A solid waste-based cementitious material water reducing agent resistant to interference of multivalent metal ions and a preparation method thereof

Abstract

The application relates to the technical field of admixtures for building materials, and discloses a solid waste-based cementitious material water reducing agent resistant to interference of multivalent metal ions and a preparation method thereof. The water reducing agent comprises a polycarboxylic acid water-soluble comb copolymer, and the copolymer comprises polyether side chain units, carboxylic acid structural units, hydroxamic acid structural units, phosphate structural units and sulfonate structural units; in terms of 100 parts of the mass of an unsaturated polyether macromonomer, monomer raw materials for preparing the copolymer comprise 8-25 parts of a carboxylic acid monomer, 0.1-3 parts of an unsaturated monomer containing a hydroxamic acid precursor group, 1-8 parts of an unsaturated monomer containing a phosphate group and 2-10 parts of an unsaturated monomer containing a sulfonic acid group or a sulfonate group. The water reducing agent can reduce the adverse effect of multivalent metal ions such as Fe 3+ , Al 3+ , Ca 2+ , Mg 2+ and the like on the dispersion structure of polycarboxylic acid water reducing agents, and improve the initial fluidity and the fluidity retention property over time of the water reducing agents in solid waste-based cementitious materials such as slag, steel slag, red mud and fly ash.

Description

Technical Field

[0001] This invention relates to the field of building material admixtures, specifically to a water-reducing agent for solid waste-based cementitious materials that resists interference from polyvalent metal ions and its preparation method. Background Technology

[0002] Solid waste-based cementitious materials refer to hydraulic cementitious materials that use industrial solid wastes such as slag, steel slag, red mud, fly ash, phosphorus slag, tailings powder, and coal gangue powder as the main cementing components. These materials can improve the resource utilization rate of industrial solid waste and have good environmental and economic value. However, compared with ordinary silicate cement, the chemical and mineral composition of solid waste-based cementitious materials is more complex. Under alkali activation or high-alkali mixing conditions, the system is prone to releasing Fe. 3+ Al 3+ Ca 2+ Mg 2+ It contains polyvalent metal ions and forms active adsorption sites containing iron, aluminum, and calcium on the particle surface.

[0003] Polycarboxylate superplasticizers typically rely on carboxylic acid adsorption groups to adsorb onto the surface of cementitious material particles, forming steric hindrance and a hydration layer through polyether side chains, thereby improving slurry dispersibility. However, in solid waste-based cementitious material systems, polyvalent metal ions readily compete with the carboxylic acid groups in polycarboxylate superplasticizers for complexation or bridging, leading to reduced effective adsorption of superplasticizer molecules on the particle surface, and even desorption and bridging flocculation. This results in problems such as insufficient initial fluidity, accelerated fluidity loss over time, and poor adaptability between different solid waste sources or batches.

[0004] To improve the adaptability of polycarboxylate superplasticizers in complex gelation systems, existing technologies have attempted to introduce functional groups such as phosphate ester groups and sulfonate groups into the polycarboxylate superplasticizer molecules to enhance their adsorption and dispersion retention capabilities in high-alkali, high-salt, or multi-mineral component systems. Other approaches involve physically compounding small-molecule chelating agents, retarders, or dispersing aids with ordinary polycarboxylate superplasticizers to mitigate the adverse effects of polyvalent metal ions or active surfaces on the dispersion performance of the superplasticizer.

[0005] However, the above-mentioned solutions still have certain shortcomings: on the one hand, a single functional group is difficult to adapt to the complex environment of multiple metal ions and multiple active surface sites coexisting in solid waste-based gelling systems; on the other hand, there is a lack of stable intramolecular synergistic relationships between the components in the physical compound system, and small molecule additives are easily migrated, diffused, or consumed in alkaline gelling systems, resulting in limited sustainability of their anti-interference effect and storage stability. In addition, if highly reactive functional monomers are directly introduced to participate in free radical copolymerization in order to enhance the ability to regulate metal ions, problems such as mismatch in polymerization activity, difficulty in controlling molecular weight, decreased water solubility, or insufficient storage stability may occur.

[0006] Therefore, how to introduce a functional structure that can resist the interference of multivalent metal ions into the polymer molecular chain while maintaining the comb-shaped dispersion structure of polycarboxylate superplasticizer, and taking into account the stability of the preparation process, dispersion performance and the retention of fluidity over time, remains a technical problem that needs to be solved in the field of solid waste-based cementitious material admixtures. Summary of the Invention

[0007] The purpose of this invention is to provide a water-reducing agent for solid waste-based cementitious materials that resists interference from polyvalent metal ions and its preparation method, in order to solve the problems mentioned in the background art.

