Airport Runway Pavement Materials and Cracking

Did you investigate the effect of the geology in your area?

well that maybe part of the problem. not only does the native soil contain 5% montmorillonite, which swell when wet, but there is an underlying impervious calcite rock layer only about 1 meter down. however, the soil was well compacted to 96% plus. and there was a sub-base for the concrete. But even our CE is stumpped by this. IMHO a 250,000 kg jet landing at 200mph is a very heavy load for 14" - 18" slabs of 4000 psi concrete with no rebar, only welded wire fabric..

I remember somebody telling me many years back that concrete will always crack. I believe the little grooves put into the thin slab of a sidewalk are to allow aesthetically graceful cracks to happen. I'm mildly surprised that you have no reinforcing bars in a runway. The flexing of that bed from landings and takeoffs will repeatedly put the slab under tension conditions. The rock and aggregate under bed along with the soil compaction, drainage, and composition will also be a factor.

Take my civil engineering comments with a pound of salt. As you know, I'm not a civil engineer. If this is more than just casual speculation, you need a licensed civil engineer to to look at the design and execution of this runway.

Hopefully Capt. Moosie can provide some insight that won't require a fee.

I don't know the answers but this is an interesting post.

I suspect "people in the know" will need to know a little more to give a good answer. What country are you in? You may or may not want to give the exact location but temperature extremes, geology, typical materials/procedures in that area, concrete and water chemistry, woven wire fabric details, etc. might all help.

Davis??

Who is that?

you're kidding me right? the soil beneath your surface is known to swell and you're wondering if a different surface wont crack?? where is Moosie and his compaction machine? attempting to patch poor soil preparation is too late, tear it out, do it correctly and move on to other issuers.

Now I am curious about the other 95% at the top.

Have you gone on FAA's website. Here in the US they are the ones that design airport runways.

Not sure who did your design work, but FAA requires 7 lifts. Totaling 78" starting below the surface. Usually 6" of asphalt concrete 16" of cement concrete the rest is subgrade Mixture. Concrete slabs are poured slip form, no slabs. This is also the design matrix we used at several military bases here in the US including Luke Airforce base Glendale, AZ.

You mean with no rebars? I'd be as surprprised by that as Redfred in #3, but then I'm not a civil engineer either.

Rbear is never used is in slip form for roadways or run ways. The not like something going to be sitting on it. The object is on then off rapidly. You don't believe me ask moosie or read up with a road design manual.

OK I wasn't questioning your ability, just curious

It's good to question, it's how we learn. Captain Moose should be able to verify or correct my statement. I've work in heavy construction in all phases design, construction, and maintenaince; but I've specialized in QC, materials, environmental, and safety in those phases.

BakerJohn is correct. Slip-formed concrete pavements have no rebar.

Your slabs are 6 X 6 meters and the corners show cracks?

How are they put in place? Do you have full cut through seems between the panels?

Are they poured on the spot?

What is the distance between the wheels of your jets? Perhaps you should change the

width to a different size (reducton), so that the landing tracks are more diverted away from the edges.

Some pictures would help us show how the cracks occur and what to be done as remedy.

What is your WWF made of and where in the slab is it situated?

You sound as though you are in fact the Civil Engineer in charge of the repavement . Who doesn't know what country Heathrow is in ? Corners cracking is a good one , other than high PSI concrete , in order to increase the weight capacity in your heavy aircraft landing zone you would almost have to experiment with some sort of elastic polymer . I would be interested in finding the one that could withstand large aircraft hitting it myself . May I make a recomendation ? There is a little known technique whereby when concrete is poured and mixed , a polymer fiber is added to enhance concrete's elastic properties . Various strong thread fibres come to mind , the toughest may be Boron . Boron is added to resin matrix for the same reason , it's a fiberous thread , but has qualities which make it one of the toughest re inforcement fibres available .

Dragon113 Canada

I believe that if u want ZERO cracks on the landing patch of a runway (at both ends) U need to drive pillars (stilts) into the ground at the said location. and build on that. I am SURE nothing will give once settled.

An 'exaggerated' runway on stilts is Madeira Airport in Portugal. Nothing moves.

Im not the CE in charge of this. The CE, is scratching his head on has no answers to this one. The native soil is "gatch" defined here http://www.sciencedirect.com/science/article/pii/0013795268900136

which does indeed swell when wet. The 6m x 6m slabs are poured in place. And of course the slab is kept wet while curing in the 50 degrees C ambient. Cracking does not occur during the curing process, but for example 6 - 12 months after the pour.

