The road to hell is paved with asphalt
devonzuegel.com
devonzuegel.com
Of fucking course asphalt will look more damaged. If you try to use Roman roads for buses and trucks, they'll be destroyed completely within a couple of years (road damage scales as the fourth power of the axle weight). Cobblestone is also slippery when wet or iced.
Paving stones might look nice, but they can get dislodged, or the road can warp if drainage is not done properly.
Everything in engineering is a trade-off. You can use concrete for paving and for a small neighborhood road it'll last for decades with little maintenance. But it's much more cost-effective to use asphalt on a gravel bed, and just periodically do spot repairs.
As asphalt becomes more expensive with the winding down of fossil fuels, we'll switch to more concrete roads. But we sure as hell won't be using paving stones.
As far as I understand it, asphalt is also highly recyclable. https://www.researchgate.net/publication/344252166_Asphalt_P... , referenced from the Wikipedia page about "Asphalt concrete" (https://en.wikipedia.org/wiki/Asphalt_concrete ), includes this quote in the abstract:
"The asphalt industry remains the country’s most diligent recycler with more than 99 percent of reclaimed asphalt pavement being put back to use."
Can't that be interpreted as them just not reclaiming asphalt they can't reuse? Genuinely asking, since things like this are often optimally worded for good publicity.
The next chunk in the abstract I quoted is:
"The average percentage of RAP used in asphalt mixtures has increased from 15.6 percent in 2009 to 21.1 percent in 2019. In 2019, the estimated RAP tonnage used in asphalt mixtures was 89.2 million tons. This represents 4.5 million tons (24 million barrels) of asphalt binder conserved, along with the replacement of more than 84 million tons of virgin aggregate."
That gives some context as to how much is actually being reused.
The claim and wording is valid and correct, though. You cannot recycle asphalt if you leave it in place. And what is removed is recycled at a rate of 99%.
If you don't reclaim the asphalt, then it's still in place, and technically still in use.
Cement is a chemical process that can't be easily undone so once you use cement you are hooped, very limited recycling options other than grind it up and use it as filler in the new batch.
If you look at the cobbles it's relatively clear that the wear patterns have something to do with the hardness of the stones/bricks. If you sorted the recovered stones by height, and built a new road with matched cobbles, you would still get wear of course, but the variance would be less, right?
Take three city blocks of cobble. Sort them into three groups, one containing the softest and the broken cobbles, then use each of the remaining to pave one block each.
Is there a theoretical basis for this? It looks like the "fourth power law" comes from an empirical test conducted in the 50s: https://en.wikipedia.org/wiki/AASHO_Road_Test
However, that article says:
> ...critics point out that its data is only valid under the specific conditions of the test with regard to the time, place, environment, and material properties present during the test. Extrapolating the data to different situations has been "problematic".[3] Other studies have attempted to refine the results, either through further empirical studies, or by developing mathematical models, with varying success.
I have some intuition for why certain physical systems would scale quadratically or cubically, but where on earth is the quartic scaling coming from here??
Two quadratic processes working at the same time, perhaps?
My guess: increased weight pushes tires deeper into the pavement, allowing them to grab and dislodge larger particles. At the same time, axle weight is a good proxy for torque, so a vehicle with a larger weight can also exert more force on the particles that it grabbed.
For the last decade or so many busses through the heart of town were forced to use a cobblestone street for about 200 meters, resulting juddering that was unpleasant for both passenger and bus. One time I saw a handrail rattle loose and start donging around. So in the final cost / benefit analysis of the optimal street surface, we also need to calculate the increased wear and tear to vehicles and dentstry.
Fortunately someone higher up saw sense and asphalted over that section of road, much to everyone's relief.
The problem with old cobblestoney towns like mine is that the urge to preserve every shred of the past, often so tourists can get a nice Instagram shot, is at conflict with what the locals require to live in the 21st century.
It's my pet theory that this is the opposite of what happened with energy drinks - decaf coffee became popular, so suddenly we had a surplus of relatively pure caffeine (once you let the hexane boil off).
Bitumen is the byproduct, and it's cheap because of that. But IIRC it wasn't just the cost that made it attractive. It's easier to work with then concrete, and maintenance via resurfacing is easier as well. It's a fair bit more flexible as vs concrete which can be desirable as the soil under the road settles and shifts over time; a concrete road will crack under those circumstances.
I don't know now if that was misremembered on my part or someone's wishful thinking getting the better of them. "Everybody's doing it." Well, you and three other people isn't 'everybody'.
Decaf still has enough caffeine that if you're super-sensitive (by genetics, reduced metabolism brought on by age, or both) it can cause problems anyway.
