A mass concrete and a method for producing the same

Abstract

The application relates to the technical field of concrete preparation, and particularly discloses a mass concrete and a preparation method thereof. The mass concrete is prepared from the following raw materials in parts by weight: cement 330-450 parts, fine aggregate 430-510 parts, coarse aggregate 1000-1200 parts, viscosity reducer 3-9 parts, additive 3-10 parts, fly ash 50-100 parts and MXene composite phase change material 5-15 parts. By introducing the MXene composite phase change material, the internal and external temperature difference and the temperature peak caused by the hydration reaction heat release of the mass concrete before and during maintenance are effectively reduced, so that the generation of temperature cracks is inhibited. In addition, the concrete effectively reduces the temperature stress caused by the uneven temperature distribution in a large temperature difference environment, and improves the volume stability of the structure. The concrete has excellent working performance, weather resistance and construction performance, high early strength and stable performance.

Description

Technical Field

[0001] This invention belongs to the field of concrete preparation technology, specifically relating to a large-volume concrete and its preparation method. Background Technology

[0002] Concrete, an indispensable engineering material in the construction field, is abundant, inexpensive, and easy to construct, leading to its widespread application in building and bridge engineering. However, due to its intense hydration reaction during pouring, the internal temperature rises too quickly, resulting in a significant increase in the temperature difference between the inside and outside, thus forming temperature cracks, affecting structural safety and shortening service life. Compared to ordinary concrete, mass concrete is characterized by its heavy structure, large volume, high technical requirements, and large heat of hydration. Different countries have different definitions of mass concrete. The current concrete construction specifications in the United States, Japan, and my country have relatively vague definitions of mass concrete, but all agree that when the concrete size reaches a certain level, temperature control measures must be taken to inhibit the internal hydration reaction, prevent excessive temperature rise, and thus prevent temperature cracks and ensure structural safety. The foundations, abutments, and main towers in bridge engineering all belong to mass concrete. Its specific characteristics are as follows: ① Large size, large amount of various materials used; for large bridge structures, the construction environment is complex, the technical requirements are high, and it is greatly affected by the external environment, making temperature control difficult; ② Low tensile strength, usually used in conjunction with steel reinforcement, the excellent tensile properties of the steel reinforcement optimize its own load-bearing capacity. However, due to the reduced reinforcement in large-volume concrete, it requires stronger tensile strength compared to ordinary reinforced concrete structures. ③ For large-volume concrete in bridge engineering, not only sufficient strength, stiffness, and stability are needed, but also strong impermeability and waterproofing capabilities. Bridge piers and abutments are both large-volume concrete structures. During concrete pouring, the internal hydration reaction generates a large amount of heat. Due to the poor heat dissipation performance of concrete itself, internal heat accumulates continuously, and the temperature rises steadily. When the temperature reaches its peak, without necessary temperature control measures, a large temperature difference will form between the inside and outside of the concrete. Initially, the concrete strength is low, and its load-bearing capacity is poor, unable to withstand thermal shrinkage stress. Once this load-bearing capacity is exceeded, cracks will inevitably form. Continued development of these cracks will further lead to more serious structural cracks, reducing structural stability and affecting service safety and lifespan.

[0003] Current methods for controlling temperature cracking in mass concrete mainly include increasing the water-cement ratio, adding alkali-activated slag cementitious materials, layered pouring, and laying cooling pipes inside the concrete. However, these methods suffer from problems such as low early strength, high construction difficulty, limited applicability to various structural forms, and high economic costs. Based on the above analysis, it is essential to provide a mass concrete method with low temperature cracking. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned shortcomings of the prior art by providing large-volume concrete and its preparation method, thereby solving the problem that large-volume precast concrete is prone to large-scale temperature crack formation during the curing process due to uneven internal and external temperature distribution.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first objective of this invention is to provide a large-volume concrete, made from the following raw materials in parts by weight: 330-450 parts cement, 430-510 parts fine aggregate, 1000-1200 parts coarse aggregate, 3-10 parts admixture, 3-9 parts viscosity reducer, 50-100 parts fly ash, and 5-15 parts MXene composite phase change material. The MXene composite phase change material is prepared by the following method: a mixture of MXene nanosheets, oleophilic modified microcrystalline graphite, phase change aggregate, modified peanut shell powder, and polyvinyl alcohol is spread evenly on a metal mold, then glutaraldehyde solution is added dropwise, stirred evenly, and heated to obtain an MXene composite phase change film; then the MXene composite phase change film is shredded, and polyvinyl alcohol is coated onto the MXene composite phase change film fragments using a suspension spray method, and dried to obtain the MXene composite phase change material.

