A concrete thickening water-retaining agent, a preparation method and application thereof

Abstract

The application belongs to the field of admixtures, and particularly relates to a concrete thickening water-retaining agent and a preparation method and application thereof. The concrete thickening water-retaining agent is obtained by free radical polymerization reaction of an unsaturated acid monomer I, an unsaturated amide monomer, an unsaturated sulfonate monomer and a functional monomer; and the functional monomer is an esterification reaction product of rhamnolipid and an unsaturated acid monomer II. The key of the application is to introduce the esterification reaction product of rhamnolipid and the unsaturated acid monomer II as a copolymerization monomer into a copolymerization reaction system of the unsaturated acid monomer I, the unsaturated amide monomer and the unsaturated sulfonate monomer, so that the molecular structure of the concrete thickening water-retaining agent can be changed, the obtained concrete thickening water-retaining agent not only has excellent thickening and water-retaining properties, but also can improve the stability thereof in concrete.

Description

Technical Field

[0001] This invention belongs to the field of admixtures, specifically relating to a concrete thickening and water-retaining agent, its preparation method, and its application. Background Technology

[0002] Concrete, as an important building material, plays a crucial role in the construction of infrastructure such as buildings, roads, and bridges. However, traditional concrete materials often suffer from problems such as poor fluidity, high bleeding, and easy segregation during preparation and application. These problems seriously affect the workability and quality of concrete projects. Therefore, developing a thickening and water-retaining agent that can effectively improve concrete performance and enhance its workability and durability is of paramount importance.

[0003] Thickening and water-retaining agents are chemical additives that increase the consistency of concrete mixtures while reducing moisture loss. They form a stable network structure within the concrete, effectively preventing moisture migration and evaporation, thus improving the concrete's water retention performance. Furthermore, thickening and water-retaining agents significantly improve the fluidity of concrete, making it easier to construct and vibrate, reducing construction work.

[0004] Currently, there are various concrete thickeners and water-retaining agents on the market, but it is often difficult to balance thickening and water-retaining performance with stability. For example, some thickeners and water-retaining agents can improve the water retention of concrete, but they have poor storage stability and are prone to separation or gelation after a period of time; while other thickeners and water-retaining agents can ensure long-term storage, but they can have a serious negative impact on the fluidity of concrete. Summary of the Invention

[0005] The primary objective of this invention is to overcome the shortcomings of existing concrete thickening and water-retaining agents, which are unable to simultaneously achieve both thickening and water-retaining properties and stability, and to provide a concrete thickening and water-retaining agent that possesses both excellent thickening and water-retaining properties and good stability.

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned concrete thickening and water-retaining agent.

[0007] A third objective of this invention is to provide the application of the above-mentioned concrete thickening and water-retaining agent in the construction field.

[0008] The concrete thickening and water-retaining agent provided by the present invention is obtained by free radical polymerization of unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer; the functional monomer is the esterification product of rhamnolipid and unsaturated acid monomer II.

[0009] The method for preparing the concrete thickening and water-retaining agent provided by the present invention includes a free radical polymerization reaction of unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer.

[0010] The key to this invention lies in introducing the esterification product of rhamnolipid and unsaturated acid monomer II as a comonomer into the copolymerization reaction system of unsaturated acid monomer I, unsaturated amide monomer, and unsaturated sulfonate monomer. This can change the molecular structure of the concrete thickener and water-retaining agent, so that the resulting concrete thickener and water-retaining agent not only has excellent thickening and water-retaining properties, but also improves its stability in concrete. Detailed Implementation

[0011] The concrete thickening and water-retaining agent provided by this invention is obtained by free radical polymerization of unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer, and functional monomer. The preferred mass ratio of the unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer, and functional monomer is 6:(10-20):(5-10):(0.5-2). Specifically, the preferred mass ratio of the unsaturated acid monomer I to the unsaturated amide monomer is 6:(10-20), such as 6:10, 6:12, 6:14, 6:16, 6:18, 6:20, or any value between them. The preferred mass ratio of the unsaturated acid monomer I to the unsaturated sulfonate monomer is 6:(5-10), such as 6:5, 6:6, 6:8, 6:10, or any value between them. The preferred mass ratio of the unsaturated acid monomer I to the functional monomer is 6:(0.5-2), such as 6:0.5, 6:0.8, 6:1, 6:1.2, 6:1.4, 6:1.6, 6:1.8, 6:2 or any value between them.

