Know Your Construction Materials - Concrete Block! {Liberia Edition}

This is the second installment in my blog series "Know Your Construction Materials".  Last week we talked about Concrete and what goes into making concrete. Next we move onto what is commonly called concrete block or concrete masonry units (CMU).

CMU is literally the basic building block of construction in Liberia, and much of the world.  Being from the Northwest, where residential and light commercial construction typically use wood, I didn't come to Liberia with much experience using CMU.  Because it is easy to make and relatively inexpensive, almost every structure in Liberia is made of CMU.

Like the cement depots that dot the side of the road, you can't travel far without passing a micro block factory.  These factories have 2-5 young men who are trying to "hustle" and earn money by casting blocks in a country with high unemployment.  The number you hear most of time in Liberia is 85% unemployment.  That number is a little deceptive though, because 85% of the people in Liberia may not have official jobs, but they are working doing things like making blocks or busting rock to make gravel as you saw last week.

So the basic ingredients in CMU blocks are the same as concrete, just without the coarse aggregate.  You have:

* Water
* Sand
* Cement

Pretty basic.


Your average block making establishment will either buy a dump truck load of sand and stockpile it, or if they are close to the beach they use wheelbarrows to bring sand from the beach.  They have a round "bowl" area that they've used so many times to mix the sand, cement and water together that it is now sometimes up to a foot thick in hardened cement and sand.  So the three elements are mixed together on the Bowl and one by one, the work crew starts to make block.  The mixture is shoveled into the metal block mold that the block makers can buy from their local steel fabrication shop for around $50.  The mixture is tamped down with a shovel, smoothed off, and then the form is removed leaving the block to dry in the sun.

The block dimensions are 8" tall x 16" long x either 4", 6" or 8" deep.  On your typical 8" block the crew would mix about 3 wheelbarrows of sand with one bag of cement.  That mixture will yield approximately 25 blocks if they are making 8" block.  Of course there are no set standards and a crew that might try to maximize their profit might mix a little more sand in and stretch their yield to 28...30...or even more blocks.  The more you thin the cement the weaker the blocks though.

When selecting their block a good mason will go and feel how strong the blocks are by rubbing their fingers on them to see how much sand comes falling off, or take the block and drop it from head height and see if it breaks.

Block making is a hot job with long hours in the African sun.  The block crew gets paid $100 Liberian dollars per bag of cement they mix.  In a day a 4 man crew will typically work through 10-16 bags of cement, netting $250 - $400 Liberian Dollars per day (about $3-$5 USD per day).

Those who can afford to make or buy a block making machine use the manually operated machine to make blocks that are more dense and stronger.  The machines are rare though...for every block making machine you probably have 50 guys making them by hand on the side of the road.  The process with a machine is about the same...the steel form is filled with the cement-sand mixture, a packing ram is pulled down repeatedly by hand to pack the block, the form is lifted and block removed.  Here are some pictures of the block making at the site:

The form is filled with sand.

The metal ram is pulled down to pack the block.

The form is pulled off the block.

And the block is taken out into the sun to dry.

A typical block in Liberia has a solid bottom.  The blocks that our project is using are the more typical  "American Style" blocks that are hollow all the way through.  The contractor had to custom make the mold because they are not available in Liberia.

 Here are some pictures of a two man crew making block with a typical 6" form just outside the fence at ELWA.

The mold.

 And this weeks video, making blocks for the hospital.  

Up next, Steel

Know Your Construction Material - Concrete! {Liberia Edition}

 As we get started on the Outpatient Clinic and Administration building I thought I'd start a new series, Know Your Construction Materials {Liberian Edition}.  Nothing is easy here and even the seemingly simple materials, like concrete, require a lot of energy to produce.  In Liberia most of that energy is in the form of manual labor and sweat.

A mason plumbing up a column

Concrete has 4 basic ingredients.  That is the same anywhere you build.  They are:
*Water
*Cement
*Fine Aggregate (sand)
*Coarse Aggregate (rock)

In the US when you want to cast a concrete foundation you call up your local ready mix company and tell them how many cubic yards you want and where to deliver...and you are finished.  Here in Liberia we don't have that luxury.  Well, that's not entirely true.  West Construction started delivering concrete about 6 months ago.  For the low price of $200/CY you can get concrete delivered to your job site.  Besides the trouble they have had keeping their trucks with the wheels facing the road, Liberian's are generally skeptical of what you will actually get when it all shows up already mixed together.

Waiting in line to deliver the concrete

So where do the materials come from...

The first component is water.  Something that seems pretty straight forward, but water can be a problem by itself.  Liberia has a government water and sewer utility, but it has a very limited distribution network.  Here at ELWA we have to rely on our own network of wells and pumps.  They are generally unreliable and this time of year specifically it can be hard to get water of significant volume because it is dry season and the wells are running low/dry.  Yesterday we had to send a truck with water drums in the back down the the lowest point on the ELWA campus because the pressure was so low the water wasn't running at all at the hospital site.  Concrete mixing was delayed for about 30 minutes while they waited for the drums to fill.

