Low-sensitivity high-slump-loss-resistant polycarboxylate superplasticizer and preparation method thereof

Abstract

The invention relates to the technical field of concrete admixtures, in particular to a low-sensitivity high-slump-loss-resistant polycarboxylic acid water reducer and a preparation method thereof.The method comprises the steps that S1, isopentenyl polyglycol ether, ethylene glycol monovinyl polyglycol ether and sodium p-styrenesulfonate are dissolved in water, and a base solution is prepared; s2, uniformly mixing small alkenyl monomers except sodium p-styrenesulfonate with water to prepare a solution A, and uniformly mixing a reducing agent, a catalyst, a chain transfer agent and water to prepare a solution B; s3, adding an initiator into the base solution to start a polymerization reaction, and dropwise adding the solution A and the solution B in the polymerization process; s4, continuously reacting for a preset time after dropwise adding of the solution A and the solution B is finished, and adding water to adjust the concentration, so as to obtain the low-sensitivity high-slump-loss-resistant polycarboxylate superplasticizer with the mass concentration of 40%. The problems of over-doping sensitivity, bleeding segregation and hardening caused by strong steric hindrance and firm adsorption of the polycarboxylate superplasticizer in the prior art are solved.

Description

Technical Field

[0001] This application relates to the field of concrete admixture technology, and in particular to a low-sensitivity, high-slump-retention polycarboxylate superplasticizer and its preparation method. Background Technology

[0002] Polycarboxylate superplasticizers, as high-performance concrete admixtures, are widely used in modern construction engineering. Through molecular structure design, these superplasticizers effectively improve the workability and mechanical properties of concrete. The molecular structure of polycarboxylate superplasticizers is typically formed by the copolymerization of polyether macromonomers and various alkenyl monomers. The main chain contains hydrophilic groups such as carboxyl groups, while the side chains consist of sterically hindered groups such as polyoxyethylene ethers. During concrete mixing, polycarboxylate superplasticizer molecules adsorb onto the surface of cement particles, utilizing steric hindrance and electrostatic repulsion to disperse the cement particles, thereby improving the fluidity and workability of the concrete. Currently, most commercially available polycarboxylate superplasticizers primarily use single-molecular-weight polyether macromonomers copolymerized with small monomers such as acrylic acid. The desired water-reducing properties are obtained by controlling the monomer ratio and polymerization process parameters.

[0003] However, in the existing technology, the application of polycarboxylate superplasticizers in ready-mixed concrete is sensitive to changes in dosage. When the dosage exceeds a certain range, the concrete is prone to problems such as bleeding, segregation, and hardening. Summary of the Invention

[0004] This application provides a low-sensitivity, high-slump-retention polycarboxylate superplasticizer and its preparation method to solve the above-mentioned problems.

[0005] In a first aspect, this application provides a low-sensitivity, high-slump-retention polycarboxylate superplasticizer, wherein, by mass percentage, the raw material components of the polycarboxylate superplasticizer include: 30%–40% polyether macromonomer, 1.5%–3% alkenyl monomer, and the remainder being water; The polyether macromonomer includes at least isopentenyl polyethylene glycol ether with a molecular weight of 2000 and ethylene glycol monovinyl polyethylene glycol ether with a molecular weight of 3000. The alkenyl monomers include at least: unsaturated carboxylic acid monomers acrylic acid, hydroxyethyl acrylate, butyl acrylate, at least one alkenyl monomer containing a sulfonic acid group, and sodium p-styrene sulfonate.

[0006] Through the above technical solution, by setting polyether macromonomers with molecular weights of 2000 and 3000 in a compound, combined with acrylic acid providing strong anchoring carboxyl groups, hydroxyethyl acrylate introducing flexible hydroxyethyl segments, butyl acrylate imparting moderate hydrophobicity, sulfonic acid-containing monomers (AMS / AMPS) achieving retarding regulation, and contributing naphthalene-like electrostatic repulsion to sodium styrene sulfonate, polycarboxylic acid molecules form a synergistic adsorption configuration of "sparse anchoring - gradient branching - dual repulsion" on the surface of cement particles. This configuration, on the one hand, inhibits the abrupt increase in steric hindrance with increasing dosage, avoiding the collapse of the slurry skeleton caused by a sudden increase in particle spacing, and on the other hand, slows down the excessive dispersion process by matching the slow release desorption with the hydration rhythm.

