Ultrahigh-performance polycarboxylate superplasticizer for UHPC (Ultra High Performance Concrete) and preparation method thereof

Abstract

The invention relates to the technical field of preparation of building materials, and discloses an ultra-high performance polycarboxylate superplasticizer for UHPC (Ultra High Performance Concrete). The superplasticizer composition comprises the following components in parts by weight: 20-30 parts of ethyl acrylate; 20 to 30 parts of sodium acrylate; the invention also provides a preparation method of the ultra-high performance polycarboxylate superplasticizer for UHPC, and the preparation method comprises the following steps: S1, raw material preparation: dissolving ethyl acrylate, sodium acrylate, sodium allylsulfonate, hexadecyl acrylate and diene peroxide in 50-100 parts of water to form a uniform solution; and S2, mixing and pre-polymerizing. By introducing nano silicon dioxide, an ultrasonic dispersion technology and a low-temperature vacuum dehydration technology, the dispersity and anti-permeability of the water reducing agent and the fluidity of concrete are improved, meanwhile, high strength is kept, and the problems that concrete is uneven in performance and poor in constructability are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of building material preparation, and specifically to a super high-performance polycarboxylate water reducer for UHPC and its preparation method. Background Art

[0002] In the construction of modern buildings and infrastructure, ultra-high performance concrete (UHPC) is widely used due to its excellent mechanical properties and durability, especially in bridges, high-rise buildings and special projects. However, the application of UHPC faces a relatively high viscosity, which brings many difficulties to construction. To overcome this problem, the use of water reducers is particularly important. Water reducers can significantly improve the fluidity of concrete, facilitate the mixing, transportation and pouring of concrete, and maintain the strength of concrete.

[0003] Currently, the polycarboxylate water reducer technology in the market has been widely used in concrete production. Such water reducers can improve the fluidity of concrete to a certain extent and effectively improve the workability. Especially, polycarboxylate water reducers can better reduce the adhesion force between cement particles through their unique molecular structure, thereby improving the workability of concrete. While reducing the water-cement ratio, these water reducers can also maintain the high strength of concrete, and most polycarboxylate water reducers will not have a significant negative impact on the compressive strength of concrete while improving the fluidity, and can effectively improve the construction efficiency and the pouring performance of concrete.

[0004] However, the water reducers in the prior art still have some deficiencies, which limit their application in ultra-high performance concrete; firstly, traditional water reducers are prone to problems such as poor dispersibility and particle agglomeration while improving the fluidity of concrete, which affects the uniform distribution of water reducers in concrete; secondly, the improvement effect of the impermeability of existing water reducers is limited. Although they can improve the fluidity, they lack sufficient impermeability, resulting in the problem of water seepage in concrete during long-term use; more importantly, traditional water reducers cannot effectively solve the contradiction between fluidity and compressive strength. After adding traditional water reducers to high-strength concrete, the fluidity is often poor and it is difficult to maintain high strength; finally, traditional dispersion methods usually rely on mechanical stirring and cannot ensure the uniform distribution of polymer molecular chains, resulting in unstable performance. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a super high-performance polycarboxylate water reducer for UHPC and its preparation method, which solves the problems of poor dispersibility, insufficient impermeability and the contradiction between fluidity and strength of water reducers in the prior art.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: a super high-performance polycarboxylate water reducer method for UHPC, and the water reducer composition includes the following components in parts by weight: Ethyl acrylate: 20 - 30 parts. Ethyl acrylate has strong hydrophilicity and can interact with the negative charges on the surface of cement particles, enhancing the dispersibility and stability of the water reducer. Ethyl acrylate forms hydrogen bond interactions with the hydroxide ions on the surface of cement particles through its acrylic acid group, thereby reducing the adhesion force between cement particles and decreasing the viscosity of the cement paste. The hydrophilicity of its polymer structure ensures the dispersibility of the water reducer in the cement paste and avoids the occurrence of particle agglomeration; Sodium acrylate: 20 - 30 parts. Sodium acrylate dissociates into sodium ions and acrylate ions in aqueous solution, and its polar groups give it good hydrophilicity in the cement paste. On the surface of cement particles, the negative charges of sodium acrylate have electrostatic interactions with the positive charges on the cement surface, enhancing the affinity between the water reducer and cement particles; Sodium allylsulfonate: 2 - 5 parts. The sulfonic acid group of sodium allylsulfonate can have strong electrostatic interactions with calcium ions on the surface of cement particles, increasing the surface charge density of cement particles and forming a strong repulsive force to prevent cement particle agglomeration. When used together with sodium acrylate, sodium allylsulfonate can further enhance the dispersibility of the water reducer in the cement paste and effectively improve the fluidity of concrete; Hexadecyl acrylate: 10 - 15 parts. The long alkyl side chain of hexadecyl acrylate has significant hydrophobicity, and it interacts with the more hydrophobic regions on the surface of cement particles, thereby reducing the adsorption force between cement particles and enhancing the fluidity of the water reducer. The long-chain alkyl improves the dispersibility of the water reducer by reducing the mutual attraction between cement particles, and can also improve the workability of concrete and reduce the viscosity of the cement paste; Nano-silica: 1 - 2 parts. The extremely high specific surface area of nano-silica helps to enhance the dispersion stability between cement particles and, by refining the pore structure, improves the impermeability of concrete. In addition, the property of nano-silica filling micro-pores can enhance the density and compressive strength of concrete and further improve its mechanical properties; Auxiliary components: 0.5 - 1.0 part.