[0008] This invention is achieved through the following technical solution: On the one hand, the present invention proposes a water-reducing agent for solid waste-based cementitious materials that resists interference from polyvalent metal ions. The water-reducing agent includes a water-soluble comb copolymer of polycarboxylic acid. The water-soluble comb copolymer of polycarboxylic acid includes polyether side chain units, carboxylic acid structural units, hydroxamic acid structural units, phosphate ester structural units and sulfonate structural units formed by unsaturated polyether macromonomers. Based on 100 parts by weight of the unsaturated polyether macromonomer used to prepare the polycarboxylic acid water-soluble comb copolymer, the monomer raw materials used to prepare the polycarboxylic acid water-soluble comb copolymer include: 8-25 parts of carboxylic acid monomer, 0.1-3 parts of unsaturated monomer containing hydroxamic acid precursor group, 1-8 parts of unsaturated monomer containing phosphate ester group, and 2-10 parts of unsaturated monomer containing sulfonic acid group or sulfonate group; The polycarboxylic acid water-soluble comb copolymer is formed by free radical polymerization of the unsaturated polyether macromonomer, the carboxylic acid monomer, the unsaturated monomer containing hydroxamic acid precursor group, the unsaturated monomer containing phosphate ester group, and the unsaturated monomer containing sulfonic acid group or sulfonate group in aqueous solution to obtain a polycarboxylic acid comb copolymer containing hydroxamic acid precursor group, and then undergoing a hydroxamication reaction. The hydroxamic acid structural unit, the phosphate ester structural unit, and the sulfonate structural unit are all introduced as structural units into the polycarboxylic acid-based water-soluble comb copolymer; the hydroxamic acid structural unit contains —C(=O)—NHOH and —C(=O)—NHO-M + One or two of the structures, M + It consists of alkali metal ions, ammonium ions, or organic ammonium ions.

[0009] Optionally, the unsaturated polyether macromonomer includes at least one of isopentenyl polyoxyethylene ether, methyl allyl polyoxyethylene ether, allyl polyoxyethylene ether, vinyl butyl ether polyoxyethylene ether, methoxy polyethylene glycol acrylate, and methoxy polyethylene glycol methacrylate, wherein the number average molecular weight of the unsaturated polyether macromonomer is 800 to 4000.

[0010] Optionally, the carboxylic acid monomer includes at least one of acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid; the unsaturated monomer containing a hydroxamic acid precursor group includes at least one of acrylate monomers, methacrylate monomers, maleic anhydride monomers, and itaconic anhydride monomers.

[0011] Optionally, the unsaturated monomer containing phosphate ester groups includes at least one of hydroxyethyl methacrylate phosphate, hydroxyethyl acrylate phosphate, polyethylene glycol methacrylate phosphate, and polyethylene glycol acrylate phosphate; the unsaturated monomer containing sulfonic acid groups or sulfonate groups includes at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium allyl sulfonate, sodium methyl allyl sulfonate, sodium vinyl sulfonate, and sodium styrene sulfonate.

[0012] Optionally, based on 100 parts by mass of the unsaturated polyether macromonomer used to prepare the polycarboxylic acid water-soluble comb copolymer, the carboxylic acid monomer is 10-18 parts, the unsaturated monomer containing the hydroxamic acid precursor group is 0.2-1.0 parts, the unsaturated monomer containing the phosphate ester group is 2-7 parts, and the unsaturated monomer containing the sulfonic acid group or sulfonate group is 4-8 parts.

[0013] Optionally, the polycarboxylic acid water-soluble comb copolymer has a weight-average molecular weight of 10,000 to 80,000, the water-reducing agent has a solid content of 20% to 50%, and a pH of 6 to 9.

[0014] Optionally, the solid waste-based cementitious material includes at least one of slag, steel slag, red mud, fly ash, phosphorus slag, iron tailings powder, coal gangue powder, nickel slag, copper slag, manganese slag, and desulfurization gypsum, and the solid waste component accounts for more than 30% of the total mass of the cementitious material.