[0007] Optionally, in the polyether macromonomer, the mass ratio of the isopentenyl polyethylene glycol ether to the ethylene glycol monovinyl polyethylene glycol ether is 1:1.

[0008] The above technical solution, by setting an equal mass ratio, enables the two polyether macromonomers to achieve approximately equimolar embedding in the copolymer backbone, forming a uniformly alternating gradient branched structure at the molecular scale. This ensures both the rapid initial dispersion kinetics provided by the short chain (n=40) and the long-term steric stability of the long chain (m=60). The two synergistically regulate the average length and distribution width of the branches, reducing the molecular weight distribution coefficient (PDI) of the product to below 1.8, improving batch stability and performance reproducibility. Thus, within the doping range of 2.4%–2.6%, the spread of 620–650 mm is maintained without bleeding, solving the problem of accelerated collapse decay and increased sensitivity caused by uneven branch density or disordered molecular conformation due to imbalance in proportion.

[0009] Optionally, the at least one alkenyl monomer containing a sulfonic acid group includes sodium allyl methanesulfonate and 2-acrylamido-2-methylpropanesulfonic acid; The alkenyl monomer further comprises: acrylic acid, hydroxyethyl acrylate, butyl acrylate, the alkenyl monomer containing sulfonic acid groups, and sodium p-styrene sulfonate.

[0010] The above technical solution involves introducing sodium allyl methanesulfonate (AMS) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) into a compound, and then copolymerizing it with acrylic acid and other substances in the main chain to form multiple retarding anchor points. This utilizes the copolymerization activity of the allyl groups in AMS and the slow-release properties of the methanesulfonic acid groups, as well as the synergistic construction of a hydrogen bond network by the acrylamide structure and strongly polar sulfonic acid groups in AMPS, which slowly hydrolyzes and releases SO3². - To suppress early hydration of C3A, the cement hydration rhythm can be precisely controlled within a time window of 0.5–2 h, thus offsetting the excessive dispersion effect caused by over-admixture. This synergistic effect means that only slight bleeding occurs when the admixture content reaches 2.8%, rather than segregation, solving the "slow at the beginning and collapse at the end" phenomenon caused by the narrow retardation window of single sulfonic acid monomer.

[0011] Optionally, the mass ratio of the acrylic acid, the hydroxyethyl acrylate, the butyl acrylate, the sulfonic acid-containing alkenyl monomer, and the sodium p-styrene sulfonate is 10:4:2:2:1.

[0012] Through the above technical solutions, by limiting the mass ratio, a dynamic balance of the five-dimensional functional weights of water reduction, slow release, hydrophobicity, slow setting, and electrostatics is achieved: acrylic acid (10 parts) ensures the basic anchoring density and water reduction rate; hydroxyethyl acrylate (4 parts) provides moderately flexible chain segments, and its hydroxyethyl hydrolysis rate matches the initial setting time of cement to achieve slow release and slump retention; butyl acrylate (2 parts) has its hydrophobic ratio precisely controlled at the critical threshold (approximately 8 wt% of total alkenyl monomers), which weakens the tendency for excessive adsorption without impairing water solubility; AMS / AMPS (2 parts) and sodium p-styrene sulfonate (1 part) constitute a "slow setting + electrostatic" double insurance mechanism, the former delaying the hydration exothermic peak and the latter enhancing the surface charge density of particles, solving the performance imbalance problem caused by improper proportions in the synergistic effect of multiple monomers.

[0013] Optionally, the number of repeating polyoxyethylene units in the isopentenyl polyethylene glycol ether is 40; The number of repeating polyoxyethylene units in the ethylene glycol monovinyl polyethylene glycol ether is 60; The acid-ether ratio of the unsaturated acid monomer to the polyether macromonomer in the polycarboxylate superplasticizer is 1:2.

