A low-sensitivity admixture for small-slump concrete and its preparation method

Abstract

The present invention discloses a low-sensitivity admixture for low-slump concrete and a preparation method thereof, belonging to the technical field of water-reducing agent preparation. The low-sensitivity admixture for low-slump concrete comprises the following components by weight: 500-550 parts of a dispersed component A, 300-350 parts of a linear dispersed component B, and 100-200 parts of a desensitizing component C. The low-sensitivity admixture of the present invention can effectively reduce the sensitivity of concrete to changes in the water-reducing agent dosage and the water-cement ratio, and can accurately control the slump of concrete between 140 and 170 cm. It has significant significance for the application and development of hydraulic concrete.

Description

Technical Field

[0001] The invention relates to the technical field of water reducing agent preparation, in particular to a low-sensitivity admixture for small-slump concrete and a preparation method thereof. Background Art

[0002] With the rapid development of water conservancy, the requirements for the construction quality of water conservancy projects are becoming increasingly stringent. Hydraulic concrete, due to its long service life, high compressive strength, and durability, has become the most widely used building material in water conservancy project construction. During the construction of hydraulic diversion tunnels, the slump is typically controlled between 140 and 170 cm. This reduces the water-cement ratio, cement usage, and the heat of hydration, improving the concrete's crack resistance and water erosion resistance. Furthermore, as the concrete chutes down the low-slump concrete chute, the aggregates are less likely to separate and bleed, ensuring the quality of the poured concrete. Furthermore, during the construction of diversion tunnel sidewalls, low-slump concrete resists deformation after forming, allowing for quick formwork removal, which has significant economic benefits in terms of increased formwork turnover efficiency.

[0003] Polycarboxylic acid high-performance water-reducing agents (PCAs) are widely used in the concrete industry due to their high water-reducing rate, high slump retention, and low dosage. However, due to their high water-reducing rate and strong dispersibility, their application in the production of low-slump hydraulic concrete is difficult. This is primarily due to the low dosage of PCAs and their high sensitivity, making it difficult to control the slump of the produced concrete within the range of 140-170mm. Even slight adjustments to the dosage can result in excessive or insufficient slump, increasing bleeding and setbacks, seriously impacting the concrete placement process.

[0004] Therefore, the preparation of a low-sensitivity admixture for small slump concrete has significant significance for the application and development of hydraulic concrete. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-sensitivity admixture for small-slump concrete and a preparation method thereof, so as to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a low-sensitivity admixture for small-slump concrete, comprising the following components in parts by weight: 500-550 parts of a dispersing component A, 300-350 parts of a linear dispersing component B, and 100-200 parts of a desensitizing component C;

[0008] The preparation method of the dispersed component A comprises the following steps: adding TPEG2400, TPEG1200 and TPEG400 to a solvent, adding an initiator, an acrylic acid solution, and a mixed solution of ascorbic acid and mercaptopropionic acid after heating, and adjusting the pH to 8-9 after the reaction to obtain the dispersed component A;

[0009] The solid content of the dispersed component A is 40%;

[0010] The preparation method of the linear dispersed component B comprises the following steps: mixing glyoxal, melamine and m-hydroxybenzoic acid, adjusting the pH to 8.5-9.5, adding sodium bisulfite after heating reaction, and adjusting the pH to 10-12, continuing heating reaction, adjusting the pH to 4.5-5.5, adding sodium bisulfite again after heating reaction, heating reaction, and drying to obtain the linear dispersed component B;

[0011] The desensitizing component C comprises the following components in parts by weight: 50 parts of montmorillonite, 3 to 8 parts of triethanolamine, 3 to 8 parts of sodium polyacrylate and 440 parts of water.

[0012] Furthermore, when preparing the dispersed component A, the mass ratio of the mixed solution of TPEG2400, TPEG1200, TPEG400, solvent, initiator, acrylic acid solution, ascorbic acid and mercaptopropionic acid is (200-300): (50-80): (15-25): 200: 10: 145: 153.5.

[0013] Furthermore, when preparing the dispersed component A, the heating temperature is 40-50°C.