[0015] On the other hand, the present invention proposes a method for preparing the above-mentioned water-reducing agent for solid waste-based cementitious materials that resists interference from polyvalent metal ions, comprising the following steps: S1. Add unsaturated polyether macromonomers, carboxylic acid monomers, unsaturated monomers containing hydroxamic acid precursor groups, unsaturated monomers containing phosphate ester groups, and unsaturated monomers containing sulfonic acid groups or sulfonate groups to water to obtain a monomer mixture system. S2. In the presence of an initiator and a chain transfer agent, the monomer mixture system is subjected to aqueous free radical polymerization to obtain a polycarboxylic acid comb copolymer containing a hydroxyoxime acid precursor group; S3. Add a hydroxylamine source to the polycarboxylic acid comb copolymer containing the hydroxyoxime acid precursor group, and carry out a hydroxyoxime reaction at a pH of 7-12 and a temperature of 20-70°C to obtain a polycarboxylic acid comb copolymer containing hydroxyoxime acid structural units. S4. Adjust the pH of the reaction system to 6-9 to obtain the solid waste-based cementitious material water-reducing agent that resists interference from polyvalent metal ions.

[0016] Optionally, the hydroxylamine source includes at least one of hydroxylamine hydrochloride, hydroxylamine sulfate, free hydroxylamine, aqueous hydroxylamine solution, and a hydroxylamine system obtained by neutralizing hydroxylamine salt with alkali; the pH of the hydroxyoximation reaction is 8.5–10.5, and the temperature is 40–60°C; the initiator includes at least one of ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, and an ascorbic acid-peroxide-hydrogen-reduction system; the chain transfer agent includes at least one of mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol, and sodium hypophosphite.

[0017] Compared with the prior art, the present invention provides a water-reducing agent for solid waste-based cementitious materials that resists interference from polyvalent metal ions and its preparation method, which has the following beneficial effects: 1. This invention introduces hydroxamic acid structural units into water-soluble comb copolymers of polycarboxylic acids, enabling the hydroxamic acid structural units to be distributed along with the polycarboxylic acid molecules near the particle interface of the cementitious material. This facilitates the adsorption and dispersion of Fe during the polycarboxylic acid water-reducing agent process. 3+ Al 3+ Ca 2+ Mg 2+ The coordination regulation effect of polyvalent metal ions reduces the competitive complexation and bridging effect of the above ions on the carboxylic acid structural units, thereby improving the problem of easy failure of polycarboxylic acid water-reducing agents in solid waste-based cementitious material systems.

[0018] 2. This invention introduces phosphate ester structural units into the same polycarboxylic acid water-soluble comb copolymer system, which can enhance the adsorption stability of water-reducing agent molecules on the surfaces of active phases such as calcium and aluminum, and is beneficial to improving the problems of uneven adsorption and insufficient initial dispersion caused by the complex particle surface composition and large differences in active sites in solid waste-based cementitious materials.

[0019] 3. This invention introduces sulfonate structural units into the same polycarboxylic acid water-soluble comb copolymer system, which can improve the solubility and charge stability of water-reducing agent molecules in strong alkali, high salt and multi-ionic porous solutions, reduce the adverse effects of salt ions on the conformation and dispersion ability of polycarboxylic acid molecules in solid waste systems, thereby improving the retention performance of fluidity over time.

[0020] 4. In this invention, the hydroxamic acid structural unit, phosphate ester structural unit, sulfonate structural unit, and polyether side chain unit are all introduced into the same polycarboxylic acid water-soluble comb copolymer system, enabling synergistic regulation of the failure process in solid waste-based gelling systems: "dissolution of polyvalent metal ions—competitive complexation of carboxylic acid groups—particle bridging flocculation—rapid loss of fluidity." Compared with single-functional group modification, ordinary polycarboxylic acid water-reducing agents, and physical compounding schemes using small molecule chelating agents, this invention can achieve better initial dispersibility, retention of fluidity over time, and resistance to polyvalent metal ion interference in solid waste-based gelling materials.

[0021] 5. The present invention adopts a preparation route of first forming a polycarboxylic acid comb copolymer containing hydroxamic acid precursor groups through free radical polymerization in aqueous solution, and then carrying out a hydroxamication reaction. This avoids the problems that may occur when using unsaturated monomers containing hydroxamic acid groups to participate in free radical copolymerization, such as mismatch of polymerization activity, difficulty in controlling molecular weight, and decrease in water solubility. This is beneficial for obtaining polycarboxylic acid water-reducing agents with suitable molecular weight, good water solubility, and good storage stability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the preparation process of the water-reducing agent of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] The "unsaturated monomer containing a hydroxamic acid precursor group" described in this invention refers to an unsaturated monomer containing an acyl precursor that can react with hydroxylamine to form a hydroxamic acid structure, which, after participating in free radical polymerization, can be converted into a hydroxamic acid structural unit via a hydroxamication reaction. The acyl precursor includes ester groups, anhydride groups, or other hydroxamicizable groups; for example, methyl methacrylate, maleic anhydride, itaconic anhydride, and similar monomers can all serve as the unsaturated monomer containing the hydroxamic acid precursor group.

