Concrete structural elements of bridges or tunnels may be in contact with water containing chloride during the winter. Furthermore, marine structures are permanently exposed to seawater containing chlorides. In all these cases, penetration of chlorides through the covercrete is a major risk and the service life of structures may be reduced considerably if permeability is too high. Early repair measures are both an economical and an ecological problem nowadays. By adding appropriate admixtures to the fresh concrete, it is possible to produce an internally water repellent material. It is shown that it is possible to substantially reduce chloride penetration through ECC (Engineered Cementitious Composites) in this way, thereby considerably extending the service life of new structures and of repair layers. The properties of the modified ECC are described in detail.

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