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Karuma, Isimba dam cracks blamed on Ugandan sand

A soil scientist with National Environment Management Authority (NEMA) says the cracks that developed on Karuma and Isimba hydro-power dams were caused by use of poor quality sand rather than poor workmanship.
 
The cracks with width varying from 0.2 to 1.48 millimetres were noticed in the spillway concrete. Some engineers blamed the cracks on Karuma dam on shoddy work by Chinese state-owned engineering and construction company, Sinohydro Corporation. But Dr Jerome Lugumira, a specialist in soils and land, blames the cracks on materials used especially locally-sourced sand.
 
"It was understood that sand was not the problem by people who specialise in materials science. Unfortunately, we have many who specialise in metals and not many in earth materials. They understood only the size of the grain - how rough it is would be the most appropriate. Little did they understand that, even when it is cleaned, you will have residues oxides that really escape with the grains. After all, the agreement is that you can’t clean it 100 percent. Unfortunately the syndicates that escape with the grain are oxides that allow expansion and contraction", he said. 

Cracks at Karuma dam

Dr Lugumira suggests that the sand had elements of shrink and swell clay which is not recommended in the construction industry. Shrink and swell clay is said to contain vermiculite mineral. Vermiculate is highly porous and is prone to contractions when mixed with cement.
 
Cracks at Karuma hydro power dam were discovered after about 30 percent of the construction works had been done. Similar cracks were also reported at the construction of the 183MW Isimba dam.
 
The cracks at the over $2 billion projects reportedly angered President Yoweri Museveni leading to the sacking of some officials at the ministry of energy and mineral development.
 
President Museveni later appointed former Electoral Commission chairperson, Dr Badru Kiggundu, to head a project steering committee on the two projects. The committee was tasked with fixing the cracks.
 
Dr Lugumira suggests that the two projects could have been started without specifically identifying where the right sand for the projects would be obtained.

He explained that there are different grades of sand that can be used for different construction works. Lugumira says an initiative has not been taken in Uganda to determine what quality of sand is available in the country.
 
"Quite recently in Karuma the sand that was being used was got from Nakasongola. And this is sand that is not clean in a way and was used to construct part of the structure. Little did they know that it was sand that has elements that can expand the clay. So cracks emerged. We had not learnt what happens on Owen Falls Dam.

The three turbines which were constructed using materials from the UK up today have no single crack. The two turbines which were constructed using local materials developed cracks after 10 years and are non-functional", Lugumira said.
 
Lugumira says he is not shocked by the fact that poor sand is causing cracks in dams being constructed in Uganda. He says even some of the biggest dams in United States of America have developed cracks because of geological forces but mostly due to structural inefficiencies in materials.
 
Engineer Hillary Onek, the minister for relief and disaster preparedness, in a presentation at the Uganda Institute of Professional Engineers said incidences of cracks in dams most often occur due to hydration heat differential.
 
But Onek, who once headed the ministry of energy, ruled out tremors as the likely cause. He said there has not been a recorded tremor since construction of Karuma dam started.
 
There is another side to the cracks at Karuma. A study by Energy Infratech Pvt published by the International Academic Journals Network says the cracks revealed that they were thermal in nature due to heat of hydration.

Comments   

+1 #1 Bwire Patrick 2017-07-14 17:11
I like what I am reading, looks like the old owen falls dam in Jinja was constructedusing imported sand from UK.

I rest my case.
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+1 #2 Charles Bereket 2017-07-14 23:06
I welcome this debate on the quality of materials used in construction.

For a long time Materials Engineering has been shunned by the majority of Ugandan Engineers.
.
I believe this is the time to ignite local research in the segment and to encourage young civil engineers to pursue this field of science.
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+1 #3 ejakait engoraton 2017-07-15 21:55
One of the main reasons why concrete cracks because of issues related to sand is mostly because of impurities in the sand, most notably clay.

But any construction company worth its name and especially where concrete is one of the major materials should not only have a fully fledged concrete plant but a material cleaning facility.
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+1 #4 ejakait engoraton 2017-07-15 21:59
The same company should also have facilities for enhanced testing which should be able to simulate the performance of concrete made from available materials to establish how it will perform over a given period of time
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+1 #5 Etesot 2017-07-16 10:18
This is the problem we have in Uganda!

A PhD holder doesn't put science into practice! What was the materials engineer doing? Was the sand being tested?

Were the right parameters being tested? We're the results correctly interpreted?

Was there a materials cleaning & conditioning facility in place? Were simulation studies being done?
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+1 #6 Etesot 2017-07-16 10:24
With these application issues not done does the good Dr. still believe the contractors didn't do shoddy work?

Owen and Nalubaale dams were built using Ugandan sand, we're cracks reported during construction?
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0 #7 Akot 2017-07-16 17:28
Quoting Bwire Patrick:
I like what I am reading, looks like the old owen falls dam in Jinja was constructedusing imported sand from UK.


Thanks!

UK must get free from Brussels & start functioning as a real Free Nation so that we ask British to help us through partnership in business/development!

After all was the once good Health-Education British letf gave us chance to knowledge that we still use on this forum & remind oursleves of what Uganda used to be & what our aspirations were?

Are we going to wait another 30 years for museveni to get things started in Uganda?

2021 election will only bring more trouble: there is no National opposition leader to Unite Ugandans & if there will be 1, museveni will lock him/her in prison-put under house arrest immediately after election!
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