Zwitterionic concrete internal curing hydrogel based on humidity-pH dual responsiveness and preparation method of zwitterionic concrete internal curing hydrogel

Abstract

The invention discloses zwitterionic concrete internal curing hydrogel based on humidity-pH dual responsiveness and a preparation method of the zwitterionic concrete internal curing hydrogel, and belongs to the technical field of building materials. The water-based cleaning agent is prepared from the following raw material components in percentage by weight: 6%-8% of N-vinyl imidazole, 8%-12% of 2-methylimidazole, 6%-8% of 2-acrylamido-2-methylpropanesulfonic acid, 2%-4% of sodium p-styrenesulfonate, 26%-30% of acrylic acid, 18%-21% of N-vinyl pyrrolidone, 15%-18% of glycidyl methacrylate, 2%-5% of nano montmorillonite powder, 0.05%-0.1% of divinyl benzene, 0.05%-0.15% of N, N-dimethylformamide and the balance of water. The invention discloses an anti-freezing agent which is prepared from the following components in percentage by weight: 0.1%-0.3% of N, N-methylene bisacrylamide, 0.1%-0.3% of 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-ketone, 0.5%-0.8% of ammonium persulfate and 0.5%-0.8% of sodium hydrogen sulfite. Double response to the internal humidity and pH value of the concrete can be achieved, and the requirement for precise internal curing of modern high-performance concrete is met.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, and relates to concrete internal curing materials, specifically to a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response and its preparation method. Background Technology

[0002] Concrete, with its high strength, good plasticity, and excellent durability, has become an indispensable core material in the construction of modern buildings, transportation, water conservancy, and other infrastructure. However, during the hardening process of concrete, shrinkage deformation is inevitable due to factors such as the large amount of water consumed during cement hydration, water loss through evaporation, and changes in internal humidity gradients. Once early shrinkage cracks form, they not only reduce the mechanical properties of concrete but also provide channels for the intrusion of harmful external media (such as chloride ions and sulfates), accelerating the deterioration of the concrete structure and seriously threatening the safety and service life of engineering structures. Statistics show that problems caused by early shrinkage cracks account for more than 60% of various concrete structural defects. Therefore, how to effectively suppress early shrinkage cracks in concrete has become a long-term focus of attention in the materials science and engineering fields.

[0003] The emergence of superabsorbent polymer (SAP) internal curing technology has provided a new approach and method for solving the problem of early shrinkage in concrete. SAP is a type of polymer with a three-dimensional network structure, capable of absorbing tens or even thousands of times its own weight in water and slowly releasing it under appropriate conditions. Incorporating SAP into concrete creates numerous uniformly distributed micro-reservoirs within the concrete. During the concrete hydration process, when the internal humidity decreases, SAP releases the stored water to replenish the water needed for cement hydration, reducing the internal humidity gradient, alleviating shrinkage stress, and thus effectively inhibiting crack formation. Compared to traditional external curing techniques (such as water spraying and covering curing), SAP internal curing technology can provide continuous moisture replenishment from within the concrete, is not limited by the construction environment and curing conditions, and has significant advantages, gradually becoming a research hotspot in the field of concrete crack resistance.

[0004] Despite the significant application potential of SAP (Super Acid-Based Polymer) internal curing technology, traditional SAP internal curing materials widely used in engineering still face numerous unresolved issues. Firstly, their moisture migration behavior is random, making it difficult to precisely release moisture according to different shrinkage stages of concrete and environmental conditions. In the early rapid shrinkage stage of concrete, traditional SAP materials cannot provide sufficient moisture in time, leading to shrinkage cracks; while in the later stages, excessive moisture release may occur, causing localized bleeding and affecting concrete strength and durability. Secondly, the interior of concrete is highly alkaline (pH typically between 12 and 13), and traditional SAP materials have poor compatibility with the complex alkaline environment inside concrete. Under the influence of the "common ion effect," their network structure shrinks rapidly, causing SAP water release disorder and significantly reducing the internal curing effect. Furthermore, traditional SAP materials have limited responsiveness to environmental changes, unable to sense dynamic changes in internal humidity and pH levels of concrete, making intelligent moisture control difficult.

[0005] In recent years, although some studies have attempted to modify SAP materials to improve their performance, most have focused on improving single properties, such as increasing water absorption ratio or enhancing alkali resistance, lacking a comprehensive design to address the complex internal environment of concrete (humidity changes, pH fluctuations, etc.). Existing internal curing materials cannot simultaneously achieve dual responses to humidity and pH, making it difficult to meet the precise internal curing requirements of modern high-performance concrete. Therefore, developing an internal curing material that can intelligently adjust water release behavior based on changes in internal humidity and pH of concrete holds promise for providing a new approach to solving the shortcomings of traditional SAP materials, and has significant theoretical and engineering application value for promoting the high-performance and intelligent development of concrete materials. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention aims to provide a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response and its preparation method, thereby preparing a novel internal curing material that can achieve dual response to internal humidity and pH value of concrete, meeting the needs of precise internal curing of modern high-performance concrete, and solving the above-mentioned technical status and the technical problem of water release disorder in cement concrete during internal curing.

