At present, there are many classification methods for concrete water reducers. They are generally divided into three generations in China according to the use of algebra: the first generation is the Lignin as an ordinary water-reducing agent, the second generation is the water-soluble resin high-efficiency water-reducing agent, and the third generation is the polycarboxylic acid-based high-performance water-reducing agent.
The first generation of ordinary water reducers – lignin water reducer
The lignin-based water-reducing agent is one of the earliest used water-reducing agents. In 1935, E.W. Scripture in the United States included sulfurous Sour pulp waste liquid fermented to remove sugar and then add some other chemical components and successfully developed a lignosulfonate as the main Ingredient superplasticizer. In the 1950s, lignosulfonate water reducer was used in concrete such as slip form, dams, and winter construction in the United States.
The second generation of high-efficiency water reducers — water-soluble resin water reducers
The second generation of superplasticizers mainly refers to water-soluble resin water-reducing agents, mainly including naphthalene sulfonate formaldehyde series, melamine sulfamate formaldehyde, aliphatic sulfonate, sulfamate water reducers, etc.
(1) Naphthalene water reducers (FDN)
Naphthalene series water reducing agent is made of naphthalene and naphthalene homologs through sulfonation and condensation. Its main component is naphthalene sulfonic acid formaldehyde concentrate, which is an anionic surfactant.
(2) Aliphatic sulfonate water reducing agent (ASF)
Aliphatic sulfonate water reducing agent is produced by sulfonation and condensation reaction of acetone, sodium sulfite, or sodium bisulfite in a certain proportion under alkaline conditions.
(3) Melamine sulfonate formaldehyde water reducing agent (SMF)
Melamine sulfonate formaldehyde water reducing agent is a water-soluble polymer formed by polycondensation of melamine, formaldehyde, and sodium sulfite in a certain proportion.
(4) Sulfamate water reducing agent (ASP)
Sulfamate water reducing agent is a water-reducing agent formed by condensation of sodium p-aminobenzene sulfonate, phenol, and formaldehyde as the main raw materials under certain temperature conditions.
The third generation of high-performance water reducer — polycarboxylate superplasticizer
The polycarboxylate superplasticizer is made of anionic monomers with double bonds (such as methacrylic acid, sodium methacrylate sulfonate, 2-acrylamide-2-methyl propane sulfonic acid, etc.) and branches with double bonds. Chain macromonomers (such as HPEG, IPEG/TPEG, etc.) are obtained by the free-radical polymerization reaction, domestic scholars call it a high-performance water reducer.
Compared with the second-generation superplasticizers, polycarboxylate superplasticizers have many very obvious advantages:
Compared with the second-generation superplasticizers, polycarboxylate superplasticizers have many very obvious advantages:
(1) Low dosage, when the dosage is 0.15%-0.20%, it can exert good dispersing performance.
(2) High water reduction rate, effective in the range of the water-cement ratio of 0.15-0.35.
(3) Strong dispersing force, good flow performance of mixed concrete, good slump retention, basically no loss of slump within 60min.
(4) Good workability, under the same conditions, the concrete mixed with polycarboxylate superplasticizer has excellent expansion and bleeding rate.
Concrete mixed with naphthalene water reducer under the same conditions.
(5) The molecular structure is highly variable, and polycarboxylic acid molecules can be adjusted by changing different reaction monomers and reaction conditions.
Section its molecular structure, so as to obtain an ideal design target, with broad design space.
(6) Green and environmental protection, the raw materials of polycarboxylate superplasticizer do not contain toxic substances such as formaldehyde and have little environmental pollution.