Internal curing agent for ultra-high performance concrete and preparation method thereof

Abstract

The present invention discloses an internal curing agent for ultra-high performance concrete and its preparation method, belonging to the technical field of concrete admixture preparation. The internal curing agent comprises the following components, measured by weight: 650-700 parts of a slow-release component A; 200-250 parts of an isolating and water-retaining component B; and 50-150 parts of a shrinkage-reducing component C. The slow-release component A is a mixture of functional polymers containing sulfonic acid groups, amide groups, carboxylic acid groups, and ester groups; the isolating and water-retaining component B is a mixture of a polymeric water-retaining component B1 and a surfactant-coated component B2; and the shrinkage-reducing component C is composed of an air-entraining agent, a defoamer, and water. The internal curing agent disclosed herein can be used in concrete to effectively reduce the shrinkage of UHPC, while minimally affecting its workability and setting time, while significantly improving both the early and late strength of the concrete.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete admixture preparation, and in particular relates to an internal curing agent for ultra-high performance concrete and a preparation method thereof. Background Art

[0002] With the booming development of the transportation and civil engineering industries, the industry's requirements for concrete are also increasing. Modern building structures are developing towards high-rise, lightweight, and long-span structures. The defects of traditional concrete, such as low strength, poor tensile strength, and poor crack resistance, have seriously restricted the development of new structures. Ultra-high performance concrete (UHPC) has become a research focus for new concrete materials due to its excellent properties such as high toughness, high strength, high durability, and strong self-healing ability of microcracks. However, due to the large amount of cementitious materials used, low water-cement ratio (≤0.2), and the addition of ultrafine powder, UHPC's shrinkage during the plastic and hardening stages increases significantly, increasing the risk of premature cracking in UHPC. Currently, shrinkage cracking has become one of the technical difficulties that urgently need to be solved in the engineering application of UHPC.

[0003] Internal curing agents are materials with water-absorbing and water-releasing properties added to concrete during the initial mixing phase. After the concrete is formed, they release the absorbed water within it, providing internal curing. Internal curing agents can significantly reduce the maintenance costs of concrete structures during use, increase internal humidity, enhance the hydration of cementitious materials, improve concrete density, effectively mitigate early shrinkage cracking, and extend the service life of concrete structures. However, the addition of common internal curing agents such as SAP resin and lightweight porous materials (ceramsite, expanded perlite) to ultra-high performance concrete can significantly reduce the initial fluidity of the concrete and reduce its early and later strength, seriously impacting the on-site pouring and use of ultra-high performance concrete.

[0004] Therefore, preparing an internal curing agent that improves the early shrinkage cracking of ultra-high performance concrete without affecting the initial flow properties and strength is of significant significance to the application and development of ultra-high performance concrete. Summary of the Invention

[0005] In response to the above technical problems, the present invention proposes an internal curing agent for ultra-high performance concrete and a preparation method thereof.

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

[0007] One of the technical solutions of the present invention:

[0008] An internal curing agent for ultra-high performance concrete, comprising the following components in parts by weight:

[0009] Slow-release component A 650-700 parts; isolation and water retention component B 200-250 parts; shrinkage reduction component C 50-150 parts;

[0010] The sustained-release component A is a mixed solution of functional polymers containing sulfonic acid groups, amide groups, carboxylic acid groups, and ester groups;

[0011] The isolation and water-retaining component B is a mixture of a polymer water-retaining component B1 and a surfactant-coated component B2;

[0012] The shrinkage-reducing component C consists of an air-entraining agent, a defoaming agent and water.

[0013] Optionally, the preparation process of the sustained-release component A is as follows:

[0014] Ethylene glycol monovinyl polyoxyethylene ether (GPEG), 2-acrylamide-2-methylpropanesulfonic acid, N,N'-methylenebisacrylamide, deionized water, and an initiator were uniformly mixed, and then liquids a and b were added dropwise while stirring, and then reacted to obtain a functional polymer, and the concentration was adjusted to 40% with deionized water to obtain a sustained-release component A;

[0015] Wherein, according to parts by weight, the liquid a is composed of 30 parts of acrylic acid, 25 parts of hydroxypropyl acrylate, 25 parts of vinyl methacrylate and 100 parts of deionized water;

[0016] The solution B consists of 1 part ascorbic acid, 1 part mercaptopropionic acid and 150 parts deionized water.

[0017] Furthermore, the molecular weight of the ethylene glycol monovinyl polyoxyethylene ether is 3000;

[0018] The initiator comprises, by weight, 3 parts of hydrogen peroxide (mass concentration is 30%) and 2 parts of ferrous sulfate solution (mass concentration of ferrous sulfate in the ferrous sulfate aqueous solution is 1 wt.%).

[0019] Furthermore, the mass ratio of the GPEG, 2-acrylamide-2-methylpropanesulfonic acid, N,N'-methylenebisacrylamide and deionized water is: 400-500:45-55:3-5:300.

