Although there are many types of pavement, all of the hard surfaced pavements fall into one of two categories; either flexible or rigid. A rigid pavement has several layers with the best quality material located nearest the surface. A flexible pavement offers an elastic surface and is made of a thin surface of hot-mix asphalt poured over a base. Where people once travelled over gravel, cobble stone or granite surfaces, since about 1920, asphalt has been the star of our roadways. It’s relatively easy and financially feasible to install, is easily repaired, and is durable even in temperature extremes.
Hot Mix Asphalt
Also referred to as HMA, blacktop or bitumen, and one of the most common asphalts poured in the United States, this is an economical and durable choice. It stands up to wear and tear and is considered an all purpose material. Most often this type of pavement is made using recycled asphalt pavement. Hot mix asphalt is poured at temperatures in the range of 150 degrees Celsius. (There are also warm and cold asphalt mixes, which are poured at lower temperatures.)
This type of asphalt is also known as permeable asphalt; it allows water to penetrate the surface and channels it into soil as opposed to a storm sewer. With this type of material, water does not often pool or puddle on the surface, and pavement runoff is almost eliminated. This asphalt would be most often used in light traffic areas or in parking lots where heavy loads aren’t likely to damage its more fragile surface. This asphalt is also used to reduce the noise of traffic.
Fine or Coarse Grade Asphalt
Fine or coarse grade asphalt fall into the “Dense Grade Asphalt” category and fall further into subcategories depending on their particle size. Sand grain sized particles will fall into the fine grade while anything larger tends to fall into the coarse grade. These are considered to be fine in most applications of paving, for both high and low traffic areas, and are good for rut resistance.
Stone Mastic Asphalt
Otherwise known as SMA, this asphalt wasn’t popularly used outside of Europe until the 1990’s. This is considered by many to be better than Dense Grade Asphalt for its resistance to ruts and other regularly occurring damage. This is a great option for high traffic areas including highways and interstates as well as busy intersections.
Other types of paving include concrete, composite and recycled pavement.
This is often used on local, low traffic areas and is generally categorized into JPCP, JRCP or CRCP depending on their joint systems. The joint systems are there to help avoid cracks from forming and concrete tends to be a long lasting solution, requiring little maintenance, although its high cost can be prohibitive.
Composites aren’t generally used as a main paving material, but are brought into use as maintenance and repair material for pavement. Generally made of both asphalt and concrete, this is often seen as asphalt overlay in damaged areas, or to fill cracks and holes.