Polycarboxylic acid admixture for enhancing low-activity admixture and preparation method of polycarboxylic acid admixture

Abstract

The invention relates to the technical field of admixtures for cement concrete, in particular to a polycarboxylic acid admixture for enhancing low-activity admixtures and a preparation method thereof, the polycarboxylic acid admixture is formed by polymerizing the following components: polyether macromonomer, unsaturated carboxylic acid I, exciting functional monomer A, slump retaining functional monomer B, rheological functional monomer C, oxidizing agent, reducing agent, chain transfer agent and water; the exciting functional monomer A, the slump retaining functional monomer B and the rheological functional monomer C are sequentially added, and the exciting functional monomer A is formed by polymerizing polyhydric alcohol, unsaturated carboxylic acid II, an initiator, phosphonic acid and an alcohol amine small monomer. Through molecular design, key functional groups such as phosphonic acid groups, amino groups and sulfonic acid groups are innovatively introduced into a polycarboxylic acid main chain, so that the polycarboxylic acid admixture has multiple synergistic functions of reducing the cement consumption, effectively activating a low-activity cementing material, stably improving the working performance of concrete and the like.

Description

Technical Field

[0001] This invention relates to the field of admixtures for cement concrete, and in particular to a polycarboxylate admixture for reinforcing low-activity admixtures and its preparation method. Background Technology

[0002] In engineering construction in resource-constrained areas, concrete preparation faces two prominent raw material problems: first, cement quality fluctuates greatly and its performance is unstable; second, available industrial solid waste (such as fly ash) generally has low activity. Due to the lack of effective activation and control technologies, the utilization rate of these low-activity cementitious materials is low, and their potential cementitious properties are not fully realized, resulting in unstable concrete performance.

[0003] In such engineering practices, when using inferior cement and low-activity admixtures to prepare concrete, relying solely on conventional admixtures is insufficient to effectively control performance. A common problem is that slightly increasing the amount of water-reducing agent to improve workability easily leads to severe bleeding, segregation, and aggregate sticking to the bottom, resulting in a "lean paste" phenomenon that damages the homogeneity and cohesiveness of the concrete. Consequently, the measured strength of the concrete is difficult to guarantee, and the risk to durability increases significantly. Therefore, the key technology to solve this problem lies in effectively improving the utilization efficiency and chemical reactivity of low-activity cementitious materials (especially low-activity fly ash) to overcome the inherent defects of raw materials and meet the comprehensive performance requirements of concrete in engineering projects.

[0004] In response to the above problems, some admixture products have emerged on the market that reduce cement usage and improve other cementitious materials, such as binder reducers and activators. Their main function is to activate the performance of various cementitious materials by adding alkanolamines and salts to the admixtures.

[0005] For example, Chinese invention patent CN115784662A discloses a concrete binder reducing agent. This agent comprises organic alcohol amines, polycarboxylate superplasticizers, early-strength components, antifreeze components, water-retaining and thickening components, and water. This invention, by adding comb-shaped polycarboxylate superplasticizers and organic alcohol amines, can reduce the water consumption per cubic meter of concrete, lower the water-cement ratio, and thus improve the early strength of concrete. However, excessive early-strength components and organic alcohol amines in this solution may adversely affect the later-stage strength development of concrete. Furthermore, if the additionally introduced polycarboxylate superplasticizer is not properly coordinated with the superplasticizer in the main concrete mixing system, it can easily cause post-bleeding problems during mixing, making it difficult to accurately control the workability of the concrete.

[0006] Chinese invention patent CN112358228A discloses another concrete binder and its preparation method. This invention adds quaternary ammonium salt surfactants and silicone oil to the raw materials. In the preparation process, a methyl allyl polyoxyethylene ether polycarboxylate superplasticizer is first added to water, followed by organic amines and organic alcohols for stirring and reaction. Then, cellulose ether is added and stirred for a certain period. Finally, a mixture of quaternary ammonium salt surfactants and silicone oil is added and stirred to produce the concrete binder. When used in concrete, this binder increases the degree of cement hydration, reduces cement dosage, and effectively improves the mechanical properties and density of concrete, as well as its workability and volume stability. However, this invention also adds a polycarboxylate superplasticizer. The addition of the superplasticizer makes it difficult to control the amount used during normal concrete mixing, easily leading to segregation and bleeding.

[0007] Chinese invention patent CN120289724A discloses a durability-enhancing polycarboxylate superplasticizer and its preparation method. This method introduces functional monomers such as sodium methacrylate sulfonate through a specific process, aiming to utilize their sulfonic acid groups to enhance the electrostatic repulsion between the superplasticizer molecules and cement particles, thereby improving the dispersion performance of the superplasticizer and inhibiting cement particle agglomeration, thus helping to maintain the fluidity of concrete. However, the core of this technology lies in synthesizing a high-performance polycarboxylate superplasticizer; it does not improve the performance of reducing cement usage or stimulating the activity of low-reactivity or inactive admixtures.

