A concrete water-retaining agent and preparation method thereof

Abstract

The invention provides a concrete water retaining agent and a preparation method thereof. The concrete water retaining agent comprises the following raw materials in parts by weight: 60 to 80 parts of polyacrylamide, 20 to 28 parts of 2-acrylamide-2-methylpropane sulfonic acid macromolecular polymer, 14 to 22 parts of cellulose ether, 18 to 26 parts of castor oil polyoxyethylene ether, 14 to 20 parts of silane coupling agent, 20 to 32 parts of montmorillonite, 25 to 30 parts of diatomaceous earth, 12 to 18 parts of sodium hydroxide solution, and 18 to 26 parts of water-soluble latex powder. The present invention can form a uniform and stable network structure protective film by compounding polyacrylamide with montmorillonite and diatomite, and can form a stable suspension system by synergistic action with raw materials such as 2-acrylamide-2-methylpropanesulfonic acid macromolecular polymer, thereby effectively retaining water for concrete, reducing the loss of free water in concrete, and effectively reducing the degree of cracking of concrete. In addition, montmorillonite and diatomite can penetrate into concrete to fill the voids of concrete, thereby improving the compactness of concrete, effectively improving the strength of concrete, and reducing the cracking of concrete.

Description

Technical Field

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

[0002] Concrete is in great demand as a basic material for infrastructure construction. At present, concrete is needed in projects such as roads, bridges and subways. In order to meet the rapid development of the construction industry, the performance requirements for concrete are getting higher and higher. Concrete water retainer is an admixture added in the process of making concrete. Excellent water retainer can reduce the loss of water in concrete during production and use, enhance the density and strength of concrete, reduce the generation of pores in concrete, improve the compactness of concrete, and reduce the degree of cracking of concrete. At present, various water retainers have appeared on the market, but due to the mismatch of formula raw materials and preparation process, the various raw material components in the water retainer cannot play a synergistic role, the stability is poor, the water in the concrete is lost in large quantities, the water retention capacity is reduced, and the compactness of the concrete is reduced, which affects the strength of the concrete and the service life is low, which limits the application of concrete. Summary of the invention

[0003] In view of this, the present invention proposes a concrete water retaining agent and a preparation method thereof. The present invention uses a scientific and reasonable combination of water retaining agent raw materials and a better production process, so that the various raw materials in the water retaining agent can play a synergistic role, have good water retention performance in concrete, and can also improve the compactness of concrete, enhance the strength of concrete, reduce concrete cracking, and have a good use effect.

[0004] The technical solution of the present invention is achieved in this way:

[0005] A concrete water-retaining agent comprises the following raw materials in parts by weight: 60-80 parts of polyacrylamide, 20-28 parts of 2-acrylamide-2-methylpropane sulfonic acid macromolecular polymer, 14-22 parts of cellulose ether, 18-26 parts of castor oil polyoxyethylene ether, 14-20 parts of silane coupling agent, 20-32 parts of montmorillonite, 25-30 parts of diatomaceous earth, 12-18 parts of sodium hydroxide solution and 18-26 parts of water-soluble latex powder.

[0006] Furthermore, the concrete water retaining agent comprises the following raw materials in parts by weight: 80 parts of polyacrylamide, 25 parts of 2-acrylamide-2-methylpropane sulfonic acid polymer, 14 parts of cellulose ether, 26 parts of castor oil polyoxyethylene ether, 20 parts of silane coupling agent, 25 parts of montmorillonite, 30 parts of diatomaceous earth, 18 parts of sodium hydroxide solution, and 18 parts of water-soluble latex powder.

[0007] Furthermore, the concentration of the sodium hydroxide solution is 3-5wt%.

[0008] Furthermore, the cellulose ether includes one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl cellulose.

[0009] Furthermore, the preparation method of the 2-acrylamide-2-methylpropane sulfonic acid polymer is as follows: acrylic acid is added to distilled water to prepare an acrylic acid solution with a concentration of 18-26wt% for standby use; 2-acrylamide-2-methylpropane sulfonic acid is added to distilled water to prepare a 2-acrylamide-2-methylpropane sulfonic acid solution with a concentration of 25-30wt%, and sodium hydroxide solution is added while stirring to neutralize to obtain a neutralized mixture; acrylic acid solution is added while stirring at a low speed under a nitrogen atmosphere, and then an initiator and a cross-linking agent are added to react by high-speed stirring to obtain the 2-acrylamide-2-methylpropane sulfonic acid polymer.

