Bonding between the concrete and Fiber Reinforced Plastic, FRP, rods

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Soong, Wai How
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The bonding between the Fiber Reinforced Plastic (FRP) rods and concrete is one important factor that determines the performance of FRP reinforced concrete structure. The objective of this study is to measure the interfacial bond strength and to understand the factors that influence this. Two types of interfacial bond strength, Intrinsic Interfacial Bond Strength and Apparent Interfacial Bond Strength have been defined and measured using a single fiber pull-out test. Composite tendons with various surface profiles such as smooth, with lugs, sand coated and machined surface, were tested to study the effect of surface roughness, frictional resistance and bearing resistance on the measured intrinsic and apparent shear strength values. Loading rates were also varied to study their influence on the debond progression and on the measured apparent shear strength. Based on the experimental results following conclusions can be made: (a) Apparent bond strength between the FRP-concrete interface is attributed to bonding mechanisms such as chemical bonding, confinement pressure, frictional resistance and bearing resistance. (b) Contribution from intrinsic bonding mechanisms such as chemical bonding and confinements pressure alone is not sufficient to achieve high FRP-concrete bond strength. (c) Further improvement of the apparent bond strength can be achieved by additional mechanisms such frictional resistance and bearing resistance. (d) Apparent bond strength of sand particle coating (ISOROD(tm)) is influenced by the loading rate due to relatively higher contribution from frictional resistance.