[0014] Furthermore, when preparing the dispersed component A, the initiator comprises hydrogen peroxide and ferrous sulfate solution with a mass ratio of 1:1 and a concentration of 1 wt.%;

[0015] The acrylic acid solution comprises acrylic acid and water in a mass ratio of 45:100;

[0016] The mixed solution of ascorbic acid and mercaptopropionic acid comprises ascorbic acid, mercaptopropionic acid and water in a mass ratio of 1:2.5:150.

[0017] Furthermore, when preparing the dispersed component A, the acrylic acid solution, the mixed solution of ascorbic acid and mercaptopropionic acid are added dropwise, and the addition time is independently 2.5 to 3.5 hours; and the reaction time after the addition is completed is 60 to 120 minutes.

[0018] Furthermore, when preparing the linear dispersed component B, the mass ratio of glyoxal, melamine, m-hydroxybenzoic acid, and sodium bisulfite is (260-300): (200-250): (25-40): (135-195).

[0019] Furthermore, when preparing the linear dispersed component B, the pH is adjusted to 8.5-9.5 and then the heating reaction temperature is 60-70°C for 60-120 minutes;

[0020] Adjust the pH to 10-12 and heat the reaction at 70-80°C for 90-150 minutes.

[0021] Adjust the pH to 4.5-5.5 and heat the reaction at 45-55°C for 120 min.

[0022] Sodium bisulfite was added again and the reaction temperature was heated to 75-85°C for 120 min.

[0023] Furthermore, the montmorillonite is an organic montmorillonite modified with carboxyl groups and organic ammonium.

[0024] The second technical solution of the present invention is a method for preparing the above-mentioned low-sensitivity admixture, comprising the following steps:

[0025] The dispersed component A, the linear dispersed component B and the desensitizing component C are uniformly mixed to obtain the low-sensitivity admixture.

[0026] The third technical solution of the present invention: an application of the above-mentioned low-sensitivity admixture in the preparation of small slump concrete.

[0027] The present invention discloses the following technical effects:

[0028] (1) The low-sensitivity admixture of the present invention can effectively reduce the sensitivity of concrete to the amount of water-reducing agent and the sensitivity of the water-cement ratio to changes, and can accurately control the slump of concrete between 140 and 170 cm, which has significant significance for the application and development of hydraulic concrete.

[0029] (2) The dispersing component A in the low-sensitivity admixture of the present invention is a comb-shaped dispersant synthesized from polyether macromonomers with different side chain lengths. This dispersant is more adaptable to the dispersion of cement particles under different water-cement ratios than conventional polycarboxylic acid single-side chain water reducers. After the dispersing component A is adsorbed on the cement particles, it stretches in water to form adsorption films of different thicknesses due to the polyoxyethylene ethers with different side chain lengths. After the side chains overlap, an adsorption layer is formed, generating spatial repulsion. Due to the different side chain lengths, the spatial repulsion varies in size in a gradient, reducing the sensitivity of the single side chain to the dispersion of cement particles.

[0030] The molecular structure of the linear dispersing component B is linear. On the one hand, it can disperse the cement particles. On the other hand, it can entangle with the comb-like structure of the dispersing component A to increase the plastic viscosity of the cement paste, avoiding the problem of excessive release of free water, which affects the viscosity of the cement paste and causes large changes in slump and high sensitivity.

[0031] The desensitizing component C can be adsorbed on the side chain of the dispersing component A, which can destroy the hydration film around the side chain of the polyoxyethylene ether, thereby increasing the friction between the cement particles (the increase in friction can inhibit the dispersing effect of the dispersing component A on the cement particles and reduce the sensitivity of the dispersing component A to the dispersion of cement particles). At the same time, the desensitizing component C can absorb some of the excess free water and reduce the sensitivity caused by changes in the water-cement ratio. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice 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 any conflict with any incorporated document, the contents of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0038] In a first aspect, the present invention provides a low-sensitivity admixture for small-slump concrete, comprising the following components in parts by weight: 500-550 parts of a dispersing component A, 300-350 parts of a linear dispersing component B, and 100-200 parts of a desensitizing component C;

