Early-strength functional monomer and early-strength polycarboxylate superplasticizer as well as preparation method and application of early-strength functional monomer and early-strength polycarboxylate superplasticizer

Abstract

The invention belongs to the technical field of building materials, and provides an early-strength functional monomer, an early-strength polycarboxylic acid water reducing agent and application of the early-strength functional monomer and the early-strength polycarboxylic acid water reducing agent. The chemical structural formula of the early strength functional monomer is as shown in formula (I). The preparation method of the early-strength polycarboxylate superplasticizer comprises the step of carrying out free radical polymerization reaction on an unsaturated polyether macromonomer, an early-strength functional monomer as shown in the formula (I), unsaturated carboxylic acid and a polysaccharide-based graft copolymer to obtain the early-strength polycarboxylate superplasticizer. The early strength functional monomer provided by the invention is obtained by reacting N-(beta-aminoethyl)-alpha-aminopropyltrimethoxysilane and an acrylic monomer, the raw materials are easy to obtain, the cost is low, the early strength functional monomer can be prepared only by one-step reaction, the synthesis process is simple, the post-treatment is convenient, the reaction condition is mild, and the early strength functional monomer can be applied to the polycarboxylate superplasticizer, so that the early strength functional monomer has a good application prospect. The polycarboxylate superplasticizer can generate a synergistic effect with the unsaturated polyether macromonomer, unsaturated carboxylic acid and the polysaccharide-based graft copolymer, so that the polycarboxylate superplasticizer has excellent early strength effect and binding material environmental adaptability. Formula (I).

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, and relates to an early-strength functional monomer and an early-strength polycarboxylate superplasticizer, as well as their preparation methods and applications. Background Technology

[0002] Modern concrete technology, in order to balance cost and performance, generally adopts a design approach that incorporates large amounts of mineral admixtures (such as fly ash and slag powder). This mix design not only reduces heat of hydration, improves crack resistance and long-term durability, but also offers significant environmental benefits. However, this technological approach also brings significant challenges: the relatively reduced cement content in the cementitious system leads to a slow early hydration rate and insufficient early strength development in the concrete, severely impacting construction progress and formwork turnover efficiency. This problem is particularly pronounced under low-temperature or winter construction conditions, not only prolonging setting time but also increasing energy costs.

[0003] Polycarboxylate superplasticizers have advantages such as high water reduction rate, low slump loss, strong molecular structure designability, and environmental friendliness, and are currently widely used in concrete materials. However, traditional polycarboxylate superplasticizers have slow early strength development, especially under low temperature or winter construction conditions. Therefore, to improve the early performance of concrete, the common practice is to compound early-strength components into polycarboxylate superplasticizers. For example, CN103304181A discloses the compounding of calcium chloride, sodium nitrite, and triethanolamine with polycarboxylate superplasticizers to form an early-strength high-performance polycarboxylate superplasticizer. CN109665737A discloses the formation of a nano-cement stone early-strength superplasticizer for sulfoaluminate cement by combining silicate cement, polycarboxylate superplasticizer, calcium formate, aluminum nitrate, and triethanolamine. Adding the prepared nano-cement stone early-strength superplasticizer to sulfoaluminate cement at a dosage of 2-4% can increase the early strength of sulfoaluminate cement and shorten the hardening time, without affecting the later strength. However, the aforementioned patents do not fundamentally design or improve the molecular structure of polycarboxylate superplasticizers, relying solely on physical mixing. This results in generally poor adaptability of the products to different cements and admixtures, and very limited room for performance adjustment and improvement. Therefore, developing an early-strength polycarboxylate superplasticizer that can simultaneously improve early-strength performance and environmental adaptability of cementitious materials from the molecular level has become a major research direction in this field.