[0007] Furthermore, the mass ratio of the MXene nanosheets, oleophilic modified microcrystalline graphite, phase change aggregate, modified peanut shell powder, and polyvinyl alcohol solution is 1:(0.02~0.05):(0.2~0.4):(0.05~0.1):(0.3~0.5).

[0008] Furthermore, the particle size range of MXene nanosheets is 200~800nm.

[0009] Furthermore, the MXene composite phase change membrane is shredded to a particle size of 0.5~2mm, and then polyvinyl alcohol is coated onto the MXene composite phase change membrane fragments using a suspension spray method and dried to obtain the MXene composite phase change membrane.

[0010] Furthermore, the preparation process of the oleophilic modified microcrystalline graphite is as follows: 0.5-1 parts of stearic acid are dissolved in a solvent composed of 250 parts of deionized water and 50 parts of anhydrous ethanol, followed by the addition of 10 parts of microcrystalline graphite and 0.55 parts of aluminum chloride hexahydrate as a catalyst to obtain a first suspension; then the water bath temperature is raised to 70-80℃, the stirring rate is 200-300 r / min, and the stirring is carried out for 2-2.5 h, followed by washing and drying to obtain the oleophilic modified microcrystalline graphite.

[0011] Furthermore, the preparation process of the phase change micro-aggregate is as follows: 0.5-1 parts of disodium hydrogen phosphate dodecahydrate and 1 part of sodium sulfate dihydrate are uniformly mixed to obtain a phase change core material, and 0.1-0.2 parts of glycerol are added to inhibit phase separation of the phase change material; 1 part of the phase change core material is mixed with 0.5 parts of expanded perlite, and then heated to completely melt the phase change core material; subsequently, negative pressure is applied to allow the phase change core material to be absorbed into the expanded perlite to obtain the phase change aggregate.

[0012] Furthermore, the cement is P.O42.5 low-alkali cement; the viscosity reducer is K-335.

[0013] Furthermore, the fine aggregate is natural river sand with a mud content of 0.9% and a fineness modulus of 2.6-2.8; the coarse aggregate is continuously graded basalt crushed stone with a particle size of 5-20 mm and an apparent density of 2740-2900 kg / m³. 3 The crushing value is 7-9%.

[0014] Furthermore, the fly ash is Class F, Grade I fly ash, with a loss on ignition of 1.5-3.5% and a water requirement ratio of 90-95%.

[0015] The second objective of this invention is to provide a method for preparing the above-mentioned large-volume concrete, wherein cement, fine aggregate, coarse aggregate, fly ash, viscosity reducer and MXene composite phase change material are mixed evenly, water and admixtures are added, and the mixture is mixed, stirred and cured to obtain large-volume concrete with low temperature cracking degree.

[0016] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are:

[0017] (1) The mass concrete prepared in this application effectively reduces the internal and external temperature differences and temperature peaks caused by the exothermic hydration reaction before and during the curing process by introducing MXene composite phase change material, thereby inhibiting the formation of temperature cracks. In addition, this concrete effectively reduces the temperature stress caused by uneven temperature distribution in a large temperature difference environment, and improves the volume stability of the structure. This concrete has excellent workability, weather resistance and construction performance, high early strength and stable performance.

[0018] (2) This application uses concentrated hydrochloric acid and hydrogen fluoride as etching solutions to treat titanium aluminum carbide, which effectively increases the specific surface area of ​​titanium aluminum carbide, improves the compatibility of titanium aluminum carbide with polyvinyl alcohol, makes it more uniformly distributed, and improves the stability and safety of MXene composite phase change material; at the same time, titanium aluminum carbide has high thermal conductivity, which improves the sensitivity and response of phase change material to concrete temperature changes.

[0019] (3) This application introduces oleophilic modified microcrystalline graphite to improve the compatibility of graphite and polyvinyl alcohol, which can greatly improve the uniformity of graphite distribution. Microcrystalline graphite has excellent thermal conductivity, which significantly improves the thermal sensitivity of MXene composite phase change material and makes the response speed and accuracy of concrete temperature control higher.

