Early strength concrete water retaining agent and preparation method thereof

Abstract

The present invention belongs to the technical field of concrete, and specifically relates to an early-strength concrete water retaining agent and a preparation method thereof. The early-strength concrete water retaining agent is made of unsaturated amide monomers, unsaturated ester monomers, unsaturated sulfonic acid monomers, cross-linking monomers, initiators, reducing agents, water, graphene oxide and intercalating agents; wherein the cross-linking monomer is 1,8-bismaleimide-diglycol, and the intercalating agent is potassium nitrate. The present invention solves the problems of poor state of concrete mixed with machine-made sand, segregated bleeding, and low early strength when using polycarboxylic acid water reducers.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete, and particularly relates to an early-strength concrete water-retaining agent and a preparation method thereof. Background Art

[0002] Concrete is the world's most widely used man-made material and building material. It has become the foundation of modern society. The huge consumption of concrete has led to a shortage of high-quality river sand resources, and a large amount of machine-made sand has been used. Machine-made sand is mainly composed of coarse particles and stone powder. Due to the lack of fine particles, its gradation is poor. Concrete mixed with machine-made sand has defects such as poor workability, easy loss of slurry, and high water seepage rate, which will reduce the quality of the project and even cause serious engineering accidents.

[0003] Adding water retaining agent is an effective way to reduce the water seepage of concrete. As a commonly used water retaining agent, cellulose ether has a certain water retaining effect, but it will significantly affect the flow properties of concrete. For this reason, a large number of scholars have conducted research and synthesized new concrete water retaining agents in order to obtain ideal application effects.

[0004] Chinese patent CN115536779A discloses a carboxyl-hydroxyl condensation cross-linking concrete water retainer and its preparation method. The carboxyl-hydroxyl condensation cross-linking concrete water retainer comprises the following raw materials in proportion by weight: 5-25 parts of unsaturated carboxylic acid monomer, 30-50 parts of unsaturated amide monomer, 20-40 parts of functional monomer, 2-5 parts of cross-linking agent, and 3-7 parts of initiator. In this patent, due to the introduction of the cross-linking agent, a highly water-absorbing network structure is formed, which effectively inhibits the loss of free water in the concrete and improves the effect of the concrete's anti-segregation and water bleeding; but this method also has the disadvantage of having a greater impact on the fluidity of the concrete.

[0005] Chinese patent CN101538351A discloses a method for preparing a polycarboxylate type concrete water reducing agent thickening and water retaining agent, which uses corn starch, acrylic acid, methacrylic acid, butyl acrylate, etc. as raw materials, firstly degrades the starch appropriately, and then copolymerizes with acrylic acid, methacrylic acid, and butyl acrylate to obtain a polycarboxylate type concrete high-efficiency water reducing agent thickening and water retaining agent. The use of the thickening and water retaining agent can significantly improve the defects of concrete slurry bleeding, water bleeding, and sand and gravel segregation, and will not affect the flow properties of concrete; however, due to the presence of a large number of carboxyl groups in the molecular structure of the thickening and water retaining agent, the setting time of the concrete mixed with the thickening and water retaining agent will be further prolonged, and its early strength will be reduced. Summary of the invention

[0006] The purpose of the present invention is to provide an early-strength concrete water retaining agent to solve the problems of poor concrete state and segregation and bleeding when mixing concrete with machine-made sand and low early strength when using polycarboxylate water reducer; the present invention also provides a preparation method of the early-strength concrete water retaining agent.

[0007] The early-strength concrete water-retaining agent of the present invention is made of unsaturated amide monomers, unsaturated ester monomers, unsaturated sulfonic acid monomers, cross-linking monomers, initiators, reducing agents, water, graphene oxide and intercalating agents; wherein the cross-linking monomer is 1,8-bismaleimide-diglycol and the intercalating agent is potassium nitrate.

[0008] The unsaturated amide monomer is acrylamide or N-hydroxymethyl acrylamide, the unsaturated ester monomer is hydroxyethyl acrylate or hydroxypropyl acrylate, the unsaturated sulfonic acid monomer is sodium allyl sulfonate or sodium methacrylic sulfonate, and the molar ratio of the unsaturated amide monomer, the unsaturated ester monomer, the unsaturated sulfonic acid monomer and the crosslinking monomer is 1:0.2-0.3:0.05-0.1:0.01-0.02.

