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Homepage > Vicat Group > News from the Group > France - New coastal highway on Réunion Island goes offshore

France - New coastal highway on Réunion Island goes offshore

The new coastal highway on Réunion Island is an outstanding project, one of the largest infrastructure operations currently under way in France*. The 12.5-km-long road is being built on inshore embankments and two offshore viaducts perched atop concrete piers emerging from the ocean. 

Date of the news: June 2017

Plans for construction of the new coastal highway were set in motion by the local government in 2013. In 2021 the road will connect Saint Denis, the main town on the island, to the town of La Possession, via Le Port. Its 12.5 km will replace the existing national highway No. 1 that skirts the coast between vertiginous cliffs and the sea. It carries 60,000 vehicles per day but is subject to disruption due to landslides, washouts, and submersion. The striking feature of this four-lane divided highway is that it is being built offshore, a good distance from the towering but fragile cliffs; this involves building two offshore viaducts, several inshore embankments, and an interchange. Right now the interchange has been completed and the first embankments have been under construction since May 2016. 

Heading up this enormous project, the total cost of which is budgeted at 1.66 billion euros, is construction consortium GTOI/SBTPC/VCT, which contracted supply of concrete for the interchange and embankments to Vicat subsidiary SATM Grands Travaux. Two batching plants are being used to supply the 280,000 m3 of concrete required. “It is the only French project for which concrete durability criteria—including porosity, chloride diffusion, and resistivity—were determined at the design stage and during concrete suitability tests, as well as during production, to ensure a lifetime of 100 years”, explains business-development engineer with SATM Grands Travaux. “The studies and suitability tests were carried out with our partner Sigma Béton, and we’re using Condensil silica fume to obtain the required performance. The major difficulty arises from the use of local aggregate, which is of volcanic origin and very porous”.

* Despite being in the Indian Ocean, Réunion Island is as much part of France as is Paris.


Another challenge for the project: keeping concrete temperatures below 29°C when the ambient temperature is close to 35°C.
“We set up two water and air cooling systems for our batching plants. And every truckload is checked for composition, temperature, and slump before it is placed”