A reduced-type MXene polycarboxylic acid water reducing agent and a preparation method thereof

Abstract

A reduced shrinkage MXene polycarboxylic acid water reducing agent and a preparation method thereof. The raw materials of the reduced shrinkage MXene polycarboxylic acid water reducing agent include, in parts by mass, 0.2-1.0 parts of MXene, 0.1-2.0 parts of methacryloyloxysilane, 0.001-0.005 parts of a catalyst, 175-225 parts of a polyether monomer, 15-40 parts of an unsaturated carboxylic acid small monomer, 0.6-1.0 parts of a chain transfer agent, 0.4-1.0 parts of an initiator, 0.2-0.5 parts of a reducing agent, and an alkali liquor. The MXene polycarboxylic acid water reducing agent has a large steric hindrance, can improve the fluidity of a concrete mixture, and the rich active groups and surface charges of MXene enable it to be well combined with concrete through electrostatic action, van der Waals force, hydrogen bonding and other forces, increase the workability of the polycarboxylic acid water reducing agent, and the water reducing agent provided by the application shows good water reducing, slump retaining and shrinkage reducing performance.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, specifically relating to a shrinkage-reducing MXene polycarboxylate superplasticizer and its preparation method. Background Technology

[0002] Polycarboxylate superplasticizers are commonly used additives in concrete and cement products. They are widely used in the building materials industry due to their advantages such as reducing the water-cement ratio, increasing fluidity, and improving workability. However, polycarboxylate superplasticizers often encounter problems during application, such as poor compatibility with concrete materials, cracking, and shrinkage, making it difficult to guarantee concrete quality.

[0003] MXene, as an emerging two-dimensional nanomaterial, mainly includes transition metal carbides, nitrides, and nitrocarbides. Due to its large specific surface area, excellent mechanical strength, and abundant chelating sites (such as -F, =O, and -OH), it has attracted widespread attention in various research and application fields. Adding appropriate amounts of MXene to cement paste, mortar, or concrete is expected to improve mechanical properties. However, the large specific surface area and high surface energy of solid powdered MXene limit its diffusion ability in cement paste, making it prone to micron-level agglomeration. Although dispersion can be achieved through physical blending with polycarboxylate superplasticizers, this leads to the use of polycarboxylate superplasticizers far exceeding the maximum dosage required by the cement paste, potentially causing severe retardation problems in cement-based materials. Therefore, how to prepare a shrinkage-reducing MXene polycarboxylate superplasticizer using a simple and low-cost method is a problem urgently needing to be solved by those skilled in the art. Summary of the Invention

[0004] To solve all or part of the above-mentioned technical problems, the present invention provides the following technical solutions:

[0005] One objective of this invention is to provide a shrinkage-reducing MXene polycarboxylate superplasticizer, wherein, by weight, the raw materials of the shrinkage-reducing MXene polycarboxylate superplasticizer include 0.2-1.0 parts MXene, 0.1-2.0 parts methacryloxysilane, 0.001-0.005 parts catalyst, 175-225 parts polyether monomer, 15-40 parts unsaturated carboxylic acid monomer, 0.6-1.0 parts chain transfer agent, 0.4-1.0 parts initiator, 0.2-0.5 parts reducing agent, and alkali solution.

[0006] This invention significantly improves the water-reducing, slump-retaining, and shrinkage-reducing properties of polycarboxylate superplasticizers by introducing MXene. Adding the MXene polycarboxylate superplasticizer provided by this invention to concrete makes it less prone to bleeding. The introduction of MXene increases the steric hindrance of the superplasticizer, enhancing its dispersibility. Furthermore, the active groups on MXene (e.g., negatively charged F) can react with the positively charged calcium silicate groups (Ca) in silicate cement. 2+ It generates static electricity, increasing the workability of polycarboxylate superplasticizer.

[0007] In some embodiments, the MXene contains one or more active groups, such as hydroxyl groups and F ions. For example, the MXene is a two-dimensional carbon nanosheet containing hydroxyl groups prepared by in-situ hydrogen fluoride etching.

[0008] In some embodiments, the methacryloyloxysilane includes at least one of methacryloyloxypropyltrimethoxysilane, methacryloyloxypropyltriethoxysilane, and methacryloyloxypropyltriisopropoxysilane.

[0009] In some embodiments, the catalyst includes at least one of sodium sulfite, potassium sulfite, sodium bisulfite, and ferrous sulfate.

[0010] In some embodiments, the polyether monomer includes at least one of isobutylene polyethylene glycol ether (e.g., HPEG2400), isopentenyl polyethylene glycol ether (e.g., TPEG2400), and ethylene glycol monovinyl polyethylene glycol ether (e.g., EPEG3000).

[0011] In some embodiments, the unsaturated carboxylic acid monomer includes at least one of acrylic acid and methacrylic acid.

