A temperature self-balancing fine stone concrete and a preparation method thereof

Abstract

The application discloses a temperature self-balancing fine stone concrete and a preparation method thereof, and belongs to the technical field of building materials. The concrete comprises the following components in parts by weight: cementing material, high-thermal-conductivity and high-heat-storage aggregate, fine stone, sand, high-thermal-conductivity boron nitride fiber, water and additive. The preparation method of the high-thermal-conductivity and high-heat-storage aggregate is as follows: S1. uniformly mixing coal gangue, fly ash and mineral powder, adding pore-forming agent and water, aging, granulating, sintering and then obtaining high-heat-storage fine stone ceramsite; S2. uniformly mixing cement, fly ash and mineral powder, adding water and stirring, then adding boron nitride powder, uniformly mixing to obtain a slurry, and then adding the high-heat-storage fine stone ceramsite into the slurry, and taking out and curing to obtain the high-thermal-conductivity and high-heat-storage aggregate. The high-thermal-conductivity and high-heat-storage aggregate and the high-thermal-conductivity boron nitride fiber are introduced into the concrete, and the two components are used in combination to improve the rapid temperature change response capability of the fine stone concrete, so that the internal temperature gradient of the fine stone concrete is self-balanced with the change of the external temperature.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of building materials, and particularly relates to a temperature self-balancing fine stone concrete and a preparation method thereof. BACKGROUND

[0002] Fine stone concrete is a structural material with a coarse aggregate particle size usually less than 15 mm, and has the characteristics of high fluidity, weak segregation and uniform stability, and is often applied to the reinforced dense parts of industrial and civil buildings and some thin-walled concrete components. However, since concrete is a multiphase composite material composed of coarse aggregate and hardened cement paste, some initial defects such as capillary pores, voids and material cracks are inevitably formed during pouring and shaping, which provides favorable conditions for the initiation and development of cracks in the concrete structure during the service period.

[0003] The average temperature in summer in the middle and lower reaches of the Yangtze River, South China and Xinjiang regions of China is relatively high, and the outer structures of industrial and civil buildings are directly exposed to sunlight for a long time. The surface temperature of key parts such as the parapet wall and roof protection layer of the building is often very high, and can even reach above 60℃. A temperature gradient is formed from shallow to deep in the interior of the concrete structure under the action of high temperature, and since the thermal conductivity of each component of the concrete is poor, the rate of heat exchange at different depths of the concrete is slow. However, the summer and plum rain seasons overlap in time, and when the weather changes dramatically, the outer structure of the concrete exposed to sunlight will experience a process of temperature drop in a short time; in addition, some cities in Xinjiang have a temperate desert climate, and there is also a 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 difference in thermal expansion coefficient. Under the action of long-term temperature change, the components at the initial defects in the concrete interact with each other, stress concentration is formed, and micro-cracks are induced to initiate; on the other hand, the bonding interface of each component in the concrete is a weak link, which will separate and form interface cracks under the action of external environmental factors, and develop into micro-cracks; when the external factors continue to act repeatedly, these micro-cracks will further develop, converge and penetrate, and then form macro-cracks, causing high engineering repair costs in the later period.

[0004] Therefore, the present application provides a temperature self-balancing fine stone concrete, which can achieve internal temperature gradient self-balancing with the change of external temperature, reduce the influence of repeated changes of external environmental temperature on the internal damage of the fine stone concrete structure, and enhance the long-term durability of the fine stone concrete structure. SUMMARY

[0005] In view of the above prior art deficiencies, one of the purposes of the present application is to provide a temperature self-balancing fine stone concrete, by introducing high-thermal-conductivity and high-thermal-storage aggregate and high-thermal-conductivity boron nitride fiber into the concrete, the high-thermal-conductivity and high-thermal-storage aggregate can transfer the heat absorbed by the surface layer of the concrete to the high-thermal-conductivity and high-thermal-storage aggregate, and through the synergistic effect of the two, the rapid temperature change response capability of the fine stone concrete is improved, so that the internal temperature gradient of the fine stone concrete is self-balanced with the change of the external temperature, thereby reducing the influence of the repeated change of 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-mentioned purposes, the specific technical solutions of the present application are as follows:

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

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

[0009] S1. Mix coal gangue, fly ash and mineral powder uniformly, add pore-forming agent and water, stir uniformly, then age, and then granulate, and after drying and sintering, high-thermal-storage fine stone ceramsite is obtained;

[0010] S2. Mix cement, fly ash and mineral powder uniformly, add water and stir, then add boron nitride powder, mix uniformly to obtain a high-thermal-conductivity slurry, then add the high-thermal-storage fine stone ceramsite obtained in step S1 to the high-thermal-conductivity slurry, and after taking out and curing, the high-thermal-conductivity and high-thermal-storage aggregate is obtained.

