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® 3D), double (Dramix® 4D) and triple hooked-end (Dramix® 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 ( $${\mathrm{RI}}_{\mathrm{v}}$$RI v ) as inputs and provides excellent results when validated against the data obtained in this study for FRAASC.

The use of alkali‐activated concrete (AAC) as an alternative construction material to Portland cement‐based concrete (PCC) has been widely encouraged by its enhanced mechanical and durability performance and environmental benefits. However, AAC exhibits low flexural and tensile strength, limiting its application in areas where high post‐cracking flexural and tensile load‐bearing capacity are needed. Steel fibers can be added to improve the composite ductility and toughness. Steel fiber‐reinforced alkali‐activated concrete (SFRAAC) is a new emerging technology with research studies evaluating the effect of fiber addition on its mechanical properties still in the early stages. To promote the application of SFRAAC, analytical models predicting their mechanical performance are needed. This study evaluates the applicability to SFRAAC of previously published analytical models developed for steel fiber‐reinforced cement‐based concrete (SFRPCC). Experimental data available in the literature have been collected to create an extensive database to validate and then calibrate these currently available correlations between mechanical properties for SFRAAC. The prediction models considered in this study correlate the mechanical performance of SFRAAC, that is, compressive strength, modulus of elasticity, splitting tensile strength, flexural and residual flexural strength, to the compressive strength of the reference concrete without fibers, the fiber volume fraction and the fiber reinforcing index. Thus, by knowing the performance of the AAC matrix and the fiber properties and dosage, it is possible to predict the overall mechanical behavior of the steel fiber‐reinforced composite.