[0025] The main raw materials used in the following examples and comparative examples are as follows: methyl allyl alcohol polyoxyethylene ether, number average molecular weight 2400, denoted as HPEG-2400; isopentenyl alcohol polyoxyethylene ether, number average molecular weight 2400, denoted as TPEG-2400; acrylic acid, denoted as AA; methyl methacrylate, denoted as MMA, used as a precursor monomer for hydroxamic acid; maleic anhydride, denoted as MAH, used as a precursor monomer for hydroxamic acid; hydroxyethyl methacrylate phosphate, denoted as HEMAP; 2-acrylamide-2-methylpropanesulfonic acid, denoted as AMPS; sodium methyl allyl sulfonate, denoted as SMAS; hydroxylamine hydrochloride, denoted as NH2OH·HCl; ammonium persulfate, denoted as APS; mercaptopropionic acid, denoted as MPA.

[0026] In this process, MMA or MAH forms a hydroxamic acid precursor group in the polymer molecular chain after polymerization, and is subsequently converted into a hydroxamic acid structural unit through a hydroxamication reaction.

[0027] In this embodiment of the invention, unless otherwise specified, the amounts of carboxylic acid monomers, unsaturated monomers containing hydroxamic acid precursor groups, unsaturated monomers containing phosphate ester groups, and unsaturated monomers containing sulfonic acid groups or sulfonate groups are recorded based on 100 parts by mass of the unsaturated polyether macromonomer. The hydroxamic acid structural unit refers to the actual —C(=O)—NHOH and / or —C(=O)—NHO-M formed after the hydroxamication reaction. + Structural calculations. Unless otherwise stated, the present invention does not calculate the molar percentage of polyether side chain units based on the number of repeating olefin oxide units in the polyether segment.

[0028] Solid content test: Take about 2.000g of polycarboxylate superplasticizer sample, dry it in an oven at 105℃ until constant weight, and calculate the solid content.

[0029] pH test: The pH value of the polycarboxylate superplasticizer aqueous solution was tested using a pH meter.

[0030] Molecular weight test: The weight-average molecular weight of polycarboxylate superplasticizer was tested by gel permeation chromatography.

[0031] Hydroxime acid structural unit confirmation: The polymer was tested using infrared spectroscopy. After the hydroxyoximation reaction, the absorption peaks related to the ester group or anhydride decreased, and characteristic absorption peaks related to the hydroxyoxime acid group appeared. Hydroxime acid group titration or nuclear magnetic resonance integration can also be used for auxiliary confirmation. In this invention, the content of the hydroxyoxime acid structural unit is based on the actual hydroxyoxime acid structural units formed after the hydroxyoximation reaction; in specific embodiments, the conversion rate of the hydroxyoximation reaction is 75%–90%.

[0032] Cement paste fluidity test: The total amount of cementitious material is 300g, the water-cement ratio is 0.30-0.32, and the dosage of polycarboxylate superplasticizer is 0.20%-0.30% of the total mass of cementitious material based on the weight of the cement paste. The test is conducted according to the cement paste fluidity test method, and the initial fluidity, 30-minute fluidity, and 60-minute fluidity are measured respectively.

[0033] The flowability retention rate R60 over time is calculated using the following formula: R60 = 60 min flowability / initial flowability × 100%.

[0034] The retention rate of metal ion interference, Rm, is calculated using the following formula: Rm = 60 min flow rate after adding metal ions / 60 min flow rate without adding metal ions × 100%.

[0035] Example 1 This embodiment provides a solid waste-based cementitious material water-reducing agent, PCE-1, which is resistant to interference from polyvalent metal ions. PCE-1 comprises a water-soluble comb copolymer of polycarboxylic acid, which includes polyether side chain units formed by HPEG-2400, carboxylic acid structural units formed by AA, hydroxyoxime acid structural units formed by hydroxyoximeization of MMA, phosphate ester structural units formed by HEMAP, and sulfonate structural units formed by AMPS.

