A long-lasting salt-alkali resistant concrete internal curing material and its preparation method

Abstract

This invention provides a long-lasting salt-alkali resistant concrete internal curing material and its preparation method, belonging to the field of building materials technology. The material, by weight fraction, is made from the following components: 12%–17% nano-calcium carbonate, 3%–5% halloysite, 10%–12% sodium humate, 6%–8% 3-aminopropyltriethoxysilane, 5%–10% sodium carboxymethyl cellulose, 3%–4% λ-type carrageenan, 1%–2% locust bean gum, 1%–1.8% slaked lime, 26%–30% first part N-hydroxymethylacrylamide, 20%–23% hydroxyethyl methacrylate, 5%–8% methacrylic acid, 0.2%–0.3% alumina, 0.2%–0.5% second part N-hydroxymethylacrylamide, and 0.5%–1% ammonium sulfite. This material not only possesses salt-alkali resistance but also significantly reduces concrete shrinkage and improves mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a long-lasting salt and alkali resistant concrete internal curing material and its preparation method. Background Technology

[0002] Infrastructure construction is closely related to concrete engineering. In some special environments, civil engineering construction requires concrete to be formulated according to local environmental characteristics to meet specific performance requirements. Otherwise, environmental factors can easily cause varying degrees of damage to the concrete. Especially in some high-altitude areas, strong winds, dryness, and large temperature differences negatively impact concrete construction, hydration, and curing. Furthermore, high-altitude areas often have abundant salt lake resources, resulting in water quality in many cold regions that is slightly alkaline, high in minerals, and hard. This complex, cold water environment, interacting with highly corrosive ions, causes the rate of cracking and damage in local cement concrete to be much higher than in inland areas. During service, the concrete is also more prone to cracking and loosening, leading to durability problems such as leakage and freeze-thaw damage.

[0003] In recent years, internal curing has become the most effective curing method for concrete and one of the most effective ways to alleviate self-drying and shrinkage cracking in concrete. This method is simple and easy to operate, eliminating the need for additional equipment and processes such as covering, demolding, and repeated watering. It replaces traditional curing techniques like watering, spraying, watering, covering, and mulching, thereby improving construction efficiency. It is particularly suitable for large-scale concrete construction in some high-altitude and cold regions. Among internal curing materials, polymer-based internal curing materials currently show significant effects. These materials primarily use acrylic acid and acrylamide as monomers, utilizing their hydroxyl and carboxyl groups to adsorb moisture through their three-dimensional network structure and the hydrophilicity of their functional groups. This adsorbed moisture can be easily released according to hydration needs, or replenished by moisture lost through evaporation or self-drying, thereby improving the hydration degree of cementitious materials and alleviating concrete shrinkage deformation.

[0004] However, the vast majority of polymer-based internal curing materials commonly used in concrete are acrylic and acrylate polymers, which have poor salt and alkali resistance and low water absorption rates in alkaline and salt solutions. Therefore, the application of polymer-based internal curing materials in the construction engineering field currently lacks a scientific design philosophy for their synthesis and development, and has failed to develop well-suited concrete internal curing materials. Most existing polymer-based internal curing material preparations focus on synthesis and modification aimed at increasing water absorption rates, with little molecular structure design considering the alkaline environment within the concrete mixture and the application environment. Especially when applied to certain saline-alkali environments, they are prone to premature release of pre-absorbed water, causing concrete bleeding and consequently weakening concrete performance and internal curing efficiency. Summary of the Invention

[0005] To overcome the problems existing in the internal curing process of concrete in saline-alkali environments in the prior art, the present invention aims to provide a long-lasting saline-alkali resistant concrete internal curing material and its preparation method. This material not only has saline-alkali resistance but also significantly reduces concrete shrinkage and improves mechanical properties. This ensures the long-term internal curing efficiency of concrete in certain regions, where strong winds, dryness, and large temperature differences hinder its effectiveness. Furthermore, the internal curing material maintains good moisture absorption and storage characteristics in saline-alkali environments, thereby controlling drying shrinkage and early thermal shrinkage in concrete, reducing the generation of microcracks, improving the mechanical properties and service life of concrete materials, and reducing maintenance costs.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention provides a long-lasting salt-alkali resistant concrete internal curing material, which is made from the following raw materials by weight: 12%–17% nano-calcium carbonate, 3%–5% halloysite, 10%–12% sodium humate, 6%–8% 3-aminopropyltriethoxysilane, 5%–10% sodium carboxymethyl cellulose, 3%–4% λ-type carrageenan, 1%–2% locust bean gum, 1%–1.8% slaked lime, 26%–30% first part N-hydroxymethylacrylamide, 20%–23% hydroxyethyl methacrylate, 5%–8% methacrylic acid, 0.2%–0.3% alumina, 0.2%–0.5% second part N-hydroxymethylacrylamide, and 0.5%–1% ammonium sulfite.

[0008] In one embodiment, the nano-calcium carbonate has a particle size of 15-40 nm, a calcium carbonate content of ≥98.5%, a pH of 8.5-10, and an impurity content of <0.1%.

[0009] Halloysite has a particle diameter of 0.1–0.4 μm, a length of <0.5 μm, and a purity of ≥99%.

[0010] The sodium humate has a particle diameter of 120 mesh, a sodium humate content (dry basis) ≥85%, a water-insoluble matter content <5%, a pH of 9-11, and a moisture content <12%.

[0011] In one embodiment, the sodium carboxymethyl cellulose is food grade and has a degree of substitution ≥0.9.

[0012] In one embodiment, the nano-calcium carbonate, halloysite, sodium humate, and 3-aminopropyltriethoxysilane are used to prepare an organic nano-calcium carbonate-sodium humate-haloysite composite.

