Recognising the urgency of natural sand getting scarce, a unique material that could replace natural sand in the construction sector has been developed by the scientists at the Centre for Sustainable Technologies (CST), Indian Institute of Science (IIS), Bengaluru as per the news reporting in April 2024. It has been predicted that natural sand would get exhausted by 2050. Therefore, construction industry has been facing a looming crisis. The industry has also aggravated climate change due to the carbon dioxide (CO2) emissions due to the manufacturing of cement and fired clay bricks.
India has been generating roughly about 150 million tonnes of construction and demolition (C&D) waste every year. Only about one per cent of it is recycled.
The scientists from the CST, led by Assistant Professor Souradeep Gupta have been researching for methods to segregate CO2 from industrial flue gas and mix it in excavated soil found in construction and demolition waste. This CO2-enriched material could then be used as an alternative to natural sand for construction. The scientists have observed improvements in the stabilisation of soil when combined with lime and cement. Thus, the surface area and pore volume of the clay decreased. Due to reduced reactivity of the soil to lime, the overall engineering qualities of the material was also enhanced.
Significance of the Research
While doing their research, the scientists found that using CO2-treated construction waste in mortar alongside curing in a CO2-rich environment would substantially increase the strength of the material. This material would reduce the environmental impact of construction materials. It would also impart properties that could increase its use in construction. Carbon dioxide utilisation and sequestration would help in the production of low-carbon prefabricated construction materials. Furthermore, this technology would aid in the country’s decarbonisation goals. Sequestering CO2 in cement-soil materials leads to the formation of calcium carbonate crystals, which lead to an increase in the density of interfacial zones and enhanced compressive strength of 20 to 22 per cent.
The scientists endeavour to make use of CO2 in the excavated soil for developing cement-lime-soil materials. This could be used to replace up to 25 per cent and 50 per cent of fine aggregates by mass in mortar. This technique would also promote the formation of calcium carbonate crystals, leading to improved strength and reduced pore space. Thus, early-age strength would be increased by 30 per cent and curing would also be accelerated due to the exposure of these materials to CO2.
Further, using stabilised excavated soil combined with binders like cement, slag, and fly ash, the researchers have also developed 3D-printable materials.
Way forward
The researchers now focus on the impact of industrial flue gas consisting of carbon dioxide, sulphur dioxide, and nitrogen oxide on the properties of the materials. This would pave the way for industrial applications of the developed material and for potentially revising standards for cement-based construction materials.
Moreover, the researchers intend to collaborate with prominent construction companies on revising standards for natural and recycled aggregates in cement-based construction materials as a part of a national committee.
© Spectrum Books Pvt Ltd.