[0012] In some embodiments, the chain transfer agent includes at least one of sodium hypophosphite, mercaptoethanol, mercaptoacetic acid, and mercaptopropionic acid.

[0013] In some embodiments, the initiator includes at least one of hydrogen peroxide, sodium persulfate, ammonium persulfate, and potassium persulfate.

[0014] In some embodiments, the reducing agent includes at least one of vitamin C and sodium formaldehyde sulfoxylate.

[0015] In some embodiments, the alkaline solution includes at least one of NaOH solution and KOH solution.

[0016] A second objective of this invention is to provide a method for preparing a shrinkage-reducing MXene polycarboxylate superplasticizer, comprising:

[0017] S1: React a mixed reaction system containing polyether monomers, unsaturated carboxylic acid monomers, methacryloxysilane, chain transfer agent, reducing agent, catalyst and initiator to obtain polycarboxylic acid water-reducing agent;

[0018] S2: Mix the polycarboxylate superplasticizer with MXene uniformly and carry out esterification and coupling reactions to obtain a shrinkage-reducing MXene polycarboxylate superplasticizer.

[0019] The preparation method provided by this invention utilizes the coupling reaction between methacryloyloxysilane and MXene, and the esterification reaction between the carboxylic acid groups of the polycarboxylate superplasticizer and the hydroxyl groups of MXene, successfully grafting MXene onto the superplasticizer to obtain an MXene polycarboxylate superplasticizer. By using methacryloyloxysilane grafting, not only can it graft MXene, but it can also enhance the adhesion between the superplasticizer and cement particles, thereby improving the mechanical strength of cement. Through the transverse and longitudinal grafting morphology of polyether monomers and MXene, a three-dimensional hydrophilic-hydrophobic layer of the superplasticizer is increased, improving the fluidity and slump retention of cement-based materials, and exhibiting good advantages in shrinkage reduction.

[0020] In some embodiments, S1 specifically includes:

[0021] Solution A, solution B and solution C are provided, wherein solution A includes a polyether monomer, an unsaturated carboxylic acid monomer, a catalyst and an initiator, solution B includes an unsaturated carboxylic acid monomer, methacryloxysilane and a chain transfer agent, and solution C includes a reducing agent;

[0022] The solutions B and C are added to the solution A at a constant rate to obtain the mixed reaction system.

[0023] Furthermore, solution B was added at a uniform rate over a period of 0.5-2.0 hours.

[0024] Furthermore, the solution C was added at a uniform rate over a period of 0.5-2.5 hours.

[0025] Furthermore, the reaction temperature of the mixed reaction system is 10–30°C.

[0026] Furthermore, the reaction time of the mixed reaction system is 0.5 to 1.5 hours.

[0027] In some embodiments, after the mixed reaction system has completed the reaction, the reaction product is adjusted to neutral using an alkaline solution.

[0028] In a typical embodiment, S1 (i.e., the preparation method of polycarboxylate superplasticizer) includes the following steps:

[0029] The polyether monomer and the unsaturated carboxylic acid monomer are dissolved in deionized water to prepare solution A (i.e., solution A); the unsaturated carboxylic acid monomer, methacryloxysilane, molecular weight regulator and deionized water are mixed to prepare solution B; the reducing agent and deionized water are mixed to prepare solution C.

[0030] Add catalyst and initiator to liquid A at the bottom of the reactor, and then add solution B and solution C dropwise at a uniform rate. After the addition is completed, keep the temperature to obtain the unmodified polycarboxylate superplasticizer solution.

[0031] In some embodiments, S2 specifically includes: removing water from the polycarboxylate superplasticizer prepared in S1, then adding MXene solid powder and mixing it evenly, adjusting the temperature to 60-80℃ to carry out the esterification reaction and coupling reaction, and after the reaction is completed, using an alkaline solution to adjust the reaction product to neutral to obtain the shrinkage-reducing MXene polycarboxylate superplasticizer.

[0032] In a typical embodiment, S2 includes the following steps: after removing water from the polycarboxylate superplasticizer by vacuum distillation, it is added to a round-bottom flask, then MXene solid powder is added, stirred evenly, heated to the reaction temperature to carry out esterification and coupling reactions, and after the reaction is completed, alkali solution is added dropwise to adjust the pH value of the reaction product to neutral, and the product is cooled and discharged to obtain MXene polycarboxylate superplasticizer.

[0033] In some embodiments, the MXene contains one or more active groups, such as hydroxyl groups and F ions.

[0034] In some embodiments, the total reaction time for the esterification and coupling reactions is 2-6 hours.

[0035] In some embodiments, the mixed reaction system contains, by weight, 175-225 parts of polyether monomer, 15-40 parts of unsaturated carboxylic acid monomer, 0.1-2.0 parts of methacryloxysilane, 0.6-1.0 parts of chain transfer agent, 0.2-0.5 parts of reducing agent, 0.001-0.005 parts of catalyst, and 0.4-1.0 parts of initiator.

