| The corrosion of steel bar is one of the important reasons for the deterioration of structural durability and the premature failure of structures.The total volume of steel bar after corrosion generally increases 1-3 times more than the original volume of steel bar,corrosion products will produce extrusion pressure on the surrounding concrete surface,which would be causing cracks in the concrete protective cover.After cracking,the steel bar inside the concrete is in direct contact with the external corrosive environment,which further improves the corrosion rate of the steel bars.The factors can cause cracks on the surface of the concrete protective cover and continues to expand,and finally leads to the damage of the concrete structure,which crucially reduces the durability and service life of the concrete structure.In this paper,the electrochemical method has been used to accelerate corrode the steel bars inside concrete.Different protective layer thicknesses and stirrups rust swelling and cracking tests has been performed to investigate the expansion law of concrete rust swelling cracks.The correspondence of specimen surface and the mass loss rate has been studied based on test results and the theory of elasticity.The main research contents are as follows:(1)Firstly,the test of rust swelling cracking of reinforced concrete specimen has been carried out.Next.Electrochemical accelerated corrosion test has been carried out by half immersion method,the influence of the corrosive cracking of the specimens has been studied by various protective layer cover and the circumstances of stirrups,and the critical corrosion rate of the specimens under different thickness of protective layer has been tested.The realtime strain value of each measuring point during the corrosion process of reinforced concrete specimen has been obtained by strain gauge inside the concrete,and the variation curve of internal strain with time in reinforced concrete has been established.Finally.the transmission rule of corrosion expansion force in concrete has been analyzed.(2)The relationship between the crack width of the protective layer and the corrosion rate of reinforcement has been obtained.The influence of stirrup configuration on crack propagation law of the specimen surface has been obtained by through the observation of crack propagation on the surface of the specimen.The distribution rule of cracks in the concrete has been studied,and the three types of concrete cracking caused by longitudinal reinforcement corrosion cracking has been pointed out.The filling condition of steel corrosion products inside the specimen has been analyzed,and the relationship between the expansion degree of corrosioninduced expansion cracks of concrete protective layer and the corrosion rate of steel bars has been established.It provides reference for estimating the corrosion degree of steel bar in service structure according to the width of corrosion swelling crack.(3)The finite element model of rust swelling cracking of reinforced concrete has been established.Based on the theory of elasticity,the law of concrete crack propagation caused by steel corrosion has been analyzed,the damage and softening of concrete after cracking has been considered,and the relationship model between corrosion rate and rust expansion stress of steel bar under the condition of non-uniform corrosion has been established.Combined with the finite element software Abaqus has been used to define the corresponding contact between the mortar inside the aggregate interface and the outside of the aggregate interface.By applying non-uniform radial loads on the inner surface of concrete specimens,the numerical simulation of corrosion swelling and cracking of reinforced concrete has been carried out,and the initiation and propagation process of concrete cracks under the constraint of stirrups and the influence of the thickness of the protective cover has been obtained.A good agreement has been observed between the theoretical predictions and experimental observations. |
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