A method for 3D printing bio-cemented spatial structures using sand and urease active calcium carbonate powder

The substitution of Portland cement with microbially based bio-cement for the production of construction materials 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 deposited within a print volume and treated with a cementation solution. This method provided conditions for calcite precipitation in the powder-containing areas, whereas areas of pure 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-sand mix was suitable for the production of high-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. [Display omitted] •Lyophilized urease active calcium carbonate powder facilitates fixation of bacteria in sand during cementation.•Spatial structures cemented using urease active calcium carbonate powder demonstrate sharply defined boundaries.•Non-cementable channels facilitate the penetration of the cementation solution into the depth of a 3D printed volume.•Bio-cemented cylindrical samples (d = 20 mm, h = 20 mm) demonstrate compressive strengths of up to 23 MPa.•Lyophilized urease active calcium carbonate powder retains 83 % of its initial activity after 6 months storage at -20 °C.