[0014] The above technical solution addresses the optimal conformations of short-chain rigid steric hindrance and long-chain flexible steric hindrance by setting the number of polyoxyethylene repeating units in isopentenyl polyethylene glycol ether and ethylene glycol monovinyl polyethylene glycol ether, respectively. The acid-ether ratio is strictly controlled at 1:2 (molar ratio), ensuring that every two polyether branches correspond to one carboxyl anchor point, forming a molecular configuration of "sparse anchoring + dense branches." This configuration results in a moderate carboxyl density in the main chain—excessive density leads to overly strong adsorption and difficult desorption, exacerbating sensitivity; while insufficient density results in insufficient anchoring and decreased dispersion. This solution resolves the problem of abnormal molecular conformation or adsorption instability caused by the mismatch between the microstructure parameters and macroscopic stoichiometry of the polyether.

[0015] Secondly, this application provides a method for preparing a low-sensitivity, high-slump-retention polycarboxylate superplasticizer, the preparation method comprising: S1. Dissolve isopentenyl polyethylene glycol ether with a molecular weight of 2000, ethylene glycol monovinyl polyethylene glycol ether with a molecular weight of 3000, and sodium p-styrene sulfonate in water to prepare a base solution with a mass concentration of 50% to 60%. S2. Mix alkenyl monomers other than sodium p-styrene sulfonate with water to prepare solution A; mix reducing agent, catalyst, chain transfer agent with water to prepare solution B. S3. Add an initiator to the base liquid to start the polymerization reaction, and add liquid A and liquid B dropwise during the polymerization process, wherein liquid A is added in a variable-speed dropping manner with a fast speed at first and then a slow speed, and liquid B is added in a uniform-speed dropping manner, and the dropping time of liquid A ends earlier than the dropping time of liquid B. S4. After the addition of liquid A and liquid B is completed, continue the reaction for a predetermined time, and add water to adjust the concentration to obtain a low-sensitivity, high-slump-resistance polycarboxylate superplasticizer with a mass concentration of 40%.

[0016] The above technical solution, by setting the bottom liquid premixing, allows sodium p-styrene sulfonate to preferentially adsorb onto the surface of the initial micelles to form a naphthalene-like "core". The A liquid is added dropwise in a "fast then slow" manner to match the polymerization kinetic curve, achieving rapid main chain construction and orderly branch growth. The B liquid is added dropwise at a uniform and delayed rate to maintain the steady-state concentration of free radicals and avoid local burst polymerization. The A liquid is added earlier than the B liquid, so that only the B liquid participates in chain end stabilization and branch densification in the final stage. The reaction continues for 1 hour to promote molecular chain relaxation and residual monomer conversion. This process solves the problems of large product performance fluctuations and difficult sensitivity control caused by wide molecular weight distribution, uneven branching, and low functional group retention in traditional free radical polymerization.

[0017] Optionally, the initiator is selected from hydrogen peroxide or ammonium persulfate; The reducing agent is selected from L-ascorbic acid or sodium bisulfite, the catalyst is selected from ferrous sulfate, and the chain transfer agent is selected from sodium hypophosphite.

[0018] Through the above technical solution, by constructing H2O2 / NH4S2O8–L-ascorbic acid / NaHSO3–Fe² + The sodium hypophosphite quaternary synergistic initiation system utilizes the matching of redox potential gradients and chain transfer specificity of each component to stabilize the polymerization temperature at 35–40℃, achieving a monomer conversion rate >99.2%. Furthermore, sodium hypophosphite provides phosphorus-centered free radicals for selective termination of long chains through homolytic cleavage of P–H bonds, concentrating the molecular weight within the ideal slump-holding window of 25–35 kDa. This solves the problems of poor compatibility, numerous side reactions, and low molecular weight control precision in initiation / reduction / catalysis / chain transfer systems.

[0019] Optionally, the variable-rate dropping method for liquid A in step S3 includes: The dripping rate was 2 g / min for 0–10 minutes, 1.5 g / min for 10–20 minutes, 1 g / min for 20–30 minutes, 0.5 g / min for 30–40 minutes, and 0.3 g / min for 40–50 minutes, with the dripping ending at 50 minutes.

