Fracture properties of slag/fly ash-based geopolymer concrete cured in ambient temperature

Abstract

Slag/fly ash (FA)-based geopolymer cured in ambient temperature as a green alternative to Portland cement is attracting increasing attentions. The fracture properties of slag/FA-based geopolymer concrete (SFGC) was studied by conducting three-point bending (TPB) tests on precut beams. The effects of material parameters including the alkali concentration, the modulus of alkali activator, the slag/FA mass ratio and the liquid/binder ratio on the fracture properties of SFGC were assessed. The results exhibit that the fracture behaviors of SFGC are influenced significantly by the material parameters. The fracture energy and the ultimate load of TPB tests of SFGC beams increase with the increase of the alkali concentration, the modulus of alkali activator as well as the slag/FA ratio while decrease with the increase of liquid/binder ratio. The Bažant and Becq-Giraduon model predicts well whereas the CEB-FIP model underestimates the fracture energy of SFGC beams. Besides, the characteristic length of SFGC decreases with the increase of compressive strength regardless of the mix proportion, and is higher than the prediction for Portland cement concrete (PCC) given the similar compressive strength, suggesting that SFGC might be more ductile. In addition, the relationships between compressive strength, splitting tensile strength, elastic modulus and material parameters of SFGC specimens are also discussed.