Robustness to water and temperature, and activation energies of metakaolin-based geopolymer and alkali-activated slag binders

The aim of this paper is to evaluate the properties of four alkali-activated materials subjected to precasting and in situ concreting conditions: fluctuations in water content (+/- 5%) and in temperature (10 degrees C, 20 degrees C, 30 degrees C). The initial slump and compressive strengths at 1, 2, 7, 28 and 90 days of a metakaolinbased geopolymer, and of sodium silicate-activated slag, sodium metasilicate-activated slag and sodium carbonate-activated slag mortars were determined, then compared to the properties of an ordinary Portland cement mortar (CEM I). A total of 50 mortars were cast for the five formulations studied and the different conditions. This paper reports that alkali-activated materials are as robust as CEM I in precasting and in situ concreting conditions. However, some adjustments should be made to offset the low reactivity in cold weather, such as hot water or hot curing, or reducing the water/binder ratio. The apparent activation energies were determined for the five pastes to explain these observations. (c) 2021 Elsevier Ltd. All rights reserved.