Schneider

Technology

Green Bricks

February 2011

R Rajamani explains how we can modernise the brick-making process to make it more sustainable, economical and efficient.

India is the only developing country in the world that produces bricks by hand while the rest of the world uses clay processing machinery. The need of the hour is to modernise brick-making processes to produce high-quality green ceramic building materials by optimising usage of resources without endangering the environment and human health.

Current scenario

Conventional brick-making is becoming difficult because of nonavailability of labour; pollution control norms are becoming stringent by the day; and getting coal at concessional rates in the future is doubtful. The quality of handmade bricks is extremely poor. They display poor dimensional accuracy with variations up to +/ 10 mm; poor compressive strength of not more than 35 kg/sq cm and high breakage during transportation up to 15 per cent; and high porosity, making them unsuitable for exposed brick facades. There is high consumption of cement mortar owing to irregular shape and clay cannot be dug from agri fields.

This has resulted in widespread use of cement hollow blocks. Their use pushes up building costs as they weigh twice as much as burnt clay; for instance, a 400 × 200 × 200 mm cement block weighs somewhere around 24 kg compared to 12 kg of burnt clay blocks of the same dimensions with the same strength. This also means more labour is required. Cement is not a green product, cement blocks cost relatively more, and they cannot be used without plaster.

The solution

The prices of conventional handmade coalfired bricks are increasing every year by about 57 per cent. Current costs now range from Rs 3.50 in Chennai to Rs 5.50 in Bengaluru. On the other hand, machinemade bricks are uniformly extruded and dimensionally accurate. They can be moulded with as little as two workers per shift and hollow blocks can be made
5060 per cent lighter than cement blocks.

Besides, these extruded products also save money. The builder saves 1722 per cent of cement mortar in buildings. There is no plaster necessary owing to low porosity, reducing the cost of construction. Special sections can be made for arches and other shapes, again resulting in savings. Green bricks from an extruder dry faster because of less moisture content, thus saving cost. In multistoreyed buildings, because of the light weight of burnt clay hollow blocks (half that of cement blocks), the RCC shell cost is almost reduced to half.

The advantages

There are many advantages of machine made burnt clay products. There is more than 60 per cent saving of concrete in building construction depending on the dimension of the blocks and 17 to 22 per cent saving in mortar jointing cost using modular blocks. They act as a natural insulator; display low water absorption; provide sound-proofing plus insulation; and entail zero plastering cost. There is no child labour or cruelty to animals involved. With a price on par or even lower than ordinary traditional bricks, they are much superior to handmade conventional bricks in terms of finish, load bearing capacity, and water absorption. Bricks, hollow blocks and facing bricks can be manufactured to suit aesthetic choices. And, perhaps most significant, only 8 tonne of coal is used to fire 1 lakh bricks against 2224 tonne in the conventional process.

The project

The proposed project for a minimum viable capacity of 1 lakh bricks or equivalent hollow blocks per day requires an investment of around Rs 35 crore. India needs over 4,000 such plants to cater to its 160 billion brick demand.

Plant and machinery/technology include a box feeder; heavy-duty grinder; connecting conveyors; combined mixer extruder; multiwire automatic cutter; one lot handling machines; chamber dryer (drying cycle of 2448 hours); and a tunnel kiln with kiln cars and coal pulverising and producer gas plant. The technology and design are from Spain for the entire plant, while the dryer and kiln are made in India as importing refractory bricks and steel does not make sense and enough expertise is available with companies like UNIFIRE Kolkata, who have built over 300 kilns for diverse industries. The extrusion section is imported from Spain.

Suggested locations

Tamil Nadu: Chengalpet, Kanjeevaram, Tirunelveli, Coimbatore, Tiruchirapalli, Tanjore, Hosur. Karnataka: Hubli, Hasan, outskirts of Bengaluru. Andhra Pradesh: Visakhapatnam, Vijayawada, Guntur, Rajamundry, Chittoor

Why clay?