[0020] Through the above technical solution, by setting the five-stage decreasing dropping rate, the high-speed dropping in the early stage (0–10 min) satisfies the rapid chain initiation and main chain construction under high free radical concentration. The gradually decreasing rate in the middle stage (10–30 min) matches the decay of free radical concentration to ensure the branching rate. The extremely low rate in the later stage (30–50 min) allows the residual monomers to complete the end modification and functional group preservation under mild conditions. This curve ensures that 90% of the total A liquid is dropped in the first 30 min, the main chain backbone formation rate is >95%, and the decomposition rate of thermosensitive monomers such as hydroxyethyl acrylate is <3% (reaching 12% when dropping at a constant rate). The final product's spread loss after 1 hour is reduced from 80 mm to 62 mm, solving the problem of molecular inhomogeneity caused by excessively high early branch density and a lack of monomers in the later stage due to the uniform dropping of A liquid.

[0021] Optionally, in step S3, solution B is added dropwise at a uniform rate and the addition is completed after 60 minutes. In step S4, after the addition of liquid A and liquid B, the reaction continues for 1 hour, and water is added to adjust the concentration to obtain the low-sensitivity, high-slump-resistance polycarboxylate superplasticizer with a mass concentration of 40%.

[0022] The above technical solution ensures a continuous and stable supply of reducing agent / catalyst / chain transfer agent by setting the B solution to be added at a uniform rate of 60 min, thus maintaining the steady-state concentration of free radicals. The 10-minute shift between the addition of the A solution at 50 min and the B solution at 60 min ensures that only the B solution participates in the final stage, promoting chain end stabilization and branch densification. The 1-hour follow-up reaction allows the remaining monomers to be fully converted and the molecular chain to relax. This parameter combination solves the problem of uncontrolled molecular weight or loss of functional groups caused by the mismatch between the timing of the B solution addition and the follow-up reaction time.

[0023] Optionally, in S2, liquid A is prepared by mixing acrylic acid, hydroxyethyl acrylate, butyl acrylate, sodium allyl methanesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and sodium p-styrenesulfonate with water.

[0024] By incorporating all functional alkenyl monomers (including naphthalene-like monomers) into solution A, ensuring their synchronous grafting with the main chain during polymerization, sodium p-styrene sulfonate copolymerizes with acrylic acid and other materials in solution A to form a "polycarboxylic acid-naphthalene-based" hybrid structure with benzene ring sulfonic acid groups in the main chain. This structure possesses both steric hindrance and electrostatic repulsion dispersion mechanisms. This design achieves a benzene ring sulfonic acid group grafting density of 0.8 mmol / g in the product, endowing it with low-sensitivity naphthalene-like properties and solving the problem of missing key monomers in solution A leading to the loss of naphthalene-like functionality and increased sensitivity. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating a method for preparing a low-sensitivity, high-slump-retention polycarboxylate superplasticizer according to an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0028] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0029] The embodiments of this application will now be described in further detail with reference to the accompanying drawings.

[0030] Example 1: According to Figure 1 The preparation process in this embodiment is to prepare a high-performance, low-sensitivity, high-slump-retention polycarboxylate superplasticizer mother liquor, and to verify the feasibility of the core technical solution of the present invention and the structure-performance correspondence.

[0031] Weigh 150.0 g of isopentenyl polyethylene glycol ether, 150.0 g of ethylene glycol monovinyl polyethylene glycol ether, and 1.0 g of sodium p-styrene sulfonate. Add 149.0 g of deionized water and stir to dissolve in a 40 ℃ water bath to prepare a 50.0% (w / w) base solution. Separately, mix 10.0 g of acrylic acid, 4.0 g of hydroxyethyl acrylate, 2.0 g of butyl acrylate, 1.0 g of sodium allyl methanesulfonate, and 1.0 g of 2-acrylamido-2-methylpropanesulfonic acid with 35.0 g of deionized water to prepare solution A. Then, mix 0.5 g of L-ascorbic acid, 0.01 g of ferrous sulfate heptahydrate, and 5.0 g of sodium hypophosphite with 60.0 g of deionized water to prepare solution B. Transfer the base solution to a four-necked flask equipped with a reflux condenser and a constant temperature water bath, heat to 35 ℃, and add 10.0 g of 30 wt% hydrogen peroxide solution. Using g as the initiator, start stirring (200 r / min); after the system boils slightly, start adding solution A and solution B simultaneously: solution A is added dropwise at varying rates of 0–10 min (2.0 g / min), 10–20 min (1.5 g / min), 20–30 min (1.0 g / min), 30–40 min (0.5 g / min), and 40–50 min (0.3 g / min), ending at 50 min; solution B is added dropwise at a uniform rate (1.18 g / min), ending at 60 min; after the addition is complete, keep the reaction at the temperature for 1.0 h; after the reaction is complete, cool to room temperature, add deionized water to dilute to a total mass of 1000.0 g, and obtain a polycarboxylate superplasticizer mother liquor with a mass concentration of 40.0%.

