Fire resistance of geopolymer concrete produced from Ferrochrome slag by alkali activation method

The effect of high temperatures up to 700°C on compressive strength and water absorption of two alkali-activated aluminosilicate composites (one of them with river sand aggregates, the second crushed sand aggregates) and ordinary Portland cement (OPC) concretes is analyzed in this paper. Binding geopolymer material was obtained after grinding the Elazığ Ferrochrome slag (EFS) as fine as cement and alkaline activating with chemical materials (NaOH-Na₂SiO₃). Geopolymer concrete samples were produced by using this binding material with aggregates. Produced concrete samples were exposed to temperature for 1 hour, after reaching the maximum temperature. Fire resistance and water absorption of geopolymer and OPC concrete samples was obtained experimentally. Compressive strength of river aggregates and crushed sand aggregates concrete increased at 100 and 300°C temperatures compared to unexposed samples, and the maximum compressive strength for these geopolymer concrete sample was obtained at 300°C. Water absorption of all concrete samples increased at 700°C temperature compared to unexposed samples. But there appeared to be a slight decrease of water absorption in the all concrete samples up to 300°C temperatures compared to unexposed samples. Scanning electron microscopy and XRD tests were also conducted to examine microstructure and mineralogical changes during the thermal exposure.