Additive manufacturing for concrete: a 3D printing principle

Additive manufacturing is nowadays a well-known production process for the production of single objects or small series, mostly in plastics or metals. By showing the possibilities of these processes, a growing interest is shown by civil engineering projects. The presented principle should reduce the amount of labor and simplify the creation of concrete structures with complex geometries. Also the possibility to create non solid concrete structures should be a big advantage in material savings and reduced loads. The paper presents the 3D printing possibilities for the selective depositioning of High Performance Concrete for non-loadbearing building components. Starting from a predefined concrete mixture the rheological behaviour of the mixture is studied to develop and optimize a pumping system for the use in a 3D printing depositioning system. Two different pumping systems are selected, the progressive cavity pump and the Archimedes screw pump. A proof of concept is given, resulting in an optimisation cycle to improve the flow behaviour of the concrete. A mixer and excitator is introduced in the design to overcome the thixotropic behavior of concrete. A labo-scale functional prototype is constructed and tested to produce small scale prisms. The compressive and flexural-tensile strength of the printed concrete show an almost equal result compared to traditional compacted concrete.status: publishe