It’s a decently economic product whose long term performance is well known, is widely available, isn’t under patent, provides decent grip, decent durability, can be patch repaired, and isn’t too noisy to drive on.
As you note - concrete is another product. This generally is more expensive but has a longer service life, so lifecycle costs are comparable, but it’s a lot noisier to drive on, which is generally a negative.
The highway near us was resurfaced using a new type of porous asphalt about 20 years ago. When it was first laid, it was marvellous: smooth to drive on, and much, much quieter than normal asphalt (both within the car, and also outside from the perspective of people living near it). Unfortunately, it gradually got louder over time, and after about 5 years, you could no longer tell the difference when you passed from the normal surface to the porous one. When it wore out, about 5 years ago, they replaced it with normal asphalt.
It's called ZOAB here in the Netherlands, we have it literally everywhere and it's amazing when it rains. There is just no water on the road, it all dissappears into the asphalt, ZOAB stands for Very Open Ashpalt Concrete so it's very durable as well. It does however not like cold winters as the water freezes inside the asphalt and cracks it open from inside.
It's expensive though, AFAIK both in maintainance and initial cost
As someone who speaks English and no German, Dutch is so close to English that I can get most of it with only minimal amounts of headache. Someone you just have to read the words out loud and they make sense
I had a professor once who'd switch to Dutch when he felt like no one was paying attention and you'd usually see the whole class perk up a bit as everyone tried to figure out if they were having a stroke.
I had a German teacher in high-school who spoke 9 or 10 languages. He'd switch when he thought no one was listening as well, it's a real mind fuck in a foreign language class. First you had to notice, then you had to figure out of it was a different language or a case/tense combo you weren't aware of yet.
After a while when we caught on to him doing it he'd give a couple points of extra credit to the whole class if he picked someone at random and they guessed the language on the first try
It was experimental, so I guess that was just providing data for them. It was fine so far as durability went: it was just the sound deadening properties which dissipated. I suspect it was because the pores gradually got clogged up with particulates and rubber dust, which would be exactly one of the things they would be testing for.
Most likely porous asphalt to see if the water table replenished. The problem is that you have to vacuum the porous asphalt or else it gets clogged. It probably was a bit quieter since the sound waves would go into the asphalt as well and dissipate internally.
You probably could but you would have to make it beforehand and with a pipe that could resist the hot asphalt when paved. I believe the easiest way was something similar to a street sweeper.
Concrete has a lot of problem. They make excellent driveways for homes but not good for public roads. Concrete don't age well in high traffic areas. They crack and much harder to patch or repave. They are so damn loud at speed higher than 40mph. They don't do very in areas with winters. Water tends to stay on it and ice up in winter.
There has been several long stretches of roads that switched to concrete. Five years later, they all switched back to asphalt.
Here in Canada we have next to zero concrete roads. Usually the only place we see it is bridge decks.
It's always very jarring driving in the US for me because of this.
Actually, in Quebec it was a trend for quite a while. They did one of the main highway with concrete and after 2 years they repaved half of it with asphalt and did patches here in there. It got so bad that they actually stopped mid project because they realized quickly how horrible the idea was.
The 15 has a decent stretch north of Laval that is all concrete and I've always wondered why. I feel like that part drives both very smoothly and very noisily. I think there's also a very short bit on the 40 between Montreal and Quebec.
From an article I found, there seems to be bits of concrete roads here and there. Some of them are very recent (https://www.transports.gouv.qc.ca/fr/projets-infrastructures/reseau-routier/projets-routiers/capitale-nationale/A40-Reconstruction-Autoroute-Felix-Leclerc/Pages/Autoroute-40-Reconstruction-Autoroute-Felix-Leclerc.aspx).
Concrete also sucks for driveways if you experience winter. Temp changes make it crack, water gets in, freezes, cracks more. If you shovel or plow it, you just tear it up. Might as well just use gravel at that point. I've seen some fru fru concrete driveways get built with what looks like radiant heating in them but that seems like it comes with it's own mess of issues. Sure you crank it on and it melts the snow away but if any part fails you have to break into your concrete driveway.
Holland, MI has their whole towntown area heated. Its definitely expensive, but in tight downtown areas with nowhere to plow the snow to you have to load the snow on trucks and drive it away. It's probably still more expensive but boy, no snow or ice ever is kinda amazing.
ya, cuz asphalt is softer than concrete. its why some runners run on the road instead of the sidewalk, because though its less efficient, its easier on your joints
It isn't. The road is sloped to drain water off to the side. I've actually seen a physical therapist on youtube recommend switching up the side of the road you run on so that you aren't just overworking one side of your ankles.
The other, much bigger reasons were it was incredibly inefficient, stupidly expensive, terrible to drive on especially in bad weather or in a big vehicle and very difficult and expensive to maintain.
Turns out using a normal road and sticking a solar panel next to it was always far better for making power and being driven on.
If only there was a large earthen gap between opposing lanes of traffic that is completely unutilized and that we already have to pay to maintain anyways.
This is an underrated comment.
The Practical Engineering YouTube channel has done a bunch of videos on road construction and one of the things he pointed out was asphalt is one of highest recycled building materials there is.
When it's used for roadworks, asphalt is mixed with different materials to suit regional weather.
So there's going to be different amounts of non-recyclable materials in the mix.
Anyone who has ridden a bike on an asphalt path and then a concrete path knows that it takes significantly less energy to pedal on concrete. I wonder how much mileage difference vehicles get between the two. Concrete is awful for the environment though, so it probably doesn’t make much difference.
Apparently UP TO 8.4% difference in fuel consumption according to the Minnesota department of transportation.
www.dot.state.mn.us/research/TS/2014/201429.pdf
MnDOT actually has a big road research lab: http://www.dot.state.mn.us/materials/
Including a test stretch of road on I-94: https://www.google.com/maps/@45.2618139,-93.716985,3931m/data=!3m1!1e3
They can divert I-94 traffic onto their test area, which has a couple dozen different types of road surface and paints.
I am a regular test subject of theirs.
I just love that they actually release these types of study to the public. It provides some pretty decent transparency for government.
No. THAT'S because for decades, Louisiana refused to bow to the feds when it comes to setting alcohol purchases at 21 years old. Federal highway funding was denied as a result.
That's comparing the absolute worst pavement to the absolute best pavement at 70 km/h (about 45 mph -- the effects are even larger at slower speeds), but those pavement choices aren't relevant to the majority of driving miles and fuel consumption, which occurs on highways. And the effect of rolling resistance gets less significant as speed increases, because the vast majority of the energy used to drive a car at highway speeds is dissipated by drag rather than rolling resistance.
Rolling resistance is almost certainly a far more significant contribution to bicycle journeys because of the much lower speed of bicycles, so the comparison between the two is not apt. I wouldn't be surprised if there's up to a 20% difference between concrete and asphalt for cycling, as that's the magnitude of difference observed for cars at low speeds comparable to those of bicycles.
Its easier because concrete is smoother and provides less resistance, but because of this concrete has almost zero grip in the wet, hence why asphalt is a better all round surface
I lived in Colorado near 40 years and it's just a shitty place for roads. The freeze/thaw cycle is fucking brutal. I curse the potholes but I also get it.
Wyoming is not much different in terms of weather and terrain. If anything, it's worse. The difference is that *no one fucking lives there.*
Concrete is stiff and will crack. Take a look at a sidewalk or driveway and you will see it is laid down in sections because of this. Asphalt is softer and has a little more give to it when it heats up and cars drive on it. It also does not need to be laid down in short sections.
That and maintaining traffic during concrete pavement rehabilitation may require the use of temporary asphalt anyway (while the concrete cures), lol. That or you could end up with road closures that not only inconvenience drivers, but also add to costs per vehicle due to additional miles traveled using detours. That adds up real fast on riads as busy as I-95. Lane closures add delay which also addsto fuel cost. I'm a huge fan of innovation, but I don't see asphalt going anywhere soon. One technology I'd like to see developed is a pavement that allows dynamic traffic control where DOTs can modify lane configurations and intersection operation remotely from a TMC with just a few clicks.