[0036] Add 100.0 parts of HPEG-2400 and 160.0 parts of deionized water to a reactor equipped with a stirrer, thermometer, and dropping device. Stir to dissolve and heat to 40°C. Prepare solution A: 12.5 parts of AA, 0.36 parts of MMA, 4.0 parts of HEMAP, 5.5 parts of AMPS, and 35.0 parts of deionized water; prepare solution B: 1.2 parts of APS dissolved in 20.0 parts of deionized water; prepare solution C: 0.45 parts of MPA dissolved in 15.0 parts of deionized water. Simultaneously add solutions A, B, and C at 40°C, with solution A added over 2.5 hours and solutions B and C added over 3 hours. After addition, maintain the temperature for 1.5 hours to obtain a polycarboxylate comb copolymer solution containing hydroxamic acid precursor groups. Dissolve 0.52 parts of NH2OH·HCl in 20.0 parts of deionized water, and adjust the pH to 9.5 with 30% NaOH solution to obtain a hydroxylamine system. Add the hydroxylamine system to the polymer solution and react for 3 hours at 50℃ and pH 9.0-10.0. After the reaction is completed, adjust the pH to 7.2 and add water to adjust the solid content to 40% to obtain PCE-1.

[0037] The obtained PCE-1 had a weight-average molecular weight of approximately 38,500, a hydroxyoxime conversion rate of approximately 82.4%, a pH of 7.2, and a solid content of 40.1%.

[0038] Example 2 This embodiment provides a solid waste-based cementitious material water-reducing agent, PCE-2, which is resistant to interference from polyvalent metal ions. PCE-2 comprises a water-soluble comb copolymer of polycarboxylic acid, which includes polyether side chain units formed by HPEG-2400, carboxylic acid structural units formed by AA, hydroxyoxime acid structural units formed by hydroxyoximeization of MMA, phosphate ester structural units formed by HEMAP, and sulfonate structural units formed by AMPS.

[0039] The preparation method is basically the same as in Example 1, except that the amount of MMA is adjusted to 0.64 parts, the amount of AA is adjusted to 11.4 parts, the amount of AMPS is adjusted to 4.8 parts, and the amount of NH2OH·HCl is adjusted to 0.92 parts. Other raw materials and preparation steps are the same as in Example 1.

[0040] The obtained PCE-2 had a weight-average molecular weight of approximately 40,200, a hydroxyoxime conversion rate of approximately 84.6%, a pH of 7.3, and a solid content of 39.8%.

[0041] Example 3 This embodiment provides a solid waste-based cementitious material water-reducing agent, PCE-3, which is resistant to interference from polyvalent metal ions. PCE-3 comprises a water-soluble comb copolymer of polycarboxylic acid, which includes polyether side chain units formed from HPEG-2400, carboxylic acid structural units formed from AA, hydroxyoxime acid structural units formed from MMA via hydroxyoxime conversion, phosphate ester structural units formed from HEMAP, and sulfonate structural units formed from AMPS.

[0042] The preparation method is basically the same as in Example 1, except that the amount of MMA is adjusted to 0.23 parts, the amount of HEMAP is adjusted to 6.5 parts, the amount of AMPS is adjusted to 6.4 parts, and the amount of AA is adjusted to 10.8 parts. Other raw materials and preparation steps are the same as in Example 1.

[0043] The obtained PCE-3 had a weight-average molecular weight of approximately 37,600, a hydroxyoxime conversion rate of approximately 79.5%, a pH of 7.1, and a solid content of 40.3%.

[0044] Example 4 This embodiment provides a solid waste-based cementitious material water-reducing agent, PCE-4, which is resistant to interference from polyvalent metal ions. PCE-4 comprises a water-soluble comb copolymer of polycarboxylic acid, which includes polyether side chain units formed by HPEG-2400, carboxylic acid structural units formed by AA, hydroxyoxime acid structural units formed by hydroxyoximeization of MAH, phosphate ester structural units formed by HEMAP, and sulfonate structural units formed by SMAS.

[0045] The preparation method is basically the same as in Example 1, except that, based on 100.0 parts of HPEG-2400, MMA is replaced with 0.35 parts of MAH and AMPS is replaced with 4.20 parts of SMAS. The amounts of other raw materials and preparation steps are the same as in Example 1.

[0046] The obtained PCE-4 had a weight-average molecular weight of approximately 39,200, a hydroxyoxime conversion rate of approximately 81.7%, a pH of 7.0, and a solid content of 40.0%.

[0047] Example 5 This embodiment provides a solid waste-based cementitious material water-reducing agent, PCE-5, which is resistant to interference from polyvalent metal ions. PCE-5 comprises a water-soluble comb copolymer of polycarboxylic acid, which includes polyether side chain units formed from TPEG-2400, carboxylic acid structural units formed from AA, hydroxyoxime acid structural units formed from MMA via hydroxyoxime conversion, phosphate ester structural units formed from HEMAP, and sulfonate structural units formed from SMAS.

[0048] The preparation method is basically the same as in Example 1, except that, based on 100.0 parts of TPEG-2400, HPEG-2400 is replaced with 100.0 parts of TPEG-2400, and AMPS is replaced with 4.20 parts of SMAS. The amounts of other raw materials and preparation steps are the same as in Example 1.

