Preliminary Study On Strength And Microstructure Characteristics Of Nano-CaCO₃ Red Clay

Red clay is widely distributed in Guangxi as a special kind of soil,along with the development plan of Beibu Gulf Economic Zone in Guangxi to implement urban and rural construction,road infrastructure,freeway of goods building and a series of related projects continue to increase.Caused by special engineering geological properties of red clay such as slope instability,ground collapse,uneven foundation settlement and other engineering diseases are common,which have caused great harm to human life and property safety.Therefore,it is very important practical engineering significance to reduce and prevent such engineering diseases caused by the special engineering geological properties of red clay.Calcium carbonate is a widely available and easy-to-exploit low-cost material distributed in the red clay area.At the same time,the calcium carbonate industry is one of Guangxi"13th Five-Year"plan focused on creating"14+4"one hundred billion yuan industry.With the development of nanotechnology,nano-CaCO₃ as a kind of nano-material has different characteristics from ordinary particles.In practical application,nano-CaCO₃ can be used as a modified material to improve the bad properties of engineering materials such as concrete.Therefore,in this paper,nano-CaCO₃ as a modified material to explore the strength characteristics and microstructure characteristics of red clay under the influence of nano-CaCO₃.In this paper,the red clay in Yanshan District of Guilin was used to study the different initial dry density in different nano-CaCO₃ content gradient nano-CaCO₃ red clay peak intensity,stress-strain curves,microstructure and micro pore change analysis,Concluded as follow:?1?Through the triaxial shear test,the dry density of 1.35g·cm^-33 and 1.45g·cm^-3nano-CaCO₃ red clay sample stress-strain curves were respectively elastic ideal plastic and strain hardening,and did not change with the dosage of nano-CaCO₃.The stress strain curve of remolded red clay soil with dry density of 1.40g·cm^-3 was changed from elastic ideal plastic to strain hardening after adding nano-CaCO₃.The peak strength of nano-CaCO₃ red clay decreased first and then increased with the incorporation of nano-CaCO₃.?2?The changes of micro-morphology of red clay before and after the addition of nano-CaCO₃ and its variation were studied by electron microscopy.The results show that the microstructural morphology of nano-CaCO₃ red clay is mainly composed of stacked,flocculated,floc and granular basic units.The basic units formed plate-like and granular aggregates through different contact forms.Finally,these aggregates formed the microstructure characteristics of nano-CaCO₃ red clay through irregular arrangement and cementation material connection.?3?Through mercury injection test,the pore distribution of red clay before and after incorporation of nano-CaCO₃ was compared.The change of chemical composition in samples was analyzed by X ray fluorescence spectrometer,and the mechanism of nano-CaCO₃ on remolded red clay soil was explored.The results show that the trend of the transition from large pores to small pores in red clay samples after adding nano-CaCO₃,and with the increase of nano-CaCO₃ content,the peak value of pore size 0.01⁰.1?m shifted to the left,and the pore size 1¹0?m shifted to the right.Full chemical analysis shows that as the amount of nano-CaCO₃ incorporated increases,the colloidal balance in the red clay changes,resulting in the loss of Fe₂O₃ and other mineral elements in the sample.