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Question for the techies among you. Please reply as if to a ten year old as my tech knowledge is low!

Driving on the motorways in the rain in the Netherlands is generally a relatively stress-free affair as there is virtually no spray, even in the heaviest rainfall, due to the use of Z.O.A.B. (Extremely Porous Asphalt). It's very smooth, very quiet, and visibility is improved substantially over traditional asphalt used elsewhere.

So my question is: why don't they use this on race tracks? I appreciate street circuits would be different, but wouldn't permanent tracks benefit from a surface where even heavy rainfall would not present a safety hazard? Is there some other property that would make it otherwise unsuitable for the rigours of racing?

I know that it can be problematic in ice and snow, but AFAIAA most F1 tracks don't operate in those temperatures anyway. I understand it may offer greater dry braking distances, but again I should have thought tyres may compensate for that. Is there another technical reason, or is it basically cost (my understanding is that it needs replacing more frequently)?

Cheers in advance

Edit: I hope this is the right forum! Thought as it's technical it might belong here. Apologies to the Mods if not so

I have left this a while before replying as I am surmising, not speaking from knowledge.
I think it is due to the undersurface rather than the top layer its self. The shape puts a crown below the top layer that flows water to the margins and drainage. There is also a loss of cohesion of the top layer, which causes pile up when a high load is put through "grippy" rubber, as in high acceleration or stopping as the "lumps" are not bonded as tightly.

There is a similar surface made of broken glass which was tested in my area, but despite being hard wearing and good drainage did not stay in place on the substrata so was abandoned.


(If anyone cares to tell me I am talking rubbish, please do, I will not argue, but do not like posts with out replies)

Edit

By "pileup", I mean all the material pushed into a lump or ditch

Thanks for the reply. So if I understand you correctly you're saying the high loads generated by F1 tyres would effectively rip it up?

After considering it, a 40 ton truck stopping hard is going to apply more force than a F1 car accelerating, so it does not sound right. Wish I had shut up now

Just looked up the tec sheets on it and found this.

It seems they allow for the surface coating to be peeled off anyway, which is what I thought would be the concern in my post, but the "rubbering in" F1 cars spend so much time doing nullifies the drainage, and it seems there is not so much grip for the corners, acceleration or slowing.


However, there are some disadvantages to be offset against these favourable aspects:
- The open structure of ZOAB can become blocked due to dirt, exerting a negative influence
on the advantages offered by the asphalt mixture. The cleaning of ZOAB should
therefore be a point of attention.
- ZOAB contributes less to the construction integrity of the road surface in comparison to
dense hot-rolled asphalt (DAB).
- When the road surface is dry, the maximum braking deceleration is less than is the case
for dense asphalt. Th·~ is because the coarser macro texture reduces the contact area
between tyre and road. In addition, the stone skeleton on the upper surface of newly laid
draining asphalt is still covered by a bitumen fIlm, thereby reducing the initial friction.
After a period of time, this fIlm wears off, depending on the volume of traffic. Measurements
have shown that the average deceleration while braking with locked wheels

(http://www.swov.nl/rapport/D-94-25.pdf)

Thanks. I get some of the longevity issues, but there again this stuff is put on motorways in one of the most densely populated countries in the world. Any race track is surely not going to generate anywhere near as much traffic to make that a concern, is it? That goes for the dirt issue, too.

The braking distance might be a reason I guess, but I should have thought the massive tyres and brakes on racing cars might negate that. But there again this may be offset by the much superior wet weather performance?

Sorry, not trying to be argumentative and appreciate you've taken the trouble to help, but I guess I'm just thinking out loud!

Perhaps another thing to consider: road cars don't have open wheels. Part of the water they displace, gets stopped by the overhanging bodywork. In formula racing the open wheels launch much of the water into the air, causing spray.
So perhaps with ZOAB, the spray wouldn't be less, because (perhaps) most of the spray comes from not having anything block the upwards slingshotting of the water?

I'm no engineer so it's pure speculation on my part.

Having said that though - a truck would push it's force downwards so might not be a problem. An F1 car though may "pull" the tarmac upwards due to aero etc?

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Its torn up, as a dog skuffing in grass. to move 20 ton forward it has to push 20 ton backward, but the worst is hard braking as its over a far shorter distance for the same energy

I think the problem would not be a one off braking instance, but the REPEATED braking F1 cars would subject to that more porous, and therefore weaker and less consistent material, at EXACTLY the same point, over and over and over...

In fact, one of the most expensive parts of road construction is soil base compacting. This can be done to 95% compacting with relative ease, but it is incredibly difficult to go from there to 98% say... And it is at those high figures where you can be sure the road will not deteriorate much in time. To achieve this extra compacting it is not useful to bring a heavier machine to roll over the soil, but it needs to make countless passes... So, you see my point... It will be the countless hard braking passes by cars at exactly the same points which will make those ripples (even ripping) in the asphalt we have seen sometimes...

After searching through the lovely fia rule book i came across this beauty

https://www.fia.com/file/61776/download/12827?token=w98tRQRu

Which unfortunately doesn't give exact specs but does tell you what classifies as a "grade 1" track needed to host a F1 race.

But i did find a link to another forum which had quite a in depth discussion on this very topic with some interesting points.

https://www.f1technical.net/forum/viewtopic.php?t=3138

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