Environmental and economic impact assessment of innovative concrete recycling systems

Over the last few years, the construction sector has experienced increasing demand for raw materials due to the rapid growth of the urban population. At the same time, most of the post-war buildings in Europe have reached the end of their service life. As a consequence, a period of intense demolition activities withsignificant waste generation is expected in the upcoming years. Both situations are eventually translated into significant environmental pressure. Concrete is the main component in construction and demolition waste (C&DW). Due to the high environmental footprint of this material, it is crucial to eliminate its consumptionthrough recycling and re-use. Currently, concrete rubbles are crushed with regular crushers and used mainly for low-grade applications (down-cycling) such as road foundations. Despite the environmental and financial benefits, this practice is still not at a sustainable level since raw materials are still needed for new structures, while the demand for low-quality secondary materials in the construction sector has already declined.Two innovative recycling technologies called C2CA and Smart crushing (SC) developed recently in the Netherlands, aiming to close the material loop in the construction sector. These technologies recover most of the original concrete materials at high-quality, which can be use in the production of new concrete athigher rates than traditionally. This research focuses on the environmental and financial implications of the novel C2CA and SC recycling systems as alternative solutions to the Traditional crushing (TC) method. The evaluation was conducted based on an integrated LCA&LCC analysis framework in which the monetisedenvironmental impacts (shadow costs) were internalised in the actual costs occurred within the supply chain of recycled concrete (production of primary materials, recycling, transports). On this basis, the recycling systems were compared from two different perspectives. First, the recycled materials produced were used for concrete production according to the current European standards. In this case, the traditional recycled coarse aggregates (TRCAs) were used to replace 50% of the primary gravel, while the innovative coarse (IRCAs) and fine (IRFAs) aggregates from the innovative systems replaced 100% of primary gravel and 60% of primary sand respectively. The maximum potentials of the innovative systems were investigated in a second scenario in which IRCAs and IRFAs completely replaced the primary concrete aggregates. In addition to that, the produced recycled concrete powder (RCP) was used as supplementary cementitious material (SCM) to replace 20% of the primary cement. In this study, the innovative recycling systems were considered mobile units located at the demolition site. In contrast, the TC recycling was executed off-site at a stationary plant to secure the sufficient quality of TRCAs. The results of the integrated LCA&LCC study revealed that both C2CA and SC systems were financially better options than the traditional recycling route. Especially when the SC system was used to replace higher quantities of primary materials, the total cost was reduced by up to 19% relative to the TC method. On the other hand, the C2CA technology showed better performance when following the current standards, where about an 8% cost reduction was achieved. However, environmental improvements were reported only for maximum utilisation of the SC products, resulting in about 17% lower shadow cost than the traditional method. In the case of the C2CA system, the environmental impact was found 5% increase for both scenarios. Both innovative systems displayed overall benefits over the TC method regarding social cost (internalised environmental impacts), with the SC system exhibiting the best overall performance for maximum use of its products. In this case, the overall benefits reached almost 19%, while the rest scenarios were not higher than 5%.The sensitivity analysis emerged that the innovative recycling systems presented benefits only when they were located close to the demolition site due to increased transportation of EoL concrete. For the same locations and up to 23 km away from the demolition site, only the SC2 scenario (maximum use of SC products) was more efficient than the traditional recycling route. The rest scenarios became more effective as the traditional plant was placed away from the demolition site. On the other hand, changes in the recycling phase, such as energy consumption and equipment operating costs, had a negligible impact on the results. Even if renewable energy sources would power the recycling plants, the environmental and cost benefits throughout the supply chain were not higher than 5% and 2.5%, respectivelyCivil Engineering | Building Engineering - Structural Desig