Low-carbon bricks developed using C&D waste for energy-efficient walling envelopes

Context

Researchers have developed a technology to produce energy-efficient walling materials using construction and demolition (C&D) waste and alkali-activated binders.

Key highlights about technology

• The technology produces alkali-activated bricks/blocks by utilising fly ash and furnace slag and characterising the thermal, structural, and durability characteristics of Low-C bricks and their masonry. 
  • Low-carbon bricks do not require high-temperature firing, and avoid the use of high-energy materials such as Portland cement. 
• After ascertaining the Physico-chemical and compaction characteristics of the CDW, the optimum mix ratios of the materials were obtained, and then the 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.
• This technology will also mitigate the disposal problems associated with the C&D wastes.

Alkali activation process 

• Alkali-activation is a globally growing technology that involves the chemical reaction between a solid aluminosilicate precursor and an alkaline activator, at room temperatures, giving a hardened product 
• The technology will also solve the disposal problems associated with C&D waste mitigation.

Carbon emission by making Building envelopes  

• 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.
• 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 construction and demolition waste (CDW). 
• In order to promote sustainable construction, two important issues need to be addressed while manufacturing the masonry units –
• Conserving mined raw material resources 
• Emission reduction.