[0039] The preparation method of the dispersed component A comprises the following steps: mixing 200-300 parts by mass of TPEG2400 (prenol polyoxyethylene ether with a molecular weight of 2400), 50-80 parts by mass of TPEG1200 (prenol polyoxyethylene ether with a molecular weight of 1200), 15-25 parts by mass of TPEG400 (prenol polyoxyethylene ether with a molecular weight of 400), and 200 parts by mass of water; heating the mixture to 40-50°C, setting the rotation speed to 250-300 r / min, adding 10 parts by mass of an initiator (5 parts by mass of hydrogen peroxide); and , 5 parts by mass of a 1 wt.% aqueous ferrous sulfate solution), mixed thoroughly, and then dropwise added with solution A and solution B (liquid A consisting of 45 parts by mass of acrylic acid and 100 parts by mass of water; solution B consisting of 1 part by mass of ascorbic acid, 2.5 parts by mass of mercaptopropionic acid, and 150 parts by mass of water). The addition time was 2.5 to 3.5 hours. After the addition was complete, the reaction was continued for 60 to 120 minutes. After the reaction, the system temperature was lowered to room temperature, the solution pH was neutralized to 8 to 9 with a 30 wt.% NaOH solution, and the concentration (solids content) was adjusted to 40% by water to obtain dispersed component A. The weight-average molecular weight (Mw) was 20,000 to 22,000 g / mol as measured by gel permeation chromatography, and the conversion rate was greater than 90%.

[0040] Conversion rate (%) = (moles of polymer / moles of monomer) × 100%.

[0041] The molecular weight distribution of the polymer was determined by chromatographic separation, and the molar number of the polymer was obtained by calculus; the molar number of the monomer refers to the total molar number of TPEG2400, TPEG1200 and TPEG400.

[0042] The preparation method of the linear dispersed component B comprises the following steps: mixing 260-300 parts by mass of glyoxal, 200-250 parts by mass of melamine, and 25-40 parts by mass of m-hydroxybenzoic acid, adjusting the pH value to 8.5-9.5 with a NaOH solution (30 wt.%), and reacting at 60-70°C for 6-120 minutes; adding 120-170 parts by mass of sodium bisulfite to the reaction system, adjusting the pH value to 10-12 with a NaOH solution (30 wt.%), reacting at 70-80°C for 90-150 minutes, and keeping the mixture warm for 60 minutes after the reaction is completed. n (no stirring during insulation, stirring during the rest of the reaction process, the stirring rate is 250-300 r / min), then after the above reaction system is cooled to room temperature, the pH value of the solution is adjusted to 4.5-5.5 with HCl solution (30wt.%), and the reaction is carried out at 45-55°C for 120 minutes. After the above reaction is completed, 15-25 parts by weight of sodium bisulfite is added to the solution, and the temperature is rapidly raised to 75-85°C and kept warm for 120 minutes; after the system is cooled, a colorless viscous solution is obtained, and the viscous solution is concentrated and dried to obtain a white powder, which is the linear dispersed component B.

[0043] The desensitizing component C comprises the following components in parts by mass: 50 parts of montmorillonite (organic montmorillonite modified with carboxyl groups and organic ammonium), 3 to 8 parts of triethanolamine, 3 to 8 parts of sodium polyacrylate (weight-average molecular weight of 5 million), and 440 parts of water.

[0044] Montmorillonite was purchased from Zhejiang Fenghong New Materials Co., Ltd., model DK5.

[0045] The preparation method of the desensitizing component C comprises: mixing montmorillonite, triethanolamine, sodium polyacrylate and water, and dispersing them at high speed (8000 r / min) in a high-speed disperser to form a solution, thereby obtaining the desensitizing component C.

[0046] In a second aspect, the present invention provides a method for preparing the above-mentioned low-sensitivity admixture, comprising the following steps:

[0047] The dispersed component A, the linear dispersed component B and the desensitizing component C are uniformly mixed to obtain the low-sensitivity admixture.

[0048] The third aspect of the present invention provides a use of the above-mentioned low-sensitivity admixture in the preparation of small slump concrete.

[0049] All “parts” described in the following examples are “parts by mass”.

[0050] The weight average molecular weight of the sodium polyacrylate used in the specific embodiment of the present invention is 5 million; the montmorillonite was purchased from Zhejiang Fenghong New Materials Co., Ltd., model DK5.

