INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

Case Study #278

1. Headline: Internal recycling in a French concrete plant

reduces effluents.

2. Background: The Garon Company set up a plant

manufacturing ready-to-use concrete, in Nanterre in 1991.

In 1992, the company set up a water and granulates

recirculation equipment. This case study was carried out

in 1992. Average production of the plant : 400 m3/day.

Mixing water consumption : 200 l/m3. Rinsing water

consumption : 1 m3 by mixing unit. Washing water for the

plant : 50 m3/day.

3. Cleaner Production Principle: New technology

4. Description of Cleaner Production Application:

Information about the process and wastes

The plant uses 145 m3 of water a day, withdrawn from the

river. The water used for washing was settled in tanks (60

m3 of capacity), then stored in underground storage (about

75 m3). Excess water was discharged to the river.

The returns of concrete were discharged from the lorries

down to an area, waiting for a transfer to a quarry owned

by the company.

A water and granulates recirculation plant was set up. A

screw carries up the granulates washed by a downward water

flow which carries down the fine particles of cement.

Water loaded with fines is stored in the underground tank,

equipped with two stirring devices in order to avoid

settling. These loaded waters are recirculated for

producing concrete, washing lorries, or in the granulates

washing screw. The washed granulates are used in concrete.

Material / energy balance and substitution: Withdrawal

from the river is reduced from 145 to 80 m3/day.

5. Economics: Cost of direct investment: Total : 758 000 FF

(1992), settling tanks and feeding system of the screw

represents an amount of about 1 000 000 FF.

6. Advantages: Decrease by 50 % in the S.S. discharges.

Recirculation of sand and granulates.

No more discharges of returned concrete.

The settling tank must be large enough and a spare tank is

necessary in order to face exceptional peaks of returned

concrete or a failure of the equipment.

Technical normative may stand in the way of using concrete

which blend recycled fines or granulates. Sand and gravel,

in particular, are not separated by this plant.

It is necessary to give main instructions to all staff,

internal and external, about making good use of the

equipment. A continuous supervision of the working is

essential, night and day.

7. Constraints: No information provided.

8. Contacts:

Agence de l'Eau Seine-Normandie

Mlle MATHIEU

TEL: 33 41.20.16.23

M. BERNARD

Redland Granulats

TEL: 33 64.73.41.00

Centrale ... bÆton de Nanterre

Z.I. du Port

Rue Lavoisier

92000 NANTERRE - France

TEL: 33 64.73.41.00

FAX: 33 64.68.05.46

M. Maton

M. Chatenet

Office International de l'Eau

Direction de la Formation et des Etudes

rue Edouard Chamberland

87065 Limoges Cedex, France

TEL: 33 55114770

FAX: 33 55777115

9. Keywords: France, concrete, recycling, new technology,

recirculation, water saving

10. This case study was submitted to UNEP IE in 1994 by the

French Office International de l'Eau. It has not undergone

a formal technical review.