[0012] In this invention, the unsaturated acid monomer I and the unsaturated acid monomer II preferably each independently have the structure shown in formula (1):

[0013]

[0014] In equation (1), R 11 and R 12 Each is independently H, C1-C5 alkyl or -R 13 -COOH and R 11 and R 12 At least one of them is -R 13 -COOH, R 13 It is a single bond or a C1-C5 alkylene group; when R 11 and R 12 All are -R 13 When -COOH, R 11 and R 12 Capable of forming rings; R11 `and R 12 Each alkyl group is independently H or C1-C5 alkyl. Specific examples of C1-C5 alkyl groups 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 C1-C5 alkylene groups 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. When R 21 and R 22 All are -R 23 When -COOH, R 21 and R 22 They can bond to form a ring, thus forming an acid anhydride. For the sake of raw material availability, the unsaturated carboxylic acid I and the unsaturated acid monomer II are preferably each independently selected from at least one of acrylic acid, methacrylic acid, itaconic acid, and maleic anhydride. The terms "I" and "II" are merely for distinguishing unsaturated carboxylic acids introduced at different positions for ease of description and have no other special meaning.

[0015] In this invention, the unsaturated amide monomer preferably has the structure shown in formula (2):

[0016]

[0017] In equation (2), R 21 It is an H or C1-C5 alkyl group, R 22 The alkyl group is H or C1-C5. Specific examples of C1-C5 alkyl groups 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 C1-C5 hydroxyalkyl groups include, but are not limited to: hydroxymethyl, hydroxyethyl, hydroxyn-propyl, hydroxyisopropyl, hydroxyn-butyl, hydroxyisobutyl, hydroxytert-butyl, hydroxyn-pentyl, hydroxyisopentyl, hydroxytert-pentyl, or hydroxyneopentyl. For the sake of raw material availability, the unsaturated amide monomer is preferably selected from acrylamide, methacrylamide, and N-[2-(2-hydroxyethoxy)ethyl]acrylamide.

[0018] In this invention, the unsaturated sulfonate monomer preferably has the structure shown in formula (3):

[0019]

[0020] In equation (3), R 31 It is an H or C1-C5 alkyl group; R 32The alkyl group is a C1-C5 alkylene group, -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 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-C3 alkylene group include, but are not limited to: methylene, ethylene, n-propylene, or isopropylene. For the sake of raw material availability, the unsaturated sulfonate monomer is particularly preferably 2-acrylamido-2-methylpropanesulfonic acid and / or sodium methpropylene sulfonate.

[0021] In this invention, the functional monomer is the esterification product of rhamnolipid and unsaturated acid monomer II. The molar ratio of rhamnolipid to unsaturated acid monomer II is preferably 1:(1-2), such as 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, or any value between them. The esterification reaction conditions preferably include a temperature of 70℃-90℃, such as 70℃, 72℃, 75℃, 78℃, 80℃, 82℃, 85℃, 88℃, 90℃, or any value between them; and a time of 3h-8h, such as 3h, 4h, 5h, 6h, 7h, 8h, or any value between them. The esterification reaction is carried out in the presence of a catalyst and a polymerization inhibitor. The catalyst may include at least one of benzenesulfonic acid, p-toluenesulfonic acid, and ethylsulfonic acid. The polymerization inhibitor may include at least one of hydroquinone, phenothiazine, and diphenylamine. The amount of catalyst used is preferably 0.5% to 5% of the total mass of rhamnolipid and unsaturated acid monomer II, such as 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value between them. The amount of polymerization inhibitor used is preferably 0.3% to 3% of the total mass of rhamnolipid and unsaturated acid monomer II, such as 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, or any value between them. Furthermore, the esterification reaction is carried out under an inert gas atmosphere. The inert gas can be, for example, nitrogen, helium, or argon.

