Innovative and Classic Approaches Drive Today's Sustainable Design
by Jennifer G. Prokopy

Everywhere you look today, there are concrete innovations. New concrete mix designs create sleeker, stronger structures that achieve amazing energy efficiency. Manufacturing refinements reduce pollution and energy use. Manufacturing and construction processes use more recycled materials—both in volume and variety. And architects, engineers, and contractors are enhancing time-tested methods that have always been sustainable.

Water flows through demonstration sample of pervious concrete pavement.

The Portland Cement Association (PCA) consulted industry experts with diverse experience to look at what’s happening today in manufacturing, design, construction and building performance. Some of the hottest trends are the growth of green building in concrete homes, the use of pervious concrete pavements for water conservation, and the continuing drive to achieve unique, optimal concrete mix designs using supplementary cementitious materials.

New Directions in the Industry

With sustainable building practices rapidly becoming a common consideration, the concrete industry has shifted its thinking, putting more emphasis on educating the building community on the techniques and benefits of using concrete and other cement-based products. Dave Frentress, marketing director for cement and ready-mixed concrete manufacturer Glacier North West, has made it his mission to spread the word about concrete. He recently was named Promoter of the Year by the National Ready Mixed Concrete Association.

“In this age of vanishing resources, we must choose our building materials wisely, balancing the expenditure of natural resources with the benefits of a material over its useful life,” says Frentress. “Concrete draws upon some of the earth’s most common and abundant materials for its raw materials. Concrete also offers thermal mass, lowers urban heat island effects, is recyclable, uses local materials, creates energy-efficient structures, is economical and highly versatile, and comes in tons of textures and colors.”

Frentress argues that in many cases, concrete can minimize the material requirements of a structure. Minimizing or eliminating unnecessary components or processes is often an easy solution. This kind of thinking, says David Shepherd, director of sustainable development for PCA, is what the industry needs most. There are many innovations in concrete, but even more important: “There are often simpler ways of doing things. There are methods that have been working well for decades.”

Catching Up: Concrete Builds Green Homes

Awareness of sustainable design in homebuilding is on the rise, according to Shepherd. “What we’re seeing in the residential market today is what was happening three or four years ago in commercial building,” he says.

Eric Fulton, communications manager for the Building Systems Councils of the National Association of Home Builders (NAHB), says that approximately 16 percent of new homes use some sort of abovegrade concrete wall system. This is, in part, why NAHB established its Concrete Home Building Council: “A lot of builders may not realize the capabilities and properties of concrete and cement-based products, and their contribution to green building,” he explains.

Concrete’s homerun for any residential application is its energy performance, says Shepherd. “Houses are relatively simple. You can use a high-performance wall or roof system and make a huge difference in how your house impacts the environment, over decades or even a century.”

Green- and rose-colored pervious pavement sidewalks were used in Guadalupe Dunes County Park in California’s Santa Barbara County. The park is located just above the high tide line on the Pacific Ocean.

In addition to wall systems, concrete can contribute to home building in many other ways. Concrete creates long-lasting driveways and sidewalks. Made with pervious concrete pavement, they can reduce stormwater runoff, as can decorative concrete pavers, which create safe, ecologically friendly patios and decks. Concrete floors are decorative, functional, and durable, as are concrete roof systems and fiber-cement siding. Concrete countertops are a cost-effective alternative to expensive stone finishes. And with limitless color and texture options, all of these components can be specified to achieve a fabulous aesthetic.

NAHB also recently released voluntary Model Green Home Building Guidelines. John Loyer, construction, codes and standards specialist in NAHB’s Energy and Green Building Department, says the guidelines grew out of member interest. “We created a document that delineates, for the mainstream homebuilder, how to ‘green up’ building practices—or for a builders’ association to start a green building program,” says Loyer. The guidelines, representing the expertise of more than 100 organizations, will be updated every two to three years to incorporate cutting-edge technologies.

The U.S. Green Building Council, creator of the Leadership in Energy and Environmental Design (LEED^®) Green Building Rating System, is also in the game with LEED for Homes. Jim Hackler, program manager, says the program was launched Aug. 3, 2005, in 11 markets across the country. While it does not call out specific products, says Hackler, “the core of the program is examining energy. Certainly, in a concrete home, performance levels will be incredible.” The program will also offer innovation points, which concrete systems may be able to achieve. “It shouldn’t be about fighting point-for-point,” adds Hackler. “It’s about practices that make sense for a specific home and a specific home buyer.”

Saving Water with Pervious Concrete Pavements

One concrete technology currently gaining attention across the nation is pervious concrete pavement. Made with the same ingredients as conventional concrete, without fine aggregates, the material is primarily used for parking lots. This simple mix creates a concrete with large voids, allowing water to pass through the concrete and into the ground.

The City of Encinitas, Calif., used pervious pavement for sidewalks, parking lots and the park’s entry area. While the parking lots are gray, sidewalks (like those in this image) are colored red and buff.

“Pervious concrete acts in an environmentally friendly way,” says Don Wade, marketer for Missouri-based Magruder Construction. The firm is constructing pervious pavements all over the U.S., says Wade, because its benefits serve almost any community. “It allows rainfall to pass through to the ground underneath, minimizing or eliminating stormwater runoff. Pollutants are captured, water is retained and purified, recharging the aquifer,” he explains. He adds that every state currently has programs testing the viability of the material.