[0011] The present application first prepares fine stone ceramsite with high heat storage performance, and then introduces boron nitride powder in the form of pre-wrapping slurry on the surface of the fine stone ceramsite, thereby enhancing the thermal conductivity of the fine stone ceramsite, and the high-thermal-conductivity and high-thermal-storage aggregate and the high-thermal-conductivity boron nitride fiber can synergistically form multiple staggered paths for rapid heat exchange in the concrete from shallow to deep, effectively reducing the internal temperature gradient of the concrete structure. In the high-temperature environment in summer, the high-thermal-conductivity and high-thermal-storage aggregate can absorb a large amount of external environmental heat and play a heat storage role; when the external environment changes sharply, such as from sunny to heavy rain, the temperature of the surface layer of the concrete decreases rapidly at this time, the high-thermal-conductivity and high-thermal-storage aggregate starts to release heat to the outside through the heat-conducting surface layer, and at the same time, the high-thermal-conductivity boron nitride fiber plays a role of heat exchange bridge connection, which can effectively reduce the temperature fluctuation amplitude of the internal structure of the concrete, thereby achieving the purpose of temperature self-balancing, reducing the adverse effects of temperature stress on the initial defects between the components in the concrete, and reducing the risk of the initiation and development of micro-cracks in the internal structure of the concrete peripheral structure such as the parapet wall and the roof protection layer under the action of external environmental factors.

[0012] Preferably, in step S1, the mass ratio of the coal gangue, fly ash and mineral powder is (4-5):(3-4):(1-3). Within the limited range of the application, the specific heat capacity of the fine stone ceramsite obtained is higher, which is beneficial to the heat storage performance.

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

[0014] Preferably, in step S1, the pore-forming agent comprises 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%-60% of the total mass of the cement, fly ash and mineral powder.

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

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

[0018] Preferably, the high-thermal-conductivity boron nitride fiber is a coarse boron nitride fiber synthesized by inorganic precursor conversion method, electrospinning method, organic precursor conversion method or chemical reaction synthesis method of boric acid and melamine, and then treated at 10-15GPa and 1500-2000℃. The boron nitride fiber prepared under high temperature and high pressure conditions has better heat conduction effect.

[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 superplasticizer.

[0021] Another object of the application is to provide a preparation method of the temperature self-balancing fine stone concrete.

[0022] M1. The components are weighed by weight fraction;

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

[0024] Compared with the prior art, the present application has the advantages of:

[0025] (1) The present application first prepares high-thermal-storage fine stone ceramsite, and then modifies the surface of the fine stone ceramsite by using a slurry containing boron nitride powder to form a surface layer with high thermal conductivity, thereby obtaining high-thermal-conductivity and high-thermal-storage aggregate; meanwhile, the boron nitride fiber with excellent thermal conductivity is introduced into the fine stone concrete to provide a high-efficiency heat exchange bridge connection, which can effectively transfer the heat absorbed by the surface layer of the fine stone concrete to the high-thermal-conductivity and high-thermal-storage aggregate, and the two can synergistically improve the rapid temperature change response capability of the interior of the fine stone concrete, so as to achieve the purpose of self-balancing the temperature gradient in the interior of the fine stone concrete with the change of the external temperature, thereby reducing the influence of the repeated change of the external environment temperature on the damage of the structure of the fine stone concrete, and enhancing the long-term durability of the fine stone concrete structure.

