Mud-resistant polycarboxylate superplasticizer and preparation method thereof

Abstract

The invention belongs to the technical field of concrete, and particularly relates to a mud-resistant polycarboxylate superplasticizer and a preparation method thereof. The mud-resistant polycarboxylate superplasticizer is prepared from a zwitterionic monomer, an unsaturated functional monomer containing a primary amine group, an unsaturated polyether macromonomer, an unsaturated acid monomer, formaldehyde, pyrogallic phenol, a chain transfer agent, an initiator, a reducing agent and deionized water. Wherein the zwitterionic monomer is carboxyl betaine methacrylate, and the unsaturated functional monomer containing the primary amine group is 2-aminoethyl methacrylate hydrochloride. The product has the characteristics that the silt content is gt; and in a severe aggregate environment with the content of 5%, extremely high effective adsorption capacity can be maintained only by low mixing amount, and the sensitivity of the concrete to the silt content of sand and gravel is remarkably reduced.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology, specifically relating to an anti-mud polycarboxylate superplasticizer and its preparation method. Background Technology

[0002] Concrete, composed of cement, coarse and fine aggregates, and water, is the most widely used building material globally. Sand, as fine aggregate, plays a crucial role in concrete mix proportions and workability, while polycarboxylate superplasticizers (PCEs) have become standard admixtures for high-performance concrete. Their comb-like molecular structure plays a key role in reducing the water-cement ratio and maintaining slump. PCEs are widely used in the construction of infrastructure such as highways, high-speed railways, hydropower projects, and nuclear power plants. However, PCEs are extremely sensitive to clay content in sand (especially clays such as montmorillonite): clays have a layered structure, a large specific surface area, and a high cation exchange capacity, which preferentially and extensively adsorbs anionic or hydrophilic polycarboxylate molecules, leading to the depletion of the effective active agent. This results in the paste losing its dispersibility, a sharp decrease in fluidity, and ultimately, reduced concrete strength and durability.

[0003] Currently, research on anti-mud polycarboxylate superplasticizers (PCEs) focuses on molecular design and compounding strategies. One approach involves compounding with "sacrificial" additives (such as quaternized or lignin-based sacrificial additives) to preferentially interact with the clay phase in sand, thus protecting PCE activity. Publicly available patents, such as CN107129177A, propose compounding PCEs with quaternized lignin sulfonate anti-mud sacrificial additives, using the sacrificial additives to preferentially interact with the clay in sand to improve the fluidity and anti-mud properties of the paste. Another approach involves introducing functional monomers or anti-mud side groups to enhance tolerance to clay particles. Chinese patent CN113603837A proposes an anti-mud thickening slow-release PCE, which introduces anti-mud functional monomers to construct a spatial network structure and slowly release water-reducing functional units, helping to reduce non-targeted adsorption of PCE by clay and improve flow retention. Furthermore, surface modification technologies such as silanization are also used to improve adaptability to clays such as montmorillonite. Existing functional modifications are mostly concentrated on single methods, such as introducing only cationic groups for electrostatic shielding, or introducing only large groups to increase steric hindrance. Relying on a single mechanism is difficult to cope with the harsh aggregate environment with high mud content. Summary of the Invention

[0004] The purpose of this invention is to provide an anti-mud polycarboxylate superplasticizer. It introduces carboxybenzene methacrylate as an amphoteric ion center through copolymerization and utilizes an unsaturated precursor containing primary amine groups (2-aminoethyl methacrylate hydrochloride) as an active intermediate. Through the Mannich reaction, pyrogallol is grafted as a side group in a specific configuration. This molecular design forms a unique three-dimensional synergistic anti-mud mechanism of "anti-polyelectrolyte conformational support - amine electron activation - multidentate lattice matching," achieving intelligent sorting and synergistic effect of "hydration layer repelling clay" and "chemical bond locking cement" at the microscopic level. This invention also provides a method for preparing the anti-mud polycarboxylate superplasticizer.