[0008] Therefore, there are currently three solutions on the market for reducing concrete cement usage, activating low-activity cementitious materials, and improving concrete workability and fluidity. One is to use alkaline activation with alkaline amines and salts; another is to repolymerize water-reducing agents with alkaline amines and alcohols to activate them; and the third is to simply synthesize water-reducing agents with high water-reducing rates to reduce water usage and thus reduce cement usage. Each solution can basically only solve one problem and will also have adverse effects on other aspects, such as durability, strength growth rate, and concrete water-reducing agent production control.

[0009] Therefore, there is an urgent need to develop a new type of admixture that can solve the above problems at the same time, especially given the complex cementitious materials, high cement costs, and lack of production control capabilities in overseas markets.

[0010] In view of this, the present invention is proposed. Summary of the Invention

[0011] The purpose of this invention is to provide a polycarboxylate admixture for enhancing low-activity admixtures and its preparation method. The polycarboxylate admixture for enhancing low-activity admixtures of this invention, through molecular design, innovatively introduces key functional groups such as phosphonic acid groups, amino groups and sulfonic acid groups into the polycarboxylate main chain, endowing the polycarboxylate admixture with multiple synergistic functions such as reducing cement dosage, effectively activating low-activity cementitious materials, and stabilizing and improving the workability of concrete.

[0012] In a first aspect, the present invention provides a polycarboxylate admixture for reinforcing low-activity admixtures, polymerized from the following components in parts by weight: The composition includes 30-40 parts of polyether macromonomer, 0.1-5.0 parts of unsaturated carboxylic acid I, 0.1-5.0 parts of activated functional monomer A, 0.1-5.0 parts of slump-retaining functional monomer B, 0.1-2.0 parts of rheology functional monomer C, 0.1-1.0 parts of oxidant, 0.1-1.0 parts of reducing agent, 0.1-2.0 parts of chain transfer agent, and 40-60 parts of water. The activation functional monomer A, the slump-preserving functional monomer B, and the rheology functional monomer C are added sequentially, and the activation functional monomer A is polymerized from polyol, unsaturated carboxylic acid II, initiator, phosphonic acid, and alkanolamine monomer.

[0013] Traditional polycarboxylate superplasticizers mainly rely on steric hindrance to achieve water reduction and dispersion. However, when faced with complex systems containing a large amount of low-activity mineral admixtures (such as fly ash, mineral powder, and volcanic ash) or working conditions requiring long-term slump retention, they often suffer from excessively rapid loss of dispersion performance and insufficient activation of admixtures, leading to poor concrete workability, high cement content, and consequently, problems such as high heat of hydration, increased risk of cracking, and increased costs.

[0014] This invention relates to a polycarboxylate admixture for enhancing low-activity admixtures, comprising a polyether macromonomer, unsaturated carboxylic acid I, an activating functional monomer A, a slump-retaining functional monomer B, a rheology functional monomer C, and an oxidant, a reducing agent, and a chain transfer agent. Through molecular design, this invention innovatively introduces key functional groups such as phosphonic acid groups, amino groups, and sulfonic acid groups into the polycarboxylate backbone, endowing the water-reducing agent with multiple synergistic functions. First, its core water-reducing effect stems from the inherent steric hindrance effect, effectively releasing encapsulated water, reducing the water-cement ratio, and laying a foundation for high strength. Second, the strongly adsorbent phosphonic acid and sulfonic acid groups significantly enhance the anchoring stability of molecules on the surface of cement particles, effectively delaying molecular desorption and secondary flocculation of particles caused by hydration, thereby significantly improving the slump retention performance (slump retention) of concrete and meeting stringent construction requirements. Crucially, the synergistic effect of phosphonic acid groups and amino groups: phosphonic acid groups, through strong chelation, complex inert cations (such as Ca²⁺) on the surface or in solution of low-activity materials. + Al³ +The process involves breaking down the inert layer of the admixtures and exposing active sites. Amino groups help create a localized alkaline microenvironment and promote the depolymerization of the aluminosilicate glass, thereby deeply stimulating the potential activity of low-activity admixtures such as fly ash, mineral powder, and pozzolanic ash. This allows them to participate earlier and more fully in the secondary pozzolanic reaction and hydration process. This synergistic stimulation mechanism enables a significant reduction in cement usage, directly lowering costs, while ensuring or even improving concrete performance (especially later-stage strength and durability). It also reduces the total heat of hydration and peak temperature rise, effectively suppressing the risk of temperature cracking. Furthermore, the fully activated admixtures can generate more hydration products (such as CSH gel), densely filling pores, optimizing the microstructure, significantly improving the long-term durability of concrete, such as its impermeability and erosion resistance, and achieving the resource utilization of industrial solid waste.

