Internal curing agent, prepared high-strength low-shrinkage alkali-activated composite material and method

Abstract

The invention provides an internal curing agent, a high-strength low-shrinkage alkali-activated composite material prepared from the internal curing agent and a method, and belongs to the technical field of shrinkage control of alkali-activated cementing materials. According to the invention, acrylamide and acrylic copolymer (NIPAm-SA) is adopted as a template skeleton, a calcium aluminosilicate hydrate crystal nucleus (C-A-S-H) is modified through a coordinate bond self-assembly reaction, the three-dimensional network calcium aluminosilicate hydrate (C-A-S-H-coated NIPAm-SA) is synthesized, and the C-A-S-H-coated NIPAm-SA can be used as an internal curing agent. The C-A-S-H-coated NIPAm is mixed with an alkali-activated cementing material, and the prepared high-strength low-shrinkage alkali-activated composite material has the advantages of high internal curing efficiency, remarkable self-shrinkage inhibition effect, high early strength and the like. According to the invention, the synergistic effect of hydrated calcium aluminosilicate for internal curing and nucleation sites is realized, and more importantly, the hydrated calcium aluminosilicate can be suitable for a high-alkalinity environment of an alkali-activated cementing material and can be well combined with a matrix, so that the problem of large self-constriction of the alkali-activated cementing material is relieved.

Description

Technical Field

[0001] The present invention relates to the technical field of shrinkage control of alkali-activated cementitious materials, and in particular to an internal curing agent and a high-strength, low-shrinkage alkali-activated composite material and a method for preparing the same. Background Art

[0002] Alkali-activated cementitious materials are prepared by mixing industrial byproducts with alkaline activators. They eliminate the need for grinding, grinding, and calcining, reducing carbon emissions by 50% to 80%. They are considered an eco-friendly building material that can replace traditional cement-based materials. However, compared with traditional cement-based materials, alkali-activated cementitious materials suffer from more significant shrinkage, which leads to cracking and compromises durability, severely limiting their engineering applications.

[0003] Superabsorbent polymers play a crucial role in mitigating cement shrinkage. Due to their three-dimensional network structure and abundant hydrophilic groups, they absorb excess water from the matrix during the initial hydration phase, storing it and slowly releasing it later as the internal humidity of the cement decreases, thereby reducing capillary forces-induced autogenous shrinkage. However, the highly alkaline environment of alkali-activated materials and the influence of complex ions rapidly reduce the water absorption and release capacity of superabsorbent polymers, resulting in suboptimal reduction in autogenous shrinkage. Furthermore, superabsorbent polymers tend to form weak interfacial zones as small as 50 μm within cementitious materials. Using superabsorbent polymers solely as internal curing agents negatively impacts the mechanical properties of alkali-activated cementitious materials and provides limited improvement in autogenous shrinkage. Calcium aluminosilicate hydrate (CASH) has been introduced into alkali-activated systems as nanocrystalline cores. Its nucleation site effect accelerates the hydration reaction, promoting early strength development and, to a certain extent, mitigating autogenous shrinkage. However, the dense microstructure and low permeability of alkali-activated cementitious materials preclude effective external curing. Therefore, there is an urgent need to develop and design an alkali-activated composite material that can both alleviate self-shrinkage and improve mechanical properties. Summary of the Invention

[0004] The object of the present invention is to provide an internal curing agent and a high-strength, low-shrinkage alkali-activated composite material and a method for preparing the same, in order to solve the above-mentioned technical problems.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a three-dimensional network calcium aluminosilicate hydrate internal curing agent, comprising the following steps:

[0007] 1) preparing hydrated calcium aluminosilicate gel by chemical precipitation using a calcium source, a silicon source and an aluminum source;

[0008] 2) ultrasonically dispersing the hydrated calcium silicate gel in water to obtain a suspension;

[0009] 3) After mixing the suspension with the polymer monomer, an initiator, a cross-linking agent, and a catalyst are sequentially added to carry out a polymerization reaction. The obtained product is sequentially washed, dried, and crushed to obtain the CASH@NIPAm-SA internal curing agent.

[0010] Furthermore, the polymer monomers include acrylic acid and acrylamide, and the mass ratio of acrylic acid to acrylamide is 0.1-1:1-2.

[0011] Furthermore, the calcium source comprises calcium nitrate, the silicon source comprises sodium silicate, the aluminum source comprises aluminum nitrate, the molar mass ratio of the calcium source, silicon source and aluminum source is 0.8-1.2:1:0.01-0.15, and the solid-liquid ratio in the chemical precipitation method is 0.1:1.

