The standard about the drying shrinkage strain of concrete was specified by Japan Society of Civil Engineers. Moreover, Architectural Institute of Japan is going to be specified. In the opinion from the former, it was presupposed that drying shrinkage strain was correlated with unit water volume. However, it became clear in the latest investigation and research that the contribution of aggregate is higher. It came to be pointed out that a difference arises according to the kind of rock of aggregate especially. Then, when investigated about the present condition of the ready-mixed concrete industry, the average value of the concrete using the crushed stone of the kind of various kinds of rocks except limestone was close to 800 micro, and standard deviation was proved that it is about 130 micro, and it turned out that shrinkage reduction disposal is required for many of architecture concretes. However, regulation has many problems and the consideration about the solution touches on a required matter.

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JIS R 5210 “Portland Cement” was revised in 2003, and the chloride ion of ordinary portland cement was deregulated. However, the transition of cement quality including the chloride ion is not clarified. In authors' investigation results, it was confirmed that the cement quality supplied by each cement manufacturing company was almost steady, but the quality of moderate-heat portland cement and the low-heat portland cement is different according to the manufacturing company. The chloride ion of ordinary portland cement keeps increasing after 2003, and the maximum value reaches 0.030%. Even if the cement manufacturing company is the same, the chloride ion of the cement sold in various places is different.

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Crushed stone powder is limited to what passes through a 150-micrometer sieve in which the by-product is separated and/or ground at the time of manufacturing of a crushed stone and/or a crushed sand by dry process in the plant. Such crushed stone powder can be a promising material used for the purpose of decreasing the amount of bleeding of concrete with high water-cement ratio and small amount of finer part of concrete. The reason of the fineness limitation ofcrushed stone powder as mentioned above is that the indication of almost fine powder such as crushed stone powder which passes through a 150-micrometer sieve did not increase remarkably a unit content of water from experimental results of mortar and concrete. Higher compressive strength at young ages and durability such as lower carbonation can be expected when fine aggregate is replaced by crushed stone powder. Drying shrinkage, frost damage and water permeability of concrete are almost same if fine aggregate is replaced by crushed stone powder. The quality of crushed stone powder is specified in the first JIS A 5041 which will be published at Spring of 2009.

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In this study, bending and shear tests were conducted to clarify the performance of reinforced concrete beams formed by joining together two precast beam-end elements at the midspan using cast-in-place concrete with splice-bar joints of longitudinal bars. A total of 27 specimens were used, and the parameters were strength of the longitudinal bars and the cast-in-place concrete, transverse reinforcement spacing and the amount of U-shaped reinforcement in the lap splice region As a result of the test, an evaluation method for bond splitting strength taking into account the effect of the U-shaped bars and the influence of the stress gradient, developed by modifying evaluation formulas currently in use, was proposed.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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