A viscosity-reducing polycarboxylic acid water-reducing agent and a preparation method thereof

Abstract

The invention relates to the technical field of concrete admixtures, and in particular to a viscosity-reducing polycarboxylate water-reducing agent and a preparation method thereof. The viscosity-reducing polycarboxylate water-reducing agent comprises, by weight, 90-110 parts of a homemade polycarboxylate water-reducing agent mother solution, 27-45 parts of modified graphene oxide, 0.3-0.6 parts of a foam stabilizer, 1.1-1.9 parts of a defoamer, and 280-320 parts of water. The invention modifies graphene oxide by N,N-dimethyl-2-hydroxyethylamine, so that the graphene oxide has better interlayer friction performance and more active sites. The invention introduces 1-(4-bromobutyl)-pyrene on the surface of the polycarboxylate water-reducing agent with a network structure, so as to improve its dispersibility and thus reduce the viscosity of concrete.

Description

Technical Field

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

[0002] Polycarboxylate water-reducing agent is a new type of concrete admixture introduced into my country in the 1970s. It is copolymerized by unsaturated monomers containing carboxyl groups and other monomers. It is adsorbed on the surface of cement particles during the cement hydration process to form a highly dispersed, stable and uniform negative ion surfactant adsorption film, thereby giving concrete excellent performance in water reduction, slump retention, plasticization, shrinkage and environmental protection.

[0003] Among them, polycarboxylic acid high-performance water-reducing agent provides guarantee for the preparation of high-strength and high-performance concrete due to its high water reduction rate and high slump retention ability. In modern construction, high-grade concrete is increasingly used due to its advantages of fast hardening, high strength, high homogeneity and high density. However, in order to make high-grade concrete reach high strength or ultra-high strength, a large amount of cementitious materials are generally used in construction to reduce the water-cement ratio, resulting in high viscosity of fresh concrete and slow flow rate during pumping. Such operation will undoubtedly bring great difficulties to the mixing, preparation, transportation and pumping of the mixture, which will not only reduce construction efficiency, but also make it difficult to ensure the compactness of the pouring.

[0004] In order to reduce the viscosity of concrete, the general practice is: adding an appropriate amount of viscosity reducer to the polycarboxylate water reducer, but the water reduction efficiency of the existing viscosity reducer is low, and its compatibility with the water reducer is not ideal, and it cannot simultaneously meet the dual requirements of concrete for water reduction and viscosity reduction; increasing the amount of water used during mixing will cause the concrete mixture to bleed and over-retard, which is obviously not advisable; adding a certain amount of high-quality fly ash to the concrete, using the spherical glass beads contained in it to reduce the viscosity of the slurry, but the cost is high and the effect is limited.

[0005] In the prior art, there is a method of introducing tiny bubbles that play a "ball effect" into concrete to improve the fluidity of concrete. For example, in Chinese invention patent CN107382210A, two air-entraining agents are compounded to introduce beneficial small bubbles into the water-reducing agent, thereby improving the fluidity of the slurry and reducing the viscosity of the slurry. However, after the bubbles are introduced into the concrete, the strength of the concrete will be reduced to varying degrees (for every 1.0% of the volume of the concrete introduced, the compressive strength of the concrete will be reduced by 3%-5%), and the number and size of the introduced bubbles are also difficult to control.

[0006] Therefore, there is an urgent need for a viscosity-reducing polycarboxylic acid water-reducing agent that can effectively reduce the viscosity of concrete without affecting the strength of the concrete. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention aims to provide a viscosity-reducing polycarboxylic acid water-reducing agent and a preparation method thereof.

[0008] The present invention is achieved through the following technical scheme: a viscosity-reducing polycarboxylic acid water-reducing agent, which comprises, by weight, 90-110 parts of a homemade polycarboxylic acid water-reducing agent mother liquor, 27-45 parts of modified graphene oxide, 0.3-0.6 parts of a foam stabilizer, 1.1-1.9 parts of a defoamer, and 280-320 parts of water.

[0009] Furthermore, the homemade polycarboxylate water-reducing agent mother liquor comprises, by weight: 3.2-6.5 parts of pentaerythritol, 22-38 parts of acrylic acid, 9-12 parts of p-toluenesulfonic acid, 0.025-0.03 parts of hydroquinone, 36-45 parts of toluene, 4.6-6.8 parts of isobutylene polyoxyethylene ether, 0.06-0.13 parts of thioglycolic acid, 0.25-0.38 parts of ammonium persulfate, 1.8-2.7 parts of 1-(4-bromobutyl)-pyrene, 0.48-0.97 parts of sodium hydroxide, and 19-28 parts of water.

