Concrete Journal
Online ISSN : 2186-2753
Print ISSN : 0387-1061
ISSN-L : 0387-1061
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Volume 49, Issue 12
Displaying 1-16 of 16 articles from this issue
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  • Seismic Retrofit Technique of Existing Reinforced Concrete Column with Sidewall using Polymer-cement Mortar and Prefabricated Reinforcing Unit
    S. Tago, T. Sugiyama, T. Ido, Y. Matsuzaki
    2011 Volume 49 Issue 12 Pages 12_3-12_9
    Published: 2011
    Released on J-STAGE: December 01, 2012
    DOIhttps://doi.org/10.3151/coj.49.12_3
    JOURNAL FREE ACCESS
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    Authors proposed a seismic retrofi tting technique for existing RC columns with cast-in-place RC sidewall using polymer-cement mortar (PCM). In the technique, additional shear reinforcement (hoops of column and/or horizontal shear reinforcement of sidewall; prefabricated reinforcing unit) is adhered to the surfaces of existing RC columns with RC sidewall by applying PCM. The strengthened area (additional reinforcement and PCM) and existing member are strongly joined by the high adhesive strength of the PCM. The design / construction guideline of this seismic retrofi t technique obtained the technology assessment of the Japan Building Disaster Prevention Association. The present paper introduces the eff ect of this seismic technique and the outline of the guideline.
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  • Revision of JIS A 6207 “Silica fume for use in concrete”
    H. Naruse, S. Nagataki, H. Gomi, H. Jinnai
    2011 Volume 49 Issue 12 Pages 12_10-12_16
    Published: 2011
    Released on J-STAGE: December 01, 2012
    DOIhttps://doi.org/10.3151/coj.49.12_10
    JOURNAL FREE ACCESS
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    Japanese Industrial Standard (JIS) A 6207 “Silica fume for use in concrete” was revised in May 2011. The major revisions are as follows. 1) The loss on ignition of dry silica fume shall be less than 4.0%. 2) W/B for the test of activity index shall be 30%. In Japan, silica fume is primarily used for ultra-high-strength concrete. Therefore, W/B for the test of activity index set in W/B which is near to the general mixture proportion of ultra-high-strength concrete. In addition, the findings of silica fume quality (including content of trace elements and water-soluble trace elements) in Japan and abroad, the findings of overseas standards, and study results of chemical analysis by x-ray fluorescence are listed.
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  • Development of Concrete Made with Seawater and Un-washed Sea Sand
    N. Takeda, Y. Ishizeki, S. Aoki, K. Iriya
    2011 Volume 49 Issue 12 Pages 12_17-12_22
    Published: 2011
    Released on J-STAGE: December 01, 2012
    DOIhttps://doi.org/10.3151/coj.49.12_17
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    We developed high-density and hard concrete using seawater and/or unwashed sea sand. The internal organizations of that concrete was denser compared with normal concrete, and it was clear that the water-tightness, early strength, and long-term strength of seawater and unwashed sea sand concrete were increased. Reinforced concrete structures that used a non-corrosive reinforcing bar were durable in the long term. Seawater and unwashed sea sand concrete construction could be used on remote islands or on the coast to reduce CO2 emission and construction costs. This paper describes the properties of s seawater and unwashed sea sand concrete and the examination about application to the concrete structures
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  • Load Capacity Evaluation of Reinforced Concrete Girder Damaged due to Combined Effect—An Example of Clinical Study Utilizing Decommissioned Bridge—
    T. Hanai, Y. Kimura, M. Nakajima
    2011 Volume 49 Issue 12 Pages 12_23-12_30
    Published: 2011
    Released on J-STAGE: December 01, 2012
    DOIhttps://doi.org/10.3151/coj.49.12_23
    JOURNAL FREE ACCESS
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    One of the pillars of research activities of Center for Advanced Engineering Structural Assessment and Research (CAESAR) is a “clinical study”. And the research utilizing decommissioned bridges is a component of it. In this paper, CAESAR's clinical study is outlined. And as an example of that, load capacity evaluation of reinforced concrete girder damaged due to combined effect is presented.
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  • The Influence of Fine Particle Contents in Limestone Coarse Aggregate on the Properties of High-strength Concrete
    K. Hayashi, K. Tada, K. Yamada, H. Kawano
    2011 Volume 49 Issue 12 Pages 12_31-12_38
    Published: 2011
    Released on J-STAGE: December 01, 2012
    DOIhttps://doi.org/10.3151/coj.49.12_31
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    This technical report discusses the influence of increase in fine particle contents from 1.0 mass% to 5.0 mass% in limestone aggregate on the fresh and hardened properties of high-strength concrete based on significant size of experiments considering varieties of aggregate sources, cement types, and water to cement ratios. This study was carried out corresponding to the change of the regulation on fine particles contents in crushed aggregate in JIS A 5005-2009. Although the increase in fine particle content decreases fluidity in some degree, it can be compensated by the increase in the dosage of superplasticizer in realistic range such as 10%. Regarding other properties such as air content, compressive strength, and the elastic modulus, no significant effects were detected. Thus, the effect of the increase in fine particle content in limestone aggregate is judged as negligible in the range of this study, it can be concluded that it is possible to use limestone aggregate as usual before just after a simple confirmation examination of typical concrete properties even when the fine particle contents increases.
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