Super-early-strength polycarboxylate superplasticizer as well as preparation method and application thereof

Abstract

The invention discloses a super-early-strength polycarboxylate superplasticizer as well as a preparation method and application thereof, and belongs to the technical field of admixtures for concrete. The preparation method of the water reducer comprises the following steps: dropwise adding a carboxylic acid monomer aqueous solution, an ammonium persulfate aqueous solution and a vitamin C aqueous solution into a methyl allyl polyoxyethylene ether aqueous solution to prepare a prepolymer; the preparation method comprises the following steps: carrying out graft modification on a phosphate monomer and acrylamide, adding a ternary compound of triethanolamine, calcium formate and sodium citrate and an organic silicon defoamer, and adjusting the solid content to obtain the super-early-strength polycarboxylate superplasticizer. A specific monomer combination and a composite modifier are adopted to adapt to a high-sulfur-resistance cement-ultra-high-performance concrete system, the problems that a traditional water reducing agent is poor in adaptability, insufficient in early strength and weak in erosion resistance are solved, synergistic improvement of water reduction, early strength and durability is achieved, the raw materials are environmentally friendly, the preparation process is mild, and the method is suitable for industrial production. And the method is suitable for low-temperature, high-sulfur saline-alkali and other harsh construction scenes.

Description

Technical Field

[0001] This invention relates to the field of admixtures for concrete, specifically to an ultra-early strength polycarboxylate superplasticizer, its preparation method, and its application. Background Technology

[0002] In many engineering construction scenarios, especially in areas with severe sulfate attack, the durability of concrete structures faces serious challenges. These areas have high concentrations of sulfate ions in the soil and groundwater, which easily leads to cracking and damage in concrete structures, significantly shortening the service life of projects. High-sulfur-resistant cement, due to its excellent resistance to sulfate attack, is often used in engineering construction in such harsh environments; while ultra-high performance concrete, with its ultra-high strength and superior durability, is widely used in key projects such as bridges and underground structures. Combining high-sulfur-resistant cement with ultra-high performance concrete has become an important option for improving the quality of projects in harsh environments. However, the combined system suffers from slow early strength development, which can significantly reduce formwork turnover efficiency, extend construction periods, and increase maintenance costs in scenarios such as precast component production and winter construction.

[0003] Polycarboxylate superplasticizers, as third-generation high-efficiency concrete admixtures, possess outstanding advantages such as high water reduction rate, strong cement adaptability, and environmental friendliness. Furthermore, their molecular structure is highly designable; different performance requirements can be achieved by adjusting functional groups and molecular configurations, making them an indispensable component of modern high-performance concrete. However, current research on polycarboxylate superplasticizers primarily targets ordinary silicate cement systems, with limited research on their compatibility with high-sulfur-resistant cements. The low tricalcium aluminate content in high-sulfur-resistant cements directly affects the adsorption efficiency of superplasticizers, making it difficult for existing superplasticizers to fully function in this system. Simultaneously, they cannot effectively address issues such as early hydration inhibition and sulfate attack sensitivity in ultra-high-performance concrete, exhibiting significant shortcomings such as limited early strength improvement and insufficient durability.

[0004] With the increasing demands for construction efficiency and long-term stability in engineering projects, the need for specialized water-reducing agents is becoming increasingly urgent. In scenarios requiring concrete to quickly reach its design strength, such as low-temperature winter environments or emergency road repairs, traditional water-reducing agents struggle to meet the requirements of both construction schedule and quality. Furthermore, in high-sulfur, saline-alkali environments, conventional water-reducing agents cannot simultaneously guarantee early strength development and long-term erosion resistance. Currently, the market lacks an ultra-early-strength polycarboxylate water-reducing agent specifically designed for the formulation of ultra-high-performance concrete using high-sulfur-resistant cement. Existing products fail to achieve a satisfactory balance between water reduction, early strength enhancement, and durability, thus failing to provide an efficient solution for engineering projects in harsh environments. Summary of the Invention

[0005] To address the problems mentioned in the background section, this invention provides an ultra-early strength polycarboxylate superplasticizer.

