Natural sand is quickly becoming a scarce resource.

Scientists at the Indian Institute of Science (IISc) in Bengaluru have created a promising new material that can replace natural sand in construction. The development comes in response to a growing shortage of sand, an essential component of construction materials.

A team at IISc’s Center for Sustainable Technologies (CST) is exploring ways to utilize carbon dioxide (CO2) captured from industrial waste gases. They treat excavated soil and construction waste with carbon dioxide, turning it into a viable sand substitute.

“These materials can be used to partially replace natural sand. This would not only reduce the environmental impact of the construction material but also give it properties that enhance its construction use,” IISc said in a report. Press release.

Research led by Assistant Professor Souradeep Gupta shows that using CO2-treated construction waste in a mortar that is then solidified in a CO2-rich environment can significantly accelerate the development of the material’s strength.

Lab members are working around the development of carbon-sequestering building materials that are manufactured using additive manufacturing technology.
Image source: Material Group, CST, IISc

“CO2 utilization and sequestration can be a scalable and viable technology for manufacturing low-carbon prefabricated building products while aligning with the country’s decarbonization goals.” Dr. Suradip Gupta explainswhose laboratory is conducting these studies.

This innovative process increases the material’s compressive strength by 20-22%. Additionally, injecting carbon dioxide into clay soils commonly found on construction sites improves its interaction with cement and lime. This not only stabilizes the clay but also improves its overall engineering properties.

Dr. Gupta’s team’s research expanded further. They are exploring incorporating captured carbon dioxide into excavated soil to create cement-lime-soil composites that could potentially replace up to half of the fine aggregate typically used in mortars. This technology promotes the formation of calcium carbonate crystals, which increases strength and reduces pore space. Exposing these materials to CO2 further accelerates curing and increases early strength by 30%.

Researchers have also developed 3D printable materials using stabilized excavated soil combined with binders such as cement, slag and fly ash. These materials have excellent printability and can reduce cement and sand requirements by 50% each.

Future research will focus on the impact of industrial flue gases on the properties of these materials, paving the way for industrial applications and potentially revising standards for cement-based building materials.