The impact of fire flames on the mechanical characteristics of basalt fiber-reinforced geopolymer concrete composed of sustainable components

The use of geopolymer concrete (GPC) has been proposed to reduce carbon dioxide (CO2) emissions linked to the cement production. Fire poses a significant risk to concrete structures, as it causes mechanical degradation of the concrete. This research used 70% Granulated Ground Blast Furnace Slag (GGBFS) and 30 % Fly Ash (FA) to synthesis Geopolymer Concrete (GPC). The alkaline activation solution was created by mixing sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) at a concentration of 12 molarity. The ratio of the solution to the cementitious material was 0.4. The weight ratio of sodium silicate to sodium hydroxide was 2.5:1. Basalt fibres were used for reinforcement at volume fractions of 0.5 %, 0.75 %, and 1 %. The geopolymer concrete specimens were subjected to an elevated temperature of 70 °C in an oven for 4 hours, which is similar to the curing time of 2 days. After 56 days, the specimens were burned at three different temperatures of 300 °C, 500 °C, and 700 °C for one hour. The required tests (compressive strength, flexural strength, splitting tensile strength, and mass loss percentage) were conducted before and after the burning procedure. The residual compressive strength percentages obtained were 90 %, 73 %, and 61 %, the residual flexural strength percentages were 91 %, 70 %, and 51 %, the residual splitting tensile strength percentages were 89 %, 68 %, and 50 %, and the mass loss percentages were 1.271 %, 1.557 %, and 2.035% for a 1% ratio of basalt fibre at 300 °C, 500 °C, and 700 °C, respectively. Geopolymer concrete is highly resistant to flames, even at temperatures of up to 700 °C.