Material Experiments-Qi Guo, BArch 2017
After my previous field trips to the local villages and workshops, I found a lot of issues about the local housing materials and construction techniques. One particular issue that drew my attention was the local fired-brick. Traditional fired bricks have a lot of drawbacks. They are weak and dingy, and the firing process causes air pollution as well. It is a technique that is banned in a lot of other countries. But due to its low cost, it is still the most common material for the housing construction here.
However, due to the low precision and unevenness of the fired bricks, masons have to add an excessive amount of mortar (a mixture of cement and sand) to level them up and bind them together. The outcome is that the walls usually look crude and crappy with the excessive mortar outside, so the villagers have to apply another layer of plaster (also contains cement) to give the wall a finishing looking. However, plaster not only costs a lot but also seals the bricks so that the walls don’t breathe. Living in a plastered house feels hotter compared to a unplastered one. Another issue I found was the trend of using concrete blocks in the local housing projects. People want a concrete building because it is more durable, and it feels “western” and “modern-looking” to them. However, most of the local houses are only one-story height. There is no need for such strength. Besides, cement is imported and very costly. It does not work quite well with the climate and culture here unless we alter it with other local materials.
The importance of creating a housing scheme that is cost efficient and culturally and environmentally suitable is very urgent.
In St.John’s vocational training center, I found three compressed earth block machines in the storage room. Because of the poor maintenance, all the machines were broken down and they were left in the storage for many years. Compressed earth block (CEB) has a lot of advantages compare to the fired bricks. CEB is strong and neat, and there is no need for fire curing. The main ingredient for CEB is soil, which is locally available and it is also biodegradable. By adding stabilizer into the soil, CEB can also be water-proof. In this case, no plaster is needed after finishing. So I decided to fix one of the machines to start my experiments with CEB.
I asked the automobile students and teacher to gather parts from different machines to reassemble a workable one.
Now the machine is back to work!
My goal for the following experiments is to test the strength and other potentials of the CEB by adding different natural resources as fibers, aggregates, and stabilizers into the soil in order to decrease the cement stabilizer and bring down the cost.
Coir fiber is a natural fiber extracted from the husk of the coconut. It is a cheap and common material in local for bedding mattress, sitting pads, ropes, and other handicrafts. Students and I decided to add it into the soil.
The first one we made was a failure because we added too much water. But we will cure it anyway to test the strength.
Palmyra Palm Fiber
Palmyra palm is a common and valuable resource in Batticaloa. People use everything on the tree for making products. The wood can be used in roof structure; the leaves can be weaved into baskets and fences; the seeds can be made into drinks…
the stems of palmyra palm have very rich fibers that are extremely strong. I want to extract them and add into the soil.
At first, I tried to extract the fibers by hands and just realized how hard it was. A school staff came to us and showed us a local technique of doing this. He simply placed the stem on a flat surface and hit it with a rod…
whala! local wisdom.
And then we placed the fibers under the sun for one day until they totally dry.
moisten the fibers with water again for preparing the soil
We carefully sprinkled the water onto the soil
Beautiful and neat bricks with fiber texture.
The students were surprised at the outcomes. Even though they were very familiar with the palmyra palm, they never thought about using it in the construction materials.
Cow dung is one of the most commonly found wastes in the local villages. Villagers use it as fertilizer for their farms. From my previous field trip, I was surprised at its use for natural plaster on the mud house to get a polishing looking and also repel the insects.
Cow dung is very hard when it is dry, but when you break it down, you can find all the fine fibers that are not yet digested by the cow. Cow dung is a natural “clay” and the fibers inside can reinforce its strength.
The villagers today are against the use of this material in their houses because it is a humble material, and the families that use this material are poor and backward to them. I think my purpose is to teach the students to never underestimate any materials that just look humble because design can transform materials for a better value.
Afterall, can you tell if these nice-looking bricks were made out of cow dung if I did not tell you?
Different soils have different qualities and characters due to the percentage of gravels, sands, silt and clay they contain. Gravels and sands enhance the strength of the bricks but they have very low cohesion. Clay does not have strength but it is a natural binder to bind all the particles in the soil. In order to make a durable compressed earth block, we need to be very careful about the selection of the soils.
Choosing the right soil is significance to the quality of the bricks. Too sandy or too clayey soils may cause weak and cracked bricks. We experimented a lot with different kinds of soils, and also leaned from so many mistakes and failure.
Soils also have varying colors due to the minerals they contain. The locally-made compressed earth blocks also can reflect the local geographic context.
Soil jar test
The simple way of testing the percentages of gravel, sand, silt and clay in the soil is to precipitate the soil in water. The heavy gravels and sand would fall to the bottom of the jar. Silt and clay would sit on the top.
Once we know the components of the soil, we could alter its components by adding more sand or gravels for our own purposes.
Only with the right kinds of soils, we could make the strong and neat blocks.
In the meantime, I also started the tile experiments with the students last week. Tile is a big cost in the housing construction in the local community. One clay tile costs Rs 32 (around $0.25), which is about four times the cost of a fired brick. The clay tile is made by the high-precision machine, therefore,it is not friendly to the villagers with lower skills.
In the VTC’s storage room, I also found a broken vibration table for making micro cement tile, which was larger, cheaper and much stronger than the common clay tile. It also requires very low technology. However, the disadvantages are the weight and the heat. So my goal is to reduce the amount of cement in the tile to bring down both the strength (we don’t need that much in tile) and the cost.
Students and teacher from automobile section helped me to fix the vibration table.
Burned Rice Husk Ash
Burned rice husk ash is a waste product that is produced by the fired-brick workshop. I collected some samples from my previous field trip. Because I found this material has surprisingly fine texture and light weight. I tried to add it into the tiles to see how much weight it could reduce without dramatically decrease the strength.
demolding and water curing
I found a lot of wasted wood dust in the carpenter section at VTC. Wood dust has relatively larger texture but it also very light. So I decided to give it a try as well.
The bricks and the tiles are still in the process of curing. I will update the strength test in the coming weeks. For the next month, my plan is to continue the experiments and also working on the housing scheme for the low-income family house.
Read more about my project here:
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