A mass concrete and a method for producing the same

Abstract

This invention relates to the field of building materials technology, specifically to a long-life, large-volume concrete and its preparation method. It includes: multi-scale silicate cement 250–350 kg / m³. 3 ; fly ash 50~200kg / m³ 3 Mineral powder 0~150kg / m 3 Fine aggregate 700-900 kg / m³ 3 Coarse aggregate 1000-1200 kg / m³ 3 Expanding agent 20-40 kg / m³ 3 Penetrating crystallizing waterproofing agent 0-5 kg / m 3 Water-reducing agent 5-10 kg / m³ 3 Fiber 0~10kg / m 3 Water 150-180 kg / m³ 3 Multi-scale silicate cement includes three types of cement with average particle sizes of 10–15 μm, 20–25 μm, and 30–35 μm, respectively. This invention can increase the strength and self-healing ability of concrete, greatly extending its service life, with a predicted service life of up to 500 years.

Description

Technical Field

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

[0002] my country's "Standard for Construction of Mass Concrete" GB50496-2018 defines mass concrete as concrete structures with a minimum geometric dimension of not less than 1 meter, or concrete that is expected to develop harmful cracks due to temperature changes and shrinkage caused by the hydration of cementitious materials. Traditional methods often involve incorporating large amounts of mineral admixtures to reduce the heat of hydration and utilize the micro-aggregate effect to improve the durability of the concrete. Western countries have already used high-performance concrete (HPC) with large amounts of mineral admixtures to construct concrete bridges in the Middle East Gulf with a design life of 150 years, the East Sheld prestressed concrete sea lock in the Netherlands with a design life of 250 years, and the Brisbane Bridge in Queensland, Australia with a design life of 300 years.

[0003] However, the addition of large amounts of mineral admixtures can easily cause concrete cracking, severely reducing its durability. Currently, the common method to suppress concrete cracking is to use medium- and low-heat cement combined with expansive agents (e.g., patent CN111943583A, a low-shrinkage, high-crack-resistance, high-durability, long-life concrete and its preparation method, and patent CN115159923A, a low-shrinkage, freeze-thaw-resistant mass concrete). However, in actual engineering projects, the high cost of special cement leads to its limited usage; and the need for at least a week of curing after the application of expansive agents is difficult to guarantee. Therefore, it is necessary to propose new measures to increase the crack resistance and repair capacity of concrete to meet the service life requirements of concrete lasting a century or even a millennium.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a long-life, large-volume concrete and its preparation method. By using multi-scale silicate cement in combination with admixtures such as penetrating crystallizing waterproofing agents and expansion agents, the early strength and later strength of the concrete can be guaranteed under low hydration heat release conditions, thereby significantly improving the service life of the concrete.

[0006] To achieve the above objectives, the present invention provides a long-life, large-volume concrete, comprising the following materials by unit volume mass: 250–350 kg / m³ of multi-scale silicate cement. 3 ; fly ash 50~200kg / m 3 Mineral powder 0~150kg / m³ 3 Fine aggregate 700-900 kg / m³ 3Coarse aggregate 1000-1200 kg / m³ 3 Expanding agent 20-40 kg / m³ 3 Penetrating crystallizing waterproofing agent 0-5 kg / m 3 Water-reducing agent 5-10 kg / m³ 3 Fiber 0~10kg / m 3 Water 150-180 kg / m³ 3 ;

[0007] The multi-scale silicate cement includes ordinary silicate cement with an average particle size of 10-15 μm, medium-sized cement with an average particle size of 20-25 μm, and large-sized cement with an average particle size of 30-35 μm. Multi-scale silicate cement is a graded cementitious material for concrete with three particle sizes. Compared to traditional low-heat cement and medium-low-heat cement, it has higher early strength. Since multi-scale silicate cement is essentially a type of ordinary silicate cement, its tricalcium silicate content is approximately 60% or higher, which is higher than that in low-heat and medium-low-heat cement, resulting in better early strength. Furthermore, multi-scale silicate cement can reduce cement grinding time, saving energy and reducing carbon emissions, while also being less expensive than low-heat cement, making it more suitable for large-scale application in engineering projects.