[0036] In some embodiments, the amount of polycarboxylate superplasticizer in S2 is 230-270 parts by weight, and the amount of MXene is 0.2-1.0 parts by weight.

[0037] In some embodiments, solution A contains 5-10 parts by mass of unsaturated carboxylic acid monomers.

[0038] In some embodiments, solution B contains 10-30 parts of unsaturated carboxylic acid monomers.

[0039] In the “Preparation Method of Shrinkage-Reducing MXene Polycarboxylate Water-Reducing Agent” described in this invention, the specific substances that can be used, such as MXene, methacryloxysilane, catalyst, polyether monomer, unsaturated carboxylic acid monomer, chain transfer agent, initiator, reducing agent, and alkali solution, have been described in detail in the first aspect of this invention and will not be repeated here.

[0040] A third objective of this invention is to provide a shrinkage-reducing MXene polycarboxylate superplasticizer obtained according to the preparation method described in any of the above technical solutions.

[0041] The fourth objective of this invention is to provide a building material, which includes cement-based materials and the shrinkage-reducing MXene polycarboxylate superplasticizer described in any of the above technical solutions.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) In this invention, MXene material is introduced into polycarboxylate superplasticizer. The two-dimensional grid structure of MXene can increase the steric hindrance at the end of the side chain of polycarboxylate superplasticizer, reduce the side chain entanglement of polycarboxylate superplasticizer, effectively improve the thickness of the adsorption layer and improve the fluidity of concrete mixture. Furthermore, a large number of negatively charged F atoms on MXene play an anchoring role, increasing the workability of polycarboxylate superplasticizer. The MXene polycarboxylate superplasticizer shows good water reduction, slump retention and shrinkage reduction performance.

[0044] (2) The preparation method provided by the present invention utilizes the coupling reaction between methacryloyloxysilane and MXene, and the esterification reaction between the carboxylic acid group of the polycarboxylic acid superplasticizer and the hydroxyl group of MXene, to successfully graft MXene onto the superplasticizer, thereby obtaining an MXene polycarboxylic acid superplasticizer; by using methacryloyloxysilane grafting, not only can it play the role of grafting MXene, but it can also enhance the adhesion between the superplasticizer and cement particles, thereby improving the mechanical strength of cement; through the transverse and longitudinal grafting morphology of polyether monomer and MXene, a three-dimensional hydrophilic-hydrophobic layer is added, improving the fluidity and slump retention of cement-based materials, and showing better advantages in shrinkage reduction;

[0045] (3) MXenes materials have a two-dimensional sheet structure similar to graphene and a high specific surface area, as well as abundant surface functional groups and surface negative charges, which enable them to bond with concrete through electrostatic interactions, van der Waals forces, hydrogen bonds, etc. In addition, MXene has a high specific surface area and abundant functional groups, which makes it have excellent adsorption properties. It can adsorb carbon dioxide at room temperature and pressure, reducing the carbonation shrinkage of concrete. MXene has high mechanical strength and hydrophilicity, which can reduce the shrinkage and autogenous shrinkage of concrete during the plastic stage. MXene has higher electrical and thermal conductivity than most metals and alloys. Its thermal conductivity can reach or even exceed that of graphene, reducing the temperature shrinkage of concrete.

[0046] (4) The preparation method provided by the present invention is simple and fast, and easy to carry out large-scale production. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the structure of the MXene polycarboxylate superplasticizer prepared in this invention and its adsorption of cement particles. Detailed Implementation

[0049] The technical solutions of the present invention will be described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention. The specific functional details disclosed herein should not be construed as limiting, but are merely intended to form the basis of the claims and to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0050] This invention provides an MXene polycarboxylate superplasticizer and its preparation method. For example... Figure 1 As shown, because the water-reducing agent is grafted with MXene material having a two-dimensional mesh structure, the steric hindrance of the water-reducing agent is increased, thus improving its dispersion performance. The greater steric hindrance effect when the water-reducing agent adsorbs cement particles enhances the fluidity of the concrete mixture. Furthermore, in some embodiments of the present invention, MXene material containing F ions can be selected. The large number of negatively charged F atoms on MXene can react with the positively charged Ca atoms of calcium silicate in silicate cement. 2+The electrostatic effect generates an anchoring effect, increasing the workability of the polycarboxylate superplasticizer. In addition, during the research and development, the applicant used methacryloyloxysilane to copolymerize with the monomer and bridge MXene through a coupling reaction. At the same time, the carboxylic acid groups of the polycarboxylate superplasticizer and the hydroxyl groups of MXene were esterified and grafted. The synergistic effect of the esterification reaction and the coupling reaction can increase the grafting sites. Through transverse (main chain) and longitudinal (end group) grafting, the grafting morphology of MXene is enriched, which has good adaptability to complex concrete environments and further improves the shrinkage reduction performance of the superplasticizer.

