This photo shows how the pervious concrete on the right side of this parking lot allows water to pass through it.
A green street design might integrate vegetation to help manage stormwater (below), or encourage alternative transportation with bike lanes, (above).
As the demand for sustainable development increases, the concrete industry holds a responsibility to inform stakeholders about the role concrete plays in the sustainability and durability of buildings, roads, bridges and infrastructure. The industry continues to make advancements in reducing its carbon footprint; however, each of us individually carries the responsibility of getting informed and identifying opportunities in the projects on which we work to reduce the environmental impact. This includes further reducing CO2 emissions, encouraging recycling (both existing concrete and by-products of other industries), reducing the impact of stormwater runoff, minimizing waste, and designing and constructing for increased durability — all while increasing societal benefit and reducing economic impact.
At the Fall 2010 American Concrete Institute convention, industry leaders gathered to discuss newest innovations and best practices during the “Sustainability of Concrete Pavements” technical session. The session included presentations on recycled aggregate for airfield pavements, green streets, a review of the Greenroads rating system, blended cements, internal curing and a look at the cement industry’s initiatives in climate change mitigation. Following are synopses of two of the presentations by their presenters.
By John T. Kevern, Ph.D., LEED AP, Assistant Professor of Civil Engineering at University of Missouri-Kansas City
Green building and sustainability have become ubiquitous in commercial construction. The benefits range from cost savings from better energy efficiency to more recycled or reused materials, all culminating in a better quality of life for the building occupants. The sustainability movement has now expanded from buildings to streets with the ultimate goal of improving the overall quality of life of an entire community. Fortunately for the concrete community, concrete can play a huge role in the economic, environmental and social components that define a green street.
Ten main areas can help define a green street:
- Integrated design
- Pedestrian access
- Alternative modes of transportation
- Better material selection choices
- Use of regional materials
- Integrated stormwater management
- Urban heat island effects
- Light pollution
- Construction emissions
- Public education
A green street is designed to minimize its environmental impact, while inviting a variety of human users and lasting a long time. Minimizing environmental impact includes managing stormwater on site to prevent rapid runoff and installation of large downstream stormwater infrastructure. Stormwater has been recognized by the EPA as a primary cause of surface water pollution. Some techniques for cleaning and infiltrating stormwater within the street section are curb cutouts, curb extensions or pervious concrete. Curb cutouts and extensions are vegetated and can produce a natural setting to help bring more plant life to urban settings. Pervious concrete allows water to soak into the ground and significantly delay the rate of runoff.
Other ways concrete can help reduce a green street’s environmental footprint include using regional materials to minimize pollution created during transport and incorporating recycled materials such as used tires as fuel in the cement making process or fly ash replacement for cement in the concrete itself.
Concrete’s light color helps reflect the sun’s energy, reducing the urban heat island effect and allowing for more efficient street lighting. Concrete also has good durability and a long lifespan so it’s favorable when considering using environmental or economic lifecycle assessments.
Green street design considers integrating the street with the environment and integrating together all of the street’s users including public transportation, pedestrians and vehicles. Improving access can be as simple as better roadway markings for pedestrian crossing, ADA compliant sidewalks and ramps, and relocating and beautifying public transit stops. One step further to improving access involves better integration in the design process. Clearly marked bicycle lanes or under/over-grade bicycle crossings safely allow integration with vehicular traffic. Pervious concrete provides better traction and reduces the potential for slipping on ice in the winter, which is a concern for older adults. Better access to a street improves the quality of life for the public users.
Many improvements to a street or streetscape or to perception can be achieved with little physical changes. Public education helps provide a sense of ownership to the street. Cities such as Austin, Texas, have programs to reduce the amount of pet waste left to pollute stormwater and programs promoting proper use of fertilizers. A novel concrete pavement containing photocatalytic cement would be enhanced through education of its benefits since the public cannot observe the air being cleaned by the pavement. Educational programs highlighting the different aspects and benefits of green streets encourage a sense of pride for the user.
A green street integrates environmentally friendly materials with attractive, on-site stormwater management, in a design that optimizes the use of public and private transportation for the best possible roadway solution. With a long performance track record, a wide variety of shapes and applications, and the ability to incorporate large amounts of recycled materials, concrete is a key component for building the green street of the future.
Concrete’s Contribution to the Greenroads Rating System
By Lionel Lemay, PE, SE, LEED AP, Sr. Vice President, Sustainable Development, National Ready Mixed Concrete Association
Concrete’s many environmentally friendly attributes can help achieve certification using the Greenroads rating system. Greenroads is a credit-based system, allowing road projects to earn points for environmentally friendly strategies employed during the design and construction process and helps project design teams select sustainable construction strategies. Greenroads was developed by the University of Washington and CH2M HILL. Greenroads is a publicly available system that can be used by anyone.
Greenroads is a collection of sustainability best practices that are divided into mandatory and voluntary practices. There are 11 mandatory best practices called Project Requirements that must be accomplished for a project to be considered a Greenroad. There are 37 Voluntary Credits totaling 108 points. Greenroads also allows a project to create up to 10 Custom Credits, which brings the total available points to 118. Project teams apply for points by submitting specific documentation in support of the Project Requirement or Voluntary Credit they are pursuing. Table 1 provides credit details.
CategoryDescriptionPointsProject Requirements (PR)Minimum requirements for a GreenroadRequiredEnvironment & Water (EW)Stormwater, habitat, vegetation21Access & Equity (AE)Modal access, culture, aesthetics, safety30Construction Activities (CA)Construction equipment, quality, use14Materials & Resources (MR)Material extraction, processing, transport23Pavement Technology (PT)Pavement design, material use, function20Total Voluntary Credit Points108Custom Credits (CC)Write your own credit for approval10Grand Total118
Greenroads may be used to “certify” a project based on total points achieved. There are four certification levels:
- Certified: All Project Requirements plus 32-42 Voluntary Credit points
- Silver: All Project Requirements plus 43-53 Voluntary Credit points
- Gold: All Project Requirements plus 54-63 Voluntary Credit points
- Evergreen: All Project Requirements plus 64+ Voluntary Credit points
Concrete’s contribution to Greenroads certification is summarized in Table 2.
Greenroads certification provides several benefits to a roadway project. It provides a quantitative evaluation of sustainability strategies for the design team and allows innovation because of its end-result orientation. Greenroads also provides a way to confer marketable recognition to a project. You can learn more about Greenroads v1.0, University of Washington, at www.greenroads.org.
Stephen T. Muench, Jeralee Anderson and Tim Bevan, “Greenroads: A Sustainability Rating System for Roadways,” Proceedings of the International Conference on Sustainable Concrete Pavement, Sacramento, Calif., September 15-17, 2010, pp. 398-408.