Ultrasonic monitoring and property prediction of cement hydration with novel omnidirectional piezoelectric ultrasonic transducer

A novel horizontal omnidirectional piezoelectric ultrasonic transducer suitable for real-time monitoring of hardened cement paste was developed. The ultrasonic technique was employed to monitor the hydration progress and to predict the strength development of the hardened cement paste. The results show that the omnidirectional piezoelectric ultrasonic transducer has good emission omnidirectionality in horizontal 360 degrees. The ultrasonic reception waveform is weak at the initial hydration period of cement paste due to the strong attenuation of cement particles in the solution. After hydrated for 3 h, the ultrasonic central frequency shifts towards the high frequency direction due to the quick hydration reaction of the essential minerals in cement paste. The amplitude variations of the ultrasonic wave in the early hydration age of 12 h conform to the growth function distribution, which is similar to the growth curve of human, so the early hydration of cement can be regarded as a para-life process. There exists an exponential function between sound velocity and compressive strength of the hardened cement paste during hydration age of 1-28 d, which is meaningful to predict the compressive strength of hardened cement paste.