A slurry raising and viscosity reducing polycarboxylic water reducing agent suitable for low cement content concrete and a preparation method thereof

Abstract

The application discloses a slurry-lifting and viscosity-reducing polycarboxylic water reducing agent suitable for low-cement-content concrete and a preparation method thereof, and belongs to the technical field of building materials. The hydrophobic functional macromonomer is prepared by using dimerized fatty acid and bio-based dihydric alcohol as raw materials and by glycidyl methacrylate end-capping; the hydrophilic branched macromonomer is obtained by using citric acid, glycerol and monomethoxypolyethylene glycol as raw materials and by esterification and end-capping; and the target water reducing agent is obtained by the oxidation-reduction free radical copolymerization of the two kinds of macromonomers and sodium maleate in an aqueous phase. The application constructs a star-shaped multi-arm hyperbranched topological structure through molecular structure design, forms a dense adsorption layer on the surface of cement particles, has the functions of strong adsorption and dispersion, steric hindrance effect and lubrication, can reduce the viscosity of concrete mixture while significantly improving the slurry wrapping property and stability, and solves the problem that the fluidity and wrapping property of low-glue concrete are difficult to be considered simultaneously.

Description

Technical Field

[0001] This invention relates to the field of building materials, and in particular to a polycarboxylate superplasticizer for improving slurry quality and reducing viscosity, suitable for concrete with low cement content, and its preparation method. Background Technology

[0002] Current concrete engineering projects are pursuing cost reduction and efficiency improvement, and reducing the amount of cementitious materials such as cement has become an industry trend. In order to ensure the design strength of concrete, the water-cement ratio must be kept constant, which leads to a corresponding reduction in the amount of mixing water, and thus a significant reduction in the volume of the paste in the concrete that plays a lubricating and binding role.

[0003] Even if the amount of aggregate is increased to maintain stable density, insufficient paste volume will still lead to deterioration of the workability of fresh concrete, resulting in problems such as segregation, bleeding, and poor aggregate encapsulation. This restricts construction efficiency and affects the performance of hardened concrete, becoming a bottleneck for the promotion of low-binder concrete.

[0004] Polycarboxylate superplasticizers are key to improving the fluidity of concrete. However, traditional products cannot balance the contradiction between improving fluidity and enhancing aggregate encapsulation in systems with low binder and low water-binder ratio. Simply improving fluidity will exacerbate the thinning of the paste, while thickening to improve encapsulation will reduce fluidity.

[0005] Existing conventional water-reducing agents and physical compounding schemes not only fail to resolve the above contradictions, but also suffer from defects such as poor component compatibility and system instability, making it difficult to fundamentally improve the workability of low-binder concrete.

[0006] Therefore, there is an urgent need to develop a polycarboxylate superplasticizer that can enhance the coating properties of the slurry while reducing viscosity and maintaining fluidity, thereby solving industry pain points and helping engineering projects reduce costs and increase efficiency in the concrete industry. Summary of the Invention

[0007] This invention provides a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete and its preparation method. It can solve the problems in the prior art, such as the inability of conventional polycarboxylate superplasticizers and compounding techniques to balance the fluidity and aggregate encapsulation of low-cement concrete, and the poor compatibility of physical compounding schemes, which lead to the deterioration of the workability of low-cement-content concrete.

[0008] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete, having a structure as shown in formula (I):

[0009] Equation (I) Wherein, the degree of polymerization m and n are each independently 1 to 50; The degrees of polymerization, a, b, and c, are each independently between 1 and 30; R is one or a combination of two or more of -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2- or -(CH2)5-.

[0010] Secondly, the present invention provides a method for preparing a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete, comprising the following steps: S1. Under a nitrogen atmosphere, dimer fatty acids, bio-based diols and catalysts are mixed and heated to obtain hydroxyl-terminated polyester prepolymers; the mixture is cooled, glycidyl methacrylate and polymerization inhibitors are added, and the mixture is kept at a constant temperature under nitrogen protection and then cooled to obtain hydrophobic macromonomers. S2. Under a nitrogen atmosphere, citric acid, glycerol, monomethoxy polyethylene glycol and catalyst are mixed and heated to react. When the acid value drops to below 15 mg KOH / g, the system is cooled, glycidyl methacrylate and polymerization inhibitor are added, and the reaction continues until the epoxy groups are completely consumed. After cooling, hydrophilic branched macromonomer is obtained. S3. Add deionized water to the reaction vessel, then add sodium maleate and the hydrophilic branched macromonomer prepared in step S2 in sequence and stir to dissolve to obtain solution A; premix the hydrophobic macromonomer prepared in step S1 with a cosolvent and an oxidant to obtain solution B; heat the reaction system under nitrogen protection, and add the above solution B, reducing agent, and chain transfer agent dropwise to solution A; after the dropwise addition is completed, keep it at the temperature for aging, cool it to room temperature, and adjust the pH value of the system to a suitable range with alkali solution to obtain polycarboxylate superplasticizer.

[0011] Furthermore, in step S1, the hydrophobic macromonomer has a structure as shown in formula (II):

[0012] Formula (II) Wherein, the degree of polymerization n is 1 to 50; R is one or a combination of two or more of -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2- or -(CH2)5-.

[0013] Further, in step S1, the molar ratio of the dimer fatty acid, bio-based diol and glycidyl methacrylate is 1:(2-3):(2-3); the amount of catalyst is 0.1% to 0.5% of the total mass of the feed in step S1; and the amount of polymerization inhibitor is 0.01% to 0.05% of the total mass of the feed in step S1.

[0014] Further, in step S1, the temperature of the heating reaction is 180-200℃ and the time is 4-6 hours; the temperature of the cooling reaction is 90-110℃; and the time of the heat preservation reaction is 3-5 hours.

[0015] Further, in step S1, the dimer fatty acid has the molecular formula C 36 H 68 O4 has an iodine value ranging from 80 to 120 gI2 / 100g.

[0016] Further, in step S1, the bio-based diol is one or a combination of two or more of 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol.

[0017] Further, in step S1, the catalyst is tetraisopropyl titanate and the polymerization inhibitor is hydroquinone.

[0018] Furthermore, in step S2, the hydrophilic branched macromonomer has a structure as shown in formula (Ⅲ):

[0019] Formula (III) The degree of polymerization m ranges from 1 to 50.

[0020] Further, in step S2, the molar ratio of citric acid, glycerol, monomethoxy polyethylene glycol and glycidyl methacrylate is 1:(1-3):(1-3):(4-5); the amount of catalyst is 0.1% to 0.5% of the total mass of the feed in step S2; and the amount of polymerization inhibitor is 0.01% to 0.05% of the total mass of the feed in step S2.

[0021] Further, in step S2, the temperature of the heating reaction is 120-140°C and the time is 5-7 hours; the temperature of the cooling reaction is 90-110°C.

[0022] Further, in step S2, the weight-average molecular weight of the monomethoxy polyethylene glycol is 400–1200 g / mol.

[0023] Further, in step S2, the catalyst is one or a combination of two or more of p-toluenesulfonic acid, concentrated sulfuric acid, or tetraisopropyl titanate.

