Effect of elevated temperature on alkali-activated geopolymeric binders compared to portland cement-based binders

摘要

This research focused on developing thermally-stable materials based on alkali-activation of slag, fly ash, and metakaolin compared to portland cement mixtures by using a hierarchical approach to material design. At lower length scales, X-ray diffraction (XRD) characterized the mineralogy that coupled to higher length scale experiments using thermogravimetric analysis (TGA) for determining the materials thermal stability. Additionally, high-energy X-ray computed microtomography (mu CT) determined the best-performing material formulation that minimized thermal damage when exposed to high temperatures (650 degrees C). The thermal loading was ramped up to 650 degrees C from ambient temperature in 60 s and then held for a total of 10 min. The mu CT identified that the alkali-activated fly ash mortar had less initial porosity than the ordinary portland cement mixtures, with more than 66% of the pores between 20 and 50 mu m in diameter. Consequently, the alkali-activated fly ash mortar was able to dissipate approximately 565 degrees C in just 50 mm of material, outperforming all the other mixes studied in this paper with mu CT confirming minimal damage after the temperature exposure. (C) 2016 Elsevier Ltd. All rights reserved.