Temperature self-balancing fine aggregate concrete and preparation method thereof

Abstract

The invention discloses temperature self-balancing fine aggregate concrete and a preparation method thereof, and belongs to the technical field of building materials. The concrete is prepared from the following components in parts by weight: a cementing material, high-heat-conductivity and high-heat-storage aggregate, fine stone, sand, high-heat-conductivity boron nitride fibers, water and an additive, the preparation method of the high-heat-conductivity and high-heat-storage aggregate comprises the following steps: S1, uniformly mixing coal gangue, fly ash and mineral powder, adding a pore forming agent and water, aging, granulating and sintering to obtain high-heat-storage fine stone ceramsite; s2, uniformly mixing the cement, the fly ash and the mineral powder, adding water, stirring, adding the boron nitride powder, uniformly mixing to obtain slurry, adding the high-heat-storage fine stone ceramsite into the slurry, taking out, and curing to obtain the high-heat-storage fine stone ceramsite. The high-heat-conductivity and high-heat-storage aggregate and the high-heat-conductivity boron nitride fiber are introduced into the concrete and synergistically improve the rapid temperature change response capability in the fine aggregate concrete, so that the purpose that the internal temperature gradient of the fine aggregate concrete is self-balanced along with the change of the external temperature is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a temperature self-balanced fine stone concrete and a preparation method thereof. Background Art

[0002] Fine aggregate concrete is a structural material with a coarse aggregate particle size usually less than 15mm. It has the characteristics of high fluidity, weak segregation, uniformity and stability. It is often used in densely reinforced areas and some thin-walled concrete components in industrial and civil buildings. However, since concrete is a multi-phase composite material composed of coarse aggregate and hardened cement paste, it will inevitably lead to the formation of some initial defects such as capillary pores, voids and material cracks during the pouring and forming process, which provides favorable conditions for the initiation and development of cracks in the later concrete structure during service.

[0003] The average summer temperature in the middle and lower reaches of the Yangtze River, South China, and Xinjiang is relatively high. The outer structures of industrial and civil buildings are exposed to direct sunlight for a long time. The surface temperature of key parts such as the parapet and roof protection layer of the building is often very high, even reaching above 60°C. Under the action of high temperature, a temperature gradient will form from shallow to deep inside the concrete structure. Due to the poor thermal conductivity of each component of concrete, the rate of heat exchange at different depths of concrete is slow. However, summer overlaps with the plum rain season in time. When the weather changes drastically, the outer structure of the concrete exposed to the sun will experience a sudden drop in temperature in a short period of time. In addition, some cities in Xinjiang with temperate desert climates also have a sudden temperature change environment caused by the alternation of day and night in summer. At this time, a large temperature difference is formed between the surface and the interior of the concrete, and temperature stress is generated between the aggregate and the mortar due to the different thermal expansion coefficients. Under the action of long-term temperature changes, the components at the initial defects in the concrete interact with each other, forming stress concentration and inducing the germination of microcracks; on the other hand, the bonding interface of the components in the concrete is a weak link, which will be detached under the influence of external environmental factors to form interface cracks and develop into microcracks; when external factors continue to act repeatedly, these microcracks will further develop, converge, and penetrate, and then form macro cracks, causing high engineering repair costs in the later stage.

[0004] Therefore, the present invention provides a temperature self-balancing fine stone concrete, which can achieve internal temperature gradient self-balancing as the external temperature changes, reduce the impact of repeated changes in external ambient temperature on internal damage of the fine stone concrete structure, and enhance the long-term durability of the fine stone concrete structure. Summary of the invention

[0005] In view of the deficiencies of the above-mentioned prior art, one of the objects of the present invention is to provide a temperature-self-balancing fine-stone concrete. By introducing high thermal conductivity and high heat storage aggregate and high thermal conductivity boron nitride fiber into the concrete, the high thermal conductivity and high heat storage aggregate can transfer the heat absorbed by the surface of the concrete to the high thermal conductivity and high heat storage aggregate. With the synergistic effect of the two, the rapid temperature change response capability of the fine-stone concrete is improved, so as to achieve the purpose of self-balancing the internal temperature gradient of the fine-stone concrete as the external temperature changes, thereby reducing the influence of repeated changes in the external environment temperature on the internal damage of the fine-stone concrete structure, and enhancing the long-term durability of the fine-stone concrete structure.

