Preparation method of low-alkali accelerator based on pH / ion double-response type microgel

Abstract

The invention relates to a preparation method of a low-alkali accelerator based on pH / ion double-response microgel, which comprises the following steps: introducing nitrogen into a water / ethanol mixed solvent to remove oxygen, sequentially adding a hydrophilic monomer, a pH response monomer, a calcium ion response monomer and a hydrophobic synergistic monomer, stirring for dissolving, adding an RAFT (reversible addition-fragmentation chain transfer) reagent and an initiator, and stirring for reacting to obtain the low-alkali accelerator based on pH / ion double-response microgel. After the reaction is finished, carrying out post-treatment to obtain pH / ion double-response type microgel; a coagulation accelerating component solution is obtained; and adding the pH / ion double-response type microgel into the coagulating component solution to obtain the low-alkali accelerator based on the pH / ion double-response type microgel. The low-alkali coagulation accelerating component and the pH / ion double-response type microgel are adopted as core components, a large amount of free water in slurry can be adsorbed, the viscosity of the slurry is sharply increased, the coagulation and hardening time of the concrete is shortened, the rebound rate of the concrete is reduced, and the stability of the concrete is improved. The moisture absorbed by the microgel is slowly released according to the change of the internal humidity of the concrete after the concrete is hardened, so that accurate internal curing is realized, the shrinkage of the concrete is reduced, and the strength and durability of the concrete are improved.

Description

Technical Field

[0001] This invention relates to the technical field of concrete admixtures, and in particular to a method for preparing a low-alkali quick-setting agent based on a pH / ion dual-responsive microgel. Background Technology

[0002] Shotcrete, as a key building material, is widely used in numerous engineering fields such as tunnel support, slope reinforcement, and emergency repairs. During construction, accelerators, as core admixtures, play a crucial role, rapidly inducing cement hydration to achieve quick concrete setting. However, traditional accelerators, due to their high alkalinity, not only pose a potential risk of burns to construction workers but also easily trigger alkali-aggregate reactions, thus reducing concrete durability. Furthermore, during shotcreting, the slow setting speed and high rebound rate lead to significant material waste. Although low-alkali accelerators have emerged on the market, while reducing alkalinity to some extent, they still suffer from problems such as insufficient early strength.

[0003] To ensure smooth shotcrete application, excess water is typically added to the concrete to maintain its fluidity. However, this reduces the concrete's cohesiveness, leading to increased rebound, slower setting and hardening, and decreased early strength. After hardening, the evaporation of excess water causes volume shrinkage, making the concrete prone to cracking. Traditional water-curing methods cannot replenish water in a timely manner according to the dynamic changes in the concrete's internal moisture, thus failing to effectively solve this problem. Currently, internal curing agents (such as superabsorbent polymeric resins, SAP) are used to store and slowly release moisture, reducing concrete shrinkage. However, SAP is usually added during concrete mixing, and its high absorbency affects the fluidity of fresh concrete. To ensure smooth pumping and shotcreting, additional water needs to be added, resulting in a decrease in concrete strength. Therefore, there is an urgent need to develop a new type of accelerator that simultaneously possesses both rapid-setting and self-curing functions to address the synergy issues between accelerators and internal curing agents, thereby significantly improving the construction efficiency and durability of shotcrete. Summary of the Invention

[0004] The problem this invention aims to solve is to provide a method for preparing a low-alkali accelerator based on a pH / ion dual-responsive microgel, addressing the aforementioned shortcomings of existing technologies. This method utilizes a low-alkali accelerator component and a pH / ion dual-responsive microgel as core components. In an acidic low-alkali accelerator solution, the pH / ion dual-responsive microgel, due to the protonation of its functional groups and the action of hydrophilic groups, exhibits an extended molecular chain state, dissolving and dispersing in the solution. During concrete spraying, when the accelerator is mixed with the concrete slurry, the high pH and high Ca content of the slurry further enhances its effectiveness. 2+In an ionic environment, the dissolved microgel components are deprotonated in the alkaline solution, driving the collapse of the extended molecular chains. Some groups also form strong complexes with calcium ions, creating a three-dimensional microgel network that cross-links intramolecularly or intermolecularly. This network can adsorb a large amount of free water in the slurry, causing a sharp increase in the viscosity of the slurry. This shortens the setting and hardening time of the concrete, reduces the rebound rate of the concrete, and allows the water absorbed by the microgel to be slowly released after the concrete has hardened, based on changes in the internal humidity of the concrete. This achieves precise internal curing, reduces the shrinkage of the concrete, and improves the strength and durability of the concrete.