[0012] Furthermore, in the step 2), the power of ultrasonic dispersion is 500-800W, and the time of ultrasonic dispersion is 5-10 minutes;

[0013] The concentration of the suspension is 0.5-1.5 mg / mL.

[0014] Furthermore, the mass ratio of the hydrated calcium silicate gel to the polymer monomer is 0.1 to 2:1, the initiator is ammonium persulfate, and the mass ratio of the initiator to the polymer monomer is 0.01 to 0.015:1;

[0015] The cross-linking agent is N,N-methylenebisacrylamide, and the mass ratio of the cross-linking agent to the polymer monomer is 0.01 to 0.015:1;

[0016] The catalyst is tetramethylethylenediamine, and the volume mass ratio of the catalyst to the polymer monomer is 0.01-0.015 μL:1 g.

[0017] Furthermore, the polymerization reaction temperature is 20-40° C., and the polymerization reaction time is 20-30 hours.

[0018] The present invention also provides a three-dimensional network hydrated calcium aluminosilicate internal curing agent.

[0019] The present invention also provides a method for preparing a high-strength, low-shrinkage alkali-activated composite material, comprising the following steps:

[0020] After mixing a three-dimensional network calcium silicate aluminate hydrate internal curing agent, fly ash, slag powder and water, adding a composite alkaline activator, and curing the obtained mixed slurry to obtain a high-strength and low-shrinkage alkali-activated composite material.

[0021] Furthermore, the mass ratio of the three-dimensional network hydrated calcium silicate aluminate internal curing agent, fly ash, slag powder and water is 3-15:600:600:500-600, the content of the composite alkaline activator in the high-strength and low-shrinkage alkali-activated composite material is 5-10%, and the modulus is 1.5.

[0022] The present invention also provides a high-strength, low-shrinkage alkali-activated composite material.

[0023] Beneficial effects of the present invention:

[0024] The present invention uses acrylic acid-acrylamide copolymer as a template skeleton, and the CASH@NIPAm-SA synthesized and prepared by coordination bond self-assembly reaction has a three-dimensional network structure. Some hydrophilic groups in the acrylic acid-acrylamide copolymer chelate with the alkali metal ions in CASH, thereby enhancing the crosslinking degree and strength of the polymer network. While retaining the water absorption and water retention properties, the influence of the solution environment on the water absorption and release behavior is reduced. Compared with traditional internal curing agents, CASH@NIPAm-SA has obvious self-shrinkage reduction ability and higher internal curing efficiency. At the same time, compared with a single highly absorbent polymer, the incorporation of CASH@NIPAm-SA improves the compressive strength of the alkali-activated composite material. This is because CASH exerts a nucleation site effect to accelerate the hydration reaction of the alkali-activated material, improve the degree of hydration, and has no obvious interface area with the matrix.

[0025] The present invention adopts three-dimensional network hydrated calcium aluminosilicate as an internal curing agent to prepare an alkali-activated composite material, the autogenous shrinkage property of which is significantly alleviated, the early hydration degree is high, and the strength will not shrink in the later stage, and the material has broad application prospects in the field of building materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The images of CASH@NIPAm-SA and NIPAm-SA provided in Example 2 and Comparative Example 2 of the present invention before and after water absorption and swelling, as well as comparison of their water absorption rates in deionized water and pore solution; the left image is the image of the objects, and the right image is the water absorption rate image;

[0027] Figure 2 This is a comparison chart of the autogenous shrinkage results of the composite material stimulated by alkali using CASH@NIPAm-SA as an internal curing agent provided in the embodiments of the present invention;

[0028] Figure 3 This is a scanning electron microscope image of CASH@NIPAm-SA of Example 2 provided by the present invention;

[0029] Figure 4 The present invention provides a schematic flow chart of a method for preparing a high-strength, low-shrinkage alkali-activated composite material. DETAILED DESCRIPTION

[0030] The present invention provides a method for preparing a three-dimensional network calcium aluminosilicate hydrate internal curing agent, comprising the following steps:

[0031] 1) preparing hydrated calcium aluminosilicate gel by chemical precipitation using a calcium source, a silicon source and an aluminum source;

[0032] 2) ultrasonically dispersing the hydrated calcium silicate gel in water to obtain a suspension;

[0033] 3) After mixing the suspension with the polymer monomer, an initiator, a cross-linking agent, and a catalyst are sequentially added to carry out a polymerization reaction. The obtained product is sequentially washed, dried, and crushed to obtain the CASH@NIPAm-SA internal curing agent.

