Green concrete materials selection for achieving circular economy in residential buildings using system dynamics

Increasing the number of residential buildings due to rapid urbanization growth has led to the massive consumption of concrete materials and significant negative environmental impacts worldwide. Properly selecting green concrete (GC) materials in residential projects can promote sustainable construction practices and achieve a circular economy (CE). This paper aims to identify and analyze the parameters affecting GC material selection based on CE principles by developing a system dynamic (SD) model to investigate the environmental and economic benefits during the construction process. The system dynamic-based framework (SD-BF) is used to investigate the simulation interaction of the variables between the GC original scenario and several hypothetical scenarios through the simulation process, including fly ash concrete (FA) and recycled aggregate concrete (RAC). The causal loop diagrams (CLD) and stock and flow (SF) diagrams are created to investigate the inner relations among the GC variables that can achieve CE. The SD model was applied for a residential building case study in New Cairo City, Egypt, using Vensim to simulate and analyse the most appropriate GC scenarios regarding cement, natural aggregate, CO₂ emissions, cost-effectiveness, and waste generation. The results showed that using various concrete scenarios could enhance the GC selection for CE principles, in which cement reduction is the most effective variable, and the reduction reached 19.8% and 11.4% in the most optimum scenarios, while the natural aggregate (NA) reduction reached 19.1% compared with the original scenario. This development is vital for achieving CE and closing the concrete materials loop, which helps construction decision-makers select suitable concrete materials for future residential projects.