[0004] Currently, early-strength polycarboxylate superplasticizers are typically obtained by reacting polyether macromonomers, unsaturated carboxylic acids, and early-strength functional monomers. Among these, the early-strength functional monomers have a significant impact on the early-strength performance of the polycarboxylate superplasticizers. CN113248663A discloses an early-strength functional monomer, an early-strength polycarboxylate superplasticizer, and a method for preparing the same. The early-strength functional monomer is obtained by reacting an amino azo compound and an unsaturated alcohol under the action of a polymerization inhibitor and a catalyst. The early-strength polycarboxylate superplasticizer containing the above-mentioned early-strength functional monomer can significantly improve the early strength of concrete without affecting its later strength under normal conditions, and can also reduce the viscosity of concrete and improve its water retention. However, the synthesis steps of this early-strength functional monomer are cumbersome, involving complex post-processing such as reflux reaction (100℃), multiple extractions, drying, and distillation, resulting in high energy consumption. Furthermore, the aromatic azo compound used as a raw material is a special chemical with unstable supply, making it unsuitable for industrial applications. CN114316163A discloses an anti-mud early strength functional monomer, an anti-mud early strength polycarboxylate superplasticizer, and their preparation method. The anti-mud early strength functional monomer is prepared by non-covalent modification of graphene oxide with quaternary ammonium salt and grafting silane coupling agent. The anti-mud early strength polycarboxylate superplasticizer containing this anti-mud early strength functional monomer ensures excellent water reduction performance while enabling concrete to simultaneously possess excellent anti-mud performance and early strength performance. However, the synthesis process of this early strength functional monomer is complex, requiring multiple steps such as ultrasonic dispersion, pH adjustment, pre-hydrolysis, high-temperature reaction, washing and drying. Furthermore, the raw material graphene oxide used is expensive, resulting in high cost and making it unsuitable for industrial applications. CN114478962A discloses a slump-retaining and early-strength functional monomer, a slump-retaining and early-strength polycarboxylate superplasticizer, and their preparation method. The slump-retaining and early-strength functional monomer is prepared by esterification modification of graphene oxide and hydroxycarboxylic acid, followed by grafting of a silane coupling agent. The slump-retaining and early-strength polycarboxylate superplasticizer containing this slump-retaining and early-strength functional monomer ensures excellent water-reducing performance while enabling concrete to simultaneously possess excellent slump-retaining and early-strength performance. However, the synthesis route of this early-strength functional monomer is long, with many side reactions, involving steps such as reflux, vacuum distillation, pH adjustment, pre-hydrolysis, and multiple washing. Furthermore, the raw material graphene oxide used is expensive, resulting in high costs, and therefore it is not suitable for industrial applications.

[0005] In summary, the currently available early-strength functional monomers still have drawbacks such as expensive raw materials, complex processes, and harsh reaction conditions, making them unsuitable for industrial applications. Therefore, it is necessary to develop a novel early-strength functional monomer that has a simple synthesis process, mild conditions, and controllable cost, and can be used to prepare early-strength polycarboxylate superplasticizers. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, the purpose of this invention is to provide an early-strength functional monomer and an early-strength polycarboxylate superplasticizer based on the early-strength functional monomer, as well as their preparation method and application.

[0007] The chemical structural formula of the early-strength functional monomer provided by this invention is shown in formula (Ⅰ): Equation (Ⅰ), R is H or a C1-C5 alkyl group.

[0008] The method for preparing the early-strength functional monomer provided by the present invention includes a dehydration condensation reaction of N-(β-aminoethyl)-α-aminopropyltrimethoxysilane and an acrylic monomer with the chemical structure shown in formula (II) to obtain: Formula (II).

[0009] The method for preparing the early-strength polycarboxylate superplasticizer provided by the present invention includes a free radical polymerization reaction of an unsaturated polyether macromonomer, the above-mentioned early-strength functional monomer, an unsaturated carboxylic acid, and a polysaccharide-based graft copolymer.

