Investigation on the Effect of Volume, Length and Shape of Polyolefin Fibers on Mechanical Characteristics and Fracture Properties of High-Strength Concrete

Regarding to advancement of civil engineering in recent decades, using high-strength concrete is so prevalent for constructing special projects. One of the main shortcomings of concrete is its tensile strength which causes cracking and brittle behavior. Today, to enhance concrete’s performance and overcome this lack, a wide range of fibers including polymeric, steel, mineral and natural are used as well as classical solution for improving tensile strength of concrete: using steel bars. In this study, the effect of volume, length and shape of polyolefin fibers on mechanical characteristics and fracture properties of high-strength concrete is investigated. Three different fiber’s length of 19, 30 and 50 mm are used at three different volume percentages of 0.5, 1 and 1.5 with two simple and reticular shapes. Conventional experimental tests of compressive strength, tensile strength, bending strength and modulus of elasticity are implemented to determine mechanical characteristics as well as U-notched prismatic beam to evaluate fracture properties. The results have shown that increasing the length of fiber enhances mechanical and fracture properties of concrete. Also, increasing the fibers’ volume causes an increasing the resistance time of concrete specimens against bending load. The simple-shape fiber shows higher bending strength in comparison with reticular fibers but fracture energy of reticular fibers is so greater than simple-shape fibers.