Curved Bricks Make The Rounds

By Will Forester. 04/02/2021

Curved bricks, interlocked together as a rainwater catchment tank, are starting to appear in Kambiri, Kenya. The first 20,000 liter tank using these bricks was just completed near our Kakamega Technology Resource Center at the home of Africa Programs Manager, Eric Lijodi. This tank was constructed as a proof-of-concept to learn new techniques, create building drawings that can be shared with other communities and masons, and optimize design and material selection. It is the first of four planned for the community, with the next three to be placed at local secondary schools. This was our team’s first time fabricating curved bricks, creating a rainwater catchment tank from the bricks, and using a Kenyan-based engineering firm to provide training and consulting to us and our masons on interlocking stabilized soil brick fabrication and rainwater catchment tank construction.

kambiri straight bricks curing

A yard of interlocking stabilized soil bricks at the home of Eric Lijodi.

New curved bricks for rainwater catchment tanks.

Single ISSB brick

Why are Interlocking Stabilized Soil Blocks so special?

  • Non-fired (reduces pollution/climate warming) 
  • Sustainable
  • High production volume
  • Mortar is only required at joints
  • Uniform in shape, size, and properties
  • Materials can be sourced locally
  • Machine presses are portable
  • Prevent desertification
  • Less likely to rot
  • Better temperature control

Making bricks without fire (and wood)

Our curved bricks are almost identical to our standard interlocking stabilized soil brick. They are fabricated using the same kind of press but with a different, curved mold. The bricks retain the same advantages to traditional fired bricks – they help protect the environment by not requiring wood for kilns or fuel for transportation (the presses can be located right in the heart of a community), use fewer materials, and have uniform shape, size, and properties. In January, we purchased two interlocking stabilized soil presses from our Kenyan partner Makiga and had them delivered to Eric’s house. Eric recruited a team of local day-laborers and worked with Makiga on the brick fabrication process. Other than the mold shape, the only difference between making curved and straight bricks turned out to be the amount of stabilizer added to the soil mixture (we have been using cement). Curved bricks require twice the amount of cement for stabilization. The soil mixture determines the strength and uniformity of the bricks and in Kenya it starts with murrum. This is a kind of soil common in humid tropical zones, is good for compacting (it’s frequently used for roads), and is mostly impervious. Around Kakamega, Eric and his team was able to collect, sift, and test a variety of murrum types. The red you see in the bricks comes from iron oxide or what most people know as rust. Some of the murrum they tested had high clay content and required more sand in addition to the stabilizer.

kambiri murram site

Eric and team sifting murrum in Kakamega.

kakamega brick making press

Preparing the interlocking stabilized soil brick press.

kambiri bricks murrum

Bricks pressed from different kinds of murrum.

kakamega brick mold

Interlocking stabilized soil brick press curve mold.

The team set about fabricating both curved bricks for the rainwater catchment tanks and straight bricks for testing and sale. Although one person can run the operation alone, two or more team members can make 400-500 bricks per day. Each of the 20,000 liter tanks we are building requires about 1,000 bricks which are laid in interlocking layers from the foundation to the tank roof. It’s a lot of bricks. We are grateful that Eric has a property large enough to both hold them, and give them space to cure. Once the bricks are pressed, they must cure for seven days. The curing process is influenced by the local climate and weather. The bricks must be watered to ensure they don’t become brittle and break. The amount of water depends on the humidity level and heat. If the bricks are cured inside or in a shaded location, they will require less water. Eric watered his bricks three times a day. He has developed quite the green thumb. Or red thumb in this case.

Using bricks to build (and sell!)

