Projects / 4/30/2025

Structural strengthening with MapeWrap C UNI-AX on a bridge over the River Buthier in Aosta

The MapeWrap C UNI-AX system enabled structural strengthening work to be executed quickly on the beams of a bridge over the River Buthier in the Aosta Valley, in time for a famous local festival

The MapeWrap C UNI-AX system by Mapei was chosen for consolidation work on the Buthier bridge in Aosta. FRP materials and epoxy resins guaranteed effective strengthening, high shear strength and safety for heavy traffic. The work, which was executed quickly and completed during the winter, enabled the bridge to be reopened in time for the Festival of Sant’Orso.

The River Buthier is a tributary of the River Dora Baltea which flows through Aosta in Northern Italy and has a deeply rooted bond with the history of this city. Aosta, in fact, developed on a geological formation known as an “alluvial fan”, which was created by the accumulation of sediments transported by the river, influencing its geography and urbanisation. In Roman times the River Buthier flowed under the famous Stone Bridge, an engineering masterpiece that connected the two banks of the river and was part of the access system to the city. Over the centuries the river continued to influence the life of the city, as both a source of water and as part of the urban landscape.

Nowadays, various bridges in the Aosta territory cross this river and one of them, the road bridge in Via Lavoratori Vittime in Col du Mont, was reopened to traffic this year on 7^th January upon completion of consolidation work by the company VdA Structure.

Corrado Trasino was commissioned for the project design, who worked alongside Mapei Technical Services to ensure the structural strength of the bridge would be sufficient to withstand the expected stresses and loads. For the project, an important step in improving the safety and functionality of the local road network and guaranteeing a higher load capacity for the heavy traffic, a complete system by Mapei was employed, MapeWrap C UNI-AX, to ensure the structural strengthening of the reinforced concrete beams of the bridge would be sufficient.

A tried and tested strengthening system applied with success

The system proposed by Mapei, MapeWrap C UNI-AX, involved the use of FRP (fibre-reinforced polymer) composite materials, in this particular case uni-directional carbon fibre fabrics and epoxy resin to impregnate and bond the fabrics. This is an innovative system which is ideal for use in work, such as on the Buthier Bridge, where the improvement of the shear strength of concrete or masonry elements needs to be guaranteed.

The strengthening work on the bridge started by cutting the MapeWrap C UNI-AX fabric to the required dimensions.

The strengthening work started by preparing the substrates and cutting the MapeWrap C UNI-AX fabric to the required dimensions. Because work on the bridge started in the middle of winter, the substrates and resin were heated beforehand with industrial blowers to keep their temperature constantly above 5°C for the entire duration of the work.

Before applying the fabric, the substrates were treated with MapeWrap Primer.

The substrates were then consolidated with MapeWrap Primer epoxy primer and levelled off with MapeWrap 11 epoxy grout.

The surfaces were levelled off with MapeWrap 11 epoxy grout.

The next step was to apply MapeWrap C UNI-AX 600 W fabric, which was impregnated and bonded with MapeWrap 31 epoxy adhesive.

MapeWrap 31 epoxy adhesive was used to impregnate and bond the carbon fibre fabric.

To improve the connection between the fabric and the structure and prevent delamination phenomenon, structural connections were created by using MapeWrap C Fiocco 10 mm uni-directional carbon fibre cords that were inserted into holes drilled in the structure and then splayed out over the fabric applied previously.

The MapeWrap Fiocco carbon fibre cords were inserted into holes and then splayed out over the MapeWrap C UNI AX fabric to improve the connection with the structure.

So many advantages with MapeWrap C UNI-AX system

Use of the MapeWrap C UNI-AX system guaranteed numerous advantages: unlike work carried out using traditional techniques, it is characterised by the extremely low weight of the fabric and a smaller team of workers is required for application. In addition, application may be completed extremely quickly: in the case of the bridge over the River Buthier in Aosta, the structural strengthening work was completed in just a few days, thereby overcoming the problems arising from low shear strength and improving the mechanical properties of the beam.

This work enabled the load-bearing capacity of the bridge to be upgraded to the required level, reopen the bridge to traffic and guarantee that all activities related to the Festival of Sant’Orso at the end of January could go ahead in complete safety, a millennia-old tradition that Aosta dedicates every year to traditional local crafts, enriched with folklore shows, music and sampling of delicacies typical of the Aosta Valley.

The use of the MapeWrap C UNI-AX system allowed the structural strengthening work on the bridge to be completed in time to ensure that the traditional Saint Orso Festival could go ahead safely. Photo credits: La Saint Ours.