Characterisation of early stage calcium aluminate cement hydration by combination of non-destructive techniques: acoustic emission and X-ray tomography

Techniques that monitor in real time the setting and hardening of calcium aluminate cements (CAC) are now of interest to the engineering community. This paper focuses on the association of two in situ techniques, acoustic emission (AE) and X-rays computed tomography (CT). These non-destructive techniques make it possible to follow the cement hydration in the early stage from a few minutes to a few hours after mixing. Results concerning a calcium aluminate cement paste, Secar71, are presented (water to cement weight ratio: 0.33; duration: 0–24 h). Both the acoustic emission (AE) signals and X-rays absorption values were recorded and analysed. Information deduced from experiments clearly show that a close correlation exists between the variations of the X-ray absorption values and the AE activity during the early stage of hydration. Based on the experiments, the combined analysis (quantitative and qualitative) of both AE and CT data make it possible to propose a relationship between the experimental characteristics recorded during the tests and the different mechanisms taking place during the early hydration of a cement paste. A chronology of cement setting is also proposed.