EFFECT OF GGBS ADDITION ON PROPERTIES OF FLY ASH-BASED GEOPOLYMER AT HIGH TEMPERATURES

摘要

This study presents the microstructure and mechanical properties of geopolymer paste made from low-calcium fly ash and ground granulated blast-furnace slag (GGB S) after exposure at elevated temperature. Five series of specimens were prepared with different ratios of GGBS to fly ash with an aim to investigate the effect of GGBS on the high temperature resistance of the geopolymer specimens. At the age of 28 days, the specimens were exposed at elevated temperatures (500°C, 750°C, and 950°C). The microstructural investigation and compressive strength test were carried out for specimens before and after heating. The results showed that for unheated specimens, the addition of GGBS significantly improved the compressive strength due to the formation of calcium silicate hydrate gel that helps to form denser structure. However, exposure at high temperature caused excessive dehydration of water and decomposition of C-S-H gel inside the specimen, resulting in strength loss and re-crystallizations.