Development of deflection hardening geopolymer based ductile fiber reinforced cementitious composites

Abstract

Ductile fibre reinforced cementitious composites (DFRCC) are cement-based composites reinforced with short random fibres (metallic and/or non-metallic) which exhibit deflection-hardening and multiple-cracking behaviours in bending. It is a special class of high performance fibre reinforced cementitious composite (HPFRCC) that has higher deflection capacity than that of regular fibre reinforced concrete (FRC). Current DFRCCs are limited to cement-rich matrix system. This paper reports the development of geopolymer-based DFRCC where the cement binder in DFRCC is replaced by fly ash-based geopolymer binder and alkaline liquids (sodium hydroxide and sodium silicate) are used to activate the fly ash. In this study, three types of fibres are considered namely steel and two types of polyvinyl alcohol (PVA) fibres having different diameter, length and elastic modulus. The fibres used in the development of both cement-based and geopolymer-based DFRCCs are limited to single fibre type. The effects of two different sand sizes (1.18 mm and 0.6 mm) and sand/binder ratios of 0.5 and 0.75 on deflection-hardening and multiple-cracking behaviour of both types of DFRCC are also evaluated. Results reveal that deflection-hardening and multiple-cracking behaviour can be achieved in geopolymer-based DFRCC similar to that of cement-based system. For a given sand size, fibre type and sand content, comparable ultimate flexural strength and the deflection at peak load are observed in both cement and geopolymer-based composites. The proposed development exhibits a significant benefit for the use of geopolymer-based DFRCC over cement-based system as the former one is green in terms of no cement use.