A Method for 3D Printing Bio-Cemented Spatial Structures Using Sand and Urease-Active-Calcium-Carbonate-Powder (2020-08)¶

The substitution ofPortland cement withmicrobially based bio-cement for the production ofconstructionmaterials is an emerging sustainable technology. Bio-cemented building components such as bricks have been fabricated in molds, where bacteria-containing aggregates solidify when treated with a cementation solution. This restricts component size due to the limited fluid penetration depth and narrows options for component customization. The use of additive manufacturing technologies has the potential to overcome those limitations and to expand the range of bio-cement applications. In the present work an automated process for the production of spatial structures has been developed, in which sand and urease active calcium carbonate powder were selectively depositedwithin a print volume and treatedwith a cementation solution. This methodprovided conditions for calcite precipitation in the powder-containing areas, whereas areas ofpure sand served as removable support structure allowing improved fluid exchange. The 3D printed structure was geometrically stable and had sharply defined boundaries. Compressive strength tests on cylindrical specimens showed that the used powder-sandmix was suitable for the production ofhigh-strength bio-cemented material. The present work demonstrates an application of bio-cement in an additive manufacturing process, that can potentially be used to produce resource efficient sustainable building components.