Measurement and prediction of thermal properties of alkali-activated fly ash/slag binders at elevated temperatures

This paper presents a comprehensive experimental study of thermal properties of various alkali-activated binders at ambient and elevated temperatures. The binders were prepared using alkali-activated low calcium fly ash/ground granulated blast-furnace slag at ratios of 100/0, 90/10, 50/50 and 0/100 wt%. These binders can be considered as a composite of solid, water and air. Accordingly, a three-phase model is applied to predict thermal conductivity of the binders at ambient temperature. At elevated temperatures, the Hashin-Shtrikman model is used to estimate the bounds of thermal conductivity for alkali-activated binders containing of fly ash. To validate the above models, a transient plane source measurement technique was applied to measure the thermal conductivity and heat capacity at temperatures ranging from 23 to 600 Â°C. Data generated is then utilised to develop analytical expressions for estimating thermal properties as a function of temperature. The simplified relationships can be used for estimating the fire resistance of structural elements made from alkali-activated cementitious materials.