In Japan in this decade the early deterioration of concrete structures due to salt-attack, in which re-bars in concrete get corrosion by the effect of chloride ion, has been a very big problem. The countermeasures to the salt-attack has been studied widely and recently it is thought very important that the countermeasures should be considered in constructing of concrete structures. This paper describes the history of the treatment of chloride in concrete, and outlines and explanation of the countermeasures in present specifications for both building concrete and public works concrete. And it also introduces the draft of the manuals for repairing method for salt-attacked structures proposed through the research project of the Ministry of Construction.

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The quality of aggregate have mighty influence on properties of the high strength concrete. But it is not proved which quality of aggregate have influence on property of the concrete. This paper covers the influence of the quality or the kind of aggregates on compresive strength, static modulus of elasticity and the resistance against freezing and thawing action of the high strength concrete under the past research reports. And, this paper shows about the present situation of research and the way of the thinking on selection of aggregate used for the high strength concrete.

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The quality and durability of repair materials (coating, patching and corrosin protection materials) for concrete structures have not been clarified. Moreover, a method of evaluation has also not been established. Exposure tests and indoor tests were conducted to verify the characteristics of the repair materials that are available. These results show that those materials have wide variations in quality and also that some of these materials fail function and durability standards as repair materials. On the basis of these test results, this report proposes standards for coating materials.

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The new and large Tokyo underground station for keiyoline is now under construction on the south side of the existing Tokyo Station and under the city road No. 406. The Yokosuka line shield tunnels, which intersect the underground station, should be supported by B3 slab of the station structure after completion but excavation, exposure and temporary support works were required for the shield tunnels during execution. Such underpinning for the shield structure of an operating passenger railway line was the first attempt in the world, and thus the work has been executed, after adequate designing and construction planning, under eareful construction management at the site. Temporary support work was executed by an underpinning method with installed bearing plates on the excavated trench bottom and special hydraulic jacks. For this work, a monitoring and jack control system was introduced and managed strictly in order to carch any adverse effects of site condition at any time, thus enabling a quick response to such incidents during each work stage.

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The 25-story high-rise complex, in The Goten-yama Hills development project, was designed in “HiRC-II” method. In this building, the shape and dimension of load-gathering structure was unified, so that it became avairable that using some pre-fabricated and systemized members. And also the method of pumping up the column concrete from bottom, placing concrete was not obstacled by the steel beam and reinforced bars, was applied aim to assure the quality and save the durlation of the construction. As the result, it achieved that the durlation needed to construct 1 story was no more than 6 days, and the high-quality S.R.C structure using high-strength concrete was obtained.

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