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In civil engineering, it is necessary to characterise the setting and the hardening behaviour of fresh concrete. This is for instance, necessary in slip-form construction where the earliest possible ending time has to be determined to operate economically but also deliver high quality. A significant disadvantage of the currently applied methods for the assessment of setting and hardening behaviour, such as the Vicat needle method or the penetration method, is that these methods mostly give only a snapshot in time of the material’s properties and the hydration process cannot be continuously monitored with them. [1]

Additionally, information about the effect of concrete admixtures or precise information about concrete-mortar mixtures is often requested Here the ultrasound technique comes into play. As the propagation velocity, the damping and the frequency content of ultrasound waves depend on the medium and thus on the setting and hardening of the concrete, ultrasound measurement is especially suitable here. [2]

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LaTeX Math Inline
body\sigma_{dyn} = \dfrac{\frac{1}{2} * v_p^2 - v_s^2}{v_p^2 - v_s^2}
(1)

LaTeX Math Inline
bodyE_{dyn} = \dfrac{(1 + \sigma_{dyn}) * (1 - 2\sigma_{dyn})}{(1 - \sigma_{dyn})} * v_s^2 * p_c
(2)

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Material parameters such as dynamic Young’s modulus 

LaTeX Math Inline
bodyE_{dyn}
and the dynamic shear modulus
LaTeX Math Inline
bodyG_{dyn}
can be directly determined. In contrast to the above mentioned methods, sensors are used here that are sensitive to compressor waves as well as to shear waves. This dynamic method thus offers a precise solution for the determination of dynamic material parameters.

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