Mineral wool within construction and demolition waste (CDW) is considered largely unrecyclable. It is formed at a rate of 2.5 Mt/year and although it is only 0.2 % of total CDW, it requires disproportionally large space due to low density. The WOOL2LOOP project aims to close this material loop by introducing novel technology and value chain to CDW sorting, pretreatment, and processing. The quality of sorted mineral wool is upgraded by comparing and combining the following approaches: pre-demolition audit, robotized demolition and sorting, novel on-site analysis with time-gated Raman spectroscopy, and smart demolition practices. Pre-treatment involves logistical considerations and milling of the mineral wool waste to sufficiently small particles. Processing utilizes alkali-activation (i.e., geopolymerization) technology to convert reactive silica and alumina of the mineral wool into new building material products. Alkali-activation in this context is a completely new approach and it enables to diversely adjust the resulting material properties. Therefore, a broad selection of products were selected for WOOL2LOOP, ranging from relatively low to high value products: hollow core and pavement slabs, facade elements, acoustic panels, dry concrete, floor screed and 3D-printing equipment, for instance. All the required technologies and product manufacturing cases will be demonstrated in large-scale pilots with a wide geographic coverage within the EU. The consortium includes several leading large construction material enterprises and innovative SMEs to cover the whole value chain. Safety, health, environmental, and economic aspects are considered throughout the project. According to the preliminary calculations, there is a strong business potential in the WOOL2LOOP concept. Finally, the constantly increasing landfilling costs (approx. 250 M€ for mineral wool in the EU) create a clear economic driver for the project.