Freeze-thaw durability of red mud slurry-class F fly ash-based geopolymer: Effect of curing conditions

Freeze-thaw (F-T) durability of geopolymers synthesized from the mixture of red mud slurry-Class F fly ash (RMSFFA) was investigated in this study, with an emphasis on the influence of curing conditions (i.e., curing time and curing temperature). F-T durability was evaluated on the basis of the sustained mechanical strength of RMSFFA geopolymer specimens after subjected to 50E-T conditioning cycles. The change in their chemical bonding, mineralogy, and pore characteristics at various F-T conditioning cycles was examined with Fourier transform infrared spectroscopy, X-ray diffractometer, and Brunauer-Emmett-Teller testing, respectively, to reveal the underlying processes during F-T conditioning. The results of both mechanical strength and microstructural characterization indicate that curing conditions influence F-T resistance of RMSFFA geopolymer samples through affecting their strength development. For 14-day cured RMSFFA samples at 50 degrees C, they experienced further geopolymerization at the early stage of F-T conditioning but the partial dissolution of geopolymer gel at the later stage of F-T conditioning. For 28-day cured samples at 50 degrees C, only the partial dissolution of geopolymer gel was likely to occur during the F-T conditioning because the strength development was likely to complete prior to the conditioning. (C) 2019 Published by Elsevier Ltd.