How thick are the concrete runways at commercial airports?

Question

Just curious on how thick they must be to support the massive weight in landing airplanes everyday.

Answer 1

One to 3 feet, usually. I worked for a contractor once who had to give an airport runway repair job back because they didn't have saws big enough to cut clear thru the runways.

Answer 2

very

Answer 3

It depends on the sizes of aircraft expected.  They range from as shallow as about one foot up to about four, or even five feet.

Answer 4

My company has installed the aprons (the area where the planes are parked by the gates) at several Bay Area airports. The concrete where they are parked is 16 inches thick. The area directly in front of the terminal where the fuel trucks and baggage trucks travel is 8 to 10 inches thick.

I am sorry but I do not have a runway thickness for you.

Answer 5

More than a foot.

Answer 6

The stress on a runway during landing is dependant on a number of factors. These include strut load, number of tyres per strut, tyre spacing, tyre size, and even tyre pressure.  

At major airports the concrete thickness is between 29cm and 33cm

Answer 7

am not sure on this but I heard an American made runway in  its former base outside of the US is more than 4 feet with interlaying rubber foam to have a shock absorbing effect on landing aircraft.

Answer 8

To answer your question will depend on the location of the airport, type of soil, weight of the aircraft and how many landing are required over a given time.  The information is available in AC 150/5320-6.  In round numbers 18-inches or thicker, however if you read the following it should help you understand why thick is important and we get there.  I know it’s a bit long, but it’s worth it.  At the end is a example how to determine thickness.

To build a runway involves the ground under the concrete or top coating and that will determine the thickness.

Throughout the 20th century, aircraft manufacturers accepted and followed the 1958 policy and designed aircraft landing gears that conformed to it-even though aircraft gross weights have long exceeded 350,000 pounds (159 000 kg). Despite the greater weights, manufacturers were able to conform to the policy by increasing the number and spacing of landing gear wheels.  AC 150/5320-6 does not affect the 1958 policy with regard to landing gear design.

The methods were adopted in 1978 to exploit advances in pavement technology and thus provide better performing pavements and easier-to-use design curves than were previously available.  Generally speaking, new guidance requires somewhat thicker pavement sections than were required prior to 1978.

The pavement design guidance presented now implements layered elastic theory based design procedures.  The FAA adopted this methodology to address the impact of new landing gear configurations such as the triple dual tandem (TDT) gear, which aircraft manufacturers developed and implemented in the early 1990s.  The TDT gear produces an unprecedented airport pavement-loading configuration, which appears to exceed the capability of the previous methods of design.  Previous methods incorporated some empiricism and have limited capacity for accommodating new gear and wheel arrangements.

Airport pavements are constructed to provide adequate support for the loads imposed by aircraft using an airport and to produce a firm, stable, smooth, all-year, all-weather surface free from dust or other particles that may be blown or picked up by propeller wash or jet blast. In order to satisfactorily fulfill these requirements, the pavement must be of such quality and thickness that it will not fail under the load imposed. In addition, it must possess sufficient inherent stability to withstand, without damage, the abrasive action of traffic, adverse weather conditions, and other deteriorating influences. To produce such pavements requires a coordination of many factors of design, construction, and inspection to assure the best possible combination of available materials and a high standard of workmanship.

To make a runway you have to consider these four factors:

(1) Surface. Surface courses include portland cement concrete, hot mix asphalt, sand-bituminous mixture, and sprayed bituminous surface treatments.

(2) Base. Base courses consist of a variety of different materials which generally fall into two main classes, treated and untreated. The untreated bases consist of crushed or uncrushed aggregates. The treated bases normally consist of a crushed or uncrushed aggregate that has been mixed with a stabilizer such as cement, bitumen, etc.

(3) Subbase. Subbase courses consist of a granular material, a stabilized granular material, or a stabilized soil.

(4) Geotextile. Geotextiles are permeable, flexible, textile materials sometimes used to provide separation between pavement aggregate and the underlying subgrade. Geotextile needs and requirements within a pavement section are dependent upon subgrade soil and groundwater conditions and on the type of overlying pavement aggregate.

The structural design of airport pavements requires determining both the overall pavement thickness and the thickness of the component parts of the pavement. There are a number of factors that influence the thickness of pavement required to provide satisfactory service. These include the magnitude and character of the aircraft loads to be supported, the volume of traffic, the concentration of traffic in certain areas, and the quality of the subgrade soil and materials that make up the pavement structure.

The pavement would be designed for 16,241 annual departures of a dual wheel aircraft weighing 190,500 pounds (86 410 kg).  The design, however, should provide for the heaviest aircraft in the traffic mixture, the B747-100, when considering depth of compaction, thickness of asphalt surface, drainage structures, etc.

Concrete Flexural Strength.  The required thickness of concrete pavement is related to the strength of the concrete used in the pavement.  Concrete strength is assessed by the flexural strength, as the primary action of a concrete pavement slab is flexure.  Concrete flexural strength should be determined by ASTM C 78 test method.  The design flexural strength of the concrete should be based on the age and strength the concrete will be required to have when it is scheduled to be opened to traffic.  Thickness design strength of 600 to 650 psi is recommended for most airfield applications.  Unless expedited construction is required, the strength specified for material acceptance during construction should be specified as a 28-day strength and be 5 percent less than the strength used for thickness design.

AN EXAMPLE

As an example of the use of the design curves, assume that a rigid pavement is to be designed for dual tandem aircraft having a gross weight of 350,000 pounds (160 000 kg) and for 6,000 annual equivalent departures of the design aircraft.  The equivalent annual departures of 6,000 include 1,200 annual departures of B-747 aircraft weighing 780,000 pounds (350 000 kg) gross weight.  The subgrade modulus of 100 PCI (25 MN/m3) with poor drainage and frost penetration is 18 inches (460 mm).  The feature to be designed is a primary runway and requires 100 percent frost protection.  The subgrade soil is CL. Concrete mix designs indicate a flexural strength of 650 PSI (4.5 MN/m*) can be readily produced with locally available aggregates.  The gross weight of the design aircraft dictates the use of a stabilized subbase.  Several thicknesses of stabilized subbases should be tried to determine the most economical section. Assume a stabilized subbase of P-304 will be used. Try a subbase thickness of 6 inches (150 mm) . Using a 6-inch (150 mm) thickness of P-304 would likely increase the foundation modulus from 100 PCI (25 MN/m3) to 210 PCI (57 MN/m3). Using, dual tandem design curve, with the assumed design data, yields a concrete pavement thickness of 16.6 inches (422 mm).  This thickness would be rounded off to 17 inches (430 mm).  Since the frost penetration is only 18 inches (460 mm) and the combined thickness of concrete pavement and stabilized subbase is 23 inches (585 mm), no further frost protection is needed.  Even though the wide body aircraft did not control the thickness of the slab, the wide bodies would have to be considered in the establishment of jointing requirements and design of drainage structures.  Other stabilized subbase thicknesses should be tried to determine the most economical section.

Answer 9

The development of the pavement design proceeds along a number of paths. Exploratory borings are taken to determine the subgrade condition, and based upon relative bearing capacity of the subgrade, different pavement specifications are established. Typically, for heavy-duty commercial aircraft, the pavement thickness, no matter what the top surface, varies from as little as 10 inches (25 centimetres) to as much as 4 ft (1 m), including subgrade.

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Answer 10

to meet the faa guidlines they have to be at least 4 feet thick