Pervious Concrete


Concrete solutions for sustainable growth

The world’s population will continue to increase to about 6.9 billion by 2010! Developing countries will build more factories and homes. Their people will drive more vehicles and need more roads and parking lots. In the U.S. the number of vehicles registered increased to 226 million 1n 2006 (Source U.S. Census Bureau) More vehicles and roads mean more greenhouse gasses and atmospheric warming. Our planet, our country and our neighborhoods will feel the impact. The Census Bureau explains that for every 5 new cars registered, an area the size of a football field gets paved. Thus there now over 4 million miles of paved roads in the U.S. What is the best material for roads, parking lots and driveways?Concrete! Why not asphalt? Here is why!

Concrete Reduces High Temperatures

Urban and suburban sprawl creates heat islands as solar energy is absorbed by black or dark surfaces such as asphalt or roofs. Since concrete is light in color it reflects much of that heat back into space.

Pervious Concrete reduces temperatures even more! By allowing more rain water to remain within, below and adjacent to the Pervious Pavement, it makes more evaporation possible. This is like your perspiration cooling your skin.

Water being converted to vapor absorbs 970 BTU of heat per pound of water.. This would mean that if 1″ of rain would be absorbed by a 100′ x 100′ Pervious Concrete Parking lot it would contribute 6,234 gallons of water to the soil below. When it evaporates it creates the cooling equivalent of 25 tons of air conditioning running for seven, 24 hour days.

Urban sprawl creates heat islands because impervious surfaces, especially black, or dark colored ones, absorb sunlight and convert it to heat.

Photo Courtesy: Lawrence Berkley National Laboratory
Photo Courtesy: Lawrence Berkley National Laboratory

As many city residents can tell you, cities can be very hot places during the summer. On warm summer days, the air in a city can be 6-8ยฐF hotter than its surrounding areas. Scientists call these cities “Urban Heat Islands.” What causes this to happen?

Learn About Urban Heat Islands

  1. Concrete helps reduce global warming by reflecting much of sunlight rather than absorbing it and converting it to heat. This also reduces air conditioning loads and the electrical energy they require. The solar reflectance index is called albedo. Fresh concrete reflects 35% – 40% while freshly paved asphalt reflects only 5% to 10%. (Aging will narrow the gap somewhat.)
  2. Because of its lighter color, concrete requires less lighting at night, thus reducing the consumption of electricity. Most electricity is generated by burning fossil fuels which add to global warming.
  3. Except for energy consumed in mining, manufacturing and transporting concrete, it is environmentally friendly and its components are abundant.
  4. Concrete can be made pervious, allowing rain water to be filtered and channeled through to the aquifer below.
  5. Pervious concrete parking lots with tree islands can supply the water to tree roots. This makes possible photosynthesis through tree leaves which converts carbon dioxide into carbon used by the tree, and oxygen is released into the atmosphere. Trees not only provide shade but through transpiration of ground water, absorb heat and release moisture which can enhance rainfall.Concrete, in parking lots and driveways offers the option of being pervious. This means that it allows unsalted rain water to pass through it, and like grass allows it to go down to replenish the aquifer below. That is the source of what is an essential to keep us alive, drinking water. In coastal areas it can also help resist the intrusion of salt water.