Carbon sequestration engineer6/23/2023 ![]() ![]() Certain binders in concrete may possess different concentrations of calcium oxide, the ingredient that reacts with CO 2, and the availability and use of those binders varies widely across the United States. Material variation also introduces uncertainty. In areas with more precipitation, carbonation can occur at a greater depth in the concrete, but will also occur at a lesser magnitude than in drier areas. A number of differing climate zones exist across the United States, and each zone will affect carbonation differently. The greatest uncertainty in his model was climate. network.”īefore he could run the model, he quantified several uncertainties that could lead to variations in carbon uptake. “We developed this kind of pavement management system model for the whole U.S. “Pavement management models are a type of tool that transportation agencies can use to predict and decide where and when to implement certain treatment actions based on an available budget,” explains AzariJafari. In his work, AzariJafari and colleagues expand the scope of pavement carbonation research by developing an extensive pavement management model that can estimate carbon uptake in high resolution. To simplify calculations, most approaches tend to infer pavement properties and not incorporate challenging but important parameters, such as maintenance actions, which can “reset” the carbonation process. Past research on carbonation has struggled to manage these uncertain variables. What’s more, carbon uptake will continue even after that pavement’s demolition, depending on how its concrete waste is stored. Numerous factors like pavement geometry and maintenance, climate, and ingredients all determine a pavement’s carbon uptake. “There's a big opportunity for in concrete pavements,” says AzariJafari, “because usually the surface-to-volume ratio of concrete pavements is 10 times bigger than the surface-to-volume ratio of concrete elements in a building.”īut just because it’s easier for that uptake to occur doesn't mean it’s easy to estimate. While many buildings use concrete, the exposure of that concrete varies widely by design. That can make estimating carbon uptake challenging. Though all concrete experiences carbonation to some degree, the magnitude depends on how large the concrete surface is that's exposed to air. Co-authors on the work include civil and environmental engineering graduate student Fengdi Guo and CSHub Director Jeremy Gregory as well as Randolph Kirchain of the MIT Materials Research Laboratory. Postdoc Hessam AzariJafari, working within the MIT Concrete Sustainability Hub (CSHub), is first author of the new paper, which was published online in Resources, Conservation and Recycling on Jan. Much of those offsets, the researchers find, could occur years after pavements have been demolished, especially in states that use composite pavement designs. The study finds that the carbonation process could offset 5 percent of the CO 2 emissions generated from cement used in U.S. In a new paper, MIT researchers investigate the carbon uptake of all pavements in the United States. Estimating the extent of its carbon uptake at scale, however, has proven difficult. That’s because calcium carbonate forms when CO 2 from the air reacts with water in concrete pores, and then with calcium compounds in concrete - meaning that concrete is a potential carbon sink. Known as carbonation, this reaction forms calcium carbonate, a benign chalk-like material, but it can also affect climate change. Just along concrete’s gray surface, a chemical reaction is occurring. ![]()
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