Jim Hallock, from Colorado Earth, led two Compressed Earth Block Workshops at the Materials Lab on Thursday, March 28th. Compressed Earth Blocks (CEBs) are unfired earth masonry units made from inorganic subsoil, clay, and aggregate, formed into blocks through compression with a mechanical press and joined with standard bricklaying techniques. Stabilizers such as cement or lime are sometimes added to increase strength and water resistance. Unfired earth is one of the oldest building materials used by humans, and includes not only CEBs but also rammed earth, adobe, and other forms. Today, one third of the world's population lives in earthen buildings. Each session included a brief lecture on the history of CEBs, the material properties of unfired earth, construction techniques, and an overview of the machines used to make CEBs. Hallock also showed some of Colorado Earth's finished projects, located around the world, and discussed their larger goals for regenerative building. Hallock maintains that CEBs are "fire-proof, sound-proof, bug-proof, bullet-proof, breathable," low-maintenance, structurally sound, hurricane and tornado-resistant, durable, biodegradable, and locally available. Additionally, the material's unique ability to regulate humidity and temperature through the absorption and release of heat and water vapor particles, was explored in-depth. The demonstration that followed introduced participants to soil selection, mix testing (both on-site and at the lab), and the production of 10”x14” compressed earth blocks on site, using an AECT Impact 2001A Series machine. This workshop was funded by the UT Green Fund.