Heijmans : Wishes for our road surface

Bitumen is an important constituent of asphalt; it is a residual product from oil refineries, which holds the sand and crushed stone together. However, bitumen supplies are likely to run out because refineries are increasingly retaining bitumen for higher-quality products like fuels and oil. Bitumen is thus becoming increasingly valuable - another reason to increase recycling. Replacement using materials with a different basis, like bio-based binding agents, is also being explored.

Although Gerbert does not think the bitumen supply will run out, he and his colleagues are working hard to rejuvenate old bitumen. 'Bitumen in old asphalt is crumbly and stiff; it loses its elasticity. We recently developed a process where we mix asphalt with aged polymer bitumen; this is the highest quality means of recycling.'

Gerbert should not be seen as some kind of sorcerer, slaving away over a cauldron in an effort to find the best recipe for a magic potion. 'Often you'll come up with ideas by sparring with one another, not just sitting in your lab. That's why I enjoy talking and discussing with other asphalt experts, which always produces solutions.'

This is why we regularly collaborate with the Rijkswaterstaat. 'As a contractor, we serve as an intermediary between theory and practice. We must be able to try out innovations once lab tests have been completed. Test sections on real motorways are thus extremely important to us, and the Rijkswaterstaat is instrumental in facilitating this.'

Even though Gerbert and his colleagues simulate all manner of realistic situations in their asphalt lab, clients prefer to have results from experiments performed 'in real life'. Gerbert: 'The proof of the pudding is in the eating. That's why I like clients who are open to experiments. You'll even find them at local authorities, like in Ede, where we were allowed to lay Recoflex on various unsurfaced roads. The best ones are asphalt enthusiasts like me, who organize tenders so innovations can be validated. That's when we often get results.'

Noise nuisance is one of the biggest sources of irritation among the Dutch population. Quieter asphalt is becoming increasingly important, partly because cities are getting closer to motorways. The fact that double-layered porous asphalt is twice as quiet as single-layered porous asphalt is remarkable progress, but Gerbert believes we still have some way to go.

'People perceive abnormal noise to be a nuisance, like when one drives over expansion joints. We have found an answer to this issue: the Brainjoint. Results of the Stille Duurzame Voegovergangen ('Silent Sustainable Expansion Joints') contest, organized by Rijkswaterstaat. This shows how one innovation - double-layered porous asphalt - can encourage another.'

Sustainability is a criterion in a more and more tenders. By 2030, our road network must actually be energy-neutral. Heijmans has responded to this deadline with Greenway LE, low-temperature asphalt. Gerbert: 'But asphalt with lower rolling resistance is another option, and will help to reduce fuel consumption in cars. If asphalt is more even and more porous, it becomes easier to expel compressed air in the contact area between tyres and road surface.'

Gerbert and his colleagues are currently working on an ultra-quiet asphalt, which will help to further reduce noise thanks to the rubber in the road surface. In the end, cars will make almost no noise whatsoever. Thus plenty of benefits for the environment. The only thing asphalt cannot do at this moment in time is absorb particulate matter. Gerbert: 'There's too much of it in the air relative to the available road surface.'

Despite his passion for producing and laying asphalt, Gerbert expects these processes to change. Digitization will also offer advantages in the asphalt supply chain. 'In the past, you often had to rely on experience and gut instinct, but automated controls can now do a much more accurate job.'

Innovation requires knowledge and insight into how materials and products work, as well as knowledge of practical situations and the 'market'. Gerbert has been transferring his knowledge to several colleagues for quite some time. 'Not just technical knowledge, but also the mentality needed to innovate. Having the courage to go against the grain.'

Self-driving cars and motorways that generate energy - Gerbert hopes to experience all such innovations. 'In Den Bosch, buses are already able to charge themselves via induction whilst stopping', he says enthusiastically. It will not be long now. At present, everything situated on, over and next to the road is still an important source of information for motorists, but signs and markings will disappear.

Gerbert continues his musings: 'Eventually, all road traffic will be controlled by one big automated, monitored system. Software will direct you to your destination. If we can build that, plus a road surface on which you can charge electric vehicles, then we'll end up being a transport provider rather than a road authority or contractor.'