oly720man From United Kingdom, joined May 2004, 6182 posts, RR: 11 Reply 2, posted (2 years 6 months 6 days 10 hours ago) and read 8035 times:
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.
411A From United States of America, joined Nov 2001, 1826 posts, RR: 9 Reply 3, posted (2 years 6 months 6 days ago) and read 7819 times:
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 From United States of America, joined Mar 2009, 152 posts, RR: 0 Reply 4, posted (2 years 6 months 5 days 11 hours ago) and read 7642 times:
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.
411A From United States of America, joined Nov 2001, 1826 posts, RR: 9 Reply 7, posted (2 years 6 months 3 days 9 hours ago) and read 7195 times:
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.
A380900 From France, joined Dec 2003, 1006 posts, RR: 1 Reply 9, posted (2 years 6 months 2 hours ago) and read 6776 times:
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.
Zkpilot From New Zealand, joined Mar 2006, 4739 posts, RR: 10 Reply 10, posted (2 years 5 months 4 weeks 22 hours ago) and read 6596 times:
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.
jetblueguy22 From United States of America, joined Nov 2007, 2021 posts, RR: 1 Reply 11, posted (2 years 5 months 4 weeks 7 hours ago) and read 6406 times:
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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.
Blue
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TheSonntag From Germany, joined Jun 2005, 3347 posts, RR: 30 Reply 12, posted (2 years 5 months 4 weeks 3 hours ago) and read 6381 times:
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.
BMI727 From United States of America, joined Feb 2009, 14315 posts, RR: 26 Reply 13, posted (2 years 5 months 4 weeks 3 hours ago) and read 6376 times:
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 From Germany, joined Jun 2005, 3347 posts, RR: 30 Reply 14, posted (2 years 5 months 3 weeks 6 days 12 hours ago) and read 6289 times:
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 From United States of America, joined May 2006, 386 posts, RR: 0 Reply 15, posted (2 years 5 months 3 weeks 10 hours ago) and read 5974 times:
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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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.
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