[0010] Furthermore, the concentration of the sodium hydroxide solution is 10-12 mol / L; the neutralization degree of the neutralization mixture is 60-80 mol %; the initiator is potassium persulfate or ammonium persulfate; and the cross-linking agent is N,N'-methylenebisacrylamide.

[0011] Furthermore, the mass ratio of the 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, initiator and crosslinking agent is (5-7):(2-4):(0.05-0.1):(0.08-0.2).

[0012] Furthermore, the temperature of the low-speed stirring is 60-80°C, and the stirring speed is 150-200 r / min; the temperature of the high-speed stirring reaction is 60-80°C, the stirring speed is 400-700 r / min, and the reaction time is 2-3h.

[0013] The preparation method of concrete water retaining agent comprises the following steps:

[0014] S1, adding polyacrylamide to water and stirring to form a polyacrylamide suspension, then adding montmorillonite, diatomaceous earth and silane coupling agent to perform ultrasonic dispersion, and keeping warm for 30 to 60 minutes to obtain a mixture;

[0015] S2, stirring and mixing the mixture of S1, 2-acrylamide-2-methylpropane sulfonic acid polymer, cellulose ether, castor oil polyoxyethylene ether, sodium hydroxide solution and water-soluble latex powder to obtain a concrete water-retaining agent.

[0016] Furthermore, in step S1, the mass ratio of the polyacrylamide to water is (1-2):(6-8).

[0017] Furthermore, in step S1, the ultrasonic dispersion temperature is 60-90°C, the ultrasonic power is 300-600W, the stirring speed is 200-300r / min, and the processing time is 3-5h.

[0018] Furthermore, in step S2, the stirring and mixing temperature is 50-60° C., the stirring speed is 150-180 r / min, and the stirring time is 60-180 min.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention can form a uniform and stable network structure protective film by compounding polyacrylamide with montmorillonite and diatomite, and can form a stable suspension system by synergistic action with 2-acrylamide-2-methylpropanesulfonic acid macromolecular polymer, cellulose ether, castor oil polyoxyethylene ether and water-soluble latex powder, thereby effectively retaining water for concrete, reducing the segregation of concrete, reducing the water bleeding rate of concrete, and making concrete have good workability. In addition, montmorillonite and diatomite can penetrate into concrete to fill the gaps of concrete, improve the compactness of concrete, effectively improve the strength of concrete, improve the mechanical properties and durability of concrete, and reduce the cracking and shrinkage of concrete surface. In addition, the present invention obtains a macromolecular polymer containing more hydrophilic hydroxyl groups by polymerizing 2-acrylamide-2-methylpropanesulfonic acid and acrylic acid through a specific preparation method, thereby improving the water retention of concrete and effectively reducing water loss.

[0021] The present invention adopts a reasonable preparation process in the process of compounding polyacrylamide with montmorillonite and diatomaceous earth, which can effectively improve the stability of the mixture, play a synergistic role, increase the water absorption multiple and water absorption speed of the water retaining agent, thereby effectively improving various properties of concrete, and can effectively improve the segregation, bleeding and other problems of concrete. DETAILED DESCRIPTION

[0022] In order to better understand the technical content of the present invention, specific embodiments are provided below to further illustrate the present invention.

[0023] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods.

[0024] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0025] Example 1

[0026] The concrete water retaining agent of this embodiment comprises the following raw materials in parts by weight: 80 parts of polyacrylamide, 25 parts of 2-acrylamide-2-methylpropane sulfonic acid polymer, 14 parts of cellulose ether, 26 parts of castor oil polyoxyethylene ether, 20 parts of silane coupling agent, 25 parts of montmorillonite, 30 parts of diatomaceous earth, 18 parts of 3wt% sodium hydroxide solution, and 18 parts of water-soluble latex powder; the cellulose ether is obtained by mixing carboxymethyl cellulose and hydroxypropyl methyl cellulose in a mass ratio of 1:1;

