Utilization of solid mine waste in the building materials for 3D printing.

3D printing technology is gradually considered to be a rapid development of a green revolution in the field of architecture. Recently, utilizing solid mine waste to replace natural sand not only greatly reduces the 3D printing costs, but also contributes to an environmental sustainability development. However, most solid waste inevitably has an impact on the inherent mechanical strength and printability of concrete materials. It is an urgent requirement to expand the alternative materials and improve the overall property of 3D concrete materials. This paper reported an innovative concrete material that replaced natural sand with fine limestone powders for 3D concrete printing applications. The experimental measurements were performed including microstructures characteristics, flowability, buildability, shrinkability, layer-interface properties, mechanical properties and interlayer bonding strength. Besides, an effective method was proposed to characterize the printable properties of concrete materials and then the reasonable limestone powder replacement ratio was determined. Based on the investigation results, appropriate substituting limestone powder (40%) can effectively improve the grading of the concrete, thus promoting its printability and buildability. Moreover, the microstructures of the 3D printing concrete materials after curing were denser and their mechanical property improved by approximately 45%. With the further increase of replacement ratio, the reduction in the flowability led to a decrease of the printability. A large number of fine particles increased the shrinkage of the curing process and some bubbles were stranded inside the materials due to its increase in the viscosity, thereby reducing the mechanical properties of the hardened material. The produced concrete for 3D printing can be treated as an eco-friendly building material that contributes to the rational development and resource utilization of solid water, thus promoting the sustainable development of construction field.