Application of calorimetry and other thermal methods in the studies of granulated blast furnace slag from the old storage yards as supplementary cementitious material

Abstract

The calorimetric and DTA/TG measurements were applied in testing the effect of granulated blast furnace slag originated from the storage yards of different age, added as a supplementary cementing material to the Portland cement clinker. The studies were performed with aim to evaluate the kinetics of cement hydration and the modification of hydrated paste composition in the presence of additive. The material after 20-year storage, the crushed slag after approximately 2-years storage and the new slag from the current production in the metallurgical plant were used. The slag percentage was 5 ÷ 50%. The addition of granulated blast furnace slag stored for a long time affects the standard properties of cement reducing the compressive strength at longer maturing and with the percentage of additive. This is related mainly to the reduction in the vitreous component. However, at the additive content up to 50% the binder complying with the requirements of the relevant European standards for common cements could be produced. Basing on the results of TG measurements the role of calcium carbonate, being the product resulting from the slag weathering process, acting as a grindability and setting/hardening modifying agent, was highlighted.