Classiifcation Of Durability Of Concrete Structures Based On Environmental Action

The durability failure of concrete structure is caused by environmental factors which are direct reasons of durability of concrete structure. On the basis of comparison to relevant researches at home and abroad, the problems about distribution of environmental factors and the carbonation damage to concrete structures should be figured out before dividing the classification of concrete carbonation under common atmospheric environment. Since our country with a vast cover in territory and geographical span, while regional differences of the environment are oblivious, thus the concrete structures in different regions are subjected to different damage. The grades are necessary to be partitioned according to the influences of environmental action to the durability of concrete structures. The classification of environmental conditions is qualitatively described in existing norms; it is allowed that designers had different opinions in the choice of classes. According to the problems, the following aspects were included in the thesis:(l)The specifications of durability at home and abroad were compared; it is thought that the prerequisites of design of concrete structures are environmental classes and the design working life, the problem which the lack of quantitative description of the division of categories of environmental in the specification was pointed out.(2) The corrosion mechanism of concrete structures under common atmospheric environment was introduced. The impacts of different environmental factors on concrete carbonation were analyzed.(3) The climatic condition of temperature and relative humidity which had important impacts on concrete carbonation, and they were chosen as main factors to grading. On the basis of partition for the influence degrees of temperature and relative humidity to the concrete carbonation, the classification of environmental action in concrete structures is partitioned with a comprehensive evaluation method. Taking the carbonation depth which is calculated with the average of positive temperature and relative humidity as control index, the carbonation depth of corresponding ranges of each grade was presented.