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

[0027] (3) The concrete of the present application uses high-thermal-conductivity and high-thermal-storage aggregate to replace part of the coarse aggregate, which can significantly reduce the mining and processing cost of natural aggregate and reduce the consumption of natural resources, and has significant economic value and environmental protection significance. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Temperature change graph of the concrete slab specimen of Example 1 at different depths;

[0029] Figure 2 Temperature change graph of the concrete slab specimen of Example 2 at different depths;

[0030] Figure 3 Temperature change graph of the concrete slab specimen of Comparative Example 1 at different depths;

[0031] Figure 4 Temperature change graph of the concrete slab specimen of Comparative Example 2 at different depths;

[0032] Figure 5 Temperature change graph of the concrete slab specimen of Comparative Example 3 at different depths;

[0033] Figure 6 Temperature change graph of the concrete slab specimen of Comparative Example 4 at different depths;

[0034] Figure 7 Temperature variation graph at different depths of the concrete slab test piece of Comparative Example 5. DETAILED DESCRIPTION

[0035] The technical solutions of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

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

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

[0038] S1. Mix coal gangue, fly ash, and mineral powder uniformly, add pore-forming agent and water, stir uniformly, then age, and then granulate, and after drying and sintering, obtain high-heat-storage fine stone ceramsite;

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

[0040] In some embodiments, the mass ratio of the coal gangue, fly ash, and mineral powder is (4-5):(3-4):(1-3). For example, the mass ratio of the coal 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℃ for 20-30min, and then sintering at 1050-1200℃ for 30-90min.

[0042] In some embodiments, the pore-forming agent comprises at least one of carbon powder, calcium carbonate, and magnesium carbonate.

[0043] In some embodiments, the mass of the boron nitride powder is 30%-60% of the total mass of the 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 the 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 electrostatic spinning method, an organic precursor conversion method, or a chemical reaction synthesis method of boric acid and melamine, and is obtained after being treated at 10-15 GPa and 1500-2000 DEG C.

[0045] In the present application, the SiO2 content in the coal gangue is 50-60%, the Al2O3 content is 30-35%, the Fe2O3 content is 1-2%, and the CaO content is 1-2%; the fly ash is F-class II fly ash recovered from a coal-fired power plant, with a particle size of ≤0.9 mm, a water demand ratio of ≤95%, a SiO2 content of 50-60%, an Al2O3 content of 10-15%, and a Fe2O3 content of 5-10%; the mineral powder is S95-grade mineral powder, with a SiO2 content of 30-40%, an Al2O3 content of 10-15%, and a CaO content of 40-50%; and the boron nitride powder is boron nitride powder obtained after hexagonal boron nitride powder is treated at 10-15 GPa and 1500-2000 DEG C, with a particle size of 5-50 μm, a purity of ≥99%, and an apparent density of 3000-3450 kg / m 3 ; the high-thermal-conductivity boron nitride fiber has a length of 10-15 mm, a diameter of 4-8 μm, an apparent density of 3000-3500 kg / m 3 , a tensile strength of ≥1000 MPa, an elastic modulus of ≥100 GPa, and a thermal conductivity of ≥25 W / (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 2600-2700 kg / m 3 ; the fine stone has a particle size of 5-10 mm and an apparent density of about 2700-2800 kg / m 3 ; and the polycarboxylate superplasticizer has a solid content of 35-50% and a water-reducing rate of ≥30%.

[0047] Unless otherwise specified, the following examples and comparative examples are prepared according to the following method:

[0048] M1. The components are weighed according to the proportions;

[0049] M2. The cement, fly ash, mineral powder, fine stone, and sand are sequentially added to a concrete mixer, stirred for 2 min, then the high-thermal-conductivity high-heat-storage aggregate is added and stirred for 1 min, then the polycarboxylate superplasticizer and water are mixed uniformly and poured into the concrete mixer, then the high-thermal-conductivity boron nitride fiber is added in small amounts and multiple times until completely mixed and uniform, to obtain a concrete slurry;

[0050] M3. Pour the concrete slurry into the mold, after vibrating and compacting, take mold curing for 20~30h, then standard curing for 28~30d, after demolding, the temperature self-balanced fine stone concrete is obtained.

[0051] Example 1

[0052] The temperature self-balanced fine stone concrete comprises the following components by weight: ordinary Portland cement P•O 42.5 170 parts, fly ash 50 parts, mineral powder 70 parts, high-thermal-conductivity and high-thermal-storage aggregate 311 parts, fine stone 802 parts, sand 900 parts, high-thermal-conductivity boron nitride fiber 45 parts, water 170 parts, and polycarboxylic acid water reducer 5 parts.

