Experimental study on static and dynamic properties of fly ash-slag based strain hardening geopolymer composites

Strain hardening geopolymer composite (SHGC) is a special group of fibre reinforced geopolymer composites, which exhibits ultra-high ductility and multiple microcracks under tension. This paper presents an experimental study on the effect of polyvinyl alcohol (PVA) fibre content (0%, 1%, 1.5%, and 2%) on engineering properties of fly ash-slag based SHGC cured at ambient temperature in terms of flowability, drying shrinkage and mechanical properties, with a special focus on strain hardening behaviour and dynamic compressive behaviour. Single-crack tension test and three-point bending test were conducted to determine the micromechanical properties of SHGC, dynamic properties of which were explored using Split Hopkinson pressure bar. Results indicate that the flow ability, drying shrinkage and compressive strength of SHGC reduce with the increase of PVA fibre content, while the tensile strength and ultimate strain of SHGC under uniaxial tension are significantly improved because of the fibre bridging effect. The dynamic compressive behaviour of SHGC is strongly associated with the strain rate. The dynamic compressive strength of SHGC with various PVA fibre dosages is increased by 9.26-29.97% and 41.59-69.78% as the strain rate increases from 50 s(-1) to 100 s(-1) and 150 s(-1), respectively. Overall, the mixture containing 1.5% PVA fibre can be regarded as the optimal mixture for SHGC considering static mechanical properties and dynamic compressive behaviour.