AIJ Standard for Structural Calculation of Reinforced Concrete Structures was revised in eight and a half year from the last edition. The following three points were revised mainly: bond, foundations, and shear walls. In the provision of bond, verification of safety (ultimate strength) was reviewed. In particular, new knowledge of bond around continuous reinforcement and cut-off bars have been reflected, and calculating method have been simplified. In calculation of shear in foundations, the arch mechanism can now be taken into consideration specifically for foundation slabs that meet special regulations concerning shear reinforcement and other conditions. In the commentary on shear walls, more explanations for beams confining wall, the reduction factor related to opening height, and so on, have been added.
T. C. Powers is a researcher who developed physically and chemically systematic research for the first time concerning the moisture condition of the cement materials. The model expressing the change in the moisture composition accompanying the progress of hydration has been reviewed several times since it was formulated in the mid-1940s by Powers and Brownyard. In this study, water in the cement materials treated as three compositions of “capillary water”, “gel water” and “chemically bound water”. Although Powers et al. had formulated moisture composition for hardened cement paste, but in this commentary, it is expressed as a model extended to concrete.
This paper reports the results of experimental and analytical study regarding the fi ve items that need to be considered when the concrete temperature during placing is expected to exceed 35°C, as indicated in the Japan Society of Civil Engineers' “Standard Specifi cations for Concrete Structures─Materials and Construction”. No remarkable changes in the quality of fresh concrete and hardened concrete and the workability of concrete were observed at the 35°C temperature demarcation point. The points of note regarding design and construction, and reference data to take countermeasures were shown On the other hand, with regard to thermal cracking and high-temperature history at an early age, the results showed that it is necessary to clarify the performance requirements and consider eff ective measures from the planning and design stages.