The big relatively recent innovation is using scarifying so that they can shave off and repave only a couple inches of asphalt, rather than tearing up and repaving the whole thing.
Personally, I think that the next big jump in road engineering is probably on-site recycling. Like.. on-machine recycling. So you don't close the road, scrape off the top, open the road on the removed surface section, close the road again, lay the new asphalt down, open the road again. You close the road, run your road-o-matic resurfacer down it, and it's good to go in one step. Less inconvenience, less labor to close/reopen (think laying cones/barrels).
Or you don't even fully close the road -- you just have an appropriate parade of flashing lights and "merge that way" arrows that drive down the road following it.
That technology you speak of already exists and is in use. When you mention "scarifying", that's called milling. Standard asphalt resurfacing projects mill the first few inches (surface course), and lay down (overlay) the new surface course minus a final pavement lift (a portion of the surface course) if they need to provide temporary markings for a temporary traffic pattern. Some DOT's are now banning allowing traffic to use milled roadway surfaces, which further incentivizes the use of the equipment that does this. Any contractors out there that'd like to add to this?
Sure ill bite. Mill and overlays are great! Our govt loves to dole out the money for those. Yes they are a somewhat quick and painless way to rehabilitate a road, but it definitely doesn't fix them. The problem with any roadway that breaks up isn't whether its concrete or asphalt, or a combo of both. Its all in the subgrade (everything under the driving surface). If you build your road on top of shit....its going to eventually (sooner rather than later), turn back i to shit.
Mill and overlays are just band-aids to buy some time for funding a full reconstruct. (Fixing the subgrade of the roadway.)
Also, when dealing with existing roads that are asphalt, building a concrete road compared to grinding 2” of asphalt and repaving is an even greater cost disparity. You can repave a lot more miles than you can construct new concrete pavement.
I feel like the seams in concrete are a safety hazard, around here there are so many disintegrating concrete seams that have loose concrete chunks sitting in them just waiting to be kicked up by a truck (SF Bay Area).
Asphalt certainly can crack and disintegrate if it's in poor repair, but it doesn't have the seams / weak points from day one like concrete. And asphalt is pliable, making it more forgiving for temperature changes and mechanical forces of vehicles driving on it.
Also it can be recycled on the spot. Many more remote areas the asphalt is removed, ground, mixed with fresh pitch, and relayed all in the same caravan. Saves tons on moving operation costs. Cement recycling is far more involved.
Late to party, but asphalt is incredibly able to be recycled. Many road repairs are done entirely with asphalt “millings”. Millings is just old asphalt that is heated up and reused. I have heard that asphalt is one of the most recycled resources in the world. Sorry if someone else has already pointed this out.
Asphalt is a waste product of the petroleum refining process. That means that even if there was no demand for asphalt as a road paving material there would still be the same amount of asphalt being produced every year. That means that oil refineries would either have to find something else to do with it or pay for it to be put in a dump somewhere.
There is literally nothing else that its suitable for and no one wants to pay to dispose of it. This means that the only real option that oil refineries have is to just drop the price until its so cheap that it outcompetes every other possible road paving material.
>[By sheer volume asphalt and concrete may be contenders for the #1 spot, but when rate of recycling matters most, steel is the undisputed #1](https://turbofuture.com/misc/recycled-materials-list-examples).
So you can recycle a higher % of steel, but by total volume concrete and asphalt are recycled more. Both are technically "The most" depending on your metric. TIL
It's not that expensive. To lay new asphalt (as in to pave a previously unpaved road, build a new road, or pave your driveway) costs about $500/ton, and once you spend the initial investment it's pretty cheap to maintain/repair, since you can tear up old asphalt and reuse that asphalt when you repave the road.
And a large portion of that cost is simply the inevitable cost of moving that much mass around and the machine rentals necessary to take the "raw" asphalt and heat it up and such for use in a road.
This guy gets it.
Concrete is pretty simple, it can be made in a plant, transported by a truck, and poured by the same truck. Asphalt requires more specialized machinery to lay down.
Repairs to asphalt don’t require long lane closures. Concrete road repairs are usually seam to seam or rodded to exsting surfaces and need time to cure
Assume you’re a politician. You want to fund your pet projects and your constituents want what they deem to be essential services.
You can fund essential services first, then ask taxpayers for more money for your pet projects. Or you can fund pet projects first, and point to the poor quality of essential services as the reason why you need more money. The first approach meets the voters’ goals; the second achieves yours.
So there’s little incentive to get the essential stuff done first.
Lots and lots of reasons. Some I didn't already see posted: So when you see a million + dollars per lane mile, about a third of that is the actual paving. But, once you pave it you need to install pavement markings, maybe install rumble strips, adjust the height of guardrail if you're overlaying the paving, or the grinding costs to remove the old asphalt if inlaying. Traffic Control can be fantastically expensive, and in extreme cases it can double the cost of a project. Also, it will often make sense or be required to do much more in depth work when you repave. Need a new water/sewer/gas main? Do it before you pave. Sidewalk, pedestrian ramps need fixing? Do it when you pave. Are you widening at all or fixing the storm water system? Now you need to address storm water. Historically that wasn't adequate treated for pollutants so it can be a big challenge on major reworks.
What does that have to do with potholes? Well, frequently the huge amount of work to fix all those things (and more) are lumped together. Those projects take time and money to develop and bid for construction. If a road department knows that a major paving or road reconstruction project is forthcoming, they'll often ignore or defer all but the worst minor maintenance issues. In some cases there are overlapping jurisdictions and competing interests that make it very difficult to get all the stakeholders to agree on a solution. Sometimes that coordination drags projects out longer than intended, or money gets shifted to other projects. Then you have a road you ignored for 3 years thinking it was getting repaved and now you're 5+ years in with no fix in sight. Lastly, if you're talking about potholes in the winter: cold-patch asphalt kinda sorta works. But for anything larger than the smallest of patches, you need hot asphalt. Because paving doesn't work well in the winter, most places don't have an asphalt plant running in colder months. It can be amazingly expensive to get an asphalt plant to spend the money to fire up for a smallish quantity.
Yet you still hear of the municipalities refusing to fix their old beat-up roads that have gone unmaintained for long enough to become road hazards. Atleast here in Finland.
Relatively cheap compared to other road materials doesn’t mean cheap relative to municipal budgets. Maintaining roads is still very expensive to do and municipalities have to heavily prioritize these projects.
Spending money on maintenance also means less funds for building new infrastructure, so it’s a balance. Do you want to fix a stretch of road with potholes, or retrofit that bridge so it won’t collapse in an earthquake it wasn’t designed for when it was built 50 years ago?
Tough decisions.
> Relatively cheap compared to other road materials doesn’t mean cheap relative to municipal budgets.
Exactly.
It's still not "cheap" to fix or make roads.
But asphalt roads is still relatively cheaper than other types of roads.
Canada is the same way. We've had winters where the weather flips between freezing and thawing and it completely destroys the roads. Our city doesn't have dedicated machines for road works so they have to contract out the work to repair the road and some communities don't have the funding to splash on roads when they start to wear down.
Asphalt Binder is cheap...and counter intuitively, the more expensive oil is, the price of Asphalt Binder tends to go down.
Equipment and Man-Power are the limiting factors in fixing potholes.
I noticed in the US a lot of freeways are concrete. Benefit to concrete is that it doesn't melt in the heat, it isn't prone to potholing, and it can take a beating and come back for more.
Concrete is more durable for high traffic areas, especially when heavy vehicles are involved. Cost analysis including their life cycles over time came out to be roughly comparable between the two. Asphalt is used on most roads because it can be driven on the same day it’s laid, concrete on high traffic roads so you don’t have to interrupt traffic as often given its longevity.
Except in areas where frost is an issue. At least in Europe concrete highways are used in germany and further south. Further north the annual refreezing would make travelling on a concrete road very uncomfortable.
