Modern concrete materials are generally characterised by durability qualities. However, under certain circumstances the interaction with water may lead to serious chemical alterations which shorten the service life of buildings. In the case of tunnels and other underground constructions the costs for renovations are extremely high. In order to initiate protective countermeasures against corrosive damages it is important to understand the deterioration processes.
Although concrete corrosion has many different faces, there are some general phenomena, which are observed in most field studies of deteriorated concrete.
The objective of the project is an investigation of damage mechanisms that lead to concrete corrosion.
In this study the underlying mechanisms of short and long term concrete-water interactions in selected tunnel buildings are investigated which lead to deterioration of corrosion.
Based on the description of macro- and microscopic textures and the chemical alterations, a succession of corrosive reactions are postulated. The reactions include leaching and dissolution, transportation, (re)precipitation and formation of new products.
Thereby it is important to note that physical parameters like permeability or inhomogeneities are at least as important as chemical parameters like the composition of the paste, pH-values and composition of the interacting water or the pore solution.
The observed textural relationships indicate that chemical attack is triggered by permeable inhomogenities which serve as pathways for the percolating water. Leaching and dissolution of the cement paste seems to be restricted to the neighborhood of these pathways. Inhomogenities, permeability, porosity and the flow rate of water are considered as first order parameters which determine wheter or not serious deterioration occurs.
Investigation of damage mechanisms that lead to concrete corrosion.