In recent years 3D printing has conquered markets all over the world. This technology has become so common and accessible that everyone can now buy and use a simple 3D printer that can produce polymeric elements of their own design. A broken flap from the TV remote control or a lost toy element are no longer a problem. At the industrial level, the technology has developed in different directions – we have advanced materials, better quality, larger workspace, new incremental technologies, including 3D concrete printing technologies.
The history of 3D printing with concrete, nowadays often referred to as 3DCP (from 3D Construction Printing or 3D Concrete Printing), dates back to around 2010, when the process called Contour Crafting using a Cartesian machine with concrete extruder was presented. The idea was developed by Dr. Behrokh Khoshnevis of the University of Southern California. Despite attempts to further develop the technology, many patents and the launch of the same name company, the technology was not adopted in the US and remained rather an attraction, while Khoshnevis himself focused on collaborating with NASA and researching the possibility of building automatically on the moon and other planets.
It was only in the last few years after the explosion of interest in 3D printing, at a time when construction prices rose, that the topic of 3D printing in construction came back. According to various sources, in 2020 the entire construction market will be worth more than $10 trillions, and the 3DCP market alone will be worth nearly $250 million with fast-growing tendencies. Along with these trends there showed up new startups interested in the topic. Currently, on the global market there are several dozen entities operating in the 3DCP industry, of which around a dozen operate in the hardware sector – the construction and implementation of printers for 3DCP. Growth trends for the 3DCP market are also confirmed by the growing interest of the leaders of the classical construction industry such as Strabag, Skanska or Vinci, who invest in the growing new 3DCP startups.
Despite the rapid development of construction, building materials and 3DCP technology, the 3D concrete printing industry still has a lot of challenges ahead of it. Currently, most companies operating in the 3DCP industry have mastered the extrusion of concrete mixes to a degree that allows the printing of small objects. However, this is still not enough for the needs of a larger construction industry. Firstly, there are no uniformly defined materials to be used in 3DCP, and the ones used by startups are their own recipes, which are most often a secret of the company. Not a secret, however, is that the extrusion of the material itself is already a demanding process – the mixture must be printable (printability) and pumpable (pumpability), and its consistency and parameters during printing and after printing must hit the right spot (sweet spot). These three basic parameters for a mortar are a challenge in themselves and require quality control, such as aggregate granules or proportions of ingredients to ensure the right consistency and parameters to allow subsequent layers to be laid.
However, even a perfect mortar and an excellent printing machine will not allow 3DCP to enter the construction phase of large buildings. There is a second challenge here – reinforcement and supports, which are essential elements known from classical construction. So far, none of the companies has proposed an effective method of automating the process of reinforcement of the printout and erecting supports and formwork enabling the printing of lintels, beams and ceilings. This is undoubtedly the biggest technological challenge in the 3DCP industry. The remaining milestones in the transition are related to legal and legislative conditions and social moods. At the moment, there are no norms, legal acts, certificates, permits or standards enabling the construction of buildings using the 3DCP method or the use of materials or prefabricated elements in construction. Appropriate steps in this direction must be taken to allow for automation of the construction industry. The same is true of the conviction of society, entrepreneurs and developers. Printing buildings is the inevitable future. It is estimated that with the 3DCP technology it will be possible to reduce construction time and costs by up to 50-70%, and the whole process will be much safer and more ecological. It will also allow for more design freedom and free shapes. Speaking of the 3DCP industry, everyone thinks about large construction and buildings, but it should be remembered that 3D printing with concrete is also, or maybe even most importantly, the construction of structures. While the common 3D printing of houses is still a distant topic, the printing of prefabricated elements (manholes, chambers, supports, poles), small architecture (benches, tables, fountains), or decorations (monuments, façade decors, stuccowork) is as achievable, right away. In this form, 3DCP technology is already building its position on the market.