Abstract
This paper deals with the additive manufacturing of metakaolin-based geopolymers and with the use of microalgal biomass from wastewater treatment plants as biofiller in this kind of cementitious material. The study was developed following the evolution stages of the material, which was prepared and printed as a soft paste and then hardened thanks to an inorganic polymerization reaction (geopolymerization). Thus, the characterization techniques adopted encompassed rheometry, mechanical tests performed on the hardened material, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and mercury intrusion porosimetry (MIP). Microalgal biomass addition, evaluated in this study at 1, 3 and 5 php with respect to the powder weight, affected both the properties of the fresh and of the hardened material. Regarding the former aspect, biomass reduced the yield stress of the pastes, improving the ease of the extrusion process, but potentially worsening the ability to build structures in height. When hardened, geopolymers containing microalgae showed mechanical properties comparable to the unfilled material and a microstructure characterized by smaller pores. Finally, a printing test was successfully performed with a larger printer to assess the feasibility of producing large-scale structures. Taking into account these results, this study demonstrates the possibility of using microalgal biomass as biofiller in geopolymers for additive manufacturing.
Highlights
The possibility to produce objects directly from a 3D digital model has made additive manufacturing (AM), popularly known as 3D printing, attractive for a wide range of applications in many different sectors
In extrusion-based processes the cementitious material is extruded in a fresh state to build freeform structures layer-by-layer; resolution is lower with respect to powder-based techniques, printing speed is much higher and in principle, there are no limitations on the dimensions of the structure [10,11]
This paper discussed the effect of microalgal biomass on the rheological, mechanical and microstructural properties of geopolymers for the application of liquid deposition modeling (LDM)
Summary
The possibility to produce objects directly from a 3D digital model has made additive manufacturing (AM), popularly known as 3D printing, attractive for a wide range of applications in many different sectors. In extrusion-based processes the cementitious material is extruded in a fresh state to build freeform structures layer-by-layer; resolution is lower with respect to powder-based techniques, printing speed is much higher and in principle, there are no limitations on the dimensions of the structure [10,11]. Because of these aspects, in this paper an extrusion-based process, called liquid deposition modeling (LDM) [12,13], is studied
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