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Nishi-Tokyo-shi, Japan

Koyama Y.,Tokyo Polytechnic University | Hayakawa M.,Tokyo Polytechnic University | Jinnai H.,Taisei Corporation | Nakamura M.,Tokyo Kensa Co.
Journal of Structural and Construction Engineering | Year: 2012

This paper deals with the influence of the eccentric loading in the compressive strength test of high-strength concrete. In the experiment, five kinds of concretes (water binder ratio is 65% to 20%) were examined. The range of eccentric distance is 0 mm to 9 mm. Conclusions are as follows. (1) The influence of eccentric loading becomes large as concrete becomes more high-strength. (2) The experimental result of (1) can be presumed based on vertical strain of specimen. (3) The compressive strength test result in the tolerance level of JIS A 1108(within 1mm) becomes almost equivalent. (4) Under eccentric loading, the horizontal strain of the upper part of specimen became small. This result has suggested increasing the restraint of the upper part of specimen under eccentric loading. Source


Koyama Y.,Tokyo Kensa Co. | Hayakawa M.,Tokyo Polytechnic University | Jinnai H.,Taisei Corporation | Nakamura M.,Tokyo Kensa Co.
Journal of Structural and Construction Engineering | Year: 2013

This paper deals with the influence of conveyance vibration on compressive strength of specimen of high-strength concrete. In the experiment, six kinds of concretes (water binder ratio is 60% to 20%) were examined. Conclusions are as follows. (1) The conveyance vibration affects compressive strength of specimen. Immediately after production of concrete, conveyance vibration causes strength reduction of specimen. Then, if concrete begins to harden, conveyance vibration will contribute to the improvement in compressive strength. Furthermore, if time passes too much since production of concrete, conveyance vibration will cause strength reduction. (2) Concrete with low water binder ratio is hardly subject to the influence of conveyance vibration. One of the reasons of this is that water and air hardly move in concrete with low water binder ratio. (3) It is not desirable to carry a test specimen immediately after mixing of concrete. Moreover, after time passes very much since mixing of concrete, it is not desirable to carry a test specimen, either. Source


Koyama Y.,Tokyo Polytechnic University | Koyama Y.,Tokyo Kensa Co. | Hayakawa M.,Tokyo Polytechnic University | Jinnai H.,Taisei Corporation | Nakamura M.,Tokyo Kensa Co.
Journal of Structural and Construction Engineering | Year: 2010

In this research, the relation between the flatness of the end of the high strength concrete specimen and its compressive strength was examined The results of the examination are shown as follows. (1) The flatness of the end of the specimen can be evaluated by measuring 17 points with a device shown in JIS A 5308. (2) Flatness of the end of the specimen will change with the time passing. Therefore, specimens should be ground just before the strength test. (3) Every flatness of the end of the grounded specimen was within the limits regulated in JIS A 1132. (4) In this experiment, compressive strength decreased as the roughness of the end of the specimen increased. (5) In this experiment, the influence of the flatness on the strength reduction rate increased with the rise of the compressive strength level. Source

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