[0015] As a preferred embodiment of this technical solution, the molar ratio of the polyol, the unsaturated carboxylic acid II, the phosphonic acid, the initiator, and the alkanolamine monomer is (0.5-1.0):(1-1.5):(0.1-0.5):(0.01-0.1):(0.1-1.0).

[0016] More preferably, the polyol includes any one or more combinations of diethylene glycol, glycerol, and sorbitol.

[0017] More preferably, the unsaturated carboxylic acid II includes any one or more combinations of acrylic acid and fumaric acid.

[0018] More preferably, the phosphonic acid includes any one or more combinations of hydroxyethylidene diphosphonic acid, hydroxyethylidene diphosphonic acid, and aminotrimethylene phosphonic acid, with a purity > 99%.

[0019] More preferably, the initiator is ammonium persulfate ((NH4)2S2O8) with a purity ≥95%.

[0020] More preferably, the alcoholamine monomer includes any one or a combination of triethanolamine, ethylene glycol monoisopropanolamine, triisopropanolamine, and N-methyldiethanolamine.

[0021] As a preferred embodiment of this technical solution, the slump-preserving functional monomer B comprises any one or more combinations of hydroxyethyl acrylate, hydroxypropyl acrylate, and diethyl maleate, with a purity > 98%.

[0022] As a preferred embodiment of this technical solution, the rheological functional monomer C comprises any one or more combinations of capped amide phosphate, sodium methyl allyl sulfonate, sodium acrylate-2-acrylamide-2-methylpropanesulfonate, and sodium allyl sulfonate, with a purity > 95%.

[0023] As a preferred embodiment of this technical solution, the polyether macromonomer includes any one or a combination of methyl allyl polyoxyethylene ether, isopentenyl polyoxyethylene ether, allyl polyoxyethylene ether, ethylene glycol monovinyl polyethylene glycol ether, and polyethylene glycol monomethyl ether.

[0024] More preferably, the molecular weight of the polyether macromonomer is 1200-4000.

[0025] More preferably, the molecular weight of the polyether macromonomer is 1200, 2400, 3000 or 4000.

[0026] As a preferred embodiment of this technical solution, the unsaturated carboxylic acid I includes any one or more combinations of acrylic acid (CH2=CHCOOH), cinnamic acid (C6H5CH=CHCOOH), maleic acid (HOOCCH=CHCOOH), and fumaric acid (HOOCCH=CHCOOH).

[0027] As a preferred embodiment of this technical solution, the oxidant includes any one or more combinations of hydrogen peroxide, ammonium persulfate, potassium persulfate and sodium peroxide, with a purity > 98%.

[0028] As a preferred embodiment of this technical solution, the reducing agent includes any one or more combinations of vitamin C, sodium formaldehyde sulfoxylate (sodium formaldehyde sulfoxylate), sodium bisulfite (NaHSO3), and ferrous sulfite, with a purity > 98%.

[0029] As a preferred embodiment of this technical solution, the chain transfer agent includes any one or more combinations of mercaptoacetic acid, mercaptopropionic acid and mercaptoethanol, with a purity > 98%.

[0030] Secondly, the present invention also discloses a method for preparing the above-mentioned polycarboxylate admixture for reinforcing low-activity admixtures, comprising the following steps: Add the polyether macromonomer to the reactor and a small amount of water, heat and stir until the polyether macromonomer is completely dissolved, then add functional monomer A and oxidant; Then, add an aqueous solution of rheology functional monomer C and chain transfer agent dropwise to the reactor. After 20-40 minutes of dropwise addition, simultaneously add an aqueous solution of unsaturated carboxylic acid I and slump-retaining functional monomer B. After 2-4 hours, the simultaneous addition is complete. After the addition is complete, keep warm at 40-50℃ for 1-3 hours to obtain polycarboxylate admixture that enhances low-activity admixtures.

[0031] The present invention provides a method for preparing polycarboxylate admixtures that enhance low-activity blends. This method employs a double-drop addition process. First, a rheology functional monomer C and a chain transfer agent are added dropwise to introduce functional groups such as sulfonic acid groups with strong adsorption and rapid dispersion in the early stages of polymer chain growth, forming chain segments with good initial dispersion capabilities. Then, unsaturated carboxylic acid I and slump-retaining functional monomer B are added dropwise simultaneously. Unsaturated carboxylic acid I continuously polymerizes and elongates the main chain, while slump-retaining functional monomer B and the continuously added rheology functional monomer C are randomly incorporated. Since the activating functional monomer A has already been added in the initial stage of the reaction, its double bonds will continuously participate in the reaction throughout the polymerization process. Therefore, the activating functional monomer A can be incorporated into the growing polymer main chain as a multifunctional branching point or block unit.

