Slump-retaining water-reducing agent and preparation method therefor

Abstract

The present invention relates to a slump-retaining water-reducing agent and a preparation method therefor. The slump-retaining water-reducing agent is prepared from the following raw materials in parts by weight: 8-12 parts of a synthetic monomer, 180-300 parts of an unsaturated polyether monomer, 8-12 parts of an unsaturated carboxylic acid monomer, 15-30 parts of a functional monomer, 1.6-3.0 parts of an oxidizing agent, 0.2-0.8 parts of a reducing agent, 0.6-1.5 parts of a chain transfer agent, and 2-5 parts of a pH regulator, wherein the preparation raw materials of the synthetic monomer comprise an amino acid and a hydroxyalkyl acrylate. By introducing the synthetic monomer in the present invention, on one hand, hydrophilic groups hydrolyzed from an ester group can supplement a carboxyl consumed in a cement paste, and on the other hand, polyhydroxy and long-chain structures contained in the synthetic monomer also further improve the adsorption and dispersion capacity. The water-reducing and slump-retaining water-reducing agent of the present invention can alleviate the problems of a high mixing amount, serious losses, etc. of concrete admixtures, has both water-reducing and slump-retaining properties, and does not influence the strength of concrete. In addition, the water-reducing agent has relatively good adaptability to auxiliaries, such as common water-reducing agents, water-retaining agents, and defoaming agents.

Description

A slump-retaining water-reducing agent and preparation method thereof Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, in particular to a slump-retaining water-reducing agent and a preparation method thereof. Background Art

[0002] Polycarboxylate superplasticizers offer advantages such as high water reduction rate, good dispersibility, low dosage, low concrete shrinkage, strong molecular structure adjustability, and high-performance potential. In recent years, with my country's rapidly developing construction industry, superplasticizers have seen huge demand and development.

[0003] However, mixing plants are typically located some distance from construction sites, and the long transportation time can degrade concrete performance, hindering construction. While it's possible to incorporate a slump-preserving agent into a water reducer through compounding techniques, the increased complexity and cost create an urgent need for a water reducer that balances both water-reducing and slump-preserving properties.

[0004] Summary of the Invention

[0005] Based on this, it is necessary to provide a slump-retaining water-reducing agent and a preparation method thereof.

[0006] To achieve the above object, the present invention provides a technical solution:

[0007] A slump-retaining water reducer, wherein the raw materials for preparing the slump-retaining water reducer include, in parts by weight:

[0008] The raw materials for preparing the synthetic monomer include amino acid and hydroxyalkyl acrylate.

[0009] Preferably, the structural formula of the synthetic monomer is as follows:

[0010] wherein n is an integer of 1-4, and X is H or OH.

[0011] Preferably, the amino acid comprises one of tyrosine and phenylalanine. Preferably, the unsaturated polyether monomer comprises at least one of isopentanol polyoxyethylene ether and ethylene glycol vinyl polyoxyethylene ether.

[0012] Preferably, the unsaturated carboxylic acid monomer includes at least one of acrylic acid, methacrylic acid, and maleic anhydride.

[0013] Preferably, the oxidant is at least one of hydrogen peroxide, ammonium persulfate, and sodium persulfate, preferably hydrogen peroxide.

[0014] Preferably, the reducing agent is at least one of bleaching agent, vitamin C, ferrous sulfate, and sodium hypophosphite, preferably vitamin C.

[0015] Preferably, the functional monomer includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, and methyl methacrylate.

[0016] Preferably, the chain transfer agent includes at least one of mercaptoethanol, mercaptopropanol, and thioglycolic acid.

[0017] The present invention also provides a method for preparing the above-mentioned slump-retaining water-reducing agent, comprising the steps of:

[0018] dissolving an unsaturated polyether macromonomer in water and adding an oxidant to obtain a reactant solution;

[0019] Mix unsaturated carboxylic acid monomer and functional monomer in water to obtain dropwise addition solution A;

[0020] Mix the reducing agent and chain transfer agent in water to obtain solution B;

[0021] Mix the synthetic monomers in water to obtain dropwise solution C;

[0022] The solution A, the solution B and the solution C are added dropwise to the reactant solution, and after the addition is completed, the reaction is carried out by heat preservation. After the reaction is completed, a pH regulator is added to prepare a slump-retaining water reducer.

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention introduces a hydrophobic long side chain through an unsaturated polyether macromonomer to provide a steric hindrance effect and enhance the dispersibility of the polycarboxylate water reducer.

[0025] 2. The present invention introduces tyrosine / phenylalanine, which, on the one hand, introduces rigid groups, which can effectively reduce the aggregation of concrete; on the other hand, it introduces amino flexible hydrophilic groups, which can increase the adsorption effect, improve the dispersion effect and the adaptability to concrete.

[0026] 3. The water-reducing agent of the present invention can improve the problems of high concrete admixture dosage and severe loss without affecting the concrete strength. In addition, it has good compatibility with additives such as water-retaining agents and defoaming agents. DETAILED DESCRIPTION

[0027] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to specific embodiments.