[0020] Furthermore, the dripping conditions are: dripping for 2.5h-3.5h at 10-15°C and a rotation speed of 250-300r / min; and / or,

[0021] The reaction time is 60-120 min.

[0022] Furthermore, the weight average molecular weight Mw of the functional polymer is 40,000-45,000 g / mol.

[0023] Optionally, the preparation process of the polymer water-retaining component B1 is:

[0024] 2-Acrylamide-2-methylpropanesulfonic acid, acrylamide, acrylic acid, deionized water, ammonium persulfate, ferrous sulfate solution (concentration of 1 wt.%) and ascorbic acid were mixed, stirred for reaction, and then water was added for swelling to obtain a high molecular weight water-retaining component B1.

[0025] Furthermore, the mass ratio of the 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, acrylic acid, deionized water, ammonium persulfate, ferrous sulfate solution and ascorbic acid is: 4-8: 35-45: 50-60: 300: 3-5: 1-2: 1-2.

[0026] Further, the conditions of the stirring reaction are:

[0027] The rotation speed is 150-200 r / min; the reaction temperature is 70-80° C., and the reaction time is 3-5 hours.

[0028] Optionally, the preparation process of the surfactant-coated component B2 is as follows:

[0029] Deionized water, sodium lauryl sulfate, and surfactant (EFS4070) were stirred evenly, and then solutions c and d were added dropwise to the mixture for reaction. After the reaction was completed, the mixture was cooled to room temperature, and then ammonia water (ammonia concentration was 0.1 mol / L) was added and stirred evenly to obtain B2;

[0030] Wherein, according to parts by weight, the liquid C is composed of 150 parts of vinyl methacrylate, 100 parts of butyl acrylate, 50 parts of acrylic acid, 35 parts of styrene, and 15 parts of ethylene glycol ethyl ether;

[0031] The solution d is composed of 5 parts of ammonium persulfate and 150 parts of deionized water.

[0032] Furthermore, the mass ratio of the deionized water, sodium lauryl sulfate, EFS4070 and ammonia water is: 400-500:25-35:50-70:20.

[0033] Furthermore, the rotation speed during the stirring process is 150-200 r / min, and the stirring temperature is 75-80°C.

[0034] Furthermore, the mass ratio of the polymer water-retaining component B1 to the surfactant-coated component B2 is 4:1.

[0035] Optionally, the shrinkage-reducing component C is composed of 4 to 6 parts of triterpenoid saponin air-entraining agent solution, 2 to 3 parts of polyether defoaming agent, 2 to 3 parts of silicone defoaming agent and 90 parts of deionized water, calculated by weight.

[0036] The second technical solution of the present invention:

[0037] A method for preparing an internal curing agent for ultra-high performance concrete comprises the following steps:

[0038] The above components in parts by weight are directly mixed and uniformly obtained.

[0039] The third technical solution of the present invention:

[0040] A kind of concrete, the raw materials of which include the above-mentioned internal curing agent.

[0041] Optionally, the concrete includes the following components:

[0042] Cement, composite admixtures, expansive agent, quartz sand, water, steel fiber and admixtures;

[0043] The admixture is obtained by mixing a polycarboxylate water reducer (six-carbon type P6), an internal curing agent, water and a defoaming agent (polyether type).

[0044] Furthermore, the mass ratio of the polycarboxylate water reducer (six-carbon type P6), internal curing agent, water and defoaming agent (polyether type) is 800:100:99:1.

[0045] Compared with the prior art, the present invention has the following advantages and technical effects:

[0046] The internal curing agent proposed in the present invention can not only effectively reduce the shrinkage of UHPC, but also has minimal impact on its workability and setting time, while also significantly improving the early and late strength of concrete, and has broad application prospects. DETAILED DESCRIPTION

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0052] The embodiment of the present invention discloses an internal curing agent for ultra-high performance concrete, which can effectively reduce the shrinkage and cracking of ultra-high performance concrete during the plasticity and hardening stages without affecting the initial fluidity and strength of the concrete.

[0053] The internal curing agent is obtained by compounding a slow-release component A, an isolation and water-retention component B, and a shrinkage-reducing component C in a certain proportion;

[0054] Among them, the active ingredient in the slow-release component A is a polymer synthesized by the polymerization reaction of low-molecular substances containing different hydrophilic groups. The molecular chain contains a large number of hydrophilic groups (sulfonic acid groups, amide groups, carboxylic acid groups) that form hydrogen bonds with water, which can promote cement hydration and secondary hydration of mineral admixtures, reduce concrete shrinkage and cracking, and improve concrete strength and durability. At the same time, the slow-release component A contains an ester group, which hydrolyzes in the alkaline solution of cement, further helping the cement particles to deflocculate, release free water, promote the hydration of cement and mineral admixtures, and improve the density of ultra-high performance concrete.