[0024] Further, in step S2, the polymerization inhibitor is one or a combination of two or more of hydroquinone, phenothiazine, or 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy free radical.

[0025] Further, in step S3, the molar ratio of sodium maleate, the hydrophobic macromonomer prepared in step S1, and the hydrophilic branched macromonomer prepared in step S2 is (3.0~5.0):(0.2~0.4):(0.6~0.8) based on the number of moles of double bonds contained in each.

[0026] Further, in step S3, the amount of the co-solvent is 10% to 30% of the total mass of the feed in step S3; the amount of the oxidant is 0.5% to 2% of the total mass of the feed in step S3; the amount of the reducing agent is 0.1% to 2% of the total mass of the feed in step S3; and the amount of the chain transfer agent is 0.5% to 2% of the total mass of the feed in step S3.

[0027] Furthermore, in step S3, the temperature for heating is 60–75°C; the dripping time is 2–4 hours; and the time for heat preservation and maturation after dripping is completed is 1–2 hours.

[0028] Further, in step S3, the co-solvent is one or a combination of two or more of isopropanol, ethanol, acetone or N,N-dimethylformamide.

[0029] Further, in step S3, the oxidant is one or a combination of two or more of ammonium persulfate, potassium persulfate, hydrogen peroxide, or tert-butyl hydroperoxide.

[0030] Further, in step S3, the reducing agent is one or a combination of two or more of vitamin C, sodium bisulfite, sodium metabisulfite, and ferrous sulfate.

[0031] Further, in step S3, the chain transfer agent is one or a combination of two or more of mercaptoacetic acid, 3-mercaptopropionic acid, 2-mercaptoethanol, dodecyl mercaptan or isopropanol.

[0032] Further, in step S3, the alkaline solution is one or a combination of two or more of sodium hydroxide solution, potassium hydroxide solution, or monoethanolamine, used to neutralize the system to pH 6.5-7.0.

[0033] The beneficial effects of this invention are: 1. The polycarboxylate superplasticizer prepared by this invention has a star-shaped multi-arm hyperbranched structure. After adsorbing onto the surface of cement particles, it can effectively compress and diffuse the double electric layer and water film thickness, releasing more free water. At the same time, the hydrophobic arms (dimeric fatty acid-diol-glycidyl methacrylate end-capped polymer) provide lubrication, and the hydrophilic branched arms (citric acid-glycerol-polyethylene glycol-glycidyl methacrylate end-capped polymer) enhance the viscosity of the continuous phase of the paste. Together, they significantly reduce the plastic viscosity of concrete and improve the paste's ability to encapsulate aggregates, overcoming segregation and bleeding.

[0034] 2. The polycarboxylate superplasticizer prepared by this invention has a high density of carboxyl groups, which can ensure rapid and strong adsorption. The three-dimensional hyperbranched side arms provide a strong steric hindrance effect, making the cement particles more uniformly dispersed and maintaining the dispersion state for a longer period of time.

[0035] 3. The core raw materials (dimer acid, citric acid, and bio-based diol) of the polycarboxylate superplasticizer prepared in this invention are derived from renewable biomass, which is in line with the direction of green chemistry. The molecular design integrates multiple functions such as viscosity reduction, slurry improvement, water reduction, and slump retention into a single structure, avoiding compatibility problems caused by complex compounding.

[0036] 4. The synthesis process of the polycarboxylate superplasticizer prepared by this invention is controllable: a two-step method is adopted, which first prepares functional macromonomers and then copolymerizes them with free radicals. The reaction conditions are mild, and the structures of intermediate products in each step are clear, which facilitates quality control and molecular structure customization. Detailed Implementation

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0038] In a first aspect, the present invention provides a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete, having a structure as shown in formula (I):

[0039] Equation (I) Wherein, the degree of polymerization m and n are each independently 1 to 50; The degrees of polymerization, a, b, and c, are each independently between 1 and 30; R is one or a combination of two or more of -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2- or -(CH2)5-.

[0040] The polycarboxylate superplasticizer prepared in this invention possesses a star-shaped, multi-arm hyperbranched structure. When adsorbed onto the surface of cement particles, it effectively compresses the thickness of the diffused double layer and hydration film at the particle interface, releasing free water from the system. Simultaneously, the hydrophobic arms (dimeric fatty acid-diol-glycidyl methacrylate end-capped segments) in the molecular structure act as lubricants, while the hydrophilic branched arms (citric acid-glycerol-polyethylene glycol-glycidyl methacrylate end-capped segments) regulate the viscosity of the continuous phase of the paste. The synergistic effect of these two components significantly reduces the plastic viscosity of concrete and enhances the paste's ability to encapsulate aggregates, thereby effectively improving the problems of segregation and bleeding in concrete mixtures.

[0041] Secondly, the present invention provides a method for preparing a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete, comprising the following steps: S1. Under a nitrogen atmosphere, dimer fatty acids, bio-based diols and catalysts are mixed and heated to obtain hydroxyl-terminated polyester prepolymers; the mixture is cooled, glycidyl methacrylate and polymerization inhibitors are added, and the mixture is kept at a constant temperature under nitrogen protection and then cooled to obtain hydrophobic macromonomers. Under nitrogen protection and catalytic conditions, the above steps involve the condensation reaction of dimer fatty acids and bio-based diols to generate a hydroxyl-terminated polyester prepolymer with a hydrophobic framework. Subsequently, glycidyl methacrylate is added, causing it to undergo a ring-opening addition reaction with the terminal hydroxyl groups of the prepolymer, introducing polymerizable double bonds to obtain a hydrophobic macromonomer. This step, through the construction of a long-chain hydrophobic structure, endows the water-reducing agent molecule with excellent lubrication and viscosity-reducing abilities, which is beneficial for reducing the plastic viscosity of the concrete system and improving the flowability of the mixture.

[0042] S2. Under a nitrogen atmosphere, citric acid, glycerol, monomethoxy polyethylene glycol and catalyst are mixed and heated to react. When the acid value drops to below 15 mg KOH / g, the system is cooled, glycidyl methacrylate and polymerization inhibitor are added, and the reaction continues until the epoxy groups are completely consumed. After cooling, hydrophilic branched macromonomer is obtained. Under nitrogen and catalytic conditions, the above steps involve a polyol-acid condensation reaction between citric acid, glycerol, and monomethoxy polyethylene glycol to form a hyperbranched, multi-hydrophilic prepolymer. This prepolymer is then capped with glycidyl methacrylate to introduce unsaturated double bonds, yielding a hydrophilic branched macromonomer. This process constructs a multi-branched, strongly hydrophilic molecular structure, significantly enhancing the water-reducing agent's ability to retain, thicken, and encapsulate cement paste, thus inhibiting concrete segregation and bleeding.