People have been firing the earth´s red treasure for more than 5,000 years to make their houses more secure.

  • Clay creates a protective shield that can resist any weather condition.
  • Clay is a natural material with a long life expectancy.
  • Once they have reached the end of their life, clay products are harmless to the environment and can be recycled for new applications.
  • Cay houses are healthy and provide a natural environment.
  • Clay products save on carbon emission compared to cement.

Green process

Harmful wastewater emissions are avoided, thanks to the closed circulation systems used in production plants. The modern filtration systems ensure that the load on the environment caused by emissions is kept low. This has been confirmed in a study commissioned by the WWF on the impact of brick and tile production on ecology. Great care is taken in redeveloping clay pits, letting them evolve into natural reserves and habitats for endangered birds, animals and plants, or other landscape solutions. Alternatively, they can be developed as land-fills using municipal garbage to produce methane gas that can be used to fire green bricks, as it is being done in the UK.

Benefits of hollow clay bricks

The countless pores in hollow clay bricks and blocks favour the exchange of humidity between the indoor and outdoor environments, hence ensuring better thermal insulation. These bricks absorb interior moisture, which means having a dry surface in every season and a comfortable room climate. A clay hollow brick house does not cool down quickly in winter, but also remains pleasantly cool in summer. With their low relative humidity and rapid drying, such constructions quickly develop optimal thermal insulation. They are long lasting with no maintenance effort.

Each individual stage of work is subjected to strict quality controls—local laboratories check the manufacturing process and the quality of products on a regular basis. Bricks don’t burn as they are baked and in case of fire do not produce any harmful vapours.

At wall thicknesses of 8 cm and above (e.g. non load-bearing internal walls), they achieve a value of F90; this means 90 minutes of time to get yourself and your family to safety. Solid exterior clay hollow brick walls exhibit excellent sound insulation values. The mechanised production of clay hollow bricks ensures high compressive strength. Clay hollow brick structures have excellent stability even in regions prone to earthquakes.

Conclusion

The demand for ecofriendly building materials is on the rise in India and the world over. This project will provide highquality natural building materials that reduce construction costs, in some cases as much as 50 per cent, and available from a reliable supplier. The demand for these materials will increase rapidly. In India, the project will provide architects with solutions and incorporate their suggestions while deciding the product profile. Many product ranges, like KORAMIC clay roof tiles and ARGETON façade tiles, are imported from European plants and can be made in India itself. Ventilated facades using terracotta tiles are an intelligent solution to save energy used for cooling office space and look great. In fact, ARGETON has become the most popular ventilated façade solution in only two years, with projects ranging from 200 sq m residential houses to 24,000 sq m hotels.

Carbon credits from energy efficient brick manufacture

Assumptions/Remarks:

Total coal consumed in baseline scenario to fire 1 lakh bricks: T24
Total coal consumed in project scenario to fire 1 lakh bricks: T8

Total coal savings per 1 lakh bricks: T16
Total coal savings per 400 lakh bricks: T6,400

Total CER/annum CO219008 Emission factor for coal = 2.97 tCO2/t Coal

Total CER revenue/annum: INR12773376
CER price = 12 Euro/unit and I Euro = 56 INR

Note: As estimated by a CDM consultant, this revenue will be available every year for 10 years assuming there is a market for CERs post 2012.

About the author:

Reynold Rajamani, an IIT Madras engineer, has been associated for over 20 years with propagating innovative and modern technologies for the manufacture of green, ecofriendly and economical to use building construction materials like tiles, hollow blocks and bricks from waste like flyash, clay, agrowaste, etc. He has been associated with international companies London Bricks in London, Walter Craven in Germany and Interkiln in Houston, USA as a consultant for projects to manufacture ceramic and clay products since the early eighties. Reynold Rajamani was a member of the advisory panel for Flyash Utilisation of Department of Science & Technology in 198586. Interested entrepreneurs can contact him on Tel: (0)93677 07733/ (0)96290 07733; Website: www.tdcl.in