Effect of simulative pore solution on the hydration kinetics of GGBFS

To characterise the hydraulic activity of ground granulated blast-furnace slag (GGBFS) in a low alkaline solution, the hydration degree, heat evolution and hydration products of GGBFS–water (de-ionised water) paste, GGBFS–5%CaO–water paste and GGBFS–5%CaO–simulative pore solution (SPS) pastes were investigated. The Ca(OH)₂ content and composition of pore solution of GGBFS pastes were also determined. The experimental results show that the dissolution rate of the vitreous phase of GGBFS increases significantly with increases in alkalinity of the SPS. The hydraulic activity of GGBFS is relatively low and hydration of GGBFS mainly takes place slowly after 7 days in GGBFS–5%CaO–water paste. In contrast, the hydration rate increases dramatically in the first 3 days. Meanwhile, large amounts of hydration products (mainly C–S–H gel and C₂ASH₈) are generated, indicating the enhancement of hydraulic activity of GGBFS even in low alkaline solution.