[0013] The organic nano-calcium carbonate-sodium humate-haloite composite was prepared by the following process:

[0014] Nano-calcium carbonate and halloysite were respectively mixed with deionized water to prepare nano-calcium carbonate suspension A with a weight of 2% and halloysite suspension B with a weight of 1%.

[0015] 3-Aminopropyltriethoxysilane was prepared into a 3% (w / w) dilute solution, and then acetic acid was added to adjust the pH to obtain 3-aminopropyltriethoxysilane hydrolysate C.

[0016] Nano-calcium carbonate suspension A and halloysite suspension B were sequentially and uniformly dispersed in 3-aminopropyltriethoxysilane hydrolysate C. The mixture was heated and stirred in a water bath, sodium humate was added, and stirring was continued. The mixture was then cooled, filtered, washed, dried, and ground to obtain an organic nano-calcium carbonate-sodium humate-haloysite composite.

[0017] In one embodiment, the acetic acid is used to adjust the pH to 5.5-6.

[0018] This invention also provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, comprising the following steps:

[0019] An organic nano-calcium carbonate-sodium humate-halolite composite was prepared by using nano-calcium carbonate, halloysite, sodium humate, and 3-aminopropyltriethoxysilane, denoted as composite D. Then, composite D was prepared into a suspension E by adding water.

[0020] λ-type carrageenan and locust bean gum were sequentially dispersed in deionized water to prepare a dilute solution F;

[0021] Deionized water was added to methacrylic acid to prepare a dilute methacrylic acid solution. Quicklime was added and the mixture was cooled to room temperature. During stirring, the first portion of N-hydroxymethylacrylamide and hydroxyethyl methacrylate were added to obtain mixture G.

[0022] Sorbitol monostearate and cyclohexane were stirred in a constant temperature water bath to form an oil phase;

[0023] A suspension E of organic nano-calcium carbonate-sodium humate-haloite composite was added to the oil phase and stirred continuously. During the stirring process, dilute solutions F of sodium carboxymethyl cellulose, λ-type carrageenan, and locust bean gum were added in sequence. After a set time, ammonium sulfite was added to obtain a mixed solution H.

[0024] Mixture G was added dropwise to mixture H. After the addition was complete, alumina and the second part of N-hydroxymethylacrylamide were added and reacted to obtain complex I.

[0025] The compound I was removed, soaked and cleaned to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0026] In one embodiment, the suspension E has a weight percentage of 2%; the dilute solution F has a mass concentration of 1%; and the dilute methacrylic acid solution has a mass concentration of 15%.

[0027] In one embodiment, the sorbitan monostearate and cyclohexane are stirred at 250 r / min for 30 min in a constant temperature water bath at 30°C to 35°C to form an oil phase;

[0028] The sorbitan monostearate has a cyclohexane mass fraction of 5% to 7%, and the volume ratio of the oil phase to the aqueous phase is 4 to 4.5:1.

[0029] In one embodiment, the specific process for obtaining the mixture H is as follows:

[0030] The suspension E of the organic nano-calcium carbonate-sodium humate-halolite composite was slowly added to the oil phase. Nitrogen gas was introduced, and the mixture was stirred at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, the weighed sodium carboxymethyl cellulose and the pre-mixed dilute solution F of λ-type carrageenan and locust bean gum were added sequentially. The mixture was stirred at 450 r / min, and after a set time of 15 min, ammonium sulfite was added. After stirring for another 20 min, the mixture H was obtained.

[0031] In one embodiment, the specific preparation process of the complex I is as follows:

[0032] Mixture G was slowly added dropwise to mixture H over a period of 2 to 3 hours. After the addition was complete, alumina and a second part of N-hydroxymethylacrylamide were added. The temperature was controlled between 42°C and 45°C throughout the process, and argon gas was introduced. After reacting for 3 to 4 hours, complex I was obtained.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This invention provides a long-lasting, salt-alkali resistant concrete internal curing material. Firstly, this material contains nano-calcium carbonate with a particle size of 15-40 nm, exhibiting a large specific surface area and significantly impacting the mechanical properties of concrete. The addition of nano-calcium carbonate enhances the compressive strength, flexural strength, bond strength, fracture properties, splitting tensile strength, microhardness, and elastic modulus of concrete. As an auxiliary and filler material within the rigid framework of the internal curing material, it significantly improves the hardness and water retention of the internal curing gel and increases the interfacial bond strength between the internal curing material and the concrete, thus playing a supporting role in resisting shrinkage, bending, deformation, and fracture during concrete curing. Furthermore, nano-calcium carbonate significantly enhances the salt-alkali resistance of the internal curing material, ensuring that it maintains good water absorption and retention characteristics in the alkaline environment of concrete.

[0035] Secondly, this material contains halloysite, an aluminosilicate compound with high porosity and a large specific surface area. This halloysite provides the initial three-dimensional framework for long-lasting, salt-alkali-resistant internal curing materials, and its numerous pores also offer attachment points for organic monomers during polymerization. Furthermore, the halloysite crystals contain a large number of hydroxyl groups, which can react with olefin monomers to form polymer gels. In addition, the composite between inorganic materials and organic monomers increases the three-dimensional network density of the internal curing material, resulting in excellent water retention properties in the long-lasting, salt-alkali-resistant concrete internal curing material. The slow release of moisture from the internal curing material replenishes the water consumption of the concrete, controls and reduces concrete shrinkage, and ensures full hydration of the concrete material. Moreover, the halloysite dispersed within the internal curing material plays a supporting role in reducing volume deformation during the concrete internal curing process.