[0009] The initiator is sodium peroxide or ammonium persulfate, and the amount of the initiator is 1.0-1.8wt.% of the total mass of the unsaturated amide monomers, the unsaturated ester monomers, the unsaturated sulfonic acid monomers and the crosslinking monomers.

[0010] The reducing agent is sodium bisulfite or sodium bleaching powder, and the mass ratio of the initiator to the reducing agent is 1:0.5-1.

[0011] The ratio of the total mass of unsaturated amide monomers, unsaturated ester monomers, unsaturated sulfonic acid monomers, cross-linking monomers, initiators, reducing agents and water to the mass of graphene oxide is 997-999:1-3.

[0012] The mass ratio of graphene oxide to intercalant is 1:1-2.

[0013] The amount of water used is 88.6-90.3wt.% of the total mass of the early-strength concrete water-retaining agent.

[0014] The preparation method of the early-strength concrete water-retaining agent of the present invention comprises the following steps:

[0015] (1) preparing a base liquid by mixing unsaturated amide monomers, unsaturated ester monomers, unsaturated sulfonic acid monomers, crosslinking monomers and water and heating the base liquid to obtain a heated base liquid;

[0016] (2) preparing a reducing agent and water into solution A, and preparing an initiator and water into solution B;

[0017] (3) adding solution A and solution B simultaneously to the heated base solution obtained in step (1), keeping the temperature to react, cooling, and adding water to obtain a water retaining agent solution;

[0018] (4) adding graphene oxide to the water retaining agent solution obtained in step (3) and stirring to obtain a water retaining agent-graphene oxide solution;

[0019] (5) Water-retaining agent: Add intercalating agent to graphene oxide solution and stir to obtain early-strength concrete water-retaining agent.

[0020] In step (1), the concentration of the base liquid is 30-40 wt.%, and the heating temperature is 40-50°C.

[0021] In step (2), the concentration of solution A is 20-30 wt.%, and the concentration of solution B is 1.0-3.0 wt.%.

[0022] In step (3), the addition time of solution A is 0.5-1.5h, and the addition time of solution B is 1.0-2.0h; the insulation reaction temperature is 40-50°C, and the insulation reaction time is 0.5-1.0h; the temperature is lowered to below 35°C, and the solid content of the water retaining agent solution is 9.5-10.5wt.%.

[0023] The stirring time in step (4) is 3.0-6.0h.

[0024] The stirring time in step (5) is 0.5-1.0h.

[0025] The solid content of the early strength concrete water retaining agent in step (5) is 9.7-11.4wt.%.

[0026] When the early-strength concrete water retaining agent of the present invention is applied to concrete, the dosage of the early-strength concrete water retaining agent is 0.01-0.05wt.% of the dosage of the cementitious material.

[0027] The present invention adopts unsaturated sulfonic acid monomers to replace the commonly used unsaturated carboxyl monomers, and the sulfonic acid group will not complex with calcium ions to cause a delayed effect on cement hydration. After the sulfonic acid group is introduced into the molecular structure of the water retaining agent, it has a dispersing effect on cement particles due to its electrostatic repulsion, reducing the influence of the water retaining agent on the dispersibility of the water reducing agent. At the same time, the unsaturated sulfonic acid monomer also has a chain transfer effect, which can effectively prevent the explosion phenomenon when the water retaining agent is polymerized. The cross-linking monomer 1,8-bismaleimide-diglycol is polymerized into the molecular structure of the water retaining agent. In addition to cross-linking to form a network structure, it can also provide an oxyethylene ether group, play a surface activity and steric hindrance role, increase the dispersibility of the water retaining agent to cement, and effectively disperse graphene oxide. In addition, the potassium ions in the intercalating agent potassium nitrate can enter the interlayer of graphene oxide, corrode the interlayer structure of graphene oxide, increase its surface area, provide a larger nucleation site for cement hydration, promote the hydration reaction, and improve the early strength of concrete.

[0028] The beneficial effects of the present invention are as follows:

[0029] (1) The present invention introduces sulfonic acid groups into the concrete water retaining agent molecules, which, due to the electrostatic repulsion, will increase its dispersibility on cement particles and reduce the impact on the fluidity of concrete. At the same time, since the sulfonic acid groups will not form a complex with calcium ions, they will not cause a slow setting effect on cement, thereby avoiding the reduction of the early strength of concrete. Unsaturated sulfonic acid monomers have a chain transfer effect, which can effectively adjust the molecular weight of the water retaining agent and prevent the occurrence of implosion.