[0006] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0007] A temperature self-balanced fine stone concrete, comprising the following components in parts by weight: 220-360 parts of cementitious material, 311-733 parts of high thermal conductivity and high heat storage aggregate, 474-802 parts of fine stone, 850-950 parts of sand, 45-70 parts of high thermal conductivity boron nitride fiber, 150-250 parts of water, and 3-6 parts of admixture;

[0008] The preparation method of the high thermal conductivity and high heat storage aggregate comprises the following steps:

[0009] S1. The gangue, fly ash and mineral powder are mixed evenly, a pore-forming agent and water are added, stirred evenly and aged, and then granulated, dried and sintered to obtain high heat storage fine stone ceramsite;

[0010] S2. Mix cement, fly ash and mineral powder evenly, add water and stir, then add boron nitride powder, mix evenly to obtain high thermal conductivity slurry, then add high thermal storage fine stone ceramsite obtained in step S1 to the high thermal conductivity slurry, take out and cure to obtain the high thermal conductivity and high thermal storage aggregate.

[0011] The present invention first prepares fine stone ceramsite with high heat storage performance, and then introduces boron nitride powder on its surface in the form of pre-coating, thereby enhancing its thermal conductivity, which can work synergistically with high thermal conductivity boron nitride fiber to form multiple staggered paths for rapid heat exchange in the direction from shallow to deep inside the concrete, effectively reducing the temperature gradient inside the concrete structure. In the high temperature environment in summer, high thermal conductivity and high heat storage aggregate can absorb a large amount of external environmental heat and play a heat storage role; when the external environment changes drastically, such as from sunny to heavy rain, the temperature of the concrete surface layer drops rapidly, and the high thermal conductivity and high heat storage aggregate begins to release heat to the outside through the thermal conductive surface layer. At the same time, the high thermal conductivity boron nitride fiber plays a heat exchange bridge role, which can effectively reduce the temperature fluctuation amplitude inside the concrete structure, thereby achieving the purpose of temperature self-balance, reducing the adverse effects of temperature stress on the initial defects between the components in the concrete, and reducing the risk of micro cracks in the concrete peripheral structure such as parapets and roof protection layers germinating and developing under the action of external environmental factors.

[0012] Preferably, in step S1, the mass ratio of the gangue, fly ash and mineral powder is (4-5): (3-4): (1-3). When the mass ratio of the gangue, fly ash and mineral powder is within the range defined in the present invention, the obtained fine stone ceramsite has a higher specific heat capacity, which is beneficial to heat storage performance.

[0013] Preferably, in step S1, the sintering conditions are: pre-sintering at 400-500°C for 20-30 min, and then sintering at 1050-1200°C for 30-90 min.

[0014] Preferably, in step S1, the pore-forming agent includes at least one of carbon powder, calcium carbonate and magnesium carbonate.

[0015] Preferably, in step S2, the mass of the boron nitride powder is 30% to 60% of the total mass of cement, fly ash and mineral powder.

[0016] Preferably, in step S2, the boron nitride powder is a boron nitride powder obtained by treating hexagonal boron nitride powder at 10-15 GPa and 1500-2000° C. The boron nitride powder prepared under high temperature and high pressure conditions has better thermal conductivity, and the obtained aggregate has better thermal conductivity.

[0017] Preferably, the apparent density of the high thermal conductivity and high heat storage aggregate is ≤1800kg / m 3 , cylinder pressure strength ≥5MPa, thermal conductivity ≥4W / (m•K), specific heat capacity ≥1100J / (kg•K), lead metal leaching ≤0.05mg / L, chromium metal leaching ≤0.05mg / L.

