CN-121991306-A - Star polycarboxylate water reducer, preparation method thereof and application thereof in UHPC

CN121991306ACN 121991306 ACN121991306 ACN 121991306ACN-121991306-A

Abstract

The invention relates to the technical field of building material chemical additives, in particular to a star polycarboxylate water reducer, a preparation method thereof and application thereof in UHPC. The invention adopts reversible addition-fragmentation chain transfer activity controllable polymerization technology to construct a unique star-shaped molecular structure which takes a phosphorylated carbon point with a surface rich in phosphate groups as a core and a polycarboxylic acid ether copolymer as an arm, the phosphorylated carbon point core realizes instant anchoring of cement and silica fume particles through the super chelating capacity of the phosphate groups and calcium ions, the star-shaped structure with high branched chain density provides three-dimensional steric hindrance of far super comb-shaped molecules, the re-flocculation of the particles is effectively inhibited, the water reducer shows ultra-fast dispersibility, excellent dispersion retention and obvious viscosity reduction effect in UHPC with the water-gel ratio less than or equal to 0.20, the compressive strength of each stage of the water reducer can be improved to a certain extent, and the preparation method has strong molecular designability and controllable product structure and provides a new generation solution for UHPC working regulation.

Inventors

ZHENG CHUNYANG
CHEN BENWEN
QU HAOJIE
WANG XUECHUAN
QIAN CHUNXIANG
YU PENGCHENG
WANG KEHAN
Li Hongma
DU XINKANG
WANG JIAN

Assignees

江苏奥莱特新材料股份有限公司
东南大学

Dates

Publication Date: 20260508
Application Date: 20260205

Claims (10)

1. A star-shaped polycarboxylate water reducer is characterized by having a star-shaped structure with a phosphorylated carbon point as a core and a polycarboxylate ether copolymer as an arm, wherein the surface of the phosphorylated carbon point core contains a phosphate group, and the polycarboxylate ether arm is formed by reversible addition-fragmentation chain transfer polymerization of a polyether macromonomer and an alkenyl carboxylic acid small monomer.
2. The star polycarboxylate water reducer of claim 1, wherein the polyether macromonomer is methyl polyethylene glycol acrylate and the alkenyl carboxylic acid small monomer is acrylic acid.
3. The star polycarboxylate water reducer according to claim 2, wherein the number average molecular weight of polyethylene glycol chain segments in the methyl polyethylene glycol acrylate is 500 g/mol-2000 g/mol.
4. A method for preparing the star polycarboxylate water reducer according to any one of claims 1 to 3, comprising the steps of: Step one, synthesizing a phosphorylated carbon dot, namely synthesizing the phosphorylated carbon dot with carboxyl and a phosphate group by a hydrothermal method by taking citric acid as a carbon source and phosphoric acid as a phosphorus source, and performing dialysis purification and freeze drying for later use; Step two, preparing a carbon dot macromolecular chain transfer agent, namely covalently connecting the phosphorylated carbon dot obtained in the step one with a carboxyl-containing trithiocarbonate RAFT reagent in the presence of a carboxyl activating agent through amidation reaction to prepare the chain transfer agent taking the carbon dot as a core, wherein the carboxyl-containing trithiocarbonate RAFT reagent is S-1-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate; And thirdly, synthesizing the star polycarboxylate water reducer, namely initiating polymerization reaction by using the carbon-point macromolecular chain transfer agent obtained in the second step, taking methyl polyethylene glycol acrylate and acrylic acid as comonomers, and grafting a polycarboxylate branched chain on the surface of a carbon-point core through RAFT polymerization reaction to obtain the star polycarboxylate water reducer.
5. The preparation method of the star polycarboxylate water reducer, according to claim 4, is characterized in that in the first step, the mass ratio of citric acid to phosphoric acid is 1.5:1-2.5:1, the hydrothermal reaction temperature is 160-200 ℃, and the reaction time is 4-8 hours.
6. The preparation method of the star polycarboxylate water reducer, according to claim 4, is characterized in that in the second step, the carboxyl activating agent is a combination of 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide, and the mass ratio of 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride in the carbon phosphorylate, the carboxyl activating agent and the carboxyl-containing trithiocarbonate RAFT reagent is 1:1.5-5.5:1.5-5.0.
7. The preparation method of the star polycarboxylate water reducer, according to claim 4, is characterized in that in the third step, the ratio of the carbon-point macromolecular chain transfer agent to the total mass of the comonomer is 0.5% -2.5%, and the molar ratio of the methyl polyethylene glycol acrylate to the acrylic acid in the comonomer is 1:1-1:5.
8. The preparation method of the star polycarboxylate water reducer, which is disclosed in claim 4, is characterized in that in the third step, the RAFT polymerization reaction is performed under the protection of inert gas, the reaction temperature is 60-80 ℃, the reaction time is 4-12 hours, the polymerization reaction uses azodiisobutyronitrile as an initiator, and the dosage of the azodiisobutyronitrile is 10-30% of the mass of the carbon-point macromolecular chain transfer agent.
9. The method for preparing a star polycarboxylate water reducer according to claim 4, wherein in the third step, the number average molecular weight of the polyethylene glycol segment in the methyl polyethylene glycol acrylate is 500 g/mol to 2000 g/mol.
10. The application of the star polycarboxylate water reducer as claimed in any one of claims 1 to 3 as a cement-based material additive in UHPC, wherein the cement-based material is one of cement paste, mortar, concrete and ultra-high performance concrete.

