Salt water, CO2 and electricity are the new recipe to create more sustainable cement and concrete

Cement is one of the most used artificial materials on the planet, but has two problems. The first, environmentalsince its production emits a remarkable amount of greenhouse gases. The second, the shortage of raw materials such as sand, whose mined also has an environmental impact.

A new material. A team of researchers from the Northwestern University and the company ️Cemex Innovation Holding has developed A new construction material through a process that combines marine water, carbon dioxide (CO2) and electricity.

This new material can be used in the production of cement and concrete and, according to its developers, in its production more CO2 than it emits. That is why the new material has the ability to make the most sustainable cement and concrete production.

Salt water, CO2 and current. The method to create the new material begins by introducing electrodes in the salt water to circulate an electric current that separates water molecules into hydrogen gas and hydroxide ions. As explained by the development responsibleWhile the current circulates, CO2 bubbles are added to the water in order to change the chemical composition of the water by increasing the concentration of bicarbonate ions.

The ions of these two compounds (hydroxide and bicarbonate) react with other ions that can be dissolved in marine water, such as calcium and magnesium. From these chemical reactions both calcium carbonate (CACO3) and magnesium hydroxide arise. The first compound, Continue explaining the teamit is in itself a carbon sink; The second, on the other hand, is able to capture additional carbon interacting with CO2 molecules.

Copying nature. According to its developers, the process is similar to that used by corals and mollusks to build their structures and shells. The key difference is that these animals use their own metabolism instead of electrical energy to detonate the chemical process.

Different uses. The resulting material, a Mixture of calcium carbonate and magnesium hydroxidecan be used as a substitute for the sand or gravel used in concrete manufacturing, but can also be used to produce cement, plaster and even paint.

More control. The resulting material has an important advantage and that its properties can be altered by introducing small changes in the elaboration process such as the current and its voltage, or the duration of the injection of CO2, among others. Thus it is possible to achieve a more porous or more dense and hard substance.

The details of the process and its results were published In an article In the magazine Advanced Sustainable Systems.

Optimizing the capture of CO2. Another important factor is the calcium carbonate ratio and magnesium hydroxide obtained in the resulting material. This ratio depends, for example, the captured amount of carbon dioxide. According to The developers explaina 50/50 mixture of the compounds can allow to capture a ton of CO2 for every two tons of material.

A more harmless waste. The process, as we indicated at the beginning, begins with the separation of water molecules. This generates, in addition to the ions used to unleash the subsequent chemical, hydrogen reactions. This gas is not only harmless but can also be used as an energy reserve.

Of course, because electricity is part of the manufacturing process of this material, it must be taken into account that the net emissions of its production will depend on the mix energetic. That is, if the energy used in the process emits CO2 that is not captured, part of the capture would be lost.

Another detail to keep in mind is that a good part of CO2 emissions associated with cement production They are generated at a different stage of its manufacture, when the sand is crushed with the limestone and heated at high temperatures capable of decomposing calcium carbonate. This problem occurs if the material is used in the creation of the cement and not when it is mixed later with it in the production of concrete.

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Image | Northwestern University