| Popis: |
Concrete panels are often used along tunnel walls for technical and aesthetic purposes. Generally, the environment in contact with such materials is aggressive. Emission gases from the vehicles, sulphates, chlorides coming from the winter salt spreading, high temperature and humidity promote an acceleration of the deterioration phenomena. In this work 30 years old concrete panels placed along a 16 km long highway tunnel across the Alps were investigated with respect to their durability. The focus was given to the tunnel entrance zone. This region of the tunnel exhibited a critical environment with respect to the durability of the cementitious material and the steel rebar. An asymmetrical physical leaching caused by the water droplets transported by the vehicles was observed for the cementitious binder along the wall panels on the entrance lane of the tunnel. The concrete panels placed more inside the tunnel were less prone to degradation because of the higher temperature and reduced humidity. The lower part of the panels were susceptible to chloride degradation and rebar corrosion because of the presence of humidity from the splash zone. The upper part of the panels were more exposed to carbonation degradation and induced rebar corrosion caused by the increased dry atmosphere. The sulphate content slightly increased on the surface. This derived from the tunnel atmosphere in addition to the sulphate present within the cementitious material. The degradation type, the intensity and the distribution contributed to plan reasonable restoration and material replacement with a limited closing time of the important and busy roadway. |
