Flexural Behavior of Concrete Beams Reinforced with Carbon Fiber-Reinforced Polymer (CFRP) Prestressed Prisms

This paper describes the construction of carbon fiber-reinforced polymer (CFRP) prestressed concrete prisms (PCPs) and their use as flexural reinforcement in beams for the purpose of limiting deflection and crack width under service loads. Nine 2.3 m long PCP reinforced simply supported beams were tested. The main variable in the test program was the level of prestress in the PCP. The total tension reinforcement in all the PCP reinforced beams was 98 mm2 of CFRP. Two companion beams were similarly tested as control specimens. One of the beams, designated ST, was reinforced with mild steel, with total tension steel area of 400 mm2, and the other, designated L, was reinforced with two CFRP nonprestressed bars (98 mm2). The test results showed that an effective prestress of approximately 13.5 MPa or higher in the PCP will lead to maximum deflection and crack width values at service load level comparable with those in the companion Beam ST, despite having only 1/4 of the reinforcement compared with the Beam ST. Compared with Beam L, the maximum deflection in the previously mentioned PCP reinforced beams was 25% of the corresponding deflection of Beam L. The ultimate strength of the PCP reinforced beam was 47% higher than that of Beam ST, and 15% higher than Beam L. The performance of the PCP reinforced beams shows that PCP can overcome the serviceability problems associated with the low elastic modulus/strength ratio of CFRP.