Reuse of spent catalyst as fine aggregate in cement mortar

This study examined the feasibility of reusing spent zeolite catalyst, after fluidized catalytic cracking, as a substitute for fine aggregate (sand) in cement mortars. The tested result shows that spent catalyst can replace up to 10% of fine aggregate without decreasing the mortar strength. In fact, the substituted mortars show higher compressive strength than the unsubstituted samples. The flowability of the fresh mortars decreases with increasing substitution level and the mortars incorporated with spent catalyst show less bleeding. In the hardened state, the water absorption of the resulting mortar increases with longer curing age, higher substitution level and smaller water-to-cement (W/C) ratio. Toxicity characteristic leaching procedure (TCLP) analysis confirms that the spent catalyst meets the standard, and thus should be classified as general nonhazardous industrial waste.