In the last century, innovations in the concrete industry have been mainly focusing on improvements of the concrete properties leading to systems with a high performance, high efficiency and/or enhanced sustainability. This latter has been strongly driven by the concrete industry, which committed itself to turn its “grey” image into a “greener” and a more environmentally friendly one. The modern concrete industry deals with the major challenge to reduce their CO2 emissions and to increase their efficiency in energy use. Among many other solutions, the integration of Phase Change Materials (PCMs) into cement-based systems, is a way to enhance the thermal storage density and a levelling out temperature fluctuations. Incorporating PCMs in cement pastes is a very efficient way to reduce energy demand in modern buildings due to their ability to absorb and liberate large quantities of heat energy at almost constant temperature. This work presents the current research activities running at the Institute of Construction and Building Materials (WiB) of TU-Darmstadt, and deals with the investigation of advanced coupling of two physical mechanisms represented by a heat problem and by the microstructural heterogeneities that are inherent for cement-based composites. The thermal response of those pastes, along with occurring phase transformation phenomena will be simulated at the microscale level. Particularly, virtual 3D porous microstructures with embedded Microencapsulated-(M)PCMs, created with available hydration models, will provide a fundamental basis for the analysis of the morphological influence on the effective thermal energy storages in such composites. The work is mainly focussing on investigating the influence of morphological imperfections on the thermal properties of hydrating cement paste systems by using a cement hydration and microstructure model, with embedded MPCMs. Laboratory characterization of MPCMs and MPCM-pastes were also performed using several test methods. Specifically, the thermal performance of cement paste systems with and without PCMs were experimentally evaluated at WiB of TU Darmstadt, and are used for benchmark and calibration purposes. The research activities here presented are developed within the framework of the “2CENENRGY” (A Coupled multiscale approach for modelling ENERGY storage phenomena in Cementitious systems) project founded by the Alexander von Humboldt-Foundation.
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