[0007] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which is prepared by weight fraction from the following raw materials: 6%~8% N-vinylimidazolium, 8%~12% 2-methylimidazolium, 6%~8% 2-acrylamido-2-methylpropanesulfonic acid, 2%~4% sodium styrene sulfonate, 26%~30% acrylic acid, 18%~21% N-vinylpyrrolidone, 15%~18% glycidyl methacrylate, 2%~5% nano-montmorillonite powder, 0.05%~0.1% divinylbenzene, 0.05%~0.15% N,N-methylenebisacrylamide, 0.1%~0.3% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 0.5%~0.8% ammonium persulfate and 0.5%~0.8% sodium bisulfite.

[0008] In one embodiment, the N-vinylimidazole is a colorless to pale yellow transparent liquid with a purity ≥99% and a moisture content ≤0.3%; the nano-montmorillonite powder has a particle size of 20~50 nm.

[0009] In one embodiment, the 2-acrylamido-2-methylpropanesulfonic acid is a white crystalline powder with non-volatile matter ≥99.5%, acid value 275±5 mgKOH / g, water content ≤0.5%, and iron ion content ≤0.0005%.

[0010] In one embodiment, the 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one is a grayish-white powder with a molecular weight of 224.3, a melting point of 86~90℃, and absorption peaks of 274 nm and 330 nm in methanol solution.

[0011] In another aspect, this invention provides a method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, comprising the following steps: 2-Acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate were mixed and dissolved in deionized water to prepare mixture A; Acrylic acid was diluted with deionized water in an ice-water bath to obtain a dilute solution. Then, it was neutralized with 2-methylimidazole until the set degree of neutralization was reached. The solution was stirred until completely dissolved to obtain solution B. The photoinitiator 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one was dissolved in deionized water to prepare an aqueous solution C; Under nitrogen and constant temperature water bath conditions, solution B was added dropwise to mixture A. After the addition was completed, N-vinylimidazolium and N-vinylpyrrolidone were added and stirred to obtain mixture D. Add glycidyl methacrylate to mixture D and continue stirring until emulsified. Then add divinylbenzene and N,N-methylenebisacrylamide and continue stirring to obtain mixture E. Nano-montmorillonite powder, sodium bisulfite, and ammonium persulfate were respectively prepared into nano-montmorillonite powder aqueous solution, sodium bisulfite aqueous solution, and ammonium persulfate aqueous solution with tap water. The nano-montmorillonite powder aqueous solution, sodium bisulfite aqueous solution, and ammonium persulfate aqueous solution were added to the mixture E in sequence, with the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution added at a set time interval to obtain the mixture. Under nitrogen protection, an aqueous solution C was added to the mixture, and the reaction was continued under constant temperature water bath to obtain prepolymer hydrogel F; Prepolymer hydrogel F was poured into a polytetrafluoroethylene mold, covered with plastic wrap, and cured by ultraviolet light to obtain hydrogel G. After shearing the hydrogel G, it was soaked in deionized water, then freeze-dried and ground to obtain a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0012] In one embodiment, the mass concentration of 2-acrylamido-2-methylpropanesulfonic acid and sodium styrenesulfonate in the mixture A is 50%.

[0013] In one embodiment, the mass fraction of acrylic acid in the dilute solution is 35%; and the mass fraction of the aqueous solution C is 0.5%.

[0014] In one embodiment, the mass fraction of the nano-montmorillonite powder aqueous solution is 6%, the mass fraction of the sodium bisulfite aqueous solution is 6%, and the mass fraction of the ammonium persulfate aqueous solution is 6%.

[0015] In one embodiment, the set neutralization degree is 60%~70%; the pH of the solution B is 6~7; the constant temperature water bath environment is 30 ℃~35 ℃; the dripping time is 50 min~80 min; and the interval between the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution is set to 2 min~5 min.

[0016] In one embodiment, the wavelength of the ultraviolet light curing is 365 nm, and the power is 100~150 mW / cm². 2 The freezing time is 5~20 min; the freeze-drying temperature is -50℃, the vacuum degree is 10 Pa, and the time is 48 h.

