Mechanical behaviour at high temperature of alkali-activated aluminosilicates (geopolymers): Fid-Bau Portal

Mechanical behaviour at high temperature of alkali-activated aluminosilicates (geopolymers)

Martin, Antonia / Pastor, Jose Y. / Palomo, Angel / Fernández Jiménez, Ana

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Highlights • Mechanical behaviour of alkali-activated aluminosilicates (geopolymers) in situ. • Pseudo-plastic behaviour in vivo trials at temperatures over 600°C. • Residual strength after 1-h exposure to different temperatures (200–1000°C). • Mineralogical (DRX) and microstructural (porosity) changes a high temperature.

Abstract This study was designed to determine the effect of temperature on the mechanical strength (in both in vivo and post-exposure trials) of two alkaline cements (without OPC): (a) 100% fly ash (FA) and (b) 85% FA+15% bauxite, the activated alkaline solution used was 85% 10-M NaOH+15% sodium silicate. A Type I 42.5 R Portland cement was used as a control. Two series of trials were conducted: (i) in vivo trials in which bending and compressive strength, fracture toughness and modulus of elasticity were determined at different temperatures; and (ii) post-firing trials, assessing residual bending and compressive strength after a 1-h exposure to high temperatures and subsequent cooling. The findings showed that from 25 to 600°C, irrespective of the type of test (in vivo or post-firing), compressive mechanical strength rose, with the specimens exhibiting elastic behaviour and consequently brittle failure. At temperatures of over 600°C, behaviour differed depending on the type of test: (i) in the in vivo trials the high temperature induced pseudo-plastic strain and a decline in mechanical strength that did not necessarily entail specimen failure; (ii) in the post-firing trials, compressive strength rose.