Nano-silica modified concrete material and preparation method thereof
By optimizing the preparation process of silica nanomicrospheres, using a vacuum insulation device to control the insulation effect and time, nanomicrospheres with uniform particle size were prepared, which solved the problem of poor performance of nanosilicon dioxide in concrete materials and significantly improved the mechanical properties of concrete.
Patent Information
- Application Number
- CN202510365687.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-26
- Publication Date
- 2025-08-05
AI Technical Summary
In the prior art, the poor particle size uniformity of nanosilica affects its performance in concrete materials, especially mechanical properties.
By optimizing the preparation process of silica nanomicrospheres, using a vacuum insulation device for insulation treatment, controlling the insulation energy efficiency and time, ensuring integrity of crystal forms and uniform particle size, high-quality silica nanomicrospheres were prepared and applied to concrete materials.
The mechanical properties of concrete materials, especially compressive strength, are significantly improved. Through the optimization process, nano-microspheres can exert balling and filling effects in concrete, improving the micropore structure.
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Figure CN120423818A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of concrete materials, and in particular to a nano-silicon dioxide modified concrete material and a preparation method thereof. Background Art
[0002] Cement is the most widely used cementitious material in the construction industry, having been used for two centuries. Its widespread use has fueled the rapid development of the construction industry, but this growth has also brought numerous challenges. Firstly, the production of Portland cement consumes enormous amounts of energy and resources, and emits large amounts of greenhouse gases (CO2) and other harmful gases into the atmosphere, causing environmental pollution. Reducing the amount of Portland cement clinker used can reduce energy consumption, lower carbon emissions, and increase economic and environmental benefits. However, while reducing the amount of Portland cement clinker, it is also necessary to ensure that the essential properties of cement are not affected. Therefore, the addition of various mineral admixtures to ordinary cement has become a common method for improving the properties of cementitious materials.
[0003] Studies have found that adding nano-silica to cementitious materials can improve the mechanical properties, durability, and microstructure of cement-based materials. The mechanism of action is:
[0004] Silica nanospheres (SiO2) incorporated into cementitious composites exhibit strong pozzolanic activity and a filling effect. They can undergo a secondary hydration reaction with the cement hydration product Ca(OH)2 in the interfacial transition zone (ITZ) to form C–S–H. This effectively improves the pore structure and density of the ITZ, thereby enhancing the macroscopic properties of cementitious materials. This is manifested in the following ways: the incorporation of nano-SiO2 enhances the compressive strength of the cement matrix, primarily due to the rolling effect of its nanoparticles. This fills the concrete while enhancing its workability, improving the microscopic pore structure within the cement paste. Nano-SiO2 can also compact the pore structure within concrete, significantly improving its impermeability. Furthermore, the surface tension and agglomeration effect of NS accelerate the cement hydration process in concrete through a nucleation effect.
[0005] The preparation process of nanosilica affects its particle size uniformity, which in turn affects the performance of nanosilica and cement gel materials. The present invention aims to provide a nanosilica-modified concrete that improves the particle size uniformity and the mechanical properties of the modified concrete material by optimizing the preparation process of silica nanospheres. Summary of the Invention
[0006] The technical problem to be solved by the present invention is to provide a nano-silica modified concrete material, by optimizing the preparation process of silica nanospheres, improving their particle size uniformity, and thus improving the mechanical properties of the modified concrete material.
[0007] The technical solution of the present invention is:
[0008] A nano-silica modified concrete material comprising a gel material, aggregate, admixture, silica nano-microspheres and water;
[0009] The gel material includes cement and fly ash, and the aggregate includes ordinary stone, gangue stone, ordinary sand and gangue sand;
[0010] The solid content of the admixture is 25-35%, the water reduction rate is 26-36%, and its mass is 1.8-3.3% of the mass of the gel material;
[0011] The mass of the silica nanoparticles is 0.6-4% of the mass of the gel material, and the silica nanoparticles are prepared by the following preparation method:
[0012] Step S1, weighing appropriate amounts of deionized water and anhydrous ethanol, mixing them with appropriate amounts of aqueous ammonia, and mixing them under ultrasonic conditions;
[0013] Step S2, heating the mixed solution to 35-45° C., adding an appropriate amount of a mixed solution of tetraethyl orthosilicate and anhydrous ethanol, and stirring to react for 3-5 hours;
[0014] Step S3, washing, filtering, and vacuum drying the product of step S2 to obtain silica gel;
[0015] Step S4, dispersing the silica gel from step S3 in water at 90-100° C., and then placing the silica gel in a vacuum insulation device and letting it stand for 6-18 hours, wherein the insulation energy efficiency of the vacuum insulation device is level I or level II, wherein the insulation effect gradually decreases from level I to level II;
[0016] Step S5: filtering, washing, vacuum drying, and then sintering to prepare silica nanoparticles.