[0022] In this invention, the rhamnolipid can be any existing compound containing a rhamnosine ring and saturated or unsaturated fatty acids of different carbon chain lengths, preferably selected from at least one of disaccharide diester rhamnolipid, disaccharide monoester rhamnolipid, monoester rhamnolipid, and monoester monoester rhamnolipid. Preferably, the disaccharide diester rhamnolipid has the structure shown in formula (4-1), the disaccharide monoester rhamnolipid preferably has the structure shown in formula (4-2), the monoester diester rhamnolipid preferably has the structure shown in formula (4-3), and the monoester monoester rhamnolipid preferably has the structure shown in formula (4-4).

[0023]

[0024] In equations (1) to (4), R 41 R 41 `、R 42 R 43 R 43 `and R 44 Each independently is C1-C 10 Alkyl group. C1-C 10 The alkyl group can be, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, etc. In a preferred embodiment, the rhamnolipid is a disaccharide-diester rhamnolipid having the structure shown in formula (4-1) and / or a disaccharide-monoliposide rhamnolipid having the structure shown in formula (4-2), wherein R1, R1', and R2 are each independently C1-C1. 10 The alkyl group can at this point give the concrete thickening and water-retaining agent higher water retention and stability.

[0025] In this invention, the free radical polymerization reaction is typically carried out in the presence of a free radical initiator and a regulator. The free radical initiator may be selected from at least one of azo initiators, peroxide initiators, and redox initiators, preferably a redox initiator. The oxidant in the redox initiator is preferably selected from at least one of potassium persulfate, sodium persulfate, and ammonium persulfate. The reductant in the redox initiator is preferably selected from at least one of sodium bisulfite, potassium bisulfite, and ascorbic acid. The mass ratio of the oxidant to unsaturated acid monomer I is preferably 6:(0.5–2), such as 6:0.5, 6:0.8, 6:1, 6:1.2, 6:1.4, 6:1.6, 6:1.8, 6:2, or any value between them. The mass ratio of the reductant to unsaturated acid monomer I is preferably 6:(0.2–1), such as 6:0.2, 6:0.5, 6:0.8, 6:1, or any value between them. The modifier may include at least one of triethanolamine, diethanolamine, diisopropanolamine, triisopropanolamine, tetraethanolamine, and tetraisopropanolamine. Furthermore, the mass ratio of the modifier to unsaturated acid monomer I is preferably 6:(0.2–2), such as 6:0.2, 6:0.5, 6:0.8, 6:1, 6:1.2, 6:1.4, 6:1.6, 6:1.8, 6:2, or any value between them. In a preferred embodiment, the raw materials for preparing the thickening and water-retaining agent contain 6 parts by weight of unsaturated acid monomer, 10–20 parts by weight of unsaturated amide monomer, 5–10 parts by weight of unsaturated sulfonate monomer, 0.5–2 parts by weight of functional monomer, 0.5–2 parts by weight of oxidant, 0.2–1 part by weight of reducing agent, and 0.2–2 parts by weight of modifier.

[0026] In this invention, the thickening and water-retaining agent is preferably used in the form of an aqueous solution, and the concentration of the aqueous solution of the thickening and water-retaining agent is preferably 10-20 wt%, such as 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, or any value between them.

[0027] The method for preparing the concrete thickening and water-retaining agent provided by the present invention includes a free radical polymerization reaction of unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer.

