Keeping the Processability of a Clay Mortar for Extrusion 3D Printing While Decreasing Shrinkage and Increasing the Green Strength

Growing concern about climate change has spurred the construction industry's exploration of alternative building materials, with particular interest in clay and earth due to its widespread availability and low carbon footprint. Although earth has been used historically, the use of traditional methods in Europe is currently unprofitable and limited to a few pioneering projects due to high labor costs. Recent advances in digital manufacturing techniques have opened up new ways of using earth and clay-based materials. For example, clay mortar can be used in a digitally controlled extrusion 3D printing process to create natural, recyclable building components or formwork for concrete structures. However, the mechanical properties of clay mortars fall short of those of materials such as concrete, and the issue of clay shrinkage and low green strength poses a significant challenge. This paper investigates strategies to reduce the shrinkage and increase the green strength of clay mortar while ensuring that its workability for the extrusion 3D printing process is maintained. According to the results, it is found that shrinkage can be mitigated, and the green strength can be increased by reducing the water content (water to clay ratio), further reducing the water content by incorporating a deflocculant, incorporating fibers, and increasing the sand content without compromising its suitability for extrusion processes. This research represents a significant step towards realizing the potential of clay-based materials as an environmentally friendly alternative in modern construction practice.