[0051] Unless otherwise specified, all raw materials and reagents used in this invention are commercially available.

[0052] The preparation method of the MXene material used in the following embodiments of the present invention is as follows:

[0053] In a fume hood, 60 mL of 9 mol / L HCl and 5 g of lithium fluoride powder were placed in a 200 mL polytetrafluoroethylene beaker and magnetically stirred in a 35°C water bath for 2 h. Then, 3 g of titanium aluminum carbide powder (Ti3AlC2) was added in small amounts several times, and the mixture was stirred at 30°C for 30 h to obtain a black liquid. The black liquid was centrifuged at 3500 rpm, the supernatant was discarded, and the precipitate was washed with 2 mol / L HCl and deionized water. The centrifugation was repeated 6-8 times until the pH of the supernatant was about 6, resulting in a blackish-gray precipitate. This blackish-gray precipitate was multilayered MXene with a large number of residual groups (e.g., -F, -OH, =O, etc.) on its surface. Under a nitrogen atmosphere, the mixture was sonicated in an ice-water bath for 60 min and centrifuged at 2500 rpm for 0.5 h to obtain a dark green upper dispersion (i.e., a few-layered MXene). The dark green upper dispersion was freeze-dried to obtain MXene solid powder.

[0054] Of course, MXene solid powder obtained through other means, such as purchasing, is also applicable to the technical solution of this invention.

[0055] The raw materials used in the following embodiments of the present invention—polyether monomers HPEG2400, TPEG2400, and EPEG3000—were all purchased from Lianyungang Petrochemical Co., Ltd. Methacryloxysilane, unsaturated carboxylic acid monomers, catalysts, chain transfer agents, initiators, reducing agents, and caustic soda flakes were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Unless otherwise specified, the purity of the chemical reagents and raw materials used in the following embodiments of the present invention is industrial grade or higher.

[0056] Example 1

[0057] This embodiment provides a shrinkage-reducing MXene polycarboxylate superplasticizer and its preparation method:

[0058] (1) Mix 213 parts of polyether monomer HPEG2400, 0.4 parts of methacryloxypropyltrimethoxysilane and 175 parts of deionized water, then add 5 parts of acrylic acid and stir mechanically until dissolved to obtain bottom solution A; mix 10 parts of acrylic acid, 0.9 parts of chain transfer agent sodium phosphite and 20 parts of deionized water to obtain solution B; mix 0.4 parts of reducing agent vitamin C and 40.0 parts of deionized water to prepare solution C;

[0059] (2) Add 0.005 parts of catalyst sodium sulfite and 0.5 parts of initiator hydrogen peroxide to the prepared bottom liquid A, and then add dropwise solution B (added in 50 min) and solution C (added in 60 min) at a uniform rate. After the dropwise addition is completed, keep warm for 1 h to obtain polycarboxylate superplasticizer solution.

[0060] (3) After removing water from the prepared polycarboxylate superplasticizer by vacuum distillation, add it to a round bottom flask, add 0.2 parts of MXene solid powder, stir evenly, heat to 70°C, and after 4 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain MXene polycarboxylate superplasticizer.

[0061] Example 2

[0062] (1) Mix 213 parts of polyether monomer TPEG2400, 0.4 parts of methacryloxypropyltriethoxysilane and 175 parts of deionized water, then add 5 parts of methacrylic acid and stir mechanically until dissolved to obtain bottom solution A; mix 10 parts of methacrylic acid, 0.9 parts of mercaptoethanol and 20 parts of deionized water to prepare solution B; mix 0.4 parts of reducing agent and 40.0 parts of deionized water to prepare solution C;

[0063] (2) Add 0.005 parts of catalyst potassium sulfite and 0.5 parts of initiator sodium persulfate to the prepared bottom liquid A, and then add dropwise solution B (added in 50 min) and solution C (added in 60 min) at a uniform rate. After the dropwise addition is completed, keep warm for 1 h to obtain polycarboxylate superplasticizer solution.

[0064] (3) After removing water from the prepared polycarboxylate superplasticizer by vacuum distillation, add it to a round-bottom flask, add 0.4 parts of MXene solid powder, stir evenly, heat to 70°C, and after 4 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain MXene polycarboxylate superplasticizer.

[0065] Example 3

[0066] (1) Mix 213 parts of polyether monomer EPEG3000, 0.4 parts of methacryloxypropyltriisopropoxysilane and 175 parts of deionized water, then add 5 parts of acrylic acid and stir mechanically until dissolved to obtain bottom solution A; mix 10 parts of methacrylic acid, 0.9 parts of chain transfer agent mercaptoacetic acid and 20 parts of deionized water to prepare solution B; mix 0.4 parts of reducing agent vitamin C and 40.0 parts of deionized water to prepare solution C;

[0067] (2) Add 0.005 parts of catalyst sodium bisulfite and 0.5 parts of initiator ammonium persulfate to the prepared bottom liquid A, and then add dropwise solution B (added in 50 min) and solution C (added in 60 min) at a uniform rate. After the dropwise addition is completed, keep warm for 1 h to obtain polycarboxylate superplasticizer solution.

