The post on portland cement manufacturing features is prepared in cooperation with Telling, the architectural company widely using hydraulic lime, lime mortar and concrete materials in its projects.
Plasticized portland is the product of pulverizing portland cement clinker with gypsum dihydrate (3-5%) and with addition of about 0.25% of yeast mash sulfide or other plasticizing additives at a grinding stage. These additives are adsorbed on the surface of the cement particles, improve wetting of cement with water and preventing their interaction. The additives reduce the friction between the grains of cement in concrete mixtures – and between grains of filler, thereby increasing their mobility, which can reduce the consumption of cement in the concrete by 5-10%.
Hydrophobic Portland cement is the product of pulverizing portland cement clinker with gypsum dihydrate (3-5%) and with the addition of 0.1-0.2% of hydrophobic additives – oil soap, synthetic fatty acids, etc., during grinding. Synthetic fatty acids, their salts and other particles are adsorbed on the surface of the grains of cement, to form thinnest water repellent films, reducing wettability. As a result, the hydrophobic cements can stay a long time in air with high humidity without losing its qualities.
While stirring concrete the integrity of hydrophobic film is disrupted, after which the cement reacts with water easily. The remaining additives in the concrete improve its quality, such as increasing the frost resistance, resistance to aggressive environments, etc.
The material presented in the article is intended primarily for the staff of organisations that use ultrasonic cavitation treatment plants for liquid media in ultrasonic equipment. The information is kindly provided by Hilsonic, a far-famed British company, now specialising in the production of high-tech ultrasonic cleaning equipment for 7 years.
The principle of operation of the ultrasonic reactor & the effect of static pressure
The functioning of ultrasonic reactor is based on the ultrasonic cavitation in the thin layer of pumped liquid to be treated through the reactor. The ultrasonic oscillator generates the ultrasonic frequency voltage received by ultrasonic transducer, which converts the high frequency voltage in an ultrasonic frequency and mechanical vibrations. These vibrations are transmitted to the emitter, which comprises a hub, whereby high frequency fluctuations are amplified and on the output they may generate up to 100 microns or more. Converter with a radiator attached to the body of the reactor through the support mechanism.
In case of fluctuations of the radiator at an ultrasonic frequency to be treated in the reactor liquid medium having alternation of compression and expansion, which create additional pressure change in a relatively constant static pressure of this environment. These pressure fluctuations in the liquid medium are defined by sound pressure, emitted by transmitter.
As a result, the liquid medium is observed closely associated with the sound pressure effect called ultrasonic cavitation, which refers to the formation of steam and gas in a liquid medium (cavitation) cavities in the negative phase of the sound pressure of the acoustic oscillations of ultrasonic frequency, followed by slamming them into the positive phase sound pressure with the formation of shock waves.
The emergence of cavitation bubble and the effects associated with it slamming depend on a number of parameters: acoustic characteristics (sound pressure and frequency), the thermodynamic parameters (pressure and external temperature) and parameters of the liquid (density, viscosity, surface tension, vapor pressure and solubility of liquid gas therein). (more…)