Cement Americas provides comprehensive coverage of the North and South American cement markets from raw material extraction to delivery and tranportation to end user.
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NEWS MIT RESEARCHERS PROVIDE AMERICAS COMPREHENSIVE LCA FOR BUILDINGS The need to decrease energy usage and subsequent emissions from the building sector has been at the fore- front of U.S. green movement. To ad- dress this, researchers at the Massachusetts Institute of Technology's (MIT) Concrete Sustainability Hub con- ducted a life-cycle assessment (LCA) study to evaluate and improve the en- vironmental impact and study how the "dual use" aspect of concrete—its abil- ity to offer a durable structure while providing thermal mass benefits for en- ergy loads—affects the environmental footprint of the structure. "Methods, Impacts, and Opportuni- ties in the Concrete Building Life Cycle" provides a comprehensive analysis that advances three key areas relevant to the buildings LCA field: methodology, benchmarking, and impact-reduction opportunities. The study is a major de- velopment for construction-related, life-cycle assessment as it thoroughly examines all phases of the complete life cycle of a building—from acquisi- tion of materials to construction, the use of the building, and finally demoli- tion and end of life. "Most environmental assessments do not move beyond the construction phase and only provide a partial picture of the full impact a particular material can have on a building. This is short- sighted," said David Shepherd, director of sustainable development for Portland Cement Association. "The heating, cool- ing, and general operations of buildings and homes in the United States account for approximately 70% of national en- ergy consumption each year, and an ac- curate LCA needs to include the operational phase." Concrete has largely been chosen as a building material for its structural properties rather than its energy-sav- ing properties. Although sustainable builders have known the thermal mass attributes of concrete significantly re- duce heating and cooling needs, the energy consumption required to pro- duce its key ingredient, cement, has raised questions about its environmen- tal viability. In its environmental as- sessment, MIT researchers found concrete homes produce lower green- house gas emissions than current best practice code—compliant wood-frame residences throughout a 60-year serv- ice life. Concrete homes did have a higher embodied global warming potential (GWP) associated with the pre-use phase of LCA when raw materials are harvested and turned into construction materials, transported to the site, and assembled into the finished home. However, this phase accounts for only about 2% to 12% of the overall global warming potential for the life of the home. For the 60-year period of the study, houses constructed with insu- lated concrete forms have 5% to 8% lower GWP than current code-compli- ant, light frame wood houses, based on greater thermal mass and higher R-val- ues. Researchers found similar results when evaluating multifamily residences. Commercial office buildings built with a concrete structural frame produce slightly less greenhouse gas emissions over a 60-year service life than com- mercial structures built with steel frames, based on the results of the comprehensive MIT assessment. MIT researchers then evaluated strategies to lower a concrete build- ing's carbon footprint and overall envi- ronmental impact. A major advancement was the incorporation of a cost-impact analysis to determine whether or not a given environmental reduction strategy made economic sense. Among the strategies evalu- ated, the two that reduced embodied emissions—increased fly ash and re- ducing the thickness of concrete walls from a 6-in. to a 4-in. concrete core— were found to be both economical and effective ways to reduce emissions. PUBLICATION Pavement guide now available August 2010. Guide to Cement-Based Inte- grated Pavement Solutions pro- vides a clear, concise, and cohesive presentation of cement- bound materials options for 10 specific engineering pavement applications. Developed by the National Concrete Pavement Technology Center at Iowa State University's Institute for Trans- portation, the publication pro- vides the benefits, considerations, brief descriptions, and summary of materials, de- sign, and construction require- ments, as well as a list of sustainable attributes for each technology. The Guide is designed so that the most up-to-date and rel- evant information is easily ex- tractable. It is ideal for practitioners, including engineers and managers who face deci- sions regarding what materials to specify in the pavement systems they design or manage. City and county engineers, along with the A/E firms that often represent them, and state DOT engineers at all levels who are seeking al- ternatives in this era of changing markets will also find the publi- cation useful. The publication is currently being offered in PDF format from the Portland Cement Association Bookstore; a printed version is also in the works. www.cementamericas.com • November/December 2011 • CEMENT AMERICAS 5 Morp:/ ht t e inf b e / or.mit w mat.e ion c du/ an be f s c ound at hub/ :