[0030] (2) 1,8-bismaleimide-diglycol is polymerized into the molecular structure of the water retainer. Since it contains two unsaturated double bonds, it can promote the cross-linking of the water retainer to form a network structure, which can effectively inhibit the loss of water in the concrete. At the same time, the ethylene oxide ether group in 1,8-bismaleimide-diglycol gives the water retainer surface activity, which can effectively disperse graphene oxide, reduce graphene oxide flocculation, and improve the homogeneity of the early strength concrete water retainer.

[0031] (3) The potassium ions of the intercalant potassium nitrate enter the crystal plane space of graphene oxide, play an etching role, increase the surface area, provide a larger nucleation area for cement hydration, increase the early generation of cement hydration products, and promote the improvement of the early strength of concrete; in addition, graphene oxide is hygroscopic and can maintain the humid environment required for cement hydration, which is beneficial to the growth of concrete strength.

[0032] (4) After the ethylene oxide group in 1,8-bismaleimide-diglycol is introduced into the molecular structure of the water retaining agent, it is easy to adsorb potassium ions in the intercalant due to the large number of oxygen atoms in the ethylene oxide group. When graphene oxide is added to the water retaining agent solution and stirred, the water retaining agent molecules will adsorb onto the graphene oxide. The ethylene oxide group on the water retaining agent molecule can promote potassium ions to enter the crystal plane space of graphene oxide more easily.

[0033] (5) The preparation method of the present invention adopts a redox initiation system, which improves the initiation efficiency.

[0034] (6) When the dosage of the early strength concrete water retaining agent in the present invention is 0.01-0.05wt.% of the cement dosage, it can not only ensure a good water retention effect, but also improve the early strength of concrete. DETAILED DESCRIPTION

[0035] The present invention is further described below with reference to the embodiments.

[0036] The substances are abbreviated as follows:

[0037] BMPEG stands for 1,8-bismaleimido-diglycol, AM stands for acrylamide, NAM stands for N-hydroxymethylacrylamide, MBA stands for N,N-methylenebisacrylamide, HEA stands for hydroxyethyl acrylate, HPA stands for hydroxypropyl acrylate, Na2O2 stands for sodium peroxide, AA stands for acrylic acid, APS stands for ammonium persulfate, SFA stands for sodium formaldehyde sulfite, NaHSO3 stands for sodium bisulfite, SAS stands for sodium allyl sulfonate, MAS stands for sodium methyl methacrylate sulfonate, and GO stands for graphene oxide.

[0038] Example 1

[0039] (1) 1 mol AM, 0.2 mol HEA, 0.05 mol SAS and 0.01 mol BMPEG were added into a four-necked reaction bottle equipped with a stirring and dropping device, and a certain amount of deionized water was added to prepare a 40 wt.% base liquid. The stirring was started and the temperature was raised to 40 °C in a water bath to obtain a heated base liquid.

[0040] (2) Mix NaHSO3 and an appropriate amount of water to prepare a 20wt.% solution A; add the initiator Na2O2 to a certain amount of water to prepare a 1.0wt.% solution B; wherein the amount of the initiator Na2O2 is 1.3wt.% of the total mass of AM, HEA, SAS and BMPEG, and the mass ratio of Na2O2 to NaHSO3 is 1:0.5;

[0041] (3) Solution A and Solution B are simultaneously and uniformly added dropwise to the heated base solution (40°C) obtained in step (1), and the addition time of Solution A and Solution B is 1.0 h and 1.5 h, respectively. After the addition of Solution B is completed, the reaction is continued at 40°C for 1.0 h, then the temperature is lowered to below 35°C, and water is added to obtain a water retaining agent solution with a solid content of 10 wt.%, denoted as BS1.

[0042] (4) Add GO to BS1, where the mass ratio of BS1 to GO is 998:2, and stir for 3.0 h until GO is completely dispersed to obtain a water-retaining agent-graphene oxide solution;

[0043] (5) Add the intercalating agent KNO3 to the water retaining agent-graphene oxide solution, where the mass ratio of GO to KNO3 is 1:2, and stir for 1.0 h to finally obtain an early-strength concrete water retaining agent with a solid content of 10.6 wt.%, which is denoted as GBS1. The test shows that the early-strength concrete water retaining agent has good homogeneity.

