Study On Macroscopic Properties And Microstructure Of Cement-based Materials Of Sulfate Corrosion Resistance In Saline Soil Area

In recent years,with the expansion of large structures such as bridges and highways towards to saline soil area,the durability of structures has been paid attention to,especially of the cement-based materials in saline soils.To solve the cement-based materials in the saline soil area of the erosion problem,will greatly improve the durability of the saline soil area structure.The elevation of the Bai-Ming Expressway is relatively high,the climate is dry,the degree of salinity is serious.In this paper,combined with the conditions of Bai-Ming Expressway and the laboratory,from the following directions to study the macroscopic properties and microstructure of different types of cement-based materials for sulfate corrosion resistance:1.The dry and wet cycle-sulfate erosion in the laboratory is to simulate the half buried structures in saline soil of Bai-Ming Expressway,the long-term full immersion erosion is to simulate the full buried structures in saline soil of Bai-Ming Expressway,and then compared the erosion degree of the two.2.Comparison of different water cement ratio and different dosage of mineral admixture,different materials,different block size of cement-base material's erosion resistance in sulfate.3.Use the block appearance changes,flexural erosion coefficient,compressive erosion coefficient,dynamic elastic modulus loss coefficient to judge the anti-erosion degree of different erosion age of cement-based materials,and then compare the sensitivity of the three indexs.4.Through the microscope to observe the different magnification of the cross section,compared with the law of distribution of different material cross-section under different types erosion patterns.5.Use the gas content,average chord length,pore spacing coefficient and pore size distribution as the indexes of the changes of pore structure parameters,test the changes of pore structure parameters of cement-based materials before and after erosion,and analyze the correlation between the intensity change of cement mortar and the change of pore structure parameters after erosion.By comparing the macroscopic and microscopic indexes of cement-based materials under different age of erosion,the variation law of the cement-based materials was analyzed and compared,the research shows that: In the long-term full immersion erosion,when the water-cement ratio is low,the anti-sulfur cement shows good anti-erosion performance;The smaller the size of the test block,the greater the water-cement ratio,the worse the erosion resistance;Under the same external conditions,the dry-wet circulation is more serious than the long-term full immersion on the erosion of cement-based materials.The erosion resistanceof cement paste is earlier than that of cement mortar;The erosion resistance of cement-based materials is earlier than that of cement mortar.The erosion resistance coefficient of cement-based materials is increasing first and then decreasing,and its index sensitivity degree is: flexural resistance coefficient is most sensitive,the dynamic elastic modulus loss coefficient is least sensitive;The distribution of cross-section products of different materials under different erosion patterns is not exactly the same;The pore structure parameters of the cement-based materials are increasing after sulfate erosion,and the pore structure parameters are increasing in different degrees,the pore size is coarsened and the large pores are increased.The change of the pore structure parameters under the dry and wet cycle-sulfate erosion shows grater variation that of the long-term full immersion;Before and after cement mortar erosion,the correlation coefficient is the largest between the change of Bubble average chord length and the change of intensity.In this paper,the sulfate corrosion resistance of cement-based materials in saline soil area are analyzed and some preliminary rules are obtained,which not only can make a reference for the study of different erosion temperature and corrosion resistance of cement-based materials under different curing conditions,but also can provide a theoretical basis for the cement-based material structure of the durability problem.