Green concrete with high-volume fly ash and slag with recycled aggregate and recycled water to build future sustainable cities

Building sustainable green cities for the future can be difficult or highly challenging as such cities need to reduce their environmental footprint through eco-friendly materials, resource and energy conservation, as well as renewable energy generation. A recent paper by the first author has proposed sustainable concrete with 80% ground granulated blast furnace slag (GGBFS) to build Masdar City in the UAE with a 153 kg/m³ carbon footprint. This paper proposes three new types of sustainable concretes in an attempt to further reduce the carbon footprint. In Type I, a total of 4 concrete mixes were made with a high volume GGBFS with 60, 70, 80, and 90% replacement of ordinary portland cement (OPC), 100% recycled water (RW), and 100% recycled aggregate (RA). The same replacement ratios were used in Type II but with only 100% RA. In Type III, a total of four concrete mixes made with a high volume fly ash (FA) cement with 40, 50, 60, and 70% replacement of OPC. The paper provides information on the mix design, full justification of CO₂ footprint, and the cost for each concrete mix. The hardened and plastic properties and durability test parameters for each mix are presented. The results showed that the fly ash and slag significantly reduced the carbon footprint and meet the requirements of future sustainable cities. An economical mix with 90% GGBFS and 10% OPC was nominated for use in the future construction of sustainable cities with 125 kg/m³ emissions.