Adobe Bricks are one way to incorporate local materials, both natural and recycled, into the project. Adobe bricks have been used for aeons by pre-industrial civilisations to construct houses, temples and other structures. The reason adobe bricks are so widely used is because they require very few materials and very little technology to produce. The recipe for Adobe bricks goes something like this;
- Sand - 4 to 8 parts
- Clay - 4 parts
- Water - 4 parts
Adobe bricks are susceptible to humidity so other materials such as manure, tar, burnt oil or plant fibre such as straw can be used to change the properties of the bricks and help to resist humidity and cracking.
As for recycling of materials, plastic or glass bottles can be embedded into the bricks serving a dual purpose of recycling unwanted waste and creating voids which lighten the brick.
Now sourcing local materials is not generally considered flat pack, however, to make an adobe brick you need a mold. It was my intention that these molds be fabricated in Australia, quickly and cheaply and then sent over along with other tools such as wheel barrows, buckets and anything that might be needed to make the bricks.
MOLD DESIGN
THE TEST
Ingredients
- Sand - 4 to 8 parts
- Clay - 4 parts
- Water - 4 parts
- Generous helpings of dry grass
Method
- Measure out the right quantities of sand and clay then mix well in a bucket until there it is of the same consistency throughout.
- Add water to the mix and keep stirring with hands until all the water has been absorbed and there are no more dry patches in the mix.
- Add the straw to the mix and stir through evenly
- Line the moulds with some waterproofing (you can use tar or burnt oil, but I only had grease proof paper handy at the time and it worked out fine)
- take mixture and pack it into the moulds
- leave in a warm dry place to harden (do not leave exposed to direct sunlight as the bricks will crack from drying too quickly. Covering the bricks with straw or grass solves this problem)
For this test there two different sizes of brick and two different mixtures were used to see what changes in water content and the addition of plastic bottles of various shapes would do to the end product.
The first brick had no bottle and was made with the standard recipe. This produced a very runny mixture that took a very long time to set and oozed out the bottom of the mold. The second brick was made from less water and held together much better. The second brick also had a plastic bottle embedded in the middle of it, this was achieved by packing down a third of the mixture in the bottom of the mould then placing the bottle in the middle and then packing the adobe around it. The bottle was very flimsy and would have caused cracking of the adobe so it was filled with excess sand. This did not save any weight but it did recycle the bottle. In future bricks it would be advisable to use either plastic bottles that are thicker or ones that are reinforced by their shape (ie curved coke bottles).
The bricks were left to dry for 3 days but this was clearly not long enough as they were still mailable during the presentation. Another thing I learnt was find a good spot for the mold BEFORE putting the adobe in. Despite putting a tarp underneath the mold to stop water leaking everywhere it was still very hard to carry from where the water source (ie tap) was to where the sun was. To apply this to Timor Leste methods of transporting the raw materials to the drying site would be required such as wheel barrows and large water drums.
Much of the information on adobe bricks and their manufacture was obtained from a book called the barefoot architect and it is a book I highly recommend to anyone who is interested in traditional building methods and building simply with natural materials.