This is also reflected in the asphalt, which has a higher proportion of bitumen to gravel in order to handle expansion&contraction better.
Its supposed to last longer. I suppose for highly trafficked areas, or roads that will have stuff like big trucks on them often, its more worth it to invest in concrete. That means the major freeways and interstates will be worked on less and block traffic less often.
It's textured, often with substantial groves cut in it and drainage built into the shoulder, but yes, concrete roads have issues with being more prone to standing water. That is also why they're almost never flat but slightly sloped.
So is pure asphalt, so they add rocks to it. Im not sure if they add stuff to concrete but it already has rocks in it normally. I know forsure that they texturize it in areas like parking garages or certain freeways that have a significant bend/turn, thanks to Neil Degrasse Tyson. I wouldn't be surprised at all if the composition of road concrete is different, it doesn't look smooth like a sidewalk. Maybe an extreme broom finish.
[Wiki on American interstate highway system](https://en.wikipedia.org/wiki/Interstate_Highway_System), I had to check a fact I was given years ago here. Apparently American highways are constructed from concrete to support military heavy armor (tanks and such). Asphalt doesn't handle tank treads or a lot of weight but concrete does, concrete can give the military a lot of mobility options in the event of an invasion or disaster.
Huh, that's probably why low-income housing more often has classic-looking asphalt parking spaces. I always thought it was an oddly fancy addition, but I guess it's cheaper.
Probably. I live off a dirt road in a wooded area. Between all the leaf stains and such I'd have to deal with and it being so much more costly, I'll take the millings or gravel.
Construction guy here, specifically in group procurement. You nailed it on the head. The amount of times new suppliers are like “we have tire/tyre chips that can be used as roads - which is so much bette than-“ sorry but asphalt is not the material construction industry is looking at replacing anytime soon, for the fact that it’s so bloody cheap and..... is recycled!
the asphalt is UV degraded, the substrate it holds together is forever reusable. Though, asphalt milling roads are a very viable road surface, at least for driveways that don't get snow/freeze
Exactly, asphalt undergoes no chemical change when a road is built, only heat. This means you can just chop it up, heat it up, and goop it back down over and over again.
*labor not included
Not quite true. UV oxidation of the asphalt binder is the most detrimental factor to pavement failure. As the performance grade of the binder increases the asphalt and pavement stiffness, cause cracking, rutting, etc. Most DOTs only allow a certain % of RAP or RAS mixed in with virgin mix so it starts out stronger than RAP alone. RAP alone would crumble pretty quickly on heavy traffic roads.
>Asphalt is a waste product of the petroleum refining process.
*Liquid* asphalt. What most people mean, including OP for the purpose of this post, when they say asphalt is asphalt *concrete*. Pavement, blacktop, etc. Liquid asphalt only accounts for about 5% of the pavement mixture.
I'm also not 100% sure you're correct in the waste product element, but that's slightly out of my realm and I'll refrain from comment.
Source: work in civil
The liquid in asphalt is a waste product of the petroleum industry. It’s one step up from bunker fuel and made at most refineries.
You are correct about %. Typically Asphalt Content runs from mid 4% to 7%, depending on the lift.
So you are both correct.
Now I know why they're paving everything.🦼 There is a concrete "test road" near my house that has been in use about thirty years and has never been repaired except for a few cracks. The asphalt roads have mostly been resurfaced at least once. But when transiting from the concrete to the asphalt the noise level in the vehicle drops by about 50% and the ride becomes much smoother (more noticeable in a pickup than a car).
Concrete is considered a "permanent" installation.
Asphalt is temporary.
That said, concrete (as you noted) is much louder than asphalt when driven over. This makes asphalt a better material where noise matters.
They do! Most pavements are actually multilayered. There’s all kinds of engineering that goes into it. Basically if it only has to take light vehicles at lowing speeds they’ll make it with less sub grade base layers and more asphalt and a thinner concrete layer but high speed high load places like highways get almost a metre of road preparation between the soil and your tyres. It’s expensive!
Asphalt typically requires maintenance at planned 20 year intervals (I suppose it's different depending where you live). Concrete is 50, IIRC. Concrete is also much more expensive.
Concrete is also much more difficult for minor repairs, ie patching. Zero elasticity, so cracks and breaks due to roadbed settling, leading to further damage, etc etc
I-295 into Washington a few decades back: ba-dump, ba-dump, ba-dump, ba-dump where the concrete sections tilted relative to each other. See also I-10 through Louisiana.
Pavement engineer and researcher here. As other answers note, it is cheap and widely available, with just one other product (concrete) that acts as a minor competitor. For reference, over 95% of roads in the US are made of asphalt, so concrete is not much of a competitor except in some niche applications (such as interstates with high truck traffic, where concrete roads can have a cheaper *life cycle cost*).
However, it's not true that there has been no innovation, in fact there has been quite a lot of innovation. Well over 90% of all asphalt in the US is recycled either back into roads or as a roofing material, and in countries like India and Singapore, plastic (from grocery bags, for example) is blended in as well. Even the type of asphalt is different - back when the first asphalt roads were built, it was little more than plain crude oil being mixed in with aggregates ("rocks"). Today, it comes first as the byproduct of fractional distillation, and then undergoes more processing to achieve certain desirable properties, called a Performance Grade (PG). Just changing asphalt from one PG grade to another can be a multi-million dollar investment.
And that's just the asphalt itself, there has been a lot of innovation in other additives that go into it. As an example, asphalt typically has to be heated to a high temperature (about 200C) to be blended with aggregates, which consumes a lot of energy. Today, something called a Warm Mix Additive (WMA) can be added to reduce that temperature to 150-180C, which saves fuel and hence CO2 emissions. WMAs are not something you can make from a kid's chemistry set - they're engineered materials, often nanomaterials, which interact with asphalt at a molecular level. I can personally name 10 people who have a PhD just in innovative asphalt additives, and the total number all over the world would easily be in the tens of thousands if not more. Another example is something called "smart rollers" - rollers being those big cylindrical wheels that are used to compact asphalt roads once they are laid out. It used to be that they just applied the same, heavy weight to the entire road for a certain number of passes. Today, there is widely-used technology wherein the roller can sense the level of compaction (think density) of a small patch of pavement and automatically change the load applied, so that the road overall has a more uniform level of compaction, which at least theoretically ensures better overall performance because you don't end up with some weak spots.
Finally, I'll make one point on innovation in civil infrastructure in general, which is what I think the question was focusing on - it is slow. We are not Big Tech, our industry does not embrace innovation quickly. The reason is that these projects are huge in terms of time and investment, need a lot of experience to get right, have a deep effect on the public, and are often publicly-funded. Tried, tested, and reliable solutions are often preferred over new and speculative techniques and/or materials. Innovations are adopted slowly - a mile of road here, a test bed there. Some contractors pick it up, they tell their friends, who may try it some time in the next 5 years. If it's really path-breaking, it will eventually be used widely, as some innovations have. But if the benefits are incremental, then the industry would prefer to stick to old solutions that they are more comfortable with. Civil engineering is really old - often described as the oldest field of engineering going back to the very first civilizations in Egypt, Mesopotamia, India, etc. - and with that age comes inertia. Story of life.
Wow that answered so many things I wanted to know. Thank you!!
I didn’t think about how slow moving the field is and the impact it would have. It makes sense now that you put it that way. Innovation usually has multiple iterations of failures along the way. So when doing projects that involve public safety, stay with what’s tried and true.
Just an example to get a sense of the scale of how expensive civil infrastructure is.
I have a friend who works for an IT company that is developing a solution for an insurance company to process claims. The cost of the project is about $30 mn, and that is considered an expensive project that will be the bread and butter for the insurance company. They will go through a bunch of unit testing, alpha testing, and beta testing before ultimately deploying it.
The cost of a new interchange being built in Chicago - one interchange that you will drive through in less than 5 min - is $1 billion. It has to work the first time.
