|Cute kids in the nearby village - a good way to start any blog post|
PART IV of VI
Saturday February 1st
Yesterday, a chunk of concrete fell off the top of the large thatched roof over the dining hall (there is a 2-foot wide concrete cap at the ridge line of the thatched roof to protect water from getting in). It’s a tall structure (30 feet), so if anyone had been struck it probably would have killed them. Fortunately that was not the case. So today, the ministry hired a contractor to come replace the entire concrete cap.
|The chunk of concrete that fell off the roof|
|The dining hall - the concrete chunk fell from the peak of this|
roof and then slid down the back side to the ground.
|The chunk landed on this patio - fortunately no one was injured|
The workers were out early in the morning removing the remaining cap, so I got the chance to look at it. It was easy to see the problem. First, the concrete mixture was very weak – I could break small pieces off with my hands. But also, the only reinforcement used was chicken wire, and this had merely been laid on top of the thatching such that it wasn’t actually embedded into the concrete.
The ministry director asked me to take a look at it and advise the workers. So, I spoke with the contractor, who this time was a concrete specialist, to find out his plan. He had already purchased a thicker gauge wire mesh, plus some long rebar sticks. He also had bags of cement and some piles of sand and aggregate - which wasn’t used in the original mix, so an improvement). Overall, his plan was sound, but I was able to make a few suggestions.
|The workers came the next day to begin removing the concrete|
cap at the ridge line and replace it with an improved cap.
First, his concrete mixture was to use one bag of cement, 2 wheelbarrows full of sand, and 4 wheelbarrows full of aggregate (rock). That 1:2:4 ratio is correct, however, the units need to be the same for all materials, otherwise that mix ratio is much different. One bag of concrete is actually about 1/2 of the wheelbarrow they use. I also told them that the original mix had used too much water – the correct ratio is 1-water to 2-cement. (Honestly, it's pretty rare for builders to *not* use too much water - even in the US!
|The concrete ingredients, dropped off by delivery trucks|
The other suggestion I made was to ensure the rebar was ‘lifted’ up into the concrete. Reinforced concrete is strong because the steel is good for tensile forces (i.e. resisting things from being pulled) and the concrete is good for compression forces (i.e. pushing in on something). However, if the rebar is not fully encased inside the concrete, the two will act separately and the system is weak.
It was nice to be able to be here at the right time so I could advise on this little mini-project. But thinking about it later, I realized the importance of the partnership that took place. The builder was using the materials he had selected and purchased, and the methods he was using were common for Uganda. I would have likely paid much more for the right materials and spent much more time getting them since I have less of an idea of what’s available out near the site. Also, with such a tall and steep thatched roof, I wouldn’t have known how best to get up to the ridge to do the work given the limited equipment available here.
|The ladder the workers built and used to reach the ridge line.|
They also installed a ramp next to the ladder, and as seen here,
used it to haul the wet concrete to the ridge for the new cap.
However, what I did know was a few things about how to use the materials best, and how to slightly modify the technique to ensure that the system worked well. It reminded me of how important EMI’s Construction Management program is, whereby some of the projects EMI has designed are shepherded through the construction process to make sure that the designs we provide are properly implemented.
But just as was the case in this situation, it is always important to remember that it is a partnership. We Westerners have training in best practices that may not be as available here in Africa. But the local builders have something to offer us in the process as well: a good knowledge of the materials available and the most appropriate techniques for building in Africa.
A few more random picts:
|Mike and I drove into the EMI office during the trip one night|
and I got to see one of our old EMI guards, Wilson. This
guy was like family to us - Jonah spent hours and hours out
in the yard with Wilson, planting a garden, doing yard work, etc.
|Jaz used a luggage scale to measure ingredients|
for the birthday cake she made for intern Abby.
|Interns Natalie (L) and Abby (R) enjoying dinner. We left these|
two behind in the UK when we left, which was sad because we
had got to know them pretty well in the short time we had.
|I tend to stare off into middle space when I'm concentrating,|
unlike the much more civilized and disciplined Mike, who
actually looks at the person who's talking.
|Volunteer Terry (Agriculture), distracting intern Abby.|
|In the Dining hall - Terry in the background is enjoying his coffee,|
Graham is about to enjoy his coffee, Mike has already enjoyed
some of his coffee, and Dave appears to be pretending to
have a coffee presumably to fit in with the others.