Torsional Behavior of Polyolefin Fiber Reinforced Concrete Beams of Different Strength Levels

Abstract

• The use of fibers has become widely adopted to improve the characteristics of concrete in structures, enabling them to withstand various loads. In this research, an experimental study was conducted to investigate the effect of adding polyolefin fibers (PF) in different ratios on the structural behavior of reinforced concrete beams under a pure torsional load. The study examined four polyolefin fiber ratios (PFR) (0.0%, 0.5%, 1.0%, 1.5%) for both normal and high strength concrete. A total of 8 reinforced concrete beam specimens were fabricated; four specimens were made of normal concrete and the remaining four were made of high strength concrete. In addition to assessing the torsional behavior of the specimens, the mechanical characteristics of the concrete were investigated. The results demonstrated that the PF had a negligible influence on the concrete compressive strength of both levels. However, the tensile and flexural concrete strengths showed an improvement as the fiber content increased. Specifically, the tensile strength increased by approximately 78% and 41% for normal and high strength concrete, respectively when using a 1.5% PFR. Likewise, the flexural strength increased by approximately 88% and 65% for normal and high strength concrete, respectively, with 1.5% PFR. The experimental torsional test results indicated that torsional performance improved with increasing PFR. The ultimate torsional load increased by about 74% and 45% for a 1.5% PFR compared to specimens without fibers for normal and high strength concrete, respectively. Additionally, the twist angle of the specimens increased with increasing PFR, reflecting an improvement in their ductility. It is worth noting that the rate of improvement decreased after reaching a PFR of 1.0%.