A polycarboxylic acid system-containing double-system composite water reducing agent for concrete and a preparation method thereof

Abstract

This invention discloses a two-system composite water-reducing agent containing polycarboxylate for concrete and its preparation method, belonging to the field of building material admixture processing technology. The two-system composite water-reducing agent for concrete includes component A and component B; component A is a passivating agent for acidic soil; component B is a polycarboxylate water-reducing agent mother liquor with a pH of 7-7.5; the amount of component A is 5%-10% of the mass of component B; component A includes a boric acid-modified MXene / chitosan, a sodium alginate-coated ammonium-modified polyacrylic acid polymer composite, an organotin catalyst, or an organic base catalyst; wherein the sodium alginate in the sodium alginate-coated ammonium-modified polyacrylic acid polymer composite is isocyanate cross-linked modified sodium alginate; component B includes a polymer prepared using isopentenyl alcohol polyoxyethylene ether, isomeric ester, acrylic acid, and itaconic acid as monomers, and alkylamide betaine. This application is applicable to concrete systems containing acidic soil.

Description

Technical Field

[0001] This invention belongs to the field of building material admixture processing technology, and relates to a two-system composite water-reducing agent containing polycarboxylic acid for concrete and its preparation method. Background Technology

[0002] Polycarboxylate-based high-performance water-reducing agents, as the third generation of concrete water-reducing agents, have advantages over traditional lignin sulfonate and naphthalene sulfonate water-reducing agents, including high water reduction rate, high slump retention, and environmental friendliness, and are widely used in the construction field. However, with the rapid development of the construction industry, high-quality sand resources are gradually decreasing, resulting in sand with a high mud content. The mud content of sand has a significant impact on concrete performance. In particular, clay minerals in the soil have a strong adsorption effect on water-reducing agents, which reduces their performance.

[0003] In existing technologies, boric acid groups are generally used to adsorb onto the clay surface to reduce the impact of clay on water-reducing agents. However, for acidic soils, in the initial stage of concrete mixing, the pH of the local microenvironment where the acidic soil is located is not neutralized and is in an acidic environment. The acidic environment reduces the adsorption of boric acid on the clay surface, and the clay still has a significant adverse effect on the water-reducing agent. Summary of the Invention

[0004] The purpose of this invention is to provide a two-system composite water-reducing agent containing polycarboxylic acid for concrete and its preparation method. This invention solves the problem that when using boric acid groups to adsorb onto the clay surface to reduce the influence of clay on the water-reducing agent, the effect of boric acid groups is not obvious in acidic soil, and the clay still has a significant impact on the water-reducing agent.

[0005] The technical solution adopted in this invention is as follows: A two-system composite water-reducing agent for concrete containing polycarboxylate, comprising component A and component B; wherein component A is a passivating agent for acidic soil; and component B is a polycarboxylate superplasticizer mother liquor with a pH of 7-7.5; the amount of component A is 5%-10% of the mass of component B. Component A includes a boric acid-modified MXene / chitosan, a complex of sodium alginate-coated ammonium-modified polyacrylic acid polymer, an organotin catalyst, or an organic base catalyst; wherein, the sodium alginate in the complex of sodium alginate-coated ammonium-modified polyacrylic acid polymer is isocyanate crosslinked modified sodium alginate. Component B includes a polymer prepared using isopentenyl alcohol polyoxyethylene ether, isomeric ester, acrylic acid, and itaconic acid as monomers, as well as alkylamide betaine.

[0006] Further, the boric acid-modified MXene / chitosan is prepared by the following method: MXene powder is prepared by hydrofluoric acid etching; MXene powder is added to NaOH aqueous solution, stirred evenly, and then ultrasonically treated for 1-2 hours; after ultrasonic treatment, it is filtered, washed until neutral, and dried to obtain polyhydroxy MXene material; amino-protected chitosan is dissolved in acetic acid solution, ethylenediaminetetraacetic anhydride / methanol dispersion and 4-dimethylaminopyridine are added, and the reaction is carried out at 75-80℃ for 4-8 hours under inert gas protection; after the reaction, ethanol is added to precipitate the precipitate, and the precipitate is washed and dried to obtain modified chitosan; modified chitosan is added to MES buffer, EDC and NHS are added to activate the carboxyl groups, and then it is mixed with polyhydroxy MXene material at a mass ratio of 1:3-4; the reaction is stirred for 20-24 hours, centrifuged, washed and dried to obtain MXene / amino-protected chitosan complex; MXene / amino-protected chitosan complex and 4-carboxyphenylboronic acid were added to DMF and stirred until homogeneous. Then, EDC and DIPEA were added, and the mixture was stirred at 50°C for 30-35 hours. After the reaction was completed, the mixture was cooled, filtered, washed, and dried to obtain boric acid-modified MXene / amino-protected chitosan complex. After deamination of the boric acid-modified MXene / amino-protected chitosan complex, boric acid-modified MXene / chitosan was obtained. The molar ratio of 4-carboxyphenylboronic acid, EDC, and DIPEA was 1.2:1.5:2, and the mass ratio of MXene / amino-protected chitosan complex to 4-carboxyphenylboronic acid was 2-2.5:1.

[0007] Furthermore, MXene is for Ti3C2T x MXene material.

[0008] Furthermore, the sodium alginate-coated ammonium-modified polyacrylic acid polymer composite was prepared by the following method: S3.1 In a four-necked flask equipped with a stirrer, reflux condenser, constant pressure dropping funnel and nitrogen inlet, deionized water and polyethylene glycol monomethyl ether acrylate are added, nitrogen is passed through to remove oxygen, and after heating, acrylic acid, hydroxyethyl acrylate and ammonium persulfate are added. The reaction is kept at 70°C and then cooled to room temperature to obtain polyacrylic acid polymer. S3.2 Add epichlorohydrin and trimethylamine aqueous solution to polyacrylic acid polymer, adjust pH to 8.0~8.5 with NaOH, react at 45℃ for 4 h, and after the reaction is completed, adjust pH to 7.0 with dilute hydrochloric acid to obtain liquid ammonium modified polyacrylic acid polymer; S3.3. An HDI crosslinked modified sodium alginate solution was prepared using hexamethylene diisocyanate (HDI) with one end closed as a crosslinking agent. Liquid ammonium modified polyacrylic acid polymer was added dropwise to the HDI crosslinked modified sodium alginate solution. The mass ratio of liquid ammonium modified polyacrylic acid polymer to sodium alginate in the HDI crosslinked modified sodium alginate solution was 2:1. The dropping rate was 0.8-1.5 mL / min. After the addition was complete, the mixture was stirred at low speed at 30-35℃ for 2.5 h. Then, the temperature was raised to 50℃ and kept at that temperature for 1 h. After cooling to room temperature, the mixture was filtered, the precipitate was collected, and dried to obtain the sodium alginate-coated ammonium modified polyacrylic acid polymer composite.