[0008] Furthermore, the volumes of the ordinary silicate cement, medium-sized cement, and large-sized cement account for 30-70%, 20-60%, and 10-20% of the total volume of the multi-scale silicate cement, respectively.

[0009] Furthermore, the specific surface area of ​​the ordinary Portland cement is no greater than 360 m². 2 / kg, the specific surface area of ​​the medium-sized cement is not greater than 340m². 2 / kg, the specific surface area of ​​the large-size cement is no greater than 320m². 2 / kg.

[0010] Furthermore, the surface of the penetrating crystallizing waterproofing agent is coated with a layer of hydrophobic silane, such as polymethylhydrosilane. The penetrating crystallizing waterproofing material primarily relies on the reaction of calcium hydroxide produced during cement hydration to fill the voids created in the early stages of hydration, thereby increasing the strength of the concrete. In the later stages of hydration, the reaction between the penetrating crystallizing material and cement can also give the concrete self-healing capabilities. The hydration-inhibiting penetrating crystallizing material used in this invention, coated with a layer of hydrophobic silane, allows for a longer dormancy period in cement concrete, delaying the reaction between the penetrating crystallizing material and the cement base, thus better preserving the self-healing ability of the penetrating crystallizer and ensuring reactivity and a certain degree of repair capability during its extended service life.

[0011] The further described expansive agent is a type II composite expansive agent of calcium sulfoaluminate-calcium oxide. This expansive agent compensates for concrete shrinkage, fundamentally inhibiting shrinkage cracking. Considering the effectiveness of the expansive agent, the concrete production process typically requires freshly prepared concrete to be cured in its formwork for 7 days.

[0012] Furthermore, the fiber is one or more of polypropylene fiber, basalt fiber, polyvinyl alcohol fiber, polyoxymethylene fiber, and steel fiber.

[0013] Furthermore, the sum of the amounts of fly ash and mineral powder added is ≤200 kg / m³. 3 Preferably, the mineral powder content is 0–50 kg / m³. 3 More preferably, mineral powder 0-30 kg / m³ 3 Long-life, large-volume concrete often incorporates large amounts of auxiliary cementitious materials such as fly ash and mineral powder. These materials undergo secondary hydration, consuming calcium hydroxide in the concrete. Therefore, this invention limits the amount of auxiliary cementitious materials to a maximum of 200 kg / m³. 3 At the same time, increasing the average volume of cement particles slows down the reaction rate of cement, thereby ensuring that the penetrating material can react with cement during its ultra-long service life, improving the strength and self-healing properties of concrete.

[0014] Furthermore, the fine aggregate is river sand with a fineness modulus of 2.3 to 3.0, and the coarse aggregate is limestone with a particle size of 5 to 20 mm.

[0015] Further preferred long-life, large-volume concrete includes the following materials by unit volume mass: multi-scale silicate cement 260–300 kg / m³ 3 ; fly ash 100~150kg / m³ 3 Mineral powder 0~50kg / m 3 Fine aggregate 700-800 kg / m³ 3 Coarse aggregate 1000-1100 kg / m³ 3 Expanding agent 20-40 kg / m³ 3 Penetrating crystallizing waterproofing agent 2-5 kg / m 3 Water-reducing agent 5-10 kg / m³ 3 Fiber 0~5kg / m 3 Water 150-180 kg / m³ 3 .

[0016] The present invention also provides a method for preparing long-life, large-volume concrete as described in any one of the above claims, comprising: adding various raw materials for long-life, large-volume concrete into a concrete mixer, mixing (for about 100-150 seconds), then adding the mixture into a mold, curing it in the mold for 7 days, and then demolding it. The fiber is added simultaneously with the mixing process using a specialized feeder.

[0017] Furthermore, the concrete surface is also coated with an inorganic silicon anti-corrosion coating, the main component of which is inorganic silicate material, which can achieve the same service life as the concrete.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) The long-life, large-volume concrete provided by this invention, through the design of the cementitious material scale, can ensure the early strength of the concrete and its later strength during an ultra-long service life under conditions of low hydration heat release. The chloride ion diffusion coefficient at 56 days is ≤0.5×10⁻⁶. -12 m 2 / s, with an expected service life of over 500 years.

