In April 2018, assistant professor Michelle Bernhardt-Barry at the University of Arkansas was awarded a National Science Foundation research grant of $500,000 to support the development of 3D printed construction materials.
Two months on, and further information about the 5 year project has been revealed, showing that it aims to use an usual method of binding natural materials like soil and sand.
Gypsum and sand
As a proof of concept, Bernhardt-Barry has been working with binder jet 3D printing technology capable of making bricks from gypsum. Though gypsum is a common ingredient of plaster, these bricks are not waterproof, and so Bernhardt-Barry is planning to further her research with a 3D printer capable of working with sand. Such industrial 3D printers include equipment from ExOne 3D printers and machines from Voxeljet.
In each of these processes a proprietary binder is used to fuse gypsum or sand grains together to produce a 3D printed part. An alternate direction that Bernhardt-Barry would like to explore is the ability to use bacteria in place of a binder.
Buildings 3D printed from bacteria
One of the methods in experimentation at Arkansas is a bio-geochemical process known as microbiologically induced calcium carbonate precipitation (MICP).
Calcium carbonate is naturally found in sedimentary rocks, and is the main component of pearls, snail shells and eggs. It is produced in the MICP process by introducing certain types of bacteria to soil.
By mastering the specifics of this process, Bernhardt-Barry’s team will hopefully apply calcium carbonate as a soil-binder, and replicate its natural strength.
The team is also exploring a material extrusion technique for the gypsum mixture, similar to the way cement is 3D printed.
By 2023, the team at Arkansas will complete a lifecycle analysis of its material with the hope of finding a commercial partner.
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Featured image shows a 3D printed gypsum brick. Photo via Talk Business/ University of Arkansas