[0028] In a preferred embodiment, the method of the free radical polymerization reaction includes:

[0029] S1. Prepare a base by mixing unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer with water; prepare solution A by mixing reducing agent with water; prepare solution B by mixing oxidizing agent with water; prepare solution C by mixing regulator with water;

[0030] S2. Add solutions A, B and C to the base material. The initial reaction temperature is controlled at 20℃~50℃, the dripping time is controlled at 1h~2h, and the reaction is kept at the temperature for 1h~3h after the dripping is completed to obtain the concrete thickening and water-retaining agent.

[0031] Furthermore, the present invention also provides the application of the concrete thickening and water-retaining agent in the construction field.

[0032] The present invention will be described in detail below through embodiments.

[0033] In the following examples and comparative examples, the parts of each raw material refer to parts by weight.

[0034] Preparation Example 1

[0035] 50g of disaccharide-diester rhamnolipid (having the structure shown in formula (4-1), wherein R...) 41 and R 41 5.5 g of acrylic acid and 1.0 g of hydroquinone were added to a reaction vessel and mixed. Under nitrogen protection, the temperature was adjusted to 70 °C, and then 0.8 g of benzenesulfonic acid was added and the reaction was carried out for 8 h to obtain the functional monomer, which was denoted as GD-1.

[0036] Preparation Example 2

[0037] 45g of disaccharide monolipide rhamnolipide (having the structure shown in formula (4-2), wherein R...) was used. 42 8.1 g of methacrylic acid and 0.9 g of diphenylamine were added to a reaction vessel and mixed. Under nitrogen protection, the temperature was adjusted to 85 °C, and then 0.77 g of ethyl sulfonic acid was added and the reaction was maintained at this temperature for 6 h to obtain the functional monomer, denoted as GD-2.

[0038] Preparation Example 3

[0039] 25g of monosaccharide monolipide (having the structure shown in formula (4-3), wherein R...) was used. 43 and R 43 All of them are -(CH2)6CH3), 7.3g of acrylic acid and 0.7g of hydroquinone are added to a reaction vessel and mixed. Under nitrogen protection, the temperature is adjusted to 90℃, and then 0.6g of p-toluenesulfonic acid is added and the reaction is maintained at the temperature for 4h to obtain the functional monomer, which is denoted as GD-3.

[0040] Preparation Example 4

[0041] 40g of monosaccharide dilipase rhamnolipid (having the structure shown in formula (4-4), wherein R 447.4 g of methacrylic acid and 0.95 g of phenothiazine were added to a reaction vessel and mixed. Under nitrogen protection, the temperature was adjusted to 80 °C, and then 0.8 g of p-toluenesulfonic acid was added and the reaction was maintained at this temperature for 6 h to obtain the functional monomer, denoted as GD-4.

[0042] Example 1

[0043] S1. Mix 6 parts acrylic acid, 15 parts acrylamide, 6 parts 2-acrylamide-2-methylpropanesulfonic acid, 0.5 parts functional monomer (GD-1), and 100 parts water to form a base material; mix 0.4 parts ascorbic acid and 25 parts water to form solution A; mix 1 part ammonium persulfate and 25 parts water to form solution B; mix 0.5 parts diethanol monoisopropanolamine, 0.5 parts triisopropanolamine, and 20 parts water to form solution C;

[0044] S2. Control the temperature of the base material at 30℃, add solution A, solution B and solution C dropwise to the base material, the dropwise addition time of solution A, solution B and solution C is 1h, after the dropwise addition is completed, keep it at a constant temperature for 1h, add water to adjust to obtain a thickening and water-retaining agent with a mass concentration of 15wt%.