[0010] Compared with the prior art, the present invention has the following significant advantages: 1. The early-strength functional monomer provided by this invention is obtained by reacting N-(β-aminoethyl)-α-aminopropyltrimethoxysilane and acrylic monomers. The raw materials are readily available and the cost is low. It can be prepared in only one step. The synthesis process is simple, the post-processing is convenient, and the reaction conditions are mild. It is suitable for industrial applications. When applied to polycarboxylate superplasticizers, it can have a synergistic effect with the unsaturated polyether macromonomers, unsaturated carboxylic acids, and polysaccharide graft copolymers in polycarboxylate superplasticizers, thereby giving the polycarboxylate superplasticizers excellent early-strength effect and environmental adaptability of cementitious materials. 2. The polycarboxylate superplasticizer provided by this invention is obtained by polymerization reaction of unsaturated polyether macromonomer, early strength functional monomer, unsaturated carboxylic acid, polysaccharide graft copolymer and other components. The early strength functional monomer used is obtained by reaction of N-(β-aminoethyl)-α-aminopropyltrimethoxysilane and acrylic acid monomer. It is an unsaturated amide silane functional monomer. The unsaturated amide group in the early strength functional monomer can accelerate the dissolution of tricalcium silicate and the crystal precipitation of hydration products, thereby improving the early strength of concrete. The silane can improve the pore structure of concrete, reduce the penetration and erosion of harmful substances, and improve the durability of concrete. At the same time, combined with the synergistic effect of polyether segments, through its good steric hindrance effect, it can ensure that the superplasticizer can continue to exert its early strength effect under complex working conditions. 3. In the polycarboxylate superplasticizer of the present invention, the alkoxy groups of the early-strength functional monomers generate silanol groups through hydrolysis, which are chemically adsorbed on the surface of cement particles to form a stable film, reducing the interaction forces between cement particles and further preventing the aggregation and sedimentation of cement particles; in addition, the rigid main chain structure of the polysaccharide graft copolymer in the polycarboxylate superplasticizer can act as a steric barrier in a strong ionic environment, effectively regulating the aggregation behavior of superplasticizer molecules, preventing them from undergoing ineffective aggregation and phase separation, thereby maintaining molecular stability and dispersion efficiency in complex cementitious material systems and improving the adaptability of the superplasticizer to the application environment; 4. The early-strength polycarboxylate superplasticizer provided by this invention has good compatibility with mainstream polycarboxylate products. It can be used directly as a single component or compounded with other types of superplasticizers. It has flexible application methods and good industrialization prospects. 5. The present invention can prepare early-strength polycarboxylate superplasticizer by using a room temperature free radical solution copolymerization process. The entire preparation process has mild reaction conditions, does not require precise temperature control or external heating, has a simple process flow, and is easy to implement on a large scale, with outstanding economic and practical advantages. Detailed Implementation

[0011] The chemical structural formula of the early-strength functional monomer provided by this invention is shown in formula (Ⅰ): Equation (Ⅰ), R is H or a C1-C5 alkyl group. Specific examples of the C1-C5 alkyl group include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, or neopentyl.

[0012] The method for preparing the early-strength functional monomer provided by the present invention includes a dehydration condensation reaction of N-(β-aminoethyl)-α-aminopropyltrimethoxysilane and an acrylic monomer.

[0013] In the preparation process of the above-mentioned early-strength functional monomer, the molar ratio of N-(β-aminoethyl)-α-aminopropyltrimethoxysilane to acrylic monomer is preferably (1.2-1.3):1, such as 1.2:1, 1.22:1, 1.24:1, 1.26:1, 1.28:1, 1.3:1, etc.

[0014] In the preparation of the above-mentioned early-strength functional monomers, there is no particular limitation on the type of acrylic monomers, as long as they have the structure shown in formula (II), and acrylic acid and / or methacrylic acid are particularly preferred.

[0015] Formula (II) In the preparation of the aforementioned early-strength functional monomers, the dehydration condensation reaction generally needs to be carried out in the presence of a catalyst. The catalyst is preferably at least one selected from triethylamine, 4-dimethylaminopyridine (DMAP), dicyclohexylcarbodiimide (DCC), pyridine, and imidazole.

[0016] In the preparation of the above-mentioned early-strength functional monomer, the conditions of the dehydration condensation reaction preferably include a temperature of 45℃-70℃, such as 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, etc.; and a time of 2h-5h, such as 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc.

[0017] In one specific embodiment, the preparation method of the early-strength functional monomer includes the following steps: N-(β-aminoethyl)-α-aminopropyltrimethoxysilane, acrylic acid monomer, catalyst and organic solvent are added to a reactor and stirred at 45-70°C for 2-5 hours under nitrogen protection. After the reaction is completed, the mixture is filtered and the organic solvent is removed by vacuum distillation of the filtrate to obtain the early-strength functional monomer.

[0018] In one specific embodiment, the organic solvent is at least one of dichloromethane, trichloromethane, dimethyl carbonate, methyl acetate, tetrahydrofuran, and 2-methyltetrahydrofuran.

[0019] The method for preparing the early-strength polycarboxylate superplasticizer provided by the present invention includes a free radical polymerization reaction of an unsaturated polyether macromonomer, the above-mentioned early-strength functional monomer, an unsaturated carboxylic acid, and a polysaccharide-based graft copolymer.

