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Inspections were carried out on 64 normal weight reinforced concrete structures situated along the North Sea coast of the Netherlands. Nearly all had been made with various amounts of blast furnace slag cement. At the time of inspection the ages ranged from 3 to 63 years. Visible signs of deterioration above the low water level were looked for, such as, spalling of the concrete surface, corrosion of the reinforcement and cracks. Also, the concrete cover and the depth of the carbonation were measured at some places. From 5 of these structures cores of 16 to 49 year old concrete were taken, and their compressive strength, the depth of carbonation, total porosity and cement content were determined. In addition, the amount of chloride penetrated into the concrete as a function of the depth was measured, both away from cracks and near cracks. Conclusions are given herein as to which properties appear to be decisive for the durability of such structures in the sea environment.

This report describes laboratory and field tests on the corrosion preventive effects of resin coating, galvanizing, cathodic protection, concrete surface coating and commercial inhibitors used as a protection measures for steel in concrete. The following conclusions were drawn from the test results: (1) The best in protective performance among the epoxy coatings is the powder epoxy. For protective performance, a coating thickness of 150um or greater is required, but for good bond to concrete, the thickness is preferably less than 150um. Thus the coating thickness of 150um is considered to be optimum. The liquid type tar epoxy coating is not satisfactory in its protective performance or for bond to concrete. (2) Galvanization gives good protective performance but is not always satisfactory at the splash zone. (3) Cathodic protection has an excellent protective effect in the tidal area and in seawater. The voltage to be applied is preferably -1000 to -1200mV. When it is higher than -800mV, the effect is not satisfactory, and when lower than -1500 mV, over-protection may result. (4) Urethane coating over the concrete surface failed to give a satisfactory cutoff effect in the tests and proved to be of no protective value. (5) Sodium sulfite series inhibitors had no protective effect.

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.

Different types of blast furnace slag cement with increasing amounts of slag were tested for sulfate resistance according to the ASTM C 452, the Koch and Steinegger test and the Mehta test; the results were compared with the performances of portland cement under same conditions. The evolution of the strengths as a function of time and of composition of the liquid phase (sea water or salt solution of 5% Na2S04 - 5% MgS04 and 5% MgC12 ) was investigated on mortar bars. The conclusions are that the chemical resistance of the blast furnace slag cement improves with the slag content; a high fineness of grinding improves both the chemical resistance and the mechanical strength. Exemples of marine structures made with blast furnace slag cements in the Netherlands are given. Some of these structures are more than 50 years old and still in an excellent condition. The best chemical resistance is obtained when the slag content of the cement is higher than 65-70%. This is imputable to the fact that, in these conditions, the formation of ettringite is impossible, due to the low content of free calcium hydroxide in the cement paste. A magnesia content of the slag higher than 5% is harmless, because Mg0 is entirely in the glass phase and not present as the expanding periclase variety.

This paper presents data, based on extensive rehabilitation of the underside of concrete pier in the harbor of Portland, Maine, of the compressive strengths of shotcrete used as the sole repair material. This paper reviews the principal causes of damage to concrete in a marine environment, including erosion by "scour action," alternate wetting and drying in the "splash zone" and the problems resulting from intrusion of the salts contained in sea water into the concrete. Recommendations as to proper proportioning and mix designs for shotcrete to be used as the repair material for such structures is presented as well as criteria for the use of accelerating admixtures in the shotcrete material. A discussion of the use of both latex modified and calcium aluminate cement shotcrete for rehabilitating deteriorated concrete in an aquatic environment is offered. This paper also considers the proper preparation of the surfaces to be repaired as well as the special problems associated with the placement of shotcrete while working in areas subjected to tidal and wave action.