[0051] Example 1

[0052] A preparation method of a low-sensitivity admixture for small slump concrete:

[0053] (1) The low-sensitivity admixture is composed of the following components in parts by mass: 500 parts of dispersing component A, 300 parts of linear dispersing component B and 200 parts of desensitizing component C.

[0054] (2) Preparation method of dispersed component A

[0055] 200 parts by mass of TPEG2400, 50 parts by mass of TPEG1200, 15 parts by mass of TPEG400 and 200 parts by mass of deionized water were added to a reactor equipped with a stirrer, a dropping device and a heating device. The mixture was heated to 40°C and the speed was set to 250 r / min. 10 parts by mass of initiator (5 parts by mass of hydrogen peroxide, 5 parts by mass of 1 wt.% ferrous sulfate aqueous solution) was added, and 145 parts by mass of liquid a and 153.5 parts by mass of liquid b (liquid a consisted of 45 parts by mass of acrylic acid and 100 parts by mass of deionized water; liquid b consisted of 1 part by mass of ascorbic acid, 2.5 parts by mass of mercaptopropionic acid and 150 parts by mass of deionized water) were added dropwise. The addition time was 2.5 hours. After the addition was completed, the reaction was continued for 60 minutes. After the reaction was completed, the temperature of the system was lowered to room temperature, the pH value of the solution was neutralized to 8 with NaOH solution (30 wt.%), and the concentration was adjusted to 40% by adding deionized water to obtain dispersed component A.

[0056] The weight average molecular weight Mw was measured by gel permeation chromatography and was 20497 g / mol, with a conversion rate of 92%.

[0057] (3) Preparation method of linear dispersed component B

[0058] In a reactor equipped with a stirrer, a dropping device, a reflux condenser and a heating device, 260 parts by mass of glyoxal, 200 parts by mass of melamine and 25 parts by mass of m-hydroxybenzoic acid were added, the pH value was adjusted to 8.5 with a NaOH solution (30 wt.%), and the reaction was carried out at 60°C for 60 minutes; 120 parts by mass of sodium bisulfite was added to the above reaction system, and the pH value was adjusted to 10 with a NaOH solution (30 wt.%), and the reaction was carried out at 70°C for 90 minutes. After the reaction was completed, the temperature was kept for 60 minutes (the temperature was kept at 70°C for 1 minute). No stirring was performed, and stirring was performed during the remaining reaction process at a stirring rate of 250 r / min). Then, after the above reaction system was cooled to room temperature, the pH value of the solution was adjusted to 4.5 with HCl solution (30 wt.%), and the reaction was carried out at 45°C for 120 min. After the above reaction was completed, 15 parts by mass of sodium bisulfite was added to the solution, and the temperature was rapidly raised to 75°C and kept warm for 120 min. After the system was cooled, a colorless viscous solution was obtained, and the viscous solution was concentrated and dried to obtain a white powder, which was the linear dispersed component B.

[0059] (4) Preparation method of desensitizing component C

[0060] 50 parts by mass of montmorillonite (organic montmorillonite modified with carboxyl groups and organic ammonium), 3 parts by mass of triethanolamine, 3 parts by mass of sodium polyacrylate and 440 parts by mass of deionized water were mixed and dispersed at high speed (8000 r / min) in a high-speed disperser to form a solution to obtain a desensitizing component C.

[0061] (5) The dispersed component A, the linear dispersed component B and the desensitizing component C are mixed evenly to obtain a low-sensitivity admixture.

[0062] Example 2

[0063] A preparation method of a low-sensitivity admixture for small slump concrete:

[0064] (1) Hyposensitive admixture, consisting of the following components in parts by weight: 550 parts of dispersing component A, 350 parts of linear dispersing component B and 100 parts of desensitizing component C.

