Comparison between Organic and Inorganic Matrices for RC Beams Strengthened with Carbon Fiber Sheets

The objective of this paper is to study and compare the performance of concrete beams strengthened with carbon fiber sheets bonded with inorganic and organic resin matrices. The experimental study consisted of testing two groups of steel-reinforced concrete beams. The first group of beams was strengthened with carbon fiber sheets bonded with an organic matrix, and the second with carbon fiber sheets bonded with an inorganic matrix. The first group of beams was strengthened with 2, 3, and 4 layers of carbon fiber sheets, while the second group was strengthened with 2, 3, 4, and 5 layers of carbon fiber sheets. Strength, stiffness, ductility, deflection, failure pattern, and cracking of beams strengthened with the two systems were compared. Results showed that the inorganic matrix system is as effective in increasing strength and stiffness of reinforced concrete beams as the organic matrix. The failure mechanism of the inorganic system, however, seems more brittle. The failure of beams strengthened with inorganic matrix showed crack formation in the composite and a minimum buildup of strain along the interface of the composite and concrete. Analytical models were proposed to predict deflection and moment capacity of the strengthened beams. The experimental values compared well with those predicted by the analytical models.