ABSTRACT
An investigation was carried out on the effect of sulfate attack on the sulfate durability of mortars produced with natural zeolite and silica fume having pozzolanic character. Experiments were accomplished on the standard Rilem sand and portland cement mortars where the cement was replaced by various rates of natural zeolite (Z) and silica fume (SP) separately and together. 5% sodium sulfate solution and 5% magnesium sulfate solution were 5% sulfate exposures of mortars were initiated after 28 days of lime saturated water curing, compressive strength and density were determined at the beginning of exposure and at the 2nd, 7th, 28th, 90th days. Water and solutions were renewed after each period of experimental time, 14 days. Mass changes were determined at the time of renewing the solutions. The effects of sodium sulfate solutions on the properties of mortars were related to the zeolite and silica fume ratio. It is found that zeolite and silica fume replacement had caused significant increase in sulfate durability of mortars even at the highest sulfate concentration up to 90 days of exposure. The durability to sulfate attack was obtained with silica fume replacement 5-10%, but strength loss of 10 15% can be expected. Mortars with SF and Z were damaged in magnesium sulfate solution. The compressive strengths decreased with increasing SF and Z content. The test results showed that the use of Z and SF in concrete exposed to magnesium sulfate environment is not recommended.
