Methods for the modelling of concrete mesostructures: a critical review

Numerical modelling at the mesoscale is a time- and cost-efficient tool to optimize concrete mix design and to analyse the phenomenological causes of mechanical failure, e.g. when developing novel concrete with unconventional materials. A successful mesoscale model strongly depends on a compromise between a realistic and an efficient representation of the mesoscale phases of concrete - coarse aggregates, mortar matrix, and interfacial transition zone (ITZ). Different approaches to achieve this goal have been developed. This paper identifies relevant parameters that are needed for general geometric modelling, including geometric properties of aggregates (shape, grading, volumetric fraction), and intrinsic phenomena of the mesostructure of concrete - the ITZ, wall effects and aggregate settlement, as well as model size and boundary. Methods to integrate these parameters into modelling are presented. The main topics of the paper are: (1) methods to model aggregate's geometry, either by parametric equations or by image analysis reconstruction; (2) critical review and evaluation of strategies to construct the mesostructure regarding convenience and realistic modelling; (3) methods related to random aggregate modelling and respective strategies to implement overlapping detection algorithms to be used during the random placement of aggregates; (4) evaluation of methods that deal with the modelling of the ITZ, voids, and fibres. The paper also argues that certain options of mesostructural models are not yet experimentally validated.