Captain Arif Mahmud
ince the year 1990 Bangladesh is going through numerous development projects. Roads, bridges, flyovers are being constructed by the public sector in the country. To keep pace with the public sector, residential and commercial buildings are being built by the private sector. For all these constructions there is always endless demand for bricks but still the century old techniques are used here to produce bricks. The raw brick is made from soft mud and then it is kept in fire for long time to make them real hard and then used for construction purpose. There are more than 1000 brick kilns around the Greater Dhaka region spread across six districts. With the century old technologies these brick kilns run only in the dry seasons, namely from October to March and the kilns cannot produce bricks in the monsoon seasons. Most of these brick manufacturing plants use energy inefficient fixed chimney bull trench kiln technology and predominantly using coal, furnace oil, oil sludge, wood and agricultural waste as fuel.
The emissions from all these fixed chimney bull trench kilns are estimated to be 23,300 tone of Particulate Matter (PM2.5) 15,000 tons of sulfur dioxide (SO2) , 302,000 tons of carbon monoxide (CO), 6,000 tons of black carbon and 1.8 million tons of CO2 gas emissions from these brick kilns to produce approximately 3.5 million of bricks per year. Brick kilns are primarily associated with PM, CO, SO2, volatile organic compounds, nitrogen oxides (NOx), and heavy metals depending on the type of fuel burnt. At the brick kilns in the Greater Dhaka region, the energy required for baking 100,000 bricks is estimated at 20 t of coal with a calorific value of 22 MJ/kg and the majority of the energy
needs is supplemented by coal ( about 80 %) and occasional use of gas ( about 10 %) and heavy fuel oil ( about 10 % ).
Brick kilns are marked to be one of the major sources of rural and urban air pollution throughout Bangladesh. The size of particles is directly linked to their potential for causing health problems. Small particles less than 10 micrometers in diameter pose the greatest problems, because they can get deep into human lungs, and some may even get into human bloodstream. Exposure to such particles can affect both human lungs and heart. Numerous scientific studies have linked particle pollution exposure to a variety of problems, including, premature death in people with heart or lung disease, nonfatal heart attacks, irregular heartbeat, aggravated asthma , decreased lung function, increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing. People with heart or lung diseases, children, and older adults are the most likely to be affected by particle pollution exposure.
Fine particles (PM2.5) are the main cause of reduced visibility (haze) in parts of Bangladesh, including many areas of greater Dhaka district. Particles can be carried over long distances by wind and then settle on ground or water. Depending on their chemical composition, the effects of this settling may include, making lakes and streams acidic, changing the nutrient balance in coastal waters and large river basins, depleting the nutrients in soil, damaging sensitive forests and farm crops, affecting the diversity of ecosystems, contributing to acid rain effects.
It can be seen from the previous explanation that producing conventional bricks with conventional energy inefficient fixed chimney bull trench kiln technology is actually consuming mainly coal, natural gas and furnace oil. The natural gas produces less air pollution but using of natural gas in brick fields is limited in Bangladesh. So the major fuels for firing the bricks are coal and heavy fuel oil and the use of coal in all the brick kilns is about 80%. Thus the air pollution created by the coal smoke in the dry months in Bangladesh is devastating for the mass population living in all the six districts of the Greater Dhaka Division. All these smoke and dust are serious health hazard for people specially the children and aged people.
To stop this serious air pollution, instead of conventional bricks the ‘Concrete Blocks’ can be used in construction of the buildings. In Bangladesh for making roofs and columns cement, stones and mild steel rods are used. The use of conventional bricks are mostly for erecting the walls either for outer walls or for making partitions in different rooms inside of a building. For making all these vertical walls the concrete blocks can be used very easily. The concrete blocks are heavy, durable and are thought to be stronger than the conventional bricks.
A concrete block is primarily used as a building material in the construction of walls. It is sometimes called a concrete masonry unit (CMU). A concrete block is one of several precast concrete products used in construction. The term precast refers to the fact that the blocks are formed and hardened before they are brought to the job site. Concrete blocks may be produced with hollow centers to reduce weight or with improved insulation. The use of block work allows structures to be built in the traditional masonry style with layers of staggered blocks. Blocks come in many sizes. This type of block manufacturers offer many types of blocks and these can be used for partition wall, footpath, car parking, side walk, container yard, house lane, market Street, industrial yard, airport’s taxiways, hanger etc.
The benefits of Concrete Blocks
Greatly reduced construction cost : Using concrete block in construction significantly reduces cost in various ways. To produce brick hectors of land, tons of wood and coal are wasted. If we practice using concrete block we can save these natural resources to build our home, offices, roads and any other construction. Each concrete block is about 25% cheaper than the bricks.
Reduced Maintenance cost : For long run concrete Buildings and pavements that “stand the test of time” through their low maintenance requirements have a significant sustainable advantage over the conventional brick structures. Moisture, which can undermine other building materials through rust or rot, has no weakening effect on concrete. Neither termites nor mold take any toll on concrete. In fact, concrete continues to strengthen over
time, which is why concrete structures built thousands of years ago are still intact.
Extremely Durable : Concrete is one of the most durable materials on Earth. Concrete homes are far less likely to suffer damage in the event of a fire and earthquake. Concrete bricks can be reinforced to protect against high winds or earth tremors. If damage does occur, the structural integrity of the home typically remains intact, allowing for easier rebuilding. Concrete block is unquestionably the most practical home building material. There’s no rotting or wall warping.
Energy Saver : 80% or more of the greenhouse gases generated from structures are released through energy produced for their on-going heating and cooling. Insulated concrete wall systems provide good insulation and thermal mass with low air infiltration to provide superior thermal efficiency and optimal energy performance over the long life of the building. Since homes and buildings constructed with insulated concrete walls are not subject to large daily temperature fluctuations, owners can lower heating and cooling bills by up to 25%. Heating, ventilating and air-conditioning can also be designed with smaller-capacity equipment for additional savings.
Design Flexibility : Concrete block is an extremely flexible building material. Concrete block can be used to build just about any type of house feature imaginable. Columns, archways and other intricate designs are all easily achieved with the material. Building with concrete block means you have the flexibility to do just about anything you want. Whether it be a one- story home or a three story home with such options as high ceilings and tall windows concrete block provides the needed flexibility for every type of job.
If we practice using concrete block we can save these natural resources to build our home, offices, roads and any other construction. Each concrete block is about 25% cheaper than the bricks.
It can be said that the making of conventional bricks has many demerits. It consumes heavy amount of coal or heavy fuel oil which will produce huge amount of smoke and other harmful gases which will affect the public health. More over the most fertile top soil of the fields are taken for producing conventional bricks as a result the fertile lands are losing the fertility.
On the other hand concrete blocks can be easily manufactured and it does not require any fire for burning. So there is no emission of any harmful gases and no threat to public health. More over the concrete blocks are cost effective and highly durable.
So , definitely it will be better in all the aspects and for all the concerned parties to use the concrete blocks instead of the conventional bricks.
Author is an Assistant Professor , Maritime Science Department, Bangabandhu Sheikh Mujibur Rahman Maritime University, Dhaka, Bangladesh.