[0055] The isolating and water-retaining component B presents a macromolecular network structure in the liquid to lock the free water in the cement paste, and is adsorbed on the surface of the concrete to form a hydrophobic film, reducing the evaporation loss of water on the concrete surface and preventing the migration of water. At the same time, it provides time for the early hydration of the slow-release component A, reducing the drying shrinkage of the ultra-high performance concrete caused by water evaporation during the early hydration process.

[0056] Shrinkage-reducing component C uses air-entraining agents and defoamers to eliminate large bubbles introduced during the mixing process of ultra-high performance concrete. Instead, it introduces tiny bubbles to absorb the autogenous shrinkage caused by the decrease in water content in the capillaries and the increase in negative pressure within the pores. This also provides space for the later hydration of slow-release component A. These tiny bubbles also create a rolling effect, improving the concrete's workability and reducing the impact of internal curing agents on initial flow properties.

[0057] The ultra-high performance concrete internal curing agent comprises the following raw materials in parts by weight:

[0058] The sustained-release component A accounts for 650-700 parts; the isolation and water-retaining component B accounts for 200-250 parts; the shrinkage-reducing component C accounts for 50-150 parts;

[0059] (1) The preparation process of sustained-release component A is as follows:

[0060] In a reactor equipped with a stirrer, a dropping device and a heating device, 400-500 parts of GPEG 3000 (ethylene glycol monovinyl polyoxyethylene ether with a molecular weight of 3000), 45-55 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3-5 parts of N,N'-methylenebisacrylamide, and 300 parts of deionized water are added. Ice cubes are added to lower the initial temperature to 10-15°C. The speed is set to 250-300 r / min. An initiator (3 parts of hydrogen peroxide and 2 parts of ferrous sulfate solution (concentration of 1 wt.%)) is added. Liquid a and liquid b (liquid a consists of 30 parts of acrylic acid, 25 parts of hydroxypropyl acrylate, 25 parts of vinyl methacrylate, and 100 parts of deionized water; liquid b consists of 1 part of ascorbic acid, 1 part of mercaptopropionic acid, and 150 parts of deionized water) is added dropwise for 2.5 h to 3.5 h. h. After the dropwise addition is complete, the reaction is continued for 60-120 min. After the reaction is completed, the system temperature is lowered to room temperature and the concentration is adjusted to 40% with deionized water to obtain a sustained-release component A. The weight-average molecular weight Mw measured by gel permeation chromatography is 40,000-45,000 g / mol, and the conversion rate is greater than 90%. The conversion rate is calculated as follows:

[0061] Conversion rate (%) = (moles of polymer / moles of monomer) × 100%.

[0062] 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 GPEG 3000, 2-acrylamido-2-methylpropanesulfonic acid, and N,N'-methylenebisacrylamide.

[0063] (2) The preparation process of the isolated water-retaining component B is as follows:

[0064] In a reactor equipped with a stirrer, a dropping device, and a heater, set the speed to 150-200 r / min, add 4-8 parts of 2-acrylamido-2-methylpropanesulfonic acid, 35-45 parts of acrylamide, 50-60 parts of acrylic acid, and 300 parts of deionized water. Then, add 3-5 parts of ammonium persulfate, 1-2 parts of ferrous sulfate solution, and 1-2 parts of ascorbic acid. Stirring is initiated, and the mixture is heated to 70-80°C. After mixing evenly, the mixture is allowed to stand at 70-80°C for 3-5 hours. 400-500 parts of water is added, and the mixture is allowed to swell for 8-10 hours. After stirring for 2 hours, component B1 is obtained. The weight-average molecular weight (Mw) of component B1 is 1.5 million to 2 million, as determined by gel permeation chromatography.

[0065] In a reactor equipped with a stirrer, a dropping device and a heating device, 400-500 parts of deionized water, 25-35 parts of sodium lauryl sulfate, and 50-70 parts of EFS4070 (purchased from Shanghai Zhongcheng Fine Chemical Co., Ltd.) were added. After stirring evenly, the temperature was raised to 75-80°C and stirring was started. The speed was set to 150-200 r / min, and liquids c and d (liquid c composed of 150 parts of vinyl methacrylate, 100 parts of butyl acrylate, 50 parts of acrylic acid, 35 parts of styrene, and 15 parts of ethylene glycol ethyl ether; liquid d composed of 5 parts of ammonium persulfate and 150 parts of deionized water) were added dropwise. The reaction was allowed to proceed dropwise for 2-3 hours, and the mixture was kept warm for 2 hours. After the reaction was completed, the temperature of the system was lowered to room temperature, 20 parts of aqueous ammonia (0.1 mol / L) were added, and the mixture was stirred evenly to obtain B2.

[0066] 800 parts of B1 and 200 parts of B2 were mixed and stirred evenly to obtain the isolation and water retention component B.