[0010] Furthermore, the viscosity-reducing polycarboxylic acid water-reducing agent includes, by weight: 98 parts of homemade polycarboxylic acid water-reducing agent mother liquor, 32 parts of modified graphene oxide, 0.45 parts of foam stabilizer, 1.7 parts of defoamer, and 305 parts of water.

[0011] Furthermore, in parts by weight, the homemade polycarboxylate water-reducing agent mother liquor includes: 5.9 parts of pentaerythritol, 35 parts of acrylic acid, 11 parts of p-toluenesulfonic acid, 0.029 parts of hydroquinone, 42 parts of toluene, 5.8 parts of isobutylene polyoxyethylene ether, 0.1 parts of thioglycolic acid, 0.36 parts of ammonium persulfate, 2.5 parts of 1-(4-bromobutyl)-pyrene, 0.82 parts of concentrated sulfuric acid, and 24 parts of water.

[0012] Furthermore, the foam stabilizer is sodium rosin acid; and the defoamer is a polyether defoamer.

[0013] Furthermore, the preparation step of the modified graphene oxide is as follows: at room temperature, N, N-dimethyl-2-hydroxyethylamine is added to anhydrous ethanol to disperse and prepare an N, N-dimethyl-2-hydroxyethylamine ethanol solution, graphene oxide is added to anhydrous ethanol to disperse and prepare a graphene oxide ethanol solution, and the N, N-dimethyl-2-hydroxyethylamine ethanol solution is added dropwise to the graphene oxide ethanol solution under stirring, and stirring is continued for 2 hours after the dropwise addition, ultrasonic dispersion is carried out at 60°C for 24 hours, and the reaction is carried out at room temperature for 6 hours, and the precipitate is filtered, washed with ethanol 3 times, and the modified graphene oxide is obtained after drying.

[0014] Furthermore, the preparation method of the homemade polycarboxylate water-reducing agent mother solution is:

[0015] Pentaerythritol and a portion of acrylic acid are added to a four-necked flask with a magnetic stirrer, and p-toluenesulfonic acid and hydroquinone are added in sequence. When the temperature reaches 90°C, toluene is added, and the reaction temperature is controlled at 80-90°C. The reaction product water is collected, and after reacting for 7 hours, the toluene is removed by vacuum to obtain the first product;

[0016] The first product, isobutylene polyoxyethylene ether and another part of acrylic acid are added to a four-necked flask and mixed evenly, and a certain amount of water is added for dilution, the temperature is set to 65°C, after stirring evenly, thioglycolic acid aqueous solution and ammonium persulfate aqueous solution are added dropwise to the flask, and the mixture is reacted at a constant temperature for 5 hours and then cooled to obtain the second product;

[0017] The second product and 1-(4-bromobutyl)-pyrene were added to a reaction container, sodium hydroxide was added, the reaction temperature was raised to 50° C., and after reacting for 6 hours, a homemade polycarboxylate water-reducing agent mother liquor was obtained.

[0018] Furthermore, the homemade polycarboxylate water-reducing agent mother solution and modified graphene oxide were added to the reaction container in sequence, and after stirring for 45 minutes, a foam stabilizer and a defoamer were added in sequence, and stirred for 10 minutes to obtain a viscosity-reducing polycarboxylate water-reducing agent.

[0019] Furthermore, the polyether defoamer used in the present invention is purchased from Foshan Jingqi Chemical Technology Co., Ltd.

[0020] Furthermore, the foam stabilizer with sodium rosin acid as raw material used in the present invention is purchased from Henan Qiantelu Chemical Products Co., Ltd.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] 1. In the process of modifying graphene oxide with N,N-dimethyl-2-hydroxyethylamine, N,N-dimethyl-2-hydroxyethylamine will cause graphene oxide to undergo epoxy ring-opening reaction, thereby introducing more hydroxyl groups on the surface of graphene oxide. Since the presence of C-O bonds will hinder the interlayer sliding of graphene oxide, this reaction can reduce the content of C-O bonds on the surface of graphene oxide, and hydroxyl groups can improve the interlayer friction performance of graphene oxide, thereby increasing the fluidity of cement and reducing the viscosity of cement.

