THE RIGHT SULFATE TEST MAKES A DIFFERENCE

Many soils contain enough sulfate to damage concrete. As a consequence, the test method for determining sulfate concentration recently has come under scrutiny. Although the United States Bureau of Reclamation (USBR) criteria for determining the severity of exposure is widely cited and used, their test method is less well known. This article discusses the effects of variation in test procedure on the results. The article shows how variations in the extraction procedures used can lead to substantially different conclusions about the severity of sulfate exposure. Since there are number of published methods that are referred to as water-soluble sulfate tests, it is essential that these tests be correlated with the published criteria based on the USBR tests before they are used to determine the severity of sulfate exposure. One significant difference among test methods is the ratio of water to sample in the extraction procedure. The more water used, the more sulfate can be dissolved. The time and temperature of the extraction can also affect the results. In order to address some of these issues, the American Society for Testing and Materials is in the process of developing a standardized test method for use with the USBR criteria.