Roads take us from A to B – that much we know. What most of us don’t know, however, is that they also have the potential to convert heat to electricity, to provide a source of light, to monitor themselves for damage, to divert harmful particulates away from the breathing space above them and much more besides.
In fact, the concept of the ‘smart’ road is more than providing Wi-Fi access or being able to open up the emergency hard shoulder as an additional running lane in times of heavy traffic. Smart roads, as perceived by specialists such as Shell Bitumen can bring wide-ranging societal benefits.
And professor John Read, general manager technology (bitumen and sulphur) at Shell International Petroleum is on a mission to help society understand the full scope of what roads are capable of providing, both now and into the future. Changing perceptions, he says will also ensure the company has “societal license” to continue its business in the longer term. To do this, he needs to engage with industry – and tunnelling is one industry sector in the cross hairs.
Currently, the typical tunnel road surface is essentially the same as any other, fulfilling the same safety and durability criteria. One key difference is the thickness of the road structure.
“Believe it or not, the only reason we build roads is because we can’t drive on the mud – if we could, we would,” says Read. “We build roads to protect the soil beneath and if you have weak soil you have to build very thick, strong structures in order to prevent them flexing and to enable them to carry heavy loads. “In a tunnel you have a concrete tube, which is a great base to build upon, so the road structure can be very thin.”
THINKING TUNNELS
That’s not to say tunnels haven’t featured innovative road surfaces and notable examples include those built with Shell’s Mexphalte C.
“Mexphalte C came from our research and development programme,” says Read. We developed a synthetic bitumen – it’s not refined in the same way you refine bitumen but is synthesised out of other components to mimic bitumen rheology.”
Recent applications of Mexphalte C include Luxembourg’s Grouft and Stafelter tunnels. These tunnels – 2.96km and 1.85km respectively – link the capital, Luxembourg City, to the north of the country and opened in September 2015. The contract specified the use of a clear synthetic binder for the production of coloured pavements for the tunnel sections of the motorway.
“The old Henry Ford adage of ‘you can have any colour you want as long as it’s black’ also used to apply to asphalt but colour can be used to demarcate areas,” says Read. “Also, when we pigment Mexphalte C with titanium oxide it produces a whitening effect. When that is used with a light coloured aggregate, the net effect is a very light coloured pavement. And if you have a light coloured pavement you need less lighting.”
This has obvious benefits in terms of reducing lighting maintenance and energy costs as well as improving safety. In the Grouft and Stafelter tunnels the Mexphalte C was used in combination with another technology, which enables the production of low temperature (LT) binders. The resulting product is known as Mexphalte C LT.
“One of the issues we have had in tunnels in the past, not just with Mexphalte C, but with all paving, is that the sprinkler systems are typically set at around 60 degrees Celsius and when you are paving with a material that is 150-180 degrees Celsius the air temperature increases pretty quickly – and of course the hot air rises to the top of the tunnel. There have been quite a few occasions where the sprinklers have been accidentally activated.”
The low temperature binder reduces the temperature by 30- 50 degrees, depending on which form of the technology is used, and is a real benefit, says Read.
“We also brought polymer modification into Mexphalte C LT,” he added. “This was initially developed for conventional roads in order to raise the performance of the asphalt and prolong its life. So we now have a highly modified low temperature asphalt that is light coloured, so you can reduce your ambient lighting and that lasts significantly longer than its predecessors.”
Mexphalte C and LT are technologies that have already been adopted but there are many more that remain in Shell’s research and development pipeline. Some are wedged there because of the absence of a clear route to market or simply by government bureaucracy.
RESEARCH AND DEVELOPMENT
Certainly Read and the R&D team at Bangalore (a newly opened, purpose built research facility that will eventually house up to 1,500 researchers in a state-of-the-art campus environment) are focused on extending the use of roads beyond their principal purpose of linking A to B. And the line the research takes is usually prompted by a series of “what if…?” questions.
“As an example, asphalt is usually black and it is well known that black absorbs heat,” says Read. “One of the reasons roads fail is through permanent deformation or rutting that occurs when it is very hot, because of the viscoelastic nature of bitumen. If you can take that heat away you can improve the longevity of the road – and heat is a form of energy so can you do something with that energy?
