In this study, the effects of alkaline accelerating admixture and its dosage on cementitious material’s behavior at early ages were evaluated through a series of ultrasound Pulse echo measurements. Thus, those measurements consist on following the evolution of frequency dependent attenuation coefficient during cementitious material age. Four stages can be identified on the attenuation coefficient vs. mortar age graphs, indicating that the development of the attenuation parameter is closely related to the setting and the hardening phenomena. Also, the ultrasound histograms, representing the evolution of the different echoes backscattered by the media of the container, filled with cementitious material’s samples, were characterized in order to assess the attenuative effect of alkaline accelerator and its dosage during the setting and the hardening period. Thus, the combined use of ultrasound P-wave measured density and young modulus parameters results in a comprehensive ultrasound method that gives a more effective picture of the void volume and resistivity of the accelerated cementitious materials. Ultrasound P-waves were generated using a 1 MHz central frequency immersion transducer and mortar samples were prepared with Portland composite cement CPJ 45.

Beams are the constituent elements of several machine parts and sophisticated structures. In this paper, efforts are made to develop suitable methods that can serve as the basis to detect crack location and to crack size from measured axial vibration data. This method is used to address the inverse problem of assessing the crack location and crack size in various beam structure. The method is based on measurement of axial natural frequencies, which are global parameter and can be easily measured from any point on the structure. In theoretical analysis, the relationship between the natural frequencies, crack location, and crack size has been developed. For identification of crack location and crack size, it was shown that data on the variation of the first two natural frequencies is sufficient. The experimental analysis is done to verify the practical applicability of the theoretical method developed.