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

Abstract

The invention belongs to the field of additives, and particularly relates to a concrete thickening and water-retaining agent as well as a preparation method and application thereof. The concrete thickening water-retaining agent is obtained by performing free radical polymerization reaction on an unsaturated acid monomer I, an unsaturated amide monomer, an unsaturated sulfonate monomer and a functional monomer, the functional monomer is an esterification reaction product of rhamnolipid and an unsaturated acid monomer II. The preparation method is characterized in that an esterification reaction product of rhamnolipid and an unsaturated acid monomer II is introduced into a copolymerization reaction system of an unsaturated acid monomer I, an unsaturated amide monomer and an unsaturated sulfonate monomer to serve as a copolymerization monomer, so that the molecular structure of the concrete thickening and water-retaining agent can be changed; the concrete thickening and water-retaining agent has excellent thickening and water-retaining properties, and the stability of the concrete thickening and water-retaining agent in concrete can be improved.

Description

Technical Field

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

[0002] As an important building material, concrete plays a vital role in the construction of infrastructure such as buildings, roads, and bridges. However, during the preparation and application of traditional concrete materials, there are often problems such as poor fluidity, large water seepage, and easy stratification and segregation, which seriously affect the construction performance and engineering quality of concrete. In view of this, it is particularly important to develop a thickening and water-retaining agent that can effectively improve the performance of concrete and enhance the workability and durability of concrete.

[0003] Thickeners are chemical additives that can increase the consistency of concrete mixtures while reducing water loss. Thickeners can form a stable network structure inside the concrete, effectively preventing the migration and evaporation of water, thereby improving the water retention performance of the concrete. In addition, thickeners can also significantly improve the fluidity of concrete, making it easier to construct and vibrate the concrete, reducing construction time.

[0004] At present, there are many types of 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, although some thickeners and water-retaining agents can improve the water-retaining performance of concrete, they have poor storage stability and are prone to stratification or gelation after being placed for a period of time; while other thickeners and water-retaining agents can ensure long-term storage, but will have a serious negative impact on the fluidity of concrete. Summary of the invention

[0005] The first purpose of the present invention is to overcome the defect that the existing concrete thickener and water-retaining agent is difficult to take into account both thickening and water-retaining performance and stability, and to provide a concrete thickener and water-retaining agent with both excellent thickening and water-retaining performance and good stability.

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

[0007] The third object of the present invention is to provide application of the above concrete thickening and water-retaining agent in the field of construction.

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

[0009] The preparation method of the concrete thickening and water-retaining agent provided by the invention comprises the steps of subjecting unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer to free radical polymerization reaction.

[0010] The key to the present invention is to introduce the esterification product of rhamnolipid and unsaturated acid monomer II as a copolymerization monomer into the copolymerization reaction system of unsaturated acid monomer I, unsaturated amide monomer and unsaturated sulfonate monomer, thereby changing the molecular structure of the concrete thickening and water-retaining agent, so that the obtained concrete thickening and water-retaining agent not only has excellent thickening and water-retaining properties, but also can improve its stability in concrete. DETAILED DESCRIPTION

[0011] 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 mass ratio of the unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer is preferably 6: (10-20): (5-10): (0.5-2). Specifically, the mass ratio of the unsaturated acid monomer I to the unsaturated amide monomer is preferably 6: (10-20), such as 6: 10, 6: 12, 6: 14, 6: 16, 6: 18, 6: 20 or any value therebetween. The mass ratio of the unsaturated acid monomer I to the unsaturated sulfonate monomer is preferably 6: (5-10), such as 6: 5, 6: 6, 6: 8, 6: 10 or any value therebetween. The mass ratio of the unsaturated acid monomer I to the functional monomer 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 therebetween.

