Experimental Study On Mechanical Properties And Durability Of Steel Slag Powder Pi Sandstone Cement Composite Soil Under Alkali Excitation

The Pi sandstone is a kind of weakly consolidated rock with low diagenetic degree.It is distributed in Ordos area bordering Shanxi,Shaanxi and Mongolia in the northern part of the Loess Plateau.With the development of civil engineering industry,arsenic sandstone is mostly used for foundation backfilling.Due to the backfilling,exposed surface soil of arsenic sandstone becomes sand when exposed to wind and breaks up when exposed to water,resulting in soil and water loss,which has a huge impact on local economic development.Therefore,in order to reduce soil and water loss,soft sandstone is made into cement according to local conditions.In this thesis,the red Pi sandstone in Jungeer Banner,Ordos City,Inner Mongolia is taken as the research object.The waste steel slag powder is used to partially replace cement,and the steel slag powder Pi sandstone cement composite soil is prepared by alkali excitation method.By means of WDW-50 universal testing machine,X-ray diffractometer,scanning electron microscope,three-dimensional ultra-depth of field microscope,mercury pressure meter and other equipment,mechanical properties,durability and microstructure of steel slag silt sandstone cement composite soil were analyzed,and the following conclusions were obtained:1.From the comprehensive consideration of the utilization rate of steel slag powder and the strength of composite soil,11% steel slag powder content is the largest waste utilization rate,the most economical steel slag powder content,2% alkali activator is the optimal alkali equivalent.2.The increase of alkali equivalent can promote the increase of hydration products of steel slag powder,and better play the role of cementing soil particles and filling internal pores.The surface structure uniformity is improved,the internal structure can be the most small aperture to move to the direction of small aperture,crack aperture peak to move to the direction of large aperture,so that the compressive strength is improved,and the alkali activator dosage of 2%,the best effect.3.The strength,mass,total energy U,total energy Up at peak point,elastic strain energy Ue at peak point and dissipated strain energy Ud at peak point of steel slag powder Pi sandstone cement composite soil under different alkali equivalent conditions all show a decreasing trend with the increase of the number of water-freeze-thaw cycles and freeze-thaw salt-penetration coupling cycles(magnesium chloride),that is,the failure resistance of specimens is weakened.4.With the increase of the number of coupling cycles of freeze-thaw and salt penetration,the complex Mg-S-H with extremely poor cementification and corroded crystals: Friedel ’salt content increase,and the cross zeolite with high strength decreases,which leads to the deterioration of the microstructure and the decrease of compactness of steel slag powder Pi sandstone cement composite soil,leading to the decreasing trend of the compressive strength of steel slag powder Pi sandstone cement composite soil.When the number of coupling cycles of freeze-thawing and salt-invasion were the same,The compressive strength of the test block containing 2% alkali equivalent and 11% steel slag powder is higher than that of the other three groups,which indicates that its resistance to freeze-thaw and salt-invasion coupling is the strongest,and its freezing resistance and salt-tolerance are the best.