As fuel prices rise and the debate over global warming heats up, we watch our communities become more and more environmentally conscious. Whether its energy efficient appliances or bamboo flooring, everyone, builders and consumers alike are looking for ways to build and buy green. While helping to lead this movement, concrete has been at the forefront of sustainable development. Concrete being recyclable, produced locally and having a high reflectivity demonstrates a few of the ways using concrete helps buildings obtains points on the (LEED) system, a green building rating system put out by the U.S. Green Building Council. Now by tackling storm water management, concrete has found a way to be even greener. Pervious concrete is quickly becoming the next testimonial to the environmental advantages that concrete can offer.
Picture this, a 20 home development with 32,000 square feet of paved surfaces including driveways, sidewalks and streets, all of which is done with a material that generates zero runoff! This is a reality in Sultan Washington, where an entire development was done in pervious concrete, allowing the rainwater to pass thru the pavement and recharge the natural ground water table instead of draining into a municipal system. The concrete that made this possible is porous, made like traditional concrete but little or no sand or fine aggregate, leaving a void percentage between 15 and 35 percent to allow for the movement of water through the pavement.
This along with proper placement techniques gives you a pavement that water can infiltrate at a rate of 3 to 8 gallons per square foot per minute. While being slightly less edible that a Rice Crispy Treat it has a similar appearance and structure. The cement paste like the marshmallow, acts as a glue holding the aggregate or Rice Crispies together, while still leaving space for water to pass thru to the base layer of stone aggregate, before reentering the earth. This system has been used in freeze thaw environments since 1985 and is beginning to pick up steam here in Michigan, with just under a dozen projects on the ground and approximately 20 more being planned for next year.
With all of the environmental advantages of traditional concrete, pervious concrete is even friendlier to our ecosystem. In pavement applications concrete offers a reflective surface that prevents the increase of the ambient air temperature, consequently preventing the heat island effect and helping to lower cooling bills in the summer. This same reflectivity makes it easier to light concrete streets in comparison to those paved with a darker materials, allowing you to save on energy cost. Pervious concrete not only gives these benefits but adds several others, like the mediation of first flush pollutants and allowing you to pave up to the root line of adjacent trees and shrubs.
The first halve inch to inch of rain carries away many pollutants from the surface of pavement oil, break dust, coolant and other pollutants typically make their way into a storm sewer and eventually end up in a local water source. Occurring within the pconcrete and stone base that sits underneath are microbes that eliminate 80% to 90% of these first flush pollutants prier to returning the water to the water table. Also with water passing thru the pervious, you no longer have to worry about plant and tree roots not getting enough water or nutrients because of adjacent pavement. So with pervious concrete you get all of the sustainable advantages of traditional concrete and even more environmental perks.
Pervious concrete is giving Michigan one more option in our journey toward sustainable development and helping us to build green.