[0018] Preferably, the high thermal conductivity boron nitride fiber is a crude boron nitride fiber synthesized by an inorganic precursor conversion method, an electrostatic spinning method, an organic precursor conversion method, or a boric acid and melamine chemical reaction synthesis method and treated at 10-15 GPa and 1500-2000° C. The boron nitride fiber prepared under high temperature and high pressure conditions has a better thermal conductivity.

[0019] Preferably, the cementitious material comprises cement, fly ash and mineral powder in a mass ratio of (150-200):(20-60):(50-100).

[0020] Preferably, the cement is ordinary Portland cement; and the admixture is polycarboxylic acid high-efficiency water reducing agent.

[0021] Another object of the present invention is to provide a method for preparing the temperature self-balanced fine stone concrete, comprising the following steps:

[0022] M1. Weigh each component by weight;

[0023] M2. The cementitious material, fine stone and sand are dry-mixed evenly, and high thermal conductivity and high heat storage aggregate are dry-mixed evenly, and then admixtures and water are added and mixed evenly, and then high thermal conductivity boron nitride fiber is added and mixed evenly to obtain concrete slurry.

[0024] Compared with the prior art, the present invention is beneficial in that:

[0025] (1) The present invention first prepares high-heat storage fine stone ceramsite, and then modifies the surface of the fine stone ceramsite by a slurry containing boron nitride powder, so that the fine stone ceramsite forms a surface layer with high thermal conductivity, thereby obtaining a high-heat conductivity and high-heat storage aggregate; at the same time, boron nitride fibers with excellent thermal conductivity are introduced into the fine stone concrete to provide an efficient heat exchange bridging effect, which can effectively transfer the heat absorbed by the surface layer of the fine stone concrete to the high-heat conductivity and high-heat storage aggregate. The two work together to improve the rapid temperature change response capability of the fine stone concrete, so as to achieve the purpose of self-balancing the internal temperature gradient of the fine stone concrete as the external temperature changes, thereby reducing the influence of repeated changes in the external environment temperature on the internal damage of the fine stone concrete structure, and enhancing the long-term durability of the fine stone concrete structure.

[0026] (2) The present invention uses coal gangue to prepare high thermal conductivity and high heat storage aggregate, which can reduce the coal gangue reserves formed in the process of mining coal resources and reduce the risk of harmful heavy metal elements in the coal gangue polluting the air, water and soil environment.

[0027] (3) The concrete of the present invention uses high thermal conductivity and high heat storage aggregate to replace part of the coarse aggregate, which significantly reduces the mining and processing costs of natural aggregates and reduces the consumption of natural resources, and has significant economic value and environmental significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The temperature variation diagram at different depths of the concrete slab specimen in Example 1;

[0029] Figure 2 The temperature variation diagram at different depths of the concrete slab specimen in Example 2;

[0030] Figure 3 The temperature variation diagram at different depths of the concrete slab specimen of comparative example 1;

[0031] Figure 4 The temperature variation diagram at different depths of the concrete slab specimen of comparative example 2;

[0032] Figure 5 The temperature variation diagram at different depths of the concrete slab specimen of comparative example 3;

[0033] Figure 6 The temperature variation diagram at different depths of the concrete slab specimen of comparative example 4;

[0034] Figure 7 This is a temperature variation diagram at different depths of the concrete slab specimen in comparative example 5. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The temperature self-balanced fine stone concrete of the present invention comprises the following components in parts by weight: 220-360 parts of cementitious material, 311-733 parts of high thermal conductivity and high heat storage aggregate, 474-802 parts of fine stone, 850-950 parts of sand, 45-70 parts of high thermal conductivity boron nitride fiber, 150-250 parts of water, and 3-6 parts of admixture;

[0037] The preparation method of the high thermal conductivity and high heat storage aggregate comprises the following steps:

[0038] S1. The gangue, fly ash and mineral powder are mixed evenly, a pore-forming agent and water are added, stirred evenly and aged, and then granulated, dried and sintered to obtain high heat storage fine stone ceramsite;

[0039] S2. Mix cement, fly ash and mineral powder evenly, add water and stir, then add boron nitride powder, mix evenly to obtain high thermal conductivity slurry, then add high thermal storage fine stone ceramsite obtained in step S1 to the high thermal conductivity slurry, take out and cure to obtain the high thermal conductivity and high thermal storage aggregate.

