Scientists create “artificial sand” that eats carbon dioxide that can change the construction industry

Due to innovative processes developed by Northwestern University researchers, the construction industry may soon be built using materials that actively remove carbon dioxide, which have essentially found a way to grow sand from seawater and carbon dioxide.

A team led by civil engineer Alessandro Rotta Loria has created a carbon-negative material that can replace conventional sand in concrete while permanently storing greenhouse gases. Their findings, published Wednesday in Advanced Sustainable Systems, showcase a process that not only captures carbon, but also produces hydrogen as a clean fuel by-product.

“We have developed a new approach that allows us to use seawater to create carbon-negative building materials,” said Rotta Loria, assistant professor of civil and environmental engineering at the Northwest McCormick School of Engineering. “Cement, concrete, paint and gypsum are often derived from minerals based on calcium and magnesium, which are often derived from aggregates – what we call sand.”

This technology has undergone a significant change compared to current practice. “Currently, sand is sourced from mining through mountains, riverbeds, coasts and seabeds,” explains Rotta Loria. “With Cemex, we designed an alternative method to source sand – not by digging the earth, but by using electricity and carbon dioxide to grow sand-like materials in seawater.”

From seawater to building materials

The process started unexpectedly and simply: the researchers inserted the electrodes into the sea water and applied an electric current. This breaks down water molecules into hydrogen and hydroxide ions. While keeping current flowing, they bubbling carbon dioxide gas through seawater, changing its chemical composition and increasing bicarbonate ion concentration.

These chemical changes trigger the reaction of calcium and magnesium ions naturally occurring in seawater, producing solid minerals such as calcium carbonate and magnesium hydroxide, similar to materials from shells and corals.

“Our research team is trying to use electricity to innovate construction and industrial processes,” said Rotta Loria. “We also like to use seawater because it is a natural rich resource. It is not as scarce as freshwater.”

The researchers found that they can not only plant these minerals into sand-like materials, but also accurately control their properties. By adjusting factors such as voltage, current, carbon dioxide injection rate and seawater flow, they can produce from sheet and porous to dense and hard substances.

“We show that when we generate these materials, we have full control over their properties, such as chemical composition, size, shape and porosity,” Rotta Loria notes. “This gives us some flexibility in developing materials suitable for different applications.”

Dual climate solutions

These materials have excellent carbon capture capabilities – they can store more than half of their weight in CO2. For example, one ton of material (calcium carbonate and half of magnesium hydroxide) can permanently isolate half of metric tons of carbon dioxide.

For the critical moment of the construction industry, this development faces pressure from an increasing carbon footprint. According to the World Economic Forum, the cement industry alone accounts for about 8% of global carbon dioxide emissions, making it the fourth largest carbon emitter in the world. This environmental impact will grow even greater with the combination of concrete production.

Northwest Research, co-written by Jeffrey Lopez, assistant professor of chemical and biological engineering, along with postdoctoral fellow Nishu Devi and several doctoral students, represents part of the global building materials company Cemex, a global building materials company focused on sustainable architecture.

Rotta Loria stressed that the integration of the material into concrete or cement will not damage structural integrity. “This approach will enable complete control over the chemistry of water sources and water wastewater, and it can only be reinjected into open seawater after proper treatment and environmental verification,” he said.

From laboratory to industry

Researchers envision extending their technology using modular reactors rather than implementing it directly in the ocean, which could interfere with marine ecosystems. This method may be particularly effective in cement and concrete plants located near the coastline, resulting in a circular system that captures carbon dioxide emissions and converts them into useful building materials.

“We can create a circularity that allows us to isolate carbon dioxide at the source,” explains Rotta Loria. “And if the concrete and cement plants are on the shoreline, we can use the ocean next to us to feed dedicated reactors where CO2 is converted into materials that can be used for countless applications in the construction industry by cleaning electricity. These materials will then really turn into carb sinks.”

The natural-style process reflects how marine organisms such as corals and molluscs form shells – using energy to convert dissolved ions into calcium carbonate. However, instead of metabolizing energy, the researchers applied electricity and enhanced mineralization by injecting CO2.

While many climate solutions focus on capturing carbon dioxide and storing it underground, the Northwest approach enhances value by turning greenhouse gases into available materials to make concrete, cement, stucco and paint while using hydrogen as a clean fuel, including a variety of applications, including transportation.

As the construction industry is looking for ways to reduce climate impacts, this technology shows a future where building materials can help solve climate crises rather than promote them – transforming us from everything that environmental responsibility creates into environmental assets.