Concrete Journal

Frost Damage of Concrete Structures in Tohoku District

M. Shoya, Y. Tsukinaga

2004 Volume 42 Issue 12 Pages 3-8
Published: December 01, 2004
Released on J-STAGE: April 26, 2013

DOIhttps://doi.org/10.3151/coj1975.42.12_3

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Based on the investigations on the actual frost susceptibility of concrete structures in Tohoku districts, conducted by JCI Tohoku branch in 2,000, not only the manner and degree of deteriorations, the direction and location of damaged parts in the public and architectural structures, but also the causes of deterioration, were summarized. In addition, the spreading amount and the kinds of deicing chemicals influencing the scaling of concrete, were described. Mechanisms of frost damage of concrete and the frost susceptibility depending on the different pore structure of coarse aggregates, were mentioned. Finally, the research concerns for predicting and estimating the frost damage were also described.

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Actual Condition of Control for Unit Water Content in Ready-Mixed Concrete Factory

T. Yoshikane, K. Suzuki, K. Tsujimoto

2004 Volume 42 Issue 12 Pages 9-14
Published: December 01, 2004
Released on J-STAGE: April 26, 2013

DOIhttps://doi.org/10.3151/coj1975.42.12_9

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Actual condition was investigated, About the control width of unit water content of case that manufactures Read-Mixed concrete, frequency of the inspection for acceptance, Standard value of determination and test procedure.

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One Proposal of the Young's Modulus setting Method in the Survey of the Young's Modulus of the Concrete in the Kansai Area, and a Structure Design

T. Iwashimizu, A. Sumi

2004 Volume 42 Issue 12 Pages 15-22
Published: December 01, 2004
Released on J-STAGE: April 26, 2013

DOIhttps://doi.org/10.3151/coj1975.42.12_15

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In the Kansai area, the design value of the Young's modulus calculated by RC standard formula turns into a small value in many cases as compared with the Young's modulus of actual concrete. From the former, it is known that the Young's modulus of concrete will be greatly influenced of the quality of coarse aggregate, and it is thought that the abovementioned phenomenon has arisen by the kind of the coarse aggregate currently generally used in the Kansai area. In this report, the actual condition of the Young's modulus in the Kansai area is investigated for the purpose of making more nearly actually near the setting value of the Young's modulus in a structure design, and the result which analyzed every kind coarse aggregate is shown. Furthermore, based on the result of analysis, it proposed also about the setting method of the Young's modulus in the structure design based on RC standard formula.

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Outline and Future Themes of Anchorage Operation Manual Applying JASS 5

J. Fukushima

2004 Volume 42 Issue 12 Pages 23-31
Published: December 01, 2004
Released on J-STAGE: April 26, 2013

DOIhttps://doi.org/10.3151/coj1975.42.12_23

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Due to the revision of the AIJ standard for reinforced concrete structures in 1999, 90-degree bending was defined as a 90-degree hook which assures the horizontal anchorage length to be the same as the other hooks. From this revision, AIJ JASS 5 was also revised, and it was revealed that approximately 20% of the existing column-beam joints failed to comply with the new provisions. This paper describes the validity of limiting value from the results of analysis of the reasons for these failures. On the other hand, the author proposes trials and a solution plan for the re-bar anchorage provision of beam and nonstructural element.

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A Petrological and Mineralogical Consideration on Unusual Cracking of Concrete Structures

A. Maru

2004 Volume 42 Issue 12 Pages 32-42
Published: December 01, 2004
Released on J-STAGE: April 26, 2013

DOIhttps://doi.org/10.3151/coj1975.42.12_32

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The unusual cracking of concrete is mostly attributable to factors related to the materials such as the aggregate and cement used in concrete, and cracking caused by the alkali-aggregate reaction is one of the typical examples. A petrological and mineralogical survey was conducted on specimens from various concrete structures throughout the country. The results indicated that the unusual cracking of concrete might be influenced to the abnormal cement reaction by insufficient curing and the elution of some constituents of aggregate. The conventional theory, which ascribes unusual cracking to the alkali-aggregate reaction, is inapplicable to the many caces. Gel generation has also been considered to cause cracking by the alkali-aggregate reaction. However, this paper reports that gel generation is not directly involved in concrete swelling and suggests that the need to review the mechanism of unusval concrete cracking, including the alkali-aggregate reaction.

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[title in Japanese]

[in Japanese], [in Japanese], [in Japanese], [in Japanese]

2004 Volume 42 Issue 12 Pages 44-49
Published: December 01, 2004
Released on J-STAGE: April 26, 2013

DOIhttps://doi.org/10.3151/coj1975.42.12_44

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[title in Japanese]

[in Japanese], [in Japanese], [in Japanese], [in Japanese]

2004 Volume 42 Issue 12 Pages 50-54
Published: December 01, 2004
Released on J-STAGE: April 26, 2013

DOIhttps://doi.org/10.3151/coj1975.42.12_50

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