[0040] In some embodiments, the mass ratio of the gangue, fly ash and mineral powder is (4-5): (3-4): (1-3). For example, the mass ratio of the gangue, fly ash and mineral powder can be 5:3:2, 4:3:3, 5:4:1, etc.

[0041] In some embodiments, the sintering conditions are: pre-sintering at 400-500° C. for 20-30 min, and then sintering at 1050-1200° C. for 30-90 min.

[0042] In some embodiments, the pore former includes at least one of carbon powder, calcium carbonate, and magnesium carbonate.

[0043] In some embodiments, the mass of the boron nitride powder is 30% to 60% of the total mass of cement, fly ash and mineral powder. For example, the mass of the boron nitride powder can be 30%, 40%, 50%, 60%, etc. of the total mass of cement, fly ash and mineral powder.

[0044] In some embodiments, the high thermal conductivity boron nitride fiber is a crude boron nitride fiber synthesized by an inorganic precursor conversion method, an electrospinning method, an organic precursor conversion method, or a boric acid and melamine chemical reaction synthesis method and then treated at 10-15 GPa and 1500-2000°C.

[0045] In the present invention, the coal gangue has a SiO2 content of 50% to 60%, an Al2O3 content of 30% to 35%, a Fe2O3 content of 1% to 2%, and a CaO content of 1% to 2%; the fly ash is Class F II fly ash recovered from a coal-fired power plant, with a particle size of ≤0.9 mm, a water requirement ratio of ≤95%, a SiO2 content of 50% to 60%, an Al2O3 content of 10% to 15%, and a Fe2O3 content of 5%. ~10%; the mineral powder is S95 grade mineral powder, in which the SiO2 content is 30%~40%, the Al2O3 content is 10%~15%, and the CaO content is 40%~50%; the boron nitride powder is the boron nitride powder obtained by treating the hexagonal boron nitride powder at 10~15GPa and 1500~2000℃, the particle size of the boron nitride powder is 5~50μm, the purity is ≥99%, and the apparent density is 3000~3450kg / m 3 ; The length of high thermal conductivity boron nitride fiber is 10~15mm, the diameter is 4~8μm, and the apparent density is 3000~3500kg / m 3 , tensile strength ≥ 1000MPa, elastic modulus ≥ 100GPa, thermal conductivity ≥ 25W / (m·K).

[0046] The cement is ordinary Portland cement P•O 42.5; the sand is machine-made sand with a fineness modulus of 2.4~2.6 and an apparent density of about 2600~2700kg / m 3 ; The particle size of fine stone is 5~10mm, and the apparent density is about 2700~2800kg / m 3 ; The solid content of polycarboxylic acid water reducer is 35~50%, and the water reduction rate is ≥30%.

[0047] Unless otherwise specified, the temperature self-balancing fine stone concrete in the following examples and comparative examples are prepared according to the following method:

[0048] M1. Weigh each component by weight;

[0049] M2. Add cement, fly ash, mineral powder, fine stone and sand to a concrete mixer in sequence, stir for 2 minutes, then add high thermal conductivity and high heat storage aggregate, stir for 1 minute, then mix the polycarboxylate water reducer and water evenly and pour into the concrete mixer, then add high thermal conductivity boron nitride fiber in small amounts and multiple times until it is completely mixed to obtain concrete slurry;

[0050] M3. Pour the concrete slurry into the mold, and after vibrating and compacting, cure it in the mold for 20 to 30 hours, and then standard cure it for 28 to 30 days. After removing the mold, the temperature-self-balanced fine stone concrete will be obtained.

