Recent advances in CDW-based geopolymers: A review of mechanical performance, structural application, 3D printing, durability and sustainability.

The increasing demand for sustainable construction materials has intensified research into geopolymers, with a particular focus on construction and demolition waste (CDW). CDWs present a promising opportunity for reducing the environmental impact of construction by serving as recycled precursors and aggregates in sustainable geopolymeric materials. Recent studies have confirmed the viability of CDW-based geopolymers, demonstrating numerous advantages, including enhanced mechanical durability, cost-efficiency, and overall sustainability characteristics compared to Ordinary Portland Cement (OPC)-based materials. Nevertheless, several challenges continue to impede their broader adoption in the construction industry. This review synthesizes the latest findings on the mechanical properties, durability, 3D printing applications, structural performance, and sustainability features of CDW-based geopolymers, highlighting critical factors such as the influence of CDW precursors and aggregates, mix design parameters, particle packing and shape characteristics. Literature underscores the necessity for enhanced design methodologies and standardized criteria to improve the practical application of CDW-based geopolymers, particularly in optimizing the mechanical performance, durability, and 3D printing formulations. Important limitations regarding the need for research in critical areas of CDW-geopolymers have been given.