[0065] (2) Preparation method of dispersed component A

[0066] In a reactor equipped with a stirrer, a dropping device and a heating device, 300 parts by mass of TPEG2400, 80 parts by mass of TPEG1200, 25 parts by mass of TPEG400, and 200 parts by mass of deionized water were added, and the mixture was heated to 50°C, the speed was set to 300 r / min, 10 parts by mass of initiator (5 parts by mass of hydrogen peroxide, 5 parts by mass of 1 wt.% ferrous sulfate aqueous solution) was added, and 145 parts by mass of liquid a and 153.5 parts by mass of liquid b (liquid a consisted of 45 parts by mass of acrylic acid and 100 parts by mass of deionized water; liquid b consisted of 1 part by mass of ascorbic acid, 2.5 parts by mass of mercaptopropionic acid, and 150 parts by mass of deionized water) were added dropwise. The addition time was 3.5 hours. After the addition was completed, the reaction was continued for 120 minutes. After the reaction was completed, the temperature of the system was lowered to room temperature, the pH value of the solution was neutralized to 9 with NaOH solution (30 wt.%), and the concentration was adjusted to 40% by adding deionized water to obtain dispersed component A.

[0067] The weight average molecular weight Mw was measured by gel permeation chromatography and was 21887 g / mol, with a conversion rate of 94%.

[0068] (3) Preparation method of linear dispersed component B

[0069] In a reactor equipped with a stirrer, a dropping device, a reflux condenser and a heating device, 300 parts by mass of glyoxal, 250 parts by mass of melamine and 40 parts by mass of m-hydroxybenzoic acid were added, the pH value was adjusted to 9.5 with a NaOH solution (30 wt.%), and the reaction was carried out at 70°C for 120 minutes; 170 parts by mass of sodium bisulfite was added to the above reaction system, and the pH value was adjusted to 12 with a NaOH solution (30 wt.%), and the reaction was carried out at 80°C for 150 minutes. After the reaction was completed, the temperature was kept at 40°C for 60 minutes (heat preservation). The mixture was stirred for 120 minutes without stirring during the reaction, and stirred for the rest of the reaction at a stirring rate of 300 r / min). The reaction system was then cooled to room temperature, and the pH value of the solution was adjusted to 5.5 with HCl solution (30 wt.%), and the reaction was carried out at 55°C for 120 minutes. After the reaction was completed, 25 parts by mass of sodium bisulfite was added to the solution, and the temperature was rapidly raised to 85°C and kept warm for 120 minutes. After the system was cooled, a colorless viscous solution was obtained, which was then concentrated and dried to obtain a white powder, which was the linear dispersed component B.

[0070] (4) Preparation method of desensitizing component C

[0071] 50 parts by mass of montmorillonite (organic montmorillonite modified with carboxyl groups and organic ammonium), 8 parts by mass of triethanolamine, 8 parts by mass of sodium polyacrylate and 440 parts by mass of deionized water were mixed and dispersed at high speed (8000 r / min) in a high-speed disperser to form a solution to obtain a desensitizing component C.

[0072] (5) The dispersed component A, the linear dispersed component B and the desensitizing component C are mixed evenly to obtain a low-sensitivity admixture.

[0073] Example 3

[0074] A preparation method of a low-sensitivity admixture for small slump concrete:

[0075] (1) Hyposensitive admixture, consisting of the following components in parts by weight: 550 parts of dispersing component A, 300 parts of linear dispersing component B and 150 parts of desensitizing component C.

[0076] (2) Preparation method of dispersed component A

[0077] In a reactor equipped with a stirrer, a dropping device and a heating device, 250 parts by mass of TPEG2400, 65 parts by mass of TPEG1200, 20 parts by mass of TPEG400, and 200 parts by mass of deionized water were added, and the mixture was heated to 45°C, the speed was set to 280 r / min, 10 parts by mass of initiator (5 parts by mass of hydrogen peroxide, 5 parts by mass of 1 wt.% ferrous sulfate aqueous solution) was added, and 145 parts by mass of liquid a and 153.5 parts by mass of liquid b (liquid a consisted of 45 parts by mass of acrylic acid and 100 parts by mass of deionized water; liquid b consisted of 1 part by mass of ascorbic acid, 2.5 parts by mass of mercaptopropionic acid, and 150 parts by mass of deionized water) were added dropwise. The addition time was 3 h. After the addition was completed, the reaction was continued for 90 min. After the reaction was completed, the temperature of the system was lowered to room temperature, the pH value of the solution was neutralized to 8.5 with NaOH solution (30 wt.%), and the concentration was adjusted to 40% by adding deionized water to obtain dispersed component A.

