High-heat-transfer cement-based material and preparation method thereof

Abstract

The invention discloses a high-heat-transfer cement-based material and a preparation method thereof, and the high-heat-transfer cement-based material is prepared from 200-230 parts of cement, 75-105 parts of a mineral admixture, 600-700 parts of sand, 1350-1450 parts of gravel, 3-12 parts of a heat transfer enhancing material, 105-120 parts of water, 3-6 parts of a water reducing agent and 0.1-0.3 part of a defoaming agent. Wherein the heat transfer enhancing material is two or three of modified boron nitride particles, polydopamine modified carbon nanotubes and modified graphite. On the basis of the synergistic effect of material characteristics and structural design, a gradient heat conduction network from micron to nanoscale is formed by constructing a multi-element hybrid gradient heat conduction network system, the heat conduction performance of the cement-based material is remarkably improved, efficient heat dissipation and heat regulation of concrete are facilitated, and the risk of generation of concrete temperature stress cracks is reduced. The raw materials are wide in source and reasonable in price, the preparation technology is simple, and large-scale application and popularization are facilitated.

Description

Technical Field

[0001] The present invention relates to the field of building materials, and in particular to a high heat transfer cement-based material and a preparation method thereof. Background Art

[0002] As the construction industry moves toward intelligent, green, and large-scale development, building structures and functions are becoming increasingly complex and diverse. This places comprehensive and stringent demands on concrete performance, such as the heat dissipation requirements of large-volume concrete structures and the need for heat conduction control in building energy conservation. However, ordinary concrete is primarily composed of cement, aggregate, and water, and its internal microstructure exhibits discontinuous and limited heat conduction paths. Cement stone serves as the matrix, and aggregate is dispersed within it. The significant difference in thermal conductivity between the two creates thermal resistance at the interface, significantly limiting heat transfer efficiency. Concrete generally has poor thermal conductivity, with a thermal conductivity coefficient typically ranging from 1.0 to 2.0 W / (m·K), far from meeting the requirements for efficient heat dissipation or precise heat regulation.

[0003] In large-volume concrete structures, such as large foundation rafts and dams, the cement hydration process releases a significant amount of heat. Since concrete is a poor conductor of heat, this heat cannot be dissipated quickly, easily leading to large temperature gradients within and on the surface. This can cause thermal stress cracks, seriously impacting the durability and safety of the structure. According to relevant research, in some large-volume concrete projects where effective heat dissipation measures are not implemented, the cost of structural repair and reinforcement due to thermal cracks accounts for 10% to 15% of the total construction cost. Currently, traditional methods for controlling thermal cracks in large-volume concrete include using low-heat cement, replacing part of the mixing water with ice chips, surface insulation and curing, pre-buried cooling water pipes, and layered pouring. While these measures can control thermal cracks to a certain extent, they are complex and expensive.

[0004] To improve the thermal conductivity of concrete, existing technologies have attempted to add various types of thermally conductive fillers, such as metal powder (copper powder, aluminum powder) and graphite, but the following problems exist: ① Metal particles are easily oxidized, resulting in reduced durability; ② The amount of addition is difficult to control, the dispersion is poor, and they are prone to agglomeration, which affects their thermal conductivity and has an adverse effect on the mechanical properties and durability of concrete; ③ The thermal conductivity path is discontinuous, and the improvement in thermal conductivity efficiency is limited; ④ Existing technologies often involve multiple complex pretreatment steps, special mixing equipment, etc., and the overall preparation process is complex and costly, which is not conducive to large-scale promotion and application.

[0005] The Chinese patent publication number CN 110304878 A discloses a high-thermal-conductivity, high-toughness mass concrete and its preparation method. Modified plant fibers are obtained by uniformly dispersing nano-metal oxides (magnesium oxide, aluminum oxide) and graphene on the surface and internal cavity walls of plant fibers. The nanomaterials utilize the cavity structure inside the plant fibers to construct heat-conducting channels, thereby enhancing the thermal conductivity of the mass concrete. However, the invention uses high-cost nanomaterials and a complex preparation process for nanomaterial-modified plant fibers. In addition, the nanomaterials themselves are prone to agglomeration, which affects their dispersion performance. The thermal insulation effect of the plant fibers themselves can lead to a decrease in the thermal conductivity of the concrete. The performance test results only show the 24-hour core temperature of the mass concrete, and no data on the thermal conductivity coefficient of the concrete is available.

[0006] Chinese patent publication number CN 110510955 A discloses a high-thermal-conductivity cement concrete and its preparation method. The high-thermal-conductivity cement concrete is prepared using low amounts of graphene and thermally conductive fibers, forming an effective graphene-carbon fiber-aggregate thermal network within the concrete to improve the thermal conductivity of the concrete. However, this invention places high demands on the properties of the graphene, carbon fibers, and aggregates, such as graphene sheet thickness of 0.55-3.74 nm, total oxygen content of 3%-5%, preferably less than 10 layers, thermal conductivity of 1326-1852 W / (m·K), carbon fiber diameter of 10 mm, aspect ratio of 100, and basalt crushed stone in a three-graded mass ratio of 2:5:3 (5-10 mm, 10-20 mm, and 20-30 mm). However, the thermal conductivity of the concrete is still relatively low (≤4.0 W / (m·K)), only 79%-190% higher than the control, which is of limited effectiveness.

[0007] Chinese patent publication number CN 119263713 A discloses a recycled concrete with high thermal conductivity and its preparation method. It utilizes a thermal conductor-halloysite nanotube composite material, with halloysite nanotubes loaded with graphene, boron nitride, and aluminum oxide as thermal conductors, forming a continuous thermal path. Furthermore, polyacrylonitrile-based carbon fibers can form a three-dimensional thermal network, significantly improving the thermal conductivity of the concrete. However, the invention (1) targets green recycled concrete, with applications in areas such as factory buildings and concrete pavements requiring heat dissipation. The thermal conductivity of lightweight aggregate concrete is much lower than that of natural aggregate concrete, so the effectiveness of the thermal conductor-halloysite nanotube composite material in ordinary concrete is unknown. (2) In the example, after curing concrete panels at 30°C and 60% humidity for 28 days, the thermal conductivity was 3.5 to 5.0 W / (m·K), a limited improvement over the comparative example (2.5 to 3.0 W / (m·K)).

[0008] Chinese patent publication number CN 104193232 B discloses a high-thermal-conductivity concrete and its preparation method. By adding chromium carbide powder, silicon nitride powder, and aluminum nitride powder to concrete, the thermal conductivity, durability, and strength of the concrete are improved. However, the invention (1) utilizes a large amount of kyanite, mullite, wollastonite, ceramsite, as well as pyrite powder, steel fiber, and other materials, and the specific components that contribute to the thermal conductivity are unknown. (2) The experimental data only includes concrete strength and slump, with no results for thermal performance parameters such as thermal conductivity, making the effectiveness of the concrete unknown.

[0009] Chinese patent publication number CN 118420294 B discloses a high-thermal-conductivity, low-temperature-rise, large-volume concrete and its preparation method. Carbon fibers are modified with grafted graphene oxide, and phase-change materials such as paraffin wax, fatty acids, and polyols are compounded with carbon black particles to prepare a high-thermal-conductivity, energy-storage phase-change coarse aggregate. The phase-change temperature-regulating properties of the phase-change material are utilized to reduce the temperature rise within the concrete and improve the thermal conductivity. However, the present invention ① uses expanded perlite, diatomaceous earth, and sepiolite porous materials to prepare the phase-change coarse aggregate for use in concrete, which is costly and unfavorable for large-scale promotion and application; ② The thermal conductivity of the concrete slab tested in the embodiment is 0.5-0.6 W / (m·K), while the thermal conductivity of the comparative concrete is 0.4-0.5 W / (m·K), resulting in limited effectiveness.

[0010] Chinese patent publication number CN 117447157 A discloses a low-temperature-rise, high-thermal-conductivity, and high-crack-resistance cement-based composite material and its preparation method. By introducing low-melting-point alloy phase-change microspheres with high volume latent heat and high-thermal-conductivity carbon fibers into the cement-based material, the two work synergistically to improve the flexural strength and thermal conductivity of the cement-based composite material. However, ① the low-melting-point alloy phase-change microspheres are polyvinyl alcohol-coated indium-bismuth-tin alloy (melting point approximately 60°C), so the thermal conductivity of the material is directly related to the low-melting-point alloy; ② data from the examples show that excessive addition of low-melting-point metals is detrimental to improving the flexural strength of the cement-based composite material; ③ the hydration temperature rise of the cement-based material in the examples can be reduced by 2 to 10°C, but the thermal conductivity of the material is only 1.3 to 1.4 W / (m·K), limiting the effect.