[0009] Furthermore, the amount of hexamethylene diisocyanate with one end blocked in the HDI crosslinked modified sodium alginate solution is 5-8% of the mass of sodium alginate; the hexamethylene diisocyanate with one end blocked uses N-hydroxyphthalimide as the blocking agent, and the molar ratio of N-hydroxyphthalimide to hexamethylene diisocyanate is 1:1.

[0010] Furthermore, the degree of deacetylation of chitosan is greater than 90%.

[0011] Furthermore, the amino-protected chitosan is amino-protected using phthalic anhydride in a DMF solution containing 5% water.

[0012] Further, component B is prepared by the following method: isopentenyl alcohol polyoxyethylene ether is added to a four-necked flask, heated to 60-70°C, stirred until completely dissolved, and nitrogen gas is passed through for 30 min to remove oxygen, to obtain an isopentenyl alcohol polyoxyethylene ether solution for later use. Two dropping solutions were prepared separately: Dropping solution A: Acrylic acid, itaconic acid, and isomeric ester were mixed evenly, and deionized water was added at a solid-liquid mass ratio of 1:1. The mixture was stirred evenly to obtain dropping solution A; Dropping solution B: Ammonium persulfate was dissolved in deionized water to prepare a 5% solution by mass. The amount of ammonium persulfate used was 0.8-1.2% of the total mass of acrylic acid, itaconic acid, isomeric ester, and isopentenyl alcohol polyoxyethylene ether. The isopentenyl alcohol polyoxyethylene ether solution was heated to 75-80℃, and dropping solutions A and B were slowly added dropwise. The dropping rate was controlled to be 2-3 mL / min for dropping solution A and 1-2 mL / min for dropping solution B. After the addition was complete, the reaction was kept at 80℃ for 4-5 hours. After the reaction was completed, the solution was cooled to 40-50℃, and alkylamide betaine was added and stirred until completely dissolved. The pH was adjusted to 7.0-7.5 with 1 mol / L NaOH solution, and the solution was diluted with water to a solid content of 40% to obtain component B.

[0013] Furthermore, for concrete systems containing ≤5% acidic soil in the sand, the pH of the acidic soil is 4.5-5.5.

[0014] The preparation method of the polycarboxylate-based dual-system composite water-reducing agent for concrete includes the following steps: S1. Preparation of Component A: The boric acid-modified MXene / chitosan and sodium alginate-coated ammonium-modified polyacrylic acid polymer composite were mixed at a mass ratio of 2:1 and dispersed in anhydrous N,N-dimethylformamide. 0.1% (by mass) of dibutyltin dilaurate of the total mass of the boric acid-modified MXene / chitosan and sodium alginate-coated ammonium-modified polyacrylic acid polymer composite was added. Under nitrogen protection, the temperature was raised to 80-100℃ and the reaction was stirred for 4-6 hours. After the reaction was completed, the mixture was cooled, filtered, washed with anhydrous ethanol, and dried to obtain Component A. S2. Preparation of component B: Add isopentenyl alcohol polyoxyethylene ether to a four-necked flask, heat to 60-70℃, stir until completely dissolved, purge with nitrogen for 30 minutes to remove oxygen, and obtain isopentenyl alcohol polyoxyethylene ether solution for later use. Two dropping solutions were prepared separately: Dropping solution A: Acrylic acid, itaconic acid, and isomeric ester were mixed evenly, and deionized water was added at a solid-liquid mass ratio of 1:1. The mixture was stirred evenly to obtain dropping solution A; Dropping solution B: Ammonium persulfate was dissolved in deionized water to prepare a 5% solution by mass, and the amount of initiator was 0.8-1.2% of the total mass of acrylic acid, itaconic acid, isomeric ester, and isopentenyl polyoxyethylene ether; wherein, the isomeric ester is a cycloisomeric ester of acrylic acid; The isopentenyl alcohol polyoxyethylene ether solution was heated to 75-80℃, and dropping solutions A and B were slowly added dropwise. The dropping rate was controlled to be 2-3 mL / min for dropping solution A and 1-2 mL / min for dropping solution B. After the addition was complete, the reaction was maintained at 80℃ for 4-5 hours. After the reaction was completed, the solution was cooled to 40-50℃, and alkylamide betaine was added and stirred until completely dissolved. The pH was adjusted to 7.0-7.5 with 1 mol / L NaOH solution, and the solution was diluted with water to a solid content of 40% to obtain component B. The mass ratio of isopentenyl alcohol polyoxyethylene ether, acrylic acid, itaconic acid, isomeric ester, and alkylamide betaine was 100:12:3:5:2. S3. Mixing Component A and Component B: Add Component B to the mixing tank, adjust the temperature to 30-35℃, and the stirring rate to 200-300 r / min; add Component A slowly to Component B at a ratio of 5%-10% of the mass of Component B, stirring continuously. After Component A is added, continue stirring for 1.5-2 hours. After stirring, take a sample to test the pH value, ensuring that the pH of the entire system is 7.0-7.5, thus obtaining a two-system composite water-reducing agent for concrete containing polycarboxylate.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This invention discloses a dual-system composite water-reducing agent for concrete containing polycarboxylic acid, using boric acid-modified MXene / chitosan as an anchoring agent. Chitosan can be protonated in a locally acidic environment and adsorbed onto the clay surface, reducing the local acidity of the clay and compensating for the weak adsorption of boric acid in the initial stage of concrete mixing. As the pH of the concrete system increases, the pH of the environment surrounding the clay also increases. The boric acid groups and the ammonium-modified polyacrylic acid polymer released in an alkaline environment synergistically adsorb the clay, significantly reducing the impact of the clay on the polycarboxylic acid water-reducing agent. 2. In this invention, the boric acid modified MXene / chitosan mainly uses MXene as a carrier, and there is a chemical bond between the boric acid modified MXene / chitosan and the sodium alginate-coated ammonium modified polyacrylic acid polymer. The whole component A has strong integrity and can be stably dispersed in the presence of component B. It can also be distributed around the soil as a whole, avoiding other components in the concrete from blocking the ammonium modified polyacrylic acid polymer, which is beneficial to improving the coating properties of component A on clay. 3. In this invention, chitosan plays a major role in blocking clay in the initial stage of concrete mixing when the clay is still in a locally acidic environment; boric acid and ammonium-modified polyacrylic acid polymer plays an adsorption and blocking role on clay when the concrete system is significantly hydrated and the pH is significantly increased to a strongly alkaline environment; the synergistic effect of multiple components can extend the action time of polycarboxylate superplasticizer in concrete. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a flowchart of the preparation method of Embodiment 1 of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0019] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0020] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0021] This invention provides a two-system composite water-reducing agent for concrete containing polycarboxylate, comprising component A and component B; component A is a passivating agent for acidic soil; component B is a polycarboxylate water-reducing agent stock solution with a pH of 7-7.5; the amount of component A is 5%-10% of the mass of component B. Component A includes a boric acid-modified MXene / chitosan, a complex of sodium alginate-coated ammonium-modified polyacrylic acid polymer, an organotin catalyst, or an organic base catalyst; wherein, the sodium alginate in the complex of sodium alginate-coated ammonium-modified polyacrylic acid polymer is isocyanate crosslinked modified sodium alginate. Component B includes a polymer prepared using isopentenyl alcohol polyoxyethylene ether, isomeric ester, acrylic acid, and itaconic acid as monomers, as well as alkylamide betaine.

