Fundamental understanding of the setting behaviour of the alkali activated binders based on ground granulated blast furnace slag and fly ash

This study aims to investigate the setting of alkali activated ground granulated blast furnace slag and fly ash mixtures by following the mechanical and chemical evolution of structure of the precursor-activator suspension during early ages. The mechanical evolution was followed by measuring the evolution of storage modulus. The chemical evolution was followed by measuring the amount of hydrates formed at different times. The dependence of setting time of alkali activated slag mixtures on the amount of incorporated fly ash, molar modulus and activator dosage was also studied. This study shows that the quick setting of alkali activated slag mixtures is due to rapid coagulation followed by rapid rigidification of network with the formation of hydration products. In comparison, the setting in OPC systems is due to a network formed by partially hydrated or anhydrous cement particles. The proportion of fly ash in GGBFS-fly ash mixture and molar modulus of the activator were found to have a significant effect on the setting time of alkali activated ground granulated blast furnace slag and fly ash binders. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the setting of alkali activated ground granulated blast furnace slag and fly ash mixtures by analyzing the mechanical and chemical evolution of the structure during early ages. The quick setting of slag mixtures was found to be due to rapid coagulation and rigidification of the network with the formation of hydration products, while the setting in OPC systems is attributed to a network formed by partially hydrated or anhydrous cement particles. The proportion of fly ash and molar modulus of the activator were found to significantly affect the setting time of the alkali activated binders.