Middle stage of Portland cement hydration influenced by different portions of silica fume, metakaolin and ground granulated blast-furnace slag

Abstract

Two Portland cement (PC) replacement levels (35, 45 mass%) and three locally available supplementary cementitious materials (SCMs; metakaolin (MK, 5–15 mass%), silica fume (SF, 5, 10 mass%), ground granulated blast-furnace slag (BFS, 10–35 mass%)) in different ratios were used for the preparation of multicomponent binders, the hydration of which was studied up to 365 days by means of thermal analysis. The suitable compositions were found for both PC replacement levels. In the case of the lower one as well as in the compositions prepared with higher SF amount, 20 mass% of BFS appeared as beneficial. When lower amounts of SF and cement were used, samples with larger quantity of BFS reached better results. Concerning compressive strength (CS), synergic influence of SCMs overcame the dilution effect already after 28 days of curing and no significant dependence on the PC content was determined. Later, the majority of the blended samples reached higher CSs than the corresponding referential ones. With respect to the coefficient of pozzolanic activity, the combination of higher SF level (10 mass%) mainly with higher amount of BFS seemed to be more desirable in general.