ABSTRACT
Two types of silica fumes and a low-lime fly ash were used as admixtures in mortar mixtures. In addition to the ASTM C1012 test procedure, experiments were performed on mortar specimens which were immersed in separate groups in water, 10% sodium sulfate and 8.4% magnesium sulfate solutions. Mass loss of the specimens were determined periodically and their progressive deterioration was assessed using a “visual durability index” concept. The compressive strength of the specimens was determined at 28 days and at 60 weeks for comparison purposes. All admixtures improved the resistance of mortars to sodium sulfate, ferrosilicon fume being the most and fly ash being the least effective at 15% replacement level. On the other hand, silica fume addition was detrimental to the magnesium sulfate resistance of mortars while fly ash addition did not seem to have adverse effect.
