Raw material composition of geopolymer slurry, geopolymer slurry and preparation method and application thereof

Abstract

The present application relates to the field of oil and gas well cementing, and discloses a raw material composition of a geopolymer slurry, the geopolymer slurry, and a preparation method and application thereof.The composition comprises modified SiO2-Al2O3 nanocomposites, metakaolin, and an activator.The modified SiO2-Al2O3 nanocomposites comprise SiO2-Al2O3 nanocomposite particles and hydrophobic functional groups attached to the surfaces of the particles.In the present application, the modified SiO2-Al2O3 nanocomposites are first introduced into the geopolymer slurry.On the one hand, the nanometer Si-Al2O3 can play a role in plugging voids, and on the other hand, the nanometer Si-Al2O3 can react with the geopolymer to generate additional aluminum silicate hydrate (CASH) and sodium aluminum silicate hydrate (NASH), so that the compressive strength, bending strength, and elastic modulus of the geopolymer slurry are increased, and the pores or cracks are filled to form a dense and strong geopolymer.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well cementing, specifically to a raw material composition for a geopolymer slurry, the geopolymer slurry itself, its preparation method, and its application. Background Technology

[0002] When ordinary Portland cement is used in well cementing projects, it often exhibits cracking, high brittleness (poor ductility), and microcracks due to volume shrinkage under temperature and pressure. The instability of silicate cement exacerbates the risk of material failure, affecting wellbore integrity. Based on these issues, researchers are seeking alternatives to silicate cement. Bismuth-based materials, resins, and geopolymers are currently recognized as viable alternatives, with geopolymers already used in the construction industry. Geopolymers are inorganic polymers formed by the polymerization of long-chain aluminosilicates. This material consists of SiO4 and AlO4 tetrahedra, which form a 3-D network gel with alternating Si-O-Al-O bonds through shared oxygen ions. The geopolymerization process is activated by mixing the geopolymer precursor with a hardener (alkali metal silicate solution), generating a gelling substance. Compared to traditional silicate cement, geopolymers offer advantages such as corrosion resistance, low permeability, high structural flexibility, low chemical shrinkage, and lower CO2 emissions during production. However, geopolymer slurries may develop microcracks at high temperatures, leading to reduced mechanical strength and limiting their application in well cementing.

[0003] In recent years, nanomaterials (1-100 nm) have shown great potential in solving engineering problems related to the oil and gas industry. Due to their extremely small size and high specific surface area, nanoparticles have been extensively studied for their effects on the mechanical properties of traditional building cements, such as increasing compressive strength, flexural strength, tensile strength, and reducing permeability. Researchers in well cementing are also incorporating nanomaterials into their cementitious systems to improve the performance of oil well cement materials. Many studies have shown that nanoparticles have a significant effect on regulating the microstructure, chemical shrinkage, density, and porosity of cement paste. However, few studies have investigated the influence of nanoparticles on the properties of geopolymers used in oil well cementing.

[0004] There is limited research in China on geopolymers for cementing, and research on the strength adjustment of geopolymers is still in its infancy, with only some studies focusing on the formulation of cementing fluid components.

[0005] CN114105548B discloses a geopolymer cementing fluid with controllable thickening time. This geopolymer cementing fluid has advantages such as adjustable thickening time, excellent compressive strength, good settling stability, good rheological properties, and environmental friendliness. To improve compressive strength, this invention introduces spherical, highly active ultrafine fly ash into the raw materials of the geopolymer to improve its strength, and also improves the strength of the geopolymer by partially replacing calcium hydroxide with barium hydroxide. However, this patent mainly improves the strength of the geopolymer through spherical, highly active ultrafine fly ash, without mentioning the research on the synthesis of the material.

[0006] CN103435313A discloses a fly ash-based geopolymer concrete with controllable strength. This concrete uses crushed stone and natural sand as aggregates, fly ash as the main cementing material, silica fume as a siliceous modifier, sodium tripolyphosphate as a water-reducing agent, and sodium hydroxide solution and industrial sodium silicate solution as activators. It is prepared at room temperature using industrial waste fly ash as the main cementing material. By adjusting the proportions of each material, the compressive strength of the geopolymer concrete can be controlled. Specifically, by controlling the amount of silica fume, the amount of sodium silicate solution and NaOH solution in the cementing material, and the molar concentration of the NaOH solution, geopolymer concrete of different strength grades can be obtained. This invention achieves strength control through adjusting the formula proportions without the use of additional admixtures.

