The Role of Water and Aqueous Solutions in the Formation of Induction Periods of Hydration and Structure Formation of Cement Stone

The study of the induction periods of hydration and structure formation of cement stone is one of the most urgent problems of modern building materials science. Water and aqueous solutions of inorganic salts are the most widespread forms of mixing liquids for cement systems. The properties of distilled water and aqueous solutions of sodium chloride with different concentrations have been investigated by dielectrometry. It is proposed to consider the structural organization of water and aqueous solutions as a combination of strongly and weakly bound water. The strongly bound water is the result of manifestation of hydrogen bond forces; this type of water specifies the ordered state of the system. Weakly bound water causes fragmentation of the initial water continuum into smaller structural units. The change in the impedance and admittance spectra of cement paste during hardening has been analyzed. Spectra were measured in the frequency range from 20 Hz to 2 MHz using a capacitor measurement cell. Investigations have been performed to find the optimal equivalent electric circuits describing the transformation of the electrical properties of cement paste and the interface phenomena occurring in the near-electrode layer of the measurement cell in dependence of the hardening time. It is found that the equivalent circuit parameters are sensitive to different stages of cement paste hardening. A relationship between the spectra of electrical parameters and the processes of cement stone hardening is demonstrated.