A large-volume concrete and its preparation method

Abstract

This invention relates to the field of building materials technology, and in particular to a large-volume concrete and its preparation method, to alleviate the technical problem of cracking in large-volume concrete. The large-volume concrete includes a low-heat-of-hydration composite cementitious material and a hydration inhibitor. The low-heat-of-hydration composite cementitious material is prepared by mixing the following components in the following mass ratio: modified electrolytic manganese slag powder: modified steel slag ultrafine powder: alkali-activated glass micro powder: fly ash = (5-8):(3-6):(2-4):(6-8); wherein, the hydration inhibitor is prepared by mixing the following components in the following mass ratio: aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid complex: zinc gluconate: modified calcium lignin sulfonate: nano calcium carbonate = (35-40):(40-45):(15-20):(3-5); wherein, in the aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid complex, the mass ratio of aminotrimethylenephosphonic acid to hydroxyethylidene diphosphonic acid is 3:1. The large-volume concrete of this invention can effectively inhibit cracking.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a large-volume concrete and its preparation method. Background Technology

[0002] Due to their large size and thickness, the massive heat of hydration released during cement hydration in large-volume concrete structures is difficult to dissipate, leading to significant temperature differences and gradients between the interior and surface. This uneven temperature field directly induces uneven volume shrinkage, which in turn creates thermal stress within the concrete. When this stress exceeds the tensile strength of the concrete at a certain moment, the structure will crack. Such temperature cracks not only affect the structural integrity, load-bearing capacity, and appearance, but also provide channels for the intrusion of harmful media, seriously threatening the long-term durability and service life of the structure.

[0003] To control temperature cracking in large-volume concrete, the engineering community has developed various technical measures, but all of them have certain limitations: Physical cooling methods, such as pre-embedded cooling water pipes, use circulating water to remove heat from the concrete. While this method is direct and effective, it significantly increases construction costs, the complexity of construction procedures, and the difficulty of on-site management. Pre-embedded pipes may interfere with the arrangement of reinforcing steel, create weak points, damage the integrity of the concrete, and pose risks such as pipe blockage and leakage.

[0004] Material-based slow-release methods, such as using retarders, delay the onset of hydration heat peaks by slowing down cement hydration, thus avoiding concentrated heat release in the early stages. However, this method cannot fundamentally eliminate the total heat release and internal / external temperature differences, and may excessively delay setting, affecting early strength development and construction progress.

[0005] Mineral admixtures, such as those using large amounts of fly ash and mineral powder, partially replace cement with less reactive mineral admixtures, reducing the total heat of hydration per unit volume of concrete. However, this method typically sacrifices early strength, potentially extending construction time. Furthermore, the availability of some high-quality admixtures, such as high-quality fly ash, is increasingly scarce, making it difficult to meet the demands of large-scale projects. In addition, this method provides holistic temperature field control, failing to precisely address the differentiated temperature control requirements between the internal and external environments of the structure.

[0006] Shrinkage compensation methods, such as adding expansive agents, aim to compensate for shrinkage caused by temperature drops and drying through the moderate expansion of the concrete itself. However, the expansion aging time of traditional shrinkage compensation components, such as sulfoaluminates and calcium oxides, is difficult to perfectly match with the shrinkage process of concrete, which may lead to ineffective expansion or insufficient expansion in the later stages. More importantly, their mechanism of action tends to produce uniform volume compensation and cannot identify and respond to the non-uniform shrinkage differences between the inside and outside of large-volume concrete caused by temperature gradients. Therefore, they cannot fundamentally solve the cracking problem caused by uneven stress distribution.

[0007] In summary, existing technologies either focus on removing heat from the outside or on slowing down, reducing heat, and compensating for the overall setting of concrete, failing to address the material system itself. In particular, there is a lack of selective inhibition technology for different mineral components in cement, such as the highly exothermic C3A and C3S, and there is also a lack of innovative solutions that can utilize industrial solid waste on a large scale to construct an inherently low-heat cementitious system. Summary of the Invention

[0008] This invention provides a method for preparing large-volume concrete to alleviate the technical problem of large internal and external temperature differences and easy temperature cracking caused by the heat of hydration in large-volume concrete.

