Concrete thickening water-retaining agent as well as preparation method and application thereof

Abstract

The invention belongs to the field of concrete admixtures and relates to a concrete thickening water-retaining agent as well as a preparation method and application thereof. According to the concrete thickening water-retaining agent, alkyl acrylamide, hydroxyl unsaturated amide, hydroxyl / aminobenzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid and a cross-linking agent are subjected to free radical polymerization reaction. The preparation method is characterized in that alkyl acrylamide, hydroxyl unsaturated amide, hydroxyl / aminobenzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid and a cross-linking agent which have specific structures are subjected to free radical polymerization reaction, so that the obtained concrete thickening water-retaining agent has very excellent time-dependent water retention performance and working performance.

Description

Technical Field

[0001] The present invention belongs to the field of concrete admixtures, and particularly relates to a concrete thickening and water retaining agent, a preparation method thereof, and an application thereof. Background Art

[0002] As a basic material widely used in the field of construction engineering, the performance of concrete directly affects the project quality and service life. During the preparation of concrete, in order to optimize the construction performance and physical properties, various admixtures are usually added. Among them, the thickening and water retaining agent is a crucial type of admixture, which plays an important and non-negligible role in improving the fluidity, cohesiveness, and water retention of concrete.

[0003] However, the current concrete thickening and water retaining agents on the market still face some challenges. Specifically, cellulose ether thickeners and some liquid thickening and water retaining agents, although they can improve the consistency of concrete to a certain extent, sometimes have poor compatibility with mainstream admixtures such as polycarboxylate water reducers. In practical applications, if the dosage is too large, these thickeners are prone to precipitation or separation, affecting the overall performance of concrete; while if the dosage is insufficient, it is difficult to achieve the ideal water retention effect. In addition, some liquid thickening and water retaining agents are unable to meet the dual requirements of high-performance concrete for workability and water retention performance, and are difficult to meet high-standard requirements such as slurry lifting and water locking. Summary of the Invention

[0004] The first object of the present invention is to provide a concrete thickening and water retaining agent with excellent water retention performance over time and workability.

[0005] The second object of the present invention is to provide a preparation method of the above-mentioned concrete thickening and water retaining agent.

[0006] The third object of the present invention is to provide an application of the above-mentioned concrete thickening and water retaining agent in the construction field.

[0007] The concrete thickening and water retaining agent provided by the present invention is prepared by subjecting alkyl acrylamide, hydroxy unsaturated amide, hydroxy / amino benzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid, and a crosslinking agent to a free radical polymerization reaction; the structures of the alkyl acrylamide, hydroxy unsaturated amide, hydroxy / amino benzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid, and crosslinking agent are respectively shown in formulas (1) to (6);

[0008]

[0009] In formula (1), R1 is H or an alkyl group with 1 to 5 carbon atoms;

[0010] In formula (2), R2 is H or an alkyl group of C1-C5; R3 is -C-, -(CH2)x-C- or -(CH2)xPh-, where x is an integer from 1 to 3; R4, R5 and R6 are each independently H, an alkyl group of C1-C5, OH, -(CH2)y-OH or COOH, and at least one of R4, R5 and R6 is OH or -(CH2)y-OH, where y is an integer from 1 to 3;

[0011] In formula (3), R7 is an alkylene group of C1-C3; R8, R9 and R 10 are each independently H, OH, a halogen or NH2 and at least one of R8, R9 and R 10 is OH or NH2;

[0012] In formula (4), R 11 is H or an alkyl group of C1-C5; R 12 is an alkylene group of C1-C3, -CO-NH-C(CH3)2-(CH)n-, where n is an integer from 0 to 5; A is H, K or Na;

[0013] In formula (5), R 13 and R 15 are each independently H or an alkyl group of C1-C5; R 14 and R 16 are each independently H, an alkyl group of C1-C5 or -R 17 -COOH and at least one of R 14 and R 16 is -R 17 -COOH, R 17 is a single bond or an alkylene group of C1-C5; when both R 14 and R 16 are -R 17 -COOH, R 14 and R 16 can form a ring by bonding;

[0014] In formula (6), R 17 and R 18 are each independently H or an alkyl group of C1-C5; m is an integer from 1 to 3.