[0034] In the present invention, the polymer monomers include acrylic acid and acrylamide, and the mass ratio of acrylic acid to acrylamide is 0.1-1:1-2, preferably 0.25:1.

[0035] In the present invention, the calcium source comprises calcium nitrate, the silicon source comprises sodium silicate, and the aluminum source comprises aluminum nitrate. The molar mass ratio of the calcium source, silicon source, and aluminum source is 0.8-1.2:1:0.01-0.15, preferably 1.0:1.0:0.1. The solid-to-liquid ratio in the chemical precipitation method is 0.1:1.

[0036] In the present invention, in step 1), the chemical precipitation method is specifically as follows: a calcium source, a silicon source, and an aluminum source are respectively dissolved in deionized water to obtain a calcium source solution, a silicon source solution, and an aluminum source solution; the calcium source solution is gradually added dropwise to a mixture of the silicon source solution and the aluminum source solution; the pH of the reaction solution is adjusted to 13.50±0.05 with a sodium hydroxide solution; the reaction is continued in a 25°C water bath for 24 hours with a constant stirring speed maintained at 400-800 rpm; after the reaction, the formed CASH gel is washed, dried, and ground into a fine powder for standby use; the concentration of the sodium hydroxide solution is 8-10 mol / L, preferably 9 mol / L.

[0037] In the present invention, in step 2), the power of ultrasonic dispersion is 500-800 W, preferably 600-700 W; the time of ultrasonic dispersion is 5-10 min, preferably 5-8 min.

[0038] In the present invention, the concentration of the suspension is 0.5 to 1.5 mg / mL, preferably 0.5 to 1.0 mg / mL.

[0039] In the present invention, the mass ratio of the calcium silicate aluminate hydrate gel to the polymer monomer is 0.1 to 2:1, preferably 0.5 to 1.5:1, and more preferably 1:1.

[0040] In the present invention, the initiator is ammonium persulfate, and the mass ratio of the initiator to the polymer monomer is 0.01 to 0.015:1, preferably 0.01 to 0.012:1.

[0041] In the present invention, the cross-linking agent is N,N-methylenebisacrylamide, and the mass ratio of the cross-linking agent to the polymer monomer is 0.01 to 0.015:1, preferably 0.01 to 0.012:1;

[0042] The catalyst is tetramethylethylenediamine, and the volume mass ratio of the catalyst to the polymer monomer is 0.01-0.015 μL:1 g, preferably 0.01-0.012 μL:1 g.

[0043] In the present invention, the polymerization reaction temperature is 20-40° C., preferably 25-35° C.; the polymerization reaction time is 20-30 h, preferably 24 h.

[0044] In the present invention, in step 3), the cleaning is to cut the product and soak it in deionized water for 24 hours to remove unreacted monomers; the drying temperature is 50-60°C, preferably 55°C.

[0045] The present invention also provides a three-dimensional network hydrated calcium aluminosilicate internal curing agent.

[0046] The present invention also provides a method for preparing a high-strength, low-shrinkage alkali-activated composite material, comprising the following steps:

[0047] After mixing a three-dimensional network calcium silicate aluminate hydrate internal curing agent, fly ash, slag powder and water, adding a composite alkaline activator, and curing the obtained mixed slurry to obtain a high-strength and low-shrinkage alkali-activated composite material.

[0048] In the present invention, the mass ratio of the three-dimensional network hydrated calcium aluminosilicate internal curing agent, fly ash, slag powder and water is 3-15:600:600:500-600, preferably 3.6-11:600:600:600;

[0049] The content of the composite alkaline activator in the high-strength, low-shrinkage alkali-activated composite material is 5-10%, preferably 6%, and the modulus is 1.5.

[0050] In the present invention, the composite alkaline activator is a mixture of industrial-grade water glass and sodium hydroxide.

[0051] The present invention also provides a high-strength, low-shrinkage alkali-activated composite material.