[0020] (2) The long-life, large-volume concrete proposed in this invention can significantly improve the service life of concrete, reduce carbon emissions throughout the entire life cycle of buildings, and provide strong technical support for large-volume, ultra-long-service projects. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0022] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. All reagents or instruments without specified manufacturers are conventional products that can be purchased through legitimate channels.

[0023] The cement used in the experimental concrete was PO 42.5 cement. The medium-sized and large-sized cement particles were prepared using the same batching as PO 42.5 cement, with parameters such as the final grinding time and air volume of the vertical mill being varied. The concrete formulation is shown in Table 1.

[0024] Table 1. Concrete mix proportions (kg / m³) 3 )

[0025]

[0026]

[0027] Example 1

[0028] This embodiment provides a long-life, large-volume concrete (C7), which comprises the following materials:

[0029] Multi-scale cement (PO 42.5 cement, medium-sized cement, large-sized cement = 7:2:1), grade II fly ash, river sand, fineness modulus 2.6, limestone aggregate (5-20mm), penetrating crystallizing waterproofing agent, polycarboxylate superplasticizer, type II expansion agent, polypropylene fiber.

[0030] The concrete uses the mix proportions of Formula 1, and the preparation method includes the following steps:

[0031] (1) Add various raw materials of long-life large-volume concrete into the concrete mixer and mix for 120 seconds. Fiber is added while mixing through a special feeder.

[0032] (2) Add the mixed concrete into the mold, cure it in the mold for 7 days, and then demold it.

[0033] Example 2

[0034] This embodiment provides a long-life, large-volume concrete (C5), which comprises the following materials:

[0035] Multi-scale cement (PO 42.5 cement, medium-sized cement, large-sized cement = 5:3:2), grade II fly ash, river sand, fineness modulus 2.6, limestone aggregate (5-20mm), penetrating crystallizing waterproofing agent, polycarboxylate superplasticizer, type II expansion agent, polypropylene fiber.

[0036] The concrete uses the mix proportions of Formula 1, and the preparation method includes the following steps:

[0037] (1) Add various raw materials of long-life large-volume concrete into the concrete mixer and mix for 120 seconds. Fiber is added while mixing through a special feeder.

[0038] (2) Add the mixed concrete into the mold, cure it in the mold for 7 days, and then demold it.

[0039] Example 3

[0040] This embodiment provides a long-life, large-volume concrete (C3), which comprises the following materials:

[0041] Multi-scale cement (PO 42.5 cement, medium-sized cement, large-sized cement = 3:6:1), grade II fly ash, river sand, fineness modulus 2.6, limestone aggregate (5-20mm), penetrating crystallizing waterproofing agent, polycarboxylate superplasticizer, type II expansion agent, polypropylene fiber.

[0042] The concrete uses the mix proportions of Formula 1, and the preparation method includes the following steps:

[0043] (1) Add various raw materials of long-life large-volume concrete into the concrete mixer and mix for 120 seconds. Fiber is added while mixing through a special feeder.

[0044] (2) Add the mixed concrete into the mold, cure it in the mold for 7 days, and then demold it;

[0045] Example 4

[0046] This embodiment provides a long-life, large-volume concrete (C7T), which comprises the following materials:

[0047] Multi-scale cement (PO 42.5 cement, medium-sized cement, large-sized cement = 7:2:1), grade II fly ash, river sand, fineness modulus 2.6, limestone aggregate (5-20mm), penetrating crystallizing waterproofing agent, polycarboxylate superplasticizer, type II expansion agent, polypropylene fiber.

[0048] The concrete uses the mix proportions of Formula 1, and the preparation method includes the following steps:

[0049] (1) Add various raw materials of long-life large-volume concrete into the concrete mixer and mix for 120 seconds. Fiber is added while mixing through a special feeder.

[0050] (2) Add the mixed concrete into the mold, cure it in the mold for 7 days, and then demold it.