[0005] The anti-mud polycarboxylate superplasticizer of the present invention is made from zwitterionic monomers, unsaturated functional monomers containing primary amine groups, unsaturated polyether macromonomers, unsaturated acid monomers, formaldehyde, pyrogallol, chain transfer agents, initiators, reducing agents and deionized water; wherein, the zwitterionic monomer is carboxybetaine methacrylate, and the unsaturated functional monomer containing primary amine groups is 2-aminoethyl methacrylate hydrochloride.

[0006] The unsaturated polyether macromonomers are methyl allyl polyoxyethylene ether or isopentenyl polyoxyethylene ether; The structural formula of methyl allyl polyoxyethylene ether is as follows: In the formula, n1 is 25-100; The structural formula of isopentenyl polyoxyethylene ether is as follows: In the formula, n1 is 25-100.

[0007] The unsaturated acid monomer is acrylic acid, and the molar ratio of zwitterionic monomer, unsaturated functional monomer containing primary amine group, unsaturated polyether macromonomer, unsaturated acid monomer, formaldehyde and pyrogalactosyl is 0.03-0.05:0.3-0.5:1:3-4:0.2-0.4:0.2-0.4.

[0008] The chain transfer agent is mercaptoacetic acid or mercaptopropionic acid, and the amount of chain transfer agent is 1.6-2.0% of the total mass of zwitterionic monomers, unsaturated functional monomers containing primary amine groups, unsaturated polyether macromonomers and unsaturated acid monomers; the initiator is ammonium persulfate or sodium persulfate, and the amount of initiator is 1.5-2.5% of the total mass of zwitterionic monomers, unsaturated functional monomers containing primary amine groups, unsaturated polyether macromonomers and unsaturated acid monomers.

[0009] The reducing agent is sodium formaldehyde sulfoxylate or sodium bisulfite, and the mass ratio of the initiator to the reducing agent is 1:0.5-0.8.

[0010] The preparation method of the anti-mud type polycarboxylate superplasticizer of the present invention includes the following steps: (1) Prepare solution A by mixing zwitterionic monomer, unsaturated functional monomer containing primary amine group, unsaturated acid monomer, chain transfer agent, reducing agent and deionized water; prepare solution B by mixing initiator and deionized water; prepare base liquid by mixing unsaturated polyether macromonomer and deionized water, and heat to obtain preheated base liquid. (2) Under N2 protection, solution A and solution B are simultaneously added dropwise to the preheated base liquid for reaction. After the addition is complete, the reaction is kept warm and then cooled. Sodium hydroxide is added to adjust the pH value to obtain polycarboxylate superplasticizer solution. (3) Under N2 protection, formaldehyde was added to the polycarboxylate superplasticizer solution obtained in step (2) and stirred to obtain a reaction solution; (4) Under N2 protection, pyrogallol is added to the reaction solution obtained in step (3), and the temperature is raised for stirring reaction. After the reaction is completed, water is added for dilution to obtain anti-mud polycarboxylate superplasticizer.

[0011] In step (1), the concentration of solution A is 35-45 wt.%, the concentration of solution B is 2.0-3.0 wt.%, the concentration of the base solution is 45-55 wt.%, and the solution is heated to 45-55℃.

[0012] In step (2), the reaction temperature is 45-55℃, the drop time of solution A is 2.5-3.0h, the drop time of solution B is 3.0-3.5h, the reaction temperature is kept at 45-55℃ for 1.0-2.0h, the temperature is lowered to 20-30℃, and sodium hydroxide is added to adjust the pH value to 7.0-8.0.

[0013] In step (3), the stirring reaction temperature is 20-30℃ and the stirring reaction time is 1.0-1.5h.

[0014] In step (4), the temperature is raised to 55-65℃ and the stirring reaction time is 2.0-2.5h; the solid content of the anti-mud polycarboxylate superplasticizer is 38-42wt.%.

