Accelerated test for measuring sulfate resistance of calcium sulfoaluminate, calcium aluminate, and portland cements

Sulfate ions present in soil, ground water, seawater, decaying organic matter, and industrial efffluents are known to have an adverse effect on long-term durability of concrete. However, ASTM test methods for predicting sulfate resistance have been critized for failing to adequately predict field performance. In this investigation, cement pastes were tested by an accelerated test method where pH and sulfate concentration remained constant, conditions that are more representative of field conditions. A total of eight cements were tested: Three portland cements (Type I/II, Type III, and Type V); one calcium aluminate cement (CAI1); two calcium sulfoaluminate cements (CSA1 and CSA2); and two blends containing calcium aluminate, anhydrite, and portland cement (CAPC1 and CAPC2). After 63 days of exposure to a 4% Na₂SO₄ solution where the pH was maintained at 7.2, sulfate resistance of the cements can be described by: CA1 = CSA2 = Type I/II > Type V 〉 Type III > CAPC2 > CAPC1 > CSA1.