[0044] Example 2

[0045] (1) 1 mol AM, 0.2 mol HPA, 0.05 mol MAS and 0.01 mol BMPEG were added into a four-necked reaction bottle equipped with a stirring and dropping device, and a certain amount of deionized water was added to prepare a 30 wt.% base solution. Stirring was started and the temperature was raised to 50 °C in a water bath to obtain a heated base solution.

[0046] (2) SFA was mixed with an appropriate amount of water to prepare a 30 wt.% solution A; the initiator APS was added to a certain amount of water to prepare a 2.0 wt.% solution B; wherein the amount of the initiator APS was 1.5 wt.% of the total mass of AM, HPA, MAS and BMPEG, and the mass ratio of APS to SFA was 1:1;

[0047] (3) adding solution A and solution B simultaneously and uniformly to the heated base solution (50°C) obtained in step (1), the adding time of solution A and solution B being 1.0 h and 1.5 h respectively; after the addition of solution B is completed, the mixture is kept at 50°C for 1.0 h, then cooled to below 35°C, and water is added to obtain a water retaining agent solution having a solid content of 9.5 wt.%, denoted as BS2;

[0048] (4) Add GO to BS2, where the mass ratio of BS2 to GO is 997:3, and stir for 4.0 h until GO is completely dispersed to obtain a water-retaining agent-graphene oxide solution;

[0049] (5) Add the intercalating agent KNO3 to the water retaining agent-graphene oxide solution, where the mass ratio of GO to KNO3 is 1:1, and stir for 1.0 h to finally obtain an early-strength concrete water retaining agent with a solid content of 10.1 wt.%, which is denoted as GBS2. The test shows that the early-strength concrete water retaining agent has good homogeneity.

[0050] Example 3

[0051] (1) 1 mol NAM, 0.3 mol HEA, 0.07 mol MAS and 0.015 mol BMPEG were added into a four-necked reaction bottle equipped with a stirring and dropping device, and a certain amount of deionized water was added to prepare a 35 wt.% base solution. Stirring was started and the temperature was raised to 45 °C in a water bath to obtain a heated base solution.

[0052] (2) Mix NaHSO3 and an appropriate amount of water to prepare a 20wt.% solution A; add the initiator Na2O2 to a certain amount of water to prepare a 1.0wt.% solution B; wherein the amount of the initiator Na2O2 is 1.8wt.% of the total mass of NAM, HEA, MAS and BMPEG, and the mass ratio of Na2O2 to NaHSO3 is 1:0.5;

[0053] (3) adding solution A and solution B simultaneously and uniformly to the heated base solution (45°C) obtained in step (1), the adding time of solution A and solution B being 0.5 h and 1.0 h respectively; after the addition of solution B is completed, the mixture is kept at 45°C for 1.0 h, then cooled to below 35°C, and water is added to obtain a water retaining agent solution having a solid content of 10.5 wt.%, denoted as BS3;

[0054] (4) Add GO to BS3, where the mass ratio of BS3 to GO is 999:1, and stir for 5.0 h until GO is completely dispersed to obtain a water-retaining agent-graphene oxide solution;

[0055] (5) Add the intercalating agent KNO3 to the water retaining agent-graphene oxide solution, where the mass ratio of GO to KNO3 is 1:1.5, and stir for 0.5 h to finally obtain an early-strength concrete water retaining agent with a solid content of 10.8 wt.%, denoted as GBS3. The test shows that the early-strength concrete water retaining agent has good homogeneity.

[0056] Example 4

[0057] (1) 1 mol NAM, 0.3 mol HEA, 0.1 mol MAS and 0.01 mol BMPEG were added into a four-necked reaction bottle equipped with a stirring and dropping device, and a certain amount of deionized water was added to prepare a 35 wt.% base solution. Stirring was started and the temperature was raised to 45 °C in a water bath to obtain a heated base solution.

