mehairy7
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What Is The Thickness Of An Asphalt Runway?

Tue Nov 16, 2010 12:20 pm

From a civil engineering view, can you build an asphalt runway without using concrete underneath it?

Any input or links much appreciated.
 
cobra27
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RE: What Is The Thickness Of An Asphalt Runway?

Tue Nov 16, 2010 1:58 pm

I don't know about the runway, but I think than terminal 5 at Heathrow has around 40-50 cm of asphalt or concrete
 
oly720man
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RE: What Is The Thickness Of An Asphalt Runway?

Tue Nov 16, 2010 4:15 pm

Quoting mehairy7 (Thread starter):
can you build an asphalt runway without using concrete underneath it?

Yes, though there is a hardcore of gravel/crushed stone to provide a base layer. The thickness and design of the runway depends on the expected loads which, of course, depends on the aircraft using the airport.

This document probably covers how things are done

http://www.eapa.org/usr_img/position_paper/airfield.pdf

"Airfield uses of Asphalt"
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411A
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RE: What Is The Thickness Of An Asphalt Runway?

Wed Nov 17, 2010 1:50 am

Three general types of runway construction are used...

Concrete
Asphaltic concrete
Asphalt.

Concrete is classified as rigid pavement, and can be as much as six feet thick.
Asphaltic concrete is classified as semi-rigid, and can be as much as six feet thick.
Asphalt is classified as flexible pavement, and is laid over a bed of crushed stone (agregate) and is generally in excess of four feet thick...at airline airports.
 
rolypolyman
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RE: What Is The Thickness Of An Asphalt Runway?

Wed Nov 17, 2010 3:18 pm

Holy cow... six feet thick. To extend a 200 ft wide runway just 1 ft, that's 44 cu yd, or about $4400 last time I checked the price of concrete, not counting rebar and labor. Of course I'm sure that the airport gets hefty discounts because of the volume.
 
tdscanuck
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RE: What Is The Thickness Of An Asphalt Runway?

Thu Nov 18, 2010 4:49 am

The pavement data section of the ACAP documents gives a good overview of how this is handled, and provides references for the detailed calculations if you want more:
http://www.boeing.com/commercial/airports/acaps/7772sec7.pdf

Tom.
 
a380900
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RE: What Is The Thickness Of An Asphalt Runway?

Fri Nov 19, 2010 3:30 pm

Is the runway the same everywhere or are the "touchdown zones" stronger?

Can you revamp a runway or do you need to redo it from scratch?
 
411A
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RE: What Is The Thickness Of An Asphalt Runway?

Fri Nov 19, 2010 4:40 pm

Quoting A380900 (Reply 6):
Is the runway the same everywhere or are the "touchdown zones" stronger?

Sometimes, it depends on the agreed to specifications with the local airport authority.

Quoting A380900 (Reply 6):
Can you revamp a runway or do you need to redo it from scratch?

It largely depends on the underlying original base material.
Some concrete runways, just as one example, can be very successfully re-paved with asphalt, with good results.

However, one runway in particular (34L in JED) was completely torn up twice, and the touchdown zone twice again, because...the original contractor did not take into account the very high sub-surface water table, and the underlying subsurface composition...coral.
The airport opened six years late, as a direct result of this fiasco.
 
TheSonntag
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RE: What Is The Thickness Of An Asphalt Runway?

Mon Nov 22, 2010 11:07 pm

The thickness is hardly surprising. Even german Autobahn-motorways are already 2-3 feet thick of asphalt, with crushed stone beyond it.
 
a380900
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RE: What Is The Thickness Of An Asphalt Runway?

Tue Nov 23, 2010 12:34 am

Quoting TheSonntag (Reply 8):
Even german Autobahn-motorways are already 2-3 feet thick of asphalt, with crushed stone beyond it.

20 years ago I've heard a French engineer saying that highway in Germany were built to incredibly high standard. So maybe that's not an average comparison.
 
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Zkpilot
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RE: What Is The Thickness Of An Asphalt Runway?

Wed Nov 24, 2010 3:57 am

Quoting TheSonntag (Reply 8):
The thickness is hardly surprising. Even german Autobahn-motorways are already 2-3 feet thick of asphalt, with crushed stone beyond it.

Most of the older ones were built out of thick concrete so that one Herr Hitler's tanks could use them to move around the country.
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jetblueguy22
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RE: What Is The Thickness Of An Asphalt Runway?

Wed Nov 24, 2010 7:07 pm

Well that explains the extreme costs of building a runway. I always thought it just had to have a strong base underneath it and they just put down a light layer of concrete/rebar or asphalt like they would on an interstate.
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TheSonntag
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RE: What Is The Thickness Of An Asphalt Runway?

Wed Nov 24, 2010 10:42 pm

Quoting Zkpilot (Reply 10):

Most of the older ones were built out of thick concrete so that one Herr Hitler's tanks could use them to move around the country.

Thats more or less an urban myth, but it is correct that the Autobahn-motorways are indeed built of high standards. This pays off, of course, as the tracks last several decades before needing replacement. The old concrete surfaces of pre-ww2 autobahnen are still beneath some asphalt motorways, like the A8 between Munich and Salzburg. They are usually replaced when the motorways are expanded, because they get constructed after entirely new standards then.

But even modern tracks are built to high standards. I have once read that the Autobahn has the double price per km compared to US interstates. Still, runways are build to even higher standards.

One illustration about the Autobahn-thickness:

http://de.wikipedia.org/wiki/Datei:Oberbau.Autobahn.jpg
 
BMI727
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RE: What Is The Thickness Of An Asphalt Runway?

Wed Nov 24, 2010 11:06 pm

Quoting TheSonntag (Reply 12):
I have once read that the Autobahn has the double price per km compared to US interstates.

   But I don't know if that is purely construction costs, or if that includes the better maintenance of German roads or their more advanced traffic control systems.
Why do Aerospace Engineering students have to turn things in on time?
 
TheSonntag
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RE: What Is The Thickness Of An Asphalt Runway?

Thu Nov 25, 2010 1:56 pm

Quoting BMI727 (Reply 13):
But I don't know if that is purely construction costs, or if that includes the better maintenance of German roads or their more advanced traffic control systems.

It can also mean higher prices for the expropriated land, more efforts for noise protection and the like (since Germany is more densely populated than some stretches of the US). However I do think it also, at least to some extent, means better quality.
 
SP90
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RE: What Is The Thickness Of An Asphalt Runway?

Wed Dec 01, 2010 3:39 pm

Quoting TheSonntag (Reply 8):

The thickness is hardly surprising. Even german Autobahn-motorways are already 2-3 feet thick of asphalt, with crushed stone beyond it.

The roads around NYC are mostly asphalt but there is concrete underneath for a roadbed. I'm unsure as to the thickness but the top layer of asphalt is only about 4-6 inches maybe. The section of the I-90 that runs from Syracuse to Rochester (NY) is getting redone in all concrete. Quick look as I was driving by I would guesstimate it's about 2 feet thick. What strange is they would choose to use concrete there because of all the salt they put down during the winters. With runways its not a problem since they don't use salt for snow melting.

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