[0017] Compared with the prior art, the present invention has the following beneficial effects: First, the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel provided by this invention constructs a humidity-pH coupled "smart switch" system through the molecular design of a zwitterionic network: the imidazole rings of N-vinylimidazole and 2-methylimidazole undergo deprotonation in the alkaline environment of concrete (pH≈12-13), forming dynamic ion pairs with the sulfonic acid groups of 2-acrylamido-2-methylpropanesulfonic acid and sodium styrenesulfonate. This synergistic regulation of the hydrogel's swelling balance through hydrogen bonding and electrostatic interactions further enhances its ability to absorb water. When the internal humidity of the concrete decreases, the exposure of the network's hydrophilic groups increases, improving water absorption; conversely, when humidity is saturated, the association degree of the ion pairs increases, automatically inhibiting excessive water absorption. This molecular-level synergistic response mechanism solves the problem of "mismatched water release timing and disordered water release" in the complex microenvironment of concrete found in traditional single-response hydrogels, significantly improving the utilization rate of internal curing water. Secondly, this invention innovatively introduces nano-montmorillonite powder into the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel. Through the ring-opening reaction between the interlayer hydroxyl groups and the epoxy groups of glycidyl methacrylate (Mg2+), a three-dimensional network with "organic-inorganic" covalent bonds is formed. This structure not only significantly enhances the strength of the internal curing hydrogel by utilizing the nanosheet effect of montmorillonite, but also slows down the erosion rate of the network by alkaline media through the sheet barrier effect. Simultaneously, the gradient crosslinking design of divinylbenzene (rigid crosslinking) and MBA (flexible crosslinking) enables precise control of the network's elastic modulus, matching the volume deformation requirements of concrete at different ages and reducing the risk of interfacial stress cracking. Then, using 2-acrylamido-2- The "electroneutral zwitterion pair" formed by the strongly ionized sulfonic acid groups of methylpropanesulfonic acid and sodium styrene sulfonate and the imidazole cation significantly improves the stability of the internal curing hydrogel in high-salt environments (such as concrete systems containing chlorides and sulfates) through the "anti-polyelectrolyte effect." This effectively solves the problem of excessively rapid and premature water release from internal curing materials in special environments such as coastal areas and saline-alkali lands. Furthermore, the introduction of N-vinylpyrrolidone, through multiple hydrogen bonds between its lactone ring and water molecules, further broadens the humidity response range, adapting to the curing needs of concrete in different climatic zones. Finally, the entire preparation process of this invention is relatively simple, requiring no professional technical personnel guidance; it can be performed simply by following the description in this invention. Attached Figure Description

[0018] Figure 1 The graph shows the test performance indicators for embodiments and comparative examples of the present invention. Detailed Implementation

[0019] The purpose of this invention is to provide a zwitterionic hydrogel for internal curing of concrete based on humidity-pH dual-responsiveness and its preparation method. This hydrogel is produced by introducing functional groups sensitive to humidity and pH values ​​onto the surface of molecular channels through molecular self-assembly and interface modification technology, endowing the material with humidity-pH dual-responsive characteristics. This curing material not only has high cementitious strength, excellent salt resistance, and maintains structural stability in strongly alkaline (pH>12) and high ion concentration environments of concrete, but also ensures that the strength of the concrete does not decrease, and significantly improves its resistance to ion penetration and freeze-thaw resistance.

[0020] On the one hand, a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response is provided, which, by weight fraction, is composed of the following raw materials: 6%~8% N-vinylimidazolium, 8%~12% 2-methylimidazolium, 6%~8% 2-acrylamido-2-methylpropanesulfonic acid, 2%~4% sodium styrene sulfonate, 26%~30% acrylic acid, 18%~21% N-vinylpyrrolidone, 15%~18% glycidyl methacrylate, 2%~5% nano-montmorillonite powder, 0.05%~0.1% divinylbenzene, 0.05%~0.15% N,N-methylenebisacrylamide (MBA), 0.1%~0.3% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), and 0.5%~0.8% [other ingredients]. Ammonium persulfate, 0.5%~0.8% sodium bisulfite.

[0021] N-vinylimidazole is a colorless to pale yellow transparent liquid with an imidazole group (C3H4N2). - It is a pH-sensitive zwitterionic group, and its protonation degree is affected by both environmental pH and humidity. Its purity is ≥99% and its moisture content is ≤0.3%.

[0022] 2-Acrylamido-2-methylpropanesulfonic acid is a white crystalline powder with a melting point of 185℃. Its molecule contains polymerizable vinyl groups and hydrophilic sulfonic acid groups, allowing it to copolymerize with various monomers. This 2-acrylamido-2-methylpropanesulfonic acid has a non-volatile content ≥99.5%, an acid value of 275±5 mgKOH / g, a water content ≤0.5%, and an iron ion content ≤0.0005%.

[0023] The particle size of nano montmorillonite powder is 20~50 nm. Nano montmorillonite powder contains a large number of hydroxyl groups, has strong hydrophilicity, and is a layered mineral composed of hydrated aluminosilicate. Its cation exchange properties can be used to make montmorillonite organic complexes.

[0024] The crosslinking agent is composed of divinylbenzene and N,N-methylenebisacrylamide.

[0025] 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959) is a photoinitiator, initiated by UV light (365 nm, 100~150 m W / cm²). 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one is a grayish-white powder with a molecular weight of 224.3 and a melting point of 86~90℃. Its absorption peaks in methanol solution are at 274 nm and 330 nm.

[0026] Ammonium persulfate is used as an oxidizing agent and is used in combination with sodium bisulfite as a reducing agent in a 1:1 ratio.

[0027] On the other hand, a method for preparing a humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel is provided. This method uses the formulation of the above-mentioned humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel preparation method, and includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them, and dissolve them in deionized water. The total mass concentration of 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate in the deionized water is 50%, thus obtaining mixture A. Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 60%~70%. During the neutralization process, slowly add 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959) in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a constant temperature water bath at 30~35℃; the dropwise addition time is 50 min~80 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, and stir for 5 min~15 min to obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 15 min to 30 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence. The time interval between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution is 2 min to 5 min. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 30~35℃ for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 100~150 mW / cm²). 2 Irradiate for 5-20 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel.

