Asphalt serves a variety of purposes, from roads to airplane runways. So how is asphalt such a diverse material that does so many things? The real answer is that there are different types of asphalt that serve different purposes. According to the National Asphalt Pavement Association, there are six primary types of asphalt. This week and next week, we are exploring those six different types of asphalt. Read on to learn the composition and uses of the different types of asphalt.

  1. Stone-Matrix Asphalt

Stone-matrix asphalt is also known as SMA or stone mastic asphalt. It originated 60 years ago in Germany and became widely used in the United States by the early 1990s. Stone mastic asphalt is a heavy-duty asphalt, designed for use on roads where there is heavy duty traffic. The ultimate goal of stone-matrix asphalt is to resist ruts that originate with consistent heavy traffic. This means that SMA resists the deep ruts that trucks often leave in lighter types of asphalt.

Pavers often use SMA for heavily used roads such as highways. However, the ultra-sturdy asphalt is also used on regular streets, racetracks, and even aircraft runways. It is particularly popular for those types of places because it also reduces noise pollution quite a bit. Contractors mix stone-matrix asphalt with a gap-graded aggregate structure. Then, pavers use a binder with high asphalt content to bind everything together with extra strength.

  1. Perpetual Pavement

Perpetual pavement is a type of asphalt that uses a layering process to improve the smoothness of the ride as well as longevity of the road. There are three main layers at play here.

  • The first layer is a strong and flexible mix. This means that it holds weight, but doesn’t crack from heavy traffic.
  • Layer number two is the main layer that supports vehicular weight. It is heavy duty and the main structural component.
  • The top layer is mainly a finishing layer and it is also rut-resistant.

  1. Porous Asphalt

Porous asphalt is perfect for commercial projects, particularly parking lots, that require water flow control. It is very cost-effective and thus attractive to public works projects. Ultimately, porous asphalt allows water to pass through it into the ground. This prevents the buildup of water on the surface of the asphalt. In turn, there are less injuries or car accidents on the surface.

Usually, the key to functional porous asphalt is the subgrade. The subgrade must consist of stones with plenty of space in them to allow the water through. Once the water passes through the paving, it sinks into the soil beneath it, effectively getting absorbed once again. The matriculation has to occur at an exact rate to ensure that the water does not build up and flood the subgrade.

Come Back Next Week

To learn more about different types of asphalt.