Jun 26, 2018 | By Thomas

The U.S. Army Corps of Engineers (USACE), a federal agency under the Department of Defense, has developed and patented a 3D printable concrete composition that provides high structural strength for building components.

Credit: US Army Engineer Research and Development Center (Photo by Mike Jazdyk)

3D printing has been around for more than 30 years. But now, with the development of new printable material, it's possible to build increasingly more complex parts and products. USACE is at the forefront of developing 3D printing technologies for rapid construction of buildings for military and civilian operations. However, a significant limiting factor for 3D construction projects has been the requirement to construct buildings of concrete rather than cement.

Concrete is no-homogenous in nature, however, concrete derives its strength from the presence of “aggregate” of rocks and stone. Because of its non-homogeneous composition, concrete has a high tendency to clog machinery. Cement is a homogeneous mixture that does not clog machinery, but does not have the structural strength required to ensure buildings will not collapse under stress.

US army therefore invented a printable concrete composition made from the combination of a solid mix, water, and various liquid admixtures. The solid mix includes quantities of aggregate, coarse sand, a binding agent, and fine sand. a clay admixture, a fly ash admixture, and a silica fume admixture. The Aggregate, coarse sand, and fine sand are present in an approximately 1:1:1 critical aggregate ratio, whereas, clay admixture, fly ash admixture and silica fume admixture are present in amounts approximately 1.5%, 10% and 5% respectively. This solid mix may be prepackaged for later combination with the water and liquid admixtures on-site to form printable concrete composition.

Liquid admixtures include flow control, plasticizer, accelerator and shrinkage-reducing admixtures. The flow control admixture controls the rheology of printable concrete composition by altering its viscosity. This improves the flow and pumping of printable concrete composition at high pressures. The plasticizer admixture allows a reduction in the amount of water used in printable concrete composition, by increasing dispersion of the components of printable concrete composition at lower levels of water. The shrinkage reducing admixture reduces cracking and shrinkage of composition during drying, whereas, the accelerator admixture decreases the set time and increases the strength of printable concrete composition.

Credit: US Army Engineer Research and Development Center (Photo by Mike Jazdyk)

This new printable concrete composition allows 3D printing for constructing building components that require high strength. Once the printable concrete composition is prepared, a user may print a structure without further modification of the composition. Users may embed mesh between layers of the printable concrete composition to reinforce or stabilize the structure.



Posted in 3D Printing Materials



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yzorg wrote at 7/2/2018 4:59:33 PM:

US Army "Invents" .... :)

marc wrote at 6/29/2018 10:47:11 AM:

i wonder if layer adhesion is a problem with concrete? otherwise shoot little steel wires through 2 layers to make them stronger, like the wire fibre concrete

Skip wrote at 6/27/2018 2:59:18 PM:

You could also print with infill between outer shells giving both much increased strength and also insulation. If they would trowel it as the layers go up, it could have a decent interior and exterior finish too.

Dean wrote at 6/27/2018 5:07:20 AM:

The two links on this article just point back to this article.

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