Effect Of The Curing Age On The Chloride Diffusivity Of Concrete

The durability of concrete structures and materials is one of the major issues which are commonly paid attention to by academics and engineers. The penetration of chloride ions into concrete is the primary factor that affects the durability of concrete structures and materials. Since there are few studies on the long-term chloride diffusivity of concrete at home and abroad, the effect of the curing age on the chloride diffusivities of cement paste and concrete is studied by considering two factors of water/cement ratio and aggregate volume fraction and using the NEL method.The experimental results show that the chloride diffusivities of cement paste and concrete decrease with the increase of the curing age but the rate of decrease becomes smaller after118days. Further data analysis shows that, for a given aggregate volume content, the chloride diffusivity of concrete increases with an increase in water/cement ratio and the larger the water/cement ratio is, the more obviously the chloride diffusivity of concrete decreases with time. For a given water/cement ratio, the chloride diffusivity of concrete decreases by increasing the aggregate volume content and the larger the aggregate volume content is, the more obvious the chloride diffusivity of concrete decreases with time.A calculation formula of the chloride diffusivities of cement paste and concrete with time is proposed through theoretical analyses, and the the validity of the formula is preliminarily verified with experimental results. The effects of the degree of hydration and water/cement ratio on the chloride diffusivity of cement paste are evaluated in a quantitative manner. Through the numerical inverse method, the chloride diffusivity of interfacial transition zone is obtained. It is found that the chloride diffusivity of interfacial transition zone also decreases by increasing the curing age. Finally, a relationship between the chloride diffusivity of concrete with time is given for different aggregate volume contents.