Quantifying future post-demolition concrete in Germany: A multi-model projection until 2080

To meet climate targets, the environmental impacts of concrete production must be reduced, particularly those associated with cement manufacture. While recycled aggregates primarily contribute to resource conservation, secondary cementitious materials derived from recycling offer direct CO$_2$ mitigation potential. Post-demolition concrete (PDC) represents a critical secondary resource for both substitution pathways. Reliable projections for future availability are therefore essential for climate-oriented material and circular construction strategies. This study aims to quantify and spatially resolve future availability of PDC in Germany at district level until 2080. A novel multi-model approach is applied, integrating concrete waste statistics, material stocks modelling of buildings and infrastructure, and historical concrete production data. Findings based on the production-based approach indicate that by 2040 approximately 50 million tons of PDC will become available as a secondary raw material, with the highest volumes concentrated in urban regions such as Hamburg and Berlin. Despite its considerable recycling potential, PDC is currently predominantly landfilled or used in low-value applications, indicating substantial underutilization. ... mehrIn parallel, landfill capacity is decreasing, while certain primary raw materials required for concrete production face increasing supply constraints. The projected PDC volumes provide a quantitative basis for assessing future substitution potentials in concrete production. Under the assumption of 35% replacement of primary aggregate and 30% substitution of Portland cement, the annual production of recycled concrete could reach up to 165 million tons annually by 2080. Overall, the results highlight the strategic relevance of PDC for advancing circular material cycles, reducing CO$_2$ emissions, and mitigating pressure on primary resources.