Low-sensitivity admixture for small-slump concrete and preparation method of low-sensitivity admixture

Abstract

The invention discloses a low-sensitivity additive for small-slump concrete and a preparation method of the low-sensitivity additive, and belongs to the technical field of preparation of water reducing agents. The invention relates to a low-sensitivity admixture for small-slump concrete. The low-sensitivity admixture comprises the following components in parts by mass: 500-550 parts of a dispersion component A, 300-350 parts of a linear dispersion component B and 100-200 parts of a sensitivity reduction component C. The low-sensitivity admixture disclosed by the invention can effectively reduce the sensitivity of concrete to the mixing amount of a water reducing agent and the sensitivity of water-binder ratio change, can accurately control the slump of the concrete within 140-170cm, and has remarkable significance for the application and development of hydraulic concrete.

Description

Technical Field

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

[0002] With the rapid development of the water conservancy industry, the requirements for the construction quality of water conservancy projects are also getting higher and higher. During the construction of water conservancy projects, due to the advantages of long service life, high compressive strength, and strong durability of hydraulic concrete, it has become the most widely used building material in water conservancy project construction. During the construction of hydraulic diversion tunnels, the slump is usually controlled between 140 and 170 cm. On the one hand, it can reduce the water-cement ratio, reduce the consumption of cement, reduce the hydration heat of concrete, improve the crack resistance of concrete, and enhance the water erosion resistance of concrete; on the other hand, during the sliding process of the low-slump concrete chute, the aggregates of the concrete are not easily separated and bleed, and the quality of the poured concrete is more guaranteed. At the same time, during the construction of the side walls of the diversion tunnel, the low-slump concrete is not easily deformed after molding, and the formwork can be removed in a short time, which has good economic benefits for improving the turnover efficiency of the formwork.

[0003] Polycarboxylate high-performance water reducing agents have the characteristics of high water reduction, high slump retention, and low dosage, and are widely used in the concrete industry. However, due to their high water reduction rate and strong dispersibility, it is difficult to apply them in the production of low-slump hydraulic concrete. The main reason is that the dosage of polycarboxylate high-performance water reducing agents is low and the sensitivity is high, resulting in the slump of the produced concrete being difficult to control within the range of 140 - 170 mm. A slight adjustment of the dosage will cause the slump of the concrete to be too large or too small, and at the same time, it will also increase problems such as bleeding and post-placement of the concrete, seriously affecting the use of concrete pouring.

[0004] Therefore, preparing a low-sensitivity admixture for low-slump concrete is of 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 low-slump concrete and a preparation method thereof to solve the problems existing in the above-mentioned prior art.

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

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

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

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

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

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

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

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

[0014] Further, when preparing the dispersion component A, the components of the initiator include hydrogen peroxide and a ferrous sulfate solution with a concentration of 1 wt.% in a mass ratio of 1:1;

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

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

[0017] Further, when preparing the dispersion component A, the acrylic acid solution and the mixed solution of ascorbic acid and mercaptopropionic acid are added dropwise, and the dropping time is independently 2.5-3.5 h; the reaction time after the dropping is completed is 60-120 min.

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

[0019] Further, when preparing the linear dispersion component B, after adjusting the pH to 8.5 - 9.5, the temperature for the heating reaction is 60 - 70°C, and the time is 60 - 120 min;

[0020] after adjusting the pH to 10 - 12, the temperature for the heating reaction is 70 - 80°C, and the time is 90 - 150 min;

[0021] after adjusting the pH to 4.5 - 5.5, the temperature for the heating reaction is 45 - 55°C, and the time is 120 min;

[0022] after adding sodium bisulfite again, the temperature for the heating reaction is 75 - 85°C, and the time is 120 min.

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

[0024] The second technical solution of the present invention: A preparation method of the above low-sensitivity admixture, comprising the following steps:

[0025] Mix the dispersion component A, the linear dispersion component B, and the sensitivity-reducing component C evenly to obtain the low-sensitivity admixture.

