Study On Mechanical Properties And Impermeability Of Concrete By Taklimakan Desert Sand

The southern Xinjiang region is short of natural river sand resources,but it has the largest desert area in China,the Taklamakan Desert.The prospect of using desert sand to replace natural sand to prepare concrete is very promising.In order to apply desert sand concrete to the construction of hydraulic structures in southern Xinjiang(cold regions),this study prepared desert sand concrete(DSC)by replacing river sand with Taklamakan desert sand in a certain proportion.The replacement rate of desert sand(the percentage of desert sand in fine aggregate),water cement ratio,and sand ratio were used as influencing factors.Firstly,a single factor experiment was conducted to explore the influence of different factors on the mechanical properties of DSC,Secondly,the influence of different factors on the low-temperature compressive strength and impermeability performance of DSC was explored through multi factor orthogonal experiments.Finally,combined with scanning electron microscopy(SEM)to observe the microstructure of desert sand particles and DSC specimens,the mechanism of the influence of desert sand on DSC strength is revealed,providing a theoretical and technical basis for the use of Taklamakan desert sand in engineering construction.The main research content and conclusions of this article are as follows:(1)Using desert sand with substitution rates of 0%(reference group),10%,20%,30%,40%,and 50% to replace natural sand,explore the impact of desert sand substitution rate on DSC mechanical properties.The experimental results show that as the replacement rate of desert sand increases,the compressive strength,flexural strength,splitting tensile strength,and water absorption of DSC generally show a trend of first increasing and then decreasing.Overall,when the replacement rate of desert sand is 10%,the mechanical properties of DSC are the best;When the replacement rate of desert sand is less than 30%,the compressive strength,flexural strength,and splitting tensile strength of DSC are all greater than the strength of the reference group;When the replacement rate of desert sand is less than 20%,the water tightness performance of DSC is better than the benchmark group.(2)Exploring the influence of water cement ratio and sand ratio on the mechanical properties of DSC,the experimental results show that with the increase of water cement ratio,the compressive strength,flexural strength,and splitting tensile strength of DSC show a trend of first increasing and then decreasing.When the water to adhesive ratio is 0.4,the DSC mechanical properties reach the best;When the water cement ratio is 0.55,the mechanical properties of DSC are the worst.As the sand content increases,the compressive strength,flexural strength,and splitting tensile strength of DSC show a trend of first increasing and then decreasing.When the sand ratio is 34%,DSC compressive strength and flexural strength reach the best;When the sand ratio is 31%,the DSC splitting tensile strength reaches the best,but the splitting tensile strength of 34% sand ratio is similar to that of 31% sand ratio;When the sand content is40%,the mechanical properties of DSC are the worst.Based on the analysis of DSC compressive strength,flexural strength,and splitting tensile strength,the optimal water cement ratio for DSC is 0.4,and the sand content is 34%.(3)Orthogonal experiments were used to investigate the influence of desert sand replacement rate,water cement ratio,and sand ratio on DSC compressive strength under low temperature conditions.The experiment was set up in three environmental states:-20 ℃,-10 ℃,and room temperature.Two testing methods(immediate test after low temperature and static test after low temperature)were used to test the DSC compressive strength.The experiment shows that under different test temperature conditions,the water cement ratio has the greatest impact on the compressive strength of DSC.In the experiment immediately after low temperature,the influence of sand content on DSC compressive strength is greater than that of desert sand replacement rate;In the low-temperature static test,the influence of desert sand replacement rate on DSC compressive strength is greater than that of sand rate.As the replacement rate of desert sand increases,the compressive strength of DSC shows a trend of first increasing and then decreasing.When the replacement rate of desert sand is 10%,the maximum DSC compressive strength is taken.But when the replacement rate of desert sand is less than 30%,the DSC compressive strength under different test indicators is greater than the reference group.(4)Exploring the influence of desert sand substitution rate,water cement ratio,and sand ratio on DSC impermeability and water absorption,the orthogonal test results show that the degree of influence on DSC water absorption and impermeability is in descending order: water cement ratio,desert sand substitution rate,and sand ratio.The observation of the microstructure of the specimen by SEM shows that the C-S-H gel material generated in the DSC specimen is more obvious,the cracks in the interface transition zone are smaller,and the overall structure density is high.