Environmentalists have for years pointed to parking lots as a source of pollution for lakes and rivers, but pervious pavement can stop that process. Andrew Marks, managing director of the Puget Sound Concrete Specification Council, says that in his region (in the state of Washington), its key benefit is wildlife protection. “We have a heavy emphasis on protecting the water for salmon propagation,” he says. “All the streams in this area feed into the Puget Sound, and salmon stocks have depleted over the years.” David Akers, senior engineer for the California Nevada Cement Promotion Council, says stormwater maintenance is a key selling point in the southwest. Pervious pavements are being used all over the region to conserve water in ballparks, parking lots, sidewalks, hardscaping, and more.

Pervious pavements can also save space and money, says Marks. In property development, the impervious surface area will determine the space set aside for stormwater retention ponds, as well as pipes and other structures. Pervious pavement can minimize or eliminate the need for retention ponds and other structures. That increases the land area available for use, which translates into increased savings— or profits—for owners, while improving water quality at the same time.

For some, the misperceptions that pervious pavement doesn’t tolerate freeze-thaw cycles, or that it can become clogged with debris, have been stumbling blocks. But anecdotal evidence shows that the pavements perform well in cold environments, says Paul Tennis, consulting engineer for PCA. The large voids prevent saturation and allow the concrete to heat faster, melting snow and ice and draining the liquid, so it can’t linger in voids and cause cracking as the temperatures cycle. And according to Wade, while some pavements can become clogged, the material can be vacuumed, bringing permeability back to levels close to those at installation.

In the Mix: Supplementary Cementing Materials

Interest in using supplementary cementitious materials (SCMs) to enhance concrete’s performance continues to grow. “SCMs can increase the sustainable attributes of a green building material like concrete in many ways,” says Shepherd. “Optimized concrete mixes with SCMs like slag cement, fly ash, silica fume and others can provide enhanced benefits, creating structures of the likes we have never seen before.”

Jan Prusinski, executive director of the Slag Cement Association (SCA), says the hottest thing going in SCMs is ternary mixes. “Ternary mixes that incorporate portland cement, slag cement, and fly ash are the next wave in utilization of supplementary cementitious materials,” says Prusinski. “They are an excellent way to reduce the total cement in a mix while improving durability.”

In fact, SCA has recently begun a two-year research project (with Materials Service Life, LLC) to examine the properties of ternary mixtures with slag cement, portland cement, and fly ash (classes C and F). The goal of the research is to create a life cycle program to help in optimizing mixes.

Using a performance-based approach for specifying fly ash and other SCMs is key, says Dave Goss, executive director of the American Coal Ash Association (ACAA). For example, while some state Department’s of Transportation (DOTs) specify 20 percent or 25 percent replacement with fly ash, there are some applications where that isn’t enough material to combat alkali-silica reactivity, which can cause deterioration. Goss says the industry must push for intelligent specifications. “One size doesn’t fit all.”

A longtime proponent of using fly ash in concrete, Frentress says that in Glacier North West’s market, the green building movement has led to higher-than-normal fly ash content specifications (30 percent to 50 percent) for sustainable commercial projects, often made without consulting the ready-mixed concrete producers. “In our market, the industry has experienced periodic fly ash shortages, so we utilize what ash we can get on a job in order to adhere to the specifications. When we don’t have enough ash, we are forced to remove it from residential jobs where it is not explicitly specified but is typically used,” he explains.

As a result, the larger volumes specified often don’t have an additional positive effect on the environment: “There really are no savings on CO₂ reductions since the fly ash was simply moved from one load of concrete to another,” says Frentress. “In most cases in our market, specifying over 30 percent fly ash content can be too much of a good thing.” A better alternative, he says, is for mix designs to focus on performance, not on simply including maximum SCMs to achieve recycled content credits.

Like Prusinski, Goss says ternary mixes are rapidly gaining in popularity. But many state DOTs still do not allow ternary mixes, according to Mark Luther, technical service engineer for Holcim (US) Inc. It’s hard to say when that might change. Even so, many recent landmark projects have incorporated SCMs, including Seven World Trade Center, the Maumee River Bridge (the largest ever built by the Ohio DOT), and the Oklahoma Federal Building.

And manufacturers are becoming increasingly creative when it comes to using fly ash and slag cement, using it more frequently for structural fills, soil stabilization, road construction— even creating architectural elements with it.

Concrete from the Ground Up

Cement Manufacturing: •Limestone, the predominant raw ingredient of cement, is the most abundant mineral on earth • While cement manufacturing requires high energy, cement is only a small portion of concrete (10 percent to 15 percent) • Industrial byproducts can be used to fire kilns or as raw materials where cement is manufactured, instead of being landfilled

Construction: • Concrete is ordered and mixed for each job, minimizing waste •Leftover concrete can be recycled • Materials are derived and manufactured locally, minimizing transportation • Industrial byproducts like slag cement and fly ash can be used in concrete as supplementary cementitious materials

Building Operation: • Thermal mass increases energy efficiency, reduces temperature swings, and increases comfort • High reflectivity reduces urban heat island effect • Durability means concrete structures outlast many others and typically require less maintenance • Virtually inert, concrete improves indoor air quality

Demolition: • Almost all concrete can be crushed and recycled, for road building or as aggregate for new concrete

About the Author: As principal of Orange Grove Media, an independent communications firm, Jennifer G. Prokopy provides expert writing, editing and media relations services to the construction industry. As president of the Construction Writers Association (CWA), Jenni works with the nation’s top construction journalists and publicists to improve the quality of construction communications. She is a winner of the CWA Marketing Communications Award, recognizing her writing on sustainable construction with concrete, and a graduate of Northwestern University’s Medill School of Journalism.

All photos courtesy of the California Nevada Cement Promotion Council.

 
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