[0036] Finally, the sodium humate in this material contains a large number of hydroxyl groups in its structure, which can provide the initial organic three-dimensional framework for long-lasting salt and alkali resistant internal curing materials. Under the action of an initiator, free radicals are generated, and organic monomers can copolymerize at these positions. N-hydroxymethylacrylamide and hydroxyethyl methacrylate are both non-ionic monomers, and their copolymers exhibit good salt and alkali resistance. They continuously graft and polymerize with sodium carboxymethyl cellulose, λ-carrageenan, and locust bean gum, continuously filling the nano-calcium carbonate-sodium humate-halolite composite, which can significantly improve the liquid absorption ratio of the curing material. In addition, the superior salt and alkali resistance can, to a certain extent, more effectively adjust the humidity distribution inside the concrete and ensure the internal curing efficiency of the internal curing material in alkaline environments and other salt and alkali media. Therefore, the salt and alkali resistant concrete internal curing material prepared by this invention makes a significant contribution to the shrinkage, durability, and service life of concrete internal curing processes in salt and alkali environments. Detailed Implementation

[0037] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0038] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0039] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0040] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0041] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0042] This invention provides a long-lasting salt and alkali resistant concrete internal curing material and its preparation method.

[0043] This invention provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which is composed of the following raw materials: nano-calcium carbonate, sodium humate, halloysite, 3-aminopropyltriethoxysilane and acetic acid, a first part of N-hydroxymethylacrylamide, hydroxyethyl methacrylate, methacrylic acid, sodium carboxymethyl cellulose, λ-type carrageenan, locust bean gum, sorbitan monostearate (Span 60), cyclohexane, ammonium sulfite, alumina, a second part of N-hydroxymethylacrylamide, isopropanol, and slaked lime.

[0044] The above-mentioned nano-calcium carbonate, sodium humate, halloysite, 3-aminopropyltriethoxysilane and acetic acid were used to prepare an organic nano-calcium carbonate-sodium humate-haloysite composite.

[0045] By weight fraction, the long-lasting salt-alkali resistant concrete internal curing material is composed of the following raw materials: 12%–17% nano-calcium carbonate, 3%–5% halloysite, 10%–12% sodium humate, 6%–8% 3-aminopropyltriethoxysilane, 5%–10% sodium carboxymethyl cellulose, 3%–4% type λ carrageenan, 1%–2% locust bean gum, 1%–1.8% slaked lime, 26%–30% first part N-hydroxymethylacrylamide, 20%–23% hydroxyethyl methacrylate, 5%–8% methacrylic acid, 0.2%–0.3% alumina, 0.2%–0.5% second part N-hydroxymethylacrylamide, and 0.5%–1% ammonium sulfite.

[0046] The organic nano-calcium carbonate-sodium humate-halolite composite is prepared from the following raw materials: nano-calcium carbonate, sodium humate, halloysite, 3-aminopropyltriethoxysilane, and acetic acid.

[0047] The preparation process of the above-mentioned organic nano-calcium carbonate-sodium humate-halolite composite is as follows:

[0048] Step 1: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain nano-calcium carbonate suspension A and halloysite suspension B.

[0049] Step 2: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0050] Step 3: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2. Purge with argon gas, heat the mixture in a water bath to 45°C, and stir magnetically for 1 hour at a constant temperature. Add the weighed sodium humate, and continue stirring magnetically for 3 hours at a constant temperature. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate-haloysite composite.

[0051] The nano-calcium carbonate powder has a particle size of 15–40 nm, a calcium carbonate content ≥98.5%, a pH of 8.5–10, and an impurity content <0.1%. Nano-calcium carbonate is a white, fine crystalline powder, an inexpensive, and naturally abundant inorganic material that is insensitive to salt and alkali ions. Introducing nano-calcium carbonate into internal curing materials can improve their salt resistance and compressive strength, and also reduce the preparation cost. Furthermore, nano-calcium carbonate can exert micro-aggregate, nucleation, and filling effects in concrete. Small amounts of nano-calcium carbonate can promote cement hydration to a certain extent. As a filler in cement, it has good performance, improving the flexural and compressive strength of concrete, accelerating the hydration rate of calcium silicate, and making the microstructure of concrete more compact.

[0052] Halloysite powder has a particle diameter of 0.1–0.4 μm, a length of <0.5 μm, and a purity of ≥99%. Halloysite is an aluminosilicate compound with high porosity, large volume, light weight, low bulk density, and large specific surface area. Its crystal layers contain a large number of hydroxyl groups, which can react with olefin monomers to form polymer gels. In this application, it is used as an auxiliary material and filler material for the rigid skeleton of the internal health care material.

[0053] The sodium humate particles have a diameter of 120 mesh, a sodium humate content (dry basis) ≥85%, a water-insoluble content <5%, a pH of 9-11, and a moisture content <12%.

[0054] Sodium carboxymethyl cellulose is food grade with a degree of substitution (DS) ≥ 0.9. Sodium carboxymethyl cellulose is a white to pale yellow powder with a three-dimensional structure containing numerous hydrophilic groups such as hydroxyl and carboxyl groups. It has strong water absorption, is easily soluble in water, and exhibits good salt resistance.

[0055] Among them, λ-type carrageenan is a white powder that dissolves in hot water at about 80°C to form a viscous, transparent or slightly milky white, easily flowing solution. Its properties are less affected by salt and alkali and can be used in the synthesis of internal health care materials to improve the elasticity and water retention of these materials.

[0056] Hydroxyethyl methacrylate has the molecular formula C6H. 10 O3 is a colorless, transparent, and easily flowing liquid that is soluble in common organic solvents and miscible with water. It is mainly used for the modification of resins and coatings. When copolymerized with other acrylic monomers, it can produce acrylic resins with active hydroxyl groups in the side chains. It can undergo esterification and cross-linking reactions and is used as an important monomer in the synthesis of internal health care materials.

[0057] In another aspect, this invention provides a method for preparing a long-lasting salt-alkali resistant internal curing material for concrete. This method uses the aforementioned formula for preparing the long-lasting salt-alkali resistant internal curing material for concrete, and is carried out according to the following steps:

[0058] Step 1: Weigh the above raw materials according to their weight;

[0059] Step 2: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain nano-calcium carbonate suspension A and halloysite suspension B.

