The behavior of self-compacting concrete containing micro-encapsulated Phase Change Materials

In order to come to a sustainable built environment the construction industry requires new energy saving concepts. One concept is to use Phase Change Materials (PCM), which have the ability to absorb and to release thermal energy at a specific temperature. This paper presents a set of experiments using different amounts of PCM in self-compacting concrete mixes. The study focuses on the direct mixing of micro-encapsulated PCM with concrete and its influence on the material properties. Therefore, the fresh concrete properties and the hardened properties are investigated. The hardened properties comprise strength tests and a thorough assessment of the thermal properties. It will be shown that increasing PCM amounts lead to lower thermal conductivity and increased heat capacity, which both significantly improve the thermal performance of concrete and therefore save energy. On the other hand a significant loss in strength and micro-structural analysis both indicate that a large part of the capsules is destroyed during the mixing process and releases its paraffin wax filling into the surrounding matrix. However, the compressive strength of our specimens still satisfies the demands of most structural applications.