[0078] The weight average molecular weight Mw was measured by gel permeation chromatography and was 21068 g / mol, with a conversion rate of 96%.

[0079] (3) Preparation method of linear dispersed component B

[0080] In a reactor equipped with a stirrer, a dropping device, a reflux condenser, and a heating device, 280 parts by mass of glyoxal, 230 parts by mass of melamine, and 30 parts by mass of m-hydroxybenzoic acid were added, the pH value was adjusted to 9 with a NaOH solution (30 wt.%), and the reaction was carried out at 65°C for 90 min. 145 parts by mass of sodium bisulfite was added to the reaction system, and the pH value was adjusted to 11 with a NaOH solution (30 wt.%). The reaction was carried out at 75°C for 120 min. After the reaction was completed, the reaction system was kept warm for 60 min (no stirring during the holding period; stirring was performed during the remaining reaction at a stirring rate of 280 r / min). The reaction system was then cooled to room temperature, the pH value of the solution was adjusted to 5 with an HCl solution (30 wt.%), and the reaction was carried out at 50°C for 120 min. After the reaction was completed, 20 parts by mass of sodium bisulfite was added to the solution, the temperature was rapidly raised to 80°C, and the temperature was maintained for 120 min. After the system was cooled, a colorless viscous solution was obtained. The viscous solution was then concentrated and dried to obtain a white powder, which is the linearly dispersed component B.

[0081] (4) Preparation method of desensitizing component C

[0082] 50 parts by mass of montmorillonite (organic montmorillonite modified with carboxyl groups and organic ammonium), 5 parts by mass of triethanolamine, 5 parts by mass of sodium polyacrylate and 440 parts by mass of deionized water were mixed and dispersed at high speed (8000 r / min) in a high-speed disperser to form a solution to obtain a desensitizing component C.

[0083] (5) The dispersed component A, the linear dispersed component B and the desensitizing component C are mixed evenly to obtain a low-sensitivity admixture.

[0084] Example 4

[0085] A preparation method of a low-sensitivity admixture for small slump concrete:

[0086] (1) Hyposensitive admixture, consisting of the following components in parts by weight: 550 parts of dispersing component A, 300 parts of linear dispersing component B and 150 parts of desensitizing component C.

[0087] (2) Preparation method of dispersed component A

[0088] In a reactor equipped with a stirrer, a dropping device and a heating device, 250 parts by mass of TPEG2400, 65 parts by mass of TPEG1200, 20 parts by mass of TPEG400, and 200 parts by mass of deionized water were added, and the mixture was heated to 45°C, the speed was set to 280r / min, 10 parts by mass of initiator (5 parts by mass of hydrogen peroxide, 5 parts by mass of 1wt.% ferrous sulfate aqueous solution) was added, and 145 parts by mass of liquid a and 153.5 parts by mass of liquid b (liquid a consisted of 45 parts by mass of acrylic acid and 100 parts by mass of deionized water; liquid b consisted of 1 part by mass of ascorbic acid, 2.5 parts by mass of mercaptopropionic acid, and 150 parts by mass of deionized water) were added dropwise. The addition time was 3h. After the addition was completed, the reaction was continued for 90min. After the reaction was completed, the temperature of the system was lowered to room temperature, the solution was neutralized with NaOH solution (30wt.%) to a pH of 8.5, and deionized water was added to adjust the concentration to 40% to obtain dispersed component A.

[0089] The weight average molecular weight Mw was measured by gel permeation chromatography and was 21068 g / mol, with a conversion rate of 96%.

