Study On Modification And Mechanism Of Soft Soil By Concrete Admixture

The soft soil is distributed widely in our country, it has low strength, poor water permeability, high compression and other bad engineering properties. In the construction of road in these area, the treatment of soft soil is one of the technical problems must be solved. Soil stabilizer is regarded as a common method to improve the properties of the soil. However, the most widely used are still lime and cement,which achieved some success at the same time there are some shortcomings.Concrete admixtures is widely used in concrete, mostly of them are ionic surfactants. Taking advantages of these properties, the effects of concrete admixtures on the mechanical properties, deformation and water stability of soft soil have been studied in this paper. The effects of concrete admixtures on lime soil and cement soil have also been explored. Taking the mechanism of soil stabilizer and concrete admixtures, and the characteristics of clay particle for reference, the modification mechanism of concrete admixtures has been finally analyzed based on the microscopic test.The results show that: retarding high range water reducing agent, effective naphthalene water-reducing agent and air entraining agent can increase the unconfined compressive strength and shear strength of soft soil, decrease its deformation and improve water stability; The unconfined compressive strength of lime soil would be higher if retarding high range water reducing agent or effective naphthalene water-reducing agent added in; The addition order of effective naphthalene water-reducing agent and cement has great influence on the modification effect, when added in soil 6 hours earlier than effective naphthalene water-reducing agent, the unconfined compressive strength will further improve.Through microscopic test analysis, concrete admixtures can change the arrangement of soft soil, which is more compact. When retarding high range water reducing agent or effective naphthalene water-reducing agent is added in soft soil, some cementing material would generate on the surface of the soil particle. The space structure of air entraining agent modified soil is more compact and there are tiny sealing pores.Concrete admixtures do good to the generation of hydration products in lime modified soil and cement modified soil, and the distribution is more uniform, so as to further improve the modification effect.