[0006] In a first aspect, the present invention provides a method for preparing an ultra-early strength polycarboxylate superplasticizer, comprising the following preparation steps:

[0007] Step S1: Add acrylic acid, fumaric acid, and 3-mercaptopropionic acid to deionized water and stir until homogeneous to obtain an aqueous solution of carboxylic acid monomers;

[0008] Step S2: Add methyl allyl polyoxyethylene ether to deionized water and stir until homogeneous to obtain an aqueous solution of methyl allyl polyoxyethylene ether. Simultaneously add aqueous solutions of carboxylic acid monomers, ammonium persulfate, and vitamin C to the aqueous solution of methyl allyl polyoxyethylene ether. After the addition is complete, heat and stir to obtain the prepolymer.

[0009] Step S3: After cooling the prepolymer, add phosphate ester monomer and acrylamide, stir evenly, add sodium hydroxide aqueous solution dropwise to adjust the pH, heat and stir to obtain the grafted modified prepolymer;

[0010] Step S4: Cool the grafted and modified prepolymer, add triethanolamine and calcium formate, stir and mix, add sodium citrate ternary compound, stir evenly, add organosilicon defoamer, continue stirring, add deionized water to adjust the solid content, filter, and obtain ultra-early strength polycarboxylate superplasticizer.

[0011] Furthermore, the raw materials in the ultra-early strength polycarboxylate superplasticizer, by weight, are as follows: 88.5-113.7 parts of carboxylic acid monomer aqueous solution, 11-21 parts of ammonium persulfate aqueous solution, 10.2-15.3 parts of vitamin C aqueous solution, 6-8 parts of phosphate ester monomer, 2-3 parts of acrylamide, 2-4 parts of triethanolamine, 5-8 parts of calcium formate, 1.5-2.5 parts of sodium citrate ternary compound, and 0.3-0.5 parts of organosilicon defoamer.

[0012] Furthermore, the raw materials in the aqueous solution of the carboxylic acid monomers are, by weight, 15-18 parts of acrylic acid, 3-5 parts of fumaric acid, 0.5-0.7 parts of 3-mercaptopropionic acid, and 70-90 parts of deionized water.

[0013] Furthermore, the mass fraction of the ammonium persulfate aqueous solution is 5%-10%; the mass fraction of the vitamin C aqueous solution is 1%-3%.

[0014] Furthermore, in step S2, the dropwise addition time of the carboxylic acid monomer aqueous solution is 2.8h-3.5h, the dropwise addition time of the ammonium persulfate aqueous solution is 3.3h-4.5h, and the dropwise addition time of the vitamin C aqueous solution is 3.3h-4.5h. During the dropwise addition process, the temperature of the reaction system is maintained at 48℃-52℃.

[0015] Furthermore, the heating and stirring in step S2 specifically involves heating to 62℃-65℃, stirring for 1.5h-2.5h, and stirring at a rate of 200rpm-300rpm.

[0016] Further, in step S3, the prepolymer is cooled to 42℃-43℃, and after adding phosphate ester monomer and acrylamide, the stirring speed is 150rpm-200rpm and the stirring time is 12min-16min; sodium hydroxide aqueous solution is added dropwise to adjust the pH to 5.5-6.0, and the mass fraction of sodium hydroxide aqueous solution is 20%.

[0017] Furthermore, the heating and stirring in step S3 specifically involves heating to 55℃-58℃ and stirring for 2-3 hours.

[0018] Furthermore, in step S3, the phosphate monomer is 2-hydroxyethyl methacrylate phosphate.

[0019] Further, the specific operation of step S4 is as follows: cool the grafted modified prepolymer to 30℃-35℃, add triethanolamine and calcium formate, stir at a stirring speed of 200rpm-300rpm for 20min-30min, add sodium citrate ternary compound, stir for 20min-30min, then add organosilicon defoamer, continue stirring for 10min-20min, add deionized water, adjust the solid content of the system to 38%-42%, filter with a 200-300 mesh stainless steel filter to obtain ultra-early strength polycarboxylate superplasticizer.

[0020] Furthermore, the preparation method of the sodium citrate ternary compound is as follows:

[0021] Sodium citrate, polyethylene glycol 400, aminotrimethylene phosphonic acid and deionized water are mixed and stirred at 60℃-80℃ for 1-2 hours, and then cooled to room temperature to obtain sodium citrate ternary compound.

[0022] Furthermore, the raw materials in the sodium citrate ternary compound, by weight, are as follows: sodium citrate 1.0-1.5 parts, polyethylene glycol 400 1.5-2.5 parts, aminotrimethylenephosphonic acid 0.3-0.7 parts, and deionized water 4-6 parts.