[0023] 2. The N atoms in N,N-dimethyl-2-hydroxyethylamine can destroy the grid structure of carbon atoms in graphene oxide, resulting in defect sites on the surface of graphene oxide. These defect sites can serve as active sites on the surface of graphene oxide and improve the activity of graphene oxide, making it easier to adsorb on the cement surface, increasing the surface energy of cement particles, helping to form a hydration film on the surface of cement particles, reducing the interaction between cement particles, and facilitating the dispersion of cement particles.

[0024] 3. 1-(4-bromobutyl)-pyrene is introduced into the star-shaped polycarboxylate water-reducing agent, wherein bromine and carboxyl groups undergo substitution reaction. 1-(4-bromobutyl)-pyrene itself has a stable structure and high solubility in cement paste. Its addition can increase the distance between the side arms of the water-reducing agent and increase the exposed area of ​​the carboxyl group, making it easier for the polycarboxylate water-reducing agent to adsorb cement particles. At the same time, the structure of 1-(4-bromobutyl)-pyrene itself is stretched, making it difficult for cement particles to agglomerate, further improving the dispersion fluidity of cement and reducing its viscosity.

[0025] 4. After the modified graphene oxide is mixed with the homemade polycarboxylate water-reducing agent, part of the modified graphene oxide will be adsorbed between the star-shaped polycarboxylate water-reducing agent molecules, making the two more closely combined, thereby increasing the strength and hardness of the concrete. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment, and the illustrative embodiments of the present invention and its description are only used to explain the present invention, and are not used as limitation of the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper limit and the lower limit of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the range is also included in the present invention. The upper limit and lower limit of these smaller ranges can be independently included or excluded in the scope.

[0027] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0028] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0029] The words "include", "comprises", "have", "contains", etc. used in this article are open-ended.

[0030] The term "including but not limited to" means including but not limited to.

[0031] The "parts" indicated in the following examples are all parts by weight.

[0032] Example 1

[0033] A viscosity-reducing polycarboxylate water-reducing agent consists of 90 parts of a homemade polycarboxylate water-reducing agent mother liquor, 27 parts of modified graphene oxide, 0.3 parts of a foam stabilizer, 1.1 parts of a defoamer, and 280 parts of water, calculated by weight.

[0034] The homemade polycarboxylate water-reducing agent mother liquor is composed of 3.2 parts of pentaerythritol, 22 parts of acrylic acid, 9 parts of p-toluenesulfonic acid, 0.025 parts of hydroquinone, 36 parts of toluene, 4.6 parts of isobutylene polyoxyethylene ether, 0.06 parts of thioglycolic acid, 0.25 parts of ammonium persulfate, 1.8 parts of 1-(4-bromobutyl)-pyrene, 0.48 parts of sodium hydroxide and 19 parts of water.

[0035] Among them, the foam stabilizer is sodium rosin acid; the defoamer is a polyether defoamer; the graphite powder is purchased from Shenzhen Hanhui Graphite Co., Ltd., with a mesh size of 180 mesh.

[0036] Preparation method of graphene oxide: weigh 69 ml of concentrated sulfuric acid, add 4.8 g of sodium nitrate to dissolve, ice bath and magnetically stir, add 3 g of graphite powder, continue stirring for 45 min, slowly add 9 g of potassium permanganate, continue ice bath and continue stirring for 60 min, then move the beaker from the ice bath to a 40°C oil bath, continue stirring for 90 min, slowly add 138 ml of deionized water and move to a 100°C oil bath, continue to react for 15 min, then return to 60°C at room temperature, add 270 ml of distilled water, slowly add 45 ml of hydrogen peroxide, let stand for 12 h, then centrifuge to obtain a graphene oxide filter cake, wash it 5 times with 5% hydrochloric acid solvent, then wash it with distilled water until the solution pH = 7, filter and freeze-dry for use.

[0037] The preparation method of modified graphene oxide is:

[0038] Graphene oxide pretreatment: 10 mg of the prepared graphene oxide was added into 20 ml of anhydrous ethanol to disperse and prepare a graphene oxide ethanol solution, and the solution was allowed to stand for later use.

[0039] N,N-dimethyl-2-hydroxyethylamine pretreatment: weigh 10 ml of N,N-dimethyl-2-hydroxyethylamine and add it into 10 ml of anhydrous ethanol to disperse and prepare N,N-dimethyl-2-hydroxyethylamine ethanol solution, and let it stand for use.

[0040] At room temperature, 15 ml of N, N-dimethyl-2-hydroxyethylamine ethanol solution was added dropwise to 25 ml of graphene oxide ethanol solution under stirring. The stirring was continued for 2 h after the addition. After ultrasonic dispersion at 60°C for 24 h, the mixture was reacted at room temperature for 6 h. The precipitate was filtered, washed with ethanol three times, and dried to obtain modified graphene oxide.

