Mr. Satprem Maïni, director of the Auroville Earth Institute (AVEI) has been invited by the Chife Foundation (CF) to conduct a technology transfer for the production of CSEB and building the Anam New City with the technologies developed by the Auroville Earth Institute. The first step of this technology transfer has been a training course on CSEB production and defining the mix specifications for the particular clayey soils of Anam. This programme happened between the 28^th march and the 12^th April 2011.

Anam New City is a new sustainable development in Anambra State, Nigeria initiated by the Dr. Aloy & Gesare Chife Foundation in partnership with the greater Anam community. The project is envisioned for a Phase 1 population of 1000 on one to two years with expansion to over 100,000 in subsequent decades. Anam New City is a dynamic model for sustainable development that balances ecology with economic growth, delivers world-class quality of life across generations and leverages technology within the African culture of collective progress.

Anam is simultaneously a model city and a new model for sustainable development in Africa. It is a project that fundamentally reorganizes society in order to bring about real and lasting change. It is an alternative paradigm -- variably referred to as agropolitan or rurban in development planning circles -- that combines the benefits of modern urban living with those of rural communities and traditional productive landscapes. It is at its core an initiative to generate local economic opportunity, but it is equally a strategy for using technology - within an integrated logics framework for conceptualizing the African city - to improve people’s lives.

Toward this end, the Chife Foundation intends to utilize locally-available silt-clay and sand deposits to produce locally Compressed Stabilized Soil Blocks (CSEB). Labour-intensive and low-energy production processes are preferred, in order to maximize job production and minimize energy demand. See more information on the project at http://anamcity.com/

2.1 Soil qualities in Anam New City and Otuocha area
The locally available soils from Anam New city are normally not suitable for producing CSEB, according to normal standards and procedures. Their clay and silt content varies from 65 to 80% and the clay alone is not less than 40 %. Therefore these proportions are far too high for this kind of technique. Only a few veins of silty soils were found along the river Izuchi. But these deposits were so irregular that these soil qualities proved to be impossible to use as quickly clay layers were mixed and changed drastically the soil quality. Lateritic soils are available in Otuocha area. These are good soils but expensive and they have to be transported from far away.

2.2 Challenge with the soils available at the site of Anam New City
Clayey soils can be used for CSEB production if their proportions of clay and silt do not exceed 50% and they need to be stabilised with lime instead of cement. Lime stabilisation has been rejected because of its price (four times the price per kilo of cement). Such soils need to be amended with a lot of sand and fine aggregates which can be mixed by hand after sieving the soil.

But the soils from the site of Anam New City are too plastic to be used for the production of CSEB. Their plasticity and cohesion are too high. They miss a proper structure, as they lack coarse particles, and their compressibility is very low. Soils with such amounts of clay and silt need to be totally dried and then pulverised with specialised and heavy machinery. But the weather of Anam area is such that there are regular rains all along the year with about 2000 mm per year. The clay deposit, being along the river, is also always humid because of the capillary from the river. Therefore the ground is hardly dry.

Therefore a totally different process has been envisaged for the soil preparation, which is to dilute clay in water and mix the slurry with sand, granite dust and cement. Thus this mixture recomposes a new soil. But the difficulty with this system is to control the fluidity of the slurry in such a way that the slurry does not add too much water to the mix and add enough clay to the sand-granite dust ratio.

3.1 Laboratory tests
Three clay slurries of various proportions of clay and water with small quantities were tried in order to define a proper ratio to be added to the sand-granite dust mix.

In most cases the mix was too wet to be compressed and had a low to medium plasticity and cohesion. One of the problems of these tests was the small quantities used for the mix. Therefore these tests were not representative enough of the reality and it was preferred to try real sizes mixes which could be compressed in the press.

3.2 Preparation of tanks for mixing the clay paste
Preparing the clay slurry required tanks, where the clay should be mixed and rest at least one day.
Therefore 4 tanks were built with the means available on site in between both platforms for block making (2 per press).

1. Building the tank with dry concrete blocks	2. Reinforcing the middle wall	3. Reinforcing the side walls
4. Laying the plastic sheets for waterproofing	5. Tightening the tank with wires against the water pressure	6. Laying the water tank in between the 4 tanks

3.3 Practical tests for the clay paste
Five different clay pastes were tried simultaneously with the mix for block making.

