By Nidhi DhullReviewed by Susha Cheriyedath, M.Sc.May 23 2024Bricks have played a vital role in construction for centuries. As the world moves towards sustainability, innovative bricks are now being made from waste using advanced waste pre-treatment and pre-fabrication techniques. Given the significant amounts of waste produced across various sectors and the challenges of effective waste management, utilizing waste to develop energy-efficient construction bricks presents a viable strategy.1
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Making Bricks from Scraps
Traditionally, bricks are fabricated using a clay-firing method involving molding, sun drying, and burning. This process consumes approximately 24 million tons of coal annually.2 Given that coal is a major pollutant, researchers are exploring the use of various scraps—including wood sawdust, industrial waste, textile waste, agricultural waste, plastic waste, and sludge—in brick production.1
Both burnt and unburnt bricks can be manufactured from various scraps. For instance, unfired cementitious bricks are made using co-fired blended ash, while fired bricks can be produced by mixing textile sludge with clay in varying ratios.1 Agro-wastes like olive core flour and wheat straw can partially substitute clay in burnt bricks. Additionally, ash from sugarcane bagasse and rice husk can be used to create energy-efficient clay bricks suitable for load-bearing structures. Other woody agricultural biomasses, such as cocoa shells, sawdust, cherry seeds, and grape residues, also have the potential to replace different proportions of clay in brick-making.1,2
In the building sector, construction and demolition waste materials like sand, red earth, cement, quarry dust, and glass powder are being utilized in brick production. Moreover, sustainable geopolymer bricks can be formed by combining bioprocess by-products and industrial wastes such as sludge ash and crushed glass with quarried shale, further promoting sustainable construction practices.1
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Applications in Construction
Energy-efficient bricks made from scrap are gaining popularity in the construction sector due to their adjustable properties. For example, fired clay bricks crafted from blended dry sand from construction sites and shredded plastic wastes can exhibit up to 85 % more compressive strength compared to traditional clay bricks, making them ideal for use in harsh environments.1
Pavement blocks can also be created by mixing plastic waste with pit sand and sea sand. Additionally, houses built from plastic wastes like polyethylene terephthalate offer effective sound and thermal insulation, are bulletproof and can withstand extreme weather events such as cyclones.2
Lightweight hollow bricks can be made using plastic wastes, while bio-bricks and bio-brick panels have been successfully produced from recycled wheat husk and sugarcane bagasse.1 Moreover, compressed stabilized earth blocks (CSEBs) made by partially to fully replacing graded sand with granite sludge demonstrate enhanced compression strength and durability, withstanding aging up to five years and proving highly suitable for load-bearing applications.1
Advantages
Bricks made from scraps offer numerous environmental and structural advantages.1,2 For example, the growing number of wastewater treatment plants has increased sludge production, complicating disposal methods. However, incorporating up to 6.66 % sludge into bricks can reduce the required firing temperature, easing production processes.1
Bio-bricks from agricultural wastes such as stubble, corncobs, sugarcane bagasse, and grain husk are not only cost-effective but also have lower thermal conductivity compared to conventional bricks. This feature can reduce energy consumption by up to 36 %.1,2 Additionally, these completely organic materials help convert traditional agro-waste burning into a process that aids in carbon fixation in the atmosphere.1
The mishandling of unwanted materials from various industries can degrade air, soil, and water quality. Through innovative waste screening and recycling, the production of energy-efficient and economical bricks can secure environmental and human health. Moreover, bricks amended with sludge exhibit high compressive strength.1
Poor management of plastic waste poses irreversible ecological risks due to its non-biodegradability. Using plastic scraps in brick production, on the other hand, offers benefits in terms of reduced execution time, lower costs, improved load capacity, enhanced flexibility, significant waste reduction, and decreased energy consumption.2
Challenges
Despite several possible applications and advantages of scrap-made bricks, their commercial use is hindered by certain challenges. For instance, post-demolition scenarios of plastic-incorporated bricks are concerning. Similarly, the addition of sludge in cementitious bricks without prior treatment leads to inevitable hazardous metal leaching.1
The organic materials in agro/industrial wastes can affect their water absorption and pull down the bricks’ load-bearing capacity.1 Thus, further research is essential to determine the long-term performance and optimized strength of such bricks as per project requirements for their application in the building sector.2
Most research on sustainable bricks has primarily focused on using waste materials only as partial substitutes for raw materials. This approach lacks specific pre-treatment or fabrication methods tailored to waste materials. Consequently, despite its environmental drawbacks, firing continues to be the most commonly employed method for manufacturing bricks.1
Latest Developments
The potential of bricks made from scrap is being increasingly recognized in the construction industry. For example, engineers at RMIT University in Australia have demonstrated the practical use of such bricks in actual construction projects. They developed energy-efficient bricks by substituting at least 15 % waste glass and 20 % ash from a recycling company for clay. This innovation reduced the firing temperature by up to 20 % compared to traditional bricks, leading to cost savings for manufacturers. Moreover, using these bricks to construct a single-story building could lower household energy bills by up to 5 %, presenting a circular economy solution to significant waste challenges.3
A study published in the journal Energy and Buildings also advocated for the use of waste-incorporating porotherm bricks in hot-arid and warm-temperate climates, which could save on air conditioning costs, reduce CO2 emissions, and enhance investment returns. These porotherm blocks, made using discarded materials like plastic, tire, cloth, leather powder, rock wool, and coconut pith, have shown promising thermo-economic performance in diverse Indian climates, specifically in New Delhi and Bikaner.4
Future Prospects
Bricks remain the preferred building units and hold substantial promise for enhancing sustainability.1 Bridging the gap between academic research and the commercialization of scrap-made bricks could be achieved through advanced life cycle assessment methods, which would analyze the behavior of these bricks across various stages, including material production, utilization, and demolition.2
There is a need for innovative techniques to produce both fired and unfired bricks using waste materials, ensuring these products meet regulatory standards for structural and non-structural properties.1 The broader adoption of such bricks could address challenges related to affordable housing and effective waste management globally.
References and Further Reading
1. Saravanan, J., & Rao, P. V. (2023). Past investigations on development of sustainable bricks – A comprehensive review. Sustainable Chemistry for the Environment, 3, 100030. https://doi.org/10.1016/j.scenv.2023.100030
2. Puri, Dr. V., Kumar, S., Grover, K., & Sharma, M. (2022). Development of Eco-Friendly Bricks for Sustainable Construction. IOP Conference Series: Materials Science and Engineering, 1248(1), 012109. https://doi.org/10.1088/1757-899x/1248/1/012109
3. Wright, W. (2024). Energy-smart bricks keep waste out of landfill. RMIT University, Australia. https://www.rmit.edu.au/news/all-news/2024/apr/energy-smart-bricks0
4. Shaik, S., Roy, A., Arıcı, M., Kontoleon, K. J., Afzal, A., & Li, D. (2023). Air-conditioning cost savings, CO2 emission benefits and return on investment by using waste in porotherm bricks in hot-arid and warm-temperate climates. Energy and Buildings, 286, 112955–112955. https://doi.org/10.1016/j.enbuild.2023.112955
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