Experimental Study On Mechanical Properties And Microscopic Characteristics Of Soil Improved By Rfadyes Curing Agent

Loess is widely distributed in China,because of its special structure and mechanical properties,so it has been used as an important research object in the field of geotechnical engineering.A large number of subgrade projects and slope projects need to improve loess.Traditional lime and cement improvement soil has the disadvantages of insufficient strength,high production cost,poor water resistance and environmental pollution.The Roadyes curing agent used in this paper is a new ionic curing agent developed by the Institute of Soil,Chinese Academy of Sciences through polymer nanoparticle technology.Adding Roadyes curing agent into lime soil or cement soil can make the soil stable,increase the density,and have the advantages of high early strcngth and stable late strength growth.The use of Roadyes curing agent can also greatly reduce the amount of lime and cement,to reduce pollution and save costs.In this paper,Roadyes curing agent was used with lime or cement to improve the loess,and compaction test,no side-limit compression test,side-limit compression test,three-axis shear test and SEM were carried out on the improved soil.The compaction characteristics,compression characteristics,shear strength evolution characteristics and microstructure characteristics of the improved soil were studied.The results are as follows:(1)Adding Roadyes curing agent to loess,lime soil and cement soil can make the soil more easily compacted,the maximum dry density increases and the optimal moisture content decreases.The study found that when Roadyes curing agent is added in an amount of 0.25%,the improvement effect on loess,lime soil and cement soil is the best.(2)Roadyes curing agent can improve the structural yield pressure of loess,lime soil and cement soil structure and reduce its compressibility.The increase of curing time,lime content and cement content can increase the structural yield pressure and reduce the compressibility of the improved soil.The gel reaction of Roadyes curing agent improved loess and Roadyes curing agent improved cement soil basically ended after 3 days of curing,and the best effect was obtained when the cement content of improved cement soil was 6%.The gel reaction of Roadyes curing agent improved lime soil was basically finished after 7 days of curing,and the best effect was obtained when the lime content was 13%.(3)Adding Roadyes curing agent can improve the cohesion and internal friction angle of the soil,and the cohesion and internal friction angle of the improved soil increase with the increase of curing time,lime content and cement content.When 0.25%Roadyes curing agent improved loess was cured for 28 days,the shear strength increased by 57.42%.The curing time of lime was improved by Roadyes curing agent with lime content of 13%for 28 days,the shear strength increased by 258.52%.When Roadyes curing agent with cement content of 6%improves the curing of cement soil for 28 days,the shear strength increased by 967.89%,and all of them showed brittle failure.By Coulomb formula,the shear strength formula of the improved soil with different ratio and curing time is given.(4)Roadyes curing agent can be added into loess,lime soil and cement soil to change the filling of macropores and mesopores into micropores and micropores,reduce the pore volume and improve the compactness.The pore volume of Roadyes curing agent improved loess decreases with the increase of Roadyes curing agent content and curing time.When the content is 0.25%,it can reach a more dense state.The pore volume of Roadyes curing agent improved lime soil decreases with the increase of lime content and curing time.When the lime content is 13%,the pore volume is the smallest and the density is the highest.The pore volume of cement soil improved by Roadyes curing agent decreases with the increase of curing time.When the cement content is 6%,the pore volume is the smallest and the density is the highest.(5)The curing mechanism of Roadyes curing agent is mainly to produce two kinds of gels called Gel CaO·SiO2·H2O and Gel Al2O3·3H2O,reduce the friction between soil particles,improve the compactness,and glue the soil particles together.The reaction consumes the weakly bound and unbound water in the soil and expels some of the water not involved in the reaction and gases from the pores.The ionization of the Roadyes curing agent also resulted in an effective connection between the SiO2 and Al2O3 crystals in the soil and improved the soil strength.In summary,the mechanical properties and microscopic characteristics of soil improved by Roadyes curing agent were studied through laboratory tests,which provided theoretical reference for the application of Roadyes curing agent in the improvement of loess.