Do you know know why large parts of the M25 road surface is made up of slabs of concrete rather than a smooth road surface?
Posted by WastelandOfConfusion@reddit | AskUK | View on Reddit | 91 comments
Do you know know why large parts of the M25 road surface is made up of slabs of concrete rather than a smooth road surface?
andykn11@reddit
My Father, a Municipal Engineer, told me that it depended on the number of bridges in the section being tendered for. If there were a larger than usual number of bridges in the contract (over or under) the contractor found it cheaper to tender for the road surface to be concrete as they'd be pouring a lot of concrete anyway. But paradoxically the concrete was too heavy for the bridges so the surface there is tarmac.
danielroseman@reddit
Auto Shenanigans has the details: https://www.youtube.com/watch?v=_YBY8EHkZK8
Tirno93@reddit
I’m a dull enough person to have watched that already (no disrespect to that guy, I found it interesting!) and the tl;dr is that the ground there is too unstable for asphalt, it would just crack. There’s a reason they’re slabs rather than a continuous surface, but I can’t remember what that is, just that it’s unlikely ever to change
Worldly_Let6134@reddit
It was built quickly and cheaply. There could have been much larger slabs done by pouring concrete in a specific way.
The current setup was cheaper and used the smaller slabs as a sort of bodge.
It won't change (at least not yet) because of the sheer cost to remedy and the untold chaos of disruption that shutting the m25 for weeks at a time would cause.
Imposseeblip@reddit
Oh he knows what kind of videos he makes. One time he said something along the lines of "i keep making this crap, but you lot keep watching it, so here we are!"
PeterJamesUK@reddit
I sent a video of his to a mate of mine to illustrate the random shit I watch, expecting him to tease me about it, but he says he's one of the best presenters he's ever seen and loves it.
Perfectly_Other@reddit
Concrete requires gaps between slabs to allow for thermal expansion.
If there was no gaps the concrete would buckle and crack when it got hot under the sun as the only direction it could go would be up or down
RoutineCloud5993@reddit
They could fix it by using larger slabs, but that would mean closing down huge sections of the M25 and thag isn't practical.
danddersson@reddit
The M27 was built in the 1970s using the same construction method.
After years of disruption, lane closures and 50mph speed limits, it has just FINALLY (mostly) been resurfaced with a much quieter, smoother, ashfelt-like surface.
Many_Lemon_Cakes@reddit
Give it a year and they will find a new reason to do works on the M27. Hell all the lanes are open, but the road is still 50mph
AmarilloMike@reddit
Do you mean asphalt? Or is ashfelt a new road material I've not heard of? I hope it's the latter, ashfelt sounds heavenly to drive on!
ridiclousslippers2@reddit
She was only a road builders daughter, but she always liked her asphalt.
pslamB@reddit
Ooh err
ek54ljl@reddit
Fairly sure the good citizens of Gloucester would like ashfelt instead of the assfart they use to "repair" the potholes. Of which there are many.
Harrumph I say, and harrumph again.
danddersson@reddit
Corrected.
Altruistic_Fruit2345@reddit
I give it 3 years before it's fucked again.
daveyboi80@reddit
Love his channel!
garry_baldi@reddit
If you want to upvote this comment, there's a button specifically for that.
danielroseman@reddit
How the devil are you? Have you had a good week?
signol_@reddit
Whicked sweet awesome!
Master-Trick2850@reddit
yup, got recommended this one by youtube algorithm
Dissidant@reddit
Worth it for the reply section. Absolute theatre
firerawks@reddit
he has the details AND the delivery
SpudFire@reddit
That was interesting, thanks. I always assumed it was because they could easily be lifted up and replaced once worn down.
ross-dirext-words137@reddit
Lol you beat me to it
notmenotyoutoo@reddit
It’s awful to drive on. Thud thud thud thud thud thud thud and the white noise is sooo loud.
Character_Silver4285@reddit
Dude I just drove around the USA and it’s everywhere, mind numbing!
