Numerical and theoretical investigation on the size effect of concrete compressive strength considering the maximum aggregate size

•The influence of MAS on compressive strength and the corresponding size effect of concrete was investigated.•The compressive strength decreased with the increasing MAS.•The increasing MAS in concrete could make the size effect more obvious.•A modified Type-2 size effect law considering the MAS has been proposed. The aggregate size plays an important role in the nonlinear mechanical behaviour of concrete, which is strongly related to the size effect. In this study, the meso-mechanical modelling method has been established based on the continuous grading aggregate model to simulate the uniaxial compressive failure behaviour under quasi-static load of concrete square samples having different side lengths, maximum aggregate sizes (MAS) and concrete strength grades. The numerical results demonstrated that the MAS affected the crack propagation form in the internal components of concrete and the nominal compressive strength decreased with the increasing MAS; the increasing MAS could enhance the sensitivity of strength-to-structural size and make the size effect more obvious. In addition to the numerical analysis, a modified Type-2 size effect law considering the MAS for the nominal compressive strength has been proposed from theoretical perspective, which makes it possible to quantitatively predict the size effect behaviour of compressive strength. Mesoscopic simulation results and some experimental results have validated the modified Type-2 size effect law. [Display omitted]