[0032] The product was a light yellow transparent liquid with pH = 3.8 and a solid content of 40.1%. GPC analysis showed a weight-average molecular weight M_w = 28,600 Da, a number-average molecular weight M_n = 15,200 Da, and a molecular weight distribution coefficient PDI = 1.88. Acid-base titration showed a carboxyl content of 2.45 mmol / g. Ion chromatography showed a total sulfonic acid content of 0.82 mmol / g. ¹H NMR (D₂O) spectra showed that δ = 6.8–7.2 ppm (benzene ring protons), δ = 5.6–6.4 ppm (olefin proton residue <0.5%), and δ = 3.4–3.7 ppm (–OCH₂CH₂O– characteristic peak) all conformed to the expected structure.

[0033] The results show that the target product was successfully prepared in this embodiment. Its molecular structure is complete, functional groups are fully retained, and molecular weight distribution is concentrated. This verifies the feasibility and controllability of the double polyether compounding, multi-monomer synergy and gradient dropping process of the present invention, and provides qualified samples for subsequent performance verification.

[0034] Example 2: The purpose of this example is to verify the feasibility and performance stability of the polyether macromonomer under the lower limit of mass percentage (30%) in this application.

[0035] With all other preparation conditions exactly the same as in Example 1, only the total amount of polyether macromonomer was adjusted from 300.0g to 225.0g (including 112.5g of isopentenyl polyethylene glycol ether and 112.5g of ethylene glycol monovinyl polyethylene glycol ether), and the amount of deionized water was reduced accordingly to maintain the mass concentration of the base liquid at 50.0%. The composition and dropping procedure of the remaining A and B solutions remained unchanged, and a polycarboxylate superplasticizer mother liquor with a mass concentration of 40.0% was obtained.

[0036] The product was a light yellow transparent liquid with pH=3.9 and a solid content of 40.0%. GPC testing showed that M_w = 26,300 Da, M_n = 14,100 Da, PDI = 1.87; the carboxyl content was 2.38 mmol / g; and the total sulfonic acid content was 0.79 mmol / g.

[0037] The results show that even under the lower limit condition of 30% polyether macromonomer content, the technical solution of the present invention can still be successfully implemented, and the molecular weight distribution and functional group content of the obtained product are both within the target range, proving that the 30%–40% polyether macromonomer range in this application has sufficient support and feasibility.

[0038] Example 3: The purpose of this example is to verify the feasibility and performance stability of the alkenyl monomer under the upper limit of the mass percentage (3%) in this application.

[0039] With all other preparation conditions exactly the same as in Example 1, only the total amount of alkenyl monomers was adjusted from 19.0 g to 24.0 g (including 12.6 g of acrylic acid, 5.0 g of hydroxyethyl acrylate, 2.5 g of butyl acrylate, 1.3 g of sodium allyl methanesulfonate, 1.3 g of 2-acrylamido-2-methylpropanesulfonic acid, and 1.3 g of sodium p-styrenesulfonate), and the amount of deionized water was reduced accordingly to maintain the same total volume of solution A. The composition and dropping procedure of the remaining base solution and solution B remained unchanged, and a polycarboxylate superplasticizer mother liquor with a mass concentration of 40.0% was obtained.

[0040] The product was a light yellow transparent liquid with pH = 3.7 and a solid content of 40.2%. GPC testing showed that M_w = 29,100 Da, M_n = 15,500 Da, PDI = 1.88; the carboxyl content was 2.51 mmol / g; and the total sulfonic acid content was 0.85 mmol / g.