Unhappy_Clue701@reddit
Certainly in Houston, which I visit at least yearly, the concrete is laid differently though. The grooves in the surface run in the same direction of the traffic, instead of across the road from side to side. That substantially cuts the noise when driving along it - it’s actually pretty smooth and not much noisier than regular blacktop tarmac.
mrmazola@reddit
I have a soft spot for it, only time I ever drive on it is if I'm going on holiday or Glastonbury
Beefcakeandgravy@reddit
A303 Ilminster section?
mrmazola@reddit
Dunno, between 7 and 9 o'clock if it was a clock face
fundytech@reddit
M42 in Birmingham is the same
ARobertNotABob@reddit
An month's normal tyre wear in a single journey.
AhoyWilliam@reddit
I used to drive vans for work. This section of the M25, the slabs were exactly the same distance apart as the wheelbase of the van (L3H2 Renault Master), so both ends would skip at the same time. 'orrible
Evening-Tomatillo-47@reddit
Isn't it amazing how it can be cheap, shit AND take ages
Beancounter_1968@reddit
Like my MILs cooking
TheScrobber@reddit
My sex life right there
Jeoh@reddit
British infrastructure, baby!
Smithy2997@reddit
It's especially bad when you really need a piss, and you're in slow moving traffic at about 30mph. Every single one of those damn bumps is dreadful.
That_Ryan_D@reddit
Freaked me out when I was a new driver. Thought my car was broken.
ZekkPacus@reddit
Sets my car's TPMS off every time I drive over it. I used to panic and get off the M25 thinking I'd burst a tyre, now I just ignore it. One day I will actually burst a tyre.
Ricky_Martins_Vagina@reddit
Because concrete is regenerative, meaning you can just keep growing new slabs to replace the existing ones.
Cobuprofen@reddit
You can’t grow concrete, yes you can
Ricky_Martins_Vagina@reddit
That was Cameron, who grows trees and then cuts them down and then makes things from them. Brilliant 👌🏻
LHG_93@reddit
Iykyk
DrivingOffence@reddit
The thing i realised about this surface of the M25 is that i’ve hated driving over it since i learned to drive about 30 years ago. Which means it hasn’t needed replacing for more than 30 years. Now when i compare that to other road surfaces which are continuously having road closures to fix - I realise this stuff is really doing it’s job well. Now when i drive that bit, I appreciate it hahaha
TlanTlan@reddit
Copying the American freeway design where it’s mostly concrete.
Concrete is super hard wearing, can take trucks all day every day, and is cheap to pour a new slab for how long it will last.
But yes the downside is it sounds terrible for passenger cars. I remember driving in my bosses nice Mercedes years ago on the M25, and we still had to yell to hear each other.
Ricky_Martins_Vagina@reddit
It would be interesting to see a study comparing fuel efficiency between the two surfaces... All that noise is lost energy = more work done to maintain the same speed of travel / more fuel / more emissions 🤔 plus additional wear on tyres etc presumably.
Sharktistic@reddit
Thete ain't a clear correlation between road noise and fuel efficiency. Some surfaces are indeed much louder than others but do no necessarily provide more rolling resistance or negatively impact fuel efficiency.
Some tyres can be very quiet but very inefficient, and some can be very loud but very efficient, the same applies to road surfaces.
Ricky_Martins_Vagina@reddit
Respectfully, I find that difficult to get my head around.
Noise is energy. If a transfer of energy is generating more noise, that means energy is being lost / wasted.
It may not necessarily be a resistance / friction issue but could be vibration for example - again, energy loss through the bushes, suspension, bearings, etc...
Sharktistic@reddit
It doesn't make a great deal of sense intuitively, but then a lot of physics doesn't.
Imagine driving along a rail designed for trains. Very low rolling resistance, much smoother than asphalt, but a much harder, smoother surface. It would likely make a much higher amount of road noise. There is also much more tyre in contact with the surface of a concrete road than there would be with a rough asphalt road, this would also increase road noise (but conversely would also make one think that more contact area = higher friction). This and the lower flexibility of concrete mean that more road noise is generated as the road is more 'reflective'.
