Paste matter 3d printing in monolithic shells fabrication methods

Fabrication methods with 3d printing for monolithic shells remain largely unexplored, in terms of the technologies implemented to ensure the integrity and the essential continuity of the structure during the construction phase. This crucial condition is directly related to the matter implementation during the fabrication process, which is further exacerbated when materials are applied in wet stage (such as concrete and clay mixes), including the proper composition of the material, the support system chosen, the placement protocol, and the deposition techniques, among other factors.

This paper features some case studies of material deposition in concrete and clay for monolithic shells using robotic extrusion and spraying, aiming to identify critical aspects required for its correct execution, with an emphasis on its transformation during the construction process. The use of different digital technologies was explored, including 3d scanning, Rhino 3d, Kuka prc (interface kuka robotic arm to Rhino through a Grasshopper plug in), exposing different ways of creating robotic trajectories for the correct deposition of the material.

The 3d printing process was implemented by depositing concrete and clay through digital interface and real time recalibration. The deployments was performed in 3 main categories (actions tools): 1] Matter extrusion with no formwork; 2] Matter spraying with temporary formwork; 3] Hybrid with material extrusion on structure in progress once the temporary formwork has been removed.

The materiality chosen was paste-like materials that were carefully formulated because their composition includes several elements that were adapted for additive manufacturing: concrete composed by granular, gravel, and sand ingredients; and clay with natural or artificial fibers of different densities, sizes (from short straw pieces to long horse hair), and natural stabilizers (Roedel, Protein Cured Concrete CIFE, Stanford University, 2016).

The results of these experiments unveil that matter characteristics during the digital fabrication process has tremendous implications on the possible geometries that can be achieved. The material implementation process in 3d printing monolithic shells using clay and concrete exhibits significant challenges, such as the fundamental type of support system employed; the control of paste viscosity (water & air ratios); the presence of air bubbles; the weight of the material due to gravity and drying time; the velocity of deposition; the stirring techniques to ensure humidity and plasticity; and the drying ratios needed for each formation.