[0068] (3) After removing water from the obtained polycarboxylate superplasticizer by vacuum distillation, add it to a round bottom flask, add 0.6 parts of MXene solid powder, stir evenly, heat to 70°C, and after 4 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain MXene polycarboxylate superplasticizer.

[0069] Example 4

[0070] (1) Mix 100 parts of polyether monomer HPEG2400, 113 parts of polyether monomer TPEG2400, 0.2 parts of methacryloyloxypropyltrimethoxysilane, 0.2 parts of methacryloyloxypropyltriethoxysilane and 175 parts of deionized water, then add 2 parts of acrylic acid and 3 parts of methacrylic acid, and mechanically stir until dissolved to obtain bottom solution A; mix 10 parts of acrylic acid, 0.9 parts of chain transfer agent mercaptopropionic acid and 20 parts of deionized water to prepare solution B; mix 0.4 parts of reducing agent sodium formaldehyde sulfoxylate and 40.0 parts of deionized water to prepare solution C;

[0071] (2) Add 0.005 parts of ferrous sulfate catalyst and 0.5 parts of potassium persulfate initiator to the prepared bottom liquid A, and then add dropwise solution B (completed in 50 min) and solution C (completed in 60 min) at a uniform rate. After the dropwise addition is completed, keep warm for 1 h to obtain polycarboxylate superplasticizer solution.

[0072] (3) After removing water from the obtained polycarboxylate superplasticizer by vacuum distillation, add it to a round bottom flask, add 0.8 parts of MXene solid powder, stir evenly, heat to 70°C, and after 4 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain MXene polycarboxylate superplasticizer.

[0073] Example 5

[0074] (1) Mix 100 parts of polyether monomer HPEG2400, 113 parts of polyether monomer EPEG3000, 0.1 parts of methacryloyloxypropyltriethoxysilane, 0.1 parts of methacryloyloxypropyltriisopropoxysilane and 175 parts of deionized water, then add 5 parts of methacrylic acid and stir mechanically until dissolved to obtain bottom solution A; mix 10 parts of acrylic acid, 0.3 parts of chain transfer agent mercaptoethanol, 0.6 parts of mercaptopropionic acid and 20 parts of deionized water to prepare solution B; mix 0.2 parts of reducing agent vitamin C, 0.2 parts of reducing agent sodium formaldehyde sulfoxylate and 40.0 parts of deionized water to prepare solution C;

[0075] (2) Add 0.005 parts of ferrous sulfate catalyst and 0.5 parts of hydrogen peroxide initiator to the prepared bottom liquid A, and then add dropwise solution B (completed in 50 min) and solution C (completed in 60 min) at a uniform rate. After the dropwise addition is completed, keep warm for 1 h to obtain polycarboxylate superplasticizer solution.

[0076] (3) After removing water from the prepared polycarboxylate superplasticizer by vacuum distillation, add it to a round bottom flask, add 0.6 parts of MXene solid powder, stir evenly, heat to 70°C, and after 4 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain polycarboxylate superplasticizer.

[0077] Example 6

[0078] (1) Mix 50 parts of polyether monomer HPEG2400, 163 parts of polyether monomer EPEG3000, 0.6 parts of methacryloyloxypropyltrimethoxysilane and 175 parts of deionized water, then add 5 parts of acrylic acid and stir mechanically until dissolved to obtain bottom solution A; mix 10 parts of methacrylic acid, 0.9 parts of chain transfer agent mercaptoethanol and 20 parts of deionized water to prepare solution B; mix 0.4 parts of reducing agent vitamin C and 40.0 parts of deionized water to prepare solution C;

[0079] (2) Add 0.002 parts of catalyst sodium sulfite, 0.002 parts of catalyst potassium sulfite, 0.2 parts of initiator hydrogen peroxide, and 0.3 parts of initiator sodium persulfate to the prepared bottom liquid A. Then add dropwise solution B (added in 50 min) and solution C (added in 60 min) at a uniform rate. After the dropwise addition is completed, keep warm for 1 h to obtain polycarboxylate superplasticizer solution.

[0080] (3) After removing water from the obtained polycarboxylate superplasticizer by vacuum distillation, add it to a round-bottom flask, add 0.6 parts of MXene solid powder, stir evenly, heat to 70°C, and after 4 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain polycarboxylate superplasticizer.

