Overview of concrete modelling

Concrete is a truly multiscale material, so its properties and consequently its performance can only be explained by the use of different scale modelling techniques. Generally speaking, continuum models have been extensively (and successfully) employed to describe the scale that ranges from meters to microns (macro-scale). However, at lower scales, other techniques are increasingly required. Cellular automata, percolation theory, phase field models are just a few of the most promising techniques that have already been employed to describe the so called meso-scale (from micron to nano). Finally, at the nanoscale (from amstrongs to nanometers), nature manifests itself in a discrete way, and its description usually requires an implicit atomistic assumption. It is therefore obvious that both molecular dynamics and ab-initio calculations have presented themselves as the most useful computational tools to describe such a scale. In this work, a general overview on the description of cementitious materials by means of ab-initio calculations will be provided. Especially, it will aim to stress the tremendous capability of these techniques to explain and predict a wide range of parameters and processes which are inaccessible otherwise. In particular, some interesting examples will be discussed, such as the ability of this technique to predict geometries, formation energies or even mechanical properties for the basic building blocks of the C-S-H gel (namely tobermorite and jennite), or even more importantly, the inherent capacity of the ab-initio calculations to describe the condensation reactions that take place during the hydration process and provide crucial information with regards to the stability of the possible species.