The aims of these tests were to have the optimal fluidity of the clay-water ratio so that the mix for block making was not too wet and had enough clay to bind the aggregates. Finally the mix was not anymore a clay slurry but a clay paste. It was extremely difficult and labour intensive to mix it. Therefore we made some tools to ease the process.

First we made a hand tool to mix the slurry and it was working well as long as the mix was still fluid. But when the paste got thicker, it was too hard to pull. Therefore, we tried to manufacture a mixing machine but several problems were encountered:

• First the motor was too weak (750 W) as it was the only model available at that time.
• Then we found a 5 HP motor which was stirring the paste at the beginning. But progressively the motor slowed down and stopped when the propeller went at the bottom of the tank.
• It seemed that the propeller had too many blades and we cut half of them.
• But finally the welding of the shaft broke two times as it was not well done and the machine could not be used.

Therefore, the prototype of the mixer machine which was manufactured should be developed in order to ease the process. But in fact a better system for mixing the clay paste would be to buy a rotary tiller also called “Roto Tiller”. This machine should be equipped with blades and not discs, in order to churn properly clay.

3.4 Practical tests with the press for block making mixes
Fifteen mixes for block making were tried with various results: Some of them did not work at all and some of them gave poor results. For most of them, the mix was again too wet, as the slurry was too liquid and often the mix lacked cohesion. The aim of these tests was to get the optimum compressibility and cohesion so that they could be compressed to a maximum and handled properly.


4.1 Final clay paste
After many trials the following mix appeared to be the best.

Ratio

• Water =   900 litres
• Clay   = 2,100 litres
  

Note that clay should be as dry as possible, as it is difficult to adjust the proper moisture content of the paste. Therefore, to avoid such problems it is better to fill first only 800 litres in the tank and then pour clay. The viscosity should be tested according to the procedure described hereafter and if it is too thick, then extra water should be added progressively. This ratio will give about 2,000 litres of clay paste which should be enough for one day production of 850 blocks per press. If in case this paste is not enough for one day production, the ratio above should be increased proportionally.
 
Procedure to prepare the clay paste

4.2 Final mix for block making
The final mix was the Ref. O. It gave the best results for the cohesiveness and the compressibility. Moisture content was fine, but it was still a sandy mix. The result with the penetrometre was the best.

This mix can be used for the block making:
Ratio

Gravel 1/4”	= 17 Litres	= 1 bucket
Coarse Sand	= 58 Litres	= 1 wheelbarrow 75 litres – 1 bucket 17 litres
Fine silty sand	= 58 Litres	= 1 wheelbarrow 75 litres – 1 bucket 17 litres
Clay paste	= 68 Litres	= 4 buckets 17 litres
Cement	= 1/4 bag (12.5 Kg)	= 1 bucket 13.5 litres (1 bag divided in 4 buckets)

Note that it is essential that gravel, coarse sand and fine silty sand should be as dry as possible. If they are humid, the mix will become too wet and it will not be compressible. Therefore it will be necessary to leave the piles under the sun to dry and to cover them at night and it there is any risk or rain. On the opposite, sometime water should be added to the mix before adding the clay paste.

Percentages
This mix gives a cement ratio of 4.65 % by weight and the proportions of the recomposed soil are:
Gravel 1/4” = ~ 10 %  –  Sand = ~ 60 %  –  Silt = ~ 15 %  –  Clay = ~ 15 %
 
Procedure to prepare the mix for block making

13. Mix is ready to be compressed when there are no lumps bigger than 1/2”


5.1 Theoretical course
Two days of theoretical lecture were given to 9 people (architects, supervisors and project managers). The aims of these sessions were to give the basics on soil identification, soil improvement and stabilisation as well as design guidelines and economics.

5.2 Practical course
The practical course was conducted on 8 days and was given to 24 workers plus 2 supervisors and Mr. Ismaila Adoke, the brick factory manager. This course happened simultaneously with the elaboration of the various mixes.

 The process described hereafter is mostly for the compression, stacking the blocks for the initial curing and final stacking, as the mixing process has already been detailed.

The last day of the training course elders from the Anam community came to congratulate trainees and emphasize the importance of this fist action for the development of the new city to come.