[0015] The preparation method of the concrete thickening and water retaining agent provided by the present invention includes the following steps:

[0016] S1. Mix acrylamide, hydroxy unsaturated amide, hydroxy / amino benzoic acid unsaturated ester, unsaturated sulfonate and a part of unsaturated acid evenly, adjust the pH value of the obtained mixture to 7-8 to obtain a bottom liquid; prepare a solution A from the remaining unsaturated acid, crosslinking agent and water; prepare a solution B from a reducing agent, a chain transfer agent and water; prepare a solution C from an oxidizing agent and water;

[0017] S2. Control the temperature of the base liquid at 50°C to 60°C, dropwise add Solution A, Solution B, and Solution C into the base liquid, and after the addition is completed, keep it at a constant temperature for aging for 1 h to 5 h to obtain an aqueous solution of a concrete thickening and water-retaining agent.

[0018] The key of the present invention lies in carrying out a free radical polymerization reaction on an alkyl acrylamide, a hydroxy unsaturated amide, a hydroxy / amino benzoic acid unsaturated ester, an unsaturated sulfonate, an unsaturated acid, and a crosslinking agent having specific structures. Thus, the obtained concrete thickening and water-retaining agent has very excellent water-retaining performance over time and workability, and can still maintain a relatively low segregation height and segregation width after 3 h. Presumably, the reasons may be as follows: The hydroxy unsaturated amide having the structure shown in Formula (2) and the hydroxy / amino benzoic acid unsaturated ester having the structure shown in Formula (3) not only have extremely strong hydrophilic ability and can bind to water molecules through hydrogen bonds, but also can more effectively adsorb and lock water compared with conventional concrete thickening and water-retaining agents. This effect can significantly improve the consistency of the slurry and the wrapping property of the aggregate, and while locking water and retaining water, significantly improve the workability of the concrete; introducing the hydroxy / amino benzoic acid unsaturated ester having the structure shown in Formula (3) and the crosslinking agent shown in Formula (6) to participate in the copolymerization can construct a micro-crosslinked structure of the thickening and water-retaining agent, and introduce a rigid ring into the micro-crosslinked structure, thereby enhancing the stability and stretchability of the polymer water-locking network, enhancing the water-locking and water-retaining effects, reducing the sliding between molecules, improving the retention ability of the water-retaining network, and improving the workability over time; furthermore, the micro-crosslinked structure constructed by the free radical reaction of the alkyl acrylamide, hydroxy unsaturated amide, hydroxy / amino benzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid, and crosslinking agent having specific structures can dynamically unlock the crosslinked network in the concrete, release free water, and compensate for the internal water loss of the concrete caused by the water and the hydration reaction. At the same time, the hydrolyzed ethylene glycol ether, hydroxy / amino benzoic acid, hydroxy / amino and other groups can further act on the free water to improve the slurry consistency. This design can improve the water-retaining performance over time of the concrete while ensuring good workability, excellent stability and compatibility of the concrete, and the excellent stability and compatibility can ensure the uniform distribution of the thickening and water-retaining agent in the concrete, and will not cause precipitation or precipitation due to incompatibility with other admixtures to affect the overall performance of the mixed concrete, and at the same time helps to improve the durability and long-term stability of the concrete. Detailed implementation mode

