Study On Corrosive Cracks Development And Bond Behavior Of Corroded RC Column With CFRP

Steel corrosion is one of the main reasons that affects the durability andservice life of concrete structures. When the steel corrodes, firstly, the volumeexpansion of corrosion products pressures on the protective concrete layeraround the reinforcement bars and the cover of concrete would crack. Once thecrack turns up, the corrosion of the reinforcement would accelerate and thecrack will quickly branch out; secondly, the corrosion of steel makes theperformance of the bond between steel and concrete to be greatly damaged, bothof which results in the life and durability of concrete structures to be seriouslyaffected. Therefore, in order to extend the structure service life and durability,concrete structure has to be reinforced and maintained. Fiber reinforcedcomposite (FRP) materials have many advantages, such as corrosion resistance,fatigue resistance, lightweight, high strength, easy construction, good chemicalstability and other characteristics, etc, which is widely put into construction.Concrete structures confined by FRP can not only slow down the furthercorrosion from corrosion, but also the development of corrosive cracks andimproves the performance of the bond between steel and concrete. Therefore,rooted on the development of concrete crack under CFRP reinforcing corrosioncolumn and performance of the bond between steel bars and concrete, the mainresearch results are as follows:Based on the knowledge of the elasticity mechanics and structuralmechanics, theoretical formulas of protective layer cracking of corrodedreinforced concrete column confined by CFRP and columns circumferentialstrain are established. According to the formulas, a linear relationship betweenexpansion force and corrosion rate, crack width and corrosion rate,circumferential strain and corrosion rate and circumferential strain and crackwidth can be obtained.According to the theories above,84reinforced concrete columns of thesame size are designed considering the factors of relative protective layerthickness, the corrosion rate and the CFRP wrapped, to study the crack width of corroded reinforced concrete columns confined by CFRP. By experimental study,the relationships between crack width and corrosion rate, circumferential strainand corrosion rate and circumferential strain and crack width are investigated.Finally the comparison analysis between experiment values and theoreticalvalues is taken to verify the reasonableness of theoretical analysis.Through the experimental studying on the performance of the bond ofcorroded reinforced concrete columns confined by CFRP, the factors of relativeprotective layer thickness, the corrosion rate and the CFRP wrapped aresystemically studied. The results show that: The peak bond strength and the slipamount of UW column decrease with the increase of the corrosion rate; for Wcolumns, when the corrosion rate is small, the peak bond strength increases withthe increase of the corrosion rate. When the corrosion rate is large, the peakbond strength decreases with the increase of the corrosion rate, the increase of alittle slip increasing with the increase of the corrosion rate. The amount of slipon the peak load shows no regularity on the whole.