Influence of printing parameters on the durability of 3D-printed limestone calcined clay cement mortar: overlap between filaments and nozzle offset

Large-scale cement-based Additive Manufacturing (AM), also known as 3D Concrete Printing (3DCP), is a promising technique to innovate the construction industry. The durability properties of printed specimens have been studied and compared to those of cast samples in the literature. However, no study has evaluated and quantified the influence of printing parameters on the durability of 3DCP specimens. Aspects such as nozzle offset and the overlap between printed filaments, among others, may influence the porosity of the samples and, therefore, the durability properties. This paper aims to investigate the influence of printing parameters on the durability of 3D manufactured mortar samples. The effects of the printing height and overlap between filaments on the durability properties were analysed in the X, Y and Z axes. An experimental investigation of 39 samples was conducted. Printed and cast specimens were subjected to a curing process for up to 90 days in a water tank at a temperature of 20 °C. Durability tests (oxygen permeability, electrical resistivity, and porosity) were performed at 7, 28 and 90 days. Relationships between the printing variables and durability properties with time were derived. Based on this study, it is concluded that the long-term properties of concrete are significantly sensitive to the overlap between filaments and the nozzle offset. In general, the durability properties were enhanced by modifying the printing parameters. In particular, an overlap of 4 mm showed the most promising results in this regard.