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taylorvich [soylentnews.org] writes:

https://newatlas.com/materials/carbon-negative-cement-sand-substitute-seawater-electricity-co2/ [newatlas.com]

Concrete is the most widely used artificial material on the planet – which is a shame, because making it also happens to be one of the most polluting processes. Worse still, at a global scale it requires huge amounts of sand, which is getting harder (financially and environmentally) to mine from coasts, seafloors and riverbeds.

An unassuming new material from Northwestern could help solve both problems. Composed of calcium carbonate and magnesium hydroxide in different ratios, it’s pretty simple to make – just take some seawater, zap it with electricity and bubble some CO2 through it.

The whole process is similar to how corals and mollusks build their shells, according to the team.

If you really want to get your thinking cap on, here's how they do it: two electrodes in the tank emit a low electrical current that splits the water molecules into hydrogen gas and hydroxide ions. When CO2 gas is added, the chemical composition of the water changes, increasing levels of bicarbonate ions. These hydroxide and bicarbonate ions react with other natural ions in seawater, producing solid minerals that gather at the electrodes.

The end result is a versatile white material that not only stores carbon, but can stand in for sand or gravel in cement, and also forms a foundational powder for other building materials like plaster and paint.

Intriguingly, the researchers found the material could be tweaked by adjusting the flow rate, timing and duration of the CO2 and seawater, and the voltage and current of the electricity. By tweaking the manufacturing process, the researchers can make the material with different properties for different purposes

“We showed that when we generate these materials, we can fully control their properties, such as the chemical composition, size, shape and porosity,” said Alessandro Rotta Loria, lead author of the study. “That gives us some flexibility to develop materials suited to different applications.”

This process is far greener than the usual method of making these building materials. Not only does it reduce the need to strip mine huge quantities of sand from the natural environment, but the only gaseous byproduct is hydrogen, which can itself be captured for use as clean fuel. The CO2 used to make the material could even come from emissions from regular cement production, in which case the process could make regular cement greener as a byproduct.

“We could create a circularity where we sequester CO2 right at the source,” Rotta Loria said. “And, if the concrete and cement plants are located on shorelines, we could use the ocean right next to them to feed dedicated reactors where CO2 is transformed through clean electricity into materials that can be used for myriad applications in the construction industry. Then, those materials would truly become carbon sinks.”

Original Submission