Bond-Slip Behavior of Steel Bar and Recycled Steel Fibre-Reinforced Concrete

Abstract

Recycled steel fiber reinforced concrete is an innovative construction material that offers exceptional mechanical properties and durability. It is considered a sustainable material due to its low carbon footprint and environmental friendly characteristics. This study examines the key influencing factors that affect the behavior of this material, such as the steel fiber volume ratio, recycled aggregate replacement rate, concrete strength grade, anchorage length, and stirrup constraint. The study investigates the bond failure morphology, bond-slip, and bond strength constitutive relationship of steel fiber recycled concrete. The results show that the addition of steel fibers at 0.5%, 1.0%, and 1.5% volume ratios can improve the ultimate bond strength of pull-out specimens by 9.05%, 6.94%, and 5.52%, respectively. The replacement rate of recycled aggregate has minimal effect on the typical bond strength of pull-out specimens. However, the ultimate bond strengths of pull-out specimens with concrete strength grades C45 and C60 have improved compared to those with C30 grade. The specimens with longer anchorage lengths exhibit lower ultimate bond strength, with a reduction of 33.19% and 46.37% for anchorage lengths of 5D and 7D, respectively, compared to those without stirrups. Stirrup restraint of 1 φ 8 and 2 φ 8 improves the ultimate bond strength by 5.29% and 6.90%, respectively. Steel fibers have a significant effect on the behavior of concrete after it cracks, especially during the stable expansion stage, crack instability expansion stage, and failure stage.