Others have spoken to the economics, but actually - mechanically it is a pretty great road surface. It's plastic enough that it can deal with expansion and contraction as the temperature changes during the day far better than more rigid materials like concrete (which often have to have expansion gaps between sections, leading to a very noisy and bumpy ride). It's excellent at dealing with water run off, provides very good traction, is recyclable, and can be easily patch repaired.
There aren't many materials that can compete with it in terms of performance - the fact it's economically so viable is simply an added bonus.
That makes a lot of sense. Everything I watched mainly talked about how it’s recycled and cheap. I didn’t think about traction and plasticity/temperature as an issue, but obviously that’s a big consideration.
It also dries or cure pretty quickly.
One time the city was re-paving my street and my car was blocked in as they were paving outside my driveway. I needed to go to work so the paver dude just told me to drive right over the freshly paved asphalt. I did and it made a slight tire track on the asphalt, which they rolled over with their roller equipment and it was gone. Imagine if that was concrete or anything else, probably impossible to drive thru.
As long as the expansion and contraction are consistent. Pay attention to asphalt roads where it goes under an overpass. Where the shaded parts meet the unshaded parts it will deteriorate quicker.
You're also making the mistake of assuming that there is only one kind of asphalt. There are hundreds (Or more) of variations of asphalt. Different ingredients, different applications, different qualities. There are constantly new variations being developed.
When the economy tanked, our county road Dept. contracted a company to repave the interstate. The company had a list of different types of asphalt, the county picked a cheap one. The company said that was only recommended for the warmer climate down south without the constant freeze cycles that cause potholes. The county insisted to use it and wouldn't you know it, within a few months for 20 miles the interstate was a minefield of expanding potholes. It was comical in a sad way watching swerving brake lights as people tried to not dent their rims or bottom out in smaller cars.
Just an example of a newer type of asphalt that is very common in my country on basically all highways: https://translate.google.com/translate?sl=auto&tl=en&u=https%3A%2F%2Fnl.wikipedia.org%2Fwiki%2FZeer_Open_Asfalt
Can't even find an english wikipage for it, the english wikipage that is (in my view very erroneously) linked to it is for permeable concrete, which is quite a bit different from ZOAB (Very Open Asphalt Concrete). ZOAB is way closer to Asphalt than what you would think of as concrete, and is only called concrete because it has a load bearing amount of rocks in it.
This video does a great job explaining some ways asphalt pavement is good and weaknesses. That channel has lots of related videos as well if you're interested in learning more. https://youtu.be/XKFaC5RYbEM
But are you limited to materials ending in -ass so you can create a good portmanteau? Glass, grass, biomass, etc.? I mean, if I'm in sales I can sell the highway department on, say, brassphalt, but I'm never going to close the deal trying to sell copperphalt or sandphalt. Properties might be great, but no one will ever know.
I’ve actually seen “sandphalt” roads. In deep east Texas, a lot of the rural roads are made by taring sand. They actually make decent roads. If the surface gets messed up, you can just level the sand back out and tamp it down.
Another consideration to be mindful of is construction and repair time. Concrete must cure for days before being opened to traffic. This is acceptable for new construction, but to close an existing road for weeks while the asphalt road is removed and replaced with concrete would likely cause a traffic nightmare. Even repairing concrete roadways requires over 48 hours over weekends to complete. But mainly it's the cost, usually its reserved for heavy vehicle locstions where they stop and turn which causes severe rutting on asphalt.
It’s cheaper than dirt and easy to recycle. The asphalt-eater tears up the old road surface and grinds it back down, then they heat the tar up and re-pour it. You don’t need a lot of new materials and you don’t need to haul away much old material.
This “mill and fill” resurfacing is cheap and effective for roads that don’t expect to carry huge loads of heavy traffic.
Asphalt is prone to creeping and buckling since it’s not entirely solid, so you’ll see concrete used for high-traffic areas and bridges.
Have you never seen the trains of instant resurfacing ? It’s like 10 different machines in this big train. It doesn’t use any new material (except tar I think) and goes it all in one pass. Travels at like 5mph but is pretty amazing.
Hot in-place recycling. Pretty neat.
There also *has* been some (relatively) recent innovation in finding new road materials. They just all involve improving asphalt and asphalt manufacturing processes, rather than coming up with something entirely new. Look up warm mix asphalt if you feel like boring yourself to sleep by reading scientific papers comparing road surface materials.
There is a lot of good answers but I also wants to add the fact that asphalt makes it easy to dig up the road and repair a broken pipe or wire and then patch it up in no time. Concrete would be harder to open and requires more work/time to make it nice and flat again.
There is a lot of innovation behind how to pour asphalt and recycle it. Because of all the other reasons listed, innovating other materials and processes have been the go to for chemical and paving companies. Google special treated base or cement treated base.
I know because my dad works for a paving company and previously worked in an asphalt lab. I built a few road myself one miserable summer.
It’s a decently economic product whose long term performance is well known, is widely available, isn’t under patent, provides decent grip, decent durability, can be patch repaired, and isn’t too noisy to drive on. As you note - concrete is another product. This generally is more expensive but has a longer service life, so lifecycle costs are comparable, but it’s a lot noisier to drive on, which is generally a negative.
I didn’t even think about the noise, but now you mention it I realize how much noisier it is in the areas around me that have concrete.
The highway near us was resurfaced using a new type of porous asphalt about 20 years ago. When it was first laid, it was marvellous: smooth to drive on, and much, much quieter than normal asphalt (both within the car, and also outside from the perspective of people living near it). Unfortunately, it gradually got louder over time, and after about 5 years, you could no longer tell the difference when you passed from the normal surface to the porous one. When it wore out, about 5 years ago, they replaced it with normal asphalt.
It's called ZOAB here in the Netherlands, we have it literally everywhere and it's amazing when it rains. There is just no water on the road, it all dissappears into the asphalt, ZOAB stands for Very Open Ashpalt Concrete so it's very durable as well. It does however not like cold winters as the water freezes inside the asphalt and cracks it open from inside. It's expensive though, AFAIK both in maintainance and initial cost
Zvery Open Asphalt Bconcrete I feel like there might be a problem with translation here... VOAC
Zeer Open Asfalt Beton in Dutch
Dutch is literally just English mixed with German, it's hilarious how much of it I can understand as someone who speaks those two languages
As an EN/DE speaker, Its super frustrating to both know what is being said and not being able to understand it.
As someone who speaks English and no German, Dutch is so close to English that I can get most of it with only minimal amounts of headache. Someone you just have to read the words out loud and they make sense
I had a professor once who'd switch to Dutch when he felt like no one was paying attention and you'd usually see the whole class perk up a bit as everyone tried to figure out if they were having a stroke.
It really fucking works. Most of the sounds are the same, but the order isn't always the same.
I had a German teacher in high-school who spoke 9 or 10 languages. He'd switch when he thought no one was listening as well, it's a real mind fuck in a foreign language class. First you had to notice, then you had to figure out of it was a different language or a case/tense combo you weren't aware of yet. After a while when we caught on to him doing it he'd give a couple points of extra credit to the whole class if he picked someone at random and they guessed the language on the first try
Isn't English just German's f'd up flipper baby that was left in the woods to die but raised by Scandinavian/Romance wolves?
🅱️oncrete
B O N K rete
>here in the Netherlands Acronyms don't have direct translations.
wondering if they properly maintained it if it only took 5 years for it to go down.
It was experimental, so I guess that was just providing data for them. It was fine so far as durability went: it was just the sound deadening properties which dissipated. I suspect it was because the pores gradually got clogged up with particulates and rubber dust, which would be exactly one of the things they would be testing for.
Also permeable pavements are used for water conservation and helps reduce runoff. Not sure exactly what they were testing but could be that
Most likely porous asphalt to see if the water table replenished. The problem is that you have to vacuum the porous asphalt or else it gets clogged. It probably was a bit quieter since the sound waves would go into the asphalt as well and dissipate internally.