[0019] The preparation method of the concrete thickening and water retaining agent provided by the present invention comprises carrying out free radical polymerization reaction on alkyl acrylamide, hydroxy unsaturated amide, hydroxy / aminobenzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid and crosslinking agent. The mass ratio of the alkyl acrylamide, hydroxy unsaturated amide, hydroxy / aminobenzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid to the crosslinking agent is (10-20):(5-10):(2-5):(4-8):(3-6):(1-3). Specifically, the content of the alkyl acrylamide is preferably 10-20 parts by weight, such as 10, 12, 14, 16, 18, 20 parts by weight or any value therebetween; the content of the hydroxy unsaturated amide is preferably 5-10 parts by weight, such as 5, 6, 7, 8, 9, 10 parts by weight or any value therebetween; the content of the hydroxy / aminobenzoic acid unsaturated ester is preferably 2-5 parts by weight, such as 2, 2.5, 3, 3.5, 4, 4.5, 5 parts by weight or any value therebetween; the content of the unsaturated sulfonate is preferably 4-8 parts by weight, such as 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8 parts by weight or any value therebetween; the content of the unsaturated acid is preferably 3-6 parts by weight, such as 3, 3.5, 4, 4.5, 5, 5.5, 6 parts by weight or any value therebetween; the content of the crosslinking agent is preferably 1-3 parts by weight, such as 1, 1.5, 2, 2.5, 3 parts by weight or any value therebetween.

[0020] In the present invention, the structure of the alkyl acrylamide is shown as formula (1);

[0021]

[0022] In formula (1), R1 is H or an alkyl group of C1-C5. Specific examples of the alkyl group of C1-C5 include but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or neopentyl. Preferably, R1 is H or an alkyl group of C1-C3, such as H, methyl, ethyl, n-propyl or isopropyl. From the perspective of raw material availability, the alkyl acrylamide is preferably acrylamide and / or methacrylamide.

[0023] In the present invention, the structure of the hydroxy unsaturated amide is shown as formula (2);

[0024]

[0025] In formula (2), R2 is H or an alkyl group having 1 to 5 carbon atoms; R3 is -C-, -(CH2)x-C- or -(CH2)xPh-, where x is an integer from 1 to 3; R4, R5 and R6 are each independently H, an alkyl group having 1 to 5 carbon atoms, OH, -(CH2)y-OH or COOH, and at least one of R4, R5 and R6 is OH or -(CH2)y-OH, where y is an integer from 1 to 3. Specific examples of the alkyl group having 1 to 5 carbon atoms include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or neopentyl. x and y can each independently be 1, 2 or 3. The hydroxy unsaturated amide is preferably at least one selected from N-(hydroxymethyl)acrylamide, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-propenamide, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylpropenamide, N-(4-hydroxyphenyl)methacrylamide, N-hydroxyethylacrylamide, N-trimethylolmethylacrylamide, N-(2-hydroxypropyl)methacrylamide, N-(2-hydroxyethyl)-2-methyl-2-propenamide and 2-acrylamido glycolic acid monohydrate, and more preferably at least one selected from N-[2-(3,4-dihydroxyphenyl)ethyl]-2-propenamide, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylpropenamide and N-trimethylolmethylacrylamide. The inventors of the present invention have found that when the hydroxy unsaturated amide is preferably at least one of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-propenamide, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylpropenamide and N-trimethylolmethylacrylamide, the water retention effect of the resulting thickening water retaining agent over time is better.

[0026] In the present invention, the structure of the hydroxy / aminobenzoic acid unsaturated ester is shown in formula (3);

[0027]

[0028] In formula (3), R7 is an alkylene group having 1 to 3 carbon atoms; R8, R9 and R 10 are each independently H, OH, halogen or NH2 and at least one of R8, R9 and R 10 is OH or NH2. Specific examples of the alkylene group having 1 to 3 carbon atoms include, but are not limited to: methylene, ethylene, n-propylene or isopropyl. The halogen can be fluorine, bromine or chlorine, preferably fluorine. The hydroxy / aminobenzoic acid unsaturated ester can be exemplified by at least one of allyl hydroxybenzoate, allyl 4-aminobenzoate, allyl o-aminobenzoate and 4-amino-3-fluorobenzyl benzoate.