[0026] The third technical solution of the present invention: An application of the above 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 dosage of water reducer and the change of water-binder ratio, and can accurately control the slump of concrete between 140 - 170 cm, which has significant significance for the application and development of hydraulic concrete.

[0029] (2) The dispersion 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 can better adapt to the dispersion of cement particles under different water-binder ratios than conventional polycarboxylate single-side-chain water reducers. After the dispersion component A is adsorbed on the cement particles, due to the polyoxyethylene ethers with different side-chain lengths, it unfolds in water to form adsorption films with different thicknesses. After the side chains overlap, an adsorption layer is formed, generating steric repulsion. Due to the different side-chain lengths, the magnitude of the steric repulsion changes 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 play a role in dispersing cement particles. On the other hand, it can entangle with the comb-shaped dispersing component A, increasing the plastic viscosity of the cement paste, avoiding the problem that excessive release of free water affects the large change in the viscosity of the cement paste, resulting in large changes in slump and high sensitivity.

[0031] The sensitivity-reducing component C can adsorb on the side chains of the dispersing component A, which can destroy the hydration film around the polyoxyethylene ether side chains, thereby increasing the frictional force between cement particles (the increase in frictional force can inhibit the dispersing effect of the dispersing component A on cement particles and reduce the sensitivity of the dispersing component A to the dispersion of cement particles). At the same time, the sensitivity-reducing component C can absorb a part of the excessive free water, reducing the sensitivity caused by the change in the water-binder ratio. Specific embodiments

[0032] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0033] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0034] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can 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 related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0035] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are only exemplary.

[0036] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0037] It should be noted that the parts not described in detail in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0038] In the first aspect of the present invention, a low-sensitivity admixture for low-slump concrete is provided, which comprises the following components in parts by mass: 500-550 parts of dispersion component A, 300-350 parts of linear dispersion component B, and 100-200 parts of sensitivity-reducing component C.

[0039] Among them, the preparation method of dispersion component A includes the following steps: Mix 200-300 parts by mass of TPEG2400 (isopentenyl alcohol polyoxyethylene ether with a molecular weight of 2400), 50-80 parts by mass of TPEG1200 (isopentenyl alcohol polyoxyethylene ether with a molecular weight of 1200), 15-25 parts by mass of TPEG400 (isopentenyl alcohol polyoxyethylene ether with a molecular weight of 400), and 200 parts of water, heat up to 40-50 °C, set the rotation speed to 250-300 r / min, add 10 parts by mass of initiator (5 parts by mass of hydrogen peroxide, 5 parts by mass of an aqueous solution of ferrous sulfate with a concentration of 1 wt.%), after mixing evenly, dropwise add solution a and solution b (solution a consists of 45 parts by mass of acrylic acid and 100 parts of water; solution b consists of 1 part by mass of ascorbic acid, 2.5 parts by mass of mercaptopropionic acid, and 150 parts of water), the dropping time is 2.5-3.5 h, continue to react for 60-120 min after dropping, after the reaction is completed, cool the temperature of the system to room temperature, neutralize the pH value of the solution to 8-9 with NaOH solution (30 wt.%), and adjust the concentration (solid content) to 40% by adding water to obtain dispersion component A. The weight-average molecular weight Mw measured by gel permeation chromatography is 20000-22000 g / mol, and the conversion rate is more than 90%.

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

[0041] The molecular weight distribution of the polymer is determined by chromatographic separation, and the moles of the polymer are obtained by calculus; the moles of the monomer refer to the total moles of TPEG2400, TPEG1200, and TPEG400.

