Study On Mechanical Properties And Evolution Mechanism Of Metakaolin-Organic Polymer And Lime Modified Soil

Solution to the inherent imperfections of lime mortars including the low strength,prolonged curing time,and low toughness has long been studied and developed by geotechnical engineers and researchers who are focused on the slope stability and ground improvement.To achieve the research objectives,this thesis is committed to the study of micro-and macro-mechanical properties and microstructures of modified lime mortars,which aims to provide a new approach for the foundation treatment of lime mortars.Based on the combination of chemistry,physical chemistry,crystallography,adsorption theory,organic polymer and other disciplines with geotechnical engineering,this paper investigates the mechanisms of lime-solidified mortar,including the chemical and physical-chemical interactions of organic polymers and clay.The biomineralization template effect of organic polymers on the carbonization reaction products and the pozzolanic reaction hydration products,and the antibacterial preservation of organic polymers in the alkaline environment of lime,which has constructed the idea of green environmental protection,high strength,short hardening age and good toughness curing materials.The stress-strain model of lime mortars was established,and the model was gradually extended to metakaolin lime mortars(ML),organic polymer-metakaolin lime mortars(OML),and the relationship between calcite content and lime mortar strength was established.The macro-and micro-mechanical properties(compressive strength,flexural strength,fracture toughness,resilience modulus,plastic toughness and micro-elastic modulus)of lime mortars,ML,and OML were measured,and the mechanisms of metakaolin and organic polymer modified lime mortars were analyzed by the microscopic characterization,and problems of low strength,long hardening time and poor toughness of lime mortar were solved.The main research contents and achievements are summarized as follows:(1)In view of the mechanical properties of lime mortar and its solidification mechanisms,a model of the interaction system of lime,CO2,metakaolin(or clay),and organic polymers was proposed.The high strength,short hardening duration and high plasticity toughness ML and OML mortars were developed.(2)Based on the definition of the hyperbolic model of soil,using unconfined compressive strength test,a theoretical strength expression is derived,and the stress-strain of lime mortar with parameters of lime content,water-solid ratio and curing duration is established.The model is further extended to the ML mortar stress-strain model with the parameters of metakaolin content,lime content,water-solid ratio and curing duration.The stress-strain model of OML mortars was verified with related tests.(3)Starting from the two-dimensional strength distribution characteristics of lime mortars and ML mortars,the relationship between the solidification process of lime mortar and the lime content and water-solid ratio was revealed.Metakaolin improves the mechanical relationship between the mechanisms of lime mortar and the content of metakaolin and lime;compression resistance strength,flexural strength,fracture toughness,failure mode,elastic modulus and plastic toughness and other related tests and parameters were used to evaluate the mechanical characteristics of metakaolin,and organic polymer modified lime mortars.(4)Using characterization technologies,the mechanisms of structural characteristics,chemical reaction process and micro-mechanical properties of metakaolin and organic polymers to improve lime mortar materials are obtained from the microstructure,mineral composition changes and meso-modulus distribution.The relationship of strength and micro-mechanical properties of lime mortar are established.The prediction model of calcite content reveals the mechanism of the difference in soil mineral composition and clay content’s influence on the carbonization reaction process and strength development.The meso-elastic modulus of metakaolin and organic polymer modified lime mortar were plotted,where the modulus distribution features.With the mechanical testing and relevant characterization techniques,the mechanisms of modified metakaolin-lime mortar and modified kaolinite-organic polymer-lime mortar were unravelled in terms of the macro-and micro-mechanical properties.