Ohdaira E, Masuzawa N
Musashi Institute of Technology, Tokyo, Japan.
Ultrasonics. 2000 Mar;38(1-8):546-52. doi: 10.1016/s0041-624x(99)00158-4.
It is known that water content or moisture affects the strength of concrete. The purpose of this study is to examine the possibility of the NDE of concrete from a knowledge of the relationship between water content and ultrasonic propagation in concrete. The results of measurements made on the ultrasound velocity and the frequency component on ultrasonic propagation as a function of the water content in concrete are reported. Test pieces of concrete made from common materials were made for the fundamental studies. The test piece dimensions were 10 cm in diameter and 20 cm in length. Test pieces were immersed in water for about 50 days to saturate them. To measure the effect of different water contents, test pieces were put in a drying chamber to change the amount of water between measurements. This procedure was repeated until the concrete was completely dried and the weight no longer changed. Water contents were defined as weight percentage to full dried state. Thus water content could be changed from 8% to 0%. Using the pulse transmission method, ultrasonic propagation in the frequency range 20 to 100 kHz was measured as a function of water content. The sound velocity varied gradually from 3000 m/s to 4500 m/s according to the water content. The frequency of maximum transmission also depended on the water content in this frequency range. It is considered that the ultrasonic NDE of concrete strength is feasible.
众所周知，含水量或湿度会影响混凝土的强度。本研究的目的是从了解含水量与混凝土中超声波传播之间的关系出发，研究混凝土无损检测的可能性。报告了根据混凝土含水量对超声波传播速度和频率分量进行测量的结果。为进行基础研究制作了由常用材料制成的混凝土试件。试件尺寸为直径10厘米、长度20厘米。将试件浸泡在水中约50天使其饱和。为测量不同含水量的影响，将试件放入干燥箱中，在每次测量之间改变水量。重复此过程，直到混凝土完全干燥且重量不再变化。含水量定义为相对于完全干燥状态的重量百分比。因此，含水量可从8%变化到0%。使用脉冲传输法，测量了20至100千赫频率范围内超声波传播随含水量的变化情况。声速根据含水量从3000米/秒逐渐变化到4500米/秒。在该频率范围内，最大传输频率也取决于含水量。可以认为混凝土强度的超声无损检测是可行的。