[0009] To alleviate the above-mentioned technical problems, the technical solution provided by the present invention is as follows: A type of mass concrete comprises the following components in parts by weight: 200-220 parts cement 280-300 parts of low-hydration-heat composite cementitious material 800-900 parts fine aggregate, 1000-1100 parts coarse aggregate, 150-160 parts water 6-8 parts of water-reducing agent 2-4 parts of hydration inhibitor; The low-hydration-heat composite cementitious material is made by mixing the following components in the following mass ratio: modified electrolytic manganese slag powder: modified steel slag ultrafine powder: alkali-activated glass micro powder: fly ash = (5-8): (3-6): (2-4): (6-8); The hydration inhibitor is prepared by mixing the following components in the following mass ratio: Aminotrimethylene phosphonic acid and hydroxyethylidene diphosphonic acid complex: Zinc gluconate: Modified calcium lignosulfonate: Nano calcium carbonate = (35-40): (40-45): (15-20): (3-5); In the aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid complex, the mass ratio of aminotrimethylenephosphonic acid to hydroxyethylidene diphosphonic acid is 3:1.

[0010] Furthermore, The modified electrolytic manganese slag powder is prepared by leaching the electrolytic manganese slag with ammonium sulfate solution at 70-90℃ for 1-3 hours, filtering and washing, calcining at 450-550℃ for 1-2 hours, and then grinding it to a specific surface area of ​​not less than 450㎡ / kg.

[0011] Furthermore, The modified steel slag ultrafine powder is prepared by grinding steel slag to a specific surface area of ​​not less than 600 m² / kg, irradiating it with microwave at a power of 700-900W for 3-7 minutes, and then introducing carbon dioxide gas for carbonation treatment for 2-4 hours.

[0012] Furthermore, The method for preparing the alkali-activated glass micro powder is as follows: waste glass powder is ground to a particle size D50≤10μm, soaked in a sodium hydroxide solution with a mass concentration of 4-6% for 6-12 hours, filtered, cured in a steam environment at 100-130℃ for 4-8 hours, and then dried.

[0013] Furthermore, The fine aggregate is at least one of natural sand and manufactured sand, with a fineness modulus of 2.0-2.6.

[0014] Furthermore, The coarse aggregate is at least one of crushed stone and recycled coarse aggregate, with a particle size of 5-25 mm in continuous gradation.

[0015] A method for preparing large-volume concrete includes the following steps: (1) Weigh each raw material according to the mass fraction. (2) Mix all the raw materials evenly to obtain the final product.

[0016] Furthermore, it includes the following steps: (1) Divide into three regions in the thickness direction: CI region is the region 0-0.8m away from the side mold, CII region is the region 0.8-3.2m away from the side mold, and CIII region is the region greater than 3.2m away from the side mold; (2) Prepare concrete with different hydration inhibitor dosages for the CI zone, CII zone and CIII zone respectively, wherein the dosage of the hydration inhibitor increases in the order of CI zone, CII zone and CIII zone; (3) Use no less than the number of conveying and pouring equipment that matches the number of areas to pour the CI, CII and CIII areas simultaneously.

[0017] Furthermore, In step (3), when the casting body only has CI zone and CII zone, no less than 2 overhead pumps or cranes are used; when the casting body includes CI zone, CII zone and CIII zone, no less than 3 overhead pumps or cranes are used.

[0018] Furthermore, Step (3) also includes maintenance procedures.

[0019] The mechanism of this invention is analyzed as follows: Modified electrolytic manganese slag powder, through high-temperature calcination and ultrafine grinding, primarily functions as a physical dilution agent, directly reducing the content of high-exothermic cement clinker (C3A, C3S) per unit volume. Simultaneously, its microcrystalline nucleation effect promotes the uniform deposition of hydration products. Modified steel slag ultrafine powder, after microwave activation and carbonation treatment, develops a potentially active nano-calcium carbonate and silica gel layer on its surface. This layer slowly participates in the secondary hydration reaction in the alkaline environment of concrete, generating supplementary CSH gel. This process is slow and persistently exothermic, avoiding early thermal peaks, and the accompanying micro-expansion helps compensate for temperature drop shrinkage. Alkali-activated glass micropowder, after activation with alkali solution, forms a silicate gel on its surface, effectively encapsulating cement particles and selectively delaying the rapid dissolution and hydration of early mineral phases. Its continuous pozzolanic reaction makes a significant contribution to strength growth. Fly ash serves as an auxiliary cementitious material, using the pozzolanic effect to ensure long-term strength and density.

