Abstract
Since the initial introduction of geopolymers, these materials have been characterised as environmentally-friendly sustainable substitutes for ordinary Portland cement (OPC). There is a routine increase in the application of geopolymers, especially in advanced technologies. Because of its better rheological characteristics compared to OPC, geopolymers are appropriate materials for extrusion-based 3D printing technologies. This paper focuses on the optimisation of an ambient temperature cured geopolymer for 3D printing construction applications. The effects of mixture parameters, including the type of hydroxide solution (HS), the type of silicate solution (SS) and the mass ratio of SS to HS on the workability, extrudability, shape retention ability and mechanical performance of different geopolymer mixtures were investigated. Accordingly, an optimum mixture was identified for geopolymers cured at ambient temperatures. Mechanical properties of the optimised mixture, including flexural and compressive strengths, were measured in different directions with respect to the printed layers. Further, uniaxial tension tests were also conducted on the optimised mixture to measure its interlayer bond strength. The results showed that among the activators investigated, the sodium-based activator composed of sodium hydroxide and sodium silicate solutions, with a SiO2/Na2O ratio of 3.22, was the most effective activator, providing appropriate workability and extrudability, along with reasonable strength and a high shape retention ability. The acquired mechanical properties exhibited anisotropic behaviour in different testing direction. The strength of the interlayer bond was found to be adequate to avoid interfacial shear failure.
Highlights
Additive manufacturing (AM), or 3D printing in other terms, utilises an automated assembly procedure which manufactures layered components from digital model data
No blockage, tearing, segregation or bleeding was observed during the extrusion process of all mixtures
It can be concluded that all mixtures investigated in According to the results, no blockage, tearing, segregation or bleeding was observed during the this paper exhibited “acceptable” extrudability
Summary
Additive manufacturing (AM), or 3D printing in other terms, utilises an automated assembly procedure which manufactures layered components from digital model data. Despite the extensive application of AM in advanced areas of science such as the biomedical, aerospace and automotive fields [1], its development in the construction industry is still in its infancy. In the past few years, the application of AM in the construction industry has attracted a significant amount of attention. This is because AM can offer several benefits when compared to the conventional construction approach, such as improved geometrical freedom, increased safety in construction and reduced construction time, cost and waste [2,3]. There are a wide variety of challenges to be addressed before AM technologies could be thoroughly implemented in the construction industry. Some of the Materials 2019, 12, 902; doi:10.3390/ma12060902 www.mdpi.com/journal/materials
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