Early-age hydration kinetics of steel slags

Unlike blast-furnace slags, steel-making slag is not a normal admixture for Portland cement. However, recent work has suggested that by adjusting the chemistry and the cooling rate to generate a substantial glassy phase, the potential for hydration and strength development for the granulated product is enhanced. In order to better understand the role of glassy phases in the hydration process, isothermal calorimetry was used to determine the heat release and the rate of hydration within the 25–70°C range. Synthetic slags, of varying glass:crystal ratios, were used along with Portland cement as a reference. The reactivity of the synthetic slags was found to increase with glassy content which is in agreement with the lower activation energies calculated for these slags. Activation energies for slags were found to be greater than for Portland cement.