[0020] The hydration inhibitor, a complex of aminotrimethylene phosphonic acid and hydroxyethylidene diphosphonic acid, preferentially adsorbs onto the surface of C3A cement minerals—the most active and exothermic C3A—through calcium ion chelation, forming an inert film and inhibiting the hydration reaction. Zn²⁺ in zinc gluconate… + Ions can be incorporated into and alter the early nucleation and growth patterns of CSH gels, while interfering with the coarsening of calcium hydroxide crystals, resulting in a more uniform and fine microstructure and further smoothing the hydration process. Modified calcium lignosulfonate enhances the dispersibility of the system, ensuring sufficient contact between inhibitor molecules and gel particles; nano-calcium carbonate serves as additional nucleation sites, guiding the orderly formation of hydration products.

[0021] The technical effects of this invention are as follows: (1) Excellent temperature control and crack resistance: Through the synergistic effect of the low-heat cementitious system and the hydration inhibitor, the adiabatic temperature rise (72 hours) of the concrete of this invention can be controlled below 40°C, and the temperature peak is delayed to after 40 hours, effectively reducing the risk of early concentrated heat release. It significantly reduces the temperature stress caused by the internal and external temperature difference, and greatly reduces the risk of structural cracking from the material source.

[0022] (2) Excellent mechanical properties: While achieving low heat, the concrete of this invention exhibits excellent mechanical properties. The compressive strength stabilizes above 55 MPa after 28 days, meeting the high strength requirements of large-volume structures. Its strength development is coordinated with the temperature rise process: the early strength growth is slow, which is conducive to stress relaxation, and the middle and later strength growth is continuous and steady, ensuring the final load-bearing capacity.

[0023] (3) Green environmental protection and construction convenience: More than 60% of the cementitious material in this invention comes from modified industrial solid waste, realizing high-value utilization of solid waste resources and reducing production costs and environmental impact. Excellent self-temperature control performance can reduce or even eliminate external cooling measures, simplifying construction process and reducing overall project costs. Detailed Implementation

[0024] The testing standards used in this implementation method are as follows: Compressive strength GB / T 50081-2019.

[0025] Adiabatic temperature rise DL / T 5150-2017.

[0026] Example 1 This embodiment provides a large-volume concrete with the following composition: 210 parts of ordinary silicate cement, 290 parts of low-heat hydration composite cementitious material, 850 parts of fine aggregate, 1050 parts of coarse aggregate, 155 parts of water, 7 parts of water-reducing agent, and 3 parts of hydration inhibitor. The fine aggregate is manufactured sand with a fineness modulus of 2.3, the coarse aggregate is continuously graded crushed stone with a particle size of 5-25mm, and the water-reducing agent is a polycarboxylate-based high-performance water-reducing agent.

[0027] The low-hydration-heat composite cementitious material is premixed from the following components in the indicated mass ratio: modified electrolytic manganese slag powder: modified steel slag ultrafine powder: alkali-activated glass micro powder: fly ash = 6: 4: 3: 7.

[0028] (1) Preparation of modified electrolytic manganese slag powder: Take 10 kg of electrolytic manganese slag (moisture content ≤ 5%), place it in a reaction vessel, add 50 L of 10% ammonium sulfate solution, heat to 80℃ and leach with constant temperature stirring for 2 hours. After leaching, use a plate and frame filter press for solid-liquid separation, and wash the obtained filter cake with deionized water. Place the washed filter cake in a muffle furnace and calcine at 500℃ for 1.5 hours. After cooling, grind it with a vertical roller mill until the specific surface area is ≥ 480 m² / kg to obtain modified electrolytic manganese slag powder.

