From Sunday, June 11 to Thursday, June 15, as part of the EP22 Campaccio project, CS Consortium (CSC-Specogna) teams will perform a delicate and essential operation overnight. It involves the pouring of ultra-high-performance UA-type fiber-reinforced concrete on the deck of the approximately 290-meter-long North-South Viaduct of the same name. The various operational steps are explained in detail below:
- An operation with several phases
The casting of ultra-high-performance fiber-reinforced concrete (UHPFRC) on the deck of the phase 3E viaduct at the EP22 site in Campaccio, Ticino, involves a series of complex steps in order to enable the optimal fabrication of a 4cm-thick UHPFRC reinforced cap for reinforcing the existing platform and related widening.
The preparatory stages of the surface involve mechanical roughening of the platform and subsequent cleaning with high-pressure water. Finally, the reinforcement of the stage to be cast overnight is laid.
The UHPFRC production plant is installed downstream, in an area adjacent to the paving to minimize transshipment time; the mobile plant uses premixed Big-Bags whose recipe has been previously certified.
Traffic is interrupted on the entire north-south roadway to prevent vibrations created by adjacent circulating traffic from disrupting the newly placed material.
UHPFRC is transported by dump truck from the plant mouth to the casting stage. The 11 CS Consortium employees can then spread the 4cm of UHPFRC evenly by vibrating screed. The laying operation for a single stage of about 55m in length must finish by 1:00 a.m. so that the adjacent lane can be opened to vehicular traffic at 05:00 a.m.
Post-treatment involves applying a layer of Sika Antisol E-20, wetting the surface and covering it with plastic sheeting to prevent excessive drying of the surface.
- An important and unusual phase
This is a special job because of the special nature of the material to be placed whose consistency is "sticky."
Ultra-high performance fiber-reinforced concrete (UHPFRC has very interesting characteristics, such as strengths, both compressive and tensile, that are much higher than conventional concrete. In compression, the minimum strength at 28 days is 120 MPa, but in practice much higher values are reached. Moreover, after only 24 hours, the strength is already above 70MPa. In tensile strength, UA-type UHPFRC achieves a minimum strength of 7 MPa and is mainly characterized by work hardening behavior, which, if desired, easily allows the fabrication of structural elements without slow reinforcement.
The high strengths just mentioned and the very small diameter aggregates allow the construction of very thin elements, even with special shapes, with important material and weight savings, as well as very interesting architectural potential.
Last but not least, UHPFRC has a very dense and compact structure that makes it waterproof and significantly increases its durability over time.
- Some information about the EP22 Campaccio project
- Date of work: 2019 - 2024
- Type of work: Conservation and modernization work on the existing route and widening of the two Campaccio viaducts for a total section of 1.8 km, along the N02 highway north of the Mendrisio interchange, from km 8.200 to km 10.000.
- Client: Federal Roads Office FEDRO
The work, carried out by an average of 20 CSC employees with maximum peaks of 40, consists of upgrading the structures, roadway and safety barriers, correcting the cross slopes of the roadway according to current regulations, in particular by creating rigid banks on the Campaccio viaducts, upgrading the rainwater collection network and constructing two new roadway water treatment plants (SABA), as well as upgrading the operating and safety equipment (BSA).
The total cost of the project is about 70 million Swiss francs of which 32 million Swiss francs has been deliberated to the CS Consortium (CSC - Specogna).
1/ Start of work
In September 2021, work began on the exterior of the highway embankment with the construction of the road stormwater treatment facilities (SABA, from the German StrassenAbwasserBehandlungsAnlage), the erection of the scaffolding under the viaducts, and the structural reinforcement of the supporting shoulders of the viaducts.
2/ Main works
In spring 2022, the main works on the South-North carriageway were carried out.
In 2023, works on the opposite carriageway, North-South direction, are being carried out, while the summer period of 2024 will be used to finally complete the traffic island divider with the installation of the final gutter for water evacuation.