Influence of sulphate source on Portland cement hydration

Abstract

Synopsis Cements were synthesized by blending a Type I low alkali Portland cement clinker with sulphate salts. A quantitative X-ray diffraction method was developed to measure the rate at which the C3A and C4AFphases in these cements were consumed in pastes hydrated at 23°C. The initial high rate of aluminate phase consumption was influenced significantly by the rate of solubility of the sulphate source, and especially the rate at which it released CaSO4 into solution. Interground gypsum was far more effective than interblended gypsum in controlling aluminate hydration. Better control of the initial aluminate hydration generally led to higher 28-day paste strengths.