Eric and his team made enough straight bricks to not only test and refine the fabrication process, but also to demonstrate their building potential – a first of it’s kind Kambiri Brick Show if you will. People came from all around to see the new Interlocking Stabilized Soil Bricks. The team built up a few structures so visitors could see how they functioned and looked as walls. One of the man advantages to these bricks is their shape and aesthetic. Clay fired bricks tend to be rough and inconsistent. Our bricks are smooth and uniform and very pleasing to look at. That really appeals to people who are using them as walls for their home or in other highly visible applications. Two visitors who came to see the bricks were couple David Zarembka and Gladys Kamonya. It was very sad for us to discover that not long after their visit, both David and Gladys contracted Covid-19 and passed away. They were great friends of Eric and Getry Agizah, the Executive Director of our local partner, Transforming Communities for Social Change. David was the co-founder of the Quaker organization, Africa Great Lakes Initiative, a peace-making organization in western Kenya. He and Gladys will be missed by many. Before this tragedy, David had been so impressed by the bricks that he purchased 1,000 to extend their kitchen at home. We are sorry they will not have a chance to enjoy the new kitchen or continue advocating for the people and peace they cared for so much. Our condolences go out to their family.

kambiri brick demo

Eric demonstrating interlocking stabilized soil bricks to members of the Matsakhs Development Group.

kambiri brick house construction demo 9 website

Temporary walls to demonstrate bricks.

david zarembka visit bricks

David Zarembka and Gladys Kamonya evaluating an interlocking stabilized soil brick press.

david zarembka finished kitchen

Finished kitchen at the home of David Zarembka and Gladys Kamonya.

Eric is still selling the bricks he and his team fabricated as a way to better understand demand and how local people use them. And we have just recently purchased two new interlocking stabilized soil brick presses to be used in the community of nearby Matsakha. In between fabricating and selling these new bricks, we continued the program to build rainwater catchment tanks in Kambiri. As mentioned, the first tank was constructed at Eric’s home. The other three tanks will be built at local schools: Magale Secondary School supported by the Pentacostal Academies of God; Shanderema Secondary School supported by the Salvation Army; and Ivakale Secondary School supported by Quakers. All schools are in highly trafficked locations and the tanks are going to be sited where they can serve not just as water security for the schools, but also as billboards to raise awareness of this technology in the local community.

A new way to build rainwater catchment tanks

Curved interlocking stabilized soils bricks can be used to make above-ground rainwater catchment tanks up to 30,000 liters and below-ground of up to 200,000 liters. The curved shape and interlocking mechanism resists water well. Once you have the bricks available, the tanks can require less labor and expense than the traditional technique of troweling a cement-rich mortar onto a cylindrical mesh of chicken wire that may or may not be reinforced. The tanks cost about $1,500 and provide enough water on a single fill of rainfall (by the current Africa average of 5 gallons / day) to last three people for an entire year. As this was our first time building a curved brick tank, an engineer from Makiga walked us through their construction process. We learned a lot and are making modifications to make the design more efficient and scalable. Eric and his team started building the tank by clearing a space about 18″ deep next to his main roof. Once flat they poured a concrete slab and outlined the circumference of the tank. In future designs, we are planning on a smaller slab that may not be buried so deep in the ground.

kambiri rainwater catchment tank clearing start

Breaking ground for the new rainwater catchment tank.

kambiri rainwater catchment tank clearing measure

Measuring the ensure the space is large enough for the slab.

kambiri rainwater catchment tank clearing hoe

Clearing a large space for the 20,000 liter tank.

kambiri rainwater catchment tank plotting

Outlining the circumference of the new tank.

The next step was to build a steel cage for the center column of the tank. That column holds the roof in place. At that point, the team was ready to start laying the curved bricks. The wall went up quickly and was topped with another cage to hold the structure of the roof. For this tank we went with a Makiga designed roof that is much heavier than something we usually construct. We are evaluating whether the walls are strong enough without needing to add the support of the cement roof. The final step was reinforcing the brick walls with mortar and waiting for the entire structure to set. The tank is now complete and is a great model for a curved brick type of rainwater catchment tank. Together with our ferro-cement tank design we have two great tools to expand water security and some peace of mind in communities not connected to water infrastructure, with long walks for water, or with wells that may be polluted or periodically running dry. And Eric now has his own water supply and a great example of our technology to share with all the communities near our Kakamega Technology Resource Center.

kambiri rainwater catchment tank slab

The finished slab.

kambiri rainwater catchment tank first brick layer

The first layer of curve bricks.

kambiri rainwater catchment tank half wall

The wall half finished.

kambiri rainwater catchment tank finished walls

Completed walls prepped for the roof.

kambiri rainwater catchment tank finished

The finished rainwater catchment tank with curved interlocking stabilized soil brick walls at the home of Eric Lijodi.

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