Bond characteristics of CFRP-strengthened concrete members subjected to cyclic temperature and mechanical stress at low humidity

A total of fifty two CFRP strengthened concrete specimens were tested. In preliminary investigation, ten specimens were tested at ambient conditions with varying bond length. This indicated the effective bond length is in the range between 100 mm and 150 mm. The bond length of 150 mm was considered and forty two specimens were prepared for detailed investigation. Thirty of them were conditioned under a range (0-50%) of sustained loading. All specimens were subjected to the temperature cycles of 20-50 °C and constant relative humidity (30%) during conditioning. These specimens were tested using the single-lap shear test method at ambient conditions after 1800 h and 2250 h exposure for accelerated ageing. The conditioned specimens showed the maximum strength reduction of 24%. The test results indicate that the concrete/epoxy interface as the weakest part of the composite in service life. Reduction in peak bond stress was noted from conditioned specimens with exposed level of sustained loading.