[0049] The obtained PCE-5 had a weight-average molecular weight of approximately 36,800, a hydroxyoxime conversion rate of approximately 80.9%, a pH of 7.2, and a solid content of 39.9%.

[0050] Comparative Example 1 This comparative example, PCE-D1, uses a common polycarboxylate superplasticizer containing only polyether side chain units and carboxylic acid structural units. Specifically, based on 100.0 parts of HPEG-2400, 12.5 parts of AA were used as the carboxylic acid monomer, prepared under the same aqueous free radical polymerization conditions as in Example 1 in the presence of APS and MPA, without the addition of MMA, HEMAP, and AMPS, and without hydroxyoxime reaction. The resulting PCE-D1 was used to evaluate the retention of fluidity of the common polycarboxylate superplasticizer in solid waste-based gelling systems over time.

[0051] Comparative Example 2 This comparative example is PCE-D2. Take PCE-D1, add free salicylic acid, and make the molar amount of salicylic acid equivalent to the molar amount of the hydroxamic acid structural unit actually formed by the hydroxamication reaction of MMA in Example 1. Stir until homogeneous and adjust the pH to 7.2. Based on the MMA feed amount of 0.36 parts and the hydroxamication conversion rate of 82.4% in Example 1, the amount of salicylic acid added is 0.45 parts. This comparative example is used to illustrate the structural differences between the small molecule complex of free hydroxamic acid and the introduction of hydroxamic acid structural units into the polycarboxylic acid comb copolymer system.

[0052] Comparative Example 3 This comparative example is PCE-D3. It is basically the same as Example 1, except that HEMAP and AMPS are not added, and the polymerization system only includes HPEG-2400, AA and MMA. After polymerization, a hydroxyoximation reaction is performed to obtain a polycarboxylate superplasticizer containing only hydroxyoxim acid structural units.

[0053] Comparative Example 4 This comparative example is PCE-D4. It is essentially the same as Example 1, except that MMA is not added and the hydroxyoxime reaction is not performed. The polymerization system includes HPEG-2400, AA, HEMAP, and AMPS, yielding a polycarboxylate superplasticizer containing only phosphate ester and sulfonate structural units.

[0054] Comparative Example 5 This comparative example is PCE-D5. It is basically the same as Example 1, except that AMPS is not added, and the polymerization system includes HPEG-2400, AA, MMA and HEMAP. After polymerization, it undergoes a hydroxyoximation reaction to obtain a polycarboxylate superplasticizer containing hydroxyoxim acid structural units and phosphate ester structural units but not sulfonate structural units.

[0055] Comparative Example 6 This comparative example is PCE-D6. It is basically the same as Example 1, except that HEMAP is not added, and the polymerization system includes HPEG-2400, AA, MMA and AMPS. After polymerization, a hydroxyoximation reaction is performed to obtain a polycarboxylate superplasticizer containing hydroxyoxim acid structural units and sulfonate structural units but not phosphate ester structural units.

[0056] Comparative Example 7 This comparative example is PCE-D7. N-hydroxyacrylamide was directly used as the hydroxamic acid monomer, and aqueous free radical copolymerization was carried out with HPEG-2400, AA, HEMAP, and AMPS without a post-hydroxyoximation step. Specifically, based on 100.0 parts of HPEG-2400, the amount of AA was 12.5 parts, the amount of N-hydroxyacrylamide was 0.26 parts, the amount of HEMAP was 4.0 parts, and the amount of AMPS was 5.5 parts; wherein, the molar amount of N-hydroxyacrylamide is equivalent to the molar amount of the hydroxamic acid structural unit actually formed by the hydrooximation reaction of MMA in Example 1. The polymerization conditions were the same as in Example 1. The resulting product showed slight turbidity after standing, and its fluidity retention in the solid waste-based gelling system was lower than that in Example 1. This comparative example is used to illustrate the importance of the pre-polymerization followed by hydrooximation process for obtaining stable water-soluble comb copolymers and their dispersion retention properties.

[0057] Table 1. Monomer composition and hydroxyoxime status of the examples and comparative examples.

[0058] Table 2. Flowability of Slag-Fly Ash System Paste

[0059] The cementitious material composition is 60% slag, 30% fly ash, and 10% desulfurized gypsum; the water-cement ratio is 0.30, and the water-reducing agent dosage is 0.20% of the total mass of the cementitious material. As shown in Table 2, the embodiments PCE-1 to PCE-5 of this invention all exhibit high initial flowability and flowability retention over time, and are superior to ordinary PCE, the free hydroxamic acid compound scheme, and the comparative examples lacking any functional unit.

