Civil Engineering and Architecture 12(4): 2772-2786, 2024 http://www.hrpub.org DOI: 10.13189/cea.2024.120420 CFRP Wrapped Concrete Cylinder to Compressive Strength under A Variation of Concrete Qualities Phattaraphong Ponsorn Division of Civil Engineering, Faculty of Engineering, Bangkokthonburi University, Thailand Received February 25, 2024; Revised April 18, 2024; Accepted May 26, 2024 Cite This Paper in the Following Citation Styles (a): [1] Phattaraphong Ponsorn , "CFRP Wrapped Concrete Cylinder to Compressive Strength under A Variation of Concrete Qualities," Civil Engineering and Architecture, Vol. 12, No. 4, pp. 2772 - 2786, 2024. DOI: 10.13189/cea.2024.120420. (b): Phattaraphong Ponsorn (2024). CFRP Wrapped Concrete Cylinder to Compressive Strength under A Variation of Concrete Qualities. Civil Engineering and Architecture, 12(4), 2772 - 2786. DOI: 10.13189/cea.2024.120420. Copyright©2024 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract Strengthening and retrofitting concrete compressive structures by wrapping them with carbon fiber reinforced polymer (CFRP) composite material is currently one of the most effective solutions in civil engineering. The outcome of the solution, increasing compressive capacity, was still found to vary with a number of potential factors, for instance, numbers of wrapped layers, exposure durations and conditions, bonding efficiency of CFRP at concrete surface, shapes, and sizes of the compressive member. Yet, so far, the effect of concrete qualities on the strength increment has to be made known in research, and therefore, it was studied and aimed in this paper. A total of 15 concrete cylinders, grouped into five concrete qualities, were put in order as the first series for the original unwrapped specimens and the second and third for the CFRP-wrapped specimens. An experimental program was set up to measure the compressive strength of concrete cylinders using the rebound hammer test, ultrasonic pulse velocity test, and ultimate compression test. The compressive strength of the concrete cylinder was then compared between the original unwrapped and wrapped with CFRP. From the comparison, the compressive strength of the wrapped concrete cylinder was increased by approximately 2.0 to 2.5 times based on the original unwrapped one. Furthermore, it was observed that the compressive strength increment was in the trend of gradual diminution when the original strength of the concrete was higher. The low to high of the compressive strength of concrete cylinders have shown that the averagely increased strength of the two CFRP-wrapped series dwindled from 2.64 to 1.85 times. The strengthening of the concrete cylinder in axial compressive capacity can be improved by wrapping it with CFRP composite material. It was significantly more effective when the qualities of the concrete were poor. Keywords CFRP Wrap, Concrete Cylinder, Concrete Quality, Compressive Strengthening 1. Introduction Wrapping concrete structures with fiber-reinforced polymer (FRP) composite materials to strengthen, retrofit, and repair their compressive strength is a common approach. Even though the cost of FRP wrapping is at some level higher than the others, the approach has more significant advantages in terms of durability, effective results, and convenience for implementation in both new and existing structures. Aside from the FRP material, which was produced as a bar, tendon, rope, laminate, grid, grate, and other configurations [1, 2], as presented in Figure 1, the FRP sheet is yet another made consisting of different types of materials, for instance, carbon fiber reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP), aramid fiber reinforced polymer (AFRP) [3], and even recycled plastic material [4]. Despite the many FRP materials and configuration types, CFRP in sheet form is the most popular tool for retrofitting compression members. The flexible fabric can wrap around the member, particularly of the high elastic modulus and tensile strength based on its weight [5]. The compression members made of metallic materials such as