[0052] The purpose of the present invention is to alleviate the problem of self-shrinkage of alkali-activated gelling materials and to improve the poor water absorption and release capacity of highly absorbent polymers as internal curing agents in alkaline environments, as well as their low inherent strength. The present invention provides a three-dimensional network calcium silicate aluminate hydrate internal curing agent. The acrylamide-acrylic acid copolymer gel (NIPAm-SA) is used to modify the calcium silicate aluminate hydrate crystal nuclei through a coordination bond self-assembly reaction to synthesize a three-dimensional network calcium silicate aluminate hydrate, represented by CASH@NIPAm-SA. CASH@NIPAm-SA can serve as a nucleation site, which promotes the curing of the matrix by accelerating the hydration reaction process of the alkali-activated material. In addition, the main product formed by the hydration of the alkali-activated material is calcium silicate hydrate gel, so there is no obvious interface area within the matrix. Therefore, while alleviating self-shrinkage, the compressive strength of the alkali-activated composite material is improved.

[0053] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0054] Example 1

[0055] CASH@NIPAm-SA internal curing agent was prepared by chemical precipitation and aqueous solution polymerization. CASH was synthesized by chemical precipitation. Calcium nitrate, sodium silicate solution and aluminum nitrate were used as calcium source, silicon source and aluminum source in a molar ratio of 1.0:1.0:0.1. The three were respectively prepared into solutions. The calcium source solution was gradually added dropwise to the mixture of silicon source solution and aluminum source solution. The pH of the reaction solution was adjusted to 13.50±0.05 with sodium hydroxide solution. The constant stirring speed was maintained at 600 rpm. The reaction was carried out in a constant temperature water bath at 25°C for 24 hours and filtered and dried to obtain CASH gel.

[0056] 3.6g of CASH was pre-dispersed in 720mL of deionized water using 500W ultrasonication. 5.76g of acrylamide, 1.44g of acrylic acid, 0.072g of ammonium persulfate, 0.072g of N,N-methylenebisacrylamide, and 0.072μL of tetramethylethylenediamine were then added and mixed thoroughly. After reacting for 24 hours, the mixture was dried and ground to obtain CASH@NIPAm-SA powder, which served as the internal curing agent. 600g of fly ash, 600g of slag powder, and 540g of water were mixed with 5.4g of CASH@NIPAm-SA powder in a blender. A prefabricated composite alkaline activator (6% dosage; modulus 1.5) was added and stirred continuously. The resulting mixture was poured into a mold and cured under standard curing conditions to the specified age, yielding a high-strength, low-shrinkage alkali-activated composite material.

[0057] Example 2

[0058] CASH@NIPAm-SA internal curing agent was prepared by chemical precipitation and aqueous solution polymerization. CASH was synthesized by chemical precipitation. Calcium nitrate, sodium silicate solution and aluminum nitrate were used as calcium source, silicon source and aluminum source in a molar ratio of 1.0:1.0:0.1. The three were respectively prepared into solutions. The calcium source solution was gradually added dropwise to the mixture of silicon source solution and aluminum source solution. The pH of the reaction solution was adjusted to 13.50±0.05 with sodium hydroxide solution. The constant stirring speed was maintained at 600 rpm. The reaction was carried out in a constant temperature water bath at 25°C for 24 hours and filtered and dried to obtain CASH gel.

[0059] 7.2g of CASH was pre-dispersed in 720mL of deionized water using 500W ultrasonication. 5.76g of acrylamide, 1.44g of acrylic acid, 0.072g of ammonium persulfate, 0.072g of N,N-methylenebisacrylamide, and 0.072μL of tetramethylethylenediamine were then added and mixed uniformly. After reacting for 24 hours, the mixture was dried and ground to obtain CASH@NIPAm-SA powder, which serves as the internal curing agent. 600g of fly ash, 600g of slag powder, and 540g of water were mixed with 7.2g of CASH@NIPAm-SA powder in a blender. A pre-made composite alkaline activator (6% dosage; modulus 1.5) was added and stirred continuously. The resulting mixture was poured into a mold and cured under standard curing conditions to the specified age, resulting in a high-strength, low-shrinkage alkali-activated composite material.

[0060] Example 3

[0061] CASH@NIPAm-SA internal curing agent was prepared by chemical precipitation and aqueous solution polymerization. CASH was synthesized by chemical precipitation. Calcium nitrate, sodium silicate solution and aluminum nitrate were used as calcium source, silicon source and aluminum source in a molar ratio of 1.0:1.0:0.1. The three were respectively prepared into solutions. The calcium source solution was gradually added dropwise to the mixture of silicon source solution and aluminum source solution. The pH of the reaction solution was adjusted to 13.50±0.05 with sodium hydroxide solution. The constant stirring speed was maintained at 600 rpm. The reaction was carried out in a constant temperature water bath at 25°C for 24 hours and filtered and dried to obtain CASH gel.