[0067] (3) The preparation process of the shrinkage-reducing component C is as follows:

[0068] The shrinkage reducing component C is composed of 4 to 6 parts of triterpenoid saponin air entraining agent solution, 2 to 3 parts of polyether defoaming agent, 2 to 3 parts of silicone defoaming agent and 90 parts of deionized water.

[0069] Unless otherwise specified, the "room temperature" in the present invention refers to 20-30°C.

[0070] The "parts" described in the present invention, unless otherwise specified, refer to parts by mass.

[0071] The raw materials used in the present invention are all purchased from the market.

[0072] The technical solution of the present invention is further illustrated by the following examples.

[0073] Example 1

[0074] An internal curing agent for ultra-high performance concrete is obtained by directly and evenly mixing the following three components in parts by weight:

[0075] 650 parts of slow-release component A; 200 parts of isolation and water-retention component B; 150 parts of shrinkage-reducing component C;

[0076] Among them, the preparation process of the three components is as follows:

[0077] (1) The preparation process of sustained-release component A is as follows:

[0078] In a reactor equipped with a stirrer, a dropping device, and a heating device, 400 parts of GPEG 3000 (ethylene glycol monovinyl polyoxyethylene ether), 45 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3 parts of N,N'-methylenebisacrylamide, and 300 parts of deionized water were added. Ice cubes were added to lower the initial temperature to 10°C (the ice cubes were not added to the above-mentioned mixed system and were only used to lower the temperature of the reactor). The speed was set to 250 r / min. An initiator (3 parts of hydrogen peroxide and 2 parts of ferrous sulfate solution) was added, and liquids a and b (liquid a composed of 30 parts of acrylic acid, 25 parts of hydroxypropyl acrylate, 25 parts of vinyl methacrylate, and 100 parts of deionized water; liquid b composed of 1 part of ascorbic acid, 1 part of mercaptopropionic acid, and 150 parts 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, and the concentration was adjusted to 40% with deionized water to obtain the sustained-release component A. The weight average molecular weight Mw was measured by gel permeation chromatography and was 41476 g / mol, with a conversion rate of 93%.

[0079] (2) The preparation process of the isolated water-retaining component B is as follows:

[0080] In a reactor equipped with a stirrer, a dropping device and a heating device, the speed was set to 150 r / min, 4 parts of 2-acrylamide-2-methylpropanesulfonic acid, 35 parts of acrylamide, 50 parts of acrylic acid, 300 parts of deionized water, 3 parts of ammonium persulfate, 1 part of ferrous sulfate solution, and 1 part of ascorbic acid were added, stirring was started, and the temperature was raised to 70°C. After mixing evenly, the mixture was allowed to stand at 70°C and reacted for 3 hours; then 400 parts of water was added, and the mixture was swollen for 8 hours. After stirring for 2 hours, component B1 was obtained. The weight average molecular weight Mw of component B1 was 1.55 million as measured by gel permeation chromatography;

[0081] In a reactor equipped with a stirrer, a dropping device and a heating device, add 400 parts of deionized water, 25 parts of sodium lauryl sulfate and 50 parts of EFS4070, stir evenly, heat to 75°C, start stirring, set the speed to 150 r / min, and start dropping liquids c and d (liquid c consists of 150 parts of vinyl methacrylate, 100 parts of butyl acrylate, 50 parts of acrylic acid, 35 parts of styrene, and 15 parts of ethylene glycol ethyl ether; liquid d consists of 5 parts of ammonium persulfate and 150 parts of deionized water). The reaction is allowed to proceed dropwise for 2 hours and the temperature is kept warm for 2 hours. After the reaction is completed, the temperature of the system is lowered to room temperature, 20 parts of aqueous ammonia (0.1 mol / L) are added, and stirring is carried out to obtain B2.

[0082] 800 parts of B1 and 200 parts of B2 were mixed and stirred evenly to obtain the isolation and water retention component B.

[0083] (3) The preparation process of the shrinkage-reducing component C is as follows:

[0084] The shrinkage reduction component C consists of 4 parts of triterpenoid saponin air entraining agent (purchased from Jinan Xinhanbang Chemical Technology Co., Ltd., model: STZ12), 2 parts of polyether defoaming agent (purchased from Guangdong Zhongke Hongtai New Materials Co., Ltd., model: B-299), 2 parts of silicone defoaming agent (purchased from Guangdong Nanhui New Materials Co., Ltd., model: CI-0560) and 90 parts of deionized water.

