Degradation of flexural bond of CFRP bar in UHPFRC after exposure to elevated temperature

• Published in: Cement & concrete composites Vol. 152; p. 105627
• Main Authors: Yoo, Sun-Jae, Lee, Oh-Seong, Parr, Jean-Luc Malan, Yoon, Young-Soo
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2024
• Subjects: CFRP bar; Development length; Elevated temperatures; Flexural bond; Residual strength; UHPFRC; Flexural bond; Elevated temperatures; Development length; CFRP bar; UHPFRC; Residual strength
• ISSN: 0958-9465
• DOI: 10.1016/j.cemconcomp.2024.105627

This paper investigated degradation of flexural bond of a ribbed carbon fiber reinforced polymer (CFRP) bar in ultra-high-performance fiber reinforced concrete (UHPFRC) after exposure to elevated temperatures. For this purpose, the mechanical properties of UHPFRC and thermal properties of CFRP bars after exposure to elevated temperatures were investigated, and a total of 16 groups of hinged beams were fabricated with variables of embedment length (4db, 10db, 20db, and 40db), bar type and exposed to elevated temperatures (200 °C, 300 °C, 400 °C, 600 °C). The mechanical properties of UHPFRC increased until elevated temperatures reached 400 °C and it was shown that the reduction of the ultimate tensile strength of CFRP bars were not notable after exposure to elevated temperatures of up to 300 °C. The ultimate moment of ribbed CFRP bars after exposure to elevated temperatures at 200 and 300 °C was similar. After exposure to an elevated temperature of 400 °C, it decreased by about 29–63 % compared to non-heated specimens, with bar rupture. Although similar decomposition temperatures of ribbed and sand coated CFRP bars occurred, the residual flexural bond strength of the ribbed CFRP bar was larger than that of the sand coated CFRP bar after exposure to elevated temperature at 400 °C. In addition, a relatively lower reduction of bond strength occurred in RC-40ED-400 compared to RC-10ED-400 and RC-20ED-400. Based on the test results, development length with consideration of degradation of developed tensile and normalized bond strength of CFRP bars were proposed, and it was found that the required development length of ribbed CFRP bars after exposure to elevated temperatures at 400 °C increased by 294 % compared to ambient temperature. •The ribbed CFRP bar showed almost no residual flexural bond performance after exposure to elevated temperatures at 600 °C.•Bar rupture occurred in the ribbed CFRP bar with an embedment length of 40 db after exposure to elevated temperatures at 400 °C.•Reduction rate of ribbed CFRP bars with a deep embedment length is not remarkable after exposure to elevated temperatures.•The development length of ribbed CFRP bar after exposure at 400 °C was increased by 294 % compared to ambient temperatures.