Sulfate resistance of Portland-limestone cements in combination with supplementary cementitious materials

In this study, the sulfate resistance of five different high-C(3)A Portland and Portland-limestone cements and their combinations with 30-50 % slag were examined at both 5 and 23 A degrees C according to CSA A3004-C8 (similar to ASTM C1012). Also, XRD was used to identify the phases formed after sulfate attack. It was found that in 23 A degrees C exposure, while 100 % cement mixes deteriorated due to conventional ettringite-based sulfate attack, partially replacing the cements with 30 or 50 % slag was effective in making the mixes highly sulfate-resistant. At 5 A degrees C, all of the 100 % cement mortar bars expanded more than the test limits and eventually completely disintegrated due to the formation of thaumasite. Partially replacing cement with 30 % slag was only effective in controlling the deterioration for Portland cements but not Portland-limestone cements. However, all the Portland-limestone cements with 50 % slag were resistant to the thaumasite form of sulfate attack after 2 years.