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

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 (Na2SiO3) was used as the activator. After the two different slag-based geopolymer concrete (SGC) mixtures were prepared and molded. They were kept at 80 degrees C for 24 hr, and then the SGC samples were cured in 23 +/- 1 degrees 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.