Method for Determining Resistance of Mortars to Sulfate Attack

Recognizing that the sulfate resistance of mortars is affected by conditions of use, temperature, cement content, plasticity, and mortar defects, particularly those of aggregate‐cement bonding, a new test for sulfate resistance was developed. Samples 2 by 2 by 10 cm are half‐immersed in an MgSO4 solution. The appearance and compressive strengths of the immersed and exposed parts are recorded at intervals and compared with those of water‐stored samples. This method is quantitatively reliable, selective, rapid, and inexpensive. Results for cements tested in this way are presented, and the physical and chemical characteristics of durable mortars are elucidated. The test was used to demonstrate the sulfate resistance of a new calcium silicate cement.