[0027] The preparation method of the 2-acrylamide-2-methylpropane sulfonic acid polymer is as follows: acrylic acid is added to distilled water to prepare an acrylic acid solution with a concentration of 20wt%, and the solution is set aside; 2-acrylamide-2-methylpropane sulfonic acid is added to distilled water to prepare a 2-acrylamide-2-methylpropane sulfonic acid solution with a concentration of 25wt%, and a sodium hydroxide solution with a concentration of 10mol / L is added while stirring to neutralize the solution, so as to obtain a neutralization mixture with a neutralization degree of 80mol%; the mixture is stirred at a temperature of 60°C and a stirring speed of 200r / min under a nitrogen atmosphere, and the acrylic acid solution is added while stirring for 90min, and then an initiator potassium persulfate and a cross-linking agent N,N'-methylenebisacrylamide are added, and the mixture is stirred at a temperature of 60°C and a stirring speed of 700r / min for 3h to obtain the 2-acrylamide-2-methylpropane sulfonic acid polymer; the mass ratio of the 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, initiator and cross-linking agent is 6:2:0.06:0.08;

[0028] The preparation method of the concrete water retaining agent comprises the following steps:

[0029] S1, according to the mass ratio of polyacrylamide to water being 1:8, polyacrylamide was added into water and stirred to form a polyacrylamide suspension, and then montmorillonite, diatomaceous earth and silane coupling agent were added, and ultrasonic dispersion was performed for 4 hours at a temperature of 90° C., an ultrasonic power of 600 W and a stirring speed of 300 r / min, and the mixture was kept warm for 30 minutes to obtain a mixture;

[0030] S2. The mixture of S1, 2-acrylamide-2-methylpropane sulfonic acid polymer, cellulose ether, castor oil polyoxyethylene ether, sodium hydroxide solution and water-soluble latex powder are stirred and mixed at a temperature of 60° C. and a stirring speed of 180 r / min for 150 min to obtain a concrete water retaining agent.

[0031] Example 2

[0032] The concrete water retaining agent of this embodiment comprises the following raw materials in parts by weight: 70 parts of polyacrylamide, 20 parts of 2-acrylamide-2-methylpropane sulfonic acid polymer, 22 parts of cellulose ether, 18 parts of castor oil polyoxyethylene ether, 20 parts of silane coupling agent, 32 parts of montmorillonite, 27 parts of diatomaceous earth, 16 parts of 5wt% sodium hydroxide solution, and 22 parts of water-soluble latex powder; the cellulose ether is obtained by mixing carboxymethyl cellulose, hydroxypropyl methyl cellulose and hydroxyethyl cellulose in a mass ratio of 1:2:1;

[0033] The preparation method of the 2-acrylamide-2-methylpropane sulfonic acid polymer is as follows: acrylic acid is added to distilled water to prepare an acrylic acid solution with a concentration of 18wt% for standby use; 2-acrylamide-2-methylpropane sulfonic acid is added to distilled water to prepare a 2-acrylamide-2-methylpropane sulfonic acid solution with a concentration of 30wt%, and a sodium hydroxide solution with a concentration of 11mol / L is added while stirring to neutralize, so as to obtain a neutralized mixture with a neutralization degree of 60mol%; the mixture is stirred at a temperature of 80°C and a stirring speed of 180r / min under a nitrogen atmosphere at a low speed, the acrylic acid solution is added while stirring and stirred for 60min, and then an initiator potassium persulfate and a cross-linking agent N,N'-methylenebisacrylamide are added, and the mixture is stirred at a temperature of 80°C and a stirring speed of 600r / min for high-speed reaction for 2h to obtain the 2-acrylamide-2-methylpropane sulfonic acid polymer; the mass ratio of the 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, initiator and cross-linking agent is 5:3:0.05:0.1;

[0034] The preparation method of the concrete water retaining agent comprises the following steps:

[0035] S1, according to the mass ratio of polyacrylamide to water being 2:6, polyacrylamide was added into water and stirred to form a polyacrylamide suspension, and then montmorillonite, diatomaceous earth and silane coupling agent were added, and ultrasonic dispersion was performed for 3 hours at a temperature of 80° C., an ultrasonic power of 300 W and a stirring speed of 200 r / min, and the mixture was kept warm for 50 minutes to obtain a mixture;

[0036] S2. The mixture of S1, 2-acrylamide-2-methylpropane sulfonic acid polymer, cellulose ether, castor oil polyoxyethylene ether, sodium hydroxide solution and water-soluble latex powder are stirred and mixed at a temperature of 50° C. and a stirring speed of 150 r / min for 180 min to obtain a concrete water retaining agent.

