Shear and Flexural Behavior of Lightweight Concrete Beams Containing Hybrid Fibers

Abstract Due to the low density of lightweight concrete, work has been done in this research to develop it by adding fibers of more than one type to improve its properties. Basic tests were conducted to determine the properties of concrete before and after the addition of fibers. The variables of the models were beams in two groups (shear and flexural). The variables of these two groups included the type of fibers (steel and polypropylene) and the size of the added fibers 0 %, 0.05 %, 0.1 % for polypropylene fibers 0 %, 0.75 %, 1 % for steel fibers. This study presented an examination of 18 beam specimens and discussed the results, which included mechanical properties (air dry density, slump test, compressive strength, modulus of elasticity, flexural strength, and splitting tensile strength). The results showed that the addition of fibers had an effective effect on the compressive strength, and this led to an increase in the resistance to shear forces and flexural forces, as the highest load capacity was shown by adding polypropylene fibers at a rate of 0.1 % in both groups, and the fibers played an important role in reducing the width of cracks and controlling their spread due to modulus of elasticity of the fiber.