[0020] In the preparation process of the above-mentioned early-strength polycarboxylate superplasticizer, the amount of the unsaturated polyether macromonomer is preferably 200-208 parts by mass, such as 200, 201, 202, 203, 204, 205, 206, 207, 208 parts by mass, etc.; the amount of the early-strength functional monomer is preferably 6-12 parts by mass, such as 6, 7, 8, 9, 10, 11, 12 parts by mass, etc.; the amount of the unsaturated carboxylic acid is preferably 8-16 parts by mass, such as 8, 9, 10, 11, 12, 13, 14, 15, 16 parts by mass, etc.; and the amount of the polysaccharide-based graft copolymer is preferably 4-12 parts by mass, such as 4, 5, 6, 7, 8, 9, 10, 11, 12 parts by mass, etc.

[0021] In the preparation process of the aforementioned early-strength polycarboxylate superplasticizer, the free radical initiator used in the free radical polymerization reaction can be selected from at least one of peroxide initiators, azo initiators, and redox initiators, preferably a redox initiator. The redox initiator consists of an oxidant and a reducing agent. Examples of oxidants include at least one of hydrogen peroxide solution, ammonium persulfate, sodium persulfate, and potassium persulfate. Examples of reducing agents include at least one of ascorbic acid, sodium formaldehyde sulfoxylate, sodium bisulfite, Bruggolite FF6, and Bruggolite E01. The amount of the oxidant is preferably 0.5-2.5 parts by mass relative to 200-208 parts of unsaturated polyether macromonomer, such as 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5 parts by mass, etc.; the amount of the reducing agent is preferably 0.1-0.5 parts by mass, such as 0.1, 0.2, 0.3, 0.4, 0.5 parts by mass, etc.

[0022] In the preparation process of the aforementioned early-strength polycarboxylate superplasticizer, the free radical polymerization reaction generally requires the addition of a chain transfer agent. Examples of such chain transfer agents include at least one selected from sodium hypophosphite, mercaptoacetic acid, mercaptopropionic acid, 3-mercaptopropionic acid, and isooctyl 3-mercaptopropionic acid. The preferred amount of the chain transfer agent is 0.6-1.6 parts by weight relative to 200-208 parts of the unsaturated polyether macromonomer, such as 0.6, 0.8, 1, 1.2, 1.4, or 1.6 parts by weight.

[0023] In a preferred embodiment, the free radical polymerization reaction includes uniformly mixing unsaturated polyether macromonomers, chain transfer agents, initiators, and water; simultaneously adding solution A, formed by mixing early-strength functional monomers, unsaturated carboxylic acids, polysaccharide graft copolymers, and water, and solution B, formed by mixing a reducing agent and water, to the resulting mixed solution; continuing the polymerization reaction after the addition is complete; and adding a neutralizing agent to adjust the pH of the solution to 5.5-7.0 after the reaction is complete, thereby obtaining the early-strength polycarboxylic acid superplasticizer.

[0024] In a preferred embodiment, the free radical polymerization reaction includes the following steps: 1) Add unsaturated polyether macromonomer, chain transfer agent, initiator and water to the reactor, and stir and mix evenly at 15-45℃ to form a mixed solution; 2) Mix the early-strength functional monomer, unsaturated carboxylic acid, polysaccharide-based graft copolymer with water to form solution A; 3) Mix the reducing agent with water until homogeneous to form solution B; 4) Add solution A and solution B dropwise to the mixed solution in step 1) over a period of 60-180 minutes, maintaining the temperature of the reaction system at 15-45℃ during the dropwise addition process; 5) After the addition is complete, keep the reaction at a constant temperature for 60-120 minutes. After the reaction is complete, add a neutralizing agent and adjust the pH of the solution to 5.5-7.0 to obtain the early-strength polycarboxylate superplasticizer.

[0025] In a preferred embodiment, in step 1), the mass ratio of unsaturated polyether macromonomer: chain transfer agent: initiator: water in the mixed solution is (200-208):(0.6-1.6):(0.5-2.5):(166-184); in step 2), the mass ratio of early-strength functional monomer: unsaturated carboxylic acid: polysaccharide graft copolymer: water in solution A is (6-12):(8-16):(4-12):(20-40); in step 3), the mass ratio of reducing agent: water in solution B is (0.1-0.5):(20-30).