[0028] Example 1: This embodiment presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which is composed of the following raw materials by weight percentage: 6% N-vinylimidazolium, 12% 2-methylimidazolium, 8% 2-acrylamido-2-methylpropanesulfonic acid, 4% sodium styrene sulfonate, 30% acrylic acid, 21% N-vinylpyrrolidone, 15% glycidyl methacrylate, 2% nano montmorillonite powder, 0.05% divinylbenzene, 0.05% N,N-methylenebisacrylamide (MBA), 0.3% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0029] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 60%. During the neutralization process, slowly add solid 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a 30°C constant temperature water bath environment; the dropwise addition time is 50 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 5 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 15 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 2 min between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 30℃ for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 100 W / cm²). 2 Irradiate for 5 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0030] Example 2: This embodiment presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which is composed of the following raw materials by weight percentage: 8% N-vinylimidazolium, 12% 2-methylimidazolium, 8% 2-acrylamido-2-methylpropanesulfonic acid, 2% sodium styrene sulfonate, 30% acrylic acid, 18% N-vinylpyrrolidone, 18% glycidyl methacrylate, 2% nano montmorillonite powder, 0.05% divinylbenzene, 0.15% N,N-methylenebisacrylamide (MBA), 0.2% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0031] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 70%. During the neutralization process, slowly add solid 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a 35°C constant temperature water bath environment; the dropwise addition time is 80 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 15 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 30 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 5 min between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 35°C for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 150 mW / cm²). 2 Irradiate for 5-20 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0032] Example 3: This embodiment presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which is composed of the following raw materials by weight percentage: 6% N-vinylimidazolium, 8% 2-methylimidazolium, 6% 2-acrylamido-2-methylpropanesulfonic acid, 4% sodium styrene sulfonate, 30% acrylic acid, 21% N-vinylpyrrolidone, 18% glycidyl methacrylate, 5% nano montmorillonite powder, 0.05% divinylbenzene, 0.05% N,N-methylenebisacrylamide (MBA), 0.3% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0033] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 65%. During the neutralization process, slowly add solid 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring at a constant temperature of 32°C in a water bath. The dropwise addition time is 60 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 10 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 25 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 4 min between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 32℃ for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 100~150 mW / cm²). 2 Irradiate for 10 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0034] Example 4: This embodiment presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which is composed of the following raw materials by weight percentage: 8% N-vinylimidazolium, 8% 2-methylimidazolium, 8% 2-acrylamido-2-methylpropanesulfonic acid, 4% sodium styrene sulfonate, 26% acrylic acid, 21% N-vinylpyrrolidone, 18% glycidyl methacrylate, 5% nano montmorillonite powder, 0.05% divinylbenzene, 0.05% N,N-methylenebisacrylamide (MBA), 0.3% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0035] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 70%. During the neutralization process, slowly add solid 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a 30°C constant temperature water bath environment; the dropwise addition time is 60 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 12 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 30 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 5 min between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 34℃ for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 120 mW / cm²). 2 Irradiate for 15 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0036] Example 5: This embodiment presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which is composed of the following raw materials by weight percentage: 8% N-vinylimidazolium, 12% 2-methylimidazolium, 8% 2-acrylamido-2-methylpropanesulfonic acid, 2% sodium styrene sulfonate, 30% acrylic acid, 18% N-vinylpyrrolidone, 18% glycidyl methacrylate, 2% nano montmorillonite powder, 0.1% divinylbenzene, 0.1% N,N-methylenebisacrylamide (MBA), 0.2% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0037] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 60%. During the neutralization process, slowly add solid 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring at a constant temperature of 34°C in a water bath. The dropwise addition time is 70 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 12 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 20 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 3 minutes between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 35°C for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 140 mW / cm²). 2 Irradiate for 8 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0038] Example 6: This embodiment presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which is composed of the following raw materials by weight percentage: 8% N-vinylimidazolium, 12% 2-methylimidazolium, 8% 2-acrylamido-2-methylpropanesulfonic acid, 2% sodium styrene sulfonate, 30% acrylic acid, 18% N-vinylpyrrolidone, 18% glycidyl methacrylate, 2.7% nano montmorillonite powder, 0.1% divinylbenzene, 0.1% N,N-methylenebisacrylamide (MBA), 0.1% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.5% ammonium persulfate, and 0.5% sodium bisulfite.

[0039] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 70%. During the neutralization process, slowly add solid 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a 30°C constant temperature water bath environment; the dropwise addition time is 60 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 12 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 30 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 3 minutes between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 30℃ for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 150 mW / cm²). 2 Irradiate for 10 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0040] Example 7: This embodiment presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which is composed of the following raw materials by weight percentage: 6% N-vinylimidazolium, 8% 2-methylimidazolium, 7% 2-acrylamido-2-methylpropanesulfonic acid, 3.8% sodium styrene sulfonate, 30% acrylic acid, 21% N-vinylpyrrolidone, 18% glycidyl methacrylate, 5% nano montmorillonite powder, 0.05% divinylbenzene, 0.05% N,N-methylenebisacrylamide (MBA), 0.1% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.5% ammonium persulfate, and 0.5% sodium bisulfite.

