The effect of C3A content on sulfate durability of Portland limestone cement mortars

Abstract

The effect of C3A content on sulfate resistance of limestone incorporated cements has been investigated within the scope of this study. Cements with two different C3A contents (4.6%, 11.2%) have been used. Blended cements have been prepared by separate grinding and mixing method. Limestone incorporation ratios were 5%, 10%, 20% and 40%, respectively. Standard mortar samples of 50×50×50mm cubes and 25×25×285mm prisms have been prepared. After 1months of water curing, samples have been exposed to different sulfate solutions (Na2SO4 and MgSO4) and temperatures (5 and 20°C) for a period of 6months. During this period length changes were monitored and compressive strength values have been determined at 3 and 6months intervals of sulfate exposure. Furthermore microstructure investigations have been conducted on selected samples.Test results showed that increasing C3A content propagate the deterioration rate of limestone blended cement mortars exposed to both Na2SO4 and MgSO4 solutions. This situation is more significant at higher limestone replacement ratios and low temperatures. Microstructural investigations revealed that deterioration mechanism of limestone blended samples due to sulfate attack depend on the C3A content and cation type of sulfate solutions. As a general consideration, limestone replacement ratios at and above 20% will be a serious problem for mortars incorporating high C3A content from the view point of sulfate durability.