AbstractIncreasing the durability of concrete is one of the major challenges in terms of environmentally friendly concrete. To achieve this, it is necessary to develop smart materials, which are superior to the current materials in term of multi‐field requirements. These materials are characterized by their ability to detect starting damages and the ability to initialize the self‐healing process. Self‐healing concrete is subject of current research and performed in different ways. In terms of this work autonomous self‐healing due to the use of an epoxy‐resin, encapsulated in a core‐shell capsule is investigated. The opening of the capsules should be realized by irradiation with microwaves. Therefore, the shell of the capsules was functionalized with trigger materials. The on demand opening of the capsules was investigated with sub‐μ‐CT. According to the tomography a 3‐dimensional model of the pore system was calculated. Based on this model a pore size distribution was calculated to get insight in the opening of the capsules. These investigations showed a successful release of the active agent.