Concrete is one of the world’s favorite building materials; it’s strong, simple to mix, and generally widely available. Its dirty little secret has always been centered around one of its main ingredients: cement. To make cement, crushed rock and other ingredients are fed into a kiln that heats the components at temperatures reaching 2,700 degrees Fahrenheit. Those extreme temperatures cause large amounts of carbon dioxide to be released into the air and, combined with the carbon dioxide that’s produced just to burn the fossil fuels to heat the kiln, it makes cement one of the largest producers of greenhouse gases in the world, 5% in total.
Due to both the extreme popularity of the produce and its inherent environmental impacts, scientists are racing to create the next concrete replacement or improve upon the age old recipe. But, as researchers have just discovered, cement may not be as bad for the environment as everyone has thought. According to a group of scientists from China, cement can actually absorb carbon dioxide gases through a process called carbonation. Carbonation is the process of carbon dioxide penetrating into the concrete and reacting with the other chemicals within the concrete. The process is largely responsible for the eventual corrosion of steel reinforcement in the concrete, because it lowers the pH level of substance.
After analyzing new and existing data of cement materials from 1930 to 2013, the scientists concluded that the cement absorbs up to 43% of the carbon dioxide it emits for its creation. That reduction does not include the emissions created by burning the fossil fuels, which reduces the total reduction of carbon dioxide to 21.5% over its lifetime. The research is important because it allows scientists to better focus on specific areas to help reduce emissions. In this case, the burning of fossil fuels has been discovered as the largest source of net carbon dioxide emissions. Rob Jackson, an earth systems scientist at Stanford University in Palo Alto, California, told Science Magazine that, “If you have a choice—reduce fossil emissions or reduce cement emissions—you should prefer the fossil ones right now.”
Full study: Substantial global carbon uptake by cement carbonation | Nature Geoscience
Cement soaks up greenhouse gases | Science Magazin
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