Enhancing the printability and sustainability of 3D concrete printing using recycled waste glass as a cement substitute

This research investigates the valorization of recycled ground waste glass (GWG) as a partial substitute for ordinary Portland cement in 3D concrete printing (3DCP) applications, focusing on improving the printability, mechanical behavior, and sustainability. Printable mixes with 0% to 30% GWG were systematically developed and evaluated for fresh-state rheology, hardened properties, and environmental impact. The addition of GWG improved flowability and pumpability by reducing the dynamic yield strength, attributed to the roundness and minimal moisture retention of the glass particles. It also improves the thixotropic behavior of printable concrete, enhancing viscosity recovery and shape retention during printing. However, increasing GWG content reduced static yield stress, likely due to the presence of GWG as inert filler and reduced dissolution rate, delaying pozzolanic reactivity. The compressive strength of both cast and 3DCP samples increased for up to a 10% GWG content, beyond which the porosity increased and the strength reduced. Notably, the addition of GWG impacted positively on the alkali-silica reaction by reducing expansion. Sustainability analysis showed that 30% GWG substitution reduced embodied energy and carbon emissions by 29% and 33%, respectively. This study highlights the significance of recycled glass in 3DCP, contributing to circular economy practices and sustainable construction.