[0011] Chinese patent publication number CN 117865564 A discloses a high-thermal-conductivity, high-ductility geopolymer composite material and energy pile. The fine aggregate in this invention is silicon carbide particles and quartz sand, and copper powder is added to form an effective copper heat conduction channel within the geopolymer composite, thereby improving the effective thermal conductivity of the geopolymer composite. However, this invention: ① The energy pile uses a De25HDPE exchange fluid pipe for heat conduction; ② The data in the examples show that a certain amount of copper powder plays a major role in increasing the thermal conductivity of the geopolymer composite; ③ The thermal conductivity of the geopolymer composite in the examples is 2.5-3.5 W / (m·K). Without comparative data, it is impossible to analyze the effects of silicon carbide particles and copper powder.

[0012] Chinese patent publication number CN 116084392 B discloses a high-thermal-conductivity, low-carbon energy pile and its manufacturing method. This invention improves the effective thermal conductivity of geopolymer concrete by adding aluminum nitride particles and copper powder to the concrete. The primary effect is the formation of effective copper heat conduction channels within the concrete. However, the thermal conductivity of the geopolymer concrete in the examples presented is only 3-4 W / (m·K).

[0013] Chinese patent publication number CN 115094875 B discloses a high-thermal-conductivity, permeable energy pile and its manufacturing method. Silicon carbide is added to the concrete in the permeable energy pile to improve the concrete's thermal conductivity. The elimination of sand makes the pile permeable, allowing it to fully utilize the thermal convection of groundwater, thereby improving the heat exchange efficiency of the energy pile. The pile utilizes limestone crushed stone with a particle size of 5-12 mm and 1200-mesh green silicon carbide powder. However, the effective thermal conductivity of the pile concrete is approximately 2.0 W / (m·K), representing an improvement of no more than 44%.

[0014] Chinese patent publication number CN 117263595 A discloses a high-strength concrete for airport pavements and its preparation process. Paraffin is loaded into the micropores of porous alumina, the surface of the microcapsules is coated with a high thermal conductivity glue (containing alumina and boron nitride), and the surface of the microcapsules is grafted with modified thermally conductive carbon fibers to prepare high thermal conductivity energy storage phase change microcapsules. Because the porous alumina has good thermal conductivity and the modified thermally conductive carbon fibers can form a three-dimensional thermal conductive network inside the concrete, the thermal conductivity of the concrete is improved. However, the embodiment of the invention focuses on comparing the mechanical properties of concrete and the cracking performance after freeze-thaw. No data support is provided for the thermal conductivity of concrete, and the actual effect is unknown.

[0015] In summary, there is currently little research on high-heat-transfer cement-based materials for use in the construction industry. The thermal conductivity of concrete cannot meet the requirements for efficient heat dissipation or precise heat regulation. Low cost, high durability, and convenient application still need to be achieved. Based on the synergistic effect of material properties and structural design, the present invention proposes a high-heat-transfer cement-based material and a scientific and efficient preparation method. Summary of the Invention

[0016] This invention aims to address the shortcomings of existing technologies by innovatively constructing a "multi-component hybrid gradient thermal conductivity network system" to optimize the thermal conduction path of modified cement-based materials. This invention proposes a high-heat-transfer cement-based material and a scientific and efficient preparation method. This thermally conductive concrete not only significantly improves thermal conductivity while maintaining mechanical and durability requirements, achieving efficient heat dissipation and precise heat regulation, but also boasts a simple preparation method, low equipment and personnel requirements, and manageable production costs. This opens up new avenues for the large-scale industrial production and widespread engineering application of high-heat-transfer concrete.

[0017] The technical solution adopted in the present invention is as follows:

[0018] A high heat transfer cement-based material comprises the following components in parts by weight: 200-230 parts of cement, 75-105 parts of mineral admixture, 600-700 parts of sand, 1350-1450 parts of crushed stone, 3-12 parts of heat transfer enhancing material, 105-120 parts of water, 3-6 parts of water reducing agent, and 0.1-0.3 parts of defoaming agent.

[0019] The heat transfer enhancement material is two or three of modified boron nitride particles, polydopamine modified carbon nanotubes, and modified graphite, wherein the surface hydroxyl content of the polydopamine modified carbon nanotubes is ≥5%.

[0020] The heat transfer enhancement material is modified boron nitride particles, polydopamine modified carbon nanotubes, and modified graphite, which are added in a mass ratio of (0-2): (0-1): (0-2).

[0021] The heat transfer enhancement material is modified boron nitride particles, polydopamine modified carbon nanotubes, and modified graphite, which are added in a mass ratio of (1-2): (0-1): (1-2).

[0022] Preferably, the heat transfer enhancing material is composed of modified boron nitride particles and modified graphite, and the mass ratio thereof is (1-2):(1-2).

[0023] Further preferably, the heat transfer enhancing material is polydopamine-modified carbon nanotubes and modified graphite, and the mass ratio thereof is 1:(1-2).

[0024] More preferably, the heat transfer enhancing materials are modified boron nitride particles, polydopamine modified carbon nanotubes, and modified graphite, and the mass ratio thereof is (1-2):1:(1-2).

[0025] The modified boron nitride particles are obtained by adding hexagonal boron nitride particles to a sodium borohydride aqueous solution, heating to 80° C. to 100° C. and stirring for reaction for 1 to 2 hours, and then filtering, washing with deionized water, and drying.

[0026] The purity of the hexagonal boron nitride particles is ≥99%, and the particle size ranges from 5 to 30 μm.

[0027] The mass concentration of the sodium borohydride aqueous solution is 5% to 10%.

[0028] The mass ratio of sodium borohydride solution to boron nitride particles is 3:1 to 5:1.

[0029] The polydopamine-modified carbon nanotubes are prepared by adding multi-walled carbon nanotubes into a sodium dodecylbenzene sulfonate solution containing polydopamine, and then stirring the mixture at 40-50° C. for 1-2 hours to allow the polydopamine to be adsorbed on the surface of the carbon nanotubes to obtain a dispersion of the polydopamine-modified carbon nanotubes.

[0030] The multi-walled carbon nanotubes have a diameter of 10 to 50 nm, a length of 1 to 10 μm, and a purity of ≥95%.

[0031] Preferably, a 0.5-1 wt% aqueous solution of sodium dodecylbenzenesulfonate is prepared first, 0.5 parts of polydopamine is added and stirred for 15-30 minutes, and then multi-walled carbon nanotubes are added to the sodium dodecylbenzenesulfonate solution containing polydopamine at a solid-liquid ratio of 1:(5-10), and then stirred at a high-speed stirrer at a speed of 3000-5000 r / min for 1-2 hours at a temperature of 40-50°C to allow polydopamine to be adsorbed on the surface of the carbon nanotubes, and finally a dispersion of polydopamine-modified carbon nanotubes is obtained.

[0032] The modified graphite is modified flake graphite with a surfactant adsorbed on the surface, with a particle size distribution in the range of 50 to 200 μm and a carbon content of ≥95%.

[0033] First, a 1-2 wt% surfactant aqueous solution is prepared, and flake graphite particles are added at a solid-liquid ratio of 1:(10-20). Then, the solution is treated at an ultrasonic frequency of 40-60 kHz for 30-60 minutes to allow the surfactant to be fully adsorbed on the surface of the graphite particles. After filtering, the solution is placed in an oven at 60-80°C and dried for 12-24 hours to obtain modified flake graphite.

[0034] The surfactant is one of sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide and sodium oleate.

[0035] More preferably, the surfactant is sodium dodecylbenzenesulfonate.

[0036] The cement is general-purpose Portland cement with a strength grade of ≥42.5.

[0037] The sand is natural sand that is screened by graded screening and has a hard and clean texture, a fineness modulus between 2.6 and 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%.

[0038] The crushed stone is 5-40 mm continuously graded crushed stone, the content of needle-shaped particles is ≤5%, and the apparent density is ≥2600 kg / m 3 , the loose stacking void ratio is ≤40%, and the aggregate rock type is one of quartzite, granite, and limestone.

[0039] The water reducer is one of a polycarboxylic acid-based high-performance water reducer and a melamine-based high-efficiency water reducer, is liquid, slow-setting type, has a water reduction rate of not less than 25%, and an air content of ≤3.0%.

[0040] The defoamer is a liquid selected from amino polyether defoamers and polyether modified silicone defoamers.

[0041] The mineral admixtures are two or three of low-calcium fly ash, slag powder, and silica fume, and the ratio is (1-3): (1-3): (0-1). The low-calcium fly ash is selected from Class F Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80%; the slag powder is selected from a fly ash with a silicon dioxide content of ≥30% and a specific surface area of ​​400-500m 2 / kg, S95 grade slag powder with a 28d activity index of ≥95%; the silicon powder is selected from silica fume with a SiO2 content of ≥90%, an average particle size of 0.1-0.3μm, and a 7d activity index of ≥110%.

