Experimental Study On The Durability Of Concrete Under The Action Of Sub-High Temperature Cycles Cooled By Water And Sulfate Attack

The problem of concrete durability is widely focused on by current engineering field. The damages take place early because of pure durability of concrete structures, resulting in the service life of reinforced concrete structures can not come up to the fixed year, which has been a significant problem in practical engineering by now. Sulfate attack is one of the most complicated and critical damages to concrete, as well as an important factor which has great influence on the durability of concrete structures. Based on investigation and research, studies in this paper on the durability of concrete under specified sub-high temperature environment, which is characterized by sub-high alternate environmental temperature and sulfate attack, have been carried out. According to macro-test results and micro-analysis, concrete durability has been comprehensively estimated from the perspective of materials. It can be used as fundamental and theoretic basis for durability design of concrete structures exposed to specified environment under the action of sub-high temperature cycles cooled by water and sulfate attack. This paper has mainly done the following several tasks and made serial achievements:1. According to the results of experimental study on the deterioration law of concrete strength under sub-high temperature cycles, make clear the deterioration course of temperature cycles acting on concrete, compare and analyze the difference between 80℃cycles acting on concrete and 150℃cycles do. The deterioration mechanism is preliminarily discussed so as to do the fundamental work for study on the durability of concrete structures under double action.2. Combined with chemical analysis, the study on the law of distribution of sulfate-ion in concrete under the action of sub-high temperature cycles cooled by water and sulfate attack is carried out. The different influence on sulfate attack between under single action and under double action is compared, as well as, the law that sulfate-ion concentration in concrete changes with depth, attack age, solution concentration, analyzed. And the mechanism of sulfate attack under double action is preliminarily analyzed. Furthermore, forecasting model of distribution of sulfate-ion in concrete under double action is proposed.3. By virtue of the results of experimental study on the deterioration law of concrete strength under double action, the different influence on concrete strength between under single action and under double action is compared and analyzed. Therefore, the severity of the double action on concrete strength is proved. Besides, qualitative analysis of distribution law of sulfate-ion in concrete is done with the method of TG-DSC. And it is indicated that the conclusions deduced by TG-DSC method coincide well with the ones by chemical analysis. 4. Based on artificial neural network technique, neural network model of distribution of sulfate-ion in concrete under one action and double action is put forward. Good agreement is reached between the predicted results and the test data. In addition, the predicted results have high precision. It is indicated that artificial neural network method is more superior to traditional regression method, and has bright perspective in structure engineering application. For the sake of improving the reliability of predicted results, also, much more samples must be collected to train the neural network, so that the model can be more applicable, and the results, more precise.