[0060] Step 3: Prepare a 3% (w / w) dilute solution of 3-aminopropyltriethoxysilane by weighing the 3-aminopropyltriethoxysilane. Add acetic acid and adjust the pH to 5.5-6. Stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C.

[0061] Step 4: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2. Purge with argon gas, heat the mixture to 45°C in a water bath, and stir magnetically for 1 hour. Add the weighed sodium humate, and continue stirring magnetically for 3 hours. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate-haloysite composite, denoted as composite D. Then add water to composite D to prepare a suspension E with a weight of 2%.

[0062] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a dilute solution F with a mass concentration of 1%;

[0063] Step 6: Add methacrylic acid to deionized water to prepare a 15% (w / w) dilute solution. Add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate. After they are fully dissolved, mixture G is obtained.

[0064] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0065] Step 8: Slowly add the pre-obtained organic nano-calcium carbonate-sodium humate-halolite composite suspension E to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0066] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0067] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0068] In step seven, the sorbitan monostearate (Span 60) and cyclohexane are thoroughly mixed to form an oil phase. The sorbitan monostearate (Span 60) has a mass fraction of 5% to 7% of cyclohexane. The volume ratio of the oil phase to the aqueous phase is 4 to 4.5:1. The aqueous phase is specifically composed of suspension E (a suspension of organic nano-calcium carbonate-sodium humate-halolite complex), mixture F (an aqueous solution of λ-type carrageenan and locust bean gum), and mixture G (a mixture of dilute methacrylic acid solution, quicklime, N-hydroxymethylacrylamide, and hydroxyethyl methacrylate).

[0069] This invention first utilizes 3-aminopropyltriethoxysilane to organically modify an inorganic powder material with good salt and alkali resistance, and then prepares a suspension. Next, N-hydroxymethylacrylamide, hydroxyethyl methacrylate, and a methacrylic acid solution are added. Under the action of alumina and N-hydroxymethylacrylamide as crosslinking agents, graft polymerization continuously occurs in an organic nano-calcium carbonate-sodium humate-halothite composite, with the polymer being filled in. After the reaction, the product is dehydrated, dried, and screened using isopropanol to obtain the long-lasting salt and alkali resistant internal curing and water-retaining material. The salt and alkali resistance of the long-lasting salt and alkali resistant internal curing material prepared by this invention is improved, and the compressive strength of concrete is significantly increased. The 28-day compressive strength of the concrete is more than 120% of the benchmark concrete strength. Furthermore, it can also significantly reduce the autogenous shrinkage of concrete.

[0070] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0071] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0072] Example 1:

[0073] This example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 12% nano-calcium carbonate, 3% halloysite, 10% sodium humate, 6% 3-aminopropyltriethoxysilane, 5% sodium carboxymethyl cellulose, 3% type λ carrageenan, 1% locust bean gum, 1.7% slaked lime, 30% first part N-hydroxymethylacrylamide, 20% hydroxyethyl methacrylate, 7% methacrylic acid, 0.3% alumina, 0.5% second part N-hydroxymethylacrylamide, and 0.5% ammonium sulfite.

[0074] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0075] Step 1: Weigh the above raw materials according to their weight;

[0076] Step 2: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain suspension A and suspension B.

[0077] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0078] Step 4: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2. Purge with argon gas, heat the mixture to 45°C in a water bath, and stir magnetically for 1 hour. Add the weighed sodium humate, and continue stirring magnetically for 3 hours. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate-haloysite composite, denoted as composite D. Then add water to composite D to prepare a suspension E with a weight of 2%.

[0079] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0080] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0081] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0082] Step 8: Slowly add the pre-obtained organic nano-calcium carbonate-sodium humate-halolite composite suspension E to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0083] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0084] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0085] Example 2:

[0086] This example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 17% nano-calcium carbonate, 3% halloysite, 10% sodium humate, 6% 3-aminopropyltriethoxysilane, 5% sodium carboxymethyl cellulose, 3% type λ carrageenan, 2% locust bean gum, 1.2% slaked lime, 26% first part N-hydroxymethylacrylamide, 20% hydroxyethyl methacrylate, 5% methacrylic acid, 0.3% alumina, 0.5% second part N-hydroxymethylacrylamide, and 1% ammonium sulfite.

[0087] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0088] Step 1: Weigh the above raw materials according to their weight;

[0089] Step 2: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain suspension A and suspension B.

[0090] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0091] Step 4: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2. Purge with argon gas, heat the mixture to 45°C in a water bath, and stir magnetically for 1 hour. Add the weighed sodium humate, and continue stirring magnetically for 3 hours. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate-haloysite composite, denoted as composite D. Then add water to composite D to prepare a suspension E with a weight of 2%.

[0092] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0093] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0094] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0095] Step 8: Slowly add the pre-obtained organic nano-calcium carbonate-sodium humate-halolite composite suspension E to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0096] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0097] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0098] Example 3:

[0099] This example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 12% nano-calcium carbonate, 3% halloysite, 10% sodium humate, 6% 3-aminopropyltriethoxysilane, 6% sodium carboxymethyl cellulose, 4% λ-type carrageenan, 2% locust bean gum, 1.2% slaked lime, 26% first part N-hydroxymethylacrylamide, 23% hydroxyethyl methacrylate, 5% methacrylic acid, 0.3% alumina, 0.5% second part N-hydroxymethylacrylamide, and 1% ammonium sulfite.

[0100] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0101] Step 1: Weigh the above raw materials according to their weight;

[0102] Step 2: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain suspension A and suspension B.

[0103] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0104] Step 4: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2. Purge with argon gas, heat the mixture to 45°C in a water bath, and stir magnetically for 1 hour. Add the weighed sodium humate, and continue stirring magnetically for 3 hours. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate-haloysite composite, denoted as composite D. Then add water to composite D to prepare a suspension E with a weight of 2%.

