1982. Cover to steel reinforcement for floating concrete structures. (PDF)

Designers of fixed concrete structures at sea realise that cover acts as a safeguard against corrosion. Repair of this type of structure can be very costly; in general, the deadweight allows for a generous cover, and with a cover of over 50 mm the tolerances are not so critical that extra costs have to be spent on workmanship and quality control.

As for floating structures, the situation is completely different. For fixed floating structures, and even more for concrete ships, the deadweight has to be as low as possible; repair and maintenance by drydocking is possible and not excessively costly, and therefore the economical and technical optimum for the cover can be different from that of gravity structures.

Much research has been carried out and, fortunately, some long-term field experience is available from concrete ships that have been exposed for many years.

In our Commission, discussions often took place between engineers familiar with heavy-weight gravity structures, starting from 70 mm cover, and supporters of floating structures, who advocated 15 mm cover. I am happy that between these two positions an appreciation of both attitudes has developed.

A fundamental contribution is presented in this report, in which a mathematical solution is given for the diffusion of chloride into concrete, depending on permeability, thickness of cover, time, and carbonation.

The Working Group has been very actively chaired by K. Finsterwalder, but I would also like to mention the contributions to the discussion by A. Anderson and W. A. Ingraham.