[0051] (3) Apply inorganic silicon anti-corrosion coating to the concrete surface in two coats, with a coating dosage of 0.2 kg / m². 2 .

[0052] Example 5

[0053] This embodiment provides a long-life, large-volume concrete (C73), which comprises the following materials:

[0054] Multi-scale cement (PO 42.5 cement, medium-sized cement, large-sized cement = 7:2:1), grade II fly ash, S95 mineral powder, river sand, fineness modulus 2.6, limestone aggregate (5-20mm), penetrating crystallizing waterproofing agent, polycarboxylate superplasticizer, type II expansion agent, polypropylene fiber.

[0055] The concrete uses the mix proportion of formula 2, and the preparation method includes the following steps:

[0056] (1) Add various raw materials of long-life large-volume concrete into the concrete mixer and mix for 120 seconds. Fiber is added while mixing through a special feeder.

[0057] (2) Add the mixed concrete into the mold, cure it in the mold for 7 days, and then demold it.

[0058] Example 6

[0059] This embodiment provides a long-life, large-volume concrete (C7ST), which comprises the following materials:

[0060] Multi-scale cement (PO 42.5 cement, medium-sized cement, large-sized cement = 7:2:1), grade II fly ash, river sand, fineness modulus 2.6, limestone aggregate (5-20mm), penetrating crystallizing waterproofing agent (surface coated with a layer of polymethylhydrosiloxane), polycarboxylate superplasticizer, type II expansion agent, polypropylene fiber.

[0061] The concrete uses the mix proportions of Formula 1, and the preparation method includes the following steps:

[0062] (1) Add various raw materials of long-life large-volume concrete into the concrete mixer and mix for 120 seconds. Fiber is added while mixing through a special feeder.

[0063] (2) Add the mixed concrete into the mold, cure it in the mold for 7 days, and then demold it.

[0064] (3) Apply inorganic silicon anti-corrosion coating to the concrete surface in two coats, with a coating dosage of 0.2 kg / m². 2 .

[0065] Comparative Example 1

[0066] This comparative example provides a long-life concrete (P), the long-life concrete material being as follows:

[0067] PO 42.5 cement, grade II fly ash, river sand, fineness modulus 2.6, limestone aggregate (5-20mm), polycarboxylate superplasticizer, type II expansion agent.

[0068] The concrete uses the mix proportions of Formula 1, and the concrete preparation method includes the following steps:

[0069] (1) Add all the raw materials of long-life large-volume concrete to the concrete mixer and mix for 120 seconds;

[0070] (2) Add the mixed concrete into the mold, cure it in the mold for 7 days, and then demold it.

[0071] Comparative Example 2

[0072] This comparative example provides a long-life concrete (PX), the long-life concrete material being as follows:

[0073] PO 42.5 cement, grade II fly ash, river sand, fineness modulus 2.6, limestone aggregate (5-20mm), polycarboxylate superplasticizer, type II expansion agent, polypropylene fiber.

[0074] The concrete uses the mix proportion of Formula 1, and the preparation method includes the following steps:

[0075] (1) Add various raw materials of long-life large-volume concrete into the concrete mixer and mix for 120 seconds. Fiber is added while mixing through a special feeder.

[0076] (2) Add the mixed concrete into the mold, cure it in the mold for 7 days, and then demold it.

[0077] Comparative Example 3

[0078] This comparative example provides a long-life concrete (PXS), the long-life concrete material being as follows:

[0079] PO 42.5 cement, grade II fly ash, river sand, fineness modulus 2.6, limestone aggregate (5-20mm), penetrating crystallizing waterproofing agent, polycarboxylate superplasticizer, type II expansion agent, polypropylene fiber.

[0080] The concrete uses the mix proportion of Formula 1, and the preparation method includes the following steps:

[0081] (1) Add various raw materials of long-life large-volume concrete into the concrete mixer and mix for 120 seconds. Fiber is added while mixing through a special feeder.

[0082] (2) Add the mixed concrete into the mold, cure it in the mold for 7 days, and then demold it.

[0083] In this experiment, the performance of the above-mentioned concrete was tested according to GB 50081-2019 and GB 50082-2009, and the results are shown in Table 2.

