This study deals with the inclusion of micro encapsulated phase change materials (PCM), up to 29% in volume, in concretes and mortars. Thermal and mechanical characteristics of hardened mixes are measured and compared with classical civil engineering models. PCM microcapsules behave as voids on a mechanical point of view, and as properly dispersed spheres on a thermal point of view. It is shown that PCM included in a mineral matrix to make building blocks could have a beneficial effect on walls thermal behaviour, keeping a consistent mechanical strength. (C) 2015 Elsevier B.V. All rights reserved.