Just to be a pedant, and because this fact tends to surprise people, asphalt is concrete.
Concrete is a generally defined as any mineral aggregate (so rocks and stones) mixed with a binder (normally cement, but bitumen in the case of asphalt).
As for why roads are normally made out of “normal” concrete, it’s very expensive to build roads like that. Pavements are cheaper to build out of concrete because they only carry the weight of pedestrians, not lots of rolling vehicles. You need a pretty thick slab with rebar in it if you want to build a road surface from it, due to how weak cement concrete is under tension. Asphalt concrete cheats by being flexible, so minor imperfections in the surface or sub-base don’t become sources of critical failures (although they can become pot holes). Asphalt is also cheaper and easier to patch repair, but doesn’t last as long as proper cement road surfaces.
To be even more of a pedant, because asphalt is a subset concrete, any comparison between asphalt and concrete is automatically implied as a comparison between asphalt and non-asphalt concrete, and to specify would be redundant.
It's just like when saying "man vs animal", everyone knows that man is a type of animal, but it's implied that it's "man vs non-man animal".
any comparison between asphalt and concrete is automatically implied as a comparison between asphalt and non-asphalt concrete, and to specify would be redundant.
Sounds like the comparison isn't between asphalt and non-asphalt concrete, but between asphalt concrete and cement concrete. Unless the only two possible aggregate binders are asphalt and cement, but that seems unlikely to me.
Not really, there’s a number of different concrete binders available including cement, bitumen (used for asphalt), lime (very old binder), even epoxy.
Concrete is a material that uses any binder with rock aggregate. But in everyday usage people mean to refer to cement concrete.
Asphalt is a specific type of concrete that uses a bituminous binder. So asphalt vs non-asphalt isn’t very helpful because non-asphalt either means nothing at all, or any other concrete that uses a non-bituminous binder, and there are plenty of other options.
Clearly GP was intending comparison to be to cement concrete, rather than say, toothpaste concrete, PVA glue concrete, or a number of other technically valid concretes, but obviously not practical.
Possibly. But I noticed offhand in the DFW, Texas area there many local streets - sometimes flat ground-level parking lots - paved entirely in concrete, not just highways. Apparently for them the up front investment in "normal" (portland?) concrete is more economical.
There was a stretch of U.S. highway in my hometown that was built with concrete slabs. It is actually very durable and lasts for decades without need of repair, but it is also done in segments and the segments shift and create unevenness over time. Its not a terribly bumpy ride but it definitely isn't smooth like fresh asphalt. Anyways, at some point they grinded off a small layer of concrete and paved over the top with asphalt. When asphalt is fresh its definitely a more enjoyable drive.
As for why roads are normally made out of “normal” concrete, it’s very expensive to build roads like that.
Pavements are cheaper to build out of concrete because they only carry the weight of pedestrians, not lots of rolling vehicles.
You need a pretty thick slab with rebar in it if you want to build a road surface from it, due to how weak cement concrete is under tension.
Maybe. OTOH the bays of bus-stops tend to be made of the rebared thick slabs in a town with higher traffic I happen to know. Since about a decade at least. Before that there were always ruts in the asphalt, so deep they needed to be fixed again and again. Not so with the rebared slabs.
There's a lot of protectionism around asphalt maintenance.
I knew a city manager that got a city out of a major projected shortfall, without cutting any services, by investing in redicing long-term expenses.
He was celebrated for it, then fired, because the asphalt company that lost its contract had more political sway than the parks and recreation or public education departments that he fought for.
The cost would be a lot lower given sufficient advance planning to stop digging it up and patching it so often. Different parts of local government often don't coordinate enough with each other, so a brand new road gets put in, and then dug up and patched 1-2 months later. Asphalt is easier and thus cheaper to patch, and the result looks...well, as bad as asphalt always does, rather than the obvious patch spots/lines on concrete.
Ideally, put in concrete roads that include conduits.
Comments
Why not use concrete instead of asphalt? This person registered a 20 degree difference between the concrete sidewalk and asphalt road.
https://www.reddit.com/r/phoenix/comments/14o5bdu/a_comparis...