[0032] More preferably, the preparation method of the polycarboxylate admixture for reinforcing low-activity admixtures specifically includes the following steps: Add the polyether macromonomer to the bottom material reactor ② and add 30% of the total water. Turn on the stirrer and control the stirring speed (e.g., 30 rpm / min). Start heating and stirring until the polyether macromonomer is completely dissolved. Add the functional monomer A and oxidant, and keep the temperature constant at 45℃. Add 10% water to the dropping tank A2, add unsaturated carboxylic acid I and slump-retaining functional monomer B, stir evenly and prepare the dropping material A2; Add 20% water to the dropping tank B2, add rheology functional monomer C and chain transfer agent, stir evenly and prepare the dropping material B2; Add material B2 to the bottom mixing vessel ② and after 30 minutes, add material A2 to the bottom mixing vessel ②. After 3 hours, the addition of material A2 and material B2 is completed simultaneously. After the addition is complete, keep warm at 45℃ for 2 hours to obtain a polycarboxylate admixture that enhances low-activity admixtures.

[0033] More preferably, the method for preparing the activated functional monomer A includes the following steps: Dissolve or dilute the polyol, unsaturated carboxylic acid II, initiator, phosphonic acid and alkanolamine monomer into a solution for later use. Slowly pour the polyol, phosphonic acid solution and initiator as the base material into the base material reaction vessel ① and stir, and start heating. An unsaturated carboxylic acid II solution was pumped into a dropping tank A1 as feed A1 and started dripping into the bottom material stirring vessel for 1-3 hours. After holding at this temperature for 5-15 minutes, an alcohol amine monomer solution was pumped into a dropping tank B1 as feed B1 and dripped into the bottom material stirring vessel for 20-40 minutes. After aging for 0.5-2 hours, the activated functional monomer A was obtained.

[0034] More preferably, the preparation method of the activated functional monomer A specifically includes the following steps: Dissolve or dilute the polyol, unsaturated carboxylic acid II, phosphonic acid and alkanolamine monomers into a solution for later use. Slowly pour the polyol, phosphonic acid solution and initiator as the base material into the base material reaction vessel ① and stir (e.g., the stirring speed is 30 rpm / min), and start heating until the solution temperature is 40℃. An unsaturated carboxylic acid II solution was pumped into the dropping tank A1 as feed A1 and started dripping into the bottom material stirring vessel for 2 hours. After holding at this temperature for 10 minutes, an alcohol amine monomer solution was pumped into the dropping tank B1 as feed B1 and dripped into the bottom material stirring vessel for 30 minutes. After aging for 1 hour, the activated functional monomer A was obtained.

[0035] The polycarboxylate admixture of the present invention for enhancing low-activity admixtures has at least the following beneficial effects: 1. In the polycarboxylate admixture for reinforcing low-activity admixtures of the present invention, the present invention introduces a monomer A with an activating function. This monomer uses a polyol as a backbone and is polymerized through unsaturated carboxylic acid II, and introduces phosphonic acid groups into the molecular structure to form a comb-like configuration. After grafting the activating functional monomer A onto the polyether macromolecular backbone, the resulting polymer dissolves rapidly in cement paste. Its phosphonic acid groups can efficiently adsorb calcium / magnesium ions in the solution, forming a polymeric complex with a cross-linked network topology. This structure can significantly improve the structural density of the hydration products without interfering with the cement hydration kinetics. More importantly, this complex structure can serve as a dynamic reservoir of calcium / magnesium ions, continuously releasing ions into the system during the hydration reaction process, ensuring the continuous and rapid progress of the hydration reaction; 2. In the polycarboxylate admixture for reinforcing low-activity admixtures of the present invention, the amine component in the activated functional monomer A forms a cross-linked structure with the phosphonic acid group under the mediation of alcohol-ether bonds. After dissolving in cement paste, this structure exhibits strong electronegativity and can be effectively adsorbed onto the surface of fine particles (especially low-activity cementitious materials), forming a significant surface potential difference. This adsorption can promote the penetration of ions into the internal lattice of the particles, accelerate the formation and migration of lattice defects, thereby effectively destroying the inert layer on the particle surface and significantly stimulating the potential hydration activity of the low-activity cementitious material powder. 3. In the polycarboxylate admixture of the present invention, the introduction of slump-retaining monomer B allows the ester group structure in its molecule to precisely regulate the hydrolysis rate of the water-reducing agent molecule. While maintaining suitable initial hydrolytic activity, this structure significantly slows down the continuous hydrolysis process of the molecular chain, endowing the water-reducing agent with excellent slow-release properties, thereby achieving long-term control of concrete slump loss. 4. In the polycarboxylate admixture for reinforcing low-activity admixtures of the present invention, the introduction of the rheology functional monomer C results in a significant synergistic adsorption effect between the sulfonic acid groups carried by the monomer and the carboxyl groups on the polymer backbone. This effect greatly accelerates the adsorption kinetics of water-reducing agent molecules on the surface of cement particles, significantly improves its dispersion efficiency on cement particles, and ultimately manifests as a substantial increase in water reduction rate.