[0005] The above-mentioned objective of this invention is achieved through the following technical solutions: A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgel includes the following steps: S1 First, a water / ethanol mixed solvent was deoxygenated by purging nitrogen gas at 30-50℃ for 30-60 min. Then, hydrophilic monomers, pH-responsive monomers, calcium ion-responsive monomers, and hydrophobic co-responsive monomers were added sequentially. After stirring and dissolving, RAFT reagent and initiator were added, and the pH was adjusted to 4.0-6.0. The temperature was raised to 60-80℃, and the reaction was carried out in a nitrogen atmosphere for 5-10 h, while maintaining a stirring speed of 200-400 rpm. After the reaction was completed, post-treatment was performed to obtain pH / ion dual-responsive microgels. S2 first preheats the water to 50~60℃, then adds the low-alkali coagulant component and the organic alcohol amine coagulant component, disperses them by ultrasonication, and then cools them down to 20~30℃ to obtain the coagulant component solution; S3. Add the pH / ion dual-responsive microgel obtained in S1 to the coagulation-promoting component solution obtained in S2, adjust the pH to 4.0~6.0, and stir for 0.5~1.0h to obtain a low-alkali rapid coagulating agent based on pH / ion dual-responsive microgel.

[0006] Further, in S1, the mass ratio of the hydrophilic monomer, pH-responsive monomer, calcium ion-responsive monomer, hydrophobic co-responsive monomer, RAFT reagent and initiator is controlled to be 35~70:10~40:10~25:1~10:0.20~0.6:0.12~0.60.

[0007] Furthermore, in S1, the ethanol mass concentration of the mixed solvent is controlled to be 10-40%.

[0008] Furthermore, in S1, the mass ratio of the mixed solvent to the monomer is 1.0~3.0:1.0, and the monomer is a hydrophilic monomer, a pH-responsive monomer, a calcium ion-responsive monomer, and a hydrophobic co-monomer.

[0009] Furthermore, in S1, the hydrophilic monomer is one or a combination of several of acrylamide, N-isopropylacrylamide, N-hydroxyethylacrylamide, N-hydroxymethylacrylamide, and N-vinylpyrrolidone; The pH-responsive monomer is one or a combination of several of N,N-dimethylaminoethyl methacrylate, 3-(N,N-dimethylamino)ethyl methacrylate, and dimethylaminoethyl acrylate. The calcium ion responsive monomer is one or a combination of several of the following: hydroxyethyl methacrylate phosphate, diethyl allyl phosphate, acrylic acid, and methacrylic acid. The hydrophobic synergistic monomer is one or more of butyl methacrylate and methyl methacrylate; The RAFT reagent is one or a combination of several of the following: 4-cyano-4-(phenylthiocarboxylthio)pentanoic acid, 4-cyano-4-(dodecylthioalkylthiocarbonyl)thiopentanoic acid, and 2-(dodecyltrithiocarbonate)-2-methylpropionic acid. The initiator is one or a combination of several of 4,4'-azobis(4-cyanopentanoic acid), ammonium persulfate, and potassium persulfate.

[0010] Furthermore, in S2, the mass percentage of the low-alkali coagulant component, the organic alcohol amine coagulant component, and water is controlled to be 38~60:2~10:30~60.

[0011] Furthermore, in S2, the low-alkali coagulating component consists of sodium aluminate and inorganic aluminum compounds in a mass ratio of 20-40:60-80.

[0012] Furthermore, in S2, the inorganic aluminum compound is one or a combination of several of aluminum sulfate, polyaluminum sulfate, and nano-alumina; The organic alcohol amine coagulant component is one or more of diethanolamine, triethanolamine and N-methylethanolamine.

[0013] Furthermore, in S1 and S3, the pH adjuster is one or a combination of several of phosphoric acid, citric acid, lactic acid and oxalic acid.

[0014] Furthermore, in S3, the mass ratio of pH / ion dual-responsive microgel to coagulation-promoting component solution is controlled to be 5~15:85~95.

