In order to address the issues of dwindling resources of natural sand and the increase in carbon dioxide emissions, especially from manufacturing cement or fired clay bricks, researchers at the Indian Institute of Science (IISc.) are exploring ways to store carbon dioxide from industrial flue gas in excavated soil and construction and demolition (C&D) waste.
According to the IISc., the construction sector today faces several challenges. It said that natural sand is fast becoming a scarce resource and that it might run out of supply by 2050.
Carbon dioxide emissions, especially from manufacturing cement or fired clay bricks, are increasing every year. The amount of C&D waste is on the rise – about 150 million tonnes are generated annually in India and the recycling rate is only about 1%.
To address such challenges, researchers at the IISc.’s Centre for Sustainable Technologies (CST) are exploring ways to store carbon dioxide from industrial flue gas in excavated soil and C&D waste.
“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,” the IISc. said.
“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,” said Souradeep Gupta, Assistant Professor at CST.
Mr. Gupta’s team has shown that replacing natural sand with carbon dioxide-treated C&D waste in mortar and then curing it in a controlled, CO2-rich environment can speed up the development of the material’s engineering properties, and enhance its compressive strength by 20-22%.
His lab has also tested the effect of injecting carbon dioxide gas into clayey soil – typically excavated from construction sites. This resulted in better stabilisation of clay by cement and lime, and reduced the surface area, pore volume, and lime reactivity of clay in soil, thereby improving the bulk engineering performance of the material.
The team has also developed 3D-printable materials made of excavated soil stabilised with a combination of binders like Portland cement, blast furnace slag (a granular calcium-silicate byproduct), and fly ash.
They found that the non-expansive clay in the excavated soil acts as an excellent thickening agent (rheological modifier) and causes the material to display superior extrusion and buildability when compared to conventional cement-sand mortars. Using these materials would also reduce the amount of cement and natural sand needed in mortar by 30% and 50% respectively, they found.