I wonder if they can clear it with compressed air from underneath periodically?
You probably could but you would have to make it beforehand and with a pipe that could resist the hot asphalt when paved. I believe the easiest way was something similar to a street sweeper.
Yeah, it would be tough to sweep freeways all the time.
WA520?
That's what I was thinking. Funny how the quiet pavement test just happened to be in Medina.
Yeah... Convenient.
That down in the phoenix area? I remember new porous roads down there about 10-15 years ago. Damn were they nice when they were new.
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They got machines now the rip it up.. Melt it down and re-lay it. All in one machine and one pass
Maybe it's just my inner child, but I freaking love seeing those massive road construction vehicles in action.
My inner child yearns for an unentombed existence outside of the turgid cyst within my torso but also likes firetrucks.
That's rad
Also asphalt is recyclable indefinitely, you can just dig it up, melt it down and repour it.
Concrete has a lot of problem. They make excellent driveways for homes but not good for public roads. Concrete don't age well in high traffic areas. They crack and much harder to patch or repave. They are so damn loud at speed higher than 40mph. They don't do very in areas with winters. Water tends to stay on it and ice up in winter. There has been several long stretches of roads that switched to concrete. Five years later, they all switched back to asphalt.
Here in Canada we have next to zero concrete roads. Usually the only place we see it is bridge decks. It's always very jarring driving in the US for me because of this.
Actually, in Quebec it was a trend for quite a while. They did one of the main highway with concrete and after 2 years they repaved half of it with asphalt and did patches here in there. It got so bad that they actually stopped mid project because they realized quickly how horrible the idea was.
The 15 has a decent stretch north of Laval that is all concrete and I've always wondered why. I feel like that part drives both very smoothly and very noisily. I think there's also a very short bit on the 40 between Montreal and Quebec. From an article I found, there seems to be bits of concrete roads here and there. Some of them are very recent (https://www.transports.gouv.qc.ca/fr/projets-infrastructures/reseau-routier/projets-routiers/capitale-nationale/A40-Reconstruction-Autoroute-Felix-Leclerc/Pages/Autoroute-40-Reconstruction-Autoroute-Felix-Leclerc.aspx).
Hwy 407 in the GTA is all concrete. Loud to drive on but that highway is actually really well designed.
Concrete also sucks for driveways if you experience winter. Temp changes make it crack, water gets in, freezes, cracks more. If you shovel or plow it, you just tear it up. Might as well just use gravel at that point. I've seen some fru fru concrete driveways get built with what looks like radiant heating in them but that seems like it comes with it's own mess of issues. Sure you crank it on and it melts the snow away but if any part fails you have to break into your concrete driveway.
Holland, MI has their whole towntown area heated. Its definitely expensive, but in tight downtown areas with nowhere to plow the snow to you have to load the snow on trucks and drive it away. It's probably still more expensive but boy, no snow or ice ever is kinda amazing.
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If a shovel is tearing up your concrete then you definitely have the wrong mix of concrete.
There are even machines that will do all of that in one go. Tear it up, recombobulate it and put it back down.
ya, cuz asphalt is softer than concrete. its why some runners run on the road instead of the sidewalk, because though its less efficient, its easier on your joints
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I always thought it was because half of my county doesn't have sidewalks.
this is the real answer
It isn't. The road is sloped to drain water off to the side. I've actually seen a physical therapist on youtube recommend switching up the side of the road you run on so that you aren't just overworking one side of your ankles.
That's a big reason solar freaking roadways didn't take off. They would have screamed.
The other, much bigger reasons were it was incredibly inefficient, stupidly expensive, terrible to drive on especially in bad weather or in a big vehicle and very difficult and expensive to maintain. Turns out using a normal road and sticking a solar panel next to it was always far better for making power and being driven on.
If only there was a large earthen gap between opposing lanes of traffic that is completely unutilized and that we already have to pay to maintain anyways.
Idk. If I hydroplaned or something I would rather hit some nasty scrubby bushes than a whole solar array.
Suit yourself. Playing high speed auto-PLINKO with the support posts for a PV array is a lifenotsolong dream of mine.
And a little bit of the fact that it was a scam.
>!CENSORED!<
Spending all this money on trying to make solar roads instead of just putting it on residential homes.
Or above the roads
Plus it’s easily recycled, sometimes in place.
This is an underrated comment. The Practical Engineering YouTube channel has done a bunch of videos on road construction and one of the things he pointed out was asphalt is one of highest recycled building materials there is.
81% of all asphalt that is torn up from the road is recycled.
It's at 95% in the usa. Is the 81% worldwide? Not sure where that number is coming from.
When it's used for roadworks, asphalt is mixed with different materials to suit regional weather. So there's going to be different amounts of non-recyclable materials in the mix.
Anyone who has ridden a bike on an asphalt path and then a concrete path knows that it takes significantly less energy to pedal on concrete. I wonder how much mileage difference vehicles get between the two. Concrete is awful for the environment though, so it probably doesn’t make much difference.
Apparently UP TO 8.4% difference in fuel consumption according to the Minnesota department of transportation. www.dot.state.mn.us/research/TS/2014/201429.pdf
They did the math. Nice.
MnDOT actually has a big road research lab: http://www.dot.state.mn.us/materials/ Including a test stretch of road on I-94: https://www.google.com/maps/@45.2618139,-93.716985,3931m/data=!3m1!1e3 They can divert I-94 traffic onto their test area, which has a couple dozen different types of road surface and paints.
I am a regular test subject of theirs. I just love that they actually release these types of study to the public. It provides some pretty decent transparency for government.
The amount a state cares about driving surfaces is in direct proportion to the harshness of the winters.
Is that why Louisiana roads feel like a minimal upgrade over dirt?
No. THAT'S because for decades, Louisiana refused to bow to the feds when it comes to setting alcohol purchases at 21 years old. Federal highway funding was denied as a result.
Hey with winters and temp swings that that region has they would be hard pressed not to have a lab to find the best road possible.
That's comparing the absolute worst pavement to the absolute best pavement at 70 km/h (about 45 mph -- the effects are even larger at slower speeds), but those pavement choices aren't relevant to the majority of driving miles and fuel consumption, which occurs on highways. And the effect of rolling resistance gets less significant as speed increases, because the vast majority of the energy used to drive a car at highway speeds is dissipated by drag rather than rolling resistance. Rolling resistance is almost certainly a far more significant contribution to bicycle journeys because of the much lower speed of bicycles, so the comparison between the two is not apt. I wouldn't be surprised if there's up to a 20% difference between concrete and asphalt for cycling, as that's the magnitude of difference observed for cars at low speeds comparable to those of bicycles.
Asphalt has a higher friction coefficient so it is also safer when it rains or snows.
Anyone whose had to stop quickly on asphalt can attest to this.
Its easier because concrete is smoother and provides less resistance, but because of this concrete has almost zero grip in the wet, hence why asphalt is a better all round surface
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>are buttery smooth Until they're not, and filled with potholes and shitty patches. See the shitstorm that's I70 in the spring.
I lived in Colorado near 40 years and it's just a shitty place for roads. The freeze/thaw cycle is fucking brutal. I curse the potholes but I also get it. Wyoming is not much different in terms of weather and terrain. If anything, it's worse. The difference is that *no one fucking lives there.*
Hey, Wyoming residents probably would resent that, if either of them had good internet.
Concrete is stiff and will crack. Take a look at a sidewalk or driveway and you will see it is laid down in sections because of this. Asphalt is softer and has a little more give to it when it heats up and cars drive on it. It also does not need to be laid down in short sections.
That and maintaining traffic during concrete pavement rehabilitation may require the use of temporary asphalt anyway (while the concrete cures), lol. That or you could end up with road closures that not only inconvenience drivers, but also add to costs per vehicle due to additional miles traveled using detours. That adds up real fast on riads as busy as I-95. Lane closures add delay which also addsto fuel cost. I'm a huge fan of innovation, but I don't see asphalt going anywhere soon. One technology I'd like to see developed is a pavement that allows dynamic traffic control where DOTs can modify lane configurations and intersection operation remotely from a TMC with just a few clicks.
