Hydration of alkali-activated ground granulated blast furnace slag

The hydration of ground granulated blast furnace slag (GGBFS) at 25 degrees C in controlled pH environments was investigated during 28 days of hydrati on. GGBFS was activated by NaOH, and it was found that the rate of reaction depends on the pH of the starting solution. The main product was identifie d as C-S-H, and, in the pastes with high pH, hydrotalcite was observed at l ater stages of hydration. The pH of the mixing solution should be higher th an pH 11.5 to effectively activate the hydration of GGBFS. As deduced from very low electrical conductivity measurements, GGBFS pastes had very tortuo us and disconnected pores. The effect of the pH of the aqueous solution on the composition, microstructure and properties of alkali-activated GGBFS pa stes are also discussed. (C) 2000 Kluwer Academic Publishers.