Accelerated Corrosion Test And Durability Evaluation Of Coated Reinforced Magnesium Oxychloride Cement Concrete

Saline soil is widely distributed in Western China,which contains a large number of corrosive ions such as salt and chlorine,which will corrode ordinary concrete structures.Magnesium oxychloride cement concrete has strong applicability in saline soil because of its strong resistance to salt and brine erosion.At the same time,the research shows that due to the protective effect of the coating,the corrosion degree of the magnesium cement concrete itself to the steel bar can be neglected.However,under the protective effect of coating,the deterioration mechanism and process of durability of coated reinforced magnesium oxychloride cement concrete are still unclear.Therefore,if this problem can be solved,it will lay a foundation for the application of coated reinforced magnesium oxychloride cement concrete to the load-bearing structure of buildings,and the "magnesium hazard" problem in saline soil areas in the west can also be well alleviated.In this paper,based on the National Natural Science Fund regional fund project(Basic research of magnesium oxychloride cement reinforced concrete based on saline lake " magnesium harm" problem in western area,No.51468039),the accelerated corrosion of magnesium oxychloride cement concrete coated with steel bars under constant current is studied and its durability is evaluated.The main contents of this paper:(1)Six kinds of concrete specimens with different thickness of protective layer(D15,D25,D30,D35,D40,D50)were designed to study the durability of magnesium oxychloride cement concrete under constant current accelerated corrosion.Based on relative quality evaluation parameters and relative dynamic modulus of elasticity evaluation parameters,the durability of specimens is analyzed by combining macro and micro methods.The results show that although the thickness of protective layer of magnesia cement concrete has significant difference,its deterioration mechanism is comparatively similar.(2)Based on electrochemical analysis,the corrosion efficiency of coated steel bars in magnesium oxychloride cement concrete under accelerated corrosion is studied through macro and micro analysis of coated steel bars.The results show that the corrosion process of coated steel bar is a process of cross-section damage,which changes from regular cylinder to irregular shape,and the end of coated steel bar tends to sharpen.The mechanism of durability deterioration is in good agreement with the actual situation.(3)The crack pattern of magnesium oxychloride cement concrete under accelerated corrosion is processed by PS,and the cracks are quantitatively analyzed using the MATLAB algorithm.Combining the mathematical regression model and three-parameter Weibull distribution,the crack width of rust expansion is analyzed by non-uniformity.The results show that the crack width of magnesia cement concrete specimens increases linearly with the increase of corrosion,and the crack width of different protective layer thickness has significant inhomogeneity.(4)According to the crack width of magnesium oxychloride cement concrete and corrosion current density,corrosion depth and electrical time of coated steel bar,the correlation analysis combineing two and three factors is proposed.The results show that there is a significant correlation between the evaluation parameters of magnesia cement concrete specimens and those of coated steel bars.Based on this,the durability of magnesium oxychloride cement concrete coated with steel bars can be quantitatively and comprehensively analyzed.(5)By means of probabilistic analysis method,the accelerated corrosion life data of coated reinforced magnesium cement concrete are evaluated and predicted,and it is found that the minimum extreme value distribution accelerated corrosion life can be well evaluated and predicted through the distribution of minimum extreme value,and the predicted results are in good agreement with the actual situation.According to the evaluation of durability of magnesia cement concrete by threshold life of different durability evaluation parameters,the results show that the deterioration of durability damage of magnesia cement concrete is the result of the interaction of concrete and coated steel bar.