Breakthrough concrete mix could reduce carbon emissions by 60%

Scientists at MIT have found a way to decrease the carbon emissions that result from concrete production: reducing the ratio of calcium to the silicate-rich clay. 

September 30, 2014 |

Concrete is ubiquitous in our world, as is concern about carbon emissions. The creation of concrete is a major source of carbon emissions, because the calcium-based substances that make it up are heated at high temperatures to form the cement.

But scientists at MIT may have found a way to decrease the carbon emissions that result from concrete production: reducing the ratio of calcium to the silicate-rich clay. 

Normally, concrete is made by mixing gravel, water, sand, and cement, Gizmag reports. The cement is produced by heating calcium-rich materials (e.g., limestone) at temperatures up to 2,732 F, and researchers say that this part of the process produces the majority of the carbon emissions. 

The MIT research team examined the makeup of the concrete, and found that a calcium to silica ratio of 1.5 is the optimal mix for reducing emissions and producing quality concrete. In the industry, these ratios can vary from 1.2 to 2.2, though 1.7 is the cement production standard. Changing the standard ratio to 1.5, researchers say, could reduce carbon emissions by as much as 60%. 

This mix of concrete was also shown to have a higher resistance to fractures. According to Gizmag, the researchers claim that "this is due to the molecular structure transforming from a tightly ordered crystalline to a disordered glassy structure." Regardless of the reason why, the 1.5 ratio concrete has twice the mechanical resistance to fractures of normal cement. 

Because the analysis of this concrete mix was carried out on a molecular level, it remains to be seen whether or not these results will remain the same in engineering-scale applications. This research was published in the journal Nature Communications.

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