[0026] In the preparation process of the above-mentioned early-strength polycarboxylate superplasticizer, the unsaturated polyether macromonomer is preferably at least one of ethylene glycol monovinyl polyethylene glycol ether, 4-hydroxybutylvinyl polyoxyethylene ether, isopentenyl alcohol polyoxyethylene ether, and methyl allyl polyoxyethylene ether.

[0027] In a preferred embodiment, the molecular weight of the unsaturated polyether macromonomer is 1500-3500, such as 1500, 1800, 2000, 2200, 2500, 2800, 3000, 3200, 3500, etc.

[0028] In a preferred embodiment, the unsaturated carboxylic acid is at least one of acrylic acid, methacrylic acid, and maleic anhydride.

[0029] In a preferred embodiment, the polysaccharide-based graft copolymer is a polysaccharide-based polyacrylamide, which is composed of a polysaccharide backbone and polyacrylamide side chains.

[0030] In a preferred embodiment, the polysaccharide-based polyacrylamide has a number-average degree of polymerization of 20 to 100, such as 20, 40, 60, 80, 100, etc.

[0031] In a preferred embodiment, the polysaccharide-based polyacrylamide is at least one of starch-grafted polyacrylamide, cellulose-grafted polyacrylamide, and dextran-grafted polyacrylamide.

[0032] In a preferred embodiment, the neutralizing agent is at least one of sodium hydroxide and potassium hydroxide.

[0033] The technical solution of the present invention will be further described in detail and completely below with reference to the embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer.

[0034] In the following examples and comparative examples, the amounts of each component refer to parts by weight.

[0035] Example 1 1) Preparation of early-strength functional monomers 268 parts of N-(β-aminoethyl)-α-aminopropyltrimethoxysilane, 79 parts of acrylic acid, 5 parts of catalyst (4-dimethylaminopyridine, DMAP) and 300 parts of organic solvent (dichloromethane) were added to a reactor. Under nitrogen protection, the mixture was stirred at 50°C for 3 hours. After the reaction was completed, the reaction mixture was filtered, and the filtrate was collected. The organic solvent was removed by vacuum distillation of the filtrate using a rotary evaporator to obtain the early-strength functional monomer.

[0036] (ii) Preparation of early-strength polycarboxylate superplasticizer 1) Add 204 parts of unsaturated polyether macromonomer (ethylene glycol monovinyl polyethylene glycol ether, Mn=3000, purchased from Liaoning Aoke Chemical Co., Ltd., brand name OXAC-609), 1.0 parts of chain transfer agent (mercaptopropionic acid), 1.2 parts of initiator (ammonium persulfate) and 180 parts of water to the reactor, and stir and mix evenly at 20°C to form a mixed solution; 2) Mix 8 parts of the self-made early-strength functional monomer, 10 parts of unsaturated carboxylic acid (acrylic acid), 6 parts of polysaccharide-based graft copolymer (starch-grafted polyacrylamide, PAM branched polymerization degree of 50, purchased from Xi'an Ruixi Biotechnology Co., Ltd., number average molecular weight of 2100, molecular weight distribution of 2.0) with 30 parts of water to form solution A. 3) Mix 0.3 parts of reducing agent (ascorbic acid) with 20 parts of water until homogeneous to form solution B; 4) Add solution A and solution B dropwise to the mixed solution in step 1) at the same time. Solution A is added over 90 minutes and solution B is added over 110 minutes. During the dropwise addition, the temperature of the reaction system is maintained at 25-30℃. 5) After the addition is complete, keep the reaction at 30°C for 60 minutes. After the reaction is complete, add 4 parts of neutralizing agent (30wt% sodium hydroxide solution) and adjust the pH of the solution to 5.5 to obtain the early-strength polycarboxylate superplasticizer.

[0037] Example 2 1) Preparation of early-strength functional monomers 282 parts of N-(β-aminoethyl)-α-aminopropyltrimethoxysilane, 95 parts of methacrylic acid, 6 parts of catalyst (triethylamine), and 320 parts of organic solvent (2-methyltetrahydrofuran) were added to a reactor. Under nitrogen protection, the mixture was stirred at 55°C for 4 hours. After the reaction was completed, the reaction mixture was filtered, and the filtrate was collected. The organic solvent was removed by vacuum distillation of the filtrate using a rotary evaporator to obtain the early-strength functional monomer.

