Investigation of the properties of two different slag‐based geopolymer concretes exposed to freeze–thaw cycles

Abstract Ferrochrome slag (FS) and ground granulated blast furnace slag (GGBFS) were used as resource material in geopolymer concrete mixtures. A mixture of 10 M sodium hydroxide (NaOH) and sodium silicate (Na 2 SiO 3 ) was used as the activator. After the two different slag‐based geopolymer concrete (SGC) mixtures were prepared and molded. They were kept at 80°C for 24 hr, and then the SGC samples were cured in 23 ± 1°C water for 27 days. Samples that completed the curing times were exposed to the 300 freeze–thaw (F–T) cycles. The compressive strength, ultrasonic pulse velocity, relative dynamic elasticity modulus values, weight changes, and appearances of the SGC samples were examined at the end of every 50 F–T cycles. Scanning electron microscopy analysis was performed to examine the microstructure changes of the samples after 300 F–T cycles. As the GGBFS proportion in the SGC mix increased, the mechanical properties of the samples against the F–T effect increased. Samples containing 100% FS and 75% FS fell apart at the end of 150 and 200 F–T cycles, respectively. The deterioration of the geopolymer gel structures of the samples exposed to F–T was decreased with increasing GGBFS ratio in the mix.