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The writer was given the assignment in May 1984 of writing a new Florida concrete bridge design and construction criteria for final approval by the United States Federal Highway Administration (FHWA). Consideration was given to developing standard criteria for structure elements, such as pilings, footings, bridge decks, columns, and girders, to provide durable elements when exposed to sea or brackish water. Policy had to be developed that would be cost effective yet still provide adequate protection. Criteria were written and submitted by the writer, who chaired a committee for this purpose to representatives of the Florida concrete industry for response before final submittal to FHWA for approval. Provision was made to use the criteria on a few key projects in Florida in 1985 and 1986. The criteria are discussed in detail in the paper.

In coastal areas of Saudi Arabia underground reinforced concrete structures are frequently exposed to aggressive action of saline water and sulfate-bearing groundwater. The extent of deterioration varies from negligible to very severe depending on the type of exposure and the concentration of sulfates and chlorides, as well as the quality of concrete. Deterioration of concrete is mainly due to aggressive action of magnesium sulfates, mitigated by chloride ions, and the decomposing effect of calcium sulfates from sulfate-bearing groundwater. The procedures employed to evaluate nature, extent, and rate of deterioration consisted of a condition survey, chemical analysis of groundwater and water-borne precipitates, petrographic analysis of concrete cores, and structural evaluation of the in-place concrete. After unsound concrete is replaced and deficiencies repaired, protection from further deterioration can be achieved by tanking the surfaces with several layers of hot-applied coal tar reinforced with felt and by the installation of a subsurface drain system.

ASTM C 672 scaling tests were carried out on concretes containing 0, 5, and 10 percent silica fume, and with air-void spacing factors in the 100 to 200 æm range. Two methods of curing were compared: 7 days in water and the use of a curing compound. Water containing 2.5 percent sodium chloride was used for the scaling tests, as well as pure water. Results indicate that, although scaling tends to increase with the silica fume content, silica fume concrete can have a fair scaling resistance, and also that specimens cured in water, regardless of the silica fume content, have a lower resistance to scaling than specimens cured with a membrane. Considering previously published data by two of the authors, results further show that the critical air-void spacing factors obtained from ASTM C 666 (Procedure A) freeze-thaw cycle tests are not applicable to scaling. Spacing factors required for good scaling resistance are generally lower than those required for freeze-thaw cycle durability, and total protection against scaling does not seem possible. A short review of the literature confirms that critical spacing factors are usually higher than 200 æm.

Presents results of accelerated freezing and thawing tests on non-air-entrained concretes containing chloride when tested in water and seawater, in accordance with ASTM C 666, Procedure A. A total of 25 concrete mixes were made. The water-cement ratio of the mixes was 0.55, and the percentage of chloride content as NaCl were 0, 0.1, 0.3, 0.5, 1.0, 3.0, 5.0, and 7.0 percent of the oven-dry sand by weight. Mixing water was replaced by the seawater to add NaCl to each concrete mix. A number of test cylinders were made for testing in compression at various ages, and the test prisms were cast for determining their freezing and thawing resistance. The fundamental transverse resonant frequency, the weight, and the length change of the test prisms were measured during the freezing and thawing test. The air-void parameters of the hardened concrete were determined for using sawn sections of the test prisms. The pore-size distributions of the hardened concrete were measured by a mercury porosimeter. The test results indicated that the freezing and thawing resistance decreased with increasing chloride content in both water and seawater. The air-entrained concrete containing less than 0.3 percent NaCl showed a good freezing and thawing resistance. The air-entrained concrete containing more than 0.5 percent NaCl did not perform satisfactorily in freezing and thawing tests conducted in water and seawater.

Describes a laboratory investigation of concrete to determine the effect of the various brands of Type 10 portland cement with and without interground limestone on the strength and freeze-thaw durability. Two classes of concrete and two combinations of aggregates were used in the investigations. A variation in the strength of concrete made with the various cements was found. The limestone addition increases the concrete strength. Concretes made with each of the cements had very good resistance to freezing and thawing in water. However, there was a considerable variation in the resistance to salt scaling.