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Recycled Ash Makes Greener Bricks

Posted: 04/08/2006

Researchers at the University of New South Wales, Australia have developed bricks and building aggregate that can be manufactured entirely from waste fly ash. The result is a strong, lightweight building material that they believe could generate a thriving new "green" industry for countries such as China and India.

Coal-burning power plants spend millions of dollars disposing of waste fly ash, a fine powder loaded with toxic chemicals. An estimated 200 million tonnes of the byproduct is generated in China each year, much of it sent to waste disposal sites on increasingly scarce land and it is also responsible for serious air and water pollution.

In China it is difficult to find a clay quarry or aggregate quarry close to a city. Many brick plants are idle due to lack of clay yet most power stations have some form of brick plant close by. There is growing interest among the Chinese in reducing greenhouse gases, reducing chemical pollutants and dust emissions and stopping the alienation of the land.

In India about 100 million tonnes of fly ash is generated each year. The Indian Government passed a law in October 2005 stating that a minimum of 25 percent of fly ash must be used in the manufacture of clay bricks for use in construction activities within a 50 km radius of coal burning thermal power plants. There are also restrictions on the excavation of top soil for the manufacture of bricks.

In the Middle East there are very few coal fired power stations and there is an acute shortage of durable building materials because of the lack of suitable clay, aggregate and sand. Quality building materials are imported at considerable cost. Thus, there is a definite market for high-quality light-weight building materials in the Middle East.

Karl Shaw, one of the scientists involved, says their unique manufacturing method traps any harmful chemicals, creating an eco-friendly construction material that saves on construction costs and reduces generation of greenhouse gases. They also generate fewer emissions during manufacture as the process uses less fuel than clay bricks.

Flash Bricks are 28 percent lighter and 24 percent stronger than comparable clay bricks while the aggregate, Flashag, can be used to make concrete that is 22 percent lighter and 20 percent stronger than standard products. This results in lighter structures, shallower foundations, cheaper transportation, and less usage of cement and steel reinforcement.

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