Poly carboxylic ether
Polycarboxylic acid water reducing agent is a high-performance water reducing agent and a cement dispersant in the application of cement concrete. Widely used in highways, bridges, dams, tunnels, high-rise buildings and other projects.
According to the different structure of its main chain, polycarboxylic acid-based high-efficiency water reducing agent products can be divided into two categories: one is polyether with acrylic acid or methacrylic acid as the main chain and grafted with different side chain lengths. The other type is polyether with maleic anhydride as the main link branch with different side chain lengths. Based on this, a series of high-performance water reducing agent products with different characteristics have been derived.
Common types of concrete admixtures
Before the advent of polycarboxylic acid admixtures, there were lignin sulfonate admixtures, naphthalene sulfonate formaldehyde condensates, melamine formaldehyde condensates, acetone sulfonate formaldehyde condensates, sulfamate formaldehyde condensates, etc. In the early 80s of the 20th century, Japan took the lead in successfully developing polycarboxylic acid water reducing agents. The new generation of polycarboxylic acid high-efficiency water reducing agent overcomes some drawbacks of traditional water reducing agent, and has outstanding advantages such as low dosage, good slump retention performance, low concrete shrinkage, strong tunability in molecular structure, high performance potential, and no formaldehyde in the production process.
Synthesis method of polycarboxylate water reducing agent
For the synthesis of polycarboxylic acid water reducing agents, the design of the molecular structure is crucial, including the backbone group in the molecule, the side chain density, and the side chain length. The synthesis methods mainly include in situ polymerization grafting method, first polymerization and then functionalization method and monomer direct copolymerization method.
- In situ polymerization grafting method
Polyether is used as the medium of unsaturated monomer polymerization reaction, so that the main chain polymerization and the introduction of side chains are carried out at the same time, the process is simple, and the molecular weight of the synthesized water reducing agent can be controlled to a certain extent, but the esterification reaction involved in this method is a reversible reaction, which is carried out in aqueous solution resulting in a relatively low grafting rate and has been gradually eliminated
- First aggregation and then functionalization
This method is mainly to synthesize the main chain of water reducing agent first, and then introduce the side chain for functionalization by other methods, which is difficult to operate, the molecular structure of the water reducing agent is inflexible and the monomer compatibility is not good, so that the use of this method has been greatly limited
- Monomer direct copolymerization method
This method is to prepare the active monomer first, and then copolymerize the small monomer and the large monomer in an aqueous solution under the initiation of the initiator. With the increasing maturity and variety of the synthesis process of large monomers, this synthesis method has become the most common method for the synthesis of polygazelle acid water reducing agent at this stage
- Good compatibility with various cements, good slump maintenance performance of concrete, and prolonging the construction time of concrete.
- Low dosage, high water reduction rate and small shrinkage.
- Greatly improve the early and late strength of concrete.
- This product has low chloride ion content and low alkali content, which is conducive to the durability of concrete.
- The production process of this product is pollution-free, does not contain formaldehyde, meets the international standards of ISO14000 environmental protection management, and is a green environmental protection product.
- The use of polycarboxylate water reducing agent can replace cement with more slag or fly ash, thereby reducing costs