Why is it so expensive and is there an alternative out there that won’t break so easily especially in the winter? My state is spending like a billion dollars a year on roads that they’ll probably have to fix in 5 years, it really seems like a huge waste of money.
Good Public transportation would fix a lot of these costs I know but what other road materials/solutions are out there?
Thank you for the answers and for putting up with my follow up questions. I’m learning a lot!
asphalt is cheap (and flashy) part of road construction, the really important, expensive, non-flashy and prone to corner cutting part is building solid, thick, high-quality layer of aggregate underneath. if you don’t have that, no matter how many layers of asphalt you slap on top it will break every winter
this is an instance of https://en.wikipedia.org/wiki/XY_problem
Roman roads exist over 2000 years later, and are still in use, because they made the foundations about 30m deep.
I’m not a road enthusiast but I want to point out that such large cobblestones with irregular surfaces and gaps in between may not be optimal for heavy trucks going across them at over 100 km/h.
Metal roads. But since metal is expensive you probably want just two strips of it under the wheels. And since it will wear away at the rubber you probably would want the cars to have metal wheels as well. And at that point you could make the wheels form around the rails in order to make it easier to move fast without sliding. And then you could make the cars a lot bigger and link them together and have one big car push a whole bunch of them.
Asphalt is pretty amazing given the amount of wear it goes through. It’s basically infinitely recyclable, very flexible, goes down fast, and is relatively easy to work with.
The actual material costs for roads are only a small portion of the cost.
By far the largest cost will be wages.
Resolving drainage and everything that goes under the road is more important than whatever you put on top.
I hear people complain about prices of concrete but like you said it could be the wages. I just looked up concrete and it’s $5 for 80lbs. That doesn’t seem terribly expensive for 80lbs. How many bags do you think it would take to do an average driveway?
A pretty small driveway would be like 10 feet wide (enough for a Prius plus two feet of space on each side), 15 feet long (small yard with just enough room to park said Prius without sticking out), 4 inches deep. Quikrete has a “how many bags do you need for a 4in slab” calculator. Looks like for 80 pound bags you’re looking at 84 bags. If you can find them for $5 that puts the cost at $420, perfect for joking about over a joint after building the thing.
Specifically talking about asphalt vs. concrete:
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Asphalt is relatively cheap vs. concrete. This is partly because asphalt is a whole lot easier to recycle than concrete, which is almost un-recyclable, but also because asphalt is a relatively “simple” material - it’s mostly petroleum byproducts and gravel.
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Concrete doesn’t grip very well, compared to the relatively textured surface of asphalt. Especially when wet! This is why you often see concrete formed with “ridges” or “bumps” cast into it. However…
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This also makes concrete noisier and bumpier to drive over, making drivers less happy. It’s why it’s often used for short, low-speed uses like driveways, parking lots, or side streets.
Just about the only thing concrete has going for it is it’s endurance, which it definitely wins handily.
Every few years another engineered road solution is conceived - I’ve seen variations that would use glass which could be ‘re-fused’, concepts for recycling plastic waste, and many more. Most of these run into the issue that they’re either less ‘grippy’, or that they simply cost more even accounting for the longer lifespan.
Thanks, I had no idea asphalt was a byproduct of petroleum. Is concrete just rocks?
Concrete is gravel, sand, cement, lyme, and water, mixed in various ratios.
There’s a lot of variations and additives that can change how quickly it cures, often to speed it up or slow it down to account for weather (temperature and humidity play a huge part in how it cures), or to modify the pace of how it cures so you can keep building on it if you’re building vertically.
It’s a simple concept that gets incredibly complicated very quickly.
Big rocks, little rocks, cement, water.
Like the other comment says, concrete is rocks of various sizes (called “aggregate”) mixed with a cement and other additives to change its particular properties.
The cement is the really important point, because once water is added to the cement, it undergoes a chemical reaction which hardens it. Saying cement “dries” isn’t quite correct - yes, it stops being wet, but some of the water actually ends up incorporated into the molecules of the final cement. This is also why cement is really hard to recycle - you have to undo that chemical reaction, as opposed to asphalt which stays the same material.
Fun fact: When concrete is mixed at a big plant, it begins curing immediately. Concrete being carried in those big mixer trucks needs to be delivered before it cures in the truck!
As for city streets, wouldn’t concrete also be more dangerous for pedestrians? I can imagine that a fall on concrete is more likely to result in injury than on asphalt, with broken bones and skulls etc.
