Ceramics-Silikáty 32, (2) 159 - 164 (1988)

The 'ring tear-off' method was used to study the kinetics of changes in surface tension of cellular concrete mixes in the initial stage of structural formation. The measurement was carried out on mixes with various dispersity and water content (of. Table I), without the gas-forming addition and under isothermal conditions (temperature 24.0 ±0.2°C). The experimental arrangement (Fig. 1) was peculiar in that the system employed consisted of the piston rod and cylinder of a mechanical press instead of the usual lever suspension. The course of the force was recorded by an induction transmitter and the HP 85B desk-top computer. The constant speed of 1.666 x 10⁻⁵ m s⁻¹ was used in the tearing off. The measurement was carried out at regular time intervals of 3 minutes. The time course of surface tension of the individual mixes (Fig. 3) was extremeal in character. The method, when appropriately interpreted and compared with methods of the thermodynamics of irreversible processes and rheology, can obviously be used in the study of processes taking place in the initial stage when the structure is formed in disperse silicate systems.