“There have been different ways of thinking. One was to create a big reservoir of water, which could be heated from the heat taken from the road and either used to drive a turbine or to provide hot water for people’s homes.
“That would offset the cost of generating electricity but the other thought was, could we convert the heat directly to another form of energy? Our research scientists found they were able to do that and demonstrated that they could generate seven watts per square metre. That might not sound like much but when you consider the number of square metres in a road system it becomes very big, very quickly.” Another major problem associated with road use that has been under the Shell spotlight is air pollution. The boffins at Bangalore have developed two technologies capable of addressing this issue, Active Active Asphalt and Passive Active Asphalt.
“A road surface is typically neutral or, if anything, slightly repellent to PM10 particulates that come out of exhaust fumes, so it either does nothing to them or pushes them slightly up into the air where they are suspended and people breathe them in,” says Read.
“We asked the question, was it possible to alter the charge of the road surface so that, rather than repelling, it actually attracts PM10 particulates?
“And that’s what we did. We developed a technology using a special type of fibre incorporated into the asphalt that physically changes the polarity of the surface so that PM10 particulates from the exhaust are attracted to it. They then sit on the road surface and in the normal course of events are washed away by rain or pushed away through the channels of the road.”
In the case of a rain-free tunnel, Read anticipates the particulates would be removed from the road surface by periodic cleaning or would be dragged out on the tyres of vehicles passing through.
“This is the theory,” he says, however. “We haven’t tried it in a tunnel yet.”
This development provided a stepping-stone to the next. “The type of fibre we used is also electrically conductive, so one of my bright sparks had the idea of finding out what would happen if we actually placed a charge across the material. “We made a big slab of the material in the laboratory, put a clear polythene bag over it, filled it with smoke and applied a charge. It cleared instantly – everything was attracted to the road surface.
“So we ended up with two forms of the technology. One was called Passive Active Asphalt, which was just conventionally laid on the road and it would attract particulates because of the change in the charge at the road surface and the other, called Active Active Asphalt, would clear particulates immediately if the charge was increased massively by placing an electric charge across the material.
“Our view was that this would be a fabulous product for tunnels,” says Read. “Wouldn’t it be great if, instead of having to have enormous ventilation systems and huge fans drawing [the pollution] out, you could just flick a switch once an hour and clear the air?”
Passive Active Asphalt was trialled in Trondheim in Norway in the late 1990s. Two parallel sections of the road were laid, one with conventional asphalt, the other with Passive Active Asphalt. “It was a misty day with mist right down to the ground, you couldn’t see Trondheim at all,” says Read. “But when we’d laid the Passive Active Asphalt there was a 6ft [1.8m] gap between the road surface and where the mist started and you could see Trondheim perfectly clearly. On the other side, with the conventional surface, the mist was down to the ground.
“The Passive Active Asphalt had clearly worked. In this case it had attracted water particles instead of PM10 particulates, but it demonstrated that the change in charge actually worked.” So why aren’t the obvious benefits of these road surface technologies in evidence today?
“The trial looked fantastic but then unfortunately all sorts of political changes happened in Trondheim and the surrounding area and for one reason and another we weren’t able to go in and monitor the road, even though we had built it,” says Read. “So I don’t know whether that was an instantaneous effect or whether it was something that would have lasted the entire lifetime of the pavement. And I don’t know whether it would have attracted 1 per cent of PM10 particulates or 99 per cent of them.” It wasn’t just Trondheim that threw up barriers to advancement in road surface technology and while bright ideas and nascent technologies abounded, there was no clear route to market.
“Shell is quite an altruistic company but there comes a point when you have to say, if we can’t make any money out of this, we have to stop and do other things. So all this work was put on the shelf and we re-focused our research.”
ATTITUDE SHIFT
Around two years ago, however, Shell noted “a sea-change in attitudes”. “The previous blocks didn’t seem to be there anymore. Highways England [formerly Highways Agency] had been formed as a ring-fenced governmental company that could make its own decisions about whether it wanted to run with this type of innovative technology.” Attention and subsequent legislation is also increasingly being directed towards improving air quality by reducing emissions.