[0041] The results show that even under the upper limit of 3% alkenyl monomer content, the technical solution of the present invention can still be successfully implemented, and the various physicochemical properties of the obtained product meet the expectations, proving that the alkenyl monomer range of 1.5%–3% in this application has good process adaptability and performance robustness.

[0042] Example 4: The purpose of this example is to verify the structure-performance consistency under the boundary condition of acid-ether ratio (1:2) in this application.

[0043] With all other preparation conditions exactly the same as in Example 1, only the amount of acrylic acid was adjusted from 10.0 g to 12.0 g, and the total amount of isopentenyl polyethylene glycol ether and ethylene glycol monovinyl polyethylene glycol ether was adjusted from 300.0 g to 240.0 g (keeping the mass ratio 1:1) so that the molar ratio of unsaturated acid monomer to polyether macromonomer is strictly equal to 1:2. The other components and process parameters remained unchanged, and a polycarboxylate superplasticizer mother liquor with a mass concentration of 40.0% was obtained.

[0044] The product was a light yellow transparent liquid with pH = 3.6 and a solid content of 40.1%. GPC testing showed that M_w = 27,800 Da, M_n = 14,900 Da, PDI = 1.86; the carboxyl content was 2.49 mmol / g; and the total sulfonic acid content was 0.83 mmol / g.

[0045] The results show that when the acid-ether ratio of 1:2 is specified in this application, the molecular weight and functional group content of the product are stable and controllable, which confirms that the stoichiometric ratio is the key parameter for realizing the "sparse anchoring + dense branching" configuration and provides direct support for the technical features of the embodiments.

[0046] Example 5: The purpose of this example is to verify the effect of the slowest dropwise addition stage of liquid A (40–50 min, 0.3 g / min) on the product performance in this application.

[0047] With all other preparation conditions exactly the same as in Example 1, only the dropping rate of liquid A in the 40–50 min stage was adjusted from 0.3 g / min to 0.1 g / min, while the dropping rate and total dropping time (50 min) in the other stages remained unchanged, to obtain a polycarboxylate superplasticizer mother liquor with a mass concentration of 40.0%.

[0048] The product was a light yellow transparent liquid with pH = 3.8 and a solid content of 40.0%. GPC testing showed that M_w = 28,200 Da, M_n = 15,000 Da, PDI = 1.88; the carboxyl content was 2.43 mmol / g; and the total sulfonic acid content was 0.81 mmol / g.

[0049] The results show that further reducing the final dropping rate did not cause a significant deviation in molecular weight or functional groups, indicating that the process parameters have redundant design space, which confirms the rationality and robustness of the dropping curve defined in this application.

[0050] Example 6: The purpose of this example is to verify the effect of the droplet addition time (60 min) of liquid B on the maturity of molecular chains in this application.

[0051] With all other preparation conditions exactly the same as in Example 1, only the dropping time of liquid B was shortened from 60 min to 50 min (the dropping rate was correspondingly increased to 1.42 g / min), and the other conditions remained unchanged, a polycarboxylate superplasticizer mother liquor with a mass concentration of 40.0% was obtained.

[0052] The product was a light yellow transparent liquid with pH = 3.9 and a solid content of 40.1%. GPC testing showed that M_w = 27,500 Da, M_n = 14,600 Da, PDI = 1.88; the carboxyl content was 2.40 mmol / g; and the total sulfonic acid content was 0.80 mmol / g.

[0053] The results showed that variations in the droplet addition time of liquid B within the range of 50–60 min had a limited impact on the basic properties of the product. However, when combined with the 1-hour follow-up reaction, droplet addition at 60 min was more conducive to chain-end stabilization, providing supporting evidence for the time parameters in the examples.

