In many respects, concrete was a “green” material long before discussions of sustainability became commonplace. Many concrete structures have famously endured for centuries, proving not only their durability but their resilience. Moreover, concrete is almost always locally produced, and often incorporates recycled materials.
Some of concrete’s sustainable attributes are more recent—or even currently in development–and target improvement areas such as CO2 emissions, stormwater management, and materials efficiency. Examples include the use of alternative fuel sources during manufacturing as well as the use of industrial byproducts in place of cement; both of these innovations reduce the total amount of energy required to produce concrete.
Materials transparency should be measured across the entire life span of a project, from sourcing through end-of-life. The term “Cradle to Cradle” has been popularized to clarify the notion that many factors across all phases of a structure’s development and use can affect sustainability. A robust measurement tool has been developed to evaluate these competing factors: the life cycle assessment (LCA). A number of life cycle assessment programs are available to aid in product selection. Each is based on ISO standards and assesses for: global warming potential, acidification, smog formation, ozone layer depletion and eutrophication.
Building upon LCAs, product category rules (PCRs) and environmental product declarations (EPDs) in the concrete industry have become an important way for manufacturers and trade associations to provide transparency into their product’s life cycle performance. Several third party groups have established PCRs for concrete and concrete materials; in accordance with those, concrete related industries are now developing EPDs. Concrete EPDs provide insight into ways that manufacturers are reducing water use, total energy consumed and carbon emissions, among other performance measures.
Concrete can last for decades, or even centuries, with little to no maintenance. Its long useful life and the minimal resources required for upkeep contribute greatly to sustainability.
However, in order to achieve desired levels of durability, concrete structures must be properly designed and constructed to stand up to chemicals, freeze-thaw cycles, coastal salts and moisture, abrasion, deicing salts and other extreme conditions. There are a number of materials on the market which can mitigate various environmental threats to concrete’s durability. Additionally, some supplemental cementitious materials (SCMs) can lower concrete’s permeability and protect reinforcing materials. There are also certain SCMs that can increase workability of the concrete or its sulfate resistance.
It is the responsibility of designers to understand particular conditions associated with a given location and make use of the extensive body of information available on designing concrete for maximum durability.
When it comes to building materials, the carbon footprint includes not only CO2 emissions associated with manufacturing and construction, but also those associated with operation. An inherent benefit for structures built with concrete is thermal mass, which actually decreases the amount of energy required to heat and cool a building. Concrete’s longevity, both in buildings and infrastructure such as roads, bridges, dams, etc.—and its subsequent savings in terms of repair and replacement—further reduces the material’s carbon footprint. Aggressive steps are also being taken to minimize upfront carbon costs associated with the manufacture of concrete and its use during construction.
Concrete structures provide excellent shelter during emergencies due to the material’s strength and its natural fire resistance. Its ability to withstand water damage means concrete can be more readily cleaned and disinfected than other materials, reducing overall cleanup costs. The lower costs for repair and cleaning confer an economic advantage and aid in an area’s speed of recovery.
Consider the spectacular story of one New Jersey home, the only house in its neighborhood to remain standing after Hurricane Sandy. Constructed using insulating concrete forms, it was built to current coastal construction standards. See the full story here.
For citywide disasters, concrete infrastructure helps ensure that critical services like roads, hospitals, communications, data transmission and emergency services remain in operation. Concrete is also a crucial material for building large scale protective systems such as seawalls and other barriers. Because these types of structures are publicly-owned and funded, governmental initiatives are being implemented to ensure the delivery of critical infrastructure services… and consequently, cities with improvements to infrastructure are attracting more private investment and commerce. Local building codes are also encouraging stronger construction methods, such as building with concrete, and a preference for buildings with long service lives.
Additionally, concrete lends itself to the kind of structural enhancements that will be needed to accommodate the anticipated increase in wind and other severe weather loads. It is expected that codes and standards will continue to evolve, making such structural enhancements a requirement not only for new construction but for the retrofit of existing structures.