Construction 3D printing is booming, with hundreds of new applications emerging all over the world. The variety of solutions sometimes makes it challenging to understand exactly how materials need to behave to enable large structures to be 3D printed. In a recent video published on his channel, Jarett Gross, a Youtuber specializing specifically in this area, explains in a very clear and highly documented manner the rheology of construction 3D printing involved. If you have a direct interest in construction AM, as many of our readers do, or if you are just curious, it’s definitely worth watching.
Rheology is the study of how materials flow so that is the science being applied to concrete made for printing. Jarett gathered this information to simplify some of the material science behind these forward-thinking disruptive construction methods. These materials range from nearly free adobe mixtures of dirt and straw to ultra-strong and highly engineered custom concrete hybrid mixtures that can be cost-prohibitive with respect to affordable housing.
Currently, most groups automating large forms are using unique mixtures of concrete engineered to have properties conducive to a sturdy structure. The material needs to take hold immediately after exiting the machine. Generally, that is either achieved by a stiff mortar or a thinner mix with an accelerant added at the point of extrusion to cure the concrete faster and achieve angles that gravity would otherwise not permit (and no supports can be used).
Thixopotry is a property that allows a mixture to flow when it is being moved but remains firm after it has been placed so this is behind many of the developments in this space. Some of these mixtures include various forms of internal supports (which Jarett will cover in upcoming videos), others are strong enough to support themselves (like the recent project in Brazil by InovaHouse3D). Other companies like Twente Additive Manufacturing spray an accelerating admixture on the freshly printed layer to give it enough strength to print on angles, even capable of printing arches.