[0084] Table 2 Performance Indicators of Different Airtight Concretes

[0085]

[0086]

[0087] As shown in Table 2, compared with ordinary concrete, the concretes of Examples 1-6 of this invention exhibit a slightly lower 7-day strength, while their 56-day strength is essentially the same as that of ordinary concrete. However, the relative dynamic modulus of elasticity is significantly improved, and the chloride ion diffusion coefficient and drying shrinkage are significantly reduced. For example, compared with concrete P in Comparative Example 1, concrete C7ST in Example 6 has a 27% higher relative dynamic modulus of elasticity, a 96% lower chloride ion diffusion coefficient, and a 97% lower drying shrinkage. This demonstrates that this invention can significantly improve the durability of concrete, thereby extending its service life.

[0088] 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A long-life, large-volume concrete, characterized in that, The following materials are included by unit volume mass: multi-scale silicate cement 250~350 kg / m³ 3 Fly ash 50~200 kg / m³ 3 Mineral powder 0~150 kg / m³ 3 Fine aggregate 700~900 kg / m³ 3 Coarse aggregate 1000~1200 kg / m³ 3 Expanding agent 20~40 kg / m 3 Penetrating crystallizing waterproofing agent 2~5 kg / m 3 Water-reducing agent 5~10 kg / m³ 3 Fiber 0~10 kg / m 3 ; Water 150~180 kg / m 3 ; The multi-scale silicate cement includes ordinary silicate cement with an average particle size of 10-15 μm, medium-sized cement with an average particle size of 20-25 μm, and large-sized cement with an average particle size of 30-35 μm. The surface of the penetrating crystallizing waterproofing agent is also coated with a layer of hydrophobic silane.

2. The long-life, large-volume concrete according to claim 1, characterized in that, The volume of ordinary silicate cement, medium-sized cement, and large-sized cement accounts for 30-70%, 20-60%, and 10-20% of the total volume of the multi-scale silicate cement, respectively.

3. The long-life, large-volume concrete according to claim 1, characterized in that, The specific surface area of ​​the ordinary Portland cement is not greater than 360 m². 2 / kg, the specific surface area of ​​the medium-sized cement is not greater than 340 m² 2 / kg, the specific surface area of ​​the large-size cement is not greater than 320 m² 2 / kg.

4. The long-life, large-volume concrete according to claim 1, characterized in that, The expanding agent is a type II composite expanding agent of calcium sulfoaluminate-calcium oxide.

5. The long-life, large-volume concrete according to claim 1, characterized in that, The fiber is one or more of polypropylene fiber, basalt fiber, polyvinyl alcohol fiber, polyoxymethylene fiber, and steel fiber.

6. The long-life, large-volume concrete according to claim 1, characterized in that, The sum of the amounts of fly ash and mineral powder added is ≤200 kg / m³. 3 ; And / or, the fine aggregate is river sand with a fineness modulus of 2.3 to 3.0, and the coarse aggregate is limestone with a particle size of 5 to 20 mm.

7. The long-life, large-volume concrete according to any one of claims 1-6, characterized in that, The following materials are included by unit volume mass: multi-scale silicate cement 260~300 kg / m³ 3 ; fly ash 100~150 kg / m³ 3 Mineral powder 0~50 kg / m³ 3 Fine aggregate 700~800 kg / m³ 3 Coarse aggregate 1000~1100 kg / m³ 3 Expanding agent 20~40 kg / m 3 Penetrating crystallizing waterproofing agent 2~5 kg / m 3 Water-reducing agent 5~10 kg / m³ 3 Fiber 0~5 kg / m 3 ; Water 150~180 kg / m 3 .

8. A method for preparing long-life, large-volume concrete according to any one of claims 1-7, characterized in that, include: Various raw materials for long-life, large-volume concrete are added to a concrete mixer, mixed well, and then poured into a mold. After curing in the mold for 7 days, the concrete is demolded.

9. The method for preparing long-life, large-volume concrete according to claim 8, characterized in that, The concrete surface is also coated with an inorganic silicon anti-corrosion coating, the main component of which is an inorganic silicate material.

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