[0007] Preferably, the auxiliary components include: Antioxidant: 0.5 - 1.0 part. The main function of the antioxidant is to capture free radicals during the polymerization process, preventing oxygen molecules from reacting with the polymer molecular chains to form unstable oxidation products. Polymerization reactions are often accompanied by the generation of free radicals, which can cause the breakage or cross-linking of polymer molecular chains, resulting in a decline in product performance. By adding antioxidants, they stabilize the polymer structure by reacting with free radicals or preventing the intrusion of oxygen molecules, ensuring that the molecular chains of the water reducer remain intact, thereby enhancing the performance and durability of the water reducer; Preservative: 0.5 - 1.0 parts. The preservative protects the chemical stability of the water reducer by inhibiting the growth and reproduction of microorganisms, preventing it from being invaded by microorganisms during storage. The growth of microorganisms often leads to the degradation or transformation of certain components in the water reducer, thereby affecting the performance of the product. The preservative binds to the cell wall of microorganisms, disrupts their metabolic processes, inhibits their activities, and prevents the degradation of the components of the water reducer. In addition, the preservative can also act on the soluble components in water, reducing the impact of water-soluble impurities on the water reducer and ensuring its stable performance after long-term storage.

[0008] Preferably, the present invention also provides a preparation method of a super high-performance polycarboxylate water reducer for UHPC, comprising the following steps: S1. Raw material preparation: Dissolve ethyl acrylate, sodium acrylate, sodium allylsulfonate, hexadecyl acrylate and diene peroxide in 50 - 100 parts of water to form a homogeneous solution; S2. Mixing and pre-polymerization: Transfer the above solution to a reaction kettle, add 0.5 - 1.0 parts of sodium persulfate, heat under nitrogen protection and start the polymerization reaction. At the beginning of the polymerization reaction, sodium persulfate decomposes to generate free radicals, initiating the polymerization reaction of acrylate monomers. The formation of free radicals is a key step in the polymerization reaction. The free radicals provided by sodium persulfate react with the monomers to generate longer molecular chains. The role of nitrogen protection is to ensure that there is no oxygen in the reaction environment to avoid side reactions caused by oxygen (such as the formation of peroxides or the degradation of polymer chains); S3. Ultrasonic dispersion: Use an ultrasonic treatment device to disperse the reaction system during the polymerization process to ensure the uniform distribution of molecular chains and avoid the agglomeration of polymers. The ultrasonic dispersion technology uses high-frequency sound waves to trigger the vibration and explosion of tiny bubbles in the solution, which is called the "cavitation effect". The cavitation effect can generate high-energy local hot spots, promote the full mixing of substances in the reaction solution, and make the polymer molecular chains evenly distributed, avoiding the phenomenon of forming irregular structures due to the aggregation of molecular chains. Especially during the polymerization reaction, the aggregation between molecular chains will lead to an uneven dispersion system, thus affecting the fluidity and dispersibility of the water reducer. Ultrasonic dispersion can effectively solve this problem and ensure the uniformity of the reaction system; S4. Cooling and water extraction: After the polymerization reaction is completed, gradually cool to 23 - 27 °C, wash with deionized water to remove unreacted monomers and by-products, and ensure the purity of the water reducer. The purpose of the cooling step is to bring the reaction solution to room temperature, stop the reaction process, and reduce the impact of unreacted substances on the performance of the water reducer. The purpose of washing with deionized water is to remove unreacted monomers and by-products generated during the reaction process, such as excessive sodium persulfate, and ensure their separation from the water reducer; S5. Product Purification and Dehydration: Residual water is removed by low-temperature vacuum dehydration to obtain the final product. Low-temperature vacuum dehydration reduces the boiling point of the solvent, causing the solvent to evaporate at a lower temperature, thereby avoiding damage to the polymer molecular chains at high temperatures.