They are poured in checkerboard fashion and dowelled to each other on one side only.

This is in Kuwait desert where temperatures vary from 0 degrees C to 50 degrees C.

It does rain average 4-5" per year. Because of the different planes that use the runway (small F-16, medium C-130, heavy C-17) we cant plan on any specific wheels landing in any exact location.

What I was hoping for is:

1. something like the boron or polyester fiber admix for concrete limit cracking, or

2. a more flexible pavement than concrete, but able to handle a landing of 250,000 kg jet going 200 mph. I really think we need to go to plasticized bituminous or plasticized asphault.

The concrete is only as good as the underground. Usually streets need a good preparation for the bottom layers. The same for your runway. I would dig out the soil and replace with sand not Gatch. When reading the description it cries out loud replace me. Then any concrete will be good. Reinforcing it will depend on the loads.

The CE is scratching his head aha. I could come up with a neat little expensive solution, but it has to be paid work.

Runways should not be rocket science. If you want to know about Heathrow why not find out who build it and what they used?

Excellent!

I'm so glad you heard our calls. Your "back of the envelope" analysis of the plausible collection of reasons for these ill-defined cracks is again very rewarding for me.

The only remote possibility that comes to my layman's mind that you did not touch upon is a real geologic change in the sub-grade below all previous construction work. This could be from natural (quake, sink hole) or man made (oil extraction, water diversion) origins. Ground penetrating radar or seismic acoustic testing might reveal these possibilities without extensive excavation.

Thank you once again. That was fun.

Fred, you're very welcome!

You are correct, I didn't touch on the geology aspects too much. I have no idea if there was any soil borings and other testing conducted. I don't even know if Hydraulic Fracturing is conducted in the UK or if it was done near the airport. I don't think that's an issue here. Crappy soil and inadequate runway design most certainly is.

I don't know about sink holes developing here, as we don't know the full breathe and extent of the problems. If the panel cracking is localized, than sinkholes or subgrade soil subsistence may be a factor. If the problem is more widespread I believe that a weak subgrade and nonexistent subbase grade, coupled with an inadequate rigid pavement is more to blame.

For the life of me, I cannot understand the engineering reasoning behind the resultant construction of the runway for such an important international airport. It just doesn't make sense, or did cost or political considerations enter too much into the mix? Unfortunately, the OP hasn't given us the full history behind the runway project.

I also blame faulty engineering for the panel corner cracking...

Moosie

P-501 psi design is 4000. Breaks should usually be around 8-10k at 28 days. As you stated there is very little info. Being in Kuwait in the desert if anything like AZ swelling shouldn't be an issue, as least not enough to cause damage to a runway.

Question was runway built by US military contractors or by Kuwaiti? If by US they should have been following FAA and DOD requirements, which can easily be looked up.

If this was a US military built runway in Kuwait then there is a possibility the runway was intended to be temporary in the first place.

My thought exactly once the OP mentioned military equipment. I though of first Gulf War and the runways the US and allied forces massed produced.

Moosie

what do you think about this article?

https://books.google.com/books?id=O9nNYr-12G4C&pg=PA594&lpg=PA594&dq=kuwait+concrete+for+airport+runway&source=bl&ots=uIIZe4fUZs&sig=FmcoXvycOMz_koci2ZPtJa7s1uo&hl=en&sa=X&ei=aCIMVZb2DNLjoASCoIHQAg&ved=0CCQQ6AEwATgK#v=onepage&q=kuwait%20concrete%20for%20airport%20runway&f=false

It deals with the issues Kuwait is having with cracking and pressed concrete.

My screw up.....why was I thinking this was at Heathrow in the UK? Ughhhhh...misread a few comments.

BakerJohn: Although I've never have designed an airport runway using Prestressing tendons, at first glance it looks like it has some advantages and merit.

I tend to like this design approach a lot! Thanks!!!!

Who designed this Air Base, the US. Army corps of Engineers, or some engineering firm under contract with the DoD or the Kuwatis?

Sorry, no records available that old. No records available before 2000.

But I found what I need:

Marshall Asphault

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/33545/spec_132009.pdf

Two questions:

What will be the surface temperature of the runway in 50 degree C full sun?

Will the Marshall Asphalt support landing load stresses at that temp?

GoodGuy, this is is the same material used in military airfields (including Little Heathrow) is southern Afghanistan desert at similar climate. One of its advantages is easy maintenance, the top 4" or so is millable and replaceable as needed.

Glad to know that considered that.

Happy landings!