[0060] Table 3. Flowability of Neat Slurry in Steel Slag-Granite-Fly Ash System

[0061] The cementitious material composition is 25% steel slag, 50% blast furnace slag, 20% fly ash, and 5% desulfurized gypsum; the water-cement ratio is 0.30, and the water-reducing agent content is 0.25% of the total mass of the cementitious material. In the steel slag system, ordinary PCE exhibits significant fluidity loss over time, while the embodiment of this invention still maintains a high fluidity retention rate in high-calcium, iron-containing solid waste systems.

[0062] Table 4. Flowability of Red Mud-Slag System

[0063] The cementitious material consists of 30% red mud, 60% slag, and 10% desulfurized gypsum; the water-cement ratio is 0.32, and the water-reducing agent content is 0.30% of the total mass of the cementitious material. The red mud system contains a relatively high amount of iron, aluminum, sodium, and other components, yet the embodiments of this invention still maintain good fluidity retention, indicating its good adaptability to complex ionic solid waste systems.

[0064] Table 5 Fe 3+ Al 3+ 60-minute flowability and retention rate under disturbance conditions

[0065] Table 6 Ca 2+ Mg 2+ 60-minute flowability and retention rate under disturbance conditions

[0066] Using a slag-fly ash system as the base system, FeCl3, AlCl3, CaCl2, and MgCl2 were added respectively to make Fe 3+ Al 3 + Ca 2+ or Mg 2+ The amount of one metal ion added is 0.05% of the mass of the cementitious material. Tables 5 and 6 show that in Fe... 3 + And Al 3+ Under interference conditions, the 60-minute flowability of ordinary PCE decreased significantly. Although the comparative example showed some improvement, it was still lower than that of the embodiments of the present invention. The embodiments of the present invention all exhibited high retention rates under polyvalent metal ion interference conditions, indicating that when hydroxamic acid structural units, phosphate ester structural units, and sulfonate structural units are all introduced into the same polycarboxylic acid water-soluble comb copolymer system, the interference of polyvalent metal ions on the dispersion structure of the polycarboxylic acid water-reducing agent can be effectively reduced.

[0067] As can be seen from the above embodiments, comparative examples, and application examples, the present invention introduces hydroxamic acid structural units, phosphate ester structural units, and sulfonate structural units as structural units into the same polycarboxylic acid water-soluble comb copolymer system. Compared with ordinary polycarboxylic acid superplasticizers, ordinary polycarboxylic acid superplasticizers combined with free hydroxamic acid, hydroxamic acid-only structural units, phosphate ester / sulfonate-only modification schemes, and direct hydroxamic acid monomer copolymerization schemes, it can obtain higher initial flowability, flowability retention rate over time, and metal ion interference retention rate in solid waste-based cementitious materials.

[0068] This invention addresses the problems of competitive complexation of multivalent metal ions, insufficient adsorption of the active phase, and decreased dispersion stability under high alkali and high salt conditions in solid waste-based gelation systems by introducing hydroxamic acid structural units, phosphate ester structural units, sulfonate structural units, carboxylic acid structural units, and polyether side chain units into the same polycarboxylic acid water-soluble comb copolymer system.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Modifications, substitutions or improvements made by those skilled in the art without departing from the concept of the present invention should be included within the scope of protection of the present invention.

Claims

1. A water-reducing agent for solid waste-based cementitious materials resistant to interference from polyvalent metal ions, characterized in that, The water-reducing agent includes a water-soluble comb copolymer of polycarboxylic acid, which comprises polyether side chain units, carboxylic acid structural units, hydroxamic acid structural units, phosphate ester structural units and sulfonate structural units formed from unsaturated polyether macromonomers. Based on 100 parts by weight of the unsaturated polyether macromonomer used to prepare the polycarboxylic acid water-soluble comb copolymer, the monomer raw materials used to prepare the polycarboxylic acid water-soluble comb copolymer include: 8-25 parts of carboxylic acid monomer, 0.1-3 parts of unsaturated monomer containing hydroxamic acid precursor group, 1-8 parts of unsaturated monomer containing phosphate ester group, and 2-10 parts of unsaturated monomer containing sulfonic acid group or sulfonate group; The polycarboxylic acid water-soluble comb copolymer is formed by free radical polymerization of the unsaturated polyether macromonomer, the carboxylic acid monomer, the unsaturated monomer containing hydroxamic acid precursor group, the unsaturated monomer containing phosphate ester group, and the unsaturated monomer containing sulfonic acid group or sulfonate group in aqueous solution to obtain a polycarboxylic acid comb copolymer containing hydroxamic acid precursor group, and then undergoing a hydroxamication reaction. The hydroxamic acid structural unit, the phosphate ester structural unit, and the sulfonate structural unit are all introduced as structural units into the polycarboxylic acid-based water-soluble comb copolymer; the hydroxamic acid structural unit contains —C(=O)—NHOH and —C(=O)—NHO-M + One or two of the structures, M + It consists of alkali metal ions, ammonium ions, or organic ammonium ions.

