Temperature rise and initial shrinkage of alkali-activated fly ash cement pastes

This paper reports on core temperature development and initial shrinkage of fly ash cement pastes activated with sodium hydroxide solution at different concentrations during elevated-temperature curing at 60°C.The results indicate that a high sodium hydroxide concentration might result in a substantial rise in the core temperature of samples, dependent on the mould size and ratio of paste to oven volume.An increase in alkali concentration was also found to increase the initial shrinkage of the pastes during elevated-temperature curing.Excessive initial shrinkage and temperature increase might lead to the appearance of internal stresses in the pastes, which can affect the material performance. NotationH initial sample height (m) H 0 initial laser reading (μm) H i laser reading at time i (μm) H m depth of empty cone mould (m) H r thickness of reflector (m) H t distance from top of mould to reflector placed on the paste surface (m) L w total mass loss (%) m 1 mass of mould with paste before elevatedtemperature curing (g) m 2 mass of mould with sample after elevatedtemperature curing (g) m m mass of empty mould (g) T p peak temperature (°C) t p time of appearance of peak temperature after the start of elevated-temperature curing (min)