Durability and testing of mortar with interground fly ash and limestone cements in sulfate solutions

This study was aimed to indicate the inadequacies of the presently used methods for testing sulfate resistance of cementitious systems, especially when tested in magnesium sulfate solution, and propose proper laboratory tests for evaluating the sulfate resistance of mortars with various types of binders. The test methods involved immersion of mortar specimens in 33,800 ppm sodium sulfate and magnesium sulfate solutions. The resistance of mortars with different binders to sulfate attack was evaluated by applying several test methods. Results of an investigation on sulfate resistance of ordinary Portland cement and interground cement mortars, which were tested by the test methods of expansion, weight loss, strength reduction, and surface area loss with an image processing technique (SLIP technique), are presented. It was observed that for sodium sulfate solution, an expansion test is appropriate for performance evaluation of all tested ordinary Portland cement and blended cement mortars. In the case of an magnesium sulfate solution, weight loss or surface area loss with an image processing technique is considered suitable to test interground fly ash cement mortars while the expansion test is not. However, for OPC and interground limestone cement mortars immersed in an magnesium sulfate solution, the suitable tests are both expansion and weight loss or surface area loss with an image processing technique (SLIP technique).