Hardened properties of 3D printed concrete - experimental investigation

Abstract

At the end of the last century, 3D printing of concrete became an innovative method for producing concrete structures. The beginning of the application of 3D printing in the concrete construction industry is referred to the Contour Crafting printing method. In addition to Contour Crafting, other methods such as Fused Deposition Modeling, Shotcrete 3D Printing, and ink printing method, developed and utilized by D-Shape, have been applied in this field. Through the use of these technologies, numerous structures have been successfully created, including one-story and multi-story houses, residential buildings, pedestrian bridges, as well as individual elements like columns, walls, facade panels and outdoor furniture. However, the wider implementation of this technology has revealed various challenges, such as the lack of regulations and standards for the production and testing of these concrete materials as well as the structural analysis of 3D printed structures. The topic of this research is the investigation of the hardened properties of 3D printed concrete. The focus is on the physical and mechanical properties such as the bulk density of concrete, compressive strength, flexural strength and interlayer bond strength. This paper gives an overview of previous research on these properties, while the experimental part gives insight into the results of own research. Two types of specimen processing were used: full-notch removal (series 1) and printed samples (series 2). Additionally, samples with four or six layers were analyzed. The obtained values for bulk density were 1964.46 kg/m³ for full-notch removal samples and 1859.62 kg/m³ for printed samples. The compressive strength was 25 MPa for perpendicular and lateral directions, while the bending strength was 5.57 MPa. A significant influence of layering on fracture patterns and results was observed during the bond strength testing. The obtained values ranged from 1.59 to 2.91 MPa, the lowest value was obtained in the axial tension test, while the highest value was achieved in the shear test. The highest uniformity of results was achieved for series 1 samples tested in axial tension and splitting tests.