TERRA E-News, January 2013 – Volume 7, Number 1
Porous asphalt provides option for addressing environmental issues
Porous asphalt pavement technology was first developed in the United States more than 40 years ago. Porous pavement installations of different types are more common in Europe, but in the United States, porous asphalt primarily has been used in parking lots, recreational areas, and low-volume roadways. Today, porous asphalt is attracting attention as a tool in addressing environmental issues.
A new TERRA fact sheet about porous asphalt provides an overview of this innovative pavement technology, including details from a TERRA-initiated study about its performance in cold climates, key benefits, and several resources for more information.
Porous asphalt pavements allow water to drain directly through the open-graded pavement structure into underlying layers. This plant-mix asphalt pavement contains a reduced amount of fine aggregate particles and higher interconnected air voids between particles.
Because of its permeability, a porous asphalt pavement system helps reduce water runoff and offers other potential environmental, performance, and economic advantages for low-volume road applications.
For example, the direct infiltration of storm water through a properly designed porous asphalt pavement system into the subgrade soils can reduce both the volume and the peak intensity of storm water runoff, which in turn can decrease the need for costly drainage structures, ditches, and the purchase of additional right-of-way for storm water mitigation. And because water moves through the pavement, porous asphalt surfaces also may help reduce the use of sand and salt during winter.
In addition, porous asphalt pavement helps drivers by reducing hydroplaning, improving wet pavement friction, lowering splashing and spraying, and decreasing pavement surface glare, which leads to better visibility especially in night conditions.
Porous pavements usually have higher costs, and they may provide lower structural contribution, which makes them better candidates for low-volume facilities. Because they eventually can clog with dirt and debris, porous asphalt requires maintenance in the form of vacuuming and other cleaning methods, such as flushing with water.
A research study published in 2012 by the Minnesota Department of Transportation (MnDOT) and the Minnesota Local Road Research Board (LRRB) examined the durability, maintenance requirements, hydrologic benefits, and environmental considerations of porous asphalt pavement construction on a low-volume roadway in a cold climate. According to the findings, the porous asphalt pavement structure performed well in terms of water storage and infiltration. In addition, snow and ice was observed to melt faster on the porous pavements. The pavement also was quiet and provided significantly better skid resistance than dense-graded asphalt.
Related resources:
- Porous Asphalt Reduces Storm Water Runoff (TERRA fact sheet)
- Porous Asphalt Pavement Performance in Cold Regions (MnDOT technical summary, 2012) [1.1 MB PDF]
- “Porous Asphalt Pavements in Minnesota” (Hot Mix Asphalt Technology, 2010)
- Porous Asphalt Pavement (U.S. Environmental Protection Agency, 2009)