[0007] Based on the above problems, it is urgent to solve the issues of poor mechanical properties of geopolymers in the field of cementing engineering, the occurrence of microcracks under high temperature and high pressure, and the impact on cementing quality. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of poor mechanical properties and insufficient strength of existing geopolymers in well cementing operations, which lead to microcracks under pressure. This invention provides a raw material composition for geopolymer slurry, a geopolymer slurry, its preparation method, and its application.

[0009] To achieve the above objectives, the first aspect of the present invention provides a raw material composition for a geopolymer slurry, wherein the composition comprises a modified SiO2-Al2O3 nanocomposite material, metakaolin, and an activator; wherein the modified SiO2-Al2O3 nanocomposite material comprises: SiO2-Al2O3 nanocomposite particles and hydrophobic functional groups attached to the surface of the particles.

[0010] The second aspect of the present invention provides a method for preparing a geopolymer slurry, wherein a modified SiO2-Al2O3 nanocomposite material is mixed with metakaolin and then reacted with an activator to obtain a geopolymer slurry.

[0011] A third aspect of the present invention provides a geopolymer slurry obtained by the preparation method described above.

[0012] A fourth aspect of the present invention provides an application of the described composition or the described geopolymer slurry in the field of cementing engineering.

[0013] Through the above technical solution, in this invention, modified SiO2-Al2O3 nanocomposite material is introduced into the geopolymer slurry for the first time. On the one hand, nano-Si-Al2O3 can block the pores, and on the other hand, nano-Si-Al2O3 can react with the geopolymer to generate additional aluminosilicate hydrate (CASH) and sodium aluminosilicate hydrate (NASH), thereby increasing the compressive strength, flexural strength and elastic modulus of the geopolymer slurry, and filling the pores or cracks to form a dense and strong geopolymer. Attached Figure Description

[0014] Figure 1 These are the results of the specific surface area test of the modified SiO2-Al2O3 nanocomposite material;

[0015] Figure 2 This is a transmission electron microscope (TEM) image of the modified SiO2-Al2O3 nanocomposite material. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] The first aspect of the present invention provides a raw material composition for a geopolymer slurry, wherein the composition comprises a modified SiO2-Al2O3 nanocomposite material, metakaolin, and an activator; wherein the modified SiO2-Al2O3 nanocomposite material comprises: SiO2-Al2O3 nanocomposite particles and hydrophobic functional groups attached to the surface of the particles.

[0018] In some specific embodiments of the present invention, the modified SiO2-Al2O3 nanocomposite material is 1-10 parts by weight relative to 100 parts by weight of the metakaolin, and the activator is 20-80 parts by weight; preferably, the modified SiO2-Al2O3 nanocomposite material is 1-5 parts by weight, and the activator is 20-60 parts by weight.

[0019] In some specific embodiments of the present invention, the specific surface area of ​​the modified SiO2-Al2O3 nanocomposite material is 270-470 cm². 3 / g; preferably, the average particle size of the modified SiO2-Al2O3 nanocomposite material is 10-15nm; preferably, the silicon-aluminum molar ratio of the modified SiO2-Al2O3 nanocomposite material is (1-5):(1-3).

[0020] In some specific embodiments of the present invention, the hydrophobic functional group is selected from one or more of alkenyl, NH2, SH, epoxy, and (meth)acryloyloxy substituted hydrocarbon groups.

[0021] In some specific embodiments of the present invention, based on the total amount of the modified SiO2-Al2O3 nanocomposite material, the content of the hydrophobic functional groups is 0.1-0.5 wt%, preferably 0.1-0.3 wt%.

[0022] In this invention, the modified SiO2-Al2O3 nanocomposite material serves as a modifier material to enhance the strength of geopolymers. It can solve the problem that geopolymers have poor mechanical properties under high temperature and high pressure conditions, and are prone to microcracks, leading to a sharp decrease in strength.