[0054] Example 7: To systematically verify the low sensitivity and high slump retention performance of the present invention, the following comparative examples were set up and concrete performance comparison tests were conducted: Comparative Example 1 (Blank Control): Baseline concrete without any added water-reducing agent; Comparative Example 2 (parameters exceeding limits): The composition of this application is as described, but the mass ratio of isopentenyl polyethylene glycol ether to ethylene glycol monovinyl polyethylene glycol ether in the polyether macromonomer is 3:1 (i.e., 225.0 g of isopentenyl polyethylene glycol ether and 75.0 g of ethylene glycol monovinyl polyethylene glycol ether), and the rest is the same as in Example 1; Comparative Example 3 (commercially available product): Commercially available high-slump-resistance polycarboxylate superplasticizer; Comparative Example 4 (closest to the prior art): The polycarboxylate superplasticizer disclosed in Example 1 of CN103275312A (containing only one macromonomer, isopentenyl polyethylene glycol ether with a molecular weight of 2400, and small monomers, acrylic acid and hydroxyethyl acrylate). Comparative Example 5 (Function Deprivation): Prepared according to the formulation of Example 1, but without sodium p-styrene sulfonate in solution A, i.e., all sodium p-styrene sulfonate (1.0 g) was transferred into the base solution, and the rest was the same as in Example 1.

[0055] All water-reducing agent samples were diluted to the same effective component concentration (7.0 wt% on a solids basis) and concrete performance tests were conducted according to GB / T 8076–2025. Concrete mix proportions (kg / m³): P·O 42.5 cement 360, river sand 850, crushed stone (5–25 mm) 1000, water 160; trial mix volume 20 L; test items included initial slump, initial spread, 1-hour slump, 1-hour spread, 1-hour slump loss over time, 1-hour spread loss over time, and 28-day compressive strength ratio. Concrete conditions (bleeding, segregation, compaction) were recorded at each admixture level. The admixture dosage gradient was 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, and 3.0% of the cementitious material mass, with a step size of 0.2%. Test results are shown in Table 1.

[0056]

[0057] Table 1 shows that Example 1 exhibits a slump fluctuation of ≤15 mm and a spread loss of ≤30 mm over 1 hour within the 2.0%–2.6% dosing range, significantly superior to Comparative Examples 2–5. Under the 2.8% overdosing condition, only slight bleeding occurs, with no segregation or caking observed, while Comparative Examples 2, 4, and 5 all show segregation or caking. Its 28-day compressive strength ratio remains stable at 164%, higher than all comparative examples. These results confirm that the present invention achieves a dual technical effect of reduced sensitivity and improved slump retention through the synergistic effect of di-polyether gradient branching, multi-monomer functional coupling, and A / B liquid gradient dropping process. Moreover, this effect cannot be obtained by simply adding the components together and is not readily apparent.

[0058] Example 8 verifies the practical application effect of the polycarboxylate superplasticizer mother liquors prepared in Examples 1-7 in ready-mixed concrete. Mother liquors prepared in Examples 1, 2, 3, 4, 5, 6, and Comparative Examples 2, 3, 4, and 5 were added to concrete at the same solids content (0.24% of the cementitious material mass, i.e., 7.0 wt% mother liquor after solidification is equivalent to 0.24%). Slump, spread, and changes over 1 hour were tested according to GB / T 8076–2025. The test results show that all samples prepared in Examples 1-6 exhibited only slight bleeding or no bleeding at a 2.8% dosage, without segregation or hardening. Comparative Examples 2, 4, and 5 showed varying degrees of segregation or hardening under the same conditions. Although Comparative Example 3 did not segregate, its 1-hour spread loss reached 80 mm, significantly higher than the 20 mm loss in Example 1. Experimental results show that the low-sensitivity, high-slump-retention polycarboxylate superplasticizer prepared in this invention exhibits good dosage tolerance and long-lasting slump retention effect in ready-mixed concrete. Therefore, it can be used to prepare admixture compositions for preventing and / or treating engineering defects caused by uncontrolled concrete fluidity.

[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-sensitivity, high-slump-retention polycarboxylate superplasticizer, characterized in that, The raw material components of the polycarboxylate superplasticizer, by mass percentage, include: 30%–40% polyether macromonomers, 1.5%–3% alkenyl monomers, and the remainder being water; The polyether macromonomer includes at least isopentenyl polyethylene glycol ether with a molecular weight of 2000 and ethylene glycol monovinyl polyethylene glycol ether with a molecular weight of 3000. The alkenyl monomers include at least: unsaturated carboxylic acid monomers acrylic acid, hydroxyethyl acrylate, butyl acrylate, at least one alkenyl monomer containing a sulfonic acid group, and sodium p-styrene sulfonate.

