Since the autumn of 2023, teams from the VINCI Construction subsidiary Dumez-Auvergne have been refurbishing and extending the former Hôtel-Dieu in the centre of the Auvergne region capital. This emblematic 18th-century building was originally a hospital.
The edifice is now being transformed into the future Bibliothèque Métropolitaine de l’agglomération Clermontoise (Clermont-Ferrand municipal public library). The project is technically sophisticated in many respects, since it involves strengthening the substructure of the existing building, working with the complex geometry of the new Forum structures built in the former main courtyard, and using very specific types of concrete. All this is being carried out with difficult access conditions for deliveries.
The new part of the building, known as the Forum, features a staircase that is a listed monument and will therefore remain. Behind it, Dumez has created a new three-level space designed to accommodate one floor of archives, along with technical rooms and public meeting areas, such as an amphitheatre and a Gallo-Roman-style theatre. What is unique about these spaces, accessible to all, are their structural elements – impressive in shape and size – created on site by our teams, as well as atypical features such as seating tiers and skylights in black concrete on several levels.
Another distinctive aspect is the colour of the concrete formulas used. At the request of English architect Stanton Williams, on the Forum’s walls we reproduced a geological cross-section of the ground layers, as found in the cavities of Clermont-Ferrand’s city centre. These strata of rock were formed by the volcanic eruptions of a nearby crater. The result is the alternating use of five shades of concrete, which were lab-developed by our concrete supplier. The challenge was to ensure that the formulas would provide consistent and lasting quality and colour over the plant’s production cycle, while meeting the technical specifications required for the concrete (strength, exposure). The teams also had to be extremely careful while pouring the concrete to ensure quality recovery. This is an unprecedented achievement using low-carbon concrete.
The construction team set a target to use 80% low-carbon concrete on this large-scale project. To date, 3,000 cu. metres of concrete have been used, 76.5% of which is low-carbon, supplied by our partner BML (Bétons des Monts Lyonnais) and formulated with CEM II/A and slag. This has saved more than 57 tonnes of CO2.
Structural work will be completed in mid-October 2024, with delivery scheduled for early 2026.
