The use of frequency spectrum of ultrasonic P-waves to monitor the setting process of cement pastes

In this paper, a possibility of using a frequency spectrum of ultrasonic P-waves to monitor the formation of structure of cement pastes at early ages is studied. A new parameter, labeled as a TG parameter, is defined as a dimensionless ratio between maximum amplitudes of two dominant frequency ranges that appear in a frequency spectrum of received ultrasound signals. Four stages and three characteristic points can be identified on the TG-vs.-time graphs, indicating that the development of the frequency spectrum is closely related to the setting phenomena. By comparing the TG parameter with the P-wave velocity and temperature evolutions in time, important milestones in the process of formation of microstructure were identified, such as the time of reduced workability and a period of intensive setting. The combined use of P-wave velocity and TG parameter results in a comprehensive ultrasonic method that gives a more complete picture of setting.