Ester-ether copolymer polycarboxylate water reducer for recycled aggregate concrete and preparation method thereof

Abstract

The present invention relates to an ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete and a preparation method thereof, comprising: an esterification reaction and a copolymerization reaction. The present invention uses a highly active vinyl ether monomer, a first esterification monomer with a double-layer dispersed structure, and a lightly cross-linked second esterification monomer for free radical polymerization. The molecular structure of the first esterification monomer contains highly water-absorbing groups and rigid groups such as carboxyl groups, ester groups, and benzene rings, which can not only play a role in water retention and thickening, but also regulate the rigidity and flexibility of the molecular chain, and improve the stability of the polymer molecules at different interfaces and saline-alkali conditions. The ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete prepared by the present invention can overcome the defects of high water absorption and large slump loss of recycled aggregate concrete in practical applications without affecting the compressive strength of the concrete.

Description

Technical Field

[0001] The invention relates to the field of polycarboxylate water reducers, and in particular to an ester-ether copolymerized polycarboxylate water reducer for recycled aggregate concrete and a preparation method thereof. Background Art

[0002] With the accelerated development of urbanization and the rapid replacement of old and new buildings, a large amount of construction waste has been generated. Since construction waste contains decoration materials, plastics, rubber, etc., traditional landfill and dumping will cause a series of environmental problems. At the same time, the rapid development of urbanization is also increasing the demand for natural aggregates, and the large-scale mining of natural aggregates has caused more serious environmental damage. Therefore, in order to adapt to the rapid development of urbanization, it is urgent to find a material to replace natural aggregates.

[0003] Therefore, the recycled aggregate concrete formed by crushing, screening, and washing construction waste into aggregates and applying them to concrete is the most effective construction waste treatment method in the world. It not only increases the scope of construction waste use, but also reduces the demand for natural aggregates, thereby promoting the sustainable development of the construction industry. At the same time, with the implementation of the country's "dual carbon" strategy, the "energy conservation and carbon reduction" measures in the construction industry have attracted much attention. The use of recycled aggregate concrete can achieve green and low-carbon development of the construction industry to a certain extent.

[0004] Although recycled aggregate concrete has the advantages of being green and recyclable, it has the problems of high water absorption, large admixture adsorption, high admixture dosage sensitivity, and large slump loss, which lead to poor working performance, difficult construction, and poor durability of recycled aggregate concrete. Although the working performance of recycled aggregate concrete can be improved by pre-wetting or adding additional water, this will reduce the compressive strength of concrete. Summary of the invention

[0005] In view of the prior art, the present invention develops an ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete and a preparation method thereof. The prepared ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete can overcome the defects of high water absorption and large slump loss of recycled aggregate concrete in practical applications without affecting the compressive strength of concrete.

[0006] Based on this, the present invention provides a method for preparing an ester-ether copolymerized polycarboxylate water-reducing agent for recycled aggregate concrete, comprising the following steps:

[0007] (1) Esterification reaction: adding an unsaturated acid or an unsaturated acid anhydride, 2-(3,4-dimethoxyphenyl)ethanol, a polymerization inhibitor, a dehydrating agent and a catalyst into a tower reactor, heating at 160-180° C. under normal pressure for 2-3 hours, and then heating at 0.08 MPa under reduced pressure for 5-6 hours to obtain a light yellow mixture; washing the light yellow mixture with high-temperature distilled water to remove unreacted raw materials, polymerization inhibitors, catalysts and dehydrating agents in the light yellow mixture to obtain a viscous liquid; placing the viscous liquid in a vacuum oven to dry until its weight remains unchanged to obtain a first esterification monomer;

[0008] The unsaturated acid is 3-(3,4-dihydroxyphenyl)-2-acrylic acid, the unsaturated anhydride is citraconic anhydride, and the molar ratio of 2-(3,4-dimethoxyphenyl)ethanol to the unsaturated acid / unsaturated anhydride is 2-5:1;

[0009] The amount of the inhibitor is 0.1-0.25% of the total mass of the acid and alcohol, the amount of the catalyst is 0.2-1.0% of the total mass of the acid and alcohol, and the amount of the dehydrating agent is 10-40% of the mass of 2-(3,4-dimethoxyphenyl)ethanol;

