BACKGROUND
Most 3D printing systems sequentially apply their layers from above. Such systems have distinct challenges when creating vertically reinforced concrete structures such as walls or columns. Most vertical reinforced concrete structures contain reinforcing bars that give the structure strength after the concrete has cracked. It is possible to use other methods of reinforcing, such as internally mixed fibers, placing reinforcement inside of previously placed concrete, or reinforcing the structure externally. Methods which do not place concrete around pre-placed reinforcement bars have significant challenges. The fibers in reinforced concrete are discontinuous and they do not provide the ductility that primary reinforcement can provide. Also, these fibers require the concrete mixture to be significantly adjusted so that they can be placed. This makes them challenging to sequentially stack. The use of 3D printing to make a support structure or formwork to contain other steel and concrete requires additional multiple steps to create a structure. Also, there may be concerns about the bond between the concrete used for the forms and the concrete used to fill the cavities. The external reinforcing for a structure will be subjected to the environment and fire. This can weaken the reinforcing and cause the structure to collapse. For all these reasons, a reinforced concrete structure with internal continuous reinforcing is recognized in the engineering community as an economical, effective, resilient, and safe structural system
SUMMARY OF TECHNOLOGY
OSU Researches have created the only system in the world that can produce code compliant vertical concrete structures without formwork. Searching “3D Concrete Printing” will result in literally hundreds of videos and articles about systems that use a specialized mortar mix placed like conventional 3D printers (whether gantry or pedestal based systems). Our system utilizes what is notionally conventional concrete mix with some special additives that enable it to be “printed”, and producing vertical structures with embedded conventional rebar. This work introduces a 3D printing system that can place and consolidate the concrete for a vertical member such as a wall or a column. This system does this by delivering concrete horizontally to a preplaced reinforcing cage. The printing system does this by using a special concrete mixture with a high amount of cohesion and a traveling forming and finishing subsystem that is part of the delivery sub-system. As the delivery sub-system is moved along the printed surface, the traveling forming and finishing sub-system consolidates the concrete around the rebar and places the finish on the concrete. The traveling forming and finishing sub-system allows all of this to be created without the need for conventional formwork. This system provides significant savings in formwork, time, materials, and labor to create vertical concrete members.
Video of technology in action.
POTENTIAL AREAS OF APPLICATION
- Construction (concrete applications)
MAIN ADVANTAGES
- Allows multiple devices to turn into a 3D printer (ex. a forklift)
- Low cost compared to other solutions offered in the market
STAGE OF DEVELOPMENT
- There is a Working Model for this technology.