Investigation on the Fracture Mechanics Characteristics of High Strength Fiber Reinforced Concrete Using Laboratory Specimens with Two Different Geometries

In this research, the effect of polypropylene fibers with polyolefin coating and specimen geometry on the mechanical properties of high-strength concrete (HSC) had been investigated. In this regard, two types of polypropylene fibers (monofilament and fibrillated) with three different lengths of 19, 30, and 50 mm and volume percentages of 0.5, 1, and 1.5 were used to fabricate two types of specimens: beam and semi-circular bending (SCB). The results had been collected based on an experimental program on high-strength concrete consisting of the tensile strength test, determination of the modulus of elasticity, and three-point bending test on beam and semi-circular bending specimens. As a result of adding fibers to HSC, the tensile strength, elasticity modulus, fracture energy and characteristics length were increased up to 42%, 71%, 90 times, and 87 times, respectively. Furthermore, by using the theory of hypothesis, it is concluded that it is possible to use a semi-circular bending specimen as an alternative of a beam specimen. Finally, linear regression and power relations had been fitted on the data to convert the results of the beam and the semi-circular bending to each other.