[0043] S3. Add deionized water to the reaction vessel, then add sodium maleate and the hydrophilic branched macromonomer prepared in step S2 in sequence and stir to dissolve to obtain solution A; premix the hydrophobic macromonomer prepared in step S1 with a cosolvent and an oxidant to obtain solution B; heat the reaction system under nitrogen protection, and add the above solution B, reducing agent, and chain transfer agent dropwise to solution A; after the dropwise addition is completed, keep it at the temperature for aging, cool it to room temperature, and adjust the pH value of the system to a suitable range with alkali solution to obtain polycarboxylate superplasticizer.

[0044] The above steps use sodium maleate and hydrophilic branched macromonomers as aqueous reaction substrates. The hydrophobic macromonomers are dissolved in a co-solvent and then uniformly mixed with an oxidant. Aqueous free radical copolymerization is then carried out under a redox initiation system, allowing the hydrophilic and hydrophobic macromonomers to polymerize in situ with sodium maleate to form a star-shaped multi-arm copolymer. By controlling the polymerization rate and molecular weight distribution through stepwise dropwise addition, the resulting water-reducing agent exhibits excellent dispersibility, water retention, and viscosity reduction effects, making it suitable for low-cement-content concrete systems. It also possesses multiple functions including improving slurry quality, reducing viscosity, and preventing segregation.

[0045] In some embodiments, in step S1, the hydrophobic macromonomer has a structure as shown in formula (II):

[0046] Formula (II) Wherein, the degree of polymerization n is 1 to 50; R is one or a combination of two or more of -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2- or -(CH2)5-.

[0047] This hydrophobic macromonomer has a long-chain alkyl and polyester hydrophobic backbone. By controlling the degree of polymerization and the alkyl chain length, it can endow the water-reducing agent molecule with excellent hydrophobicity and lubrication properties. In cement paste, it can effectively reduce interfacial friction and plastic viscosity of concrete, and improve the fluidity of the mixture. At the same time, the long hydrophobic chain segments can form a stable hydrophobic adsorption layer on the particle surface, reduce the excessive consumption of free water, improve the smoothness of the paste during construction, and help solve the problem of high viscosity and poor fluidity of concrete with low cement content.

[0048] In some embodiments, in step S1, the molar ratio of the dimer fatty acid, bio-based diol, and glycidyl methacrylate is 1:(2-3):(2-3); the amount of catalyst is 0.1% to 0.5% of the total mass of the feed in step S1; and the amount of polymerization inhibitor is 0.01% to 0.05% of the total mass of the feed in step S1. Reasonably limiting the molar ratio of the dimer fatty acid, bio-based diol, and glycidyl methacrylate, as well as the amounts of catalyst and polymerization inhibitor, can ensure efficient and complete polycondensation and end-capping reactions. If the ratio of diol to glycidyl methacrylate is too low, the prepolymer's terminal hydroxyl groups will not react sufficiently, and the double bonds will not be completely capped, affecting subsequent polymerization activity; if the ratio is too high, it is easy to introduce excessive unreacted monomers, reducing product purity. If the amount of catalyst is too low, the reaction rate will be slow and the polycondensation incomplete; if the amount is too high, it is easy to lead to a darker product color and an increase in side reactions. If the amount of polymerization inhibitor is too low, self-polymerization may occur, affecting the monomer yield; if the amount is too high, it will inhibit the subsequent copolymerization reaction and reduce the synthesis efficiency of the water-reducing agent.

[0049] In some embodiments, in step S1, the heating reaction temperature is 180–200°C, and the time is 4–6 hours; the cooling temperature is 90–110°C; and the holding reaction time is 3–5 hours. Reasonable control of the heating reaction temperature, time, and holding reaction conditions can ensure the depth of the polycondensation reaction and the efficiency of double bond end-capping. If the temperature is too low or the time is too short, the polycondensation reaction will be insufficient, resulting in a low molecular weight of the prepolymer and insufficient strength of the hydrophobic structure. If the temperature is too high or the time is too long, it can easily lead to polymer thermal degradation, yellowing, or even cross-linking, affecting monomer properties. The cooling reaction range of 90–110°C ensures the smooth progress of the ring-opening reaction while avoiding high-temperature-induced self-polymerization of unsaturated double bonds, ensuring the stability of the hydrophobic macromonomer structure.

[0050] In some embodiments, in step S1, the dimer fatty acid has the molecular formula Cdimer. 36 H 68O4 has an iodine value ranging from 80 to 120 g I2 / 100 g. Using this molecular formula in a dimer fatty acid and controlling the iodine value within this range allows the hydrophobic macromonomer to possess suitable hydrophobicity, double bond reactivity, and chain flexibility. If the iodine value is too low, the molecular unsaturated sites are few, resulting in low reactivity and weak lubrication and viscosity-reducing effects; if the iodine value is too high, the unsaturation is too high, leading to easy self-polymerization during synthesis, increased side reactions, and poor product stability. A suitable iodine value and carbon chain structure can significantly improve the lubrication, viscosity-reducing, and anti-bleeding effects of concrete.

[0051] In some embodiments, in step S1, the bio-based diol is one or a combination of two or more of 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol. The length, rigidity, and spatial structure of the polyester hydrophobic segments can be flexibly adjusted. If the carbon chain is too short, the hydrophobic and lubricating effects are weak, and the viscosity-reducing ability is insufficient; if the carbon chain is too long, the monomer will be too hydrophobic and the water solubility will be poor, affecting the dispersion and compatibility of the water-reducing agent in the cement system. Using the above-mentioned bio-based diol achieves an optimal balance between hydrophobicity, water solubility, and lubricity.

[0052] In some embodiments, in step S1, the catalyst is tetraisopropyl titanate, and the polymerization inhibitor is hydroquinone. Tetraisopropyl titanate is chosen as the polycondensation catalyst because it exhibits mild catalytic activity and high selectivity, effectively promoting the polycondensation of carboxyl and hydroxyl groups, reducing side reactions, and obtaining a prepolymer with uniform molecular weight and terminal hydroxyl groups. Hydroquinone is chosen as the polymerization inhibitor because it effectively inhibits the self-polymerization of unsaturated double bonds during high-temperature reactions; however, if the dosage is too low, the polymerization inhibition effect is poor, and gelation is likely.

[0053] In some embodiments, in step S2, the hydrophilic branched macromonomer has a structure as shown in formula (Ⅲ):

[0054] Formula (III) The degree of polymerization m ranges from 1 to 50.

[0055] This hydrophilic branched macromonomer has a hyperbranched structure as shown in Formula (Ⅲ), and the degree of polymerization m is controlled in the range of 1 to 50. Its multi-branched structure can provide abundant hydrophilic groups, which can significantly enhance the hydrophilicity and water retention capacity of the water-reducing agent and effectively improve the viscosity of the continuous phase of cement paste. At the same time, the appropriate degree of polymerization can balance the degree of branching and water solubility, avoid poor water retention and anti-bleeding effect caused by insufficient branching, or abnormal viscosity and decreased dispersibility of the system caused by excessive branching. In this way, it optimizes the coating performance of the paste on aggregates, inhibits the segregation and bleeding phenomenon of low cement content concrete, and achieves the dual effect of improving paste quality and reducing viscosity in conjunction with the hydrophobic macromonomer.

