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This paper describes the results of a ten-year marine exposure test of reinforced concrete. Sixteen pre-cracked test specimens were examined. The target crack width was 0.2mm. The dimensions of the specimens were 15x15x100cm. Ordinary deformed bars and epoxy-coated deformed bars, as well as normal portland cement and portland blast-furnace slag cement were used. The water-cement ratio in the mixture proportions ranged from 0.320I to 0.483%. The effect of nitrite-based corrosion inhibitor was also examined. From the exposure test results, the following conclusions were drawn: When the water-cement ratio was low, the penetration of chloride ions into the concrete was low; the chloride-ion content on the surface of blast-furnace slag cement concrete was greater than on the surface of concrete made with ordinary cement, but was smaller inside; there was a tendency for the chloride-ion content around the reinforcing bars in concrete portions with small cracks to be greater than in portions with large cracks; ten years of exposure caused an increase in crack width due to the corrosion of the reinforcing bars; although the effectiveness of epoxy-coated reinforcing bars in preventing corrosion was obvious, severe corrosion was found in one coated bar. The epoxy-coated bars used were produced for the first time in Japan, and test results indicate that there were problems with the early production technology; there was no beneficial effect from corrosion inhibitor after ten years.

In Australia, the Cement and Concrete Association has sponsored a number of research projects addressing aspects relating to deterioration of concrete structures caused by corrosion of the reinforcement. The overall objectives of these projects were to identify the factors influencing steel corrosion and to quantify their effect on initiating corrosion and on the rate of corrosion. The ultimate objective was to provide practicing engineers with the relevant parameters that can be used in the design and specification of concrete structures to minimize the risk of corrosion of reinforcing steel. Reviews the major corrosion research carried out in Australia. Article attempts to correlate research findings to the conditions in practice and to quantitatively predict design life of reinforced concrete structures in an environment simulating severe exposure conditions in Australia. The design life predictions presented should be considered within the context of the assumptions and approximations made. Data presented in this paper showed that the influence of binder type is more in the medium-strength concretes in terms of time to potential jump (initiation) and corrosion rate (propagation). Therefore, it is recommended to optimize concrete mixture proportioning with respect to binder type in this range of concrete strengths to utilize the benefits possible from different binders.

A design method for avoiding damage due to carbonation-induced corrosion of steel reinforcement in concrete is described. It accounts for the initiation period, during which a carbonation front penetrates the cover concrete, and a propagation period, during which the reinforcement corrodes and produces visible cracking of the concrete. The initiation period is controlled by diffusion of carbon dioxide through the carbonated concrete and is dependent upon the depth of cover, the gas permeability of the carbonated cover concrete, and the quantity of cement hydrate available to buffer the carbonation reaction. The rates of carbonation and reinforcement corrosion are dependent upon the relative humidity within the cover concrete. Estimates of carbonation depth give a reasonable upper bound to a wide range of field measurements. Corrosion rates are estimated on the basis of an upper bound to a range of published laboratory and field data. A sensitivity analysis showed that the main factors influencing the choice of concrete quality were the exposure conditions, depth of cover, and the notional service life: the effects of curing period and cement type were less significant. Estimates of concrete quality for selected combinations of exposure, cover, and service life were compatible with those being considered for European codes and standards. The design method can be used to examine alternative combinations of cover, concrete quality, cement type, and curing period for providing a given notional service life under selected exposure conditions.

The corrosion of steel in reinforced concrete due to the ingress of chlorides is a major cause for the decreased durability of structures built in marine and deicing salt environments. A multitude of research has been conducted to evaluate the corrosion of steel in concrete and to develop protection systems to arrest this process. This paper critically discusses some of the more popular techniques and presents new data illustrating the importance of selecting the right corrosion tests.

A joint project of the Reinforced Concrete Research Council (RCRC) and the U.S. Army Corps of Engineers Waterways Experiment Station (WES), covering four field exposure test programs at Treat Island, Maine, was initiated in the 1950s. Two of these addressed tensile crack exposure tests for reinforced concrete to determine the effects of severe natural weathering on the performance of stressed and tensile-cracked reinforced beams. The "Series B" test program, begun in 1954, consisted of 76 reinforced concrete beams. The test variables were location of the reinforcing steel in the concrete beam at the time of casting, its deformation patterns, and the degree of tensile stress. Condition surveys were carried out annually and stopped in 1979. The physical condition and state of corrosion of the ``Series B" beams were investigated by the authors in October 1989 after a period of 10 years of unattended exposure. The overall physical condition of the beams was evaluated as severely damaged, mainly due to the repeated cycles of freezing and thawing. The damage patterns for the yoked (stressed) and control specimens were distinctively different. Six out of the thirty-two sets of yoked pairs had failed, the failure of four sets took place after 1979. Corrosion of reinforcing steel in concrete is considered to be mainly a consequence of the physical deterioration of the concrete. The overall condition of the embedded steel was evaluated as reasonably good considering 35 years of exposure in a severe marine environment.