[0009] Preferably, the parameters of the reaction kettle include: The stirring speed of the reaction kettle is set at 200 - 400 rpm to ensure uniform mixing of the reactants. The role of stirring is reflected in two aspects. On the one hand, it can improve the heat transfer efficiency of the reaction solution and ensure uniform heating of the reactants. On the other hand, it can effectively prevent the agglomeration of polymer molecules in the reaction solution. In the polymerization reaction, due to the high viscosity of acrylic monomers, if the stirring speed is too low, the reactants in the solution are likely to form local high-concentration regions in the reaction kettle, resulting in uneven reactions or irregular growth of polymer molecular chains. By stirring within the range of 200 - 400 rpm, the solution can be ensured to be uniform, avoiding precipitation or agglomeration of substances, and at the same time, it can also help sodium persulfate and monomers react better with cement particles or other solution components; The temperature at the start of the reaction is set at 60 - 70 °C. At a lower temperature, the decomposition rate of sodium persulfate is slower, resulting in a slower start of the polymerization reaction and even failure to reach the required polymerization rate. When the temperature is too high, the polymerization reaction will be too intense, producing too many by-products or polymer molecular chains that are too long, thus affecting the fluidity and performance of the water reducer. Therefore, setting the temperature at the start of the reaction at 60 - 70 °C can balance the decomposition rate of sodium persulfate and the progress rate of the polymerization reaction, ensuring stable and uniform reactions and avoiding over-polymerization or the generation of by-products.

[0010] Preferably, the polymerization reaction includes the following parameters: The reaction time is set at 4 hours - 6 hours to ensure the completeness of the polymerization reaction. If the reaction time is too short, the reaction is likely not to proceed completely, resulting in shorter polymer molecular chains and unstable performance. Therefore, this range of reaction time can ensure sufficient reaction, enabling monomers to fully participate in the reaction, forming polymer chains with moderate molecular weights, avoiding overly short or uneven polymer molecules, and thus enhancing the dispersibility, fluidity, and stability of the water reducer; During the reaction process, the temperature is maintained at 60-70°C to ensure the stable progress of the reaction. When the temperature is too low, the polymerization reaction rate will decrease significantly, resulting in incomplete polymerization, which affects the final polymer molecular weight and properties. When the reaction temperature is too high, it will lead to excessive decomposition of sodium persulfate, generating too many free radicals, which easily trigger side reactions, thus forming irregular polymer chains or by-products. Setting the reaction temperature range of 60-70°C can ensure the stable decomposition of sodium persulfate at an appropriate temperature, generating an appropriate amount of free radicals to initiate the polymerization reaction, and avoiding the reaction being too fast or too slow, thereby ensuring the uniformity and stability of the polymerization reaction; during the reaction process, nitrogen protection is maintained to ensure an anaerobic environment. In the polymerization reaction, the presence of oxygen will affect the reaction. Oxygen will react with the free radicals in the reaction to terminate the polymerization reaction, resulting in a decrease in the molecular weight of the polymer or even a complete stop of the polymerization reaction. Oxygen will also react with the reactants to generate unstable intermediates or by-products, further affecting the quality of the polymer. Therefore, maintaining nitrogen protection during the reaction process can effectively isolate the interference of oxygen and maintain the stability of the polymerization reaction.

[0011] Preferably, the ultrasonic dispersion includes the following parameters: The ultrasonic dispersion step uses an ultrasonic power of 100-200 W. By controlling the ultrasonic power, the effectiveness of the dispersion effect can be ensured, and at the same time, excessive power causing excessive decomposition or thermal degradation of the polymer can be avoided; The dispersion treatment time is 30-60 minutes to ensure the uniform distribution of polymer molecular chains and avoid polymer agglomeration. The length of the dispersion time directly affects the uniform distribution of polymer molecular chains. A shorter time will result in incomplete dispersion, and the aggregation phenomenon of molecular chains cannot be fully solved, thus affecting the dispersion effect and fluidity of the polymer in the cement paste. An overly long dispersion time, although it can ensure uniform dispersion, will also cause damage or degradation of polymer chains due to excessive energy input. A dispersion time of 30-60 minutes is sufficient to ensure the dispersion effect while avoiding the negative effects caused by over-treatment. Within this time range, ultrasonic energy can fully act on the particles in the solution, making the polymer molecular chains uniformly distributed in the cement paste and improving the fluidity and workability of the concrete.