[0012] In the present invention, the unsaturated acid monomer I and the unsaturated acid monomer II preferably each independently have a structure represented by formula (1):

[0013]

[0014] In formula (1), R 11 and R 12 Each independently represents 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 is a single bond or a C1-C5 alkylene group; when R 11 and R 12 All are -R 13 -COOH, R 11 and R 12 Able to bond into a ring; R11 ` and R 12 `Each independently represents H or a C1-C5 alkyl group. 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 -COOH, R 21 and R 22 It can be bonded to form a ring, and an acid anhydride is formed at this time. Considering the availability of raw materials, the unsaturated carboxylic acid I and the unsaturated acid monomer II are preferably independently selected from at least one of acrylic acid, methacrylic acid, itaconic acid and maleic anhydride. The terms "I" and "II" are only used to distinguish the unsaturated carboxylic acids introduced at different positions for the convenience of description, and have no other special meanings.

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

[0016]

[0017] In formula (2), R 21 is H or C1-C5 alkyl, R 22 The alkyl group of C1-C5 is H or C1-C5 hydroxyalkyl. Wherein, the specific examples of C1-C5 alkyl 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. The specific examples of the hydroxyalkyl group of C1-C5 include but are not limited to: methylol, hydroxyethyl, hydroxy-n-propyl, hydroxyisopropyl, hydroxy-n-butyl, hydroxyisobutyl, hydroxy-tert-butyl, hydroxy-n-pentyl, hydroxyisopentyl, hydroxy-tert-pentyl or hydroxyneopentyl. Considering the availability of raw materials, the unsaturated amide monomer is preferably selected from one of acrylamide, methacrylamide and N-[2-(2-hydroxyethoxy)ethyl]acrylamide.

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

[0019]

[0020] In formula (3), R 31 is H or a C1-C5 alkyl group; R 32is a C1-C3 alkylene group, -CO-NH-C(CH3)2-(CH)n-, n is an integer of 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. Considering the availability of raw materials, the unsaturated sulfonate monomer is particularly preferably 2-acrylamide-2-methylpropanesulfonic acid and / or sodium methyl propenesulfonate.

[0021] In the present invention, the functional monomer is the esterification product of rhamnolipid and unsaturated acid monomer II. Wherein, 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 therebetween. The conditions of the esterification reaction preferably include a temperature of 70°C to 90°C, such as 70°C, 72°C, 75°C, 78°C, 80°C, 82°C, 85°C, 88°C, 90°C or any value therebetween; a time of 3h to 8h, such as 3h, 4h, 5h, 6h, 7h, 8h or any value therebetween. The esterification reaction is carried out in the presence of a catalyst and an inhibitor. Wherein, the catalyst can be listed as at least one of benzenesulfonic acid, p-toluenesulfonic acid and ethylsulfonic acid. The inhibitor can be listed as at least one of hydroquinone, phenothiazine and diphenylamine. The amount of the catalyst 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 therebetween. The amount of the inhibitor 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 therebetween. In addition, the esterification reaction is carried out under the protection of an inert gas. The inert gas may be, for example, nitrogen, helium or argon.

[0022] In the present invention, the rhamnolipid can be any existing compound containing a rhamnose ring and saturated fatty acids or unsaturated fatty acids of different carbon chain lengths, preferably selected from at least one of disaccharide and disaccharide rhamnolipid, disaccharide and monolipid rhamnolipid, monosaccharide and disaccharide rhamnolipid, and monosaccharide and monolipid rhamnolipid. Among them, the disaccharide and disaccharide rhamnolipid preferably has the structure shown in formula (4-1), the disaccharide and monolipid rhamnolipid preferably has the structure shown in formula (4-2), the monosaccharide and disaccharide rhamnolipid preferably has the structure shown in formula (4-3), and the monosaccharide and monolipid rhamnolipid preferably has the structure shown in formula (4-4):

[0023]

[0024] In formula (1) to formula (4), R 41 , R 41 `、R 42 , R 43 , R 43 ` and R 44 Each independently is C1-C 10 Alkyl. C1-C 10 The alkyl group may 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 disaccharide structure rhamnolipid having a structure shown in formula (4-1) and / or a disaccharide monolipid structure rhamnolipid having a structure shown in formula (4-2), and R1, R1', and R2 are each independently C1-C 10 The alkyl group can give the concrete thickener and water-retaining agent higher water retention and stability.

