Multi-physics Modelling of Concrete Shrinkage with the Lattice Discrete Particle Model Considering the Volume of Aggregates

Concrete durability plays an important role in the serviceability of reinforced concrete structures. Deformation induced by shrinkage and thermal strains can lead to the initiation of cracks which in turn may develop into structural damage during several decades of service life. It is time-consuming and impractical to experimentally investigate the long-term mechanical behavior considering environmental influence factors. Hence, a state-of-the-art numerical simulation framework combining the Lattice Discrete Particle Modelling (LDPM) with a multi-physics framework is applied, coupling the mechanical behavior and chemical mechanisms of concrete at an early age and beyond. Based on an equivalent rheological model, the overall age-dependent deformations of concrete can be split into contributions from different physical phenomena assuming the additivity of strain and strain rate in the sense of one-way coupling. The hygro-thermal-chemical model describing the moisture transport, heat transfer and curing reaction drives the development of mechanical properties due to ongoing curing but also thermal and hygral eigenstrains. LDPM reflects the inherently heterogeneous nature of the material concrete at the mesoscale consisting of aggregates and mortar. The effect of aggregate volume and stiffness on concrete shrinkage is investigated by a newly proposed formulation for drying shrinkage of concrete. The results give robust predictions of macroscopic shrinkage for concretes with different mix proportions. A well-established experimental test campaign is selected to calibrate and validate the numerical model, which shows a good agreement and offers promising new insights into the cracking behavior of heterogeneous materials with acceptable computational cost.