[0023] Furthermore, the specific preparation method of the sodium citrate ternary compound is as follows:

[0024] Sodium citrate, polyethylene glycol 400, aminotrimethylene phosphonic acid and deionized water are mixed and stirred at 60℃-80℃ for 1-2 hours, and then cooled to room temperature to obtain sodium citrate ternary compound.

[0025] Secondly, the present invention provides an ultra-early strength polycarboxylate superplasticizer prepared by the above-described method for preparing ultra-early strength polycarboxylate superplasticizer.

[0026] Thirdly, the present invention provides an application of the above-mentioned ultra-early strength polycarboxylate superplasticizer in the preparation of high sulfur-resistant cement concrete or ultra-high performance concrete.

[0027] The beneficial effects of this invention are:

[0028] 1. Existing technologies lack specialized water-reducing agents for composite systems of high-sulfur-resistant cement and ultra-high-performance concrete. Conventional products, due to insufficient compatibility, cannot simultaneously address the issues of slow early strength development and weak resistance to sulfate attack. This invention specifically optimizes the formulation design by combining specific carboxylic acid monomers (acrylic acid, fumaric acid) with chain transfer agents (3-mercaptopropionic acid) to construct a molecular structure suitable for high-sulfur-resistant cement with low tricalcium aluminate content, ensuring efficient adsorption and dispersion. Simultaneously, components with both adsorption and anti-erosion functions, as well as composite modifiers, are introduced to form a synergistic protection mechanism, filling the market gap for specialized polycarboxylate water-reducing agents and achieving the dual goals of improving early strength and enhancing anti-erosion performance.

[0029] 2. Traditional polycarboxylate superplasticizers generally suffer from a trade-off between early strength and long-term durability, failing to meet the high comprehensive performance requirements of concrete engineering. This invention employs a specific carboxylic acid monomer system composed of acrylic acid, fumaric acid, and 3-mercaptopropionic acid during the polymerization stage, combined with methyl allyl polyoxyethylene ether. A redox initiation system composed of ammonium persulfate and vitamin C is used to precisely control the dropping time and reaction temperature of each monomer, ensuring the polymerization reaction proceeds fully and forming a prepolymer with a regular molecular structure and excellent dispersion properties. Next, in the modification stage, 2-hydroxyethyl methacrylate phosphate and acrylamide are introduced into the prepolymer for graft modification. By adjusting the reaction pH and temperature, multifunctional groups are successfully grafted onto the prepolymer molecular chain, endowing the superplasticizer with stronger adsorption capacity and anti-erosion properties. Finally, in the compounding stage, the grafted and modified prepolymer is scientifically proportioned with early-strength components such as triethanolamine and calcium formate. Then, a sodium citrate ternary compound composed of sodium citrate, polyethylene glycol 400, and aminotrimethylene phosphonic acid is added. Combined with organosilicon defoamer, and by adjusting the solid content and filtration treatment, the core properties such as water reduction, early strength, and durability are synergistically improved, breaking the limitations of traditional water-reducing agents that only optimize single performance.

[0030] 3. Some existing early-strength polycarboxylate superplasticizers pose certain environmental risks and lack adaptability to harsh construction environments such as low temperatures, high sulfur content, and saline-alkali conditions, while also facing significant challenges in industrialization. This invention selects environmentally friendly raw materials free of harmful components, aligning with the concept of green construction. Through synergistic component design, it adapts to conventional scenarios and various harsh environments, significantly expanding its application range. Furthermore, the preparation process requires no special equipment, operates under mild reaction conditions, and has low energy consumption and pollution, facilitating large-scale industrial production. This improves product practicality and environmental friendliness while reducing production costs, resulting in significant engineering application value and economic and social benefits. Detailed Implementation

[0031] To make the embodiments of the present invention easier to understand, the present invention will be described in detail below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not limited to the application scope of the present invention.

[0032] The specific parameters of the raw materials used in this invention are as follows:

[0033] The methyl allyl polyoxyethylene ether used in this invention, CAS number 90-2004-12, was purchased from Sanda Chemical (Nantong) Co., Ltd.

[0034] The fumaric acid used in this invention is of superior grade and was purchased from Wuhan Jiyesheng Chemical Co., Ltd.

[0035] The 3-mercaptopropionic acid used in this invention, CAS number 107-96-0, was purchased from Jinan Huijinchuan Trading Co., Ltd.