[0038] (ii) Preparation of early-strength polycarboxylate superplasticizer 1) Add 204 parts of unsaturated polyether macromonomer (4-hydroxybutylvinyl polyoxyethylene ether, Mn=3000, purchased from Liaoning Aoke Chemical Co., Ltd., brand name F-2088), 1.2 parts of chain transfer agent (sodium hypophosphite), 1.5 parts of initiator (potassium persulfate) and 175 parts of water to the reactor, stir and mix evenly at 25°C to form a mixed solution; 2) Mix 9 parts of the self-made early-strength functional monomer, 12 parts of unsaturated carboxylic acid (methacrylic acid), 8 parts of polysaccharide-based graft copolymer (cellulose grafted polyacrylamide, PAM branched polymerization degree of 80, purchased from Xi'an Ruixi Biotechnology Co., Ltd., number average molecular weight of 5700, molecular weight distribution of 2.3) with 35 parts of water to form solution A. 3) Mix 0.4 parts of reducing agent (ascorbic acid) with 25 parts of water until homogeneous to form solution B; 4) Add solution A and solution B dropwise to the mixed solution in step 1) at the same time. Solution A is added dropwise over 80 minutes and solution B is added dropwise over 100 minutes. During the dropwise addition, maintain the temperature of the reaction system at 25-30℃. 5) After the addition is complete, keep the reaction at 30°C for 75 minutes. After the reaction is complete, add 4 parts of neutralizing agent (30wt% sodium hydroxide solution) and adjust the pH of the solution to 7.0 to obtain the early-strength polycarboxylate superplasticizer.

[0039] Example 3 1) Preparation of early-strength functional monomers 288 parts of N-(β-aminoethyl)-α-aminopropyltrimethoxysilane, 80 parts of acrylic acid, 7 parts of catalyst (pyridine), and 350 parts of organic solvent (tetrahydrofuran) were added to a reactor. Under nitrogen protection, the mixture was stirred at 60°C for 3.5 hours. After the reaction was completed, the reaction mixture was filtered, and the filtrate was collected. The organic solvent was removed by vacuum distillation of the filtrate using a rotary evaporator to obtain the early-strength functional monomer.

[0040] (ii) Preparation of early-strength polycarboxylate superplasticizer 1) Add 204 parts of unsaturated polyether macromonomer (isoprenol polyoxyethylene ether, Mn=2400, purchased from Liaoning Aoke Chemical Co., Ltd., brand name OXAC-501), 0.8 parts of chain transfer agent (thioglycolic acid), 1.2 parts of initiator (ammonium persulfate) and 180 parts of water to the reactor, stir and mix evenly at 35°C to form a mixed solution; 2) Mix 10 parts of the self-made early-strength functional monomer, 14 parts of unsaturated carboxylic acid (acrylic acid), 10 parts of polysaccharide-based graft copolymer (dextran-grafted polyacrylamide, PAM branched polymerization degree of 30, purchased from Xi'an Ruixi Biotechnology Co., Ltd., number average molecular weight of 2100, molecular weight distribution of 2.0) with 40 parts of water to form solution A. 3) Mix 0.5 parts of reducing agent (sodium formaldehyde bisulfite) with 20 parts of water until homogeneous to form solution B; 4) Add solution A and solution B dropwise to the mixed solution in step 1) at the same time. Solution A is added over 120 minutes and solution B is added over 150 minutes. During the dropwise addition, maintain the temperature of the reaction system at 35-45℃. 5) After the addition is complete, keep the reaction at 35°C for 90 minutes. After the reaction is complete, add 4 parts of neutralizing agent (30wt% potassium hydroxide solution) and adjust the pH of the solution to 6 to obtain the early-strength polycarboxylate superplasticizer.

[0041] Example 4 1) Preparation of early-strength functional monomers 282 parts of N-(β-aminoethyl)-α-aminopropyltrimethoxysilane, 95 parts of methacrylic acid, 6 parts of catalyst (triethylamine), and 320 parts of organic solvent (2-methyltetrahydrofuran) were added to a reactor. Under nitrogen protection, the mixture was stirred at 55°C for 4 hours. After the reaction was completed, the reaction mixture was filtered, and the filtrate was collected. The organic solvent was removed by vacuum distillation of the filtrate using a rotary evaporator to obtain the early-strength functional monomer.