[0041] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 65%. During the neutralization process, slowly add solid 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a 30°C constant temperature water bath environment; the dropwise addition time is 60 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 15 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 15 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 2 min between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 35°C for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 150 mW / cm²). 2 Irradiate for 10 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0042] Example 8: This embodiment presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, comprising the following raw materials by weight percentage: 7% N-vinylimidazolium, 9% 2-methylimidazolium, 8% 2-acrylamido-2-methylpropanesulfonic acid, 3% sodium styrene sulfonate, 30% acrylic acid, 20% N-vinylpyrrolidone, 18% glycidyl methacrylate, 3% nano-montmorillonite powder, 0.05% divinylbenzene, 0.15% N,N-methylenebisacrylamide (MBA), 0.2% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0043] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 60%. During the neutralization process, slowly add solid 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a 30°C constant temperature water bath environment; the dropwise addition time is 50 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 15 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 25 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 5 min between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 30℃ for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 100 mW / cm²). 2 Irradiate for 8 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0044] Example 9: This embodiment presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which is composed of the following raw materials by weight percentage: 7% N-vinylimidazolium, 10% 2-methylimidazolium, 7% 2-acrylamido-2-methylpropanesulfonic acid, 3.7% sodium styrene sulfonate, 28% acrylic acid, 20% N-vinylpyrrolidone, 17.4% glycidyl methacrylate, 5% nano montmorillonite powder, 0.08% divinylbenzene, 0.12% N,N-methylenebisacrylamide (MBA), 0.3% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.7% ammonium persulfate, and 0.7% sodium bisulfite.

[0045] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 70%. During the neutralization process, slowly add solid 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring at a constant temperature of 35°C in a water bath. The dropwise addition time is 70 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 13 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 20 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 4 minutes between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 35°C for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 100~150 mW / cm²). 2 Irradiate for 13 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0046] Comparative Example 1: This comparative example presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, comprising the following raw materials by weight percentage: 12% 2-methylimidazole, 8% 2-acrylamido-2-methylpropanesulfonic acid, 4% sodium styrene sulfonate, 30% acrylic acid, 21% N-vinylpyrrolidone, 18% glycidyl methacrylate, 5% nano-montmorillonite powder, 0.05% divinylbenzene, 0.05% N,N-methylenebisacrylamide (MBA), 0.3% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0047] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 60%. During the neutralization process, slowly add solid 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a 30°C constant temperature water bath environment; the dropwise addition time is 50 min. After the dropwise addition is completed, add the weighed N-vinylpyrrolidone, stir for 5 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 15 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 2 min between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 30℃ for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 100 W / cm²). 2 Irradiate for 5 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel.

[0048] Comparative Example 2: This comparative example presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, comprising the following raw materials by weight percentage: 8% N-vinylimidazolium, 8% 2-acrylamido-2-methylpropanesulfonic acid, 4% sodium styrene sulfonate, 34% acrylic acid, 21% N-vinylpyrrolidone, 18% glycidyl methacrylate, 5% nano-montmorillonite powder, 0.05% divinylbenzene, 0.15% N,N-methylenebisacrylamide (MBA), 0.2% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0049] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), and dilute it with deionized water to a 35% (w / w) dilute solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a 35°C constant temperature water bath environment; the dropwise addition time is 80 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 15 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 30 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 5 min between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 35°C for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 150 mW / cm²). 2 Irradiate for 5-20 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0050] Comparative Example 3: This comparative example presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which, by weight percentage, comprises the following raw materials: 8% 2-acrylamido-2-methylpropanesulfonic acid, 4% sodium styrene sulfonate, 42% acrylic acid, 21% N-vinylpyrrolidone, 18% glycidyl methacrylate, 5% nano-montmorillonite powder, 0.05% divinylbenzene, 0.15% N,N-methylenebisacrylamide (MBA), 0.2% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0051] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), and dilute it with deionized water to a 35% (w / w) dilute solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring at a constant temperature of 32°C in a water bath. The dropwise addition time is 60 min. After the dropwise addition is completed, add the weighed N-vinylpyrrolidone and stir for 10 min to obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 25 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 4 min between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 35°C for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 100~150 mW / cm²). 2 Irradiate for 10 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0052] Comparative Example 4: This comparative example presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which, by weight percentage, comprises the following raw materials: 8% N-vinylimidazolium, 8% 2-methylimidazolium, 4% sodium styrene sulfonate, 30% acrylic acid, 25% N-vinylpyrrolidone, 18% glycidyl methacrylate, 5% nano-montmorillonite powder, 0.05% divinylbenzene, 0.05% N,N-methylenebisacrylamide (MBA), 0.3% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0053] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Dissolve the weighed sodium styrene sulfonate in deionized water to a mass concentration of 50% to obtain mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 70%. During the neutralization process, slowly add MI solid and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a 30°C constant temperature water bath environment; the dropwise addition time is 60 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 12 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 30 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 5 min between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 34℃ for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 120 mW / cm²). 2 Irradiate for 15 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0054] Comparative Example 5: This comparative example presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, comprising the following raw materials by weight percentage: 6% N-vinylimidazolium, 8% 2-methylimidazolium, 6% 2-acrylamido-2-methylpropanesulfonic acid, 30% acrylic acid, 25% N-vinylpyrrolidone, 18% glycidyl methacrylate, 5% nano-montmorillonite powder, 0.05% divinylbenzene, 0.05% N,N-methylenebisacrylamide (MBA), 0.3% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0055] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Dissolve the weighed 2-acrylamido-2-methylpropanesulfonic acid in deionized water to a mass concentration of 50% to obtain mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 70%. During the neutralization process, slowly add MI solid and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a 30°C constant temperature water bath environment; the dropwise addition time is 60 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 12 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 30 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture E in sequence, with an interval of 3 minutes between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 32℃ for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 150 mW / cm²). 2 Irradiate for 10 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0056] Comparative Example 6: This comparative example presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, which, by weight percentage, comprises the following raw materials: 8% N-vinylimidazolium, 12% 2-methylimidazolium, 38% acrylic acid, 20% N-vinylpyrrolidone, 18% glycidyl methacrylate, 2% nano-montmorillonite powder, 0.1% divinylbenzene, 0.1% N,N-methylenebisacrylamide (MBA), 0.2% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0057] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 70%. During the neutralization process, slowly add solid 2-methylimidazole and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution A; Step 3: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution B; Step 4: Transfer the mixture A into a four-necked flask, purge with nitrogen, and in a constant temperature water bath at 30°C, while continuously stirring, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, and stir for 12 minutes to obtain mixture C. Step 5: Slowly add glycidyl methacrylate to mixture C. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 30 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture D. Step 6: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture D in sequence, with an interval of 3 minutes between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 7: Under nitrogen protection, add aqueous solution B to the mixture obtained in step 6, and continue stirring and reacting in a constant temperature water bath at 30°C for 30 min to obtain prepolymer hydrogel F; Step 8: Pour the prepolymer hydrogel E into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 150 mW / cm²).2 Irradiate for 10 minutes until completely solidified to obtain hydrogel F.

