Recycling of waste concrete a must to save city environment
Wednesday, 29 October 2008
Munima Sultana
Global construction industry requires about 10 billion tonnes of natural aggregate a year to build infrastructure. The experts say that unless the waste concrete from demolished old buildings, highways and other infrastructure is reused, it would fill up land of 11 countries like Bangladesh with waste concrete each year.
They say the use of such a staggering quantity of natural aggregate for construction and disposal of waste concrete has been responsible for many environmental consequences across the world.
Bangladesh, where the construction sector is booming, is vulnerable, they say.
Dr Mohammad Tarek Uddin, professor of civil engineering in the University of Asia Pacific, says that waste concrete has already been increased in the country. It is likely increase manifold keeping pace with construction and reconstruction of buildings, highways and other infrastructures.
To meet the growing demand for infrastructure development, he say, the country would lose much of its natural resources and sustain environmental degradation unless steps are taken right now to find ways to utilise of waste concrete.
The more old buildings are demolished to reconst new ones the more waste concrete will have to be disposed, Dr Md Tarek says.
Now, it is stated, two tons of concrete is used per capita per day. Cement Association of Canada says that annual global production of concrete hovers around 5 billion cubic yards.
According to an old study of Lafarge Coppee SA, the French cement maker, concrete is second only to water as the most consumed substance on earth, with almost one ton of it used for each human every year. Concrete paving eats traffic pollution… titanium dioxide-containing paving blocks use sunlight to absorb nitrogen oxides in the atmosphere and converts them into harmless nitrogen and oxygen, it added.
Asked about the Bangladesh situation, Dr Tareq told FE that concrete waste has now dumped here and there due to lack of recycling.
But extensive studies have been carried out elsewhere to address the tremendous challenges of concrete industry for the sustainable development he said.
A two-year research done by the Department of Civil Engineering of the University of Asia Pacific (UAP) found that waste concrete from the old building can be a substitute of brick aggregate. The strength of the waste concrete, it showed, was 3000 per square inch or the same as the bricks being used for new construction.
Recently, UAP came out with the findings at a seminar where the speakers laid importance on improving the quality of construction materials and construction using recycled concrete from demolished buildings. They stressed the need for conducting more studies on the properties of recycled aggregate, recycled concrete for environmental benefits and sustainable development.
According to experts, concrete aggregate, carmac, bricks, dirt, and rocks collected from demolition sites are now dumped wherever possible. Crushing facilities accept only clean concrete, free of trash, wood, paper and other such materials. Metals, such as rebar, are accepted, since they can be removed with magnets and other sorting devices and melted down for recycling elsewhere. The remaining aggregate chunks are sorted by size. Larger chunks may go through the crusher again.
Dr Tareq said extensive research on recycling and concrete technology and other related areas would help the country property use concrete from demolished structures. It can be reused as high-level structured concrete.
Global construction industry requires about 10 billion tonnes of natural aggregate a year to build infrastructure. The experts say that unless the waste concrete from demolished old buildings, highways and other infrastructure is reused, it would fill up land of 11 countries like Bangladesh with waste concrete each year.
They say the use of such a staggering quantity of natural aggregate for construction and disposal of waste concrete has been responsible for many environmental consequences across the world.
Bangladesh, where the construction sector is booming, is vulnerable, they say.
Dr Mohammad Tarek Uddin, professor of civil engineering in the University of Asia Pacific, says that waste concrete has already been increased in the country. It is likely increase manifold keeping pace with construction and reconstruction of buildings, highways and other infrastructures.
To meet the growing demand for infrastructure development, he say, the country would lose much of its natural resources and sustain environmental degradation unless steps are taken right now to find ways to utilise of waste concrete.
The more old buildings are demolished to reconst new ones the more waste concrete will have to be disposed, Dr Md Tarek says.
Now, it is stated, two tons of concrete is used per capita per day. Cement Association of Canada says that annual global production of concrete hovers around 5 billion cubic yards.
According to an old study of Lafarge Coppee SA, the French cement maker, concrete is second only to water as the most consumed substance on earth, with almost one ton of it used for each human every year. Concrete paving eats traffic pollution… titanium dioxide-containing paving blocks use sunlight to absorb nitrogen oxides in the atmosphere and converts them into harmless nitrogen and oxygen, it added.
Asked about the Bangladesh situation, Dr Tareq told FE that concrete waste has now dumped here and there due to lack of recycling.
But extensive studies have been carried out elsewhere to address the tremendous challenges of concrete industry for the sustainable development he said.
A two-year research done by the Department of Civil Engineering of the University of Asia Pacific (UAP) found that waste concrete from the old building can be a substitute of brick aggregate. The strength of the waste concrete, it showed, was 3000 per square inch or the same as the bricks being used for new construction.
Recently, UAP came out with the findings at a seminar where the speakers laid importance on improving the quality of construction materials and construction using recycled concrete from demolished buildings. They stressed the need for conducting more studies on the properties of recycled aggregate, recycled concrete for environmental benefits and sustainable development.
According to experts, concrete aggregate, carmac, bricks, dirt, and rocks collected from demolition sites are now dumped wherever possible. Crushing facilities accept only clean concrete, free of trash, wood, paper and other such materials. Metals, such as rebar, are accepted, since they can be removed with magnets and other sorting devices and melted down for recycling elsewhere. The remaining aggregate chunks are sorted by size. Larger chunks may go through the crusher again.
Dr Tareq said extensive research on recycling and concrete technology and other related areas would help the country property use concrete from demolished structures. It can be reused as high-level structured concrete.