[0045] Example 2

[0046] S1. Mix 6 parts methacrylic acid, 10 parts methacrylamide, 8 parts 2-acrylamide-2-methylpropanesulfonic acid, 1 part functional monomer (GD-2), and 100 parts water to form a base material; mix 1 part sodium bisulfite with 25 parts water to form solution A; mix 1 part potassium persulfate with 25 parts water to form solution B; mix 0.5 parts triethanolamine, 1 part diisopropanol monoethanolamine, and 20 parts water to form solution C;

[0047] S2. Control the temperature of the base material at 40℃, add solution A, solution B and solution C dropwise to the base material, the dropwise addition time of solution A, solution B and solution C is 1.5h, after the dropwise addition is completed, keep it at a constant temperature for 2h, add water to adjust to obtain a thickening and water-retaining agent with a mass concentration of 15wt%.

[0048] Example 3

[0049] S1. Mix 6 parts acrylic acid, 20 parts N-[2-(2-hydroxyethoxy)ethyl]acrylamide, 10 parts sodium methacrylate, 2 parts functional monomer (GD-3), and 100 parts water to form a base material; mix 0.5 parts ascorbic acid with 25 parts water to form solution A; mix 1.5 parts ammonium persulfate with 25 parts water to form solution B; mix 0.8 parts triethanolamine with 20 parts water to form solution C;

[0050] S2. Control the temperature of the base material at 35℃, add solution A, solution B and solution C dropwise to the base material, the dropwise addition time of solution A, solution B and solution C is 1.5h, after the dropwise addition is completed, keep it at a constant temperature for 1.5h, add water to adjust to obtain a thickening and water-retaining agent with a mass concentration of 15wt%.

[0051] Example 4

[0052] The thickening and water-retaining agent was prepared according to the method of Example 2, except that the functional monomer (GD-1) was replaced by the same amount of functional monomer (GD-4) by weight, and the other conditions were the same as in Example 2, to obtain a thickening and water-retaining agent with a mass concentration of 15 wt%.

[0053] Comparative Example 1

[0054] The thickening and water-retaining agent was prepared according to the method of Example 2, except that no functional monomer was added, and the other conditions were the same as in Example 2, and the thickening and water-retaining agent was obtained.

[0055] Comparative Example 2

[0056] The thickening and water-retaining agent was prepared according to the method of Comparative Example 1, except that no regulator was added, and the other conditions were the same as those of Comparative Example 1, and the thickening and water-retaining agent was obtained.

[0057] Comparative Example 3

[0058] The thickening and water-retaining agent was prepared according to the method of Example 2, except that the functional monomer was replaced by the same amount of N,N'-methylenebisacrylamide by weight, and the other conditions were the same as in Example 2, to obtain a thickening and water-retaining agent with a cross-linked structure.

[0059] Comparative Example 4

[0060] A 15wt% aqueous solution of hydroxypropyl methylcellulose was used as a thickening and water-retaining agent.

[0061] Comparative Example 5

[0062] The thickening and water-retaining agent was prepared according to the method of Example 2, except that rhamnolipid was not polymerized into the thickening and water-retaining agent chain segment, but was compounded into the thickening and water-retaining agent in a mixed state. The other conditions were the same as in Example 2, and the specific steps are as follows:

[0063] S1. Mix 6 parts methacrylic acid, 10 parts methacrylamide, 8 parts 2-acrylamide-2-methylpropanesulfonic acid with 100 parts water to form a base material; mix 1 part sodium bisulfite with 25 parts water to form solution A; mix 1 part potassium persulfate with 25 parts water to form solution B; mix 0.5 parts triethanolamine, 1 part diisopropanol monoethanolamine with 20 parts water to form solution C;

[0064] S2. The temperature of the substrate is controlled at 40℃. Solutions A, B, and C are added dropwise to the substrate over a period of 1.5 hours. After the addition is complete, the substrate is kept at a constant temperature for 2 hours. Then, one part of a disaccharide monolipide structure rhamnolipid (having the structure shown in formula (4-2)) is added to the resulting reaction product. 42 The mixture of (CH2)6CH3 was stirred until homogeneous, and water was added to adjust the concentration to obtain a thickening and water-retaining agent with a mass concentration of 15wt%.