On one hand, there'll be less oil to go around. On the other hand, refineries might stop doing cracking, resulting in more heavier oil products. On the third hand, oils with high content of heavy fractions will probably be phased out first, because lighter oils will remain more profitable.
>person in tech spends 5 minutes looking into a subject and thinks they know more than the collective knowledge of every person in the industry
> We need to stop planning project primarily by spreadsheets, where the dominating inputs are costs you can measure easily. There are factors that are not reflected in those calculations that not only affect the quality of the place you're creating, but also the financial burden that the community will have to bear for decades down the line.
There are very talented people who develop modelling for urban planning and infrastructure that do look into these costs and their impacts. But there is no perfect solution, only tradeoffs.
Maybe, but now that everyone is becoming more aware of how terrible concrete is for the environment, maybe not. Work is ongoing to find a less damaging alternative to concrete.
Amazing. I had always learned it as the snap. Learn something new every day
https://en.wikipedia.org/wiki/Fourth,_fifth,_and_sixth_deriv...
Increasing vehicle weight by about 15% would be 75% more damage per passenger vehicle. Which is not nothing, but for comparison, those 5000 pound trucks are doing almost 8 times as much road damage as a midsized sedan by weighing 2/3 more.
But let's say you're right and the sedans weigh 30% more instead of 15% more, then it's about 2.8x the damage of an ICE. Trucks are still doing more damage than 3 battery electric vehicles.
Honestly the weight of these things needs to come down over time. But you need infrastructure to do that. Lighter batteries don't just materialize out of thin air. Getting battery weight down increases range. Which can either make a car with better range, or let you shrink the battery another 5%.
You can't compare a Tesla to a Honda. They're in a different customer class. Try an Acura at least. Even a Jetta only weighs 400kg less than a Tesla 3, and that's still a down-market car. Luxury cars are heavier.
Also, another hypercube law: Neuron firing rates go as temperature to the 4th power.
So, a small change in temperature increase the number of firings per second drastically. This is due to the speed at which charges can move in and out of the neuron, which going though a lot of math and fun modeling, ends up being related to the Stefan–Boltzmann law of black-body radiation.
Anyone else got fun hypercube+ laws that they know?
I agree on the conclusion, though, in an ideal world that both infrastracture is maintained perfectly, they should both be used in a city. Perfect example? Amsterdam.
My favorite is poorly maintained asphalt over cobblestones (which may or may not habe been poorly laid themselves)
The absolute audacity of the article to ask "Where would you rather take your wedding photos?" I don't know, not on infrastructure built for moving large numbers of people? Go find a meadow or something!
2, 6, and 7 share many of the same benefits and some of them are used for cycle paths in some places I've lived in.
Clearly they have only ever walked on cobbles or seen them in photos.
It definitely is ugly though.
An example https://maps.app.goo.gl/bgqmJhuaGvpfqeLz6 Note the asphalt poured between the stones to even out the steps. It cracks and goes away and the steps are there waiting for wheels. The rails too.
In my experience: small cobble stones like the ones in many of the pictures on the right column of that side don't age well with traffic. They start to move and eventually pull out. Smaller stones are worse. I drive regularly on plenty of examples of that. Stones should be very thick to stay in place because they can help each other not to form an angle with the surface of the road.
Large stones like the ones in the Street View I linked are better at staying in place but they must be thick too and when they move they create a significant step. I don't like to drive over them and I don't want to be a cyclist there.
If you zoom the stone roads in that website you see that they are not very even. Asphalt also has the purpose to protect the layers below it. If it's not replaced before it starts to crack it's like having many small stones. In both cases, stones or asphalt, water enters the gaps, washes away the material under them (sand, gravel, rocks, whatever) and heavy traffic makes the road bumpy. The only solution would be to remove the surface layer and rebuild the road, but nobody does it AFAIK. They just peel off the asphalt and lay new one. It's back to cracks and bumps in a year or two. At least it's faster and quieter to drive on than stones.
For me, asphalt on every road except pedestrian areas.
Where I've seen cobblestone replaced generally everyone was much happier with the new pavement.
Of course this depends on what the road is used for. Most streets don't get a lot of traffic though, and so the cost curves work out to favor asphalt over time. Roads with a lot of traffic (particularly truck traffic) should be concrete as the cost curves work out better.
Modular pavers that this article recommends are the most expensive. They don't lend to easy/cheap automation to replace and so there is a high maintenance cost.
When you have actual lane closures for any amount of time it has little or nothing to do with asphalt/concrete itself but actual infrastructure repair of the subbase.
I think the author underestimates the amount of warping in the underlying soil in some places. I'm sure it isn't a one-size-fits-all solution, but I agree it should be considered for suitable places.