[0012] Preferably, the cooling and water extraction include: Wash with deionized water. The flow rate of the washing water is 200 - 300 ml / min, and the duration is 15 - 30 minutes to ensure the complete removal of by-products and unreacted substances. Deionized water has strong dissolving ability and can act on water-soluble unreacted substances and by-products to dissolve and separate them from the reaction solution. The set flow rate of the washing water is 200 - 300 ml / min to ensure that the solvent and unreacted substances are fully rinsed out within the specified time. The duration of washing is 15 - 30 minutes, and this duration can ensure the complete removal of most dissolved by-products. However, too long a washing time will cause the loss of some reaction substances, thus affecting the final performance of the water reducer; The number of washing times is 2 - 3 times, and the interval range is 10 - 30 minutes to minimize the concentration of by-products in the reaction solution. Multiple washings are to ensure the complete removal of by-products in the reaction solution. The initial washing is likely to only remove some unreacted substances and by-products, so 2 - 3 washings are required. Through multiple rinses, the impurities and by-products in the reaction solution are gradually reduced. The interval time between washings (10 - 30 minutes) is to allow the washing water to fully contact and dissolve the unreacted substances and by-products in the reaction solution, avoiding the reattachment of reaction substances to the polymer surface during the washing process and ensuring the effect of each washing.

[0013] Preferably, the parameters of the low-temperature vacuum dehydration include: The vacuum degree is 0.1 - 0.3 MPa. The setting of the low vacuum degree ensures the effective evaporation of the solvent and avoids problems such as excessive polymer degradation or incomplete dehydration caused by high temperature. Too high a vacuum degree will cause too fast dehydration, which will have a negative impact on the polymer, while too low a vacuum degree will reduce the dehydration efficiency. Therefore, a vacuum degree of 0.1 - 0.3 MPa is the best setting, which can fully remove the solvent while retaining the performance of the water reducer; The dehydration temperature is 40 - 60 °C. When the set temperature is exceeded, polymer molecules will be thermally degraded, resulting in a decrease in performance, especially for polymers with a small molecular weight or an unstable structure. The dehydration temperature in this range is sufficient to promote the evaporation of the solvent. At the same time, it can ensure that the solvent evaporates rapidly while minimizing the thermal damage to the polymer and guaranteeing the quality of the final product; in addition, the lower dehydration temperature enables the product after the polymerization reaction to maintain the stability of its molecular chain, preventing the rapid evaporation of the solvent from causing irregular polymer structures or chain breaks, thus affecting the performance of the final product; The time for vacuum dehydration is between 2 - 4 hours. Too short a dehydration time will cause solvent residues, affecting the purity and stability of the water reducer; while too long a dehydration time will cause partial degradation of the polymer or adverse reactions with the solvent. Through a dehydration time of 2 - 4 hours, it can ensure the complete removal of the solvent while avoiding over-treatment of the water reducer.

[0014] The present invention provides a super-high-performance polycarboxylate water reducer for UHPC and its preparation method, with the following beneficial effects: 1. By adding nano-silica, the dispersibility and impermeability of the water reducer are improved in the present invention. Compared with the traditional technology, the introduction of nano-silica increases the density of the concrete and significantly enhances the water penetration resistance. It not only makes the concrete more durable but also reduces the dosage of the water reducer with better effects.

[0015] 2. By using ultrasonic dispersion technology, the present invention ensures the uniform distribution of the polymer in the cement paste and avoids the polymer agglomeration problem caused by conventional mechanical stirring. Through this technology, the fluidity of the water reducer is greatly improved, the concrete is more smooth during construction, and the dispersion effect is lasting and stable.

[0016] 3. By adopting the low-temperature vacuum dehydration process, the present invention can efficiently remove residual solvents and by-products without causing thermal damage to the polymer. This dehydration method can better retain the performance of the water reducer compared with traditional high-temperature dehydration, ensuring the purity and long-term stability of the product.

[0017] 4. The present invention makes innovations in the optimization of material ratios and technological processes, enabling the water reducer to still improve the fluidity, compressive strength, and impermeability of the concrete at low dosages. This efficient formulation design solves the performance bottleneck caused by inconsistent materials in the past, ensuring that the concrete not only has high strength but also better workability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the specification of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] Please refer to the attached Figure 1 : Example 1: S1. Raw material preparation: Weigh ethyl acrylate (25 parts), sodium acrylate (25 parts), sodium allylsulfonate (3 parts), hexadecyl acrylate (12 parts), nano-silica (1.5 parts), and diene-based peroxide (sodium persulfate, 0.5 part) in proportion, dissolve them in 80 parts of deionized water, and stir until the solution is uniform.

[0021] S2. Polymerization reaction: Transfer the above solution to a reaction kettle and add 0.8 parts of sodium persulfate. Fill the reaction kettle with nitrogen, set the temperature to 65 °C, set the stirring speed to 300 rpm, and react for 5 hours. During the reaction process, nitrogen protection effectively prevents the influence of oxygen and ensures the smooth progress of the reaction.

[0022] S3. Ultrasonic dispersion: During the reaction process, use an ultrasonic power of 150 W and control the dispersion time to 45 minutes to ensure the uniform distribution of polymer molecular chains and prevent agglomeration.