[0065] Test case

[0066] (1) Storage stability: The thickening and water-retaining agents obtained in the above examples and comparative examples were mixed with water to prepare a product with a concentration of 15 wt%. The product was then placed in a natural environment for three months to observe its appearance and storage stability. The results are shown in Table 1.

[0067] (2) Thickening and Water Retention Performance: To effectively verify the thickening and water retention effects of the thickener, a representative C30 mix proportion was used, with a 30kg reduction in cementitious material dosage and a 2-4% reduction in sand ratio. The initial concrete spread was 550mm-650mm, and the initial state of the concrete showed obvious stone leakage or stone accumulation. After initial exposure or a period of settling, obvious water or grout bleeding was observed. Concrete mix proportion: Cement 330kg / m³ 3 780kg / m³ of sand 3 Stone 1040kg / m 3 175 kg / m³ of water 3 The admixture formulation is: standard polycarboxylate superplasticizer: slump retainer: water = 800:200:4000, with an admixture dosage of 2.1% of the gel material mass. The standard polycarboxylate superplasticizer, brand name ZZ-S08C, was purchased from Kezhijie New Materials Group Co., Ltd., and the slump retainer, brand name ZZ-S10E, was also purchased from Kezhijie New Materials Group Co., Ltd.

[0068] The results are shown in Table 1.

[0069]

[0070] As can be seen from the results in Table 1, the appearance of the examples remained basically unchanged. Comparative Example 1 showed discoloration and mold growth, indicating that the addition of functional monomers can extend the storage time of the thickener and water-retaining agent. Comparative Examples 2 and 3 both showed increased viscosity, indicating that the polymerization reaction was still proceeding slowly. Comparative Example 4 was prone to stratification and had a lot of mold and a noticeable odor, indicating that it was prone to spoilage. Comparative Example 5 showed discoloration and began to have an odor, indicating that the effect of using compound functional monomers was not as good as participating in the polymerization reaction. Therefore, it can be concluded that the thickener and water-retaining agent provided by the present invention can be stored for a long time and has good stability.

[0071] Furthermore, compared to the examples, Comparative Examples 1, 2, and 4 not only require larger dosages but also still experience bleeding, meaning bleeding occurs both initially and during concrete loss, resulting in poor thickening and water retention effects. Comparative Example 5 uses a compounded functional monomer, which can improve bleeding, but the dosage is higher than in Example 2, and it reduces the initial and slump retention properties of the concrete. Comparative Example 3 uses a cross-linked thickening and water-retaining agent, which performs well in improving concrete bleeding, but the dosage is higher than in the examples. Therefore, it can be demonstrated that the concrete thickening and water-retaining agent provided by this invention has excellent thickening and water-retaining properties.

[0072] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled 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 spirit of the present invention.

Claims

1. A concrete thickening and water-retaining agent, characterized in that, The concrete thickening and water-retaining agent is obtained by free radical polymerization of unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer; the functional monomer is the esterification product of rhamnolipid and unsaturated acid monomer II. The mass ratio of the unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer to functional monomer is 6:(10~20):(5~10):(0.5~2).

2. The concrete thickening and water-retaining agent according to claim 1, characterized in that, The unsaturated acid monomer I and unsaturated acid monomer II each independently have the structure shown in formula (1): Equation (1), In equation (1), R 11 and R 12 Each is independently H, C1-C5 alkyl or -R 13 -COOH and R 11 and R 12 At least one of them is -R 13 -COOH, R 13 It is a single bond or a C1-C5 alkylene group; when R 11 and R 12 All are -R 13 When -COOH, R 11 and R 12 Capable of forming rings; R 11 `and R 12 Each is independently an H or C1-C5 alkyl group.

3. The concrete thickening and water-retaining agent according to claim 1, characterized in that, The unsaturated amide monomer has the structure shown in formula (2): Equation (2), In equation (2), R 21 It is an H or C1-C5 alkyl group, R 22 It is an H or C1-C5 hydroxyalkyl group.

