engleski

Analysis of Ultrasonic Impulse's Information Content in Characterisation of Cement Materials

The ultrasonic testing was used for in situ characterisation of cement materials during hydration. The exploited configuration is the through-transmission pulse mode technique in immersion. Records of ultrasonic impulse, obtained for different stages of hydration, are fitted using only one, functional, several-parameter form. Fast Fourier Transform of the signal shows gradual increase of the wave frequency toward the nominal probe frequency, corresponding to the compressive strengths of about 40 MPa, what was checked independently. The fit of the time dependence of ultrasonic impulse to the functional form, that is solution to wave pulse propagation in dispersive medium, is exploited in order to determine the relation of nominal frequency with the material properties. The origin of the frequency shift is a combination of linear and non-linear effects. The linear effects are related to the high attenuation of multi-phase (solid-liquid-air) linear elastic material, and the non-linear to micro-dynamics in the material inevitably containing small cracks and microcracks. The determined effects are caused with a complex, time-dependent, multi-phase structure of samples.

ultrasonic testing; cement hydration; attenuation; elasticity; non-linearity

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