[0042] Adding an appropriate amount of micro-nano materials, such as low-calcium fly ash, slag powder, and silica powder, to the cement paste can fill the interface pores and optimize the interface structure, which is beneficial to improving the strength of concrete and enhancing the thermal conductivity at the interface. The reuse of the three admixtures of low-calcium fly ash, slag powder, and silica powder has a better effect.

[0043] Preferably, the mineral admixtures are low-calcium fly ash and slag powder, and the mass ratio thereof is (1-3):(1-2).

[0044] The mineral admixtures are low-calcium fly ash, slag powder and silica fume, and their mass ratio is (1-3):(1-3):1. More preferably, their mass ratio is 3:3:1.

[0045] The method for preparing the high heat transfer cement-based material comprises the following steps:

[0046] 1) First, weigh water, a water reducer, a defoamer, a polydopamine-modified multi-walled carbon nanotube dispersion, and other liquid materials according to mass, and sequentially add the water reducer, defoamer, polydopamine-modified multi-walled carbon nanotube dispersion, etc. to the water and stir thoroughly to form a uniform mixed solution;

[0047] 2) Then add cement, mineral admixtures, sand, and gravel into a forced concrete mixer in sequence and dry mix for 1 to 2 minutes;

[0048] 3) Then, add the powdered heat transfer enhancement material (modified boron nitride particles / modified graphite material) evenly and slowly into the mixer and continue stirring for 1-2 minutes to allow the heat transfer enhancement material to fully contact with the cementitious material and sand and gravel aggregate and to achieve preliminary dispersion;

[0049] 4) Finally, during the stirring process, add the mixed solution at a slow and even rate. Continue stirring for 2-3 minutes to obtain high heat transfer concrete. Ensure that all components of the concrete are fully mixed and evenly distributed.

[0050] The modified boron nitride particles are prepared by using hexagonal boron nitride particles with a purity of ≥99% and a particle size range of 5 to 30 μm. A 5% to 10% sodium borohydride aqueous solution is first prepared, and the hexagonal boron nitride particles are evenly and slowly added at a solid-to-liquid ratio of 3 to 5:1. The mixture is mechanically stirred for 15 to 30 minutes, and then heated to 80 to 100°C in a high-temperature reactor for 1 to 2 hours of stirring. The mixture is then filtered, washed with deionized water, and dried at 60 to 80°C to obtain the modified boron nitride particles.

[0051] The preparation method of the polydopamine-modified carbon nanotubes comprises the following steps: adding multi-walled carbon nanotubes with a diameter of 10 to 50 nm, a length of 1 to 10 μm, and a purity of 95% or more to a sodium dodecylbenzene sulfonate solution containing polydopamine; specifically, first preparing a 0.5 to 1 wt% sodium dodecylbenzene sulfonate aqueous solution, adding 0.5 parts of polydopamine, and stirring for 15 to 30 minutes; then adding the multi-walled carbon nanotubes to the sodium dodecylbenzene sulfonate solution containing polydopamine at a solid-to-liquid ratio of 1:(5 to 10); and finally stirring the mixture at a high-speed stirrer at a speed of 3,000 to 5,000 rpm for 1 to 2 hours at a temperature of 40 to 50° C. to allow the polydopamine to be adsorbed on the surface of the carbon nanotubes, thereby obtaining a dispersion of the polydopamine-modified carbon nanotubes.

[0052] The modified graphite is prepared by first preparing a 1-2 wt% surfactant aqueous solution, adding flake graphite particles at a solid-liquid ratio of 1:(10-20), then treating the solution at a 40-60 kHz ultrasonic frequency for 30-60 minutes to allow the surfactant to be fully adsorbed on the surface of the graphite particles, filtering the solution, and drying it in an oven at 60-80° C. for 12-24 hours to obtain the modified flake graphite.

[0053] In the present invention, the addition of modified hexagonal boron nitride particles can double the thermal conductivity of concrete at 28d to 90d, and also improve its strength. Boron nitride has excellent intrinsic thermal conductivity, and after modification, it is easy to disperse evenly and strengthen its interface with the cement matrix, thereby improving the heat transfer performance of concrete. In addition, the particle size of boron nitride is between 5 and 30 μm, which is conducive to a dense internal structure and improved strength. Compared with the single addition of modified boron nitride particles, the reuse of two or three materials, namely, modified hexagonal boron nitride particles, polydopamine-modified multi-walled carbon nanotubes, and modified flake graphite, has a better effect on improving the heat transfer performance of concrete. More preferably, the addition of three heat transfer enhancing materials results in a high heat transfer cement-based material. Based on the synergistic effect of material properties and structural design, an innovative "multi-component hybrid gradient heat conduction network system" is constructed, such as Figure 1As shown, through the interaction of chemical bonds, hydrogen bonds, and van der Waals forces, a gradient thermal conductivity network is formed from the micron to the nanometer scale, significantly improving the thermal conductivity of cement-based materials. From the perspective of the materials themselves, hexagonal boron nitride particles, multi-walled carbon nanotubes, and flake graphite all have excellent thermal conductivity; from a structural design perspective, the layered construction and interconnection method further optimize the heat conduction path.

[0054] Micron-to-Nanoscale Synergy: From the micron-sized hexagonal boron nitride particles in the core, to the nanoscale multi-walled carbon nanotubes in the middle layer, to the atomically thin flake graphite in the outer layer, a gradient structure is formed from the micron to the nanometer scale. This gradient structure adapts to the different scales of heat conduction within concrete. The micron-sized hexagonal boron nitride particles serve as the primary collection point for heat conduction, absorbing heat from the cement matrix; the nanoscale multi-walled carbon nanotubes quickly transfer heat to the outer layer, acting as a bridge; and the flake graphite, composed of numerous parallel layers, is responsible for efficiently distributing heat over a wider area. The synergistic effect of materials at different scales creates a three-dimensional, interconnected, and efficient heat conduction network, avoiding the increased thermal resistance caused by a single material scale failing to fully cover the heat conduction path, and greatly improving heat conduction efficiency.

[0055] Chemical bonds, hydrogen bonds and van der Waals forces: The entire multi-component hybrid system is tightly bound by chemical bonds, hydrogen bonds and van der Waals forces. Chemical bonds are formed between the hexagonal boron nitride particles and the multi-walled carbon nanotubes. This strong chemical bond ensures stability and high efficiency during heat conduction. The polydopamine-modified multi-walled carbon nanotubes and the flake graphite sheets form a strong van der Waals force connection through the adhesion mediated by polydopamine, ensuring smooth heat transfer at the interface. At the same time, a large number of hydroxyl groups (~OH) are introduced into the surface of the hexagonal boron nitride particles after modification, which reduces the surface energy of the particles, makes them easier to disperse evenly in the concrete system, and increases the number of effective heat-conducting particles; at the same time, the hydroxyl groups can react with calcium ions (Ca) in the hydration products. 2+ ), silicate ions (SiO4 4- ) form hydrogen bonds, which not only strengthen the interfacial bonding between the boron nitride particles and the cement matrix, reducing interfacial thermal resistance, but also provide additional channels for heat transfer. These different types of interaction work together to build a continuous and efficient heat conduction network, allowing heat to be transferred quickly and stably within the concrete, thereby achieving excellent thermal conductivity enhancement.

[0056] The interface transition zone between aggregate and cement paste in concrete is a weak link in heat conduction. The present invention fills the pores in the interface transition zone between aggregate and cement paste by adding appropriate amounts of low-calcium fly ash, slag powder, silica powder and other micro-nano materials into the cementitious material, optimizes the interface structure, and enhances the heat conduction capacity at the interface.

[0057] The present invention also improves the overall thermal conductivity of concrete by selecting aggregates with relatively good thermal conductivity, such as quartzite, granite, and limestone, and optimizing aggregate gradation to increase compact packing density, reduce porosity, and lower thermal resistance. Furthermore, the use of continuously graded aggregates creates a smoother heat conduction path, facilitating heat transfer.

[0058] Beneficial effects:

[0059] ① Excellent heat transfer / thermal conductivity: Based on the synergistic effect of material properties and structural design, the "multi-hybrid gradient thermal conductivity network system" constructs an efficient heat conduction channel. Tests have shown that the thermal conductivity of the concrete of the present invention can reach 4.0-6.0W / (m·K), which is 150%-400% higher than that of ordinary concrete. It can quickly and efficiently transfer the heat inside the concrete to the outside, effectively solving the heat dissipation problem of large-volume concrete, realizing precise heat regulation in the field of building energy conservation, and significantly reducing building energy consumption.

