Mechanical properties of concrete with aggregates and voids by way of mesoscale representative volume element

Concrete is a heterogeneous material whose mechanical behaviour depends on aggregates and voids. This study develops a mesoscale modelling framework using a representative volume element (RVE) that explicitly incorporates randomly distributed aggregates and uniformly sized voids. A macro–meso homogenisation method with periodic boundary conditions was used to evaluate the effects of RVE size, aggregate distribution, and aggregate/void fractions on stiffness. A methodological novelty is the incremental stiffness degradation scheme for tensile fracture. When cracks initiate, elements under maximum principal stress lose stiffness, progressively degrading neighbours. This leads to gradual global stiffness reduction and realistic fracture propagation. Results show that an RVE size of 40 mm provides size-independent stiffness, while aggregate distribution has little influence. Increasing aggregate fraction by 20% raised elastic and shear moduli by ∼20%, whereas a 2% increase in void fraction reduced elasticity by 0.3 GPa. In tension, a 2.5% void increase lowered strength by 10%, while a 20% aggregate increase improved it by 14.3%. Fracture consistently initiated at the aggregate–cement interface. The originality lies in (i) explicit modelling of aggregates and voids within a validated mesoscale RVE and (ii) the proposed incremental stiffness degradation scheme, together offering practical insights for mixture design and structural optimisation.