[0023] In this invention, the modified SiO2-Al2O3 nanocomposite material is prepared by means of introducing the aforementioned hydrophobic functional groups onto the surface of the modified SiO2-Al2O3 nanocomposite material:

[0024] (1) A water-soluble aluminum source, a polymeric dispersant, a precipitant and a silicon source are reacted and aged to obtain a precipitate;

[0025] (2) The precipitate was washed, dried and calcined to obtain SiO2-Al2O3 nanocomposite material;

[0026] (3) The dispersed SiO2-Al2O3 nanocomposite material is subjected to a modification reaction with an ethanol solution containing a surface modifier. The resulting suspension is centrifuged, sonicated, and dried to obtain the modified SiO2-Al2O3 nanocomposite material.

[0027] In some specific embodiments of the present invention, the modified SiO2-Al2O3 nanocomposite material is prepared by means of introducing the aforementioned hydrophobic functional groups onto the surface of the modified SiO2-Al2O3 nanocomposite material:

[0028] (1) Add water-soluble aluminum source and polymeric dispersant to the reaction vessel, heat the resulting mixture to 60℃-85℃, add silicon source dropwise under strong stirring for 2 hours, then add precipitant dropwise, and then age for 3-12 hours to obtain precipitate;

[0029] (2) After washing the precipitate twice with an alcohol-water mixture (the mass ratio of alcohol to water is 1:1), the obtained filter cake was dried at 100℃ and finally calcined at 500-1300℃ to obtain SiO2-Al2O3 nanocomposite material.

[0030] (3) The SiO2-Al2O3 nanocomposite material was added to a mixed solution of ethanol and deionized water (the weight ratio of SiO2-Al2O3 nanocomposite material to the mixed solution was (1-5):(1-3)), and the resulting mixture was ultrasonically dispersed for 2 hours. An ethanol solution of the surface modifier was added to the ultrasonic product to carry out the modification reaction. Finally, the resulting suspension was centrifuged at high speed and ultrasonically treated 4 times. The solid after removing excess surface modifier and by-products was dried to obtain the modified SiO2-Al2O3 nanocomposite material.

[0031] In this invention, the modified SiO2-Al2O3 nanocomposite material is synthesized using the above-mentioned precipitation-modification method to solve the problems of easy agglomeration and poor dispersion performance of nanoparticles.

[0032] In some specific embodiments of the present invention, the surface modifier is selected from silane coupling agents, preferably one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and vinyltriethoxysilane.

[0033] In some specific embodiments of the present invention, the concentration of the surface modifier in the ethanol solution is 1wt%-9wt%.

[0034] In some specific embodiments of the present invention, the polymeric dispersant is selected from one or more of polyvinyl alcohol, polyacrylate, methylcellulose, carboxymethylcellulose, hydroxypropylcellulose, and hydroxyethylcellulose.

[0035] In some specific embodiments of the present invention, the precipitant is selected from one or more of ammonium carbonate, urea, and ammonia water.

[0036] In some specific embodiments of the present invention, the water-soluble aluminum source is selected from one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, and aluminum silicate.

[0037] In some specific embodiments of the present invention, the silicon source is selected from tetraethyl orthosilicate and / or methyl orthosilicate.

[0038] In some specific embodiments of the present invention, the weight ratio of the water-soluble aluminum source, polymeric dispersant, precipitant, silicon source and surface modifier is (20-60):(1-5):(40-80):(5-8):(10-20).

[0039] In some specific embodiments of the present invention, the conditions for the modification reaction include: a reaction temperature of 65-85°C and a reaction time of 3-5 hours.

[0040] In some specific embodiments of the present invention, the activator is selected from one or more of sodium hydroxide, sodium silicate, potassium silicate, and calcium silicate, preferably a combination of NaOH and Na2SiO3.

[0041] In some specific embodiments of the present invention, the mass ratio of Na2SiO3 to NaOH in the composition is (1-5):(1-5).

[0042] According to a particularly preferred embodiment of the present invention, a raw material composition for a geopolymer slurry is provided, the composition comprising a modified SiO2-Al2O3 nanocomposite material, metakaolin, and an activator; wherein the modified SiO2-Al2O3 nanocomposite material comprises: SiO2-Al2O3 nanocomposite particles and hydrophobic functional groups attached to the surface of the particles, preferably, the modified SiO2-Al2O3 nanocomposite material is 1-5 parts by weight relative to 100 parts by weight of the metakaolin, and the activator is 20-60 parts by weight.

[0043] The second aspect of the present invention provides a method for preparing a geopolymer slurry, wherein a modified SiO2-Al2O3 nanocomposite material is mixed with metakaolin and then reacted with an activator to obtain a geopolymer slurry.

