The Stone Spray is a research project exploring ecologically-minded construction methods using soil as a base material. From the project's website:
Stone Spray is a robot that uses soil as a main building material. It mixes the soil with a solidifier component and sprays it on surfaces to create structures. The goal of the project was to research the field of additive manufacturing in architecture and to propose a new eco-friendly, efficient and interesting system to print architecture in 3d.