[0058] Step 9: Remove the hydrogel F and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel.

[0059] Comparative Example 7: This comparative example presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, comprising the following raw materials by weight percentage: 7% N-vinylimidazolium, 10% 2-methylimidazolium, 7% 2-acrylamido-2-methylpropanesulfonic acid, 3.7% sodium styrene sulfonate, 48% N-vinylpyrrolidone, 17.4% glycidyl methacrylate, 5% nano-montmorillonite powder, 0.08% divinylbenzene, 0.12% N,N-methylenebisacrylamide (MBA), 0.3% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.7% ammonium persulfate, and 0.7% sodium bisulfite.

[0060] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution B; Step 4: Transfer the mixture A into a four-necked flask, purge with nitrogen, and slowly add 2-methylimidazole while continuously stirring in a 30°C constant temperature water bath; then add the weighed N-vinylimidazole and N-vinylpyrrolidone, stir for 15 min to obtain mixture C; Step 5: Slowly add glycidyl methacrylate to mixture C. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 15 minutes until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 minutes to obtain mixture D. Step 6: Prepare 6% (w / w) aqueous solutions of nano-montmorillonite powder, sodium bisulfite and ammonium persulfate with tap water. Then, add the nano-montmorillonite powder, sodium bisulfite and ammonium persulfate aqueous solution to the mixture D in sequence, with an interval of 2 min between adding the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution. Step 7: Under nitrogen protection, add aqueous solution B to the mixture obtained in step 6, and continue stirring and reacting in a constant temperature water bath at 35°C for 30 min to obtain prepolymer hydrogel E; Step 8: Pour the prepolymer hydrogel E into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 150 mW / cm²). 2 Irradiate for 10 minutes until completely solidified to obtain hydrogel F.

[0061] Step 9: Remove the hydrogel F and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0062] Comparative Example 8: This comparative example presents a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response, comprising the following raw materials by weight percentage: 7% N-vinylimidazolium, 11% 2-methylimidazolium, 8% 2-acrylamido-2-methylpropanesulfonic acid, 3% sodium styrene sulfonate, 30% acrylic acid, 21% N-vinylpyrrolidone, 18% glycidyl methacrylate, 0.05% divinylbenzene, 0.15% N,N-methylenebisacrylamide (MBA), 0.2% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), 0.8% ammonium persulfate, and 0.8% sodium bisulfite.

