Evaluation of the tensile strength of cement-based advanced composite wrapped specimens

The use of fiber-reinforced polymer (FRP) composite wrap is increasingly being used for repair and rehabilitation of concrete structures. In recent years, most of the mechanical properties of these materials have been studied; however, data on their tensile characteristics is still lacking. This paper presents tensile strength data for: (1) cement-based composites wrapped with FRP sheets, (2) FRP sheets without resin matrix, and (3) FRP sheets embedded in epoxy resin matrix. The tensile strength values were evaluated by using a simple hydraulic tensile technique that produces a uniform stress distribution throughout the specimen, thus, minimizing eccentricity and gripping effects. The tensile strength is derived from the hydraulic pressure and sample geometry. Three types of fiber-composite sheets, including two carbon and one glass, were applied with a two-part epoxy resin system. The tensile strength of the carbon-fiber-wrapped cement composites were in the range of 78 to 132 MPa. The glass-fiber composites were in the range of 40 to 55 MPa, while the unwrapped cement specimens were under 7 MPa. The results show a significant difference in tensile strength properties with the application of an epoxy-resin system. The tensile strength values are presented by using Weibull statistics. A rule-of-mixtures model is used to predict the tensile strength of the FRP composites. Fractography is used to locate the failure initiating defects and to identify the failure modes associated with the different composite wrap systems. (C) 1999 Elsevier Science Ltd. All rights reserved.