Modification of the hydration processes of alkali activated blast furnace slag

Granulated blast furnace slag exhibits latent hydraulic properties and its binding properties can be evoked by the addition of the alkali activator. Subsequent hydration processes during the setting and hardening processes let to origination of the solid products with the mechanical properties comparable or even better than the product obtained with ordinary Portland cement. The dominant product of the hydration processes is so called C-S-H phase. C-S-H phases are non-crystalline products of hydration with variable composition based on CaO, SiO2 and H2O. C-S-H phases are responsible for good mechanical properties of the hydrated products. The paper deals with the effect of the addition of the synthetically produced C-S-H phases on the hydration processes of granulated blast furnace slag. C-S-H phases were synthesized using the sol-gel method and were added to the granulated slag at the beginning of its hydration with the role of the nuclei of the phases responsible for strength of the final hydrated products. The mechanical properties as well as the development of the porous structure of hydrated products were used for the evaluation of the effect of the nuclei addition on the hydration process. It was proved that the addition of the synthetically prepared C-S-H nuclei has a positive effect on the development of the mechanical properties of alkali activated blast furnace slag, especially during the initial period of hardening.