Role of Porosity on Durability of Carbon Fiber-Reinforced Polymer-Concrete Bond

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Title: Role of Porosity on Durability of Carbon Fiber-Reinforced Polymer-Concrete Bond

Author(s): Mostfa Al Azzawi, Gray Mullins, and Rajan Sen

Publication: Structural Journal

Volume: 116

Issue: 6

Appears on pages(s): 75-86

Keywords: bond; carbon fiber-reinforced polymer; composite section; durability; exposure; pulloff; water

Date: 11/1/2019

Abstract:
This paper investigates the influence of concrete porosity on durability of the bond between fiber-reinforced polymer (FRP) and concrete. Twenty-four slab specimens were cast using three different concrete mixtures with water-cementitious materials ratios (w/cm) of 0.53, 0.41, and 0.21, representing high, medium, and low porosities, respectiviely. The slabs were preconditioned by oven-drying and two commercially used carbon fiber-reinforced polymer (CFRP) materials bonded to surfaces that had been sand-blasted to provide a concrete surface profile (CSP) 3 rating. Repaired specimens were submerged in 30°C (86°F) potable water for 15 weeks and residual bond was evaluated through pulloff tests. Results showed 1 to 3% bond reduction in the high-porosity, low-strength concrete compared to a reduction in excess of 20% in its low-porosity, higher-strength counterpart. The likely reason for the better performance was deeper epoxy penetration into the more porous concrete substrate. Findings suggest that surface preparation and installation methods that allow epoxy to penetrate deeper into low-porosity, high-strength concrete can result in increased durability under moisture exposure.