The influence of steel fibre addition on the flexural properties of geopolymer based cementitious matrix was investigated in the present study. Slag based geopolymer mixtures were prepared with different binder and aggregate combinations. Strength gain and hardened properties of different geopolymer concrete mixtures were evaluated using accelerated curing techniques subjected to hot air oven and steam curing. Further, the steel fibre additions on the mechanical strength properties of a high strength geopolymer mixture were studied. A comprehensive evaluation on the post-crack toughness properties was assessed using four-point bend test. Test results exhibited that a geopolymer concrete of maximum compressive strength of 56.6？MPa can be achieved with steam curing. Experimental observations also demonstrated that the steel fibre inclusions in geopolymer concrete provided adequate improvement on post-crack toughness properties and showed higher composite performance with increased volume fraction of steel fibres. 1. Introduction Geopolymer based concrete received a wider acceptance among many researchers and can be a prospective application in future construction. The production of this material is cost effective and environment friendly as it is produced primarily from the industrial waste. The considerable research towards its potential use as a concreting material has led to the production of geopolymer concrete [1]. Synthesis of different geopolymer derivatives was found to be dependent on any silicate rich source material such as fly ash, furnace slag, bentonite, metakaolin, and rice husk ash. Like cement concrete, geopolymer based cementitious material is also a highly brittle material which exhibits poor tensile properties. This necessitates a comprehensive investigation to be conducted for improving the tensile properties of geopolymer concrete. Fibre addition in brittle cementitious matrix is a well-known technique to improve the toughness properties of the composite. Fibres are typically a discrete reinforcement mechanism used in either cement concrete or a geopolymer based concrete in order to provide adequate bending resistance [2]. The binder generally used in geopolymer concrete consisted of either slag or fly ash based system. Since fly ash and furnace slag is produced in large quantity as a waste from industry and needs to be disposed safely. This inevitably finds a potential alternative to be used as a construction material which can consume a large quantity [3]. Good toughening characteristics and crack resistance of geopolymer concrete
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