aluminate (C3A) paste and CuO were characterized using transmission electron microscopy (TEM ) equipped with energy-dispersive X-ray analysis (EDAX). The results o f TEM/EDAX analyses indicated that the concentration gradient of coppe r species in the hydrated C3A region and physical entrapment of CuO wi thin five principal hydration products of C3A were attributed to the i nteractions of hydrated C3A and CuO. Additionally, no intermediate pha ses or new chemical products of copper related compounds existed in th e five typical interfaces. No diffraction patterns of metal copper, Cu O, Cu(OH)2, and CuCO3 compounds were observed in the hydrated C3A. It was thus suggested that the CuO was stabilized in the C3A paste by two major mechanisms; the heterogeneous solid solution of copper species was present in the hydrated C3A and CuO was physically entrapped by th e hydration products of C3A.