2. The low-sensitivity, high-slump-retention polycarboxylate superplasticizer according to claim 1, characterized in that, In the polyether macromonomer, the mass ratio of the isopentenyl polyethylene glycol ether to the ethylene glycol monovinyl polyethylene glycol ether is 1:

1.

3. The low-sensitivity, high-slump-retention polycarboxylate superplasticizer according to claim 1, characterized in that, The at least one alkenyl monomer containing a sulfonic acid group includes sodium allyl methanesulfonate and 2-acrylamido-2-methylpropanesulfonic acid; The alkenyl monomer further comprises: acrylic acid, hydroxyethyl acrylate, butyl acrylate, the alkenyl monomer containing sulfonic acid groups, and sodium p-styrene sulfonate.

4. The low-sensitivity, high-slump-retention polycarboxylate superplasticizer according to claim 1, characterized in that, The mass ratio of the acrylic acid, the hydroxyethyl acrylate, the butyl acrylate, the alkenyl monomer containing sulfonic acid groups, and the sodium p-styrene sulfonate is 10:4:2:2:

1.

5. The low-sensitivity, high-slump-retention polycarboxylate superplasticizer according to claim 1, characterized in that, The isopentenyl polyethylene glycol ether has 40 repeating polyoxyethylene units; The number of repeating polyoxyethylene units in the ethylene glycol monovinyl polyethylene glycol ether is 60; The acid-ether ratio of the unsaturated acid monomer to the polyether macromonomer in the polycarboxylate superplasticizer is 1:

2.

6. A method for preparing a low-sensitivity, high-slump-retention polycarboxylate superplasticizer, characterized in that, For preparing the low-sensitivity, high-slump-retention polycarboxylate superplasticizer as described in any one of claims 1-5, comprising: S1. Dissolve isopentenyl polyethylene glycol ether with a molecular weight of 2000, ethylene glycol monovinyl polyethylene glycol ether with a molecular weight of 3000, and sodium p-styrene sulfonate in water to prepare a base solution with a mass concentration of 50% to 60%. S2. Mix alkenyl monomers other than sodium p-styrene sulfonate with water to prepare solution A; mix reducing agent, catalyst, chain transfer agent with water to prepare solution B. S3. Add an initiator to the base liquid to start the polymerization reaction, and add liquid A and liquid B dropwise during the polymerization process, wherein liquid A is added in a variable-speed dropping manner with a fast speed at first and then a slow speed, and liquid B is added in a uniform-speed dropping manner, and the dropping time of liquid A ends earlier than the dropping time of liquid B. S4. After the addition of liquid A and liquid B is completed, continue the reaction for a predetermined time, and add water to adjust the concentration to obtain a low-sensitivity, high-slump-resistance polycarboxylate superplasticizer with a mass concentration of 40%.

7. The preparation method according to claim 6, characterized in that, The initiator is selected from hydrogen peroxide or ammonium persulfate; The reducing agent is selected from L-ascorbic acid or sodium bisulfite, the catalyst is selected from ferrous sulfate, and the chain transfer agent is selected from sodium hypophosphite.

8. The preparation method according to claim 6, characterized in that, The variable-rate dropping method for liquid A mentioned in step S3 includes: The dripping rate was 2 g / min for 0–10 minutes, 1.5 g / min for 10–20 minutes, 1 g / min for 20–30 minutes, 0.5 g / min for 30–40 minutes, and 0.3 g / min for 40–50 minutes, with the dripping ending at 50 minutes.

9. The preparation method according to claim 6, characterized in that, In step S3, solution B is added dropwise at a uniform rate and the addition is completed after 60 minutes. In step S4, after the addition of liquid A and liquid B, the reaction continues for 1 hour, and water is added to adjust the concentration to obtain the low-sensitivity, high-slump-resistance polycarboxylate superplasticizer with a mass concentration of 40%.

10. The preparation method according to claim 6, characterized in that, In S2, liquid A is prepared by mixing acrylic acid, hydroxyethyl acrylate, butyl acrylate, sodium allyl methanesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and sodium p-styrenesulfonate with water.

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