[0036] The 2-hydroxyethyl methacrylate phosphate used in this invention, CAS number 52628-03-2, was purchased from Guangzhou Shanghe Chemical Technology Co., Ltd.

[0037] The calcium formate used in this invention, CAS number 544-17-2, was purchased from Jinan Huijun Chemical Co., Ltd.

[0038] The triethanolamine used in this invention, CAS number 102-71-6, with an active ingredient content of 99%, was purchased from Shandong Shengjing New Material Technology Co., Ltd.

[0039] The polyethylene glycol 400 used in this invention was purchased from Haian Petrochemical Plant in Jiangsu Province.

[0040] The aminotrimethylenephosphonic acid used in this invention was purchased from Shandong Longhui Chemical Co., Ltd.

[0041] The silicone defoamer used in this invention is model S-563, purchased from Shanghai Nazhong Chemical New Materials Co., Ltd.

[0042] Example 1

[0043] A method for preparing an ultra-early strength polycarboxylate superplasticizer includes the following preparation steps:

[0044] The preparation method of the sodium citrate ternary compound is as follows:

[0045] Take 1.0 part sodium citrate, 1.5 parts polyethylene glycol 400, 0.3 parts aminotrimethylene phosphonic acid, and 4 parts deionized water by weight. Mix sodium citrate, polyethylene glycol 400, aminotrimethylene phosphonic acid and deionized water, stir at 60°C for 1 hour, and cool to room temperature to obtain sodium citrate ternary compound.

[0046] Step S1: Prepare aqueous solution of carboxylic acid monomers

[0047] Take 15 parts by weight of acrylic acid, 3 parts of fumaric acid, 0.5 parts of 3-mercaptopropionic acid, and 70 parts of deionized water. Add acrylic acid, fumaric acid, and 3-mercaptopropionic acid to the deionized water and stir until homogeneous to obtain an aqueous solution of carboxylic acid monomers.

[0048] Step S2: Preparation of prepolymer

[0049] Methyl allyl polyoxyethylene ether was added to deionized water and stirred until homogeneous to obtain an aqueous solution of methyl allyl polyoxyethylene ether. An aqueous solution of carboxylic acid monomers, an aqueous solution of ammonium persulfate (5% by mass), and an aqueous solution of vitamin C (1% by mass) were simultaneously added dropwise to the aqueous solution of methyl allyl polyoxyethylene ether. The dropwise addition time of the carboxylic acid monomers was controlled at 2.8 h, the dropwise addition time of the ammonium persulfate was 3.3 h, and the dropwise addition time of the vitamin C was 3.3 h. The reaction system temperature was maintained at 48℃ during the dropwise addition process. After the dropwise addition was completed, the temperature was raised to 62℃ and stirred at a stirring rate of 200 rpm for 1.5 h to obtain the prepolymer.

[0050] Step S3: Preparation of grafted modified prepolymer

[0051] The prepolymer was cooled to 42°C, and 2-hydroxyethyl methacrylate phosphate and acrylamide were added. The mixture was stirred at 150 rpm for 12 min. Then, a 20% sodium hydroxide aqueous solution was added dropwise to adjust the pH of the system to 5.5. The temperature was raised to 55°C and stirred for 2 h to obtain the grafted prepolymer.

[0052] Step S4: Preparation of ultra-early strength polycarboxylate superplasticizer

[0053] The grafted and modified prepolymer was cooled to 30°C, and triethanolamine and calcium formate were added. The mixture was stirred at 200 rpm for 20 min. Then, sodium citrate ternary compound was added and stirred for 20 min. Subsequently, organosilicon defoamer was added and stirred for another 10 min. Finally, deionized water was added to adjust the solid content of the system to 38%. The mixture was then filtered through a 200-mesh stainless steel filter to obtain an ultra-early strength polycarboxylate superplasticizer.

[0054] The raw materials in the ultra-early strength polycarboxylate superplasticizer, by weight, are as follows: 88.5 parts of carboxylic acid monomer aqueous solution, 11 parts of ammonium persulfate aqueous solution, 10.2 parts of vitamin C aqueous solution, 6 parts of 2-hydroxyethyl methacrylate phosphate, 2 parts of acrylamide, 2 parts of triethanolamine, 5 parts of calcium formate, 1.5 parts of sodium citrate ternary compound, and 0.3 parts of organosilicon defoamer.

