There is a common understanding that the environmental impacts of construction materials should be significantly reduced. This article provides a comprehensive environmental assessment within Life Cycle Assessment (LCA) boundaries for Ultra-High-Performance Concrete (UHPC) in comparison with Conventional Concrete (CC), in terms of carbon, material, and water footprint. Environmental impacts are determined for the cradle-to-grave life cycle of the UHPC, considering precast and ready-mix concrete. The LCA shows that UHPC has higher environmental impacts per m3. When the functionality of UHPC is considered, at case study level, two design options of a bridge are tested, which use either totally CC (CC design) or CC enhanced with UHPC (UHPC design). The results show that the UHPC design could provide a reduction of 14%, 27%, and 43% of carbon, material, and water footprint, respectively.

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In the global economy, the efficient use of resources in the building sector has become a central issue for sustainable development. Urban mining is an increasingly important area in constructing and demolishing of buildings. This article applies urban mining as a key approach for circular economy. In terms of material efficiency, the highest potential is seen in the use of concrete manufactured from recycled aggregates. The town hall building of the city of Korbach (Germany) has been dismantled and will be rebuilt with use of recycled materials from the old building. A recycling concrete (RC-scenario) is assessed from end of life (EoL) to gate within the life cycle assessment (LCA) boundaries, in comparison with conventional concrete i.e. a business as usual (BAU) scenario. The environmental assessment is done based on the product material, energy and water as well as the climate footprint. The product material footprint is determined in terms of Raw Material Input (RMI) and Total Material Requirement (TMR) and the product energy footprint in terms of Cumulated Energy Demand (CED) for non-renewable resources. The product water footprint is assessed by the Available Water Remaining (AWARE) method and the product climate footprint by values from the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). The footprints are calculated using the software openLCA with the LCA database GaBi construction materials. The RC-scenario shows no significant savings in terms of product energy, water and climate footprint, whereas advantages could be clearly seen in terms of the product material footprint. The method and selected footprints have proven to be suitable for the environmental assessment of urban mining as an approach for circular economy with regard to SDG11 and SDG12.