Citation: Alsuhaibani, E.; Alturki, M.; Alogla, S.M.; Alawad, O.; Alkharisi, M.K.; Bayoumi, E.; Aldukail, A. Compressive and Bonding Performance of GFRP-Reinforced Concrete Columns. Buildings 2024, 14, 1071. https://doi.org/10.3390/ buildings14041071 Academic Editor: Jan Foˇ rt Received: 9 March 2024 Revised: 3 April 2024 Accepted: 9 April 2024 Published: 12 April 2024 Copyright: © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). buildings Article Compressive and Bonding Performance of GFRP-Reinforced Concrete Columns Eyad Alsuhaibani * , Mansour Alturki , Saleh M. Alogla, Omar Alawad , Mohammed K. Alkharisi, Elsaid Bayoumi and Ali Aldukail Department of Civil Engineering, College of Engineering, Qassim University, Buraidah 52571, Saudi Arabia; m.alturki@qu.edu.sa (M.A.); sa.alogla@qu.edu.sa (S.M.A.); omar.awwad@qu.edu.sa (O.A.); m.alkharisi@qu.edu.sa (M.K.A.); 4152@qu.edu.sa (E.B.); a.aldukail@qu.edu.sa (A.A.) * Correspondence: e.alsuhaibani@qu.edu.sa Abstract: The use of glass-fiber-reinforced polymer (GFRP) bars as an alternative to steel bars for reinforcing concrete (RC) structures has gained increasing attention in recent years. GFRP bars offer several advantages over steel bars, such as corrosion resistance, lightweight, high tensile strength, and non-magnetic properties. However, there are also some challenges and uncertainties associated with the behavior and performance of GFRP-reinforced concrete (GFRP-RC) structures, especially under compression and bonding behavior. Therefore, there is a need for comprehensive experimental investigations to validate the effectiveness of GFRP bars in concrete columns. This paper presents a study that aims to address these issues by conducting experimental tests on GFRP- RC columns. The experimental tests examine the mechanical properties of GFRP bars and their bond behavior with concrete, as well as the axial compressive behavior of GFRP-RC columns with different reinforcement configurations, tie spacing, and bar sizes. The findings reveal that GFRP bars demonstrate a comparable, if not superior, compressive capacity to traditional steel bars, significantly contributing to the load-bearing capacity of concrete columns. The study concludes with a set of recommendations for further exploration, underscoring the potential of GFRP bars in revolutionizing the construction industry. Keywords: glass-fiber-reinforced polymer (GFRP); concrete columns; compressive behavior; bonding behavior 1. Introduction The realm of construction engineering is witnessing a shift with the introduction of glass-fiber-reinforced polymer (GFRP) bars as reinforcement for concrete members. This research presents a study to verify the effectiveness of using GFRP reinforcing bars in concrete columns as an alternative to the conventional steel bars. GFRP bars offer several advantages over steel bars, such as corrosion resistance, lightweight, high tensile strength, and non-magnetic properties. However, there are also some challenges and uncertainties associated with the behavior and performance of GFRP-reinforced concrete (GFRP-RC) structures, especially under compression, and bonding behavior. Even though extensive research studies in the literature have examined the behavior of reinforced concrete members reinforced with GFRP bars, most of these studies have focused on the flexural and shear behaviors in beams and slabs where internal stresses on the GFRP bars are tensile stresses. This is important since it is well-established in several research studies that the compressive strength of GFRP bars is about 50 to 77% of their tensile strength [1–4]. Therefore, this variation in strength raises concerns regarding the reliability of using GFRP bars as reinforcements in concrete columns where compression dominates the response such as in columns of typical residential and office buildings. This work is a continuation of limited studies evaluating the performance of such a type of column in an effort to ease design codes and specifications governing the design of GFRP-reinforced concrete columns. Buildings 2024, 14, 1071. https://doi.org/10.3390/buildings14041071 https://www.mdpi.com/journal/buildings