[0017] Furthermore, in step S4, the vacuum insulation device includes a main body having a feed port and a sealing cover sealed to the feed port, the main body includes an outer shell, an inner liner, a vacuum insulation layer formed between the outer shell and the inner liner, and an insulation coating coated on the inner wall of the inner liner, and the outer shell and the inner liner are connected near the feed port.
[0018] Furthermore, the admixture is a polycarboxylic acid water reducer or a melamine resin water reducer.
[0019] Furthermore, the gel material, aggregate, admixture, silica nanospheres and water are composed of the following components in parts by weight:
[0020] 250-300 parts of cement, 60-100 parts of fly ash, 200-700 parts of ordinary gravel, 200-600 parts of coal gangue gravel, 200-600 parts of ordinary sand, 200-600 parts of coal gangue sand, 5-9 parts of water reducer, 2-14 parts of silica nanospheres, and 150-300 parts of water.
[0021] Specifically, the weight proportion of cement can be 250 parts, 260 parts, 270 parts, 280 parts, 290 parts or 300 parts, or other values within the range; the weight proportion of fly ash can be 60 parts, 70 parts, 80 parts, 90 parts or 100 parts, or other values within the range; the weight proportion of ordinary stone can be 200 parts, 300 parts, 400 parts, 500 parts, 600 parts or 700 parts, or other values within the range; the weight proportion of coal gangue stone can be 200 parts, 300 parts, 400 parts, 500 parts or 600 parts, or other values within the range; the weight proportion of ordinary sand can be 200 parts, 300 parts, 400 parts, 500 parts or 600 parts, or other values within the range; 200 parts, 300 parts, 400 parts, 500 parts or 600 parts, or other values within this range; the weight parts of coal gangue sand can be 200 parts, 300 parts, 400 parts, 500 parts or 600 parts, or other values within this range; the weight parts of water reducer can be 5 parts, 6 parts, 7 parts, 8 parts or 9 parts, or other values within this range; the weight parts of silica nanospheres can be 2 parts, 5 parts, 8 parts, 10 parts, 12 parts or 14 parts, or other values within this range; the weight parts of water can be 150 parts, 200 parts, 250 parts or 300 parts, or other values within this range.
[0022] The present invention also provides a method for preparing a nano-silica modified concrete material, comprising the following steps:
[0023] adding an admixture to the gel material;
[0024] The gel material is evenly mixed with other raw materials to obtain nano-silica modified concrete material.
[0025] Compared with the prior art, the nano-silica modified concrete material provided by the present invention has the following beneficial effects:
[0026] The nanosilica-modified concrete material provided by the present invention is prepared using a special process involving silica nanospheres. The silica nanospheres are prepared by placing silica gel in a vacuum insulation device for thermal insulation. This thermal insulation mechanism facilitates the production of crystals with a complete crystalline form and uniform particle size. Because the silica nanospheres have more uniform grains, their addition to concrete can significantly improve the mechanical properties of the concrete. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0028] Figure 1 Schematic diagram of the structure of the vacuum insulation device of the present invention;
[0029] Figure 2 The SEM images of the silica nanospheres prepared at different holding times in the present invention are shown;
[0030] Figure 3 These are SEM images of silicon dioxide nanospheres prepared using vacuum insulation devices with different energy efficiencies in the present invention. DETAILED DESCRIPTION
[0031] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the specific implementation methods of the present invention are further described below.
[0032] The endpoints of the ranges and any values 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 endpoints of each range, the endpoints of each range and individual point values, and the 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.
[0033] Example 1
[0034] A method for preparing silicon dioxide nanoparticles comprises the following steps:
[0035] Step S1, weighing appropriate amounts of deionized water and anhydrous ethanol, mixing them with appropriate amounts of aqueous ammonia, and mixing them under ultrasonic conditions;
[0036] Step S2, heating the mixed solution to 35-45° C., adding an appropriate amount of a mixed solution of tetraethyl orthosilicate and anhydrous ethanol, and stirring to react for 3-5 hours;
[0037] The heating temperature of the mixed solution can be 35°C, 40°C or 45°C, or other values within the range; the reaction time can be 3h, 4h or 5h, or other values within the range;
[0038] Step S3, washing, filtering, and vacuum drying the product of step S2 to obtain silica gel;
[0039] The vacuum drying temperature is 55-65° C., such as 55° C., 60° C. or 65° C., or other temperature values within this range.