[0025] In the present invention, the free radical polymerization reaction is usually carried out in the presence of a free radical initiator and a regulator. The free radical initiator can be selected from at least one of an azo initiator, a peroxide initiator and a redox initiator, preferably a redox initiator. Among them, the oxidant in the redox initiator is preferably selected from at least one of potassium persulfate, sodium persulfate and ammonium persulfate. The reducing agent 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 the 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 therebetween. The mass ratio of the reducing agent to the 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 therebetween. The regulator can be at least one of triethanolamine, diethanol monoisopropanolamine, diisopropanol monoethanolamine, triisopropanolamine, tetraethanol ethylenediamine and tetraisopropanol ethylenediamine. In addition, the mass ratio of the regulator to the 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 therebetween. In a preferred embodiment, the raw materials for preparing the thickening and water-retaining agent contain 6 parts by weight of unsaturated acid monomers, 10-20 parts by weight of unsaturated amide monomers, 5-10 parts by weight of unsaturated sulfonate monomers, 0.5-2 parts by weight of functional monomers, 0.5-2 parts by weight of oxidants, 0.2-1 parts by weight of reducing agents and 0.2-2 parts by weight of regulators.

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

[0027] The preparation method of the concrete thickening and water-retaining agent provided by the invention comprises the steps of subjecting unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer to free radical polymerization reaction.

[0028] In a preferred embodiment, the free radical polymerization method comprises:

[0029] S1. Unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer are prepared with water to form a base material; reducing agent is prepared with water to form solution A; oxidizing agent is prepared with water to form solution B; regulating agent is prepared with water to form solution C;

[0030] S2. Add solution A, solution B and solution C dropwise into the base material, control the initial reaction temperature at 20°C to 50°C, control the dropping time at 1h to 2h, and keep the temperature for reaction for 1h to 3h after the dropping is completed to obtain the concrete thickening and water-retaining agent.

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

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

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

[0034] Preparation Example 1

[0035] 50 g of disaccharide and disolipid rhamnolipid (having the structure shown in formula (4-1), wherein R 41 and R 41 `All are -(CH2)6CH3), 5.5g acrylic acid and 1.0g hydroquinone are added into the reaction container and mixed. Under nitrogen protection, the temperature is adjusted to 70°C, and then 0.8g benzenesulfonic acid is added to react for 8h to obtain a functional monomer, which is recorded as GD-1.

[0036] Preparation Example 2

[0037] 45 g of disaccharide monolipid rhamnolipid (having the structure shown in formula (4-2), wherein R 42 (-(CH2)6CH3), 8.1g methacrylic acid and 0.9g diphenylamine were added into the reaction container and mixed. Under nitrogen protection, the temperature was adjusted to 85°C, and 0.77g ethylsulfonic acid was added and kept warm for 6h to obtain a functional monomer, which was recorded as GD-2.

[0038] Preparation Example 3

[0039] 25 g of monosaccharide monolipid structure rhamnolipid (having the structure shown in formula (4-3), wherein R 43 and R 43 `All are -(CH2)6CH3), 7.3g acrylic acid and 0.7g hydroquinone are added into the reaction container and mixed. Under nitrogen protection, the temperature is adjusted to 90°C, and then 0.6g p-toluenesulfonic acid is added and the reaction is kept warm for 4h to obtain a functional monomer, which is recorded as GD-3.

[0040] Preparation Example 4

[0041] 40 g of monosaccharide and dilipid rhamnolipid (having the structure shown in formula (4-4), wherein R 44(-(CH2)6CH3), 7.4g methacrylic acid and 0.95g phenothiazine were added into the reaction container and mixed. Under nitrogen protection, the temperature was adjusted to 80°C, and 0.8g p-toluenesulfonic acid was added and the mixture was kept warm for 6h to obtain a functional monomer, which was recorded as GD-4.

[0042] Example 1

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

[0044] S2. The temperature of the base material is controlled at 30°C, and solution A, solution B and solution C are added dropwise to the base material. The dropping time of solution A, solution B and solution C is 1 hour. After the dropping is completed, the base material is aged at a constant temperature for 1 hour, and water is added to adjust the mass concentration to obtain a thickening and water-retaining agent of 15wt%.