[0020] (4) This application uses expanded perlite as porous aggregate and composes a high thermal conductivity phase change core material with disodium hydrogen phosphate dodecahydrate and sodium sulfate dihydrate. It has the characteristics of low raw material cost, easy mass production, and low risk of leakage of phase change core material. The phase change core material has high temperature sensitivity and wide sensing temperature range, which makes the internal temperature regulation of concrete more stable and controllable.

[0021] (5) This application introduces organic long fibers into large-volume concrete by adding modified peanut shell powder, which effectively enhances the toughness of large-volume concrete and significantly improves the compressive and tensile strength of concrete. The modified peanut shell powder has good compatibility with MXene composite phase change material carrier and cement paste. The dosage can be adjusted arbitrarily within a large range according to the needs. It is also environmentally friendly and low in cost. Attached Figure Description

[0022] Figure 1 The image shows a transmission electron microscope (TEM) image of Mxene nanosheets; it was observed that the prepared nanosheets have a particle size of 200–800 nm and are a single-layer structure.

[0023] Figure 2 and Figure 3 The images are scanning electron microscope (SEM) images of the Mxene composite material. It is observed that the Mxene composite material has a multilayer structure with a large number of phase change aggregates embedded in the layered structure.

[0024] Figure 4 The differential scanning calorimetry (DSC) curve of the Mxene composite material shows that the phase transition temperature of the Mxene composite material is 49.1℃ and the latent heat of phase transition is 89.5 J / g.

[0025] Figure 5 Photographs of concrete surface cracks prepared in Example 6;

[0026] Figure 6 Photographs of concrete surface cracks prepared for Comparative Example 1. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments and accompanying drawings are described in further detail below. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0028] The large-volume concrete provided in this application embodiment includes 330~450 kg / m³ of cement by weight. 3 Fine aggregate 430~510kg / m³ 3 Coarse aggregate 1000~1200kg / m³ 3 Admixture 3~10kg / m 3 fly ash 50~100kg / m³ 3 MXene composite phase change material 5~15kg / m 3 The MXene composite phase change material comprises MXene nanosheets, phase change aggregate, oleophilic modified microcrystalline graphite, modified peanut shell powder, and polyvinyl alcohol. The phase change aggregate includes a phase change core composed of disodium hydrogen phosphate dodecahydrate and sodium sulfate dihydrate, and expanded perlite (as porous aggregate). The cement is P.O42.5 low-alkali cement. The viscosity reducer K-335 has a viscosity ratio of 23, a fluidity ratio of 112, and a 28-day compressive strength ratio of 92. The fine aggregate is natural river sand with a mud content of 0.9% and a fineness modulus of 2.6-2.8. The coarse aggregate is continuously graded basalt crushed stone with a particle size of 5-20 mm and an apparent density of 2740-2900 kg / m³. 3 The crushing value is 7-9%; the fly ash is Class F, Grade I fly ash, with a loss on ignition of 1.5-3.5% and a water requirement ratio of 90-95%.

[0029] Adding viscosity reducers can lower the plastic viscosity of concrete, which can effectively improve the workability and pumpability of concrete.

[0030] MXene nanosheets are prepared through the following process:

[0031] An etching solution was prepared by mixing 500 mL of concentrated hydrochloric acid and 500 mL of hydrogen fluoride in a molar ratio of 1:1. Titanium aluminum carbide was dried at 30 °C. 10 g of the dried titanium aluminum carbide was added to the etching solution (molar ratio 1:1), and the mixture was stirred continuously at 200 rpm for 1.5 h to obtain a titanium aluminum carbide suspension. The etched titanium aluminum carbide was washed five times, and then the suspension was centrifuged and freeze-dried to obtain MXene nanosheets. Figure 1 The image shown is a transmission electron microscope (TEM) image of Mxene nanosheets; it was observed that the prepared nanosheets have a particle size of 200-800 nm and are a single-layer structure.

[0032] Modified peanut shell powder is obtained through the following process:

[0033] After drying, peanut shells are crushed to below 300 mesh. A 1L solution of 0.1% HCl is prepared using deionized water and concentrated hydrochloric acid. The peanut shell powder is then immersed in the 0.1% HCl solution and acid-washed for 12 hours. Ammonia water is then added to neutralize the solution, and the mixture is dried to obtain modified peanut shell powder.