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

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

[0055] S2. The cement, fly ash and mineral powder are poured into a mixer according to a mass ratio of 6:2:2, and the mixer is started to mix for 1min; then water with a mass of 60% of the total mass of the cement, fly ash and mineral powder is added, and stirred for 60s; then boron nitride powder with a mass of 50% of the total mass of the cement, fly ash and mineral powder is added, and mixed for 2min to obtain a high-thermal-conductivity slurry; finally, a small amount of the high-thermal-storage fine stone ceramsite obtained in step S1 is uniformly poured into the mixer and stirred for 2min, and then taken out after the surface of the fine stone ceramsite is uniformly coated with the slurry, and then the excess slurry is filtered off and naturally air-dried for 24h, and then cured for 7d under the conditions of a temperature of 20±2℃ and a relative humidity of ≥95% to obtain the high-thermal-conductivity and high-thermal-storage fine stone aggregate.

[0056] Example 2

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

[0058] Comparative Example 1

[0059] The temperature self-balancing fine stone concrete of the present comparative example is basically the same as that of Example 1, except that in the preparation of the high-thermal-conductivity and high-heat-storage aggregate, step S2 is omitted.

[0060] That is, compared with Example 1, the high-heat-storage fine stone ceramsite of the present comparative example is not subjected to the surface coating modification treatment, and the concrete of the present comparative example directly uses the high-heat-storage fine stone ceramsite.

[0061] Comparative Example 2

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

[0063] Comparative Example 3

[0064] The temperature self-balancing fine stone concrete of the present comparative example is basically the same as that of Example 2, except that the high-thermal-conductivity and high-heat-storage aggregate is not added, and the weight fraction of the fine stone is 1070 parts.

[0065] Comparative Example 4

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

[0067] Comparative Example 5

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

[0069] The technical indexes of the high-thermal-conductivity and high-heat-storage fine stone aggregate of each example and comparative example are shown in Table 1.

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

[0071]

[0072] As can be seen from Table 1, compared with Comparative Example 1, the thermal conductivity and the cylinder compressive strength of the fine stone ceramsite of Examples 1 and 2 are obviously improved, which indicates that the high-thermal-conductivity coating slurry modification treatment on the surface layer of the high-heat-storage fine stone ceramsite can improve the thermal conductivity of the fine stone ceramsite.

[0073] In order to further compare the technical advantages of the temperature self-balancing fine stone concrete of the present application, the following test method is used to study the influence of repeated temperature changes on the apparent properties and the temperature change response law of each part inside the concrete:

[0074] (1) After the fine aggregate concrete of each example and comparative example was poured, the fresh concrete was poured into a 150 mm x 150 mm x 150 mm cubic mold, a 1500 mm x 300 mm x 500 mm wall type wooden mold, and a 600 mm x 600 mm x 40 mm plate type wooden mold, respectively; after being vibrated and compacted, the mold was cured for 24 h, and then standard curing was performed for 28 d. Among them, a temperature sensor was arranged every 10 mm in the depth direction at the center line section of the plate type wooden mold, the fine aggregate concrete was compacted by manual vibration, and after the curing was completed, it was naturally air-dried for 1 d.

[0075] (2) Each group of wall type test pieces was placed in a high temperature room, the indoor temperature was adjusted to 80℃±5℃, and the wall type test pieces were uniformly and constantly heated for 6 h; then the wall type test pieces were taken out, and the surface of the wall type test pieces was immediately sprayed with water and cooled for 3 min, which was 1 cycle, each group of wall type test pieces was cycled for 10 times, and after the cycle was completed, the number of surface cracks of the wall type test pieces was observed and recorded, and the results are shown in Table 2.

[0076] (3) After each group of plate type test pieces was placed in a high temperature room, one side was upward for high temperature treatment, and the other side was wrapped with heat insulation material. The indoor temperature was adjusted to 80℃±5℃, and the plate type test pieces were uniformly and constantly heated for 6 h, and then the data of each temperature sensor of the plate type test pieces was monitored and recorded; then the heated surface of the plate type test pieces was sprayed with water and cooled for 3 min, and the data of each temperature sensor of the plate type test pieces after being cooled was monitored and recorded, which was 1 cycle, each group of plate type test pieces was cycled for 3 times.

