Flexural Behavior of Lightweight Concrete Beams Reinforced with GFRP Bars and Effects of the Added Micro and Macro Fiber

This study evaluated the effect of macro steel fiber (SF), micro glass fiber (GF) and micro polypropylene fiber (PF) in lightweight aggregate concrete, (LWAC) beams reinforced with glass fiber reinforced polymer (GFRP) bars. Firstly, concrete mixtures with different volume fractions of GF, PF and SF were tested up to compressive strength, then determine the optimum fiber content GF, PF and SF added into LWAC mix by 0.3%, 0.8% and 0.25% by the volume of concrete, respectively. Meanwhile, eight rectangular cross-section beams with 100 mm (width) × 200 mm (depth) × 1500 mm (length) were tested by four-point bending beam test up to the ultimate load. The GFRP bars were used to reinforce all beams. The failure modes, load-deflection behavior, ductility, flexural capacity and energy absorption were compared in the test results. The experimental results shown added fibers into LWAC improved the flexural capacity, ductility and energy absorption also enhanced moment capacity by 10.07% to 110%. The results indicated that failure modes of GF and PF specimens were in good consistency with the ACI 440.1R-06 predicted failure modes, but for SF specimens, only concrete crushing failure modes accrued. At the end step, the correction factor ( ) obtained from calculated of the experimental results with the flexural capacity according to the ACI 440.1R-06 and ISIS design manual No. 3.