[0034] Lipophilic modified microcrystalline graphite is prepared by the following process:

[0035] 0.7 g stearic acid was dissolved in a solvent consisting of 250 mL deionized water and 50 mL anhydrous ethanol. Then, 10 g microcrystalline graphite and 0.55 g aluminum chloride hexahydrate were added as a catalyst to obtain the first suspension. The water bath temperature was then raised to 73 °C, the stirring rate was 300 r / min, and the mixture was stirred for 2 h. After washing and drying, oleophilic modified microcrystalline graphite was obtained.

[0036] Phase change aggregates are produced through the following process:

[0037] Mix 0.8g of disodium hydrogen phosphate dodecahydrate and 1g of sodium sulfate dihydrate evenly, and add 0.1~0.2mL of glycerol to obtain phase change core material. Mix 1 part of phase change core material with 0.5g of expanded perlite and place it in a 70℃ water bath environment to completely melt the phase change core material. Then, apply negative pressure to allow the phase change core material to be absorbed into the expanded perlite to obtain phase change aggregate.

[0038] MXene composite phase change materials are prepared through the following process:

[0039] A mixture of 1g MXene nanosheets, 0.05g oleophilic modified microcrystalline graphite, 0.3g phase change aggregate, 0.1g modified peanut shell powder, and 0.4g polyvinyl alcohol solution was spread evenly on a metal mold. Then, a glutaraldehyde solution accounting for 2% of the mass fraction of polyvinyl alcohol was added dropwise, stirred evenly, and heated to 70℃ for 2 hours to initially obtain an MXene composite phase change film. The MXene composite phase change film was then shredded to a particle size of 0.8mm, and polyvinyl alcohol was coated onto the MXene composite phase change film fragments using a suspension spray method. After drying, the MXene composite phase change material was obtained. Figure 2 and Figure 3 The images shown are scanning electron microscope (SEM) images of the Mxene composite material. It is observed that the Mxene composite material has a multilayered structure, with a large amount of phase change aggregate embedded within the layered structure; as shown... Figure 4 The figure shows the differential scanning calorimetry (DSC) curve of the Mxene composite material. The phase transition temperature of the Mxene composite material is 49.1℃, and the latent heat of phase transition is 89.5 J / g.

[0040] Description of raw materials used in the embodiments of this invention:

[0041] Viscosity reducer K-335: purchased from Xinda Henglian (Beijing) Engineering Materials Technology Co., Ltd.;

[0042] Admixture: Polycarboxylate superplasticizer, purchased from Jiangsu Subote Co., Ltd., with a water reduction rate of 28%;

[0043] Example 1

[0044] This embodiment 1 provides a method for preparing large-volume concrete, including the following steps:

[0045] Step S101: By weight, 1g of MXene nanosheets, 0.04g of oleophilic modified microcrystalline graphite, 0.35g of phase change aggregate, 0.075g of modified peanut shell powder, and 0.4mL of polyvinyl alcohol solution are spread evenly on a metal mold. Then, glutaraldehyde solution accounting for 2% of the mass fraction of polyvinyl alcohol is added dropwise, stirred evenly, and heated to 70℃ for 2.5h to initially obtain an MXene composite phase change film. The above MXene composite phase change film is chopped into pieces with a particle size of 0.5~1.5mm. Then, polyvinyl alcohol is coated on the MXene composite phase change film fragments using a suspension spray method and dried to obtain the MXene composite phase change material.

[0046] Step S102, by mass, 380 kg / m 3 Cement, 470kg / m 3 Fine aggregate, 1100 kg / m³ 3 Coarse aggregate, 7kg / m 3 Viscosity reducer K-335, 80 kg / m 3 fly ash, 5 kg / m³ 3 After the MXene composite phase change material is mixed evenly, 210 kg / m³ of water is added. 3 Water and admixtures are mixed and stirred to produce large-volume concrete.

[0047] In Example 1, the fine aggregate was river sand with a fineness modulus of 2.6 and a mud content of 0.9%; the coarse aggregate was 5-20mm continuously graded granite crushed stone with an apparent density of 2740 kg / m³. 3 The crushing value is 8%.

[0048] Example 2

[0049] This embodiment provides a method for preparing large-volume concrete, including the following steps:

[0050] Step S101: By weight, 1g of MXene nanosheets, 0.02g of oleophilic modified microcrystalline graphite, 0.2g of phase change aggregate, 0.05g of modified peanut shell powder, and 0.3mL of polyvinyl alcohol solution are spread evenly on a metal mold. Then, glutaraldehyde solution accounting for 2% of the mass fraction of polyvinyl alcohol is added dropwise, stirred evenly, and heated to 70℃ for 2 hours to initially obtain an MXene composite phase change film. The above MXene composite phase change film is chopped into pieces with a particle size of 0.1~2mm. Then, polyvinyl alcohol is coated on the MXene composite phase change film fragments using a suspension spray method and dried to obtain the MXene composite phase change material.