[0036] Therefore, the polycarboxylic acid admixture of the present invention, through molecular design, innovatively introduces key functional groups such as phosphonic acid groups, amino groups and sulfonic acid groups into the polycarboxylic acid backbone, endowing the polycarboxylic acid admixture with multiple synergistic functions such as reducing cement usage, effectively activating low-activity cementitious materials, and stabilizing and improving the workability of concrete. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a flowchart illustrating the preparation method of the polycarboxylate admixture for enhancing low-activity admixtures according to the present invention. Detailed Implementation

[0039] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0040] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Example 1 The polycarboxylate additive used to enhance low-activity admixtures in this embodiment comprises the following components in parts by weight: 35 parts of polyether macromonomer (methyl allyl polyoxyethylene ether, molecular weight 2400) Unsaturated carboxylic acid I (acrylic acid) 3.0 parts, 2.0 parts of functional monomer A, Slump-retaining monomer B (hydroxyethyl acrylate, purity > 98%) 0.5 parts, 0.8 parts of rheology-functionalized monomer C (terminated amide phosphate, purity > 95%) Hydrogen peroxide, purity > 98%, 0.1 parts. Vitamin C, purity > 98%, 0.1 part. Chain transfer agent (mercaptopropionic acid, purity > 98%) 0.1 parts, 58.4 portions of deionized water.

[0043] like Figure 1 As shown, the preparation method of the excitation functional monomer A in this embodiment includes the following steps: Sorbitol, acrylic acid, hydroxyethylidene diphosphonic acid, and triisopropanolamine are dissolved or diluted into a solution for later use. In the formula, the molar ratio of sorbitol, acrylic acid, hydroxyethylidene diphosphonic acid, ammonium persulfate, and triisopropanolamine is 1.0:1.5:0.3:0.01:1.0. Sorbitol, hydroxyethylidene diphosphonic acid solution and ammonium persulfate were slowly poured into the bottom material reaction vessel ① and stirred (30 rpm / min), and the solution was heated to 40℃. Acrylic acid solution was pumped into dropping tank A1 as feed A1 and started dripping into bottom material stirring vessel ① for 2 hours. After holding at this temperature for 10 minutes, triisopropanolamine solution was pumped into dropping tank B1 as feed B1 and dripped into bottom material stirring vessel ① within 30 minutes. After aging for 1 hour, activated functional monomer A was obtained and ready for use.

[0044] like Figure 1 As shown in this embodiment, the preparation method of the polycarboxylate admixture for enhancing low-activity admixtures includes the following steps: Add 35 parts of methyl allyl polyoxyethylene ether to the bottom material reaction vessel ② and add 30% of the total water. Turn on the stirrer and control the stirring speed to 30 rpm / min. Heat and stir until the methyl allyl polyoxyethylene ether is completely dissolved. Add 2.0 parts of functional monomer A and 0.1 parts of hydrogen peroxide and keep the temperature at 45℃. Add 10% water to the dropping container A2, add 3.0 parts of acrylic acid and 0.5 parts of hydroxyethyl acrylate, stir evenly, and the dropping material A2 is prepared. Add 20% water to the dropping tank B2, add 0.8 parts of capped amide phosphate, 0.1 parts of vitamin C, and 0.1 parts of mercaptopropionic acid. After stirring evenly, the dropping material B2 is prepared. Additive B2 was added to the bottom mixing vessel ②. After 30 minutes of adding, additive A2 was added to the bottom mixing vessel ②. After 3 hours, additives A2 and B2 were added simultaneously. After the addition was completed, the mixture was kept at 45°C for 2 hours to obtain a polycarboxylate admixture that reinforces low-activity admixtures.

