Properties of Concretes Produced by Single and Combined Hooked End Discontinous Discrete Steel Fibers

ABSTRACT: Steel fibers are widely used in concrete as additional industrial materials for concrete products. Because of its huge application areas it keeps its popularity to be an academic research on developing the usage of them. As concrete is naturally weak in tension, steel fibers added will improve tensile strength of concrete. Producing steel fiber reinforced concrete is not a very new technology in but these concretes are generally produced by using only one type of steel fiber (aspect ratio, diameter or length) due to economical and practical reasons and concretes having various types of these fibers are not generally produced. Finding an optimum combination of fibers that are added to concrete which develop the SFRC properties in both, fresh and hardened states would bring many benefits. This study investigates the effect of adding combined steel fibers with two different aspect ratio(80, 60) and three different length (60, 50, 30) on concrete properties in fresh and hardened states. These concretes are produced by combining these different fibers with varying volume percentages. At the end of the study, optimum combination obtained by comparing the effects of the mixes with the plain concrete, on fresh properties such as workability and hardened properties such as compressive strength, flexural strength, rebound number, ultrasonic pulse velocity and drying shrinkage. The results have shown that the adding combined fibers to the concrete, increase the compressive strength, flexural strength and rebound number, on the other hand adding fibers enhances the ultrasonic pulse velocity and drying shrinkage of concrete as well. Keywords: Steel fibers, concrete, aspect ratio, strength, shrinkage, Vebe time, pundit. ……………………………………………………………………………………………………………………………………………………………………………………………………………………