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Water reduction mechanism of polycarboxylic ether based superplasticizers

Today'' s concrete superplasticizers are basically prepared by intensifying various materials such as polycarboxylate water-reducing mommy alcohol as well as polycarboxylate slump-preserving mommy alcohol plus retarders, air-entraining representatives, and defoaming representatives. Among them, the duty of water-reducing mommy service in superplasticizer is irreplaceable. Perhaps the quantity of mommy service will certainly alter due to the modification of concrete material, but I have actually never listened to that water-reducing mommy option is not included in superplasticizer due to the fact that the sand is also excellent.
The water-reducing mom fluid is made use of as the outright main product in the water-reducing representative, as well as its feature is to decrease the concrete water-cement proportion (indirectly boost the toughness of the concrete), and at the same time ensure the fluidness and also workability of the concrete combination, and make certain the stamina of the concrete. At the exact same time, it also helps with the work of the building and construction system.

We understand that along with seal and also water in concrete, the result of the staying materials on the superplasticizer admixture particles is generally adsorption (waste), so the water reducing agent is generally targeted at concrete. So initially, let’& rsquo; s discover the hydration procedure of concrete.

The hydration process of basic portland cement is divided into three phases:

( 1) Dissolution stage: When the concrete is in contact with water, the surface of the particles starts to moisturize, and also a small amount of hydration products are generated, which are right away liquified in water. The revealed new surface area enables hydration to proceed up until a saturated service of hydration items is developed.
( 2) Gelation phase: Because of the saturation of the option, the product that remains to be hydrated can no longer be dissolved, however is straight precipitated as colloidal fragments. With the boost of hydration items, the hydration accumulations, and the concrete slurry progressively sheds its plasticity, leading to a coagulation sensation.
( 3) Condensation stage: The colloid composed of tiny crystals is not stable, and also can slowly recrystallize to form macroscopic crystals, to ensure that the mechanical strength of the solidified body of the concrete slurry is continually boosted, and ultimately it ends up being a cement rock with a specific mechanical stamina.

In the concrete slurry, the diffusion mechanism of polycarboxylic ether based superplasticizers is usually considered to be the major duty of steric obstacle and also the additional function of electrostatic repulsion. Additionally, the complexation of calcium ions and also the lubrication of hydration film additionally contribute. essential function.

1. Steric obstacle:
The hydration process of concrete will certainly make the concrete particles bring in each other, leading to a flocculation structure.
Throughout the formation of the flocculation structure, the cement molecules will envelop a component of the water particles, and also the encapsulated water make up about 10% -30% of the complete mixing water (this might be the reason that the water decreasing representative has a water minimizing price restriction). Due to the fact that it is wrapped by concrete particles, it can not join the totally free flow as well as lubrication in between concrete molecules, thus impacting the fluidness of concrete mixtures. When the polycarboxylate concrete admixture molecules very first come into call with the cement fragments, the negatively charged major chain in the polycarboxylate concrete admixture molecules can be adsorbed externally of the favorably charged cement particles, that is, an "anchoring" phenomenon occurs, while the polycarboxylate superplasticizer The long side chain in the molecule is expanded in the liquid phase of the concrete slurry to create an adsorption layer with a certain density, and also can form a three-dimensional as well as crossed long side chain with various other polycarboxylic acid superplasticizer particles expanding in the liquid stage of the cement slurry at the same time. Conformation. When the concrete fragments move toward each other, the adsorption layer overlaps, as well as the larger the overlapping array, the better the repulsion in between the concrete particles, consequently enhancing the dispersibility of the cement bits. Destroy the flocculation framework between cement particles. The release of the water entraped by concrete flocculation can also be comprehended as the water lowering representative molecules enhance the lubricating usage price of the water molecules to the cement particles, and also do not increase the water or decrease the number of water particles out of thin air.

2. The concept of electrostatic repulsion:
Polycarboxylic acid superplasticizer molecules consist of anionic groups (COO2-), and also in the very early hydration process of cement, the surface of cement bits consists of favorable charges (Ca2+), consequently, anionic Polycarboxylic acid superplasticizer particles adsorb to favorably charged cement bits surface area. Make the cement bits into a "hedgehog" with adverse charge. Because the concrete fragments with the exact same unfavorable cost ward off each other (electrostatic repulsion), the dispersibility between the concrete bits is boosted. At the very same time, the adversely charged carboxyl groups and also positively charged calcium ions in the cement paste form unstable complicateds. After the calcium ions dissolved in the concrete system are captured, the calcium ion focus decreases substantially, reducing the calcium ions in the system. It can decrease the formation of gel particles as well as therefore decrease the hydration price of cement, hinder the hydration of cement, and improve the diffusion performance of concrete bits. The better the material of carboxylate ions in the Polycarboxylic acid superplasticizer, that is, the higher the anion cost density, the better the dispersion efficiency of cement bits (acid-ether proportion). The decline of calcium ion concentration can inhibit the preliminary hydration of cement. With the continuous progress of hydration, the complicated will certainly decompose by itself, so Polycarboxylic acid superplasticizer has a particular retarding impact without affecting the strength of concrete.

3. Lubrication
The branched chain of the polycarboxylic acid superplasticizer particle has hydrophilic groups. These groups create a water film on the surface of the concrete particles by integrating with water molecules, which reduces the surface power of the cement bits. Slips quickly. The consolidated effect of the above cause separation in between the concrete particles. The macroscopic efficiency is that the concrete mixture has much better fluidness.
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