Crack Growth Resistance in Fibre Reinforced Geopolymer Concrete Exposed to Sustained Extreme Temperatures

Portland cement concrete (PCC) is now second only to potable water in per capita consumption. And notwithstanding its numerous benefits, Portland cement itself is responsible for between 4 to 5% of the world’s manmade greenhouse gas emissions. In this context, geopolymer concrete is a promising alternative, wherein the Portland cement binder is replaced entirely by supplementary cementitious materials triggered by alkaline activators. Relatively little is known on the fracture response of this system, especially when exposed to extreme temperatures. The study reported here focused on the crack growth response of such a system prepared with Class F fly ash and reinforced with steel and polymeric fibres up to 1% volume fraction. The geopolymerization was effected with a blend of sodium hydroxide and sodium silicate to achieve a compressive strength of 30 MPa at 28 days. The resulting geopolymer concrete was subjected to temperatures between-30 oC to 300 oC, sustained for 2 hours. A fibre blend of steel to polypropylene in the mass ratio of 4:1 was incorporated. Based on the results, four different stages for fracture behaviour were identified with superior fibre efficiency seen at sub-zero temperatures.