Concrete is one of the oldest and most versatile building materials on the planet. For thousands of years concrete has been the miracle material that can be molded into any shape or size imaginable; can be colored, stamped or stenciled to be made to look like brick or stone or even wood; and then, as if by magic, this "wonder" product gets hard like stone and creates strong, durable structures and pavements that last.
From the homes and offices we live and work in, to the roads, bridges and sidewalks we travel on, people have come to count on concrete every day of their lives. That sounds like a pretty amazing product. You would think a material this exciting would be on the minds of most people much of the time, and kids would dream of becoming involved in the wonderful world of concrete.
So what's up with our lackluster reputation? Why the general indifference to this "totally awesome" material? Is it because concrete has been around so long and is always there that people take it for granted? Or, because most people don't really know much about concrete? Whatever the reason for this apathy toward this magnificent building material, take heart, concrete fans, because "times, they are a changin'!"
Because of today's environmentally conscious marketplace, concrete is now beginning to stand out as a solution to sustainable construction requirements. You can't pick up a newspaper or construction-related publication today without seeing some kind of article about "green building" or "sustainable construction."
What surprises many is that concrete offers tremendous advantages from an environmental aspect. Suddenly, the construction industry is looking at this less-than-glamorous product, used in virtually every phase of construction, with a new appreciation and a willingness to recognize unique applications such as pervious pavements and insulated stay-in-place form construction.
One of the major factors driving the green building movement is the realization of how much waste goes into the construction and operation of the buildings we live and work in. Think for a moment about how much time we spend indoors. Our buildings have a huge impact on our environment, even when we are not in them. But what if we could design, construct and operate our buildings using sustainable thinking, meeting the needs of today without jeopardizing future generations from meeting their own needs?
The U.S. Green Building Council developed a program called LEED, which stands for Leadership in Energy and Environmental Design and has become the prominent green building rating system. There are four different thresholds for LEED certification recognizing varying levels of achievement: Certified, Silver, Gold and Platinum. LEED-NC (New Construction) promotes improved practices in site selection and development, water and energy use, environmentally preferred construction products, waste stream management and indoor environmental quality. Within each category, project teams choose which credits to pursue based on their environmental and performance goals.
The use of concrete can contribute to earning more points toward project certification than any other building material. For the purpose of this article let's take a look at a few credits where the use of concrete makes a difference toward earning points.
Under this category, the use of pervious concrete pavement qualifies for credits SS 6.1 Stormwater Design-Quantity Control and SS 6.2 Stormwater Design-Quality Control. Keeping our aquifers, lakes, rivers and oceans free from pollution is a massive job. Conventional impervious pavements, particularly parking lots, collect pollutants that can be washed into streams, lakes and oceans. Pervious concrete pavements can reduce or eliminate stormwater runoff and permit the treatment of pollutants on site. By capturing rainfall and allowing it to percolate into the ground, soil chemistry and biology are allowed to treat the polluted water naturally.
Since there is little to no runoff, aquifers are replenished and flooding is minimized. Costly conventional stormwater collection systems can be reduced or eliminated by using pervious concrete in a parking area to retain stormwater, which in turn allows for more efficient land development.
Earning credit SS 7.1 Heat Island Effect, Non-Roof could be accomplished by using light colored concrete pavement or an open grid pavement system like pervious concrete for at least 50 percent of the site's hardscape.
Energy & atmosphere
This category establishes energy efficiency and system performance goals, encourages renewable and alternative energy sources and supports ozone protection protocols. Once in place, concrete offers significant energy savings over the lifetime of a building or pavement. In structures, concrete's thermal mass - bolstered by insulating materials - affords high R-factors and moderates temperature swings by storing and releasing energy needed for heating and cooling. This fact allows designers to downsize the typical HVAC system, which increases energy performance even further.