[0028] In the examples, the test methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0029] A slump-retaining water reducer, wherein the raw materials for preparing the slump-retaining water reducer include, in parts by weight:

[0030] The raw materials for preparing the synthetic monomer include amino acid and hydroxyalkyl acrylate.

[0031] In one embodiment, the structural formula of the synthetic monomer is as follows:

[0032] wherein n is an integer of 1-4, and X is H or OH.

[0033] In one embodiment, the steps for preparing the synthetic monomer are as follows:

[0034] Mix the hydroxyalkyl acrylate with water, heat it to the desired reaction temperature in a water bath, then add sodium hydroxide to adjust the pH to a weak alkaline state. Then slowly add the amino acid. The reaction temperature is 70-80°C and the reaction time is 1-2 hours. After the reaction is completed, cool it to room temperature, then add sodium hydroxide to adjust the pH to a weak acidic state. Finally, concentrate under reduced pressure to obtain the synthetic monomer. Specifically, the compressed volume is 2 / 3 of the original volume.

[0035] In one embodiment, the amino acid comprises one of tyrosine and phenylalanine.

[0036] In one embodiment, the unsaturated polyether monomer includes at least one of isopentanol polyoxyethylene ether and ethylene glycol vinyl polyoxyethylene ether.

[0037] Ethylene glycol vinyl polyoxyethylene ether, due to its higher polymerization activity, reduces reaction temperature and shortens production cycle. Unsaturated carboxylic acid monomers introduce strong polar groups into the main chain, providing electrostatic adsorption. The introduction of unsaturated ester monomers allows hydrolysis in the alkaline environment of cement paste to release hydrophilic groups such as carboxyl groups, thereby improving subsequent adsorption and dispersion capabilities.

[0038] In one embodiment, the unsaturated carboxylic acid monomer includes at least one of acrylic acid, methacrylic acid, and maleic anhydride.

[0039] In one embodiment, the oxidant is at least one of hydrogen peroxide, ammonium persulfate, and sodium persulfate, preferably hydrogen peroxide.

[0040] In one embodiment, the reducing agent is at least one of bleaching agent, vitamin C, ferrous sulfate, and sodium hypophosphite, preferably vitamin C.

[0041] In one embodiment, the functional monomer includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, and methyl methacrylate, preferably hydroxyethyl acrylate.

[0042] In one embodiment, the chain transfer agent includes at least one of mercaptoethanol, mercaptopropanol, and thioglycolic acid.

[0043] In one embodiment, the pH adjuster includes at least one of sodium hydroxide and potassium hydroxide.

[0044] The present invention also provides a method for preparing the above-mentioned slump-retaining water-reducing agent, comprising the steps of:

[0045] dissolving an unsaturated polyether macromonomer in water and adding an oxidant to obtain a reactant solution;

[0046] Mix unsaturated carboxylic acid monomer and functional monomer in water to obtain dropwise addition solution A;

[0047] Mix the reducing agent and chain transfer agent in water to obtain solution B;

[0048] Mix the synthetic monomers in water to obtain dropwise solution C;

[0049] The solution A, the solution B and the solution C are added dropwise to the reactant solution, and after the addition is completed, the reaction is carried out by heat preservation at a temperature of 20° C. to 50° C. for a time of 0.5 h to 1.5 h. After the reaction is completed, a pH regulator is added to prepare a slump-retaining water reducer.

[0050] Specifically, the dropwise addition time of liquid A is 50 min-70 min, the dropwise addition time of liquid B is 60 min-80 min; and the dropwise addition time of liquid C is 60-80 min.

[0051] (1) Preparation of synthetic monomers

[0052] Dissolve hydroxyalkyl acrylate in water and place in a glass reactor equipped with a thermometer and a stirring device, add sodium hydroxide to adjust the pH to a weak alkaline pH of 8, start stirring and heat to 70-80°C in a water bath;

[0053] Under stirring, amino acid was slowly added and reacted for 1-2 hours. After cooling to room temperature, sodium hydroxide was added to adjust the pH to weak acidity (pH 6). The mixture was concentrated under reduced pressure to 2 / 3 of the original volume to obtain a synthetic monomer.

[0054] (2) Preparation of slump-retaining water reducer

[0055] dissolving an unsaturated polyether macromonomer in water and adding an oxidant to obtain a reactant solution;

[0056] Mix unsaturated carboxylic acid monomer and functional monomer in water to obtain dropwise addition solution A;

[0057] Mix the reducing agent and chain transfer agent in water to obtain solution B;

[0058] Mix the synthetic monomers in water to obtain dropwise solution C;

[0059] The solution A, the solution B and the solution C are added dropwise to the reactant solution, and after the addition is completed, the reaction is carried out by heat preservation at a temperature of 20° C. to 50° C. for 0.5 h to 1.5 h. After the reaction is completed, a pH regulator is added to prepare a slump-retaining water reducer.

[0060] Specifically, the dropwise addition time of liquid A is 50 min-70 min, the dropwise addition time of liquid B is 60 min-80 min; and the dropwise addition time of liquid C is 60-80 min.

[0061] In Examples 1 to 8, the monomer preparation raw materials and reaction conditions in step (1) are shown in Table 1.