4. The concrete thickening and water-retaining agent according to claim 1, characterized in that, The unsaturated sulfonate monomer has the structure shown in formula (3): Equation (3), In equation (3), R 31 It is an H or C1-C5 alkyl group; R 32 It is a C1-C3 alkylene group, -CO-NH-C(CH3)2-(CH)n-, where n is an integer from 0 to 5; A is H, K or Na.

5. The concrete thickening and water-retaining agent according to claim 1, characterized in that, In the preparation of the functional monomer, the molar ratio of rhamnolipid to unsaturated acid monomer II is 1:(1~2).

6. The concrete thickening and water-retaining agent according to claim 1, characterized in that, The esterification reaction conditions include a temperature of 70℃~90℃ and a time of 3h~8h.

7. The concrete thickening and water-retaining agent according to claim 1, characterized in that, The esterification reaction is carried out in the presence of a catalyst and a polymerization inhibitor, wherein the catalyst is selected from at least one of benzenesulfonic acid, p-toluenesulfonic acid and ethylsulfonic acid, and the polymerization inhibitor is selected from at least one of hydroquinone, phenothiazine and diphenylamine.

8. The concrete thickening and water-retaining agent according to claim 7, characterized in that, The amount of catalyst used is 0.5% to 5% of the total mass of rhamnolipid and unsaturated acid monomer II.

9. The concrete thickening and water-retaining agent according to claim 7, characterized in that, The amount of the polymerization inhibitor is 0.3% to 3% of the total mass of rhamnolipin and unsaturated acid monomer II.

10. The concrete thickening and water-retaining agent according to claim 1, characterized in that, The rhamnolipid is selected from at least one of the following: disaccharide diester rhamnolipid, disaccharide monoester rhamnolipid, monoester diester rhamnolipid, and monoester monoester rhamnolipid.

11. The concrete thickening and water-retaining agent according to any one of claims 1 to 10, characterized in that, The free radical polymerization reaction is carried out in the presence of a free radical initiator and a regulator.

12. The concrete thickening and water-retaining agent according to claim 11, characterized in that, The free radical initiator is a redox initiator.

13. The concrete thickening and water-retaining agent according to claim 12, characterized in that, The oxidant in the redox initiator is selected from at least one of potassium persulfate, sodium persulfate, and ammonium persulfate, and the reducing agent is selected from at least one of sodium bisulfite, potassium bisulfite, and ascorbic acid.

14. The concrete thickening and water-retaining agent according to claim 11, characterized in that, The modifier is selected from at least one of triethanolamine, diethanolamine, diisopropanolamine, triisopropanolamine, tetraethanolamine, and tetraisopropanolamine.

15. The concrete thickening and water-retaining agent according to claim 13, characterized in that, The mass ratio of the oxidant to unsaturated acid monomer I is 6:(0.5~2), and the mass ratio of the reducing agent to unsaturated acid monomer I is 6:(0.2~1).

16. The concrete thickening and water-retaining agent according to claim 11, characterized in that, The mass ratio of the regulator to unsaturated acid monomer I is 6:(0.2~2).

17. A method for preparing the concrete thickening and water-retaining agent according to any one of claims 1 to 16, characterized in that, This method involves a free radical polymerization reaction of unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer.

18. The method for preparing the concrete thickening and water-retaining agent according to claim 17, characterized in that, The method for the free radical polymerization reaction includes: S1. Prepare a base by mixing unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer with water; prepare solution A by mixing reducing agent with water; prepare solution B by mixing oxidizing agent with water; prepare solution C by mixing regulator with water; S2. Add solutions A, B and C to the base material. Control the initial reaction temperature at 20℃~50℃ and the dripping time at 1h~2h. After the dripping is completed, keep the reaction at the temperature for 1h~3h to obtain the concrete thickening and water-retaining agent.

19. The application of the concrete thickening and water-retaining agent according to any one of claims 1 to 16 in the construction field.

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