The influence of different additives on the early-stage hydration of calcium aluminate cement

Abstract

The influence of granite cutting waste and quartz sand on the early-stage hydration of calcium aluminate cement, Gorkal 70, was examined. The experiments were carried out at 25 and 50 °C temperature, when the water/cement ratio was equal to 0.5. It was determined that the mentioned additives have a significant influence on the calcium aluminate cement and its clinker hydration process at 25 °C: In the latter compound mixtures with granite cutting waste and quartz, the induction period was significantly shortened to 1 h, while, in case of calcium aluminate cement samples with additives, it was prolonged to 11 h in comparison with the pure system (10 h). It should be noted that the amount of granite cutting waste and quartz does not affect the hydration process, because the similar results were obtained, when 4 and 12% of additives were used. X-ray diffraction analysis data showed that the formation of products depends on the samples composition as well as hydration conditions. It was determined that, in clinker samples, the formation of final products at 25 °C proceeded through the intermediate compounds—C2AH8 and CAHX, while at 50 °C—directly. It was obtained that after 3 h of calcium aluminate cement hydration at 50 °C temperature two metastable hexagonal calcium aluminum hydrates, C2AH8 and CAHX, were formed. At the same time, in clinker samples, the stable phases—katoite and gibbsite, were formed. The obtained results were confirmed by simultaneous thermal analysis, microcalorimetry and X-ray diffraction analysis.