Multi-cycle and multi-scale cellular automata for hydration simulation (of Portland-cement)

Abstract

CEMHYD3D is a cellular automata (or agent) based computer model for the hydration of cementitious materials, which is able to predict the microstructure and physical properties of such hydrating systems. In this paper, CEMHYD3D is successfully extended for multi-cycle and multi-scale modelling. Multi-cycle means the possibility to zoom in and out on the hydration process with respect to time. Multi-cycle modelling enables the user to study the hydration in more detail in both the early phase (minutes) and on the long term (years). This modelling is needed, for instance to be able to model the hydration of reactants with different reaction rates (e.g. Portland cement and calcium sulphates). The multi-scale modifications enable the use of smaller particles than the standard minimum size of 1μm, which permits the incorporation of submicron particles in the model. These particles are present in most cementitious binders, and their inclusion will improve the predictions of properties during simulation.Based on statistical considerations, the dissolution and nucleation probabilities and the number of diffusion steps from the original model have been modified in order to enable multi-scale and multi-cycle modelling. For the multi-scale, two variants to obtain the microstructure at higher resolution have been applied, voxel splitting and rescaling, which differ in the way they deal with the particle shape.All modifications have been tested for the modifications separately as well as both combined, for a system consisting of an OPC cement, using CEMHYD3D. All simulations showed good agreements between the results at different resolutions (for both scaling methods) and applying different time-steps, confirming the validity of the generally applicable equations presented here.