Density Gradient Concrete Fabrication with Injection 3D Gypsum Printing (2024-04)¶

Optimizing the material distribution of concrete elements has the potential to decrease concrete consumption and improve structural efficiency by reducing weight without altering the overall geometry. The challenge lies in making variable internal material densities of concrete elements. This study introduces the fabrication method of Injection 3D Gypsum Printing (IGP), which allows for creating functionally graded density of concrete elements. IGP removes concrete locally by injecting a gypsum-based temporary support material during the concrete casting. The water-soluble temporary support material injected into the liquid concrete is later removed by jetting water after the concrete cures. This system aims to fabricate topology-optimized structure designs while minimizing the additional construction steps and formwork requirements from the conventional casting construction system. This method combines effective materialsaving digital fabrication strategies with conventional concrete construction's efficient reinforcement and casting processes. The study examines the material design and custom fabrication setup of IGP through initial feasibility experiments. Additionally, it presents IGP methods and applications through two proof-of-concept case studies. The digitally controlled material removal method introduced in this study holds potential as a material-saving strategy in future concrete construction.