[0029] In the present invention, the structure of the unsaturated sulfonate is shown in formula (4);

[0030]

[0031] In formula (4), R 11 is H or an alkyl group having 1 to 5 carbon atoms; R 12 is an alkylene group having 1 to 3 carbon atoms, -CO-NH-C(CH3)2-(CH)n-, where n is an integer from 0 to 5; A is H, K or Na. Specific examples of the alkyl group having 1 to 5 carbon atoms include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or neopentyl. Specific examples of the alkylene group having 1 to 3 carbon atoms include, but are not limited to: methylene, ethylene, n-propylene or isopropylene. n is 0, 1, 2, 3, 4 or 5. Preferably, R 11 is H or methyl; R 12 is an alkylene group having 1 to 3 carbon atoms, -CO-NH-C(CH3)2-(CH)n-, where n is an integer from 0 to 3; A is H or Na. From the perspective of raw material availability, the unsaturated sulfonate is particularly preferably 2-acrylamido-2-methylpropanesulfonic acid and / or sodium methallylsulfonate.

[0032] In the present invention, the structures of the unsaturated acids are respectively shown in formula (5);

[0033]

[0034] In formula (5), R 13 and R 15 are each independently H or an alkyl group having 1 to 5 carbon atoms; R 14 and R 16 are each independently H, an alkyl group having 1 to 5 carbon atoms or -R 17 -COOH and at least one of R 14 and R 16 is -R 17 -COOH, R 17 is a single bond or an alkylene group having 1 to 5 carbon atoms; when R 14 and R 16 are both -R 17 -COOH, R 14 and R 16It can form a ring by bonding. Specific examples of the C1-C5 alkyl group include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or neopentyl. Specific examples of the C1-C5 alkylene group include, but are not limited to: methylene, ethylene, n-propylene, isopropylene, n-butylene, sec-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene or neopentylene. From the perspective of raw material availability, the unsaturated acid is particularly preferably at least one selected from acrylic acid, methacrylic acid, maleic anhydride and itaconic acid.

[0035] In the present invention, the crosslinking agent has the structure shown in formula (6):

[0036]

[0037] In formula (6), R 17 and R 18 are each independently H or a C1-C5 alkyl group; m is an integer from 1 to 3. Specific examples of the C1-C5 alkyl group include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or neopentyl. m can specifically be 1, 2 or 3. The crosslinking agent can be exemplified by at least one of triethylene glycol dimethacrylate, diethylene glycol dimethacrylate and tetraethylene glycol dimethacrylate.

[0038] In the present invention, the radical polymerization reaction generally needs to be carried out in the presence of a radical initiator and a chain transfer agent. Among them, the radical initiator can be selected from at least one of azo initiators, peroxide initiators, and redox initiators. Among them, specific examples of the azo initiator include, but are not limited to: at least one of dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylpropionamidine) hydrochloride, azodicarbonamide, 2,2'-azobis(2-isopropylimidazoline) hydrochloride, 2-cyano-2-propylazoformamide, 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-isopropylimidazoline), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylvaleronitrile), and 2,2'-azobis(2,4-dimethylvaleronitrile). Specific examples of the peroxide initiator include, but are not limited to: at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, benzoyl peroxide, and tert-butyl peroxybenzoate. The redox initiator includes an oxidizing agent and a reducing agent. Among them, examples of the oxidizing agent include at least one of potassium persulfate, sodium persulfate, and ammonium persulfate. Examples of the reducing agent include at least one of ascorbic acid, sodium hypophosphite, sodium formaldehyde sulfoxylate, and sodium bisulfite. Specific examples of the chain transfer agent include, but are not limited to: at least one of mercaptoethanol, mercaptopropionic acid, and mercaptoacetic acid. In addition, the amounts of the oxidizing agent, reducing agent, and chain transfer agent are preferably each independently 0.5 to 5 wt% of the total mass of alkyl acrylamide, hydroxy unsaturated amide, hydroxy / amino benzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid, and crosslinking agent, such as 0.5 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt% or any value therebetween.

