Crix!!

by Craig

In September 2023, we bought a machine to make our own bricks for construction projects at the hospital. This machine makes bricks by compressing soil mixed with cement, and the combination of compression and cement makes them resistant to damage from weather. These blocks have a special shape which allows them to interlock with all their neighbors above, below, and side to side. This means when building a wall, we don’t need to use any mortar to bind the bricks to each other like we do with the traditional bricks. These bricks go by different names, Interlocking Stabilized Soil Blocks (ISSBs), Compressed Earth Blocks (CEBs), but we have just been calling them Crix (a stylized portmanteau for "Craig’s Bricks"). It's an honor (but not my idea) to have my name integrated,  but it’s not because I deserve any credit for them, I am just the person who is most excited about them.

Our press, when it was still shiny and new, and some of the first Crix it produced

side by side comparison

stock of traditional bricks (top) and Crix (bottom)

There are a few good reasons why I am so excited about Crix, and why you should be too! They save on time, labor, fuel, firewood, sand, and cement; and all of those things lead to saving money. They also look really smart…in my opinion.

These Crix walls look nice, right?!
I know, I know, it looks like the Crix on the right have been mortared in place. But truly, they have been dry-stacked, and we just filled in the chamfer with a tiny bit of mortar to make it look a little nicer.

Traditional, local made bricks in Burundi have served us well for many years, but there are some inherent characteristics that can be improved upon. Those bricks are stabilized by heating them with a large fire, which consumes a lot of firewood – a precious commodity in Burundi. They also are far from uniform in shape, which requires a lot of mortar to make up for the inconsistencies. I measured a typical section of wall and estimated that only 52% of the wall was made of bricks, the other 48% was mortar! Another challenge is that these bricks are made in various locations around Kibuye and need to be transported here. This increases the cost, and is dependent on the availability of diesel, which can not be taken for granted here. Whereas, Crix don't require any firewood, they are uniform, use almost no mortar, and are made right here on site.

But, just because Crix offer an improvement on all of those challenges that are baked into the local bricks, doesn’t mean they are a slam dunk solution. Bringing in a new technology like this can really upset the order that we have worked for a long time to establish. Even though it seems much easier and faster to build with Crix, it is completely different from what the masons are used to doing, so it takes a lot of adjustment for them to get comfortable and fast at laying the Crix. We also didn’t really know if the community or the hospital administration would like Crix, they have a different value system than an American engineer. And, we needed to invest quite a bit of time and money into buying the equipment and learning how to use it well, before we could start to save any time or money in the construction process. Regardless, there will still be some applications where traditional bricks are more appropriate...but now we have options.

So, after buying the machine, we started slow and small in our brick production. We played around with our soil mixture and moisture content, the force required for compression, and the rhythm of many people working together to use the machine safely. We only produced 20-50 bricks per day in those first days. But steadily we improved our production to grow to roughly 200 per day! We also started using the Crix for small, low-risk structures to see how they would perform, how the masons would use them, and how others would like the look of them.

Two days worth of production in the early days

Our very first structure being built... a chicken coop

A privacy wall (left) and some small cookhouses (top and right)

We learned a lot along the way, and eventually found success in our small production and construction. And, everyone involved seemed to like the Crix! So, we started to ramp up the production in order to do bigger projects. 

First, we agreed to pay our workers per brick produced instead of per day of work, which took our daily production from 200 to over 400. But, it became hard to sift our soil fast enough to keep up with the brickmakers, so we built a rotary sifter to speed up that part of the process. We also realized that it was difficult and slow for the masons to cut the Crix, when laying them. So to help with this, we built a slicer to add on to our brick press, which slices the bricks before they have hardened, as they are being ejected from the press. 

Compressing a Crix

Approximately 400 Crix made in one day

Top: Dirt being shoveled into the rotary sifter
Bottom: Turning the crank on the end where the rocks are removed 

Nicely sifted dirt piling up

Brick slicer in action

After making these improvements we were able to build some larger projects with great success, including a 150-meter perimeter wall around hospital staff housing, and a new kitchen/dining area for the hospital.

150-meter wall made of roughly 9,000 Crix

New hospital kitchen and patient dining area under construction

This technology has proven itself to make a positive impact in the construction practices at Kibuye. But, if we zoom out and look at all of Burundi, then it is just a drop in the bucket. That’s why we recently took the opportunity to help facilitate a workshop in Bujumbura focused on this technology. I took seven of our workers who have been involved in making Crix to teach others what we have been learning over the past 8 months. It was awesome to see our guys – many of whom have not finished high school – teaching a group of architects, engineers, and professors about how to make and use Crix!! 

Our workers (in yellow shirts) attending the workshop

they were featured in the presentation

participants sifting soil

answering participants questions

everyone was excited by the first brick

All the participants and facilitators of the workshop