What is polycarboxylate superplasticizer?

(What is polycarboxylate superplasticizer? )

What is polycarboxylate superplasticizer? 

Polycarboxylate superplasticizer is a kind of high-performance water reducer and a kind of cement dispersant in the application of cement concrete. 

They are widely used in highways, bridges, dams, tunnels, high-rise buildings and other projects. 

The product is green, non-flammable, non-explosive, and can be safely transported by train and car. 

Principle of polycarboxylic acid superplasticizer. 

The principle of polycarboxylic acid superplasticizer is as follows: 

1. Steric hindrance effect

When polycarboxylic acid superplasticizer molecules are added to cement concrete, the main anion chain is adsorbed on the surface of cement particles, and their hydration products and the side chain is inserted into the liquid phase. Thus, an adsorption layer with a branched-chain and side chain is formed on the surface of cement particles. When the cement particles are close to each other, to overlap the adsorption layer. 

The steric repulsion force is produced between the branched chain and the side chain of polycarboxylic acid superplasticizer on the surface of cement particles, which turns the water between cement particles into free water, promoting cement concrete's fluidity. 

The longer the side chain and branch chain of polycarboxylate superplasticizer, the thicker the adsorption layer formed on the surface of cement particles, and the greater the steric repulsion between cement particles, the more beneficial to the dispersion of cement particles and the improvement of concrete fluidity. 

2. Wetting and lubrication effect: polycarboxylic acid superplasticizer molecules contain a large number of strong polar hydrophilic groups such as carboxyl, sulfonic acid, and hydroxyl groups, which can associate with water molecules and form a hydration film on the surface of cement particles. It can significantly reduce the interfacial tension between water and cement particles under the condition of constant water consumption and the number of cement particles, the smaller the interfacial tension between water and cement particles. 

The larger the wetting area of moisture on the surface of cement particles, the easier it is for cement particles to slide. It disperses relatively, and it is not easy to agglomerate to improve the fluidity of cement concrete. 

3. Air entraining isolation ball effect: polycarboxylic acid superplasticizer has a certain air-entraining effect; when it is added to concrete, tiny bubbles will be produced in concrete, and the charge of air bubbles is the same as that of cement particles, and electrostatic repulsion will occur between them so that cement particles can be dispersed. 

In addition, bubbles can cause physical isolation between cement particles and prevent agglomeration between cement particles. At the same time, bubbles themselves can play a ball-like role and promote the sliding of cement particles, which is beneficial to the fluidity of concrete. 

The advantages of polycarboxylic acid superplasticizers include the following: 

1. The content is low

In the case of the same fluidity, it has little effect on the setting time of cement and can well solve the contradictions such as water reduction, air intake, retarding, and so on. 

2. High intensity

It can improve the early and later strength of concrete and significantly improve the wear resistance, frost resistance, chloride ion permeability, and crack resistance of concrete. 

3. The cost is low

Reduce the water consumption of concrete and the amount of cement, thus reducing the cost. 

4. Good durability

Improve the sulfate resistance of concrete and inhibit the reaction of alkali-aggregate to improve the durability of concrete. 

5. Good environmental performance

Polycarboxylic acid superplasticizer does not contain formaldehyde, belongs to green environmental protection products, and does not affect human health. 

The content of polycarboxylic acid superplasticizer

The content of polycarboxylic acid superplasticizer is expressed as a percentage of the total amount of cementitious materials. 

According to different engineering conditions and requirements, the optimum content is determined through experiments. 

The content range of polycarboxylic acid superplasticizer is 0.4%-2.5%, and the commonly used content is 0.8%-1.5%.

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(What is polycarboxylate superplasticizer? )