[0077] (4) Each group of cubic test pieces was subjected to cubic compressive strength test according to the “Standard for Test Methods of Physical and Mechanical Properties of Concrete” (GB / T 50081-2019), and the mechanical properties of each group of test pieces were evaluated.

[0078] Table 2: Apparent properties of each wall type test piece and compressive strength of each cubic test piece

[0079]

[0080] Note: The compressive strength data in the table is the compressive strength value of three groups of cubic test pieces without high temperature-cooling cycle.

[0081] As can be seen from Table 2, compared with Comparative Examples 1-5, the number of micro-cracks per unit area of the wall specimens of Examples 1 and 2 is reduced after 10 high-temperature-cooling cycles, because the high-thermal-conductivity boron nitride fibers and the high-thermal-conductivity high-heat-storage fine stone aggregates can work together to form a heat exchange system, rapidly transferring the energy released by the external environment to the inside of the fine stone concrete, reducing the negative impact of temperature stress on the internal structure of the fine stone concrete; in addition, it can also be found that the number of micro-cracks per unit area of the specimen of Example 2 is less than that of Example 1, indicating that increasing the content of high-thermal-conductivity boron nitride fibers and high-thermal-conductivity high-heat-storage fine stone aggregates can improve the ability of fine stone concrete to resist the negative effects of repeated temperature changes in the external environment, but the 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 1-2 and Comparative Examples 1-5 are shown in Figures 1 to 7 As can be seen from the figure, as the number of one-sided high-temperature-cooling cycles experienced by the slab specimen increases, the temperature gradient at each depth of Examples 1 and 2 gradually decreases, indicating that a large number of high-thermal-conductivity boron nitride fibers arranged in a staggered manner can rapidly transfer heat to the surface of high-thermal-conductivity high-heat-storage fine stone aggregates, which in turn store the absorbed heat; after the surface of the slab specimen cools down, the high-thermal-conductivity high-heat-storage fine stone aggregates in the fine stone concrete begin to release heat, which is transferred to the temperature-cooled area through the high-thermal-conductivity boron nitride fibers, delaying the rate of temperature decrease and gradually making the temperature of each layer inside the fine stone concrete slab consistent, reducing the adverse effects of external temperature changes on the initial defects in the fine stone concrete. The synergistic heat exchange system composed of high-thermal-conductivity boron nitride fibers and high-thermal-conductivity high-heat-storage fine stone aggregates has a significant temperature self-balancing effect in the fine stone concrete.

[0083] Compared with Example 1, Comparative Example 1 did not modify the surface of the high-heat-storage fine stone aggregate with high-thermal-conductivity grouting, resulting in a large temperature gradient at each depth during the first one-sided high-temperature-cooling cycle, and as the number of cycles increases, the temperature at 20mm and 30mm of the slab specimen tends to be consistent, but the difference with the surface temperature is still large.

[0084] Comparative Example 2 only contains high-thermal-conductivity high-heat-storage fine stone aggregates without high-thermal-conductivity boron nitride fibers, resulting in a low heat exchange efficiency in the fine stone concrete slab and a large temperature gradient at each depth.

[0085] The comparative example 3 only incorporates high-thermal-conductivity boron nitride fibers, and does not incorporate high-thermal-conductivity high-heat-storage fine stone aggregates, resulting in poor heat preservation capacity of the fine stone concrete slab specimen when subjected to repeated temperature changes, and the temperature gradient at the depths of 10 mm and 20 mm is significantly increased; the comparative example 4 is a fine stone concrete blank control group, and with the increase of the number of high-temperature-cooling cycles, the temperature gradient at each depth is large, and there is no trend of temperature tending to be consistent, which is prone to induce the formation of microcracks.

[0086] The comparative example 5 only incorporates high-heat-storage fine stone ceramsite and boron nitride powder, and compared with the comparative example 1 incorporating boron nitride fibers, the number of effective heat exchange paths formed in the fine stone concrete in this example is relatively small, and at the same time, the surface of the fine stone ceramsite is not modified by slurry, resulting in a large temperature gradient in the slab specimen after multiple cycles.