[0015] This invention provides a mud-resistant polycarboxylate superplasticizer modified by the Mannich reaction, possessing pyrogallol (1,2,3-phenylpyrogallol) side groups and zwitterionic centers. This invention utilizes carboxybetaine methacrylate (CBMA) to introduce a betaine structure, and grafts pyrogallol via a condensation reaction through the Mannich reaction, generating a superplasticizer with dual functions of "hydration shielding" and "chemical anchoring".

[0016] When the anti-mud polycarboxylate superplasticizer of the present invention is applied to concrete, the dosage of the anti-mud polycarboxylate superplasticizer is 0.25-0.5% of the mass of the concrete cementitious material.

[0017] This invention constructs an "electronic-conformation dual synergistic" mechanism within the molecule through specific molecular topological structure design. By leveraging the interactions of the components under specific chemical conditions, it achieves a nonlinear synergistic effect far exceeding the simple summation of the functions of individual monomers. The specific mechanism is as follows: 1. Rigid conformational rejection mechanism against sludge induced by "cation-π electron lock-in" This invention does not simply utilize the hydration repulsion of CBMA, but creatively leverages the unique electronic interaction between the functional groups of CBMA and the side groups of pyrogallol. The CBMA structural unit contains quaternary ammonium cation groups (-N) with high charge density. + R3), while the grafted pyrogallol side group contains an electron-rich polyhydroxybenzene ring (π-electron system). In the microscopic environment of the polymer chain, the strongly positively charged center (quaternary ammonium group) of CBMA can generate a strong "intramolecular cation-π interaction" with the electron-rich benzene ring of pyrogallol. This specific electron attraction acts like a "molecular lock," tightly "anchoring" the pyrogallol side group to the extension direction of the CBMA side chain, greatly restricting the free rotation and hydrophobic involution of the pyrogallol benzene ring. The two work together to transform the originally flexible organic side chain into a "molecular needle" structure with extremely high bending stiffness. The interlayer adsorption of clays such as montmorillonite usually requires the polymer chain to enter through flexible peristalsis, but the rigid chain segment locked by the "CBMA quaternary ammonium group-pyrogallol benzene ring" in this invention cannot enter the interlayer domain of clay in terms of geometric scale and mechanical stiffness, thus completely cutting off the intercalation adsorption path of clay to water-reducing agent in a physical sense. Without the electron locking of the quaternary ammonium group of CBMA, pyrogallol will undergo hydrophobic curling and be adsorbed by clay; without the benzene ring coordination of pyrogallol, CBMA alone cannot maintain long-term steric hindrance in the face of clay with a large specific surface area.

[0018] 2. Amine-bridged bond-induced electronic activation and the "kinetic competitive advantage" anti-sludge mechanism Since pyrogallol itself cannot directly participate in free radical polymerization, this invention utilizes an unsaturated functional monomer (2-aminoethyl methacrylate hydrochloride) containing a primary amine group as a key carrier, cleverly introducing pyrogallol into the main chain as a side group via the Mannich reaction. In this structure, 2-aminoethyl methacrylate hydrochloride (AEMA) is not only a linker arm, but its transformed secondary amine structure also generates a significant electronic synergistic anti-sludge effect with pyrogallol. The rigid secondary amine bridge located ortho to pyrogallol acts as an electron donor and a local "proton pump," increasing the electron cloud density of the benzene ring through an inductive effect and lowering the dehydrogenation barrier of the phenolic hydroxyl group; combined with the three "naked" and unmodified phenolic hydroxyl groups retained on pyrogallol, a synergistic effect against Ca2+ is formed. 2+A highly reactive "super ligand." This "amine-activated-naked chelation" structure endows the PCE molecule with an overwhelming advantage in adsorption kinetics: in a competitive system where cement and clay coexist, this molecule can react with Ca on the cement surface at an extremely fast rate. 2+ Multi-point chemical anchoring (chemisorption) occurs, while the adsorption of PCE by clay mainly relies on slower physical diffusion and hydrogen bonding. Through this kinetic competition mechanism, PCE molecules are firmly locked on the surface of cement particles before being captured by clay, thus effectively avoiding the "diversion" and consumption of effective components by clay, and significantly improving the adaptability of water-reducing agents in harsh clay-containing aggregates.

