Performance evaluation of fiber reinforced self compacting alkali activated concrete mixes—a DoE approach

Abstract

Alkali-activated concrete (AAC) has emerged as a sustainable alternative to conventional concrete due to its lower carbon emissions and effective use of industrial by-products. Several studies have explored the performance of AAC in both fresh and hardened states. However, the broader application of these mixes in real-time applications can be enhanced through further modifications to meet current needs. Fiber-reinforced self-compacting alkali-activated concrete (FSAAC) mixes represent one such class of innovative concrete mixes. This study evaluates the fresh-state, mechanical, and fracture properties of FSAAC mixes optimized using Taguchi’s design of experiments (DOE) methodology. An L9 orthogonal array was employed with three variables at three levels: fly ash (FA) content (30%, 40%, 50%) as partial replacement of blast furnace slag, steel fiber (SF) content (0.25%, 0.5%, 0.75% by concrete volume), and fiber aspect ratio (AR) (40, 60, 80). A control mix without FA and SF was included in the comparison study. All FSAAC mixes satisfied EFNARC guidelines for fresh-state properties. Fracture parameters were determined through three-point bending (TPB) tests. The F30-S0.75-A80 mix exhibited superior performance with compressive strength of 66.33 MPa, flexural strength of 7.05 MPa, initial fracture toughness (KICini) of 0.813 MPa?m, unstable fracture toughness (KICuns) of 6.123 MPa?m, fracture energy (G<inf>F</inf>) of 5513.80 N/m, and a toughness ratio of 0.133. Compared to the control mix, the mix F30-S0.75-A80 showed 22.6%, 14.35%, 313.15% and 2518% rise in flexural strength, KICini, KICuns and G<inf>F,</inf> respectively. Taguchi analysis identified optimal mix proportions for slump flow at FA 50%, SF 0.25%, AR 40, and for KICini at FA 30%, SF 0.75%, AR 60. For other properties, proportions were optimized at FA 30%, SF 0.75%, AR 80. Regression models developed exhibited high degree of predictive accuracy, closely aligning with experimental outcomes. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.