3D printing earth: Local, circular material processing, fabrication methods, and Life Cycle Assessment

Abstract

Additive manufacturing with earth is an emerging, though largely uncharacterized, approach to fabricating low embodied carbon structures. It is critical to establish methods for processing 3D printed, locally sourced earthen materials in different environments to validate large-scale earthen additive manufacturing as a tool to address a growing global need for housing and climate-resilient architecture. We present a set of reproducible design guidelines for sourcing, processing, and characterizing locally sourced earthen materials. Soil type, moisture and fiber content, particle size distribution, and unconfined compressive strength are determined. Additionally, novel bridging, cantilevering, and hydrostatic pressure (formwork) testing methods are developed to link design constraints for full-scale printed structures to material characteristics. Modular and conformally printed full-scale wall prototypes are printed with a 6-axis robotic system. A Life Cycle Assessment of the prototypical earth printing system is conducted, establishing a point of comparison to the climate impact of other construction systems, including rammed earth, concrete masonry units, and 3D printed mortar. We demonstrate that printing highly functional building elements with repeatable mechanical characteristics is possible using locally sourced earth mixtures. By illustrating a range of reproducible material and geometric possibilities, we expand the design space of additive earth and its applications.