Biomass Ash and Phase Change Material (PCM) for Energy Efficiency of Sustainable Cement–Lime Composites

Sustainability and nearly zero-energy consumption of new and existing buildings is a keystone in the new guidelines established by the European Commission. Likewise, waste management is in the focus of reducing the impact of industrial processes. The use of industrial byproducts, such as biomass ashes (BA), can be an interesting solution for waste valorization, reducing the carbon footprint and enhancing sustainability. In addition, Phase Change Materials (PCMs) can be used for improving energy efficiency due to their thermal storage capacity. An experimental study on the effect of biomass ash (BA) and PCM on the microstructure, chemical, physical and mechanical properties of cement–lime pastes was carried out. The partial replacement of cement with BA reduced compressive strength although did not substantially modify other paste properties, while the addition of PCM had a huge impact on microstructure and, therefore, physical and mechanical properties. PCM had a remarkable effect on thermal properties, endowing thermal storage capacity and reducing thermal conductivity, and the combination with BA further improved paste thermal properties.