Potential use of FCC spent catalyst as partial replacement of cement or sand in cement mortars

This paper studies the effect of using FCC spent catalyst, produced from local refineries on the compressive strength of mortars. The main constituents of mortar; sand and cement were partially replaced by different percentages of spent catalyst. Five levels of sand replacement were used ranging from 5% to 25% by weight of sand. The same was done for cement but with different proportions from 2% to 10% by weight of cement. Three water-to-binder ratios were used; 0.50, 0.55 and 0.60 whereas the binder-to-sand ratio was kept constant at 1:3. The specimens were tested at 7, 14, 28, 56 and 91 days of curing. Encouraging results were achieved when Sohar Refinery's spent catalyst was used as sand replacement. The substitution reached up to 20% without affecting the mortars' compressive strength. Spent catalysts from both refineries showed negligible effect on the strength of cement mortars when used as partial substitute of cement. Leachate tests showed that mixtures prepared using both spent catalysts contained small traces of heavy metals that are far below the international limits. Hence, no environmental harm should be anticipated from the use of these spent catalysts in construction.