The present work establishes a reliable model to describe the influence due to the interfacial transition zone (ITZ) between cement paste and aggregates on the mechanical, thermal and diffusion properties of concrete. The mesostructure of concrete consists of aggregates with a random distribution embedded in the cement paste as well as the interface elements with zero-thickness representing the ITZ. In this work, the cohesive zone model (CZM) is used to model the debonding at the ITZ between cement paste and aggregates. Furthermore, a traction-separation law in CZM combined with micromechanically motivated thermal flux-separation relation and diffusion flux-separation relation is developed, thus enabling to describe the temperature jump and humidity jump across the cohesive crack.