Investigation On Soft Soil Solidified By Cement-soda Residue

Soft soil is widely distributed in China's inland and coastal areas.Due to its poor physical and mechanical properties such as high natural moisture content,large void ratio,high compressibility,low shear strength,low water permeability,thixotropic and creep properties,The construction of the project or the construction of roads in the area,the treatment of the soil is a technical problem that is very necessary to solve.In actual engineering,cement is usually used as an admixture to reinforce the soil to change the original bad properties.In order to alleviate the problems of resource consumption and environmental pollution,the addition of a part of alkali slag in the cement can not only improve the performance of the soil,but also solve the problem of stacking and pollution of the soda residue.In order to study the engineering properties of cement soda residue reinforced soil,this paper first obtains some basic physical and mechanical indexes of soil by laboratory test,and then carries out standard maintenance of soil samples with different cement soda residue ratios for 7d,28 d,60d and 90 d.Then,the samples were subjected to 0,3,5,10,and 20 dry and wet cycles,and the samples after the cycle were subjected to an unconfined compressive strength test and a compression test without a dry-wet cycle.The microscopic structure of the soil affects the macroscopic performance of the soil mechanical properties.This paper selects the optimum cement mixing ratio,that is,the total admixture of the admixture is 15%,and the cement soda residue blending ratio is 7:3.The structure and morphology of cement alkali soil were studied by X-ray diffraction,scanning electron microscopy and mercury intrusion test.The testing results show that:(1)The unconfined compressive strength of different cement soda residue ratios varies,and the strength decreases with the increase of soda residue.According to the test results,the optimal ratio of cement stabilized soil and industrial waste stabilized soil is selected as the base material of pavement.(2)The compressibility decreases with the increase of cement soda residue incorporation ratio and the increase of curing age;when the total admixture dosage of 15% cement soda residue is 7:3,the soil is cured for 7 days.It is reduced to low compressibility soil.When the total dosage of admixture is 15%,the cement soda residue blending ratio is 0:10,the curing is reduced to medium compressive soil for 7 days,and the admixture is added to significantly reduce the compressibility of the soil.(3)Under the number of different wet and dry cycles,the sample showed a more consistent law,that is,in the early stage of the wet and dry cycle,the strength showed an increasing trend.As the number of dry and wet cycles progressed,the strength gradually decreased small.However,the optimal ratios of the wet and dry cycle of 3 times,5 times,10 times and 20 times can meet the requirements of the standard for the strength of the pavement base layer.(4)XRD,SEM and MIP test analysis techniques were used to study the microstructure of the sample.It was found that hydrated gels such as CSH,CAH and CASH were distributed in the solidified soil and filled with a part of the pores.Cement the soil particles together.Thereby,the strength of the sample is increased;as the number of dry and wet cycles increases,the structure of the soil is loose and the hydration product is reduced;the change of hydration products and pore size and the change of macroscopic properties of the soil confirm each other.