[0015] In summary, the beneficial technical effects of the present invention are as follows: 1. The novel low-alkali quick-setting agent of the present invention has a lower alkalinity than traditional products, which can effectively reduce the possibility of alkali-aggregate reaction, thereby improving the long-term stability of concrete structures and ensuring the durability and safety of buildings. 2. The novel low-alkali quick-setting agent of this invention is in solution form and is mixed with concrete slurry during concrete spraying. It is effective in situations where the cement slurry is high in alkali and high in calcium. 2+ In an ionic environment, the dissolved polymer is triggered to respond, undergoing a molecular conformational change and ion complexation. The dissolved polymer is rapidly transformed into an intramolecularly cross-linked microgel structure, which can quickly absorb excess free water in the concrete, thereby significantly increasing the viscosity of the concrete and promoting rapid setting of the concrete. This effectively reduces the rebound rate and meets the stringent requirements of engineering construction such as shotcrete. 3. In the novel low-alkali quick-setting agent of the present invention, the pH / ion dual-responsive microgel can form a microgel with high water absorption in cement alkali solution. This gel can continue to provide curing effect after the concrete has hardened. By reducing water evaporation, it promotes the later hydration process of cement, thereby reducing the shrinkage rate of concrete and improving the strength and durability of concrete, thus ensuring the long-term performance of concrete structures. Detailed Implementation

[0016] To make the technical means, creative features, objectives and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0017] Example 1: A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgels, comprising the following steps: In S1, 160g of deionized water and 40g of anhydrous ethanol were stirred evenly in a 40℃ water bath, and nitrogen gas was purged for 30 min to remove oxygen. Then, 48g of acrylamide, 40g of N,N-dimethylaminoethyl methacrylate, 19g of hydroxyethyl methacrylate phosphate, and 3g of butyl methacrylate were added sequentially, and stirred until completely dissolved. 0.6g of 4-cyano-4-(phenylthiocarbamoylthio)valerate and 0.3g of 4,4'-azobis(4-cyanopentanoic acid) were added, and the pH of the reaction solution was adjusted to 5.0 with citric acid. The temperature was then raised to 70℃, and the reaction was carried out for 8 h under a nitrogen atmosphere, with a stirring speed of 300 rpm. After the reaction was completed, the reaction solution was quickly poured into liquid nitrogen and frozen. After reconstitution, the crude product was added dropwise to acetone, and a white fibrous precipitate was formed. The precipitate was filtered, washed three times with acetone, and freeze-dried to obtain a pH / ion dual-responsive microgel. S2 heats 250g of deionized water to 55℃, then adds 70g of sodium aluminate, 165g of aluminum sulfate and 15g of triethanolamine, and disperses them by ultrasonication until dissolved, then cools them to 20℃ to obtain a coagulation-promoting component solution. S3 added 50g of the pH / ion dual-responsive microgel obtained in S1 to 500g of the coagulation-promoting component solution prepared in S2, and added citric acid to adjust the pH of the solution to 5.5. After stirring for 1.0h, a low-alkali rapid coagulating agent based on the pH / ion dual-responsive microgel was obtained.

[0018] Example 2: A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgels, comprising the following steps: In a 40°C water bath, 160g of deionized water and 40g of anhydrous ethanol were stirred until homogeneous. Nitrogen gas was purged for 30 minutes to remove oxygen. Then, 48g of N-hydroxyethyl acrylamide, 40g of ethyl 3-(N,N-dimethylamino)acrylate, 19g of diethyl allyl phosphate, and 3g of methyl methacrylate were added sequentially, and stirred until completely dissolved. 0.6g of 4-cyano-4-(phenylthiocarbamoylthio)valerate and 0.3g of 4,4'-azobis(4-cyanopentanoic acid) were added, and the pH of the reaction solution was adjusted to 5.0 with citric acid. The temperature was then raised to 70°C, and the reaction was carried out for 8 hours under a nitrogen atmosphere, maintaining a stirring speed of 300 rpm. After the reaction was complete, the reaction solution was quickly poured into liquid nitrogen and frozen. After reconstitution, the crude product was added dropwise to acetone, resulting in a white fibrous precipitate. The precipitate was filtered, washed three times with acetone, and freeze-dried to obtain a pH / ion-responsive microgel. S2 heats 250g of deionized water to 55℃, then adds 70g of sodium aluminate, 165g of aluminum sulfate and 15g of triethanolamine, and disperses them by ultrasonication until dissolved, then cools them to 20℃ to obtain a coagulation-promoting component solution. S3 added 50g of the pH / ion dual-responsive microgel obtained in S1 to 500g of the coagulation-promoting component solution prepared in S2, and added citric acid to adjust the pH of the solution to 5.5. After stirring for 1.0h, a low-alkali rapid coagulating agent based on the pH / ion dual-responsive microgel was obtained.