[0081] Example 7

[0082] (1) Mix 175 parts of polyether monomer EPEG3000, 0.1 parts of methacryloxypropyltriethoxysilane and 175 parts of deionized water, then add 8 parts of acrylic acid and stir mechanically until dissolved to obtain bottom solution A; mix 24 parts of acrylic acid, 0.6 parts of chain transfer agent sodium hypophosphite and 20 parts of deionized water to prepare solution B; mix 0.2 parts of reducing agent vitamin C and 40.0 parts of deionized water to prepare solution C;

[0083] (2) Add 0.001 parts of ferrous sulfate catalyst and 0.4 parts of hydrogen peroxide initiator to the prepared bottom liquid A, and then add solution B (added in 30 min) and solution C (added in 30 min) at a uniform rate. After the addition is completed, keep warm for 1 h to obtain polycarboxylate superplasticizer solution.

[0084] (3) After removing water from the obtained polycarboxylate superplasticizer by vacuum distillation, add it to a round bottom flask, add 1.0 part of MXene solid powder, stir evenly, heat to 60°C, and after 2 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain polycarboxylate superplasticizer.

[0085] Example 8

[0086] (1) Mix 225 parts of polyether monomer HPEG2400, 2.0 parts of methacryloxypropyltriisopropoxysilane and 175 parts of deionized water, then add 10 parts of methacrylic acid and stir mechanically until dissolved to obtain bottom solution A; mix 30 parts of acrylic acid, 1.0 part of chain transfer agent mercaptoethanol and 20 parts of deionized water to prepare solution B; mix 0.3 parts of reducing agent sodium formaldehyde sulfoxylate and 40.0 parts of deionized water to prepare solution C;

[0087] (2) Add 0.003 parts of catalyst potassium sulfite and 1.0 parts of initiator ammonium persulfate to the prepared bottom liquid A, and then add dropwise solution B (to be added in 2.0h) and solution C (to be added in 2.5h) at a uniform rate. After the dropwise addition is completed, keep warm for 1h to obtain polycarboxylate superplasticizer solution.

[0088] (3) After removing water from the obtained polycarboxylate superplasticizer by vacuum distillation, add it to a round bottom flask, add 1.0 part of MXene solid powder, stir evenly, heat to 80°C, and after 6 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain polycarboxylate superplasticizer.

[0089] Comparative Example 1

[0090] The only difference between Comparative Example 1 and Example 3 is that MXene solid powder and methacryloxysilane are not added. The preparation method is as follows:

[0091] (1) Mix 213 parts of polyether monomer HPEG2400 and 175 parts of deionized water, then add 5 parts of acrylic acid and stir mechanically until dissolved to obtain bottom solution A; mix 10 parts of acrylic acid, 0.9 parts of sodium hypophosphite and 20 parts of deionized water to prepare drop solution B; mix 0.4 parts of reducing agent vitamin C and 40.0 parts of deionized water to prepare drop solution C;

[0092] (2) Add 0.005 parts of catalyst sodium sulfite and 0.5 parts of initiator hydrogen peroxide to the prepared bottom liquid A, and then add material B (completed in 50 min) and material C (completed in 60 min) at a uniform rate. After the addition is completed, keep warm for 1 h to obtain polycarboxylate superplasticizer solution.

[0093] (3) After removing water from the obtained polycarboxylate superplasticizer by vacuum distillation, add it to a round-bottom flask, stir evenly, heat to 70°C, and after 4 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain polycarboxylate superplasticizer.

[0094] Comparative Example 2

[0095] The only difference between Comparative Example 2 and Example 3 is that methacryloxysilane is not added. The preparation method is as follows:

[0096] (1) Mix 213 parts of polyether monomer EPEG3000 and 175 parts of deionized water, then add 5 parts of acrylic acid and stir mechanically until dissolved to obtain bottom solution A; mix 10 parts of methacrylic acid, 0.9 parts of chain transfer agent mercaptoacetic acid and 20 parts of deionized water to prepare solution B; mix 0.4 parts of reducing agent vitamin C and 40.0 parts of deionized water to prepare solution C;

[0097] (2) Add 0.005 parts of catalyst sodium bisulfite and 0.5 parts of initiator ammonium persulfate to the prepared bottom liquid A, and then add dropwise solution B (added in 50 min) and solution C (added in 60 min) at a uniform rate. After the dropwise addition is completed, keep warm for 1 h to obtain polycarboxylate superplasticizer solution.

[0098] (3) After removing water from the obtained polycarboxylate superplasticizer by vacuum distillation, add it to a round bottom flask, add 0.6 parts of MXene solid powder, stir evenly, heat to 70°C, and after 4 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain MXene polycarboxylate superplasticizer.

[0099] Comparative Example 3

[0100] The only difference between Comparative Example 3 and Example 3 is that MXene solid powder is not added. The preparation method is as follows:

[0101] (1) Mix 213 parts of polyether monomer EPEG3000, 0.4 parts of methacryloxypropyltriisopropoxysilane and 175 parts of deionized water, then add 5 parts of acrylic acid and stir mechanically until dissolved to obtain bottom solution A; mix 10 parts of methacrylic acid, 0.9 parts of chain transfer agent mercaptoacetic acid and 20 parts of deionized water to prepare solution B; mix 0.4 parts of reducing agent vitamin C and 40.0 parts of deionized water to prepare solution C;

[0102] (2) Add 0.005 parts of catalyst sodium bisulfite and 0.5 parts of initiator ammonium persulfate to the prepared bottom liquid A, and then add dropwise solution B (added in 50 min) and solution C (added in 60 min) at a uniform rate. After the dropwise addition is completed, keep warm for 1 h to obtain polycarboxylate superplasticizer solution.

