How to ensure the qualities of building construction materials
A home of our own is the dream and necessity of everyone. A home brings about social status and dignity. But above all else it provides shelter and protection from natural disasters like cyclone, flood, earthquake etc. It's a enclosure of comfort and durability which isn't always possible if not done right.
For instance, during winter, a house made up of CGI sheet (locally called Dhew Tin) serves less protection from bitter cold than that of a house built with Reinforced Cement Concrete-RCC (locally called Pukka Bari) or even the house made with mud. The latter two structures retain heat that is much needed in winter. But even what we call the Pukka Bari may turn into a hub of irritation and hypertension unless the stakeholders (the home owners and engineers) choose the appropriate construction materials during its construction.
It is very crucial part of home building process to select the proper material and ensure their quality before incorporating them in construction works. This selection procedure must have scientific basis. It has to be confirmed that the materials that are going to be used in building construction works have been tested in laboratory and re-tested in field level.
A graduate civil engineer prepares a structural drawing in which he/she mentions the properties of all materials to be used in a building construction project. Prior to beginning of the erection works some samples of all materials (rod, cement, sand, stone chips but not concrete) specified by an engineer who will supervise the construction works, have to be sent to laboratory for testing the specimens. The lab authority will provide reports for individual materials mentioning the test results of the specimens. Then the engineer in charge will check the test result weather they comply with values that are mentioned in the design/drawings or not. If the test result shows inferior values to that is already mentioned in the supplied design/drawings, the engineers in charge deny allowing the materials to use in the construction works.
The main property of reinforcing steel (rod) that is required in constriction work is its tensile strength. Normally, this property represents its ability to resist tensile force and it is measured by dividing the tensile force that a steel specimen can resist until its rupture by the specimens cross-sectional area. According to engineers, strength of steel means its yield strength and it is tested in a physical testing or concrete laboratory by means of highly sophisticated equipment named Universal Testing Machine (UTM). Yield strength is also termed as the grade of steel. Another vital property of the rod is its size which is the measurement of its diameter. This is generally checked on-field by the engineer in-charge and does not need laboratory test.
Unlike rods, the major property of concrete that is required in construction work is its compressive strength. Normally, this property represents its ability to resist compressive force and it is measured by dividing the compressive force that a concrete specimen (cylindrical or rectangular in shape) can resist until it is crushing by the specimens cross-sectional area. This property is tested in a physical testing or concrete laboratory by means of Universal Testing Machine (UTM) also.
In the structural design, the design engineer guides the mix proportion for ingredients of concrete. The designer suggests not only concrete but also the properties of constituents (cement, stone chips, sand and even water) of the concrete to be used in mix. Among the constituents, normally cement, stone chips and sand are tested in laboratory. The water is tested in field level. Interesting thing is that it is not necessary to be an expert to test the quality of water. All drinkable water can be used in construction works. An engineer or a group of engineers who supervise the filed works follow the guidance of the design/drawing. Concrete is prepared in the filed by mixing the components following the suggested mix ratio of the design/drawing. Some concrete is taken from the first mix to prepare cylindrical specimen for laboratory test. The authority of laboratory provides the test result within 5 to 30 days depending upon the requirements of engineer in charge.
In Bangladesh there have many institutes where building construction materials can be tested. Most of the institutes have very nice lab facilities. Among them Housing and Building Research Institute (HBRI), is the only research organization in the field of building construction in Bangladesh which has well-equipped laboratories and experienced staff. All types of construction material can be tested there. Other than HBRI, there have several organizations providing material test facilities namely Bangladesh University of Engineering and Technology (BUET), Local Government Engineering Department Laboratory and so forth. In Chittagong, Khulna, Rajshahi and Sylhet divisional cities testing facilities are available in CUET (Chittagong University of Engineering and Technology), KUET(Khulna University of Engineering and Technology), RUET (Rajshahi University of Engineering & Technology) and SUST (Shahjalal University of Science & Technology) respectively. Apart from this, most of the public polytechnic institutes have limited testing facilities as well.
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Boni Amin
B.Sc in Civil Engineering (KUET)
Research Engineer
Structural Engineering & Construction Division
Housing and Building Research Institute (HBRI)
Email: baminhbri@gmail.com