[0019] The beneficial effects of this invention are as follows: (1) Significant conformational synergistic effect anti-mud mechanism: The strong positive charge center (quaternary ammonium group) of CBMA can generate a strong "intramolecular cation-π interaction" with the electron-rich benzene ring of pyrogallol. This "1+1>2" synergistic effect enables the product to maintain a very high effective adsorption capacity with only a low dosage in harsh aggregate environments with mud content >5%, which significantly reduces the sensitivity of concrete to the mud content of sand and gravel.

[0020] (2) Excellent dispersion retention and cost-effectiveness: Thanks to the electronic activation effect of the secondary amine bridge bond of 2-aminoethyl methacrylate hydrochloride on the phenolic hydroxyl group, the adsorption rate and adsorption fastness of the product of this invention are significantly better than those of ordinary physical compound products. Under the same water reduction rate requirements, this invention reduces the amount of admixture required compared with conventional anti-mud water-reducing agents, while giving concrete excellent rheological properties and cohesiveness, effectively inhibiting segregation and bleeding, and greatly improving the efficiency of pumping construction.

[0021] (3) Precise and controllable process with universality: The preparation process adopts mild neutral / slightly acidic and medium-low temperature conditions, with low equipment requirements and easy industrial scale-up. By precisely adjusting the molar ratio of zwitterionic monomers to pyrogallol, the charge density and grafting density of molecular chains can be flexibly controlled, thereby achieving customized production for different clay types (such as montmorillonite and kaolin) and ensuring the performance stability between product batches. Detailed Implementation

[0022] The present invention will be further described below with reference to embodiments.

[0023] Example 1 (1) Prepare a solution A with a concentration of 35 wt.% by mixing carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, acrylic acid, mercaptoacetic acid, sodium bisulfite and a certain amount of deionized water; prepare a solution B with a concentration of 2 wt.% by mixing ammonium persulfate and a certain amount of deionized water; add 1 mol of isopentenyl polyoxyethylene ether (molecular weight 3000) to a reaction flask equipped with a stirring and dropping device, and add a certain amount of deionized water to prepare a bottom liquid with a concentration of 55 wt.%; turn on the stirrer, introduce N2 as a protective gas, and heat to 45°C to obtain a preheated bottom liquid. The molar ratio of carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, isopentenyl polyoxyethylene ether, and acrylic acid is 0.04:0.5:1:3.3; the amount of mercaptoacetic acid used is 2.0% of the total mass of carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, isopentenyl polyoxyethylene ether, and acrylic acid; the amount of ammonium persulfate used is 1.5% of the total mass of carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, isopentenyl polyoxyethylene ether, and acrylic acid; and the mass ratio of ammonium persulfate to sodium bisulfite is 1:0.5. (2) Under N2 protection, solution A and solution B were simultaneously added dropwise to the preheated base liquid at 45°C and reacted at 45°C. Solution A was added dropwise at a uniform rate for 3.0 h, and solution B was added dropwise at a uniform rate for 3.5 h. After solution B was added, the reaction was continued at 45°C for 2 h. The temperature was then lowered to 25°C, and sodium hydroxide was added to adjust the pH to 8.0 to obtain a polycarboxylate superplasticizer solution. (3) Under N2 protection, formaldehyde was added dropwise to the polycarboxylate superplasticizer solution obtained in step (2) at a controlled temperature of 25°C and stirred for 1.2 h to obtain a reaction solution; wherein the molar ratio of formaldehyde to isopentenyl polyoxyethylene ether in step (1) was 0.40:1. (4) Under N2 protection, pyrogallol was added to the reaction solution obtained in step (3), and the temperature was raised to 55°C and stirred for 2.0 h; wherein the molar ratio of pyrogallol to formaldehyde in step (3) was 1:1; (5) After the reaction is complete, deionized water is added for dilution to obtain anti-mud polycarboxylate superplasticizer S1 with a solid content of 40 wt.%.