[0105] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0106] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0107] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0108] Step 8: Slowly add the pre-obtained organic nano-calcium carbonate-sodium humate-halolite composite suspension E to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0109] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0110] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0111] Example 4:

[0112] This example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 12% nano-calcium carbonate, 3% halloysite, 10% sodium humate, 6% 3-aminopropyltriethoxysilane, 5% sodium carboxymethyl cellulose, 3% type λ carrageenan, 1% locust bean gum, 1% slaked lime, 27% first part N-hydroxymethylacrylamide, 23% hydroxyethyl methacrylate, 8% methacrylic acid, 0.3% alumina, 0.2% second part N-hydroxymethylacrylamide, and 0.5% ammonium sulfite.

[0113] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0114] Step 1: Weigh the above raw materials according to their weight;

[0115] Step 2: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain suspension A and suspension B.

[0116] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0117] Step 4: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2. Purge with argon gas, heat the mixture to 45°C in a water bath, and stir magnetically for 1 hour. Add the weighed sodium humate, and continue stirring magnetically for 3 hours. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate-haloysite composite, denoted as composite D. Then add water to composite D to prepare a suspension E with a weight of 2%.

[0118] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0119] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0120] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0121] Step 8: Slowly add the pre-obtained organic nano-calcium carbonate-sodium humate-halolite composite suspension E to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0122] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0123] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0124] Example 5:

[0125] This example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 13% nano-calcium carbonate, 4% halloysite, 10% sodium humate, 7% 3-aminopropyltriethoxysilane, 5% sodium carboxymethyl cellulose, 3% type λ carrageenan, 1% locust bean gum, 1% slaked lime, 28% first part N-hydroxymethylacrylamide, 21% hydroxyethyl methacrylate, 6% methacrylic acid, 0.2% alumina, 0.3% second part N-hydroxymethylacrylamide, and 0.5% ammonium sulfite.

[0126] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0127] Step 1: Weigh the above raw materials according to their weight;

[0128] Step 2: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain suspension A and suspension B.

[0129] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0130] Step 4: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2. Purge with argon gas, heat the mixture to 45°C in a water bath, and stir magnetically for 1 hour. Add the weighed sodium humate, and continue stirring magnetically for 3 hours. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate-haloysite composite, denoted as composite D. Then add water to composite D to prepare a suspension E with a weight of 2%.

[0131] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0132] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0133] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0134] Step 8: Slowly add the pre-obtained organic nano-calcium carbonate-sodium humate-halolite composite suspension E to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0135] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0136] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0137] Example 6:

[0138] This example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 12.7% nano-calcium carbonate, 5% halloysite, 10% sodium humate, 6% 3-aminopropyltriethoxysilane, 5% sodium carboxymethyl cellulose, 3% λ-type carrageenan, 1.5% locust bean gum, 1.8% slaked lime, 27% first part N-hydroxymethylacrylamide, 22% hydroxyethyl methacrylate, 5% methacrylic acid, 0.3% alumina, 0.2% second part N-hydroxymethylacrylamide, and 0.5% ammonium sulfite.

[0139] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0140] Step 1: Weigh the above raw materials according to their weight;

[0141] Step 2: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain suspension A and suspension B.

[0142] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0143] Step 4: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2. Purge with argon gas, heat the mixture to 45°C in a water bath, and stir magnetically for 1 hour. Add the weighed sodium humate, and continue stirring magnetically for 3 hours. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate-haloysite composite, denoted as composite D. Then add water to composite D to prepare a suspension E with a weight of 2%.

[0144] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0145] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0146] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0147] Step 8: Slowly add the pre-obtained organic nano-calcium carbonate-sodium humate-halolite composite suspension E to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0148] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0149] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0150] Example 7:

[0151] This example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 12% nano-calcium carbonate, 3% halloysite, 12% sodium humate, 8% 3-aminopropyltriethoxysilane, 5% sodium carboxymethyl cellulose, 3% λ-type carrageenan, 1% locust bean gum, 1.4% slaked lime, 26% first part N-hydroxymethylacrylamide, 20% hydroxyethyl methacrylate, 7% methacrylic acid, 0.3% alumina, 0.4% second part N-hydroxymethylacrylamide, and 0.9% ammonium sulfite.

[0152] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0153] Step 1: Weigh the above raw materials according to their weight;

[0154] Step 2: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain suspension A and suspension B.

[0155] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0156] Step 4: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2. Purge with argon gas, heat the mixture to 45°C in a water bath, and stir magnetically for 1 hour. Add the weighed sodium humate, and continue stirring magnetically for 3 hours. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate-haloysite composite, denoted as composite D. Then add water to composite D to prepare a suspension E with a weight of 2%.

[0157] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0158] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0159] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0160] Step 8: Slowly add the pre-obtained organic nano-calcium carbonate-sodium humate-halolite composite suspension E to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0161] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0162] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0163] Example 8:

[0164] This example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 12% nano-calcium carbonate, 3% halloysite, 10% sodium humate, 6% 3-aminopropyltriethoxysilane, 10% sodium carboxymethyl cellulose, 3% type λ carrageenan, 1% locust bean gum, 1% slaked lime, 26% first part N-hydroxymethylacrylamide, 20% hydroxyethyl methacrylate, 7% methacrylic acid, 0.2% alumina, 0.2% second part N-hydroxymethylacrylamide, and 0.6% ammonium sulfite.

[0165] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0166] Step 1: Weigh the above raw materials according to their weight;

[0167] Step 2: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain suspension A and suspension B.

[0168] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0169] Step 4: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2. Purge with argon gas, heat the mixture to 45°C in a water bath, and stir magnetically for 1 hour. Add the weighed sodium humate, and continue stirring magnetically for 3 hours. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate-haloysite composite, denoted as composite D. Then add water to composite D to prepare a suspension E with a weight of 2%.

