Development of construction demolition waste-based geopolymeric composites suitable for three-dimensional additive manufacturing

Conventional concrete, the main building block of our infrastructure, uses Portland cement (PC) as the main binder, consumption of which is increasing rapidly on a global scale. PC production is significantly energy-inefficient and accounts for up to 9% of total human-driven CO2 emissions worldwide. On the other hand, the construction and demolition waste (CDW) industry is recognized as one of the main sectors contributing to the global solid waste production, constituting 30-40% of total urban waste. Therefore, development of greener binders and proper handling of CDW is of great importance to benefit environment-, social- and economy-wise. In addition, along with the material-related breakthroughs, operation-related breakthroughs utilizing advanced manufacturing technologies need to be made to achieve truly sustainable construction practices. The traditional formwork system in the construction industry requires high cost, workmanship, energy and causes significant waste generation and operational challenges. Thus, three-dimensional additive manufacturing (3D-AM) method can be applied to concrete-like materials as a promising alternative to the existing methods for construction and can contribute to a paradigm shift. This thesis study aims (i) to develop innovative alternative green construction materials by using out of waste materials obtained from construction and demolition activities, and (ii) to merge these developed green materials into 3D-AM for the achievement of truly sustainable construction practices both at the material and operational levels. In that context, to begin with, geopolymer paste mixtures were produced by using CDW-based components with a primary focus on fresh/rheological properties. After that, CDW-based geopolymers were incorporated with CDW-based fine recycled concrete aggregates (FRCA) to obtain geopolymer mortars with fresh properties fitted for 3-dimensional printability. In conclusion, the performance of selected geopolymer mortar mixture with the properties fitted for 3 dimensional-printability was validated via laboratory-scale 3D-AM application. It is believed that adoption and implementation of all novel cost-effective solutions proposed by the current thesis study will provide a great opportunity for valorising waste materials for use in high-grade building products, reducing CO2 emissions by closing the human-driven carbon cycle, increasing energy efficiency and ensuring proper resource management; which will help boost green construction in favour of human health, natural ecosystems, global economy and future circularity of valuable raw materials and products, and tackling the global issue of climate change.