Durability Research Of The Corrosion Resistance Concrete In Ningxia Salty Areas

The mineralization degree of the environmental water is very high in Ningxia salty areas where exists many kinds of corrosion ions. In which, SO42-is of extreme great amount and over proofed, the content is mostly higher than1000mg/L, and even exceeds4000mg/L in some areas, numbered4911mg/L. According to the "Durability Design and Construct Guide of Concrete" it could be classified as "severe corrosion" for most areas and "extremely severe corrosion" for some parts of areas. The corrosion ions cause severe damage to the local concrete engineering, and apply undesirable influence on economy and environment of society.According to the analysis of the concrete failure mechanism and reasons of corrosion caused by the environmental water in Ningxia, the main factors of concrete failure were thus determined. To develop a kind of concrete mixture ratio with low price and relatively superior corrosion resistance performance, meanwhile, fully utilize local fly ash resources. Bi-adding technology of I-class fly ash and high performance water reducer was thus adopted to study concrete corrosion resistance performance. The large scale use of this bi-adding concrete in engineering will not only lower the construction cost but also obtain the goal of environment protection and economy circulation development. For breakthrough of the traditional usage limit of large amount mixture of fly ash in engineering. Reference concrete and bi-adding concrete with30%,40%,50%,60%fly ash were dipped in different corrosive solution for9months. Corrosion resistance performance was compared according to strength after different immersion time and different corrosive solution. Meanwhile, another experiment was carried out in Ningxia with local material, it was more close to construction reality, and the influence on experiment by material from different places was identified.Beyond the corrosion resistance performance, there are other more factors influenced the concrete durability indexes, in order to determine the optimum mixtrue ratio of concerned concrete, it is necessary to fully consider all these impacts. Thus, Bi-adding concrete’s other durable performance was studied by performed manual speed-up carbonation experiment, permeable experiment, freeze-thaw experiment and crack resistance experiment. Permeable experiment and freeze-thaw experiment was also performed in Ningxia for comparison. The influence of the fly ash content on concrete’s several kinds of durable performance was identified. It is obtained through tests that the SO42-" corrosion resistance performance is advanced with the increase of fly ash, the permeable resistance performance is at best, with good verification of tests in two places, when fly ash content percentage in concrete is about40%. It is also detected that while the performance of carbonation resistance and freeze-thaw resistance are deteriorated with the growth of the fly ash content, but the other groups of bi-adding concrete can meet the work demand of50a except the bi-adding concrete with fly ash of60%mixture amount. Meanwhile, the freeze-thaw resistance performance of the concrete with30%fly ash is close to that of the reference concrete when air generation agent is not considered, and40%fly ash with4.7%air content is recommended to meet freeze-thaw resistance demand. At last, analyzed the feasibility of concrete crack reduction by using shrinkage reduce agent through comparison tests, and provided some ideas for reduction of the early shrinkage crack of the bi-adding concrete.Because of the long time of each concrete test periods with multi test groups. The test data is enormous; the relations of arguments and corresponding dependents are quite complex and stagger, to reveal the objective laws hidden in these large sample data, it is of great importance to find out a more effective mathematic algorithm beside common statistical analysis methods. The erected algorithm should be accurate enough to describe the implicit relationship of arguments and dependents in each test, which can be further used for indexes forecasting research. Thus, according to the features of concerned research work, the paper used nonlinear regression method to erect non-destructive strength forecasting equations for bi-adding concrete based on corrosion data, and revised carbonization depth computation equation. The paper further combined the powerful nonlinear mapping characteristics of artificial neural network and global optimum performance of genetic algorithm. With this coupled method, the paper erected a genetic artificial neural network model to analyze the influence of each environment to the concrete strength, and carried out strength analysis and forecast for the bi-adding concrete. It is approved to be effective and reliable through durability tests of bi-adding concrete. These two mathematic measures provide analysis fundaments and scientific rules with important reference values for long term healthy detection and damage evaluation of bi-adding concrete structures in Ningxia salty areas and northwestern territories of similar conditions. The researches show that it is quite feasible to adopt bi-adding concrete technology to solve the concrete corrosion problems in Ningxia salty areas. Fully consider concrete durability performance of multi aspects, recommend fly ash of40%, air content of4.7%, and for some engineering concrete impacted sever environmental water corrosion, further suggest shrinkage reduce agent to reduce early shrinkage crack of bi-adding concrete. Taken above measures, the durability of corrosion resistance concrete will be guaranteed for Ningxia salty areas.