[0085] Example 2

[0086] An internal curing agent for ultra-high performance concrete is obtained by directly and evenly mixing the following three components in parts by weight:

[0087] 700 parts of slow-release component A; 250 parts of isolation and water retention component B; 50 parts of shrinkage-reducing component C;

[0088] Among them, the preparation process of the three components is as follows:

[0089] (1) The preparation process of sustained-release component A is as follows:

[0090] In a reactor equipped with a stirrer, a dropping device, and a heating device, 500 parts of GPEG 3000 (ethylene glycol monovinyl polyoxyethylene ether), 55 parts of 2-acrylamide-2-methylpropanesulfonic acid, 5 parts of N,N'-methylenebisacrylamide, and 300 parts of deionized water were added. Ice cubes were added to lower the initial temperature to 5°C. The speed was set to 300 r / min. An initiator (3 parts of hydrogen peroxide and 2 parts of ferrous sulfate solution (1 wt.%)) was added. Liquids a and b (liquid a composed of 30 parts of acrylic acid, 25 parts of hydroxypropyl acrylate, 25 parts of vinyl methacrylate, and 100 parts of deionized water; liquid b composed of 1 part of ascorbic acid, 1 part of mercaptopropionic acid, and 150 parts 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, and the concentration was adjusted to 40% with deionized water to obtain the sustained-release component A. The weight average molecular weight Mw was measured by gel permeation chromatography and was 44379 g / mol, with a conversion rate of 95%.

[0091] (2) The preparation process of the isolated water-retaining component B is as follows:

[0092] In a reactor equipped with a stirrer, a dropper, and a heater, set the speed to 200 r / min. Add 8 parts of 2-acrylamido-2-methylpropanesulfonic acid, 45 parts of acrylamide, 60 parts of acrylic acid, and 300 parts of deionized water. Then, add 5 parts of ammonium persulfate, 2 parts of ferrous sulfate solution (1 wt.%), and 2 parts of ascorbic acid. Stirring is initiated, and the mixture is heated to 80°C. After mixing thoroughly, the mixture is allowed to stand at 80°C for 5 hours. Then, 500 parts of water is added, and the mixture is allowed to swell for 10 hours. After stirring for 2 hours, component B1 is obtained. Gel permeation chromatography (GPC) analysis shows a weight-average molecular weight (Mw) of 1.94 million for component B1.

[0093] In a reactor equipped with a stirrer, a dropping device and a heating device, 500 parts of deionized water, 35 parts of sodium lauryl sulfate and 70 parts of EFS4070 (Shanghai Zhongcheng Fine Chemical Co., Ltd.) were added. After stirring evenly, the temperature was raised to 80°C and stirring was started. The speed was set to 200 r / min, and liquids c and d (liquid c consisted of 150 parts of vinyl methacrylate, 100 parts of butyl acrylate, 50 parts of acrylic acid, 35 parts of styrene, and 15 parts of ethylene glycol ethyl ether; liquid d consisted of 5 parts of ammonium persulfate and 150 parts of deionized water) were added dropwise. The reaction was allowed to proceed for 3 hours and the temperature was kept warm for 2 hours. After the reaction was completed, the temperature of the system was lowered to room temperature, 20 parts of aqueous ammonia (0.1 mol / L) were added, and stirring was carried out to obtain B2.

[0094] 800 parts of B1 and 200 parts of B2 were mixed and stirred evenly to obtain the isolation and water retention component B.

[0095] (3) The preparation process of the shrinkage-reducing component C is as follows:

[0096] The shrinkage-reducing component C consists of 6 parts of triterpenoid saponin air-entraining agent solution, 3 parts of polyether defoaming agent, 3 parts of silicone defoaming agent and 90 parts of deionized water.

[0097] Example 3

[0098] An internal curing agent for ultra-high performance concrete is obtained by directly and evenly mixing the following three components in parts by weight:

[0099] The slow-release component A accounts for 680 parts; the isolation and water-retention component B accounts for 220 parts; the shrinkage-reducing component C accounts for 100 parts;

[0100] Among them, the preparation process of the three components is as follows:

[0101] (1) The preparation process of sustained-release component A is as follows:

[0102] In a reactor equipped with a stirrer, a dropping device, and a heating device, 450 parts of GPEG 3000 (ethylene glycol monovinyl polyoxyethylene ether), 50 parts of 2-acrylamide-2-methylpropanesulfonic acid, 4 parts of N,N'-methylenebisacrylamide, and 300 parts of deionized water were added. Ice cubes were added to lower the initial temperature to 12°C, the speed was set to 280 r / min, and an initiator (3 parts of hydrogen peroxide and 2 parts of ferrous sulfate solution (1 wt.%)) was added. Liquid a and liquid b (liquid a composed of 30 parts of acrylic acid, 25 parts of hydroxypropyl acrylate, 25 parts of vinyl methacrylate, and 100 parts of deionized water; liquid b composed of 1 part of ascorbic acid, 1 part of mercaptopropionic acid, and 150 parts 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, and the concentration was adjusted to 40% with deionized water to obtain the sustained-release component A. The weight average molecular weight Mw was measured by gel permeation chromatography and was 43258 g / mol, with a conversion rate of 97%.

