News information

Synthesis and compound method of high efficiency water reducing agent

Release time:

2022-06-25

Source:

高效减水剂的合成和复配方法

a kindSuperplasticizerThe synthesis and compounding method of the invention includes the following steps: 1) using the solution method, using methacrylic acid, acrylic acid and polyethylene glycol as raw materials, preparing an aqueous solution according to a certain molar ratio, adding a catalyst and a polymerization inhibitor into a four-neck flask with a reflux condenser and a mechanical stirrer to obtain a preformed polyoxyethylene acrylate macromonomer; 2) heating the water bath to a certain temperature and completing dropwise addition within a certain time. An aqueous ammonium persulfate solution of a certain concentration was added dropwise, and the reaction was continued for a certain period of time. After cooling to room temperature, the pH of the product is adjusted to 7-8 with 30% NaOH. A new type of dendritic polycarboxylic acid high performance and high efficiency water reducing agent was synthesized. 3) Polycarboxylic acid systemSuperplasticizerThe compounding system obtained by the compounding process with naphthalene-based high-efficiency water reducing agent.

On the other hand, in order to improve the compactness and strength, it is necessary to lower the water-cement ratio. The consequence of reducing the water-cement ratio is that the viscosity of the concrete increases and the rheological properties become worse. At present, the effective and realistic way to solve the above contradictions is to add high-efficiency water reducing agent. OrdinarySuperplasticizerThe function is:(1) in the case of keeping the water cement ratio unchanged, greatly improve the workability of fresh concrete, improve the workability, make it meet the pumping requirements. The high water reduction rate of high efficiency water reducing agent further reduces the water cement ratio, further improves the strength of concrete, and develops to the stage of high performance concrete, which greatly promotes the development of construction industry and is a great progress of modern construction industry. specific technology. At the same time, by stimulating the activity of steel slag, fly ash, etc., and the coordination between high-efficiency water reducing agent, high-efficiency water reducing agent can partially replace cement and become an excellent admixture in high-performance concrete. agents and them. Significant economic and social benefits are also in line with the sustainable development strategy, and its development and application level has become one of the important indicators to measure the level of a country's economic development. At present, from the perspective of technological development, it has entered the stage of high-performance and high-efficiency water reducing agent. As a key material, high-efficiency water-reducing agent not only requires better water-reducing effect, but also better control the loss of concrete fluidity over time, and solve the problems of air-entraining, retarding and bleeding of concrete, so as to achieve coordination and unity of high fluidity and high plasticity. At present, the widely used naphthalene series, melamine series, and sulfamic acid series superplasticizers generally have problems such as excessive slump loss or serious bleeding when used alone; while naphthalene series and melamine series superplasticizers also have high raw material prices and lack of raw materials. In particular, some toxic and harmful chemicals are used in the production process, which is not conducive to sustainable development. deficiencies, partially restricted the further promotion and application.

Steric hindrance effect theory: This theory is mainly applicable to polycarboxylic acid superplasticizer. When the thickness of the adsorption layer on the surface of cement particles increases, it is beneficial to the dispersion of cement particles and the release of free water between cement particles. The presence of a large number of comb-like side chains-(CH2-CH2-O)n-in the polymer molecules of polycarboxylic acid superplasticizer makes the molecular structure appear comb-like and forms larger adsorption layer particles on the surface of cement. Its water-reducing effect is mainly caused by the steric hindrance effect caused by the macromolecular chain and its branches. It contains more longer branched chains. After being adsorbed on the surface of cement particles, a thicker three-dimensional cladding can be formed on the surface of cement particles, so that the cement can achieve a better and more lasting dispersion effect.

Slow-release theory of active polymer: This theory is similar to the theory of steric hindrance effect and is mainly used for the study of water reduction and slump retention of polycarboxylic acid-based polymers.

Key words:

Superplasticizer

What are the types of superplasticizer?

The main function of high efficiency water reducing agent

All