[0022] In the following embodiments, the boric acid-modified MXene / chitosan was prepared by the following method: MXene powder was prepared by hydrofluoric acid etching, and the MXene powder was Ti3C2T. xMXene material; add MXene powder to 0.3 In a mol / L NaOH aqueous solution, after stirring until homogeneous, the mixture was ultrasonically treated for 2 hours. After ultrasonic treatment, it was filtered, washed until neutral, and dried to obtain polyhydroxy MXene material. Amino-protected chitosan was added to glacial acetic acid solution to obtain a chitosan solution. Ethylenediaminetetraacetic dianhydride was dispersed in methanol at a mass-to-volume ratio of 1:2 mg / ml to obtain an ethylenediaminetetraacetic dianhydride / methanol dispersion. The chitosan solution and the ethylenediaminetetraacetic dianhydride / methanol dispersion were mixed thoroughly, and then 4-dimethylaminopyridine was added at a mass ratio of 1:1 (ethylenediaminetetraacetic dianhydride to chitosan) and a molar ratio of 1:20 (4-dimethylaminopyridine to ethylenediaminetetraacetic dianhydride). Under inert gas protection, the reaction system was heated to 80℃ and stirred for 6 hours. After the reaction, the reaction solution was poured into excess anhydrous ethanol to precipitate the mixture. The precipitate was collected by filtration, washed, and dried to obtain modified chitosan. The modified chitosan was dissolved in 0.1M pH... A 2% (w / w) modified chitosan solution was prepared in MES buffer solution of 5.5-6.5. EDC and NHS were added to the modified chitosan solution at a molar ratio of 1:1, and the molar ratio of EDC to ethylenediaminetetraacetic dianhydride was 4:1. After stirring at room temperature for 30-40 minutes, polyhydroxy MXene was added at a mass ratio of 1:3.5 between modified chitosan and polyhydroxy MXene. The reaction was stirred for 22 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the MXene / amino-protected chitosan complex. MXene / amino-protected chitosan complex and 4-carboxyphenylboronic acid were added to DMF and stirred until homogeneous. Then, EDC and DIPEA were added, and the mixture was stirred at 50°C for 33 hours. After the reaction was completed, the mixture was cooled, filtered, washed, and dried to obtain boric acid-modified MXene / amino-protected chitosan complex. After deamino protection of the boric acid-modified MXene / amino-protected chitosan complex, boric acid-modified MXene / chitosan was obtained. The molar ratio of 4-carboxyphenylboronic acid, EDC, and DIPEA was 1.2:1.5:2, and the mass ratio of MXene / amino-protected chitosan complex to 4-carboxyphenylboronic acid was 2.3:1.

[0023] In the following embodiments, the sodium alginate-coated ammonium-modified polyacrylic acid polymer composite was prepared by the following method: S3.1 In a 500mL four-necked flask equipped with a stirrer, reflux condenser, constant pressure dropping funnel and nitrogen inlet, add 200g of deionized water and 20.0g of polyethylene glycol monomethyl ether acrylate with a molecular weight of 1000. Purge with nitrogen to remove oxygen for 30min. After heating to 70℃, add 15.0g of acrylic acid, 5.0g of hydroxyethyl acrylate and 0.5g of ammonium persulfate. Keep the reaction at 70℃ for 4h. Cool to room temperature to obtain polyacrylic acid polymer. S3.2 Add 6.0 g of epichlorohydrin and 7.0 g of 35% trimethylamine aqueous solution to the polyacrylic acid polymer, adjust the pH to 8.0~8.5 with 1 mol / L NaOH, react at 45℃ for 4 h, and after the reaction is completed, adjust the pH to 7.0 with dilute hydrochloric acid to obtain liquid ammonium modified polyacrylic acid polymer; S3.3. An HDI crosslinked modified sodium alginate solution was prepared using hexamethylene diisocyanate (HDI) with one end closed as a crosslinking agent. Liquid ammonium modified polyacrylic acid polymer was added dropwise to the HDI crosslinked modified sodium alginate solution. The mass ratio of liquid ammonium modified polyacrylic acid polymer to sodium alginate in the HDI crosslinked modified sodium alginate solution was 2:1. The dropping rate was 1 mL / min. After the addition was complete, the mixture was stirred at low speed at 35 °C for 2.5 h. Then, the temperature was raised to 50 °C and kept at that temperature for 1 h. After cooling to room temperature, the mixture was filtered, the precipitate was collected, and dried to obtain a sodium alginate-coated ammonium modified polyacrylic acid polymer composite.

