An Experimental Study on Utilization of Slag and Fly Ash as an Alternative Cementitious Binder

This study investigates the utilization of slag and fly ash (FA) as alternative cementitious binder. Combination of 60% slag and 40% FA was used as new binder. In addition, for activation of slag and FA, sodium hydroxide and calcium hydroxide was used as a chemical activator by 5% weight of the binder, separately. Water to binder and sand to binder ratios was kept 0.55 and 3 in mortar preparation, respectively. Superplasticizer was used by 2.5% of the weight of binder to get reasonable flow for casting. Physical and chemical properties of slag and FA, and fresh and hardened properties of mortar of the new binder were determined and compared with that of OPC. Experimental results reveal that new binder shows slightly lower flow ability than that of OPC. New binder which was activated by sodium hydroxide sets early than OPC. Mortar as produced from new binder with sodium hydroxide shows 12.02, 18.15 and 26.20MPa compressive strength at 7, 14 and 28 days, respectively; while OPC mortar achieved 25.67, 30.08 and 35.78MPa compressive strength at the same ages and conditions. Sodium hydroxide exhibits greater activation performance than that of calcium hydroxide. Thus, depending on the preliminary test results it can be concluded that, with the presence of chemical activator, slag and FA can be used together as an alternative of OPC.