[0056] In some embodiments, in step S2, the molar ratio of citric acid, glycerol, monomethoxy polyethylene glycol, and glycidyl methacrylate is 1:(1-3):(1-3):(4-5); the amount of catalyst is 0.1%-0.5% of the total mass of the feed in step S2; and the amount of polymerization inhibitor is 0.01%-0.05% of the total mass of the feed in step S2. Reasonable control of the molar ratio of citric acid, glycerol, monomethoxy polyethylene glycol, and glycidyl methacrylate can ensure that the system fully forms a hyperbranched prepolymer and effectively capsizes the terminal hydroxyl groups, introducing sufficient active double bonds. If the monomer ratio is too low, insufficient branching and incomplete capping may occur, leading to a decrease in hydrophilicity and water retention. If the ratio is too high, excessive unreacted monomers will remain, reducing the purity and effective content of the product. Too low a catalyst dosage will result in a slow polycondensation reaction rate and incomplete reaction; too high a dosage will easily exacerbate side reactions, leading to a darker product color and uneven molecular structure. If the amount of polymerization inhibitor is too low, it will not be able to effectively inhibit the self-polymerization of double bonds and will easily produce gel; if the amount is too high, there will be residual polymerization inhibitor components, which will affect the initiation efficiency of subsequent copolymerization reactions and the molecular weight of polymers.

[0057] In some embodiments, in step S2, the heating reaction temperature is 120–140°C, and the time is 5–7 hours; the cooling temperature is 90–110°C. Controlling the heating reaction temperature and time within a reasonable range ensures that citric acid, glycerol, and monomethoxy polyethylene glycol undergo sufficient condensation polymerization to form a stable hyperbranched hydrophilic prepolymer. Too low a temperature or too short a time will lead to insufficient condensation polymerization, incomplete branching structure, and weakened hydrophilicity and water retention. Too high a temperature or too long a time can easily cause molecular thermal degradation, cross-linking, or even gelation, damaging the monomer structure. Cooling the system to 90–110°C before the end-capping reaction ensures the ring-opening efficiency of glycidyl methacrylate and avoids high-temperature self-polymerization of unsaturated double bonds, improving the stability and reactivity of the hydrophilic branched macromonomer.

[0058] In some embodiments, in step S2, the weight-average molecular weight of the monomethoxy polyethylene glycol is 400–1200 g / mol. This provides suitable hydrophilicity and steric hindrance effects for the water-reducing agent. If the molecular weight is too low, the hydrophilic segments are too short, resulting in weak water retention, encapsulation, and anti-segregation effects; if the molecular weight is too high, the segments will be too long and the hydrophilicity too strong, leading to excessively high slurry viscosity and reducing the fluidity and dispersibility of concrete. This molecular weight range allows the hydrophilic branched macromonomer to achieve an optimal balance between water solubility, water retention, and viscosity reduction, making it suitable for low-cement-content concrete systems.

[0059] In some embodiments, in step S2, the catalyst is one or a combination of two or more of p-toluenesulfonic acid, concentrated sulfuric acid, or tetraisopropyl titanate. The above-mentioned catalytic activity is mild and highly applicable, and can efficiently catalyze the condensation reaction between carboxyl and hydroxyl groups, ensuring the stable formation of hyperbranched structures.

[0060] In some embodiments, in step S2, the polymerization inhibitor is one or a combination of two or more of hydroquinone, phenothiazine, or 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy free radical. This can efficiently inhibit the self-polymerization and gelation of unsaturated double bonds under high-temperature reaction conditions, ensuring the retention rate of double bonds and polymerization activity of hydrophilic branched macromonomers.

[0061] In some embodiments, in step S3, the molar ratio of sodium maleate, the hydrophobic macromonomer prepared in step S1, and the hydrophilic branched macromonomer prepared in step S2, based on the molar number of double bonds they each contain, is (3.0–5.0):(0.2–0.4):(0.6–0.8). By rationally controlling the molar ratio of sodium maleate, the hydrophobic macromonomer, and the hydrophilic branched macromonomer, the synthesized water-reducing agent can achieve a synergistic balance between dispersion, viscosity reduction, water retention, and anti-segregation properties. If the proportion of hydrophobic macromonomer is too low, the viscosity reduction and lubrication effects are insufficient, resulting in high viscosity of the concrete mixture; if the proportion is too high, it easily leads to excessive hydrophobicity, poor water retention in the slurry, and segregation and bleeding. If the proportion of hydrophilic branched macromonomer is too low, the encapsulation and anti-segregation effects are weak; if the proportion is too high, the slurry viscosity will be too high, and the fluidity will decrease. Through the above ratio, the water-reducing agent can simultaneously possess excellent dispersibility, slurry-enhancing properties, and viscosity-reducing and anti-bleeding performance.

[0062] In some embodiments, in step S3, the amount of the co-solvent is 10% to 30% of the total mass of the materials fed in step S3; the amount of the oxidant is 0.5% to 2% of the total mass of the materials fed in step S3; the amount of the reducing agent is 0.1% to 2% of the total mass of the materials fed in step S3; and the amount of the chain transfer agent is 0.5% to 2% of the total mass of the materials fed in step S3. The amounts of co-solvent, oxidant, reducing agent, and chain transfer agent directly determine the stability, molecular weight, and distribution of the polymerization reaction. If the amount of co-solvent is too low, the hydrophobic macromonomers will have poor solubility, leading to phase separation and uneven copolymerization; if the amount is too high, it will increase costs and reduce the concentration of the reaction system. If the amounts of oxidant and reducing agent are too low, the initiation efficiency will be insufficient, resulting in low monomer conversion rate, small molecular weight, and weak water-reducing performance; if the amounts are too high, the reaction will be violent and difficult to control, and the large molecular weight will easily lead to excessive viscosity of concrete and accelerated slump loss. If the amount of chain transfer agent is too low, the polymer molecular weight will be too large and the distribution will be too wide, making it easy to thicken; if the amount is too high, the molecular weight will be too low, and the dispersibility and plasticity retention will be significantly reduced.

[0063] In some embodiments, in step S3, the heating temperature is 60–75°C; the dropping time is 2–4 hours; and the curing time after dropping is 1–2 hours. Controlling the polymerization temperature, dropping time, and curing time within appropriate ranges enables slow, uniform, and stable free radical copolymerization, ensuring sufficient copolymerization of hydrophilic and hydrophobic monomers with sodium maleate. Too low a temperature or too rapid dropping results in low initiation efficiency, high monomer residue, and uneven copolymerization; too high a temperature or too slow dropping easily leads to larger molecular weights, concentrated exothermic reactions, and a risk of gelation. Insufficient curing time results in incomplete monomer conversion and low effective product content; excessive time reduces production efficiency. Reasonable process conditions result in a uniform polymer structure, stable performance, and excellent water-reducing and plasticizing effects.

[0064] In some embodiments, in step S3, the co-solvent is one or a combination of two or more of isopropanol, ethanol, acetone, or N,N-dimethylformamide. These co-solvents have strong solubility and moderate volatility, effectively improving the solubility of hydrophobic macromonomers in aqueous systems, enabling homogeneous copolymerization of hydrophilic and hydrophobic monomers, and avoiding problems such as incomplete polymerization and product stratification caused by phase separation.

