Sodium sulfate attack on plain and blended cements

This paper presents an investigation into the sodium sulfate resistance of three portland cements of various compound compositions and 24 blended cements produced by replacing 10%, 20%, 30% and 40% of these cements with a fly ash and a natural pozzolan. Sulfate expansion of mortar specimens was evaluated using ASTM C1012 test procedure. No acid titration was made to change pH of the sulfate solution. In addition to 5% sodium sulfate concentration prescribed in the standard, 18 selected cements were also exposed to sodium sulfate of 3% concentration. A mathematical expression was developed to estimate the sulfate susceptibility of cements regarding their C 3A, C 3S/C 2S ratio, mineral additive content as well as concentration of sulfate solution.