Development of Eco-hybrid cement-based green concretes through CDW upcycling: Mechanical performance and...

This study aims to address the environmental challenges posed by construction and demolition waste (CDW) through its upcycling into a green concrete solution that supports the principles of the circular economy. To this end, a new generation Eco-hybrid cement was developed for the binder phase, using a ternary combination of CDW, calcium sulfoaluminate (CSA) cement, and Portland cement (PC). For the aggregate phase, 100% CDW-based recycled concrete aggregate was utilized. The green concrete was analyzed for its mechanical and environmental performance using comprehensive testing parameters, including compressive strength, drying shrinkage, water absorption, freeze-thaw resistance, chloride permeability, and life cycle assessment. The green concrete achieved a compressive strength of 43.8 MPa at 28 days, with acceptable early-age strength owing to CSA cement and increased strength over time due to the pozzolanic activity of CDW. Its durability was comparable to PC concrete, making it suitable for structural applications. Microstructural analyses validated that CDW components contributed to mechanical performance by forming C-S-H gel at later ages. Environmentally, Eco-hybrid cement resulted in a global warming potential of 575.34 kg CO₂-eq per ton, compared to 845 kg CO₂-eq for PC. Green concrete exhibited reductions in various environmental impact categories, ranging from 29% to 42% compared to PC concrete. Unlike conventional approaches that primarily use CDW in aggregate production, this study demonstrates the feasibility of reducing the PC phase in concrete through a well-designed ternary system, ultimately using approximately 87.8% waste material by mass in the final concrete mixture.