[0023] S4. Cooling and washing: After the reaction is completed, gradually cool the mixture to 25 °C. Wash the reaction solution with deionized water, with a washing water flow rate of 250 ml / min for 20 minutes. The number of washing times is 2, and there is a 20-minute interval after each washing.

[0024] S5. Low-temperature vacuum dehydration: Adopt a vacuum degree of 0.2 MPa, a dehydration temperature of 50 °C, and a dehydration time of 3 hours to remove residual solvents and by-products and ensure the purity of the final product.

[0025] Example 2: S1. Raw material preparation: Ethyl acrylate (28 parts), sodium acrylate (22 parts), sodium allylsulfonate (2.5 parts), cetyl acrylate (10 parts), nano-silica (2 parts), and sodium persulfate (0.7 parts) are added to 90 parts of deionized water in proportion and stirred evenly.

[0026] S2. Polymerization reaction: Transfer the solution to a reaction kettle, add sodium persulfate, fill with nitrogen, set the temperature to 70 °C, the reaction time to 4 hours, and the stirring speed to 250 rpm. Keep the reaction process anaerobic to ensure the stability of the polymer.

[0027] S3. Ultrasonic dispersion: During the reaction process, set the ultrasonic power to 120 W and the duration to 30 minutes. This time is sufficient to ensure the uniform dispersion of polymer molecules and prevent uneven distribution.

[0028] S4. Cooling and washing: After the reaction is completed, gradually cool to 23 °C and wash. Set the washing water flow rate to 200 ml / min for 25 minutes. Wash 3 times with deionized water, with a 15-minute interval after each washing to ensure the complete removal of by-products.

[0029] S5. Low-temperature vacuum dehydration: Use a vacuum degree of 0.15 MPa, set the dehydration temperature to 45 °C, and the dehydration time to 2.5 hours to remove the remaining solvents.

[0030] Example 3: S1. Raw material preparation: Weigh ethyl acrylate (23 parts), sodium acrylate (27 parts), sodium acrylsulfonate (3 parts), cetyl acrylate (11 parts), nano-silica (1 part) and sodium persulfate (0.9 part) respectively and dissolve them in 100 parts of water, and stir until completely dissolved.

[0031] S2. Polymerization reaction: Add the solution to the reaction kettle. After adding sodium persulfate, under nitrogen protection, set the temperature to 62 °C, control the reaction time to 5 hours, and the stirring speed to 350 rpm to ensure the uniform mixing of the reactants during the reaction process.

[0032] S3. Ultrasonic dispersion: During the polymerization reaction, use an ultrasonic power of 150 W for dispersion, and the dispersion time is 50 minutes. Ensure the uniform distribution of the polymer in the cement slurry.

[0033] S4. Cooling and washing: After the reaction is completed, gradually cool the temperature to 25 °C and wash with deionized water. The washing water flow rate is 300 ml / min, lasting for 30 minutes, and the number of washing times is 2 times, with an interval of 10 minutes each time to ensure the complete removal of unreacted substances and by-products in the reaction solution.

[0034] S5. Low-temperature vacuum dehydration: The dehydration conditions are a vacuum degree of 0.2 MPa, a dehydration temperature of 50 °C, and a dehydration time of 3 hours to remove excess solvent and ensure the high purity of the final product.

[0035] Example 4: S1. Raw material preparation: Dissolve ethyl acrylate (24 parts), sodium acrylate (26 parts), sodium acrylsulfonate (4 parts), cetyl acrylate (13 parts), nano-silica (1.8 parts) and sodium persulfate (0.6 part) in 75 parts of water and stir evenly.

[0036] S2. Polymerization reaction: Transfer the solution to the reaction kettle, add sodium persulfate, set the temperature to 67 °C, set the stirring speed to 320 rpm, and the reaction time to 4 hours to ensure the smooth progress of the reaction.

[0037] S3. Ultrasonic dispersion: During the polymerization reaction, use an ultrasonic power of 120 W for dispersion, and the treatment time is 40 minutes to ensure the uniform distribution of polymer chains in the reaction solution and avoid polymer agglomeration.

[0038] S4. Cooling and washing: After the reaction is completed, gradually cool to 23 °C and wash the reaction solution with deionized water. The washing water flow rate is 250 ml / min, lasting for 20 minutes, and the number of washing times is 2 times, with an interval of 15 minutes each time to completely remove by-products and unreacted substances.

[0039] S5, Low-temperature Vacuum Dehydration: With a vacuum degree of 0.25 MPa, a dehydration temperature of 45 °C, and a dehydration time of 2 hours, the solvent can be effectively removed to ensure the high purity of the product.

[0040] Effect Verification: Compared with the prior art, after introducing nano-silica and ultrasonic dispersion technology in this embodiment, the dispersibility and impermeability of the water reducer are significantly improved. At the same time, the residual solvent is completely removed through the vacuum dehydration process, ensuring the stability and performance of the final product. Compared with the traditional scheme without adding nano-materials, it shows better workability and strength.

