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How Green Pavement Works

        Science | Green Science

Permeable Pavement
Plastic pavers generally consist of the above components.
Plastic pavers generally consist of the above components.

Green pavement is catchall name for a few different types of environmentally friendly pavements and vehicle surfaces suited for different contexts, such as hot climates, high-speed traffic areas and less-traversed areas.

When people talk about green pavement, they are usually referring to permeable pavement. Unlike traditional asphalt or concrete, permeable pavement is porous; it allows water to run through it rather than pool on top or run off of it. Water percolates, as in a coffee pot, when it seeps through the pavement to a cleansing layer of gravel. The gravel or stone acts as a natural filter, clearing the water of pollutants. There are three types of permeable pavements:

  1. Traditional asphalt/concrete -- This is the standard mix, except that fine particles are left out of it to make it more porous.
  2. Plastic pavers -- These plastic grids have a honeycomb shape. Once installed, grass or other vegetation can grow through the holes.
  3. Concrete pavers -- Concrete blocks with spaces in between them. These spaces allow for better drainage and water permeability.

When installed as part of an overall system, permeable pavement can even eliminate the need for curb gutters and storm sewers [source: Green Resource Center]. Flooding concerns lessen, as rainwater soaks into the ground.

Permeable pavement has many applications. Common uses include driveways, emergency access lanes, public parks, alleys, parking lots and bike or walking paths. Today's green pavement typically does not have enough load-bearing strength to maintain highway traffic, but new breakthroughs in building materials could make that a possibility in the future. A few porous asphalt highways are in use in the United States and Europe [source: Georgia Asphalt Pavement Association].

Grass pavers (a type of plastic paver) are a very popular landscaping and building choice, as they perform the duty of pavement, but look like grass. There are many different grass paver products on the market (Grasspave2, Geoblock, Tuff Track, Grassy Paver, Grass-Cel, Checker Block and Grasscrete, for example), and all have their own pros and cons [source: Invisible Structures Inc.]. What they all have in common is that they allow grass to grow even in high-traffic areas. Grass pavers come in interlocking grid or honeycomb shapes. Once installed, grass or other vegetation can grow in the spaces of the grid. The result is a load-bearing grassy area. Some can support over 97,000 pounds (43,998 kilograms) per square foot [source: Grassy Pavers].

Next up, we'll take a look at some of the benefits and drawbacks of green pavement.