Study On Chloride Binding And Transportation Models Based On Hydrated Phases In Salt-fog Wetting-drying Environment

The reinforced concrete structures under marine environment suffer a lot, as a result, the durability of concrete structures is deteriorated seriously. Among various kinds of influencing factors, chloride ion is the most important factor inducing the corrosion of steel. The process of chloride ion erosion is complex, including adsorption, desorption, chemical reaction and a series of work. Studying the law of chloride transmission in concrete is very important to predict the service life of concrete structures. Based on above consideration, in this paper, the main work is as follows:(1) A predictive model for chloride binding isotherms of blended cements with various supplementary cementitious materials (SCMs) is established. Totally 593 data points regarding the chloride binding isotherms of 111 various cements are collected from literature. The total amount of bound chloride for each mixture is expressed a combinational function of the predicted phase assemblages and binding isotherms of various hydrated phases. New quantitative expression regarding the chloride binding isotherms of calcium-silicate-hydrate (C-S-H),3CaO·Al2O3·CaSO4-nH20 (AFm), and hydrotafcite phases (HT) is provided. New insights about the role of SCMs on binding capabilities of Portland cements is discussed. The proposed model is verified by using separate data from different sources and is shown to be reasonably accurate.(2) Aggregate content, porosity, saturation, the three main factors that affect the ability of combination are considered to modify the model, and a more suitable model for actual situation is established. Experiments is carried out in the artificial conditions which is simulated as marine atmosphere environment. Considering the course aggregates may generate random effects on the chloride ion transportion and binding properties, mortar is used to study. Six different mix ratio of motar speciments is desighed and exposed in the salt-fog environment. After some time, these specimens are studued. The model is verified through the experimental study, and the binding capacity of the six different motars is analyzed.(3) The variation of humidity in different depths of mortars with different mix proportion is tracked, the changing rule of humidity inside the mortar under wetting-drying cycle is obtained. The regularity of chloride transportation inside different mortars is obtained by the experiment, and the internal conditions which affect the transportation performance of chloride are analyzed. Based on the chloride binding model of mortars with different mix proportion, the transportation model inside the mortar in salt-fog environment is established. Using numerical method, the model is analyzed, and the calculation results are compared with the experimental results.