Effect of Macro Polyolefin Fibers on Bond Strength of Tension Lap Splices in RC Beams

The effect of macro synthetic polyolefin fibers on the bond strength of tension lap splices in reinforced concrete (RC) beams is investigated in this study. The bond between the reinforcement and concrete plays a vital role in the strength of RC beams. The presence of polyolefin fibers in the lap splice zone confines the concrete and enhances the bond strength of the steel bars. The use of synthetic fibers is preferable to steel ones since steel suffers from corrosion over time. Tests were conducted on 12 full-scale beam specimens to determine the effect of fiber volume fraction (Vf), bar diameter (db) and concrete cover-to-bar diameter (c/db) on the response. Four volume fractions (Vf = 0, 0.5, 1 and 1.5%) of polyolefin fibers and three bar sizes (db = 16, 20 and 25 mm) with the corresponding (c/db = 2.31, 1.75 and 1.30) were considered to evaluate the bond strength. The test results demonstrated that the polyolefin fibers noticeably enhanced the bond strength and ductility of spliced tension bars. Experimental results were compared with those obtained from two theoretical methods including ACI Committee 318 design provisions. The results showed that the equation proposed by the ACI Committee overestimates the bond strength.

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