[0024] In the following embodiments, the amount of hexamethylene diisocyanate (HDI) with one end blocked in the HDI crosslinked modified sodium alginate solution is 8% of the mass of sodium alginate; the hexamethylene diisocyanate with one end blocked uses N-hydroxyphthalimide as a blocking agent, and the molar ratio of N-hydroxyphthalimide to hexamethylene diisocyanate is 1:1; wherein, the HDI crosslinked modified sodium alginate solution is prepared by the following method: 10g of sodium alginate is weighed and added to 250mL of deionized water, stirred until the sodium alginate is completely dissolved, and the pH value of the sodium alginate solution is adjusted to 8.0 with NaOH solution to obtain a sodium alginate solution; then, 1.8% of the mass of sodium alginate and triethylenediamine are added to the sodium alginate solution, stirred evenly, and then 8% of the mass of sodium alginate and one end blocked hexamethylene diisocyanate (HDI) are added, and the reaction is stirred for 0.5 hours to obtain the HDI crosslinked modified sodium alginate solution. (Prepare the HDI crosslinked modified sodium alginate solution according to the required dosage) In the following examples, the degree of deacetylation of chitosan is greater than 90%.

[0025] In the following embodiments, the amino-protected chitosan is amino-protected using phthalic anhydride in a DMF solution containing 5% water.

[0026] In some embodiments, component B is prepared by the following method: adding isopentenyl alcohol polyoxyethylene ether to a four-necked flask, heating to 60-70°C, stirring until completely dissolved, and purging with nitrogen for 30 minutes to remove oxygen, thereby obtaining an isopentenyl alcohol polyoxyethylene ether solution for later use. Two dropping solutions were prepared separately: Dropping solution A: Acrylic acid, itaconic acid, and isomeric ester were mixed evenly, and deionized water was added at a solid-liquid mass ratio of 1:1. The mixture was stirred evenly to obtain dropping solution A; Dropping solution B: Ammonium persulfate was dissolved in deionized water to prepare a 5% solution by mass. The amount of ammonium persulfate used was 0.8-1.2% of the total mass of acrylic acid, itaconic acid, isomeric ester, and isopentenyl alcohol polyoxyethylene ether. The isopentenyl alcohol polyoxyethylene ether solution was heated to 75-80℃, and dropping solutions A and B were slowly added dropwise. The dropping rate was controlled to be 2-3 mL / min for dropping solution A and 1-2 mL / min for dropping solution B. After the addition was complete, the reaction was kept at 80℃ for 4-5 hours. After the reaction was completed, the solution was cooled to 40-50℃, and alkylamide betaine was added and stirred until completely dissolved. The pH was adjusted to 7.0-7.5 with 1 mol / L NaOH solution, and the solution was diluted with water to a solid content of 40% to obtain component B.

[0027] In the following embodiments, a concrete system with sand and gravel containing ≤5% acidic soil was used, wherein the pH of the acidic soil was 4.5-5.5.

[0028] Example 1 Based on the above, such as Figure 1 As shown in the embodiment of the present invention, a two-system composite water-reducing agent containing polycarboxylate for concrete is prepared by the following method: S1. Preparation of Component A: The boric acid-modified MXene / chitosan and sodium alginate-coated ammonium-modified polyacrylic acid polymer composite were mixed at a mass ratio of 2:1 and dispersed in anhydrous N,N-dimethylformamide. 0.1% (by mass) of dibutyltin dilaurate of the total mass of the boric acid-modified MXene / chitosan and sodium alginate-coated ammonium-modified polyacrylic acid polymer composite was added. Under nitrogen protection, the mixture was heated to 90°C and stirred for 5 hours. After the reaction was completed, the mixture was cooled, filtered, washed with anhydrous ethanol, and dried to obtain Component A. S2. Preparation of component B: Add isopentenyl alcohol polyoxyethylene ether to a four-necked flask, heat to 70°C, stir until completely dissolved, purge with nitrogen for 30 min to remove oxygen, and obtain isopentenyl alcohol polyoxyethylene ether solution for later use. Two dropping solutions were prepared separately: Dropping solution A: Acrylic acid, itaconic acid, and isomeric ester were mixed evenly, and deionized water was added at a solid-liquid mass ratio of 1:1. The mixture was stirred evenly to obtain dropping solution A; Dropping solution B: Ammonium persulfate was dissolved in deionized water to prepare a 5% solution by mass, and the amount of initiator was 1% of the total mass of acrylic acid, itaconic acid, isomeric ester, and isopentenyl polyoxyethylene ether; wherein, the isomeric ester was a cycloisomeric ester of acrylic acid; The isopentenyl alcohol polyoxyethylene ether solution was heated to 80℃, and dropping solutions A and B were slowly added dropwise. The dropping rate was controlled at 2 mL / min for solution A and 1 mL / min for solution B. After the addition was complete, the reaction was maintained at 80℃ for 4.5 h. After the reaction was completed, the solution was cooled to 45℃, and alkylamide betaine was added and stirred until completely dissolved. The pH was adjusted to 7.0-7.5 with 1 mol / L NaOH solution, and the solution was diluted with water to a solid content of 40% to obtain component B. The mass ratio of isopentenyl alcohol polyoxyethylene ether, acrylic acid, itaconic acid, isomeric ester, and alkylamide betaine was 100:12:3:5:2. S3. Mixing Component A and Component B: Add Component B to the mixing vessel, adjust the temperature to 30℃, and the stirring rate to 200 r / min; add Component A slowly to Component B at a ratio of 5% of the mass of Component B, stirring continuously. After Component A is added, continue stirring for 2 hours. After stirring, take a sample to test the pH value to ensure that the pH of the entire system is 7.0-7.5, thus obtaining a two-system composite water-reducing agent for concrete containing polycarboxylate.

