沖縄のコンクリ-トの基本的性状-2-
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概要
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Using sea sand and crushed stone is the distinctive feature of concrete in Okinawa Prefecture. The characteristics of such concrete has already published in many papers by the auther and others. There are two kinds of crushed stone used in Okinawa Island. One is hard and called "Motobu" crushed stone and has large density and small specific water content. So the static and dynamic Young's maduli of the concrete which uses Motobu crushed stone are much larger than ones which described in the specifications of AIJ and JSCE in the practical range of compressive strength between 150 and 400kg/cm². The other is relatively soft and called Ryukyu lime stone crushed stone. The concrete using the relatively soft crushed stone has smaller Young's moduli than the concrete with Motobu crushed stone, but still lightly larger than specified values in the AIJ specification. There are many factors which affect the values of the Young's maduli of concrete. In this study, compressive strength and unit weight of concrete are the most affecting factors. Formulae for both static and dynamic Young's moduli are presented by using the method of the least square. The formulae are described in terms of compressive strength and unit weight of concrete. The increasing pattern of compressing strength of the concrete using hard crushed stone as the time passes is almost the same as described in common technical books. The rate of increase of Young's moduli as the time passes is much slower than ones of compressive strength. The concrete using larger maximum size crushed stone exhibits much larger Young's moduli than the concrete with small maximum size. Bleeding behavior of the concrete using crushed stone and sea sand will be much improved by using "Ishigū" as a part of fine aggregate. Bleeding rate or quantity becomes half or one-third, if "Ishigū" is used properly with other materials.
- 琉球大学理工学部の論文
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