[0041] Comparative Example 1: Based on the comparison with Example 1, its technical solution is as follows: Raw Material Composition: Compared with Example 1, the dosage of nano-silica is reduced to 0.5 parts, and cetyl acrylate is not added. This comparative example only uses conventional materials such as ethyl acrylate (25 parts), sodium acrylate (25 parts), sodium allyl sulfonate (3 parts), and sodium persulfate (0.5 parts). By removing the nano-materials for enhancing efficiency, the purpose is to compare the performance of traditional polycarboxylate water reducers.

[0042] Polymerization Reaction: Transfer the above solution to a reaction kettle. After adding sodium persulfate, the temperature is set at 70 °C, the stirring speed is set at 350 rpm, and the reaction lasts for 4 hours.

[0043] Dispersion Treatment: The comparative example does not use ultrasonic dispersion technology and adopts the traditional mechanical stirring method. The stirring speed is set at 300 rpm, and the treatment time is longer, which is 90 minutes.

[0044] Cooling and Solvent Extraction: Deionized water is used for washing, with a flow rate of 300 ml / min, lasting for 30 minutes. The number of washing times is 3 times, and the interval time between each time is 15 minutes. This is slightly different from the washing process of the example, mainly to observe the effect of the conventional washing method.

[0045] Low-temperature Vacuum Dehydration: With a vacuum degree of 0.2 MPa, a dehydration temperature of 50 °C, and a dehydration time of 2 hours, which is different from the parameters of Example 1.

[0046] Comparative Example 2: Based on the comparison with Example 2, its technical solution is as follows: Raw Material Composition: In Comparative Example 2, the addition of nano-silica is removed, and only ethyl acrylate (28 parts), sodium acrylate (22 parts), sodium allyl sulfonate (2.5 parts), cetyl acrylate (10 parts), and sodium persulfate (0.7 parts) are used. By removing nano-silica, the focus is on the roles of hydrophilic and hydrophobic monomers, and their performance in fluidity and impermeability is observed.

[0047] Polymerization reaction: Transfer the above solution to a reaction kettle. After adding sodium persulfate, set the temperature to 75 °C, the reaction time to 3.5 hours, and the stirring speed to 350 rpm.

[0048] Dispersion treatment: Adopt mechanical stirring, set the stirring time to 60 minutes, and keep the stirring speed at 300 rpm. Ultrasonic dispersion is not used, and traditional mechanical methods are adopted.

[0049] Cooling and solvent extraction: Set the washing water flow rate to 250 ml / min, continue for 20 minutes, the number of washing times is 3 times, and the interval between each washing is 20 minutes.

[0050] Low-temperature vacuum dehydration: Use a vacuum degree of 0.3 MPa, the dehydration temperature is 55 °C, and the dehydration time is set to 2 hours.

[0051] Comparative Example 3: Based on the comparison with Example 3, its technical solution is as follows: Raw material composition: Compared with Example 3, reduce the dosage of ethyl acrylate to 20 parts, set sodium acrylate to 30 parts, remove hexadecyl acrylate (only use ethyl acrylate and sodium acrylate), and reduce the amount of sodium allylsulfonate (set to 2 parts). This comparative scheme uses traditional hydrophilic monomers to observe the performance of water reducing agents after removing hydrophobic components.

[0052] Polymerization reaction: Set the reaction kettle temperature to 65 °C, the reaction time to 6 hours, and the stirring speed to 300 rpm to ensure that the polymerization reaction can proceed for a long time and ensure that the monomers react fully.

[0053] Dispersion treatment: Adopt low-speed mechanical stirring for 70 minutes, and do not use ultrasonic dispersion technology. This comparative experiment mainly studies the performance differences between mechanical stirring and ultrasonic dispersion technology.

[0054] Cooling and solvent extraction: Set the washing flow rate to 200 ml / min, the washing duration to 30 minutes, the number of washing times to 2 times, and the interval time to 25 minutes.

[0055] Low-temperature vacuum dehydration: Use a vacuum degree of 0.3 MPa, the dehydration temperature is 50 °C, and the dehydration time is 3 hours.

[0056] Comparative Example 4: Based on the comparison with Example 4, its technical solution is as follows: Raw material composition: Compared with Example 4, this comparative experiment does not contain nano-silica and hexadecyl acrylate, and only uses ethyl acrylate (22 parts), sodium acrylate (26 parts), sodium allylsulfonate (3 parts), and the proportion of sodium persulfate is 1 part. Based on pure polycarboxylic acid materials, the effects of nano-materials and hydrophobic side chains are removed.

