Analytic Model Of Concrete Corrosiont Expansion Under Sustained And CFRP Circumferential Confinement

Steel Corrosion in Concrete is one of the main causes of the lack of durability of concrete structures.The effect of reinforcement corrosion corrosion protection layer will cause premature cracking,cracks in the surface of the concrete protective layer,the cracks will provide a channel for harmful medium,resulting in more serious durability problem.Cracks,as the effect of rust expansion on the protective layer,can be easily obtained.The corrosion of steel bars in the structure can be evaluated directly by the width of cracks on the surface.In addition,the actual structure corrosion occurs in the stress state,and the load-bearing will inevitably have a certain impact on the concrete rust expansion cracking.At the same time,the actual structure will be subject to circumferential restraint in the process of corrosion,in order to simulate the corrosion situation of the actual structure as far as possible.In this paper,the effects of load-carrying corrosion,circumferential restraint and other factors on concrete rust expansion process will be studied.The main contents include the following works:Considering that not all corrosion products produce rust expansion effect on concrete protective coatings in actual corrosion process,and some rust products will flow into rust expansion cracks,based on this actual situation,this paper proposes a new simplified model of rust expansion effect,and uses the assumption of equivalent perimeter to analyze the cracking process of unconstrained concrete protective coatings.On this basis,the corresponding crack width model of rust expansion is proposed,and the validity of the model is verified by the existing experimental data.The results show that increasing the thickness of the protective layer increases the bearing capacity of the protective layer and the amount of rust products flowing into the crack increases,so the width of the crack decreases,and the corrosion current is the main factor affecting the rust expansion.Considering the actual structure,corrosion occurs under the condition of carrying load.According to the relationship between bond stress and radial stress of surrounding concrete ring,a new simplified action of carrying load is put forward.The rust expansion process of concrete under the action of carrying load is analyzed.The results show that carrying load will cause initial damage to the protective layer,so the cracking time of protective layer under the condition of holding rust is ahead of schedule,and the holding load will lead to the raising of protective layer.Front cracking is not conducive to the durability of the structure.Considering the influence of CFRP circumferential restraint on concrete rust expansion process,the model of concrete rust expansion crack under CFRP restraint is deduced by using elastic-plastic mechanics.The validity of the model is verified by experimental data.Different parameters are analyzed and discussed.The results show that CFRP circumferential restraint can effectively reduce crack width and improve concrete bearing capacity.