[0060] ② Excellent material mechanical and durability properties: The selection of raw materials, modification of heat transfer enhancing materials, and optimization of mix ratios and preparation processes have resulted in a dense internal structure of cement-based materials, enhanced interfacial bonding, and excellent synergistic effects among the components. Mechanical performance tests have shown that its 28-day compressive strength can reach 47-52 MPa, and its tensile strength can reach 2.6-3.0 MPa, far exceeding the mechanical performance indicators of existing ordinary thermal conductive concrete and meeting the strength requirements of various complex and heavy-loaded building structures. The various components in the multi-component hybrid thermal conductive enhancing material system form a good interface bond with the cement matrix, increasing density, enhancing the concrete's ability to resist external erosion, improving its durability, and extending the service life of the building structure.

[0061] ③ Simple preparation process: Raw material pretreatment uses conventional industrial equipment, which is easy to operate and low-cost. The segmented mixing process is based on existing equipment, does not require special complex equipment, and is easy to apply in engineering practice, effectively reducing production difficulty and cost, and improving production efficiency.

[0062] ④ Significant cost advantage: Although some innovative raw material processing methods are adopted, the overall raw material sources are wide-ranging. By optimizing the process, the rework and maintenance costs caused by quality problems are reduced. Compared with the existing thermal conductive concrete preparation technology, the overall cost is greatly reduced, which has strong market competitiveness and is conducive to large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 Schematic diagram of the "multi-element hybrid gradient heat conduction network" of high heat transfer concrete;

[0064] Figure 2 This is the mixing state of high heat transfer concrete in Example 7;

[0065] Figure 3This is a thermal insulation temperature rise test for high heat transfer concrete;

[0066] Figure 4 This is the temperature-stress test of high heat transfer concrete. (a) is the set concrete temperature history curve, and (b) is the concrete stress development curve. DETAILED DESCRIPTION

[0067] In order to more clearly describe the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments. This embodiment is only used to better explain the content of the present invention, but does not limit the present invention. All similar embodiments listed based on the present invention should fall within the scope of protection of the present invention.

[0068] The raw materials described in the present invention can all be obtained through public channels.

[0069] Example 1

[0070] 1) The high heat transfer cement-based material consists of 230 parts cement, 75 parts mineral admixture, 3 parts heat transfer enhancement material, 680 parts sand, 1370 parts crushed stone, 110 parts water, 5 parts water reducer, and 0.1 part defoamer. The cement is ordinary Portland cement with a P·O 42.5 rating. The sand is hard, clean, natural sand that has been graded and screened, a fineness modulus of 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%. The crushed stone is 5-40 mm continuously graded, with a needle-like particle content of ≤5% and an apparent density of ≥2600 kg / m 3 , loose stacking void ratio ≤40%, aggregate rock type is limestone; water reducer is polycarboxylic acid high performance water reducer, liquid, slow setting type, water reduction rate is not less than 25%, air content ≤3.0%; defoamer is amino polyether defoamer, liquid.

[0071] 2) The heat transfer enhancement material is modified hexagonal boron nitride particles with a purity of ≥99% and a particle size range of 5 to 30 μm. A 10% sodium borohydride aqueous solution is prepared, and the hexagonal boron nitride particles are slowly and evenly added at a solid-to-liquid ratio of 3:1. Mechanical stirring is performed for 30 minutes. The mixture is then heated to 100°C in a high-temperature reactor and stirred for 2 hours. The mixture is then filtered, washed multiple times with deionized water, and dried in an 80°C oven.

[0072] 3) The mineral admixtures are low-calcium fly ash and slag powder, with a ratio of 3:2. Low-calcium fly ash is selected from Class F Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80%; slag powder is selected from Class F Grade I fly ash with a silicon dioxide content of ≥30% and a specific surface area of ​​400-500m 2 / kg, S95 grade slag powder with 28d activity index ≥95%.

[0073] 4) First, weigh the liquid materials of water, water reducer, and defoamer by mass, add them to the water in sequence, and stir thoroughly to mix; then, add cement, mineral admixtures, sand, and gravel in a forced concrete mixer in sequence, and dry mix for 1 minute; then, add the powdered heat transfer enhancement material (modified boron nitride particles) evenly and slowly into the mixer, and continue stirring for 1 minute for preliminary dispersion; finally, add the above mixed solution at a slow and uniform rate, and continue stirring for 2 minutes to obtain.

[0074] Example 2

[0075] 1) The high heat transfer cement-based material consists of 230 parts cement, 75 parts mineral admixture, 6 parts heat transfer enhancement material, 680 parts sand, 1370 parts crushed stone, 110 parts water, 5 parts water reducer, and 0.1 part defoamer. The cement is ordinary Portland cement with a P·O 42.5 rating. The sand is hard, clean, natural sand that has been graded and screened, a fineness modulus of 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%. The crushed stone is 5-40 mm continuously graded, with a needle-like particle content of ≤5% and an apparent density of ≥2600 kg / m 3 , loose stacking void ratio ≤40%, aggregate rock type is limestone; water reducer is polycarboxylic acid high performance water reducer, liquid, slow setting type, water reduction rate is not less than 25%, air content ≤3.0%; defoamer is amino polyether defoamer, liquid.

[0076] 2) The heat transfer enhancement material comprises modified boron nitride particles and modified graphite, with a ratio of 1:1. The modified boron nitride particles are hexagonal boron nitride particles with a purity of ≥99% and a particle size range of 5 to 30 μm. A 10% aqueous sodium borohydride solution is prepared, and the hexagonal boron nitride particles are slowly and evenly added at a solid-to-liquid ratio of 3:1, with mechanical stirring for 30 minutes. The solution is then placed in a high-temperature reactor, heated to 100°C, and stirred for 2 hours. The solution is then filtered, washed multiple times with deionized water, and dried in an 80°C oven. The modified graphite is flake graphite with a particle size distribution of 50 to 200 μm and a carbon content of ≥95%. A 2% aqueous sodium dodecylbenzenesulfonate solution is prepared, and the flake graphite particles are added at a solid-to-liquid ratio of 1:10. The solution is then ultrasonically treated at 60 kHz for 60 minutes. The solution is then filtered and dried in an 80°C oven for 24 hours.

[0077] 3) The mineral admixtures are low-calcium fly ash and slag powder, with a ratio of 3:2. Low-calcium fly ash is selected from Class F Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80%; slag powder is selected from Class F Grade I fly ash with a silicon dioxide content of ≥30% and a specific surface area of ​​400-500m 2 / kg, S95 grade slag powder with 28d activity index ≥95%.

[0078] 4) First, weigh water, water reducer, defoamer and other liquid materials by mass, add them to water in sequence and stir thoroughly; then, add cement, mineral admixtures, sand and gravel in a forced concrete mixer in sequence and dry mix for 1 minute; then, add the powdered heat transfer enhancement material (modified boron nitride particles and modified graphite material) evenly and slowly into the mixer and continue stirring for 1 minute for preliminary dispersion; finally, add the above mixed solution at a slow and uniform rate and continue stirring for 2 minutes to obtain.

[0079] Example 3

[0080] 1) The high heat transfer cement-based material consists of 200 parts cement, 105 parts mineral admixture, 9 parts heat transfer enhancement material, 680 parts sand, 1370 parts crushed stone, 115 parts water, 5 parts water reducer, and 0.1 part defoamer. The cement is ordinary Portland cement with a P·O 42.5 rating. The sand is hard, clean, natural sand that has been graded and screened, a fineness modulus of 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%. The crushed stone is 5-40 mm continuously graded, with a needle-like particle content of ≤5% and an apparent density of ≥2600 kg / m 3 , loose stacking void ratio ≤40%, aggregate rock type is limestone; water reducer is polycarboxylic acid high performance water reducer, liquid, slow setting type, water reduction rate is not less than 25%, air content ≤3.0%; defoamer is amino polyether defoamer, liquid.

[0081] 2) The heat transfer enhancement material comprises modified boron nitride particles and modified graphite, with a ratio of 1:1. The modified boron nitride particles are hexagonal boron nitride particles with a purity of ≥99% and a particle size range of 5 to 30 μm. A 10% aqueous sodium borohydride solution is prepared, and the hexagonal boron nitride particles are slowly and evenly added at a solid-to-liquid ratio of 3:1. Mechanical stirring is performed for 30 minutes. The solution is then heated to 100°C in a high-temperature reactor and stirred for 2 hours. The solution is then filtered, washed multiple times with deionized water, and dried in an 80°C oven. The modified graphite is flake graphite with a particle size distribution of 50 to 200 μm and a carbon content of ≥95%. A 2% aqueous sodium dodecylbenzenesulfonate solution is prepared, and the flake graphite particles are added at a solid-to-liquid ratio of 1:10 to 1:20. The solution is then ultrasonically treated at 60 kHz for 60 minutes. The solution is then filtered and dried in an 80°C oven for 24 hours.

