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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.

Specifications relating to concrete durability have been emphasized in many recent codes of practice governing the design of concrete structures. Typical examples of this trend are noted in Australian Standard AS 3600, British Standard BS 8110, and a "Guide to Durable Concrete," reported by ACI Committee 201. Apart from the requirements of higher strength grades to insure required minimum water-cement ratios for aggressive environment exposures, some advantages offered by the use of blended cements have been recognized in these documents. The use of blended slag and fly ash cements in increasing worldwide and specific information on the long-term performance of such concretes in high-chloride environments is needed. Paper presents data on the long-term corrosion characteristics in high-chloride environments of reinforcement within a series of concretes individually incorporating a high C 3A ordinary portland cement, a low C 3A cement, a slag blended cement, and an ASTM Class F fly ash blended cement. The concrete performance has been assessed using electrochemical monitoring of corrosion of the embedded reinforcement by potentiodynamic anodic polarization and concrete resistivity. Comments are made regarding current North American, British, and Australian specifications for concrete under marine service conditions. From the data presented, the specification for long-term durability of concrete for marine conditions could be based on concrete resistivity with a suggested limit of around 5000 ohm cm at 28 days.

Concrete submerged in seawater swells. The expansion is larger in seawater than in fresh water. Due to the growing interest in deep seawater applications of concrete, an investigation was carried out on the behavior of concrete in seawater under pressure. Under high pressure, the swelling is greater and faster than under atmospheric pressure. The swelling can escalate to 1 percent in a few years. In saturated lime water, the swelling is far less than in seawater. From the various parameters investigated, the cement type appeared to be the most important. Blast furnace slag cement with a high slag content appeared to swell substantially less than normal portland cement.

High-alumina cement (HAC) mortars, made at 5, 20, and 40 C, were mixed using seawater, deionized water, and reconstituted seawater. The admixtures used were an accelerator, superplasticizer, antiwashout, air-entraining and waterproofing admixtures, and an ethylene-vinyl acetate (EVA) polymer latex dispersion. Results on short-term (1 year) durability against freezing and thawing and wetting and drying in all three waters are presented and compared to the performance of the same combination over 3 years at a maritime exposure site. The samples with polymer latex performed poorly in most tests, while the control and samples with accelerator and superplasticizer performed well in both laboratory exposure conditions and on the maritime site. Temperature of mixing and curing is very important in both the early and long-term performance of HAC, but the interactions between the effects of admixtures and conditions mean that it is obligatory to carry out durability tests on any proposed combination before a decision is made regarding materials selection.

In France, a study of the behavior of cements in marine structures was initiated in 1902 with the creation of the Commission on Lime and Cements. This led to the establishment of specifications concerning the composition of cements for projects in the sea, designated as "seawater-setting." Over the years, the specifications have been modified in light of the results of research and full-scale testing in French maritime laboratories. A program of the study of resistance to seawater of cements with different mineralogical compositions was begun in 1975. This program included experiments in artificial seawater in laboratories and in water of the Le Havre Channel, and was to last for 20 years. Its purpose was to examine the behavior of cements at the limits of specifications to either confirm their soundness or make certain modifications. After 15 years, it can be concluded that the accelerated test of swelling on 2 x 2 x 16-cm specimens is sound, since it made possible the elimination of cements containing about 14 percent C 3A after 1 year, demonstrated the influence of SO 3 content at 2 years, and made possible the classification of portland cements according to their long-term behavior as early as 2 years. The results of sonic measurements on concrete specimens exposed to seawater in a tidal zone show the excellent behavior of cement with 80 percent slag and a low-lime content, and of portland cements with a C 3A content of less than 4 percent.