Study On Characteristics Of Red Mud And Its Cement-solidified Soil

Industrial alumina production process produces a large amount of red mud,red mud piled up cause serious damage to soil.In order to solve the problem of large accumulation and the comprehensive utilization of red mud,the red mud used in road base material,solidified soil replace part of cement,reduce red mud piled and reduce the cost of road cement.This paper will provide theoretical basis for understanding the res istivity characteristics of red mud.The relationship between the resistivity of red mud and the current frequency,water content,age,porosity and strain was studied by laboratory test.The feasibility of resistivity method for the application of red mud was proved.The soil in the engineering site is easily polluted by acid and alkaline wastewater,degrade the performance of solidified soil subgrade,which causes the accident of the project.Based on this concern,this paper takes acid-base pollution as typical,with the red mud cement-solidified soil are formed the polluted soil with different pollution degree and type in order to simulate the s ituation of acid-base pollution roadbed.With red mud and cement as curing agent,acid-base solution was used to adjust p H value of water to simulate solidified soil with acid-base pollution.To investigate the effects of the current frequency,curing time and p H on the electric resistivity of solidified soil,and delayed compaction time,curing time and p H on the unconfined compressive strength of solidified soil,and studied the relationship between the resistivity and unconfined compressive strength.The main conclusions are as follows:(1)When measuring res istivity of red mud cement-solidified soil specimen,the current frequency has the same change regulation to resistivity.When the current frequency is 50Hz?f<50kHz,the resistivity decreases rapidly with the increase of the current frequency.When the current frequency is 50 k Hz?f<1MHz,the resistivity tends to be stable with the increase of the current frequency.To reduce the effect of the current frequency on the test,the resistivity of the current frequency f=50kHz will be selected for the following analys is.(2)The resistivity of red mud decreases with the increase of water content.At different porosities,the resistivity of red mud increases first and then decreases with the increase of age when the water content is low,and the ages on the effect of red mud resistivity is smaller.when the water content is higher.Under certain water content,the red mud resistivity showing decreased sharply at first and then increases with the increases of porosity.The red mud resistivity decreases with the increase of strain.(3)The change regulation of the resistivity of red mud cement-solidified soil with age will change due to the delay of time.The resistivity of the specimen immediately made is divided into three stages according to the age change curve: increasing stage(1d?t<14d),decreasing stage(14d?t<21d),gentle stage(21d?t?28d);the resistivity of static 4h molding sample increases with age.When the solution is acidic,the resistivity increases with the increase of p H;when the solution is alkaline,the res istivity of solidified soil decreases with the increase of p H.(4)The unconfined compressive strength of red mud cement-solidified soil of static 4h molding sample has a tendency to decrease obviously.The compressive strength of the specimen immediately made is divided into two stages according to the change with age: rapidly increasing stage(7d?t<14d),slowly increasing stage(14d?t?28d);the compressive strength of static 4h molding sample increases linearly with the increase of age.The compressive strength of the specimens immediately mixed with ac id solution decreases with the increase of p H;the compressive strength of alkaline solution increases with the increase of p H.With the addition of acid and alkaline solution,the compressive strength of static 4h molding sample increases first and then decreases with the increase of p H.Under the same p H,the compressive strength and resistivity of static 4h molding sample have good linear correlation.