[0051] Step S102, by mass, 330 kg / m 3 Cement, 430kg / m 3 Fine aggregate, 1000 kg / m³ 3 Coarse aggregate, 3kg / m 3 Viscosity reducer K-335, 50 kg / m 3 Fly ash, 5.8 kg / m³ 3 After the MXene composite phase change material is mixed evenly, 170 kg / m³ of it is added. 3 Water and admixtures are mixed and stirred to produce large-volume concrete.

[0052] In Example 2, the fine aggregate was river sand with a fineness modulus of 2.8 and a mud content of 0.9%; the coarse aggregate was 10-20mm continuously graded granite crushed stone with an apparent density of 2740 kg / m³. 3 The crushing value is 7%.

[0053] Example 3

[0054] This embodiment provides a method for preparing large-volume concrete, including the following steps:

[0055] Step S101: By weight, 1g of MXene nanosheets, 0.04g of oleophilic modified microcrystalline graphite, 0.25g of phase change aggregate, 0.08g of modified peanut shell powder, and 0.35mL of polyvinyl alcohol solution are spread evenly on a metal mold. Then, glutaraldehyde solution accounting for 2% of the mass fraction of polyvinyl alcohol is added dropwise, stirred evenly, and heated to 70℃ for 2 hours to initially obtain an MXene composite phase change film. The above MXene composite phase change film is chopped into pieces with a particle size of 0.5~2mm. Then, polyvinyl alcohol is coated on the MXene composite phase change film fragments using a suspension spray method and dried to obtain the MXene composite phase change material.

[0056] Step S102, by mass, 330 kg / m 3 Cement, 460kg / m 3 Fine aggregate, 1050 kg / m³ 3 Coarse aggregate, 4.7 kg / m³ 3 Viscosity reducer K-335, 68 kg / m 3 Fly ash, 7.3 kg / m³ 3 After the MXene composite phase change material is mixed evenly, 195 kg / m³ of it is added. 3 Water and admixtures are mixed and stirred to produce large-volume concrete.

[0057] In Example 3, the fine aggregate was river sand with a fineness modulus of 2.8 and a mud content of 0.8%; the coarse aggregate was 5-10mm continuously graded granite crushed stone with an apparent density of 2850 kg / m³.3 The crushing value is 9%.

[0058] Example 4

[0059] This embodiment provides a method for preparing large-volume concrete, including the following steps:

[0060] In step S101, by weight, 1g of MXene nanosheets, 0.03g of oleophilic modified microcrystalline graphite, 0.36g of phase change aggregate, 0.077g of modified peanut shell powder, and 0.45mL of polyvinyl alcohol solution are spread evenly on a metal mold. Then, glutaraldehyde solution accounting for 2% of the mass fraction of polyvinyl alcohol is added dropwise, stirred evenly, and heated to 70℃ for 2 hours to initially obtain an MXene composite phase change film. The above MXene composite phase change film is chopped into pieces with a particle size of 0.7-1.8mm. Then, polyvinyl alcohol is coated on the MXene composite phase change film fragments using a suspension spray method and dried to obtain the MXene composite phase change material.

[0061] Step S102, by mass, 420 kg / m 3 Cement, 500 kg / m 3 Fine aggregate, 1160 kg / m³ 3 Coarse aggregate, 6.5 kg / m³ 3 Viscosity reducer K-335, 85 kg / m 3 Fly ash, 9.5 kg / m³ 3 After the MXene composite phase change material is mixed evenly, 188 kg / m³ of it is added. 3 Water and admixtures are mixed and stirred to produce large-volume concrete.

[0062] In Example 4, the fine aggregate was river sand with a fineness modulus of 2.6 and a mud content of 1.2%; the coarse aggregate was 5-20mm continuously graded granite crushed stone with an apparent density of 2810 kg / m³. 3 The crushing value is 7%.