[0045] Example 2 The polycarboxylate additive used to enhance low-activity admixtures in this embodiment comprises the following components in parts by weight: Polyether macromonomer (a mixture of isopentenyl polyoxyethylene ether and allyl polyoxyethylene ether, wherein the mass ratio of isopentenyl polyoxyethylene ether to allyl polyoxyethylene ether is 2:1, the molecular weight of isopentenyl polyoxyethylene ether is 1200, and the molecular weight of allyl polyoxyethylene ether is 3000), 30 parts. Unsaturated carboxylic acid I (acrylic acid and maleic acid mixed in a 2:1 ratio) 5.0 parts, 2.0 parts of functional monomer A, Slump-retaining monomer B (hydroxypropyl acrylate, purity > 98%) 5.0 parts, Rheology functional monomer C (sodium methyl allyl sulfonate and sodium acrylate-2-acrylamide-2-methylpropanesulfonate, in a 1:1 ratio, purity >95%) 1.0 part, Oxidizing agent (ammonium persulfate, purity > 98%) 0.2 parts, Reducing agent (sodium formaldehyde sulfoxylate (sodium formaldehyde sulfoxylate) and ferrous sulfite in a 1:1 ratio, purity > 98%) 0.2 parts, Chain transfer agent (thioglycolic acid, purity > 98%) 0.1 parts, 56.5 parts of deionized water.

[0046] like Figure 1 As shown, the preparation method of the excitation functional monomer A in this embodiment includes the following steps: Diethylene glycol, fumaric acid, hydroxyethylidene diphosphonic acid, and ethylene glycol monoisopropanolamine are dissolved or diluted into a solution for later use. In the formula, the molar ratio of diethylene glycol, fumaric acid, hydroxyethylidene diphosphonic acid, ammonium persulfate, and ethylene glycol monoisopropanolamine is 0.8:1.2:0.3:0.05:0.7. Diethylene glycol, ammonium persulfate, and hydroxyethylidene diphosphonic acid were slowly poured into the bottom material reaction vessel ① and stirred (30 rpm / min), and then heated to a solution temperature of 40℃. Fumaric acid solution was pumped into dropping tank A1 as feed A1 and started dripping into bottom material stirring vessel ① for 2 hours. After keeping warm for 10 minutes, ethylene glycol monoisopropanolamine solution was pumped into dropping tank B1 as feed B1 and dripped into bottom material stirring vessel ① for 30 minutes. After aging for 1 hour, activated functional monomer A was obtained and ready for use.

[0047] like Figure 1 As shown in this embodiment, the preparation method of the polycarboxylate admixture for enhancing low-activity admixtures includes the following steps: Add 30 parts of isopentenyl polyoxyethylene ether and allyl polyoxyethylene ether in a 2:1 ratio to the bottom material reaction vessel ② and add 30% of the total water. Turn on the stirrer and control the stirring speed to 30 rpm / min. Start heating and stirring until completely dissolved. Add 2.0 parts of activated functional monomer A and 0.2 parts of ammonium persulfate and keep the temperature constant at 45℃. Add 10% water to the dripping tank A2, add 5.0 parts of unsaturated carboxylic acid I (acrylic acid and maleic acid mixed in a 2:1 ratio) and 5 parts of slump-retaining functional monomer B (hydroxypropyl acrylate), stir evenly, and the dripping material A2 is prepared. Add 20% water to the dripping tank B2, then add 1.0 part of rheology functional monomer C (sodium methyl allyl sulfonate and sodium acrylate-2-acrylamide-2-methylpropanesulfonate, mixed in a 1:1 ratio), 0.1 part of reducing agent (sodium formaldehyde sulfoxylate (sodium formaldehyde sulfoxylate) and ferrous sulfite, mixed in a 1:1 ratio) and 0.1 part of mercaptoacetic acid. After stirring evenly, the dripping material B2 is prepared. Additive B2 is added dropwise to the bottom mixing vessel ②. After 30 minutes of adding, additive A2 is added dropwise to the bottom mixing vessel ②. After 3 hours, additives A2 and B2 are added simultaneously. After the addition is completed, keep the temperature at 45℃ for 2 hours to obtain the polycarboxylate admixture that enhances the low-activity blend.

[0048] Example 3 The polycarboxylate additive used to enhance low-activity admixtures in this embodiment comprises the following components in parts by weight: 40 parts of polyether macromonomer (ethylene glycol monovinyl polyethylene glycol ether and polyethylene glycol monomethyl ether, mixed in a 1:1 ratio, wherein the molecular weight of ethylene glycol monovinyl polyethylene glycol ether is 4000 and the molecular weight of polyethylene glycol monomethyl ether is 2400). Unsaturated carboxylic acid I (maleic acid) 0.5 parts, 5.0 parts of functional monomer A were used to excite the product. Slump-retaining monomer B (diethyl maleate, purity > 98%) 2.5 parts, Rheology functional monomer C (a mixture of capped amide phosphate and sodium 2-acrylamide-2-methylpropanesulfonate in a 1:1 ratio, purity >95%) 0.5 parts, Oxidizing agent (potassium persulfate and sodium peroxide mixed in a 1:1 ratio, purity > 98%) 0.2 parts, Reducing agent (sodium bisulfite and ferrous sulfite mixed in a 1:1 ratio, purity > 98%) 0.25 parts, Chain transfer agent (mercaptoethanol, purity > 98%) 0.15 parts, 50.9 parts of deionized water.