[0029] Example 2 This embodiment is based on Embodiment 1. The difference between Embodiment 1 and Embodiment 2 is that the amount of component A in this embodiment is 8% of the mass of component B, while the rest are the same.

[0030] Example 3 This embodiment is based on Embodiment 1, but differs from Embodiment 1 in that the amount of component A used in this embodiment is 10% of the mass of component B, while the rest are the same.

[0031] Comparative Example 1 Based on Example 1, unlike Example 1, this comparative example does not include component A. The polycarboxylate superplasticizer provided in this comparative example only includes component B and is prepared by the following method: Add isopentenyl alcohol polyoxyethylene ether to a four-necked flask, heat to 70°C, stir until completely dissolved, purge with nitrogen for 30 minutes to remove oxygen, and obtain isopentenyl alcohol polyoxyethylene ether solution for later use. Two dropping solutions were prepared separately: Dropping solution A: Acrylic acid, itaconic acid, and isomeric ester were mixed evenly, and deionized water was added at a solid-liquid mass ratio of 1:1. The mixture was stirred evenly to obtain dropping solution A; Dropping solution B: Ammonium persulfate was dissolved in deionized water to prepare a 5% solution by mass, and the amount of initiator was 1% of the total mass of acrylic acid, itaconic acid, isomeric ester, and isopentenyl polyoxyethylene ether; wherein, the isomeric ester was a cycloisomeric ester of acrylic acid; The isopentenyl alcohol polyoxyethylene ether solution was heated to 80℃, and dropwise addant A and dropwise addant B were slowly added dropwise. The dropping rate was controlled at 2 mL / min for dropwise addant A and 1 mL / min for dropwise addant B. After the addition was completed, the reaction was kept at 80℃ for 4.5 h. After the reaction was completed, the solution was cooled, and the pH was adjusted to 7.0-7.5 with 1 mol / L NaOH solution. The solution was then diluted with water to a solid content of 40% to obtain a polycarboxylate superplasticizer. The mass ratio of isopentenyl alcohol polyoxyethylene ether, acrylic acid, itaconic acid, isomeric ester, and alkylamide betaine was 100:12:3:5:2.

[0032] Comparative Example 2 This comparative example is an existing responsive polycarboxylate superplasticizer, which is prepared by attaching clay through boric acid groups. The preparation method is as follows: A responsive polycarboxylate superplasticizer comprises the following components in parts by weight: 360 parts ethylene glycol monovinyl polyethylene glycol ether, 20 parts acrylic acid, 16 parts functional monomer A, 13 parts functional monomer B, 25 parts adipic acid dihydrazide, 1.6 parts hydrogen peroxide, 0.5 parts ascorbic acid, 0.6 parts mercaptopropionic acid, and 300 parts water; Among them, functional monomer A is aldehyde-modified acrylic acid; functional monomer A is prepared by the following method: under nitrogen atmosphere, glyoxal solution is added dropwise to a premix of acrylic acid and hydroquinone, purified by vacuum distillation, and functional monomer A is obtained, with the mass ratio of glyoxal, acrylic acid and hydroquinone being 1:1.25:0.5; the addition is carried out at 40 °C for 1 h. Functional monomer B is 4-(2-acryloyloxyethoxy)phenylboronic acid-2-carboxaldehyde; functional monomer B is prepared by the following method: 2-aldehyde phenylboronic acid is dissolved in water by stirring, then hydroxyethyl acrylate, dicyclohexylcarbodiimide and 4-dimethylaminopyridine are added, the reaction is carried out at 80 °C for 2 h, and dried to obtain functional monomer B; the mass ratio of 2-aldehyde phenylboronic acid, hydroxyethyl acrylate, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 1.25:1:0.75:0.1; The preparation method of the above-mentioned responsive polycarboxylate superplasticizer includes the following steps: (1) Dissolve ethylene glycol monovinyl polyethylene glycol ether in water, then add hydrogen peroxide to obtain a reactant solution; prepare a mixed solution A by mixing acrylic acid, functional monomer A and functional monomer B; prepare a mixed solution B by mixing a reducing agent and a chain transfer agent; (2) Add mixed solution A and mixed solution B dropwise to the reactant solution respectively. After the addition is complete, keep the reaction at 30 °C for 0.5 h. Then add adipic acid dihydrazide and continue the reaction for 3 h. Adjust the pH to neutral to obtain the responsive polycarboxylate superplasticizer.

[0033] Among them, the mixture was added dropwise under stirring conditions at 25℃, and the addition times for mixed solution A and mixed solution B were 50 min and 80 min, respectively.

[0034] Comparative Example 3 Based on Example 1, the difference from Example 1 is that component A in this comparative example does not include boric acid-modified MXene / chitosan and organotin catalyst, but the rest are the same.

[0035] Comparative Example 4 Based on Example 1, the difference from Example 1 is that the comparative example component A does not include the sodium alginate-coated ammonium modified polyacrylic acid polymer complex and the organotin catalyst, but all other components are the same.

[0036] Comparative Example 5 Based on Example 1, the difference from Example 1 is that the ammonium-modified polyacrylic acid polymer in component A of this comparative example is not coated with sodium alginate, nor is it compounded with boric acid-modified MXene / chitosan. Instead, it is added directly to component B in the same amount as the ammonium-modified polyacrylic acid polymer in Example 1, along with boric acid-modified MXene / chitosan. The amount of boric acid-modified MXene / chitosan added is the same as in Example 1, and the rest is the same as in Example 1.

[0037] Comparative Example 6 Based on Example 1, the difference from Example 1 is that in this comparative example, component A and component B are not mixed, are stored independently, and are added to the corresponding concrete simultaneously according to the proportions of Example 1 when used. All other aspects are the same.

