End-Of-Life Materials Based Lightweight Geopolymer Mortars Suitable for Additive Manufacturing

Abstract

Traditional Portland cement is extensively employed in the building industry to satisfy the housing and transportation need of the rising human population. However, the production of Portland cement contributes to greenhouse gasses released into the atmosphere, accounting for 5-7% of global CO2 emissions. The development of a sustainable, low-carbon, and eco-friendly binder, namely geopolymer as an alternative to Portland cement is essential to ensure a sustainable built environment. Furthermore, the reuse of end-of-life materials is of vital importance for the construction of a sustainable future and the transition to a circular economy. Approximately 800 million tons of construction waste is generated annually in Europe. The employment of generated end-of-life construction and demolition waste in the production of "green" geopolymer binders is considered to be a viable methodology to minimize multiple environmental impacts sourced from CO2 emissions and ineffective disposal of end-of-life materials. Similarly, insulative construction materials play a crucial role in modern sustainable building design and construction. The main attribute of these construction materials is providing thermal insulation, which is essential for maintaining comfortable indoor temperatures and reducing energy consumption resulting in significant energy savings and reduced environmental impact. 40% of the global energy consumption is attributed to buildings. Lightweight aggregates are broadly used in the development of thermal insulative, low-density, lightweight, and energy-efficient construction materials. Another important point in the construction sector is the automation of the construction processes. 3-dimensional (3D) additive manufacturing technology is an emergent innovative automation system in the construction industry providing faster construction, reduced material waste, low energy use, and cost savings compared to traditional construction methods. The layer-by-layer production technique of 3D additive manufacturing technology enables design freedom for complex structures. With the widespread use of 3D-printing technology in the construction industry, safe and uniquely designed structures can be built without the use of formworks in a more economical, faster, and reliable way. The aim of this thesis is to develop end-of-life materials-based lightweight geopolymer mortars suitable for additive manufacturing. An entirely end-of-life construction demolition waste-based alkali-activated lightweight insulative geopolymer mortars are produced for 3D printing applications in this study. The fresh state open-time rheological properties, fresh and dry densities, mechanical properties at 7, 14, and 28 days, thermal insulation properties, as well as elevated temperature resistance of geopolymer mortars were determined. Finally, 3D-printing performance and the 3D-printing quality of the mortars were visually assessed. As a result, it is believed that developed geopolymer mortars will offer an innovative, viable, sustainable, and green solution to the multiple issues confronted in the construction industry, such as greenhouse gas emissions, management of construction and demolition wastes, high construction costs and thermal energy loss in buildings.