In August 2015, the Japan Prestressed Concrete Institute published its “the Guideline of Design and Construction for PC Bridges Applied the PE Sheath”. In addition to the performance and quality of PE sheaths, these Guidelines cover PC bridge design, construction, quality control and inspections based on these properties, for the purpose of increasing the quality of prestressed concrete (PC) bridges through the effective and appropriate use of polyethylene (PE) sheaths. This paper outlines the contents of these newly established guidelines and highlights the key findings that led to their establishment.

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This paper explains that in the field of concrete, which occupies an important position with regard to sustainable construction, a framework for the active use of environmental labels has been instituted in Japan like in a number of other countries. Focusing particularly on ready-mixed concrete, this paper reports first about the high level of interest in sustainability at the ERMCO 2015 Congress, and goes on to introduce Japan's JIS environmental label system, which is consistent with that of the ISO. This is followed by an explanation of the framework for the use of the materials sanctioned by JIS A 5308 as recycled materials, including use of the Möbius loop symbol adopted in the latest revision of the JIS standard for ready-mixed concrete. Along with the precast concrete products industry, the ready-mixed concrete industry is stepping up its contributions to sustainable construction across the entire field of concrete through the voluntary use of environmental labels.

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The rational maintenance of the large number of concrete structures built during Japan's period of high economic growth is becoming necessary, and the concrete degradation of railway tunnels such as subway tunnels has become an issue. As cross-section repair of railway tunnels can take place only at night when train service stops, the time period from repair work completion to service start is short. Thus, cross-sectional repair materials must provide good strength development and reliable workability. This report describes laboratory and field experiments for the application of a cross-sectional repair method that sprays freshly mixed mortar to which curing accelerator has been added for the repair of railway tunnels, and reports the recorded improvement in strength development of the cross-section repair material at early ages. Through the appropriate combination of quick hardening material and curing accelerator, the developed cross-section repair method secures trowel finishing time of 15 minutes, and compressive strength exceeding 5 N/mm² after 3 hours was recorded.

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Electrochemical measurements techniques are employed in the maintenance of concrete structures, but some case studies seem to indicate a lack of understanding of the theoretical background. This paper provides an overview of the information that is important for the proper evaluation of electrochemical measurement results, specifically the basics of electrochemistry, methods for measuring electrochemical property values, the evaluation of concrete performance and quality, and the evaluation of corrosion.

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Through numerical analysis combining wind field analysis and the random walk method, the amount of salt adhering to each of the surfaces of a bridge superstructure was calculated, and a set of techniques for applying these results to the prediction of the amount of chloride ingress in concrete members of the bridge superstructure is proposed. The calculation accuracy was verified by comparing the calculation results yielded by the proposed method with the actual measurement data. This paper presents the details of this study.

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Testing and Behavior of Post-installed Anchors in Cracked concrete is to verify the extent to which the tensile capacity of post-installed anchors is affected when cracks are opened in a concrete specimen after the installation. While this testing is less familiar in Japan, it is implemented at standard in Europe by European Technical Approval Guideline (ETAG). Cracked concrete testing in Japan according to the ETAG was applied and this report delineates the testing process and behavior in cracked concrete. The tensile capacity of post-installed anchors in the presence of cracks was found to be 23% to 85% for bonded anchors, and 39% to 100% for mechanical anchors, as compared with the noncracked concrete.

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[in Japanese]

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