MIT Researchers Take a Lifecycle Approach to Evaluating the Real Costs and Environmental Impacts of Infrastructure

On August 11, the Concrete Sustainability Hub at the Massachusetts Institute of Technology (MIT) released two studies looking at the lifecycle assessment (LCA) of concrete pavements and buildings.

Both studies signify major advancements for construction-related lifecycle assessments. They thoroughly examined the cost and environmental impacts for the full life of pavements and buildings – including the use and operations phase – not just the costs and embodied CO2 that occur at initial construction. Currently, most LCAs in use do not fully account for these impacts, which can include traffic delays, energy consumption and maintenance.

MIT also used this lifecycle approach to evaluate the real cost of pavement throughout a 50-year lifetime, beyond initial construction costs. Researchers started with the Federal Highway Administration's (FHWA) Lifecycle Cost Analysis in Pavement Design Interim Technical Bulletin, a process that accounts for both initial construction and future rehabilitation.

What the FHWA procedure fails to account for, however, are changes in the prices of building materials over the life of the pavement. MIT's research showed that during a 50-year timeframe, the mean real price of concrete decreases by 20 percent, while the mean real price of asphalt increases by 95 percent. To allow states to address this, MIT developed a paper and a procedure that departments of transportation can readily adopt to account for inflation.

In its environmental assessment, MIT researchers found that while concrete pavements are already sustainable in many ways, their carbon footprint can be further reduced. First, MIT developed a comprehensive methodology outlining the best-practice concepts that should be followed when conducting any pavement lifecycle assessment (LCA). Specifically, any complete LCA should include the use and rehabilitation phases, which can account for between 33 percent and 44 percent of the CO2 emissions for interstate highways.

Next, the Hub researchers applied these concepts to evaluate strategies to lower a concrete pavement's carbon footprint and overall environmental impact. A major advancement was the incorporation of a cost-effective analysis to determine whether or not a given environmental reduction strategy made sense economically. Among the strategies evaluated, the two that reduced embodied emissions - increased fly ash and reduced overdesign due to better designs - were found to lower the CO2 emissions by approximately 10 percent and 17 percent respectively, while also saving upfront costs.

Finally, researchers reviewed fuel economy from a unique perspective. Instead of focusing on the efficiency of cars and trucks, they analyzed how pavement properties affect fuel economy. MIT developed the first-ever mechanistic pavement-vehicle interaction (PVI) model that relates fuel consumption to pavement material and structural properties. This model provides realistic estimates of changes due to deflection.

Pavements that deflect or bend slightly under traffic loads cause cars and trucks to run in a slight depression that increases fuel consumption. Pavements with greater stiffness, MIT found, mean better fuel economy for the vehicles that travel on them. As an example of the initial results, MIT looked at typical material properties for concrete and asphalt pavements and found that for the same stiffness and fuel consumption, an asphalt pavement had to be up to 60 percent thicker than the concrete pavement. With fuller development of this model, it will be possible to include the impacts of pavement properties and on fuel usage in both the environmental and cost analyses.

Furthermore, the research conducted by MIT has quantified the relative CO2 contribution from buildings across all phases of a building's lifecycle. This rigorous analysis, with a similar study of whether the best environmental strategy was beneficial economically, will allow the construction industry to improve the accuracy and transparency of existing and future lifecycle assessments, providing legislators, code making bodies and building design professionals with a comprehensive and unbiased LCA.

Established in 2009 in collaboration with PCA and Ready Mixed Concrete (RMC) Research & Education Foundation MIT's Concrete Sustainability Hub is a collaborative effort to integrate the best science on concrete and similar materials into industry practices. The MIT Sustainability Hub includes researchers from MIT's School of Engineering and School of Architecture and Planning.

More information on Sustainability Hub and this ongoing research is available at http://web.mit.edu/cshub.The reports generated from the referenced studies may be downloaded at www.specifyconcrete.org/specification-resources/sustainability.

Earn PDH Credits before September 30 Deadline!

By September 30, 2011, all professional engineers, land surveyors and geologists in Pennsylvania are required to meet new continuing education requirements.

PACA/PCPC offers continuing education classes and seminars that can help engineers meet these requirements, and we can even bring these presentations right to you. Contact us to learn more!

Only 1 Month Left!

Pervious Concrete Pavements, Insulated Concrete Form Construction, Integrating Concrete Into LEED Projects, Flowable Fill and Roller Compacted Concrete Pavements and are just a few of the classes that are offered. View a complete list of continuing education programs offered by PACA/PCPC.

Professional Development Hours (credits) obtained on or after October 1, 2009 will qualify. Courses that relate to the licensee's professional practice meet the requirements, as well as courses in ethics and law. The Registration Board has final authority in the event that a course is questionable. Click here for more information on the continuing education requirements.

To learn more or to schedule a class, contact Ken Crank or Bruce Cody today.

Don’t Miss the Pervious Concrete Pavement Design Webinars – September 13 & 20

Want to learn more about pervious concrete pavement design? Join us for this two part series, Designing and Specifying Pervious Concrete Parts I & II. The webinars will take place on September 13 and September 20, both webinars will begin at 10:00 a.m.

The webinars aim help civil engineers, architects, landscape architects and public works officials understand the principles behind pervious concrete design. Contractors, product suppliers and land developers will also benefit from attending. They will provide an overview on implementing pervious concrete pavements as a solution to reducing stormwater runoff from building sites and other paved areas. Participants will learn about pervious concrete pavement systems, engineering properties and construction techniques.

Part 1 discusses hydrologic and structural design of pervious concrete pavements. Part 2 addresses the specifics that every specifier should consider when drafting pervious concrete specifications, with a focus on American Concrete Institute (ACI) Committee 522 Guide to Specification for Pervious Concrete.

Architects and engineers earn two Professional Development Hours upon completion of this program. This seminar is registered with the American Institute of Architects Continuing Education Systems.

Note: This is a free event for our attendees. Please use this registration link below and enter the code: nrmcaspecifier.

Designing and Specifying Pervious Concrete Part I: Tuesday, September 13

Designing and Specifying Pervious Concrete Part II: Tuesday, September 20

If you have any questions about this event, contact Ken Crank.

Ask the Expert!

Q: One concern that has been expressed with the use of concrete is that one of its constituent materials, cement, is a large contributor of CO2. How does cement production compare to other CO2 producing activities?

A: The U.S. cement industry accounts for approximately 1.5% of U.S. CO2 emissions, well below other sources such as heating and cooling our homes (21%), heating and cooling our buildings (18%), driving our cars and trucks (33%) and industrial operations (28%).