[0063] Example 5

[0064] Embodiment 5 of this application provides a method for preparing large-volume concrete with low temperature cracking degree, including the following steps:

[0065] Step S101: By weight, 1g of MXene nanosheets, 0.04g of oleophilic modified microcrystalline graphite, 0.31g of phase change aggregate, 0.1g of modified peanut shell powder, and 0.5mL of polyvinyl alcohol solution are spread evenly on a metal mold. Then, glutaraldehyde solution accounting for 2% of the mass fraction of polyvinyl alcohol is added dropwise, stirred evenly, and heated to 70℃ for 2 hours to initially obtain an MXene composite phase change film. The above MXene composite phase change film is chopped into pieces with a particle size of 0.5-2mm. Then, polyvinyl alcohol is coated on the MXene composite phase change film fragments using a suspension spray method and dried to obtain the MXene composite phase change material.

[0066] Step S102, by mass, 360 kg / m 3 Cement, 488kg / m 3 Fine aggregate, 1190 kg / m³ 3 Coarse aggregate, 9kg / m 3 Viscosity reducer K-335, 82 kg / m 3 Fly ash, 9.8 kg / m³ 3 After the MXene composite phase change material is mixed evenly, 174 kg / m³ of it is added. 3 Water and admixtures are mixed and stirred to produce large-volume concrete.

[0067] In Example 5, the fine aggregate was river sand with a fineness modulus of 2.8 and a mud content of 0.9%; the coarse aggregate was 5-18mm continuously graded granite crushed stone with an apparent density of 2900 kg / m³. 3 The crushing value is 8%.

[0068] Example 6

[0069] This embodiment provides a method for preparing large-volume concrete, including the following steps:

[0070] Step S101: By weight, 1g of MXene nanosheets, 0.022g of oleophilic modified microcrystalline graphite, 0.34g of phase change aggregate, 0.058g of modified peanut shell powder, and 0.41mL of polyvinyl alcohol solution are spread evenly on a metal mold. Then, glutaraldehyde solution accounting for 2% of the mass fraction of polyvinyl alcohol is added dropwise, stirred evenly, and heated to 70℃ for 2 hours to initially obtain an MXene composite phase change film. The above MXene composite phase change film is chopped into pieces with a particle size of 0.5~2mm. Then, polyvinyl alcohol is coated on the MXene composite phase change film fragments using a suspension spray method and dried to obtain the MXene composite phase change material.

[0071] Step S102, by mass, 368 kg / m 3 Cement, 495 kg / m 3 Fine aggregate, 1156 kg / m³3 Coarse aggregate, 7kg / m 3 Viscosity reducer K-335, 65 kg / m 3 Fly ash, 14.5 kg / m³ 3 After the MXene composite phase change material is mixed evenly, add 200 kg / m 3 Water and admixtures are mixed and stirred to produce mass concrete. The degree of surface cracking at low temperatures is as follows: Figure 5 As shown.

[0072] In Example 6, the fine aggregate was river sand with a fineness modulus of 2.8 and a mud content of 0.8%; the coarse aggregate was 5-20mm continuously graded granite crushed stone with an apparent density of 2870 kg / m³. 3 The crushing value is 7%.

[0073] Comparative Example 1

[0074] By mass fraction, 440 kg / m 3 Cement, 480kg / m 3 Fine aggregate, 1200 kg / m³ 3 Coarse aggregate, 9kg / m 3 Viscosity reducer, 86 kg / m 3 fly ash, 4 kg / m³ 3 Phase change aggregate, 0.8 g / m³ 3 Modified peanut shell powder, 10kg / m 3 After the MXene nanosheets are mixed evenly, 200 kg / m 3 Water and admixtures are mixed and stirred to produce mass concrete. The degree of surface cracking at low temperatures is as follows: Figure 6 As shown.

[0075] In Comparative Example 1, the fine aggregate was river sand with a fineness modulus of 2.6 and a mud content of 1.1%; the coarse aggregate was 5-20mm continuously graded granite crushed stone with an apparent density of 2760 kg / m³. 3 The crushing value is 9%.

[0076] In accordance with the requirements of GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", the mechanical properties of the concrete prepared in Example 1, Example 6 and Comparative Example 1 were tested, and the results are shown in Table 1. In accordance with the requirements of GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the adiabatic temperature rise value of the concrete prepared in Example 1, Example 6 and Comparative Example 1 was tested using a concrete adiabatic temperature rise tester, and the results are shown in Table 2.