The light color and reflectivity of concrete pavement makes it less costly to illuminate at night. During the day it keeps the surrounding areas much cooler than asphalt. This has a major impact on controlling the Heat Island Effect. The use of concrete makes earning points under EA Credit 1 Optimize Energy Performance much easier. This unique credit allows for 1 to 10 points based on achieving increasing levels of energy performance above the baseline in the prerequisite standard to reduce environmental and economic impacts associated with excessive energy use.
Materials & resources
The Materials and Resources category provides both old and new concrete the chance to affect earning more credits (MR credits 1.1 and 1.2 Building Reuse). In certain situations reusing an existing structure rather than knocking it down to make way for something new makes better environmental sense. This reduces the amount of demolition debris ending up in landfills.
Because of their durability, old concrete structures offer better opportunities to take advantage of building reuse. MR credits 2.1 and 2.2, Construction Waste Management, offer points for diverting construction, demolition and land-clearing debris from disposal in landfills and incinerators. Old concrete that has served its useful life can be crushed and reused as aggregate base. Calculations are done by weight or volume, which offers concrete a unique advantage.
MR credits 4.1 and 4.2, Recycled Content, take into account that today's concrete makes use of fly ash, a by-product of coal burning power plants; ground granulated blast furnace slag, a by-product of the iron and steel production process; and silica fume, a by-product of producing silicon metal or ferrosilicon alloys. Each of these mineral admixtures is an industrial by-product that if not used in concrete would be filling our already cramped landfill system. Not only are we disposing of other industries' unwanted by-products, but our industry has learned how to use them to enhance the qualities of our product and actually make it better.
MR credit 5.1 and 5.2, Regional Materials, focuses on reducing the environmental impacts resulting from transportation. Because concrete is often extracted, processed and manufactured at the local level, the transportation activities and the accompanying pollution required to deliver the materials to the jobsite are much less than other building materials.
Still not convinced?
It is clear that concrete can play an important role in earning points toward LEED certification. There are many other credits within the LEED Green Building Rating System that concrete also impacts in less pivotal ways. But beyond certification programs, there are many benefits of concrete that you should promote to consumers, such as sustainability, durability, energy efficiency and recyclability.
Another obvious environmental benefit of using concrete is that in most areas of the country it's made from readily available natural resources: water, sand, stone and cement. Extracting these ingredients takes a lesser toll on the environment than other construction materials.
The public, however, perceives stone quarries as being dirty, dusty, loud places with lots of heavy machinery that strips away the natural landscape. The fact is, most quarries have large areas of untouched woodlands acting as buffer zones between the quarry and local roads and houses. These areas have become sanctuaries for local wildlife while all the mining activity still goes on. And once an aggregate quarry has served its purpose, the entire site can be reclaimed for use as recreational facilities, campgrounds, pasture land, nature preserves and even little league baseball fields.
There is no denying concrete's durability. Because concrete will not rust, rot or burn, and termites and rodents can't burrow into it, it requires less energy and resources over time to repair or replace. The rugged durability of concrete creates long-lasting structures and pavements that have withstood the test of time for more than 2,000 years.
Because of the strength and durability of concrete it can withstand most natural disasters like fires, hurricanes, tornados and floods. This translates into less destruction, less property loss and less displaced families when natural disasters strike. When you consider the amount of debris hauled away from the Gulf Coast after Hurricane Katrina, the environmental costs are astonishing. If more of our homes and buildings were constructed with concrete it could mean the difference between life and death.
Compared to other building materials, concrete presents very little construction waste. You make and deliver only what you need and any leftover fresh concrete gets returned to the plant to either be reclaimed or piled on site to harden, crush and reuse as fill material.
The concrete industry has a lot to be proud of. We offer a product that is made from abundant natural resources and is locally produced. Concrete's strength and durability allow it to withstand not only natural and man-made disasters but the test of time. Concrete is recyclable, and it produces far less waste than other building materials.
Who knew concrete was such a great material? Now you do. So go out and tell someone!
Doug O'Neill, LEED AP, is National Resource Director for the National Ready Mixed Concrete Association (NRMCA). For more information about the many benefits associated with the most versatile building material on the planet, visit the NRMCA's website at www.nrmca.org.