Why do we still use concrete and asphalt for our roadways? Why have we not found a better material that is less prone to potholes and always feels smooth to drive on?
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Yeah actually we have, if you take coral and grind it down and apply it in thin layers and compact it you get a gloriously strong roadway. But the cost both environmental and logistically are too great for most places.
Fun fact: The Enola Gay took off from a runway made entirely of coral, I believe it’s still there today.
When you live in a place where taxation actually happens and governments spend responsibly you do not have to deal with crumbling infrastructure. This is especially noticable in nordic countries that get heavy frost heaves.
I remember reading an article about India melting down waste plastic and using that for roads. The article mentioned they’ve only been installed for about 10 years but show no potholes or serious signs of west even under heavy loads (weight and volume). I couldn’t find specific costs but it seemed like it require new and specialised equipment to make and install the “plastic-tar” (as it’s referred to) so I’d imagine without the government mandate it would not be financially viable
We’ll be done with winters in another couple decades, and potholes will be much less of an issue.
The other issue is the weight of modern cars. They weigh more than ever.
[https://www.jdpower.com/cars/shopping-guides/why-are-modern-cars-so-heavy](https://www.jdpower.com/cars/shopping-guides/why-are-modern-cars-so-heavy)
Electric cars too.
More SUVs
And heavier vehicles cause exponentially more damage.
[https://urbanmilwaukee.com/2017/06/22/murphys-law-how-trucks-destroy-our-roads/#:~:text=An%20off%2Dquoted%20federal%20study,the%20truck%20is%20exponentially%20greater](https://urbanmilwaukee.com/2017/06/22/murphys-law-how-trucks-destroy-our-roads/#:~:text=An%20off%2Dquoted%20federal%20study,the%20truck%20is%20exponentially%20greater).
IIRC roads in America could be made to last longer using existing materials but typically aren’t. It’s cheaper to make the bases and top layers thinner and thus last less time. Spending more money would result in roads that last longer and cost less money over time. But making a road that lasts past your term and in to the term of your successor isn’t politically expedient; nor can you funnel as much money into your brother-in-laws construction business.
We use them because they work. Concrete can get the bumps from the joints. Asphalt is by far cheaper and, done properly give you a lasting, and smooth ride.
The problem is not the surfacing materials being used… they are appropriate. There are a lot of factors at play. One of these is existing material and the subgrade materials. Another is proper drainage. It does not matter if you lay 20” of asphalt or what mix design you use… if you lay it over muck, heaving clays, or next to a shallow ditch that allows for perched water conditions to occur under the surfacing, under the base (base layer stoically stone, lime treated or other stabilized base like soil cement) and can cause “pumping” or movement under everything due to saturated soil. This will cause deep failures that will mirror through to whatever surfacing you have.
Another huge problem is the existing conditions in comparison to what that state or county or parish has for a work program budget. For example in a state like Florida – you would some pretty decent conditions… dense sand, readily available source for lime stone and some granite sourced aggregates to the north… and a hefty budget to meet the needs.
Then you could look at a state like Louisiana or Mississippi in contrast. Heaving clays plague their roads… and they are at the mercy of the 80/20 federal aid program jobs to fund most jobs. They do asphalt surface treatments (AST) to roads to try to squeeze a couple extra years out of them when they really are overdue a patch, mill, and overlay. An AST is basically a shot of emulsion (such as CRS-2P) with a graded aggregate such as a size 2 or 3 spread across the top.
If you looked at a cross section of roadway from Florida and either of those states, you’d see a huge huge difference. Significantly better subgrade, 2-3x more stabilized subgrade, more aggregate or stone for proper flexible pavement design and less “dead” hotmix under the surface of poorer states. You’d see far more in depth investigation from a geotechnical scale because again the money is there to fund it.
You will see even worse roads in the off-system, or town/county maintained roads. Even in better funded states yiu can see some counties with lack luster roads… but even still there are “giveback” projects or projects for local entities like the county that get 80%federal and 20% local funding that the FHWA has the appropriate state DOT oversee the administration of said work to facilitate the use of federal dollars to the county’s contractor.
The point is that when properly applied, in well improved or existing conditions, maintained properly, and replaced within the RIGHT time of the service life cycle asphalt and concrete are excellent materials. And really the only reason you see concrete still used in most states?… it’s because the states make commitments to local “stewards” or “organizations” representing the concrete industry to allocate x amount of roadway miles or xx $ of their budget to concrete roadway. Not saying concrete is bad but it is expensive and just observing a good hotmix operation compared to concrete… there is a clear winner in efficiency.
An asphalt roadway can be immune to potholes and last a very long time. Look at the Autobahn. It is 29 inches thick. In the US they normally only do 8 inches to save cost in the short term.(i think that measurement included the base)
In Phoenix they had a problem with asphalt melting, this causes a wavy road as well as potholes… So now all the freeways are topped with a mix made out of recycled tires…. As a side benefit
the roadway is much more quiet.
Cost.
Asphalt is insanely cheap and easy to recycle. Enough to be more than cost-competitive with rail per lane-mile. This means that while rail is still less expensive to operate, its infrastructure is more expensive to maintain. Which has pretty profound implications for transport policy, as we have seen over the past century or so.
Personally, I feel like there is something to be said for a civilization that has the confidence to build stuff with the expectation that it can and will be reused and replaced soon. Instead of trying to build something at incredible expense in the hopes that it will last a few hundred years without ever needing maintenance. It’s one of the things that separates the modern age from the middle ages, for example.
Of course you have to actually perform the maintenance. It doesn’t count if you let your roads get all pothole-y and never resurface them. <_<
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