Recently, prediction method of thermal crack analysis is spreading to construction companies in the district and civil engineering consultant companies. As the reason, the software for thermal crack analysis developed in Japan Concrete Institute committee on thermal stress of massive concrete structures is due to help it and by the popularization of the software, it is due to become general to evaluate a risk for thermal stress quantitatively. The committee on thermal stress of massive concrete structures (present Committee on computer code development for crack control in massive concrete structures) contributes for the quality improvement of concrete structures. This explanation introduces outline to until now research results on thermal crack analysis and the latest research ones.

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This article introduces characteristic points and the outline of “Recommendation for Practice of Crack Control in Reinforced Concrete Buildings (Design and Construction)” which was issued by Architectural Institute of Japan (AIJ) in February 2006. In this recommendation, two design approaches to control the shrinkage cracking are shown. One is the specification-based design approach and the other is a performance-based design approach. While the former is available for most of ordinary RC buildings, the latter is useful for some specific RC buildings which require special design criteria for shrinkage cracking.

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Shirasu concrete is defined as a concrete using Shirasu as fine aggregate entirely. Shirasu is a name of the pyroclastic flow deposits called in the southern part of Kyushu Island, Japan, where the huge volume of it accumulates. As Shirasu taken from the deposits shows a sandy state, examination was performed continuously to use it as the fine aggregate for the past approximately 20 years. Especially in a latter half of 1990's, it came to be a noteworthy material that should be examined as the substitute for sea sand more practically, because collection regulation of sea sand started to be carried out from the viewpoint of environmental protection. Consequently, Kagoshima prefectural office established the “Manual for design and construction of the concrete used Shirasu as fine aggregate (draft)” January 2006. In this paper, characteristics of Shirasu concrete, its mixture design method and the matters that require attention in the execution are briefly outlined based on the contents of the Manual, and they are followed by the introduction of some activities for practical use of Shirasu concrete in Kagoshima prefecture with the future prospects.

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In this paper, two methods to mitigate damage due to crack of R/C members are proposed. One of them is to install high performance fiber reinforced cementitious composite (HPFRCC) board as commutation of form to R/C beams. Another one is to apply polyvinyl alcohol fiber reinforcement concrete (PVA-FRC) to R/C continuous footing. The shear bending tests of R/C members, which assumed beam and continuous footing, were conducted to verify the ideas. As the results, the proposed methods could enhance seismic behavior of R/C beam and R/C continuous footing and mitigate the damage due to crack of R/C members.

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The quality control system for stabilization of compressive strength of ultra high strength concrete by selection of suitable coarse aggregate based on mechanical characteristics of raw stone was developed. The stabilization of compressive strength of ultra high strength concrete with a design strength of 150 MPa was achieved by applying the system to production of it.

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[in Japanese]

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[in Japanese]

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