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Quality materials for quality building construction
HOUSI NG is one of the basic needs of human life. Buildings are part and parcel of human activities including living, entertainment, shopping, office, factories and so on. Therefore,
buildings should be safe against natural and man-made disasters, comfortable, user friendly and durable. To ensure these requirements, building construction should be done as per following steps:
1. Preparation of architectural design.
2. Preparation of structural design.
3. Preparation of plumbing, electrical and fire safety design.
4. Building construction as per the designs mentioned above.
Comfort of living, user friendliness and optimum utilization of space of a building depends on the architectural design. A qualified and experienced architect can design a building, considering user's requirement and climatic condition of the geographical location of the building, so that the building will be user friendly and comfortable for habitation.
Safety and durability of a building depends on the quality of structural design as well as quality of construction. Following steps should be undertaken to ensure the safety and durability of a building:
1. Structural design of the building should be done by a qualified and experienced structural engineer who shall design the building as per provisions of Bangladesh National Building Code (BNBC), considering all the natural disasters like flood, storm, tidal surge and earthquake.
2. Fire safety design aspects including fire detection, protection and evacuation of a building should be done by a team of qualified and experienced architect, electrical engineer and mechanical engineer, complying fire safety provisions of BNBC.
3. Building construction should be executed under supervision of a qualified and experienced engineer who can execute the job as per design and as per BNBC.
Construction quality depends on the following aspects:
1. Use of quality construction materials. 2. Appropriate construction methodology.
In the urban area of our country, Reinforced Concrete (RC) structure is the most popular construction method. In this method the structure of the building is constructed by casting of foundation, columns, beams and slabs with concrete and reinforced with steel reinforcing bars.
In RC construction, the following materials are used:
1. Steel reinforcing bars.
2. Cement
3. Crushed stone/ brick and sand.
To ensure construction of building which will be safe and durable, the construction materials should be of good quality.
To ensure quality of construction materials and other industrial products, there are National and International Standards organizations, responsible for setting the standards for production, quality control and testing of materials. In our country, the Bangladesh Standards and Testing Institute (BSTI) is in charge of setting the standards for industrial products. Consumers will be confident about the quality of materials if those are manufactured as per BSTI standards. There are many International Standards organizations, a few among those are:
1. ASTM (American Society for Testing and Materials).
2. ISO (International Organization for Standardization).
3. EN (European Norm).
Quality aspects of the materials used to manufacture concrete in our country are briefly described below:
A. Steel Reinforcing Bars.
It is the core material used in RC construction works. It should be of good quality and manufactured as per BSTI standard. Consumers should be aware of the fact that, in some cases the steel reinforcing bars available in the local market are of poor quality and not manufactured as per BSTI standards. From strength consideration, there are three grades of steel reinforcing bars available in our market e.g. 40 grade, 60 grade and 75 grade. Building owners should buy steel reinforcing bars having quality and grade recommended by the structural engineer. Quality of steel reinforcing bars should be tested regularly from a standard testing laboratory.
B. Cement.
Cement acts as the binder in manufacturing concrete Therefore it should be of good quality and manufactured as per BSTI standard. In our country, there are many types of cement, produced by the manufacturers. The building owners should consult the structural engineer and the engineer in charge of building construction, before buying a particular type of cement. Routine tests to check the quality of cement should be done regularly from a standard testing laboratory having testing facilities as per BSTI standard.
C. Crushed stone/ Brick and Sand. Crushed stone or brick and coarse sands
are used as aggregates for manufacturing concrete. To get a good quality concrete, the aggregates should be of good quality.
Aggregates produced from crushing good quality boulders are the best as coarse aggregate. On the other hand coarse river sands, free from silts and other impurities are best as fine aggregates of concrete. Crushed stone aggregates are better than crushed brick aggregates. Though a little expensive than crushed brick aggregates, buildings constructed using crushed stone aggregates are more durable than the buildings constructed with crushed brick aggregates. On the other hand, clay bricks are manufactured by destroying the fertile top soils, gradually reducing the precious total arable lands of the country. In firing of clay bricks, woods are used along with coals, eventually eliminating the forest resources and polluting the environment of the surrounding areas. We should, therefore, gradually replace the fired clay bricks with non-fired bricks and concrete blocks. To ensure quality of aggregates, regular testing should be carried out from a standard testing laboratory.
After completion of the Reinforced Concrete (RC) frame of a building finishing works are done using different construction materials. To ensure durability, those materials should also be of good quality. We should always keep in mind that quality materials and appropriate construction method ensures construction of a safe and durable building. A few finishing construction materials are briefly described below:
Clay bricks/ Concrete blocks. Fired clay bricks are predominantly used to construct walls in buildings in our country. Quality of bricks depends on the size, shape and degree of bunting. As the fired clay bricks are not environ friendly, it should be gradually replaced with concrete blocks and non-fired bricks.
Electrical Cables, Appliances, Safety Devices.
Electrical short circuits are the main reason for fire disasters. And the happenings of short circuits are due to poor quality cables, appliances and safety devices. To avoid fire hazards due to short circuits, the electrical design and construction supervision should be done by a qualified and experienced electrical engineer.
Finally, it may be concluded that, as building construction is an engineering job and the investment is large and for long term, services of qualified and experienced engineers should be taken to construct buildings which will be comfortable, user friendly, safe and durable.
THE WRITER IS A FORMER ADDITIONAL CHIEF ENGINEER, PUBLIC WORKS DEPARTMENT. HE IS A LIFE
FELLOW OF THE INSTITUTION OF ENGINEERS, BANGLADESH (IEB).