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!
Specifically talking about asphalt vs. concrete:
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.
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…
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?
Not technical definitions:
Asphalt is for roads is small rocks held together by petroleum byproducts.
Concrete is small rocks held together by cement.
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.
I’m not honestly sure. Asphalt (or, more properly, asphalt and gravel as a mixture, which is what is mostly used as a road surface) and concrete both are pretty ‘hard’ materials.