[0039] In the present invention, the conditions for the radical polymerization reaction preferably include a temperature of 50 °C to 60 °C, such as 50 °C, 52 °C, 55 °C, 58 °C, 60 °C or any value therebetween; and a time of 1 h to 5 h, such as 1 h, 2 h, 3 h, 4 h, 5 h or any value therebetween.

[0040] In the present invention, the concrete thickening and water retention agent is preferably used in the form of an aqueous solution of the concrete thickening and water retention agent with a concentration of 10 to 30 wt% (such as 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, 28 wt%, 30 wt%, etc.).

[0041] The preparation method of the concrete thickening and water retention agent provided by the present invention includes carrying out a radical polymerization reaction on alkyl acrylamide, hydroxy unsaturated amide, hydroxy / amino benzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid, and crosslinking agent.

[0042] In a preferred embodiment, the method of the radical polymerization reaction includes the following steps:

[0043] S1. Mix alkylacrylamide, hydroxy unsaturated amide, hydroxy / amino benzoic acid unsaturated ester, unsaturated sulfonate and a part of unsaturated acid evenly, and adjust the pH value of the obtained mixture to 7 - 8 to obtain a bottom liquid; prepare solution A by dissolving the remaining unsaturated acid, crosslinking agent and water; prepare solution B by dissolving the reducing agent, chain transfer agent and water; prepare solution C by dissolving the oxidizing agent and water;

[0044] S2. Control the temperature of the bottom liquid at 50°C - 60°C, and dropwise add solution A, solution B and solution C into the bottom liquid. After the dropping is completed, carry out constant temperature curing for 1h - 5h to obtain an aqueous solution of a concrete thickening and water retaining agent.

[0045] In addition, the present invention also provides the application of the above-mentioned concrete thickening and water retaining agent in the construction field.

[0046] The present invention will be described in detail below through examples.

[0047] In the following examples and comparative examples, the dosages of each raw material are in parts by weight.

[0048] Examples 1 - 6

[0049] S1. Mix alkylacrylamide, hydroxy unsaturated amide, hydroxy / amino benzoic acid unsaturated ester, unsaturated sulfonate and 30% of unsaturated acid evenly, and then adjust the pH value of the obtained mixture to 7.5 with an aqueous sodium hydroxide solution; dissolve the remaining 70% of unsaturated acid monomer and crosslinking agent in water to prepare solution A; dissolve the reducing agent and chain transfer agent in water to prepare solution B; dissolve the oxidizing agent in water to prepare solution D;

[0050] S2. Control the temperature of the bottom liquid at 50°C - 60°C, and dropwise add solution A, solution B and solution C into the bottom liquid. Control the dropping time at 2h. After the dropping is completed, carry out constant temperature curing for 1h - 5h to obtain a concrete thickening and water retaining agent solution with a mass concentration of 20wt%.

[0051] The types and dosages of each raw material and the reaction conditions are shown in Table 1.

[0052] Comparative Example 1

[0053] Prepare a concrete thickening and water retaining agent according to the method of Example 1, except that the crosslinking agent is not added and the other conditions are the same as those in Example 1 to obtain a reference concrete thickening and water retaining agent solution.

[0054] Comparative Example 2

[0055] Prepare a concrete thickening and water retaining agent according to the method of Example 1, except that the hydroxy unsaturated amide is not added and the other conditions are the same as those in Example 1 to obtain a reference concrete thickening and water retaining agent solution.

[0056] Comparative Example 3

[0057] The concrete thickening and water retaining agent was prepared according to the method of Example 1, except that the hydroxy / aminobenzoic acid unsaturated ester was not added, and the other conditions were the same as those in Example 1, obtaining a reference concrete thickening and water retaining agent solution.

[0058] Comparative Example 4

[0059] The concrete thickening and water retaining agent was prepared according to the method of Comparative Example 2, except that the hydroxy / aminobenzoic acid unsaturated ester was not added, and the other conditions were the same as those in Comparative Example 2, obtaining a reference concrete thickening and water retaining agent solution.