[0019] Example 3: A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgels, comprising the following steps: In a 45°C water bath, 150g of deionized water and 50g of anhydrous ethanol were stirred until homogeneous. Nitrogen was purged for 60 minutes to remove oxygen. Then, 60g of acrylamide, 35g of N,N-dimethylaminoethyl methacrylate, 20g of hydroxyethyl methacrylate phosphate, and 5g of butyl methacrylate were added sequentially, and stirred until completely dissolved. 0.6g of 4-cyano-4-(phenylthiocarbamoylthio)valerate and 0.3g of ammonium persulfate were added, and the pH of the reaction solution was adjusted to 5.5 with citric acid. The temperature was then raised to 70°C, and the reaction was carried out for 8 hours under a nitrogen atmosphere, maintaining a stirring speed of 300 rpm. After the reaction was complete, the reaction solution was quickly poured into liquid nitrogen and frozen. After reconstitution, the crude product was added dropwise to acetone, resulting in a white fibrous precipitate. The precipitate was filtered, washed three times with acetone, and freeze-dried to obtain a pH / ion-responsive microgel. S2 heats 255g of deionized water to 55℃, then adds 50g of sodium aluminate, 180g of aluminum sulfate and 15g of triethanolamine, and disperses it by ultrasonication until dissolved, then cools it to 20℃ to obtain a coagulation-promoting component solution. S3 added 45g of the pH / ion dual-responsive microgel obtained in S1 to 500g of the coagulation-promoting component solution prepared in S2, and added citric acid to adjust the pH of the solution to 5.5. After stirring for 1.0h, a low-alkali rapid coagulating agent based on the pH / ion dual-responsive microgel was obtained.

[0020] Example 4: A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgels, comprising the following steps: In a 40°C water bath, 200g of deionized water and 50g of anhydrous ethanol were stirred until homogeneous. Nitrogen gas was purged for 30 minutes to remove oxygen. Then, 48g of acrylamide, 12g of N-vinylpyrrolidone, 30g of N,N-dimethylaminoethyl methacrylate, 15g of acrylic acid, and 3g of butyl methacrylate were added sequentially, and stirred until completely dissolved. 0.5g of 4-cyano-4-(phenylthiocarbamoylthio)valerate and 0.3g of 4,4'-azobis(4-cyanopentanoic acid) were added, and the pH of the reaction solution was adjusted to 5.0 with citric acid. The temperature was then raised to 70°C, and the reaction was carried out for 8 hours under a nitrogen atmosphere, maintaining a stirring speed of 300 rpm. After the reaction was complete, the reaction solution was quickly poured into liquid nitrogen and frozen. After reconstitution, the crude product was added dropwise to acetone, resulting in the precipitation of a white fibrous precipitate. The precipitate was filtered, washed three times with acetone, and freeze-dried to obtain a pH / ion-responsive microgel. S2 heats 248g of deionized water to 55℃, then adds 60g of sodium aluminate, 175g of aluminum sulfate and 17g of triethanolamine, and disperses it by ultrasonication until dissolved, then cools it to 20℃ to obtain a coagulation-promoting component solution. S3 added 50g of the pH / ion dual-responsive microgel obtained in S1 to 500g of the coagulation-promoting component solution prepared in S2, and added citric acid to adjust the pH of the solution to 5.5. After stirring for 1.0h, a low-alkali rapid coagulating agent based on the pH / ion dual-responsive microgel was obtained.