[0170] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0171] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0172] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0173] Step 8: Slowly add the pre-obtained organic nano-calcium carbonate-sodium humate-halolite composite suspension E to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0174] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0175] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0176] Comparative Example 1

[0177] This comparative example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 5% halloysite, 12% sodium humate, 8% 3-aminopropyltriethoxysilane, 10% sodium carboxymethyl cellulose, 4% type λ carrageenan, 2% locust bean gum, 1% slaked lime, 30% first part N-hydroxymethylacrylamide, 20% hydroxyethyl methacrylate, 7% methacrylic acid, 0.3% alumina, 0.2% second part N-hydroxymethylacrylamide, and 0.5% ammonium sulfite.

[0178] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0179] Step 1: Weigh the above raw materials according to their weight;

[0180] Step 2: Weigh the halloysite and deionized water to prepare a 1% halloysite suspension by weight, and ultrasonically disperse it for 30 minutes to obtain suspension B;

[0181] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0182] Step 4: Disperse halloysite suspension B evenly in 3-aminopropyltriethoxysilane hydrolysate C from Step 2, pass argon gas through, heat the mixture in a water bath to 45°C, and stir magnetically for 1 hour at a constant temperature. Add the weighed sodium humate, continue stirring magnetically at a constant temperature for 3 hours, then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic sodium humate-haloysite complex, denoted as complex D. Then add water to complex D to prepare a suspension E with a weight of 2%.

[0183] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0184] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0185] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0186] Step 8: Slowly add the pre-obtained suspension E of the organic sodium humate-halothite complex to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0187] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0188] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0189] Comparative Example 2

[0190] This comparative example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 17% nano-calcium carbonate, 10% sodium humate, 8% 3-aminopropyltriethoxysilane, 5% sodium carboxymethyl cellulose, 4% type λ carrageenan, 2% locust bean gum, 1% slaked lime, 26% first part N-hydroxymethylacrylamide, 20% hydroxyethyl methacrylate, 6% methacrylic acid, 0.3% alumina, 0.2% second part N-hydroxymethylacrylamide, and 0.5% ammonium sulfite.

[0191] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0192] Step 1: Weigh the above raw materials according to their weight;

[0193] Step 2: Weigh out the nano-calcium carbonate and deionized water to prepare nano-calcium carbonate suspensions with a weight ratio of 2%, and disperse them by ultrasonication for 30 minutes to obtain suspension A;

[0194] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0195] Step 4: Disperse the nano-calcium carbonate suspension A uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2, pass argon gas through, heat the mixture in a water bath to 45°C, and stir magnetically for 1 hour at a constant temperature. Add the weighed sodium humate, continue stirring magnetically at a constant temperature for 3 hours, then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate complex, denoted as complex D. Then add water to complex D to prepare a suspension E with a weight of 2%.

[0196] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0197] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0198] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0199] Step 8: Slowly add the pre-obtained organic nano-calcium carbonate-sodium humate composite suspension E to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixed solution H.

[0200] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0201] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0202] Comparative Example 3

[0203] This comparative example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 12% nano-calcium carbonate, 3% halloysite, 8% 3-aminopropyltriethoxysilane, 10% sodium carboxymethyl cellulose, 3% type λ carrageenan, 1% locust bean gum, 1% slaked lime, 30% first part N-hydroxymethylacrylamide, 23% hydroxyethyl methacrylate, 8% methacrylic acid, 0.2% alumina, 0.3% second part N-hydroxymethylacrylamide, and 0.5% ammonium sulfite.

[0204] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0205] Step 1: Weigh the above raw materials according to their weight;

[0206] Step 2: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain suspension A and suspension B.

[0207] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0208] Step 4: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2, pass argon gas through, heat the mixture in a water bath to 45°C, and stir magnetically for 1 hour at a constant temperature. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate and halloysite mixture, denoted as mixture D. Then add water to the complex D to prepare a suspension E with a weight of 2%.

[0209] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0210] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0211] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0212] Step 8: Slowly add the pre-obtained suspension E of organic nano-calcium carbonate and halloysite mixture to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0213] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0214] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0215] Comparative Example 4

[0216] This comparative example presents a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 17% nano-calcium carbonate, 3% halloysite, 10% sodium humate, 6% 3-aminopropyltriethoxysilane, 5% sodium carboxymethyl cellulose, 4% λ-type carrageenan, 2% locust bean gum, 1.2% slaked lime, 23% hydroxyethyl methacrylate, 27% methacrylic acid, 0.3% alumina, 0.5% N-hydroxymethylacrylamide, and 1% ammonium sulfite.

[0217] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0218] Step 1: Weigh the above raw materials according to their weight;

[0219] Step 2: Weigh out the nano-calcium carbonate, halloysite, and deionized water to prepare a 2% nano-calcium carbonate suspension and a 1% halloysite suspension, respectively. Disperse them by ultrasonication for 30 minutes to obtain suspension A and suspension B.

[0220] Step 3: Prepare a 3% (w / w) dilute solution of the weighed 3-aminopropyltriethoxysilane, add acetic acid and adjust the pH to 5.5-6, stir magnetically for 30 min to obtain 3-aminopropyltriethoxysilane hydrolysate C;

[0221] Step 4: Disperse nano-calcium carbonate suspension A and halloysite suspension B uniformly in the 3-aminopropyltriethoxysilane hydrolysate C from Step 2. Purge with argon gas, heat the mixture to 45°C in a water bath, and stir magnetically for 1 hour. Add the weighed sodium humate, and continue stirring magnetically for 3 hours. Then cool the mixture to room temperature, filter, wash the filter cake with distilled water, dry it in a vacuum oven at 60°C for 12 hours, and grind it to obtain the organic nano-calcium carbonate-sodium humate-haloysite composite, denoted as composite D. Then add water to composite D to prepare a suspension E with a weight of 2%.

