Fiber-reinforced concrete incorporating locally available natural fibers in normal- and high-strength concrete and a performance analysis with steel fiber-reinforced composite concrete

This study provides an experimental investigation on the properties of fiber-reinforced composite concrete consisting of natural fibers (coconut coir) and rounded, straight steel fibers in a comparative manner for both normal-strength concrete (NSC) and high-strength concrete (HSC). This investigation was carried out using several tests, which included workability test, compressive strength test, indirect tensile strength test, and flexural strength test. A total of 10 mix batches of NSC and HSC containing 0%, 0.5%, and 1.0% fiber volume dosage rates on coir and steel fibers were tested to determine the enhancement of mechanical properties of composite concrete. In both NSC and HSC, the workability of concrete significantly reduced as the fiber dosage rate increased. In NSC, the compressive strength test indicated that strength decreases compared to plain concrete for both types of fiber. In HSC, compressive strength decreases compared to plain concrete for coir fiber and also decreases with increasing fiber volume dosage rate and increases for steel fiber with increasing fiber volume dosage rate. In NSC, split tensile test showed that tensile strength decreased for 0.5% coir and increased for 0.5% steel compared to plain concrete. But in HSC, strength increases for 0.5% coir compared to 0.5% steel and plain concrete. In NSC, flexural strength and flexural toughness of composite concrete increased in both types of fiber. But in case of concrete with coir fiber, flexural strength for 0.5% and 1% fiber volume dosages is same and increases for steel fiber. In HSC, increase of flexural strength for 0.5% coir compared to plain concrete was observed. Flexural strength also decreases with increase of fiber volume dosage for both types of fiber. In post-cracking stage, the fibers were fully utilized when it increases the ductility and toughness of both types of concrete. This research has shown that 0.5% and 1.0% coir fibers give improved performance in flexural strength of NSC, and 0.5% coir fiber gives improved performance in flexural and tensile strengths of HSC. Also, addition of coir fibers in both types of concrete increases the ductility and toughness of concrete, whereas reduction of workability of fresh concrete and compressive strength of hardened concrete occurs using coir fibers in both types of composite concrete.