Study On The Influence Of Attapulgite Clays On The Physical Mechanics And Durability Of Cement-based Materials

Cement is the main cementing material of mortar and concrete,they are widely used in various building structures.However,the severe natural environment,the erosion of deicing salt and seawater,industrial environment lead to premature deterioration of materials,most of building structures are far from reaching design service life.Mineral admixture is one of the main ways to improve the durability of cement cementitious materials.Attapulgite has the characteristics of nano materials,and crystal structure presents a rod-like crystal,it can change the physical and mechanical properties of cement based materials.It provides a new way for the research on the durability of high performance cement based materials.There are many esearch results of cement based materials that is mixed with attapulgite,this paper supported by the National Science Foundation of China(Grant NO.1578099).The influence of attapulgite on the properties of Portland cement has been studied,the main contents are as follows:(1)The studies on the modification and dispersion of attapulgite.Improving the chemical activity of attapulgite by controlling the calcination temperature,the effect of calcination on the microstructure and composition of attapulgite were analyzed by scanning electron microscope and X-ray diffraction pattern.The dispersion of attapulgite in water was studied by acidification,surface activation and ultrasonic vibration.(2)The studies on the effect of attapulgite on the performance of cement hydration.It was studied by testing the chemical bound water content,pH value of the pore solution,stomatal content and scanning electron microscope.The relationship between compressive strength of cement paste and chemical bound water content,flexural strength and stomatal content were established.(3)The studies on the effect of attapulgite on the performance of cement mortar.The effect of the different dosage of the attapulgit on the fluidity,flexural strength and compressive strength of cement mortar were analysised.(4)The studies on the effect of attapulgite on physical mechanics and durability of concrete.The compressive strength,freezing resistance,chloride diffusion coefficient and resistivity of concrete which mixed with calcined attapulgit were studied.The relationship between the resistance and the chloride diffusion coefficient was considered.Theoretical model of the chloride diffusion process based on the heat transfer equation was established,the diffusion process of chloride ion in cylinder pier was simulated by Matlab.