[0065] In some embodiments, in step S3, the oxidant is one or a combination of two or more of ammonium persulfate, potassium persulfate, hydrogen peroxide, or tert-butyl hydroperoxide. It can form a mild and efficient redox initiation system with the corresponding reducing agent, enabling stable initiation of free radical copolymerization of hydrophilic branched macromonomers, hydrophobic macromonomers, and sodium maleate at lower temperatures, ensuring high monomer conversion and uniform polymer molecular weight distribution.

[0066] In some embodiments, in step S3, the reducing agent is one or a combination of two or more of vitamin C, sodium bisulfite, sodium metabisulfite, and ferrous sulfate. It can rapidly form redox pairs with the oxidizing agent, generating free radicals under mild conditions, thus achieving low-temperature, stable, and efficient initiation of copolymerization.

[0067] In some embodiments, in step S3, the chain transfer agent is one or a combination of two or more of mercaptoacetic acid, 3-mercaptopropionic acid, 2-mercaptoethanol, dodecyl mercaptan, or isopropanol. This effectively regulates the polymer molecular weight and chain structure, preventing excessive molecular growth and cross-linking thickening, thus giving the water-reducing agent both high dispersibility and low viscosity. Different chain transfer agents can be adapted to different reaction systems and temperatures, adjusting molecular weight distribution and improving concrete fluidity and workability. However, improper selection of the chain transfer agent can easily lead to problems such as uncontrollable molecular weight, insufficient water reduction, excessive viscosity, and rapid slump loss.

[0068] In some embodiments, in step S3, the alkaline solution is one or a combination of two or more of sodium hydroxide solution, potassium hydroxide solution, or monoethanolamine, used to neutralize the system to a pH of 6.5–7.0. This allows the polymer molecular chains to fully extend, achieving optimal solubility and stability, while avoiding the adverse effects of acidity or strong alkalinity on cement hydration, concrete setting, and strength. If the pH is too low, the polymer solubility is poor, stratification during storage is likely, and it will accelerate cement setting; if the pH is too high, the paste will be too alkaline, affecting the compatibility of admixtures and easily leading to bleeding, delayed setting, and reduced strength. A neutral to slightly acidic range allows the water-reducing agent to achieve optimal stability, compatibility, and water-reducing effect.

[0069] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0070] Example Example 1 This embodiment provides a method for preparing a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete, the steps of which are as follows: Step S1: Add dimer fatty acid C to a four-necked reactor equipped with a mechanical stirrer, a water separator, and a thermometer. 36 H 68 O4 (1.00 mol, iodine value 95 g I2 / 100 g), 1,3-propanediol (2.00 mol), and tetraisopropyl titanate catalyst (0.3% of the total mass of the feed in step S1) were slowly heated to 185 °C under a nitrogen atmosphere for a condensation reaction for 4.5 h. The mixture was then cooled to 100 °C, and glycidyl methacrylate (2.02 mol) and hydroquinone inhibitor (0.03% of the total mass of the feed in step S1) were added. The mixture was kept at this temperature for 4 h until the epoxy groups were completely consumed. After cooling, a dimer acid-propylene glycol-acrylate end-capped hydrophobic macromonomer was obtained.

[0071] In the structural formula of the hydrophobic macromonomer it generates: the degree of polymerization n is 2; R is -CH2CH2CH2-.

[0072] Step S2: Add citric acid (1.00 mol), glycerol (1.00 mol), monomethoxy polyethylene glycol mPEG-600 (1.00 mol, Mw=600 g / mol), and p-toluenesulfonic acid catalyst (0.3% of the total mass of the feed in step S2) to the reactor. Heat to 130°C under nitrogen and carry out esterification reaction for 6 hours until the acid value reaches the standard. Cool down to 100°C and add glycidyl methacrylate (4.01 mol) and hydroquinone inhibitor (0.03% of the total mass of the feed in step S2). Continue the reaction until the epoxy groups are completely consumed. Cool to obtain citric acid-glycerol-mPEG600-acrylate end-capped hydrophilic branched macromonomer.

[0073] In the hydrophilic branched macromonomer structure it generates, the degree of polymerization m is 3.

[0074] Step S3: Add deionized water (1200g) to the polymerization reactor, then add sodium maleate (4.00mol, equivalent to 536g) and the hydrophilic branched macromonomer prepared in step S2 (0.80mol, equivalent to 440g based on double bonds), stir to dissolve, and obtain solution A; then add the hydrophobic macromonomer prepared in step S1 (0.24mol, equivalent to 336g based on double bonds), the co-solvent isopropanol (15% of the total mass of the feed in step S3), and the oxidant ammonium persulfate (…). Premix the aqueous phase system with 1.2% of the total mass of the feed in step S3 to obtain solution B. Heat the aqueous phase system to 65°C and, under nitrogen protection, simultaneously add solution B, reducing agent vitamin C (0.22% of the total mass of the feed in step S3), and an aqueous solution of chain transfer agent 3-mercaptopropionic acid (0.50% of the total mass of the feed in step S3) to solution A. After adding the solution dropwise for 3 hours, keep it warm and mature for 1 hour, and then cool it. Adjust the pH to 6.8 with a 30% sodium hydroxide solution to obtain polycarboxylate superplasticizer, denoted as PCE-1.

[0075] The structural formula of the water-reducing agent produced has the following characteristics: degree of polymerization n is 2; degree of polymerization m is 3; degrees of polymerization a, b, and c are 8, 5, and 12, respectively; and R is -CH2CH2CH2-.

[0076] Example 2 This embodiment provides a method for preparing a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete, the steps of which are as follows: Step S1: Modify “1,3-propanediol (2.00 mol)” in Step S1 of Example 1 to “1,4-butanediol (2.00 mol)”. The remaining raw materials and steps are the same as in Step S1 of Example 1 to obtain dimer acid-butanediol-acrylate end-capped hydrophobic macromonomer. In the structural formula of the hydrophobic macromonomer it generates: the degree of polymerization n is 2; R is -CH2CH2CH2CH2-.

[0077] Step S2, raw materials and steps are the same as in step S2 of Example 1, to prepare citric acid-glycerol-mPEG600-acrylate-terminated hydrophilic branched macromonomer; In the structural formula of this hydrophilic branched macromonomer: the degree of polymerization m is 3; Step S3: Modify "sodium maleate (4.00 mol, equivalent to 536 g)" in Step S3 of Example 1 to "sodium maleate (3.00 mol, equivalent to 402 g)"; The phrase “the hydrophilic branched macromonomer prepared in step S2 (0.80 mol based on the double bonds contained, equivalent to 440 g)” is revised to “the hydrophilic branched macromonomer prepared in step S2 (0.84 mol based on the double bonds, equivalent to 462 g)”. The phrase "the hydrophobic macromonomer prepared in step S1 (0.24 mol based on the double bonds, equivalent to 336 g)" was modified to "the hydrophobic macromonomer prepared in step S1 (0.32 mol based on the double bonds, equivalent to 448 g)". The remaining raw materials and steps were the same as in step S3 of Example 1, and a polycarboxylate superplasticizer, denoted as PCE-2, was obtained. The structural formula of the water-reducing agent produced has the following characteristics: degree of polymerization n is 2; degree of polymerization m is 3; average values ​​of degrees of polymerization a, b, and c are 7, 4, and 13, respectively; and R is -CH2CH2CH2CH2-.

