High-Strength Solidification of Fly Ash/Carbide Slag and Its Fixing Ability for Heavy Metals

Abstract

Hydrothermal hot-pressing will occur between silica in fly ash and calcium in carbide slag and give rise to high-strength hydrates. High-strength solidified specimens were prepared with fly ash and carbide slag via hydrothermal hot-pressing at 200°C and 7 MPa. The effect of concentration of activator and content of carbide slag on compressive strength of the specimens was analyzed. It was found that when the mass ratio of fly ash to carbide slag was 1:1 and 20% 5 mol/L NaOH solution was added, the solidified specimens contained a large amount of cross-linked fibrous tobermorite with compressive strength of 70.93 MPa. The solidified specimens had a good fixation effect on such heavy metals as Cu, Zn, Cd and Pb. Hydrothermal hot-pressing, featured by simple procedures, easy automation and low cost, is an ideal potential way of utilizing fly ash and carbide slag and fixation of heavy metals.