Alteration in the Mechanical Strength of Fly Ash Based Geopolymer Mortar upon Exposure to Elevated Temperatures

摘要

Geopolymer has recently emerged as an environmentally sustainable material considered to be an alternative to conventional Portland cement. Current study exhibits and discusses the results of experiment on the alteration in mechanical strength of fly ash-based geopolymer mortar activated by alkaline solution with three different sodium hydroxide solution concentrations (etc 10M, 14M and 18M) after exposure to elevated temperatures. Temperatures, ranging from 100℃ to 1000℃ by increment of 100℃ with exposure time of 1 hour and 2 hours have been studied. The geopolymer motar exhibited its strength increase after exposure at 100℃ or 200℃, followed by the considerable strength loss in strength between 300℃ and 700℃. However the mortar strength rose slightly after exposure to temperature range from 800℃ to 1000℃ due to the viscous sintering process. And this strength gain had a tendency to rise as the sodium hydroxide solution concentration or exposure time increased. The microstructure alteration of geopolymer mortar after the exposure was identified by using scanning electron microscopy method (SEM) in order to explain their changes.