[0103] (2) The preparation process of the isolated water-retaining component B is as follows:

[0104] In a reactor equipped with a stirrer, a dropping device, and a heater, set the speed to 180 r / min, add 6 parts of 2-acrylamido-2-methylpropanesulfonic acid, 40 parts of acrylamide, 55 parts of acrylic acid, and 300 parts of deionized water. Then, add 4 parts of ammonium persulfate, 1.5 parts of ferrous sulfate solution (1 wt.%), and 1.5 parts of ascorbic acid. Stirring is initiated, and the mixture is heated to 75°C. After mixing thoroughly, the mixture is allowed to stand at 75°C for 4 hours. 450 parts of water is added, and the mixture is allowed to swell for 9 hours. After stirring for 2 hours, component B1 is obtained. The weight-average molecular weight (Mw) of component B1 is 1.84 million, as determined by gel permeation chromatography.

[0105] In a reactor equipped with a stirrer, a dropping device and a heating device, add 450 parts of deionized water, 30 parts of sodium lauryl sulfate and 60 parts of EFS4070, stir evenly, heat to 78°C, start stirring, set the speed to 180r / min, and start dropping liquids c and d (liquid c consists of 150 parts of vinyl methacrylate, 100 parts of butyl acrylate, 50 parts of acrylic acid, 35 parts of styrene, and 15 parts of ethylene glycol ethyl ether; liquid d consists of 5 parts of ammonium persulfate and 150 parts of deionized water). The reaction is allowed to proceed dropwise for 5 hours and the temperature is kept warm for 2 hours. After the reaction is completed, the temperature of the system is lowered to room temperature, 20 parts of aqueous ammonia (0.1mol / L) are added, and the mixture is stirred evenly to obtain B2.

[0106] 800 parts of B1 and 200 parts of B2 were mixed and stirred evenly to obtain the isolation and water retention component B.

[0107] (3) The preparation process of the shrinkage-reducing component C is as follows:

[0108] The shrinkage-reducing component C consists of 5 parts of triterpenoid saponin air-entraining agent solution, 2.5 parts of polyether defoamer, 2.5 parts of silicone defoamer and 90 parts of deionized water.

[0109] Example 4

[0110] An internal curing agent for ultra-high performance concrete is obtained by directly and evenly mixing the following three components in parts by weight:

[0111] The slow-release component A accounts for 680 parts; the isolation and water-retention component B accounts for 250 parts; the shrinkage-reducing component C accounts for 70 parts;

[0112] The preparation process of the three components is as follows:

[0113] (1) The preparation process of sustained-release component A is as follows:

[0114] In a reactor equipped with a stirrer, a dropping device, and a heating device, 450 parts of GPEG 3000 (ethylene glycol monovinyl polyoxyethylene ether), 50 parts of 2-acrylamide-2-methylpropanesulfonic acid, 4 parts of N,N'-methylenebisacrylamide, and 300 parts of deionized water were added. Ice cubes were added to lower the initial temperature to 12°C, the speed was set to 280 r / min, and an initiator (3 parts of hydrogen peroxide and 2 parts of ferrous sulfate solution (1 wt.%)) was added. Liquid a and liquid b (liquid a composed of 30 parts of acrylic acid, 25 parts of hydroxypropyl acrylate, 25 parts of vinyl methacrylate, and 100 parts of deionized water; liquid b composed of 1 part of ascorbic acid, 1 part of mercaptopropionic acid, and 150 parts 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, and the concentration was adjusted to 40% with deionized water to obtain the sustained-release component A. The weight average molecular weight Mw was measured by gel permeation chromatography and was 43258 g / mol, with a conversion rate of 97%.

[0115] (2) The preparation process of the isolated water-retaining component B is as follows:

[0116] In a reactor equipped with a stirrer, a dropping device, and a heater, set the speed to 180 r / min, add 6 parts of 2-acrylamido-2-methylpropanesulfonic acid, 40 parts of acrylamide, 55 parts of acrylic acid, and 300 parts of deionized water. Then, add 4 parts of ammonium persulfate, 1.5 parts of ferrous sulfate solution (1 wt.%), and 1.5 parts of ascorbic acid. Stirring is initiated, and the mixture is heated to 75°C. After mixing thoroughly, the mixture is allowed to stand at 75°C for 4 hours. 450 parts of water is added, and the mixture is allowed to swell for 9 hours. After stirring for 2 hours, component B1 is obtained. The weight-average molecular weight (Mw) of component B1 is 1.84 million, as determined by gel permeation chromatography.

