Pore scale modeling of calcium leaching in hardened cement paste

Material microstructure defines its physical and mechanical properties. With this idea, different models have been developed to effectively determine the physical and mechanical properties of a given microstructure. When the microstructure alters as a consequence of chemical processes, coupling of transport with geochemical models is essential for further extension of predictive capabilities. In order to simulate alteration of the microstructure of cement paste during chemical degradation, a new threedimensional pore scale reactive transport code has been developed. The model has the capability to account for reactive transport processes in two types of pore space representations: (1) an explicit representation of pores and solid phases for capillary pores and (2) a continuum representation for unresolved pores (pores with sizes below the spatial discretization) embedded in the solid phases. Multicomponent transport is modelled using a lattice Boltzmann (LB) method. The transport model is coupled with an established geochemical solver (iPHREEQC). Due to dissolution and precipitation reactions, both the explicit pore and the continuum domains are updated using, respectively, static update rules and constitutive relations. The model is applied to a virtual cement microstructure under the process of calcium leachinig. For calcium leaching in cementitious systems we further show the results where the chemistry is represented by a abstracted chemical model. This model abstraction allows for numerically more efficient simulations which allows for parametric studies. Finally, comparison between the simulated results and an experiment carried out under accelerated conditions is presented.