[0024] Example 2 (1) Prepare a solution A with a concentration of 40 wt.% by mixing carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, acrylic acid, mercaptopropionic acid, sodium formaldehyde sulfoxylate and a certain amount of deionized water; prepare a solution B with a concentration of 2.5 wt.% by mixing sodium persulfate and a certain amount of deionized water; add 1 mol of methyl allyl polyoxyethylene ether (molecular weight 2400) to a reaction flask equipped with a stirring and dropping device, and add a certain amount of deionized water to prepare a bottom liquid with a concentration of 50 wt.%; turn on the stirrer, introduce N2 as a protective gas, and heat to 50°C to obtain a preheated bottom liquid. The molar ratio of carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, methyl allyl polyoxyethylene ether, and acrylic acid is 0.03:0.4:1:3.5; the amount of mercaptopropionic acid is 1.6% of the total mass of carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, methyl allyl polyoxyethylene ether, and acrylic acid; the amount of sodium persulfate is 2.0% of the total mass of carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, methyl allyl polyoxyethylene ether, and acrylic acid; and the mass ratio of sodium persulfate to sodium formaldehyde bisulfite is 1:0.6. (2) Under N2 protection, solutions A and B were simultaneously added dropwise to a preheated base liquid at 50°C and reacted at 50°C. Solution A was added dropwise at a uniform rate over 2.5 hours, and solution B was added dropwise at a uniform rate over 3.0 hours. After solution B was added, the reaction was continued at 50°C for 1.0 hour. The temperature was then lowered to 20°C, and sodium hydroxide was added to adjust the pH to 7.0 to obtain a polycarboxylate superplasticizer solution. (3) Under N2 protection, formaldehyde was added dropwise to the polycarboxylate superplasticizer solution obtained in step (2) at a controlled temperature of 20°C and stirred for 1.5 h to obtain a reaction solution; wherein the molar ratio of formaldehyde to methyl allyl polyoxyethylene ether in step (1) was 0.36:1. (4) Under N2 protection, pyrogallol was added to the reaction solution obtained in step (3), and the temperature was raised to 60°C and stirred for 2.5 h; wherein the molar ratio of pyrogallol to formaldehyde in step (3) was 1:1. (5) After the reaction is complete, deionized water is added for dilution to obtain anti-mud polycarboxylate superplasticizer S2 with a solid content of 38 wt.%.

[0025] Example 3 (1) Prepare a solution A with a concentration of 45 wt.% by mixing carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, acrylic acid, mercaptopropionic acid, sodium bisulfite and a certain amount of deionized water; prepare a solution B with a concentration of 3.0 wt.% by mixing ammonium persulfate and a certain amount of deionized water; add 1 mol of methyl allyl polyoxyethylene ether (molecular weight 3000) to a reaction flask equipped with a stirring and dropping device, and add a certain amount of deionized water to prepare a bottom liquid with a concentration of 45 wt.%; turn on the stirrer, introduce N2 as a protective gas, and heat to 55°C to obtain a preheated bottom liquid. The molar ratio of carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, methyl allyl polyoxyethylene ether, and acrylic acid is 0.05:0.3:1:3.4; the amount of mercaptopropionic acid is 1.8% of the total mass of carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, methyl allyl polyoxyethylene ether, and acrylic acid; the amount of ammonium persulfate is 2.5% of the total mass of carboxybetaine methacrylate, 2-aminoethyl methacrylate hydrochloride, methyl allyl polyoxyethylene ether, and acrylic acid; and the mass ratio of ammonium persulfate to sodium bisulfite is 1:0.8. (2) Under N2 protection, solutions A and B were simultaneously added dropwise to the preheated base liquid at 55°C and reacted at 55°C. Solution A was added dropwise at a uniform rate for 2.7 hours, and solution B was added dropwise at a uniform rate for 3.2 hours. After solution B was added, the reaction was continued at 55°C for 1.5 hours. The temperature was then lowered to 30°C, and sodium hydroxide was added to adjust the pH to 7.3 to obtain a polycarboxylate superplasticizer solution. (3) Under N2 protection, formaldehyde was added dropwise to the polycarboxylate superplasticizer solution obtained in step (2) at a controlled temperature of 30°C and stirred for 1.0 h to obtain a reaction solution; wherein the molar ratio of formaldehyde to methyl allyl polyoxyethylene ether in step (1) was 0.27:1. (4) Under N2 protection, pyrogallol was added to the reaction solution obtained in step (3), and the temperature was raised to 65°C and stirred for 2.1 h; wherein the molar ratio of pyrogallol to formaldehyde in step (3) was 1:1; (5) After the reaction is complete, deionized water is added for dilution to obtain anti-mud polycarboxylate superplasticizer S3 with a solid content of 42 wt.%.