[0042] Method for preparing linear dispersion component B, comprising the following steps: Mix 260 - 300 parts by mass of glyoxal, 200 - 250 parts by mass of melamine, and 25 - 40 parts by mass of m-hydroxybenzoic acid, adjust the pH value to 8.5 - 9.5 with NaOH solution (30 wt.%), and react at 60 - 70 °C for 6 - 120 min; Add 120 - 170 parts by mass of sodium bisulfite to the above reaction system, adjust the pH value to 10 - 12 with NaOH solution (30 wt.%), and react at 70 - 80 °C for 90 - 150 min. After the reaction is completed, keep the temperature for 60 min (do not stir during heat preservation, stir during the rest of the reaction process, and the stirring rate is 250 - 300 r / min). Then, cool the above reaction system to room temperature, adjust the pH value of the solution to 4.5 - 5.5 with HCl solution (30 wt.%), and react at 45 - 55 °C for 120 min. After the above reaction is completed, add 15 - 25 parts by mass of sodium bisulfite to the solution, quickly raise the temperature to 75 - 85 °C, and keep the temperature for 120 min; After the system cools down, a colorless viscous solution is obtained, and then the viscous solution is concentrated and dried to obtain a white powder, which is the linear dispersion component B.

[0043] Sensitivity-reducing component C, comprising the following components in parts by mass: montmorillonite (including carboxyl and organoammonium-modified organophilic montmorillonite) 50 parts, triethanolamine 3 - 8 parts, sodium polyacrylate (weight-average molecular weight of 5 million) 3 - 8 parts, and water 440 parts.

[0044] The montmorillonite is purchased from Zhejiang Fenghong New Materials Co., Ltd., and the model is DK5.

[0045] Method for preparing sensitivity-reducing component C, comprising: Mix montmorillonite, triethanolamine, sodium polyacrylate, and water, and disperse them into a solution at high speed (8000 r / min) in a high-speed disperser to obtain sensitivity-reducing component C.

[0046] In the second aspect of the present invention, there is provided a method for preparing the above low-sensitivity admixture, comprising the following steps:

[0047] Mix dispersion component A, linear dispersion component B, and sensitivity-reducing component C evenly to obtain the low-sensitivity admixture.

[0048] In the third aspect of the present invention, there is provided an application of the above low-sensitivity admixture in the preparation of small-slump concrete.

[0049] All "parts" mentioned in the following examples are "parts by mass".

[0050] In the specific embodiments of the present invention, the weight-average molecular weight of the sodium polyacrylate used is 5 million; the montmorillonite is purchased from Zhejiang Fenghong New Materials Co., Ltd., and the model is DK5.

[0051] Example 1

[0052] Preparation method of a low-sensitivity admixture for low-slump concrete

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

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

[0055] Add 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 into a reactor equipped with a stirrer, a dropping device, and a heating device. Heat up to 40°C, set the rotation speed to 250 r / min, add 10 parts by mass of initiator (5 parts by mass of hydrogen peroxide, 5 parts by mass of an aqueous solution of ferrous sulfate with a concentration of 1 wt.%), and start dropping 145 parts by mass of solution a and 153.5 parts by mass of solution b (solution a consists of 45 parts by mass of acrylic acid and 100 parts by mass of deionized water; solution b consists of 1 part by mass of ascorbic acid, 2.5 parts by mass of mercaptopropionic acid, and 150 parts by mass of deionized water). The dropping time is 2.5 h. After the dropping is completed, continue the reaction for 60 min. After the reaction is completed, cool the temperature of the system to room temperature, neutralize the pH value of the solution to 8 with NaOH solution (30 wt.%), and adjust the concentration to 40% with deionized water to obtain dispersion component A.

[0056] The weight-average molecular weight Mw measured by gel permeation chromatography is 20497 g / mol, and the conversion rate is 92%.

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

[0058] Add 260 parts by mass of glyoxal, 200 parts by mass of melamine, and 25 parts by mass of m-hydroxybenzoic acid into a reactor equipped with a stirrer, a dropping device, a reflux condenser, and a heating device. Adjust the pH value to 8.5 with NaOH solution (30 wt.%), and react at 60°C for 60 min; add 120 parts by mass of sodium bisulfite to the above reaction system, and adjust the pH value to 10 with NaOH solution (30 wt.%), and react at 70°C for 90 min. After the reaction is completed, keep the temperature for 60 min (do not stir during the heat preservation, stir during the rest of the reaction process, and the stirring rate is 250 r / min). Then cool the above reaction system to room temperature, and adjust the pH value of the solution to 4.5 with HCl solution (30 wt.%), and react at 45°C for 120 min; after the above reaction is completed, add 15 parts by mass of sodium bisulfite to the solution, quickly heat up to 75°C, and keep the temperature for 120 min; after the system is cooled, obtain a colorless viscous solution, and then concentrate and dry the viscous solution to obtain a white powder, which is linear dispersion component B.

