The Sustainable Solution
GREENER CONCRETE CONSTRUCTION
Leveraging the Attributes of Reinforced Concrete in the Design of Sustainable Structures
In the built environment, the goal of sustainability is to reduce the negative environmental impacts and extend the useful application of material and energy resources in the use of a structure over its service life. This can be pursued through informed material choices, a holistic accounting of environmental impacts over all stages of a structure’s life and consideration of adaptability and resilience in a world where the climate is changing. Worldwide, the broadly accepted definition of sustainability remains the one developed in 1987 by the World Commission on Environment and Development (the Brundtland Commission). Its definition offers more useful guidance related to human needs and extends consideration of impacts to both social and economic ones.
Green Building & Economics
Both public and private organizations have traditionally considered development with a primary focus on first cost. However, there is an increasing trend towards a more holistic and responsible approach, referred to as the Triple Bottom Line, which incorporates the social and environmental impact of decisions and activities along with economic performance.
A common hurdle by early adopters of any new technology is a cost premium paid for employing something new or unfamiliar. While that may have been true for sustainable projects 15
years ago, experienced design firms now have portfolios of projects that weave sustainable strategies into the initial programming, rather than as a costly add-on. Studies reveal that when sustainability is integrated into initial design objectives, the total cost of ownership for a project is often competitive with or lower in cost than traditional design approaches.
MODERN MATERIALS – IT’S NOT THE SAME OLD CONCRETE
Portland Cements
For over a century in the United States, ordinary portland cement (OPC) has been used for making concrete. With a market share exceeding 95% for concrete, OPC (ASTM C-150) is allowed to contain up to 5% inter-ground limestone. In recent decades, tremendous advancements have been made in concrete chemistry.
Steel Reinforcement
Micro-mill technology is the latest innovation in EAF steel production, which hot rolls steel reinforcement in one continuous operation, further reducing the manufacturing energy required. Several new micro-mill plants have been constructed in the U.S in the past decade.
Steel is the most recycled material in the world, with U.S. producers recycling more than 70 million tons of scrap each year. According to the 2022 Environmental Product Declaration
(EPD) for Fabricated Reinforcing Steel, the most common reinforcing steels (ASTM A615 and A706) exceed 97% for recycled content. Specialty reinforcing steel products have a recycled material content typically greater than 75%.
After its service life is complete, both concrete and steel reinforcement can be recycled, into fill and base for the concrete and yet another steel application by the rebar.