[0078] Example 3 This embodiment provides a method for preparing a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete, the steps of which are as follows: Step S1, raw materials and steps are the same as in Step S1 of Example 1, to obtain dimer acid-propylene glycol-acrylate end-capped hydrophobic macromonomer; Step S2: Modify "glycerol (1.00 mol)" in Step S2 of Example 1 to "glycerol (2.00 mol)"; modify "monomethoxy polyethylene glycol mPEG-600 (1.00 mol, Mw=600 g / mol)" to "mPEG-1000 (1.00 mol, Mw=1000 g / mol)"; modify "glycidyl methacrylate (4.01 mol)" to "glycidyl methacrylate (4.40 mol)"; and keep the other raw materials and steps the same as in Step S2 of Example 1 to obtain citric acid-glycerol-mPEG1000-acrylate end-capped hydrophilic branched macromonomer; In the hydrophilic branched macromonomer structure it generates, the degree of polymerization m is 5; Step S3: Modify "sodium maleate (4.00 mol, equivalent to 536 g)" in Step S3 of Example 1 to "sodium maleate (5.00 mol, equivalent to 670 g)"; The phrase “the hydrophilic branched macromonomer prepared in step S2 (0.80 mol based on the double bonds contained, equivalent to 440 g)” is revised to “the hydrophilic branched macromonomer prepared in step S2 (0.72 mol based on the double bonds, equivalent to 612 g)”. The phrase "the hydrophobic macromonomer prepared in step S1 (0.24 mol based on the double bonds, equivalent to 336 g)" was modified to "the hydrophobic macromonomer prepared in step S1 (0.26 mol based on the double bonds, equivalent to 364 g)". The remaining raw materials and steps were the same as in step S3 of Example 1, and a polycarboxylate superplasticizer, denoted as PCE-3, was obtained. The structural formula of the water-reducing agent produced has the following characteristics: degree of polymerization n is 2; degree of polymerization m is 5; degrees of polymerization a, b, and c are 10, 6, and 15 respectively; and R is -CH2CH2CH2-.

[0079] Example 4 This embodiment provides a method for preparing a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete, the steps of which are as follows: Step S1, raw materials and steps are the same as in Step S1 of Example 2, to obtain dimer acid-butanediol-acrylate end-capped hydrophobic macromonomer; Step S2, raw materials and steps are the same as in step S2 of Example 3, to obtain citric acid-glycerol-mPEG1000-acrylate-terminated hydrophilic branched macromonomer; Step S3: Modify "sodium maleate (4.00 mol, equivalent to 536 g)" in Step S3 of Example 1 to "sodium maleate (3.50 mol, equivalent to 469 g)"; The phrase “The hydrophilic branched macromonomer prepared in step S2 (0.80 mol based on the double bonds it contains, equivalent to 440 g)” is revised to “The hydrophilic branched macromonomer prepared in step S2 (0.69 mol based on the double bonds it contains, equivalent to 587 g)”. The phrase "the hydrophobic macromonomer prepared in step S1 (0.24 mol based on the double bonds, equivalent to 336 g)" was modified to "the hydrophobic macromonomer prepared in step S1 (0.28 mol based on the double bonds, equivalent to 392 g)". The remaining raw materials and steps were the same as in step S3 of Example 1, and a polycarboxylate superplasticizer, denoted as PCE-4, was obtained. The structural formula of the water-reducing agent produced has the following characteristics: degree of polymerization n is 2; degree of polymerization m is 5; degrees of polymerization a, b, and c are 8, 4, and 14, respectively; and R is -CH2CH2CH2CH2-.

[0080] Example 5 This embodiment provides a method for preparing a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete, the steps of which are as follows: Step S1: Modify “1,3-propanediol (2.00 mol)” in Step S1 of Example 1 to “1,5-pentanediol (2.00 mol)”, and keep the other raw materials and steps the same as in Step S1 of Example 1 to obtain dimer acid-pentanediol-acrylate end-capped hydrophobic macromonomer; In the hydrophobic macromonomer structure it generates, the degree of polymerization n is 2; and R is -(CH2)5-.

[0081] Step S2, raw materials and steps are the same as in step S2 of Example 1, to prepare citric acid-glycerol-mPEG600-acrylate-terminated hydrophilic branched macromonomer; Step S3: Modify "sodium maleate (4.00 mol, equivalent to 536 g)" in Step S3 of Example 1 to "sodium maleate (4.50 mol, equivalent to 603 g)"; The phrase “the hydrophilic branched macromonomer prepared in step S2 (0.80 mol based on the double bonds contained, equivalent to 440 g)” is revised to “the hydrophilic branched macromonomer prepared in step S2 (0.76 mol based on the double bonds, equivalent to 418 g)”. The phrase "the hydrophobic macromonomer prepared in step S1 (0.24 mol based on the double bonds, equivalent to 336 g)" was modified to "the hydrophobic macromonomer prepared in step S1 (0.26 mol based on the double bonds, equivalent to 390 g)". The remaining raw materials and steps were the same as in step S3 of Example 1, and a polycarboxylate superplasticizer, denoted as PCE-5, was obtained. The structural formula of the water-reducing agent produced is as follows: degree of polymerization n is 2; degree of polymerization m is 3; degree of polymerization a, b, and c are 9, 5, and 14 respectively; R is -(CH2)5-.

[0082] Example 6 This embodiment provides a method for preparing a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete, the steps of which are as follows: S1. Modify “1,3-propanediol (2.00 mol)” in step S1 of Example 1 to “a mixed diol of 1,3-propanediol and 1,4-butanediol (total moles 2.2 mol, molar ratio 1:1)”. The remaining raw materials and steps are the same as in step S1 of Example 1 to obtain a dimer acid-propylene-butane mixed diol-acrylate end-capped hydrophobic macromonomer. In the structural formula of the hydrophobic macromonomer it generates: the degree of polymerization n is 2; R is a combination of -CH2CH2CH2- and -CH2CH2CH2CH2-; S2. Modify “monomethoxy polyethylene glycol mPEG-600 (1.00 mol, Mw=600 g / mol)” in step S2 of Example 1 to “mPEG-800 (1.00 mol, Mw=800 g / mol)”. The remaining raw materials and steps are the same as in step S2 of Example 1 to obtain citric acid-glycerol-mPEG800-acrylate-terminated hydrophilic branched macromonomer with a degree of polymerization m of 4. S3. Modify “the hydrophilic branched macromonomer prepared in step S2 (0.80 mol based on the double bonds contained, equivalent to 440 g)” in step S3 of Example 1 to “the hydrophilic branched macromonomer prepared in step S2 (0.75 mol based on the double bonds, equivalent to 495 g)”. The phrase "the hydrophobic macromonomer prepared in step S1 (0.24 mol based on the double bonds, equivalent to 336 g)" was modified to "the hydrophobic macromonomer prepared in step S1 (0.25 mol based on the double bonds, equivalent to 363 g)". The remaining raw materials and steps were the same as in step S3 of Example 1, and a polycarboxylate superplasticizer, denoted as PCE-6, was obtained. The structural formula of the water-reducing agent produced has the following characteristics: degree of polymerization n is 2; degree of polymerization m is 4; average values ​​of degree of polymerization a, b, and c are 8, 5, and 13, respectively; and R is a combination of -CH2CH2CH2- and -CH2CH2CH2CH2-.

