Concrete Journal
Online ISSN : 2186-2753
Print ISSN : 0387-1061
ISSN-L : 0387-1061
Volume 49, Issue 6
Displaying 1-13 of 13 articles from this issue
  • Y. Yanagimori, J. Douzono, A. Hirama, T. Tsutsui
    2011 Volume 49 Issue 6 Pages 6_11-6_17
    Published: 2011
    Released on J-STAGE: June 01, 2012
    JOURNAL FREE ACCESS
    Several problems are often found in the construction of tunnel lining, such as reduction in concrete density due to improper compaction at the tunnel crown, lower concrete strength at construction joints, and void at the back of lining due to insufficient filling. In order to address these problems, the expressway companies in Japan have regulated “Mountain Tunneling Construction Management Guidance (for tunnel lining by means of middle-performance concrete)” in August 2008. Applications of middle-performance concrete for construction of tunnel lining could be expected not only to improve the concrete quality but also the workability, on the other hand solving the future problem of manpower shortage as consequence of aging population. Owing to these merits, the number of similar applications is anticipated to increase in the near future. This paper discusses the knowledge and problems pertaining to the middle-performance concrete through a series of trials, i.e. laboratory tests, field tests using a large mock form and in-situ application on the Aratsu Tunnel at the Higashi-Kyushu Expressway.
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  • H. Manabe, K. Kuzume, T. Kamada, Y. Kimura
    2011 Volume 49 Issue 6 Pages 6_18-6_24
    Published: 2011
    Released on J-STAGE: June 01, 2012
    JOURNAL FREE ACCESS
    When voids are left ungrouted, steel tendons in prestressing cables tend to be corroded by the water, salt or other matters penetrating into the cables, ultimately being fractured. Fracture of steels results in a reduced load bearing performance of the members as well as may cause a danger of accident to a third party as concrete debris falls at the impact of fracture. Accurate evaluation of the filling of PC grout is therefore extremely important for the maintenance of prestressed concrete structures. Nondestructive inspection techniques are preferable for the PC grout evaluation due to no damage to the structures being inspected. Various methods have been developed in many fields and applied to investigations on existing bridges in recent years. This is a technical report on nondestructive inspection techniques for concrete based on elastic-wave methods, with a specific focus placed on impact elastic-wave method for transverse prestressing cables of concrete slabs and impact-echo method which is applicable to internal cables in the post-tensioning system.
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