Hydration mechanisms of supersulfated cement: The role of alkali activator and calcium sulfate content

Considerable attention has been given to special cements, capable of reducing CO2 emissions, energy and limestone consumption. Supersulfated cements are made of blast furnace slag (GBFS), calcium sulfate (CS), and small quantities of activator, but achieving their optimal proportions is complex. In this paper, the effects of the both CS and alkali activator (KOH) contents were studied. The main results showed that the compressive strength, heat of hydration, and consumption of anhydrite phase were strongly influenced by the alkaline content, while low calcium sulfate or alkaline content increased the formation of CSH. The instability of ettringite was verified: with low CS, the probable hypothesis was its conversion into monosulfate due to the scarcity of sulfate; with high CS, it was associated with intense, rapid consumption of anhydrite with high KOH content, followed by the precipitation of ettringite on the surface of slag grains and its conversion into monosulfate.