Bond Strength of GFRP Reinforcing Bars at High Temperatures with Implications for Performance in Fire
Publication: Journal of Composites for Construction
Volume 22, Issue 6
Abstract
The polymer matrices currently used for the fabrication of fiber reinforced polymer (FRP) reinforcing bars soften near their glass transition temperature , resulting in a reduction of mechanical strength. This paper discusses the effect of high temperatures on the bond behavior of three types of glass FRP (GFRP) reinforcing bars using standard pullout tests. The bars were 16 mm in nominal diameter with different surface treatments, including sand-coated and ribbed surfaces. The tests were conducted under steady-state and transient temperature protocols for a temperature range of 25°C–360°C at the concrete-to-bar interface. In addition, the effect of embedment length was investigated for a limited number of specimens. The bond failure modes were assessed in detail for different bars. The results for temperatures below 80°C are relevant for elevated service temperatures, and higher temperatures have important implications for performance in fire. At temperatures such as those that would be experienced in a fire (i.e., above 200°C), bond strength dramatically deteriorated, and the retained strength was below 17%. The glass transition temperature of the matrix material was found to be critical for the bond performance of GFRP bars in fire scenarios. The results in this paper are needed to develop rational design guidelines for embedment and anchorage of GFRP bars to obtain the required fire endurance (e.g., 2–3 h) that has been demonstrated through separate full-scale fire tests.
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Acknowledgments
The authors would like to thank the Natural Sciences and Engineering Research Council of Canada (NSERC), Queen’s University, Mathematics of Information Technology and Complex Systems (MITACS) Canada, Pultrall, BP Automation, and the Ministry of Transportation of Ontario (MTO) for their support of these experiments. Also, thanks to Schöck ComBAR for providing materials. The insightful comments of Dr. Brahim Benmokrane are highly appreciated. The assistance from John Gales, Martin Noël, Mehdi Mirzazadeh, and the technical staff at Queen’s University is also appreciated.
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Information
Published In
Journal of Composites for Construction
Volume 22 • Issue 6 • December 2018
Copyright
©2018 American Society of Civil Engineers.
History
Received: Nov 24, 2017
Accepted: Jun 14, 2018
Published online: Sep 25, 2018
Published in print: Dec 1, 2018
Discussion open until: Feb 25, 2019
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