In this thesis, two advanced non-destructive methods were used to monitor the formation of the structure within cement based materials (CBM) at early ages. The main objective of this work has been to determine the possibility of using an ultrasonic wave transmission method and an electric conductivity method to monitor the hydration process and to determine setting and hardening periods of CBM based on our own experimental research. Two methods have been used in the scope of ultrasonic method, namely ultrasonic wave transmission method and frequency spectrum of ultrasonic waves method. Simultaneously with both mentioned methods, the temperature within the CBM during hydration process has also been measured.
In addition to the confirmation of the ability to monitor initial and final setting and hardening times of CBM with both non-destructive methods, the main scientific contribution of the thesis comprises the correlation of results from both used non-destructive methods along with the analysis of possible use of these methods to determine two very important milestones in microstructure development of BCM, which are percolation of solid phase and depercolation of porosity phase. We came to the conclusion that the combination of both methods enables accurate and inevitable determination of those fundamental phenomena that occur at early ages of the formation of the structure of CBM. Both methods have shown different sensitivity to these phenomena, however important milestones occur at the same time regardless of the used method. A unique relation between both methods has been identified, regardless of cement pastes’ composition.
These findings are important for the development of the advanced measuring techniques intended for the research of structure development within CBM and to improve the understanding of the process.