This paper will briefly present the state-of-the-art of large-scale additive manufacturing and subsequently greater attention will be given to extrusion-based 3D printing. While the great development of such technologies has improved the quality of prints and expanded the availability of materials, AM still has some limitations regarding its physical scaling. Since this advent, additive manufacturing (AM) has grown steadily and found applications across all types of sectors. The future aims of the much needed research should cover both large scale column specimens and other structural elements.
The achieved results proved that it is feasible to replace traditional formwork and ordinary concrete (reinforced by steel bars and stirrups) by much more automatized 3D printing of plastic and steel fibre reinforced concrete based solution. All steel fibre reinforced concrete-plastic columns in question were characterized by highly quasi-plastic behaviour. Specimens with fractal-based cross-sections were characterized by a very smooth destruction process associated with significant deformations of formworks. Columns with traditional circular and square cross-section were characterized by sudden destruction of the formworks. The achieved results were analysed and discussed. Both the destruction characteristics and the energy dissipated during the loading up to 3.5% strain were of special interest. During the tests load-strain characteristics were recorded.
After ordinary curing, the specimens were loaded.
3D printed plastic stay-in-place formworks were filled with steel fibre reinforced concrete. Seven cross-sections representing different types of shapes of columns (from circular to fractal-based) were created. Plastic was playing the role of stay-in-place 3D printed formwork. It was stated that the type and dosage of fibers used were effective parameters in controlling this negativity.Ī concept of steel fibre reinforced concrete-plastic columns was proved and discussed in the paper. It is necessary to control dimensional-stability parameters that occur due to the high dosage of binder content of 3DPC. In addition, it was stated that the use of geopolymer, recycled aggregates and waste materials in the mix design of 3DPC mixtures can contribute to the improvement of the sustainability of 3DPC and the circular economy. It was determined that use of supplementary-cementitious-materials improves rheological properties, while the addition of nano-clay and viscosity modifying agents increases the structural build-up. It was observed that use of sulfoaluminate-cement, which has advantages of rapid-setting, high strength and low-shrinkage, positively affects the performance of 3DPC. In this article, the effects of materials used in 3DPC mixtures on the printability performance of mixtures, especially rheological properties, were investigated by examining the studies in the literature. It was observed that the development of mix design is necessary for the wider application of 3DPC. It was found that there are no acceptance criteria, standards or guidelines for 3DPC and existing standards do not provide guidance on the mix design. It was understood that 3D printing concrete mixtures (3DPC) have special requirements in terms of rheological properties compared to conventional concrete.