Microscopic Experimental Study On Rust Expansion Of Reinforced Concrete Under Electricity, Dry And Wet Conditions

Chloride induced reinforcement corrosion is the primary cause of the coastal city of performance of reinforced concrete structure deterioration,and the cracking time of concrete protective layer is an important index to evaluate the durability of concrete structures.At present,many scholars at home and abroad have devoted themselves to carry out the related research work by means of the corrosive test,empirical formula,theoretical model etc.,and a series of research results have been achieved.But so far,a lot of researches were based on only one experimental method,but ignored the various testing methods,which to compare the critical cracking time degradation parameters laterally,and improved the reliability of test results.In addition,a large number of existing researches "ignore the material factors" assumption,pay attention to a few initial defects of concrete in different location and size,impact on the durability of reinforced concrete members,can not be a true description of defective concrete structure corrosion parts failure behavior.Moreover,when it comes to the non-uniform corrosion distribution information of two–dimensional,a lot of studies are limited to the exploration of cross section of the reinforcement,there is little involved in 3D heterogeneous effective extraction of rust layer distribution,which the current study does not really reflect the natural environment of the 3D non-uniform corrosion state.Therefore,in this paper,combined with the National Natural Science Foundation of China(51278304),from the point of view of experiment analysis the cracking index and the expansion effect of the concrete structure in different corrosion environments,and combining with XCT technology,observe the relationship between corrosion of steel bars,internal defects and cracks in the different corrosion environment.And on this basis,through the XCT radiometer for specimen to carry out the situation of reinforcement corrosion,the continuous dynamic changes of the process of filling and cracking of the corrosion products were carried out.The corrosive cracking of the work for the subsequent research to provide theoretical and data support.The main contents of this paper include:(1)The cylindrical specimens used for dry/wet cycling test,impressed current test and salt fog test were obtained.Carry out the relevant corrosion experiment,receive the cover critical time index,and determine the influence of various factors on the critical time index;And the existing theoretical models have been revised;(2)The results of the XCT of the reinforced concrete specimens with the same crack width under three different corrosion methods were obtained.The three-dimensional spatial distribution,the relationship between the corrosion products and the corrosion rate and the volume expansion rate of the corrosion products were obtained.And through the SEM and EDS test,the results of XCT were verified;(3)Study the datas of the initial defective samples and quantitatively analyze the influence of each factor on the cracking time,the datas supporting the future study of the initial defects were obtained.Found that the actual engineering should be pay more attention to the middle defect;(4)Introduce the samples with various initial defects,and compare the samples with no initial defects,and use XCT to make the whole process of corrosion expansion of the reinforced concrete samples on the basis of setting multiple corrosion stages.The dynamic relationship between the three-dimensional spatial distribution and the corrosion products and the cracks wrer analyzed.The quantitative relationship between the components within the reinforced concrete was observed.In summary,this study will ultimately provides the basis of support for chinese reinforced concrete structures in chloride environment,the service life of concrete structure reinforcement and repair evaluation.