[0049] like Figure 1 As shown, the preparation method of the excitation functional monomer A in this embodiment includes the following steps: Glycerol, acrylic acid, aminotrimethylenephosphonic acid, and N-methyldiethanolamine are dissolved or diluted into a solution for later use. In the formula, the molar ratio of glycerol, acrylic acid, aminotrimethylenephosphonic acid, ammonium persulfate, and N-methyldiethanolamine is 1.0:1.5:0.5:0.01:1.0. Glycerol, aminotrimethylenephosphonic acid, and ammonium persulfate were slowly poured into the bottom material reaction vessel ① and stirred (30 rpm / min), and then heated to a solution temperature of 40°C. Acrylic acid solution was pumped into dropping tank A1 as feed A1 and started dripping into bottom material stirring tank ① for 2 hours. After keeping warm for 10 minutes, N-methyldiethanolamine solution was pumped into dropping tank B1 as feed B1 and dripped into bottom material stirring tank ① for 30 minutes. After aging for 1 hour, activated functional monomer A was obtained and ready for use.

[0050] like Figure 1 As shown in this embodiment, the preparation method of the polycarboxylate admixture for enhancing low-activity admixtures includes the following steps: Add 40 parts of polyether macromonomer (a mixture of ethylene glycol monovinyl polyethylene glycol ether and polyethylene glycol monomethyl ether in a 1:1 ratio) to the bottom material reaction vessel ②, and add 30% of the total water. Turn on the stirrer and control the stirring speed at 30 rpm / min. Start heating and stirring until completely dissolved. Add 5 parts of functional monomer A and 0.2 parts of oxidant (a mixture of potassium persulfate and sodium peroxide in a 1:1 ratio), and keep the temperature at 45℃. Add 10% water to the dripping tank A2, add 0.5 parts maleic acid and 2.5 parts diethyl maleate, stir well, and prepare the dripping material A2; Add 20% water to the dripping tank B2, add 0.5 parts of capped amide phosphate and sodium acrylate-2-acrylamide-2-methylpropanesulfonate in a 1:1 ratio, and 0.15 parts of mercaptoethanol. Stir well to prepare dripping material B2. Additive B2 was added to the bottom mixing vessel ②. After 30 minutes of adding, additive A2 was added to the bottom mixing vessel ②. After 3 hours, additives A2 and B2 were added simultaneously. After the addition was completed, the mixture was kept at 45°C for 2 hours to obtain a polycarboxylate admixture that reinforces low-activity admixtures.

[0051] Compare with Example 1 This comparative example is basically the same as Example 1, except that in the preparation of the functional monomer A, the phosphonic acid and alkanolamine monomers are replaced with equimolar amounts of unsaturated carboxylic acid acrylic acid.

[0052] Compare with Example 2 This comparative example is basically the same as Example 1, except that: the excitation functional monomer A, the slump-maintaining functional monomer B, the rheology functional monomer C and acrylic acid are mixed at one time and then added dropwise to participate in the copolymerization reaction.

[0053] This invention investigated the workability, slump loss, and compressive strength of concrete containing polycarboxylate admixtures from Examples 1-3 and Comparative Examples 1-2. The concrete slump test method was performed according to the relevant provisions of GB8076-2008 "Concrete Admixtures"; the concrete compressive strength test was performed according to the relevant provisions of GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The test mix proportions and results are shown in Tables 1-2. Table 1. Concrete mix proportions used in the experiment (kg)

[0054] Table 2 Test data for C30 concrete

[0055] As can be seen from Tables 1-2, the polycarboxylate admixtures for reinforcing low-activity admixtures prepared in Examples 1-3 of this invention significantly improve the fluidity, encapsulation, and slow-release effect of concrete mixtures. Furthermore, even with a 20% reduction in cement content, there are significant increases in 3-day, 7-day, and 28-day strengths. This further demonstrates that the polycarboxylate admixtures of this invention possess multiple synergistic functions, including reducing cement usage, effectively activating low-activity cementitious materials, and stabilizing and improving the workability of concrete.

[0056] In Comparative Example 1, replacing the phosphonic acid and alkanolamine monomers with equimolar amounts of acrylic acid resulted in the loss of the chelating inert cation (Ca) in the activated functional monomer A. 2+ Al 3+The phosphonic acid groups and amino groups that create an alkaline microenvironment significantly reduce the "deep activation" effect on low-activity admixtures. Therefore, the polycarboxylate admixture obtained in Comparative Example 1 has a significantly lower effect on early activity activation, final strength, and durability improvement in concrete than that of the present invention.

