Precast Solutions - May/June 2008 - (Page 7)

produce the most economical, sustainable and resilient products for our customers.” SRP also operates its own materials lab where new mixes are tested for compressive strength and performance. Blankenship explains how engineering specifiers often fall into the trap of overdesigning precast products by specifying the cement content and the water-tocementitious materials ratio. It would serve the engineer and the industry better, reasons Blankenship, if engineers specified the end use and the design parameters and left the mix design up to the producer. “The precast producer has the experience to determine which concrete mix can best meet the service and strength needs of the project.” Specifying engineers often are not acquainted with how the precast concrete production industry effectively uses concrete technology to not only manufacture the most appropriate product for the job, but to also use maximum recycled materials in the process. Through collaboration, producers and specifiers can work together to use the attributes of precast concrete to achieve LEED (Leadership in Energy and Environmental Design Green Building Rating System) accreditation as part of the integrated design process. ACKNOWLEDGE RESOURCE CONSERVATION AS GOOD BUSINESS In Southern California, Arto Brick California Pavers, Gardena, manufactures products that architects and specifiers can use to secure LEED credits for projects The following are some of this producer's green practices: 1. Use high SRI (Solar Reflectance Index) colors in many products to reduce heat island effect. 2. Use locally sourced raw materials to reduce transport costs, energy and carbon emissions. 3. Use recycled material that does not compromise product quality. 4. Recycle gray water into concrete mixes. Specifying smart precast concrete roof and wall panels, as in this classroom construction, takes advantage of solar radiation to reduce energy costs by up to 50 percent. Photo courtesy TermoDeck PRECAST CONCRETE ENERGY PERFORMANCE FOR LEED ACCREDITATION In a model of energy performance of mid-rise commercial buildings due to thermal mass in five climates, Martha G. Van Geem and her co-authors (M.L. Marceau and I.M. Alsamsam) have demonstrated a reduction in energy costs up to 23 percent for concrete-framed buildings (with thermal improvements to the building envelope, including walls and windows) relative to steel-framed structures. These energy savings qualify for up to four LEED points. This information on precast concrete energy performance is important news for architects and specifying engineers. With respect to LEED credits for solar reflectance of concrete and reduction of the heat island effect, Van Geem and Marceau penned a PCA (Portland Cement Association) research report in 2007 on 45 concrete mixes. “Heat island occurs where there is a preponderance of dark exterior building materials and a lack of vegetation,” says Van Geem, wherein structures absorb heat from the sun and produce warmer temperatures – in cities, for example. Higher temperatures from the heat island effect increase energy used for air conditioning. Findings indicate that the Solar Reflectance Index (SRI) of the cement in the mix (SRI = 29, meeting LEED requirements) has more effect on SRI than any other material in the concrete mixtures. Fly ash and slag cement had the second greatest effect on SRI, and slag cement can have greater SRI than ordinary portland cement or fly ash. For more information, view the full article at www.precast.org/sustainability. MAY/JUNE 2008 | PRECAST SOLUTIONS 7 http://www.precast.org/sustainability

Table of Contents Feed for the Digital Edition of Precast Solutions - May/June 2008

Precast Solutions - May/June 2008 Contents Sustainability and Practicality Security Blanket A Frank Lloyd Wright Takes Shape Concrete Joins MENSA Precast Lightens Up

Precast Solutions - May/June 2008

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