[0057] Polymerization reaction: After adding the above solution into the reaction kettle, the temperature is set at 72 °C, the reaction time is 5 hours, and the stirring speed is set at 320 rpm.

[0058] Dispersion treatment: In this comparative experiment, the mechanical stirring method is used, the stirring speed is 250 rpm, the time is 60 minutes, and the ultrasonic dispersion technology is not adopted.

[0059] Cooling and solvent extraction: Cool to 25 °C, the washing flow rate is 250 ml / min, the washing time is 25 minutes, the number of washing times is 3 times, and the interval is 20 minutes after each washing.

[0060] Low-temperature vacuum dehydration: The dehydration temperature is set at 45 °C, the vacuum degree is 0.25 MPa, and the dehydration time is 3 hours.

[0061] Comparative experiment: Experimental procedure: Raw material preparation: According to the formula of each example and comparative example, weigh ethyl acrylate, sodium acrylate, sodium acrylsulfonate, cetyl acrylate, nano-silica, and sodium persulfate. According to the requirements of the experimental design, mix and dissolve the materials in deionized water to ensure the uniformity of the solution. The weight ratio of the materials must be set strictly according to the parameters of the examples and the control group.

[0062] Polymerization reaction: Transfer the prepared solution to the reaction kettle, add sodium persulfate, and fill with nitrogen to ensure an anaerobic environment during the reaction. Set the temperature and stirring speed of the reaction kettle and react according to the requirements of each example. The specific temperature is set between 60 - 70 °C, and the reaction lasts for 4 - 6 hours.

[0063] Ultrasonic dispersion: During the reaction, use ultrasonic equipment to disperse the reaction solution. According to the experimental design, set the ultrasonic power between 100 - 200 W, and the treatment time is 30 - 60 minutes to ensure the uniform distribution of polymer molecular chains.

[0064] Cooling and solvent extraction: After the reaction is completed, gradually cool to room temperature. Wash the reaction solution with deionized water, the washing flow rate is between 200 - 300 ml / min, the washing time is 15 - 30 minutes, the number of washing times is set to 2 - 3 times, and the interval time is 10 - 30 minutes. This process ensures the complete removal of unreacted monomers and by-products.

[0065] Low-temperature vacuum dehydration: The set vacuum degree for the dehydration process is 0.1 - 0.3 MPa, the dehydration temperature is 40 - 60 °C, and the dehydration time is 2 - 4 hours. Residual solvents are removed through low-temperature vacuum dehydration to ensure the final purity and stability of the water reducer.

[0066] Experimental materials: Ethyl acrylate, sodium acrylate, sodium acrylsulfonate, cetyl acrylate, nano-silica (different ratios according to the examples) Sodium persulfate Deionized water, laboratory equipment (reaction kettle, ultrasonic equipment, washing equipment) Specific process: Material ratio, mixing, reaction: According to the experimental requirements, acrylate monomers, nano-silica and other additives are dissolved in deionized water in the specified proportions and stirred evenly.

[0067] Polymerization reaction: The dissolved solution is transferred to a reaction kettle for polymerization reaction, and appropriate reaction temperature, stirring rate and reaction time are maintained.

[0068] Ultrasonic dispersion: The polymer is dispersed by ultrasonic power to ensure uniform distribution of molecular chains and avoid agglomeration.

[0069] Washing and dehydration: After the reaction is completed, it is washed with deionized water, and the solvent is removed by low-temperature vacuum dehydration to ensure the purity of the final product.

[0070] Performance comparison of water reducers in each example and comparative example By comparing the test results of the examples and comparative examples: First of all, the water reducer in the examples shows superior performance in terms of the fluidity of concrete compared with the water reducer in the comparative examples. Specifically, the fluidity of Example 1, Example 2, Example 3 and Example 4 is significantly higher than that of the comparative example. Especially after using nano-silica and ultrasonic dispersion technology, the dispersibility of the water reducer has been significantly improved. This is because nano-silica improves the stability of the polymer chain by increasing the hydrophilicity of the water reducer, while ultrasonic dispersion technology ensures the uniform distribution of the polymer in the cement paste and avoids agglomeration. Therefore, the water reducer in the examples can maintain high fluidity at a lower dosage and meet the high workability requirements of concrete during construction.

[0071] Secondly, compared with the comparative examples, the water reducer in the examples also shows more prominent performance in terms of impermeability. This is mainly due to the introduction of nano-silica. The high specific surface area and surface activity of nano-silica enhance the dispersibility of the water reducer in concrete and further refine the pore structure of the concrete. This significantly improves the impermeability of the concrete. Compared with the formulation without nano-materials in the comparative examples, the concrete in the examples has a stronger ability to resist water penetration. In particular, Examples 3 and 4 show a more significant improvement in impermeability after using nano-silica.

