Theoretical models are developed for the prediction of the mechanical properties of mature concrete based on the morphology and interactions of its constituents. The models account for the morphology and interactions of cement hydration products, the capillary pores and microcracks. Concrete is modeled as a three-phase material composed of cement mortar, coarse aggregates and ITZ. The modulus of elasticity of concrete is determined using the Hashin's bound model for three-phase composites. Modeling of fracture toughness indicates that the frictional pull-out of coarse aggregates makes major contributions to the fracture energy of concrete. A tensile strength model is developed for concrete based on linear elastic fracture mechanics theories. The predicted theoretical models are in reasonable agreement with empirical models reflecting the experimental performance of concrete.