Author: Zhang, Yiwen
Title: FRP-coated steel rebars for durable concrete structures : development and performance
Advisors: Teng, Jin-guang (CEE)
Yu, Xiang (AMA)
Yu, Tao (CEE)
Degree: Ph.D.
Year: 2024
Subject: Reinforcing bars
Reinforced concrete
Concrete construction
Hong Kong Polytechnic University -- Dissertations
Department: Department of Civil and Environmental Engineering
Pages: xxvi, 275 pages : color illustrations
Language: English
Abstract: Many possibilities have been explored to enhance the durability of RC structures, and a common approach is the use of corrosion-resistant rebars, including stainless steel rebars, fibre-reinforced polymer (FRP) rebars, galvanized steel rebars and epoxy-coated steel rebars. However, these existing solutions suffer from high costs and/or various performance issues (e.g., inadequate durability of epoxy-coated steel rebars and brittleness of FRP rebars). Against this background, this PhD thesis presents the results from a research programme concerned with the development and performance of a new type of rebars that are both highly durable and cost-effective. These novel rebars, referred to as FRP-coated steel rebars (FCSRs), consist of a steel rebar as the core component and a thin FRP layer (i.e., the FRP coating layer) formed using the filament winding technique.
Two methods for manufacturing FCSRs were first explored in this research programme: filament winding with in-line resin impregnation and filament winding with vacuum-assisted resin infusion. The influence of winding configuration, i.e., the number of fibre plies and the fibre winding angle(s), on the microstructure of both the coating-steel interface and coating layer was investigated. The physical properties of the FRP coating layer, including its glass transition temperature coefficient of thermal expansion, roughness, and thickness were examined. The mechanical properties, including the tensile and compressive properties of FCSRs, were also studied. The in-line resin impregnation option was chosen as the preferred method for further investigations based on the test results.
The second part of this PhD research programme was focused on the corrosion and impact resistance of FCSRs. Electrochemical tests were utilised to understand the corrosion state and evolution of FCSRs. The test results were compared with those of uncoated/epoxy-coated steel rebars. The following exposure tests were conducted on FCSRs to evaluate their corrosion resistance: (a) 6-month exposure to the outdoor atmospheric environment of Hong Kong; (b) 12-month immersion in 3.5 wt% NaCl solution; (c) 2-year field exposure at a marine site near the Hong Kong-Zhuhai-Macao bridge. A systematic experimental study on the post-impact corrosion resistance of FCSRs was also carried out to evaluate the impact resistance of the FRP coating layer. The test results indicated excellent corrosion and impact resistance of FCSRs.
The third part of the PhD research programme involved experimental studies of the structurally-related performance of FCSRs. The bond performance of FCSRs in concrete and the flexural performance of concrete beams reinforced with FCSRs were studied. A modified local bond stress-slip model was established, which was found to predict closely the bond strength and stiffness for FCSRs in concrete. The results of the four-point bending beam experiments demonstrated that the structural performance of FCSR-reinforced concrete beams is comparable to uncoated steel rebars- reinforced concrete beams.
Finally, the thesis introduces two field demonstration projects which included FCSRs as one of the reinforcing materials. These projects demonstrated the process of practical implementation of FCSRs.
Rights: All rights reserved
Access: open access

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