LAUSR

Abstract Modulus of elasticity and Poisson's ratio are the main mechanical properties of concrete for assessing the flexural and shear stiffness of concrete elements. Although steel fibers are beginning to be accepted in modern building codes, equations for estimating the elasticity modulus and Poisson's ratio of Fiber Reinforced Concrete (FRC) are not provided in such building codes. Even though the direct measurement of the modulus of elasticity and the Poisson's ratio is adequately established, the use of non-destructive methods such the Ultrasonic Pulse Velocity (UPV) test offers an economical and easy alternative that must be explored. The aim of this paper is to propose empirical relationships for estimating the dynamic modulus of elasticity and Poisson's ratio of concrete reinforced with steel, synthetic and hybrid fibers, using results measured during the UPV tests. The research is also intended to assess results of models reported in a literature review, to evaluate the effect of test setup (direct, semi-direct and direct), and to establish a relationship between the dynamic modulus of elasticity of FRC and the characteristics of steel, polypropylene/polyethylene and hybrid fibers. The experimental program included dynamic non-destructive tests and static destructive tests of 29 concrete specimens. The variables included in the experimental program were the fiber type (steel, synthetic and hybrid), the fiber content and the ultrasonic pulse velocity setup (direct and semi-direct). The length, diameter and aspect ratio of fibers were 50 mm, 1.05 mm and 48 for the steel fibers, and 50 mm, 0.68 mm and 74 for the polypropylene/polyethylene synthetic fibers. Fiber volume fractions in the concrete varied between 0.17% and 0.93%. The study also compared the results obtained in the static tests with the dynamic results, in order to identify the differences between static and dynamic behavior.