[0082] 3) The mineral admixtures are low-calcium fly ash and slag powder, with a ratio of 1:1. Low-calcium fly ash is selected from Class F Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80%; slag powder is selected from Class F Grade I fly ash with a silicon dioxide content of ≥30% and a specific surface area of ​​400-500m 2 / kg, S95 grade slag powder with 28d activity index ≥95%.

[0083] 4) First, weigh water, water reducer, defoamer and other liquid materials by mass, add them to water in sequence and stir thoroughly; then, add cement, mineral admixtures, sand and gravel in a forced concrete mixer in sequence and dry mix for 1 minute; then, add the powdered heat transfer enhancement material (modified boron nitride particles and modified graphite material) evenly and slowly into the mixer and continue stirring for 1 minute for preliminary dispersion; finally, add the above mixed solution at a slow and uniform rate and continue stirring for 2 minutes to obtain.

[0084] Example 4

[0085] 1) The high heat transfer cement-based material consists of 200 parts cement, 105 parts mineral admixture, 9 parts heat transfer enhancement material, 680 parts sand, 1370 parts crushed stone, 115 parts water, 5 parts water reducer, and 0.1 part defoamer. The cement is ordinary Portland cement with a P·O 42.5 rating. The sand is hard, clean, natural sand that has been graded and screened, a fineness modulus of 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%. The crushed stone is 5-40 mm continuously graded, with a needle-like particle content of ≤5% and an apparent density of ≥2600 kg / m 3 , loose stacking void ratio ≤40%, aggregate rock type is quartzite; water reducer is polycarboxylic acid high performance water reducer, liquid, slow setting type, water reduction rate is not less than 25%, air content ≤3.0%; defoamer is amino polyether defoamer, liquid.

[0086] 2) The heat transfer enhancement material comprises modified boron nitride particles and modified graphite, with a ratio of 1:1. The modified boron nitride particles are hexagonal boron nitride particles with a purity of ≥99% and a particle size range of 5 to 30 μm. A 10% aqueous sodium borohydride solution is prepared, and the hexagonal boron nitride particles are slowly and evenly added at a solid-to-liquid ratio of 3:1. Mechanical stirring is performed for 30 minutes. The solution is then heated to 100°C in a high-temperature reactor and stirred for 2 hours. The solution is then filtered, washed multiple times with deionized water, and dried in an 80°C oven. The modified graphite is flake graphite with a particle size distribution of 50 to 200 μm and a carbon content of ≥95%. A 2% aqueous sodium dodecylbenzenesulfonate solution is prepared, and the flake graphite particles are added at a solid-to-liquid ratio of 1:10 to 1:20. The solution is then ultrasonically treated at 60 kHz for 60 minutes. The solution is then filtered and dried in an 80°C oven for 24 hours.

[0087] 3) The mineral admixtures are low-calcium fly ash, slag powder, and silica fume, with a ratio of 3:3:1. Low-calcium fly ash is selected from Class F Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80%; slag powder is selected from Class F Grade I fly ash with a silicon dioxide content of ≥30% and a specific surface area of ​​400-500m 2 / kg, S95 grade slag powder with a 28d activity index ≥95%; silicon fume is selected from silica fume with SiO2 content ≥90%, average particle size 0.1-0.3μm, and 7d activity index ≥110%.

[0088] 4) First, weigh water, water reducer, defoamer and other liquid materials by mass, add them to water in sequence and stir thoroughly; then, add cement, mineral admixtures, sand and gravel in a forced concrete mixer in sequence and dry mix for 1 minute; then, add the powdered heat transfer enhancement material (modified boron nitride particles and modified graphite material) evenly and slowly into the mixer and continue stirring for 1 minute for preliminary dispersion; finally, add the above mixed solution at a slow and uniform rate and continue stirring for 2 minutes to obtain.

[0089] The temperature in the laboratory was controlled at (20±5)℃ and the relative humidity was not less than 50%. Raw materials were weighed according to the proportion of cement-based materials. Concrete was mixed using a forced concrete mixer according to the "Test Procedure for Hydraulic Concrete" SL / T 352-2020. The slump index of the concrete mixture was tested. 150mm×150mm×150mm cubes and After 24 hours, the cylindrical specimens were demolded and placed in a standard curing room at (20±2)°C for 28 days. The concrete was then removed and tested for compressive and tensile strength. Panel specimens measuring 300 mm (length × width × height) × 300 mm (height × height) were prepared and cured for 28 and 90 days. Their thermal conductivity was then measured according to GB / T 10294-2008, "Insulating Materials - Determination of Steady-State Thermal Resistance and Related Properties - Guarded Hot Plate Method." The properties of the high heat transfer cement-based materials of Examples 1-4 are shown in Table 1.

[0090] Table 1 Concrete properties of Examples 1-4

[0091]

[0092] Example 5

[0093] 1) The high heat transfer cement-based material consists of 200 parts cement, 105 parts mineral admixture, 9 parts heat transfer enhancement material, 680 parts sand, 1370 parts crushed stone, 115 parts water, 5 parts water reducer, and 0.1 part defoamer. The cement is ordinary Portland cement with a P·O 42.5 rating. The sand is hard, clean, natural sand that has been graded and screened, a fineness modulus of 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%. The crushed stone is 5-40 mm continuously graded, with a needle-like particle content of ≤5% and an apparent density of ≥2600 kg / m 3 , loose stacking void ratio ≤40%, aggregate rock type is quartzite; water reducer is polycarboxylic acid high performance water reducer, liquid, slow setting type, water reduction rate is not less than 25%, air content ≤3.0%; defoamer is amino polyether defoamer, liquid.

[0094] 2) The heat transfer enhancing material comprises polydopamine-modified carbon nanotubes and modified graphite in a ratio of 1:2. The polydopamine-modified carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10-50 nm, a length of 1-10 μm, and a purity of ≥95%. A 1 wt% aqueous solution of sodium dodecylbenzenesulfonate is prepared, 0.5 parts of polydopamine is added, and the mixture is stirred for 15 minutes. The multi-walled carbon nanotubes are then added at a solid-to-liquid ratio of 1:10. The mixture is then stirred at 5000 rpm in a high-speed stirrer at 40-50°C for 60 minutes to obtain a dispersion of the polydopamine-modified multi-walled carbon nanotubes. The modified graphite is flake graphite with a particle size distribution in the range of 50 to 200 μm and a carbon content of 95% or more. A 2 wt% aqueous solution of sodium dodecylbenzenesulfonate is prepared, and flake graphite particles are added at a solid-liquid ratio of 1:20. The solution is then treated at a 60 kHz ultrasonic frequency for 60 minutes, filtered, and then dried in an 80° C. oven for 24 hours to obtain the modified graphite.

[0095] 3) The mineral admixtures are low-calcium fly ash, slag powder, and silica fume, with a ratio of 3:3:1. Low-calcium fly ash is selected from Class F Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80%; slag powder is selected from Class F Grade I fly ash with a silicon dioxide content of ≥30% and a specific surface area of ​​400-500m 2 / kg, S95 grade slag powder with a 28d activity index ≥95%; silicon fume is selected from silica fume with SiO2 content ≥90%, average particle size 0.1-0.3μm, and 7d activity index ≥110%.

[0096] 4) First, weigh the liquid materials such as water, water reducer, defoamer, and polydopamine-modified multi-walled carbon nanotube dispersion according to mass, add them to the water in sequence and stir thoroughly; then, add cement, mineral admixtures, sand, and gravel in a forced concrete mixer in sequence and dry mix for 2 minutes; then, add the powdered heat transfer enhancement material (modified graphite material) evenly and slowly into the mixer and continue stirring for 1 minute for preliminary dispersion; finally, add the above mixed solution at a slow and uniform rate and continue stirring for 2 minutes to obtain.

[0097] Example 6

[0098] 1) The high heat transfer cement-based material consists of 200 parts cement, 105 parts mineral admixture, 9 parts heat transfer enhancement material, 680 parts sand, 1370 parts crushed stone, 115 parts water, 6 parts water reducer, and 0.2 parts defoamer. The cement is ordinary Portland cement with a P·O 42.5 rating. The sand is hard, clean, natural sand that has been graded and screened, a fineness modulus of 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%. The crushed stone is 5-40 mm continuously graded, with a needle-like particle content of ≤5% and an apparent density of ≥2600 kg / m 3, loose stacking void ratio ≤40%, aggregate rock type is quartzite; water reducer is polycarboxylic acid high performance water reducer, liquid, slow setting type, water reduction rate is not less than 25%, air content ≤3.0%; defoamer is amino polyether defoamer, liquid.

