Partnering with Bouygues to deliver a monumental expansion to the Monaco coastline

27 March 2019

Continuous 10-day pouring of 80,000m3 of concrete, for 18 blocks weighing 9,979 tonnes. The numbers involved in the Monaco Offshore Extension project are staggering, but they only tell half the story of the logistical challenge of this huge project.


The challenge

The Monaco Offshore Extension project will create 6 hectares of new land through expansion into the sea. This is quite an undertaking and will require massive amounts of both material and expertise. 18 semi-submerged caissons will encircle the underwater area needed for the expansion, ready for filling. These structures are on a massive scale, and over 80,000 m3 of concrete had to be poured. Weighing 9,979 tonnes per block, the caissons have a guaranteed life expectancy of at least 100 years in maritime conditions.


caissons de monaco 1


Our solution

LafargeHolcim played a large role in this project, designing the concrete specific formulation and supplying two-thirds of the concrete. as well as assisting logistical and technical support efforts for Bouygues Construction, who are assembling the caissons: 

  • Installation of a concrete plant in the port,
  • A cement plant and two quarries dedicated to the project,
  • Deployment of extensive human and technical resources, allowing the project to be completed 5 months in advance,
  • LafargeHolcim’s laboratories at Capalette and the Lafarge Research Center, in conjunction with CERIB (Center for Studies and Research in the Concrete Industry) made major contributions through concrete performance studies and creating a formulation to make sure the color and appearance of the concrete is homogeneous and in line with the architect’s vision for the project.


caissons monaco 2


Construction began in July 2016 and took two and a half years to complete. Built on custom-made construction platforms in the port of Marseille, the concrete for each caisson needed to be poured continuously over ten days, requiring dedicated teams overseeing the work 24 hours a day.

These 18 titanic structures will now be towed on a three-day sea journey to the submersion site on the coast of Monaco. The bay is an important habitat for many species of plants and animals, who have been temporarily relocated to artificial reefs, to avoid disruption from the construction. The caissons will be placed to not disturb the underwater currents of the bay. The project has been a massive undertaking on the part of LafargeHolcim and Bouygues, efforts which will see Monaco’s new eco-district flourish for years to come.