Experimental investigation of eco-friendly high strength fiber-reinforced concrete developed with combined incorporation of tyre-steel fiber and fly ash

•Concrete incorporating various levels of fly ash and recycled tyre steel fiber.•Mechanical and durability Performance of fiber-reinforced concrete.•Useful insights into the development of eco-friendly fiber-reinforced concrete. Simultaneous addition of waste fibers and supplementary cementitious materials is a novel and eco-friendly approach to resolve the issues related to brittleness and environmental impact of plain-concrete (PC). This study examines the concrete mixes incorporating different levels of recycled-tyre steel fiber (RTSF) (0, 0.25, 0.5 and 1% by volume fraction) and low-calcium fly ash (FA) (0, 10, 15, 25, and 35% by volume replacement of cement). The studied properties include compressive strength-fCS (28 and 120-days), splitting-tensile strength-fSP (28-days), modulus of rupture-MOR (28-days), water-absorption-WA (28-days), ultrasonic pulse velocity-UPV (28-days) and electrical resistivity-ER (28-days). The experimental results showed that the simultaneous addition of 10–15% FA and 0.25%-0.5%RTSF can enhance the ductility and imperviousness of concrete. The maximum efficiency of RTSF in fSP and MOR was noticed in the concrete mix containing 10% FA. Whereas rise in FA content beyond 15% decreased the overall mechanical strength and efficiency of RTSF. The high strength concrete mix containing 10%FA and 0.5%RTSF showed 83%, 49% and 19% higher MOR, fSP and fCS, respectively than the reference concrete mix. FA at all levels and RTSF at 0.25–0.5% volume was beneficial to the imperviousness of high strength concrete. All FA levels (i.e., 10–35%) can minimize the electrical conductivity of RTSF-reinforced concrete mixes with respect to the reference mix.