コンクリートの内部条件が超音波伝播に及ぼす影響

概要

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Internal structure of concrete may affect on propagation properties, those may cause errors in estimating quality of concrete using ultra-sonic method. The paper dicribed an experimental study about propagation characteristics of ultra-sonics in concrete sepecimens having several internal conditions. From the tests results, it can be said firstly, that water content of concrete may influence pulse velocity, in other words decrease in water contente of 1 % may decrease in pulse velocity about 90 m/sec, or 2 % to average velocity of 4,000 m/sec., Secondly, water absorption of concrete is concidered as closely related to internal structure, may influence pulse velocity, and increase in water absorption of 1% , decrease in velocity 130 m/sec. , the value is 3 % to average velosity. Internal crack may influence pulse velocity same as that of internal structure of concrete, but this effect is rather slight and can be negrect in invesigating existing concrete structures. Thirdly, large voids in concrete may influence propagation path, and hence propagation time. With regard to dimension of large void in concrete, if larger than wave length of ultrasonics, pulse can not transmit directly from transmitter to receiver, and if smaller than wave length, pulse transmit directly, It can be said that, the critical dimension of void is almostly equal to that of wave length.
社団法人日本建築学会の論文
1991-07-30