Control of cracking due to temperature in structural concrete reinforced with CFRP bars

The effects of thermal incompatibility of carbon fibre reinforced polymers (CFRP) and concrete on the behaviour of reinforced concrete members are investigated. Concrete beams reinforced with CFRP rebars are tested under the effects of temperature gradients while the rotations at the beam ends are prevented. The bending moments and cracking developed by the temperature gradients are monitored. The results are compared with those obtained from tests on beams of the same dimensions but reinforced with steel bars. Reduction of thermal moments due to progressive stiffness degradation with crack formation is investigated analytically and compared with the moment values recorded in the tests. The test series includes beams with variable amounts of CFRP reinforcement to study their effects on thermal moments and on crack widths and spacing. Design charts are presented for determining the minimum amount of CFRP reinforcement necessary for control of cracking due to temperature.