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New concepts

Besides previous technologies, which are market-ready, there are a series of new concepts and on-going projects, which nowadays are being developed with the aim of pushing further the limits of asphalt industry. In this section, some of these are summarised with the aim of presenting an overview of the extensive and diverse innovation that is being developed nowadays around the world. Nevertheless, it must not be understood as an EAPA vision or statement about how the future of the sector should/will be.

Different companies have started to implement the latest developments in sensors and artificial intelligence into a new generation of smart construction machinery. These systems assist the operators in a wide range of tasks, obtaining higher accuracy and quality outcomes in less time and with less effort. Safety is also improved, as for example, there is no need to repeatedly get out of the machines cab to physically check grades or levels. These systems also prevent under-or-overloading and additional machine wear, making that the equipment is most of time working to its maximum efficiency.

A greater extent of this are the automated machines, which have capacity to maximise the accuracy and speed of the job and make easy for operators tedious and repetitive works. In addition, automated machines, equipped with vision systems, which allow them to detect humans and obstacles in its vicinity, are continuously under alert, follow more strictly the H&S rules and can work in dangerous places without endangering human lives (i.e. works on sloped ravines). For these reasons, reducing the human factor in construction sites might become an important milestone in H&S, significantly reducing the number of accidents and casualties in the construction sector.

Many brands have already developed different prototypes to carry out a wide range of construction tasks, such as compactors, dozers or dumpers. Some of them, are being already tested in pilot sites and quarries and may be soon co-working with humans in real spaces.

Autonomous concept tandem roller

At a more close-to-market level, intelligent equipment meant for repetitive operations, such as excavators, cranes or handling machines, have incorporated systems that learn a specific task when the operator does it manually by the first time and then the machine repeats it as necessary. This, combined with machine-to-machine communication features, allows processes, such as an excavator moving earth from a pit to a dumper, in a way that the operator does manually the first repetition and then the machine repeats the manoeuvre until the sensors detect that the desired level has been reached or the sensors of the dumper communicate the excavator that the maximum load of the dumper has been reached.

In addition, the combination of additive manufacturing (e.g. 3D asphalt printer mounted onto an automated and electric robot) and high resolution computer vision could lead to a new whole generation of machines able to autonomously construct new road layers or to drive down the existing road network in search of cracks or imperfections and repair these at a constant driving speed.

These machines could also support construction/maintenance operators by continuing the work beyond the bandwidth of the workforce employed. This would reduce road disruptions times and the exposure of un-repaired roads, which commonly produces the further deterioration of these.

Some prototypes, such as the flying drones developed at the University of Leeds, do not produce asphalt surfaces by following the conventional processes, but much more like a desktop 3D printer, which is not limited by any kind of space constrains. The use of these robots, able to identify, diagnose and repair street-works through minimally invasive techniques might contribute in the future to eliminate traffic disruptions in our cities. Other AI and robotic technologies are being developed with the aim of helping to keep workers out of dangerous working areas, such as highways, especially during high-risk times, such as night or heavy-traffic hours.

Self-Repairing Cities Project. Engineering and Physical Sciences Research Council (EPSRC), UK, grant reference: EP/N010523/1 [www.selfrepairingcities.com]

From the perspective of sustainability, switching from traditional diesel-powered machines and asphalt plants to equipment running with alternative energy sources, which produce near-zero exhaust emissions, is one of the main concepts being developed to drastically reduce the environmental impact of roads construction and maintenance. Another important solution are machines equipped with electric motors and batteries, which minimise not only exhaust but also noise emissions, improving working conditions and enabling them to be used at night in city centres, reducing congestion during the day. In this sense, some brands have already developed a range of electric compact excavators and electric wheel loaders with up to 8 hours of runtime and 80% charge in 1-2 off-board fast charging hours.

For larger excavators, these brands have developed hydraulic hybrid solutions, which utilise the boom down motion to charge accumulators and assist motors, which power the hydraulic pump.

Other alternatives being developed are equipment running on biodiesel, multi-fuel, hydrogen and synthetic fuels.

Different approaches are also being explored nowadays to produce asphalt mixes that self-repair when they get damaged. Hence, although these mixes have an increased initial cost, the extension of service life and the savings in maintenance operations could male them an economic, safe and sustainable option. One of these approaches consist on the addition of small portions of conductive particles to the mix. When the road gets damaged, the application of an external variable electromagnetic field generates microcurrents along these, which heat them up by Joules effect. Consequently, the viscosity of the embedding bitumen reduces and this expands through the cracks. As soon as the electromagnetic field stops, the bitumen cools down and the road can be used again with the cracks sealed. Another approach is the addition of capsules containing healing agents, which either release small amounts progressively with the loading cycles or simply open when cracks reach them. These capsules can be also used with rejuvenating agents to balance the ageing process in surface layers over the road service life. These materials have been already used in a few trial sections but the actual benefits and limitations over the whole life-cycle and under real conditions will have to be determined over the coming years.

There are also numerous research projects are trying to find alternative binders with potential to reduce the environmental impact of asphalt and the dependency on crude oil. These are mostly based on vegetable oils (e.g. linseed or rape), by-products of bio-fuels production, resins, lipids extracted from microalgae, etc. Their production at large-scale and the up-scaling of their use in conventional plants are still challenges to be solved but the encouraging results that are being obtained at laboratory level are rising the interest of many companies, becoming a potential solution for future roads.

Finally, one area of interest being looked at in Scandinavia is the use of penetration grade bitumens in advanced emulsions. The aim here is to be able to Cold produce high quality asphalt (with the same grading and properties of Hot mixes) while reducing environmental impact, energy consumption and safety risks.