[0037] Example 3

[0038] The concrete water retaining agent of this embodiment comprises the following raw materials in parts by weight: 60 parts of polyacrylamide, 28 parts of 2-acrylamide-2-methylpropane sulfonic acid polymer, 18 parts of cellulose ether, 20 parts of castor oil polyoxyethylene ether, 18 parts of silane coupling agent, 20 parts of montmorillonite, 25 parts of diatomaceous earth, 12 parts of 4wt% sodium hydroxide solution, and 26 parts of water-soluble latex powder; the cellulose ether is obtained by mixing hydroxypropyl methylcellulose and hydroxyethyl cellulose in a mass ratio of 1:1;

[0039] The preparation method of the 2-acrylamide-2-methylpropane sulfonic acid polymer is as follows: acrylic acid is added to distilled water to prepare an acrylic acid solution with a concentration of 26wt% for standby use; 2-acrylamide-2-methylpropane sulfonic acid is added to distilled water to prepare a 2-acrylamide-2-methylpropane sulfonic acid solution with a concentration of 28wt%, and a sodium hydroxide solution with a concentration of 12mol / L is added while stirring to neutralize, so as to obtain a neutralized mixture with a neutralization degree of 70mol%; the mixture is stirred at a low speed of 70°C and a stirring speed of 150r / min under a nitrogen atmosphere, and the acrylic acid solution is added while stirring for 30min, and then an initiator ammonium persulfate and a cross-linking agent N,N'-methylenebisacrylamide are added, and the mixture is stirred at a high speed of 70°C and a stirring speed of 400r / min for 3h to obtain the 2-acrylamide-2-methylpropane sulfonic acid polymer; the mass ratio of the 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, initiator and cross-linking agent is 7:4:0.1:0.2;

[0040] The preparation method of the concrete water retaining agent comprises the following steps:

[0041] S1. According to the mass ratio of polyacrylamide to water of 1.5:7, polyacrylamide was added into water and stirred to form a polyacrylamide suspension. Then, montmorillonite, diatomaceous earth and silane coupling agent were added, and ultrasonic dispersion was performed for 5 hours at a temperature of 70°C, an ultrasonic power of 500W and a stirring speed of 250r / min. The mixture was kept warm for 60 minutes to obtain a mixture.

[0042] S2. The mixture of S1, 2-acrylamide-2-methylpropane sulfonic acid polymer, cellulose ether, castor oil polyoxyethylene ether, sodium hydroxide solution and water-soluble latex powder are stirred and mixed at a temperature of 55° C. and a stirring speed of 160 r / min for 60 minutes to obtain a concrete water-retaining agent.

[0043] Comparative Example 1

[0044] The weight parts of the raw material components in this comparative example are adjusted on the basis of Example 1. This comparative example includes the following raw materials in weight parts: 30 parts of polyacrylamide, 40 parts of 2-acrylamide-2-methylpropane sulfonic acid polymer, 32 parts of cellulose ether, 10 parts of castor oil polyoxyethylene ether, 10 parts of silane coupling agent, 12 parts of montmorillonite, 40 parts of diatomaceous earth, 25 parts of sodium hydroxide solution, and 8 parts of water-soluble latex powder. The rest is the same as Example 1.

[0045] Comparative Example 2

[0046] The raw material composition of this comparative example is adjusted on the basis of Example 1. This comparative example does not contain montmorillonite, diatomaceous earth and silane coupling agent. The rest is the same as Example 1.

[0047] This comparative example includes the following raw materials in parts by weight: 100 parts of polyacrylamide, 50 parts of 2-acrylamide-2-methylpropane sulfonic acid polymer, 44 parts of cellulose ether, 26 parts of castor oil polyoxyethylene ether, 18 parts of 3wt% sodium hydroxide solution, and 18 parts of water-soluble latex powder;

[0048] The preparation method of the concrete water retaining agent comprises the following steps:

[0049] Mix polyacrylamide and water in a mass ratio of 0.08:1, then add 2-acrylamide-2-methylpropane sulfonic acid polymer, cellulose ether, castor oil polyoxyethylene ether, sodium hydroxide solution and water-soluble latex powder, and stir and mix for 150 minutes at a temperature of 60°C and a stirring speed of 180r / min to obtain a concrete water-retaining agent.

[0050] Comparative Example 3

[0051] The raw material composition of this comparative example is adjusted on the basis of Example 1. This comparative example does not contain 2-acrylamide-2-methylpropanesulfonic acid high molecular polymer and water-soluble latex powder. The rest is the same as Example 1.

[0052] 105 parts of polyacrylamide, 23 parts of cellulose ether, 35 parts of castor oil polyoxyethylene ether, 20 parts of silane coupling agent, 25 parts of montmorillonite, 30 parts of diatomaceous earth, and 18 parts of 3wt% sodium hydroxide solution.

