The United States military has been systematically adopting 3D printing in multiple areas and agencies over the years, as the flexible technology is useful for multiple applications, ranging from battlefield operations and surveillance to lowering the logistical footprint of convoys and just making daily life a little easier.
The barracks was the result of a three-year Army program called “Automated Construction of Expeditionary Structures,” or ACES, which explored how to use 3D printing to create semi-permanent structures from concrete that was made with locally available materials.
At the time, Dr. Michael Case, the ACES Program Manager from the Construction Engineering Research Laboratory (CERL), said, “The ACES team designed, built, and validated an additive, three-dimensional concrete printing technology that is a real game changer. Unlike previous efforts, ACES can use up to 3/8″ aggregate in the concrete that is used. In addition, the ACES project paid particular attention to methods of reinforcing printed concrete, both horizontally and vertically.”
It seems the Army has been continuing its work with concrete construction – the agency was recently awarded US Patent #20180057405 for its new concrete mixture that can be used to 3D print buildings with the necessary structural strength, which will be a major asset when quickly built structures are needed in a war zone.
According to the application for the patent, which was filed two years ago, “The present invention is a printable concrete composition made from the combination of a solid mix, water, and various liquid admixtures.”
The US Army Corps of Engineers (USACE), which counts environmental sustainability as one of its main principles, works to strengthen the security of the US by building and maintaining the country’s infrastructure, and providing military facilities where service members can train, work, and live. USACE is on the front lines of using 3D printing to develop the means to rapidly construct buildings for both military and civilian operations.
While concrete is a non-homogeneous mixture that is more likely to clog up the machinery, cement is a homogeneous mixture that doesn’t have this issue. Many concrete compositions don’t work well for 3D printing buildings, but the patented concrete composition that the Army developed is not bound by the same limitations.
This new concrete mixture for 3D printing buildings is made by combining three major elements – water, liquid admixture, and solid mix, which can be transported and combined with the other two elements on-site in order to make the composition.
According to a blog post Patent Yogi shared with us, “The solid mix includes a binding agent, an aggregate, coarse sand, fine sand, a clay admixture, a fly ash admixture, and a silica fume admixture. The Aggregate, coarse sand, and fine sand are present in equal proportions, whereas, clay admixture and fly ash admixture are present in amounts approximately 8% and 5% respectively, providing increased flow-ability and reduced set time for printable concrete composition.”
The liquid admixture includes several other admixtures, including an accelerator, flow control, plasticizer, and shrinkage reducing admixtures; each of these plays an important role in the concrete mixture. While the flow control admixture is used to improve the flow and pumping of the composition at high pressures, the plasticizer one makes it possible to lower the amount of water used. The shrinkage reducing admixture helps to decrease any cracking and shrinkage during drying. Once the mixture has been made, a structure can be 3D printed without having to make any further modifications to the composition.
The Army’s newly patented 3D printable concrete composition makes it possible to construct building components that need a lot of strength – such as those that may be built on a battlefield. In addition, mesh can be embedded between the layers of the mixture in order to stabilize or reinforce structures. The military is a very mobile organization, and this new concrete composition could make it possible to rapidly produce shelter on an as-needed basis.
This technology could also be very useful in 3D printing office buildings and homes, along with emergency housing shelters. The inventors of the Army’s new concrete composition include Ghassan Al-Chaar, Michael Patrick Case, Gerald R. Northrup, Megan A. Kreiger, Bruce A. MacAllister, and William Jacob Wagner.
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