[0051] Example 1

[0052] This embodiment provides a temperature self-balanced fine stone concrete, comprising the following components in parts by weight: 170 parts of ordinary Portland cement P•O 42.5, 50 parts of fly ash, 70 parts of mineral powder, 311 parts of high thermal conductivity and high heat storage aggregate, 802 parts of fine stone, 900 parts of sand, 45 parts of high thermal conductivity boron nitride fiber, 170 parts of water, and 5 parts of polycarboxylate water reducer;

[0053] The preparation method of high thermal conductivity and high heat storage aggregate comprises the following steps:

[0054] S1. Firstly, the coal gangue is crushed and ground by a ball mill to obtain powdered coal gangue with a diameter of less than 0.074 mm for standby use; then the coal gangue, fly ash and mineral powder are poured into a rigid container at a mass ratio of 5:3:2, and inorganic pore-forming agent calcium carbonate is added, and an appropriate amount of water is poured in and stirred until the mixture is uniform. After aging for 40 minutes, a granulator is used to granulate to obtain spherical ceramsite raw materials with a particle size range of 5-10 mm; then the spherical ceramsite raw materials are placed in an oven at 105±5℃ and dried for 30 minutes, and then placed in a high-temperature furnace, preheated at 400℃ for 30 minutes, and then the temperature in the furnace is adjusted to 1100℃ for sintering for 20 minutes, and kept warm for 40 minutes, and then cooled to room temperature to obtain high heat storage fine stone ceramsite;

[0055] S2. Pour cement, fly ash and mineral powder into a mixer in a mass ratio of 6:2:2, start the mixer and mix for 1 minute; then add water accounting for 60% of the total mass of cement, fly ash and mineral powder, and stir for 60 seconds; then add boron nitride powder accounting for 50% of the total mass of cement, fly ash and mineral powder, and mix for 2 minutes to obtain a high thermal conductivity slurry; finally, pour a small amount of high thermal storage fine stone ceramsite obtained in step S1 evenly into the mixer and stir for 2 minutes, take out after the surface of the fine stone ceramsite is evenly coated with slurry, filter out excess slurry and naturally air-dry for 24 hours, then cure for 7 days at a temperature of 20±2℃ and a relative humidity of ≥95% to prepare a high thermal conductivity and high thermal storage fine stone aggregate.

[0056] Example 2

[0057] The temperature self-balancing fine stone concrete of Example 2 is basically the same as that of Example 1, except that the weight fraction of high thermal conductivity and high heat storage aggregate is 733 parts, the weight fraction of fine stone is 474 parts, and the weight fraction of high thermal conductivity boron nitride fiber is 70 parts.

[0058] Comparative Example 1

[0059] The temperature self-balanced fine stone concrete of this comparative example is basically the same as that of Example 1, except that step S2 is omitted when preparing the high thermal conductivity and high heat storage aggregate;

[0060] That is, compared with Example 1, the high heat storage fine stone ceramsite is not subjected to surface slurry modification treatment in this comparative example, and the concrete in this comparative example directly adopts the high heat storage fine stone ceramsite.

[0061] Comparative Example 2

[0062] The temperature self-balancing fine stone concrete of this comparative example is basically the same as that of Example 1, except that high thermal conductivity boron nitride fibers are not added.

[0063] Comparative Example 3

[0064] The temperature self-balancing fine stone concrete of this comparative example is basically the same as that of Example 2, except that no high thermal conductivity and high heat storage aggregate is added, and the weight proportion of fine stone is 1070 parts.

[0065] Comparative Example 4

[0066] The temperature self-balancing fine stone concrete of this comparative example is basically the same as Example 1, except that high thermal conductivity and high heat storage fine stone aggregate and high thermal conductivity boron nitride fiber are not added, the weight proportion of fine stone is 1070 parts, and this comparative example serves as a blank control group.