[0041] The preparation method of the homemade polycarboxylate water-reducing agent mother solution is as follows:

[0042] 3.2 parts of pentaerythritol and 45% of acrylic acid were added to a four-necked flask with a magnetic stirrer, and 9 parts of p-toluenesulfonic acid and 0.025 parts of hydroquinone were added in sequence. When the temperature reached 90°C, 36 parts of toluene were added. The reaction temperature was controlled at 80-90°C, and the reaction product water was collected. After reacting for 7 hours, the toluene was removed by vacuum to obtain the first product.

[0043] The first product, 4.6 parts of isobutylene polyoxyethylene ether, and the remaining 55% of acrylic acid were added to a four-necked flask and mixed evenly, and a certain amount of water was added for dilution, and the temperature was set to 65°C. After stirring evenly, 0.06 parts of thioglycolic acid aqueous solution and 0.25 parts of ammonium persulfate aqueous solution were added dropwise to the flask, and the mixture was reacted at a constant temperature for 5 hours and then cooled to obtain the second product;

[0044] The second product and 1.8 parts of 1-(4-bromobutyl)-pyrene were added to a reaction container, 0.48 parts of sodium hydroxide were added, the reaction temperature was raised to 50° C., and after reacting for 6 hours, a homemade polycarboxylate water-reducing agent mother liquor was obtained.

[0045] The preparation method of the viscosity-reducing polycarboxylate water reducer is as follows: a homemade polycarboxylate water reducer mother liquor and modified graphene oxide are sequentially added into a reaction container, stirred for 45 minutes, and then a foam stabilizer and a defoamer are sequentially added, and stirred for 10 minutes to obtain the viscosity-reducing polycarboxylate water reducer.

[0046] The prepared polycarboxylate water-reducing agent was allowed to stand for 24 hours before being used in the C70 concrete test.

[0047] Example 2

[0048] A viscosity-reducing polycarboxylate water-reducing agent, which consists of 94 parts of a homemade polycarboxylate water-reducing agent mother liquor, 28 parts of modified graphene oxide, 0.35 parts of a foam stabilizer, 1.4 parts of a defoamer, and 290 parts of water, in parts by weight.

[0049] The homemade polycarboxylate water-reducing agent mother liquor is composed of 4.8 parts of pentaerythritol, 27 parts of acrylic acid, 10 parts of p-toluenesulfonic acid, 0.027 parts of hydroquinone, 39 parts of toluene, 5.2 parts of isobutylene polyoxyethylene ether, 0.08 parts of thioglycolic acid, 0.3 parts of ammonium persulfate, 2.2 parts of 1-(4-bromobutyl)-pyrene, 0.67 parts of sodium hydroxide and 21 parts of water.

[0050] Among them, the foam stabilizer is sodium rosin acid; the defoamer is a polyether defoamer; the graphite powder is purchased from Shenzhen Hanhui Graphite Co., Ltd., with a mesh size of 180 mesh.

[0051] Among them, the raw material procurement and preparation methods of the homemade polycarboxylate water-reducing agent mother solution, modified graphene oxide, etc. in Example 2 are consistent with those in Example 1; the prepared polycarboxylate water-reducing agent is left to stand for 24 hours and then used for the C70 concrete test.

[0052] Example 3

[0053] A viscosity-reducing polycarboxylic acid water-reducing agent, which consists of 98 parts of a homemade polycarboxylic acid water-reducing agent mother liquor, 32 parts of modified graphene oxide, 0.45 parts of a foam stabilizer, 1.7 parts of a defoamer, and 305 parts of water, in parts by weight.

[0054] The homemade polycarboxylate water-reducing agent mother liquor is composed of 5.9 parts of pentaerythritol, 35 parts of acrylic acid, 11 parts of p-toluenesulfonic acid, 0.029 parts of hydroquinone, 42 parts of toluene, 5.8 parts of isobutylene polyoxyethylene ether, 0.1 parts of thioglycolic acid, 0.36 parts of ammonium persulfate, 2.5 parts of 1-(4-bromobutyl)-pyrene, 0.82 parts of concentrated sulfuric acid, and 24 parts of water.

[0055] Among them, the foam stabilizer is sodium rosin acid; the defoamer is a polyether defoamer; the graphite powder is purchased from Shenzhen Hanhui Graphite Co., Ltd., with a mesh size of 180 mesh.