[0059] (4) Preparation method of sensitivity-reducing component C

[0060] Mix 50 parts by mass of montmorillonite (including carboxyl- and organic ammonium-modified organic montmorillonite), 3 parts by mass of triethanolamine, 3 parts by mass of sodium polyacrylate, and 440 parts by mass of deionized water, and disperse them at high speed (8000 r / min) in a high-speed disperser to form a solution, obtaining sensitivity-reducing component C.

[0061] (5) Mix dispersing component A, linear dispersing component B, and sensitivity-reducing component C 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) The low-sensitivity admixture is composed of the following components in parts by mass: 550 parts of dispersing component A, 350 parts of linear dispersing component B, and 100 parts of sensitivity-reducing component C.

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

[0066] In a reactor equipped with a stirrer, a dropping device, and a heating device, add 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, heat up to 50 °C, set the rotation speed to 300 r / min, add 10 parts by mass of initiator (5 parts by mass of hydrogen peroxide, 5 parts by mass of an aqueous solution of ferrous sulfate with a concentration of 1 wt.%), and start dropping 145 parts by mass of liquid a and 153.5 parts by mass of liquid b (liquid a consists of 45 parts by mass of acrylic acid and 100 parts by mass of deionized water; liquid b consists of 1 part by mass of ascorbic acid, 2.5 parts by mass of mercaptopropionic acid, and 150 parts by mass of deionized water). The dropping time is 3.5 h. After the dropping is completed, continue the reaction for 120 min. After the reaction ends, cool the temperature of the system to room temperature, neutralize the pH value of the solution to 9 with NaOH solution (30 wt.%), and adjust the concentration to 40% with deionized water to obtain dispersing component A.

[0067] The weight-average molecular weight Mw measured by gel permeation chromatography is 21887 g / mol, and the conversion rate is 94%.

[0068] (3) Preparation method of linear dispersing 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 are added. The pH value is adjusted to 9.5 with a NaOH solution (30 wt.%), and the reaction is carried out at 70 °C for 120 min. 170 parts by mass of sodium bisulfite are added to the above reaction system, and the pH value is adjusted to 12 with a NaOH solution (30 wt.%), and the reaction is carried out at 80 °C for 150 min. After the reaction is completed, it is kept warm for 60 min (without stirring during the heat preservation, and stirred during the rest of the reaction process, and the stirring rate is 300 r / min). Then, after the above reaction system is cooled to room temperature, the pH value of the solution is adjusted to 5.5 with a HCl solution (30 wt.%), and the reaction is carried out at 55 °C for 120 min. After the above reaction is completed, 25 parts by mass of sodium bisulfite are added to the solution, and the temperature is quickly raised to 85 °C, and kept warm for 120 min. After the system is cooled, a colorless viscous solution is obtained, and then the viscous solution is concentrated and dried to obtain a white powder, which is the linear dispersion component B.

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

[0071] 50 parts by mass of montmorillonite (including carboxyl and organically ammonium-modified organomontmorillonite), 8 parts by mass of triethanolamine, 8 parts by mass of sodium polyacrylate and 440 parts by mass of deionized water are mixed, and dispersed at high speed (8000 r / min) in a high-speed disperser to form a solution, obtaining the desensitizing component C.

[0072] (5)Mix the dispersion component A, the linear dispersion component B and the desensitizing component C evenly to obtain the low-sensitivity admixture.

[0073] Example 3

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

[0075] (1)The low-sensitivity admixture is composed of the following components in parts by mass: 550 parts of dispersion component A, 300 parts of linear dispersion component B and 150 parts of desensitizing component C.

