Water reduction mechanism of polycarboxylic ether based superplasticizers
Today'' s concrete superplasticizers are essentially prepared by intensifying different products such as polycarboxylate water-reducing mom alcohol and also polycarboxylate slump-preserving mommy liquor plus retarders, air-entraining representatives, as well as defoaming agents. Amongst them, the function of water-reducing mom solution in superplasticizer is irreplaceable. Maybe the quantity of mother solution will alter as a result of the modification of concrete material, yet I have actually never listened to that water-reducing mom service is not contributed to superplasticizer since the sand is too great.
The water-reducing mother fluid is used as the outright main product in the water-reducing agent, and its function is to lower the concrete water-cement proportion (indirectly boost the toughness of the concrete), and also at the exact same time make sure the fluidness as well as workability of the concrete mixture, and also make sure the toughness of the concrete. At the same time, it likewise facilitates the job of the building system.
We know that in addition to cement and also water in concrete, the effect of the staying materials on the superplasticizer admixture particles is essentially adsorption (waste), so the water reducing agent is generally aimed at cement. So first, let’& rsquo; s find out about the hydration procedure of cement.
The hydration procedure of basic portland cement is separated into 3 phases:
( 1) Dissolution stage: When the concrete is in contact with water, the surface area of the bits starts to hydrate, as well as a percentage of hydration items are generated, which are immediately dissolved in water. The subjected brand-new surface area permits hydration to proceed till a saturated remedy of hydration products is developed.
( 2) Gelation stage: As a result of the saturation of the option, the item that remains to be hydrated can no more be dissolved, but is straight precipitated as colloidal particles. With the rise of hydration items, the hydration accumulations, as well as the cement slurry slowly sheds its plasticity, leading to a coagulation sensation.
( 3) Formation stage: The colloid composed of tiny crystals is not stable, and also can slowly recrystallize to develop macroscopic crystals, to make sure that the mechanical strength of the hard body of the concrete slurry is continuously boosted, and also lastly it comes to be a cement rock with a certain mechanical stamina.

In the concrete slurry, the diffusion system of polycarboxylic ether based superplasticizers is typically taken into consideration to be the main role of steric obstacle as well as the additional duty of electrostatic repulsion. Additionally, the complexation of calcium ions and the lubrication of hydration movie likewise contribute. important role.
1. Steric hindrance:
The hydration procedure of concrete will certainly make the concrete particles attract each other, leading to a flocculation framework.
During the development of the flocculation structure, the concrete particles will certainly envelop a component of the water particles, as well as the encapsulated water represent around 10% -30% of the overall mixing water (this might be the reason that the water lowering representative has a water decreasing price limit). Due to the fact that it is wrapped by concrete molecules, it can not join the cost-free flow and lubrication between cement particles, hence influencing the fluidness of concrete combinations. When the polycarboxylate concrete admixture particles very first entered call with the concrete bits, the negatively billed primary chain in the polycarboxylate concrete admixture particles can be adsorbed on the surface of the positively charged concrete fragments, that is, an "anchoring" phenomenon occurs, while the polycarboxylate superplasticizer The lengthy side chain in the molecule is prolonged in the fluid stage of the cement slurry to form an adsorption layer with a specific thickness, as well as can create a three-dimensional as well as crossed lengthy side chain with other polycarboxylic acid superplasticizer particles expanding in the liquid phase of the concrete slurry at the exact same time. Conformation. When the concrete fragments move toward each various other, the adsorption layer overlaps, and also the bigger the overlapping variety, the higher the repulsion in between the concrete bits, consequently boosting the dispersibility of the concrete particles. Destroy the flocculation framework in between concrete molecules. The launch of the water trapped by cement flocculation can likewise be recognized as the water decreasing agent particles enhance the lubricating application rate of the water molecules to the concrete molecules, as well as do not increase the water or minimize the variety of water particles out of thin air.
2. The theory of electrostatic repulsion:
Polycarboxylic acid superplasticizer molecules consist of anionic teams (COO2-), and in the very early hydration procedure of concrete, the surface area of cement particles includes positive costs (Ca2+), for that reason, anionic Polycarboxylic acid superplasticizer particles adsorb to positively charged concrete particles surface area. Make the cement particles into a "hedgehog" with negative charge. Since the concrete bits with the same adverse fee fend off each other (electrostatic repulsion), the dispersibility in between the cement bits is improved. At the very same time, the adversely charged carboxyl groups and positively billed calcium ions in the cement paste kind unsteady facilities. After the calcium ions dissolved in the concrete system are recorded, the calcium ion concentration reduces significantly, lowering the calcium ions in the system. It can decrease the formation of gel particles and also therefore slow down the hydration rate of cement, inhibit the hydration of concrete, and improve the diffusion efficiency of cement particles. The better the web content of carboxylate ions in the Polycarboxylic acid superplasticizer, that is, the better the anion charge density, the greater the dispersion efficiency of cement particles (acid-ether ratio). The reduction of calcium ion focus can prevent the preliminary hydration of cement. With the continual progress of hydration, the facility will certainly decay 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 molecule has hydrophilic teams. These teams form a water film on the surface of the concrete fragments by integrating with water molecules, which reduces the surface energy of the concrete bits. Slips easily. The combined impact of the above lead to separation between the concrete fragments. The macroscopic performance is that the concrete blend has much better fluidity.
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