[0062] 3.6g of CASH was pre-dispersed in 720mL of deionized water using 500W ultrasonication. 5.76g of acrylamide, 1.44g of acrylic acid, 0.072g of ammonium persulfate, 0.072g of N,N-methylenebisacrylamide, and 0.072μL of tetramethylethylenediamine were then added and mixed thoroughly. After reacting for 24 hours, the mixture was dried and ground to obtain CASH@NIPAm-SA powder, which served as the internal curing agent. 600g of fly ash, 600g of slag powder, and 540g of water were mixed with 10.8g of CASH@NIPAm-SA powder in a blender. A prefabricated composite alkaline activator (6% content, modulus 1.5) was added and stirred continuously. The resulting mixture was poured into a mold and cured under standard curing conditions to the specified age, yielding a high-strength, low-shrinkage alkali-activated composite material.

[0063] Comparative Example 1

[0064] Weigh 600g of fly ash, 600g of slag powder and 540g of water, mix the fly ash powder evenly in a cement mixer, add the prefabricated composite alkaline activator (dosage is 6%; modulus is 1.5), continue stirring evenly, pour the resulting slurry into a mold to form, and cure it to the specified age under standard curing conditions.

[0065] Comparative Example 2

[0066] NIPAm-SA was prepared as an internal curing agent via aqueous solution polymerization. 5.76g of acrylamide, 1.44g of acrylic acid, 0.072g of ammonium persulfate, 0.072g of N,N-methylenebisacrylamide, and 0.072μL of tetramethylethylenediamine were added sequentially to 720mL of deionized water and mixed thoroughly. After reacting for 24 hours, the mixture was dried and ground to obtain NIPAm-SA powder. 600g of fly ash, 600g of slag powder, and 540g of water were mixed in a blender with 3.6g of NIPAm-SA powder. A prefabricated composite alkaline activator (6% alkali content and a modulus of 1.5) was added and stirred continuously. The resulting mixture was poured into a mold and cured under standard curing conditions to the specified age.

[0067] The water absorption rates of CASH@NIPAm-SA and NIPAm-SA in deionized water and pore solution in Example 2 and Comparative Example 2 were tested respectively. Figure 1 As shown by Figure 1 It can be seen that the water absorption capacity of CASH@NIPAm-SA and NIPAm-SA in deionized water are:

[0068] The water absorption rate of NIPAm-SA in the pore solution was 22.4 g / g, an 85% reduction compared to deionized water. The water absorption rate of CASH@NIPAm-SA in the pore solution was 27.3 g / g, a 55% reduction compared to deionized water. It should be noted that the water absorption capacity of CASH@NIPAm-SA is less affected by the alkalinity and ions in the pore solution than that of NIPAm-SA, which helps maintain the stability and integrity of CASH@NIPAm-SA as an internal curing agent.

[0069] The compressive strength of the alkali-activated composite materials prepared in the examples and comparative examples was tested at 3d, 7d and 28d, and the results are shown in Table 1:

[0070] Table 1 Compressive strength test data of alkali-activated composite materials

[0071]

[0072] As shown in the table, the addition of CASH@NIPAm-SA improves the compressive strength of the alkali-activated composites compared to those without internal curing materials and those with NIPAm-SA. This compressive strength increases with increasing CASH content. Compared to NIPAm-SA, CASH@NIPAm-SA exhibits a nucleation site effect, improving the degree of hydration. Furthermore, CASH@NIPAm-SA exhibits greater interfacial compatibility with the alkali-activated matrix material.

[0073] The alkali-activated composite materials prepared in the examples and comparative examples were tested for autogenous shrinkage, and the results were as follows: Figure 2 As shown in the figure, CASH@NIPAm-SA, as an internal curing agent in this example, effectively mitigates the autogenous shrinkage of the alkali-activated material. Compared to the alkali-activated material itself, CASH@NIPAm-SA reduces the autogenous shrinkage of the alkali-activated material by 68%, and compared to traditional NIPAm-SAA, it increases by 53.2%, indicating that the autogenous shrinkage of the alkali-activated composite material is significantly alleviated.

