Understanding The Structure And Benefits Of Porous Asphalt

2 May 2017
 Categories: , Blog


Perhaps the single most destructive enemy of asphalt is water. Not only will its presence promote accelerated degradation and break down, but it also contributes to more dangerous driving conditions by lowering traction. Fortunately, one type of asphalt is able to greatly minimize unwanted problems such as these. If you would like to learn more about innovative forms of asphalt, read on. This article will discuss the unique benefits of so-called porous asphalt.

The Basics

All asphalt is composed of two principal ingredients: asphalt tar and aggregate, which is essentially gravel, and comes in a variety of sizes. Regular asphalt uses a full range of aggregate sizes, from sand- to pebble- to larger-sized chunks. Porous asphalt is distinct in that it leaves out the smallest category of aggregate. This places it in the category of so-called open-grade asphalts.

The result of the omission of fine aggregate is that there are more gaps between aggregate pieces. This allows water to drain downward through the asphalt. What makes porous asphalt unique from other types of open-grade asphalt is that it is generally installed atop what is known as a stone reservoir—basically a base layer of even larger stones. This allows water to drain safely and completely through the asphalt and into the ground below.


The nature of porous asphalt makes it especially beneficial for handling storm runoff. Not only is the water able to percolate down through the asphalt rather than remaining on the surface, but the stone reservoir then functions like a drywell. In other words, it acts as a holding tank for all of that excess water, allowing it to gradually drain off into the soil. This ability greatly reduces the need for auxiliary storm water systems.

Safer Driving

Another key benefit of porous asphalt is that is promotes safer conditions for driving. No standing water on the surface means better traction. It also reduces the amount of tire spray, which means visibility is much better for other cars. In the wintertime, porous asphalt also permits air to circulate, thus promoting better melting of ice and snow.


The principal disadvantage of porous asphalt is that it comes with a higher initial cost, as compared to traditional varieties of asphalt. A lot of this cost is tied to the extra construction efforts needed to put in the stone reservoir. Yet it is important to realize that the more expensive nature of porous asphalt will pay dividends in the long run, since porous asphalt's relative invulnerability to water means it will require fewer maintenance and repair efforts.

To learn more, contact an asphalt paving company like Lien Transportation Co.