[0067] Comparative Example 5

[0068] The temperature self-balancing fine stone concrete of this comparative example is basically the same as that of Example 1, except that step S2 is omitted when preparing the high thermal conductivity and high heat storage aggregate, and 15 parts of boron nitride powder are added when preparing the fine stone concrete.

[0069] The technical indicators of the high thermal conductivity and high heat storage fine stone aggregates of various embodiments and comparative examples are shown in Table 1.

[0070] Table 1 Technical indicators of high thermal conductivity and high heat storage fine stone aggregate

[0071]

[0072] It can be seen from Table 1 that compared with Comparative Example 1, the thermal conductivity and cylinder pressure strength of the fine stone ceramsite in Examples 1 and 2 are significantly improved, indicating that the thermal conductivity of the fine stone ceramsite with high heat storage is improved by modifying the surface layer of the fine stone ceramsite with high thermal conductivity slurry.

[0073] In order to further compare the technical advantages of the temperature self-balanced fine stone concrete of the present invention, the following test method is used to study the influence of repeated temperature changes on its apparent performance and the temperature change response law of various internal locations:

[0074] (1) After the fine stone concrete of each embodiment and comparative example is poured, the fresh concrete is poured into a 150mm×150mm×150mm cubic mold, a 1500mm×300mm×500mm wall-type wooden mold, and a 600mm×600mm×40mm board-type wooden mold respectively; after being vibrated and compacted, it is cured with the mold for 24 hours, and then switched to standard curing for 28 days. Among them, a temperature sensor is arranged every 10mm along the depth direction at the center line section of the board-type wooden mold, and the fine stone concrete is compacted by manual vibration. After the curing is completed, it is naturally air-dried for 1 day.

[0075] (2) Each group of wall specimens was placed in a high temperature chamber and the indoor temperature was adjusted to 80℃±5℃, so that the wall specimens were heated uniformly at a constant temperature for 6 h. Then the wall specimens were taken out and the surface of the wall specimens was sprayed with water for cooling for 3 min. This was one cycle. Each group of wall specimens was cycled 10 times in total. After the cycle, the number of cracks on the surface of the wall specimens was observed and recorded. The results are shown in Table 2.

[0076] (3) After each group of plate specimens are placed in the high temperature chamber, one side is facing upward for high temperature treatment, and the other side is wrapped with heat insulation material. The indoor temperature is adjusted to 80℃±5℃, so that the plate specimens are heated uniformly and at a constant temperature for 6 hours, and then the temperature sensor data of the plate specimens are monitored and recorded; then the heated surface of the plate specimens is sprayed with water for cooling for 3 minutes, and the temperature sensor data of the plate specimens after cooling are monitored and recorded. This is one cycle, and each group of plate specimens is cycled 3 times in total.

[0077] (4) Each group of cube specimens shall be subjected to cube compressive strength test in accordance with the Standard for Test Methods for Physical and Mechanical Properties of Concrete (GB / T 50081-2019) to evaluate the mechanical properties of each group of specimens.

[0078] Table 2 Apparent properties of wall specimens and compressive strength of cube specimens

[0079]

[0080] Note: The compressive strength data in the table are the compressive strength values ​​of three groups of cubes that have not undergone high temperature-cooling cycles.

[0081] It can be seen from Table 2 that, compared with Comparative Examples 1 to 5, after experiencing 10 high temperature-cooling cycles, the number of microcracks per unit area on the surface of the wall specimens of Examples 1 and 2 is reduced. This is because the high thermal conductivity boron nitride fiber and the high thermal conductivity and high heat storage fine stone aggregate can work together to form a heat exchange system, which quickly transfers the energy released by the external environment inside the fine stone concrete, reducing the negative impact of temperature stress on the internal structure of the fine stone concrete; in addition, it can be found that the number of microcracks per unit area of ​​the specimen of Example 2 is less than that of Example 1, indicating that increasing the amount of high thermal conductivity boron nitride fiber and high thermal conductivity and high heat storage fine stone aggregate can improve the ability of fine stone concrete to resist the negative impact of repeated temperature changes in the outside world, but its compressive strength is also slightly reduced compared with Comparative Examples 3 and 4.