[0021] Example 5: A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgels, comprising the following steps: In S1, 160g of deionized water and 40g of anhydrous ethanol were stirred evenly in a 50℃ water bath, and nitrogen gas was purged for 60 min to remove oxygen. Then, 60g of N-hydroxymethylacrylamide, 10g of N-vinylpyrrolidone, 40g of ethyl 3-(N,N-dimethylamino)acrylate, 19g of hydroxyethyl methacrylate phosphate, and 3g of butyl methacrylate were added sequentially, and stirred until completely dissolved. 0.6g of 4-cyano-4-(phenylthiocarbamoylthio)valerate and 0.3g of 4,4'-azobis(4-cyanopentanoic acid) were added, and the pH of the reaction solution was adjusted to 5.0 with citric acid. The temperature was then raised to 70℃, and the reaction was carried out for 8 h under a nitrogen atmosphere, with a stirring speed of 300 rpm. After the reaction was completed, the reaction solution was quickly poured into liquid nitrogen and frozen. After reconstitution, the crude product was added dropwise to acetone, resulting in the precipitation of a white fibrous precipitate. Filter, wash three times with acetone, freeze-dry to obtain pH / ion dual-responsive microgels; S2 heats 250g of deionized water to 55℃, then adds 70g of sodium aluminate, 165g of aluminum sulfate and 15g of triethanolamine, and disperses them by ultrasonication until dissolved, then cools them to 20℃ to obtain a coagulation-promoting component solution. S3 added 70g of the pH / ion dual-responsive microgel obtained in S1 to 500g of the coagulation-promoting component solution prepared in S2, and added citric acid to adjust the pH of the solution to 5.5. After stirring for 1.0h, a low-alkali rapid coagulating agent based on the pH / ion dual-responsive microgel was obtained.

[0022] Example 6: A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgels, comprising the following steps: In a 40°C water bath, 200g of deionized water and 50g of anhydrous ethanol were stirred until homogeneous. Nitrogen gas was purged for 30 minutes to remove oxygen. Then, 48g of N-hydroxyethyl acrylamide, 40g of ethyl 3-(N,N-dimethylamino)acrylate, 19g of diethyl allyl phosphate, and 3g of methyl methacrylate were added sequentially, and stirred until completely dissolved. 0.6g of 4-cyano-4-(phenylthiocarbamoylthio)valerate and 0.3g of 4,4'-azobis(4-cyanopentanoic acid) were added, and the pH of the reaction solution was adjusted to 5.0 with citric acid. The temperature was then raised to 70°C, and the reaction was carried out for 8 hours under a nitrogen atmosphere, maintaining a stirring speed of 300 rpm. After the reaction was complete, the reaction solution was quickly poured into liquid nitrogen and frozen. After reconstitution, the crude product was added dropwise to acetone, resulting in a white fibrous precipitate. The precipitate was filtered, washed three times with acetone, and freeze-dried to obtain a pH / ion-responsive microgel. S2 heats 250g of deionized water to 55℃, then adds 70g of sodium aluminate, 165g of aluminum sulfate and 15g of triethanolamine, and disperses them by ultrasonication until dissolved, then cools them to 20℃ to obtain a coagulation-promoting component solution. S3 added 50g of the pH / ion dual-responsive microgel obtained in S1 to 500g of the coagulation-promoting component solution prepared in S2, and added citric acid to adjust the pH of the solution to 5.5. After stirring for 1.0h, a low-alkali rapid coagulating agent based on the pH / ion dual-responsive microgel was obtained.

[0023] Example 7: A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgels, comprising the following steps: In a 40°C water bath, 160g of deionized water and 40g of anhydrous ethanol were stirred until homogeneous. Nitrogen gas was purged for 30 minutes to remove oxygen. Then, 20g of acrylamide, 20g of N-isopropylacrylamide, 20g of N-hydroxyethylacrylamide, 40g of N,N-dimethylaminoethyl methacrylate, 19g of hydroxyethyl methacrylate phosphate, and 3g of butyl methacrylate were added sequentially, and stirred until completely dissolved. 0.5g of 4-cyano-4-(phenylthiocarbamoylthio)valerate and 0.3g of potassium persulfate were added, and the pH of the reaction solution was adjusted to 5.0 with citric acid. The temperature was then raised to 70°C, and the reaction was carried out for 8 hours under a nitrogen atmosphere, maintaining a stirring speed of 300 rpm. After the reaction was complete, the reaction solution was quickly poured into liquid nitrogen and frozen. After reconstitution, the crude product was added dropwise to acetone, resulting in a white fibrous precipitate. The precipitate was filtered, washed three times with acetone, and freeze-dried to obtain a pH / ion-responsive microgel. S2 heats 250g of deionized water to 55℃, then adds 70g of sodium aluminate, 165g of aluminum sulfate and 15g of triethanolamine, and disperses them by ultrasonication until dissolved, then cools them to 20℃ to obtain a coagulation-promoting component solution. S3 added 55g of the pH / ion dual-responsive microgel obtained in S1 to 500g of the coagulation-promoting component solution prepared in S2, and added citric acid to adjust the pH of the solution to 5.5. After stirring for 1.0h, a low-alkali rapid coagulating agent based on the pH / ion dual-responsive microgel was obtained.