[0076] (2)Preparation method of dispersion 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. The temperature was raised to 45 °C, the rotation speed was set at 280 r / min, and 10 parts by mass of an initiator (5 parts by mass of hydrogen peroxide and 5 parts by mass of an aqueous solution of ferrous sulfate with a concentration of 1 wt.%) was added. Then, 145 parts by mass of liquid a and 153.5 parts by mass of liquid b were started to be dropped (liquid a consists of 45 parts by mass of acrylic acid and 100 parts by mass of deionized water; liquid b consists of 1 part by mass of ascorbic acid, 2.5 parts by mass of mercaptopropionic acid, and 150 parts by mass of deionized water). The dropping time was 3 h. After the dropping was completed, the reaction continued for 90 min. After the reaction ended, the temperature of the system was lowered to room temperature, and the pH value of the solution was neutralized to 8.5 with a NaOH solution (30 wt.%). Deionized water was added to adjust the concentration to 40%, and the dispersed component A was obtained.

[0078] The weight-average molecular weight Mw measured by gel permeation chromatography was 21068 g / mol, and the conversion rate was 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 above reaction system, and the pH value was adjusted to 11 with a NaOH solution (30 wt.%), and the reaction was carried out at 75 °C for 120 min. After the reaction was completed, it was kept warm for 60 min (no stirring during the heat preservation, and stirring was carried out during the rest of the reaction process, and the stirring rate was 280 r / min). Then, after the above reaction system was 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 above reaction was completed, 20 parts by mass of sodium bisulfite was added to the solution, and the temperature was quickly raised to 80 °C, and it was kept warm for 120 min. After the system was cooled, a colorless viscous solution was obtained, and then the viscous solution was concentrated and dried to obtain a white powder, which is the linear dispersed component B.

[0081] (4)Preparation method of sensitivity-reducing component C

[0082] 50 parts by mass of montmorillonite (organic montmorillonite modified with carboxyl 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, and the sensitivity-reducing component C was obtained.

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

[0084] Example 4

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

[0086] (1) The low-sensitivity admixture is composed of the following components by mass: 550 parts of dispersed component A, 300 parts of linear dispersed component B, and 150 parts of sensitivity-reducing 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, add 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. Heat up to 45 °C, set the rotation speed to 280 r / min, add 10 parts by mass of initiator (5 parts by mass of hydrogen peroxide, 5 parts by mass of an aqueous solution of ferrous sulfate with a concentration of 1 wt.%), and start dropping 145 parts by mass of liquid a and 153.5 parts by mass of liquid b (liquid a is composed of 45 parts by mass of acrylic acid and 100 parts by mass of deionized water; liquid b is composed of 1 part by mass of ascorbic acid, 2.5 parts by mass of mercaptopropionic acid, and 150 parts by mass of deionized water). The dropping time is 3 h. After the dropping is completed, continue the reaction for 90 min. After the reaction is completed, cool the temperature of the system to room temperature, neutralize the solution to pH 8.5 with NaOH solution (30 wt.%), and adjust the concentration to 40% with deionized water to obtain dispersed component A.

[0089] The weight-average molecular weight Mw measured by gel permeation chromatography is 21068 g / mol, and the conversion rate is 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 min. 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 min. After the reaction was completed, it was kept warm for 60 min (without stirring during the heat preservation, and stirred during the rest of the reaction process, and the stirring rate was 280 r / min). Then, after the above reaction system was cooled to room temperature, the pH value of the solution was adjusted to 5.5 with a HCl solution (30 wt.%), and the reaction was carried out at 55 °C for 120 min. After the above reaction was completed, 25 parts by mass of sodium bisulfite was added to the solution, and the temperature was quickly raised to 85 °C, and it was kept warm for 120 min. After the system was cooled, a colorless viscous solution was obtained, and then the viscous solution was concentrated and dried to obtain a white powder, which was the linear dispersion component B.

[0092] (4)Preparation method of the sensitivity-reducing component C

[0093] 50 parts by mass of montmorillonite (organic montmorillonite modified with carboxyl 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, obtaining the sensitivity-reducing component C.