[0010] (2) Copolymerization reaction: adding the first esterification monomer prepared in step (1), ethylene glycol monovinyl polyoxyethylene ether with a molecular weight of 400-3000, and water into a reaction container, dissolving them uniformly to prepare solution a; uniformly mixing the mixed aqueous solution of the second esterification monomer and the unsaturated acid, the initiator aqueous solution, and the chain transfer agent aqueous solution, and dripping them into solution a for reaction, the reaction temperature is 5-50° C., the dripping time is 2.5-3 hours, and the temperature is kept for 0.5-1 hour after the dripping is completed, to obtain an ester-ether copolymerized polycarboxylic acid water-reducing agent for recycled aggregate concrete;

[0011] The mass ratio of the ethylene glycol monovinyl polyoxyethylene ether, the first esterification monomer, the second esterification monomer, the unsaturated acid, the initiator, and the chain transfer agent is 100:(5-10):(2-6):(4-15):(2-5):(0.2-2).

[0012] Furthermore, the polymerization inhibitor includes at least one of 3-methylpyridine, 1,1-diphenyl-2-trinitrophenylhydrazine, and sodium dimethyldithiocarbamate.

[0013] Furthermore, the catalyst is at least one of poly(sodium 4-styrene sulfonate), sodium anthraquinone-2-sulfonate, and sodium 1-butane sulfonate.

[0014] Furthermore, the dehydrating agent is Na 12 [(AlO 2 ) 12 (SiO 2 ) 12 ]·xH2 O, x is 0.5-5, and the pore size of the dehydrating agent is 5-12 meshes.

[0015] Furthermore, the second esterification monomer is produced by the reaction of trans-3-phenylacrylic acid and 1-phenyl-1,2-ethylene glycol.

[0016] Further, the unsaturated acid includes at least one of 2-propylacrylic acid or 2-ethylacrylic acid.

[0017] Furthermore, the initiator is a mixture of 1,1-dimethylethyl-hydroperoxide and sodium ethylthiosulfate.

[0018] Furthermore, the chain transfer agent is at least one of thioglycolic acid, 1,4-dimercaptothreitol, and 3-mercapto-1,2-propylene glycol.

[0019] Another object of the present invention is to provide an ester-ether copolymerized polycarboxylate water-reducing agent for recycled aggregate concrete obtained by the above-mentioned preparation method.

[0020] In summary, the present invention has the following beneficial effects:

[0021] 1. The present invention develops an ester-ether copolymer polycarboxylic acid water-reducing agent for recycled aggregate concrete, which can overcome the defects of high water absorption and large slump loss of recycled aggregate concrete in practical applications without affecting the compressive strength of concrete.

[0022] 2. The ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete prepared by the present invention adopts highly active vinyl ether monomers, a first esterified monomer with a double-layer dispersed structure, and a lightly cross-linked second esterified monomer for free radical polymerization. The molecular structure of the first esterified monomer contains highly water-absorbing groups and rigid groups such as carboxyl, ester, and benzene ring, which can not only play a role in water retention and thickening, but also regulate the rigidity and flexibility of the molecular chain, and improve the stability of the polymer molecules under different interfaces and saline-alkali conditions; and the second esterified monomer can make the polymer lightly cross-linked, so that it has greater steric hindrance and better anti-intercalation effect, which is reflected in better adaptability and slump retention performance. Therefore, the ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete prepared by the present invention solves the problems of poor working performance, difficult construction, and poor durability of recycled aggregate concrete caused by high water absorption of recycled aggregate concrete, large adsorption of admixtures, and high sensitivity to admixture dosage. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The experimental methods in the following examples are conventional methods unless otherwise specified. The experimental materials and reagents used in the following examples are all commercially available unless otherwise specified. The quantitative tests in the following examples were performed in triplicate, and the data are the average or average ± standard deviation of the triplicate experiments.