It's been many, many years since I encountered a concrete road but I remember some of them having a wavy or patterned texture, and even just the joints between the slabs will add to the overall noise.
The substrate beneath the concrete may well be different to the one used in asphalt roads too, but I genuinely have no idea as I'm not a road engineer.
It's Friday evening and I've been on the prosecco so I can't actually do any maths at the moment but I'm confident that in this particular case, noise is not indicative of efficiency. I probably shouldn't be on Reddit.
Ricky_Martins_Vagina@reddit
Don't worry I'm between flights and a few JD & Cokes down too 😂
I don't think rubber tyres on a smooth steel surface would be noisier than tarmac or concrete though. The road noise comes from roughness and / or looseness.
Steel wheels on a steel surface - yes, it would be noisy because the hardness of the wheels would transmit every little bit of vibration.
I think you've nailed it with the surface texture of the concrete - it needs to have some roughness because smooth concrete is a deathtrap. Some genius had the idea of instructing the contractor to polish the hard-standing lay down area outside our workshop and when wet it's like a skid pan. Forklift wheels just spin on it 😬 if you were to build a road like that, it would be very quiet no doubt but there'd be daily pile-ups
Not_A_Toaster_0000@reddit
Very quiet apart from the sound of crashing metal and the screams
Ricky_Martins_Vagina@reddit
Music to my ears 👌🏻
Not_A_Toaster_0000@reddit
Ah, a fellow Industrial fan ?
neilbartlett@reddit
It's true that noise is energy but it's a tiny amount of energy. Much too small to be a remotely significant factor in fuel efficiency when compared against the other energy outputs of the car, i.e. fighting against air resistance and rolling resistance of the tyres.
Ricky_Martins_Vagina@reddit
Sure - but the noise could also be indicative of other losses. For example when you can hear the car rattling about, that means looseness in suspension, bushes, bearings, etc which means there is undesired movement / impacts / friction / heat / and of course the noise we perceive.
WillBots@reddit
An AAA battery can make a speaker crackle loudly for a long time, that same AAA battery cannot produce much heat and can't make your car move. Not all perceived energy is equal.
TellMeManyStories@reddit
Noise is energy, sure.
But the total noise energy released by a car going past is perhaps 5 or 10 watts (ie. you could buy a 5 watt speaker and make the same amount of noise).
However, you also have heat in the tyres and heat in the road as loss. That's probably hundreds of watts, maybe a kilowatt at motorway speeds.
Therefore, the noise energy is such a small fraction of the total wheel losses as to be irrelevant.
Ricky_Martins_Vagina@reddit
Not sure that's a reasonable comparison though.
Do you mean the noise emitted within the few seconds of a car going past would amount to around 5-10w? In which case you'd have to compare the heat generated within those same few seconds only. Or otherwise calculate both over a whole journey / given distance at a given speed.
TellMeManyStories@reddit
Hang a boombox out of the window... Play a song and get an observer outside to say if the car noise or music is louder. Adjust the volume till they're the same. Measure the power going into the speaker (and add a bit, because speakers aren't 100% efficient).
JishBroggs@reddit
See it is as the sound being a symptom of a hard surface and ‘bouncing’ off (less friction ) instead of a quieter dampened sound because of a softer surface ‘squishing in ‘ increasing friction.
I’m not sure if that made as much sense as I can picture in my head. Few drinks down this Friday evening.
Ricky_Martins_Vagina@reddit
I think it's more the roughness than the hardness. Concrete roads usually have a more pronounced surface texture than asphalt. The tyres would absorb most of the hardness discrepancy.
kaveysback@reddit
Could it not be to do with the amount of sound being reflected instead of absorbed.
xdbojacx@reddit
As I understand it, concrete roads are generally better for fuel efficiency because of their lack of elasticity. Asphalt surfaces are basically an extremely viscous liquid.
