Wheels to curb collapse of buildings
By Joe Ombuor | January 19th 2017
An audit report ordered by President Uhuru Kenyatta after several buildings collapsed in Nairobi last year killing and maiming several victims singled out poor quality of concrete, lack of proper foundation and the use of substandard building stones as the principal causes.
That was only the tip of the iceberg in the lucrative but problem-laden construction sector where entrenched cartels collude with crooked urban, lands, administrative (chiefs and their assistants) and other authorities to defeat laid down rules to the detriment of innocent lives.
Hushed, but important factors include corruption and greed on the part of law enforcing authorities and property owners in a hurry for quick money, not to mention poverty that propels legions into suicidal-risk taking. Such was the case with the Huruma house built with part of its foundation submerged in the murky Nairobi River. It crumbled with 51 lives.
To help smaller clients surmount the problem, Bamburi Cement company has come up with a mobile laboratory circulating in Nairobi and its environs with a target to cover the whole country.
“Big construction projects such as malls, office blocks and others not constricted by funds follow laid out requirements to the letter. That is why they hardly collapse,” says Bernard Koskei, an engineer at Bamburi.
Besides cement, everything from water, sand, ballast to building stones or bricks is subjected to quality checks before it is committed to construction. “Sand and ballast are primary materials whose size alone can affect the strength of a building. Sand, for instance, must not have any clay or organic materials to be declared suitable,” he says.
“Water is one item generally taken for granted, yet its quality has direct impact on the final quality of construction works. That is why portable water is recommended. Fetching water from highly polluted sources such as the Nairobi River or using muddy water from puddles can have dire consequences on the end product and must be avoided,” says Koskei.
Integrity of concrete
He says ideal concrete should be cube-like as the size and orientation of ballast directly affect the integrity of concrete: “Once you get your sand, water and ballast right, then everything else falls into place. Cement is but a glue to hold the materials together.”
Koskei says it is important to test concrete in its fresh and hardened state, hence the provision of seven to 28 days to be sure of how well the concrete has cured. “We strive to achieve the best water and cement ratios without affecting the concrete while workability test is done to ascertain concrete is neither too stiff nor too soft,” he says.
“Seven days are not conclusive, but will guide you to know if you will achieve the ultimate strength of the concrete at age 28 days.” He says any doubt noticed about the quality of the concrete automatically necessitates its trashing and a fresh start made.
“One cubic metre of concrete weights about 2.4 tonnes (2,400 kilogrammes), thus it is expected to have cured sufficiently after 28 days and gained strength to enable it sustain its own and any other additional loads. In multi-storey buildings such as the one that collapsed in Huruma, it is recommended that each floor takes approximately 28 days to determine if the concrete has cured sufficiently to sustain its own and any additional loads,” says Koskei.
He says the mobile lab service that the company is using to educate its customers is a value addition: “Similar services are available at the Kenya Bureau of Standards (KEBS), the Ministries of Roads and Works and private providers at a fee that most small-scale property owners are not willing to incur as they try to maximise on profits, thus leading to expensive tragedies.”
Jonathan Murage, the architect supervising construction work at the seven-storey Zuplex Towers in Westlands, Nairobi, a beneficiary of the Bamburi’s free lab service, says concrete testing is mandatory for quality work.
He puts the cost of Zuplex Towers slated for completion later this year at between Sh380 million and Sh400 million. He says companies providing concrete testing services for a fee include Mass Lab in Nairobi.
“Concrete comes in different classes specified by the project engineer and testing a design mix costs Sh31.320 per class at Mass Lab,” he says. “Crush concrete cubes are tested in sets of three after seven and 28 days at a cost of Sh900 per test.”
Engineer Kuria Kamau from the National Construction Authority blames collapsing of buildings in Nairobi on city authorities “paid to look the other way” instead of enforcing the law and save lives.
“Not only do they look the other way during construction for the sake of their stomachs, they give approval for construction at improper sites such swamps and river banks where foundations cannot hold,” he says.
“We spell out the conditions to be followed but have no enforcement powers. Impunity is such that the owner of the Huruma building paid casual labourers to erase the X signs condemning his property. Contractors are not free of blame, for crooked ones collude with property owners to defeat the rules,” says Kamau.
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