UGANDA, Kampala | Real Muloodi News | In Part 1 of this series, we introduced Interlocking Stabilised Soil Blocks (ISSBs); a type of compressed stabilised earth block that interlocks with each other. ISSBs are made from a mixture of soil, cement, and water that is compacted under high pressure using a manual or mechanical press. These blocks have been found to have similar or even better strength characteristics than traditional bricks, while using significantly less cement than traditional bricks and concrete blocks.
In this next chapter, we explore how to make ISSBs, the different kinds of ISSBs you can make, and everything you need to know about manual ISSB machines, including where to buy one.
How to Make ISSBs
The process of making ISSBs with a manual ISSB machine involves the following steps:
- Mixing the soil, cement, and water to form a consistent mixture.
- Pouring the mixture into the mold and compacting it using the manual press.
- Removing the block from the mold and placing it on the curing tray.
- Allowing the block to dry and cure before using it in construction.
Block quality is not so much defined by the machine, but by the quality of the raw materials introduced into the mould, the method used for mixing them and the moisture content of the mix.
The recommended ratio of soil, cement, and water for ISSBs varies depending on the type of soil and the specific project requirements. However, a common ratio used is around 6:1:0.5, meaning 6 parts soil, 1 part cement, and 0.5 parts water. This ratio can be adjusted as needed based on the compressive strength and durability required for the specific project. It’s important to note that the soil must be of good quality and well-graded for the ISSBs to be strong and durable.
Moisture content is a critical factor in the quality and performance of the blocks. The soil should have a moisture content of around 12-15% prior to mixing it with cement and water.
If the soil is too dry, it will not bind well with the cement and water, resulting in weak and porous blocks. On the other hand, if the soil is too wet, it will be difficult to compact and the blocks will have a poor shape. Therefore, check the moisture content and adjusted as necessary before mixing the soil, cement and water together.
The process of mixing the soil, cement and water should be done in a controlled environment so that they are evenly mixed together, to ensure that the blocks produced are consistent in strength, density, and other properties. This is important for ensuring the structural integrity and stability of the building.
After the blocks are formed, they are usually left to cure for a few days, during which the blocks absorb some of the moisture from the air, which improves their strength and durability.
It’s worth noting that the soil type and quality, as well as the cement type and quality, can also affect the final properties of the blocks. These factors should also be taken into consideration when mixing the materials for ISSBs.
It’s recommended to consult with a local construction professional or a person who have experience in making ISSBs to determine the appropriate ratio of water to soil and cement for your specific project.
Additionally, if the building is a two-story house, the blocks need to be of higher strength and the compressive strength of the blocks should be at least 7N/mm², it is recommended to consult with a structural engineer or a local construction professional.
Makiga, the manufacturer and supplier of manual ISSB machines, offers FREE ISSB training at their Makiga blocks Training Centre. Find their contact information at the end of this article.
ISSB Blocks
Depending on the machine, different type of ISSB blocks can be produced:
1. Straight Double Interlocking Block: The most commonly used block for wall creation.
2 Curved Double Interlocking Block: Used for making water tanks and sanitation facilities.
3. Wide Format interlocking Block: Allows for stronger, thicker walls, especially useful when making high walls.
4. Straight Single Interlocking Block: Contains a larger face, hence less blocks are needed to cover wall area. This was the predecessor to the straight double interlocking block.
Manual ISSB Machines
Manual ISSB machines are the most affordable option for block making, suitable for small-scale production. They are often used in rural or remote areas where access to electricity is limited. They are also easy to use and maintain.
One of the advantages of manual ISSB machines is that they are portable, which means that they can be easily transported to different locations. They also require minimal training to operate, which makes them accessible to a wide range of users.
Manual ISSB machines are also a good option for small-scale entrepreneurs and communities who want to produce their own building blocks for housing or other construction projects.
Technical specifications of the typical manual ISSB machine used in Uganda
- Typical compression force: 80-100N
- Weight: 140kg
- 2-4 workers in an 8hr work day can produce 400-600 blocks
- Low maintenance: requires to be lubricated with engine oil.
- 130 stabilised blocks can be produced from a 50kg bag of cement.
The cost of ISSB Machines
The cost of a manual interlocking stabilised soil block (ISSB) machine in Uganda can vary depending on the manufacturer and the specific model of the machine. On average, a manual ISSB machine can cost between $1,500 and $3,000 USD. However, prices can be higher or lower depending on the features and capabilities of the machine. It’s important to note that prices may change over time and they can be affected by various factors such as exchange rates, import taxes, and transportation costs.
Where to Buy a ISSB Machine
Makiga Appropriate Technologies Ltd Uganda Office:
- Plot 70; 8th Street Industrial Area Namwongo Road
- Phone: +256 756 566566
- Email: sales@makigauganda.com
- Website: makigauganda.com
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