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

Abstract

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. Thisrestricts component size due to the limitedfluid penetration depth and narrows options for component customization. The use of additive manufacturing technologies has the potential to overcome those limitations and toexpand the range of bio-cement applications. In the present work an automated process for the production ofspatial structures has been developed, in which sand and urease active calcium carbonate powder were selectively deposited within a print volumeand treatedwith a cementation solution.This method provided conditionsfor calcite precipitation in the powder-containing areas, whereas areas of pure sand served as removable supportstructure allowing improvedfluid exchange. The 3D printed structure was geometrically stable and had sharplydefined boundaries. Compressive strength tests on cylindricalspecimens showed thatthe used powder-sandmixwas 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 resourceefficient sustainable building components.