Family Alliance For Development And Cooperation, Tanzania

Building with appropriate technology Soil Stabilized Blocks

Introduction:

FADECO is a local development NGO striving to promote sustainable socio-economic development of the grassroots communities. FADECO is involved in developing, transferring and adapting low cost technologies that are appropriate, cost effective and affordable to poor rural communities; technologies that are environmentally friendly. FADECO has concentrated her efforts on agricultural development, low cost housing and renewable energy technologies.

Involvement of individuals, groups, NGOs and Government organizations in Low Cost Housing projects:

There are so many reasons why individuals, groups, NGOs, CBOs and Government should embark on Low cost housing. Most of people in rural areas cannot afford descent housing due to poor and low incomes. Most importantly such an activity can:

- provide employment opportunities to women, youths and the entire rural community through small scale construction enterprises of cheap and better houses for people.
- provide better housing for all (esp. the most vulnerable and poor) thereby improving the standards of living
- reduce environmental degradation esp. deforestation
-improve health and living conditions of the rural households

PROBLEMS ASSOCIATED WITH CONVENTIONAL HOUSING

Every human being has a right to shelter. But the problems of poverty and unequal distribution resources deny many people the right to descent housing. A good house has many advantages and it is the desire of every one to have such a good habitat for own family. But one needs to have enough savings to be able to secure a good house.

In common practice, a good house would be one iron roof, with burnt bricks/ or concrete block walls, with proper doors/ windows, good ventilation, cemented floors, good water drainage, etc. with a water tank and a good waste disposal system (hygienic pit latrine).

Many a time, very few people in the rural areas have the resources and money to afford such a house mentioned above. The cost involved is so high that no one ever affords to have one. For the rural people, most of whom earn peanuts with an annual income of less than TShs 94,000/-, it remains but a dream.

Low cost housing Technology:

This technology tries to overcome many problems associated with conventional housing. It tries to offer an appropriate technology solution to people who want to secure better housing conditions but are constrained due to poor/ low incomes.

Ordinary (red) soil is stabilized with cement or lime and compressed using a manual machine called the BLOCK PRESS. Red means removing the top (black) soil and using the soil, which is free of organic material. Stabilization mans the block will not disintegrate (washed away) because of rainwater.

The Block Press Machine:

This machine commonly referred to as THE SOIL BLOCK PRESS is probably the best after years of building research and a development by a Kenyan NGO called APROTEC. The machine makes SOIL STABILIZED BLOCKS (SSB) for building all types of low cost houses (including Un-orts), low cost water tanks, septic tanks for sewage, pit latrines, and community houses.

With one stroke the prepared soil is compressed by 40% manual power. The second stroke just rejects the fresh block from the mould. The machine is purely manual, operated by two people and requires simple greasing and oiling.

The blocks are sun-dried (NOT FIRED as is the usual case) and are ready for use within 10 days. This tremendously reduces the fuel-wood consumption (unlike in case of brick firing) and thus a contribution towards environmental conservation. Two people operate the block press and produce 400 - 500 blocks per day.

BLOCKS PRODUCTION:

1. The red soil is sieved with a 5 mm sieve (coffee tray) while still dry.
2. The sieved soil is mixed thoroughly with cement in the ratio 1 cement to 15 soil by volume. (If lime is used, the ratio is adjusted to 1:8). Soil with sharp stones works best. So an adequate amount of sharp stones need to be present for a best block quality.
3. The mixture is wetted (using a watering can) so as to make it just damp not very wet.
4. Fill the Mould box of the machine with prepared wetted mixture.
5. Press and then eject the formed block.
6. Refill the mould box and repeat process for more blocks
7. Cover the fresh blocks with a black polythene sheet for five days
8. Remove the black polythene sheet and let the blocks dry in the sun for another five days
9. The blocks are then ready for use either on that site or to be transported to another site.

QUANTITY AND SIZE OF THE BLOCKS

a) One bag (50 Kg) of cement makes between 120 - 150 soil stabilized blocks. The best soil is murram (150 blocks) and the worst is soil without any stones in it (120 blocks) of less quality.
b) Two people can make between 400 - 500 blocks per 8-hours working day.
c) The blocks are of standard size (280 x 140 x 110 mm) or 11.5 x 5.5.x 4.5 inches.

SPECIAL DESIGNS OF THE BLOCKS:

The mould box is specially designed to produce specially designed and high quality soil stabilized blocks with the following shapes:

a) Ordinary solid blocks for building
b) Interlocking solid blocks for building
c) Interlocking keyed-surface blocks for building and water tanks
d) Fully interlocking keyed-surface blocks for building and water tanks

The fully interlocking keyed-surface blocks are the best of the four and are the focus of the present project to be promoted.

SPECIAL FEATURES OF THE BLOCKS:

The fully interlocking keyed-surface blocks are specially designed:
a) Fully interlock on four sides to increase wall strength and save mortar
b) Plastering surfaces keyed to ease and reduce plastering
c) Blocks for water tanks, septic tanks, Un-ports and pit latrines are specially curved so as to make circular shapes; therefore there are no corners, which would be the weak points on the wall.
d) Pit latrines may be constructed any where (swampy, sandy or rocky areas) below the ground.

a) The blocks are not fired but simply dried. This means that there is less effect on the environment in terms of forest destruction to get firewood for firing/ burning bricks (as is common practice), less environment pollution with smoke, no fuel costs and the environment is saved.
b) Blocks are made on site thereby avoiding unnecessary transport costs, handling charges and reduced damages, labour.
c) Soil is abundantly available on site e.g. from a pit latrine, soak pit, septic tank, building foundation, etc.
d) The interlocking mechanism of the blocks greatly reduce building mortar and increases speed (1 bag of cement binds 350 blocks). Less cement is used and so less money spent.
e) Keyed surface means that very little plastering inside the house. The outside may be left un-plastered for beauty.
f) When all costs are considered, building with Soil Stabilized Blocks is about 35% a lot cheaper than using concrete blocks. It is a lot cheaper than using any other type of bricks/ blocks and is very strong.
g) Concrete blocks, if desired may be produced using the same machine.
h) Labour requirements are minimal. Two people make 5000 blocks in 10 days which are just enough for a one 3 bed roomed house or 17 water tanks (3000 litres capacity) or 5 double room un-ports.

BASIC REQUIREMENTS:

To get the project moving and started, you would need to acquire just two machines (one for straight interlocking blocks and another for curved interlocking blocks). Each of these machines cost Us $ 1000.00
(TZS 950,000/- per machine).

Two persons need to be trained how to operate the machine, and how to lay the blocks. Those with masonry skills are better candidates, as these will need less time for the training.

FADECO collaborates with the Faculty of Science and technology of Makerere University, Kampala - Uganda. Prof. Moses Musaazi is the head of the faculty and an electrical engineer by profession.

FADECO would be interested to help everyone to learn and adapt the technology with hope that, through this way, some of the social economic problems facing our rural communities would be lessened. The technology presented here can be used and adapted everywhere.

For more information, come to fadeco offices and be assisted how to go about it.

See you then.