The Corrosion Research Of Reinforced Concrete Structures Under Chloride Environment

The durability of the concrete structure is a common concern of the engineering,and the chloride ion erosion is the important cause of coastal concrete structure durability failure.When chlorine ion reaches a certain concentration,reinforcement passivation will occur.Then,reinforcement corrosion will occur and corrosion products will form,resulting in the cracking of concrete cover and the durability failure of the structures.So the research on the durability of concrete structures under chloride environment is of great significance.This thesis combined theoretical analysis with numerical simulation,took a bridge pier in Qingdao Bay Bridge as the research object,based on COMSOL FEM software and studied the corrosion progress of the structure.The main contents are as follows:1.According to the different areas of the coastal concrete structure,the corresponding chloride ion corrosion models were established to numerically simulate the process of chloride ion corrosion process,and the chloride ion corrosion rules of coastal concrete structures were studied.2.The field test and accelerated test were introduced,and the process of chloride ion corrosion under two kinds of experiment conditions were simulated.Analyzed different degradation parameters and set up time similarity relations of the two test environments finally.3.Selected the most serious areas of chloride ion corrosion,and the circumferential and longitudinal reinforcement corrosion models were respectively established to numerical simulation the electrochemical corrosion process,the distribution and the change rules of corrosion current density,corrosion potential and oxygen concentration were studied.4.Corrosive cracking model were established,the distribution shape of corrosion products and protective layer cracking width rule were studied,and the structure durability completely destroy limit time was determined finally.The results showed that: for this example,Steel passivation appeared in submersion zone,tidal zone,tidal zone and atmosphere zone in turn.the first passivation location is about-2.200 m of tidal range zone and the passivation time is about 25 years.In the reinforced long-term corrosion process,as the chloride ion corrode,passivation area/activation area ratio decreased,and the macro-cell corrosion will gradually turn into micro-cell corrosion.As the crack width increased,the early stage of the rebar corrosion rate increased rapidly,later gradually balanced.The distribution of corrosion products contour accorded with the oval rust expansion displacement model.The critical corrosion depth of protective layer cracking was about 0.2 mm,and the critical steel corrosion rate was about 0.5%.The limited corrosion depth of structure durability completely destroy was about 2.1 mm,and the limited steel corrosion rate was about 5.3%.About 35 years later of corrosion,the structure durability completely destroyed.Without any durability design,the structure durability completely destroy limit time was about 60 years.