[0024] Example 8: A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgels, comprising the following steps: In S1, 160g of deionized water and 40g of anhydrous ethanol were stirred evenly in a 40℃ water bath, and nitrogen gas was purged for 30 min to remove oxygen. Then, 30g of N-hydroxyethylacrylamide, 30g of N-vinylpyrrolidone, 15g of N,N-dimethylaminoethyl methacrylate, 10g of hydroxyethyl methacrylate phosphate, and 5g of butyl methacrylate were added sequentially, and stirred until completely dissolved. 0.3g of 4-cyano-4-(phenylthiocarbamoylthio)valerate and 0.3g of 4,4'-azobis(4-cyanopentanoic acid) were added, and the pH of the reaction solution was adjusted to 5.0 with citric acid. The temperature was then raised to 65℃, and the reaction was carried out for 8 h under a nitrogen atmosphere, with a stirring speed of 300 rpm. After the reaction was completed, the reaction solution was quickly poured into liquid nitrogen and frozen. After reconstitution, the crude product was added dropwise to acetone, resulting in the precipitation of a white fibrous precipitate. Filter, wash three times with acetone, freeze-dry to obtain pH / ion dual-responsive microgels; S2 heats 235g of deionized water to 55℃, then adds 90g of sodium aluminate, 165g of aluminum sulfate and 10g of triethanolamine, and disperses them by ultrasonication until dissolved, then cools down to 20℃ to obtain a coagulation-promoting component solution. S3 added 45g of the pH / ion dual-responsive microgel obtained in S1 to 500g of the coagulation-promoting component solution prepared in S2, and added citric acid to adjust the pH of the solution to 5.5. After stirring for 1.0h, a low-alkali rapid coagulating agent based on the pH / ion dual-responsive microgel was obtained.

[0025] Example 9: A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgels, comprising the following steps: In a 40°C water bath, 130g of deionized water and 70g of anhydrous ethanol were stirred until homogeneous. Nitrogen gas was purged for 30 minutes to remove oxygen. Then, 30g of acrylamide, 30g of N-hydroxyethyl acrylamide, 40g of N,N-dimethylaminoethyl methacrylate, 19g of hydroxyethyl methacrylate phosphate, and 3g of butyl methacrylate were added sequentially, and stirred until completely dissolved. 0.5g of 4-cyano-4-(phenylthiocarbamoylthio)valerate and 0.3g of 4,4'-azobis(4-cyanopentanoic acid) were added, and the pH of the reaction solution was adjusted to 5.0 with citric acid. The temperature was then raised to 70°C, and the reaction was carried out for 8 hours under a nitrogen atmosphere, maintaining a stirring speed of 300 rpm. After the reaction was complete, the reaction solution was quickly poured into liquid nitrogen and frozen. After reconstitution, the crude product was added dropwise to acetone, resulting in the precipitation of a white fibrous precipitate. The precipitate was filtered, washed three times with acetone, and freeze-dried to obtain a pH / ion-responsive microgel. S2 heats 250g of deionized water to 55℃, then adds 90g of sodium aluminate, 145g of aluminum sulfate and 15g of triethanolamine, and disperses them by ultrasonication until dissolved. Then cools the solution to 20℃ to obtain a coagulation-promoting component solution. S3 added 60g of the pH / ion dual-responsive microgel obtained in S1 to 500g of the coagulation-promoting component solution prepared in S2, and added citric acid to adjust the pH of the solution to 5.0. After stirring for 1.0h, a low-alkali rapid coagulating agent based on the pH / ion dual-responsive microgel was obtained.