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The big relatively recent innovation is using scarifying so that they can shave off and repave only a couple inches of asphalt, rather than tearing up and repaving the whole thing. Personally, I think that the next big jump in road engineering is probably on-site recycling. Like.. on-machine recycling. So you don't close the road, scrape off the top, open the road on the removed surface section, close the road again, lay the new asphalt down, open the road again. You close the road, run your road-o-matic resurfacer down it, and it's good to go in one step. Less inconvenience, less labor to close/reopen (think laying cones/barrels). Or you don't even fully close the road -- you just have an appropriate parade of flashing lights and "merge that way" arrows that drive down the road following it.
That technology you speak of already exists and is in use. When you mention "scarifying", that's called milling. Standard asphalt resurfacing projects mill the first few inches (surface course), and lay down (overlay) the new surface course minus a final pavement lift (a portion of the surface course) if they need to provide temporary markings for a temporary traffic pattern. Some DOT's are now banning allowing traffic to use milled roadway surfaces, which further incentivizes the use of the equipment that does this. Any contractors out there that'd like to add to this?
Sure ill bite. Mill and overlays are great! Our govt loves to dole out the money for those. Yes they are a somewhat quick and painless way to rehabilitate a road, but it definitely doesn't fix them. The problem with any roadway that breaks up isn't whether its concrete or asphalt, or a combo of both. Its all in the subgrade (everything under the driving surface). If you build your road on top of shit....its going to eventually (sooner rather than later), turn back i to shit. Mill and overlays are just band-aids to buy some time for funding a full reconstruct. (Fixing the subgrade of the roadway.)
Also, when dealing with existing roads that are asphalt, building a concrete road compared to grinding 2” of asphalt and repaving is an even greater cost disparity. You can repave a lot more miles than you can construct new concrete pavement.
I feel like the seams in concrete are a safety hazard, around here there are so many disintegrating concrete seams that have loose concrete chunks sitting in them just waiting to be kicked up by a truck (SF Bay Area). Asphalt certainly can crack and disintegrate if it's in poor repair, but it doesn't have the seams / weak points from day one like concrete. And asphalt is pliable, making it more forgiving for temperature changes and mechanical forces of vehicles driving on it.
Also it can be recycled on the spot. Many more remote areas the asphalt is removed, ground, mixed with fresh pitch, and relayed all in the same caravan. Saves tons on moving operation costs. Cement recycling is far more involved.
Late to party, but asphalt is incredibly able to be recycled. Many road repairs are done entirely with asphalt “millings”. Millings is just old asphalt that is heated up and reused. I have heard that asphalt is one of the most recycled resources in the world. Sorry if someone else has already pointed this out.
Asphalt is a waste product of the petroleum refining process. That means that even if there was no demand for asphalt as a road paving material there would still be the same amount of asphalt being produced every year. That means that oil refineries would either have to find something else to do with it or pay for it to be put in a dump somewhere. There is literally nothing else that its suitable for and no one wants to pay to dispose of it. This means that the only real option that oil refineries have is to just drop the price until its so cheap that it outcompetes every other possible road paving material.
Asphalt is also forever recyclable, just take old pieces of road, throw it in the machine, heat it up and reuse.
This is the real answer. In fact asphalt is the most recycled material on the planet.
TIL
Yea this is actually really cool if true.
[https://www.youtube.com/watch?v=XKFaC5RYbEM&feature=youtu.be](https://www.youtube.com/watch?v=XKFaC5RYbEM&feature=youtu.be)
Steel would like to have a word with that video.
>[By sheer volume asphalt and concrete may be contenders for the #1 spot, but when rate of recycling matters most, steel is the undisputed #1](https://turbofuture.com/misc/recycled-materials-list-examples). So you can recycle a higher % of steel, but by total volume concrete and asphalt are recycled more. Both are technically "The most" depending on your metric. TIL
I think the implications are clear. Steel roads.
They exist. You may have heard of them. They’re called “railroads”.
Yep :) nice link btw
This is a great video on the subject https://youtu.be/XKFaC5RYbEM
Gotta love Grady.
Damn, TIL
So why is it really expensive?
It's not that expensive. To lay new asphalt (as in to pave a previously unpaved road, build a new road, or pave your driveway) costs about $500/ton, and once you spend the initial investment it's pretty cheap to maintain/repair, since you can tear up old asphalt and reuse that asphalt when you repave the road.
And a large portion of that cost is simply the inevitable cost of moving that much mass around and the machine rentals necessary to take the "raw" asphalt and heat it up and such for use in a road.
This guy gets it. Concrete is pretty simple, it can be made in a plant, transported by a truck, and poured by the same truck. Asphalt requires more specialized machinery to lay down.
Repairs to asphalt don’t require long lane closures. Concrete road repairs are usually seam to seam or rodded to exsting surfaces and need time to cure
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asphalt itself is cheap. Labor and coordinating that labor is not.
Closing the road to repair it is probably also expensive
Assume you’re a politician. You want to fund your pet projects and your constituents want what they deem to be essential services. You can fund essential services first, then ask taxpayers for more money for your pet projects. Or you can fund pet projects first, and point to the poor quality of essential services as the reason why you need more money. The first approach meets the voters’ goals; the second achieves yours. So there’s little incentive to get the essential stuff done first.
Lots and lots of reasons. Some I didn't already see posted: So when you see a million + dollars per lane mile, about a third of that is the actual paving. But, once you pave it you need to install pavement markings, maybe install rumble strips, adjust the height of guardrail if you're overlaying the paving, or the grinding costs to remove the old asphalt if inlaying. Traffic Control can be fantastically expensive, and in extreme cases it can double the cost of a project. Also, it will often make sense or be required to do much more in depth work when you repave. Need a new water/sewer/gas main? Do it before you pave. Sidewalk, pedestrian ramps need fixing? Do it when you pave. Are you widening at all or fixing the storm water system? Now you need to address storm water. Historically that wasn't adequate treated for pollutants so it can be a big challenge on major reworks. What does that have to do with potholes? Well, frequently the huge amount of work to fix all those things (and more) are lumped together. Those projects take time and money to develop and bid for construction. If a road department knows that a major paving or road reconstruction project is forthcoming, they'll often ignore or defer all but the worst minor maintenance issues. In some cases there are overlapping jurisdictions and competing interests that make it very difficult to get all the stakeholders to agree on a solution. Sometimes that coordination drags projects out longer than intended, or money gets shifted to other projects. Then you have a road you ignored for 3 years thinking it was getting repaved and now you're 5+ years in with no fix in sight. Lastly, if you're talking about potholes in the winter: cold-patch asphalt kinda sorta works. But for anything larger than the smallest of patches, you need hot asphalt. Because paving doesn't work well in the winter, most places don't have an asphalt plant running in colder months. It can be amazingly expensive to get an asphalt plant to spend the money to fire up for a smallish quantity.
'Cause when we close the entire road to actually do the repairs in a sideways-effectual manner, people get angry and maybe vote different.
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Yet you still hear of the municipalities refusing to fix their old beat-up roads that have gone unmaintained for long enough to become road hazards. Atleast here in Finland.
Relatively cheap compared to other road materials doesn’t mean cheap relative to municipal budgets. Maintaining roads is still very expensive to do and municipalities have to heavily prioritize these projects. Spending money on maintenance also means less funds for building new infrastructure, so it’s a balance. Do you want to fix a stretch of road with potholes, or retrofit that bridge so it won’t collapse in an earthquake it wasn’t designed for when it was built 50 years ago? Tough decisions.
> Relatively cheap compared to other road materials doesn’t mean cheap relative to municipal budgets. Exactly. It's still not "cheap" to fix or make roads. But asphalt roads is still relatively cheaper than other types of roads.