[0038] Comparative Example 7 Based on Example 1, the difference from Example 1 is that the amount of component A in this comparative example is 4% of the mass of component B, while the rest are the same.

[0039] Comparative Example 8 Based on Example 1, the difference from Example 1 is that the amount of component A in this comparative example is 11% of the mass of component B, and the rest are the same.

[0040] Comparative Example 9 Based on the examples, unlike Example 1, no alkylamide betaine was added to component B of this comparative example; all other aspects were the same.

[0041] Experimental Example 1 The stability of the products prepared in Examples 1-3 and Comparative Examples 1, 3, 4, 5, 7, 8, and 9 was tested, and whether agglomeration or precipitation occurred during the standing process was observed. The results are shown in Table 1. Test method: After sealing the product, place it in a normal temperature (25±2℃, relative humidity 60%) and high temperature (50±2℃, relative humidity 60%) environment and observe the macroscopic changes after 0 days, 14 days and 30 days of standing. Observe whether flocculation, precipitation and stratification occur. After standing for 30 days at the corresponding temperature, take a sample to test the pH value of the product. If the product is stratified or precipitated, test the pH of the supernatant as the product pH and compare it with the product pH at 0 days of standing. Measure the absolute value of the pH difference between 30 days of standing and 0 days of standing (initial state). Take the average value of the three parallel test groups. The results are shown in Table 1.

[0042] Table 1 Product stability testing Let stand at 25℃ for 0 days Let stand at 25℃ for 14 days Let stand at 25℃ for 30 days pH difference after standing at 25℃ for 30 days 50℃ stand for 0 days Let stand at 50℃ for 14 days Let stand at 50℃ for 30 days pH difference after standing at 50℃ for 30 days Example 1 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation 0.1 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No obvious stratification, but with sediment. 0.2 Example 2 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation 0 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No obvious stratification, but with sediment. 0.2 Example 3 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation 0.1 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No obvious stratification, but with sediment. 0.3 Comparative Example 1 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation 0 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation 0.1 Comparative Example 3 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation 0.1 No stratification, no sedimentation, no flocculation No obvious stratification, but with sediment. There are layers and sediment. 0.3 Comparative Example 4 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation 0.1 No stratification, no sedimentation, no flocculation There are layers and sediment. There are layers and sediment. 0.4 Comparative Example 5 No stratification, no sedimentation, no flocculation No stratification, but with sediment. There are layers and sediments 0.3 No stratification, no sedimentation, no flocculation There are layers and sediment. There are layers and sediment. 0.5 Comparative Example 7 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation 0 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No obvious stratification, but with sediment. 0.2 Comparative Example 8 No stratification, no sedimentation, no flocculation No stratification, no sedimentation, no flocculation No layering, but with sediment. 0.2 No stratification, no sedimentation, no flocculation There are layers and sediment. There are layers and sediment. 0.4 Comparative Example 9 No stratification, no sedimentation, no flocculation No stratification, but with sediment. There are layers and sediments 0.4 No stratification, no sedimentation, no flocculation There are layers and sediment. There are layers and sediment. 0.5 The product of this application can be sealed and stored at room temperature for at least 30 days without any abnormal phenomena. The pH change is a normal pH fluctuation and has no impact on use. Long-term storage at 50℃ has a certain impact on stability, but it can be stored at room temperature.

[0043] Experimental Example 2 Referring to GB 8076—2008 "Concrete Admixtures", JG / T 223—2017 "Polycarboxylate Superior Water-Reducing Agents", and the Code for Mix Proportion Design of Ordinary Concrete JGJ55-2011, the basic performance of the products in Examples 1-3 and Comparative Examples 1-9 was tested. The results are shown in Tables 3-5, and all relevant data are expressed as the average of three test results. The mix proportion of the reference concrete used in this test is shown in Table 2. The admixture content of the products in Examples 1-3 and Comparative Examples 1-9 was 0.15% of the cement mass. The materials used in the reference concrete met the requirements of GB 8076—2008 "Concrete Admixtures". The reference concrete was prepared according to the relevant provisions of GB / T 8076-2008, and the mix proportion met the requirements of JGJ55. The cement used was Shiyan Huaxin Cement P042.5. The sand used met the requirements of GB / T14684, with a fineness modulus of 2.6-2.9 and a mud content of less than 1%, wherein the mud was not acidic. The aggregate used was crushed stone or gravel with a nominal particle size of 5mm-20mm that met the requirements of GB / T14685, using a two-stage mix design, with 5mm-10mm accounting for 40% and 10mm-20mm accounting for 60%. The concrete mixing met the requirements of JG 3036. The concrete specimen preparation and curing were carried out according to GB / T 50080. In the water reduction rate test of this application: when the water reduction rate is basically the same as the initial slump, the allowable deviation of the difference in unit water consumption between the reference concrete and the tested concrete to the unit water consumption of the reference concrete is ±10 mm.

[0044] Table 2. Basic Concrete Mixing (kg / m³) 3 ) cement Sand (fineness modulus of 2.6 to 2.9, mud content less than 1%) Pebbles (5mm~10mm) Pebbles (10mm~20mm) water 360 850 415 622 165 Table 3 Product Basic Performance Testing Test sample Water-reducing agent products Water reduction rate Perfusion rate Initial slump / mm Slump change over 1 hour / mm Concrete 1 Example 1 41.8% 4.9% 205 15 Concrete 2 Example 2 43.6% 4.5% 205 10 Concrete 3 Example 3 43.8% 4.3% 205 10 Concrete 1 Comparative Example 1 32.5% 8.2% 190 40 Concrete 2 Comparative Example 2 35.2% 7.1% 190 30 Concrete 3 Comparative Example 3 36.7% 6.5% 195 30 Concrete 4 Comparative Example 4 36.3% 6.8% 190 30 Concrete 5 Comparative Example 5 34.3% 9.4% 190 35 Concrete 6 Comparative Example 6 38.5% 5.7% 200 20 Concrete 7 Comparative Example 7 37.2% 5.9% 195 25 Concrete 8 Comparative Example 8 40.1% 5.1% 205 15 Concrete 9 Comparative Example 9 33.8% 8.8% 190 45 Reference concrete No water-reducing agent added - - 200 100 Table 4 Product Performance Testing

[0045] Table 5 Product Performance Testing

[0046] Based on the data in Tables 3-5, this application meets the requirements of high-performance standard water-reducing agents. The standard 28-day compressive strength ratio shall not be less than 140%, the 28-day shrinkage ratio (%) shall not be higher than 110%, the water reduction rate shall not be less than 25%, the bleeding rate shall not be greater than 60%, and the slump change over 1 hour (mm) shall be within 80 mm.