[0056] Among them, the raw material procurement and preparation methods of the homemade polycarboxylate water-reducing agent mother solution, modified graphene oxide, etc. in Example 3 are consistent with those in Example 1; the prepared polycarboxylate water-reducing agent is left to stand for 24 hours and then used for the C70 concrete test.

[0057] Example 4

[0058] A viscosity-reducing polycarboxylic acid water-reducing agent, which is composed, by weight, of 110 parts of a homemade polycarboxylic acid water-reducing agent mother liquor, 45 parts of modified graphene oxide, 0.6 parts of a foam stabilizer, 1.9 parts of a defoamer, and 320 parts of water.

[0059] The homemade polycarboxylate water-reducing agent mother liquor is composed of 6.5 parts of pentaerythritol, 38 parts of acrylic acid, 12 parts of p-toluenesulfonic acid, 0.03 parts of hydroquinone, 45 parts of toluene, 6.8 parts of isobutylene polyoxyethylene ether, 0.13 parts of thioglycolic acid, 0.38 parts of ammonium persulfate, 2.7 parts of 1-(4-bromobutyl)-pyrene, 0.97 parts of sodium hydroxide, and 28 parts of water.

[0060] Among them, the foam stabilizer is sodium rosin acid; the defoamer is a polyether defoamer; the graphite powder is purchased from Shenzhen Hanhui Graphite Co., Ltd., with a mesh size of 180 mesh.

[0061] Among them, the raw material procurement and preparation methods of the homemade polycarboxylate water-reducing agent mother solution, modified graphene oxide, etc. in Example 4 are consistent with those in Example 1; the prepared polycarboxylate water-reducing agent is left to stand for 24 hours and then used for the C70 concrete test.

[0062] Example 5

[0063] A viscosity-reducing polycarboxylate water-reducing agent, which consists, by weight, of 125 parts of a homemade polycarboxylate water-reducing agent mother liquor, 56 parts of modified graphene oxide, 0.9 parts of a foam stabilizer, 2.3 parts of a defoamer, and 350 parts of water.

[0064] The homemade polycarboxylate water-reducing agent mother liquor is composed of 7.2 parts of pentaerythritol, 45 parts of acrylic acid, 15 parts of p-toluenesulfonic acid, 0.035 parts of hydroquinone, 52 parts of toluene, 7.9 parts of isobutylene polyoxyethylene ether, 0.2 parts of thioglycolic acid, 0.56 parts of ammonium persulfate, 3 parts of 1-(4-bromobutyl)-pyrene, 1.1 parts of sodium hydroxide and 35 parts of water.

[0065] Among them, the foam stabilizer is sodium rosin acid; the defoamer is a polyether defoamer; the graphite powder is purchased from Shenzhen Hanhui Graphite Co., Ltd., with a mesh size of 180 mesh.

[0066] Among them, the raw material procurement and preparation methods of the homemade polycarboxylate water-reducing agent mother solution, modified graphene oxide, etc. in Example 5 are consistent with those in Example 1; the prepared polycarboxylate water-reducing agent is left to stand for 24 hours and then used for C70 concrete testing.

[0067] Comparative Example 1

[0068] The only difference between this comparative example and Example 3 is that a commercially available water reducer is used instead of the homemade polycarboxylate water reducer.

[0069] A polycarboxylate water reducer, which is composed of 98 parts of a commercially available polycarboxylate water reducer, 32 parts of modified graphene oxide, 0.45 parts of a foam stabilizer, 1.7 parts of a defoamer, and 305 parts of water, by weight;

[0070] Among them, the raw material procurement and preparation methods of modified graphene oxide, foam stabilizer and expansion agent in Comparative Example 2 are consistent with those in Example 1; the prepared polycarboxylic acid water reducer is left to stand for 24 hours and then used for C70 concrete testing.

[0071] Comparative Example 2

[0072] The only difference between this comparative example and Example 3 is that no modified graphene oxide is added.

[0073] A polycarboxylate water-reducing agent, which is composed of 98 parts of a homemade polycarboxylate water-reducing agent mother solution, 0.45 parts of a foam stabilizer, 1.7 parts of a defoamer, and 305 parts of water, by weight;

[0074] The homemade polycarboxylate water-reducing agent mother liquor is composed of 5.9 parts of pentaerythritol, 35 parts of acrylic acid, 11 parts of p-toluenesulfonic acid, 0.029 parts of hydroquinone, 42 parts of toluene, 5.8 parts of isobutylene polyoxyethylene ether, 0.1 parts of thioglycolic acid, 0.36 parts of ammonium persulfate, 2.5 parts of 1-(4-bromobutyl)-pyrene, 0.82 parts of sodium hydroxide, and 24 parts of water;

[0075] Among them, the raw material procurement and preparation methods of the homemade polycarboxylate water-reducing agent mother solution, foam stabilizer and expansion agent in Comparative Example 2 are consistent with those in Example 1; the prepared polycarboxylate water-reducing agent is left to stand for 24 hours and then used for C70 concrete testing.

