Study On Mechanical Behavior And Permeability Of Cement Mortar With The Addition Of Nano Metakaolin

There are a large number of chloride ions in winter deicing salt,industrial environment,coastal areas and other environments.The chloride ions lead to the corrosion of steel in the concrete,and it is the main reason of structure failure.It is beyond people's imagination that the loss of steel corrosion is caused by the intrusion of chloride in concrete,and it has become the focus of attention of civil engineering.It is beyond people's imagination that the loss of steel corrosion is caused by the intrusion of chloride in concrete,and it has become the focus of attention of civil engineering.Nano metakaolin is a kind of nanometer material and has a high volcanic ash effect.The internal double layer structure of nano metakaolin can effectively hinder the intrusion of chloride ions into cement mortar,and it opens up a new way to study the new type of cement mortar which is resistant to chloride ion intrusion.In this paper,the effects of nano metakaolin on the physical mechanics and chloride permeability of cement mortar are studied,Combined with the research status quo of domestic scholars on the impact of nano metakaolin on the performance of cement mortar,and the main contents are as follows:(1)The studies on the dispersibility of nano metakaolin in water and cement mortar.The effects of nano metakaolin content,water reducing agent content,dispersion method,dispersion time and pH value on the precipitation rate of nano metakaolin in the mixed solution were studied.The influence of different dispersing methods,time on the nano metakaolin dispersibility in mortar was discussed by the mercury intrusion test.(2)The studies on the effect of dispersing conditions on the properties of nano metakaolin mortar.The effects of dispersion method and dispersion time on the porosity of nano metakaolin mortar were studied by the method of evaporable water content.The effects of dispersion method and dispersion time on the resistivity,mechanical properties(flexural strength and compressive strength)were discussed.(3)Analysis of reasonable content of nano metakaolin in cement mortar under chloride environment.The fluidity,mechanical properties and chloride diffusion coefficient of cement mortar were measured under different nano metakaolin content.The weight value of fluidity,mechanical properties and resistance to chloride permeability were obtained based on the method of analytic hierarchy process.Finally,mathematical expectations were used to indicate reasonable nano metakaolin content for improving the durability of cement mortars.(4)Study on physical and mechanical properties of nano metakaolin mortar under reasonable content.The effects of water cement ratio and mineral admixture on the fluidity and elastic modulus of nano metakaolin mortar were discussed.The effects of water cement ratio,curing mode and mineral admixture on the resistivity,porosity,flexural strength and compressive strength were studied.(5)Study on chloride permeability of nano metakaolin mortar under reasonable content.The influence of water cement ratio,curing mode and mineral admixture on the chloride permeability of nano metakaolin mortar was analyzed by orthogonal test.The relationship between the diffusion coefficient of chloride ion and the resistivity,porosity was discussed,respectively.The influence of nano metakaolin content on the chloride ion concentration in cement mortar samples was quantitatively analyzed based on Fick's second law.