Workflow for Earth-Based 3D-Printing

There is the need to improve the ecological footprint of modern construction; accordingly, earth as a sustainable building material is increasingly coming into focus. Besides the material itself, digital fabrication of earth-based materials offers additional ecological potential, as it is possible to create individualized components without using formwork and at the same time save resources due to a form-follows-force approach. However, the material must be adjusted for being suitable for additive manufacturing, i.e. material needs to be pumpable, extrudable and subsequently buildable. In this paper, a workflow is presented that shows the possibilities for engineering an earth-based mixture. Therefore, a systematic characterization of mixtures is carried out. For this purpose, loam to water ratio and volumetric aggregate content are systematically varied and the addition of natural fibers is investigated. For the evaluation of pumpability and buildability, the yield stress is evaluated. Mechanical strength as well as drying shrinkage are assessed as solid properties for these earth-based mixtures. The results are discussed and the developed workflow is prototypically demonstrated by the successful fabrication of a demonstrator. Therefore, six stackable 3D printed elements are fabricated with extrusion and then assembled in a 2 m high column.