The mechanical and durability properties of concrete containing hybrid synthetic fibers

Abstract

In this study, the fresh and hardened properties of concrete including hybridization of polyolefin (PO) and polypropylene (PP) fibers were investigated. The twelve mixtures consisting of different dosages of PO and PP fibers were considered. Mixtures consisted of PO fibers at the volume fractions of 0.5, 1 and 1.5% that some part of those replaced with PP fibers at volume fractions of 0.1% and 0.2%. The properties of mixtures were evaluated using slump and Inverted slump cone tests in fresh state, and using compressive, splitting, and flexural tests in hardened state. In addition, the durability properties were investigated using water absorption, electrical resistivity and chloride penetration tests. The reinforced concrete beams including fibers were made and tested under accelerated corrosion. The influence of fibers on structural performance of sound and corroded beams were assessed by four-point loading test.The results indicated that hybridization of PO with PP fibers can improve the compressive and splitting tensile strength of mixtures up to 7.5% and 23% compared to those of control mixture, respectively. However, the hybridization of these fibers did not show a positive effect on post-cracking behavior at the flexural test. From durability viewpoint, replacement of some part of PO fibers with PP fibers can control the negative effect of using PO macro fibers. However, at the high volume fraction of fibers, the hybridization of PO with PP fibers showed the negative effect. Based on an overall view of results, hybridization of PO and PP fibers at the volume fraction of 0.9% and 0.1%, respectively, can be recommended for practical usage. This combination of fibers decreased the corrosion of steel in RC beams and improved the key parameters of structural behavior such as yield and ultimate loading, and stiffness of beams.