The corrosion of steel in concrete exposed to maritime conditions is dependent on the rate of chloride penetration to activate the steel, the resistivity of the concrete and the oxygen diffusion through the cover regions. Reinforcement corrosion may result in spalling of the concrete depending on the depth of cover, the physical shape of the member and the strength of the concrete. The paper considers the mechanisms involved and relevant measurements made by the author's laboratory and others particularly in relation to offshore, coastal and land based concrete structures in the North Sea, UK and overseas. This work has implications both to the specification of concrete design details, inspection techniques and remedial measures where corrosion or damage has, or might occur.

This paper describes an experimental investigation into the behavior of sulphur-infiltrated concrete in a sodium chloride solution with respect to corrosion of the reinforcing steel. The plasticized sulphur-infiltrated concrete as well as the elemental sulphur-infiltrated concrete were used in the investigation. The electrical measurement, both for natural process and accelerated process, has been used in this study as the criterion for the determination of the time to corrosion. The minimum sulphur loading is determined for concrete with different water-cement ratios, above which, the corrosion of reinforcement in concrete will notoccur.

Deterioration of navigation lock wall concrete due to freeze/thaw cycles is a serious problem usually attributed to ineffective or a lack of air entrainment in the concrete. Most affected structures were made many years ago before air-entrained concrete was widely used. But, one of the largest locks in the world, Lower Monumental in Washington State, has been in service for only 10 years and also has serious surface deterioration. Conventional repair techniques of deteriorated surfaces call for removal of about 1 ft of face concrete, placing anchors and a reinforcing steel mat, and replacing the excavated concrete with new high-qualfty air-entrained concrete. However, at Lower Monumental, costs and repair time had to be taken into consideration. A coating which could be applied in a short period of time, could prevent continued freeze/thaw damage,.and be permanent under the adverse service conditions was needed. Six coatings of various portland cement and fine aggregate mixes were pneumatically applied to a section of the lock wall for evaluation. An accurate account of construction equipment, procedures, and production time was kept and "constructability" by these methods was evaluated. Total coating of the interior lock wall with a suitable latex-modified fiber-reinforced material was to be done in March 1980. This repair technique may be applicable to other structures, saving millions of dollars in construction costs and lost shipping time.

Tests have been carried out to determine the fatigue life of Torbar cold worked reinforcement in concrete beams in a seawater environment at a loading frequency of 0.1 Hz (near wave frequency) and also at 3.0 Hz so that long endurance tests at low stress ranges could be accomplished within a reasonable time scale. The adoption of a mechanical loading system offered a considerable saving in construction and running costs of the rigs compared with conventional servo-hydraulic systems. It also simplified the arrangements for tests at a simulated water depth of 30m which were performed in a purpose made pressure chamber. The results have indicated that the fatigue life of Torbar in seawater is lower than in air when the test duration is greater than 1 to 2 months when the conditions exist for a fatigue crack to initiate at a corrosion site. A significant feature of the research was that the beams exhibited the phenomenon of 'cyclic stiffening' resulting from a build up of deposits in the cracks in the concrete. This caused a progressive reduction in the deflection range, the applied load range remaining unchanged. While the stress range in the Torbar was correspondingly reduced, corrosion was not inhibited.

The paper discusses the results obtained by testing concrete quality and the degree of reinforcement protection in the piles of the submarine tunnel for the Coke Plant at Bakar, and in the walls of the water intake for the Rijeka Thermo-Power Plant, both placed by the tremie method. The shafts of the high chimney stacks of the Rijeka Thermo-Power Plant and the Bakar Coke Plant, erected by slip forms, were similarly investigated. The results obtained by tests and observations show that concrete for thin and highly-reinforced elements, to be placed by tremie, must be made with pure portland cement, or portland cement incorporating slag, having a low need of water for standard consistency, (measured according to Vicat), and with clean well-graded sand and coarse aggregate. Otherwise, mass concrete structures are preferred. Slipform erection of structures by the sea should be avoided, or, if used, the surface of the concrete should be protected additionally and completely (while slipform advancement is still under way) with cement mortar reinforced by the addition of polymer binders . This operation must be planned at the design stage and clearly specified.