[0076] Comparative Example 3

[0077] The only difference between this comparative example and Example 3 is that graphene oxide is used instead of modified graphene oxide.

[0078] A polycarboxylate water-reducing agent, which is composed of 98 parts of a homemade polycarboxylate water-reducing agent mother solution, 32 parts of graphene oxide, 0.45 parts of a foam stabilizer, 1.7 parts of a defoamer, and 305 parts of water, by weight;

[0079] The homemade polycarboxylate water-reducing agent mother liquor is composed of 5.9 parts of pentaerythritol, 35 parts of acrylic acid, 11 parts of p-toluenesulfonic acid, 0.029 parts of hydroquinone, 42 parts of toluene, 5.8 parts of isobutylene polyoxyethylene ether, 0.1 parts of thioglycolic acid, 0.36 parts of ammonium persulfate, 2.5 parts of 1-(4-bromobutyl)-pyrene, 0.82 parts of sodium hydroxide, and 24 parts of water;

[0080] Among them, the raw material procurement and preparation methods of the homemade polycarboxylate water-reducing agent mother solution, graphene oxide, foam stabilizer and defoamer in Comparative Example 3 are consistent with those in Example 1; the prepared polycarboxylate water-reducing agent is left to stand for 24 hours and then used for the C70 concrete test.

[0081] Comparative Example 4

[0082] The difference between this comparative example and Example 3 is that the polycarboxylate water-reducing agent to which propargylamine is added is used instead of the polycarboxylate water-reducing agent to which 1-(4-bromobutyl)-pyrene is added.

[0083] A polycarboxylate water-reducing agent, which is composed, by weight, of 98 parts of a polycarboxylate water-reducing agent mother solution to which propargylamine is added, 32 parts of modified graphene oxide, 0.45 parts of a foam stabilizer, 1.7 parts of a defoamer, and 305 parts of water;

[0084] The homemade polycarboxylate water-reducing agent mother liquor is composed of 5.9 parts of pentaerythritol, 35 parts of acrylic acid, 11 parts of p-toluenesulfonic acid, 0.029 parts of hydroquinone, 42 parts of toluene, 5.8 parts of isobutylene polyoxyethylene ether, 0.1 parts of thioglycolic acid, 0.36 parts of ammonium persulfate, 2.5 parts of propargylamine, 0.29 parts of concentrated sulfuric acid, and 24 parts of water;

[0085] The preparation method of the polycarboxylate water-reducing agent mother liquor added with propargylamine is as follows: 5.9 pentaerythritol and 45% acrylic acid are added into a four-necked flask with a magnetic stirrer, 11 parts of toluenesulfonic acid and 0.029 parts of hydroquinone are added in sequence, 42 parts of toluene are added when the temperature is raised to 90° C., the reaction temperature is controlled at 80-90° C., the reaction product water is collected, and after reacting for 7 hours, the toluene is removed by vacuum to obtain a primary product;

[0086] The primary product, 5.8 parts of isobutylene polyoxyethylene ether, and 55% of acrylic acid were added to a four-necked flask and mixed evenly, and a certain amount of water was added for dilution, and the temperature was set to 65°C. After stirring evenly, 0.1 parts of thioglycolic acid aqueous solution and 0.36 parts of ammonium persulfate aqueous solution were added dropwise to the flask, and the mixture was reacted at a constant temperature for 5 hours and then cooled to obtain a second product;

[0087] The second product, 2.5 parts of propargylamine and 0.29 parts of concentrated sulfuric acid were added into a four-necked flask and mixed evenly, and water was added for dilution. The temperature was set to 70° C., and after reacting for 8 hours, the mixture was cooled to room temperature to obtain a mother solution of polycarboxylic acid water-reducing agent with propargylamine added thereto.

[0088] Among them, the raw material procurement and preparation methods of the homemade modified graphene oxide, foam stabilizer and defoamer in Comparative Example 4 are consistent with those in Example 1; the prepared polycarboxylic acid water reducer is left to stand for 24 hours and then used for C70 concrete testing.

