How is concrete made from oyster shells?

• The department of Hérault has experimented with the use of concrete made from oyster shells for the development of a cycle path in Bouzigues.

• This material is made by the Colas company, which crushes the shells to make sand, and mix it with water and low-carbon cement.

• Before being implemented on other pedestrian or cyclist facilities, the Hérault department will study its behavior for one to two years.

The recyclability of oyster shells is amazing.

It is made into porcelain, Christmas decorations, fertilizer, food supplements for chickens, artificial reefs, spectacle frames… And concrete.

Or rather a coating, close to concrete, particularly ecologically virtuous.

In the Hérault, the department has chosen to experiment with this new kind of material, for the development of a cycle path, in Bouzigues, the country of the oyster.

It is manufactured by the public works company Colas, which recovers oyster shells from the urban area of ​​Sète, which has undertaken a collection of shellfish waste.

Those that still contain organic matter cannot be recycled.

They could make the material too unstable.

Only “the cleanest are identified, and crushed”, in a conventional crusher, “which is used for stones”, confides Romain Carai, head of the Colas establishment, in Sète.

A one or two year assessment 

Once the oyster shells have turned into sand, it is mixed with filler sand, which comes from a nearby quarry.

"It allows to correct a little the differences that we could have with the sand resulting from oyster shells", continues the professional.

A little water and low-carbon cement, which generates less CO2 emissions, is then mixed in and the mixture is ready to be used on construction sites.

For the moment, only 200 meters of a cycle track in Bouzigues are affected by the use of this new material.

But the department of Hérault does not rule out the possibility of using this "shell concrete" elsewhere, if it turns out, however, to be as efficient as the traditional one.

"An evaluation of the resistance over time, one to two years, must be made before considering its use on other facilities, while remaining within a local scope of use", indicate the department's services.

It could be used to create, as in Bouzigues, paths for pedestrians or cyclists, or parking spaces for cars, explains Romain Carai, at Colas.

And it is not, for the department of Hérault, a question of cost, but of ecology.

"The cost is equivalent to that of traditional concrete, but more virtuous in terms of the circular economy", explain the services of the community.

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• Montpellier

• Oysters

• ecology

• Cement

• Occitania

• Languedoc Roussillon

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