[0025] In addition, the "and / or" in the full text includes three solutions. Taking A and / or B as an example, it includes technical solution A, technical solution B, and a technical solution that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0026] Example 1

[0027] Preparation process of ester-ether copolymer polycarboxylate water reducer for recycled aggregate concrete:

[0028] (1) Esterification reaction

[0029] Take 120g 2-(3,4-dimethoxyphenyl)ethanol, 58g 3-(3,4-dihydroxyphenyl)-2-acrylic acid, 0.26g sodium dimethyldithiocarbamate, 0.45g poly(sodium 4-styrene sulfonate), 18g Na 12 [(AlO 2 ) 12 (SiO 2 ) 12 ]·2H 2 O(Na 12 [(AlO 2 ) 12 (SiO 2 ) 12 ]·2H 2O with a pore size of 10 mesh) is added into a tower reactor, the mixture is heated at 160° C. under normal pressure for 2 hours, and then heated at 0.08 MPa for 5 hours to obtain a light yellow mixture; the light yellow mixture is washed with a large amount of distilled water (90° C.), and unreacted raw materials, inhibitors and dehydrating agents in the light yellow mixture are removed to obtain a viscous liquid; the viscous liquid is placed in a vacuum oven at 80° C. to dry until its weight remains unchanged, to obtain a first esterification monomer.

[0030] (2) Copolymerization

[0031] 15.0 g of the first esterification monomer prepared above, 180.0 g of ethylene glycol monovinyl polyoxyethylene ether with a molecular weight of 2800, and 140.0 g of water were added to a reaction container and stirred to obtain a solution a;

[0032] Take 3.5g of 1,1-dimethylethyl-hydroperoxide, a mixed solution of sodium thiosulfate and thioglycolic acid (0.20g of sodium thiosulfate, 0.50g of thioglycolic acid, 30.00g of water), and a mixed solution of 2-propyl acrylic acid and the second esterification monomer (18.00g of 2-propyl acrylic acid, 9.00g of the second esterification monomer, 15.00g of water), and drop them into solution a for reaction. The reaction temperature is 15°C, the dropping time is 0.45h, and the temperature is kept for 0.5h after the dropping is completed to obtain an ester-ether copolymer polycarboxylic acid water reducer for recycled aggregate concrete.

[0033] The second esterification monomer is generated by the reaction of trans-3-phenylacrylic acid and 1-phenyl-1,2-ethylene glycol.

[0034] Preparation Examples 2-4

[0035] The raw materials and dosage of the first esterification monomer in Example 2-4 are shown in Table 1, and the reaction conditions are shown in Table 2; the raw materials and dosage of the ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete are shown in Table 3, and the reaction conditions are shown in Table 4.

[0036] Table 1 Formula of the first esterification monomer in Examples 1-4 (g)

[0037]

[0038]

[0039] Table 2 Reaction conditions for preparing the first esterification monomer in Examples 1-4

[0040] Example 1 Example 2 Example 3 Example 4 Reaction temperature (normal pressure) / ℃ 160 160 180 170 Reaction time (normal pressure) / h 2 2 2 2 Reaction time (0.08MPa) / h 5 5 5 5

[0041] Table 3 Formula of ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete in Examples 1-4 (g)

[0042]

[0043] Table 4 Reaction conditions of ester-ether copolymer polycarboxylate water reducer for preparing recycled aggregate concrete in Example 1-4

[0044] Example 1 Example 2 Example 3 Example 4 Reaction temperature / ℃ 15 20 5 5 Dropping time / h 0.45 0.45 0.45 0.45 Insulation time / h 0.5 0.5 0.5 0.5

[0045] The difference between Comparative Example 1 and Example 1 is that the first esterification monomer is not added to the formula of the ester-ether copolymer polycarboxylic acid water-reducing agent.

[0046] The difference between Comparative Example 2 and Example 1 is that the second esterification monomer is not added to the formula of the ester-ether copolymer polycarboxylic acid water-reducing agent.

[0047] Concrete performance tests were performed on the ester-ether copolymer polycarboxylate water-reducing agents for recycled aggregate concrete prepared in Examples 1-4, Comparative Examples 1 and 2, and a commercially available ester polycarboxylate water-reducing agent with better performance (Comparative Example 3).

[0048] The concrete mix ratio is shown in Table 5, and the water reducing agent dosage is 2.7% under the same solid content conditions.

[0049] Table 5 Concrete mix ratio (kg / m 3 )

[0050] cement Fly ash sand stone Recycled concrete coarse aggregate Mineral powder 280 80 900 600 450 40

[0051] The test results of concrete are shown in Table 6.