[0055] Example 2

[0056] A method for preparing an ultra-early strength polycarboxylate superplasticizer includes the following preparation steps:

[0057] The preparation method of the sodium citrate ternary compound is as follows:

[0058] Take 1.2 parts sodium citrate, 2 parts polyethylene glycol 400, 0.5 parts aminotrimethylene phosphonic acid, and 5 parts deionized water by weight. Mix sodium citrate, polyethylene glycol 400, aminotrimethylene phosphonic acid, and deionized water, stir at 70°C for 1.5 hours, and cool to room temperature to obtain sodium citrate ternary compound.

[0059] Step S1: Prepare aqueous solution of carboxylic acid monomers

[0060] Take 16 parts by weight of acrylic acid, 4 parts of fumaric acid, 0.6 parts of 3-mercaptopropionic acid, and 80 parts of deionized water. Add acrylic acid, fumaric acid, and 3-mercaptopropionic acid to the deionized water and stir until homogeneous to obtain an aqueous solution of carboxylic acid monomers.

[0061] Step S2: Preparation of prepolymer

[0062] Methyl allyl polyoxyethylene ether was added to deionized water and stirred until homogeneous to obtain an aqueous solution of methyl allyl polyoxyethylene ether. An aqueous solution of carboxylic acid monomers, an aqueous solution of ammonium persulfate (7% by mass), and an aqueous solution of vitamin C (2% by mass) were simultaneously added dropwise to the aqueous solution of methyl allyl polyoxyethylene ether. The dropwise addition time was controlled to be 3.1 h for the carboxylic acid monomer solution, 3.9 h for the ammonium persulfate solution, and 4.0 h for the vitamin C solution. The reaction system temperature was maintained at 50℃ during the dropwise addition. After the dropwise addition was complete, the temperature was raised to 64℃ and stirred at a stirring rate of 250 rpm for 2.0 h to obtain the prepolymer.

[0063] Step S3: Preparation of grafted modified prepolymer

[0064] The prepolymer was cooled to 42.5℃, and 2-hydroxyethyl methacrylate phosphate and acrylamide were added. The mixture was stirred at 180 rpm for 14 min. Then, a 20% sodium hydroxide aqueous solution was added dropwise to adjust the pH of the system to 5.8. The temperature was then raised to 58℃ and kept at that temperature for 2.5 h to obtain the grafted prepolymer.

[0065] Step S4: Preparation of ultra-early strength polycarboxylate superplasticizer

[0066] The grafted and modified prepolymer was cooled to 32°C, and triethanolamine and calcium formate were added. The mixture was stirred at 250 rpm for 25 min. Then, sodium citrate ternary compound was added and stirred for another 25 min. Subsequently, silicone defoamer was added and stirred for another 15 min. Finally, deionized water was added to adjust the solid content of the system to 40%, and the mixture was filtered through a 250-mesh stainless steel filter to obtain an ultra-early strength polycarboxylate superplasticizer.

[0067] The raw materials in the ultra-early strength polycarboxylate superplasticizer, by weight, are as follows: 100.6 parts of aqueous solution of carboxylic acid monomers, 16 parts of aqueous solution of ammonium persulfate, 13 parts of aqueous solution of vitamin C, 7 parts of 2-hydroxyethyl methacrylate phosphate, 2.5 parts of acrylamide, 3 parts of triethanolamine, 6.5 parts of calcium formate, 2 parts of sodium citrate ternary compound, and 0.4 parts of organosilicon defoamer.

[0068] Example 3

[0069] A method for preparing an ultra-early strength polycarboxylate superplasticizer includes the following preparation steps:

[0070] The preparation method of the sodium citrate ternary compound is as follows:

[0071] By weight, 1.5 parts sodium citrate, 2.5 parts polyethylene glycol 400, 0.7 parts aminotrimethylene phosphonic acid, and 6 parts deionized water are mixed and stirred at 80°C for 2 hours. After cooling to room temperature, the sodium citrate ternary compound is obtained.

[0072] Step S1: Prepare aqueous solution of carboxylic acid monomers

[0073] Take 18 parts by weight of acrylic acid, 5 parts of fumaric acid, 0.7 parts of 3-mercaptopropionic acid, and 90 parts of deionized water. Add acrylic acid, fumaric acid, and 3-mercaptopropionic acid to the deionized water and stir until homogeneous to obtain an aqueous solution of carboxylic acid monomers.