[0099] 2) The heat transfer enhancement material comprises modified boron nitride particles, polydopamine-modified carbon nanotubes, and modified graphite in a ratio of 2:1:2. The modified boron nitride particles are hexagonal boron nitride particles with a purity of ≥99% and a particle size range of 5 to 30 μm. A 10% sodium borohydride aqueous solution is prepared, and the hexagonal boron nitride particles are slowly and evenly added at a solid-to-liquid ratio of 3:1. The mixture is mechanically stirred for 30 minutes. The mixture is then placed in a high-temperature reactor, heated to 100°C, and stirred for 2 hours. The mixture is then filtered, washed with deionized water multiple times, and dried in an 80°C oven. The polydopamine-modified carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10 to 50 nm, a length of 1 to 10 μm, and a purity of ≥95%. A 1 wt% aqueous solution of sodium dodecylbenzenesulfonate is prepared, 0.5 parts of polydopamine is added, and the mixture is stirred for 15 minutes. The multi-walled carbon nanotubes are then added at a solid-to-liquid ratio of 1:10, and the mixture is stirred in a high-speed stirrer at 5000 rpm for 60 minutes to obtain a dispersion of the polydopamine-modified multi-walled carbon nanotubes. The modified graphite is flake graphite with a particle size distribution of 50 to 200 μm and a carbon content of ≥95%. A 2 wt% aqueous solution of sodium dodecylbenzenesulfonate is prepared, flake graphite particles are added at a solid-to-liquid ratio of 1:20, and the mixture is ultrasonically treated at 60 kHz for 60 minutes. The mixture is filtered and dried in an 80°C oven for 24 hours.

[0100] 3) The mineral admixtures are low-calcium fly ash, slag powder, and silica fume, with a ratio of 3:3:1. Low-calcium fly ash is selected from Class F Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80%; slag powder is selected from Class F Grade I fly ash with a silicon dioxide content of ≥30% and a specific surface area of ​​400-500m 2 / kg, S95 grade slag powder with a 28d activity index ≥95%; silicon fume is selected from silica fume with SiO2 content ≥90%, average particle size 0.1-0.3μm, and 7d activity index ≥110%.

[0101] 4) First, weigh the liquid materials such as water, water reducer, defoamer, and polydopamine-modified multi-walled carbon nanotube dispersion according to mass, add them to the water in sequence, and stir thoroughly; then, add cement, mineral admixtures, sand, and gravel in a forced concrete mixer in sequence, and dry mix for 2 minutes; then, add the powdered heat transfer enhancement material (modified boron nitride particles and modified graphite material) evenly and slowly to the mixer, and continue stirring for 1 minute for preliminary dispersion; finally, add the above mixed solution at a slow and uniform rate, and continue stirring for 2 minutes to obtain.

[0102] Example 7

[0103] 1) The high heat transfer cement-based material consists of 200 parts cement, 105 parts mineral admixture, 12 parts heat transfer enhancement material, 680 parts sand, 1370 parts crushed stone, 115 parts water, 6 parts water reducer, and 0.2 parts defoamer. The cement is ordinary Portland cement with a P·O 42.5 rating. The sand is hard, clean, natural sand that has been graded and screened, a fineness modulus of 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%. The crushed stone is 5-40 mm continuously graded, with a needle-like particle content of ≤5% and an apparent density of ≥2600 kg / m 3 , loose stacking void ratio ≤40%, aggregate rock type is quartzite; water reducer is polycarboxylic acid high performance water reducer, liquid, slow setting type, water reduction rate is not less than 25%, air content ≤3.0%; defoamer is amino polyether defoamer, liquid.

[0104] 2) The heat transfer enhancement material comprises modified boron nitride particles, polydopamine-modified carbon nanotubes, and modified graphite in a ratio of 2:1:2. The modified boron nitride particles are hexagonal boron nitride particles with a purity of ≥99% and a particle size range of 5 to 30 μm. A 10% sodium borohydride aqueous solution is prepared, and the hexagonal boron nitride particles are slowly and evenly added at a solid-to-liquid ratio of 3:1. The mixture is mechanically stirred for 30 minutes, then placed in a high-temperature reactor, heated to 100°C, stirred, and reacted for 2 hours. The mixture is then filtered, washed multiple times with deionized water, and dried in an 80°C oven. The polydopamine-modified carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10 to 50 nm, a length of 1 to 10 μm, and a purity of 95% or greater. A 1 wt% aqueous solution of sodium dodecylbenzenesulfonate is prepared, 0.5 parts of polydopamine is added, and the mixture is stirred for 15 to 30 minutes. The multi-walled carbon nanotubes are then added at a solid-to-liquid ratio of 1:10. The mixture is then stirred at 5000 rpm at 40 to 50°C for 60 minutes using a high-speed stirrer to obtain a dispersion of the polydopamine-modified multi-walled carbon nanotubes. The modified graphite is flake graphite with a particle size distribution of 50 to 200 μm and a carbon content of 95% or greater. A 2 wt% aqueous solution of sodium dodecylbenzenesulfonate is prepared, flake graphite particles are added at a solid-to-liquid ratio of 1:20, and the mixture is ultrasonically treated at 60 kHz for 60 minutes. The mixture is filtered and then dried in an 80°C oven for 24 hours.

[0105] 3) The mineral admixtures are low-calcium fly ash, slag powder, and silica fume, with a ratio of 3:3:1. Low-calcium fly ash is selected from Class F Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80%; slag powder is selected from Class F Grade I fly ash with a silicon dioxide content of ≥30% and a specific surface area of ​​400-500m 2 / kg, S95 grade slag powder with a 28d activity index ≥95%; silicon fume is selected from silica fume with SiO2 content ≥90%, average particle size 0.1-0.3μm, and 7d activity index ≥110%.

[0106] 4) First, weigh the liquid materials such as water, water reducer, defoamer, polydopamine modified multi-walled carbon nanotube dispersion according to mass, add them to the water in sequence and stir thoroughly; then, add cement, mineral admixtures, sand, and gravel in a forced concrete mixer in sequence and dry mix for 2 minutes; then, add the powdered heat transfer enhancement material (modified boron nitride particles and modified graphite material) evenly and slowly into the mixer and continue stirring for 1 minute for preliminary dispersion; finally, add the above mixed solution at a slow and uniform speed and continue stirring for 2 minutes to obtain a mixing state as shown in FIG. Figure 2 The adiabatic temperature rise test results are shown in Figure 3 shown.

[0107] To compare the actual effects of the high heat transfer cement-based materials in the examples, several comparison examples are provided below:

[0108] Comparative Example 1

[0109] 1) The cement-based material consists of 230 parts cement, 75 parts mineral admixture, 680 parts sand, 1370 parts crushed stone, 115 parts water, 5 parts water reducer, and 0.2 parts defoamer. The cement is ordinary Portland cement with a P·O 42.5 rating. The sand is hard, clean natural sand that has been graded and screened, a fineness modulus of 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%. The crushed stone is 5-40 mm continuously graded crushed stone with a needle-like particle content of ≤5% and an apparent density of ≥2600 kg / m 3 , loose stacking void ratio ≤40%, aggregate rock type is limestone; water reducer is polycarboxylic acid high performance water reducer, liquid, slow setting type, water reduction rate is not less than 25%, air content ≤3.0%; defoamer is amino polyether defoamer, liquid.

[0110] 2) The mineral admixture is low-calcium fly ash, and Class F, Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80% is selected.

[0111] 3) First, weigh water, water reducer, defoamer and other liquid materials by mass, add them to water in sequence and stir thoroughly; then, add cement, mineral admixtures, sand and gravel in a forced concrete mixer in sequence and dry mix for 1 minute; finally, add the above mixed solution at a slow and even rate and continue stirring for 2 minutes to obtain the final product.

[0112] Comparative Example 2

[0113] 1) The cement-based material consists of 200 parts cement, 105 parts mineral admixture, 680 parts sand, 1370 parts crushed stone, 115 parts water, 5 parts water reducer, and 0.2 parts defoamer. The cement is ordinary Portland cement with a P·O 42.5 rating. The sand is hard, clean natural sand that has been graded and screened, a fineness modulus of 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%. The crushed stone is 5-40 mm continuously graded crushed stone with a needle-like particle content of ≤5% and an apparent density of ≥2600 kg / m 3 , loose stacking void ratio ≤40%, aggregate rock type is quartzite; water reducer is polycarboxylic acid high performance water reducer, liquid, slow setting type, water reduction rate is not less than 25%, air content ≤3.0%; defoamer is amino polyether defoamer, liquid.

[0114] 2) The mineral admixtures are low-calcium fly ash, slag powder, and silica fume, with a ratio of 3:3:1. Low-calcium fly ash is selected from Class F Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80%; slag powder is selected from Class F Grade I fly ash with a silicon dioxide content of ≥30% and a specific surface area of ​​400-500m 2 / kg, S95 grade slag powder with a 28d activity index ≥95%; silicon fume is selected from silica fume with SiO2 content ≥90%, average particle size 0.1-0.3μm, and 7d activity index ≥110%.