[0103] (3) After removing water from the obtained polycarboxylate superplasticizer by vacuum distillation, add it to a round-bottom flask, stir evenly, heat to 70°C, and after 4 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain polycarboxylate superplasticizer.

[0104] Comparative Example 4

[0105] The only difference between Comparative Example 4 and Example 1 is that methacryloxysilane is replaced with vinyltriethoxysilane, and the preparation method is as follows:

[0106] (1) Mix 213 parts of polyether monomer, 0.4 parts of vinyltriethoxysilane and 175 parts of deionized water, then add 5 parts of unsaturated carboxylic acid monomer and stir mechanically until dissolved to obtain bottom liquid A; mix 10 parts of unsaturated carboxylic acid monomer, 0.9 parts of chain transfer agent and 20 parts of deionized water to prepare solution B; mix 0.4 parts of reducing agent and 40.0 parts of deionized water to prepare solution C;

[0107] (2) Add 0.005 parts of catalyst and 0.5 parts of initiator to the prepared bottom liquid A, and then add dropwise solution B (completed in 50 min) and solution C (completed in 60 min) at a uniform rate. After the dropwise addition is completed, keep warm for 1 h to obtain polycarboxylate superplasticizer solution.

[0108] (3) After removing water from the obtained polycarboxylate superplasticizer by vacuum distillation, add it to a round bottom flask, add 0.6 parts of MXene solid powder, stir evenly, heat to 70°C, and after 4 hours, add alkaline solution to adjust the pH value to neutral, cool and discharge to obtain MXene polycarboxylate superplasticizer.

[0109] Following the methods outlined in GB / 8076-2008 "Concrete Admixtures," the samples prepared in Examples 1-6 and Comparative Examples 1-3 were compared with commercially available polycarboxylate superplasticizers (purchased from Weihong New Materials Technology Co., Ltd.) in concrete performance testing. The water reduction rate of cement mortar was tested according to GBT-8077-2012 "Test Method for Homogeneity of Concrete Admixtures." The shrinkage rate of cement mortar was tested using specimens with dimensions of 25mm × 25mm × 280mm prepared according to JC / T603-2004 "Test Method for Drying Shrinkage of Cement Mortar." Standard sand was used in the tests, and reference cement was employed for testing. Concrete workability was assessed through human observation and perception, encompassing three aspects: fluidity, cohesiveness, and water retention. Fluidity was indicated using slump / spread, while cohesiveness and water retention were determined through visual inspection. The results are shown in Table 1.

[0110] Table 1. Performance test results of concrete with different types of polycarboxylate superplasticizers (constituent dosage: 0.15%)

[0111]

[0112]

[0113] As shown in Table 1, under the same folding strength dosage (0.15%), compared with the MXene polycarboxylate superplasticizer prepared in this invention (Examples 1-8), ordinary polycarboxylate superplasticizer (Comparative Example 1), and commercially available polycarboxylate superplasticizer, the MXene polycarboxylate superplasticizer prepared in this invention has better water reduction, slump retention, and shrinkage reduction properties. With the increase of MXene content (Examples 1-4), the shrinkage rates after 7 days are 26.3%, 29.8%, 33.3%, and 36.8%, respectively, and the shrinkage rates after 28 days are 25%, 33.3%, 41.7%, and 40.5%, respectively. Compared with the MXene polycarboxylate superplasticizer prepared in this invention (Example 3) and physically mixed MXene superplasticizer, the MXene polycarboxylate superplasticizer prepared in this invention (Example 3) and commercially available polycarboxylate superplasticizer are also superior. Compared to the MXene-polycarboxylate superplasticizer (Comparative Example 2), the MXene polycarboxylate superplasticizer showed significantly better water reduction and slump retention performance than the physically mixed MXene-polycarboxylate superplasticizer, and also had better shrinkage rates at 7 days and 28 days. Compared to the ordinary polycarboxylate superplasticizer (Comparative Example 1) and the polycarboxylate superplasticizer with only methacryloyloxysilane (Comparative Example 3), the polycarboxylate superplasticizer with only methacryloyloxysilane showed improved water reduction, slump retention performance, and shrinkage rates at 7 days and 28 days, but the difference was not significant. Compared to the polycarboxylate superplasticizer synthesized by replacing methacryloyloxysilane with vinyltriethoxysilane by an equal mass, the results were not significantly different in terms of water reduction and slump retention performance, but the shrinkage rates at 7 days and 28 days were reduced.