[0044] In some specific embodiments of the present invention, in the preparation method of geopolymer slurry, an activator is dissolved in water to obtain an activator solution, metakaolin and modified SiO2-Al2O3 nanocomposite material are dry mixed and added to the activator solution within 15s, and the mixture is stirred for 50s to obtain geopolymer slurry, wherein the stirring speed is 3000-5000 r / min.

[0045] In some specific embodiments of the present invention, in the method for preparing the geopolymer slurry, the modified SiO2-Al2O3 nanocomposite material is 1-10 parts by weight relative to 100 parts by weight of the metakaolin, and the activator is 20-80 parts by weight; preferably, the modified SiO2-Al2O3 nanocomposite material is 1-5 parts by weight, and the activator is 20-60 parts by weight.

[0046] A third aspect of the present invention provides a geopolymer slurry obtained by the preparation method described above.

[0047] In this invention, modified SiO2-Al2O3 nanocomposite material is introduced into the geopolymer slurry for the first time. On the one hand, the modified SiO2-Al2O3 nanocomposite material can block the pores. On the other hand, the modified SiO2-Al2O3 nanocomposite material can react with the geopolymer to generate additional aluminosilicate hydrate (CASH) and sodium aluminosilicate hydrate (NASH), which increases the compressive strength, flexural strength and elastic modulus of the geopolymer slurry, and fills the pores or cracks to form a dense and strong geopolymer.

[0048] In this invention, the modified SiO2-Al2O3 nanocomposite material mainly plays a bridging role in the slurry, enabling the formation of more Si-O-Al-O alternating structures in the geopolymer precursor, promoting the formation of a denser 3D network cementitious structure of SiO4 and AlO4 tetrahedra after curing, achieving the effect of resisting crack propagation at high temperature, thereby realizing the comprehensive improvement of the mechanical properties of the geopolymer.

[0049] In some specific embodiments of the present invention, the geopolymer formed after the slurry is cured has a 7-day compressive strength of 21.8-23.3 MPa, a flexural strength of 2.11-2.36 MPa, and an elastic modulus of 5.99-6.92 GPa, which are 20-40%, 30-50%, and 20-35% higher than those of the geopolymer formed by the unmodified SiO2-Al2O3 nanocomposite material, respectively.

[0050] In some specific embodiments of the present invention, preferably, the geopolymer formed after the slurry is cured has a 7-day compressive strength of 23.3 MPa, a flexural strength of 2.36 MPa, and an elastic modulus of 6.92 GPa. Compared with the geopolymer without modified SiO2-Al2O3 nanocomposite material, the compressive strength, flexural strength, and elastic modulus are increased by 38.6%, 43.3%, and 28.8%, respectively.

[0051] In some specific embodiments of the present invention, the geopolymer formed after the slurry is cured has a 28-day compressive strength of 31.4-37.1 MPa, a flexural strength of 4.35-4.95 MPa, and an elastic modulus of 9.62-12.31 GPa.

[0052] In some specific embodiments of the present invention, preferably, the geopolymer formed after the slurry is cured has a 28-day compressive strength of 37.1 MPa, a flexural strength of 4.95 MPa, and an elastic modulus of 12.31 GPa.

[0053] In some specific embodiments of the present invention, the geopolymer formed after the slurry is cured has a 90-day compressive strength of 46.1-56.4 MPa, a flexural strength of 5.26-5.92 MPa, and an elastic modulus of 11.50-16.47 GPa.

[0054] In some specific embodiments of the present invention, preferably, the geopolymer formed after the slurry is cured has a 90-day compressive strength of 56.4 MPa, a flexural strength of 5.92 MPa, and an elastic modulus of 16.47 GPa.

[0055] A fourth aspect of the present invention provides an application of the described composition or the described geopolymer slurry in the field of cementing engineering.

[0056] The present invention will be described in detail below through embodiments.

