Effect Of Metakaolin On Strength And Resistivity Of Soil-cement Under Magnesium Sulfate Environment

Cement is the main adhesive material of soil-cement.Soil is mixed evenly with cement slurry or cement powder according to the different mix proportion.After maintain,cement and soil occur a series of physical and chemical effects,so as to obtain the hard,the whole,water stability building materials.Soil-cement is a kind of construction engineering material with obvious economic,social and environmental benefits,and has been widely used in the reinforcement of dam foundation,seepage prevention lining of canal,and the soft foundation of industrial and civil buildings,expressways,railways and airports.Soil-cement has been widely used with good prospects,but soil-cement is easy to be eroded and its service life will be significantly reduced in polluted environment.Therefore,it is an important research content to seek the admixtures with obvious modification effect to improve the strength and durability of soil-cement.In this paper,coalmetakaolin was selected as the admixture of soil-cement.The effects of metakaolin on the compressive strength and resistivity of soil-cement were investigated through laboratory tests,and the strengthening mechanism and erosion mechanism of soil-cement were analyzed.The main research contents are as follows:(1)The effect of metakaolin on the compressive strength of soil-cement under magnesium sulfate environment was studied through indoor compressive strength test,to observe the variation laws of the compressive strength of soilcement with the content of metakaolin,the concentration of magnesium sulfate and the age.The regression model of compressive strength of soil-cement is established considering three factors.(2)The influence of metakaolin on the resistivity of soil-cement under the environment of magnesium sulfate was investigated through laboratory resistivity test.The variation of soil-cement resistivity with metakaolin content,magnesium sulfate concentration and age was analyzed.The relationship between resistivity and compressive strength of soil-cement is fitted and linear correlation is found.(3)The reaction mechanism of cement-soil in magnesium sulfate environment was analyzed,and it was concluded that cement-soil reinforcement mechanism was mainly caused by cement hydration reaction and pozzolanic effect,while cement-soil erosion mechanism was mainly caused by gypsum and ettringite expansion damage.In addition,in view of the characteristics that cement-soil is vulnerable to erosion of corrosive components in the environment,it is suggested that corresponding protection measures should be taken according to the working environment conditions of cement-soil.For instance,in order to reduce the deterioration of the environment on cement-soil,coal-metakaolin can be added,the uniformity and compactness of cement-soil should be guaranteed in the process of construction.