Water is stored in barrels next to the mixer

Next we have cement.  In Liberia you typically buy cement from cargo containers that have been set up on the side of the road as cement depots.  Usually there is one about every 100 yards along the highway.  They sell cement from the Liberian company Cemenco, which is a division of the German company Heidelberg.  We found out on the Kitchen/Laundry building that not all cement is created equal.  Because the grinding plant in Liberia can't keep up with the demand, they import cement from Turkey and Germany.  We found the cement ground in Turkey gave us concrete that was barely half as strong as cement sold in the US.  After more testing we found the Liberian ground cement and the bags imported from Germany yielded concrete that was within 10% of what we expected.

Liberian Cemenco Cement

The sand used for cement in Liberia almost exclusively came from the beach until a few months ago.  Dump trucks would back down within feet of the ocean and 5-10 men with shovels would throw the sand up into the truck.  Significant beach erosion led to the president putting a moratorium on beach sand mining in 2012. Besides the beach erosion, the use of beach sand also compromises any reinforcing steel in concrete due to the salt mixed in with the sand.  Sand now comes from a handful of different pit and river dredge locations.  None are washed and most are fairly dirty.  All the sand used on the kitchen/laundry building had to be hand screened by the contractor's crew using window screen.  We have found a source now that is much cleaner and does not require screening.

A sand pile ready for use

The last component is the coarse aggregate.  With pit mined aggregate nowhere to be found around Monrovia, all aggregate used in concrete is fractured from larger rocks.  While there are two large "rock crusher" machines that I know of, most Liberian's use hand fractured rock.  The entire process uses a tremendous amount of "man power".  It starts with burning old tires in the rock pits to create enough heat to crack large section of rock from the solid rock.  Then large rocks are slowly broken into smaller rocks with progressively smaller hammers, and usually progressively smaller workers.  Large men work in the pits and typically women or children work to break the small rocks into the 1/2" sized rock used in concrete.  A man, woman or child who works in this profession will typically bring in around $3-$5 per day for their effort.

A young woman breaking rock with a sledgehammer

A boy in the Rock Crusher community crushing rock

Not quite the typical protective footware

So all those materials are gathered and mixed together in a variety of different proportions, depending on how strong you want your concrete to be.  CJ Construction uses a 1/4 yard, diesel powered, cement mixer with a pulley and shaft run "automatic" loader.  The components are all added to the bin, which is then raised and dumped into the mixer.  The load is mixed until it all materials are well blended, then the mixing drum is rotated and cement is dumped into the waiting wheelbarrows.  With enough men working at the task, the entire mixing cycle can take less than 5 minutes.  Doing that math, that means you can cast somewhere around 3 cubic yards per hour.

A mixer being loaded with cement

Concrete strength is tested by collecting samples in sewer pipe

Run it until the wheels fall off

You can check out a short video I took of the process yesterday on Youtube:

Stay tuned for the next episode on !Concrete Block!

Children at Rock Crusher telling us goodbye

Emmanuel Part II

Today Emmanuel and his mother Doreen left for Ghana.  You can read about Emmanuel Here. He needs heart surgery and Ghana is the closest country with a pediatric cardiologist that can give him the diagnosis that he needs to qualify for help with charity organizations that sponsor children's heart surgery.

She also was able to escort another young girl named Faith who has a similar heart problem.  We heard through the grapevine that a friend with Orphan Relief & Rescue, working with a friend with Orphan Relief Network were trying to help Faith to get to Ghana to get her condition properly diagnosed.  She is an orphan and since Doreen was already going it saved ORN from having to send her with a separate escort.  Here's the three of them just before heading to the airport (and of course Blessing had to be in the picture too).

Faith came over last night to stay the night to make sure she got to our house on time for the airport trip.  A couple hours after she arrived I was thinking along the lines of Paul Harvey's old "we don't live in one world" quote.  She is 5 years old but didn't know how to use a toilet, and after she got done using the toilet she turned around and tried to wash her hands in the toilet bowl.  I showed her the sink and hand soap and after the 7th time she went back for more soap had to put it up.  Oh the joys of simple things like hand soap.  

I'm sure it was a night of many firsts for Faith, and today will be her first airplane flight.  Next week it will be back to the orphanage though.  Such is the plight of so many Liberian children who came out on the wrong side of the birth lottery.  It is fun to host children like Faith but at the same time breaks your heart to know that what Blessing knows as every day life is almost like a fairy tale.  Not to take away from the work that ORR and ORN do here, they improve the lives or orphans dramatically, but it is still...well a different world.

Blessing was thrilled to have Faith to play with for the night and asked...well more demanded I get a picture of them together before she left.

So after Faith and Emmanuel return, their information will be passed to Gift of Life for Emmanuel and Rooftop519 for Faith, and hopefully they will get the surgery they need in the next couple months.  Please continue to keep both of them in your prayers.