[0026] Example 10: A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgels, comprising the following steps: In S1, 160g of deionized water and 40g of anhydrous ethanol were stirred evenly in a 40℃ water bath, and nitrogen gas was purged for 30 min to remove oxygen. Then, 48g of acrylamide, 40g of N,N-dimethylaminoethyl methacrylate, 19g of hydroxyethyl methacrylate phosphate, and 3g of butyl methacrylate were added sequentially, and stirred until completely dissolved. 0.3g of 4-cyano-4-(phenylthiocarbamoylthio)valerate and 0.3g of 4,4'-azobis(4-cyanopentanoic acid) were added, and the pH of the reaction solution was adjusted to 5.0 with citric acid. The temperature was then raised to 70℃, and the reaction was carried out for 8 h under a nitrogen atmosphere, with a stirring speed of 300 rpm. After the reaction was completed, the reaction solution was quickly poured into liquid nitrogen and frozen. After reconstitution, the crude product was added dropwise to acetone, and a white fibrous precipitate was formed. The precipitate was filtered, washed three times with acetone, and freeze-dried to obtain a pH / ion dual-responsive microgel. S2 heats 230g of deionized water to 55℃, then adds 70g of sodium aluminate, 190g of aluminum sulfate and 10g of triethanolamine, and disperses them by ultrasonication until dissolved, then cools down to 20℃ to obtain a coagulation-promoting component solution. S3 added 70g of the pH / ion dual-responsive microgel obtained in S1 to 500g of the coagulation-promoting component solution prepared in S2, and added phosphoric acid to adjust the pH of the solution to 5.5. After stirring for 1.0h, a low-alkali rapid coagulating agent based on the pH / ion dual-responsive microgel was obtained.

[0027] Comparative Example 1: This is a low-alkali rapid-setting agent based on an acid-ion dual-sensitive hydrogel disclosed in this invention. The difference from Example 1 is that water is used instead of the acid-ion dual-sensitive hydrogel component.

[0028] Test Example 1: Under 20℃ conditions, the quick-setting agents prepared in Examples 1 to 10 and Comparative Example 1 were tested for performance at 6% of the cement content according to GB / T35159-2017. The test results are shown in Table 1.

[0029] Table 1 Initial setting time Final freezing time 1d compressive strength / MPa 28d compressive strength ratio / % 90d compressive strength retention rate / % 28-day shrinkage rate ratio / % Example 1 2 minutes 30 seconds 6min25s 8.1 117 115 65 Example 2 2min45s 6min37s 7.8 113 119 67 Example 3 2min50s 6min41s 7.9 108 106 70 Example 4 3min05s 6min40s 7.7 107 104 68 Example 5 2min35s 6min36s 7.9 103 103 54 Example 6 2min51s 6min43s 7.9 111 113 67 Example 7 2min44s 6min37s 8.0 115 110 63 Example 8 2min40s 6min26s 7.9 112 113 70 Example 9 2min55s 6min32s 7.8 106 104 58 Example 10 2min25s 6min03s 7.7 105 102 53 Comparative Example 1 3min25s 6min51s 7.3 100 100 100 As shown in Table 1, the low-alkali rapid-setting agent based on pH / ion dual-responsive microgel of this invention, compared with the comparative example, not only has advantages in setting time but also a very significant shrinkage reduction effect, with a 28-day shrinkage rate reduced by more than 30%. In terms of strength, this invention meets the standard requirements.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a low-alkali rapid-setting agent based on pH / ion dual-responsive microgels, characterized in that: Includes the following steps, S1 First, a water / ethanol mixed solvent was deoxygenated by purging nitrogen gas at 30-50℃ for 30-60 min. Then, hydrophilic monomers, pH-responsive monomers, calcium ion-responsive monomers, and hydrophobic co-responsive monomers were added sequentially. After stirring and dissolving, RAFT reagent and initiator were added, and the pH was adjusted to 4.0-6.

