Researchers at the Indian Institute of Science (IISc) in Bengaluru have developed a novel substance that shows promise as a replacement for natural sand in building. This is a reaction to the increasing scarcity of sand, an essential ingredient in construction materials.
The Centre for Sustainable Technologies (CST) at IISc is investigating ways to use carbon dioxide (CO2) recovered from waste gases from industry. Using this CO2, they treat excavated soil and construction waste, turning it into a practical substitute for sand.
“These materials can then be used to partially replace natural sand. This would not only reduce the environmental impact of construction materials but also impart properties that can enhance their use for construction,” stated IISc in a press release.
Led by Assistant Professor Souradeep Gupta, the research demonstrates that using CO2-treated construction waste in mortar, followed by curing in a CO2-rich environment, significantly accelerates the development of the material’s strength.
“CO2 utilisation and sequestration can be a scalable and feasible technology for manufacturing low-carbon prefabricated building products while being aligned with the nation’s decarbonisation targets,” explains Dr Souradeep Gupta, whose lab is carrying out these studies.
This innovative process boasts a 20-22% increase in the material’s compressive strength. Additionally, injecting CO2 into clay soil, commonly found at construction sites, improves its interaction with cement and lime. This not only stabilises the clay but also enhances its overall engineering performance.
The investigation by Dr. Gupta’s group goes farther. Researchers have looked into making cement-lime-soil composites by mixing captured CO2 with excavated soil. This could replace up to half of the fine aggregates that are normally used in mortar. By encouraging the growth of calcium carbonate crystals, this method improves strength and decreases pore space. These materials undergo an additional 30% increase in early-age strength and curing speed when exposed to CO2.
Additionally, the researchers have created 3D-printable materials by combining fly ash, slag, and cement with stabilized excavated soil. With their superior printability, these materials can eliminate the need for sand and cement by as much as 50%.
Future research will focus on the impact of industrial flue gas on these materials’ properties, paving the way for industrial applications and potentially revising standards for cement-based construction materials.
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