[0222] Step 5: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, stir magnetically for 30 minutes, and prepare a 1% dilute solution F;

[0223] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add weighed quicklime and cool to room temperature. While stirring continuously, add weighed hydroxyethyl methacrylate and let it dissolve completely to obtain mixture G.

[0224] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0225] Step 8: Slowly add the pre-obtained organic nano-calcium carbonate-sodium humate-halolite composite suspension E to the oil phase, purge with nitrogen, and stir at 300 r / min for 20 min in a constant temperature water bath at 35°C. During continuous stirring, add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. After stirring at 450 r / min for 15 min, add the weighed ammonium sulfite and continue stirring for another 20 min to obtain the mixture H.

[0226] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0227] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0228] Comparative Example 5

[0229] This comparative example provides a method for preparing a long-lasting salt-alkali resistant concrete internal curing material, which, by weight, comprises the following raw materials: 10% sodium carboxymethyl cellulose, 4% λ-type carrageenan, 2% locust bean gum, 1.8% slaked lime, 49.4% first part N-hydroxymethylacrylamide, 23% hydroxyethyl methacrylate, 8% methacrylic acid, 0.3% alumina, 0.5% second part N-hydroxymethylacrylamide, and 1% ammonium sulfite.

[0230] The preparation method of the above-mentioned long-lasting salt and alkali resistant concrete internal curing material includes the following steps:

[0231] Step 1: Weigh the above raw materials according to their weight;

[0232] Step 2: Slowly and evenly disperse the weighed λ-type carrageenan and locust bean gum into deionized water, and stir magnetically for 30 minutes to prepare a 1% dilute solution F;

[0233] Step 6: Add methacrylic acid to deionized water to prepare a 15% dilute solution, add the weighed quicklime and cool to room temperature. While stirring continuously, add the weighed first part of N-hydroxymethylacrylamide and hydroxyethyl methacrylate, and let them dissolve completely to obtain mixture G.

[0234] Step 7: Add the weighed sorbitan monostearate (Span 60) and cyclohexane to a four-necked flask, and stir at 250 r / min for 30 min in a constant temperature water bath at 30℃~35℃ to form an oil phase;

[0235] Step 8: Add the weighed sodium carboxymethyl cellulose and the pre-mixed dilute acid solution F of λ-type carrageenan and locust bean gum in sequence. Stir at 450 r / min for 15 min, then add the weighed ammonium sulfite and continue stirring for 20 min to obtain the mixture H.

[0236] Step 9: Slowly add mixture G to mixture H over 2-3 hours. After the addition is complete, add the weighed alumina and the second part of N-hydroxymethylacrylamide to a four-necked flask. The temperature is controlled between 42°C and 45°C throughout the process. Argon gas is introduced and the reaction is carried out for 3-4 hours to obtain complex I.

[0237] Step 10: Take out the compound I, soak and wash it with isopropanol 3 to 5 times, and wait until no more isopropanol evaporates to obtain the long-lasting salt and alkali resistant concrete internal curing material.

[0238] Performance testing

[0239] When using this product, the long-lasting salt-alkali resistant concrete curing material is directly added to the mixing equipment along with cement and other cementitious materials. The maximum liquid absorption ratio of the curing material in saturated Ca(OH)₂ solution and 0.9% wt CaCl₂ solution is tested, along with the compressive strength ratio and 28-day shrinkage ratio (compared to the baseline group) of the concrete after incorporation, in accordance with the requirements of JC901-2002 "Cement Concrete Curing Agent", JT / T522-2004 "Highway Engineering Concrete Curing Agent", and "Test Procedures for Cement and Cement Concrete in Highway Engineering" (JTG / E30-2005). The dosage is 0.2% of the cementitious material dosage. Specific performance indicators are as follows:

[0240]

[0241]

[0242] As can be seen from the above examples, this long-lasting salt-alkali resistant concrete internal curing material can significantly improve the compressive strength of concrete. In the eight examples, the maximum liquid absorption ratio of the internal curing material in saturated Ca(OH)2 solution was greater than 70 g / g, and the maximum liquid absorption ratio in 0.9% wt CaCl2 solution was also greater than 70 g / g. Compared with the comparative example, the internal curing material in the comparative example showed a significantly higher maximum liquid absorption ratio in saturated Ca(OH)2 solution and 0.9% wt CaCl2 solution. The maximum liquid absorption ratio in CaCl2 solution decreased significantly; and the 28-day compressive strength of concrete in all eight examples was more than 120% of that without internal curing materials, with shrinkage rates all less than 40%. Compared with the comparative example, the 28-day strength of the examples was 7-20% higher, and the shrinkage rate was at most 52% lower, showing significant effects. This indicates that the absence of materials or changes in the proportions, especially the absence of the organic nano-calcium carbonate-sodium humate-halothite composite (i.e., retaining only organic raw materials, which results in performance similar to traditional organic internal curing materials), significantly affected the liquid absorption characteristics of this salt-alkali resistant internal curing and water-retaining material in saline-alkali solutions and its internal curing effect in concrete. Therefore, this salt-alkali resistant internal curing and water-retaining material exhibits good liquid absorption characteristics in saline-alkali solutions, can play a good reinforcing role, can also greatly reduce the autogenous shrinkage of concrete, and has good applicability. It can effectively solve the problems in the current concrete curing process in some saline-alkali areas and has broad application prospects.

