The stability of the air bubble film machine is very important

by:Mengxing     2020-06-05
Air bubble film machine is the nature of the stable process of air-entraining concrete under the action of external force ( Such as mechanical stirring or mechanical mixing) , bubble film machine mechanical stirring can part into the surface free energy of concrete process. The result of the air-entraining lead to stick coagulation soil system free energy increase, air-entraining concrete become unstable thermodynamic system. Stick coagulation soil system free energy increase delta 'is mainly due to the surface of the bubble is caused by system can increase caused by the mountain, so the size of the delta C is equal to the increase of the surface free energy. Air-entraining concrete surface free energy change of delta 'seized all size can be calculated by the type: the role of air-entraining agent is to increase the stability of the concrete in the bubbles. To this day. Air-entraining agent from two aspects. 1. Reduce the system of free flipping, improve stability of air-entraining concrete system. Due to the enrichment of air-entraining agent on the gas-liquid interface reduces surface tension on the surface of the gas and liquid, which has reduced due to process of air-entraining concrete system since the d3 can she force U. 2. Additional bubbles merge dynamics barrier. The formation mechanism of the bubbles merge dynamics barrier varies with air-entraining agent type. For ionic air-entraining agent, mainly by determining mechanism of electrostatic repulsion. The first way is air-entraining agent concentration on the surface of the liquid film that form bubbles. Of air-entraining agent molecules by polar groups point to signs of water and form a layer of protective film. If the air-entraining agent molecules with electric charge, the bubbles which take charge. Under the effect of mixed air bubbles in the process of close to each other, because of the influence of the electrostatic repulsion make bubbles separated. The role and emulsifier to keep the stability of the emulsion, prevent similar to the mechanism of demulsification. In the absence of air-entraining agent in the concrete. Under the effect of mixing, when the bubble close to each other, small bubbles easily merged into big bubbles. Then, in the dual role of buoyancy and stirring loose, large bubbles rise to the surface of concrete slurry, where big bubbles burst and consumed, the air content of concrete slurry decreases. For nonionic surfactant. Mainly molecular hydration layer stability mechanism. The second mode of bubble stability related to the formation of bubbles on the surface of hydration layer. The thickness of the hydration layer may have a few water molecules, its role is to bubble separation, make the system stable and prevent flocculation system. This effect is considered to be occurred in the form of nonionic surfactant enrichment layer. As a result of the nonionic surfactant enrichment layer cannot make bubbles take charge, so the hydration layer is the only bubble stability factors play a role, air-entraining agent and eventually lead to the ions air-entraining agent and air-entraining effect comparison difference, bubble size is bigger. In addition to the bubble stability mechanism, M ielenz and others also proposed 'insoluble film mechanism' ( Insolu - ble电影机制) 。 If anion in the air-entraining agent and concrete Ca ' 'to form insoluble salt, then the insoluble calcium salt will be in the enrichment of anionic air-entraining agent layer on the surface of the bubble settle, forming hard protective 'shell', not protect bubbles merge. As is known to all, cationic and nonionic surfactant will not form insoluble calcium salt precipitation, these two kinds of surfactants, however, did it bleed air. And, with the Cat 'to form soluble calcium salt anionic admixtures such as alkyl sulfonate, also has the very good air-entraining effect. 'Insoluble film stability mechanism', therefore, is likely to be important, but not required.
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