[0074] Step S2: Preparation of prepolymer

[0075] Methyl allyl polyoxyethylene ether was added to deionized water and stirred until homogeneous to obtain an aqueous solution of methyl allyl polyoxyethylene ether. An aqueous solution of carboxylic acid monomers, an aqueous solution of ammonium persulfate (10% by mass), and an aqueous solution of vitamin C (3% by mass) were simultaneously added dropwise to the aqueous solution of methyl allyl polyoxyethylene ether. The dropwise addition time of the carboxylic acid monomers was controlled at 3.5 h, the dropwise addition time of the ammonium persulfate solution was 4.5 h, and the dropwise addition time of the vitamin C solution was 4.5 h. The reaction system temperature was maintained at 52℃ during the dropwise addition process. After the dropwise addition was completed, the temperature was raised to 65℃ and stirred at a stirring rate of 300 rpm for 2.5 h to obtain the prepolymer.

[0076] Step S3: Preparation of grafted modified prepolymer

[0077] The prepolymer was cooled to 43°C, and 2-hydroxyethyl methacrylate phosphate and acrylamide were added. The mixture was stirred at 200 rpm for 16 min. Then, sodium hydroxide aqueous solution was added dropwise to adjust the pH of the system to 6.0. The temperature was then raised to 60°C and kept at that temperature for 2.5 h to obtain the grafted modified prepolymer.

[0078] Step S4: Preparation of ultra-early strength polycarboxylate superplasticizer

[0079] The grafted and modified prepolymer was cooled to 35°C, and triethanolamine and calcium formate were added. The mixture was stirred at 300 rpm for 30 min. Then, sodium citrate ternary compound was added and stirred for another 30 min. Subsequently, organosilicon defoamer was added and stirred for another 20 min. Finally, deionized water was added to adjust the solid content of the system to 42%, and the mixture was filtered through a 300-mesh stainless steel filter to obtain an ultra-early strength polycarboxylate superplasticizer.

[0080] The raw materials in the ultra-early strength polycarboxylate superplasticizer, by weight, are as follows: 113.7 parts of carboxylic acid monomer aqueous solution, 21 parts of ammonium persulfate aqueous solution, 15.3 parts of vitamin C aqueous solution, 8 parts of 2-hydroxyethyl methacrylate phosphate, 3 parts of acrylamide, 4 parts of triethanolamine, 8 parts of calcium formate, 2.5 parts of sodium citrate ternary compound, and 0.5 parts of organosilicon defoamer.

[0081] Comparative Example 1

[0082] Compared with Example 1, this comparative example replaces "fumaric acid" with an equal mass of "deionized water". All other steps and parameters are the same, and will not be repeated here. The final result is an ultra-early strength polycarboxylate superplasticizer.

[0083] Comparative Example 2

[0084] Compared with Example 1, this comparative example replaces "3-mercaptopropionic acid" with an equal mass of "deionized water". All other steps and parameters are the same, and will not be repeated here. The final result is an ultra-early strength polycarboxylate superplasticizer.

[0085] Comparative Example 3

[0086] Compared with Example 1, this comparative example replaces the "sodium citrate ternary compound" with an equal mass of "sodium citrate". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, an ultra-early strength polycarboxylate superplasticizer is obtained.

[0087] Comparative Example 4

[0088] Compared with Example 1, this comparative example replaces "2-hydroxyethyl methacrylate phosphate" with an equal mass of "methyl methacrylate". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, an ultra-early strength polycarboxylate superplasticizer is obtained.

[0089] Comparative Example 5

[0090] Compared with Example 1, this comparative example does not add vitamin C aqueous solution, and all other steps and parameters are the same. The details of this comparative example will not be repeated here. Finally, an ultra-early strength polycarboxylate superplasticizer is obtained.

[0091] Performance testing

[0092] The performance of the ultra-early strength polycarboxylate superplasticizers prepared in Examples 1-3 and Comparative Examples 1-5 was tested, and the test results are recorded in Table 1.

[0093] Test methods for ultra-early strength polycarboxylate superplasticizers:

[0094] Spreadability test: Referring to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", concrete containing ultra-early strength polycarboxylate superplasticizer was prepared according to the mix proportion of ultra-high performance concrete (UHPC) (high sulfur-resistant cement: silica fume: quartz sand: quartz powder: water = 1:0.2:1.2:0.3:0.22, water-cement ratio 0.22). The superplasticizer dosage was maintained at 0.15%. After mixing according to the standard steps, a spreadability test was conducted using a spreadability cylinder. The maximum diameter of the concrete mixture after free expansion was recorded as the spreadability test result.

[0095] Compressive strength test: Referring to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" and adjusting the test scheme according to the actual engineering application scenario, ultra-early strength polycarboxylate superplasticizer concrete was prepared using a mix ratio of high sulfur-resistant cement-ultra-high performance concrete (UHPC) (high sulfur-resistant cement: silica fume: quartz sand: quartz powder: water = 1:0.2:1.2:0.3:0.22, water-cement ratio 0.22). The superplasticizer dosage was 0.15% (converted to solids). Standard concrete specimens of 150mm×150mm×150mm were formed and the compressive strength was measured after standard curing for 3d, 7d, and 28d, respectively. The test focused on reflecting the early strength characteristics and long-term strength development ability of the product, ensuring that the test results closely reflect the stress state and performance of concrete in real engineering projects.

[0096] Corrosion resistance test: According to GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", the mix proportion of high sulfur-resistant cement-UHPC (high sulfur-resistant cement: silica fume: quartz sand: quartz powder: water = 1:0.2:1.2:0.3:0.22, water-cement ratio 0.22) was adopted, and the water-reducing agent dosage was 0.15%. 100mm×100mm×100mm concrete specimens were formed. After standard curing for 28 days, they were immersed in 5% sodium sulfate solution for 56 days of corrosion. The compressive strength before and after corrosion was measured.

[0097] Calculation formula: .

[0098] Table 1: Test data of ultra-early strength polycarboxylate superplasticizer

[0099]

[0100] As shown in Table 1, the ultra-early strength polycarboxylate superplasticizers prepared in Examples 1-3 all exhibited excellent performance in terms of spread, early strength, long-term strength, and resistance to sulfate attack, and the data were stable, indicating that their preparation process and formulation have excellent repeatability and comprehensive performance advantages.

[0101] Comparison of Example 1 and Example 1 shows that replacing "fumaric acid" with an equal mass of "deionized water" resulted in a decrease in spread, a reduction in 7-day strength, and a decrease in corrosion resistance. Fumaric acid, as a copolycarboxylic acid monomer, not only provides additional adsorption groups, enhancing the anchoring ability of the water-reducing agent on the surface of cement particles, but its rigid structure also promotes the formation of early hydration products, significantly improving early strength and corrosion resistance.

[0102] Comparison of Example 2 and Example 1 shows that replacing "3-mercaptopropionic acid" with an equal mass of "deionized water" significantly reduces the spread and 7-day strength. 3-mercaptopropionic acid, as a chain transfer agent, can effectively regulate the molecular weight and distribution of the polymerization reaction, ensuring that the water-reducing agent has a suitable comb-like structure and dispersion stability; its absence leads to an excessively wide molecular weight distribution, decreased dispersibility, and poorer slurry stability.

[0103] Comparison of Example 3 and Example 1 shows that replacing the "sodium citrate ternary compound" with an equal mass of "sodium citrate" reduces the spread and the corrosion resistance coefficient. Sodium citrate itself can act as a dispersant and retarder, providing certain water-reducing and slump-retaining effects, but its single function has limitations in improving early strength and long-term erosion resistance. In the sodium citrate ternary compound used in this invention, sodium citrate serves as the basic framework, polyethylene glycol 400 enhances the interfacial lubrication effect between cement particles, and aminotrimethylene phosphonic acid can strongly chelate calcium ions and form a protective film, significantly improving the system's erosion resistance. Through synergistic effects, the three components complement each other in terms of dispersion, lubrication, early strength activation, and durability improvement. Its comprehensive effect is significantly better than that of sodium citrate alone, thus demonstrating a clear advantage in improving spread, early strength, and long-term durability.

[0104] Comparison of Example 4 and Example 1 shows that replacing "2-hydroxyethyl methacrylate phosphate" with an equal mass of "methyl methacrylate" significantly reduces the spread, 7-day strength, and corrosion resistance coefficient. The phosphate group has strong adsorption and charge effect, preferentially adsorbing onto cement particles and clay surfaces, improving mud resistance and early hydration promotion; replacing it with ordinary ester groups significantly weakens the adsorption capacity and early activation effect.