[0063] The above-mentioned method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response includes the following steps: Step 1: Weigh the above raw materials according to their weight; Step 2: Weigh out 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate, mix them and dissolve them in deionized water to obtain a mass concentration of 50% to prepare mixture A; Step 3: Place the weighed acrylic acid in an ice-water bath (to prevent self-polymerization), dilute it with deionized water to a 35% mass fraction solution, and then neutralize it with 2-methylimidazole to a neutralization degree of 60%. During the neutralization process, slowly add MI solid and stir until completely dissolved (solution pH=6~7, monitored with a pH meter) to obtain solution B; Step 4: Dissolve the weighed photoinitiator Irgacure 2959 in deionized water to prepare a 0.5% aqueous solution C; Step 5: Transfer solution A to a four-necked flask, purge with nitrogen, and slowly add solution B dropwise while continuously stirring in a 30°C constant temperature water bath environment; the dropwise addition time is 50 min. After the dropwise addition is completed, add the weighed N-vinylimidazolium and N-vinylpyrrolidone, stir for 15 min, and obtain solution D. Step 6: Slowly add glycidyl methacrylate to mixture D. The solution may become slightly turbid at this time (glycidyl methacrylate is partially hydrophobic). Continue stirring for 25 min until emulsified. Then, add divinylbenzene and MBA, and continue stirring for 10 min to obtain mixture E. Step 7: Prepare 6% (w / w) aqueous solutions of sodium bisulfite and ammonium persulfate separately with tap water. Then, add the sodium bisulfite and ammonium persulfate aqueous solutions to the mixture E in sequence, with an interval of 5 min between adding the sodium bisulfite and ammonium persulfate aqueous solutions. Step 8: Under nitrogen protection, add aqueous solution C to the mixture obtained in step 7, and continue stirring and reacting in a constant temperature water bath at 35°C for 30 min to obtain prepolymer hydrogel F; Step 9: Pour the prepolymer hydrogel F into a polytetrafluoroethylene mold, cover the surface with plastic wrap (to prevent moisture evaporation), and place it under a UV lamp (wavelength 365 nm, power 100 mW / cm²). 2 Irradiate for 8 minutes until completely cured to obtain hydrogel G; Step 10: Remove the hydrogel G and cut it into 1cm pieces. 3 Small pieces were soaked in deionized water for 24 hours, with the water changed every 6 hours to remove unreacted monomers and small molecule impurities. They were then freeze-dried (-50℃, vacuum degree 10Pa) for 48 hours and ground into powder to obtain the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

[0064] Performance testing In use, the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel is directly ground to 150-250 mesh, and then added to the mixing equipment along with cement and other cementitious materials. The maximum liquid absorption ratio of the curing material in saturated Ca(OH)2 solution, as well as the compressive strength ratio and 28-day shrinkage ratio (compared to the baseline group) of the concrete after incorporation are tested according to the requirements of JC901-2002 "Cement Concrete Curing Agent", JT / T522-2004 "Highway Engineering Concrete Curing Agent", and "Test Procedures for Cement and Cement Concrete in Highway Engineering" (JTG / E30-2005). The dosage is 0.2% of the cementitious material dosage. The stability of the internal curing hydrogel is determined by immersing the sample in a NaOH solution with pH=13 for 7 days, maintaining a solution volume to sample mass ratio of 20:1 during immersion, and changing the solution every 24 hours to ensure stable solution concentration. After soaking, the sample was removed and rinsed repeatedly with deionized water, then vacuum dried at 60℃ to constant weight. The mass loss rate was calculated; a lower mass loss rate indicates better material stability in an alkaline environment. The humidity-pH dual-response test involved incorporating the novel internal curing hydrogel into the concrete mixture to observe whether it caused localized water bleeding.

[0065] Specific performance indicators are as follows: Figure 1As shown in the above embodiments and Figure 1, the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel not only significantly improves the mechanical strength of concrete but also exhibits excellent stability in strongly alkaline solutions. In the nine embodiments, the maximum liquid absorption ratio of the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel in saturated Ca(OH)2 solution was greater than 105 g / g. Compared with the comparative example, the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel in the comparative example showed stronger stability in strongly alkaline solutions. Furthermore, the addition of the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel in the nine embodiments significantly improved the 7-day and 28-day compressive strength of concrete, especially at 28 days. The increase in compressive strength of d was over 10% in all nine examples, and the shrinkage rate was no higher than 30%. Furthermore, in all nine examples, the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel exhibited water bleeding in the concrete mixture. Compared to the comparative examples, the examples showed good humidity-pH dual-responsiveness and stability in an alkaline environment. This indicates that the absence of materials or changes in the proportions, especially the simultaneous absence of N-vinylimidazole and 2-methylimidazole, significantly affected the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel's humidity-pH sensitivity. The absence of some organic monomers and nano-montmorillonite powder also had a significant impact on the saturated liquid absorption performance, shrinkage performance, mechanical properties, and stability in an alkaline environment of the humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel. Therefore, this humidity-pH dual-responsive zwitterionic concrete internal curing hydrogel exhibits good liquid absorption characteristics and stability in alkaline solutions. It can also improve the early bleeding status of concrete by providing good humidity-pH dual-responsiveness, and can also greatly reduce the autogenous shrinkage of concrete. It also has good applicability and is expected to provide a new way to solve the defects of traditional SAP materials. It has important theoretical significance and engineering application value for promoting the high-performance and intelligent development of concrete materials.

[0066] This invention provides a humidity-pH dual-responsive zwitterionic hydrogel for internal curing of concrete and its preparation method. First, a humidity-pH coupled-response "smart switch" system is constructed. The imidazole rings of N-vinylimidazolium and 2-methylimidazolium are deprotonated in the alkaline environment of concrete, forming dynamic ion pairs with the sulfonic acid groups of 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate. The swelling balance of the hydrogel is synergistically regulated through hydrogen bonding and electrostatic interactions. Next, nano-montmorillonite powder is introduced, and its interlayer hydroxyl groups react with the epoxy groups of glycidyl methacrylate to form a ring-opening reaction, creating a three-dimensional network framework with "organic-inorganic" covalent bonds. Organic monomers such as acrylic acid and N-vinylpyrrolidone undergo continuous graft polymerization under the action of initiators and crosslinking agents. After the reaction, the product is dehydrated, dried, and screened to obtain the humidity-pH dual-responsive zwitterionic hydrogel for internal curing of concrete. The humidity-pH dual-responsive zwitterionic concrete curing hydrogel prepared by this invention improves the alkali resistance and significantly enhances the compressive strength and shrinkage performance of concrete. The 28-day compressive strength of the concrete is more than 110% of the benchmark concrete strength, and the shrinkage rate is no higher than 30%. In addition, it can achieve good humidity-pH dual-responsiveness, thereby improving the early bleeding condition of concrete.