0. The temperature was raised to 60-80℃, and the reaction was carried out in a nitrogen atmosphere for 5-10 h, while maintaining a stirring speed of 200-400 rpm. After the reaction was completed, post-treatment was performed to obtain pH / ion dual-responsive microgels. S2 first preheats the water to 50~60℃, then adds the low-alkali coagulant component and the organic alcohol amine coagulant component, disperses them by ultrasonication, and then cools them down to 20~30℃ to obtain the coagulant component solution; S3. Add the pH / ion dual-responsive microgel obtained in S1 to the coagulation-promoting component solution obtained in S2, adjust the pH to 4.0~6.0, and stir for 0.5~1.0h to obtain a low-alkali rapid coagulating agent based on pH / ion dual-responsive microgel.

2. The method for preparing a low-alkali rapid-setting agent based on a pH / ion dual-responsive microgel according to claim 1, characterized in that: In S1, the mass ratio of hydrophilic monomer, pH-responsive monomer, calcium ion-responsive monomer, hydrophobic co-responsive monomer, RAFT reagent and initiator is controlled to be 35~70:10~40:10~25:1~10:0.20~0.6:0.12~0.

60.

3. The method for preparing a low-alkali rapid-setting agent based on a pH / ion dual-responsive microgel according to claim 2, characterized in that: In S1, the ethanol mass concentration of the mixed solvent is controlled to be 10-40%.

4. The method for preparing a low-alkali rapid-setting agent based on a pH / ion dual-responsive microgel according to claim 3, characterized in that: In S1, the mass ratio of the mixed solvent to the monomer is 1.0~3.0:1.0, and the monomer is a hydrophilic monomer, a pH-responsive monomer, a calcium ion-responsive monomer, and a hydrophobic co-monomer.

5. The method for preparing a low-alkali rapid-setting agent based on a pH / ion dual-responsive microgel according to claim 2, characterized in that: In S1, the hydrophilic monomer is one or a combination of several of acrylamide, N-isopropylacrylamide, N-hydroxyethylacrylamide, N-hydroxymethylacrylamide, and N-vinylpyrrolidone. The pH-responsive monomer is one or a combination of several of N,N-dimethylaminoethyl methacrylate, 3-(N,N-dimethylamino)ethyl methacrylate, and dimethylaminoethyl acrylate. The calcium ion responsive monomer is one or a combination of several of the following: hydroxyethyl methacrylate phosphate, diethyl allyl phosphate, acrylic acid, and methacrylic acid. The hydrophobic synergistic monomer is one or more of butyl methacrylate and methyl methacrylate; The RAFT reagent is one or a combination of several of the following: 4-cyano-4-(phenylthiocarboxylthio)pentanoic acid, 4-cyano-4-(dodecylthioalkylthiocarbonyl)thiopentanoic acid, and 2-(dodecyltrithiocarbonate)-2-methylpropionic acid. The initiator is one or a combination of several of 4,4'-azobis(4-cyanopentanoic acid), ammonium persulfate, and potassium persulfate.

6. The method for preparing a low-alkali rapid-setting agent based on a pH / ion dual-responsive microgel according to claim 1, characterized in that: In S2, the mass percentage of the low-alkali coagulant component, the organic alcohol amine coagulant component, and water is controlled to be 38~60:2~10:30~60.

7. The method for preparing a low-alkali rapid-setting agent based on a pH / ion dual-responsive microgel according to claim 6, characterized in that: In S2, the low-alkali coagulating component consists of sodium aluminate and inorganic aluminum compounds in a mass ratio of 20~40:60~80.

8. The method for preparing a low-alkali rapid-setting agent based on a pH / ion dual-responsive microgel according to claim 7, characterized in that: In S2, the inorganic aluminum compound is one or a combination of several of aluminum sulfate, polyaluminum sulfate, and nano-alumina; The organic alcohol amine coagulant component is one or more of diethanolamine, triethanolamine and N-methylethanolamine.

9. The method for preparing a low-alkali rapid-setting agent based on a pH / ion dual-responsive microgel according to claim 1, characterized in that: In S1 and S3, the pH adjuster is one or a combination of several of phosphoric acid, citric acid, lactic acid and oxalic acid.

10. The method for preparing a low-alkali rapid-setting agent based on a pH / ion dual-responsive microgel according to claim 1, characterized in that: In S3, the mass ratio of pH / ion dual-response microgel to coagulation-promoting component solution is controlled to be 5~15:85~95.