Observation of microstructure formation process of cement paste using non-destructive methods

摘要

Three types of non-destructive techniques including ultrasonic pulse velocity (UPV), non-contact electrical resistivity (NER) and X-ray computed tomography (CT) were employed continuously to monitor in situ the early microstructure evolution of fresh cement paste. The experimental results show that the ultrasonic method may effectively monitor solid phase changes occurring during hydration process. In comparison, the electrical resistivity is sensitive to the evolution of capillary pores involved in cement hydration. The two and three-dimensional information from CT provides visual insight into the microstructure formation process. In addition, three stages can be classified by the ultrasonic method, while five stages can be observed by NER. Two characteristic points are clearly identified from UPV curves. To aid in better understanding of cement hydration, an isothermal conduction calorimeter was also used to measure the release of heat of hydration. Finally, the correlation between the volume of phases and the evolution of UPV is explored.