| In the coastal areas,especially in the island areas,it is often necessary to build the superstructure on the soft soil foundation with high moisture content,large porosity and low bearing capacity,which needs to be solidified.The physical and mechanical properties of cement soil can be improved by grinding steel slag into steel slag powder instead of part of cement and adding active activator into cement soil.The improved cement soil can be used in marine engineering construction,promote the safe use of marine engineering,and open up a wider space for the secondary use of steel slag powder.In this paper,through the laboratory test,mainly studied on silt solidified by cement,cement-steel slag powder,cement-steel slag powder-NaOH.After different curing ages,it is soaked in high and low concentration sodium chloride solution and distilled water solution respectively.At the same time,the dry-wet cycles erosion test is carried out to analyze mass change rate,water content,unconfined compressive strength,strength change rate and compression and corrosion resistance coefficient of the solidified soil.At the same time,two groups of comparative tests were carried out to study the relationship between the dry-wet cycles of chloride and the long-term immersion of chloride,and the difference between the erosion degradation of SO42-on solidified soil and Cl' erosion degradation was analyzed.(1)With the development of cyclic erosion of chloride,the mass changes of cement-solidified silt(CS)and cement-steel slag powder solidified silt(CS-SSP)first increase and then decrease or stabilize,and the mass change rate of CS-SSP-A increases first and then decreases and finally stabilizes except for 7 days of low concentration in sodium chloride solution.(2)With the increase of dry-wet cycles,the water content of CS and CS-SSP-A solidified soil samples decreased firstly and then increased with the increase of erosion time,while the water content of CS-SSP solidified soil samples decreased with the increase of dry-wet cycles.(3)After 7 and 28 days of curing,the strength of CS increased first and then decreased,and that of CS-SSP-A increased first and then decreased and then increased.After 60 days of curing,the strength of CS sample decreases first,then increases and then decreases,and the strength of CS-SSP-A sample decreases first,then increases and then decreases.The strength of CS-SSP decreased first and then increased at 7 days,and increased first and then decreased and then increased at 28 and 60 days.After curing for 7 days,the unconfined compressive strength of CS-SSP-A is less than the unconfined compressive strength of CS.When the curing time is 28 or 60 days,the unconfined compressive strength of CS-SSP is close to or even more than the unconfined compressive strength of CS.However,even after curing for 60 days,the unconfined compressive strength of CS-SSP is only half of CS,which indicates that it is necessary to use steel slag powder instead of part of cement to solidify silt The activation activator can stimulate the activity of steel slag powder,increase the amount of hydrate,increase its unconfined compressive strength,and ensure the strength of solidified silt to meet the engineering design requirements.(4)Through the comparative test,the mass change rate of CS and CS-SSP samples has a linear function relationship between the long-term immersion of chlorine salt and the dry-wet cycle of chlorine salt.In the long-term immersion state,the strength of the sample is greater than that in the dry wet cycle state.The mass change rate of three kinds of solidified soil samples under the action of sulfate dry-wet cycle is smaller than that under the action of chloride dry-wet cycle,and the effect of Cl-on the strength of samples is smaller than that of SO42-.(5)Based on the theory,the paper analyzes the mechanism of chloride dry-wet cycles on the cement-steel slag solidified soil.When eroded in chloride solution,Cl-eroded solidified soil will produce CaCl2 and F's salt,and the non gelling property of F's salt will lead to the deterioration of solidified soil.The sodium chloride in the pore solution on the surface of the solidified soil sample is continuously crystallized under the action of dry-wet cycles.Due to the crystallization pressure,the pore inside the solidified soil sample is destroyed.In the dry-wet cycles test of chlorine salt,the solidified soil is affected by the carbonation reaction and chlorine salt.The carbonation reaction reduces the pH value,which will promote the dissolution of F's salt.When chlorine salt erodes,F's salt is generated,which reduces the volume of pores in the solidified soil,enhances the compactness of cement soil,and reduces the carbonation speed of the solidified soil to a certain extent.In the solution of sodium chloride,the cracks of solidified soil are less than that of distilled water. |
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