Sandrini Metalli selects ArcelorMittal's Granite^® HDXtreme for road tunnel refurbishment

When the Maritime Alps Department in southern France was looking to refurbish two road tunnels in the Provence region, Italian company Sandrini Metalli proposed Granite^® HDXtreme from ArcelorMittal Europe – Flat Products. This organic coated steel was the preferred material to line the ceilings of the tunnels, protecting traffic from water infiltration and enhancing safety. Granite^® HDXtreme is an ideal choice as it can withstand the humid atmosphere in the tunnels and the corrosive atmosphere created by passing vehicles.

Sandrini Metalli is a family-owned business with more than 70 years of experience in profiling material for roofing and facade solutions. [Copyright: Sandrini Metalli]

Built in the early 1990s, the Tunnel de la Mescla (1,014 metres long) and Tunnel du Reveston (330 m) had never been lined. This enabled ground water from the mountain above to infiltrate the rock and drip onto the roadway below. As part of an overall refurbishment of the tunnels, the Maritime Alps Department decided to line the ceilings of the tunnels, redirecting water to the sides where it can be drained away easily.

Sandrini Metalli proposed organic coated steel from ArcelorMittal Europe – Flat Products for the refurbishment of the Tunnel de la Mescla and Tunnel du Reveston. [Copyright: Sandrini Metalli]

Granite^® HDXtreme withstands corrosive tunnel environment

“Our customer had specified that a galvanised material should be used for the ceiling lining,” notes Marco Savoldelli, Building Division Manager for Sandrini Metalli. “From our extensive experience, we knew that a simple batch-galvanised metal would not withstand the tunnel environment. Instead, we recommended Granite^® HDXtreme for this application. The customer was happy with this solution – in part because ArcelorMittal is a well-known brand in France with a very high reputation.”

Granite^® HDXtreme was the preferred material to line the ceilings of the tunnels, protecting traffic from water infiltration and enhancing safety. [Copyright: Corte Aperta s.r.l.]

As with all public projects, guarantees and value for money were key considerations when it came to material selection for the two tunnels in France notes Marco Savoldelli: “Granite^® HDXtreme has a strong paint layer which is a big advantage over standard batch-galvanised material. That paint layer allows the metal to withstand corrosion, even in maritime environments. This allowed us to offer a guarantee which was in-line with the customer’s expectations.”

The customer selected G735X (light grey) as the final paint colour for the new ceiling explains Marco Savoldelli. “The colour increases the reflectivity of light in the tunnels without being too bright. A satin finish with a reflectivity of 15 gloss units was specified to avoid distractions for drivers.”

External solution for interior project

To ensure the long-term viability of the ceiling, the organic coating was applied to both sides of the steel. “This protects the reverse side of the ceiling from the effects of water infiltration,” notes Marco Savoldelli. “Humidity and pollution are still an issue, this is an internal application for a product that is normally used in external applications in more corrosive environments. We are confident that Granite^® HDXtreme is the perfect product for this application.”

To ensure the long-term viability of the ceiling, the organic coating was applied to both sides of the steel. [Copyright: Sandrini Metalli]

Sandrini Metalli formed the Granite^® HDXtreme into their standard ‘SAND 28’ profile which is typically used for roofing and facade solutions. “We tailored the bending of the profiles to accommodate the different radii of the tunnels,” says Marco Savoldelli. “This was done in our own manufacturing facilities in northern Italy before the steel was transported to France for installation.”

Today Sandrini Metalli employs circa 150 people and operates four manufacturing facilities in the north of Italy. [Copyright: Sandrini Metalli]

Sandrini Metalli formed the Granite^® HDXtreme into their standard ‘SAND 28’ profile which is typically used for roofing and facade solutions. [Copyright: Sandrini Metalli]

The two tunnels reopened to traffic in July 2024 and will carry around 4,900 vehicles daily. The sides of the tunnels will be left as bare rock.

Granite^® HDXtreme is an ideal choice as it can withstand the humid atmosphere in the tunnels and the corrosive atmosphere created by passing vehicles. [Copyright: Corte Aperta s.r.l.]