Analysis Of Ingression Of Chloride Into Cement-based Materials

It is important to analyse the process of the intrusion of harmful medias into cement-based materials (concrete, mortar). According to the durability assessment and life prediction of the cement-based materials under harmful medias, not only the potential dangers can be detected to avoid the major accidents, but also the unnecessary cost and loss can be reduced.The chloride ion is one of the harmful medias.When the chloride ion invades concrete, its greatest harm is the corrosion of reinforcement, the reduction in the durability and the decrease in the life of the concrete. Researchers have investigated extensively on both the environmental factors (temperature, relative humidity, the degree of saturation, etc.) and the characteristics of pore structure (porosity, pore size, pore tortuosity, etc.) that influence the ingression of chloride into concrete. If we can consider them separately, it is more useful for studying the performance of porous materials. And it can predict the durability of porous materials better.First, the current statuses of durability about concrete and chloride diffusion are summarized in this paper. Then, the transfer process of chloride ion in cement-based materials is analyzed, in which the environment factors and the features of the porous materials are considered separately. The diffusion model is established in the ideal state, and the influence of the environment factors and pore structure are analyzed separately. Combined with actual situation, the diffusion process is simulated using Matlab programme in this paper, and the influence of the environment factors and pore structure are studied separately. Finally, we can assess the quality of concrete by applying the diffusion model.The above analysis shows that the diffusion performance of chloride ion can be affected by both environment factors and the characteristics of pore structure. But the mechanism of effect of the two types of factors is different:the diffusion performance of chloride ion is decided by the characteristics of pore structure; whilst the environmental factors change the speed of transmission by changing the microenvironment of porous materials, which thus affect the diffusion quantity.