[0047] Experimental Example 3 Using the test samples concrete 1, concrete 2, concrete 3, control concrete 1, and control concrete 2 corresponding to the water-reducing agent products in Examples 1-3 and Comparative Examples 1-2 in Experimental Example 2 as reference concretes, the sand used in the reference concretes was washed to make the mud content of the sand less than 0.5%. This data was ignored when calculating the mud content of acidic soil. Then, acidic yellow soil with a pH of 4.5-5.5 was mixed into the sand, and the acidic soil content in the sand was 0.8%, 3%, and 5%, respectively. Taking the reference concrete described in this comparative example as the standard, the total sand content and total water content remained unchanged. The amount of water-reducing agent added to achieve the same initial slump as the reference concrete for concrete systems with different acidic soil contents was tested. The difference in initial slump of ±10mm was recorded as basically the same. The change in slump of concrete with different amounts of water-reducing agent added was measured over 1 hour in mm. Each group was tested three times and the average value was taken. The results are shown in Table 6.

[0048] Table 6. Test results of water-reducing agent dosage in acidic soil. Increased acidic clay content significantly reduces the initial slump of concrete. When the acidic clay content in concrete is less than 1%, the water-reducing agent of this application does not need to be added more. The slump of concrete can be maintained for 1 hour with a low addition amount. Acidic clay with a clay content of less than 1% has virtually no adverse effect on the water-reducing agent of this application. When the acidic clay content in sand is 3%-5%, the target slump can be obtained by adjusting the amount of water-reducing agent added, and the slump of concrete can be maintained for 1 hour.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A two-system composite water-reducing agent for concrete containing polycarboxylate, characterized in that: It includes component A and component B; component A is a passivating agent for acidic soil; component B is a polycarboxylate superplasticizer mother liquor with a pH of 7-7.5; the amount of component A is 5%-10% of the mass of component B; Component A includes a boric acid-modified MXene / chitosan, a complex of sodium alginate-coated ammonium-modified polyacrylic acid polymer, an organotin catalyst, or an organic base catalyst; wherein, the sodium alginate in the complex of sodium alginate-coated ammonium-modified polyacrylic acid polymer is isocyanate crosslinked modified sodium alginate. Component B includes a polymer prepared using isopentenyl alcohol polyoxyethylene ether, isomeric ester, acrylic acid, and itaconic acid as monomers, as well as alkylamide betaine.

2. The two-system composite water-reducing agent for concrete containing boric acid and polycarboxylate as described in claim 1, characterized in that: The boric acid-modified MXene / chitosan was prepared by the following method: MXene powder was prepared by hydrofluoric acid etching; the MXene powder was added to NaOH aqueous solution, stirred evenly, and then ultrasonically treated for 1-2 hours. After ultrasonic treatment, the mixture was filtered, washed until neutral, and dried to obtain polyhydroxy MXene material; amino-protected chitosan was dissolved in acetic acid solution, and ethylenediaminetetraacetic anhydride / methanol dispersion and 4-dimethylaminopyridine were added. The mixture was reacted at 75-80℃ for 4-8 hours under inert gas protection. After the reaction was completed, ethanol was added to precipitate the precipitate. The precipitate was washed and dried to obtain modified chitosan. Modified chitosan was added to MES buffer, and EDC and NHS were added to activate the carboxyl groups. Then it was mixed with polyhydroxy MXene material at a mass ratio of 1:3-4. The mixture was stirred for 20-24 hours, centrifuged, washed and dried to obtain MXene / amino-protected chitosan complex. MXene / amino-protected chitosan complex and 4-carboxyphenylboronic acid were added to DMF and stirred until homogeneous. Then, EDC and DIPEA were added, and the mixture was stirred at 50°C for 30-35 hours. After the reaction was completed, the mixture was cooled, filtered, washed, and dried to obtain boric acid-modified MXene / amino-protected chitosan complex. After deamination of the boric acid-modified MXene / amino-protected chitosan complex, boric acid-modified MXene / chitosan was obtained. The molar ratio of 4-carboxyphenylboronic acid, EDC, and DIPEA was 1.2:1.5:2, and the mass ratio of MXene / amino-protected chitosan complex to 4-carboxyphenylboronic acid was 2-2.5:

1.

3. The two-system composite water-reducing agent for concrete containing boric acid and polycarboxylic acid as described in claim 2, characterized in that: MXene is Ti3C2T x MXene material.

4. The two-system composite water-reducing agent for concrete containing polycarboxylate as described in claim 1, characterized in that: The sodium alginate-coated ammonium-modified polyacrylic acid polymer composite was prepared by the following method: S3.1 In a four-necked flask equipped with a stirrer, reflux condenser, constant pressure dropping funnel and nitrogen inlet, deionized water and polyethylene glycol monomethyl ether acrylate are added, nitrogen is passed through to remove oxygen, and after heating, acrylic acid, hydroxyethyl acrylate and ammonium persulfate are added. The reaction is kept at 70°C and then cooled to room temperature to obtain polyacrylic acid polymer. S3.2 Add epichlorohydrin and trimethylamine aqueous solution to polyacrylic acid polymer, adjust pH to 8.0~8.5 with NaOH, react at 45℃ for 4 h, and after the reaction is completed, adjust pH to 7.0 with dilute hydrochloric acid to obtain liquid ammonium modified polyacrylic acid polymer; S3.

