Study On Durability Of High Performance Reinforced Concrete Structure

At present, the urban constructions of Lianyungang city are developing dramatically. Since the urban district of Lianyungang (in particular, the eastern part of the city) is adjacent to the beach, newly-built reinforced concrete structure is ready to be corroded by some corrosive media in seawater or soil, for example, sulfate radical ion or chloride ion, which results in an early damage of structure and loss of durability, therefore, it is extremely urgent to develop research on durability of high performance reinforced concrete structure. Based on the previous research on durability, a lot of study is conducted on the durability of high performance reinforced concrete structure in Lianyungang district where the seawater or soil is abundant with sulfate radical ion and chloride ion, and the following is the main work involved in this thesis, of which the research methods and results will be favorable for other coastal cities.1. The corrosion mechanism of sulfate radical ion and chloride ion. Because of corroding of sulfate, the volumes of common concrete and high performance concrete are expanding, and their strength is decreasing. However, both the volume expansion and strength change of high performance concrete are slighter than those of common concrete; on the other hand, due to corroding of chloride solution, the penetrating depth in common concrete and high performance concrete is increasing, and the steel reinforcing bars in them are rusted to some extent, but the penetrating depth and rusting degree of high performance concrete are slighter than those of common concrete. Meanwhile, factors that cause rust have been analysed, and some relevant measures of corrosion protection have been put forwarded.2. The calculation formula for calculating diffusivity of chloride ion was identified and Fick's second law for calculating content of chloride ion was revised with the help of MATLAB. The values calculated with the revised calculation formula conform better to the experimental ones. It is discovered that the corrode-resistance of high performance concrete is stronger than that of the common concrete and it can guarantee the security of reinforced concrete structure.3. The critical value on the amount of chloride ion that causes steel reinforcing bar in concrete is determined by experiment, which provides a forceful reference for revising standard of durability design on reinforced concrete projects in coastal area.4. The physical models, which are used to evaluate the strength of reinforced concrete structure and the portion of chloride ion, are modeled by use of neural network based on the datum of the corroded experiments of reinforced concrete structure. The results show the values from the physical models conform to those of experiments.5. Based on the knowledge of Neural Network and Expert Systems, an intelligent system evaluating the durability of reinforced concrete structures was developed. The intelligent evaluation system can be spread among ordinary engineers and helpful to improve their ability of evaluating the durability of reinforced concrete structures. It is proved to be with practical value.