[0105] Comparison of Example 5 and Example 1 shows that without the addition of vitamin C aqueous solution, all properties decreased, including reduced spread, 7-day strength, and corrosion resistance. Vitamin C, as a reducing agent, participates in the redox initiation system to ensure a stable and complete polymerization reaction; its absence leads to low initiation efficiency, incomplete polymerization, incomplete molecular structure of the water-reducing agent, and significant deterioration of overall performance.

[0106] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing an ultra-early strength polycarboxylate superplasticizer, characterized in that, The preparation steps include the following: Step S1: Add acrylic acid, fumaric acid, and 3-mercaptopropionic acid to deionized water and stir until homogeneous to obtain an aqueous solution of carboxylic acid monomers; Step S2: Add methyl allyl polyoxyethylene ether to deionized water and stir until homogeneous to obtain an aqueous solution of methyl allyl polyoxyethylene ether. Simultaneously add aqueous solutions of carboxylic acid monomers, ammonium persulfate, and vitamin C to the aqueous solution of methyl allyl polyoxyethylene ether. After the addition is complete, heat and stir to obtain the prepolymer. Step S3: After cooling the prepolymer, add phosphate ester monomer and acrylamide, stir evenly, add sodium hydroxide aqueous solution dropwise to adjust the pH, heat and stir to obtain the grafted modified prepolymer; Step S4: Cool the grafted and modified prepolymer, add triethanolamine and calcium formate, stir and mix, add sodium citrate ternary compound, stir evenly, add organosilicon defoamer, continue stirring, add deionized water to adjust the solid content, filter, and obtain ultra-early strength polycarboxylate superplasticizer.

2. The preparation method of an ultra-early strength polycarboxylate superplasticizer according to claim 1, characterized in that, The raw materials in the ultra-early strength polycarboxylate superplasticizer, by weight, are as follows: 88.5-113.7 parts of carboxylic acid monomer aqueous solution, 11-21 parts of ammonium persulfate aqueous solution, 10.2-15.3 parts of vitamin C aqueous solution, 6-8 parts of phosphate ester monomer, 2-3 parts of acrylamide, 2-4 parts of triethanolamine, 5-8 parts of calcium formate, 1.5-2.5 parts of sodium citrate ternary compound, and 0.3-0.5 parts of organosilicon defoamer.

3. The preparation method of an ultra-early strength polycarboxylate superplasticizer according to claim 1, characterized in that, The raw materials in the aqueous solution of the carboxylic acid monomers, by weight, are: 15-18 parts acrylic acid, 3-5 parts fumaric acid, 0.5-0.7 parts 3-mercaptopropionic acid, and 70-90 parts deionized water.

4. The preparation method of an ultra-early strength polycarboxylate superplasticizer according to claim 1, characterized in that, The ammonium persulfate aqueous solution has a mass fraction of 5%-10%; the vitamin C aqueous solution has a mass fraction of 1%-3%.

5. The preparation method of an ultra-early strength polycarboxylate superplasticizer according to claim 1, characterized in that, In step S3, the phosphate monomer is 2-hydroxyethyl methacrylate phosphate.

6. The preparation method of an ultra-early strength polycarboxylate superplasticizer according to claim 1, characterized in that, In step S2, the aqueous solution of carboxylic acid monomers is added over a time of 2.8h-3.5h, the aqueous solution of ammonium persulfate is added over a time of 3.3h-4.5h, and the aqueous solution of vitamin C is added over a time of 3.3h-4.5h. During the addition process, the temperature of the reaction system is maintained at 48℃-52℃.

7. The preparation method of an ultra-early strength polycarboxylate superplasticizer according to claim 1, characterized in that, The preparation method of the sodium citrate ternary compound is as follows: Sodium citrate, polyethylene glycol 400, aminotrimethylene phosphonic acid and deionized water are mixed and stirred at 60℃-80℃ for 1-2 hours, and then cooled to room temperature to obtain sodium citrate ternary compound.

8. The preparation method of an ultra-early strength polycarboxylate superplasticizer according to claim 7, characterized in that, The raw materials in the sodium citrate ternary compound, by weight, are as follows: sodium citrate 1.0-1.5 parts, polyethylene glycol 400 1.5-2.5 parts, aminotrimethylenephosphonic acid 0.3-0.7 parts, and deionized water 4-6 parts.

9. An ultra-early strength polycarboxylate superplasticizer prepared by the preparation method of any one of claims 1-8.

10. The application of the ultra-early strength polycarboxylate superplasticizer of claim 9 in the preparation of high sulfur-resistant cement concrete or ultra-high performance concrete.

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