Effect And Performance Analysis Of Different Active Admixtures For Curing Soft Foundation

In recent years,the rapid increase of cars has led to a surge in traffic,which promotes the significant development of road construction.However,the problems of soft ground gradually appear in the project.The grouting construction has become a major engineering method of treating the soft foundation problems.The key of the grouting technology lies in the grouting materials,which directly decides the engineering quality of the project.Therefore,it is of great significance to study grouting materials.To address the above issues,three different admixtures were chosen to solidify soft clay.Combined with the method of micro-analysis,the main tests were practiced.(1)By orthogonal test,cement ratio,water-binder ratio and admixture proportion were analyzed on the compressive strength of the solidified soil through unconfined compressive tests;(2)The triaxial tests were used to study the variation of stress-strain characteristics and strength parameters of soils with different admixtures,and a model to fit the stress-strain curve was established;(3)Through XRD and SEM experiments,the solidified soils in phase and micro-morphology were analyzed,which could further study the reaction mechanism and provide a theoretical basis for the use of different kinds of admixtures in actual engineering.Based on the analysis of the experimental data,the main conclusions were as follows:1)Through the orthogonal unconfined compressive strength test analysis,this paper finds that the cement content has a significant effect on the compressive strength,i.e.,the greater the cement content,the greater the compressive strength;the water-binder ratio has less effect on the compressive strength,i.e.,the smaller the water-binder ratio,the greater the strength;the admixture has a certain effect on the strength,i.e.,the higher the content of magnesium oxide and aluminum sulfate,the higher the strength,and the higher the content of calcium nitrate,the lower the strength.2)According to the triaxial test,the stress-strain changes rules of the three materials are basically the same,but the strain corresponding to the peak stress of the sample mixed with calcium nitrate is greater than the other two admixtures,and the soften degree of the specimen after failure is also more obvious;the peak partial stress of the aluminum sulfate-incorporated sample is the largest,and the strain at failure is less change at low confining pressure and larger at high confining pressure than the first two samples.According to the characteristics of the stress-strain curve of the solidified soil,build a nonlinear model in two stages.The fitting results show that the established model has a good fit.3)Through XRD and SEM experiments,the content changes and micro-morphology of various products with different admixtures are analyzed.When magnesium oxide is used as an admixture,the main hydration products are magnesium hydroxide,CSH,and basic calcium carbonate;when calcium nitrate is used as an admixture,the main hydration products are magnesium hydroxide,CSH,and calcium aluminum nitrate hydrate,When aluminum sulfate is used as an admixture,the main hydration products are magnesium hydroxide,CSH,and ettringite;when the number of the above products is large,the microstructure of the solidified soil is denser and the macroscopic strength characteristics are better.After analyze the microscopic morphology of the test,it is found that the content of magnesium oxide is 4%,the content of calcium nitrate is 4%,and the content of aluminum sulfate is 5%.The best effect is consistent with the previous test law.