[0053] Comparative Example 4

[0054] In this comparative example, the preparation method is adjusted on the basis of Example 1, and the process parameters of S1 are adjusted. The specific steps of S1 in this comparative example are as follows:

[0055] S1. According to the mass ratio of polyacrylamide to water being 1:8, polyacrylamide was added into water and stirred to form a polyacrylamide suspension. Then, montmorillonite, diatomaceous earth and silane coupling agent were added and mixed at a temperature of 50° C. and a stirring speed of 80 r / min for 2 h to obtain a mixture.

[0056] Comparative Example 5

[0057] In this comparative example, the preparation method is adjusted on the basis of Example 1, and the process parameters of S2 are adjusted. The specific steps of S2 in this comparative example are as follows:

[0058] S2. Mix the mixture of S1 and water in a mass ratio of 0.08:1, then add 2-acrylamide-2-methylpropane sulfonic acid polymer, cellulose ether, castor oil polyoxyethylene ether, sodium hydroxide solution and water-soluble latex powder, and stir and mix for 240 minutes at a temperature of 90° C. and a stirring speed of 60 r / min to obtain a concrete water retaining agent.

[0059] Comparative Example 6

[0060] In this comparative example, the 2-acrylamide-2-methylpropanesulfonic acid polymer is replaced with pure 2-acrylamide-2-methylpropanesulfonic acid, and the rest is the same as Example 1.

[0061] Comparative Example 7

[0062] In this comparative example, the preparation process of 2-acrylamide-2-methylpropane sulfonic acid polymer is adjusted on the basis of Example 1, and the rest is the same as Example 1, specifically as follows: the preparation method of the 2-acrylamide-2-methylpropane sulfonic acid polymer is as follows: acrylic acid is added to distilled water to prepare an acrylic acid solution with a concentration of 35wt%, and the solution is set aside; 2-acrylamide-2-methylpropane sulfonic acid is added to distilled water to prepare a 2-acrylamide-2-methylpropane sulfonic acid solution with a concentration of 60wt%, and a sodium hydroxide solution with a concentration of 10mol / L is added while stirring to neutralize the solution to obtain a neutralized mixture with a neutralization degree of 80mol%; under a nitrogen atmosphere, the acrylic acid solution, an initiator potassium persulfate and a cross-linking agent N,N'-methylenebisacrylamide are added to react at a temperature of 50°C and a rotation speed of 200r / min for 1.5h to obtain a 2-acrylamide-2-methylpropane sulfonic acid polymer.

[0063] Experimental situation

[0064] The concrete water retaining agents prepared in Examples 1-3 of the present invention and Comparative Examples 1-7 were subjected to performance tests. The test standards were based on GB / T 50080-2016 "Standard for Performance Test Methods of Ordinary Concrete Mixtures" and GB / T8076-2008 "Concrete Admixtures" to determine the water seepage rate (%), and the compressive strength, flexural strength, splitting tensile strength of the concrete samples after curing for 28 days were tested, and the concrete performance test was performed. The test results are shown below.

[0065] Table 1 Basic proportion of raw materials used in concrete

[0066] project <![CDATA[Cement / (kg / m 3 )]]> <![CDATA[Fly ash / (kg / m 3 )]]> <![CDATA[Sand / (kg / m 3 )]]> <![CDATA[Crushed stone / (kg / m 3 )]]> <![CDATA[Water / (kg / m 3 )]]> C30 260 80 900 1030 165

[0067] Among them, the cement is P·O 42.5 conch cement; the fly ash is grade I; the sand is standard sand with a fineness modulus of 2.6-2.9; the crushed stone particle size is 20-40 mm, and 0.2% water retaining agent is added to the 9% solid content polycarboxylate water reducer, and then the effects of the concrete water retaining agents prepared in Examples 1-3 of the present invention and Comparative Examples 1-7 on the performance of concrete are tested.

