Study On Mechanical Properties And Curing Mechanism Of Nickel Iron Slag Cement Soil

In recent years,in order to meet the rapid economic development of the country,China produces a huge amount of various types of metal materials every year.These metal materials produce a large amount of various metallurgical residues in the production process.The nickel-iron slag powder is a major component one.It has been studied that nickel-iron slag powder is a mineral admixture that is as active as granulated blast furnace slag,fly ash,etc,but its early activity is low.Therefore,combining the present research results of cement soil and the full utilization of resources,In this paper,the use of cement-soil in the single-doped nickel-iron slag powder and nickel-iron slag powder and granulated blast furnace slag mixed research forms,to study the impact of mineral admixture on the mechanical properties of cement soil and curing mechanism.Based on the experimental results and the scope of the study,the main conclusions are summarized as follows:(1)Through the unconfined compressive tests on different proportions of cement soil,It is concluded that the incorporation of nickel-iron slag powder has a great influence on the mechanical properties of cement-soil in early age,however,with the increase of age,the strength reduction rate of cement soil mixed with nickel-iron slag becomes smaller and smaller.At 60d and 90d,the strength of cemented soil with 10%nickel-iron slag powder exceeded that of the reference group.When nickel-iron slag powder and granulated blast furnace slag mixed,cement soil shows better performance in the early age than the single-doped nickel-iron slag powder,but as the age increases,the advantage becomes smaller and smaller.Experimental study shows that when single-doped nickel iron slag powder,nickel-iron slag powder content of 20%for the better incorporation value;When nickel-iron slag powder and granulated blast furnace slag mixed,nickel-iron slag powder content of 20%,mineral powder instead of 30%of the quality of nickel-iron slag powder for the optimal combination of values.(2)Consolidated undrained triaxial test were carried out on different ratios of nickel-iron slag cement soil,The stress-strain relationship and the triaxial shear failure mode under different confining pressures were studied.The main failure mode of the nickel-iron slag cement soil is brittle failure,but in the early age,the failure process under high confining pressure still shows relatively large plastic deformation.In the early age,the shear strength parameters and modulus of deformation of cement-soil mixed with mineral admixtures all decreased greatly,however,with the increase of age,the decreasing rate of shear strength parameters and deformation modulus will gradually decrease,and the strength of 60d age group is very close to the baseline group.(3)XRD test and SEM test were used to study the condensation and solidification process of nickel-iron slag cement soil.In the early age,the microstructure of cement-soil with Nickel iron slag powder was very loose,nickel-iron slag powder is only filled in the cement soil in the form of micro-aggregate.However,after the 28d age,nickel-iron slag powder in soil began to react with the hydration products of cement to produce ettringite and other substances,so that the microstructure of nickel-iron slag cement soil becomes more and more dense,increasing strength.Mercury intrusion test obtained at different ages of nickel iron slag cement soil pores,this result can be further explained for the mechanics phenomena of the nickel-iron slag cement soil with the change of age and dosage in the third chapter.