Local Bond-Slip Behavior of Reinforcing Bars in High-Performance Steel Fiber-Reinforced Concrete Beams

This paper presents the results of a comprehensive experimental study on the impact of the tensile properties of high-performance steel fiber-reinforced concrete (HPFRC) on the characteristic local bond-slip relationship of steel reinforcement. Due to the tensile toughness of the material, hoop stresses develop in the cover when the bar ribs displace relative to the surrounding concrete. This hoop action enhances the overall bond-slip performance. To quantify this effect, 13 beam specimens comprising HPFRC and containing a short embedment length of a 16 mm (0.63 in.) diameter, deformed reinforcing bar were investigated to quantify experimentally the average local bond strength and bond stress distribution over the anchorage. Two study variables were considered: a) the concrete cover (1D(b) and 2D(b)) as the exclusive confining factor; and b) the tensile strength and toughness of the mixtures used as the concrete matrix. The average bond strength was found to be proportional to the equivalent flexural tensile strength of concrete, reaching a peak value up to 20 MPa (3 ksi) and a substantial bar-slip of 19 mm (0.75 in.) at the end of testing. The smaller concrete cover provided sufficient confinement to develop bar yielding over an anchorage length of 5D(b) without additional transverse reinforcement. Increasing the cover resulted in a tougher pullout-splitting failure mode with reduced deterioration over the cover.