[0089] C70 concrete mix ratio: In this experimental example, the mix ratio of cement, fly ash, mineral powder, sand, crushed stone, water and admixture is 5.2:1:1:7.8:14:1.8:0.09. The cement used in the experiment is Onoda 52.5RPII cement; fly ash (grade I); mineral powder was purchased from Lingshou County Hongsheng Mineral Products Processing Plant; aggregate: fine aggregate is natural river sand with a fineness modulus of 2.6, and coarse aggregate has a particle size of 15-20mm; the dosage of polycarboxylic acid water reducer is 0.25% (solid content).

[0090] Application Test Example 1

[0091] The reference test standard for concrete expansion is GB50080-2016 "Standard for test methods for performance of ordinary concrete mixtures". The experimental results are shown in Table 1.

[0092] Table 1

[0093]

[0094] Analysis of test results: The expansion degree of concrete measures the flow dispersion of concrete and can reflect the viscosity of cement. The viscosity of concrete prepared by the optimal ratio of Example 3 in the embodiment is lower than that of other ratios. At the same time, the viscosity of concrete obtained by the ratios of Examples 1-4, in which the ratios of each raw material are within the protection scope of the present invention, is significantly lower than that of Example 5. The 0 min expansion degree of Example 5 is reduced by 13% compared with the 0 min expansion degree of Example 3. The possible reason is that excessive modified graphene oxide will agglomerate, thereby causing cement particles to clump together, resulting in increased viscosity of concrete.

[0095] It can be seen from the experimental data that the viscosity reduction effects of Examples 1-4 are significantly better than those of Examples 5 and Comparative Examples 1-4, indicating that the viscosity-reducing polycarboxylate water-reducing agent provided by the present invention can indeed effectively reduce the viscosity of concrete. It is worth mentioning that the viscosity reduction effects of Comparative Examples 1 and 2 are significantly lower than that of Example 3, indicating that the modified graphene oxide and the homemade polycarboxylate water-reducing agent can further reduce the viscosity of concrete when mixed.

[0096] The 0min extension of Comparative Example 4 is reduced by 9% compared with the 0min extension of Example 3, but the extension of Comparative Example 4 is worse than that of Comparative Example 1, indicating that the addition of propargylamine does improve the viscosity of the polycarboxylate water-reducing agent, but the improvement effect is not as good as the improvement effect of 1-(4-bromobutyl)-pyrene on the polycarboxylate water-reducing agent provided in this scheme. The possible reason is that pyrene itself can form a stable dispersion layer on the surface of cement particles to prevent the attraction between cement particles, and pyrene can act between the side arms of the star-shaped water-reducing agent to better expose the carboxyl group, which can further improve the dispersibility of cement.

[0097] Comprehensive analysis: Graphene oxide modified with N,N-dimethyl-2-hydroxyethylamine can indeed have better interlayer friction performance, and modified graphene oxide with more active sites is indeed easier to adsorb on the surface of cement particles; homemade polycarboxylate water reducer itself can also reduce the viscosity of concrete.

[0098] Application Test Example 2

[0099] Compressive strength test: The compressive strength test of concrete was carried out in accordance with the relevant provisions of GB / T50081-2016 "Standard for Test Methods for Mechanical Properties of Ordinary Concrete"; the experimental results are shown in Table 2.

[0100] Table 2

[0101]

[0102] Analysis of test results: The compressive strength test of cement can reflect the strength of cement. From the analysis of the test data, the compressive strengths of 3d, 7d and 28d of the optimal ratio embodiment 3 are better than those of other ratios; the early strength performance of embodiment 5 in which all raw material ratios are outside the protection scope of the present invention is also not ideal; it shows that the viscosity-reducing polycarboxylic acid water-reducing agent provided by the present invention not only does not reduce the strength of concrete while improving the viscosity of concrete, but also promotes its strength performance.

[0103] It should be emphasized that the improvement in the early strength performance of concrete in Comparative Example 4 is not as good as that in Example 3. The possible reason is that the structure of pyrene itself is stable, resulting in the cement particle adsorption layer formed having higher stability and durability than propargylamine, which can increase the hydration rate and degree of cement and effectively prevent the agglomeration and agglomeration of cement particles.

[0104] Comprehensive analysis: Introducing 1-(4-bromobutyl)-pyrene on the surface of star-shaped polycarboxylate water-reducing agent can indeed form a stable cement particle adsorption layer and improve the strength of concrete; after the modified graphene oxide is mixed with the homemade polycarboxylate water-reducing agent, part of the modified graphene oxide will indeed be adsorbed between the star-shaped polycarboxylate water-reducing agent molecules, making the water-reducing agent molecular structure more compact, thereby increasing the strength and hardness of the concrete.

