Low-Carbon Durable Concrete for the New Genoa’s San Giorgio Bridge
Gilberto Artioli, Anna Bravo, Stefano Broggio, Giorgio Ferrari, Francesco Santonicola, Francesco Surico, Luca Torelli, Luca Valentini, Andrea Zecchini
Appears on pages(s):
carbonation, chloride penetration, durability, homogeneous nucleation, microstructure, PCE-nanocomposites, water permeability
The new San Giorgio bridge replaced the Polcevera viaduct, built between 1963 and 1967 and collapsed during a storm in summer 2018. The new bridge was designed by Renzo Piano and is made by 19 steel spans supported by 18 concrete pillars. Beside the architectural aspects, special attention was devoted to the mix-design of the pillars, to ensure the production of durable concrete in the marine environment. The use of slag cement combined with limestone filler and polycarboxylate superplasticizers allowed to cast flowable concrete associated with low water to cement ratio and high final compressive strength. A new generation accelerating admixtures, working on the homogeneous nucleation technology, was used to accelerate the cement hydration and gain early compressive strength to speed-up the elevation of the pillars. In the present paper, the advantage of using the new admixture is discussed both in terms of early strength development and microstructure of the cement paste. Beside the improvement of the early strength development, the new admixture reduced the water permeability and the chloride diffusion and improved the resistance to carbonation of the concrete used for the pillars, with further advantages for the durability of this structure.