[0026] Comparative Example 1 Without adding 2-aminoethyl methacrylate hydrochloride, the other steps are the same as in Example 1, to obtain polycarboxylate superplasticizer PC1 with a solid content of 40 wt.%.

[0027] Comparative Example 2 Without adding pyrogallol, the other steps are the same as in Example 1, to obtain polycarboxylate superplasticizer PC2 with a solid content of 40 wt.%.

[0028] Comparative Example 3 Without adding carboxybetaine methacrylate, the other steps are the same as in Example 1, to obtain polycarboxylate superplasticizer PC3 with a solid content of 40 wt.%.

[0029] Concrete performance testing was conducted according to GB8076-2008 standard. The experiment used reference cement; the sand was zone II medium sand with a fineness modulus of 2.8 and a mud content of 6%; the aggregate was crushed stone with a nominal particle size of 5mm-20mm, using a two-stage mix design (40% 5-10mm and 60% 10-20mm), meeting the requirements of continuous gradation. The mix proportion of the reference concrete was set as cement:sand:aggregate:water = 360:855:965:230. Polycarboxylate superplasticizer was added at 0.25% (constituent dosage) of cement mass. The water consumption after adding PCE was the minimum water consumption required to achieve an initial slump of (210±10)mm. Performance tests were conducted on the corresponding concrete after adding the polycarboxylate superplasticizers from Examples 1-3 and Comparative Examples 1-3, and the results are shown in Table 1.

[0030] Table 1. Performance test results of concrete after incorporation with polycarboxylate superplasticizers from Examples 1-3 and Comparative Examples 1-3, respectively.

[0031] 1. Analysis of the synergistic anti-sludge effect of amino-bridged bond induction and CBMA conformational locking (S1 vs PC1 vs PC3): PC1 is a polycarboxylate superplasticizer without the introduction of 2-aminoethyl methacrylate hydrochloride (AEMA). Under conditions of 6% mud content, its initial water reduction rate is only 21.8%, and it suffers extremely severe slump loss after 1 hour (slump drops to 150 mm, loss of spread). AEMA is a key carrier and activation bridge connecting the polymer backbone and pyrogallol in the Mannich reaction. Without AEMA, pyrogallol cannot be effectively grafted onto the PCE backbone, and it loses the electron activation effect of the amino-group bridging bond as a "proton pump," failing to form a bond on the cement surface. 2+ It possesses an "ultraligand" with extremely high reactivity. Therefore, PC1 completely loses its "kinetic adsorption advantage" in the competitive system where cement and clay coexist, and its effective molecules are rapidly and extensively adsorbed and depleted by the clay.

[0032] Although PC3 successfully introduced the pyrogallol side group, it lacked the crucial zwitterionic monomer CBMA. Table 1 shows that while PC3's performance (initial water reduction rate 23.8%, 1-hour slump 175 mm) was slightly better than PC1, it was still significantly lower than S1. This is because it lacks the "cation-π" electron locking effect of the quaternary ammonium cation in CBMA on the pyrogallol benzene ring. Without CBMA synergy, the hydrophobic pyrogallol side group easily undergoes intramolecular hydrophobic association and coiling in the high-salt environment of cement, losing its rigid support. It readily enters the clay interlayer through flexible peristalsis or is physically adsorbed by hydroxyl groups on the clay surface via hydrogen bonds.