[0067] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A zwitterionic hydrogel for internal curing of concrete based on humidity-pH dual response, characterized in that, It is prepared from the following components by weight fraction: 6%~8% N-vinylimidazolium, 8%~12% 2-methylimidazolium, 6%~8% 2-acrylamido-2-methylpropanesulfonic acid, 2%~4% sodium styrene sulfonate, 26%~30% acrylic acid, 18%~21% N-vinylpyrrolidone, 15%~18% glycidyl methacrylate, 2%~5% nano montmorillonite powder, 0.05%~0.1% divinylbenzene, 0.05%~0.15% N,N-methylenebisacrylamide, 0.1%~0.3% 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 0.5%~0.8% ammonium persulfate, and 0.5%~0.8% sodium bisulfite.

2. The zwitterionic concrete internal curing hydrogel based on humidity-pH dual response according to claim 1, characterized in that, The N-vinylimidazole is a colorless to pale yellow transparent liquid with a purity ≥99% and a moisture content ≤0.3%; the nano-montmorillonite powder has a particle size of 20~50 nm.

3. The zwitterionic concrete internal curing hydrogel based on humidity-pH dual response according to claim 1, characterized in that, The 2-acrylamido-2-methylpropanesulfonic acid is a white crystalline powder with non-volatile matter ≥99.5%, acid value 275±5 mgKOH / g, water content ≤0.5%, and iron ion content ≤0.0005%.

4. The zwitterionic concrete internal curing hydrogel based on humidity-pH dual response according to claim 1, characterized in that, The 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one is a grayish-white powder with a molecular weight of 224.3, a melting point of 86~90℃, and absorption peaks of 274 nm and 330 nm in methanol solution.

5. A method for preparing a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response as described in any one of claims 1 to 4, characterized in that, Includes the following steps: 2-Acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate were mixed and dissolved in deionized water to prepare mixture A; Acrylic acid was diluted with deionized water in an ice-water bath to obtain a dilute solution. Then, it was neutralized with 2-methylimidazole until the set degree of neutralization was reached. The solution was stirred until completely dissolved to obtain solution B. The photoinitiator 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one was dissolved in deionized water to prepare an aqueous solution C; Under nitrogen and constant temperature water bath conditions, solution B was added dropwise to mixture A. After the addition was completed, N-vinylimidazolium and N-vinylpyrrolidone were added and stirred to obtain mixture D. Add glycidyl methacrylate to mixture D and continue stirring until emulsified. Then add divinylbenzene and N,N-methylenebisacrylamide and continue stirring to obtain mixture E. Nano-montmorillonite powder, sodium bisulfite, and ammonium persulfate were respectively prepared into nano-montmorillonite powder aqueous solution, sodium bisulfite aqueous solution, and ammonium persulfate aqueous solution with tap water. The nano-montmorillonite powder aqueous solution, sodium bisulfite aqueous solution, and ammonium persulfate aqueous solution were added to the mixture E in sequence, with the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution added at a set time interval to obtain the mixture. Under nitrogen protection, an aqueous solution C was added to the mixture, and the reaction was continued under constant temperature water bath to obtain prepolymer hydrogel F; Prepolymer hydrogel F was poured into a polytetrafluoroethylene mold, covered with plastic wrap, and cured by ultraviolet light to obtain hydrogel G. After shearing the hydrogel G, it was soaked in deionized water, then freeze-dried and ground to obtain a zwitterionic concrete internal curing hydrogel based on humidity-pH dual response.

6. The method for preparing the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response according to claim 5, characterized in that, The mass concentration of 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate in the mixture A is 50%.

7. The method for preparing the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response according to claim 5, characterized in that, The mass fraction of acrylic acid in the dilute solution is 35%; the mass fraction of the aqueous solution C is 0.5%.

8. The method for preparing the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response according to claim 5, characterized in that, The mass fraction of the nano-montmorillonite powder aqueous solution is 6%, the mass fraction of the sodium bisulfite aqueous solution is 6%, and the mass fraction of the ammonium persulfate aqueous solution is 6%.

9. The method for preparing the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response according to claim 5, characterized in that, The set neutralization degree is 60%~70%; the pH of solution B is 6~7; the constant temperature water bath environment is 30 ℃~35 ℃; the dropping time is 50 min~80 min; the interval between the sodium bisulfite aqueous solution and the ammonium persulfate aqueous solution is set to 2 min~5 min.

10. The method for preparing the zwitterionic concrete internal curing hydrogel based on humidity-pH dual response according to claim 5, characterized in that, The ultraviolet light curing wavelength is 365 nm, and the power is 100~150 mW / cm². 2 The freezing time is 5~20 min; the freeze-drying temperature is -50℃, the vacuum degree is 10 Pa, and the time is 48 h.

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