[0105] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A viscosity-reducing polycarboxylate water-reducing agent, characterized in that: The viscosity-reducing polycarboxylate water-reducing agent comprises, by weight: 90-110 parts of a homemade polycarboxylate water-reducing agent mother solution, 27-45 parts of modified graphene oxide, 0.3-0.6 parts of a foam stabilizer, 1.1-1.9 parts of a defoamer, and 280-320 parts of water; The self-made polycarboxylate water-reducing agent mother liquor comprises: 3.2-6.5 parts of pentaerythritol, 22-38 parts of acrylic acid, 9-12 parts of p-toluenesulfonic acid, 0.025-0.03 parts of hydroquinone, 36-45 parts of toluene, 4.6-6.8 parts of isobutylene polyoxyethylene ether, 0.06-0.13 parts of thioglycolic acid, 0.25-0.38 parts of ammonium persulfate, 1.8-2.7 parts of 1-(4-bromobutyl)-pyrene, 0.48-0.97 parts of sodium hydroxide, and 19-28 parts of water; The preparation steps of modified graphene oxide are: At room temperature, N,N-dimethyl-2-hydroxyethylamine is added to anhydrous ethanol to disperse and prepare an N,N-dimethyl-2-hydroxyethylamine ethanol solution, graphene oxide is added to anhydrous ethanol to disperse and prepare a graphene oxide ethanol solution, and the N,N-dimethyl-2-hydroxyethylamine ethanol solution is added dropwise to the graphene oxide ethanol solution under stirring, and stirring is continued for 2 hours after the dropwise addition. After ultrasonic dispersion at 60°C for 24 hours, the reaction is carried out at room temperature for 6 hours, and the precipitate is filtered, washed with ethanol 3 times, and dried to obtain modified graphene oxide.

2. The viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: In parts by weight, the viscosity-reducing polycarboxylic acid water-reducing agent includes: 98 parts of homemade polycarboxylic acid water-reducing agent mother liquor, 32 parts of modified graphene oxide, 0.45 parts of foam stabilizer, 1.7 parts of defoamer, and 305 parts of water.

3. The viscosity-reducing polycarboxylate water-reducing agent according to claim 2, characterized in that: The homemade polycarboxylate water-reducing agent mother liquor comprises, by weight: 5.9 parts of pentaerythritol, 35 parts of acrylic acid, 11 parts of p-toluenesulfonic acid, 0.029 parts of hydroquinone, 42 parts of toluene, 5.8 parts of isobutylene polyoxyethylene ether, 0.1 parts of thioglycolic acid, 0.36 parts of ammonium persulfate, 2.5 parts of 1-(4-bromobutyl)-pyrene, 0.82 parts of concentrated sulfuric acid, and 24 parts of water.

4. The viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The foam stabilizer is sodium rosin acid; the defoamer is a polyether defoamer.

5. The viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The preparation method of the homemade polycarboxylate water-reducing agent mother solution is: Pentaerythritol and 45% acrylic acid are added to a four-necked flask with a magnetic stirrer, and p-toluenesulfonic acid and hydroquinone are added in sequence. When the temperature reaches 90°C, toluene is added, and the reaction temperature is controlled at 80-90°C. The reaction product water is collected, and after reacting for 7 hours, the toluene is removed by vacuum to obtain the first product. The first product, isobutylene polyoxyethylene ether, and the remaining 55% of acrylic acid are added to a four-necked flask and mixed evenly, and a certain amount of water is added for dilution, and the temperature is set to 65°C. After stirring evenly, a thioglycolic acid aqueous solution and an ammonium persulfate aqueous solution are added dropwise to the flask, and the mixture is reacted at a constant temperature for 5 hours and then cooled to obtain a second product; The second product and 1-(4-bromobutyl)-pyrene were added to a reaction container, sodium hydroxide was added, the reaction temperature was raised to 50° C., and after reacting for 6 hours, a homemade polycarboxylate water-reducing agent mother liquor was obtained.

6. The method for preparing the viscosity-reducing polycarboxylate water-reducing agent according to any one of claims 1 to 5, characterized in that: The homemade polycarboxylate water-reducing agent mother liquor and modified graphene oxide were added to the reaction container in sequence, and after stirring for 45 minutes, a foam stabilizer and a defoamer were added in sequence, and stirred for 10 minutes to obtain a viscosity-reducing polycarboxylate water-reducing agent.

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