基于不同防火保护的磷酸镁无机胶粘贴CFRP布加固混凝土梁耐火性能试验研究OA

To investigate the effect of fire insulations on the fire resistance of concrete beams strengthened with CFRP sheets pasted by magnesium phosphate inorganic adhesive(referred to as CFRP-MPIA strengthened beams),this study considered fire insulation material(cement mortar and MPIA),thickness(10,20 mm,and 30 mm),and configuration(insulation height of 140 mm and 300 mm on beam side)as experimental parameters.A total of 14 specimens were designed and fabricated,and fire tests were conducted under sustained loading.During the tests,the fire behaviors of CFRP-MPIA strengthened beams,including temperature and mid-span deflection progressions,failure time of the strengthening system,fire resistance,and failure modes,were monitored.Moreover,the effects of fire insulation(material,thickness,and configuration)on the fire performance of the beams were investigated,and the failure mechanisms of both the fire insulation and strengthening system under fire exposure were clarified.The results show that the excellent high-temperature resistance of MPIA enables the"adhesive-CFRP sheet-adhesive"sandwich structure to provide effective thermal insulation for the CFRP sheets,and the service life of the CFRP-MPIA strengthening system without additional fire protection is thereby extended by nearly twice that of the CFRP-epoxy strengthening system with a 20-mm-thick cement mortar layer under fire conditions.In addition,used as the fire protection material,MPIA exhibits stronger adhesion to both the strengthening system and the concrete beam than cement mortar,reducing the risk of falling off and thereby extending the collaborative action between the strengthening system and the beam.This can enhance the fire resistance of the CFRP-MPIA strengthened beams with MPIA insulation by more than 90%compared with that without any fire insulation,which verifies the feasibility of employing MPIA as both a bonding agent and a fire protection material for CFRP strengthening.