Experimental Study On The Characteristics Of Cement-soil Improved By Bentonite

Cement-soil has excellent physical and mechanical properties as a result of the addition of cementitious materials,and is widely used in engineering construction.In recent years,many scholars have used physical or chemical methods to improve cement-soil to meet the latest requirements for the performance of cement soil in engineering requirements.Bentonite is regarded as a candidate enhancement material because of its water absorption,adsorption,and ion exchange properties.To improve cement-soil efficiency,it is both theoretically and practically valuable to conduct experimental research on the properties of bentonite.In this paper,by conducting single-factor experiments and orthogonal experiments,the effects of cement content,bentonite content,and curing age on the permeability and compressive strength of bentonite-modified cement-soil were investigated.Furthermore,an in-depth discussion of the chemical mechanism of improvement effect of bentonite content is presented by conducting scanning electron microscopy experiments.The experimental results were routinely analyzed by mathematical statistics,and a regression model of bentonite-improved cement-soil performance indexes under multiple factors was constructed.Research indicates:(1)Through chemical principles,the chemical process of the ion exchange of bentoniteimproved cement-soil is revealed;Analyzed the SEM image of the corresponding sample,and discussed the formation of aggregates and the filling effect of cement soil into the soil pores after adding bentonite,which improves the compactness of the soil,thereby revealing the mechanism of bentonite reducing the permeability of cement soil and increasing the strength.(2)In the single factor test,when the cement content is 12% and the curing age is 28 days,as the content of bentonite increases,the permeability coefficient of the modified cement soil gradually decreases,the compressive strength increases,and the cohesive force gradually increases.The friction angle is almost unchanged.(3)When the water-cement ratio is the same,the permeability coefficient of bentonitemodified soil-cement is inversely related to the cement content,bentonite content,and age of curing;the unconfined compressive strength is positive related to the cement content,bentonite content,and curing age.;as the cement content increases and the age of curing increases,the cohesive and the internal friction angle gradually increase.With the increase of the bentonite content,the cohesive changes little and the internal friction angle gradually increases.(4)Cement content has the greatest influence on the permeability coefficient,followed by bentonite content,and the age of curing is the smallest;cement content has the greatest influence on the unconfined compressive strength,followed by the age of curing,and bentonite content is the smallest;for cohesion,cement content has the greatest impact,followed by the age of curing,and the bentonite content is the smallest;for the internal friction angle,the cement content has the greatest impact,followed by the bentonite content,and the age of curing is the smallest.(5)When the cement content is low(8% and 12%),the change of the bentonite content has a significant impact on the physical and mechanical properties of the modified cement soil.When the cement content is 16% and 20%,the effect of the bentonite content is small.The cement content is 8% and the bentonite content is 15%,and the cement content is 12%and the bentonite content is 10%.Two ratios meet the engineering requirements and are economical.