[0068] Table 2 Concrete performance test results

[0069]

[0070]

[0071] The above results show that by adding the concrete water retaining agent prepared in Examples 1-3 of the present invention, the cohesiveness of the concrete can be increased and a mesh structure with good water retention performance can be formed, so that the concrete has good water retention performance, reduces the loss of free water in the concrete, and the water bleeding rate is 3.09-4.63%. The concrete has no water bleeding after 1 hour and has good wrapping and fluidity; compared with Example 1, the water bleeding rate of Comparative Examples 1-7 is increased due to the unreasonable raw material formula component content or preparation process of the water retaining agent, and different degrees of water bleeding occur. In addition, through the synergistic effect of the raw material formula of the present invention, the compressive strength, flexural strength and splitting tensile strength of the concrete can be effectively enhanced, and the strength of the concrete can be improved. Similarly, the unreasonable raw material ratio and poor preparation process of Comparative Examples 1-7 will also affect the water retaining agent, thereby affecting the performance of the concrete. In addition, by preparing a high molecular polymer with 2-acrylamide-2-methylpropanesulfonic acid, the performance of the water retaining agent can be improved.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A concrete water retaining agent, characterized in that: The invention comprises the following raw materials in parts by weight: 60-80 parts of polyacrylamide, 20-28 parts of 2-acrylamide-2-methylpropane sulfonic acid polymer, 14-22 parts of cellulose ether, 18-26 parts of castor oil polyoxyethylene ether, 14-20 parts of silane coupling agent, 20-32 parts of montmorillonite, 25-30 parts of diatomaceous earth, 12-18 parts of sodium hydroxide solution, and 18-26 parts of water-soluble latex powder; The preparation method of the 2-acrylamide-2-methylpropane sulfonic acid polymer comprises the following steps: adding acrylic acid to distilled water to prepare an acrylic acid solution with a concentration of 18-26 wt % for standby use; adding 2-acrylamide-2-methylpropane sulfonic acid to distilled water to prepare a 2-acrylamide-2-methylpropane sulfonic acid solution with a concentration of 25-30 wt %, adding a sodium hydroxide solution while stirring to neutralize, to obtain a neutralized mixture; adding the acrylic acid solution while stirring at a low speed under a nitrogen atmosphere, and then adding an initiator and a cross-linking agent to react at a high speed to obtain the 2-acrylamide-2-methylpropane sulfonic acid polymer; The preparation method of the concrete water retaining agent comprises the following steps: S1, adding polyacrylamide to water and stirring to form a polyacrylamide suspension, then adding montmorillonite, diatomaceous earth and silane coupling agent to perform ultrasonic dispersion, and keeping warm for 30-60 minutes to obtain a mixture; S2, stirring and mixing the mixture of S1, 2-acrylamide-2-methylpropane sulfonic acid polymer, cellulose ether, castor oil polyoxyethylene ether, sodium hydroxide solution and water-soluble latex powder to obtain a concrete water-retaining agent.

2. The concrete water retaining agent according to claim 1, characterized in that: The concrete water retaining agent comprises the following raw materials in parts by weight: 80 parts of polyacrylamide, 25 parts of 2-acrylamide-2-methylpropane sulfonic acid macromolecular polymer, 14-22 parts of cellulose ether, 26 parts of castor oil polyoxyethylene ether, 20 parts of silane coupling agent, 25 parts of montmorillonite, 30 parts of diatomaceous earth, 18 parts of sodium hydroxide solution and 18 parts of water-soluble latex powder.

3. The concrete water retaining agent according to claim 1, characterized in that: The concentration of the sodium hydroxide solution is 3-5wt%; the cellulose ether includes one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl cellulose.

4. The concrete water retaining agent according to claim 1, characterized in that: The concentration of the sodium hydroxide solution is 10-12 mol / L; the neutralization degree of the neutralization mixture is 60-80 mol %; the initiator is potassium persulfate or ammonium persulfate; and the crosslinking agent is N,N'-methylenebisacrylamide.

5. The concrete water retaining agent according to claim 1, characterized in that: The mass ratio of the 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, initiator and crosslinking agent is (5-7): (2-4): (0.05-0.1): (0.08-0.2).

6. The concrete water retaining agent according to claim 1, characterized in that: The temperature of the low-speed stirring is 60-80°C, and the stirring speed is 150-200 r / min; the temperature of the high-speed stirring reaction is 60-80°C, the stirring speed is 400-700 r / min, and the reaction time is 2-3h.

7. The concrete water retaining agent according to claim 1, characterized in that: In step S1, the mass ratio of the polyacrylamide to water is (1-2):(6-8).

8. The concrete water retaining agent according to claim 1, characterized in that: In step S1, the ultrasonic dispersion temperature is 60-90°C, the ultrasonic power is 300-600W, the stirring speed is 200-300r / min, and the processing time is 3-5h; in step S2, the stirring and mixing temperature is 50-60°C, the stirring speed is 150-180r / min, and the stirring time is 60-180min.

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