[0040] Step S4, dispersing the silica gel from step S3 in water at 90-100° C., and then placing the silica gel in a vacuum insulation device and letting it stand for 6-18 hours, wherein the insulation energy efficiency of the vacuum insulation device is level I or level II, wherein the insulation effect gradually decreases from level I to level II;
[0041] The temperature of the dispersion may be 90°C, 95°C or 100°C, or other temperature values within this range, and the holding time may be 6h, 12h or 18h, or other values within this range;
[0042] The structure of the vacuum insulation device is as follows Figure 1 As shown, the vacuum insulation device includes a main body 1 with a feed port 11, and a sealing cover 2 sealed with the feed port 11. The main body 1 includes an outer shell 12, an inner liner 13, a vacuum insulation layer 14 formed between the outer shell 12 and the inner liner 13, and a thermal insulation coating 15 coated on the inner wall of the inner liner 13. The outer shell 12 and the inner liner 13 are connected near the feed port. After the material is injected from the feed port, the sealing cover is covered for thermal insulation treatment. Among them, the outer shell and the inner liner are made of stainless steel material, and the thermal insulation coating is a copper-plated layer or a silver-plated layer. The structure of the vacuum insulation device in the present invention is similar to that of a vacuum insulation cup. The vacuum insulation layer 14 is in a vacuum state, and the energy efficiency level of the vacuum insulation device is regulated by adjusting the vacuum degree in the vacuum insulation layer 14. The insulation principle of the vacuum insulation device in the present invention is: by evacuating the vacuum insulation layer, no heat is transferred in a vacuum state, thereby isolating heat transfer; by coating the inner wall of the inner liner with an insulation coating to form a heat-locking network, heat loss caused by thermal radiation is reduced; through the double-layer sealing structure of the inner liner and the outer shell, convection between the heat in the device and the outside air can be avoided, thereby reducing heat convection.
[0043] The energy efficiency level of the vacuum insulation device refers to the stainless steel vacuum insulation container GBT40355-2021. The insulation effect of the insulation device deteriorates from level I to level V. Therefore, the insulation effect of the insulation device with an insulation energy efficiency of level I is the best.
[0044] Step S5, filtering, washing, vacuum drying, and then sintering to prepare silica nanoparticles;
[0045] The vacuum drying temperature is 60-68°C, specifically 60°C, 65°C or 68°C, or other temperature values within this range; the sintering temperature is 900-1000°C, specifically 900°C, 950°C or 1000°C, or other temperature values within this range.
[0046] In the present invention, tetraethyl orthosilicate first undergoes a hydrolysis reaction, and the alkoxy group (-OR) in the tetraethyl orthosilicate molecule is replaced by a hydroxyl group (-OH), and the reaction formula is as follows:
[0047]
[0048] The silicic acid (Si(OH)4) generated by the hydrolysis reaction or the silicic acid and tetraethyl orthosilicate undergoes a condensation reaction to form Si-O-Si bonds, thereby generating silicon dioxide oligomers. The reaction formula is as follows:
[0049]
[0050] As the reaction proceeds, these oligomers will further polymerize to form a skeleton structure with long chains extending into space, and finally form silica gel. The obtained gel is dried to remove the moisture therein. The dried gel is heat-treated at high temperature to further remove the organic matter and residual moisture therein, and promote the crystallization and densification of the silica particles, and finally obtain nano-scale or micron-scale silica powder. The reaction mechanism of preparing silica by tetraethyl orthosilicate sol-gel method is a complex process, involving multiple steps such as hydrolysis reaction, polycondensation reaction and sol-gel transformation. The present invention optimizes the heat treatment mechanism and controls the temperature and time of insulation to regulate the morphology, structure and properties of silica.
[0051] Example 2
[0052] The preparation method of the silica nanospheres of the present invention is described in detail below through specific examples to obtain the optimal process parameters.
[0053] Weigh a certain amount of deionized water and anhydrous ethanol, mix them with a certain amount of ammonia water, and use an ultrasonic cleaner to ultrasonically mix for 15 minutes;
[0054] The mixture was placed in a three-necked round-bottom flask equipped with a stirrer, a condenser, and a constant-pressure dropping funnel. After the reaction temperature reached 40°C, a certain amount of a mixture of tetraethyl orthosilicate (TEOS) and anhydrous ethanol was added and stirred for 4 hours.
[0055] The product was washed with anhydrous ethanol, filtered, and dried under vacuum at 60°C for 12 h to obtain silica gel;
[0056] The above operation was repeated four times, and the silica gel was divided into 6 parts, dispersed in 95°C water, and placed in a vacuum insulation device with energy efficiency I to V at room temperature for 6 hours, 12 hours, 18 hours, and 24 hours respectively;
[0057] After standing, the precipitate was collected by filtration, washed by suction, and then dried at 65°C under vacuum conditions for 24 hours, then dried at 105°C for 2 hours, and finally sintered and cured at 950°C for 10 minutes to prepare silica nanospheres.
[0058] The prepared silica nanospheres were analyzed by SEM test, and the results are as follows: Figure 2 and Figure 3 As shown, Figure 2 SEM images of silica nanospheres in insulation devices with insulation energy efficiency levels of I to V under different insulation time conditions. Figure 2 A represents the SEM image of silica nanospheres in the insulation device with energy efficiency levels of I to V at room temperature corresponding to a 6-hour insulation time. Figure 2 B represents the SEM image of silica nanospheres in the insulation device with energy efficiency levels of I to V at room temperature corresponding to a 12-h insulation time. Figure 2 C represents the SEM image of silica nanospheres in the insulation device with energy efficiency levels of I to V at room temperature corresponding to an 18-hour insulation time. Figure 2 D represents the SEM images of silica nanospheres in the insulation devices with energy efficiency levels I to V at room temperature corresponding to a 24-hour insulation time; Figure 3 The SEM images of silica nanoparticles obtained by heat preservation for different time periods in heat preservation devices with different energy efficiency levels are shown in FIG. Figure 3 A represents the SEM images of silica nanoparticles obtained after different insulation times in an insulation device with energy efficiency level I. Figure 3 B represents the SEM images of silica nanospheres obtained after different insulation times in an insulation device with energy efficiency level II. Figure 3 C represents the SEM images of silica nanospheres obtained after different insulation times in an insulation device with energy efficiency level III. Figure 3 D represents the SEM images of silica nanospheres obtained after different insulation times in an insulation device with energy efficiency level IV. Figure 3 E represents the SEM images of silica nanospheres obtained after different insulation times in an insulation device with energy efficiency level V.
[0059] The insulation effect gradually deteriorates from level I to level V, and as the insulation efficiency level deteriorates, the stage of gentle temperature drop in the insulation device shifts later. Figure 2 and Figure 3 It can be seen that when the temperature changes slowly (the temperature drops less per unit time), it is more conducive to obtaining crystals with complete crystal form and uniform particle size. This shows that the better the thermal insulation effect, the more uniform the silica nanospheres.
[0060] The particle sizes of silica nanoparticles obtained by heating for different times in vacuum insulation devices with different insulation efficiencies are shown in Table 1:
[0061] Table 1: Particle size test results of silica nanospheres
[0062]
[0063]
[0064] Combine Figure 2 and Figure 3 As shown in Table 1, when the thermal insulation energy efficiency is level I and the thermal insulation time is 12h, the grains of silica nanospheres are more uniform and their performance is better.
[0065] Examples 3-9
[0066] The vacuum insulation device in Example 2 was used for an insulation time of 12 hours, and the prepared silicon dioxide nanospheres were applied to a concrete material to obtain a nano-silicon dioxide-modified concrete material.
[0067] Nano-silica modified concrete material includes gel material, aggregate, polycarboxylate water reducer, silica nano-microspheres and water, wherein the polycarboxylate water reducer has a solid content of 30% and a water reduction rate of 30%.
[0068] Nano-silica microspheres prepared with different thermal insulation efficiencies were added to obtain concrete materials with different proportions, forming Examples 3-9. The proportions of the components of Examples 3-9 are shown in Table 2:
[0069] Table 2: Ingredient ratios of Examples 3-9 Unit: kg / m 3
[0070]
[0071]
[0072] The mechanical properties of the concrete materials of Examples 3-9 are shown in Table 3:
[0073] Table 3: Test results of mechanical properties of concrete materials in Examples 3-9
[0074]
[0075]
[0076] As can be seen in Table 3, the compressive strength of gangue concrete varies significantly with the thermal insulation efficiency of the microspheres. The compressive strength of gangue concrete prepared using microspheres with thermal insulation efficiency level I is the highest. This is because the particle size uniformity of the silica nanospheres used in Examples 4, 6, 7, 8, and 9 is not as uniform as that of the silica nanospheres used in Example 5.
[0077] Examples 10-14
[0078] The insulation energy efficiency of the vacuum insulation device in Example 2 is set to level I, and the insulation time is 12 hours. The prepared silica nanospheres are applied to coal gangue concrete to obtain coal gangue concrete modified with different nano-silica addition amounts.
[0079] The nano-silica modified concrete material comprises a gel material, aggregate, a polycarboxylate water reducer, nano-silica and water, wherein the polycarboxylate water reducer has a solid content of 30% and a water reduction rate of 30%.
[0080] The silica nanospheres were added at 0.6%, 1.4%, 2.3%, 3.1%, and 4% of the gel material to obtain gangue concrete materials with different proportions, forming Examples 10-14. The proportions of the components of Examples 10-14 are shown in Table 4:
[0081] Table 4: Composition ratio of Examples 10-14 Unit: kg / m 3
[0082]
[0083] The mechanical properties of the gangue concrete of Examples 10-14 are shown in Table 5:
[0084] Table 5: Mechanical properties test results of coal gangue concrete of Examples 10-14
[0085]
[0086]
[0087] It can be seen from Table 5 that with the increase of the amount of silica nanoparticles added, the compressive strength of the gangue concrete shows a trend of first increasing and then decreasing. 3 When the amount added is 2.3% of the combined mass of the gel material and aggregate, the compressive strength of the gangue concrete is the highest. This is because an appropriate amount of microspheres can optimize the interface transition zone between the cement matrix and aggregate, but an excessive amount of microspheres can weaken the interface, forming a weak zone and reducing the overall strength.
[0088] Examples 15-19
[0089] The insulation energy efficiency of the vacuum insulation device in Example 2 is set to level I, and the insulation time is 12 hours. The prepared silica nanospheres are applied to coal gangue concrete material to obtain nano-silica-modified coal gangue concrete material.
[0090] Nano-silica modified coal gangue concrete includes gel material, aggregate, melamine resin water reducer, silica nano-microspheres and water. The melamine resin water reducer has a solid content of 30% and a water reduction rate of 30%.
[0091] The silica nanosphere admixture was added at a mass ratio of 0.6%, 1.4%, 2.3%, 3.1%, and 4% of the gel material to obtain coal gangue concrete materials with different proportions, forming Examples 15-19. The proportions of the components of Examples 15-19 are shown in Table 6:
[0092] Table 6: Ingredient ratios of Examples 15-19 Unit: kg / m 3
[0093]
[0094] The mechanical properties of the gangue concrete of Examples 15-19 are shown in Table 7:
[0095] Table 7: Mechanical properties test results of coal gangue concrete of Examples 15-19
[0096]
[0097] It can be seen from Table 7 that with the increase of the amount of silica nanoparticles added, the compressive strength of the gangue concrete shows a trend of first increasing and then decreasing. 3 When the addition amount is 2.3% of the gel material, the compressive strength of gangue concrete is highest. This is because an appropriate amount of microspheres can optimize the interface transition zone between the cement matrix and aggregate, but an excessive amount of microspheres can weaken the interfacial bond, forming weak areas and reducing overall strength. Furthermore, Table 5 shows that when using melamine resin, polycarboxylate superplasticizers are more advantageous in improving the strength of gangue concrete at the same mix ratio. This is because polycarboxylate superplasticizers are more sensitive and have a better water-reducing effect. They can effectively reduce the water-cement ratio of gangue concrete, reducing the amount of water aggregated within the gangue, thereby achieving the goal of enhancing compressive strength.
[0098] Comparative Examples 1-5
[0099] Silica fume is used to replace silica nanospheres in coal gangue concrete to obtain silica fume modified coal gangue concrete.
[0100] Silica fume modified coal gangue concrete includes cementitious materials, aggregates, polycarboxylate superplasticizer, silica fume and water, wherein the solid content of the polycarboxylate superplasticizer is 30% and the water reduction rate is 30%.
[0101] Silica fume was added at 0.6%, 1.4%, 2.3%, 3.1% and 4% of the mass of the gel material to obtain coal gangue concrete with different proportions, forming comparative examples 1-5. The proportion table of each component of comparative examples 1-5 is shown in Table 8:
[0102] Table 8: Composition ratio of comparative examples 1-5 Unit: kg / m 3
[0103]
[0104] The mechanical properties of the gangue concrete of Comparative Examples 1-5 are shown in Table 9:
[0105] Table 9: Mechanical properties test results of coal gangue concrete of comparative examples 1-5
[0106]
[0107]
[0108] Comparative Examples 6-10
[0109] Silica fume is used to replace silica nanospheres in coal gangue concrete to obtain silica fume modified coal gangue concrete.
[0110] Silica fume modified coal gangue concrete includes cementitious materials, aggregates, melamine resin water reducer, silica fume and water, wherein the solid content of the melamine resin water reducer is 30% and the water reduction rate is 30%.
[0111] Silica fume was added at 0.6%, 1.4%, 2.3%, 3.1% and 4% of the mass of the gel material to obtain gangue concrete with different proportions, forming comparative examples 6-10. The proportions of the components of comparative examples 6-10 are shown in Table 10:
[0112] Table 10: Ingredient ratios of comparative examples 6-10 kg / m 3
[0113]
[0114] The mechanical properties of the gangue concrete of Comparative Examples 6-10 are shown in Table 9:
[0115] Table 11: Mechanical properties test results of coal gangue concrete of comparative examples 6-10
[0116]
[0117] It can be seen from Table 9 and Table 11 that the compressive strength of coal gangue concrete prepared with silica fume is related to the amount of silica fume added. 3 Gangue concrete achieves its highest compressive strength when the silica fume content is 3.1% of the gel material. Further increasing the silica fume content slightly decreases the compressive strength of gangue concrete. This is because an appropriate amount of silica fume fills the pores in the mortar, improving density and strength. However, excessive silica fume can lead to uneven particle packing, creating new pores or weak areas, and reducing strength.
[0118] In summary, the nano-silica modified concrete material of the present invention has a more uniform crystal form of silica nanospheres, and adding the nano-silica to the concrete material can significantly improve the mechanical properties of the concrete material.
[0119] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention are still within the scope of protection of the present invention.
Claims
1. A nano-silica modified concrete material, characterized in that: It includes gel material, aggregate, admixture, silica nanoparticles and water; The gel material includes cement and fly ash, and the aggregate includes ordinary stone, gangue stone, ordinary sand and gangue sand; The solid content of the admixture is 25-35%, the water reduction rate is 26-36%, and its mass is 1.8-3.3% of the mass of the gel material; The mass of the silica nanoparticles is 0.6-4% of the mass of the gel material, and the silica nanoparticles are prepared by the following preparation method: Step S1, weighing appropriate amounts of deionized water and anhydrous ethanol, mixing them with appropriate amounts of aqueous ammonia, and mixing them under ultrasonic conditions; Step S2, heating the mixed solution to 35-45° C., adding an appropriate amount of a mixed solution of tetraethyl orthosilicate and anhydrous ethanol, and stirring to react for 3-5 hours; Step S3, washing, filtering, and vacuum drying the product of step S2 to obtain silica gel; Step S4, dispersing the silica gel from step S3 in water at 90-100° C., and then placing the silica gel in a vacuum insulation device and letting it stand for 6-18 hours, wherein the insulation energy efficiency of the vacuum insulation device is level I or level II, wherein the insulation effect gradually decreases from level I to level II; Step S5: filtering, washing, vacuum drying, and then sintering to prepare silica nanoparticles.
2. The nano-silica modified concrete material according to claim 1, characterized in that: In step S4, the vacuum insulation device includes a main body with a feed port and a sealing cover sealed to the feed port, the main body includes an outer shell, an inner liner, a vacuum insulation layer formed between the outer shell and the inner liner, and an insulation coating coated on the inner wall of the inner liner, and the outer shell and the inner liner are connected near the feed port.
3. The nano-silica modified concrete material according to claim 1, characterized in that: The admixture is a polycarboxylic acid water reducer or a melamine resin water reducer.
4. The nano-silica modified concrete material according to claim 1, characterized in that: The gel material, aggregate, admixture, silicon dioxide nanospheres and water are composed of the following components in parts by weight: 250-300 parts of cement, 60-100 parts of fly ash, 200-700 parts of ordinary gravel, 200-600 parts of coal gangue gravel, 200-600 parts of ordinary sand, 200-600 parts of coal gangue sand, 5-9 parts of water reducer, 2-14 parts of silica nanospheres, and 150-300 parts of water.
5. A method for preparing a nano-silica modified concrete material according to claim 1, characterized in that: The steps include: adding an admixture to the gel material; The gel material is evenly mixed with other raw materials to obtain nano-silica modified concrete material.