[0033] In contrast, S1 exhibits deep synergy between specific groups: the AEMA amino bridging ensures effective grafting and chemical anchoring of pyrogallol, while the quaternary ammonium center of CBMA "locks" the pyrogallol benzene ring in a rigid extended state through electronic interactions. This rigid conformation induced by electronic effects makes the S1 molecular chain act like a "hard thorn" to keep out the clay layers, thus achieving a significant nonlinear improvement in water reduction (25.7%) and slump retention (195 mm).

[0034] 2. Analysis of the multi-tooth anchoring and three-dimensional synergistic mechanism of pyrogallol (S1 vs PC2): PC2 retains the CBMA monomer and AEMA, but does not introduce pyrogallol side groups to participate in the Mannich reaction. Table 1 shows that PC2's slump retention (160mm) is also extremely poor. The lack of pyrogallol causes PCE molecules to lose a key ligand for strong "multidentate chemical anchoring" with the cement surface, preventing them from actively and firmly binding to cement minerals. More critically, the quaternary ammonium cation of CBMA loses its π-electron target, causing the core "cation-π" rigid conformation rejection mechanism of this invention to completely fail. Therefore, PC2 can only rely on the limited physical repulsion effect remaining in CBMA, exhibiting extremely weak anti-slump and slump retention capabilities on a macroscopic scale. The superiority of S1 proves that pyrogallol is not only an anchoring group, but also an indispensable link in maintaining the rigid conformation of the molecular chain; it is indispensable along with CBMA and AEMA.

[0035] 3. Comparison of concrete compressive strength and mapping analysis of macroscopic properties: By comparing the 28-day compressive strength, it can be found that the compressive strength of the examples (S1-S3) (42.3-44.9 MPa) is significantly higher than that of the comparative examples (PC1-PC3, 39.6-41.2 MPa). This significant difference in compressive strength is a direct reflection of the microscopic anti-mud mechanism on the macroscopic mechanical properties. Due to the aforementioned molecular structure defects in the comparative examples (PC1-PC3), a large number of water-reducing agent molecules are unhelpfully adsorbed by clay. This not only leads to uneven dispersion of cement particles and incomplete hydration, but also forms a weak layer with a local high water-cement ratio in the concrete interior and interfacial transition zone. In contrast, the examples such as S1 successfully avoid the interference of clay through the dual mechanisms of "anti-polyelectrolyte conformation support" and "highly active chemical anchoring," ensuring complete hydration of cement particles at extremely low dosages. This results in lower microscopic porosity and a denser structure in the hardened concrete, thereby achieving higher compressive strength on a macroscopic scale.

[0036] In summary, the performance data of Example S1 are far superior to those of PC1, PC2 and PC3. This fully demonstrates that the quaternary ammonium cation center of CBMA, the amino bridging bond of AEMA conversion and the π-electron system of pyrogallol in this invention produce a significant nonlinear chemical synergistic effect in the three dimensions of electronic induction, conformational locking and lattice matching.

Claims

1. A mud-resistant polycarboxylate superplasticizer, characterized in that... It is made from zwitterionic monomers, unsaturated functional monomers containing primary amine groups, unsaturated polyether macromonomers, unsaturated acid monomers, formaldehyde, pyrogallol, chain transfer agents, initiators, reducing agents and deionized water; wherein, the zwitterionic monomer is carboxybetaine methacrylate and the unsaturated functional monomer containing primary amine groups is 2-aminoethyl methacrylate hydrochloride.