“There has been a lot of legislation around the world with regards to emission standards and sustainability. However, it tended to only impact very big companies and major manufacturing sites, such as refineries. They didn’t ever really apply to a single asphalt plant, for example.
“But now, in Switzerland, they do and suddenly there has been a fiscal imperative to start to use more low temperature technology, to start to use more recycled material and so on in order to avoid paying a carbon tax.”
There is equal emphasis on lowering emissions elsewhere in the world. China is a prime candidate for technology that helps manage air quality, for example and in major cities such as London there is talk of applying levies to “toxic cars”. “Everywhere you look you can see fiscal drivers being put into place that will enable innovative technology to be brought in,” says Read.
He added that, at a worldwide political level, some traction had been achieved on action against air pollution.
“COP21 [the 2015 United Nations Climate Change Conference] was the first time China and America, the two biggest road builders and consumers of bitumen in the world signed up [agreed to limit greenhouse emissions],” he says. The other, equally fundamental change in attitudes, says Read, relates to cost. Those people who have wanted to wear the sustainability badge but have baulked at the cost are now more willing to consider paying the price.
“I’ve been working in this sector for 32 years now and this is the first time I have felt that attitudes are aligning with these new technologies and there is a chance of success,” he says. “Mega-trends”, such as reducing global emissions, are now driving some of Shell Bitumen’s research, as are specific requests from industry.
“The development of low temperature binders was a response to questions from industry,” says Read. “The emissions from asphalt are a rate controlled reaction – so for every 10- 12 degrees Celsius you can drop the temperature you halve emissions. If you can reduce the temperature by 30 degrees you can reduce your emissions eightfold – it’s as simple as that.” He added, however, that the reduced emissions were almost a bonus and that what had really driven the LT development was the fact that operating at lower temperatures meant the asphalt plant used less fuel and saved money.
“Yes, there was a cost in making the binders low temperature but it was more than offset by the savings in fuel. On top of that there was the benefit of sustainability, and that is why that particular technology took off in the last decade when all the others didn’t.”
Many more development ideas are springing from the blue sky thinking Read encourages the Shell Bitumen research team to engage in.
One idea being looked at is the possibility of charging electric vehicles as they travel, rather than at static charging points. “I know that Highways England wants to run trials to see if there is a way to be able to pass an electric charge through the roads that would charge a vehicle as it drives. We know we are able to convert heat from the road to electricity, so if we can convert that to electricity in the road, can we use the road itself as a charging body?
“This is just one of the ways we may be able to extend the work we have already done, increase its value to society and overcome the initial cost hurdle. You may be able to say to people, ‘you have to pay a bit more for the roads but you don’t need to fill up with petrol, you just charge your vehicle as you drive’. I think it would be quite an easy sell.”
Of course, even if the technology was available today, it could only exist in a patchwork system because replacing the road infrastructure takes decades. Resurfacing on the major network is every 14-20 years, while for the rest of the road network it is every 80 years.
However, Shell’s scenario planning looks up to 100 years in the future and for this particular potential solution it is thinking about what the roads of 2050 will look like.
“Yes, it’s a long time in the future, but it is all grounded in developments that are being made today,” says Read. Staying with electricity, other research is looking at the applications of piezoelectrics. Shell has worked with Pavegen, a company that has developed kinetic tiles that capture the energy of footsteps and convert it into electricity.
In Rio some lucky children are now able to play football in the evenings thanks to free floodlighting powered by electricity created by their own footsteps on the pitch during the day.
Aside from fostering the talents of Brazilian footballers, the piezoelectric technology is now being conceptualized as a means to inform local authorities and or contractors when a road is failing. As a road deforms or cracks, the piezo would give out a higher electrical current, which could then be converted as an indication of damage – it would be a really ‘smart’ road.
“Wouldn’t it be great if, instead of having to have vehicles constantly travelling around assessing the road condition, the network could tell you itself?” Read asks.
