Test Methods for Resistance of Concrete to Sulfate Attack – A Critical Review

Abstract

Sulfate attack comprises a series of chemical reactions between sulfate ions and the components of hardened concrete. As these reactions may lead to cracking, spalling or strength loss of concrete structures, appropriate test methods are needed to determine the resistance of concrete under sulfate exposure. Accelerated test methods are most suitable since sulfate attack is typically a long term process. The current ASTM C1012 (2004) test method accelerates the attack mechanism by using a solution with a high sulfate concentration in which mortar specimens are immersed. The SVA procedure (see Table 10.1 for more detail) uses smaller specimens to obtain results earlier (Mielich and Öttl 2004). In the Wittekindt method not only smaller specimens are used but also the w/c-ratio is increased (Wittekindt 1960). However, these tests still require several months. Test methods such as ASTM C452 (2006) and the Chatelier-Anstett test use a mixture of cement and gypsum. Since in this case the sulfate source is located internally, no more time is needed for sulfate ingress. With these test methods results are obtained after 2 weeks, but the attack mechanism no longer represents field conditions in a realistic way.KeywordsSulfateEttringiteThaumasiteSalt crystallizationDelayed ettringite formationStandard methodsDegradation measurementsExpansion