2. The anti-mud polycarboxylate superplasticizer according to claim 1, characterized in that... The unsaturated polyether macromonomers are methyl allyl polyoxyethylene ether or isopentenyl polyoxyethylene ether; The structural formula of methyl allyl polyoxyethylene ether is as follows: In the formula, n1 is 25-100; The structural formula of isopentenyl polyoxyethylene ether is as follows: In the formula, n1 is 25-100.

3. The anti-mud polycarboxylate superplasticizer according to claim 1, characterized in that... The unsaturated acid monomer is acrylic acid, and the molar ratio of zwitterionic monomer, unsaturated functional monomer containing primary amine group, unsaturated polyether macromonomer, unsaturated acid monomer, formaldehyde and pyrogalactosyl is 0.03-0.05:0.3-0.5:1:3-4:0.2-0.4:0.2-0.

4.

4. The anti-mud polycarboxylate superplasticizer according to claim 1, characterized in that... The chain transfer agent is mercaptoacetic acid or mercaptopropionic acid, and the amount of chain transfer agent is 1.6-2.0% of the total mass of zwitterionic monomers, unsaturated functional monomers containing primary amine groups, unsaturated polyether macromonomers and unsaturated acid monomers; the initiator is ammonium persulfate or sodium persulfate, and the amount of initiator is 1.5-2.5% of the total mass of zwitterionic monomers, unsaturated functional monomers containing primary amine groups, unsaturated polyether macromonomers and unsaturated acid monomers.

5. The anti-mud polycarboxylate superplasticizer according to claim 1, characterized in that... The reducing agent is sodium formaldehyde sulfoxylate or sodium bisulfite, and the mass ratio of the initiator to the reducing agent is 1:0.5-0.

8.

6. A method for preparing the anti-mud-type polycarboxylate superplasticizer according to any one of claims 1-5, characterized in that... Includes the following steps: (1) Prepare solution A by mixing zwitterionic monomer, unsaturated functional monomer containing primary amine group, unsaturated acid monomer, chain transfer agent, reducing agent and deionized water; prepare solution B by mixing initiator and deionized water; prepare base liquid by mixing unsaturated polyether macromonomer and deionized water, and heat to obtain preheated base liquid. (2) Under N2 protection, solution A and solution B are simultaneously added dropwise to the preheated base liquid for reaction. After the addition is complete, the reaction is kept warm and then cooled. Sodium hydroxide is added to adjust the pH value to obtain polycarboxylate superplasticizer solution. (3) Under N2 protection, formaldehyde was added to the polycarboxylate superplasticizer solution obtained in step (2) and stirred to obtain a reaction solution; (4) Under N2 protection, pyrogallol is added to the reaction solution obtained in step (3), and the temperature is raised for stirring reaction. After the reaction is completed, water is added for dilution to obtain anti-mud polycarboxylate superplasticizer.

7. The preparation method of the anti-mud type polycarboxylate superplasticizer according to claim 6, characterized in that... In step (1), the concentration of solution A is 35-45 wt.%, the concentration of solution B is 2.0-3.0 wt.%, the concentration of the base solution is 45-55 wt.%, and the solution is heated to 45-55℃.

8. The preparation method of the anti-mud type polycarboxylate superplasticizer according to claim 6, characterized in that... In step (2), the reaction temperature is 45-55℃, the drop time of solution A is 2.5-3.0h, the drop time of solution B is 3.0-3.5h, the reaction temperature is kept at 45-55℃ for 1.0-2.0h, the temperature is lowered to 20-30℃, and sodium hydroxide is added to adjust the pH value to 7.0-8.

0.

9. The preparation method of the anti-mud type polycarboxylate superplasticizer according to claim 6, characterized in that... In step (3), the stirring reaction temperature is 20-30℃ and the stirring reaction time is 1.0-1.5h.

10. The preparation method of the anti-mud type polycarboxylate superplasticizer according to claim 6, characterized in that... In step (4), the temperature is raised to 55-65℃ and the stirring reaction time is 2.0-2.5h; the solid content of the anti-mud polycarboxylate superplasticizer is 38-42wt.%.

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