[0072] In addition, the water reducer in the examples not only improves the fluidity and impermeability of the concrete but also shows excellent performance in compressive strength. The compressive strengths of Examples 1 and 2 are 90 MPa and 85 MPa respectively, which are significantly higher than the values of only 75 MPa and 70 MPa in the comparative examples. This improvement in performance is mainly attributed to the addition of nano-silica and the improvement of the dispersion process. The addition of nano-silica not only improves the compactness of the concrete but also increases the bonding strength of the cement matrix, thus effectively enhancing the compressive strength. At the same time, ultrasonic dispersion ensures the uniform distribution of polymer molecules and reduces the generation of internal defects.

[0073] Finally, by introducing ultrasonic dispersion technology, compared with traditional mechanical stirring, the dispersion effect of the polymer in the concrete is significantly improved. The ultrasonic dispersion technology in the examples can evenly distribute the polymer molecular chains in a shorter time, prevent agglomeration, and thus improve the stability and dispersibility of the water reducer. This forms a sharp contrast with the mechanical stirring method in the comparative examples, which is prone to polymer agglomeration and affects the performance of the final product. Specifically, the water reducer in the examples can still maintain good dispersibility at low dosages, enabling the concrete to exhibit high fluidity and stability during construction.

[0074] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A superplasticizer for ultra-high performance concrete (UHPC), characterized in that, The water reducing agent composition comprises the following components in parts by weight: Ethyl acrylate: 20 - 30 parts; Sodium acrylate: 20 - 30 parts; Sodium allylsulfonate: 2 - 5 parts; Hexadecyl acrylate: 10 - 15 parts; Nano-silica: 1 - 2 parts; Auxiliary component: 0.5 - 1.0 part.

2. The superplasticizer for UHPC according to claim 1, characterized in that, The auxiliary component includes: Antioxidant: 0.5 - 1.0 part; Preservative: 0.5 - 1.0 part.

3. Preparation method of superplasticizer for ultra-high performance concrete (UHPC), characterized in that, Using a super high-performance polycarboxylate water reducing agent for UHPC according to any one of claims 1 or 2, the method comprises the following steps: S1. Raw material preparation: Dissolve ethyl acrylate, sodium acrylate, sodium allylsulfonate, hexadecyl acrylate and diene-based peroxide in 50 - 100 parts of water to form a homogeneous solution; S2. Mixing and pre-polymerization: Transfer the above solution to a reaction kettle, add 0.5 - 1.0 part of sodium persulfate, heat under nitrogen protection and start the polymerization reaction; S3. Ultrasonic dispersion: Use ultrasonic treatment equipment to disperse the reaction system during the polymerization process to ensure uniform distribution of molecular chains and avoid agglomeration of polymers; S4. Cooling and water extraction: After the polymerization reaction is completed, gradually cool to 23 - 27 °C, wash with deionized water to remove unreacted monomers and by-products, and ensure the purity of the water reducing agent; S5. Product purification and dehydration: Remove residual water by low-temperature vacuum dehydration to obtain the final product.

4. The preparation method of the superplasticizer for UHPC according to claim 3, characterized in that, The parameters of the reaction kettle include: The stirring speed of the reaction kettle is set to 200 - 400 rpm to ensure uniform mixing of reactants; The temperature at the start of the reaction is set to 60 - 70 °C.

5. The preparation method of the superplasticizer for UHPC according to claim 3, characterized in that, The polymerization reaction includes the following parameters: The reaction time is set to 4 - 6 hours to ensure the completeness of the polymerization reaction; The temperature during the reaction process is maintained at 60 - 70 °C to ensure stable progress of the reaction; During the reaction process, maintain nitrogen protection to ensure an anaerobic environment.

6. The preparation method of the super high performance polycarboxylate water reducer for UHPC according to claim 3, characterized in that, The ultrasonic dispersion includes the following parameters: The ultrasonic power used in the ultrasonic dispersion step is 100 - 200 W; The dispersion treatment time is 30 - 60 minutes to ensure uniform distribution of polymer molecular chains and avoid agglomeration of polymers.

7. The preparation method of the superplasticizer for UHPC according to claim 3, characterized in that, The cooling and water extraction include: Wash with deionized water, the flow rate of the washing water is 200 - 300 ml / min, and the duration is 15 - 30 minutes to ensure thorough removal of by-products and unreacted substances; The number of washing times is 2 - 3 times, and the interval range is 10 - 30 minutes to minimize the concentration of by-products in the reaction solution.

8. The preparation method of the super high performance polycarboxylate water reducing agent for UHPC according to claim 3, characterized in that, The parameters of the low-temperature vacuum dehydration include: The vacuum degree is 0.1 - 0.3 MPa; The dehydration temperature is 40 - 60 °C; The time for vacuum dehydration is between 2 - 4 hours.

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