Researchers have developed a technology called low-C bricks that produces energy-efficient walling material using construction and demolition waste (CDW) and alkali-activated binders. These bricks do not require high-temperature firing and avoid the use of high-energy materials such as Portland cement.

“Scientists of the Indian Institute of Science (IISc) have developed a technology for producing alkali-activated bricks/blocks by utilising fly ash and furnace slag. The team of researchers developed low embodied carbon bricks from CDW through an alkali activation process using fly ash and ground slag and characterising the thermal, structural, and durability characteristics of Low-C bricks and their masonry,” an official statement from Science and Technology Ministry said.

Optimum mix ratios

It further added that after ascertaining the physico-chemical and compaction characteristics of the CDW, the optimum mix ratios of the materials were obtained, and then production process was evolved to produce low-C bricks. Based on the optimum binder proportions, the compressed bricks were manufactured. The bricks were examined for engineering characteristics.

Conventionally, building envelopes consist of masonry walls built with burnt clay bricks, concrete blocks, hollow clay blocks, fly ash bricks, lightweight blocks, and so on. The envelopes spend energy during their production, thus incurring carbon emission (i.e., possess embodied carbon) consume mined raw material resources which lead to unsustainable constructions.

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“The masonry units are manufactured either through the process of firing or using high-energy/embodied carbon binders such as Portland cement. As a result, the annual consumption of bricks and blocks in India is about 900 million tonnes. Besides, the construction industry generates vast amounts (70 – 100 million tonnes per annum) of CDW. In order to promote sustainable construction, two important issues need to be addressed while manufacturing the masonry units – conserving mined raw material resources and emission reduction,” the statement added.

Mitigate disposal problems

The major beneficiary of this development, undertaken by IISc Bangalore with funding from the Department of Science and Technology, Government of India, is the construction industry in general and the building sector in particular. This technology will also mitigate the disposal problems associated with the CDWs.

“A start-up has been registered which will be functional within 6–9 months to manufacture low-C bricks and blocks with IISc technical help. The start-up unit will act as a technology dissemination unit through training, capacity building, and providing technical know-how for establishing such commercial units across India,” said B V Venkatarama Reddy, Professor in IISc Bangalore.