[0090] (3) Preparation method of linear dispersed component B

[0091] In a reactor equipped with a stirrer, a dropping device, a reflux condenser and a heating device, 300 parts by mass of glyoxal, 250 parts by mass of melamine and 40 parts by mass of m-hydroxybenzoic acid were added, the pH value was adjusted to 9.5 with a NaOH solution (30 wt.%), and the reaction was carried out at 70°C for 120 minutes; 170 parts by mass of sodium bisulfite was added to the above reaction system, and the pH value was adjusted to 12 with a NaOH solution (30 wt.%), and the reaction was carried out at 80°C for 150 minutes. After the reaction was completed, the temperature was kept at 40°C for 60 minutes (heat preservation). The reaction mixture was stirred at 280 r / min for the remaining reaction period without stirring. The reaction mixture was then cooled to room temperature, and the pH value of the solution was adjusted to 5.5 using HCl solution (30 wt.%), and the reaction was carried out at 55°C for 120 min. After the reaction was completed, 25 parts by mass of sodium bisulfite was added to the solution, and the temperature was rapidly raised to 85°C and kept warm for 120 min. After the system was cooled, a colorless viscous solution was obtained, which was then concentrated and dried to obtain a white powder, which was the linear dispersed component B.

[0092] (4) Preparation method of desensitizing component C

[0093] 50 parts by mass of montmorillonite (organic montmorillonite modified with carboxyl groups and organic ammonium), 8 parts by mass of triethanolamine, 8 parts by mass of sodium polyacrylate and 440 parts by mass of deionized water were mixed and dispersed at high speed (8000 r / min) in a high-speed disperser to form a solution to obtain a desensitizing component C.

[0094] (5) The dispersed component A, the linear dispersed component B and the desensitizing component C are mixed evenly to obtain a low-sensitivity admixture.

[0095] Comparative Example 1

[0096] The same as Example 3, except that the dispersing component A is replaced by an equal amount of polycarboxylate water-reducing agent (solid content 40%, purchased from Shandong Xinmaoyuan Chemical Co., Ltd.).

[0097] Comparative Example 2

[0098] The same as Example 3, except that the linear dispersed component B is replaced by an equal mass fraction of sulfonated melamine water reducer (purchased from Shanghai Qishuo Industrial Co., Ltd.).

[0099] Comparative Example 3

[0100] The same as Example 3, except that the low-sensitivity admixture is composed of the following components in parts by mass: 600 parts of the dispersing component A, 250 parts of the linear dispersing component B, and 150 parts of the desensitizing component C.

[0101] Comparative Example 4

[0102] The same as Example 3, except that TPEG2400 in the dispersing component A is replaced with HPEG2400 (methyl allyl alcohol polyoxyethylene ether with a molecular weight of 2400).

[0103] Effect Example 1

[0104] Concrete testing to test the sensitivity of low-sensitivity admixtures:

[0105] The performance of the admixtures prepared in the examples and comparative examples was tested by concrete tests. The cement was Esheng P·O42.5 cement; the machine-made sand had a fineness modulus of 2.8, a stone powder content of 6%, and a methylene blue MB value of 1.0; and the gravel was 5-40 mm continuously graded crushed stone. The mix ratio is shown in Table 1.

[0106] The sensitivity test of low-sensitivity concrete admixtures, slump, specimen forming, production and curing refer to GBT50080-2016 "Standard Test Method for Performance of Ordinary Concrete Mixtures", and the concrete strength is in accordance with GBT 50081-2019 "Standard Test Method for Physical and Mechanical Properties of Concrete".

[0107] No low-sensitivity admixture was added to the blank control, and the composition ratio of the compound water reducer was:

[0108] Polycarboxylate water reducer (six-carbon type P6): slump retaining agent (six-carbon type C8): retarder (sodium gluconate): air entraining agent (triterpenoid saponin): water = 300:100:20:1:579.

[0109] In each embodiment and comparative example, a low-sensitivity admixture is added, and the component ratio of the composite water reducer is:

[0110] Polycarboxylate water reducer (six-carbon type P6): slump retaining agent (six-carbon type C8): retarder (sodium gluconate): low-sensitivity admixture: air-entraining agent (triterpenoid saponin): water = 200:100:20:100:1:579.

[0111] The test results of concrete properties are shown in Table 2.

[0112] Table 1 Concrete mix ratio (kg / m 3 )

[0113]

[0114] Among them, the dosage of compound water reducer is 0.7%, 0.8% and 0.9% of the total mass of cement and fly ash respectively.

