Scola Kamau
27 August 2009
opinion
Last year was filled with collapsing buildings in various parts of Kampala. According to media reports; it was observed that only 10 per cent of new buildings in Kampala conform to construction requirements. However, when the average person considers those requirements he doesn't bear in mind material testing, which is a major prerequisite in the construction industry.
If a building collapses from an excavation of a nearby site, it indicates that the foundation wasn't strong enough to support the building hence it was overloaded. Ignorance is the biggest part to blame for such disasters. "We take these things for granted. One must confirm that the right materials are used to create a ground strong enough to hold the estimated load," says Nancy Kajwalo, a Laboratory Engineer at TecLab Limited in Nalukolongo.
Many times clients give contracts to unreliable structural engineers who defraud you by hiring cheap and unqualified constructors who in turn mix ingredients without accurate measures. Alongside the right materials Ms Kajwalo says the right mixture should be applied depending on the purpose. For example the right mixture for the bedroom would be different from that of a classroom or a conference room. This is because the load expected for the two is different. The bedroom holds lesser weight as few people spend limited time there whereas a conference hall would hold a larger group of people.
What measures were used to validate the strengths of the buildings we live in? A laboratory material test would be required to confirm the strength of the construction materials. This is an investigation to find out the parameters of the material in question and later relate the outcomes to specifications.
"The tests can either be carried out from the field or in the laboratory depending on the client's choice," says Ms Kajwalo.
The materials that require a lab test include: concrete, sand, soil, cement, bricks, steel and water. Concrete can take from seven to twenty eight days to test depending on the specifications of the project by the structural designer. The concrete is left to dry and then it's put between two bars where it is compressed. Its ability to resist compression determines its strength although Laboratory software reads the values to confirm the rate of compression. "While using class 25 of concrete, after seven days, the value should be about 70 per cent of 25,"says Kajwalo.
However, she says many clients wake up one day and they expect all tests to be carried out in one day. Little do they know that different materials have different time specifications for the best outcome. "The clients don't understand why a material test should take so long, they demand for the results as soon as possible," she says.
If one tests building materials to find out whether there is any problem, then he should agree with the results. Ms Kajwalo says explaining to a client the need to change the ingredients doesn't go down well with them. At times the results can call for demolition of a weak foundation. Imagine a case where a client calls for material testing when the building is in its final phase. "It's risky and one needs precaution to drill down and reach the components of an existing building," says Ms Kajwalo.
The cost of material testing is meager compared to the many lives and properties that would be destroyed in case the building collapsed in future due to a problem in the mixing of the materials. Prevention is better than cure and Ms Kajwalo says failing to invest now for a safer future is a misconception. "We reduce the life span of not only buildings but our own lives," she says.
Have you ever set up a building? What was the source of the water that was used to mix the concrete? Many people reach for any water, from boreholes, dams or even rivers. The type of water used to set up a building determines contributes to its strength. "Any water suitable for drinking is suitable for building, if you can't drink it, do not use it for construction," she says.
Water is tested using a device known as spectrometer for physical and chemical values. This sample test costs between Shs 80, 000 to Shs180,000 depending on how many components will be tested in the water in question. If the water in the sample is not right, the client is advised accordingly. "Either to reduce the amount of water or to improve the mix," adds Ms Kajwalo.
The lab engineer works closely with a structural engineer who gives him the loading capacity of a given site. It is easier for a structural engineer to explain it to a layman than a laboratory engineer would. This implies that if you contract a genuine structural engineer, he would ensure that the right lab tests are carried out.
The material testing also includes roads construction which can determine the strength of the road and the vehicles that can move on a road at a given time. In this particular case, the vehicles are the load. Just like any other policies, there are rules in material testing.
"There are set national and international standards for carrying out tests. Although they keep on varying from time to time, we always use the latest," she says.
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