Abstract: In mesoscopic sense, concrete is a three-phase composite material which is composed of aggregate, mortar and the interface layer between them. The interface layer is the weakest part of concrete, and is also the main cause of concrete’s low tensile strength. MATLAB software is used to establish three random aggregate models of circle, polygon and elliptic shape and to generate the interface layer of certain thickness. Furthermore, finite element software ABAQUS is employed to establish two-dimensional mesoscopic numerical model of concrete. Computation examples show that the algorithm is simple and the model is reliable. By introducing interface layer and grid subdivision, we provide a foundation for the numerical simulation of concrete’s damage fracture mechanism, and effectively solve the problem of connection among MATLAB, AUTOCAD and finite element software.

Key words: concrete, random aggregate, tensile strength, numerical simulation, MATLAB