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

[0095] Comparative Example 1

[0096] Same as Example 3, the only difference was that the dispersion component A was replaced with an equal mass fraction of polycarboxylate superplasticizer (solid content 40%, purchased from Shandong Xinmaoyuan Chemical Co., Ltd.).

[0097] Comparative Example 2

[0098] Same as Example 3, the only difference was that the linear dispersion component B was replaced with an equal mass fraction of sulfonated melamine superplasticizer (purchased from Shanghai Qishuo Industry Co., Ltd.).

[0099] Comparative Example 3

[0100] Same as Example 3, the only difference was that the low-sensitivity admixture was composed of the following components in parts by mass: 600 parts of dispersion component A, 250 parts of linear dispersion component B and 150 parts of sensitivity-reducing component C.

[0101] Comparative Example 4

[0102] Same as Example 3, with the only difference being that TPEG2400 in the dispersion component A is replaced with HPEG2400 (methallyl alcohol polyoxyethylene ether with a molecular weight of 2400).

[0103] Effect Example 1

[0104] The sensitivity of the low-sensitivity admixture for concrete was tested:

[0105] The performance of the admixtures prepared in the examples and comparative examples was detected through concrete tests. The cement used was Esheng P·O42.5 cement; the fineness modulus of the manufactured sand was 2.8, the stone powder content was 6%, and the methylene blue MB value was 1.0; the gravel was 5 - 40 mm continuously graded crushed stone, and the mix proportion was as shown in Table 1.

[0106] For the sensitivity test of the low-sensitivity admixture for concrete, the slump, specimen molding, production, and curing were carried out with reference to GBT50080 - 2016 "Standard Test Method for Properties of Ordinary Concrete Mixtures", and the concrete strength was determined according to GBT 50081 - 2019 "Standard Test Method for Physical and Mechanical Properties of Concrete".

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

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

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

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

[0111] The results of the performance determination of the concrete are shown in Table 2.

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

[0113]

[0114] Among them, the dosages of the compound water reducer were 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 admixture prepared in the embodiment of the present invention is applied to concrete, compared with the blank control group, the addition or reduction of 0.1% dosage of the compound water reducer has little effect on the slump of concrete, and the slump difference of the embodiment under different dosages is less than that of the blank control group. From the perspective of adding 5 kg and 10 kg of water to the concrete mix ratio, the increase in the slump of the embodiment caused by the change in the water-binder ratio is much smaller than that of the blank group. From the perspective of the compressive strength of the samples molded at the dosage of 0.8% at 3 days, 7 days, and 28 days, the compressive strength of the embodiment is relatively higher than that of the blank control.

[0118] The above embodiments are only described for the preferred mode of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A low-sensitivity admixture for small slump concrete, characterized in that: The composition 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 into 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.

2. The low-sensitivity admixture according to claim 1, characterized in that: When preparing the dispersed component A, the mass ratio of the TPEG2400, TPEG1200, TPEG400, solvent, initiator, acrylic acid solution, and a mixed solution of ascorbic acid and mercaptopropionic acid is (200-300): (50-80): (15-25): 200: 10: 145: 153.

5.

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

4. The low-sensitivity admixture according to claim 1, characterized in that: When preparing the dispersed component A, the initiator comprises hydrogen peroxide in a mass ratio of 1:1 and ferrous sulfate solution in 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.

5. 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 time of dropwise addition is independently 2.5 to 3.5 hours; the reaction time after the dropwise addition is completed is 60 to 120 minutes.

6. The low-sensitivity admixture according to claim 1, characterized in that: 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).

7. 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 min. and / or, adjusting the pH to 10-12 and 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 heating the reaction at a temperature of 45-55° C. for 120 min; And / or, after adding sodium bisulfite again, the temperature of the heating reaction is 75-85° C. and the time is 120 min.

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

9. A method for preparing the low-sensitivity admixture according to any one of claims 1 to 8, 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.

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

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