[0060] Test Example

[0061] To effectively verify the effect of the thickening and water retaining agent, based on the representative C30 mix ratio, the amount of cementitious materials was reduced by 30 kg, and the sand ratio was reduced by 2 - 4% for testing and verification, so that the initial slump flow of the concrete was 500 mm - 600 mm, and there should be obvious exposed stones or stone accumulation in the initial state of the concrete, and obvious bleeding or bleeding slurry after initial or static for a period of time. The concrete mix ratio is as follows: cement 330 kg / m 3 、sand 780 kg / m 3 、stone 1 (5 mm - 10 mm) 200 kg / m 3 、stone 2 (10 mm - 20 mm) 820 kg / m 3 、water 175 kg / m 3 。The admixture used is a standard polycarboxylate water reducer, and the thickening and water retaining agent is compounded into the admixture for use. The dosage is the amount in 1 t of the admixture, expressed in kg / t. The test results of the concrete are shown in Table 2, and the admixture dosage is 2.0%. Among them, the segregation height represents the stacking height of the stones, reflecting the improvement effect of the thickening and water retaining agent on the workability. The higher the segregation height, the smaller the improvement; the segregation width is the bleeding width, and the smaller the bleeding width, the better the water retaining effect.

[0062]

[0063]

[0064] As can be seen from Table 2, the thickening and water retention agents obtained in Examples 1-6 can significantly improve the slurry of concrete, improve the workability of concrete and have excellent thickening and water retention effects. Among them, Examples 1, 4 and 6 introducing N-trimethylolmethylacrylamide, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide and N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide have better water retention performance over time. In Comparative Example 1, no crosslinking agent was added, resulting in poor thickening and water retention effects and poor workability of the concrete. In Comparative Example 2, no hydroxy unsaturated amide was added, and the water retention effect was worse than that of Example 1. In Comparative Example 3, no hydroxy / aminobenzoic acid unsaturated ester C was added, and the water retention effect was also slightly worse than that of Example 1. In Comparative Example 4, neither hydroxy unsaturated amide nor hydroxy / aminobenzoic acid unsaturated ester was added, and the thickening and water retention effects were significantly reduced. Therefore, based on the copolymerization of alkyl acrylamide, unsaturated sulfonate and unsaturated acid, the micro-crosslinked thickening and water retention agent constructed by introducing hydroxy unsaturated amide and hydroxy / aminobenzoic acid unsaturated ester copolymerization of the present invention has excellent water retention effect over time and also greatly improves the workability of concrete over time.

[0065] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A concrete thickening and water-retaining agent, characterized in that: The concrete thickening and water-retaining agent is prepared by free radical polymerization of alkyl acrylamide, hydroxy unsaturated amide, hydroxy / amino benzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid and crosslinking agent; the structures of the alkyl acrylamide, hydroxy unsaturated amide, hydroxy / amino benzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid and crosslinking agent are respectively shown in formula (1) to formula (6); In formula (1), R1 is H or a C1-C5 alkyl group; In formula (2), R2 is H or a C1-C5 alkyl group; R3 is -C-, -(CH2)xC- or -(CH2)xPh-, and x is an integer from 1 to 3; R4, R5 and R6 are each independently H, a C1-C5 alkyl group, OH, -(CH2)y-OH or COOH, and at least one of R4, R5 and R6 is OH or -(CH2)y-OH, and y is an integer from 1 to 3; In formula (3), R7 is a C1-C3 alkylene group; R8, R9 and R 10 are each independently H, OH, halogen or NH2 and R8, R9 and R 10 At least one of them is OH or NH2; In formula (4), R 11 is H or a C1-C5 alkyl group; R 12 is a C1-C3 alkylene group, -CO-NH-C(CH3)2-(CH)n-, n is an integer from 0 to 5; A is H, K or Na; In formula (5), R 13 and R 15 Each independently represents H or a C1-C5 alkyl group; R 14 and R 16 Each independently represents H, C1-C5 alkyl or -R 17 -COOH and R 14 and R 16 At least one of them is -R 17 -COOH, R 17 is a single bond or a C1-C5 alkylene group; when R 14 and R 16 All are -R 17 -COOH, R 14 and R 16 Able to bond into rings; In formula (6), R 17 and R 18 Each is independently H or a C1-C5 alkyl group; m is an integer of 1 to 3.

