Durability Of Damaged Structural Concrete

The practical structural concretes suffer varying degrees of damage caused by different effects. Damage will influence the ingression of erosion medium, and change the durability of structural concrete. The durability of structural concrete without consideration of damage deviates from the realities, and also makes people overestimate the durability and service life of concrete structure. Therefore, considering main factors causing damage-high temperature and external loads, the durability of damaged structural concrete was experimental studied in our research. For the durability of thermal damaged concrete, residual compressive strength, chloride ion transportation coefficient and ultrasonic velocity were respectively tested by strength test, RCM test and ultrasonic test. The ingression rules of chloride ion of thermal damaged concrete were also studied by RCT test, and the chloride ion diffusion coefficients were fitted on basis of Fick’s second law. Relative ultrasonic velocity was also fitted with other three indices. The mechanical properties and endurance equalities of thermal damaged concrete after water repair were tested, and the effect of water repair for concrete was experimental studied. For the durability of loading damaged concrete, the ingression rules of chloride ion in concrete subjected to sustained compressive loads were studied by test. The loading levels and loading ages were considered, and so was the creep of concrete. Chloride transportation in concrete under tensile stresses was also experimental studied with the consideration of loading history.For the durability of thermal damaged concrete, the experimental results show that the strength of concrete increases firstly at200℃, and then decreases with the increase of temperature. The unstable state chloride ion transportation coefficient increases continuously with the increase of temperature. The ultrasonic velocity in concrete decreases with the rising of temperature, but the chloride ion diffusion coefficients increase with the rising of temperature. The mechanical properties and endurance equalities of thermal damaged concrete increase after water repair, and the effects are better when the concretes suffer higher temperature. The relativity between relative ultrasonic velocity and durability of thermal damaged concrete turns out good.For the durability of external load damaged concrete, the experimental results show that the stress of concrete subjected to sustained compressive load increases with the increase of loading level. The ultrasonic velocity stays the same firstly, and then increases with the rise of loading level. The critical level is0.4. The chloride ion diffusion coefficient of concrete under the sustained compressive load firstly decreases, and then increases with the rising of loading level, and the critical level is0.4.The effect of early age compressive load to concrete is low. The chloride ion diffusion coefficient of pure bending section of intact concrete beam under sustained flexural load increases with the rising of loading level. The effect of early age flexural load to concrete is low. The ingression of chloride ions decreases with the increase of the distance between the sampling position and cracks.