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Volcanic Ash Additive Makes Cement Stronger
With the production of concrete being responsible for 5 percent of the world's carbon dioxide emissions, Massachusetts Institute of Technology engineers, working in conjunction with scientists from Kuwait, have found that concrete made with pulverized volcanic rocks reduces the energy that goes into producing concrete, thus lessening overall pollution.
According to the team’s calculations, 16 percent less energy is required to construct a pilot neighborhood with 26 concrete buildings made with 50 percent volcanic ash, in comparison with the same structures being made entirely of Portland cement.
Volcanic Ash Additive
Oral Buyukozturk, a professor in MIT’s Department of Civil and Environmental Engineering, was the head investigator on the research endeavor.
“Cement production takes a lot of energy because there are high temperatures involved, and it’s a multistage process,” said undergraduate Stephanie Chin of CEE. “That’s the main motivation for trying to find an alternative. Volcanic ash forms under high heat and high pressure, and nature kind of does all those chemical reactions for us.”
As part of the research, the team investigated how much energy it would take to make concrete from a mixture of cement and volcanic ash, rather than just cement alone. Researchers consulted several databases in order to calculate the embodied energy tied to various industrial processes.
What they found was that replacing 50 percent of traditional cement with volcanic ash with an average particle size of 17 micrometers could bring down concrete’s embodied energy by 16 percent. This compromised the strength of the concrete, however, and as a result they ground down the particles to 6 micrometers.
Focusing on a neighborhood in Kuwait with 13 residential and 13 commercial buildings made from Portland cement, the team calculated the neighborhood’s existing embodied energy and then calculated the change in embodied energy if the buildings had been constructed with the augmented concrete. As with prior findings, the team found that less energy would have been consumed if the alternate concrete mixture had been used.
“What we’ve found out is that concrete can be manufactured with natural additives with desired properties, and reduced embodied energy, which can be translated into significant energy savings when you are creating a neighborhood or a city,” Buyukozturk said.
The research was published in the Journal of Cleaner Production, and was funded in part by the Kuwait Foundation for the Advancement of Sciences.