2. The water-reducing agent for solid waste-based cementitious materials resistant to interference from multivalent metal ions according to claim 1, characterized in that, The unsaturated polyether macromonomer includes at least one of isopentenyl alcohol polyoxyethylene ether, methyl allyl alcohol polyoxyethylene ether, allyl polyoxyethylene ether, vinyl butyl ether polyoxyethylene ether, methoxy polyethylene glycol acrylate, and methoxy polyethylene glycol methacrylate, wherein the number average molecular weight of the unsaturated polyether macromonomer is 800 to 4000.

3. The water-reducing agent for solid waste-based cementitious materials resistant to interference from multivalent metal ions according to claim 1, characterized in that, The carboxylic acid monomers include at least one of acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid; the unsaturated monomers containing hydroxamic acid precursor groups include at least one of acrylate monomers, methacrylate monomers, maleic anhydride monomers, and itaconic anhydride monomers.

4. The water-reducing agent for solid waste-based cementitious materials resistant to interference from multivalent metal ions according to claim 1, characterized in that, The unsaturated monomer containing phosphate ester groups includes at least one of hydroxyethyl methacrylate phosphate, hydroxyethyl acrylate phosphate, polyethylene glycol methacrylate phosphate, and polyethylene glycol acrylate phosphate; the unsaturated monomer containing sulfonic acid groups or sulfonate groups includes at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium allyl sulfonate, sodium methyl allyl sulfonate, sodium vinyl sulfonate, and sodium styrene sulfonate.

5. The water-reducing agent for solid waste-based cementitious materials resistant to interference from multivalent metal ions according to claim 1, characterized in that, Based on 100 parts by weight of the unsaturated polyether macromonomer used to prepare the polycarboxylic acid water-soluble comb copolymer, the carboxylic acid monomer comprises 10-18 parts, the unsaturated monomer containing a hydroxamic acid precursor group comprises 0.2-1.0 parts, the unsaturated monomer containing a phosphate ester group comprises 2-7 parts, and the unsaturated monomer containing a sulfonic acid group or a sulfonate group comprises 4-8 parts.

6. The water-reducing agent for solid waste-based cementitious materials resistant to interference from multivalent metal ions according to claim 1, characterized in that, The polycarboxylic acid water-soluble comb copolymer has a weight-average molecular weight of 10,000 to 80,000, the water-reducing agent has a solid content of 20% to 50%, and a pH of 6 to 9.

7. A method for preparing a water-reducing agent for solid waste-based cementitious materials resistant to interference from polyvalent metal ions as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Add unsaturated polyether macromonomers, carboxylic acid monomers, unsaturated monomers containing hydroxamic acid precursor groups, unsaturated monomers containing phosphate ester groups, and unsaturated monomers containing sulfonic acid groups or sulfonate groups to water to obtain a monomer mixture system. S2. In the presence of an initiator and a chain transfer agent, the monomer mixture system is subjected to aqueous free radical polymerization to obtain a polycarboxylic acid comb copolymer containing a hydroxyoxime acid precursor group; S3. Add a hydroxylamine source to the polycarboxylic acid comb copolymer containing the hydroxyoxime acid precursor group, and carry out a hydroxyoxime reaction at a pH of 7-12 and a temperature of 20-70°C to obtain a polycarboxylic acid comb copolymer containing hydroxyoxime acid structural units. S4. Adjust the pH of the reaction system to 6-9 to obtain the solid waste-based cementitious material water-reducing agent that resists interference from polyvalent metal ions.

8. The preparation method according to claim 7, characterized in that, The hydroxylamine source includes at least one of hydroxylamine hydrochloride, hydroxylamine sulfate, free hydroxylamine, aqueous hydroxylamine solution, and a hydroxylamine system obtained by neutralizing hydroxylamine salt with alkali; the pH of the hydroxyoximation reaction is 8.5–10.5, and the temperature is 40–60°C; the initiator includes at least one of ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, and an ascorbic acid-peroxide-hydrogen-reduction system; the chain transfer agent includes at least one of mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol, and sodium hypophosphite.

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