Bridges, viaducts and other road and rail works constitute a strategic infrastructural heritage, often not without historical, architectural as well as functional value. For the same reason equally frequent are the interventions dictated by the need to maintain them in efficiency, restore any phenomena of degradation, adapt their performance and safety.

One of these examples is the Pianello Bridge located in the municipality of Muro Lucano (Potenza - Italy), one of the first reinforced concrete bridges built in the South of Italy, for the reinforcement of which RureGold structural solutions, based on FRCM composite materials, were used. RureGold specialises in systems for reinforcing concrete and masonry structures with FRCM (Fiber Reinforced Cementitious Matrix) solutions, consisting of long PBO and carbon fibers with high performances, embedded in a special inorganic matrix capable of securing their adhesion to the substrate.

Built between 1916 and 1918 to replace a small medieval bridge, the Pianello Bridge still connects the district of Borgo Pianello with the hamlet of Capodigiano, 3 km from the urban center. The structural features of the work are those of an arched bridge, with an overall span of about 77 meters and a maximum height of about 105 meters. The main structure consists of four parallel parabolic arches having a span of 38.2 meters and a deflection of 11.2 meters, diposed at cross spacing of 1.3 m and mutually connected. Prominent on the four arches are the piers that, together with frames arranged outside of the arches and resting directly on rock, supporting the deck truss. The latter runs the entire length of the bridge with a continuous beam pattern on 21 supports at an average spacing of about 3.9 meters.

The advanced age of the structure, and in particular the extensive deterioration of the reinforced concrete of the support structure, necessitated timely intervention aimed at restoring and securing the structure. After a series of detailed tests and analyses aimed at investigate the effective state of preservation of the bridge, the choice of the designer, Eng. Rosario Cerone with, the A.P. Costruzioni of Casapesenna (CE), fell on RureGold reinforcement systems based on FRCM composite materials, which due to their technical and application characteristics appeared to be the most suitable ones for an intervention of a certain complexity also due to the characteristics of the site.

In the case at hand, the reinforcement system consisting of PBO-Mesh 70/18, a bidirectional PBO fiber mesh of 70 g/m2 in warp and 18 g/m2 in weft available in two heights (50 and 100 cm) and the inorganic fibered matrix MX-PBO Concrete, which allows for the optimal transfer of stresses from the structural element to the reinforcing mesh, was chosen.

The application of the system included the removal of the deteriorated parts of the concrete cover, the passivation of existing rebars and, where necessary, the volumetric reconstruction of the concrete cover and the subsequent application of the Ruregold system by laying the first coat of MX-PBO Concrete mortar, following the application of PBO-Mesh 70/18 by embedding it in the first layer of still fresh matrix and laying a second coat of MX-PBO Concrete mortar. A total of about 5,000 m2 of reinforcement was laid, which resulted in the restoration of the complete functionality of the structure.

THE CONSTRUCTION SYSTEM

FRCM Structural Reinforcement With PBO-Mesh 70/18
For the structural reinforcement of the bridge, the FRCM PBO-Mesh 70/18 reinforcement system consisting of the bidirectional 70+18 g/ m2 PBO mesh and the specific cement matrix MX-PBO Concrete was used. The system consists of a first 3-5mm layer of technical mortar and the PBO mesh covered by a second layer of mortar.

Thanks to the high performance of the PBO fiber and the mortar specifically formulated to ensure perfect adhesion to the system, structural reinforcement offers high reliability while improving the ductility of reinforced concrete elements.