The chloride transport properties of cement-based materials are determined via the physicochemical interactions between the pore solution and the cement hydrates. Herein, a thermodynamic model based on surface complexation reactions and dissolution/precipitation reactions was established to investigate the essential physicochemical interactions. The effects of chloride concentration, temperature, and saturation degree (the ratio of water volume to pore volume) on the physicochemical interactions were studied in detail using the resulting thermodynamic model. The published experimental results indicate that the resulting thermodynamic model accurately reflects the adsorption capacity of cement hydrates for chloride ions. Thus, this thermodynamic model can be coupled to the transport equations to achieve the durable designs for new reinforced concrete structures (RCSs) or to predict the service life of existing RCSs. It can also optimize corrosion control strategies for RCSs based on the thermodynamics and kinetics of the material. (C) 2018 Elsevier Inc. All rights reserved.