3. An HDI crosslinked modified sodium alginate solution was prepared using hexamethylene diisocyanate (HDI) with one end closed as a crosslinking agent. Liquid ammonium modified polyacrylic acid polymer was added dropwise to the HDI crosslinked modified sodium alginate solution. The mass ratio of liquid ammonium modified polyacrylic acid polymer to sodium alginate in the HDI crosslinked modified sodium alginate solution was 2:

1. The dropping rate was 0.8-1.5 mL / min. After the addition was complete, the mixture was stirred at low speed at 30-35℃ for 2.5 h. Then, the temperature was raised to 50℃ and kept at that temperature for 1 h. After cooling to room temperature, the mixture was filtered, the precipitate was collected, and dried to obtain the sodium alginate-coated ammonium modified polyacrylic acid polymer composite.

5. A two-system composite water-reducing agent for concrete containing polycarboxylate as described in claim 4, characterized in that: The amount of hexamethylene diisocyanate with one end blocked in the HDI crosslinked modified sodium alginate solution is 5-8% of the mass of sodium alginate; the hexamethylene diisocyanate with one end blocked uses N-hydroxyphthalimide as the blocking agent, and the molar ratio of N-hydroxyphthalimide to hexamethylene diisocyanate is 1:

1.

6. A two-system composite water-reducing agent for concrete containing polycarboxylate as described in claim 2, characterized in that: Chitosan has a degree of deacetylation greater than 90%.

7. A two-system composite water-reducing agent for concrete containing polycarboxylate as described in claim 2, characterized in that: The amino-protected chitosan is amino-protected using phthalic anhydride in a DMF solution containing 5% water.

8. A two-system composite water-reducing agent for concrete containing polycarboxylate as described in claim 1, characterized in that: Component B is prepared by the following method: isopentenyl alcohol polyoxyethylene ether is added to a four-necked flask, heated to 60-70°C, stirred until completely dissolved, and nitrogen gas is passed through to remove oxygen, to obtain isopentenyl alcohol polyoxyethylene ether solution for later use. Two dropping solutions were prepared separately: Dropping solution A: Acrylic acid, itaconic acid, and isomeric ester were mixed evenly, and deionized water was added at a solid-liquid mass ratio of 1:

1. The mixture was stirred evenly to obtain dropping solution A; Dropping solution B: Ammonium persulfate was dissolved in deionized water to prepare a 5% solution by mass. The amount of ammonium persulfate used was 0.8-1.2% of the total mass of acrylic acid, itaconic acid, isomeric ester, and isopentenyl alcohol polyoxyethylene ether. The isopentenyl alcohol polyoxyethylene ether solution was heated to 75-80℃, and dropping solutions A and B were slowly added dropwise. The dropping rate was controlled to be 2-3 mL / min for dropping solution A and 1-2 mL / min for dropping solution B. After the addition was complete, the reaction was kept at 80℃ for 4-5 hours. After the reaction was completed, the solution was cooled to 40-50℃, and alkylamide betaine was added and stirred until completely dissolved. The pH was adjusted to 7.0-7.5 with 1 mol / L NaOH solution, and the solution was diluted with water to a solid content of 40% to obtain component B.

9. A two-system composite water-reducing agent for concrete containing polycarboxylate as described in claim 1, characterized in that: For concrete systems where the sand contains ≤5% acidic soil with a pH of 4.5-5.

5.

10. A method for preparing a polycarboxylate-based dual-system composite water-reducing agent for concrete according to any one of claims 1-9, characterized in that: Includes the following steps: S1. Preparation of Component A: The boric acid-modified MXene / chitosan and sodium alginate-coated ammonium-modified polyacrylic acid polymer composite were mixed at a mass ratio of 2:1 and dispersed in anhydrous N,N-dimethylformamide. 0.1% (by mass) of dibutyltin dilaurate of the total mass of the boric acid-modified MXene / chitosan and sodium alginate-coated ammonium-modified polyacrylic acid polymer composite was added. Under nitrogen protection, the temperature was raised to 80-100℃ and the reaction was stirred for 4-6 hours. After the reaction was completed, the mixture was cooled, filtered, washed with anhydrous ethanol, and dried to obtain Component A. S2. Preparation of component B: Add isopentenyl alcohol polyoxyethylene ether to a four-necked flask, heat to 60-70℃, stir until completely dissolved, purge with nitrogen to remove oxygen, and obtain isopentenyl alcohol polyoxyethylene ether solution for later use. Two dropping solutions were prepared separately: Dropping solution A: Acrylic acid, itaconic acid, and isomeric ester were mixed evenly, and deionized water was added at a solid-liquid mass ratio of 1:

1. The mixture was stirred evenly to obtain dropping solution A; Dropping solution B: Ammonium persulfate was dissolved in deionized water to prepare a 5% solution by mass, and the amount of initiator was 0.8-1.2% of the total mass of acrylic acid, itaconic acid, isomeric ester, and isopentenyl polyoxyethylene ether; wherein, the isomeric ester is a cycloisomeric ester of acrylic acid; The isopentenyl alcohol polyoxyethylene ether solution was heated to 75-80℃, and dropping solutions A and B were slowly added dropwise. The dropping rate was controlled to be 2-3 mL / min for dropping solution A and 1-2 mL / min for dropping solution B. After the addition was complete, the reaction was maintained at 80℃ for 4-5 hours. After the reaction was completed, the solution was cooled to 40-50℃, and alkylamide betaine was added and stirred until completely dissolved. The pH was adjusted to 7.0-7.5 with 1 mol / L NaOH solution, and the solution was diluted with water to a solid content of 40% to obtain component B. The mass ratio of isopentenyl alcohol polyoxyethylene ether, acrylic acid, itaconic acid, isomeric ester, and alkylamide betaine was 100:12:3:5:

2. S3. Mixing Component A and Component B: Add Component B to the mixing tank, adjust the temperature to 30-35℃, and the stirring rate to 200-300 r / min; add Component A slowly to Component B at a ratio of 5%-10% of the mass of Component B, stirring continuously. After Component A is added, continue stirring for 1.5-2 hours. After stirring, take a sample to test the pH value, ensuring that the pH of the entire system is 7.0-7.5, thus obtaining a two-system composite water-reducing agent for concrete containing polycarboxylate.

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