According to the World Business Council for Sustainable Development, ''concrete is the most widely used material on earth, apart from water, with nearly three tons used annually for each man. woman, and child." There are four basic components common to all concrete: Portland cement, water, coarse aggregate, and fine aggregate. Additionally, ingredients may be added to the concrete mix to improve both the fresh and hardened properties, including supplementary cementitious materials and/or chemical admixtures. Despite the relatively few ingredients that go into a concrete mix. the proportions of these ingredients can vary significantly. This variability leads to significant differences in the carbon emissions associated with any given concrete mix. Added over the many cubic yards of concrete used in all building projects, seemingly small changes in the concrete mix design can effectively reduce the embodied carbon inherent in the construction of the built environment. The SEAOC Sustainable Design Committee (SDC) has collected over 300 concrete mixes used in California projects the last few years, and performed a Life-Cycle Assessment (LCA) on the mixes to quantify their environmental impacts. Using the data from the mix designs collected, the committee has determined where the industry average is in California, how this average compares to the NRMCA national average, and has explored what major factors affect the environmental performance of concrete materials. Note the NRMCA national averages were published in 2016, and they summarize the environmental impacts of concrete mix designs collected from 90 different concrete suppliers and 2,800 plants across the U.S. The SEAOC SDC has determined which components in a mix design most greatly impact the environmental performance and explores cost comparisons between typical concrete mixes and low carbon (cement) mixes. The forthcoming low carbon concrete code, that may soon be adopted in the Bay Area, is also discussed. Lastly, the committee makes recommendations to all structural engineers on how to specify more sustainable concrete and encourages them to build with lower carbon footprints.
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