Description

Star polycarboxylate water reducer, preparation method thereof and application thereof in UHPC Technical Field The invention relates to the technical field of building material chemical additives, in particular to a star polycarboxylate water reducer, a preparation method thereof and application thereof in UHPC. Background Ultra-high performance concrete (UHPC) has wide application prospect in modern civil engineering such as large bridges, key infrastructure, high-rise buildings and the like by virtue of excellent mechanical strength, toughness and durability. The performance of UHPC is achieved by the synergistic effect of extremely low water to gel ratio (usually less than or equal to 0.20) and high proportion of active or inert ultra-fine powder (such as silica fume, quartz powder, etc.). However, the extremely compact component system directly leads to extremely high viscosity and extremely poor fluidity of the freshly mixed slurry, and the strong van der Waals force among particles makes the materials extremely easy to flocculate, thus bringing great difficulty to construction. Therefore, unprecedented stringent requirements are placed on the performance of water reducers, particularly their dispersion efficiency and adsorption rate. The high-efficiency water reducer must be capable of rapidly adsorbing on the surface of cement and mineral admixture particles in a complex slurry environment with high solid content and high specific surface area, and provide strong and durable dispersing force. To address the challenges described above, polycarboxylic acid water reducer (PCE) optimization studies for UHPC have been mainly developed in two directions, but both have inherent drawbacks: (1) Chemical modification of linear PCE molecules this strategy focuses on adjusting the side chain length, the degree of main chain polymerization of the PCE molecule or introducing special functional monomers to optimize its hydrophilic-hydrophobic balance and adsorption behavior. For example, chinese patent application publication No. CN117843882a discloses a UHPC-specific water reducing agent prepared by introducing a modified polyol and a vinylaromatic monomer. Although the method improves the water reduction rate and slump retention of the product to a certain extent through molecular design, the method still belongs to a linear or slightly branched molecular structure in nature. In linear configurations, the adsorption conformation of the molecular chains on the particle surface is relatively single, the adsorption sites are limited, in UHPC extremely dense multiphase systems, the adsorption process can be relatively slow, and the steric hindrance effect provided is limited. Thus, conventional linear PCEs tend to have difficulty in completely inhibiting rapid flocculation of ultrafine particles (e.g., silica fume), and in meeting the dual demands of UHPC for initial fluidity and flow retention. (2) Physical blending modification of PCE with inorganic nanomaterials to enhance dispersion effects, researchers have attempted to physically blend PCE with nanomaterials (e.g., nanosilica, carbon nanotubes, etc.) in an effort to take advantage of the surface and filling effects of the nanomaterials. For example, chinese patent application publication No. CN120349113a proposes adding nano silica to a polycarboxylate water reducer in combination with ultrasonic dispersion treatment. The method can improve the dispersibility and the impermeability of the slurry in a short period of time, but has the essential defects that firstly, uniform and stable dispersion of nano particles in an organic phase is difficult to realize by physical blending, the nano particles are extremely easy to generate reagglomeration, so that the performance is unstable and even fails, and secondly, the interface compatibility between an inorganic nano material and an organic polymer PCE is poor, the chemical bonding is lacking, the phase separation is easy to occur in a complex concrete hydration environment, and the durable molecular-level synergistic effect cannot be realized. In recent years, carbon Dots (CDs) have been attracting attention as a novel zero-dimensional nanocarbon material because of the surface of the material being rich in functional groups such as carboxyl groups and hydroxyl groups, good biocompatibility, simple preparation, and the like. Preliminary studies have been conducted to explore the use of carbon dots directly as cement dispersants. However, the original carbon point which is not subjected to functional design has limited functional group types and density, weak chelating ability to calcium ions, insufficient adsorption strength and specificity on the surface of cement particles, and the efficiency of the original carbon point is far lower than that of a mature PCE product when the original carbon point is independently used as a dispersing agent, and cannot meet the high-performance requirement of UHPC. In view of the a