MEASUREMENT OF H IGH-ALUMINA CEMENT- CALCIUM CARBONATE REACTIONS US ING DTA

reported to be capable of providing strength inconcrete and so may provide an alternative to the minerals normally found in the hydration of high-alumina cement, which may under certain conditions convert to other minerals with a loss in strength. Some doubt has been cast on the stability of calcium carboaluminate hydrate and it has been found that in hydrated high-alumina cement, calcium carboaluminate hydrate decomposes at temperatures in excess of 60 ~ Cube compressive strength tests on high-alumina cement and high-alumina cement-calcium carbonate pastes have shown that the latter have a lower strength than pastes made with high-alumina cement alone. When cured at 50 ~ the high-alumina cement-calcium carbonate pastes how a loss in strength with curing time. Cements made with the high-alumina cement-calcium carbonate mixture always have a lower strength than those made with high-alumina cement alone and so no advantage is gained from their use. Calcium carboaluminate hydrate has been suggested as a mineral which would replace the metastable mineral mono-calcium aluminate decahydrate as the primary hydration product in hydrating high-alumina cement if calcium carbonate powder is added (Cussino et al., 1980; Negro et al., 1976; Negro et al., 1982). The first product of hydration o