Performance Testing of Hydraulic Cements: Measuring Sulfate Resistance

The sulfate resistance of cements used in the construction industry is traditionally assessed by measuring the expansion of a prism of 280 mm (11inch) length and 25 mm (1 inch) square cross section immersed in a sodium sulfate solution for at least one year. The duration of the experiment limits this test from being used as a performance-based determination of innovative mixtures of cementitious materials. In response to the need for a more rapid test protocol, the National Institute of Standards and Technology (NIST) has developed a new test method that measures the expansion of smaller bars (10 mm × 10 mm × 60 mm) made with neat cement paste. With these bars, similar expansion is achieved in less than 3 months, reducing the test duration by a factor of at least 4. This accelerated test method provides more rapid results consistent with the traditional test procedure, allowing for a shorter decision time and the screening of more materials.