[0115] 3) First, weigh water, water reducer, defoamer and other liquid materials by mass, add them to water in sequence and stir thoroughly; then, add cement, mineral admixtures, sand and gravel in a forced concrete mixer in sequence and dry mix for 1 minute; finally, add the above mixed solution at a slow and even rate and continue stirring for 2 minutes to obtain the final product.

[0116] Comparative Example 3

[0117] 1) The high heat transfer cement-based material consists of 230 parts cement, 75 parts mineral admixture, 3 parts heat transfer enhancement material, 680 parts sand, 1370 parts crushed stone, 110 parts water, 5 parts water reducer, and 0.1 part defoamer. The cement is ordinary Portland cement with a P·O 42.5 rating. The sand is hard, clean, natural sand that has been graded and screened, a fineness modulus of 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%. The crushed stone is 5-40 mm continuously graded, with a needle-like particle content of ≤5% and an apparent density of ≥2600 kg / m 3 , loose stacking void ratio ≤40%, aggregate rock type is limestone; water reducer is polycarboxylic acid high performance water reducer, liquid, slow setting type, water reduction rate is not less than 25%, air content ≤3.0%; defoamer is amino polyether defoamer, liquid.

[0118] 2) The heat transfer enhancement material is unmodified boron nitride particles, using hexagonal boron nitride particles with a purity of ≥99% and a particle size range of 5 to 30 μm.

[0119] 3) The mineral admixtures are low-calcium fly ash and slag powder, with a ratio of 3:2. Low-calcium fly ash is selected from Class F Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80%; slag powder is selected from Class F Grade I fly ash with a silicon dioxide content of ≥30% and a specific surface area of ​​400-500m 2 / kg, S95 grade slag powder with 28d activity index ≥95%.

[0120] 4) First, weigh the liquid materials such as water, water reducer, and defoamer by mass, add them to the water in sequence, and stir thoroughly; then, add cement, mineral admixtures, sand, and gravel in a forced concrete mixer in sequence, and dry mix for 1 minute; then, add the boron nitride particles evenly and slowly to the mixer, and continue stirring for 1 minute for preliminary dispersion; finally, add the above mixed solution at a slow and uniform rate, and continue stirring for 2 minutes to obtain.

[0121] Comparative Example 4

[0122] 1) The cement-based material consists of 200 parts cement, 105 parts mineral admixture, 12 parts heat transfer enhancement material, 680 parts sand, 1370 parts crushed stone, 115 parts water, 6 parts water reducer, and 0.2 parts defoamer. The cement is P·O42.5 ordinary Portland cement; the sand is graded, screened, hard, clean natural sand with a fineness modulus of 3.0, a mud content of ≤1.0%, and a mica content of ≤1.0%; the crushed stone is 5-40mm continuously graded crushed stone with a needle-like particle content of ≤5% and an apparent density of ≥2600kg / m 3 , loose stacking void ratio ≤40%, aggregate rock type is quartzite; water reducer is polycarboxylic acid high performance water reducer, liquid, slow setting type, water reduction rate is not less than 25%, air content ≤3.0%; defoamer is amino polyether defoamer, liquid.

[0123] 2) The heat transfer enhancement material comprises unmodified boron nitride particles, unmodified carbon nanotubes, and unmodified graphite in a ratio of 2:1:2. The boron nitride particles are hexagonal boron nitride particles with a purity of ≥99% and a particle size range of 5 to 30 μm. The carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10 to 50 nm, a length of 1 to 10 μm, and a purity of ≥95%. The multi-walled carbon nanotubes are mixed with water at a solid-to-liquid ratio of 1:10, and then stirred in a high-speed stirrer at 5000 rpm for 60 minutes to obtain a multi-walled carbon nanotube dispersion for later use. The graphite is flake graphite with a particle size distribution of 50 to 200 μm and a carbon content of ≥95%.

[0124] 3) The mineral admixtures are low-calcium fly ash, slag powder, and silica fume. The low-calcium fly ash is selected from Class F Grade I fly ash with a calcium oxide content of less than 10% and a strength activity index of ≥80%. The slag powder is selected from Class F Grade I fly ash with a silicon dioxide content of ≥30% and a specific surface area of ​​400-500m 2 / kg, S95 grade slag powder with a 28d activity index ≥95%; silicon fume is selected from silica fume with SiO2 content ≥90%, average particle size 0.1-0.3μm, and 7d activity index ≥110%.

[0125] 4) First, weigh the liquid materials such as water, water reducer, defoamer, and unmodified multi-walled carbon nanotube dispersion by mass, add them to the water in sequence, and stir thoroughly; then, add cement, mineral admixtures, sand, and gravel in a forced concrete mixer in sequence and dry mix for 2 minutes; then, add the powdered heat transfer enhancement material (boron nitride particles and graphite material) evenly and slowly to the mixer and continue stirring for 1 minute for preliminary dispersion; finally, add the above mixed solution at a slow and uniform rate and continue stirring for 2 minutes to obtain.

[0126] The laboratory temperature was controlled at (20±5)°C and the relative humidity was not less than 50%. Raw materials were weighed according to the cement-based material ratio. Concrete was mixed using a forced concrete mixer according to the "Test Procedure for Hydraulic Concrete" SL / T 352-2020. The slump index of the concrete mixture was tested. A fully automatic concrete thermophysical parameter tester was used to measure the adiabatic temperature rise of concrete. The temperature acquisition step was 0.5h and the temperature tracking accuracy was 0.02°C. The pouring temperature was controlled at about 20°C. The test lasted for 28 days. 150mm×150mm×150mm cubes and After 24 hours, the cylindrical specimens were demolded and placed in a standard curing room at (20±2)°C for curing until 28 days. The concrete was then removed for compressive and tensile strength testing. Referring to the "Relative Permeability Test" in SL / T 352-2020, the water pressure was increased to 0.8 MPa and maintained constant for 24 hours before the test was terminated. The specimens were split and the water seepage height was measured.

[0127] Panel specimens with a length × width × height of 300mm × 300mm × 50mm were prepared and cured for 28 days and 90 days. The thermal conductivity was measured according to GB / T 10294-2008, "Determination of Steady-State Thermal Resistance and Related Properties of Insulating Materials - Guarded Hot Plate Method". A temperature-stress testing machine was used to control the concrete mixing temperature at around 20°C before pouring into the mold. Dumbbell-shaped specimens with a size of 150 × 150 × 1500 mm were cast and cast. The temperature matching mode was selected to simulate and evaluate the actual temperature history (e.g. Figure 4 (a) Comprehensive crack resistance of concrete, measuring the concrete cracking stress and cracking temperature drop.

[0128] The relevant test results of Examples 5-7 and Comparative Examples 1-4 are shown in Table 2. As can be seen from Table 2, the concretes of Comparative Examples 1 and 2 do not contain heat transfer enhancing materials. Comparative Example 1 uses a single admixture of low-calcium fly ash and limestone aggregate. The thermal conductivity of the concrete from 28 days to 90 days is relatively low, only 1.2 to 1.3 W / (m·K); the slump is 65 mm, and the 28-day compressive and tensile strengths are 42.5 MPa and 2.30 MPa, respectively, both within the normal range. However, the 28-day adiabatic temperature rise is 43.1°C, which is relatively high, and the temperature-stress cracking temperature drop is only 19.5°C, indicating a high risk of overall cracking of the concrete. Comparative Example 2 uses a combination of three mineral admixtures: low-calcium fly ash, slag powder, and silica fume, and quartzite aggregate. The concrete strength is improved, the adiabatic temperature rise is reduced by 1.4°C, and the crack resistance is slightly improved. In addition, the addition of micro-nano materials optimizes the interface structure and enhances the interface thermal conductivity. The thermal conductivity of quartzite aggregate is generally higher than that of limestone aggregate. Therefore, the thermal conductivity coefficient of concrete from 28d to 90d is slightly improved compared with Comparative Example 1, which is 1.4 to 1.6 W / (m·K), but it is still relatively low.

[0129] As can be seen from Tables 1 and 2, compared with Comparative Examples 1-2, ① the slump of the concrete of Examples 1-7 is also in the range of 50-70 mm, and the incorporation of the heat transfer enhancing material has little effect on the workability of the concrete; ② the thermal conductivity of the concrete is significantly increased from 28 days to 90 days, among which the thermal conductivity of the concrete of Examples 3-7 can reach 4.0-6.0 W / (m·K), an increase of 150%-400%. The improved heat transfer performance of the concrete is more conducive to efficient heat dissipation, and the 28-day adiabatic temperature rise can be reduced by 5-6°C; ③ Thanks to the optimization of raw materials and mix ratio, the internal structure of the material is dense and the interface bonding is enhanced. The 28-day compressive strength of the concrete can reach 47-52 MPa and the tensile strength can reach 2.6-3.0 MPa. The cracking temperature drop in the temperature-stress test increases by 6-10°C, and the 0.8 MPa water seepage height is reduced by 75%-90%. The strength, impermeability, and crack resistance of the concrete are also improved to varying degrees.

