Study On Sulfate Resistance And Damage Mechanism Of Nano Modified Recycled Concrete

With the continuous expansion of the application scope of concrete materials,the research on the physical and mechanical properties of concrete materials is also in-depth,the research methods are also constantly improved,and the research results are relatively rich.However,the research on the durability of concrete materials is relatively late,especially how to improve the durability of concrete materials is relatively less.In recent years,with the research and development of nano materials,the application of nano materials is more and more extensive,and gradually applied to the research of concrete material modification and durability improvement.In this paper,nano materials are mainly used to improve the sulfate resistance of concrete.The research results have certain theoretical significance and engineering application value.In this paper,nano-Si O₂material is selected to improve the performance of recycled aggregate concrete.The main work is to use water reducing agent as surfactant,combine ultrasonic and other methods to disperse nano materials,mix them with concrete aggregate after dispersion,and test their mechanical and sulfate resistance properties according to standard test methods.At the same time,through CT scanning and other methods,the sulfate resistance and damage mechanism of nano modified recycled concrete are studied In this paper,the modification mechanism and rule of nano-Si O₂on recycled concrete are analyzed,and some new research conclusions and suggestions are obtained for further research.The results show that if the mass loss rate,compressive strength and ultrasonic velocity of recycled concrete are taken as the main evaluation parameters,the compressive strength and durability of the modified recycled concrete will increase with the increase of the content of Nano-Si O₂when the content of Nano-Si O₂material is lower than 4%;when the content of Nano-Si O₂material reaches 4%,the mass loss rate of recycled concrete is the lowest When the content of nano materials is more than 4%,the main performance of nano modified recycled concrete is not improved obviously,sometimes it will be reduced.In addition,the microstructure of recycled concrete with nano materials under uniaxial compression and sulfate drying and wetting cycles was analyzed by using CT imaging technology.After 25,50,75 and 100 cycles of sulfate drying and wetting,the micro mechanism of nano modified recycled concrete is analyzed by using CT scanning technology through two or three-dimensional imaging and quantitative comparison of porosity and average diameter.That is to say,after nano-Si O2 modified recycled concrete,needle like products will appear in its internal structure,making the original smooth C-S-H junction The structure becomes rough,which shows that the internal structure of recycled concrete is more compact,so it can effectively prevent the appearance and development of micro cracks,and improve the physical and mechanical properties of recycled concrete.