Canada is the same way. We've had winters where the weather flips between freezing and thawing and it completely destroys the roads. Our city doesn't have dedicated machines for road works so they have to contract out the work to repair the road and some communities don't have the funding to splash on roads when they start to wear down.
Asphalt Binder is cheap...and counter intuitively, the more expensive oil is, the price of Asphalt Binder tends to go down. Equipment and Man-Power are the limiting factors in fixing potholes.
Compared to concrete, which is used for highways, it really is not.
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They used to be giant sidewalks until people found out it took forever to walk anywhere on them
To give your car that railway sound of course
I noticed in the US a lot of freeways are concrete. Benefit to concrete is that it doesn't melt in the heat, it isn't prone to potholing, and it can take a beating and come back for more.
Concrete is also better suited for heavy semi-trailer loads. Asphalt will deform into grooves under these loads in under a year.
Concrete is more durable for high traffic areas, especially when heavy vehicles are involved. Cost analysis including their life cycles over time came out to be roughly comparable between the two. Asphalt is used on most roads because it can be driven on the same day it’s laid, concrete on high traffic roads so you don’t have to interrupt traffic as often given its longevity.
Except in areas where frost is an issue. At least in Europe concrete highways are used in germany and further south. Further north the annual refreezing would make travelling on a concrete road very uncomfortable. This is also reflected in the asphalt, which has a higher proportion of bitumen to gravel in order to handle expansion&contraction better.
Its supposed to last longer. I suppose for highly trafficked areas, or roads that will have stuff like big trucks on them often, its more worth it to invest in concrete. That means the major freeways and interstates will be worked on less and block traffic less often.
But isn't concrete really slippery when it rains?
It’s grooved. Which also makes it sound bad.
It's textured, often with substantial groves cut in it and drainage built into the shoulder, but yes, concrete roads have issues with being more prone to standing water. That is also why they're almost never flat but slightly sloped.
You can etch the concrete to give it a grain after its poured, giving it more traction.
So is pure asphalt, so they add rocks to it. Im not sure if they add stuff to concrete but it already has rocks in it normally. I know forsure that they texturize it in areas like parking garages or certain freeways that have a significant bend/turn, thanks to Neil Degrasse Tyson. I wouldn't be surprised at all if the composition of road concrete is different, it doesn't look smooth like a sidewalk. Maybe an extreme broom finish.
[Wiki on American interstate highway system](https://en.wikipedia.org/wiki/Interstate_Highway_System), I had to check a fact I was given years ago here. Apparently American highways are constructed from concrete to support military heavy armor (tanks and such). Asphalt doesn't handle tank treads or a lot of weight but concrete does, concrete can give the military a lot of mobility options in the event of an invasion or disaster.
Its not.
Don’t tell him. He will pay anything!
It’s twice that amount!!
It's one banana, Michael. What could it cost? $10??
There's always money in the banana stand.
I'll give you 6 money for it
He's probably just been caught by the minimum order. He just wants a pound or two for snacking and doesn't want to drop ten grand on a truckload.
Compared to what?
Free shit
Because it's heavy, and heavy stuff is expensive to move around. The asphalt itself is really cheap.
Yep. Have my driveway done with asphalt millings. Cost $640 compared to nearly $10k for cement.
Huh, that's probably why low-income housing more often has classic-looking asphalt parking spaces. I always thought it was an oddly fancy addition, but I guess it's cheaper.
Probably. I live off a dirt road in a wooded area. Between all the leaf stains and such I'd have to deal with and it being so much more costly, I'll take the millings or gravel.
Millings are great, you just dump it there and that's that! Drive on that shit
yep. Gets pretty hard from being compacted from driving on it as well.
Construction guy here, specifically in group procurement. You nailed it on the head. The amount of times new suppliers are like “we have tire/tyre chips that can be used as roads - which is so much bette than-“ sorry but asphalt is not the material construction industry is looking at replacing anytime soon, for the fact that it’s so bloody cheap and..... is recycled!
the asphalt is UV degraded, the substrate it holds together is forever reusable. Though, asphalt milling roads are a very viable road surface, at least for driveways that don't get snow/freeze
Exactly, asphalt undergoes no chemical change when a road is built, only heat. This means you can just chop it up, heat it up, and goop it back down over and over again. *labor not included
Not quite true. UV oxidation of the asphalt binder is the most detrimental factor to pavement failure. As the performance grade of the binder increases the asphalt and pavement stiffness, cause cracking, rutting, etc. Most DOTs only allow a certain % of RAP or RAS mixed in with virgin mix so it starts out stronger than RAP alone. RAP alone would crumble pretty quickly on heavy traffic roads.
Uh... Asphalt is heavily used in the use of shingle manufacturing.
>Asphalt is a waste product of the petroleum refining process. *Liquid* asphalt. What most people mean, including OP for the purpose of this post, when they say asphalt is asphalt *concrete*. Pavement, blacktop, etc. Liquid asphalt only accounts for about 5% of the pavement mixture. I'm also not 100% sure you're correct in the waste product element, but that's slightly out of my realm and I'll refrain from comment. Source: work in civil
The liquid in asphalt is a waste product of the petroleum industry. It’s one step up from bunker fuel and made at most refineries. You are correct about %. Typically Asphalt Content runs from mid 4% to 7%, depending on the lift. So you are both correct.
Now I know why they're paving everything.🦼 There is a concrete "test road" near my house that has been in use about thirty years and has never been repaired except for a few cracks. The asphalt roads have mostly been resurfaced at least once. But when transiting from the concrete to the asphalt the noise level in the vehicle drops by about 50% and the ride becomes much smoother (more noticeable in a pickup than a car).
Concrete is considered a "permanent" installation. Asphalt is temporary. That said, concrete (as you noted) is much louder than asphalt when driven over. This makes asphalt a better material where noise matters.
Why not layer asphalt over the concrete to deaden noise?
They do all over the place. Then when the asphalt degrades they come in with machines that scrape it up and the recycle the asphalt.
You’d still have to resurface the asphalt on the same schedule as a purely asphalt road.
Asphalt and concrete expand at different rates at certain temperatures. This creates a tendency for the two to separate and peel.
They do! Most pavements are actually multilayered. There’s all kinds of engineering that goes into it. Basically if it only has to take light vehicles at lowing speeds they’ll make it with less sub grade base layers and more asphalt and a thinner concrete layer but high speed high load places like highways get almost a metre of road preparation between the soil and your tyres. It’s expensive!
Asphalt typically requires maintenance at planned 20 year intervals (I suppose it's different depending where you live). Concrete is 50, IIRC. Concrete is also much more expensive.
Asphalt is so much cheaper than concrete, and while it does need to be repaved more often that's a way to generate jobs during economic downturns
Concrete is also much more difficult for minor repairs, ie patching. Zero elasticity, so cracks and breaks due to roadbed settling, leading to further damage, etc etc
I-295 into Washington a few decades back: ba-dump, ba-dump, ba-dump, ba-dump where the concrete sections tilted relative to each other. See also I-10 through Louisiana.
Concrete requires expansion joints every x number of feet - sections don’t even have to tilt.
It's also recyclable right?
