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Cool Down and Count Up to Sustainability

The effort to reduce SDOT’s carbon footprint has us counting up, as it were, and cooling down.  That’s because the more sustainable “green concrete” takes about seven days to cure, or solidify, whereas the more common mixture takes only three; and, the more sustainable asphalt is a warm mix versus a hot one.  SDOT’s NE Ravenna Blvd paving project is using both of these more sustainable road construction products.










By the way, there is such a thing as concrete that cures in just 24 hours but it is no longer the norm since it requires a lot of the key ingredient Portland Cement.  According to a 2009 New York Times article, “The manufacturing of Portland cement is responsible for about 5 percent of human-caused emissions of the greenhouse gas carbon dioxide.”  Portland Cement is what makes the gravel or other aggregate hold together to create concrete, so it’s a necessary evil, though new recipes are reducing the amount needed.  Of course, those new recipes mean more days for the concrete to cure so environmental responsibility is increasing the need for patience (another limited resource).

In the Ravenna project crews are utilizing green concrete for all base repair except where work is in the center of the roadway and traffic impacts for a full week would just be too significant.  In those instances a three-day mix (three days to cure) will be utilized.  All new asphalt along this stretch of Ravenna will come from a warm mix truck, meaning less heat on the street (about 250 degrees versus 300) and a significant reduction in the use of fossil fuels.  It’s good news for the earth, which we’re all counting on.