[0052] Table 6 Test results of concrete

[0053]

[0054] As shown in Table 6, under the condition of a certain concrete mix ratio, by changing the amount of water used in the concrete, the initial expansion of the concrete of Examples 1-4 and Comparative Examples 1-3 is controlled at 550-570 mm, the amount of water used in Comparative Example 1 is the highest, and the amount of water used in the concrete of Examples 1-4 in the present invention is significantly reduced, and the change in expansion is still within the control range, which fully demonstrates that the ester-ether copolymer polycarboxylate water-reducing agent prepared by the present invention has a higher water reduction rate and lower sensitivity. When the ester-ether copolymer polycarboxylate water-reducing agent in the present application is applied to recycled aggregate concrete, the amount of water used in the concrete can be significantly reduced, and the strength of the recycled aggregate concrete can be maintained.

[0055] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0056] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing an ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete, characterized in that: The steps include: (1) Esterification reaction: unsaturated acid or unsaturated acid anhydride, 2-(3,4-dimethoxyphenyl)ethanol, polymerization inhibitor, dehydrating agent and catalyst are added to a tower reactor, heated at 160-180°C under normal pressure for 2-3 hours, and then heated at 0.08 MPa under reduced pressure for 5-6 hours to obtain a light yellow mixture; the light yellow mixture is washed with high-temperature distilled water to remove unreacted raw materials, polymerization inhibitor, catalyst and dehydrating agent in the light yellow mixture to obtain a viscous liquid; the viscous liquid is placed in a vacuum oven to dry until its weight remains unchanged to obtain a first esterification monomer; The unsaturated acid is 3-(3,4-dihydroxyphenyl)-2-acrylic acid, the unsaturated anhydride is citraconic anhydride, and the molar ratio of 2-(3,4-dimethoxyphenyl)ethanol to the unsaturated acid / unsaturated anhydride is 2-5:1; The amount of the inhibitor is 0.1-0.25% of the total mass of the acid and alcohol, the amount of the catalyst is 0.2-1.0% of the total mass of the acid and alcohol, and the amount of the dehydrating agent is 10-40% of the mass of 2-(3,4-dimethoxyphenyl)ethanol; (2) Copolymerization reaction: the first esterification monomer prepared in step (1), ethylene glycol monovinyl polyoxyethylene ether with a molecular weight of 400-3000, and water are added to a reaction container, and dissolved uniformly to prepare solution a; the mixed aqueous solution of the second esterification monomer and the unsaturated acid, the initiator aqueous solution, and the chain transfer agent aqueous solution are mixed uniformly, and then dripped into solution a for reaction, the reaction temperature is 5-50°C, the dripping time is 2.5-3h, and the temperature is kept for 0.5-1h after the dripping is completed, to obtain a recycled aggregate concrete. Ester-ether copolymer polycarboxylic acid water-reducing agent for soil; the second esterification monomer is generated by the reaction of trans-3-phenylacrylic acid and 1-phenyl-1,2-ethylene glycol, the unsaturated acid includes at least one of 2-propyl acrylic acid or 2-ethyl acrylic acid, and the mass ratio of ethylene glycol monovinyl polyoxyethylene ether, the first esterification monomer, the second esterification monomer, the unsaturated acid, the initiator, and the chain transfer agent is 100:(5-10):(2-6):(4-15):(2-5):(0.2-2).

2. The method for preparing an ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete according to claim 1, characterized in that: The polymerization inhibitor includes at least one of 3-methylpyridine, 1,1-diphenyl-2-trinitrophenylhydrazine, and sodium dimethyldithiocarbamate.

3. The method for preparing an ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete according to claim 1, characterized in that: The catalyst is at least one of poly (sodium 4-styrene sulfonate), sodium anthraquinone-2-sulfonate and sodium 1-butane sulfonate.

4. The method for preparing an ester-ether copolymerized polycarboxylate water-reducing agent for recycled aggregate concrete according to claim 1, characterized in that: The dehydrating agent is Na 12 [(AlO2) 12 (SiO2) 12 ]·xH2O, x is 0.5-5, and the pore size of the dehydrating agent is 5-12 mesh.

5. The method for preparing an ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete according to claim 1, characterized in that: The initiator is a mixture of 1,1-dimethylethyl-hydroperoxide and sodium ethylthiosulfate.

6. The method for preparing an ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete according to claim 1, characterized in that: The chain transfer agent is at least one of thioglycolic acid, 1,4-dimercaptothreitol, and 3-mercapto-1,2-propylene glycol.

7. An ester-ether copolymer polycarboxylate water-reducing agent for recycled aggregate concrete, obtained by the preparation method according to any one of claims 1 to 6.

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