Jun 27, 2018 | By Thomas

Michelle Bernhardt-Barry, assistant professor of civil engineering at the University of Arkansas, has been studying the structure of soil and how to make it more effective for bearing heavy loads, with a view to 3D printing optimized soil material in future construction projects. In April 2018, Bernhardt-Barry received a $500,000 grant to expand her research into the use of soil as a 3D printing material. The five-year grant will allow her to hire two doctorate students to deepen her investigation of mechanisms in nature that have proven to be efficient at bearing loads.

Michelle Bernhardt-Barry, assistant professor of civil engineering at the University of Arkansas. Credit: University of Arkansas

Bernhardt-Barry has been working with binder jet 3D printing technology, an additive manufacturing method that creates parts additively with a binding agent such as plaster, starch, or gypsum powder. She has used gypsum to create a synthetic material that is similar to sand, but a downside to the gypsum is it’s not waterproof. So she is planning to apply for a grant for a new 3D printer capable of working with sand.

In the 3D printing process the binder jet 3D printer lays down a special proprietary binder or “glue” to form complex parts on a flat bed of gypsum powder, one layer after another. An alternate direction Bernhardt-Barry would like to explore is the ability to bind the materials without having to use the proprietary glue. One option is to use bacteria to harden soils.

A 3D printed material made with gypsum and shaped into a design to increase its strength. Credit: University of Arkansas via TalkBusiness 

She’s currently studying microbial induced calcium carbonate precipitation (MICP), a bio-geochemical process that induces calcium carbonate precipitation within the soil matrix. Calcium carbonate's most common natural forms are chalk, limestone, and marble, produced by the sedimentation of the shells of small fossilized snails, shellfish, and coral.

MICP has been extensively examined for applications in self-healing concrete. In this process, calcium carbonate precipitation (CCP)-capable bacteria and nutrients are embedded inside the concrete. These bacteria are expected to increase the durability of the concrete by precipitating calcium carbonate in situ to heal cracks that develop in the concrete.

Through the use of 3D printing, Bernhardt-Barry wants integrate load-bearing mechanisms into the construction of soil layers, and apply calcium carbonate to bind them together. This process would involve gathering soil as a raw material on site and then enhancing its load-bearing ability through the 3D printing process. By adding calcium carbonate as a soil-binder, the researcher hopes to improve 3D printed soil layers' ability to bear weight.

By 2023, the researchers will complete a life-cycle analysis to determine the material’s longevity and if the material could be commercially viable. Then she will look for a commerial partner to take her product to market.



Posted in 3D Printing Applications



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