[0083] Comparative Example Comparative Example 1 This comparative example uses conventional linear monomers for copolymerization to provide structural comparison. The specific steps are as follows: Deionized water (1400g), sodium maleate (4.00mol, equivalent to 536g), and methoxy polyethylene glycol methacrylate (MPEG-1000MA, Mw=1000g / mol, 1.00mol) were added to the reactor. The temperature was raised to 65℃, and under nitrogen protection, ammonium persulfate (0.08mol), vitamin C (0.04mol), and an aqueous solution of mercaptopropionic acid (0.15mol) were added dropwise over 3 hours. After post-treatment, a linear polycarboxylate superplasticizer was obtained, denoted as CPCE-1.

[0084] Comparative Example 2 The only difference between this comparative example and Example 1 is that the hydrophobic macromonomer is omitted. The specific steps are as follows: Step S1: Following Step S2 of Example 1, a citric acid-glycerol-mPEG600-acrylate-terminated hydrophilic branched macromonomer was prepared. Step S2: Add deionized water (1200g), sodium maleate (4.00mol, equivalent to 536g), and the hydrophilic branched macromonomer prepared in step S1 (1.00mol, equivalent to 550g, based on double bonds) to the reactor. Perform a copolymerization reaction, with the remaining raw materials and steps the same as in step S3 of Example 1, to obtain the water-reducing agent CPCE-2.

[0085] Comparative Example 3 The only difference between this comparative example and Example 1 is that the hydrophilic branched macromonomer is omitted. The specific steps are as follows: Step S1: Prepare a dimer acid-propylene glycol-GMA-terminated hydrophobic macromonomer according to Step S1 of Example 1; Step S2: Add deionized water (1200g) and sodium maleate (4.00mol, equivalent to 536g) to the reactor and mix to obtain solution A; premix the dimer acid-propylene glycol-GMA end-capped hydrophobic macromonomer (1.00mol, equivalent to 1400g as double bond) obtained in step S1 with the cosolvent isopropanol (15% of the total mass of the feed in step S2) and the oxidant ammonium persulfate (1.2% of the total mass of the feed in step S2) to obtain solution B. Heat to 65℃ and under nitrogen protection, simultaneously add solution B with the reducing agent vitamin C (0.04mol) and the chain transfer agent 3-mercaptopropionic acid aqueous solution (0.15mol) to solution A. After 3 hours of addition, the water-reducing agent is obtained after post-treatment and is designated CPCE-3.

[0086] Comparative Example 4 This comparative example uses ARIT-416 (50% solids content) as the water-reducing agent, denoted as CPCE-4.

[0087] Test case Test Example 1 To verify the basic performance of the water-reducing agent of this invention in conventional concrete, concrete performance tests were conducted on the samples obtained in Examples 1-6 and Comparative Examples 1-4, referring to GB / T50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". The tests used a fixed mix proportion (C40 concrete, Conch P·O42.5 cement 420 kg / m³). 3 Sand ratio 40%, water-cement ratio 0.38, bulk density 2380 kg / m³ 3 The dosage of each water-reducing agent was controlled at 0.12% (based on the weight of cement after bending) to compare the effects of water-reducing agents with different molecular structures on the workability, viscosity and strength of concrete under the same dosage. The test results are shown in Table 1.

[0088] Table 1 Comparison of water-reducing agent performance data under benchmark concrete mix proportions

[0089] Test results show that the initial slump of the PCE series water-reducing agents is mostly 220mm, with a minimum of 215mm. The slump remains relatively stable with no significant loss after 1 hour, and the pull-out time is between 7.53 and 8.55 seconds. The overall viscosity is relatively low, and the 7-day compressive strength is 42.5 to 43.5 MPa, while the 28-day compressive strength is 51.5 to 53.2 MPa. In contrast, the initial slump of the CPCE series is the highest at 220mm and the lowest at 205mm. The slump loss after 1 hour is significant (with a maximum decrease of 50mm), and the pull-out time is 12.51 to 15.84 seconds. The viscosity is much higher than that of the PCE series, and the 28-day compressive strength is the highest at 51.5 MPa and the lowest at 50.0 MPa. Overall, the CPCE series performs worse than the PCE series.

[0090] Test Example 2 To verify the core value of the water-reducing agent of this invention in supporting the reduction of cementitious materials in concrete, the cement content was further reduced from 420 kg / m³. 3 Gradient reduced to 400, 380 kg / m 3 The experiment maintained a constant concrete density (2380 kg / m³) by adjusting the aggregate dosage. 3 The water-cement ratio remained at 0.38. To fairly evaluate the performance differences of different water-reducing agents under the harsh condition of reduced paste volume, the dosage of water-reducing agents was adjusted to ensure that the initial slump of all concrete mixes reached the same target of 210±10mm. Under this premise, the concrete lift-off time, workability retention, and compressive strength corresponding to each water-reducing agent were compared systematically. The test results are shown in Table 2.

[0091] Table 2 Comparison of water-reducing agent performance under low adhesive material conditions

[0092] Data shows that PCE-1 increases with cement usage from 420 kg / m³. 3 Reduced to 380kg / m 3 With the dosage increased to 0.14%, the initial slump stabilized at 215-220 mm, with only slight loss of slump after 1 hour. The pull-out time was 8.22-9.65 s, the viscosity was low, the 7-day compressive strength was 41.8-43.5 MPa, the 28-day compressive strength was 51.0-52.8 MPa, and the workability remained good. At the same dosage, CPCE-4 showed more significant slump loss, and the pull-out time (15.81-18.77 s) was much longer than that of PCE-1. The 7-day and 28-day compressive strengths were lower than those of PCE-1. Moreover, as the cement dosage decreased, the workability deteriorated from slight bleeding to severe bleeding and segregation, resulting in poor overall performance.

[0093] In summary, this invention successfully prepared a polycarboxylate superplasticizer with a star-shaped multi-arm hyperbranched topology through innovative molecular design. This unique structure forms a thick, dense, and stable three-dimensional adsorption layer on the surface of cement particles: its high-density carboxyl groups ensure rapid and efficient adsorption; the three-dimensionally extended multi-arm structure provides strong and lasting steric hindrance, ensuring excellent workability; and the specially introduced hydrophobic segments play a crucial role in micro-lubrication, synergistically releasing free water and reducing interparticle friction with the three-dimensional structure. This multi-mechanism synergistic effect is the fundamental reason for the leap in slurry improvement and viscosity reduction performance at the molecular level. The process route of this invention is clear and the conditions are mild, and the core raw materials are partially derived from biomass, which aligns with the development direction of green chemistry and has good application prospects.

