Durability performance of hybrid reinforced concretes (steel fiber + polyolefin fiber) in a harsh marine tidal zone of Persian Gulf Hadi Bolooki Poorsaheli a,c , Amir Behravan b,⇑ , Seyed Taha Tabatabaei Aghda c a Civil Engineering Department, Islamic Azad University- Bandar Abbas Branch, Iran b Civil & Environmental Engineering Department, Oklahoma State University, OK, USA c Road, Housing & Urban Development Research Center (BHRC), Persian Gulf Branch, Bandar Abbas, Iran highlights  Fibers bridge between cracks and prevent propagation of cracks.  Steel fibers increase the risk of corrosion while polyolefin fibers reduce it.  Polyolefin fibers are more effective than steel fibers in improving flexural strength.  Fibers have not considerable effects on compressive strength. article info Article history: Received 23 April 2020 Received in revised form 22 September 2020 Accepted 29 September 2020 Keywords: Fiber reinforced concrete Hybrid fiber reinforced Steel fiber Polyolefin fiber Durability Corrosion Harsh medium Persian Gulf abstract Adding fibers into concrete mixture has been an attractive subject for researchers to determine how var- ious forms of fibers change the performance of concrete. This paper reports the findings of a study on the impact of using steel fibers and polyolefin fibers at three volume ratios on the long-term performance of concrete when subjected to a high chloride medium. The concrete properties that were measured include compressive strength, flexural strength, water permeability under pressure, electrical resistivity, half-cell test, and water absorption. Results showed that fibers have no considerable impact on compressive strength while they can improve the flexural strength by up to 28%. Electrical resistivity and half-cell test results showed that polyolefin fibers improve the concrete performance against corrosion while steel fibers reduce the corrosion resistance of concrete. Moreover, steel fibers in hybrid mixtures attenuate the positive impact of polyolefin fibers on the corrosion performance of concrete. Ó 2020 Elsevier Ltd. All rights reserved. 1. Introduction Concrete is the most human-made consuming material in the world because of its advantages. Concrete has disadvantages including low tensile strength, poor resistance to crack opening and propagation, and high weight of components built with con- crete, problems of electrical conductivity, higher magnetic fields, and corrosion [1–4]. The shortage of tensile strength can be improved by adding fibers to the concrete mixture [1]. Over the past years, there has been more emphasis on researching how the insert of various forms of fibers change the performance of concrete [5–9]. Steel fiber is the most-widely used reinforcing fiber due to its high modulus of elasticity (E  200 GPa) and tensile strength (r  500–1000 MPa) [2,9–13]. Despite the effectiveness of steel fibers in concrete, steel fibers have some disadvantages in mixing and construction processes and even during the service life by being corroded [14–16]. There are a number of researches that focused on the study of steel fiber reinforced concrete (SFRC) under different circumstances and different concretes [17–24]. Among all types of fibers that commercially are available, the properties of SFRC are well studied. In recent years new materials have been examined as possible fiber reinforcement elements in structural concrete members to overcome some problems of using steel fibers [25–36]. One of the materials that has been a practical choice as a fiber- reinforcement element in concrete is a type of polymer called https://doi.org/10.1016/j.conbuildmat.2020.121176 0950-0618/Ó 2020 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: amir.behravan@okstate.edu (A. Behravan). Construction and Building Materials 266 (2021) 121176 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat