Supporter: Shell

Author: Alex Conacher

Rebuilding a racetrack requires precision timing, immense coordination and a lot of trust between everyone involved. Circuit Zandvoort, the iconic post-WW2 racetrack in the Netherlands was no exception. Beloved by fans of all flavours of motorsport, it recently redesigned and resurfaced its track in the hope of hosting the first Dutch Grand Prix since 1985.

To do this required the design of some of the steepest banked corners in the world, the construction of which pushed the supply chain and the equipment to the limits. In fact there was so much to coordinate, that the project team described it as a ballet. Multiple types of machinery operated in concert, balanced at a precarious angle just so they could do the job. The site was blasted with wind, rain and sand, such that it could be simultaneously wet while being swept with wind-dried sand that could form dunes. Materials were supplied from manufacturing sites overseas, timed so that they would arrive at the perfect temperature. If the schedule slipped, the trucks would be carrying waste. Effective choreography of all of these moving parts was critical for the job to be a success.

Timing critical

“Circuit Zandvoort is known as one of the circuits that built after the war,” says Niek Oude Luttikhuis who is responsible for all the construction and maintenance works on the circuit. “And it still exist as an old school racing track. It looks like most of the circuits you will find in England. Still, a lot of gravel runoffs. Yeah, how do we call it… ‘cosy’.” 

The course runs for 4.2km and has 14 turns. “Not a real huge circuit, as you’re seeing in Shanghai or other Formula One circuits, but what makes it so special is it’s one of the few tracks I think, maybe the only track in the world that goes through the dunes. And that makes it very special and beautiful.”

Lateral thinking

Beautiful, but it is constrained by housing and the natural environment surrounding the coastal course. But Niek says this is not unusual for Holland where thinking outside the box is normal and was required if the team were to bring the Dutch Grand Prix back to this beloved, undulating track, nestled among the windswept dunes. “Formula One Management was looking if it was possible, to get the Formula One driven around here. And one of the biggest issues we had with them was the straight.”

Modern Formula One cars have the driver operated DRS or ‘drag reduction system’ consisting of an adjustable bodywork flap on the rear wing of the car that can be opened up to reduce drag and give the car a speed boost at the expense of downforce, which allows them to corner better. It requires a long straight section of the course to be safely opened up. “And we don’t have that,” says Niek. “We have environmental issues on both sides of the circuit. And therefore we couldn’t lengthen, or change the circuit as a layout.”

But there was still a way that DRS could be used, which made the very last turn, turn 14 very special. 

“The DRS could already open in the corner but the G forces with the system open with a Formula One car can have is the maximum of 2.5 G’s.”

All of the virtual testing showed that the G force would be greater than this in some corners and then they had a brilliant idea, one that would reduce the G force and make the track one of the most exciting on the racing calendar. “We came up with the idea to bank the corner.”

Steep gradient to lower G Force

With a corner on a sharp enough gradient, the G-force would no longer be purely horizontal, but would be directed partially into the ground. And the cars would be able to open up the DRS, giving the spectators the chance of seeing a dazzling overtake at speed. It was something that had never been attempted for an F1 track before and it would require special permission from the FIA, the ‘Federation Internationale De L’Automobile’, whose guidelines suggest never exceeding 10%.

And this is before the physical challenges of laying a road at an angle that could be as high as 35 degrees in places. They wanted to accomplish this with standard equipment that was not designed to be used on a slope. “Gravity was not our friend at that moment.”

So they approached Jarno Zafelli from designer Studio Dromo, which had experience redesigning another particularly exciting racetrack: Silverstone, in the UK. “It was a real challenge for a lot of reasons. We said okay, we will never do something as complicated as Silverstone,” says Jarno.

But then came Zandvoort. “Zandvoort was between dunes on the seashore. In the winter, that is a mix of the worst things that you can imagine. So you can have freeze, you can have snow you can have wet, you surely have rain. Wind, wind, wind, a lot of wind and sand blowing everywhere because as soon as you start the worksite, you have sand everywhere is not is not enough to have it wet. Because the problem is that the wind dries the sand on the surface, and then the sand is just blowing everywhere. So not content with this. we have loads of water coming from the bottom. Because the sea level, you know, is very high.”

Investigating solutions

High groundwater is fact known to every construction project ever undertaken in the Netherlands. But the biggest challenge here was the unusual banked corners. “So the challenge we got is that the concept from Zandvoort was quite was quite demanding because they came up with this idea of using bankings. We were working with banking since 10 years ago. But we never got the opportunity to have a banking built in a proper Formula One race track.”

Not only did they have to design something new, they had to convince the FIA that it was safe and appropriate for F1. “The problem is that FIA at the time was asking for 10% maximum of lateral inclination. Not only this, the reason why they’re asking 10% of inclination is mainly because on a construction perspective, you cannot build something with regular machine more than 8- 10% of lateral inclination.”

The team at Zandvoort had to convince the F1 community that banked corners would work. Meetings with the FIA, and with tyre manufacturer Pirelli were set up, simulations were done and

“We got some confirmation that to have the DRS open, we need minimum 15 degrees,”

In other words 15 degrees is just over 32 percent. Was it even possible to build? “Is the contractor able to build something like that? Is the mix design able to be stable at 15 degrees? What if we’re going steeper than 15 degrees, because actually, we went up to 19 degrees,” says Jarno

This is over 34 percent. They knew that for an asphalt racetrack, the very steepest inclination in existence was at the Daytona Speedway in Florida. “It is 32 degrees in Daytona, and 30 degrees is the real maximum. But to have also 19 degrees as we did, it is roughly 34-35% of inclination instead of the maximum 10% of the guideline were saying before, we had to do something with a contractor and on the mix.”

Track surface critical

The mix, or the asphalt which acts as the surface layer of the racetrack. Getting this right also enabled other innovations. “We said as a designer, okay, the track is beautiful, but we can improve it. We have special machines, we have special skills, we have a tight, tight time frame and a mix that will be designed for the last corner, what not, why not do some of the other corners like that,” says Jarno

And that is where the idea of the Hugenholtz corner or turn number three, was born. This corner also needed to be moved for the new circuit layout. This corner was originally named after John Hugenholtz, a legendary Dutch racetrack designer who passed away in 1995. He is considered one of the greatest, if not the greatest track designer of all time, and a hero to Jarno, who went on something of a pilgrimage to meet his son and racing driver, Hans Hugenholtz. “He was quite sceptical, but we were good enough to explain the concept and he was enthusiastic on that concept and he couldn’t believe that we were going to do something like that. But in the end, we did it,” says Jarno. 

The team had convinced all of the right people. Next it was time to deliver and this is where particular attention fell on the road surface. “The only way to be sure that the mix works is testing, testing, testing and testing selecting, we passed the almost three months to select the material to understand, which was the right bitumen to be used.”

The team also faced a hard deadline of the end of February, meaning construction of the mix was happening in the middle of winter. “What was important was the work in the lab. So all the material were tested in our labs and tested against each other to try to understand also which was the better compatibility, chemical compatibility between the materials that we had different kinds of bitumen different kind of aggregate, different blending, different mixtures, and testing a different temperature. Because in the end, you have to think that when you are designing a surfacing for racetrack, you have a lot of things to consider,” says Jarno.

So, it can be compacted properly. The asphalt needs to be workable and transportable, but also needs to meet the complex requirements of the surface. “A road is indeed made of bitumen, but it’s not only bitumen,” says Jean-Nicolas Desprez, from Shell. “A road is a mixture of aggregates sands and bitumen and the idea is that bitumen will act as a binder for the different elements in order to make it agglomerate all together. And the bitumen will also bring elastic properties. It will viscoelastic properties it will bring a certain resistance to deformation and to come back in position which will help the road to be able to withstand loads to deform and to also come back in position without fracturing or breaking like what can happen with stiffer material.”

Grip is everything

The most important aspect for the racetrack is to have a good grip, “You want to ensure that in fact your car take a corner at high speed. So, grip is really one of the key elements of a racetrack,” says Jean Nicolas. “Now, if you talk about grip, what will happen is that you will have also a lot of shear force applied on your road.”

Shear force is the pressure exerted by race cars on the road surface as they break and turn. Shear force resistance comes from the bitumen. “The sheer force resistance will be many brought by your bitumen by your binder, which will ensure that it will be cohesive enough to maintain all these aggregates together,” says Jean Nicolas.

Bitumen itself comes from crude oil processing. So, the first element that you that that you are using in order to produce bitumen is crude oil, which will go through a refinery and you will get many distillation steps. This ‘base bitumen’, or ‘penetration grade bitumen’ can be used for most applications. But a racetrack is not just any application and the bitumen is modified with polymers and chemical additives to further improve performance and make sure there is not deformation from the cars or bikes that race over it. It also means it can withstand higher and lower temperatures. “One of the main differences between a penetration grade and a polymer modified bitumen will be the elasticity of the two products,” says Jean-Nicolas. “One test that we carry out is elastic recovery. For this test, we take a sample of a given length and we pull on it to a length of about 200 millimetres. Once done we cut it in two and after 30 minutes, we measure the length of the sample. While for penetration grade, you may even not be able to deform it up to 200 millimetre because it will break before with polymer modified bitumen, you will deform it to 200 millimetre, and after 30 minutes, it will have recovered almost its original length meaning that you will get an elastic recovery close to 100%.”

In fact this can be even higher for PMB. “You can reach lengths of 400, 500, sometimes even 600 millimetres before it breaks,” says Jean-Nicolas. 

Synthesising the PMB is done in a specific unit at the production site and left to mature for a fixed time depending on the mix. “You will have a maturation time the maturation time in fact will be used to really close a polymer to develop a network inside the inside the pitchman and to really connect to the different molecules in the in the bitumen and to get a strong network which will improve drastically its elasticity and the performance of bitumen.”

But as well as getting the highest performance from the bitumen the site temperature was a difficult constraint. “Zandvoort has been laid on during winter and laying down a bitumen during cold weather is something which is very it’s more difficult because in fact you will have your asphalt mix which will start to cool down faster. And once you start to cool down the workability of the asphalt is not as easy as when you’ve got a hot asphalt mix,” says Jean-Nicolas. 

The team had to find a compromise between the requirements of Dromo in terms of resistance, which would increase the viscosity of the asphalt and on the constraints of the contractor KWS. “The idea was really to ensure that they can have a workable asphalt mixture that they can apply and they can compact in order really to get the void contents that Dromo was looking for.”

Coordinated delivery

On every sophisticated road project, there is a dance between the contractor, designer, owner and supplier to make sure that the requirements of each are satisfied, which means the mix is reformulated, tested, adjusted, reformulated again and again. And Jean-Nicolas just mentioned another challenge. The ‘void content’ relates to the amount of compaction that the road surface is subjected to. And in order to make sure that you can compact properly the contractor must be able to control the temperature at which this is carried out. “You can also answer workability by using different type of additives, which will make the asphalt more workable at lower temperature, but still once it’s cold, keep it’s interesting characteristics and its performance,” says Jean-Nicolas.

If you are wondering what these additives and polymers are you will unfortunately have to keep wondering. The exact combination is a secret recipe.

Finally there was one remaining challenge for the road getting the material to site, at a workable temperature, in the bleakest of winter weather. This very specific binder was coming from Stanlow near Liverpool in the UK.  Again this was all about timing. 

On time to the local asphalt mix plant, which Jean-Nicolas says is itself a fair distance from Zandvoort. When transporting this material you need heated trucks at a temperature of 170 degrees Celsius, and if delayed the mix could lose more than 10 degrees per day. Coordination and timing are therefore vital. “On the construction site, you’ve got the ballet because you need to get the asphalt tracks coming over offloading to the finishers behind the finishers, you will get the compactors in order really to make sure that everything is even, you need to get a continuous supply,” says Jean-Nicolas. “But to be able to make this happen you also need to get to continuous supply of bitumen. And being done from UK to the Netherlands was indeed an additional challenge. But a lot of coordination has been done by the operation team. And they’ve been able to really deliver all the product with no undue delay and all the product was perfectly on spec.”

True proof of the success of the newly redesigned Circuit Zandvoort will be from the F1 drivers when it finally hosts a Dutch Grand Prix, although local racing superstar Max Verstappen has tried Zandvoort out along with lots of other drivers from other racing series. “Everybody was afraid we would ruin the circuit,” says Neik. “But we did the opposite.” 

The feedback has been fantastic, which is good as there was a lot to live up to. The course is known to local fans as the Dutch roller coaster, and is now living up to that reputation even more.And although the racetrack may indeed be a Dutch rollercoaster, the design and construction work to make it so, was more “like ballet,” says Niek. A ballet that was perfectly choreographed and elegantly delivered.