[0029] (2) Preparation of modified steel slag ultrafine powder: Take 10 kg of steel slag, first coarsely crush it with a jaw crusher, and then grind it with a ball mill. Spread the ground steel slag powder evenly in a microwave reactor with a thickness of 2-3 cm, and microwave irradiate it at 800 W for 5 minutes. Then transfer the material to a sealed carbonation reactor, introduce carbon dioxide gas with a purity ≥99%, control the pressure at 0.3 MPa, and carbonate it at room temperature for 3 hours. After the treatment is completed, take out the material and pass it through a 0.08 mm square hole sieve to obtain modified steel slag ultrafine powder.

[0030] (3) Preparation of alkali-activated glass micropowder: Waste flat glass was collected, cleaned, crushed, and then ground to D50=8μm using an air jet mill. 5kg of glass micropowder was placed in an alkali-resistant container, and 50L of 5% sodium hydroxide solution was added. The mixture was soaked at room temperature for 8 hours, with stirring every hour during the soaking process. After soaking, the mixture was filtered and separated. The filter cake was transferred to a steam curing chamber and cured in a saturated steam environment at 120℃ for 6 hours. After curing, the mixture was dried in an oven at 105℃ to constant weight, cooled, and then passed through a 0.045mm square-hole sieve to obtain alkali-activated glass micropowder.

[0031] (4) Preparation of hydration inhibitor: The aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid complex were accurately weighed according to a mass ratio of 38:42:17:4, wherein the ratio of aminotrimethylenephosphonic acid to hydroxyethylidene diphosphonic acid was 3:1; the particle size of zinc gluconate, modified calcium lignin sulfonate, and nano-calcium carbonate was 30-50 nm. The aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid complex were first dissolved in an appropriate amount of deionized water and stirred in a 60°C water bath until completely dissolved. Then, zinc gluconate and modified calcium lignin sulfonate were added sequentially and stirred for 30 minutes until uniformly mixed. Finally, nano-calcium carbonate was slowly added under the stirring of a high-speed shear emulsifier and shear dispersion was continued for 20 minutes to obtain a uniform and stable hydration inhibitor slurry.

[0032] (5) Preparation of low-hydration heat composite cementitious material: Weigh the prepared modified electrolytic manganese slag powder, modified steel slag ultrafine powder, alkali-activated glass micro powder and fly ash according to the proportion, put them into a twin-shaft screw mixer, mix for 30 minutes until the color is uniform, and seal and package for later use.

[0033] (6) Preparation method of mass concrete: Weigh all raw materials according to the formula. Put coarse aggregate and fine aggregate into a forced concrete mixer and dry mix for 30 seconds. Add cement and low heat of hydration composite cementitious material, and continue to dry mix for 60 seconds. Add water-reducing agent and hydration inhibitor to the total water volume, mix evenly beforehand to form a mixture. Slowly add the mixture to the mixer, and wet mix all materials for 180 seconds until the concrete mixture is uniform, has a consistent color, and no visible lumps. Discharge and test the performance of the fresh concrete.

[0034] Test results: 7-day compressive strength 35.2 MPa; 28-day compressive strength 58.6 MPa; adiabatic temperature rise (72h) 38.5℃; peak adiabatic temperature rise 42.1℃ (occurring at 42h).

[0035] Example 2 This embodiment provides a large-volume concrete with a composition basically the same as that of Embodiment 1, except that the mass fractions of each component are slightly adjusted: cement: 205 parts; low heat of hydration composite cementitious material: 295 parts; fine aggregate: 830 parts; coarse aggregate: 1080 parts; water: 152 parts; water-reducing agent: 6.5 parts; hydration inhibitor: 3.5 parts; the mass ratio of each component in the low heat of hydration composite cementitious material is: modified electrolytic manganese slag powder: modified steel slag ultrafine powder: alkali-activated glass micro powder: fly ash = 7: 5: 2: 6.

[0036] The composition and preparation method of the hydration inhibitor are the same as in Example 1.

[0037] The preparation methods of modified electrolytic manganese slag powder, modified steel slag ultrafine powder, and alkali-activated glass micro powder, the mixing method of low-hydration heat composite cementitious materials, and the detailed mixing and preparation process of concrete are all the same as in Example 1.