[0114] The dosage of the admixture was increased to 0.17%, and the concrete performance and working conditions of Example 3 and Comparative Examples 1-3 were tested and compared. The results are shown in Table 2.

[0115] Table 2. Performance test results of concrete with different types of polycarboxylate superplasticizers (constituent dosage: 0.17%)

[0116]

[0117] As shown in Table 2, when the dosage is increased to 0.17%, the concrete with MXene polycarboxylate superplasticizer (Example 3) has a better state. However, ordinary polycarboxylate superplasticizer (Comparative Example 1), physically mixed MXene-polycarboxylate superplasticizer (Comparative Example 2), polycarboxylate superplasticizer with only methacryloyloxysilane introduced (Comparative Example 3), and polycarboxylate superplasticizer with methacryloyloxysilane replaced by an equal mass of vinyltriethoxysilane (Comparative Example 4) all showed bleeding. Therefore, it can be seen that the MXene polycarboxylate superplasticizer prepared in this invention can make the concrete less prone to bleeding.

[0118] All aspects, embodiments, features, and examples of this invention are to be regarded as illustrative in all respects and are not intended to limit the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0119] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0120] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A method for preparing a shrinkage-reducing MXene polycarboxylate superplasticizer, characterized in that, include: S1: By weight, a mixed reaction system containing 175-225 parts of polyether monomer, 15-40 parts of unsaturated carboxylic acid monomer, 0.1-2.0 parts of methacryloxysilane, 0.6-1.0 parts of chain transfer agent, 0.2-0.5 parts of reducing agent, 0.001-0.005 parts of catalyst and 0.4-1.0 parts of initiator is reacted at 10-30℃ for 0.5-1.5 h to obtain polycarboxylic acid water-reducing agent; S2: Mix the polycarboxylate superplasticizer with 0.2-1.0 parts of MXene uniformly and react at 60-80°C for 2-6 h to obtain a shrinkage-reducing MXene polycarboxylate superplasticizer, wherein the MXene is a two-dimensional carbon nanosheet containing hydroxyl groups prepared by in-situ hydrogen fluoride corrosion method.

2. The preparation method according to claim 1, characterized in that, S1 specifically includes: Solution A, solution B and solution C are provided, wherein solution A includes a polyether monomer, an unsaturated carboxylic acid monomer, a catalyst and an initiator, solution B includes an unsaturated carboxylic acid monomer, methacryloxysilane and a chain transfer agent, and solution C includes a reducing agent; The solutions B and C are added to the solution A at a constant rate to obtain the mixed reaction system.

3. The preparation method according to claim 2, characterized in that: Solution B was added at a constant rate over a period of 0.5-2.0 hours.

4. The preparation method according to claim 2, characterized in that: Solution C was added at a constant rate over a period of 0.5-2.5 hours.

5. The preparation method according to claim 2, characterized in that: After the reaction in the mixed reaction system is completed, the reaction product is adjusted to neutral using an alkaline solution.

6. The preparation method according to claim 1, characterized in that, S2 specifically includes: removing water from the polycarboxylate superplasticizer prepared in S1, then adding MXene solid powder and mixing it evenly, adjusting the temperature to 60-80°C for reaction, and after the reaction is completed, using an alkaline solution to adjust the reaction product to neutral to obtain the shrinkage-reducing MXene polycarboxylate superplasticizer.

7. The preparation method according to claim 1, characterized in that: The MXene contains hydroxyl groups and F ions.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The methacryloyloxysilane includes at least one of methacryloyloxypropyltrimethoxysilane, methacryloyloxypropyltriethoxysilane, and methacryloyloxypropyltriisopropoxysilane; the catalyst includes at least one of sodium sulfite, potassium sulfite, sodium bisulfite, and ferrous sulfate; the polyether monomer includes at least one of isobutylene polyethylene glycol ether, isopentenyl polyethylene glycol ether, and ethylene glycol monovinyl polyethylene glycol ether; the unsaturated carboxylic acid monomer includes at least one of acrylic acid and methacrylic acid; the chain transfer agent includes at least one of sodium hypophosphite, mercaptoethanol, mercaptoacetic acid, and mercaptopropionic acid; the initiator includes at least one of hydrogen peroxide, sodium persulfate, ammonium persulfate, and potassium persulfate; and the reducing agent includes at least one of vitamin C and sodium formaldehyde sulfoxylate.

9. The preparation method according to claim 2, characterized in that: By mass, solution A contains 5-10 parts of unsaturated carboxylic acid monomers, and solution B contains 10-30 parts of unsaturated carboxylic acid monomers.

10. The shrinkage-reducing MXene polycarboxylate superplasticizer obtained by the preparation method according to any one of claims 1-9.

11. A building material, characterized in that, Includes cement-based materials and the shrinkage-reducing MXene polycarboxylate superplasticizer as described in claim 10.

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