But that’s just an initial thought. Taking it a step further, could piezos generate enough electricity to run, not just half a dozen floodlights, but enough to feed into the grid?
“We just don’t know,” says the evercandid Read. “We clearly know that roads move every time a vehicle travels over it and that would generate a charge, but whether or not that charge when done millions and millions of times would be enough to warrant the cost of generating electricity, we don’t know.”
Another “warning” technology in development is a phosphorescent binder, which absorbs light during the day and releases it at night, and which could be used to imprint signs on a road. And another includes a system using Mexphalte C, which changes colour when the temperature drops.
“If the road is freezing it would change colour to warn drivers to take extra care,” says Read. “This would certainly be useful at the entrance and exits of tunnels.”
Meanwhile, titanium oxide, which reacts with nitrous oxides in the atmosphere to form nitrates that fall to the road surface to be washed away is being added to create “DeNox” paving. R&D ideas are clearly coming thick and fast and the start of 2017 saw Read’s team begin a new three-year cycle in which all the aforementioned technologies have been taken down from the shelf and are back in the research domain.
“One of the questions we are looking at is whether we can improve the delivery system, so that we can apply them to existing roads and tunnels without having to rebuild the entire structure. Another question is whether we can combine technologies.
“Certain things we know we could combine, but not everything. For example, we know we could apply the phosphorescent road surface technology alongside or inside Mexphalte C because that was the original delivery system developed for it.
“What we don’t know is if the ambient lighting in a tunnel would charge the photochromic pigments that we use to get the phosphorescent effect. Could a system work in a tunnel where the lights are turned on for half the time and that charges the road surface sufficiently for you to then turn the lights off for the other half, reducing the cost and the environmental impact of running the tunnel?
“Can we make a conductive asphalt with Mexphalte C LT and use the electricity generated in it to power the already reduced lighting resulting from the light surface? I don’t know. We would need to work with someone to trial that. Can we use Active Active Asphalt for tunnels and see if we can really clear the air and reduce the amount of ventilation needed? I don’t know because we have only looked at it in the laboratory so far.” Read is convinced that some of these technologies, or combinations of them, will be suitable for tunnels but what is needed now is more industry engagement to turn some of the questions into answers.
Thus far, Shell has had very little engagement with the decision makers within the tunnelling sector and that is something Read is keen to address – hence the call out to the industry in T&TI’s February issue.
A closer relationship would not only lead to further laboratory and field tests, dialogue would also ensure the company was aware of issues and opportunities to provide solutions. “Our customers are asphalt suppliers and while they speak to a main contractor, who then works with a tunnelling contractor, we are so far removed that we don’t know the correct routes to be able to have the necessary conversations.
“I know we already have products that we know work in tunnels and I know we already have products that we think will work in tunnels but I currently have no conduit to have those discussions. I think it would be beneficial to at least be able to understand what the true needs are and what we can do to help address them. It may be a lot, it may be a little – I just have no feel at this point because we don’t have those sorts of engagements.”
As an example, a recent conversation turned to fire protection.
“We’re not working on anything at the moment but we have developed fire retardant bitumens for the roofing industry in the past, because it has to meet very stringent fire regulations, just as the tunnelling industry does. “We could possibly use or adapt the technology we have already developed but we would have to look at what difference it would make versus how much it would cost. We do have solutions but we’ve never applied them in a tunnel. And this is exactly why we need to engage with the sector because we don’t necessarily know what its concerns and needs are.”
Ask Read what he thinks would constitute the perfect tunnel road surface and aside from the obvious “anything that contains Shell products”, he suggests combinations of light coloured and phosphorescent materials that would minimize the need for artificial lighting; porous, rather than dense, material that can absorb noise; and conductive material that can generate electricity to power any ambient lighting and ventilation that is needed.
“And if you could combine those with Active and DeNox technology so you can take PM10 particulates and nitrous oxides out of the air and improve the user’s experience of being in a tunnel, then that would constitute a perfect road surface. “But – at this moment I don’t know if you can combine all these things and I don’t know if all of them can work in a tunnel. So, in fact, I don’t think the perfect road tunnel surface exists or has even been thought of yet. “There is work to do”.
