Meso-scale modelling of mechanical behaviour and damage evolution in normal strength concrete

Modelling concrete at the meso-scale has been a topic of intensive research in the last decade, as this approach allows for improved understanding of meso-structure effects on the damage and failure of concrete. The majority of previous works focus on simple stress state, either tension or compression, which does not allow for clarifying the most suitable description of the behaviour of concrete constituents: aggregates, mortar, interfacial transition zones (ITZ) between aggregates and mortar, and entrapped voids. Here all these constituents are represented explicitly and a new combination of their behaviours is explored, applicable to both tension and compression. The work is based on synthetically generated concrete with spherical coarse aggregates and voids randomly packed without overlapping. The meso-structure is meshed and zero-thickness cohesive elements are inserted at ITZs. Aggregates are considered elastic, concrete damage plasticity (CDP) model with both tension and compression hardening is adopted for mortar, and cohesive zone model is used for ITZs. The results presented demonstrate very good agreement with experiments in both tension and compression, in terms of stress-strain curves as well as crack patterns. The proposed development is a promising step towards more realistic representation of concrete behaviour, which is required in practical cases where concrete experiences complex triaxial stress states.