[0082] The temperature changes at different depths of the concrete slab specimens of Examples 1 to 2 and Comparative Examples 1 to 5 are shown in Figure 2. Figures 1 to 7 . It can be seen from the figure that as the number of unilateral high temperature-cooling cycles experienced by the plate specimen gradually increases, the temperature gradient at each depth of Example 1 and Example 2 gradually decreases, indicating that a large number of staggered high thermal conductivity boron nitride fibers can quickly transfer surface heat to the surface of high thermal conductivity and high heat storage fine stone aggregate, and the high thermal conductivity and high heat storage fine stone aggregate then stores the absorbed heat; as the surface of the plate specimen cools, the high thermal conductivity and high heat storage fine stone aggregate in various parts of the fine stone concrete begins to release heat, and transfers heat to the temperature cooling area through the high thermal conductivity boron nitride fibers, slowing down the temperature reduction rate, and making the temperature of each layer inside the fine stone concrete plate specimen gradually tend to be consistent, reducing the adverse effect of the external environment temperature change on the initial defects inside the fine stone concrete, and the synergistic heat exchange system composed of high thermal conductivity boron nitride fibers and high thermal conductivity and high heat storage fine stone aggregates has played an obvious temperature self-balancing effect in the fine stone concrete.

[0083] Compared with Example 1, Example 1 did not perform high thermal conductivity slurry modification treatment on the surface of high heat storage fine stone aggregate, resulting in a large temperature gradient at various depths inside under the first unilateral high temperature-cooling cycle. As the number of cycles gradually increased, the temperature at 20mm and 30mm of the plate specimen tended to be consistent, but the difference with the surface temperature was still large.

[0084] Comparative Example 2 only added high thermal conductivity and high heat storage fine stone aggregate, and did not add high thermal conductivity boron nitride fiber, resulting in low heat exchange efficiency in the fine stone concrete plate specimen and large temperature gradients at various depths.

[0085] Comparative Example 3 only added high thermal conductivity boron nitride fiber, and did not add high thermal conductivity and high heat storage fine stone aggregate, resulting in poor thermal insulation ability of the fine stone concrete plate specimen when experiencing repeated temperature changes, and the temperature gradient at the depth of 10mm and 20mm increased significantly; Comparative Example 4 is a blank control group of fine stone concrete. As the number of high temperature-cooling cycles increases, the temperature gradient at each depth is large, and there is no trend of temperature tending to be consistent, which easily induces the formation of microcracks.

[0086] Comparative Example 5 only incorporates high-heat storage fine stone aggregate and boron nitride powder. Compared with Comparative Example 1 in which boron nitride fiber is incorporated, the number of effective heat exchange paths formed in the fine stone concrete in this example is relatively small. At the same time, the surface of the fine stone aggregate is not modified by slurry coating, resulting in a large temperature gradient in the plate specimen after multiple cycles.

[0087] In addition, the inventors have found through experiments that compared with conventional gangue ceramsite or fly ash ceramsite, the high heat storage fine stone ceramsite prepared by the present invention through coal gangue, fly ash and mineral powder in a specific proportion has a higher specific heat capacity and is more conducive to improving the heat storage performance.

