Microstructural Analysis of OPC/Silica Fume/Na-Bentonite Interactions in Cement Based Solidification of Organic-Contaminated Hazardous Waste

Abstract

As one of major deficiencies in cement-based waste stabilization/solidification (S/S) processes is their difficulty in treating inorganic wastes containing organic material, silica-fume and Na-bentonite are studied as potential pozzolanic reagent and pre-solidification adsorbent of organic components. This paper presents microstructural studies of interactions between silica fume, Na-bentonite, containing adsorbed organically contaminated harzardous wastes, and a cement matrix. The scanning electron microscopy/ energy dispersive spectroscopy (SEM/EDS) analysis of the waste/OPC mix showed that the ettringite crystals were in needle shape deposited in the voids or on the surface of hydration material. Microstructural studies of solidified wastes with silica fume and/or Na-bentonite showed that their presence caused an inhibition to the ettringite formation. The results indicated that the incorporation of silica fume and/or Na-bentonite into the cement matrix minimized the detrimental effects of organic materials on the cement hydration reaction.