Three-dimensional printing in construction has become, if not casual, then an increasingly common phenomenon. Annually new developments in this field are demonstrated at the world’s leading exhibitions; demonstrational videos showing the process of printing both individual building fragments and buildings as a whole, gather millions of views. But what about the introduction of 3D printing in road construction and repair? Let’s figure it out.
Potholes, cracks, chipped strips… While for the road workers the elimination of these phenomena represents a daily effort, for motorists they can become not only the cause of damages to a vehicle, but the cause of accidents, a threat to health and life, both drivers and pedestrians. Therefore, prompt and scheduled repairs, as well as timely replacement of the road surface is not only an important task, but is literally vital. And such a pun, given the state of roads in a large number of Russian regions and the related statistics of traffic accidents, sounds not at all that fun…
Obviously, both road repairs and road construction require innovative technologies that would improve the quality of the coating and make the repaired sections of the roads more safe for traffic. One of such technologies, which is being actively experimented in different countries today, and, first of all, in the USA is the use of three-dimensional printing, both for filling damaged areas with asphalt concrete, and for creating large sections of road surface. A man with a textbook American name, John Smith, developed a brand new printer-asphalt paver for repairing roads. In order to implement the idea, in 2015 he founded the start-up Advanced Paving Tech and collected funds sufficient to further work on his invention. In addition to a group of like-minded people, John Smith attracted the specialists of the research center of the University of California in Davis to improve the printer-asphalt paver. Thanks to this cooperation, Smith’s road repair machine must learn to print better, faster, more accurately, more economically; The issue of sustainability of a new method of «road printing» is also taken into account.
How exactly does an asphalt paver work? There are three stages in his work. On the first one, it scans the geometry of the damage with a three-dimensional LIDAR — for example a road crack. Then, using a special computer program, a virtual road map is simulated. And, finally, stacks according to it asphalt concrete layer by layer, using the technology of multi-segmented variable screed.
Speaking about the advantages of the new method of road repair, first of all, it is necessary to note the denser and smoother layers of the material laid into the pothole compared to conventional road repair methtods. In addition, no special preparaiton of the road crack is necessary except for some basic cleaning — this reduces repair time. Another important point — the amount of special equipment for this method is just one unit- this is actually the printer-asphalt paver produced by John Smith’s company.
Interest in innovative development was shown on both sides of the Atlantic Ocean. In particular, among the interested companies — Transtec Group and Century Construction, holders of patents for the manufacture of road repairs in the United States and the European Union.
Impressive? Yes, certainly. However, in North America, most of the roads are made of concrete — and there are many such in Europe; in recent years, interest in road surfaces from concrete canvas is growing in Russia as well. For laying millions of kilometers of such road surface the aforementioned device is not very useful: it can not lay large sections of the roadway efficiently. Strictly speaking, it would be more correct to call it a «road repairman» rather than an asphalt paver… But there already exists a concrete paver: this prototype road construction machinery was also presented in the United States, at an event called the International Manufacturing Technology Show. The innovative 3D-concrete paver is able to print kilometers of roads from a mixture of concrete and polymer resins. Such road surface are characterized by great resilience, resistance to vibration and the effects of precipitation and ice. The service life of such coatings is much greater than that of the existing ones; for this reason, the American specialized press has already dubbed the printer-concrete paver developers «the creators of immortal roads». Perhaps the press was also inspired by the very name of the project: it’s called Infinite-Build, something like «eternity» (not implying the actual road construction time!).
The printer-concrete paver, following the instructions of the computer program, puts the layers of concrete — the higher the layer, the more polymer resins are added. But the integrity of the roadway is not a hindrance, but rather, on the contrary: microcracks, faults, patches, heterogeneous density areas are minimized and after drying out, it becomes resistant to strong and diverse loads. In addition to all the advantages listed above, such a coating can provide a stronger grip on the wheels of the car — and the markings applied to it will be, figuratively speaking, eternal. Prospects for savings on repairs for owners of such a road are also very tempting.
Developers of Infinite-Build expect in the coming twenty to thirty years to modify two-thirds of the road infrastructure of the United States — not only roads, but also infrastructure — tunnels, bridges. The potential of the project has already attracted the interest of the Rockefeller Foundation.
However, what is good for the federal government is not so good for others. The prospect of creating «eternal» roads, bridges, tunnels and other printer-concrete paver, controlled by a computer program, will deprive many thousands of specialists — road-builders, special machinery and repair equipment operators… perhaps only those dispatchers watching the cars, and serving brigades, very small in the scale of the country. Many of those who could act as investors for Infinite-Build are not attracted by such a prospect. Some experts are of the opinion that the printer-concrete paver will find recognition in Europe rather than in the States. Let’s add, in Russia, where the support for the concrete roads has recently noticeably intensified, this technology could also be an application.
Of course, fundamentally new types of machines for road repair and paving, no matter how innovative they are, will not solve the issue of the transition of motorways to a fundamentally new realitty. As is evident from the example of the Infinite-Build project, new materials must meet new machines. And there are many such materials in the world. Not being able to cover even the most promising of them in a single journal article, we list here only a few of them. All of them were mentioned in the framework of the review of the respected magazine «Popular Mechanics».
The first of these is the Durawhisper road surface, which makes it possible to build noise-suppressing and, at the same time, relatively inexpensive highways (if compared with those protected by soundproofing shields). According to this technology, asphalt concrete is mixed with rubber chips — as a result, a surface is obtained that absorbs most of the acoustic vibrations. The preparation of tons of such a mixture makes it possible to solve the urgent issue of disposing unnecessary rubber — primarily automobile tires.
The issue of ecology mattered for the developers of another product — the Duraclime road surface. Lafarge’s goal was to create a road surface that, even during and immediately after laying, smells less and not as dramatically as most asphalt concrete. But this is not the most pressing issue being solved. More importantly, in the production of Duraclime, less oil is used — and the price of the finished product does not exceed the cost of asphalt concrete, prepared according to standard technology.
Another innovative material is Lafarge — porous coating of asphalt or concrete, capable of absorbing atmospheric precipitation. The water thus collected, passing through such a road surface, is cleaned to a certain degree and, collected by a special drainage system, can be used for various purposes. While the implementation of this technology is quite expensive — and the developers are researching cost reducing methods for the material. And at the same time they experience coverage in natural areas, where there are strong seasonal frosts. At the same time, today the system based on porous concrete or asphalt concrete will be effective and at the same time economically justified, for example, for parking lots or pedestrian paths.
A separate topic is coatings, completely or mostly consisting of products of secondary processing. About such products you can talk very, very expensive — which, in fact, ecologists do, by omitting questions of profitability and performance characteristics or reducing them to the level of secondary ones. Nevertheless, in this area of pavement production, there are truly successful, balanced products. Such, for example, as Vegecol. The technology for the preparation of this mixture is the North American company Canadian Road Builders Inc. developed on the basis of 100% vegetable raw materials.
And, finally, in conclusion — an example of the application of innovations, not directly related to either special equipment or raw materials — but, undoubtedly, their complement. Specialists of the design bureau Alberta Roadbuilders & Heavy Construction Association hold the opinion that engineering calculations based on modern models allow to ideally build interchanges, intersections, multi-level lines, not only reducing traffic jams and reducing distances to optimal ones — but also significantly saving on materials and operation of road construction equipment. And in this, Canadian engineers are absolutely right.