[0038] Performance parameters: 7d compressive strength 33.8 MPa; 28d compressive strength 56.4 MPa; adiabatic temperature rise (72h) 39.8℃; peak adiabatic temperature rise 43.5℃ (occurring at 45h).

[0039] Example 3 To verify the effectiveness of differential temperature control, the concrete from Example 1 was used for the construction of a 4.0m thick foundation slab. Three zones were defined along the thickness: Zone CI (0-0.8m from the side formwork), Zone CII (0.8-3.2m), and Zone CIII (>3.2m). Concrete with hydration inhibitor dosages of 2 parts (Zone CI), 3 parts (Zone CII), and 4 parts (Zone CIII) were prepared and simultaneously poured using three overhead concrete pumps. Monitoring showed that the temperature peak in the core zone (Zone CIII) was delayed by approximately 9 hours compared to the surface zone (Zone CI), with a maximum internal-external temperature difference of only 12°C. No temperature cracks appeared in the structure, indicating that differential temperature control and simultaneous pouring effectively reduced the risk of cracking.

[0040] Comparative Example 1 This comparative example provides a comparative concrete with a composition basically the same as that of Example 1, except that it does not contain modified electrolytic manganese slag powder. The remaining components in the low heat of hydration composite cementitious material are adjusted proportionally to maintain a total mass of 290 parts, and the adjusted composition is: modified steel slag ultrafine powder : alkali-activated glass micro powder : fly ash = 5 : 3 : 8.

[0041] The modified steel slag ultrafine powder and alkali-activated glass micro powder are the same as in Example 1, except that the preparation and incorporation steps of the modified electrolytic manganese slag powder are missing. The mixing method of the low heat of hydration composite cementitious material and the detailed preparation process of the concrete are the same as in Example 1.

[0042] Performance parameters: 7d compressive strength: 28.5 MPa; 28d compressive strength: 48.7 MPa; adiabatic temperature rise (72h): 46.2℃; peak adiabatic temperature rise: 50.1℃ (occurring at 36h).

[0043] Comparative Example 2 This comparative example provides a comparative concrete with a composition basically the same as that of Example 1, except that it does not contain modified steel slag ultrafine powder. The remaining components in the low heat of hydration composite cementitious material are adjusted proportionally to maintain a total mass of 290 parts, and the adjusted composition is: modified electrolytic manganese slag powder : alkali-activated glass micro powder : fly ash = 7 : 4 : 7.

[0044] The modified electrolytic manganese slag powder and alkali-activated glass micro powder are the same as in Example 1, except that the preparation and incorporation steps of the modified steel slag ultrafine powder are missing. The mixing method of the low heat of hydration composite cementitious material and the detailed preparation process of the concrete are the same as in Example 1.

[0045] Performance parameters: 7d compressive strength 30.1 MPa; 28d compressive strength 50.3 MPa; adiabatic temperature rise (72h) 44.5℃; peak adiabatic temperature rise 48.6℃ (occurring at 38h).

[0046] Comparative Example 3 This comparative example provides a comparative concrete with a composition basically the same as that of Example 1, except that it does not contain alkali-activated glass micropowder. The remaining components in the low heat of hydration composite cementitious material are adjusted proportionally to maintain a total mass of 290 parts, and the adjusted composition is: modified electrolytic manganese slag powder : modified steel slag ultrafine powder : fly ash = 8 : 6 : 6.

[0047] The modified electrolytic manganese slag powder and modified steel slag ultrafine powder are the same as in Example 1, except that the preparation and incorporation steps of alkali-activated glass micropowder are missing. The mixing method of the low heat of hydration composite cementitious material and the detailed preparation process of concrete are the same as in Example 1.

[0048] Performance parameters: 7d compressive strength 27.8 MPa; 28d compressive strength 47.5 MPa; adiabatic temperature rise (72h) 48.7℃; peak adiabatic temperature rise 52.9℃ (occurring at 34h).

[0049] Comparative Example 4 This comparative example provides a comparative concrete with the same composition as Example 1, except that no hydration inhibitor is added.