[0094] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A polycarboxylate superplasticizer for improving slurry quality and reducing viscosity, suitable for low-cement-content concrete, characterized in that, It has a structure as shown in equation (Ⅰ): Equation (I) Wherein, the degree of polymerization m and n are each independently 1 to 50; The degrees of polymerization, a, b, and c, are each independently between 1 and 30; R is one or a combination of two or more of -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2- or -(CH2)5-.

2. A method for preparing a slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer suitable for low-cement-content concrete, used to prepare the slurry-enhancing and viscosity-reducing polycarboxylate superplasticizer as described in claim 1, characterized in that, Includes the following steps: S1. Under a nitrogen atmosphere, dimer fatty acids, bio-based diols and catalysts are mixed and heated to obtain hydroxyl-terminated polyester prepolymers; the mixture is cooled, glycidyl methacrylate and polymerization inhibitors are added, and the mixture is kept at a constant temperature under nitrogen protection and then cooled to obtain hydrophobic macromonomers. S2. Under a nitrogen atmosphere, citric acid, glycerol, monomethoxy polyethylene glycol and catalyst are mixed and heated to react. When the acid value drops to below 15 mg KOH / g, the system is cooled, glycidyl methacrylate and polymerization inhibitor are added, and the reaction continues until the epoxy groups are completely consumed. After cooling, hydrophilic branched macromonomer is obtained. S3. Add deionized water to the reaction vessel, then add sodium maleate and the hydrophilic branched macromonomer prepared in step S2 in sequence and stir to dissolve to obtain solution A; premix the hydrophobic macromonomer prepared in step S1 with a cosolvent and an oxidant to obtain solution B; heat the reaction system under nitrogen protection, and add the above solution B, reducing agent, and chain transfer agent dropwise to solution A; after the dropwise addition is completed, keep it at the temperature for aging, cool it to room temperature, and adjust the pH value of the system with alkali solution to obtain polycarboxylate superplasticizer.

3. The preparation method of the polycarboxylate superplasticizer for improving slurry quality and reducing viscosity suitable for low-cement-content concrete as described in claim 2, characterized in that, In step S1, the hydrophobic macromonomer has a structure as shown in formula (II): Formula (II) Wherein, the degree of polymerization n is 1 to 50; R is one or a combination of two or more of -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2- or -(CH2)5-.

4. The preparation method of the polycarboxylate superplasticizer for improving slurry quality and reducing viscosity suitable for low-cement-content concrete as described in claim 2, characterized in that, In step S1, the molar ratio of the dimer fatty acid, bio-based diol, and glycidyl methacrylate is 1:(2-3):(2-3). The amount of catalyst used is 0.1% to 0.5% of the total mass of the feed in step S1; The amount of the polymerization inhibitor is 0.01 to 0.05% of the total mass of the feed in step S1.

5. The preparation method of the polycarboxylate superplasticizer for improving slurry quality and reducing viscosity suitable for low-cement-content concrete as described in claim 2, characterized in that, In step S1, the temperature of the heating reaction is 180-200°C, and the time is 4-6 hours. The cooling temperature is 90–110°C; The heat preservation reaction time is 3-5 hours; The dimer fatty acid has the molecular formula C. 36 H 68 O4, whose iodine value ranges from 80 to 120g I2 / 100g; The bio-based diol is one or a combination of two or more of 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol. The catalyst is tetraisopropyl titanate, and the polymerization inhibitor is hydroquinone.

6. The preparation method of the polycarboxylate superplasticizer for improving slurry quality and reducing viscosity suitable for low-cement-content concrete as described in claim 2, characterized in that, In step S2, the hydrophilic branched macromonomer has a structure as shown in formula (Ⅲ): Formula (III) The degree of polymerization m ranges from 1 to 50.

7. The preparation method of the polycarboxylate superplasticizer for improving slurry quality and reducing viscosity suitable for low-cement-content concrete as described in claim 2, characterized in that, In step S2, the molar ratio of citric acid, glycerol, monomethoxy polyethylene glycol and glycidyl methacrylate is 1:(1-3):(1-3):(4-5). The amount of catalyst used is 0.1% to 0.5% of the total mass of the feed in step S2; The amount of the polymerization inhibitor is 0.01 to 0.05% of the total mass of the feed in step S2.

8. The preparation method of the polycarboxylate superplasticizer for improving slurry quality and reducing viscosity suitable for low-cement-content concrete as described in claim 2, characterized in that, In step S2, the temperature of the heating reaction is 120-140°C, and the time is 5-7 hours. The cooling temperature is 90–110°C; The weight-average molecular weight of the monomethoxy polyethylene glycol is 400–1200 g / mol; The catalyst is one or a combination of two or more of p-toluenesulfonic acid, concentrated sulfuric acid, or tetraisopropyl titanate. The polymerization inhibitor is one or a combination of two or more of hydroquinone, phenothiazine, or 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy radical.

9. The preparation method of the polycarboxylate superplasticizer for improving slurry quality and reducing viscosity suitable for low-cement-content concrete as described in claim 2, characterized in that, In step S3, the molar ratio of sodium maleate, the hydrophobic macromonomer prepared in step S1, and the hydrophilic branched macromonomer prepared in step S2, based on the number of moles of double bonds contained in each, is (3.0~5.0):(0.2~0.4):(0.6~0.8). The amount of the co-solvent used is 10% to 30% of the total mass of the materials fed in step S3; The amount of oxidant used is 0.5% to 2% of the total mass of the feed in step S3; The amount of reducing agent used is 0.1% to 2% of the total mass of the materials fed in step S3; The amount of chain transfer agent used is 0.5% to 2% of the total mass of the feed in step S3.

10. The preparation method of the polycarboxylate superplasticizer for improving slurry quality and reducing viscosity suitable for low-cement-content concrete as described in claim 2, characterized in that, In step S3, the temperature for heating is 60–75°C; The dripping time is 2–4 hours; The time for heat preservation and maturation after the dripping is completed is 1 to 2 hours; The co-solvent is one or a combination of two or more of isopropanol, ethanol, acetone or N,N-dimethylformamide; The oxidant is one or a combination of two or more of the following: ammonium persulfate, potassium persulfate, hydrogen peroxide, or tert-butyl hydrogen peroxide. The reducing agent is one or a combination of two or more of vitamin C, sodium bisulfite, sodium metabisulfite, and ferrous sulfate. The chain transfer agent is one or a combination of two or more of the following: mercaptoacetic acid, 3-mercaptopropionic acid, 2-mercaptoethanol, dodecyl mercaptan, or isopropanol. The alkaline solution is one or a combination of two or more of sodium hydroxide solution, potassium hydroxide solution, or monoethanolamine, used to neutralize the system to pH 6.5–7.0.

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