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A newly developed ultrasound method that acquires at the same time both reflected and transmitted P-waves, at different angles, using two immersion transducers of 0.5 MHz central frequency, is described in this present study. This non-destructive method allows calculating the longitudinal and transverse velocities, and thus, the Young modulus, so that its evolutions is followed in time domain. The closely correlation between the evolution in time domain of those calculated parameters and hydration properties of cement based materials was used to characterize the effects of different water-cement ratio and curing temperatures on early age hydration behaviour of cement pastes. To do so, cement samples were prepared by mixing Portland cement and freshwater. Results indicates that lower water to cement ratio reduces the workability and increases the Young modulus of resulted cement medium. Also, both ultrasound velocities and Young modulus values increases linearly with increasing curing temperature. [ABSTRACT FROM AUTHOR]

The reflection technique of ultrasonic waves was used for monitoring and nondestructively characterization of a mortar during its evolution. Using Argand Diagram to measure the resonant ultrasonic wave frequency and its width shows that they follow the rapidly changing in mechanical properties of the material at the young age. Both parameters increase during the time of hardening and also prove the effect of the sand particle size and temperature of the mortar properties. Moreover, measuring the width of the ultrasonic wave resonance allows distinguishing the different hydration phases of material. [ABSTRACT FROM AUTHOR]

Introduction. Fish quality is traditionally controlled by chemical and microbiological analysis. The non-destructive control presents an enormous professional interest thanks to the technical contribution and precision of the analysis to which it leads. This paper presents the results obtained from a characterisation of fish thawing process by the ultrasonic technique, with monitoring thermal processing from frozen to defrosted states. Material and methods. The study was carried out on fish type red drum and salmon cut into fillets of 15 mm thickness. After being frozen at -20°C, the sample is enclosed in a plexiglas vessel with parallel walls at the ambient temperature 30°C and excited in perpendicular incidence at 0.5 MHz by an ultrasonic pulser-receiver Sofranel 5052PR. the technique of measurement consists to study the signals reflected by fish during its thawing, the specific techniques of signal processing are implemented to deduce informations characterizing the state of fish and its thawing process by examining the evolution of the position echoes reflected by the sample and the viscoelastic parameters of fish during its thawing. Results. The obtained results show a relationship between the thermal state of fish and its acoustic properties, which allowed to deduce the optimal time of the first thawing in order to restrict the growth of microbial flora. For salmon, the results show a decrease of 36% of the time of the second thawing and an increase of 10.88% of the phase velocity, with a decrease of 65.5% of the peak-to-peak voltage of the signal reflected, thus a decrease of the acoustic impedance. Conclusions. This study shows an optimal time and an evolution rate of thawing specific to each type of fish and a correlation between the acoustic behavior of fish and its thermal state which approves that this technique of ultrasonic monitoring can substitute the control using the destructive chemical analysis in order to monitor the thawing process and to know whether a fish has suffered an accidental thawing. [ABSTRACT FROM AUTHOR]

• Evaluation of the possibility to use the ultrasound non-destructive reflection method and P-waves for the identification of the different stages of mortar hydration. • Identification of four stages of mortar hydration using characteristic points on the evolution curves in time scale of attenuation coefficient and modulus of reflection coefficient ultrasound parameters. • Physico-chemical characterization of river sand and Portland cement powder used for the preparation of mortar samples. • Characterization of the effects of sand grading and salinity of mixing water on early age behavior of mortars. This paper aims to study the effects of different sand grading and salinity of mixing water on setting and hardening of cement mortar. For this purpose, a newly developed measurement method based on ultrasound pulse echo technique was used. Using this method, the attenuation coefficient and the modulus of reflection coefficient are measured to characterize the early age behavior of tested mortars. Ultrasound P-waves were generated using a 1 MHz central frequency immersion transducer and mortar samples were prepared with Portland composite cement CPJ 45. Mortar samples were classified into two series: first series considered mortar mixes prepared using fresh water and different sand grading form 56 μ m to 400 μ m. These laboratory tests (series 1) aimed to obtain the optimum grain size of respective mortar mixes in terms of optimum workability and rheology. Continually, the optimum grain size (from series 1) is used in the second series of experiments (series 2) mortar mixes prepared using artificial sea water with different concentrations of sea salt, i.e., 0 g/l, 10 g/l, 20 g/l, 37 g/l and 50 g/l. The results show that the increase of sand size grading in mortar allows faster setting and hardening and earlier occurrence of aluminate hydrates phase transition AFt – AFm, precipitates the solid percolation and achieves denser microstructure. Also, the stepwise increase of Sea Salt dosage in mixing water from 0 g/l to 37 g/l resulted in a later achieve of final set and later occurrence of AFt – AFm transition. [ABSTRACT FROM AUTHOR]