Superplasticizer in Concrete
Development history of superplasticizers
According to different molecules, water reducing agents can be divided into the first generation of ordinary water reducing agents represented by lignin, the second generation of superplasticizers represented by naphthalene series and the third generation of water reducing agents represented by polycarboxylic acid series. Substitute high performance water reducer.
The first generation of lignin-based superplasticizers has gradually withdrawn from the stage of history; the second generation of superplasticizers is represented by naphthalene series, in addition to aliphatic, sulfamate and other superplasticizers.
Naphthalene-based superplasticizer in concrete has the advantages of high water-reducing rate and strong adaptability to various cements, and have occupied the mainstream for a long time in my country. Since 2006, the third-generation polycarboxylic acid-based high-performance water reducer has developed rapidly and has now become a mainstream product in the market, accounting for 78% of its output in 2017.
Compared with naphthalene series, polycarboxylate superplasticizer in concrete has more hydrophilic active groups in the side chain due to its comb-like molecular structure, compared with the linear molecular structure of naphthalene series, and the steric resistance is larger. It is more difficult to coagulate again, and the dispersion performance is stronger, so the dosage of polycarboxylate superplasticizer is lower and the water reduction rate is higher.
In addition, as the polycarboxylate upstream raw material ethylene oxide broke the monopoly of PetroChina and Sinopec, and began to adopt technical routes such as alcohol method and coal chemical industry, the era of huge profits for ethylene oxide has ended, and the cost and price of polycarboxylate It is significantly reduced, which further promotes the replacement of traditional naphthalene-based water-reducing agents by polycarboxylic acid-based water-reducing agents.
The working principle of water reducing agent
- Improve the strength and workability of concrete, and reduce the amount of cement: Concrete water reducer can reduce the amount of mixing water and improve the strength of concrete under the condition that the amount of concrete cement is unchanged; under the condition of constant workability and strength, it can save Additives for cement dosage.
- From the molecular structure of water reducing agent, it has two main functions
- Dispersion: After adding water to cement, a flocculation structure will be formed due to factors such as molecular cohesion between cement particles. The molecules of the water reducing agent are composed of hydrophilic groups and hydrophobic groups. When the water reducing agent is added to the cement slurry, its hydrophobic group points to the cement particles, and is directionally adsorbed on the surface of the cement particles to form an adsorption film, which makes the cement particles With the same electric charge, under the action of electrostatic repulsion, the flocculation structure disintegrates and becomes a smaller structure.
- Lubrication: When the flocculation structure is destroyed, the encapsulated water is also released and participates in the flow, which enhances the fluidity; in addition, due to the strong polarity of the hydrophilic group of the water-reducing agent, the water-reducing agent on the surface of the cement particles adsorbs the film It can form a stable volume hydration film with water molecules, which can play a good lubricating effect and further enhance the fluidity.
Supply potential of polycarboxylate superplasticizers in China
In recent years, the manufacturers of superplasticizers inside and outside the market are developing products and expanding the market, and the production and supply capacity has increased significantly. At present, the production and supply system of raw materials in my country has been established, and the development of polycarboxylate superplasticizers in my country in the next few years already has a solid raw material foundation.
Another main raw material of polycarboxylate superplasticizer in concrete is methacrylic acid and acrylic acid. At present, the relevant manufacturers in my country are strengthening the quality and expanding the scale, which will meet the market demand.
my country’s high-efficiency water-reducing agent export market has developed for many years and has been exported to more than 100 countries around the world, but the export destination countries are mainly developing countries such as the Middle East, Southeast Asia, and Africa. Opportunities are always accompanied by risks.
Although the export of concrete admixtures in my country has formed a certain scale, with the continuous expansion of the export scale, more and more problems are gradually exposed. The impact of a series of problems such as the turbulent international financial environment and rising costs on exports cannot be ignored. How to seize opportunities and avoid risks is a problem that the industry must seriously consider.
Only by breaking through these challenges can we seek business opportunities in the fiercely competitive international market.