The Laboratory Experiment of the Effect of Quantity and Length of Plastic Fiber on Compressive Strength and Tensile Resistance of Self-Compacting Concrete

Self-compacting concrete (SCC) is known as a high-performance concrete that molds by its weight and without the need for vibration or impact and easily crosses the small spaces between the rebars. Various additives have been used in recent research to construct the self-compacting concrete in order to achieve higher strengths and improved performances. Because of the utilization of self-compacting concrete in bulk concreting like dams, silos, and tanks, the optimized use for reducing the final costs of the project is important and essential. A fundamental question in improving the fiber self-compacting concrete behavior is that what is the optimum amount of fiber addition for low fiber concentrations. In this research, the effect of the addition of fiber with concentrations lower than 1,000 gr (100, 250, 500, and 1,000 gr) on the self-compacting concrete behavior with different fiber lengths have been studied. This research examined the effect of the quantity and length of recycled plastic fiber on the compressive strength and tensile resistance of self-compacting concrete. Slump flow experiment L box and sieve and compressive and tensile strength experiment were done on samples. In this study, 13 plans of concrete mixing were surveyed with ratio of water to cement 0.4. One plan without fiber was chosen as a reference sample and 12 self-compacting concrete with plastic Fibers were made in the laboratory with dimensions of 1, 2, 3 cm with their amounts equal 100, 250, 500 and 1,000 g/m(3). Laboratory results showed that increasing the amount and length of fibers led to decreased flowability and passability plus increased detachment in samples. By increasing plastic fibers, compressive strength increased by 8.4% and tensile resistance increased by 4.22%. Their elevation depends on fibers amount. Fiber length did not affect the compressive strength and tensile resistance very much. The increase was such that the tensile strength increased by about 100% and 200% as the length increased from 1 to 2 cm and 1 to 3 cm, respectively. The 1 cm plastic fiber length could be selected as the optimum length for increasing the compressive strength by considering the efficiency.