EXPERIMENTAL INVESTIGATION OF FLEXURAL AND CRACKING BEHAVIOR OF POLYPROPYLENE FIBER REINFORCED LIGHTWEIGHT CONCRETE BEAMS

Abstract

This study experimentally evaluates the effect of polypropylene fiberincorporation on the flexural performance and cracking behavior ofstructural lightweight concrete beams. The lightweight concrete wasproduced using locally available lightweight aggregates with a targetcompressive strength of 25 MPa and a water-cement ratio of 0.41.Polypropylene fibers were added at a dosage of 0.45% by volume ofconcrete. The experimental program included compressive strength,splitting tensile strength, flexural strength, and crack width tests. A totalof 10 cylindrical specimens and 6 reinforced lightweight concrete beamspecimens measuring 200 × 300 × 1800 mm were prepared and tested.All specimens were water-cured for 28 days before testing. The resultsshowed that polypropylene fibers improved the mechanical and crackingperformance of structural lightweight concrete. The compressivestrength increased from 23.73 MPa to 24.81 MPa, while the splittingtensile strength increased from 2.09 MPa to 2.31 MPa. In addition, theflexural strength increased from 3.28 MPa to 3.51 MPa. The addition ofpolypropylene fibers also reduced the maximum crack width from 0.75mm to 0.47 mm and produced narrower and more uniformly distributedcracks along the beam span, indicating improved crack resistance andpost-cracking behavior. The novelty of this study lies in the experimentalinvestigation of crack propagation and flexural behavior of structurallightweight concrete beams incorporating polypropylene fibers usinglocally sourced lightweight aggregates under three-point loadingconditions.