General Question

Observing members: 0 Composing members: 0

21 Answers

Yellowdog's avatar

Expense, I think. is the only reason

There used to be concrete streets and concrete highways. Even they got in bad condition and were often paved over with asphalt

I could be wrong but I think some classes of asphalt roads DO have concrete beds.

In any case, my understanding is that it was the expense of building concrete streets and highways is why it was discontinued. And the cracks in any highway which will inevitably develop have to be repaired with tar and asphalt anyway.

kritiper's avatar

Concrete is more expensive. Asphalt is easier to work with during repairs.

ARE_you_kidding_me's avatar

On major highways they are, concrete is covered with asphalt.

elbanditoroso's avatar

Down here, most freeways and many other roads are concrete. In the south, the problem with asphalt is that it gets too soft in the summer.

It also tends to make potholes when the asphalt breaks apart.

I fon’t know where you live, @flo, but concrete roads are very common in and around Atlanta.

kritiper's avatar

Another point of asphalt is that it can be ground up, reheated and mixed with fresh asphalt, and reused. Concrete, for those that may not know, can’t be reused.

Patty_Melt's avatar

I worked for DOT in bridge and highway construction.
Asphalt has more give. In changing weather, it suffers damage, but easier damage to patch or replace than concrete.
Asphalt is quicker to be driveable. When a concrete mile is poured, as for a base, roads must be closed for much longer than with asphalt.
Concrete is rougher on tires.

Response moderated (Spam)
flo's avatar

But isn’t the expense of reparing potholes over and over and over high too when it’s asphalte?
apparently as @elbanditoroso says in and around Altlanta, concrete is it. But I wonder what the opposers of it say about that where concrete is being used.

flo's avatar

@Patty_Melt re. the tires that’s what I suspected too. I thought everyone would say that’s why asphalte is the prevalent one.

Patty_Melt's avatar

There are lots of things involved with the expense of any item, and that includes rock. I’m not familiar with the accounting end, but asphalt uses river rock. Concrete requires gravel, and gravel involves a lot more hours. It has to be mined, but also cut down into bits, and sized. Yes, sized. There are different sizes for various uses. One of the jobs I did with the DOT was aggregate and concrete testing. It was a process. Samples of gravel and sand had to be retrieved from the various supplying quarries. Each sample had to be washed, and not with tap water, which would affect the outcome.The runoff had to be kept because even the percentage of dust must be calculated. After washing, the sample must be heated, but not too hot, or quickly, because steam will pop big pieces into smaller pieces and ruin the results.
When the sample is cooled to room temp, it is dropped through a tower of stacked screens. Each screen is a different size, largest at the top. They are fitted in wood frames which contains the gravel of each descending size. Each size must then be weighed, and the dust also, accounting for the total weight, and weight of each size. This is a also done with sand but in a screen tower fitted for much finer aggregate, and that tower is shaken by a machine similar to paint mixers. All that cooking and shaking comes from science which has determined the best aggregate size percentage for various uses.
Each quarry also tests their aggregate with the same process to ensure the quality of any given stockpile.
All that involves man-hours. River rock is already precut.

I also tested concrete on site using simple tools to dump a sample into a stack. When the form is removed, the height is measured to determine the amount of slump which occurs, revealing the moisture content, and whether it is too much or too little.
One more test involved packing a sample into a metal box, and curing the proper amount of time. I then removed it from the box and loaded it into a machine to apply gradual pressure, and marking the PSI applied at the moment it breaks. Tim the tool man, whoa ho ho.
Asphalt only needs to cool, concrete must cure, which takes significantly longer. Deep south experiences a much lesser change in temperature and humidity, so they can get away with fewer repairs. Further north, concrete is fine for a base, but without asphalt on top, every crack would be a potential blowout for our tires. A crack in concrete is much sharper than a crack in asphalt.

I feel like I just provided an entry for Wikipedia. I hope at least somebody now understands.

Patty_Melt's avatar

Sorry for the spell check messes, I will fix as many as I can before time runs out.

flo's avatar

@Patty_Melt I’m exhausted just reading it.

Patty_Melt's avatar

You did ask. ;-)

flo's avatar

I did. Now I wait for what the other side says about that. I just heard some city is planning to use concrete.

Patty_Melt's avatar

If they haven’t got the equipment for asphalt, they would balk at the expense. For an idea of that, I refer you to Disney Pixar’s Cars.
Those machines are big, heavy, and costly. They can be borrowed. In a sparsely populated area concrete might be a better deal. The tire shop and mechanic’s garage will see an increase in business, but in a small community that is less expensive than where taxes would go to cover new equipment.

flo's avatar

@Patty_Melt Alright. Thanks

Temprature difference (expanding and contracting) that makes potholes and cracks, right?

Patty_Melt's avatar

It does.
Asphalt is damaged also by the elements, but it is more easily dealt with. For damaged can concrete, a full replacement must be done. Patching might be annoying, but it is faster and cheaper.

One of my jobs was to Wal down a few miles of rural highway with a can of spray paint, and mark the cracks a Nd potholes. That way the assessors could drive down the road later counting patches, and we here full depth replacement would take place. From my markings they could calculate the approximate tonnage needed and manhours it would take to finish the job. Just thought you might like to know a little bit about what takes place so repairs can happen. It is like some guys with trucks get to the company and somebody says, “Hey, maybe we should get maple Street today.”
A lot of planning and calculation happen first and accountability during.
Anyway, travel safe.
By the way, flaggers have an awful job of staff here in the sun ad hold this. Where I worked rural highways, locals would sometimes hand cold water or other beverage on their way past them. It is a nice gesture.
I wasn’t a flagger, but I would stand in for their breaks and when they had to… you know.

flo's avatar

Ok. But there is no (or hardly?) cracking and potholes when it’s concrete, right?

Patty_Melt's avatar

Concrete is also affected by weather conditions, but differently.
It depends on geographic location, weather types, and quality of concrete. Mostly it tends to chip and crack, and takes much longer to form holes of any real size. However, it has sharper edges, and that is so bad for tires. Also, those loose chunks get tossed under your car with a lot of force, which can cause other damage.
There is no process for patching damage, and replacement is costly, and keeps road sections out of use for much longer.
If I were going to use concrete, I would only want it for a road which does not get much use.

Response moderated (Spam)

Answer this question




to answer.

This question is in the General Section. Responses must be helpful and on-topic.

Your answer will be saved while you login or join.

Have a question? Ask Fluther!

What do you know more about?
Knowledge Networking @ Fluther