Control Measures of Bleeding After Using Superplasticizer

The use of superplastificante policarbossilate béton, compared to the use of traditional naphthalene series, aliphatic superplasticizer concrete, most of the time bleeding will be lower, less bleeding will be larger. But once the use of carboxylic acid concrete excessive bleeding, often difficult to adjust up.

1.Molecular mechanism design of polycarboxylate superplasticizer

Polycarboxylate superplasticizer can reduce bleeding in different ways. Prima, polycarboxylate superplasticizer reduces water consumption on the premise of guaranteeing the workability of cement-based materials. When the water consumption of mixing materials decreases, bleeding water will be significantly reduced. Siconda, the polycarboxylate water-reducing agent has an excellent dispersion effect, which can fully disperse cement particles into the water to prevent the sedimentation of larger particles, thereby reducing bleeding. Terzu, polycarboxylate molecules were adsorbed on the surface of cement particles, making cement particles repel each other, reducing the effective cement particle size of flocculation in a mass, delaying the sedimentation rate and reducing bleeding water. Another advantage is that the polycarboxylate superplasticizer molecules are highly customizable. Smaller molecular weight, dispersion will increase, bleeding slightly reduced, but at the same time brought concrete liquidity loss should be considered. Similar to the effect of molecular weight on bleeding, the content of the main chain adsorption group in polycarboxylate molecules, the density of graft chain, length of branch chain and other factors have an effect on concrete bleeding.

2 Polycarboxylate superplasticizer added excipients

Adding auxiliary materials in polycarboxylate superplasticizer, such as air-conditioner, antischiuma, coagulant promoter, retarder, viscosity regulator, ecc., can improve concrete bleeding.

Air entrainer can reduce the surface tension of water and introduce tiny bubbles. Due to the different polarity of the static charge, these tiny bubbles will adsorb on the surface of cement particles, and the average density of the cement particles adsorbing the bubbles will decrease, which will reduce the sedimentation speed and thus reduce bleeding. Antifoaming agents have a similar mechanism but the opposite effect. Coagulant can shorten the coagulation time, so the solid particle deposition time will be shortened, u sanguinamentu di a superficia serà ridutta. À l'inverse, i ritardanti aumentanu i tassi di sagnamentu perchè allarganu u tempu chì ci vole à l'acqua per risaltà à a superficia di u slurry appena mistu.. U regulatore di viscosità hè adupratu per migliurà a viscosità di l'acqua di mischju, è poi aghjustà a tarifa di sedimentazione di particeddi solidi, per ottene a regulazione di u sanguinamentu.

3.Gradazione di aggregate di béton

Gradazione aggregata adatta, aiuta à riduce u sanguinamentu, principarmenti riflessu in a tarifa di sabbia, modulu di sabbia dui aspetti.

Quandu a tarifa di sabbia hè troppu chjuca, a quantità di mortar hè insufficiente, è abbastanza capa di mortar ùn pò esse furmatu intornu à aggregate grossu per lubricazione è riempimentu, chì riducerà a fluidità di a mistura, fà chì a cuesione è a retenzioni d'acqua di u mischju di cimentu diventanu poviri, facendu chì a mistura di cimentu pare ruvida, segregazione aggregata grossa, perdita di slurry di cimentu, l'acqua hè faciule per precipitate. Un aumentu adattatu di a tarifa di sabbia pò riduce u sanguinamentu; Altrimenti, u sanguinamentu pò esse aumentatu. L'influenza di u modulu di sabbia nantu à l'acqua sanguinante si riferisce in realtà à a particella più chjuca di l'agregatu., in particulare a parte chì a dimensione di particella hè menu di 0,315 mm, chì hè soprattuttu criticu à u rendiment di ritenzione d'acqua di u béton. Reduce u modulu di sabbia in modu adattatu, o aghjunghje a quantità ghjusta di limo, aiutanu à riduce u sanguinamentu di béton; Altrimenti, u sanguinamentu pò esse aumentatu.

4 Mistura di béton

U sanguinamentu di u béton essenzialmente pò esse vistu cum'è un livellu più fine di segregazione, acqua cum'è una fase liquida, tutte e particelle solide sò una fase solida, u prucessu di sanguinamentu hè a resistenza viscosa di l'acqua ùn hè micca abbastanza per superà a gravità di u prucessu di particelle di cimentu. Then consider adding some fine mixing materials, such as a fine fly ash, silicon ash, because these material particles is small, not be separated from water, and water evenly mixed together constitute the liquid phase, increasing the liquid viscosity, to enhance ability to prevent cement particles under the effect of gravity settlement, thus can reduce bleeding.

5 Cimentu

The contribution of cement to concrete bleeding is mainly two aspects, one is fineness, the other is admixture.

The increase in cement fineness has two positive effects on the reduction of bleeding. Primu, the decrease of cement particle size means that the sedimentation speed is slowed down. In più, the finer the cement particles, the larger the specific surface area, the faster the reaction rate with water, the higher the viscosity, the faster the condensation and hardening of the system will be, thus leading to a decrease in the effective time of solid particles deposition, and thus the reduction of bleeding water.

Different types of cement admixtures also lead to differences in bleeding rate, which is the same as the role of concrete admixtures.

Concrete bleeding is a double-edged sword, only control the appropriate bleeding rate, in order to ensure the smooth concrete pouring and hardening of the indicators. The index of bleeding water is affected by many factors such as water-reducing agent, mischju, cimentu, aggregatu, air temperature, mixing ratio, and construction method. When it is found that the concrete bleeding rate is too high or too low, the relevant units in the upstream and downstream, including construction parties, concrete companies, fornitori di materie prime, in particulare i pruduttori di miscele, deve piglià misure puntuale per selezziunà unu o più schemi per cuntrullà a rata di sanguinamentu in un intervallu raghjone, chì conduce à eliminà i periculi oculati è assicurendu a qualità di u prugettu.

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