[0243] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A long-acting salt-tolerant type of concrete internal curing material, characterized by, The following components are used to make the composition: 12-17% nanometer calcium carbonate, 3-5% halloysite, 10-12% sodium humate, 6-8% 3-aminopropyl triethoxysilane, 5-10% sodium carboxymethyl cellulose, 3-4% lambda carrageenan, 1-2% locust bean gum, 1-1.8% slaked lime, 26-30% first N-methylol acrylamide, 20-23% hydroxyethyl methacrylate, 5-8% methacrylic acid, 0.2-0.3% aluminum oxide, 0.2-0.5% second N-methylol acrylamide, and 0.5-1% ammonium sulfite.

2. The long-lasting saline-alkaline resistant type of concrete internal curing material according to claim 1, characterized in that, The nanometer calcium carbonate has a particle size of 15-40 nm, a calcium carbonate content of ≥98.5%, a pH of 8.5-10, and an impurity content of <0.1%. The halloysite has a particle diameter of 0.1-0.4 μm, a length of <0.5 μm, and a purity of ≥99%. The sodium humate has a particle diameter of 120 mesh, a humic acid dry base content in the sodium humate of ≥85%, a water-insoluble content of <5%, a pH of 9-11, and a moisture content of <12%.

3. The long-term salt-tolerant and alkali-tolerant concrete internal curing material according to claim 1, characterized in that, The sodium carboxymethyl cellulose is food grade and has a degree of substitution of ≥0.

9.

4. The long-term salt-tolerant and alkali-tolerant concrete internal curing material according to claim 1, characterized in that, The nanometer calcium carbonate, halloysite, and sodium humate are used to prepare an organic nanometer calcium carbonate-sodium humate-halloysite compound. The organic nanometer calcium carbonate-sodium humate-halloysite compound is prepared by the following process: The nanometer calcium carbonate and halloysite are mixed with deionized water to prepare a nanometer calcium carbonate suspension A with a weight fraction of 2% and a halloysite suspension B with a weight fraction of 1%, respectively. The 3-aminopropyl triethoxysilane is prepared into a 3-aminopropyl triethoxysilane dilute solution with a mass concentration of 3%, and then acetic acid is added to adjust the pH, and a 3-aminopropyl triethoxysilane hydrolysis solution C is obtained. The nanometer calcium carbonate suspension A and halloysite suspension B are uniformly dispersed in the 3-aminopropyl triethoxysilane hydrolysis solution C in sequence, heated in a water bath, and stirred, and then sodium humate is added and the stirring is continued, and the mixture is cooled, filtered, washed, dried, and ground to obtain the organic nanometer calcium carbonate-sodium humate-halloysite compound.

5. The long-lasting saline-alkaline resistant concrete internal curing material according to claim 4, characterized in that, The acetic acid is used to adjust the pH to 5.5-6.

6. A method of preparing the long-term salt-tolerant and alkali-tolerant concrete internal curing material according to any one of claims 1 to 5, characterized in that, The process includes the following steps: The nanometer calcium carbonate, halloysite, and sodium humate are used to prepare an organic nanometer calcium carbonate-sodium humate-halloysite compound, which is denoted as compound D, and then the compound D is added to water to prepare a suspension E; The lambda carrageenan and locust bean gum are dispersed in deionized water in sequence to prepare a dilute solution F; The methacrylic acid is added to deionized water to prepare a methacrylic acid dilute solution, and then slaked lime is added and cooled to room temperature, and in the stirring process, the first N-methylol acrylamide and hydroxyethyl methacrylate are added to obtain a mixture G; The sorbitan monostearate and cyclohexane are stirred in a constant-temperature water bath environment to form an oil phase; The organic nanometer calcium carbonate-humic acid sodium- halloysite compound suspension E is added to the oil phase, stirring is continued, and the dilute solution F of sodium carboxymethyl cellulose, lambda carrageenan and locust bean gum is sequentially added in the stirring process, ammonium sulfite is added after a set time, and a mixed solution H is prepared; The mixture G is added dropwise to the mixed solution H, and after the dropwise addition is completed, aluminum oxide and a second N-methylol acrylamide are added to obtain a compound I; The compound I is taken out, soaked and cleaned to prepare the long-acting salt-tolerant and alkali-tolerant type concrete internal curing material.

7. The method for preparing long-acting saline-alkali resistant concrete internal curing material according to claim 6, characterized in that, The weight fraction of the suspension E is 2%, the mass concentration of the dilute solution F is 1%, and the mass concentration of the methacrylic acid dilute solution is 15%.

8. The method for preparing long-acting salt-tolerant type concrete internal curing material according to claim 6, characterized in that, The sorbitan monostearate and cyclohexane are stirred at 250 r / min for 30 min in a constant temperature water bath environment at 30°C to 35°C to form the oil phase; The mass fraction of the sorbitan monostearate in the cyclohexane is 5% to 7%, and the volume ratio of the oil phase to the aqueous phase is 4 to 4.5:

1.

9. The method for preparing long-acting salt-tolerant type concrete internal curing material according to claim 6, characterized in that, The specific process for preparing the mixed solution H is as follows: The organic nanometer calcium carbonate-humic acid sodium- halloysite compound suspension E is slowly added to the oil phase, nitrogen is passed, stirring is performed at a speed of 300 r / min for 20 min in a constant temperature water bath environment at 35°C, the weighed sodium carboxymethyl cellulose and the previously mixed dilute solution F of lambda carrageenan and locust bean gum are sequentially added in the continuous stirring process, stirring is performed at a speed of 450 r / min, ammonium sulfite is added after a set time of 15 min, and the mixed solution H is obtained after continuous stirring for 20 min.

10. The method for preparing long-acting salt-tolerant type concrete internal curing material according to claim 6, characterized in that, The specific preparation process of the compound I is as follows: The mixture G is slowly added dropwise to the mixed solution H, the dropwise addition time is 2 h to 3 h, aluminum oxide and a second N-methylol acrylamide are added after the dropwise addition is completed, the temperature is controlled to be between 42°C and 45°C during the whole process, argon is passed, and the compound I is obtained after the reaction is performed for 3 h to 4 h.

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