Ricky_Martins_Vagina@reddit
Interesting hypothesis 🧐
In which case I'd ask how much of an impact that has on a relatively light vehicle like your average car vs a heavier vehicle like a lorry. I could see the difference between concrete and asphalt being fairly negligible for a car, for example, while a lorry may have a more measurable difference between the two surfaces.
Kieran293@reddit
Yeah unfortunately I did one of my papers at uni on this topic and concrete is definitely better in terms of reducing car emissions. Although concrete itself is not great regarding carbon unless you design it to have micobubbles filled with additional CO2.
PARFT@reddit
I live half a mile from a stretch - it’s a joke.
mooninuranus@reddit
I thought it wasn’t supposed to be used near residential areas.
I mean it’s London so I can see the flaw in my statement but still.
PARFT@reddit
It’s the bit that goes across the surrey hills area of outstanding natural beauty between reigate and leatherhead. Residents were given payments to buy double glazing etc when it was being built and again when it was widened.
It was beautiful too but no point crying over spilt milk.
The local mp was hoping to discuss resurfacing with the authorities but she won’t get anywhere as it will be too expensive /disruptive.
f8rter@reddit
Yes it’s so fcukin noisy to drive on!!!!!
MKMK123456@reddit
Is it not possible to lay a layer of macadam/tar to reduce the noise ?
audigex@reddit
As with most things in the UK that are shit: money. It was cheaper to install
Unfortunately you can't easily fix it without ripping the whole thing up and replacing it
Beneficial-Pitch-430@reddit
Cheapy cheap cheap
Long_Huckleberry1751@reddit
No, it's bah dump, bah dump, bah dump
tricky12121st@reddit
The m1 into london to. They used to have signs regarding road sound
Sergeant_Fred_Colon@reddit
It was cheap and quick, it was also done incorrectly with the wrong concrete for roads, and is in desperate need of replacing but we can't shut the M25 and do it correctly.
BloodAndSand44@reddit
The section clockwise where they have ground and grooved it is much better.
SnooDucks5078@reddit
I think it’s because the ground was unstable so they had to use concrete.
xdbojacx@reddit
You would ideally not use it on unstable ground, especially clay, because jt cannot flex to accommodate the expansion and contraction of the subsoil. It can be used on the sandy soils which exist in some parts of the SE and in places like Lincolnshire (a long stretch of the A1 was once like this) or East Yorkshire (M62 previously noted)
Even asphalt or stone mastic can only cope with so much ground movement. One of the reasons that road surfaces in the UK are so poor relative to continental Europe is that we have so much clay which expands in wet winters and then shrinks in summer. On the whole, continental Europe has a geology that is much more sand and rock.
Nervous_Week_684@reddit
Don’t they have something similar on the M6 through Birmingham? The repetitive thudding drove me nuts when I last used it. Has it hopefully been resurfaced??
FarmerJohnOSRS@reddit
Costs more but lasts much longer, meaning less shutting down of the road for resurfacing.
Does anyone number on your car though.
FlossieAnn@reddit
They used this on the Hull end of M62 as well. I used to love the noise when driving over it - almost a train like clackety-clack rhythm and it meant you were nearly home. Looking at google maps, most of it seems to still be there
tom56@reddit
Yes I do
IranianAlan@reddit
They tried to do this all over its something to do with hard wearing or anti slip or something
Boldboy72@reddit
it was all concrete at one point
Stephen_Dann@reddit
The sections that are concrete always have been and those that are not, never were. So no, this is not the case.
ResplendentBear@reddit
It's amazing what you talk about in the pub in your 40's as this very subject came up.
So I know someone who has a lot to do with the M25 maintenance contracts, and he had two reasons:
- The M25 wasn't just one road, it was bit of existing roads joined up by new bits to make a motorway. Hence there isn't just one surface.
- The concrete block stuff is super hard-wearing. and easily replaced. Not nice to drive on but will handle hundreds of thousands of lorries a year, then you just drop a new bit in.
Derr_1@reddit
Cheaper
Low-Rooster5398@reddit
Hate the thudding when I go over it, really annoying.
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