Polycarboxylate Superplasticizer

Polycarboxylate superplasticizer is the third generation of concrete reducer. It is a type of high-performance superplasticizer developed after the common superplasticizer represented by wood calcium and superplasticizer represented by naphthalene series. Polycarboxylic acid series high-performance water reducing agent is a kind of surface active agent. And its molecular structure is carboxyl-containing graft copolymer. The molecular structure is comb-shaped, which is mainly obtained by the copolymerization of unsaturated monomers under the action of initiators. The main chain is polymerized by carboxyl-containing living monomers. And the side chain is composed of reactive monomers with functional function groups and the main link. It is formed by branch copolymerization. So it has a high water reducing rate and can make the commercial concrete mixture with good fluidity retention effect.

• Suitable for precast and cast-in-place concrete, reinforced concrete and prestressed concrete for high-speed railways, passenger dedicated lines, industrial and civil buildings, roads, bridges, ports, airports, etc.
• It is especially suitable for projects that require a long construction time for preparing concrete and high requirements for maintaining concrete slump, such as nuclear power projects.
• PCE chemical is a high-performance polycarboxylate superplasticizer powder specially used in high-aluminum and sulphur-aluminum cement systems. It is a white water-soluble powder. It has very excellent dispersing ability. SNF powder can significantly improve the fluidity of cement-based materials, endow the material with excellent workability and high mechanical strength. It also has a very fast plasticizing speed. After mixing it with water, it can quickly play a role, significantly improve construction efficiency and meet different construction requirements.
• Polycarboxylate based superplasticizer can be compounded with various admixtures to form a multifunctional admixture, such as pumping agent, early strength agent, impermeable waterproofing agent, retarder, etc.
• Polycarboxylate superplasticizer powder has excellent adaptability, especially suitable for sulphur-aluminum, high-aluminum and gypsum systems. It can be widely used in various products systems such as dry mortar and concrete. It is especially suitable for the preparation of various high-end value-type mortar products and concrete products, such as surface self-leveling mortar, bearing mortar, etc.

Polycarboxylate concrete admixtures is not a stereotyped product, but a series of products with a certain commonality. Due to the different molecular structure, the degree of improvement on the performance of commercial concrete is slightly different.

According to the different raw materials used in the main chain, it is divided into acrylic acid, methacrylic acid series and maleic anhydride, maleic acid series, etc.

According to the different types of active monomers and other raw materials used, it can be divided into binary and ternary copolymers.

Based on the different nature of surfactants, it can be divided into non-ionic water-reducing agent and anionic water-reducing agent.

According to different purposes, it is divided into: pre-mixed high-fluidity commercial concrete and pre-cast commercial concrete products.

1. Before use, carry out a trial mix test of concrete first to find the best mixing amount. The mixing amount of polycarboxylate ether superplasticizer it 0.4%-2.5% of the total weight of the gelling material, and the usual mixing amount is 0.8%-1.5%.
2. When using polycarboxylic acid superplasticizer, mix it directly in the form of original solution, or formulate itinto a solution of a certain concentration.
3. As the water reduction rate of concrete mixed with polycarboxylate ether superplasticizeris relatively large, the slump is highly sensitive to water consumption, and water consumption must be strictly controlled during use.
4. Polycarboxylic acid superplasticizer has good adaptability to most cements, but for individual cements, the water reduction rate may be low and the slump loss may be large.In addition, the fineness and storage time of cement may also affect the use effect of polycarboxylate superplasticizer. So it is recommended to appropriately increase the dosage or compound other retarding components to solve this problem.
5. Polycarboxylate ether powdercan’t be mixed with naphthalene superplasticizers. So when using PCE superplasticizer, the mixers and mixer trucks that have used naphthalene superplasticizers must be rinsed or they may lose water reduction effect.

Hydration film lubrication

Due to the presence of hydrophilic polar groups in the molecular structure, polycarboxylate superplasticizers can form a solvated water film with a certain mechanical strength on the surface of cement particles. The formation of the hydration film can destroy the flocculation structure of the cement particles, release the mixing water enclosed in it, make the cement particles fully dispersed, and improve the wettability of the surface of the cement particles. It has a lubricating effect, so macroscopically, it shows that the fluidity of fresh concrete is increased, and the workability is good.

Electrostatic repulsion

The stability of cement particles is mainly determined by the balance of electrostatic repulsion and van der Waals attraction. When polycarboxylate superplasticizer is added to fresh concrete, the negative ions in it will be directionally adsorbed on the surface of the cement particles under the astion of the positive charge of the cement particles. Thus, the ion distribution of the diffused electric double layer is formed, so that the surface of the cement particles is charged with the same electric charge, resulting in electrostatic repulsion. The flocculation structure of cement particles disintegrates, and the particles disperse each other, releasing the free water encapsulated in the floc, thereby effectively increasing the fluidity of the mixture.

Steric hindrance

The polycarboxylate water-reducing agent adsorbed on the surface of the cement particles can reduce the negative potential of the cement particles less, and the electrostatic repulsion is less. However, since the main chain is connected to the surface of the cement particles, the branched chain extends into the liquid phase to form a thicker adsorption layer of polymer molecules, which has a large steric repulsion. Therefore, when the dosage is small, it has a significant dispersing effect on the cement particles.

Air bleed isolation

The polycarboxylate superplasticizer has a certain air-entraining effect because it can reduce the liquid-gas interfacial tension. When adding water reducing agent to concrete mixture, it can not only be adsorbed on the solid-liquid interface, but also easily form many tiny air bubbles in the concrete mixture. The molecules of the superplasticizer are arranged on the liquid-gas cross section of the bubbles, so that a layer of hydration film is formed on the surface of the bubbles, and at the same time, it is charged with the same electric charge as the cement particles. The electrostatic repulsion is generated between the air bubbles and the air bubbles, and between the air bubbles and the cement particles, which can isolate the cement particles and prevents the cement particles from agglomerating.

Moreover, the ball-and-floating action of air bubbles also contributes to the relative sliding between cement particles and aggregate particles in fresh concrete. Therefore, the air-entraining isolation effect of superplasticizers can improve the workability of concrete mixtures.