Longitudinal wave (P-wave) velocity is sensitive to the formation of hydrates and can characterize very early microstructural changes associated with setting.

 

Uppalapati, S. et al. (2021) - Monitoring the setting process of alkali-activated slag-fly ash cements with ultrasonic P-wave velocity

doi: https://doi.org/10.1016/j.conbuildmat.2020.121592