[0057] Unless otherwise specified in the following examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0058] Preparation Example 1

[0059] 10g of aluminum sulfate was added to a reaction vessel containing 100g of water. 0.5g of polyvinyl alcohol dispersant was added with stirring and the mixture was heated to 60℃. 20g of tetraethyl orthosilicate solution was added with stirring and the reaction proceeded for 2 hours. Then, 2.5g of ammonium carbonate was added to the reaction vessel with stirring at 1400 rpm. The mixture was then aged for 3 hours to obtain a precipitate. The precipitate was washed twice with an alcohol-water mixture (mass ratio 1:1) and dried at 100℃. Finally, it was calcined at 500℃ to obtain a SiO2-Al2O3 nanocomposite material. The calcined SiO2-Al2O3 nanocomposite material was added to a mixed solution of ethanol and deionized water (mass ratio 1:1) at a mass ratio of 1:1, and the solution was ultrasonically dispersed for 2 hours. Then, 5g of an ethanol solution of γ-aminopropyltriethoxysilane was added to the above solution and the mixture was stirred at 75℃ for 4 hours. Finally, the suspension was centrifuged at 8000 r / min for 5 min, ultrasonicated twice to remove excess surface modifier and byproducts, and dried to obtain the modified SiO2-Al2O3 nanocomposite a1.

[0060] Preparation Example 2

[0061] 30g of aluminum chloride was added to a reaction vessel containing 100g of water. 2.5g of sodium polyacrylate dispersant was added while stirring and the mixture was heated to 75℃. 40g of methyl orthosilicate was added while stirring and the reaction proceeded for 2 hours. Then, 4g of urea was added to the reaction vessel while stirring at 1400 rpm. The mixture was then aged for 4 hours to obtain a precipitate. The precipitate was washed twice with an alcohol-water mixture (mass ratio 1:1) and dried at 100℃. Finally, it was calcined at 800℃ to obtain a SiO2-Al2O3 nanocomposite material. The calcined SiO2-Al2O3 nanocomposite material was added to a mixed solution of ethanol and deionized water (mass ratio 1:1) at a mass ratio of 1:1, and the solution was ultrasonically dispersed for 2 hours. Then, an ethanol solution of 10g of γ-glycidyl etheroxypropyltrimethoxysilane was added to the above solution and the mixture was stirred at 65℃ for 5 hours. Finally, the suspension was centrifuged at 8000 r / min for 5 min, ultrasonicated 4 times to remove excess surface modifier and byproducts, and dried to obtain modified SiO2-Al2O3 nanocomposite material a2.

[0062] Preparation Example 3

[0063] 25g of aluminum nitrate was added to a reaction vessel containing 100g of water. 1.5g of hydroxyethyl cellulose dispersant was added with stirring and the mixture was heated to 85℃. 25g of tetraethyl orthosilicate was added with stirring and reacted for 2 hours. Then, 3g of ammonia water was added to the reaction vessel with stirring at 1400 rpm. The mixture was then aged for 5 hours. The precipitate was washed twice with an alcohol-water mixture (mass ratio 1:1) and dried at 100℃. Finally, it was calcined at 1300℃ to obtain SiO2-Al2O3 nanocomposite material. The calcined SiO2-Al2O3 nanocomposite material was added to a mixed solution of ethanol and deionized water (mass ratio 1:1) at a mass ratio of 1:1, and the solution was ultrasonically dispersed for 2 hours. Then, an ethanol solution of 7.5g of vinyltriethoxysilane was added to the above solution and stirred at 85℃ for 3 hours. Finally, the suspension was centrifuged at 8000 r / min for 5 min, ultrasonicated twice to remove excess surface modifiers and byproducts, and dried to obtain the modified SiO2-Al2O3 nanocomposite a3.

[0064] The modified SiO2-Al2O3 nanocomposites obtained in Examples 1-3 were characterized, and the performance parameters are shown in Table 1.

[0065] Table 1 Performance parameters of modified SiO2-Al2O3 nanocomposites

[0066] serial number Silicon-aluminum molar ratio <![CDATA[Specific surface area / cm 3 / g]]> Particle size / nm Preparation Example 1 3:2 275 10-15 Preparation Example 2 2:1 435 10-15 Preparation Example 3 1:1 470 10-15

[0067] The specific surface area test results of the modified SiO2-Al2O3 nanocomposites a1, a2, and a3 prepared in Examples 1, 2, and 3 are as follows: Figure 1As shown (where the same shape indicates the adsorption-desorption isotherms of the same material, solid isotherms represent adsorption, and hollow isotherms represent desorption), the specific surface areas of a1, a2, and a3 are 275 cm². 3 / g, 435cm 3 / g and 470cm 3 / g. Transmission electron microscopy image of modified SiO2-Al2O3 nanocomposite a1 is shown below. Figure 2 As shown, from Figure 2 As can be seen, the particle size of the modified SiO2-Al2O3 nanocomposite material is between 10nm and 15nm.

