Environmental actions on concrete exposed in marine and road environments and its response - Consequences for the initiation of chloride induced reinforcement corrosion
Doctoral thesis, 2003
The object of the study presented here has been to describe, further explain and model the influence of the exposure conditions on reinforced concrete structures and the consequences on their expected service life. The focus has been on investigating and quantifying the exposure conditions for structures in marine and road conditions exposed to chloride ions. This has been done by literature studies complemented by field studies, where data on the behaviour of concrete have been gathered and analysed. The literature study has shown that the exposure conditions have a large influence, e.g. due to variations in the severity of exposure to chlorides.
Field studies have been made in both marine and road conditions, where the influence of the exposure conditions has been measured as the environmental response of concrete and mortar. In marine conditions identical concrete specimens, exposed at different submerged locations, have been investigated. The results show that the temperature of the seawater has a large influence on chloride ingress. In road conditions both existing structures and specimens have been investigated. The results show that the exposure to chlorides and the chloride ingress into concrete depend on several factors, e.g. height above and distance to the road and surface orientation towards traffic.
Service life predictions have been made for structures in marine and road conditions, to exemplify the effect of the exposure conditions. The results of the predictions show that the exposure conditions have a large influence on the expected service life. The predictions also showed that the level of the chloride threshold level, Ccrit, has a large influence on the predicted service life.
The environmental actions, and their variations, have been found to have a large influence on the chloride ingress into and the service life of reinforced concrete structures. Therefore it is not enough to describe these by rough divisions into exposure classes, but instead the true exposure conditions should be taken into account. Preferably each structure should be treated separately, but this is usually not possible. For these structures the methodology described in this thesis can be used to describe and model the environmental actions.
service life predictions