[0045] Example 2

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

[0047] S2. The temperature of the base material is controlled at 40°C, and solution A, solution B and solution C are added dropwise to the base material. The dropping time of solution A, solution B and solution C is 1.5h. After the dropping is completed, the mixture is aged at a constant temperature for 2h, and water is added to adjust the mass concentration to obtain a thickening and water-retaining agent of 15wt%.

[0048] Example 3

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

[0050] S2. The temperature of the base material is controlled at 35°C, and solution A, solution B and solution C are added dropwise to the base material. The dropping time of solution A, solution B and solution C is 1.5h. After the dropping is completed, the mixture is aged at a constant temperature for 1.5h, and water is added to adjust the mass concentration to obtain a thickening and water-retaining agent of 15wt%.

[0051] Example 4

[0052] A 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 functional monomer (GD-4) of the same weight, and the other conditions were the same as those of Example 2, to obtain a thickening and water-retaining agent with a mass concentration of 15 wt%.

[0053] Comparative Example 1

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

[0055] Comparative Example 2

[0056] A 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 to obtain a thickening and water-retaining agent.

[0057] Comparative Example 3

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

[0059] Comparative Example 4

[0060] A 15 wt % hydroxypropyl methylcellulose aqueous solution 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 the 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 those of Example 2, and the specific steps were as follows:

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

[0064] S2. The temperature of the base material is controlled at 40°C, and solution A, solution B and solution C are added dropwise to the base material. The addition time of solution A, solution B and solution C is 1.5 hours. After the addition is completed, the base material is kept at a constant temperature for 2 hours. Then, 1 portion of disaccharide monolipid structure rhamnolipid (having the structure shown in formula (4-2), wherein R 42 -(CH2)6CH3) was stirred and mixed evenly, and water was added to adjust the mass 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 form a product with a concentration of 15 wt %, and then placed in a natural environment for three months to observe the product appearance and storage stability. The results are shown in Table 1.

[0067] (2) Thickening and water retention performance: In order to effectively verify the thickening and water retention effect of the thickening and water retention agent, the representative C30 mix ratio was used, the amount of cementitious materials was reduced by 30kg, and the sand ratio was reduced by 2-4% for testing and verification, so that the initial expansion of the concrete was 550mm-650mm. The initial state of the concrete should have obvious leakage or stone accumulation, and obvious water or slurry bleeding at the beginning or after standing for a period of time. Concrete mix ratio: cement 330kg / m 3 、Sand 780kg / m 3 、Stone 1040kg / m 3 , water 175kg / m 3 The admixture formula is: standard polycarboxylic acid water reducing agent: slump preventing agent: water = 800:200:4000, and the admixture dosage is 2.1% of the mass of the gel material. Among them, the standard polycarboxylic acid water reducing agent was purchased from Kezhijie New Materials Group Co., Ltd., with the brand name ZZ-S08C. The slump preventing agent was purchased from Kezhijie New Materials Group Co., Ltd., with the brand name ZZ-S10E.

[0068] The results are shown in Table 1.

[0069]

[0070] From the results in Table 1, it can be seen that the appearance of the embodiment is basically unchanged, while the comparative example 1 shows discoloration and mold, indicating that the addition of functional monomers can extend the storage time of the thickening and water-retaining agent, and the viscosity of the comparative examples 2 and 3 increases, indicating that the polymerization reaction is still proceeding slowly; the comparative example 4 is prone to stratification and mold, and has obvious odor, indicating that it is easy to deteriorate; the comparative example 5 shows discoloration and begins to have an odor, indicating that the effect of using a compound functional monomer is not as good as participating in the polymerization reaction. It can be shown that the thickening and water-retaining agent provided by the present invention can be stored for a long time and has good stability.

