Chapter 18 - Properties of Extrusion-Based 3D Printable Geopolymers for Digital Construction Applications

Abstract

An optimum 3D printable fly ash-based geopolymer mixture has recently been developed by the authors of this study for digital construction applications. The first part of this chapter reports the hardened properties of the developed optimum 3D printed geopolymer mix including the compressive and flexural strengths in different directions, along with the interlayer bond strength. The optimum 3D printed geopolymer mixture exhibited anisotropic compressive and flexural strengths of 18.4–27.7MPa and 7.7–8.2MPa, respectively, depending on the orientation of the loading relative to the printed layers. A high inter-layer bond strength of 3.0MPa was achieved for the optimum 3D printed geopolymer mixture. The second part of this chapter reports the influence of type of fiber on the interlayer bond and flexural strengths of the optimum 3D printed geopolymer mixture. Three types of fibers, namely polyvinyl alcohol, polypropylene, and polyphenylene benzobisoxazole fibers were used to reinforce the optimum 3D printed geopolymer mixture at a constant volume fraction of 0.25%. The incorporation of fibers reduced the inter-layer bond strength of optimum 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 optimum 3D printed geopolymer mix with no fiber. The rate of increase in the flexural strength depended on the type of fiber. The flexural failures of the 3D printed geopolymer specimens were due to the tensile failure of the bottom layer, rather than the shear failure of the interfaces.