[0057] In Comparative Example 2, the activation functional monomer A, slump-retaining functional monomer B, and rheology functional monomer C were mixed with acrylic acid and added at once. The activity of acrylic acid was much greater than that of the other monomers, which led to a significant reduction in the grafting efficiency of the groups in monomers A / B / C. Furthermore, it may have caused the distribution of different functional monomers on the polymer backbone to become random and disordered, making it impossible to achieve the expected structural design effect of the molecular chain. The synergistic effect between the functions was weakened, resulting in poor performance of polycarboxylate admixture on the flowability, concrete encapsulation and flowability, and slow-release effect of concrete mixture.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A polycarboxylate admixture for enhancing low-activity blends, characterized in that, Polymerized from the following components by weight parts: Polyether macromonomer 30-40 parts, unsaturated carboxylic acid I 0.1-5.0 parts, excitation functional monomer A 0.1-5.0 parts, anti-slump functional monomer B 0.1-5.0 parts, rheological functional monomer C 0.1-2.0 parts, oxidizing agent 0.1-1.0 parts, reducing agent 0.1-1.0 parts, chain transfer agent 0.1-2.0 parts and water 40-60 parts; Wherein, the excitation functional monomer A, the anti-slump functional monomer B and the rheological functional monomer C are added in turn, and the excitation functional monomer A is polymerized from polyol, unsaturated carboxylic acid II, initiator, phosphonic acid and alcohol amine small monomer.

2. The polycarboxylate admixture of claim 1, wherein, The molar ratio of the polyol, the unsaturated carboxylic acid II, the phosphonic acid, the initiator and the alcohol amine small monomer is (0.5-1.0):(1-1.5):(0.1-0.5):(0.01-0.1):(0.1-1.0). Wherein, the phosphonic acid includes any one or combination of hydroxyethylidene diphosphonic acid, hydroxyethylidene diphosphonic acid and aminotri (methylene) phosphonic acid; The alcohol amine small monomer includes any one or combination of triethanolamine, ethylene glycol monoisopropanolamine, triisopropanolamine and N-methyl diethanolamine.

3. The polycarboxylate admixture of claim 1, wherein, The anti-slump functional monomer B includes any one or combination of hydroxyethyl acrylate, hydroxypropyl acrylate and maleic acid diethyl ester.

4. The polycarboxylate admixture of claim 1, wherein, The rheological functional monomer C includes any one or combination of blocked amide phosphate, sodium methyl allyl sulfonate, acrylic acid-2-acrylamide-2-methyl propane sulfonic acid sodium and allyl sulfonic acid sodium.

5. The polycarboxylic acid admixture for enhancing low-activity admixture according to claim 1, wherein, The polyether macromonomer includes any one or combination of methyl allyl polyoxyethylene ether, prenyl polyoxyethylene ether, allyl polyoxyethylene ether, ethylene glycol mono vinyl polyethylene glycol ether and polyethylene glycol monomethyl ether.

6. The polycarboxylate admixture of claim 1, wherein, The unsaturated carboxylic acid I includes any one or combination of acrylic acid, cinnamic acid, maleic acid and fumaric acid.

7. The polycarboxylate admixture of claim 1, wherein the low-activity blend is enhanced. The oxidizing agent includes any one or combination of hydrogen peroxide, ammonium persulfate, potassium persulfate and sodium peroxide.

8. The polycarboxylate admixture of claim 1, wherein, The reducing agent includes any one or combination of vitamin C, formaldehyde sodium sulfite, sodium bisulfite and ferrous sulfite.

9. The polycarboxylate admixture of claim 1, wherein, The chain transfer agent includes any one or combination of mercaptoacetic acid, mercaptopropionic acid and mercaptoethanol.

10. A method of producing a polycarboxylate admixture for enhancing low-activity blends, characterized by, Comprising the following steps: The polyether macromonomer is added to the reaction kettle and a small amount of water is added, heated and stirred until the polyether macromonomer is completely dissolved, the excitation functional monomer A and the oxidizing agent are added; then the rheological functional monomer C and the aqueous solution of the chain transfer agent are added dropwise to the reaction kettle, and after 20-40 min, the aqueous solution of the unsaturated carboxylic acid I and the anti-slump functional monomer B is added dropwise, and after 2-4 h, the dropwise addition is completed; after the dropwise addition is completed, the temperature is kept at 40-50℃ for 1-3 h, and the polycarboxylic acid admixture for enhancing low-activity admixture is obtained.

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