[0058] (2) SFA was mixed with an appropriate amount of water to prepare a 25 wt.% solution A; the initiator Na2O2 was added to a certain amount of water to prepare a 2.0 wt.% solution B; wherein the amount of the initiator Na2O2 was 1.0 wt.% of the total mass of NAM, HEA, MAS and BMPEG, and the mass ratio of Na2O2 to SFA was 1:0.6;

[0059] (3) adding solution A and solution B simultaneously and uniformly to the heated base solution (45°C) obtained in step (1), the adding time of solution A and solution B being 0.5 h and 1.0 h respectively; after the addition of solution B is completed, the reaction is continued at 45°C for 0.8 h, then the temperature is lowered to below 35°C, and water is added to obtain a water retaining agent solution with a solid content of 10 wt.%, denoted as BS4;

[0060] (4) Add GO to BS4, where the mass ratio of BS4 to GO is 998:2, and stir for 6.0 h until GO is completely dispersed to obtain a water-retaining agent-graphene oxide solution;

[0061] (5) Add the intercalating agent KNO3 to the water retaining agent-graphene oxide solution, where the mass ratio of GO to KNO3 is 1:1, and stir for 0.8 h to finally obtain an early-strength concrete water retaining agent with a solid content of 10.4 wt.%, which is denoted as GBS4. ​​The test shows that the early-strength concrete water retaining agent has good homogeneity.

[0062] Example 5

[0063] (1) 1 mol NAM, 0.25 mol HPA, 0.1 mol SAS and 0.02 mol BMPEG were added into a four-necked reaction bottle equipped with a stirring and dropping device, and a certain amount of deionized water was added to prepare a 40 wt.% base solution. The stirring was started and the temperature was raised to 50 °C in a water bath to obtain a heated base solution.

[0064] (2) Mix NaHSO3 and an appropriate amount of water to prepare a 30wt.% solution A; add the initiator APS to a certain amount of water to prepare a 3.0wt.% solution B; wherein the amount of initiator APS is 1.5wt.% of the total mass of NAM, HPA, SAS and BMPEG, and the mass ratio of APS to NaHSO3 is 1:0.5;

[0065] (3) Solution A and Solution B are simultaneously and uniformly added dropwise to the heated base solution (50°C) obtained in step (1), and the addition time of Solution A and Solution B is 1.5 h and 2.0 h, respectively. After the addition of Solution B is completed, the reaction is continued at 50°C for 0.5 h, then the temperature is lowered to below 35°C, and water is added to obtain a water retaining agent solution with a solid content of 10 wt.%, denoted as BS5.

[0066] (4) Add GO to BS5, where the mass ratio of BS5 to GO is 999:1, and stir for 6.0 h until GO is completely dispersed to obtain a water-retaining agent-graphene oxide solution;

[0067] (5) Add the intercalating agent KNO3 to the water retaining agent-graphene oxide solution, where the mass ratio of GO to KNO3 is 1:1, and stir for 1.0 h to finally obtain an early-strength concrete water retaining agent with a solid content of 10.2 wt.%, which is denoted as GBS5. The test shows that the early-strength concrete water retaining agent has good homogeneity.

[0068] Comparative Example 1

[0069] SAS was changed to AA, and the other steps were the same as in Example 1 to obtain a concrete water retaining agent with a solid content of 10.6 wt.%, which was recorded as BC1.

[0070] Comparative Example 2

[0071] Without adding GO, the other steps were the same as in Example 1, and a concrete water retaining agent with a solid content of 10.4 wt.% was obtained, which was recorded as BC2.

[0072] Comparative Example 3

[0073] Without adding the intercalant KNO3, the other steps were the same as in Example 1, and a concrete water retaining agent with a solid content of 10.2 wt.% was obtained, which was recorded as BC3.

[0074] Comparative Example 4

[0075] BMPEG was changed to MBA, and the other steps were the same as those in Example 1 to obtain a concrete water retaining agent with a solid content of 10.6 wt.%, which was recorded as BC4. Testing showed that the concrete water retaining agent had poor homogeneity.

[0076] The effects of Examples 1-5 and Comparative Examples 1-4 were tested:

[0077] According to the national standard GB8076-2008, the concrete was tested, and the standard cement was selected. The sand was machine-made sand with a fineness modulus of 3.1 and a mud content of 0.8%. The gravel was crushed stone with a nominal particle size of 5-20 mm, and the grading type was secondary, of which 5-10 mm crushed stone accounted for 30% and 10-20 mm crushed stone accounted for 70%, meeting the continuous grading requirements. The polycarboxylate water reducer (NOF-AS standard type) was manufactured by Shandong Huawei Yinkai Building Materials Technology Co., Ltd. The standard concrete mix ratio was standard cement: sand: gravel: water = 360: 895: 1005: 230, in kg; the amount of polycarboxylate water reducer (NOF-AS standard type) was 1.0 wt.% of the standard cement amount. The amount of the early strength concrete water retainer of Examples 1-5, the concrete water retainer of Comparative Examples 1-4, and the methyl cellulose ether was all 0.02 wt.% of the standard cement amount. The water bleeding rate, initial slump and 1d, 3d and 28d compressive strength of the benchmark concrete added with different water-retaining agents were tested, and the results are shown in Table 1.