[0117] In a reactor equipped with a stirrer, a dropping device and a heating device, add 450 parts of deionized water, 30 parts of sodium lauryl sulfate and 60 parts of EFS4070, stir evenly, heat to 78°C, start stirring, set the speed to 180r / min, and start dropping liquids c and d (liquid c consists of 150 parts of vinyl methacrylate, 100 parts of butyl acrylate, 50 parts of acrylic acid, 35 parts of styrene, and 15 parts of ethylene glycol ethyl ether; liquid d consists of 5 parts of ammonium persulfate and 150 parts of deionized water). The reaction is allowed to proceed dropwise for 5 hours and the temperature is kept warm for 2 hours. After the reaction is completed, the temperature of the system is lowered to room temperature, 20 parts of aqueous ammonia (0.1mol / L) are added, and the mixture is stirred evenly to obtain B2.

[0118] 800 parts of B1 and 200 parts of B2 were mixed and stirred evenly to obtain the isolation and water retention component B.

[0119] (3) The preparation process of the shrinkage-reducing component C is as follows:

[0120] The shrinkage-reducing component C consists of 5 parts of triterpenoid saponin air-entraining agent solution, 2.5 parts of polyether defoamer, 2.5 parts of silicone defoamer and 90 parts of deionized water.

[0121] Comparative Example 1

[0122] The only difference from Example 3 is that the GPEG 3000 in the sustained-release component A is replaced with TPEG3000 (prenol polyoxyethylene ether with a molecular weight of 3000) in equal parts by weight. Other procedures are the same as Example 3.

[0123] Comparative Example 2

[0124] The only difference from Example 3 is that the reaction temperature for synthesizing B1 and B2 in the isolation and water retention component B is set to 65° C., and the rest is the same as Example 3.

[0125] Comparative Example 3

[0126] The only difference from Example 3 is that the triterpenoid saponin air-entraining agent solution in the shrinkage-reducing component C is replaced with an equal mass fraction of sodium lauryl sulfate K12 air-entraining agent (purchased from Guangzhou Nanjia Chemical Co., Ltd.). Other preparation conditions are the same as those in Example 3.

[0127] Comparative Example 4

[0128] The only difference from Example 3 is that the internal curing agent for ultra-high performance concrete includes the following raw materials, calculated by weight: 850 parts of slow-release component A; 130 parts of isolation and water-retention component B; and 20 parts of shrinkage-reducing component C. Other preparation conditions are the same as those in Example 3.

[0129] Effect verification

[0130] The performance of the internal curing agents obtained in Examples 1-4 and Comparative Examples 1-4 was tested through concrete tests. The cement used was Esheng P·O 52.5 cement, and the mix ratios are shown in Table 1. In Table 1, 280 kg of composite admixture was composed of 120 kg of silica fume, 80 kg of first-grade fly ash, and 80 kg of mineral powder. The expansive agent used was UEA expansive agent (purchased from Jiangsu Dejiatuoda Building Materials Co., Ltd., model: UEA), which primarily contains multiple expansion sources such as aluminum sulfate, aluminum oxide, and potassium aluminum sulfate. Quartz sand was mixed in a mass ratio of 2:2:1 for 20-40 mesh, 40-70 mesh, and 70-120 mesh. The steel fiber used was copper-coated microfilament steel fiber, 0.2 ± 0.02 mm, and non-straight. The admixture amounted to 1.5% (1100 × 1.5% = 16.5) of the total mass of the cementitious material (cement + composite admixture + expansive agent). No curing agent was added to the blank mixture. The admixture formula per ton was: polycarboxylate superplasticizer (hexacarbon type P6): water: defoamer (polyether type) = 800:199:1 (mass ratio). The internal curing agents prepared in Examples 1-4 and Comparative Examples 1-4 were compounded with the admixture. The admixture formula per ton was: polycarboxylate superplasticizer (hexacarbon type P6): internal curing agent: water: defoamer (polyether type) = 800:100:99:1.

[0131] The impact of internal curing agents on the initial flow properties of concrete is determined by the expansion test method specified in T / CECS203-2021, "Technical Specification for the Application of Self-Compacting Concrete." The closer the expansion is to that of the blank control, the smaller the impact. Concrete setting time is determined by referring to GBT50080-2016, "Standard Test Methods for Performance of Ordinary Concrete Mixtures." Concrete specimen molding, preparation, and curing are performed in accordance with TCCPA7-2018, "Basic Properties and Test Methods of Ultra-High Performance Concrete." Concrete strength is determined in accordance with GBT 50081-2019, "Standard Test Methods for Physical and Mechanical Properties of Concrete." Concrete shrinkage deformation was measured according to GB / T 50082-2024, "Test Methods for Long-term Properties and Durability of Concrete." Samples measuring 100 mm × 100 mm × 515 mm were sealed with plastic wrap and cured in a constant-temperature curing room at 20 ± 5°C and 50% relative humidity. The length shrinkage of the samples was measured using a CABR-NES non-contact shrinkage deformation instrument. The length shrinkage of the samples was measured again after 7 and 28 days of curing. The test results are shown in Table 2.

