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Water reduction mechanism of polycarboxylic ether based superplasticizers

Today'' s concrete superplasticizers are primarily prepared by worsening numerous products such as polycarboxylate water-reducing mommy liquor and also polycarboxylate slump-preserving mommy alcohol plus retarders, air-entraining agents, as well as defoaming representatives. Among them, the role of water-reducing mother service in superplasticizer is irreplaceable. Perhaps the amount of mommy solution will certainly alter due to the modification of concrete material, yet I have never listened to that water-reducing mother option is not included in superplasticizer since the sand is as well great.
The water-reducing mom liquid is used as the outright main material in the water-reducing representative, as well as its feature is to lower the concrete water-cement proportion (indirectly boost the stamina of the concrete), as well as at the very same time make sure the fluidness and workability of the concrete blend, as well as make certain the toughness of the concrete. At the very same time, it also assists in the work of the construction device.

We know that along with seal as well as water in concrete, the effect of the remaining materials on the superplasticizer admixture particles is primarily adsorption (waste), so the water reducing agent is primarily targeted at cement. So initially, let’& rsquo; s discover the hydration process of cement.

The hydration process of general portland concrete is separated into 3 phases:

( 1) Dissolution stage: When the concrete is in contact with water, the surface of the bits begins to moisturize, and also a small amount of hydration products are produced, which are instantly liquified in water. The subjected new surface permits hydration to proceed till a saturated solution of hydration items is developed.
( 2) Gelation phase: As a result of the saturation of the solution, the item that remains to be moisturized can no longer be dissolved, yet is directly sped up as colloidal particles. With the increase of hydration products, the hydration aggregates, and also the concrete slurry gradually sheds its plasticity, causing a coagulation sensation.
( 3) Condensation stage: The colloid composed of microscopic crystals is not stable, as well as can progressively recrystallize to create macroscopic crystals, to ensure that the mechanical stamina of the hard body of the cement slurry is constantly enhanced, and also ultimately it ends up being a concrete rock with a specific mechanical stamina.

In the concrete slurry, the diffusion device of polycarboxylic ether based superplasticizers is generally considered to be the primary duty of steric hindrance and also the second duty of electrostatic repulsion. Additionally, the complexation of calcium ions as well as the lubrication of hydration film also contribute. important role.

1. Steric limitation:
The hydration procedure of concrete will certainly make the cement molecules attract each various other, causing a flocculation framework.
During the development of the flocculation framework, the concrete molecules will certainly envelop a part of the water molecules, and also the encapsulated water make up about 10% -30% of the complete mixing water (this may be the reason that the water lowering representative has a water decreasing price restriction). Because it is covered by concrete molecules, it can not participate in the free circulation and lubrication in between concrete particles, hence impacting the fluidity of concrete combinations. When the polycarboxylate concrete admixture particles initial entered into contact with the concrete fragments, the adversely billed main chain in the polycarboxylate concrete admixture particles can be adsorbed on the surface of the favorably charged cement bits, that is, an "anchoring" sensation takes place, while the polycarboxylate superplasticizer The lengthy side chain in the molecule is expanded in the liquid phase of the concrete slurry to form an adsorption layer with a particular density, and can create a three-dimensional and also went across lengthy side chain with other polycarboxylic acid superplasticizer particles extending in the fluid stage of the cement slurry at the very same time. Conformation. When the concrete fragments approach each various other, the adsorption layer overlaps, and also the bigger the overlapping variety, the higher the repulsion between the cement particles, therefore enhancing the dispersibility of the cement fragments. Ruin the flocculation framework in between cement molecules. The release of the water caught by cement flocculation can also be understood as the water lowering agent molecules boost the lubricating utilization price of the water particles to the concrete molecules, and also do not boost the water or lower the number of water particles out of slim air.

2. The theory of electrostatic repulsion:
Polycarboxylic acid superplasticizer particles have anionic teams (COO2-), and also in the very early hydration procedure of cement, the surface area of concrete particles has favorable charges (Ca2+), for that reason, anionic Polycarboxylic acid superplasticizer molecules adsorb to positively billed cement particles surface. Make the cement particles into a "hedgehog" with negative cost. Due to the fact that the cement bits with the same unfavorable fee repel each various other (electrostatic repulsion), the dispersibility in between the concrete fragments is boosted. At the exact same time, the adversely billed carboxyl teams and positively charged calcium ions in the concrete paste kind unstable complexes. After the calcium ions liquified in the concrete system are caught, the calcium ion focus lowers considerably, decreasing the calcium ions in the system. It can reduce the formation of gel fragments as well as thus decrease the hydration price of concrete, inhibit the hydration of concrete, as well as enhance the diffusion performance of concrete particles. The greater the web content of carboxylate ions in the Polycarboxylic acid superplasticizer, that is, the greater the anion charge thickness, the better the diffusion performance of cement bits (acid-ether proportion). The decrease of calcium ion concentration can prevent the first hydration of concrete. With the continuous progress of hydration, the complex will decompose by itself, so Polycarboxylic acid superplasticizer has a specific retarding result without affecting the toughness of concrete.

3. Lubrication
The branched chain of the polycarboxylic acid superplasticizer particle has hydrophilic groups. These groups form a water film on the surface of the concrete particles by combining with water molecules, which reduces the surface energy of the concrete bits. Slides quickly. The mixed result of the above results in separation in between the cement particles. The macroscopic efficiency is that the concrete mix has much better fluidness.
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