Transport mechanism of chloride in nonsaturated concrete

Considering the change of water mass by convection in water mass conservation equation, a new chloride transport model was developed based on Fick's first law and mass conservation law. The solution of this new chloride transport equation was derived by alternating-direction implicit (ADI) finite-difference method and the results are compared with chloride transport model by Ababneh and experimental data of American Association of Roads and Transport. Capacity matrix, transfer matrix and chloride passing rate vector are associated with variables in transient heat balance equation, a numerical simulation method by ANSYS thermal analysis module for chloride transport in nonsaturated concrete is derived based on mass conservation law, and the results are compared with the new chloride transport model and experimental data. The results indicate that the new chloride transport model is more consistent with experimental data of American Association of Roads and Transport than Ababneh model. The difference of different models is very small, and considering the change of water mass by convection gives a little influence on practical engineering. The model of considering the change of water mass by convection is more consistent with chloride transport process in nonsaturated concrete, and can improve the theoretical system of chloride transport in nonsaturated concrete. The numerical simulation method based on ANSYS is less accuracy than the theoretical model but it's more convenient for application in engineering practice.