Restorability of strength and stiffness of fire damaged concrete using various composite confinement techniques

In this paper, an experimental study was carried out to investigate the effectiveness of various composite confinement repairing techniques for the restoration of strength and stiffness of concrete cylinders. A total of 42 plain concrete cylinders were heated to a range of temperatures from 400 to 800 °C. They were tested under uniaxial compression. The test specimens were placed into six groups: undamaged non-repaired, fire damaged non-repaired, undamaged repaired with exclusively carbon fibre reinforced polymer (CFRP) composite jacket, fire damaged repaired with exclusively CFRP composite jacket, fire damaged repaired with cement slurry injection along with CFRP composite jacket and fire damaged repaired with epoxy resin mortar injected steel wire mesh jointly confined with CFRP composite wrapping system. The results indicated that the exclusively CFRP and epoxy resin mortar injected steel wire mesh jointly confined with CFRP composite wrapping systems were ineffectual to restore the stiffness, although it was noted that they were extremely useful to increase the strength, ductility, deformation capacity and energy dissipation capacity of fire damaged concrete specimens. However, it was found that the cement slurry injection along with CFRP composite wrapping system was functional in the restorability of stiffness, strength, ductility, energy dissipation capacity, and serviceability of fire damaged concrete equivalent to the undamaged concrete or even beyond that without increasing the cross-sectional size of specimens.