[0050] The preparation methods for modified electrolytic manganese slag powder, modified steel slag ultrafine powder, and alkali-activated glass micropowder, as well as the mixing method for low-heat-of-hydration composite cementitious materials, are the same as in Example 1. The concrete preparation process is the same as in Example 1, except that all mixing water is added directly during mixing, without adding hydration inhibitors.

[0051] Performance parameters: 7d compressive strength 36.5 MPa; 28d compressive strength 59.2 MPa; adiabatic temperature rise (72h) 52.3℃; peak adiabatic temperature rise 58.7℃ (occurring at 28h).

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A type of large-volume concrete, characterized in that, The components include the following parts by mass: 200-220 parts cement 280-300 parts of low-hydration-heat composite cementitious material 800-900 parts fine aggregate, 1000-1100 parts coarse aggregate, 150-160 parts water 6-8 parts of water-reducing agent 2-4 parts of hydration inhibitor; The low-hydration-heat composite cementitious material is made by mixing the following components in the following mass ratio: modified electrolytic manganese slag powder: modified steel slag ultrafine powder: alkali-activated glass micro powder: fly ash = (5-8): (3-6): (2-4): (6-8); The hydration inhibitor is prepared by mixing the following components in the following mass ratio: Aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid complex: Zinc gluconate: Modified calcium lignosulfonate: Nano calcium carbonate = (35-40): (40-45): (15-20): (3-5); In the aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid complex, the mass ratio of aminotrimethylenephosphonic acid to hydroxyethylidene diphosphonic acid is 3:

1.

2. The mass concrete according to claim 1, characterized in that, The modified electrolytic manganese slag powder is prepared by leaching the electrolytic manganese slag with ammonium sulfate solution at 70-90℃ for 1-3 hours, filtering and washing, calcining at 450-550℃ for 1-2 hours, and then grinding it to a specific surface area of ​​not less than 450㎡ / kg.

3. The mass concrete according to claim 1, characterized in that, The modified steel slag ultrafine powder is prepared by grinding steel slag to a specific surface area of ​​not less than 600 m² / kg, irradiating it with microwave at a power of 700-900W for 3-7 minutes, and then introducing carbon dioxide gas for carbonation treatment for 2-4 hours.

4. The mass concrete according to claim 1, characterized in that, The method for preparing the alkali-activated glass micro powder is as follows: waste glass powder is ground to a particle size D50≤10μm, soaked in a sodium hydroxide solution with a mass concentration of 4-6% for 6-12 hours, filtered, cured in a steam environment at 100-130℃ for 4-8 hours, and then dried.

5. The mass concrete according to claim 1, characterized in that, The fine aggregate is at least one of natural sand and manufactured sand, with a fineness modulus of 2.0-2.

6.

6. The mass concrete according to claim 1, characterized in that, The coarse aggregate is at least one of crushed stone and recycled coarse aggregate, with a particle size of 5-25 mm in continuous gradation.

7. A method for preparing large-volume concrete according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Weigh each raw material according to the mass fraction. (2) Mix all the raw materials evenly to obtain the final product.

8. The method for preparing large-volume concrete according to claim 7, characterized in that, Includes the following steps: (1) Divide into three regions in the thickness direction: CI region is the region 0-0.8m away from the side mold, CII region is the region 0.8-3.2m away from the side mold, and CIII region is the region greater than 3.2m away from the side mold; (2) Prepare concrete with different hydration inhibitor dosages for the CI zone, CII zone and CIII zone respectively, wherein the dosage of the hydration inhibitor increases in the order of CI zone, CII zone and CIII zone; (3) Use no less than the number of conveying and pouring equipment that matches the number of areas to pour the CI, CII and CIII areas simultaneously.

9. The method for preparing mass concrete according to claim 8, characterized in that, In step (3), when the casting body only has CI zone and CII zone, no less than 2 overhead pumps or cranes are used; when the casting body includes CI zone, CII zone and CIII zone, no less than 3 overhead pumps or cranes are used.

10. The method for preparing large-volume concrete according to claim 8, characterized in that, Step (3) also includes maintenance procedures.