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

ABSTRACT

Publication date: December 2016 Source:Cement and Concrete Research, Volume 90 Author(s): O.G. Rivera, W.R. Long, C.A. Weiss Jr., R.D. Moser, B.A. Williams, K. Torres-Cancel, E.R. Gore, P.G. Allison

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 (μCT) determined the best-performing material formulation that minimized thermal damage when exposed to high temperatures (650°C). The thermal loading was ramped up to 650°C from ambient temperature in 60s and then held for a total of 10min. The μCT 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 50μm in diameter. Consequently, the alkali-activated fly ash mortar was able to dissipate approximately 565°C in just 50mm of material, outperforming all the other mixes studied in this paper with μCT confirming minimal damage after the temperature exposure.