URBCON will reduce the high primary raw material consumption and CO2 emissions, that result from the construction and maintenance of the urban built environment (e.g. buildings, pavements, sewer pipes, bridges). The focus is on concrete, being the most used building material. The overall objective is to apply by-products (such as metallurgical slags and combustion ashes) as alternative raw materials for concrete in the urban NWE region, and as demonstrated in metropolitan areas Rotterdam and Ghent, and in a circular office building. Despite NWE’ circular economy drive and leading role in recycling of wastes, the high-end use of by-products in construction remains limited because of a lacking transregional approach (need for critical mass in policy making, wider availability of by-products). By replacing primary raw materials with by-products, 84 million tonnes of construction minerals will be saved per annum. The project steps and main outputs are: 1) to develop concrete mixes with up to 100% by-product aggregates and low carbon footprint cements; 2) to match by-product providers with the construction sector in a web-based platform, forecasting availability and considering the logistical chains underlying the construction demand; 3) to test and demonstrate the URBCON technology in three pilots; 4) to prepare the roll-out of the technology through a transition roadmap, with a proposed policy framework, life cycle assessment, pre-standardisation, and business viability of urban cements, aggregates and concretes. The consortium combines world-leading know-how in by-product based construction minerals, supplementary cementitious materials, alkali-activated binders, high-alumina cement, digital mapping of resources, and life cycle assessment and costing. URBCON will establish the technology and remove implementation barriers, bringing the new capacity to construct and maintain infrastructure with eco-efficient high-end concrete across NWE and Europe.