Acid resistance and durability properties of steel fiber-reinforced concrete incorporating rice husk ash and recycled aggregate Mahdi Koushkbaghi a , Mahyar Jafar Kazemi b , Hossein Mosavi c , Ehsan Mohseni d,⇑ a Department of Civil Engineering, University of Hormozgan, Qeshm, Iran b Department of Civil Engineering, Islamic Azad University, West Tehran Branch, Tehran, Iran c Department of Civil and Coastal Engineering, University of Florida, PO Box 116580, Gainesville, FL 32611-6580, USA d School of Architecture and Built Environment, The University of Newcastle, NSW 2308, Australia highlights  The RHA improved the resistivity against acid.  The RHA increased the rate of hydration of concrete at later ages of concrete.  The durability of RCA concrete increase with incorporating RHA.  The RHA mitigated the inferior performance of the recycled aggregate concrete. article info Article history: Received 8 October 2018 Received in revised form 24 December 2018 Accepted 31 December 2018 Keywords: Rice husk ash Recycled concrete aggregate Acid resistance Chloride diffusion Durability abstract Recycled concrete aggregate (RCA) produced from concrete waste has recently been a good alternative to natural aggregate because of the increased focus on sustainable development and environmental bene- fits. However, concrete incorporating RCA has inferior properties when compared to natural aggregate concrete. The inferior properties of RCA concrete can be improved by incorporating supplementary cementitious materials (SCMs). Fly ash and silica fume are commonly used SCMs in the concrete industry which improve the mechanical properties and durability of concrete. Nevertheless, there is an imminent deficiency of material in certain parts of the world, and finding a replacement is a challenge for the future of the concrete industry. Rice husk ash (RHA) is a waste material that can be used as a partial replacement to improve the inferior property of RCA concrete. In this study, mechanical properties such as compres- sive strength and splitting tensile strength are studied. Durability properties such as water absorption, chloride diffusion and acid attack were also investigated. Furthermore, fibrous and non-fibrous concrete were made to study the effect of RHA and RCA. The results revealed that RHA can be used to mitigate the poor performance of RCA concrete and improve the bond between concrete and fibers. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction The production of cement has rapidly grown in the recent years because of the overwhelming increase in the demand for infras- tructure development. Satisfying this demand requires an immense supply of cement or any partial replacement material. In 2018, the production of cement surpassed 4.1 billion tons a year, which is the highest production of any material after water. Cement production is a very energy intensive process. Currently, the cement industry produces about 5% of global CO 2 . It is expected that the increase in the demand will be more than 8% for the coming years, which is particularly high for one industry. It is also reported that replacing 30% of cement used with supplementary cementitious materials (SCMs) will reverse the rise in CO 2 emission [1–3]. Moreover, in the recent decades, a massive amount of concrete waste has been produced due to urbanization. The waste from the demolished concrete causes environmental issues when it is dis- posed of in landfill sites [4]. Instead, the wastes can be turned into a valuable material by crushing them into a suitable size for use as concrete aggregate. The crushed materials are ground, sieved, and cleaned to be turned into what is known as recycled concrete aggregate (RCA). The use of crushed aggregate also reduces the extraction of raw materials from the earth, further diminishing the adverse environmental impact. The recycled aggregates https://doi.org/10.1016/j.conbuildmat.2018.12.224 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: ehsan.mohseni@uon.edu.au (E. Mohseni). Construction and Building Materials 202 (2019) 266–275 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat