Effects of Diameter on the Durability of Glass Fiber–Reinforced Polymer Bars Conditioned in Alkaline Solution
Publication: Journal of Composites for Construction
Volume 21, Issue 5
Abstract
Current standards do not consider the diameter of glass fiber-reinforced polymer (GFRP) bars used as internal reinforcement in concrete structures to be a factor influencing bar durability. This paper investigates the effects of bar diameter on the physical and mechanical properties as well as the durability of GFRP reinforcing bars conditioned for three months at 60°C in an alkaline solution simulating a concrete environment. Five diameters (nominal diameters of 9.5, 12.7, 15.9, 19.1, and 25.4 mm) were considered; bar properties were assessed before and after conditioning. Microstructural analyses and measurement of physicochemical properties were also carried out. The results show that bar size had no significant effect on bar physical properties, except for water absorption. The smaller diameter bars had higher water absorption than the larger ones because of their higher surface area-to-volume ratios. In the case of the unconditioned bars, the tensile strength and modulus were not significantly affected by bar diameter, but there was a size effect for interlaminar shear strength and flexural strength. Conversely, the conditioning in the alkaline solution had a greater negative effect on the tensile strength of the larger bars than on the smaller ones. Scanning electron microscope (SEM) observations and Fourier transform infrared spectroscopy (FTIR) analysis revealed that the degradation remained at the surface of all the conditioned specimens. Nevertheless, there were only small variations between the physical and mechanical properties of the GFRP bars of different diameters. This indicates that the current provisions in standards that do not relate strength retention limit to bar size are acceptable.
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Acknowledgments
The authors would like to acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), NSERC Research Chair in Innovative FRP Reinforcement for Concrete Infrastructures, the Fonds Québécois de la Recherche sur la Nature et les Technologies (FQR-NT), and Pultrall, Inc. (Thetford Mines, Quebec) for the GFRP materials support. The technical assistance from the staff of the structural laboratory in the department of civil engineering, faculty of engineering at the University of Sherbrooke, are also acknowledged. The second author also acknowledges the scholarship granted by the Australian Government Endeavour Research Fellowships to undertake his research and professional development at the University of Sherbrooke.
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©2017 American Society of Civil Engineers.
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Received: Sep 20, 2016
Accepted: Jan 27, 2017
Published online: May 27, 2017
Published in print: Oct 1, 2017
Discussion open until: Oct 27, 2017
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