[0130] Comparison between Example 1 and Comparative Example 1 shows that the addition of 3 parts of modified hexagonal boron nitride particles can double the thermal conductivity of concrete from 28d to 90d, and increase the strength by 14% to 17%. Boron nitride has excellent intrinsic thermal conductivity. After modification, it is easy to disperse evenly and enhance the interface bonding with the cement matrix, thereby improving the heat transfer performance of concrete. In addition, the boron nitride particle size is between 5 and 30 μm, which is conducive to a dense internal structure and improved strength.

[0131] In Comparative Example 3, the concrete was added with 3 parts of hexagonal boron nitride particle heat transfer enhancement material, but was not modified. The thermal conductivity of the concrete was 1.7-1.8 W / (m·K) from 28d to 90d, and the adiabatic temperature rise was 42.2°C after 28 days. Although this was significantly improved compared with Comparative Example 1, the unmodified hexagonal boron nitride particles agglomerated and had poor dispersion. In addition, the interface between the boron nitride particles and the cement matrix was not firmly bonded, and there were often obvious gaps, which would affect the thermal conductivity of the material. Compared with Example 7, the thermal conductivity of the concrete was reduced by 23% to 28%, and the strength was also reduced by about 4%.

[0132] Comparing Examples 1 to 7, it can be seen that ① compared with the single addition of modified boron nitride particles, the use of two or three materials, modified hexagonal boron nitride particles, modified multi-walled carbon nanotubes, and modified flake graphite, has a better effect on improving the thermal conductivity of concrete. Among them, the use of 12 parts of the three heat transfer enhancing materials, thanks to the construction of the "multi-component hybrid gradient thermal conductivity network system", can achieve a thermal conductivity coefficient of 6.0W / (m·K) for concrete. ② Compared with limestone aggregate, quartzite aggregate has better thermal conductivity. Quartzite, granite and other igneous rock aggregates are generally selected, and their thermal conductivity is generally 2.0-3.5W / (m·K), which is higher than that of ordinary limestone aggregate (thermal conductivity is about 1.5-2.0W / (m·K)). ③ Adding an appropriate amount of micro-nano materials, such as low-calcium fly ash, slag powder, and silica powder, to the cement paste can fill the interface pores and optimize the interface structure, which is beneficial to improving the strength of concrete and enhancing the heat conduction capacity at the interface. The reuse of the three admixtures of low-calcium fly ash, slag powder, and silica powder has a better effect.

[0133] In Comparative Example 4, the concrete was mixed with 12 parts of three heat transfer enhancing materials: hexagonal boron nitride particles, multi-walled carbon nanotubes, and flake graphite, but none of them were modified. The thermal conductivity of the concrete was 3.1-3.5 W / (m·K) from 28 days to 90 days, and the adiabatic temperature rise was 40.2°C after 28 days. Although this was a significant improvement over Comparative Examples 1 and 2, the filling and dispersibility of the unmodified heat transfer enhancing materials were quite poor, which greatly affected the thermal transfer performance of the material. Compared with Example 7, the thermal conductivity of the concrete was reduced by 40% to 70%, the adiabatic temperature rise after 28 days was increased by 2.8°C, and the strength was also reduced by 3% to 8%.

[0134] Table 2 Concrete properties of Examples 5-7 and Comparative Examples 1-4

[0135]

[0136] In summary, the high heat transfer cement-based material and its preparation method described in the present invention have excellent concrete heat transfer performance and a thermal conductivity coefficient as high as 4.0 to 6.0 W / (m·K) due to the synergistic effect of material properties and structural design. This allows for efficient heat transfer and heat dissipation in high-strength concrete, helping to reduce the temperature difference between the inside and outside of large-volume, high-strength concrete and lower the risk of cracking due to temperature drop. The multi-component micro-nano admixture and heat transfer enhancement material work together effectively, resulting in a dense internal structure, enhanced slurry-aggregate interface bonding, and excellent concrete mechanical and durability properties. Furthermore, the material has the advantages of a simple preparation method and controllable production costs, opening up new avenues for the engineering application of high heat transfer concrete.

[0137] The above embodiments are only for illustrating the better performance of the present invention and do not constitute a limitation on the present invention. It should be pointed out that any form of modification made by technicians in this professional field without departing from the core concept of the present invention and the obvious changes derived therefrom fall within the scope of protection of the present invention.

Claims

1. A high heat transfer cement-based material, characterized in that: The composition comprises the following components by weight: 200-230 parts of cement, 75-105 parts of mineral admixture, 600-700 parts of sand, 1350-1450 parts of crushed stone, 3-12 parts of heat transfer enhancement material, 105-120 parts of water, 3-6 parts of water reducer, and 0.1-0.3 parts of defoaming agent; The heat transfer enhancement material is at least one of modified boron nitride particles, polydopamine-modified carbon nanotubes, and modified graphite.

2. The high heat transfer cement-based material according to claim 1, characterized in that: The heat transfer enhancement material is modified boron nitride particles, polydopamine-modified carbon nanotubes, and modified graphite, which are added in a mass ratio of (0-2):(0-1):(0-2).

3. The high heat transfer cement-based material according to claim 1, wherein: The mineral admixtures are two or three of low-calcium fly ash, slag powder and silica fume, and the ratio thereof is (1-3):(1-3):(0-1).

4. The high heat transfer cement-based material according to claim 1, wherein: The modified boron nitride particles are obtained by adding hexagonal boron nitride particles to a sodium borohydride aqueous solution, heating to 80° C. to 100° C. and stirring for reaction for 1 to 2 hours, filtering, washing with deionized water, and drying at 60° C. to 80° C.

5. The high heat transfer cement-based material according to claim 1, wherein: The polydopamine-modified carbon nanotubes are prepared by adding multi-walled carbon nanotubes into a sodium dodecylbenzene sulfonate solution containing polydopamine, and then stirring the solution at 40-50° C. for 1-2 hours to allow the polydopamine to be adsorbed on the surface of the carbon nanotubes to obtain a dispersion of the polydopamine-modified carbon nanotubes.

6. The high heat transfer cement-based material according to claim 1, characterized in that: The modified graphite is modified flake graphite with a surfactant adsorbed on the surface.

7. The high heat transfer cement-based material according to claim 6, characterized in that: The surfactant is one of sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide and sodium oleate.

8. The method for preparing the high heat transfer cement-based material according to any one of claims 1 to 7, wherein: The steps include: 1) Add water, water reducing agent, defoaming agent, and dispersion of polydopamine-modified carbon nanotubes into water in sequence and stir thoroughly to form a uniform mixed solution; 2) Add cement, mineral admixtures, sand, and gravel into a concrete mixer in sequence and dry mix for 1-2 minutes; 3) Slowly and evenly add the modified boron nitride particles and / or modified graphite into the mixer and continue stirring for 1-2 minutes to ensure that the heat transfer enhancement material is fully in contact with the cementitious material and sand and gravel aggregates and initially dispersed; 4) Finally, add the mixed solution from step 1) during the stirring process and continue stirring for 2-3 minutes to obtain high heat transfer concrete.

9. The method for preparing a high heat transfer cement-based material according to claim 8, wherein: The preparation method of the polydopamine-modified carbon nanotube dispersion comprises the following steps: first preparing a 0.5-1 wt% sodium dodecylbenzenesulfonate aqueous solution, adding 0.5 parts of polydopamine and stirring for 15-30 minutes, then adding multi-walled carbon nanotubes to the sodium dodecylbenzenesulfonate solution containing polydopamine at a solid-liquid ratio of 1:(5-10), and then stirring at a temperature of 40-50° C. and a speed of 3000-5000 r / min for 1-2 hours to allow the polydopamine to be adsorbed on the surface of the carbon nanotubes, thereby obtaining a dispersion of the polydopamine-modified carbon nanotubes.

10. The method for preparing a high heat transfer cement-based material according to claim 8, wherein: The modified graphite is prepared by first preparing a 1-2 wt% surfactant aqueous solution, adding flake graphite particles at a solid-liquid ratio of 1:(10-20), then treating the solution at a 40-60 kHz ultrasonic frequency for 30-60 minutes to allow the surfactant to be fully adsorbed on the surface of the graphite particles, filtering the solution, and drying it in a 60-80° C. oven for 12-24 hours to obtain the modified flake graphite.

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