A study on fracture toughness of ultra-high toughness geopolymer composites based on double-K criterion

Ultra-high toughness geopolymer composites (UHTGC) were fabricated based on the matrix of binder composed of alkali-activated fly-ash and granulated blast furnace slag and polyvinyl alcohol (PVA) fibres in this research. The tensile behaviour and fracture toughness of UHTGC are investigated on both macro and microscales experimentally and analyzed based on Double-K Criterion. With slag content of 20 % and curing temperature ³ 60 ℃, the average strain of the composite under uniaxial tension load is more than 3 %. Both initial fracture toughness and unstable fracture toughness of geopolymer is improved by adding PVA fibers. The fracture energy of UHTGC is up to 77 times than that of mix proportions without fibre. The results of nanoindentation test verified that the modulus of elasticity increases with curing temperature, while the fracture energy decreases slightly with curing temperature