3D cementitious printing (3DcP) – dual delivery nozzle integration

Abstract

The interest in 3D concrete printing (3DCP) has been gradually increasing for the last 20 years with new research and applications in the construction industry and can allow for more intricate designs with complex geometry than conventional concrete formwork but 3DCP in the construction sector is not yet widely adopted as the weak interlayer bond strength between layers and strips need to be reinforced to be stronger and less prone to failure. Simultaneous printing of concrete and reinforcement is a solution to overcome this major hurdle. An improvement or adaptation of existing dual-delivery nozzle models should be developed and a method for testing sample prints should be implemented to obtain data and to test if simultaneous reinforcement printing is a viable solution. After concept generation and adapting from existing models, a prototype nozzle is developed with printing samples with a rectangular concrete profile and a circular epoxy resin profile in the centre of the filament. The prototype nozzle was fabricated using SLA and used to print the samples with desired profile. The printed samples are then left to cure before doing a three-point flexural test based on a testing standard adapted from ASTM C293M. The results of the three-point flexural test show that the epoxy resin reinforcement aids in improving the qualities of the printed concrete such as maximum load, extension at max load and time taken to max load. These results show that the dual-delivery nozzle prototype can simultaneously print concrete and polymer reinforcement and additional experimentation with different polymers at a larger scale should be done to obtain more data on simultaneous printable polymer reinforcements.