One of the major problems in studying cement is the large number of interactions at work during hydration. This interaction happens between different materials and different particles at the same time. As most of these processes occur at the micro-scale, they cannot be directly observed and indirect experimental techniques are used to study them. For example, while calorimetry is widely used to study the rate of hydration of cement, since only the total heat-evolved from samples is measured, the individual reaction rates of individual phases are not available. Similarly, while electron microscopy is widely used to study the evolution of cement microstructures, since most of the high-resolution techniques require a drying of the sample, the progress of hydration on the same sample cannot be observed.

Since most of our understanding of the mechanism of cement hydration depends on various indirect experimental techniques, the results are often open to interpretation. While most experimental techniques provide bulk-values of the properties, the underlying mechanisms occur at the micrometre or nanometre scale, interpretation of the link between mechanisms and properties requires simplifications regarding interactions which are difficult to test. However, with the continuous development of computational techniques, it has now become possible to numerically simulate these processes and to observe their macroscopic effects, which can be compared to experimental results.

Numerical models use combinations of fundamental processes to simulate systems and processes. The processes underlying these models generally define the behaviour of smaller discrete sub-systems and the interactions between these sub-systems. Since smaller and simpler elements of the system are considered, the behavioural laws are much simpler to formulate analytically and the task of integration of the behaviour of the entire system is left to the computer. Numerical models can, therefore, can be used as an important technique, which works in a way complimentary to the experiments, in order to further our understanding of cement hydration.

Still, most of the currently available numerical models on cement remain empirical and highly dependent on experimental results. While this is not surprising, given the wide range of parameters on which the properties of cements depend, these models can only serve a limited purpose in the advancement of our understanding of the processes underlying cement hydration. Empirical models are mathematical expressions that are designed to follow the experimental results and do not necessarily represent the mechanisms that control these properties. Even if used only for predicting properties for different conditions, empirical models are only applicable over a limited range of conditions and are hard to extend beyond this range.

For these reasons, the need for a numerical microstructural model which can incorporate customised mechanisms in simulations was felt. µic provides a modelling platform on which different theories concerning cement hydration could be explicitly modelled and studied. At the same time, µic provides an effective means to reconstruct numerical microstructures resulting from complex processes that occur at the level of individual particles. These microstructures can be analysed for the calculation of different properties, such as mechanical and transport properties in the case of cement.

© 2008 Shashank Bishnoi

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