[0077] Table 1: Test results of workability and mechanical properties of concrete prepared in Examples 1-5 and Comparative Example 1

[0078]

[0079] Table 2: Test Results of Concrete Insulation Temperature Rise Test

[0080]

[0081] As shown in Table 1, within a certain range, adding more MXene composite phase change material is beneficial to reducing the scale of temperature cracks, which is reflected in the gradual reduction of the width of cracks on the concrete surface. Compared with the comparative example, the maximum width of surface cracks in Example 6 was reduced by 55.2%.

[0082] As shown in Table 2, with the increase of MXene composite phase change material content, the adiabatic temperature rise value of each example group at 7d gradually decreased. This is attributed to the solid-liquid phase change of the phase change material, which absorbed some of the heat released during cement hydration.

[0083] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A mass concrete, characterized by, The cement 330-450 parts, fine aggregate 430-510 parts, coarse aggregate 1000-1200 parts, additive 3-10 parts, viscosity reducer 3-9 parts, fly ash 50-100 parts, MXene composite phase change material 5-15 parts are prepared by weight parts of raw materials, the MXene composite phase change material is prepared by the following method: MXene nanosheet, lipophilic modified microcrystalline graphite, phase change aggregate, modified peanut shell powder, polyvinyl alcohol solution mixture is spread on the metal mold, then drop the glutaraldehyde solution, stir evenly, heat, the MXene composite phase change film is obtained; then the MXene composite phase change film is cut into pieces, then the polyvinyl alcohol is covered on the MXene composite phase change film fragments by using the suspension spray method, dried, the MXene composite phase change material is obtained; the additive is polycarboxylic acid type water reducing agent.

2. Mass concrete according to claim 1, characterized in that The mass ratio of the MXene nanosheet, lipophilic modified microcrystalline graphite, phase change aggregate, modified peanut shell powder, polyvinyl alcohol solution is 1: (0.02-0.05): (0.2-0.4): (0.05-0.1): (0.3-0.5).

3. Mass concrete according to claim 2, characterized in that The particle size of the MXene nanosheet is 200-800 nm.

4. Mass concrete according to claim 3, characterized in that The MXene composite phase change film is cut into pieces, the particle size is 0.5-2 mm, then the polyvinyl alcohol is covered on the MXene composite phase change film fragments by using the suspension spray method, dried, the MXene composite phase change film is obtained.

5. Mass concrete according to claim 4, characterized in that The preparation process of the lipophilic modified microcrystalline graphite is as follows: 0.5-1 parts of stearic acid is dissolved in a solvent composed of 250 parts of deionized water and 50 parts of anhydrous ethanol, then 10 parts of microcrystalline graphite and 0.55 parts of aluminum chloride hexahydrate as catalyst are added to obtain a first suspension; then the water bath temperature is increased to 70-80℃, the stirring rate is 200-300 r / min, stirring for 2-2.5 h, washing and drying to obtain the lipophilic modified microcrystalline graphite.

6. Mass concrete according to claim 5, characterized in that The preparation process of the phase change aggregate is as follows: 0.5-1 parts of disodium hydrogen phosphate dodecahydrate and 1 part of sodium sulfate dihydrate are uniformly mixed to obtain a phase change core material, and 0.1-0.2 parts of glycerol is added to inhibit the phase separation of the phase change material; 1 part of the phase change core material is mixed with 0.5 parts of expanded perlite, and then heated to completely melt the phase change core material; then, negative pressure is drawn, so that the phase change core material is absorbed into the expanded perlite to obtain the phase change aggregate.

7. Mass concrete according to claim 1, characterized in that The cement is P.O42.5 low alkali cement.

8. Mass concrete according to claim 1, characterized in that The fine aggregate is natural river sand, the clay content of which is 0.9%, and the fineness modulus is 2.6~2.8; the coarse aggregate is continuous gradation basalt gravel with a particle size of 5~20mm, and the apparent density is 2740~2900kg / m 3 , and the crushing value is 7~9%.

9. Mass concrete according to claim 1, characterized in that The fly ash is F-class I-grade fly ash, the loss on ignition is 1.5-3.5%, and the water requirement ratio is 90-95%.

10. A method for the production of mass concrete according to any one of claims 1 to 9, characterized in that After the cement, fine aggregate, coarse aggregate, fly ash, viscosity reducer and MXene composite phase change material are uniformly mixed, water and additive are added, mixed, stirred and cured, the low temperature crack degree of mass concrete is obtained.

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