[0132] Table 1 Ultra-high performance concrete mix ratio (kg / m 3 )

[0133]

[0134] Table 2 Test results of ultra-high performance concrete

[0135]

[0136] Table 2 shows that the prepared internal curing agent for ultra-high performance concrete significantly reduced the 7-day and 28-day shrinkage of the Example concrete compared to the blank control, demonstrating that the curing agent effectively reduces shrinkage in ultra-high performance concrete. The Example concrete exhibited minimal impact on initial and 1-hour expansion. The addition of the internal curing agent to the Example concrete exhibited minimal effect on setting time, with virtually no negative impact. The addition of the internal curing agent to the Ultra-High Performance Concrete exhibited a significant increase in strength, as measured by the 7-day and 28-day compressive and flexural strengths. Compared to the Comparative Example concrete, the Example concrete exhibited lower 7-day and 28-day shrinkage. The Comparative Example concrete exhibited a significant impact on initial and 1-hour expansion. Furthermore, the Comparative Example concrete delayed initial and final setting by approximately 0.5 to 2 hours, impacting construction performance. The Example concrete exhibited higher compressive and flexural strengths at 7 and 28 days.

[0137] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. An internal curing agent for ultra-high performance concrete, characterized in that: According to parts by weight, it includes the following components: Sustained-release component A: 650-700 parts; Isolation and water retention component B 200-250 parts; Shrinkage reducing component C 50~150 parts; The sustained-release component A is a mixed solution of functional polymers containing sulfonic acid groups, amide groups, carboxylic acid groups, and ester groups; The isolation and water-retention component B is a mixture of a polymer water-retention component B1 and a surfactant coating component B2; The shrinkage-reducing component C consists of an air-entraining agent, a defoaming agent and water; The preparation process of the sustained-release component A is as follows: Ethylene glycol monovinyl polyoxyethylene ether, 2-acrylamide-2-methylpropanesulfonic acid, N,N'-methylenebisacrylamide, water and an initiator were mixed uniformly, and then liquid a and liquid b were added dropwise while stirring, and then reacted to obtain a functional polymer, and then water was added to obtain a sustained-release component A with a concentration of 40wt%; Wherein, according to parts by weight, the liquid a is composed of 30 parts of acrylic acid, 25 parts of hydroxypropyl acrylate, 25 parts of vinyl methacrylate and 100 parts of water; The liquid B is composed of 1 part ascorbic acid, 1 part mercaptopropionic acid and 150 parts water; The preparation process of the surfactant-coated component B2 is as follows: Mix water, sodium lauryl sulfate, and a surfactant, then dropwise add liquid C and liquid D to the mixture to react. After the reaction is complete, cool to room temperature, then add ammonia water and stir evenly to obtain a surfactant-coated component B2. Wherein, according to parts by weight, the liquid C is composed of 150 parts of vinyl methacrylate, 100 parts of butyl acrylate, 50 parts of acrylic acid, 35 parts of styrene and 15 parts of ethylene glycol ethyl ether; The solution d is composed of 5 parts of ammonium persulfate and 150 parts of water; The surfactant is EFS4070.

2. The internal curing agent for ultra-high performance concrete according to claim 1, characterized in that: The mass ratio of the ethylene glycol monovinyl polyoxyethylene ether, 2-acrylamide-2-methylpropanesulfonic acid, N,N'-methylenebisacrylamide and water is: (400-500): (45-55): (3-5):

300.

3. The internal curing agent for ultra-high performance concrete according to claim 1, characterized in that: The preparation process of the polymer water-retaining component B1 is as follows: 2-Acrylamide-2-methylpropanesulfonic acid, acrylamide, acrylic acid, water, ammonium persulfate, 1 wt.% ferrous sulfate solution and ascorbic acid were mixed, stirred for reaction, and then swelled to obtain a high molecular weight water-retaining component B1.

4. The internal curing agent for ultra-high performance concrete according to claim 3, characterized in that: The mass ratio of the 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, acrylic acid, water, ammonium persulfate, 1 wt.% ferrous sulfate solution and ascorbic acid is: (4-8): (35-45): (50-60): 300: (3-5): (1-2): (1-2).

5. The internal curing agent for ultra-high performance concrete according to claim 1, characterized in that: The mass ratio of the water, sodium lauryl sulfate, surfactant and ammonia water is: 400-500:25-35:50-70:

20.

6. The internal curing agent for ultra-high performance concrete according to claim 1, characterized in that: The mass ratio of the polymer water-retaining component B1 to the surfactant coating component B2 is 4:

1.

7. The internal curing agent for ultra-high performance concrete according to claim 1, characterized in that: In terms of weight, the shrinkage-reducing component C is composed of 4 to 6 parts of triterpenoid saponin air entraining agent, 2 to 3 parts of polyether defoaming agent, 2 to 3 parts of silicone defoaming agent and 90 parts of water.

8. A method for preparing an internal curing agent for ultra-high performance concrete, characterized in that: The composition according to any one of claims 1 to 7 is directly mixed and uniformly obtained.

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