INTERLOCKING STABILISED SOIL BRICKS [ISSB]
In January 2010, the Henry van Straubenzee Memorial Fund purchased a brick making machine from the Haileybury Youth Trust. Our decision was principally made for economic and environmental reasons, although we had some reservations, because, in the majority of our school building projects, the local communities contributed to new buildings by making a significant quantity of the bricks to be used.
The traditional method of making bricks has remained unchanged for hundreds of years. Small kilns are used and local forests are raided for wood to burn. This is unsustainable as there is no afforestation programme in most areas. The bricks have to be fired for 100 hours, with the resultant carbon emission and wood usage, and cool for 4 days. The “burnt bricks” are then stored for up to 6 months before use. The size and shape of the bricks are never uniform. With cement in Uganda demanding a premium price, buildings become unnecessarily expensive.
The ISSB is made by compressing a mixture of the local Murram soil with a small amount of cement and water, to make a uniform size block. The brick needs no firing and is ready for use in 6 hours. Our machine can produce 300-400 bricks per day on site, saving transport costs. Each brick is uniformly shaped and is interlocking, thereby requiring a fraction of the amount of cement required with burnt bricks. It is also stronger and twice the size.
In order not to discourage local community involvement, we still welcome their gift of burnt bricks, but use them for the foundations of the buildings.
We have now purchased a second ISSB machine which makes a curved brick. As we build a growing number of 20,000 litre water tanks, these bricks are essential to ensure no leakage and produce a vandal proof tank to harvest the plentiful rain water off the roofs of our buildings. In the past we would supply a 10,000 litre plastic crest tank and then encase it in burnt bricks. A completed 20,000 litre ISSB water tank costs the same as a completed 10,000 litre crest tank and is a more efficient, economic and eco-friendly process.
Having now witnessed our team of builders working with our two ISSB machines, we realise what a good investment we have made. The machines are transportable and require no power apart from builder’s muscle. The technology is not new but, as yet, there are only a few of these machines in Uganda. In summary, the main advantages to our building programme are: