A high-fluidity and high-thermal-conductivity concrete and its preparation method

Abstract

The present invention discloses a high-fluidity and high-thermal-conductivity concrete and a preparation method thereof, relating to the field of high-thermal-conductivity concrete; the low thermal conductivity of the existing underground power pipeline encapsulating concrete leads to low heat dissipation efficiency. The present invention comprises, by mass parts: 16-17 parts of high-iron-phase Portland cement, 2-2.5 parts of steel slag, 0.4-0.6 parts of ultrafine graphite powder, 3-4 parts of graphite particles, 24-27 parts of quartz sand, 42-45 parts of high-thermal-conductivity aggregate, 0.32-0.34 parts of functional admixture, and 6.8-7.0 parts of water. By adding high-thermal-conductivity admixtures, high-thermal-conductivity materials and high-thermal-conductivity aggregates into cement, and through the fluidity adjustment of the functional admixture, while ensuring high workability, its thermal conductivity is significantly higher than that of ordinary concrete, which not only improves the construction efficiency of engineering construction, but also its high thermal conductivity can effectively reduce the risk of heat loss generated during the power transmission of the cable, and improve the current-carrying capacity of the power transmission system.

Description

Technical Field

[0001] The present invention relates to the field of high - thermal - conductivity concrete, and particularly to a high - fluidity and high - thermal - conductivity concrete and a preparation method thereof. Background Art

[0002] The safe and stable operation of underground power pipelines is the lifeline of urban industry and residents' lives. During operation, the wire is prone to heat generation, and heat is easily accumulated in the enclosed space of the power pipeline, causing system temperature rise. As a result, all existing underground power systems operate at a degraded level, and the power transmission efficiency cannot be normally exerted. Moreover, improper use is likely to lead to safety risks. How to design the heat conduction path and construct an efficient heat dissipation method for underground power pipelines is the most potential technical direction for improving the carrying capacity of underground power systems and solving potential risks. The main structure of underground power pipelines includes wires, pipelines, and encapsulated concrete structures. From the perspective of the heat transfer path, heat is conducted through the pipeline to the encapsulated concrete and then to the environment (soil). Among them, the concrete structure is the first stage of heat conduction, and its heat conduction ability determines whether heat can be quickly and stably exported.

[0003] In the power pipe - laying project, the encapsulated material that plays an important supporting and protecting role usually adopts C20 concrete. For special channels that require high load - bearing capacity, the concrete grade will be increased, but the influence of the concrete grade on the thermal conductivity is not significant. Generally, the thermal conductivity of concrete is 1.4 - 1.7 W / (m·K). For example, for reinforced concrete, the thermal conductivity will increase slightly, up to 2.5 W / (m·K) at most, because the thermal conductivity of iron is about 80 W / (m·K). From a microscopic composition perspective, concrete materials include cement paste, aggregates, and pore structures, etc. The thermal conductivity of cement paste is about 1.2 W / (m·K), the thermal conductivity of concrete aggregates is 1.0 - 2.5 W / (m·K), and the thermal conductivity of pore structures is close to that of air, 0.025 W / (m·K). Therefore, the heat conduction ability of concrete can be optimized by introducing high - thermal - conductivity materials into the cement paste, selecting high - thermal - conductivity aggregates, and reducing the porosity, etc.

[0004] However, there are uncertainties in the selection of heat - conducting materials and the design of the heat conduction path. At the same time, there are also uncertainties in the influence of the addition of high - thermal - conductivity materials on the workability, mechanical properties, and durability of concrete, as well as the need to evaluate the influence of high - thermal - conductivity aggregates on the long - term properties of concrete.

[0005] Therefore, the development of high - thermal - conductivity encapsulated materials is of great significance for constructing the heat conduction channel of underground power pipelines, improving the current - carrying capacity of lines, and ensuring safe and stable operation. Summary of the Invention

[0006] The technical problem to be solved and the technical task proposed by the present invention are to improve and refine the existing technical solutions, and provide a high-fluidity and high-thermal-conductivity concrete, aiming to solve the problems such as insufficient thermal conductivity of the existing underground power pipeline encapsulating concrete, resulting in low heat dissipation efficiency, degradation operation of the underground power system, and inability to give full play to the normal transmission efficiency. For this purpose, the present invention adopts the following technical solutions.

[0007] A high-fluidity and high-thermal-conductivity concrete, by mass parts, includes:

[0008] 16 - 17 parts of high-iron-phase Portland cement, 2 - 2.5 parts of steel slag, 0.4 - 0.6 parts of ultrafine graphite powder, 3 - 4 parts of graphite particles, 24 - 27 parts of quartz sand, 42 - 45 parts of high-thermal-conductivity aggregate, 0.32 - 0.34 parts of functional admixture, and 6.8 - 7.0 parts of water;

[0009] Among them, the high-thermal-conductivity aggregate is prepared from the following raw materials by mass percentage: 55 - 65% ultrafine quartz sand, 15 - 25% steel slag, 15 - 25% ground lime, and 5 - 7% carbon nanotubes.

[0010] In this technical solution, high-thermal-conductivity admixtures, high-thermal-conductivity materials, and high-thermal-conductivity aggregates are added to the cement, and through the fluidity adjustment of the functional admixture, while ensuring high workability, its thermal conductivity is significantly higher than that of ordinary concrete. It not only improves the construction efficiency of engineering construction, but also its high thermal conductivity can effectively reduce the risk of heat loss generated during the power transmission of the cable and improve the current-carrying capacity of the power transmission system. The "trinity" strategy of "compounding of high-thermal-conductivity materials - regulation of functional admixtures - design of aggregate structure" breaks through the technical bottlenecks of poor fluidity and strength attenuation of high-thermal-conductivity concrete, and provides a new material solution with both efficient heat dissipation and construction convenience for fields such as electric power and construction. Specifically, the concrete prepared by this technical solution has a high thermal conductivity, which is more than 100% higher than that of traditional concrete. Ultrafine graphite powder fills the micropores of the cement paste to reduce the pore thermal resistance; graphite particles form a macroscopic thermal conduction network and cooperate with carbon nanotubes to construct a multi-level thermal conduction path; the ultrafine quartz sand in the high-thermal-conductivity aggregate provides a stable thermal conduction base, the thermal conductivity of steel slag is higher than that of Portland cement, strengthening the thermal conduction ability of the aggregate; the tubular structure of carbon nanotubes bridges the interface, reducing the "break points" in the heat conduction path and enhancing the interfacial bonding force between the aggregate and the cement, inhibiting the propagation of microcracks; the graded quartz sand and graphite particles meet the grading standard of GB / T14684 - 2022, reducing the inter-particle frictional resistance. At the same time, the functional admixture inhibits the agglomeration of ultrafine graphite to avoid fluidity loss, making the slump ≥ 220mm. The hydrophobicity of graphite and the hydrophilicity of steel slag may cause interfacial conflicts, but the surface of graphite is stably dispersed by coating with the functional admixture; during the prefabrication of the high-thermal-conductivity aggregate, carbon nanotubes and ultrafine quartz sand are forcibly dispersed by mechanical granulation to avoid agglomeration in the subsequent concrete.

[0011] As a preferred technical measure: the content of tetracalcium ferroaluminate in the high-speed railway Portland cement silicate is ≥ 15%, the specific surface area of steel slag is ≥ 450 m² / kg, and the particle size D50 of ultrafine graphite powder is ≤ 3 μm.

[0012] Tetracalcium ferroaluminate has high early strength, a fast hydration rate, which promotes the early strength development of concrete. The hydration products formed by tetracalcium ferroaluminate are dense, reducing the chloride ion permeability and enhancing the durability of underground power pipelines. The thermal conductivity of iron-containing minerals is higher than that of ordinary Portland phases, enhancing the thermal conductivity of the cement matrix. Ultrafine graphite powder fills the micropores of the cement paste, reducing the pore thermal resistance and forming a "micro-nano" dual-scale thermal conduction network with graphite particles. The iron-phase cement synergistically improves the density and compensates for the negative impact of graphite powder on strength. Ultrafine graphite powder optimizes the thermal conductivity, while high fluidity ensures the dense pouring of cable pipelines, avoiding the cavity thermal resistance caused by insufficient manual vibration. It realizes a synergistic breakthrough in high thermal conductivity and high fluidity; and comprehensively optimizes strength, durability, and environmental friendliness.

[0013] As a preferred technical measure: the ultrafine quartz sand content is ≥ 90%, and the specific surface area is ≥ 350 m² / kg; the content of CaO in the ground lime is ≥ 70%, and the specific surface is ≥ 350 m 2 / kg; the carbon nanotubes have a diameter of 30 - 50 nm and a length of 10 - 50 μm.

[0014] As a preferred technical measure: the functional admixture contains a polycarboxylate water reducer with a solid content of 9 - 11%, and a defoamer and a cellulose ether thickener of 0.1 - 0.5% and 0.01 - 0.05% of the total mass of the water reducer are added. The water reducer reduces the water-cement ratio and improves the strength; the defoamer reduces the pores and enhances the density; the thickener prevents segregation and ensures homogeneity.

[0015] Another technical solution of the present invention is: a preparation method of high-fluidity and high-thermal-conductivity concrete, and the preparation method includes the following steps:

[0016] a. Prepare high-thermal-conductivity aggregate:

[0017] Mix ultrafine quartz sand, steel slag, ground lime, and carbon nanotubes in proportion, add water to granulate to a particle size of 5 - 21 mm;

[0018] Perform steam curing at 75 - 85 °C for 5 - 7 hours, and then perform autoclaving at 180 - 200 °C for 8 - 12 hours;

[0019] b. Prepare concrete:

[0020] Mix each component by mass fraction, stir at 20 - 28 r / min for 5 - 10 minutes to obtain a slurry;

[0021] After pouring, let it stand for a set time and then demold to obtain concrete.

[0022] As a preferred technical measure: the particle size range of the graphite particles is 0.5 - 5 mm, and they form a continuous gradation with the quartz sand.

[0023] The continuous gradation of the graphite particles (0.5 - 5 mm) and the quartz sand realizes the maximization of density, the improvement of the thermal conductivity coefficient; the synergistic optimization of strength-fluidity-crack resistance; the efficient construction of a full-scale thermal conduction network (nano-micro-millimeter scale).

[0024] As a preferred technical measure: the humidity in the steam curing stage is ≥90%, and the pressure in the autoclaving stage is 1.0 - 1.5 MPa.

[0025] The humidity ≥90% prevents premature evaporation of water, ensures the complete pozzolanic reaction of steel slag, ground lime and cement, and generates dense C-S-H gel; reduces drying shrinkage stress, reduces the crack rate in the interfacial transition zone, and improves impermeability. In a high-humidity environment, the hydrogen bond interaction between the hydroxyl groups (–OH) on the surface of carbon nanotubes and water molecules is enhanced, avoiding agglomeration during the granulation process; the pressure of 1.0 - 1.5 MPa compresses the internal pores of the aggregate, improving the thermal conductivity coefficient. The high pressure drives the carbon nanotubes to be oriented along the heat flow direction, forming a low-thermal-resistance heat conduction channel.

[0026] As a preferred technical measure: when preparing the high-thermal-conductivity aggregate, first steam-cure at 80 °C for 6 hours, and then autoclave to obtain the high-thermal-conductivity aggregate. The high-thermal-conductivity aggregate prepared by steam-curing at 80 °C for 6 hours takes into account its microstructure, performance stability and production efficiency.

[0027] Beneficial effects:

[0028] 1. The high-fluidity and high-thermal-conductivity concrete prepared by the present invention can solve the key problems of low thermal conductivity and low heat transfer capacity of traditional encapsulation materials, greatly enrich new materials for energy infrastructure construction, and lay a solid foundation for the high-quality development of subsequent power grid engineering construction.

[0029] 2. The thermal conductivity coefficient of the high-fluidity and high-thermal-conductivity concrete prepared by the present invention can be increased by more than 100% compared with ordinary concrete. This is because the addition of high-thermal-conductivity materials and high-thermal-conductivity aggregates improves the thermal conductivity coefficient of the concrete. Secondly, under the action of functional admixtures to regulate fluidity, the high-thermal-conductivity materials and aggregates can be more evenly dispersed in the internal structure of the concrete. Specific embodiments

[0030] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0031] The raw material indexes for preparing the high-fluidity and high-thermal-conductivity concrete of each embodiment of the present invention are:

[0032] The content of tetracalcium aluminoferrite in high-speed rail Portland cement is ≥ 15%;

[0033] The specific surface area of steel slag powder is ≥ 450 m 2 / kg;

[0034] The particle size D50 of ultrafine graphite powder is ≤ 3 μm;

[0035] The gradation of quartz sand and graphite particles meets the standard GB / T 14684-2022;

[0036] Ultrafine quartz sand The content is ≥ 90%, and the specific surface area is ≥ 350 m 2 / kg;

[0037] The specific surface area of steel slag is ≥ 450 m 2 / kg;

[0038] The lime is ground lime, with a specific surface area of ≥ 350 m 2 / kg and a CaO content of ≥ 70%;

[0039] The carbon nanotubes have a diameter of 30 - 50 nm and a length of 10 - 50 μm.

[0040] The functional admixture is a commercially available polycarboxylate water reducer with a solid content of 9 - 11%, and a commercially available defoamer is added in an amount of 0.1 - 0.5% of the total mass of the water reducer, and a cellulose ether thickener is added in an amount of 0.01 - 0.05% of the total mass of the water reducer.

[0041] Next, the present invention will be described in detail with reference to the embodiments.

[0042] First, 55 - 65% of ultrafine quartz sand, 15 - 25% of steel slag, 15 - 25% of lime, and 5 - 7% of carbon nanotubes are weighed and stirred evenly, then an appropriate amount of water is added for granulation, and the particle size is 15 mm. Steam curing is carried out at 80°C for 6 hours, and then autoclaving is carried out at a temperature of 200°C for 10 h to obtain high - thermal - conductivity aggregate materials A - 1, A - 2, A - 3, A - 4, A - 5, and A - 6. The mix proportion and other parameters of the high - thermal - conductivity aggregate materials used in the examples are shown in Table 1 below.

[0043] Table 1 Mix proportion and other parameters of high - thermal - conductivity aggregate materials

[0044]

[0045] Next, configure the functional admixtures required for the examples. The functional admixture is a commercially available polycarboxylate water reducer with a solid content of 10%, and a commercially available defoamer is added in an amount of 0.1 - 0.5% of the water reducer, and a cellulose ether thickener is added in an amount of 0.01 - 0.05% of the water reducer. The configuration table of the functional admixtures is shown in Table 2 below. The specific operation is as follows: Weigh the commercially available polycarboxylate water reducer in a beaker, and then sequentially add the defoamer and cellulose ether thickener with the corresponding solid content. Place the mixed solution on a magnetic stirrer and stir at 600 r / min for 3 h to obtain the functional admixtures B-1, B-2, B-3, B-4, B-5, and B-6 used in the examples.

[0046] Table 2 Configuration Table of Functional Admixtures (%)

[0047]

[0048] A high-fluidity and high-thermal-conductivity concrete of Examples 1 - 18 was prepared by the following method, which specifically includes the following steps:

[0049] Weigh the high-iron-phase Portland cement, steel slag, ultrafine graphite powder, graphite particles, quartz sand, high-thermal-conductivity aggregates A1 - A6, functional admixtures B1 - B6, and water according to the dosages in Mix Ratio Table 3. The water-cement ratio is 0.4. Place the weighed raw materials in a concrete mixer, set the mixer speed to 25 r / min and stir for 5 min to obtain a slurry. After loading it into a mold and standing for 1 d, demold it to obtain the high-fluidity and high-thermal-conductivity concrete. Finally, place the demolded specimens in a standard curing room for curing, and test the compressive strength of Examples 1 - 18 at 3 d, 7 d, and 28 d and the thermal conductivity of the concrete at 28 d.

[0050] Among them, the air humidity in the standard curing room is set to 75%, and the indoor temperature is set to 20°C. In the blank group, the cement is ordinary Portland cement, the mineral admixture is fly ash, the fine aggregate is machine-made sand, the coarse aggregate is granite gravel, the admixture is PCE polycarboxylate water reducer, and the water-cement ratio is 0.4.

[0051] Table 3 Mix Ratio Design of Examples

[0052]

[0053] According to the information in Table 3, the mixing ratios of the components in the examples can be understood. For example, the component composition of Example 1 is as follows: 16.5 parts of high-iron phase cement, 2 parts of steel slag, 0.5 part of nano graphite powder, 3.9 parts of graphite particles, 24.2 parts of quartz sand, 45.68 parts of A-1 type high thermal conductivity aggregate, 6.9 parts of water, and 0.32 part of B-2 type functional admixture. Among them, the A-1 type high thermal conductivity aggregate component is 25.12 parts of ultra-fine quartz sand, 6.85 parts of steel slag, 11.42 parts of limestone, and 2.28 parts of carbon nanotubes; the solid content of the B-2 type functional admixture is 9.5%.

[0054] During the experimental process, the curing method adopted in Examples 1-10 is normal temperature curing, with a temperature of 20°C and a humidity of 75%; the curing method in Examples 11-18 is steam curing, with a constant temperature of 65°C and a humidity of 90%. Among them, the hydration rate of normal temperature curing is lower than that of steam curing, resulting in a higher porosity and poorer component distribution uniformity of the concrete cured at normal temperature. The higher the porosity, the higher the air content. Since the thermal conductivity of air is lower, the higher its content, the greater the impact on internal heat transfer, resulting in a decrease in thermal conductivity.

[0055] To further enrich the experimental data, the aggregate gradation of Examples 5-8 is gap gradation. The missing intermediate particle sizes cause some internal pores to increase, which has a negative effect on heat transfer, thereby reducing the thermal conductivity. In contrast, Examples 1-4 and 9-18 adopt continuous particle gradation, with finer aggregates, forming a denser aggregate skeleton, making the hydration products of the concrete more uniform and dense, increasing the heat transfer channels, and thus enhancing the thermal conductivity.

[0056] Referring to the standard GB / T50080-2016 "Standard Test Method for Properties of Ordinary Concrete Mixtures", the slump and spread of a high-fluidity and high-thermal conductivity concrete paste in Examples 1 to 18 were detected. During the test, the water retention and cohesion of the concrete were observed, and the fluidity of the concrete was evaluated based on the final results. The slump and spread results of high-fluidity and high-thermal conductivity concrete paste with different mixing ratios are shown in Table 4.

[0057] Referring to the standard GB / T50081-2002 "Standard Test Method for Mechanical Properties of Ordinary Concrete", the mechanical properties of a high-fluidity and high-thermal conductivity concrete specimen in Examples 1 to 18 were tested, and the test results are shown in Table 4.

[0058] The 28-day thermal conductivity of Examples 1 to 18 was measured using a QTM-500 type thermal conductivity measuring instrument. The measuring range of the instrument is: 0.02-6 W / (m·K), and the test results are shown in Table 4.

[0059] Table 4 Test results of various properties of examples

[0060]

[0061] As can be seen from Table 4, with the addition of the functional admixtures configured in the experiments, the slump and spread of Examples 1 to 18 are significantly better than those of the blank group. Among them, the slump and spread of Example 3 are increased by 43.6% and 19.8% respectively compared with the blank group. This shows that, compared with the raw material combination of the blank group, although materials such as graphite powder and graphite particles that affect the fluidity of the paste are added in the examples, with the addition of the functional admixtures, the uniformity of the dispersion of these two materials in the concrete is improved, and the fluidity is enhanced.

[0062] The same rule can be found in other examples, and during the experiment, the working performance of the mixture is good, no segregation and bleeding phenomenon occurs, and the slump and spread of the mixtures in Examples 1 to 18 all meet the construction requirements.

[0063] As can be seen from Table 4, compared with the blank group, the 3d, 7d, and 28d compressive strengths of Examples 1 to 18 are all lower than those of the blank group. The most obvious one is Example - 14, which is decreased by 30.9%, 34.6%, and 21.7% respectively compared with the blank group. This is because the addition of graphite powder and graphite particles as high - thermal - conductivity materials cannot provide sufficient mechanical strength support for the concrete. During the hydration process of cement, the two cannot provide effective compounds to promote the hydration reaction.

[0064] On the contrary, the thermal conductivity coefficients of Examples 1 to 18 are much higher than those of the blank group. As can be seen from Table 4, graphite with a relatively high thermal conductivity coefficient and high - thermal - conductivity aggregates have greatly improved the thermal conductivity of the concrete. Among them, the most obvious one is that the thermal conductivity coefficient of Example 17 reaches 3.0 W / (m·K), which is increased by 122% compared with the 28d thermal conductivity coefficient of 1.35 W / (m·K) of the blank group. This is not only due to the action of graphite and high - thermal - conductivity aggregates, but also because the particle size of graphite powder is relatively low. Under the condition that the functional admixture makes it evenly dispersed, it has a certain filling effect on the pores of the concrete, increasing the density and greatly improving the thermal conductivity coefficient of the concrete.

[0065] Among them, the 28 d thermal conductivity coefficients of Examples 2, 7, and 17 are 2.85 W / (m·K), 2.89 W / (m·K), and 3.00 W / (m·K) respectively. Examples 2 and 17 have continuous particle gradations, and the aggregates are finer, forming a denser aggregate skeleton. Moreover, the content of graphite particles in Example 2 is lower than that in Example 17, so the thermal conductivity coefficient of Example 17 is higher. Examples 2 and 7 are cured at normal temperature, and Example 17 is cured by steam. Steam curing makes the hydration products of the concrete more uniform and dense compared with normal - temperature curing. The above variables partially offset the thermal - conductivity contributions of graphite powder and steel slag, so the 28 d thermal conductivity coefficient of Example 17 is greater than that of Example 7.

[0066] By adding highly thermally conductive admixtures, highly thermally conductive materials, and highly thermally conductive aggregates to cement, and through the regulation of the fluidity of functional admixtures, while ensuring high workability, its thermal conductivity is significantly higher than that of ordinary concrete, which not only improves the construction efficiency of engineering construction, but also its own high thermal conductivity can effectively reduce the risk of heat loss generated during the power transmission of cables and improve the current-carrying capacity of the power transmission system.

[0067] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-fluidity and high-thermal-conductivity concrete, characterized in that: By mass fraction, it includes: 16 - 17 parts of high-iron phase portland cement, 2 - 2.5 parts of steel slag, 0.4 - 0.6 parts of ultrafine graphite powder, 3 - 4 parts of graphite particles, 24 - 27 parts of quartz sand, 42 - 45 parts of high thermal conductivity aggregate, 0.32 - 0.34 parts of functional admixture and 6.8 - 7.0 parts of water; Among them, the high thermal conductivity aggregate is prepared from the following raw materials by mass percentage: 55 - 65% of ultrafine quartz sand, 15 - 25% of steel slag, 15 - 25% of ground lime and 5 - 7% of carbon nanotubes; after mixing ultrafine quartz sand, steel slag, ground lime and carbon nanotubes in proportion, add water to granulate, steam cure and autoclave.

2. The highly flowable and highly thermally conductive concrete according to claim 1, wherein: The content of tetracalcium ferroaluminate in the high-iron phase portland cement is ≥15%, the specific surface area of the steel slag is ≥450 m² / kg, and the particle size D50 of the ultrafine graphite powder is ≤3 μm.

3. A highly fluid and highly thermally conductive concrete according to claim 1, characterized in that: The ultrafine quartz sand has a content of ≥90% and a specific surface area of ≥350 m² / kg; the ground lime has a CaO content of ≥70% and a specific surface area of ≥350 m 2 / kg; the carbon nanotubes have a diameter of 30 to 50 nm and a length of 10 to 50 μm.

4. A highly fluid and highly thermally conductive concrete according to claim 1, wherein: The functional admixture contains a polycarboxylate water reducer with a solid content of 9 - 11%, and adds an antifoaming agent of 0.1 - 0.5% of the total mass of the water reducer and a cellulose ether thickener of 0.01 - 0.05%.

5. A method for preparing a highly fluid and highly thermally conductive concrete according to claim 1, characterized in that: It includes the following steps: a. Prepare the high thermal conductivity aggregate: Mix ultrafine quartz sand, steel slag, ground lime and carbon nanotubes in proportion, and add water to granulate until the particle size is 5 - 21 mm; Steam cure at 75 - 85 °C for 5 - 7 hours, and then autoclave at 180 - 200 °C for 8 - 12 hours; b. Concrete preparation: Mix each component by mass fraction, stir at 20 - 28 r / min for 5 - 10 minutes to obtain a slurry; After casting, stand for a set time and then demold to obtain the concrete.

6. The preparation method according to claim 5, characterized in that: The particle size range of the graphite particles is 0.5 - 5 mm, and it forms a continuous gradation with the quartz sand.

7. The preparation method according to claim 5, characterized in that: The humidity in the steam curing stage is ≥90%, and the pressure in the autoclaving stage is 1.0 - 1.5 MPa.

8. The preparation method according to claim 5, characterized in that: When preparing the high thermal conductivity aggregate, first steam cure at 80 °C for 6 hours, and then autoclave to obtain the high thermal conductivity aggregate.

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