Time-Dependent Variation of Chloride Ion Diffusion Coefficients in Concretes with Various Phase Compositions and Pore Structures Using A Different Type of Cement

摘要

Concrete specimens with different phase compositions and pore structures were prepared using various cement-based materials and different mix proportions, and their apparent and effective diffusion coefficients Da and De were measured to know how they are influenced by the phase composition, pore structure and environmental conditions such as exposure temperature and marine tidal or splash zone environment. This paper verifies the applicability of analytical solutions of diffusion equations to the evaluation of Da with variations in surface chloride ion (Cl) concentration depending on the immersion time. Over-time changes of Da and De are then discussed from the viewpoint of variations in influential factors depending on the mix proportions and environmental conditions. For the present study, specific focus is placed on the factors influencing Da including linear binding of Cl, cement content and pore structure factors as well as tortuosity and constrictivity as typical pore structure parameters.