Comparative performance of alkali-activated slag and fly ash at elevated temperatures

This paper aims to investigate the compressive strength of various alkali-activated binders at elevated temperatures of 300C and 600C. The binders were prepared by alkali-activated low calcium fly ash/ ground granulated blast-furnace slag at ratios of 100/0, 50/50, 10/90 and 0/100 wt.%. Specimens free of loading were heated to a desirable temperature by keeping the furnace temperature constant until the specimens reached a steady state. The specimen was then loaded to failure while hot. For comparison purposes, Ordinary Portland Cement (OPC) binder with a similar strength level was also prepared and tested under the same conditions. Compared to OPC binder, the binders containing fly ash exhibited better performance at elevated temperatures. On the other hand, the alkali-activated slag had the worst high-temperature performance among all the binders. The reasons for the strength variation in a hot state are discussed based on the results of X-ray diffraction and scanning electron microscope.