[0078]

[0079] It can be seen from Table 1 that compared with the benchmark concrete added with BC1, BC2, BC3, BC4 and methyl cellulose ether, the benchmark concrete added with early-strength GBS1, GBS2, GBS3, GBS4 and GBS5 has a lower bleeding rate, less effect on the slump of concrete and higher early strength (1d and 3d compressive strength); this shows that the early-strength concrete water retaining agent has a low bleeding rate, less effect on the slump of concrete, better early strength, and higher later strength.

Claims

1. An early strength concrete water retaining agent, characterized in that It is made of unsaturated amide monomers, unsaturated ester monomers, unsaturated sulfonic acid monomers, cross-linking monomers, initiators, reducing agents, water, graphene oxide and intercalating agents; wherein the cross-linking monomer is 1,8-bismaleimide-diglycol, and the intercalating agent is potassium nitrate; The preparation method of the early strength concrete water retaining agent comprises the following steps: (1) preparing a base liquid by mixing unsaturated amide monomers, unsaturated ester monomers, unsaturated sulfonic acid monomers, crosslinking monomers and water and heating the base liquid to obtain a heated base liquid; (2) preparing a reducing agent and water into solution A, and preparing an initiator and water into solution B; (3) adding solution A and solution B simultaneously to the heated base solution obtained in step (1), keeping the temperature to react, cooling, and adding water to obtain a water retaining agent solution; (4) adding graphene oxide to the water retaining agent solution obtained in step (3) and stirring to obtain a water retaining agent-graphene oxide solution; (5) Water-retaining agent: Add intercalating agent to graphene oxide solution and stir to obtain early-strength concrete water-retaining agent.

2. The early strength concrete water retaining agent according to claim 1, characterized in that The unsaturated amide monomer is acrylamide or N-hydroxymethyl acrylamide, the unsaturated ester monomer is hydroxyethyl acrylate or hydroxypropyl acrylate, the unsaturated sulfonic acid monomer is sodium allyl sulfonate or sodium methacrylic sulfonate, and the molar ratio of the unsaturated amide monomer, the unsaturated ester monomer, the unsaturated sulfonic acid monomer and the crosslinking monomer is 1:0.2-0.3:0.05-0.1:0.01-0.

02.

3. The early strength concrete water retaining agent according to claim 1, characterized in that The initiator is sodium peroxide or ammonium persulfate, and the amount of the initiator is 1.0-1.8wt.% of the total mass of the unsaturated amide monomers, unsaturated ester monomers, unsaturated sulfonic acid monomers and cross-linking monomers; the reducing agent is sodium bisulfite or bleaching powder, and the mass ratio of the initiator to the reducing agent is 1:0.5-1.

4. The early strength concrete water retaining agent according to claim 1, characterized in that The mass ratio of the total mass of unsaturated amide monomers, unsaturated ester monomers, unsaturated sulfonic acid monomers, crosslinking monomers, initiators, reducing agents and water to the mass of graphene oxide is 997-999:1-3, and the mass ratio of graphene oxide to the intercalating agent is 1:1-2.

5. The early strength concrete water retaining agent according to claim 1, characterized in that In step (1), the concentration of the base liquid is 30-40 wt.%, and the heating temperature is 40-50°C.

6. The early strength concrete water retaining agent according to claim 1, characterized in that In step (2), the concentration of solution A is 20-30 wt.%, and the concentration of solution B is 1.0-3.0 wt.%.

7. The early strength concrete water retaining agent according to claim 1, characterized in that In step (3), the addition time of solution A is 0.5-1.5h, and the addition time of solution B is 1.0-2.0h; the insulation reaction temperature is 40-50°C, and the insulation reaction time is 0.5-1.0h; the temperature is lowered to below 35°C, and the solid content of the water retaining agent solution is 9.5-10.5wt.%.

8. The early strength concrete water retaining agent according to claim 1, characterized in that The stirring time in step (4) is 3.0-6.0h.

9. The early strength concrete water retaining agent according to claim 1, characterized in that The stirring time in step (5) is 0.5-1.0h.

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