Limes with Hydraulic Properties for 3D Printing Mortars

The adoption of 3D printing in the global construction industry is still in its infancy, but the technology is already being used to build street furniture, bridges, and even multistory buildings. While this technology allows using fewer resources than some conventional construction processes, most of the printing-adapted mortars available on the market are cement-based, with a high mechanical performance that is suitable for many uses. But these mortars have a high ecological footprint and may not be the most suitable as interior finishes because they have low hygroscopicity and do not contribute significantly to regulating the relative humidity inside buildings. To address some of the concerns mentioned above, a 3D printing mortar was developed using limes with hydraulic properties, namely, hydraulic lime and natural hydraulic lime, as the main binder. The combination of fine sand, limestone powder, superplasticizer, viscosity modifiers, and setting accelerators allowed to achieve the required characteristics for a printing mortar. To develop the lime mortars, comparing them with conventional mortars used in the literature, extrusion tests were performed using a robotic arm and an auger extruder. Through the extrusion tests, it was possible to confirm that cement can be replaced by lime to build nonstructural elements. The study evaluates the change in workability over time. The proposed mortars exhibit very similar behavior, but over time they show different properties in comparison with the 3D ready-mix mortar. The buildability test shows that lime-based mortars can support self-height deformation as any cement-based mortars.