[0115] Table 2 Concrete sensitivity test results

[0116]

[0117] As can be seen from Table 2, when the low-sensitivity admixtures prepared in Examples of the present invention are applied to concrete, increasing or decreasing the compound water-reducing agent dosage by 0.1% has little effect on concrete slump compared to the blank control group. The difference in slump at different dosages in the Examples is smaller than that in the blank control group. The increase in slump caused by changes in the water-binder ratio in the Examples is much smaller than that in the blank control group, as seen when adding 5kg or 10kg of water to the concrete mix. The compressive strength of the Examples at 0.8% dosage after 3, 7, and 28 days of ex-pressing is higher than that in the blank control group.

[0118] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A low-sensitivity admixture for small slump concrete, characterized in that: The invention comprises the following components in parts by weight: 500-550 parts of a dispersing component A, 300-350 parts of a linear dispersing component B and 100-200 parts of a desensitizing component C; The preparation method of the dispersed component A comprises the following steps: adding TPEG2400, TPEG1200 and TPEG400 to a solvent, adding an initiator, an acrylic acid solution, and a mixed solution of ascorbic acid and mercaptopropionic acid after heating, and adjusting the pH to 8-9 after the reaction to obtain the dispersed component A; The solid content of the dispersed component A is 40%; The preparation method of the linear dispersed component B comprises the following steps: mixing glyoxal, melamine and m-hydroxybenzoic acid, adjusting the pH to 8.5-9.5, adding sodium bisulfite after heating reaction, and adjusting the pH to 10-12, continuing heating reaction, adjusting the pH to 4.5-5.5, adding sodium bisulfite again after heating reaction, heating reaction, and drying to obtain the linear dispersed component B; The desensitizing component C comprises the following components in parts by weight: 50 parts of montmorillonite, 3 to 8 parts of triethanolamine, 3 to 8 parts of sodium polyacrylate and 440 parts of water; When preparing the dispersed component A, the mass ratio of the TPEG2400, TPEG1200, TPEG400, solvent, initiator, acrylic acid solution, ascorbic acid and mercaptopropionic acid mixed solution is (200-300): (50-80): (15-25): 200: 10: 145: 153.5; When preparing the linear dispersed component B, the mass ratio of glyoxal, melamine, m-hydroxybenzoic acid, and sodium bisulfite is (260-300): (200-250): (25-40): (135-195).

2. The low-sensitivity admixture according to claim 1, characterized in that When preparing the dispersed component A, the heating temperature is 40-50°C.

3. The low-sensitivity admixture according to claim 1, characterized in that When preparing the dispersed component A, the initiator comprises hydrogen peroxide and ferrous sulfate solution with a mass ratio of 1:1 and a concentration of 1 wt.%; And / or, the acrylic acid solution comprises acrylic acid and water in a mass ratio of 45:100; And / or, the mixed solution of ascorbic acid and mercaptopropionic acid comprises ascorbic acid, mercaptopropionic acid and water in a mass ratio of 1:2.5:

150.

4. The low-sensitivity admixture according to claim 1, characterized in that When preparing the dispersed component A, the acrylic acid solution, the mixed solution of ascorbic acid and mercaptopropionic acid are added dropwise, and the addition time is independently 2.5 to 3.5 hours; the reaction time after the addition is completed is 60 to 120 minutes.

5. The low-sensitivity admixture according to claim 1, characterized in that When preparing linear dispersed component B, adjust the pH to 8.5-9.5 and heat the reaction at 60-70°C for 60-120 minutes. and / or, adjusting the pH to 10-12 and then heating the reaction at a temperature of 70-80° C. for 90-150 min; and / or, adjusting the pH to 4.5-5.5 and then heating the reaction at a temperature of 45-55° C. for 120 min; And / or, sodium bisulfite is added again and the reaction temperature is heated to 75-85° C. for 120 min.

6. The low-sensitivity admixture according to claim 1, characterized in that The montmorillonite is an organic montmorillonite modified with carboxyl and organic ammonium.

7. A method for preparing the low-sensitivity admixture according to any one of claims 1 to 6, characterized in that: The following steps are involved: The dispersed component A, the linear dispersed component B and the desensitizing component C are uniformly mixed to obtain the low-sensitivity admixture.

8. Use of the low-sensitivity admixture according to any one of claims 1 to 6 in the preparation of low-slump concrete.

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