[0071] In addition, compared with the embodiment, comparative examples 1, 2 and 4 not only require a larger dosage, but also still have bleeding, that is, the initial and loss of concrete have bleeding, so the thickening and water retention effect is poor; comparative example 5 adopts compounding and adding functional monomers, although it can improve the bleeding, but relative to embodiment 2, the dosage is higher, and the initial and collapse retention performance of concrete is reduced; and comparative example 3 uses a thickening and water-retaining agent with a cross-linked structure, although it performs well in improving concrete bleeding, the dosage is higher than the embodiment. It can be shown that the concrete thickening and water-retaining agent provided by the present invention has excellent thickening and water-retaining properties.

[0072] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent 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 subjecting unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer to free radical polymerization reaction; the functional monomer is the esterification reaction product of rhamnolipid and unsaturated acid monomer II.

2. The concrete thickening and water-retaining agent according to claim 1, characterized in that: The mass ratio of the unsaturated acid monomer I, the unsaturated amide monomer, the unsaturated sulfonate monomer and the functional monomer is 6:(10-20):(5-10):(0.5-2).

3. The concrete thickening and water-retaining agent according to claim 1, characterized in that: The unsaturated acid monomer I and the unsaturated acid monomer II each independently have a structure shown in formula (1): In formula (1), R 11 and R 12 Each independently represents 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 is a single bond or a C1-C5 alkylene group; when R 11 and R 12 All are -R 13 -COOH, R 11 and R 12 Able to bond into a ring; R 11 ` and R 12 `Each independently is H or a C1-C5 alkyl group.

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

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

6. The concrete thickening and water-retaining agent according to claim 1, characterized in that: In the preparation process of the functional monomer, the molar ratio of the rhamnolipid to the unsaturated acid monomer II is 1:(1-2); Preferably, the conditions of the esterification reaction include a temperature of 70°C to 90°C and a time of 3h to 8h; Preferably, 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; Preferably, the amount of the catalyst is 0.5% to 5% of the total mass of rhamnolipid and unsaturated acid monomer II; Preferably, the amount of the polymerization inhibitor is 0.3% to 3% of the total mass of rhamnolipid and unsaturated acid monomer II; Preferably, the rhamnolipid is selected from at least one of disaccharide rhamnolipid with a dual lipid structure, disaccharide rhamnolipid with a single lipid structure, monosaccharide rhamnolipid with a dual lipid structure, and monosaccharide rhamnolipid with a single lipid structure.

7. The concrete thickening and water-retaining agent according to any one of claims 1 to 6, characterized in that: The free radical polymerization reaction is carried out in the presence of a free radical initiator and a regulator; Preferably, the free radical initiator is a redox initiator; Preferably, the oxidizing agent 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; Preferably, the regulator is selected from at least one of triethanolamine, diethanol monoisopropanolamine, diisopropanol monoethanolamine, triisopropanolamine, tetraethanol ethylenediamine and tetraisopropanol ethylenediamine; Preferably, the mass ratio of the oxidizing agent to the unsaturated acid monomer I is 6:(0.5-2), and the mass ratio of the reducing agent to the unsaturated acid monomer I is 6:(0.2-1); Preferably, the mass ratio of the regulator to the unsaturated acid monomer I is 6:(0.2-2).

8. The method for preparing the concrete thickening and water-retaining agent according to any one of claims 1 to 7, characterized in that: The method comprises the steps of subjecting unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer to free radical polymerization.

9. The method for preparing a concrete thickening and water-retaining agent according to claim 8, characterized in that: The free radical polymerization method comprises: S1. Unsaturated acid monomer I, unsaturated amide monomer, unsaturated sulfonate monomer and functional monomer are prepared with water to form a base material; reducing agent is prepared with water to form solution A; oxidizing agent is prepared with water to form solution B; regulating agent is prepared with water to form solution C; S2. Add solution A, solution B and solution C dropwise into the base material, control the initial reaction temperature at 20°C to 50°C, control the dropping time at 1h to 2h, and keep the temperature for reaction for 1h to 3h after the dropping is completed to obtain the concrete thickening and water-retaining agent.

10. Use of the concrete thickening and water-retaining agent according to any one of claims 1 to 7 in the field of construction.

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