2. The concrete thickening and water-retaining agent according to claim 1, characterized in that: The mass ratio of the alkyl acrylamide, hydroxy unsaturated amide, hydroxy / aminobenzoic acid unsaturated ester, unsaturated sulfonate, unsaturated acid and crosslinking agent is (10-20):(5-10):(2-5):(4-8):(3-6):(1-3).

3. The concrete thickening and water-retaining agent according to claim 1, characterized in that: The hydroxy unsaturated amide is selected from at least one of N-(hydroxymethyl)acrylamide, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide, N-(4-hydroxyphenyl)methylacrylamide, N-hydroxyethylacrylamide, N-trihydroxymethylmethylacrylamide, N-(2-hydroxypropyl)methylacrylamide, N-(2-hydroxyethyl)-2-methyl-2-acrylamide and 2-acrylamidoglycolic acid monohydrate.

4. The concrete thickening and water-retaining agent according to claim 1, characterized in that: The hydroxy / aminobenzoic acid unsaturated ester is selected from at least one of allyl hydroxybenzoate, allyl 4-aminobenzoate, allyl o-aminobenzoate and 4-amino-3-fluoroallyl benzoate.

5. The concrete thickening and water-retaining agent according to claim 1, characterized in that: The unsaturated sulfonate is 2-acrylamide-2-methylpropanesulfonic acid and / or sodium methyl propenesulfonate.

6. The concrete thickening and water-retaining agent according to claim 1, characterized in that: The unsaturated acid is selected from at least one of acrylic acid, methacrylic acid, maleic anhydride and itaconic acid.

7. The concrete thickening and water-retaining agent according to claim 1, characterized in that: The crosslinking agent is selected from at least one of triethylene glycol dimethacrylate, diethylene glycol dimethacrylate and tetraethylene glycol dimethacrylate.

8. The concrete thickening and water-retaining agent according to claim 1, characterized in that: The free radical polymerization reaction is carried out in the presence of a free radical initiator and a chain transfer agent; Preferably, the free radical initiator is a redox initiator; the oxidant in the redox initiator is selected from at least one of potassium persulfate, sodium persulfate and ammonium persulfate; the reducing agent in the redox initiator is selected from at least one of ascorbic acid, sodium hypophosphite, sodium formaldehyde sulfoxylate and sodium bisulfite; Preferably, the chain transfer agent is selected from at least one of mercaptoethanol, mercaptopropionic acid and thioglycolic acid; Preferably, the conditions of the free radical polymerization reaction include a temperature of 50° C. to 60° C. and a time of 1 h to 5 h.

9. The method for preparing the concrete thickening and water-retaining agent according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: S1. uniformly mix alkyl acrylamide, hydroxy unsaturated amide, hydroxy / aminobenzoic acid unsaturated ester, unsaturated sulfonate and a portion of unsaturated acid, and adjust the pH value of the obtained mixture to 7-8 to obtain a base solution; prepare the remaining unsaturated acid, crosslinking agent and water into solution A; prepare the reducing agent, chain transfer agent and water into solution B; prepare the oxidant and water into solution C; S2. The temperature of the base liquid is controlled at 50°C to 60°C, and solution A, solution B and solution C are added dropwise to the base liquid. After the addition is completed, the solution is aged at a constant temperature for 1h to 5h to obtain an aqueous solution of a concrete thickening and water-retaining agent.

10. Use of the concrete thickening and water-retaining agent according to any one of claims 1 to 8 in the field of construction.

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