Performance evaluation of fly ash-based sustainable reactive powder concrete reinforced with hybrid steel–glass fibers

Reactive Powder Concrete (RPC) is a high-strength cement-based composite and low water-to-cementitious ratio; however, it is characterized by a high cement content, which raises sustainability concerns. The objectives were to produce eco-friendly products. RPC with replacing cement partially with fly ash and to optimize hybrid reinforcement with steel–glass fibers to enhance mechanical strength and, subsequently, lower environmental impacts. The fly ash replaced cement at the rate of 20%, and the total fibers were fixed at a constant of 1% by volumetric ratios of hybrid steel to glass fibers (1:0 steel, 0.75:0.25, 0.50:0.50, 0.25:0.75, and 0:1 glass). Compressive strength at 28 days, flexural, and splitting tensile strengths of the 20% fly ash with the incorporation of micro steel fibers (1%) were found to be higher than reference mix without fly ash under thermal curing increased by 4.47%, 2.39% and 2.01% respectively, In contrast, Partial replacement of steel fiber with glass fiber at different hybrid ratios The findings showed gradual compressive strength reduction (1.05–3.33%), flexural strength (1.62–17.67%), and splitting tensile strength (1.57–14.61%) as compared to control mix containing 1% micro steel fibers. Both fly ash and fiber hybridization influenced the density, water absorption, and porosity of RPC.