Effect of Fiber Reinforcement on Bond Strength of Tension Lap Splices in HighStrength Concrete

The primary objective of the research reported in this paper was to evaluate the effect of steel fiber reinforcement on the bond strength and ductility of the mode of bond failure of tension lap splices anchored in high-strength concrete (HSC) test specimens. What makes this study significant is that ACI Committee 408 (Bond and Development) is working on proposing recommendations specifying minimum transverse reinforcement on anchored reinforcement in HSC (fc¢ > 70 MPa) to provide ductility to the mode of failure. To meet the objective, 12 full-scale HSC beam specimens were tested. Each beam was designed with bars spliced in a constant moment region at midspan. The variables were bar size db = 20, 25, or 32 mm, and the volume fraction of steel fibers added in the splice region Vf = 0.5, 1.0, or 2.0%. Test results indicated that the use of steel fibers in the splice region increased the bond strength and the ductility of the mode of failure of the beam specimens. The increase in bond strength with high fiber content exceeded 3, the maximum increase in bond strength of a reinforced concrete beam that could be achieved by using transverse reinforcement in the splice region.