The Marseillaise Tower: A Demonstration of Concrete Innovation and Durability

Phil Michael
Jul 10, 2017 · 4 min read

On the quays of Arenc, in the city of Marseille, the tower of “La Marseillaise” is emerging. Designed by Jean Nouvel, this 135m building and surrounding business district uses concretes with enhanced performance attributes; a material with increased strength and is easily manoeuvrable thanks to super-plasticizers.

The design of the façade is indeed atypical since it is made up of 3,500 pieces of unique solar shading, which will cover the glass facades. The structural elements, built from ultra-high performance fibre reinforced concrete, will be assembled in a very precise order, in the form of 3D puzzle. This material guarantees lightness, aesthetics, robustness, durability and economy. It has a compressive strength 6 to 8 times greater than that of a traditional concrete, and contains metallic fibres that make it ductile. In this way, the structure can be freed from passive steels, which eliminates coating thicknesses while reducing structural thicknesses and rendering.

Concrete Requirements: Durability and Repairs

One of the most important advantages of concrete is its durability and the reduced requirement for maintenance; provided that, as with any building technique, it is well designed and well constructed. Although concrete requires little maintenance, it should not be neglected. Dedication to maintenance and repairs will ensure that the ongoing costs of a property is minimised, while substantially extending the service life of the material.

For each problem, there is a suitable solution. Current concrete maintenance techniques include:

  • The relining of the joints.
  • Repair of localised defects and cracks.
  • Strengthening the structure at the end of its service period.

Re-filling/Lining of Joints

The purpose of this operation is to restore the sealing of the joints. It consists mainly of stripping the joint, then resealing it to eventually bring it to the correct width (minimum 8 mm). Then expose the concrete to ensure a good binding of the filling product, which is typically a modified mortar for patch and thin bond repairs. Once the gasket has been washed and dried, and after applying a primer if necessary, a seal base is placed and the sealant is cast.

Repair of Localised Defects

Prior to repairing the sealing of the joints, these minor defects (breaks, seam grooves) are repaired with pressure/vacuum injected epoxy resin mortar, polyester and cementitious grouts

Strengthening The Structure At The End Of Its Service

The purpose of a pavement is to ensure a well managed highway infrastructure for the passage of vehicles for a certain period of time, which is the service life of the structure; during which the material must ensure the comfort and safety of the users. Throughout this period, structural maintenance and repairs of the concrete coating is sometimes necessary. This is implemented in two ways:

In the case of an old concrete lining, the reinforcement of the structure can be achieved with a layer of thin bonded concrete. This technique consists of preparation of the surface by shot blasting, sandblasting or possibly by milling, then application of a cement slurry, followed by the application of concrete to 5 to 10 cm in thickness. The new joints are sawn in line with existing joints.

This technique increases the structural potential of the coating by increasing its thickness and at the same time improves the uniformity and the adhesion. The pavement must be in good condition from the point of view of load transfer, surface erosion of the foundation and rate of cracking. This is in fact a preventive reinforcement or an adaptation of the structure to new service uses. In the case of a poorly degraded coating, the reinforcement of thin bonded concrete results in a structure better suited to the traffic observed.

In the case of an old bituminous coating, the reinforcement of the structure can be done with a bonded cement concrete (B.C.M.C.). This technique consists of cleaning the old coating by shot blasting, milling followed by the application of the concrete to a thickness of between 5 and 10 cm. The joints, made by sawing, are arranged transversely and longitudinally by creating a square mesh whose side is between 1 m and 3 m.

Conclusion

Thanks to the structural qualities, concrete coverings are durable and require little maintenance for operation. All the techniques described in this article are well known and may be perfectly mastered by reputable concrete repairs professionals. Furthermore, it is now possible to carry out progressive reinforcement works to adapt the concrete structure to the evolution of traffic.

The Marseillaise Tower and business district — Marseille, France
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