کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
295157 | 511529 | 2013 | 9 صفحه PDF | دانلود رایگان |
The relationship between Rayleigh wave velocity at ultrasonic frequencies and capillary porosity is investigated in dry and water saturated cement paste. Capillary porosity is varied by changing the water/cement (w/c) ratio. Water saturation is set at four levels – 100, 70, 30 and 0% – by drying the fully saturated specimen. Rayleigh wave (RW) wavefront and phase velocities are measured using air-coupled ultrasonic transducers as transmitter and receiver. The measurement accuracy is evaluated using a reference specimen made up of a non-dispersive material. As expected, a linear decrease of RW velocity vs. porosity is observed for the intermediate saturation states, but not for the fully and dry states, possibly due to micro-cracks induced during the drying phase and to the presence of bubbles in the specimens with low w/c ratio. The comparison of phase velocity in specimens with low and high w/c ratio shows an inversion of the porosity gradient perpendicular to the surface of measurements, which is due to segregation of cement at high w/c ratio. Finally, the correlation between RW velocity and capillary porosity is analyzed and compared with results obtained in mortar.
► A non-contact ultrasonic device is used to measure Rayleigh wave (RW) velocity in cement paste.
► RW phase velocity dispersion underlines the occurrence of segregation in cement paste.
► The relationship between RW velocity and capillary porosity is described by a linear relationship with a slope close to 1.
Journal: NDT & E International - Volume 54, March 2013, Pages 75–83