[0088] In summary, the present invention prepares high heat storage fine stone ceramsite by using coal gangue, fly ash and mineral powder as raw materials, and uses high thermal conductivity slurry to modify its surface, and simultaneously adds high thermal conductivity boron nitride fiber to prepare fine stone concrete. When the external ambient temperature changes suddenly, the synergistic heat exchange system formed by high thermal conductivity and high heat storage fine stone aggregate and high thermal conductivity boron nitride fiber in the fine stone concrete responds quickly, adjusts and balances the temperature at each depth of the fine stone concrete, reduces the adverse effect of repeated temperature changes caused by the seasons on the initial defects in the fine stone concrete to induce the formation of microcracks, and achieves the purpose of temperature self-balance without significantly affecting the strength of the fine stone concrete, reduces the risk of cracks in the outer structure of the building, and reduces the cost of later engineering repairs.

[0089] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A temperature self-balanced fine stone concrete, characterized in that: The invention comprises the following components in parts by weight: 220-360 parts of cementitious material, 311-733 parts of high thermal conductivity and high heat storage aggregate, 474-802 parts of fine stone, 850-950 parts of sand, 45-70 parts of high thermal conductivity boron nitride fiber, 150-250 parts of water, and 3-6 parts of admixture; The preparation method of the high thermal conductivity and high heat storage aggregate comprises the following steps: S1. The gangue, fly ash and mineral powder are mixed evenly, a pore-forming agent and water are added, stirred evenly and aged, and then granulated, dried and sintered to obtain high heat storage fine stone ceramsite; S2. Mix cement, fly ash and mineral powder evenly, add water and stir, then add boron nitride powder, mix evenly to obtain high thermal conductivity slurry, then add high thermal storage fine stone ceramsite obtained in step S1 to the high thermal conductivity slurry, take out and cure to obtain the high thermal conductivity and high thermal storage aggregate.

2. The temperature self-balancing fine stone concrete according to claim 1, characterized in that: In step S1, the mass ratio of the coal gangue, fly ash and mineral powder is (4-5): (3-4): (1-3).

3. The temperature self-balancing fine stone concrete according to claim 1, characterized in that: In step S1, the sintering conditions are: pre-sintering at 400-500°C for 20-30 min, and then sintering at 1050-1200°C for 30-90 min.

4. The temperature self-balancing fine stone concrete according to claim 1, characterized in that: In step S1, the pore-forming agent includes at least one of carbon powder, calcium carbonate and magnesium carbonate.

5. The temperature self-balancing fine stone concrete according to claim 1, characterized in that: In step S2, the mass of the boron nitride powder is 30% to 60% of the total mass of cement, fly ash and mineral powder.

6. The temperature self-balancing fine stone concrete according to claim 1, characterized in that: In step S2, the boron nitride powder is boron nitride powder obtained by treating hexagonal boron nitride powder at 10-15 GPa and 1500-2000°C.

7. The temperature self-balancing fine stone concrete according to claim 1, characterized in that: The apparent density of the high thermal conductivity and high heat storage aggregate is ≤1800kg / m 3 , cylinder pressure strength ≥5MPa, thermal conductivity ≥4W / (m•K), specific heat capacity ≥1100J / (kg•K).

8. The temperature self-balancing fine stone concrete according to claim 1, characterized in that: The high thermal conductivity boron nitride fiber is obtained by treating a crude boron nitride fiber synthesized by an inorganic precursor conversion method, an electrostatic spinning method, an organic precursor conversion method or a boric acid and melamine chemical reaction synthesis method at 10-15 GPa and 1500-2000°C.

9. The temperature self-balancing fine stone concrete according to claim 1, characterized in that: The cementitious material comprises cement, fly ash and mineral powder in a mass ratio of (150-200):(20-60):(50-100).

10. The method for preparing the temperature self-balanced fine stone concrete according to any one of claims 1 to 9, characterized in that: The following steps are involved: M1. Weigh each component by weight; M2. The cementitious material, fine stone and sand are dry-mixed evenly, and high thermal conductivity and high heat storage aggregate are dry-mixed evenly, and then a water reducer and water are added and mixed evenly, and then high thermal conductivity boron nitride fiber is added and mixed evenly to obtain concrete slurry, and the temperature self-balanced fine stone concrete is obtained after molding.

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