Compressive behaviour of alkali-activated slag-based concrete and Portland cement concrete incorporating novel multiple hooked-end steel fibres

This study investigates the effect of single and multiple hooked-end steel fibres on the mechanical properties of alkali-activated slag-based concrete (AASC) and compares its performance with a similar strength-grade Portland cement concrete (PCC). Three different fibre geometries, i.e. single (Dramix (R) 3D), double (Dramix (R) 4D) and triple hooked-end (Dramix (R) 5D) steel fibres, and three different volume fractions, i.e. 0.25%, 0.50% and 0.75% are considered. Compressive strength, modulus of elasticity and stress-strain response under uniaxial compression are evaluated. Hooked-end steel fibres have a limited effect on the compressive strength and modulus of elasticity of both AASC and PCC, regardless of fibre geometry and content. Although hooked-end steel fibres improve the compressive stress-strain behaviour of both composites, higher enhancement of peak stress, corresponding strain and post-peak response is observed for fibre-reinforced AASC (FRAASC) mixtures. To predict the stress-strain response under uniaxial compression of steel FRAASC a new analytical model is proposed and calibrated using an extensive dataset of experimental stress-strain curves available in the literature for both steel fibre-reinforced PCC and AASC. This model can predict the compressive stress-strain behaviour of FRAASC using the compressive peak stress and corresponding strain of the unreinforced matrix and the steel fibre reinforcing index (RIv) as inputs and provides excellent results when validated against the data obtained in this study for FRAASC.