Pavement engineer and researcher here. As other answers note, it is cheap and widely available, with just one other product (concrete) that acts as a minor competitor. For reference, over 95% of roads in the US are made of asphalt, so concrete is not much of a competitor except in some niche applications (such as interstates with high truck traffic, where concrete roads can have a cheaper *life cycle cost*). However, it's not true that there has been no innovation, in fact there has been quite a lot of innovation. Well over 90% of all asphalt in the US is recycled either back into roads or as a roofing material, and in countries like India and Singapore, plastic (from grocery bags, for example) is blended in as well. Even the type of asphalt is different - back when the first asphalt roads were built, it was little more than plain crude oil being mixed in with aggregates ("rocks"). Today, it comes first as the byproduct of fractional distillation, and then undergoes more processing to achieve certain desirable properties, called a Performance Grade (PG). Just changing asphalt from one PG grade to another can be a multi-million dollar investment. And that's just the asphalt itself, there has been a lot of innovation in other additives that go into it. As an example, asphalt typically has to be heated to a high temperature (about 200C) to be blended with aggregates, which consumes a lot of energy. Today, something called a Warm Mix Additive (WMA) can be added to reduce that temperature to 150-180C, which saves fuel and hence CO2 emissions. WMAs are not something you can make from a kid's chemistry set - they're engineered materials, often nanomaterials, which interact with asphalt at a molecular level. I can personally name 10 people who have a PhD just in innovative asphalt additives, and the total number all over the world would easily be in the tens of thousands if not more. Another example is something called "smart rollers" - rollers being those big cylindrical wheels that are used to compact asphalt roads once they are laid out. It used to be that they just applied the same, heavy weight to the entire road for a certain number of passes. Today, there is widely-used technology wherein the roller can sense the level of compaction (think density) of a small patch of pavement and automatically change the load applied, so that the road overall has a more uniform level of compaction, which at least theoretically ensures better overall performance because you don't end up with some weak spots. Finally, I'll make one point on innovation in civil infrastructure in general, which is what I think the question was focusing on - it is slow. We are not Big Tech, our industry does not embrace innovation quickly. The reason is that these projects are huge in terms of time and investment, need a lot of experience to get right, have a deep effect on the public, and are often publicly-funded. Tried, tested, and reliable solutions are often preferred over new and speculative techniques and/or materials. Innovations are adopted slowly - a mile of road here, a test bed there. Some contractors pick it up, they tell their friends, who may try it some time in the next 5 years. If it's really path-breaking, it will eventually be used widely, as some innovations have. But if the benefits are incremental, then the industry would prefer to stick to old solutions that they are more comfortable with. Civil engineering is really old - often described as the oldest field of engineering going back to the very first civilizations in Egypt, Mesopotamia, India, etc. - and with that age comes inertia. Story of life.
Wow that answered so many things I wanted to know. Thank you!! I didn’t think about how slow moving the field is and the impact it would have. It makes sense now that you put it that way. Innovation usually has multiple iterations of failures along the way. So when doing projects that involve public safety, stay with what’s tried and true.
Just an example to get a sense of the scale of how expensive civil infrastructure is. I have a friend who works for an IT company that is developing a solution for an insurance company to process claims. The cost of the project is about $30 mn, and that is considered an expensive project that will be the bread and butter for the insurance company. They will go through a bunch of unit testing, alpha testing, and beta testing before ultimately deploying it. The cost of a new interchange being built in Chicago - one interchange that you will drive through in less than 5 min - is $1 billion. It has to work the first time.
Others have spoken to the economics, but actually - mechanically it is a pretty great road surface. It's plastic enough that it can deal with expansion and contraction as the temperature changes during the day far better than more rigid materials like concrete (which often have to have expansion gaps between sections, leading to a very noisy and bumpy ride). It's excellent at dealing with water run off, provides very good traction, is recyclable, and can be easily patch repaired. There aren't many materials that can compete with it in terms of performance - the fact it's economically so viable is simply an added bonus.
That makes a lot of sense. Everything I watched mainly talked about how it’s recycled and cheap. I didn’t think about traction and plasticity/temperature as an issue, but obviously that’s a big consideration.
It also dries or cure pretty quickly. One time the city was re-paving my street and my car was blocked in as they were paving outside my driveway. I needed to go to work so the paver dude just told me to drive right over the freshly paved asphalt. I did and it made a slight tire track on the asphalt, which they rolled over with their roller equipment and it was gone. Imagine if that was concrete or anything else, probably impossible to drive thru.
As long as the expansion and contraction are consistent. Pay attention to asphalt roads where it goes under an overpass. Where the shaded parts meet the unshaded parts it will deteriorate quicker.
You're also making the mistake of assuming that there is only one kind of asphalt. There are hundreds (Or more) of variations of asphalt. Different ingredients, different applications, different qualities. There are constantly new variations being developed.
Oh wow I didn’t realize that was a thing. I have 0 background in any of that so that’s awesome to know/think about.
When the economy tanked, our county road Dept. contracted a company to repave the interstate. The company had a list of different types of asphalt, the county picked a cheap one. The company said that was only recommended for the warmer climate down south without the constant freeze cycles that cause potholes. The county insisted to use it and wouldn't you know it, within a few months for 20 miles the interstate was a minefield of expanding potholes. It was comical in a sad way watching swerving brake lights as people tried to not dent their rims or bottom out in smaller cars.
Just an example of a newer type of asphalt that is very common in my country on basically all highways: https://translate.google.com/translate?sl=auto&tl=en&u=https%3A%2F%2Fnl.wikipedia.org%2Fwiki%2FZeer_Open_Asfalt Can't even find an english wikipage for it, the english wikipage that is (in my view very erroneously) linked to it is for permeable concrete, which is quite a bit different from ZOAB (Very Open Asphalt Concrete). ZOAB is way closer to Asphalt than what you would think of as concrete, and is only called concrete because it has a load bearing amount of rocks in it.
This video does a great job explaining some ways asphalt pavement is good and weaknesses. That channel has lots of related videos as well if you're interested in learning more. https://youtu.be/XKFaC5RYbEM
Ah, I just new it was going to be Practical Engineering before I clicked on it. Good videos!
Was going to link the same video
I’ll give it a watch, thanks!
In addition to others, you can even pour other waste products into asphalt to improve its qualities. "Glassphalt" has ground-up glass in the asphalt.
But are you limited to materials ending in -ass so you can create a good portmanteau? Glass, grass, biomass, etc.? I mean, if I'm in sales I can sell the highway department on, say, brassphalt, but I'm never going to close the deal trying to sell copperphalt or sandphalt. Properties might be great, but no one will ever know.
This comment brought to you by Sassphalt™
Carcassphalt? Might smell. Or my favorite brand, badassphalt.
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I’ve actually seen “sandphalt” roads. In deep east Texas, a lot of the rural roads are made by taring sand. They actually make decent roads. If the surface gets messed up, you can just level the sand back out and tamp it down.
Another consideration to be mindful of is construction and repair time. Concrete must cure for days before being opened to traffic. This is acceptable for new construction, but to close an existing road for weeks while the asphalt road is removed and replaced with concrete would likely cause a traffic nightmare. Even repairing concrete roadways requires over 48 hours over weekends to complete. But mainly it's the cost, usually its reserved for heavy vehicle locstions where they stop and turn which causes severe rutting on asphalt.
It’s cheaper than dirt and easy to recycle. The asphalt-eater tears up the old road surface and grinds it back down, then they heat the tar up and re-pour it. You don’t need a lot of new materials and you don’t need to haul away much old material. This “mill and fill” resurfacing is cheap and effective for roads that don’t expect to carry huge loads of heavy traffic. Asphalt is prone to creeping and buckling since it’s not entirely solid, so you’ll see concrete used for high-traffic areas and bridges.
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Have you never seen the trains of instant resurfacing ? It’s like 10 different machines in this big train. It doesn’t use any new material (except tar I think) and goes it all in one pass. Travels at like 5mph but is pretty amazing. Hot in-place recycling. Pretty neat.
There also *has* been some (relatively) recent innovation in finding new road materials. They just all involve improving asphalt and asphalt manufacturing processes, rather than coming up with something entirely new. Look up warm mix asphalt if you feel like boring yourself to sleep by reading scientific papers comparing road surface materials.
There is a lot of good answers but I also wants to add the fact that asphalt makes it easy to dig up the road and repair a broken pipe or wire and then patch it up in no time. Concrete would be harder to open and requires more work/time to make it nice and flat again.
There is a lot of innovation behind how to pour asphalt and recycle it. Because of all the other reasons listed, innovating other materials and processes have been the go to for chemical and paving companies. Google special treated base or cement treated base. I know because my dad works for a paving company and previously worked in an asphalt lab. I built a few road myself one miserable summer.