Comment stocker de l'eau dans des jarres en ciment

Jarre de ciment d'une capacité de 1,0 m3 - Étude de cas - Fiche technique

Brève description

• Problème :
• Idée :
• Information : Application / Principes
• Difficulté :
• Game de prix :
• Matériel utilisé :
• Zone géographique :
• Compétences:
• Combien de personnes ?
• Combien de temps cela prend-il ?

Introduction

Cette étude de cas est tirée de ‘Rainwater Harvesting - The collection of rainfall and runoff in rural areas’, Pacey and Cullis by IT Publications, 1986. L'information a donc été utilisée à partir d'un programme récent financé par l'UE sur l'eau et les installations sanitaires en Tanzanie.

Ce type de réservoir d'eau qui à l'origine a été développé en Thaïlande, mais a été utilisé très largement et souvent avec des modifications, en Afrique de l'Est. De nombreuses variantes de ce type de réservoir ont été développées au fil des ans.

Figure 1: 'jarre thai' en cours de construction dans le cadre d'un des programmes d'eau et d'installations sanitaires en Tanzanie

Détails de construction

Le moule ou le coffrage pour une jarre en mortier de ciment de 1m3 est fabriqué à partir 2 morceaux de tissu de jute ou de toile de jute, coupés et cousus ensemble avec de la ficelle comme indiqué à la figure 19. Après la couture, le sac sans fond est tourné à l'envers.

Figure 19: Dimensions for cutting sacking

• To make the bottom of the tank, mark out a circle on the ground of 1m diameter and place ½ bricks or other suitable material around its circumference to act as a formwork.

• Spread paper or plastic sheeting on the ground within the circle to stop the mortar sticking. Mix a 1:3 cement: sand mortar and spread within the circle to a depth of 15mm.

• When the bottom plate has set, place the sacking bag narrow end down on the plate and begin filling it with sand, sawdust or rice husks. Make sure that the mortar base sticks out from under the sack and tuck the edges of the sacking under the filling material, so that the weight of the filling holds the sacking on the plate.

• Fill the sack, fold the top and tie it closed. Then fold and smooth the sack into a regular shape. Make a circular ring from wood or cement mortar and place this on top as the formwork for the opening in the top of the jar.

• Spray the sacking with water until it is thoroughly wet, then plaster on the first layer of cement mortar to a thickness of up to 10mm.

• Plaster on the second 5 - 7mm layer in the same manner as the first, checking the thickness by pushing a nail in. Build up any thin spots.

• Remove the sack and its contents 24hrs after the plastering is completed. Repair any defects with mortar and paint the inside of the jar with cement slurry. Then cure the jar for 2 weeks protecting it from sun and wind under damp sacking.

General information

This type of jar can be manufactured in any size. However, as the tank size gets bigger the mould becomes unwieldy, and different methods have been devised for making the former. One such example saw the construction of 1.8m³ jars using specially made curved bricks to construct the formwork. The blocks are built into shape using mud as a temporary mortar and are then removed once the tank is complete. The formwork can then be reused again and again.

In East Africa, the use of chicken mesh between the first and second coats of plaster is a common addition which gives extra strength to the structure and helps prevent crack propagation. This type of ferrocement tank can be loaded onto a truck for delivery, and therefore has the advantage that it can be made centrally for later distribution. Watt, 1978, gives detailed instructions for the construction of a 0.25m³ jar in ‘Ferrocement Water Tanks’. He suggests that similar tanks can be built up to 4m³ in size. The smaller mortar jars replace the traditional ceramic Thai jars and can be manufactured at about a tenth of the price. The quality of workmanship for this type of jar should be of high standard, as any flaws in the jar can quickly result in failure.

Material requirements

The quantities below are taken from a similar 1m³ jar used during a recent water and sanitation programme in Tanzania. This tank had reinforcing and a tap and a washout fitted.

Materials	Unit price	Qty	Cost
(TSh) 1997 Prices	(TSh)
Cement (bag)	6,200	2	12,400
Chicken wire (roll)	25,000	0.25	6,250
Binding wire (kg)	900	0.50	450
G.I Pipe 1" (m)	2,000	1	2,000
G.I F-F connectors 1"	300	2	600
G.I. Elbows	185	2	370
Locking Tap 1"	2,500	1	2,500
G.I. Male plug 1"	800	1	800
(2100 TSh. = £1 Sterling at the time of writing)		Total	35,220

*sand and stone are not accounted for here as they were provided by the community as part of a self-help initiative.

** approximately 1 skilled and 1 unskilled person days are required per tank.

References and further reading

This Howtopedia entry was derived from the Practical Action Technical Brief Energy from the Wind.
To look at the original document follow this link: http://www.practicalaction.org/?id=technical_briefs_

Adresse utile

Practical Action The Schumacher Centre for Technology & Development, Bourton on Dunsmore, RUGBY, CV23 9QZ, United Kingdom.
Tel.: +44 (0) 1926 634400, Fax: +44 (0) 1926 634401 e-mail: practicalaction@practicalaction.org.uk web: www.practicalaction.org

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