Modeling of cementitious materials exposed to isothermal calcium leaching, considering process kinetics and advective water flow. Part 1: Theoretical model

Part 1 of the paper presents a new mathematical model of hydro-chemo-mechanical behavior of cementitious materials exposed to contact with the deionized water. For analyzing the calcium leaching process, an equation describing kinetics of the process is proposed instead of an equilibrium curve commonly used in previous models. This allows taking directly into account the characteristic time of calcium leaching which affects the time evolution of the process, especially that with a relatively fast decrease of the concentration of calcium in pore water. Constitutive relationships describing the transport and strength properties of concrete during chemical degradation are discussed. They are expressed in terms of the leaching degree, an internal variable of the model describing the material decalcification. The governing equations of the model and boundary conditions are expressed in terms of the state variables: gas pressure, capillary pressure, calcium concentration and displacement vector. Numerical solution of the model equations with the finite element method, as well as several examples of application of the model for analysis of various problems, are presented in the part 2 paper.