| With the development of economy, the civil industry of our country is changing gradually from the stage of 'build'to'maintain and reinforce'. In numerous methods of structural reinforcing, the method of bonding the concrete and CFRP (carbon fiber reinforced polymer) using glues is being used widely and widely due to the lightweight high strength and corrosion resistance of CFRP. At present, the glues used are mainly organic epoxy resin, whose transformation temperature to glass is relatively low (65℃～150℃), resulting that the bonding strength of glues is easily lost in fires and the CFRP is easy to fall off from the concrete. According to this problem, this paper conducted a study on the high temperature behavior of RC beams strengthened with CFRP by inorganic paste through a series of laboratory tests.The main components of the inorganic paste MOC used in this study are magnesium chloride, magnesia and silica powder. Its mechanical properties at ordinary temperature are similar with the organic paste except that the flexural strength is a little lower. Through compression and transverse tests on the MOC blocks without fire protection which have been burned under high temperatures, this paper makes a study on the high temperature behavior of MOC and obtained a relationship between the compression and flexural strength and the burning temperatures. Test results showed that the compression strength of MOC blocks does not decrease within 200℃,but increases a little. However, when the burning temperature exceeds 200℃, the compression strength drops suddenly, e.g., it is only 59.74% of the compression strength at normal temperature when the burning temperature is 300℃and the MOC blocks have been totally destroyed when the burning temperature reaches 400℃. Through compression and transverse tests on the MOC blocks with fire protection which have been burned under high temperatures, this paper makes a study on fire resistance of refractory coating. Test results showed that the compression strength at 400℃for the MOC blocks with fire protection is 4.68 times as the strength without fire protection, proving the effect of fire resistance using refractory coating.Then, through transverse tests on three RC beams which is bonded using inorganic paste with fire protection, bonded using inorganic paste without fire protection and bonded using organic paste with fire protection respectively, this paper makes a study on the high temperature behavior of RC beams strengthened with CFRP by inorganic paste. Comparison between test results of RC beams which is bonded using inorganic paste with fire protection and bonded using organic paste with fire protection showed that the temperature field of RC sections are similar, indicating that the heat conduction performance of the two pastes is similar. However, the CFRP of RC beams using organic paste has been burned to be filamentous after the test and has fall off the concrete, besides that the CFRP using inorganic paste still stick to the concrete, proving that the performance of fire resistance of inorganic paste is better than that of organic paste. Moreover, the midspan deflection of RC beams using organic paste is 1.5 times as that using inorganic paste. Comparison between test results of RC beams which is bonded using inorganic paste with fire protection and bonded using inorganic paste without fire protection showed that the temperatures of RC sections, RC surfaces and steels without fire protection are all much higher than that with fire protection, indicating that the fire resistance of refractory coating. Moreover, the midspan deflection of RC beams without fire protection is 13.8 times as that with fire protection and has exceeded the limited value, besides that the RC beams with fire protection could still work. |