[0042] (ii) Preparation of early-strength polycarboxylate superplasticizer 1) Add 204 parts of unsaturated polyether macromonomer (methyl allyl polyoxyethylene ether, Mn=2400, purchased from Liaoning Aoke Chemical Co., Ltd., brand name OXAC-608), 1.0 parts of chain transfer agent (mercaptopropionic acid), 1.2 parts of initiator (ammonium persulfate) and 180 parts of water to the reactor, stir and mix evenly at 40°C to form a mixed solution; 2) Mix 9 parts of the self-made early-strength functional monomer, 9 parts of unsaturated carboxylic acid (maleic anhydride), 7 parts of polysaccharide-based graft copolymer (starch-grafted polyacrylamide, PAM branched polymerization degree of 50, purchased from Xi'an Ruixi Biotechnology Co., Ltd., number average molecular weight of 3550, molecular weight distribution of 2.1) with 30 parts of water to form solution A. 3) Mix 0.3 parts of reducing agent (ascorbic acid) with 20 parts of water until homogeneous to form solution B; 4) Add solution A and solution B dropwise to the mixed solution in step 1) at the same time. Solution A is added over 90 minutes and solution B is added over 110 minutes. During the dropwise addition, the temperature of the reaction system is maintained at 25-40℃. 5) After the addition is complete, keep the reaction at 30°C for 60 minutes. After the reaction is complete, add 4 parts of neutralizing agent (30wt% sodium hydroxide solution) and adjust the pH of the solution to 5.5 to obtain the early-strength polycarboxylate superplasticizer.

[0043] Comparative Example 1 Commercially available early-strength polycarboxylate superplasticizer RHEOPLUS® 411.

[0044] Comparative Example 2 The difference between this comparative example and Example 1 is that the early-strength functional monomer in Example 1 is replaced with the same mass of acrylamide, while the rest is the same as in Example 1.

[0045] Comparative Example 3 The difference between this comparative example and Example 1 is that the polysaccharide-based graft copolymer in Example 1 is replaced with the same amount of acrylic acid by mass, while the rest is the same as in Example 1.

[0046] Comparative Example 4 The difference between this comparative example and Example 1 is that the early-strength functional monomer in Example 1 is replaced with the same mass of vinyltrimethoxysilane, while the rest is the same as in Example 1.

[0047] Comparative Example 5 The difference between this comparative example and Example 1 is that the polysaccharide-based graft copolymer used is the same mass of starch-acrylic acid graft copolymer Water Lock A-100.

[0048] Test case According to GB 8076-2008 "Concrete Admixtures" standard, the above examples and comparative examples were tested for cement concrete workability. The water-reducing agent dosage was uniformly set at 0.2%. The concrete mix proportions are shown in Table 2, and the concrete performance test results are shown in Table 2.

[0049] Table 1 Concrete mix proportions (unit: kg / m³) 3 )

[0050] Table 2 Concrete Workability Test

[0051] As shown in Tables 1 and 2, under the same dosage, in complex cementitious material environments such as different cement, fly ash, and slag powder, the concrete using the water-reducing agent in the examples showed better initial (0h) slump (210-225mm) and spread (525-540mm) compared to the concrete using the water-reducing agent in the comparative example. This indicates that the water-reducing agent in the examples provides superior fresh concrete fluidity compared to the water-reducing agent in the comparative example, resulting in better initial workability and easier construction and pouring. The slump retention rate of the examples after 2h was approximately 93%, and the spread retention rate was approximately 85%, demonstrating that the water-reducing agent in the examples has superior slump retention capacity (slump retention), effectively overcoming the challenges of concrete... The problem of fluidity loss of soil during transportation and waiting; the early strength (1d, 3d) of the embodiment is significantly higher than that of the comparative example, indicating that the water-reducing agent of the embodiment can significantly promote the early hydration of cement and greatly improve the early strength of concrete compared with the water-reducing agent of the comparative example; the later strength (28d) of the embodiment is higher than that of the comparative example in all aspects, indicating that the water-reducing agent of the embodiment ensures the healthy and stable growth of the later strength of concrete while ensuring excellent early strength performance compared with the water-reducing agent of the comparative example; therefore, the water-reducing agent provided in the embodiments of the present invention has high slump retention, high early strength and excellent later strength compared with the water-reducing agent of the comparative example, and at the same time has better workability, improving the adaptability of early strength water-reducing agent in complex cementitious material environment.

