-The construction industry is expected to go through large transformations since construction automation is anticipated to drastically alter standard processing technologies and could lead to possible disrupting technologies such as 3D concrete printing (3DCP). While 3D printing techniques have been successfully applied in a wide range of industries such as aerospace and automotive, its application in concrete construction industry is still in its infancy. 3DCP can allow freeform construction without the use of expensive formwork, which in return offers excellent advantages compared to conventional approach of casting concrete into a formwork. In the last few years, different 3DCP technologies have been developed. This paper presents the current progress of 3DCP technologies. An innovative methodology recently developed by the authors of this study for formulating geopolymer-based material for the requirements and demands of commercially available powder-based 3D printers is also briefly presented.
Extrusion-based 3D concrete printing is analogous to fused deposition modeling method, which extrudes cementitious materials from a nozzle to build a complex concrete structure layer-by-layer without the use of expensive formwork. This study aims to investigate the influence of type of fiber on inter-layer bond strength and flexural strength of extrusion-based 3D printed geopolymer. An extrudable fly ash-based geopolymer composition previously developed by the authors was reinforced by three types of fibers, namely polyvinyl alcohol (PVA), polypropylene (PP) and polyphenylene benzobisoxazole (PBO) fibers. Control geopolymer specimens with no fiber were also 3D printed for comparison purposes. The results indicated that the incorporation of fibers reduced the inter-layer bond strength of 3D printed geopolymer. This pattern was true regardless of the type of fiber. On the other hand, the flexural strength of 3D printed fiber-reinforced geopolymer mixtures was substantially higher than that of the 3D printed geopolymer with no fiber. The rate of increase in the flexural strength depended on the type of fiber. The flexural failures of the specimens were due to the tensile failure of the bottom layer, rather than the shear failure of the interfaces.
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