Just to be a pedant, and because this fact tends to surprise people, asphalt is concrete.
Concrete is a generally defined as any mineral aggregate (so rocks and stones) mixed with a binder (normally cement, but bitumen in the case of asphalt).
As for why roads are normally made out of “normal” concrete, it’s very expensive to build roads like that. Pavements are cheaper to build out of concrete because they only carry the weight of pedestrians, not lots of rolling vehicles. You need a pretty thick slab with rebar in it if you want to build a road surface from it, due to how weak cement concrete is under tension. Asphalt concrete cheats by being flexible, so minor imperfections in the surface or sub-base don’t become sources of critical failures (although they can become pot holes). Asphalt is also cheaper and easier to patch repair, but doesn’t last as long as proper cement road surfaces.
https://en.wikipedia.org/wiki/Asphalt_concrete
To be even more of a pedant, because asphalt is a subset concrete, any comparison between asphalt and concrete is automatically implied as a comparison between asphalt and non-asphalt concrete, and to specify would be redundant.
It's just like when saying "man vs animal", everyone knows that man is a type of animal, but it's implied that it's "man vs non-man animal".
Sounds like the comparison isn't between asphalt and non-asphalt concrete, but between asphalt concrete and cement concrete. Unless the only two possible aggregate binders are asphalt and cement, but that seems unlikely to me.
Not really, there’s a number of different concrete binders available including cement, bitumen (used for asphalt), lime (very old binder), even epoxy.
Concrete is a material that uses any binder with rock aggregate. But in everyday usage people mean to refer to cement concrete.
Asphalt is a specific type of concrete that uses a bituminous binder. So asphalt vs non-asphalt isn’t very helpful because non-asphalt either means nothing at all, or any other concrete that uses a non-bituminous binder, and there are plenty of other options.
Clearly GP was intending comparison to be to cement concrete, rather than say, toothpaste concrete, PVA glue concrete, or a number of other technically valid concretes, but obviously not practical.
Possibly. But I noticed offhand in the DFW, Texas area there many local streets - sometimes flat ground-level parking lots - paved entirely in concrete, not just highways. Apparently for them the up front investment in "normal" (portland?) concrete is more economical.
There was a stretch of U.S. highway in my hometown that was built with concrete slabs. It is actually very durable and lasts for decades without need of repair, but it is also done in segments and the segments shift and create unevenness over time. Its not a terribly bumpy ride but it definitely isn't smooth like fresh asphalt. Anyways, at some point they grinded off a small layer of concrete and paved over the top with asphalt. When asphalt is fresh its definitely a more enjoyable drive.
Iirc, part of the problem with putting asphalt on top of a well-made roadbed in DFW was the asphalt never lasted because of the heat.
They are now paving the concrete roads in Plano with a temperature resistant asphalt.
The road noise difference is palpable
Maybe. OTOH the bays of bus-stops tend to be made of the rebared thick slabs in a town with higher traffic I happen to know. Since about a decade at least. Before that there were always ruts in the asphalt, so deep they needed to be fixed again and again. Not so with the rebared slabs.
A lot of states use JPCP now for highways that doesn’t require rebar.
There's a lot of protectionism around asphalt maintenance.
I knew a city manager that got a city out of a major projected shortfall, without cutting any services, by investing in redicing long-term expenses.
He was celebrated for it, then fired, because the asphalt company that lost its contract had more political sway than the parks and recreation or public education departments that he fought for.
Huge temperature swings is a big part. Most people don't realize how cold it can get in the desert at night.
Cost.
The cost would be a lot lower given sufficient advance planning to stop digging it up and patching it so often. Different parts of local government often don't coordinate enough with each other, so a brand new road gets put in, and then dug up and patched 1-2 months later. Asphalt is easier and thus cheaper to patch, and the result looks...well, as bad as asphalt always does, rather than the obvious patch spots/lines on concrete.
Ideally, put in concrete roads that include conduits.