[0062] Table 1: Raw materials and reaction conditions for preparing synthetic monomers in Examples 1 to 8

[0063] In Examples 1 to 8, the raw materials for preparing the slump-retaining water-reducing agent in step (2) are shown in Table 2, and the reaction conditions are shown in Table 3.

[0064] Table 2. Raw materials and reaction conditions for preparing slump-retaining water-reducing agent in Examples 1 to 8

[0065] Table 3 Reaction conditions of Examples 1 to 8

[0066] Comparative Example 1

[0067] The formulation and preparation method of this comparative example are the same as those of Example 1, except that no synthetic monomer is added.

[0068] Comparative Example 2

[0069] The formulation and preparation method of this comparative example are the same as those of Example 1, except that no synthetic monomer is added and the amount of hydroxyethyl acrylate used is 24 g.

[0070] Comparative Example 3

[0071] The formulation and preparation method of this comparative example are the same as those of Example 1, except that hydroxyethyl acrylate is not added and the amount of synthetic monomer used is 24 g.

[0072] (3) Experimental testing

[0073] The water reducers in the embodiments of the present invention and the comparative examples were subjected to concrete trial mix tests. The concrete performance tests were conducted in accordance with GB 8076-2008 "Concrete Admixtures", and the slump, expansion, etc. were tested. The cement in the concrete used China Resources Cement and Conch Cement, the apparent density of the machine-made sand was 2730 kg / m3, the crushed stone was continuously graded from 10 to 20 mm, and the water reducer content was 0.35 wt% to 0.45 wt% of the cementitious material. The test results are shown in Tables 4 and 5.

[0074] Table 4 Concrete performance test C 30 (China Resources Cement)

[0075] Table 5 Concrete performance test C30 (Conch Cement)

[0076] Concrete tests were carried out using different machine-made sands, and the results are shown in Table 6.

[0077] Table 6 Test results of different machine-made sand concrete

[0078] From the results in Table 4 and Table 5, it can be seen that in different cement systems, the dosage of Examples 1-8 is less than that of Comparative Examples 1-2, which indicates that the synthetic functional monomer has good adaptability to concrete.

[0079] It can be seen from Table 4 and Table 5 that the collapse retention performance of Examples 1-8 is better than that of Comparative Examples 2-3, which indicates that hydroxyethyl acrylate has a good synergistic effect with the synthetic functional monomer.

[0080] As shown in Table 6, for different manufactured sand systems, the dosage of Example 1 is lower than that of Comparative Example 1, indicating that the introduction of the synthetic functional monomer enhances adaptability. Furthermore, the concrete performance of Example 1 is superior to that of Comparative Example 1, demonstrating the strong synergistic effect of the synthetic functional monomer and hydroxyethyl acrylate.

[0081] It should be noted that the specific parameters or some reagents in the above embodiments are specific embodiments or preferred embodiments under the concept of the present invention, and are not intended to limit the present invention; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

Claims

1. A slump-retaining water reducing agent, characterized in that: The raw materials for preparing the slump-retaining water-reducing agent include, by weight: The raw materials for preparing the synthetic monomer include amino acid and hydroxyalkyl acrylate.

2. The slump-retaining water reducing agent according to claim 1, characterized in that: The structural formula of the synthetic monomer is as follows: Wherein, n is an integer of 1-4, and X is H or OH.

3. The slump-retaining water reducing agent according to claim 1, characterized in that: The amino acid includes one of tyrosine and phenylalanine.

4. The slump-retaining water reducing agent according to claim 1, characterized in that: The unsaturated polyether monomer includes at least one of isopentanol polyoxyethylene ether and ethylene glycol vinyl polyoxyethylene ether.

5. The slump-retaining water reducing agent according to claim 1, characterized in that: The unsaturated carboxylic acid monomer includes at least one of acrylic acid, methacrylic acid and maleic anhydride.

6. The slump-retaining water reducing agent according to claim 1, characterized in that: The oxidant is at least one of hydrogen peroxide, ammonium persulfate and sodium persulfate.

7. The slump-retaining water reducing agent according to claim 1, characterized in that: The reducing agent is at least one of bleaching agent, vitamin C, ferrous sulfate and sodium hypophosphite.

8. The slump-retaining water reducing agent according to claim 1, characterized in that: The functional monomer includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate and methyl methacrylate.

9. The slump-retaining water reducing agent according to claim 1, characterized in that: The chain transfer agent includes at least one of mercaptoethanol, mercaptopropanol, and thioglycolic acid.

10. A method for preparing the collapse-retaining water reducing agent according to any one of claims 1 to 9, characterized in that: Includes steps: Dissolving an unsaturated polyether macromonomer in water and adding an oxidant to obtain a reactant solution; Mix unsaturated carboxylic acid monomer and functional monomer in water to obtain dropwise solution A; Mix the reducing agent and chain transfer agent in water to obtain dropwise solution B; Mix the synthetic monomers in water to obtain dropwise solution C; The A solution, the B solution and the C solution are added dropwise to the reactant solution, and after the addition is completed, a heat preservation reaction is carried out. After the reaction is completed, a pH regulator is added to prepare a slump-retaining water-reducing agent.

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