Pavers are not practical on anything but low-traffic, pedestrian, historical, or vanity roads.
Pavers don't work because the city needs to remove the snow, and the pavers would get removed by the plows. I don't know of a viable road alternative that is also economical for places with snow.
I've always thought thick concrete was the higher-investment alternative.
https://www.plowsite.com/threads/downtown-cobblestone-street...
It is actually a little disorienting. The signal of “this is not a well maintained road, you are probably heading away from the population center” is no longer provided.
Anyway, hopefully that was an amusing anecdote. The real point is that there are whole regions that don’t care about plowing I guess.
It involves lasers (lots of them) mounted on the front of a heavy vehicle/paver, melting the asphalt as it moves and simultaneously "ironing" it.
If anyone has an idea for a really compact nuclear power source, contact me to discuss it ;-)
SMRs (Small Modular Reactors) on the other hand are very much real and I hope in a few decades will be more practical for all sorts of things, including my laser-paver :-)
Unfortunately from everything I've seen it doesn't work well because the aggregate mix becomes from the bitumen mix without mechanical mixing and the surface of the material is weaker and gets bumps faster.
When they repave a road they rip up the old material and take it to the mixing plant where it's remixed in with new material, no nuclear reactor needed.
Completely agree. Building a rocket? Plan by spreadsheet. Building a computer system for a data center? Definitely plan by spreadsheet. You know what those two things have in common: no one has to see them.
Things that are in public, like streets, bridges, and facades, ought to not just be cost effective. They ought to be beautiful.
Of course, it can be poorly done, too.
US101 in Silicon Valley through ~San Carlos is a dumpster fire every time it rains. They spent a decade repaving the damn thing, and now in each rainstorm massive potholes are generated. It's like a slalom course out there right now. This after the "repairs" from last year when dozens of cars got flat tires and bent wheels on the same day, after hitting massive craters.
But I don't have any memories of it having these problems before the extensive repave in the 2008-2014 timeframe.
I think there's gotta be something wrong with the asphalt mix, yeah.
I’m surprised security is not discussed at all here.
"An anti-lock braking system (ABS) is a safety anti-skid braking system used on aircraft and on land vehicles, such as cars, motorcycles, trucks, and buses.[1] ABS operates by preventing the wheels from locking up during braking, thereby maintaining tractive contact with the road surface and allowing the driver to maintain more control over the vehicle."
If I understand both correctly, the implication is that asphalt provides a better (safer / "more secure") grip with vehicle tires, including when ABS kicks in. This is backed up by other comments here talking about how other road surfaces, especially cobblestones, are very slick in rain and even above certain speeds.
So yeah, slightly weird usage of "security" but it does make sense with a bit of context.
Have a good day, all.
> At 4 P.M. on July 13, "the children numbering 233, were quietly seated in their school rooms, playing in the nursery, or reclining on a sick bed in the Hospital when an infuriated mob, consisting of several thousand men, women and children, armed with clubs, /brick bats/ etc. advanced upon the Institution."
"brick bats" means chunks of paver stones and bricks, typically pried out of the street, used as improvised projectiles.
0: https://press.uchicago.edu/Misc/Chicago/317749.html&title=Th...
Unless of course you put bus traffic over them, which creates ruts and generally warps the surface.
I live in a city where some roads are laid with cobblestone without good reason.
They're:
-loud even at low speeds.
-shaky.
-unsafe, as your braking distance will be significantly higher.
https://imt-atlantique.hal.science/hal-01204741/file/Audo201...
Sure, the Appian Way has lasted thousands of years, but that's because it's in a moderate climate, that never freezes, on stable ground, and with (very) light traffic.
Author has no civil engineering background.
But if all they wanted was to ragebait, success!
At least do a proper comparison: https://pavetool.com/collections/optimas
> Modular materials also tend to reduce traffic speeds, since [they] create a surface that is not as seamless as fresh asphalt or concrete. In one brick installation project, the average speed dropped from 41 mph to 29 mph. This represents 30% decrease in speed, and the risk of death when a pedestrian is hit by a vehicle is approximately 4x higher at 40 mph versus at 30 mph.
I mean ... this pretty much says it all? For the vast majority of roads this is simply unacceptable. The main reason asphalt is used is that during its effective lifetime, the road surface is smooth and even.
Brick roads are known for making cars lose control and forcing sudden changes in direction.
What makes you think oil processing will decline soon? It seems like we have an ever-increasing appetite for the stuff (with a possible exception in Norweigan production) [1].
[1] https://ourworldindata.org/grapher/oil-production-by-country