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

[0088] In summary, the present application prepares high-heat-storage fine stone ceramsite by taking coal gangue, fly ash and mineral powder as raw materials, and modifies the surface of the high-heat-storage fine stone ceramsite by high-thermal-conductivity slurry, and at the same time, incorporates high-thermal-conductivity boron nitride fibers to prepare fine stone concrete. When the external environment temperature changes suddenly, the synergistic heat exchange system formed by the high-thermal-conductivity high-heat-storage fine stone aggregates and the high-thermal-conductivity boron nitride fibers in the fine stone concrete quickly responds, adjusts and balances the temperature at each depth of the fine stone concrete, reduces the adverse effects of repeated temperature changes caused by seasons on the formation of microcracks at the initial defects in the fine stone concrete, achieves the purpose of temperature self-balancing without significantly affecting the strength of the fine stone concrete, reduces the risk of cracks in the peripheral structure of the building, and reduces the later engineering repair costs.

[0089] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A temperature self-compensating fine aggregate concrete, characterized by, The concrete comprises the following components in parts by weight: cementitious material 220-360 parts, high-thermal-conductivity and high-thermal-storage aggregate 311-733 parts, fine stone 474-802 parts, sand 850-950 parts, high-thermal-conductivity boron nitride fiber 45-70 parts, water 150-250 parts, and additive 3-6 parts. The preparation method of the high-thermal-conductivity and high-thermal-storage aggregate comprises the following steps: S1. uniformly mixing coal gangue, fly ash, and mineral powder, adding pore-forming agent and water, stirring uniformly, aging, then granulating, drying, and sintering to obtain high-thermal-storage fine stone ceramsite; S2. uniformly mixing cement, fly ash, and mineral powder, adding water and stirring, then adding boron nitride powder, mixing uniformly to obtain high-thermal-conductivity slurry, then adding the high-thermal-storage fine stone ceramsite obtained in step S1 into the high-thermal-conductivity slurry, and taking out and curing to obtain the high-thermal-conductivity and high-thermal-storage aggregate.

2. A temperature self-compensating fine aggregate concrete according to claim 1, wherein In step S1, the mass ratio of the coal gangue, fly ash, and mineral powder is (4-5):(3-4):(1-3).

3. A temperature self-compensating fine aggregate concrete according to claim 1, wherein In step S1, the sintering conditions are: pre-sintering at 400-500℃ for 20-30min, and then sintering at 1050-1200℃ for 30-90min.

4. A temperature self-compensating fine aggregate concrete according to claim 1, wherein In step S1, the pore-forming agent comprises at least one of carbon powder, calcium carbonate, and magnesium carbonate.

5. A temperature self-compensating fine aggregate concrete according to claim 1, wherein In step S2, the mass of the boron nitride powder is 30%-60% of the total mass of the cement, fly ash, and mineral powder.

6. A temperature self-compensating fine stone concrete according to claim 1, wherein In step S2, the boron nitride powder is boron nitride powder obtained by treating hexagonal boron nitride powder at 10-15GPa and 1500-2000℃.

7. A temperature self-compensating fine stone concrete according to claim 1, wherein The apparent density of the high-thermal-conductivity high-thermal-storage aggregate is less than or equal to 1800 kg / m 3 The barrel pressure strength is greater than or equal to 5 MPa, the thermal conductivity is greater than or equal to 4 W / (m.K), and the specific heat capacity is greater than or equal to 1100 J / (kg.K).

8. A temperature self-compensating fine stone concrete according to claim 1, wherein The high-thermal-conductivity boron nitride fiber is obtained by treating coarse boron nitride fiber synthesized by inorganic precursor conversion method, electrospinning method, organic precursor conversion method, or chemical reaction synthesis method of boric acid and melamine at 10-15GPa and 1500-2000℃.

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

10. Process for the production of a temperature self-balancing fine aggregate concrete according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: M1. taking components by weight; M2. dry mixing the cementitious material, fine stone, and sand uniformly, adding the high-thermal-conductivity and high-thermal-storage aggregate, dry mixing uniformly, then adding the additive and water, mixing uniformly, then adding the high-thermal-conductivity boron nitride fiber, mixing uniformly to obtain a concrete slurry, and then molding to obtain the temperature self-balancing fine stone concrete.

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