Updates From Batticaloa|Material Experiments|Qi Guo|B.Arch2017|
Afer a week of curing in the water, the first batch of the roof tiles was ready for testing. First, we checked the surface. We got rid of those with holes and cracks on the surfaces. These holes were caused by the improper handling during the vibration process. These products were not good for roofing.
We brought the smooth and intact one to the further tests.
We weighted each product and compared each weight to the weight of the common clay tile.
A common clay tile is around 2.75 kg. Since out tile is 30% larger than the clay one. We need to control our tile under 3.6 kg in order to beat the clay tile. The picture below is the one with rice husk ash in the cement mixture. It greatly reduced the weight of the tile to 3.25 kg, which is 10% lighter than the clay tile with the same size as our tile.
For testing the ultimate tensile strength, we loaded 10 kg sand each time into a bag on the top of the testing machine.
Most of the tiles we tested can withstand 80kg, which was over the strength requirement (60kg) for local housing roof tile.
The tile broke when the load surpassed its ultimate tensile strength. We examined the cracks and broken pieces carefully to study their properties.
One of the benefits of having fiber reinforcement in the tile is that the fiber material binds the tile together when cracks appear.
Some tiles broke easily, and we found that it was contaminated by other materials during the mixing process.
For the brick, we also made some progress in the past a few weeks. Even we have not yet tested those bricks, which require a long curing time (one month). The bricks looked very neat and felt very sturdy in hands. I have confidence that the coming strength tests will have some pleasing outcomes. In the meantime, I also thought about how to improve the brick wall construction. I want the brick wall to be clean and neat without exposing any mortar. I also want to minimize the use of mortar in the joints to bring down the cost. So I looked into the design of interlocking brick.
The mould of the machine determines the shape of the bricks. By altering the mould, we could get a variety of shapes according to our needs. In STVTC, I found another compressed brick machine that loses its mould. I decided to design a new mould for it.
I designed a mould that could make bricks with dovetail joint on the short sides so that no mortar is needed to join the bricks in the horizontal direction. The bottom of the brick has a channel to fit the upper extruding parts. Only minimal amount of mortar is needed to fill the gap between the extrusions and the channel. It also saves the masons a lot of time in leveling and aligning the bricks. The wall would look absolutely clean and straight with this kind of brick construction.
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In order to minimize the production cost, we visited the local junkyard shop to search for used materials that we need for the mould.
We got a few 10mm and 12mm used industry steel plates. However, we encountered an issue. The manufacture of the mould required the work of milling machine and lathe machine, which supposed to be provided by machinery workshop at STVTC. But because of some financial problems, STVTC closed down their machinery section a few years ago. We had to find another way. Finally, we decided to cooperate with the students and teachers from the Eastern Technical Institute (ETI), which is another vocational training center in the local district. A lot of the faculty at STVTC received their training from ETI.
ETI has larger machinery workshop and better facilities.
Oxy-fuel cutting to cut the steel plate in approximate sizes.
Milling machine for cutting exact and complicated shapes.
Further finishing by hands.
One bottom Plate of the mould in progress.
It will take about ten days to finish the mould. I will update the result when we finish. Although the mould could be done easily and accurately with modern CNC machine and laser cutter in the capital city Colombo, I decided to do it locally with the less developed tools and machines. Such decision was made based on the core idea of my research, which is to work with the limitations of the local resources. Also by giving such task to the local people, it would help them gaining more experience, which could be helpful in producing other modifications in the future.
Read more about my project here: