Influence of Mix Design Parameters on the Fresh and Compressive Strength of Steel Fiber-Reinforced Self-Compacting Geopolymer Concrete

Abstract

Self-compacting geopolymer concrete (SCGC) is a sustainable alternative to ordinary Portland cement (OPC)-based concrete because it combines the environmental benefits of geopolymer binders with the superior workability of self-compacting concrete. This study investigated the effects of the water-to-binder (W/B) ratio, alkaline activator-to-fly ash (AAS/FA) ratio, and superplasticizer dosage on the fresh and compressive strength performance of fly ash-based SCGC reinforced with 1% straight steel fibers under ambient curing conditions. Two mixture formulations were evaluated. Fresh properties were assessed using slump flow, V-funnel, and L-box tests in accordance with EFNARC (2005), while compressive strength was determined at 7, 28, and 56 days. SCGC-B (W/B = 0.075, AAS/FA = 0.35, superplasticizer = 4.5%) exhibited the best performance, achieving a slump flow of 705 mm, a V-funnel flow time of 9 s, an L-box ratio of 0.89, and compressive strengths of 15.08, 26.40, and 33.52 MPa at 7, 28, and 56 days, respectively. The results demonstrate that optimizing mixture composition enables the production of structural-grade SCGC satisfying EFNARC requirements under ambient curing conditions. This study also provides an experimental basis for the development and optimization of sustainable geopolymer concrete using locally available Class F fly ash.