Modelling of the microstructure and transport properties of concrete

Theoretical understanding of how the properties and performance of cement-based materials relate to microstructure is complicated by the large range of relevant size scales. Processes occurring in the nanometre-sized gel pores ultimately affect the performance of these materials at the structural level of metres and larger. One approach to alleviating this complication is the development of a suite of models, consisting of individual digital-image-based structural models for the calcium silicate hydrate gel at the nanometre level, the hydrated cement paste at the micrometre level, and a mortar or concrete at the millimetre to metre level. Computations performed at one level provide input properties to be used in simulations of performance at the next higher level. This methodology is demonstrated for the property of ionic diffusivity in saturated concrete. in addition, the ideas of percolation theory are shown to unify microstructure and many physical phenomena at various length scales in concrete.