[0052] Furthermore, as can be seen from Examples 1, 2, and 4, and Tables 1 and 2, the early-strength functional monomer (unsaturated amide-based silane functional monomer) provided by the present invention, compared with traditional functional monomers (acrylamide, vinyltrimethoxysilane), can synergistically interact with other components in the polycarboxylate superplasticizer when applied to it, thereby effectively improving the early-strength effect of the superplasticizer and the environmental adaptability of the cementitious material. As can be seen from Examples 1 and 3, and Tables 1 and 2, in the polycarboxylate superplasticizer provided by the present invention, the polysaccharide-based graft copolymer can synergistically interact with other components in the superplasticizer, thereby effectively improving the early-strength effect of the superplasticizer and the environmental adaptability of the cementitious material. As can be seen from Examples 1 and 5, and Tables 1 and 2, in the polycarboxylate superplasticizer provided by the present invention, the polysaccharide-based polyacrylamide-type polysaccharide-based graft copolymer has a better effect on improving the performance of the superplasticizer compared with other types of polysaccharide-based graft copolymers.

[0053] Finally, it should be noted that the above are only some preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention shall fall within the scope of protection of the present invention.

Claims

1. An early-strength functional monomer, characterized in that, The chemical structural formula of the early-strength functional monomer is shown in formula (Ⅰ): Equation (Ⅰ), R is H or a C1-C5 alkyl group.

2. The method for preparing the early-strength functional monomer according to claim 1, characterized in that: This method involves a dehydration condensation reaction of N-(β-aminoethyl)-α-aminopropyltrimethoxysilane and an acrylic monomer with the chemical structure shown in formula (II) to obtain: Formula (II).

3. The method for preparing the early-strength functional monomer according to claim 2, characterized in that, The molar ratio of N-(β-aminoethyl)-α-aminopropyltrimethoxysilane to acrylic monomer is (1.2-1.3):

1.

4. The method for preparing the early-strength functional monomer according to claim 2, characterized in that, The conditions for the dehydration condensation reaction include a temperature of 45℃-70℃ and a time of 2h-5h.

5. A method for preparing an early-strength polycarboxylate superplasticizer, characterized in that, The method comprises a free radical polymerization reaction of an unsaturated polyether macromonomer, an early-strength functional monomer, an unsaturated carboxylic acid, and a polysaccharide-based graft copolymer, wherein the early-strength functional monomer is the early-strength functional monomer as described in claim 1.

6. The preparation method of the early-strength polycarboxylate superplasticizer according to claim 5, characterized in that, The unsaturated polyether macromonomer is at least one of ethylene glycol monovinyl polyethylene glycol ether, 4-hydroxybutylvinyl polyoxyethylene ether, isopentenyl alcohol polyoxyethylene ether, and methyl allyl polyoxyethylene ether.

7. The preparation method of the early-strength polycarboxylate superplasticizer according to claim 5, characterized in that, The unsaturated carboxylic acid is at least one of acrylic acid, methacrylic acid, and maleic anhydride.

8. The preparation method of the early-strength polycarboxylate superplasticizer according to claim 5, characterized in that, The polysaccharide-based graft copolymer is a polysaccharide-based polyacrylamide; the polysaccharide-based polyacrylamide is at least one of starch-grafted polyacrylamide, cellulose-grafted polyacrylamide, and dextran-grafted polyacrylamide.

9. The preparation method of the early-strength polycarboxylate superplasticizer according to claim 5, characterized in that, The amount of the unsaturated polyether macromonomer is 200-208 parts by mass, the amount of the early-strength functional monomer is 6-12 parts by mass, the amount of the unsaturated carboxylic acid is 8-16 parts by mass, and the amount of the polysaccharide-based graft copolymer is 4-12 parts by mass.

10. The preparation method of the early-strength polycarboxylate superplasticizer according to claim 5, characterized in that, The free radical polymerization reaction includes mixing unsaturated polyether macromonomers, chain transfer agents, initiators, and water uniformly; simultaneously adding solution A, formed by mixing early-strength functional monomers, unsaturated carboxylic acids, polysaccharide graft copolymers, and water, and solution B, formed by mixing reducing agents and water, to the resulting mixed solution; continuing the polymerization reaction after the addition is complete; and adding a neutralizing agent after the reaction is complete to adjust the pH of the solution to 5.5-7.0, thereby obtaining the early-strength polycarboxylic acid superplasticizer.

11. An early-strength polycarboxylate superplasticizer prepared by the method according to any one of claims 5-10.

12. The application of the early-strength polycarboxylate superplasticizer according to claim 11 in the construction field.

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