[0074] As can be seen from the above embodiments, the present invention provides an internal curing agent and a high-strength, low-shrinkage alkali-activated composite material and method for preparing the same. The present invention uses acrylamide and acrylic acid copolymer (NIPAm-SA) as a template skeleton to modify the calcium silicate aluminate hydrate nucleus (CASH) through a coordination bond self-assembly reaction to synthesize a three-dimensional network calcium silicate aluminate hydrate (CASH@NIPAm-SA). CASH@NIPAm-SA can be used as an internal curing agent. CASH@NIPAm is mixed with an alkali-activated cementitious material to obtain a high-strength, low-shrinkage alkali-activated composite material with the advantages of high internal curing efficiency, significant self-shrinkage inhibition effect, and high early strength. The present invention realizes the synergistic effect of calcium silicate aluminate hydrate for internal curing and nucleation sites. What is important is that it can be applied to the high alkaline environment of alkali-activated cementitious materials, and is well combined with the matrix, alleviating the problem of large self-shrinkage of alkali-activated materials.

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a three-dimensional network calcium aluminosilicate hydrate internal curing agent, characterized in that: The following steps are involved: 1) preparing hydrated calcium aluminosilicate gel by chemical precipitation using a calcium source, a silicon source and an aluminum source; 2) ultrasonically dispersing the hydrated calcium silicate gel in water to obtain a suspension; 3) After mixing the suspension with the polymer monomer, an initiator, a cross-linking agent, and a catalyst are sequentially added to carry out a polymerization reaction. The obtained product is sequentially washed, dried, and crushed to obtain the CASH@NIPAm-SA internal curing agent.

2. The method for preparing the three-dimensional network calcium aluminosilicate hydrate internal curing agent according to claim 1, characterized in that: The polymer monomers include acrylic acid and acrylamide, and the mass ratio of acrylic acid to acrylamide is 0.1-1:1-2.

3. The method for preparing the three-dimensional network calcium aluminosilicate hydrate internal curing agent according to claim 1 or 2, characterized in that: The calcium source comprises calcium nitrate, the silicon source comprises sodium silicate, and the aluminum source comprises aluminum nitrate. The molar mass ratio of the calcium source, the silicon source, and the aluminum source is 0.8-1.2:1:0.01-0.15, and the solid-liquid ratio in the chemical precipitation method is 0.1:

1.

4. The method for preparing the three-dimensional network calcium aluminosilicate hydrate internal curing agent according to claim 3, characterized in that: In the step 2), the power of ultrasonic dispersion is 500-800W, and the time of ultrasonic dispersion is 5-10 minutes; The concentration of the suspension is 0.5-1.5 mg / mL.

5. The method for preparing the three-dimensional network calcium aluminosilicate hydrate internal curing agent according to claim 2 or 4, characterized in that: The mass ratio of the hydrated calcium silicate gel to the polymer monomer is 0.1 to 2:1, the initiator is ammonium persulfate, and the mass ratio of the initiator to the polymer monomer is 0.01 to 0.015:1; The cross-linking agent is N,N-methylenebisacrylamide, and the mass ratio of the cross-linking agent to the polymer monomer is 0.01 to 0.015:1; The catalyst is tetramethylethylenediamine, and the volume mass ratio of the catalyst to the polymer monomer is 0.01-0.015 μL:1 g.

6. The method for preparing the three-dimensional network calcium aluminosilicate hydrate internal curing agent according to claim 5, characterized in that: The polymerization reaction temperature is 20-40° C., and the polymerization reaction time is 20-30 hours.

7. The three-dimensional network calcium aluminosilicate hydrate internal curing agent prepared by the preparation method according to any one of claims 1 to 6.

8. A method for preparing a high-strength, low-shrinkage alkali-activated composite material, characterized in that: The following steps are involved: After mixing the three-dimensional network calcium aluminosilicate hydrate internal curing agent described in claim 7, fly ash, slag powder and water, adding a composite alkaline activator, and curing the obtained mixed slurry, a high-strength and low-shrinkage alkali-activated composite material is obtained.

9. The method for preparing a high-strength, low-shrinkage alkali-activated composite material according to claim 8, characterized in that: The mass ratio of the three-dimensional network hydrated calcium aluminosilicate internal curing agent, fly ash, slag powder and water is 3-15:600:600:500-600, the content of the composite alkaline activator in the high-strength and low-shrinkage alkali-activated composite material is 5-10%, and the modulus is 1.

5.

10. The high-strength, low-shrinkage alkali-activated composite material prepared by the preparation method according to any one of claims 7 to 9.

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