[0068] Example 1

[0069] 20g of sodium silicate was dissolved in 53g of water to obtain an activator solution. 100g of metakaolin and 1g of modified SiO2-Al2O3 nanocomposite material a1 were dry-mixed and added to the activator solution within 15s. The mixture was stirred for 50s to obtain geopolymer slurry A1. The stirring speed was 4000r / min.

[0070] Example 2

[0071] Activator solution is obtained by dissolving 20g sodium silicate and 10g sodium hydroxide in 58g water. Activator solution is obtained by dry mixing 100g metakaolin and 2g modified SiO2-Al2O3 nanocomposite material a2 and adding it to the activator solution within 15s. Stirring is continued for 50s to obtain geopolymer slurry A2. The stirring speed is 4000r / min.

[0072] Example 3

[0073] 40g of sodium silicate and 20g of sodium hydroxide were dissolved in 72g of water to obtain an activator solution. 100g of metakaolin and 3g of modified SiO2-Al2O3 nanocomposite material a3 were dry-mixed and added to the activator solution within 15s. The mixture was stirred for 50s to obtain geopolymer slurry A3. The stirring speed was 4000r / min.

[0074] Example 4

[0075] 50g of sodium silicate and 20g of sodium hydroxide were dissolved in 79g of water to obtain an activator solution. 100g of metakaolin and 10g of modified SiO2-Al2O3 nanocomposite material a1 were dry-mixed and added to the activator solution within 15s. The mixture was stirred for 50s to obtain geopolymer slurry A4. The stirring speed was 4000r / min.

[0076] Example 5

[0077] 50g of sodium silicate and 30g of sodium hydroxide were dissolved in 81g of water to obtain an activator solution. 100g of metakaolin and 5g of modified SiO2-Al2O3 nanocomposite material a2 were dry-mixed and added to the activator solution within 15s. The mixture was stirred for 50s to obtain a geopolymer slurry A5. The stirring speed was 4000r / min.

[0078] Comparative Example

[0079] 40g of sodium silicate and 20g of sodium hydroxide were dissolved in 70g of water to obtain an activator solution. 100g of metakaolin was added to the activator solution within 15s, and the mixture was stirred for another 50s to obtain a geopolymer slurry A0. The stirring speed was 4000r / min.

[0080] Test case

[0081] The geopolymer slurry formulation with the modified SiO2-Al2O3 nanocomposite material prepared in this invention is shown in Table 2.

[0082] Table 2 Geopolymer Slurry Formulation

[0083]

[0084] After adding the modified SiO2-Al2O3 nanocomposite material prepared in this invention, the compressive strength and flexural strength of the geopolymer were improved. The measurement results are shown in Table 3.

[0085] Table 3 Compressive and flexural strengths of geopolymer slurries

[0086]

[0087]

[0088] The elastic modulus of the metakaolin geopolymer was also improved after adding the modified SiO2-Al2O3 nanocomposite material prepared in this invention. The measurement results are shown in Table 4.

[0089] Table 4 Elastic Modulus of Geopolymer Slurry

[0090]

[0091] The results in Tables 2, 3, and 4 show that after adding the modified SiO2-Al2O3 nanocomposite material prepared in this invention, the compressive strength of the geopolymer slurry reached a maximum of 23.3 MPa, the flexural strength reached 2.36 MPa, and the elastic modulus reached 6.92 GPa after 7 days of curing. Compared with the geopolymer without the modified SiO2-Al2O3 nanocomposite material, the compressive strength, flexural strength, and elastic modulus increased by 38.6%, 43.3%, and 28.8%, respectively. This indicates that the modified SiO2-Al2O3 nanocomposite material prepared in this invention has a significant enhancing effect on the mechanical properties of geopolymers.

