The marvels of engineering are all around us, yet we often go about our daily business without thinking too much about it. Materials like asphalt and concrete are great examples, because we see them virtually everywhere we look, yet we seldom pay close attention. There are also plenty of engineering applications for concrete – it’s one of the strongest and most useful materials in the world, and it’s used all the time in construction. We may not be able to see a lot of this concrete with our naked eyes, but it’s definitely there, holding up the office and apartment buildings we use on a daily basis.
Here’s another example: Airport runways. We all know the feeling when the pilot hits the gas and the plane speeds down the concrete, gathering the required amount of velocity for liftoff. Inevitably, there will be a few bumps along the way, since no paved surface (especially one that’s subject to so much weight and constant traffic) is absolutely perfect. However, these bumps aren’t necessarily imperfections, and they’re actually very useful. Most airport runways are “grooved” after the pavement has been applied. This creates better drainage for rainfall and snowmelt. It also provides better traction and reduces the “hydroplane” effect during takeoff and landing.
Before we get further into the discussion of how airport runways are paved, it’s worth noting that not all designs are the same. The main material for airport runways can be asphalt or concrete, or a combination of the two.
The materials and thickness of the runway will be determined by a detailed analysis of the projected weight and frequency of airport traffic. When this analysis is done, it’s not always true that the heaviest aircraft is used to determine the necessary dimensions of the pavement. Some lighter aircraft actually require a thicker paved surface due to their landing gear and distribution of weight. All of these factors must be taken into account when airport runways are designed.
Most of the big airports we use for commercial air travel have pavement installations between 1 and 4 feet in depth, including the base layers or “subgrade.” Again, the exact thickness and dimensions of the runway will be determined by detailed analysis.
Once the design is in place, it’s really a matter of skilled crews using cutting edge tools and years of experience to install massive quantities of pavement, using the highest professional standards. These are big industrial paving projects, and they require a huge amount of organization and professionalism across the board. It typically takes 2-4 years to complete a large scale runway pavement project, and these installation are generally designed to last anywhere from 20 to 30 years.
We all need runways, and many of us need driveways
Believe it or not, many of the same design elements go into the pavement of residential driveways. There are general standards involving the weight and frequency of traffic, and most asphalt driveways easily last 20 years with no major repairs needed. Concrete typically lasts longer, averaging 30 years or more. This is assuming, of course, that the pavement has been installed by a skilled and experienced professional.