[0092] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A raw material composition for a geopolymer slurry, characterized in that, The composition comprises modified SiO2-Al2O3 nanocomposite material, metakaolin, and activator; The modified SiO2-Al2O3 nanocomposite material includes: SiO2-Al2O3 nanocomposite particles and hydrophobic functional groups attached to the surface of the particles; The preparation method of the modified SiO2-Al2O3 nanocomposite material is as follows: (1) A water-soluble aluminum source, a polymeric dispersant, a precipitant and a silicon source are reacted and aged to obtain a precipitate; (2) The precipitate is washed, dried and calcined to obtain SiO2-Al2O3 nanocomposite material; (3) The dispersed SiO2-Al2O3 nanocomposite material is reacted with an ethanol solution containing a surface modifier to obtain the modified SiO2-Al2O3 nanocomposite material after centrifugation, sonication and drying. The modified SiO2-Al2O3 nanocomposite material is 1-10 parts by weight relative to 100 parts by weight of the metakaolin, and the activator is 20-80 parts by weight.

2. The composition according to claim 1, characterized in that, The modified SiO2-Al2O3 nanocomposite material is 1-5 parts by weight, and the activator is 20-60 parts by weight.

3. The composition according to claim 1, characterized in that, The specific surface area of ​​the modified SiO2-Al2O3 nanocomposite material is 270-470 cm². 3 / g.

4. The composition according to claim 1, characterized in that, The average particle size of the modified SiO2-Al2O3 nanocomposite material is 10-15 nm.

5. The composition according to claim 1, characterized in that, The silicon-aluminum molar ratio of the modified SiO2-Al2O3 nanocomposite is (1-5):(1-3).

6. The composition according to claim 1, characterized in that, Based on the total amount of the modified SiO2-Al2O3 nanocomposite material, the content of the hydrophobic functional groups is 0.1-0.5 wt%.

7. The composition according to claim 6, characterized in that, Based on the total amount of the modified SiO2-Al2O3 nanocomposite material, the content of the hydrophobic functional groups is 0.1-0.3 wt%.

8. The composition according to claim 1, characterized in that, The surface modifier is selected from silane coupling agents.

9. The composition according to claim 8, characterized in that, The surface modifier is selected from one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and vinyltriethoxysilane.

10. The composition according to claim 1, characterized in that, The polymeric dispersant is selected from one or more of polyvinyl alcohol, polyacrylate, methylcellulose, carboxymethylcellulose, hydroxypropylcellulose, and hydroxyethylcellulose.

11. The composition according to claim 1, characterized in that, The precipitant is selected from one or more of ammonium carbonate, urea, and ammonia water.

12. The composition according to claim 1, characterized in that, The water-soluble aluminum source is selected from one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, and aluminum silicate.

13. The composition according to claim 1, characterized in that, The silicon source is selected from tetraethyl orthosilicate and / or methyl orthosilicate.

14. The composition according to claim 1, characterized in that, The weight ratio of the water-soluble aluminum source, polymeric dispersant, precipitant, silicon source and surface modifier is (20-60):(1-5):(40-80):(5-8):(10-20).

15. The composition according to claim 1, characterized in that, The conditions for the modification reaction include: a reaction temperature of 65-85℃ and a reaction time of 3-5h.

16. The composition according to claim 1, characterized in that, The activator is selected from one or more of sodium hydroxide, sodium silicate, potassium silicate, and calcium silicate.

17. The composition according to claim 16, characterized in that, The activator is a combination of NaOH and Na2SiO3.

18. The composition according to claim 17, characterized in that, In the composition, the mass ratio of Na2SiO3 to NaOH is (1-5):(1-5).

19. A method for preparing a geopolymer slurry, characterized in that, Using the raw material composition as described in any one of claims 1-18, the modified SiO2-Al2O3 nanocomposite material is mixed with metakaolin and then reacted with an activator to obtain a geopolymer slurry, wherein the reaction is carried out at room temperature.

20. The preparation method according to claim 19, characterized in that, The modified SiO2-Al2O3 nanocomposite material is 1-10 parts by weight relative to 100 parts by weight of the metakaolin, and the activator is 20-80 parts by weight.

21. The preparation method according to claim 20, characterized in that, The modified SiO2-Al2O3 nanocomposite material is 1-5 parts by weight, and the activator is 20-60 parts by weight.

22. A geopolymer slurry obtained by the preparation method according to any one of claims 19-21.

23. The slurry according to claim 22, characterized in that, The geopolymer formed after the slurry solidifies has a 7-day compressive strength of 21.8-23.3 MPa, a flexural strength of 2.11-2.36 MPa, and an elastic modulus of 5.99-6.92 GPa.

24. The application of the composition according to any one of claims 1-18 or the geopolymer slurry according to claim 22 or 23 in the field of cementing engineering.

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