Preparation method of bagged concrete composition and bagged concrete slurry

Abstract

The present invention relates to a kind of preparation method of mold bag concrete composition and mold bag concrete slurry, wherein, mold bag concrete composition, including being placed separately and by weight: 15 35 parts of cement, 15 25 parts of slag powder, 5 10 parts of silica fume, 2 4 parts of carbide slag, 35 40 parts of graded aggregate, 0.8 1.2 parts of modified nano-carbon fibers, 3 4 parts of nano-silicon dioxide, 1.5 2.5 parts of anti-seepage agent, 1.5 2.0 parts of water-reducing agent, and 0.2 0.4 parts of auxiliary dispersant;Wherein, the mass ratio of slag powder to slag powder and cement total mass is 0.3 0.5;The water reducing rate of water-reducing agent is ≥35%;Auxiliary dispersant is used for uniformly dispersing modified nano-carbon fibers;Anti-seepage agent and modified nano-carbon fibers can undergo dehydration condensation reaction.Its beneficial effect is that, the mold bag concrete takes into account the comprehensive improvement of strength, impermeability, fluidity and durability.

Description

Technical Field

[0001] The present invention relates to the technical field of water conservancy engineering, in particular to a bagged concrete composition and a method for preparing bagged concrete slurry. Background Art

[0002] Geo-bag concrete (also known as geo-bag concrete) is a structural material created by pouring concrete into specially designed geotextile bags. This technology combines the advantages of geosynthetics and traditional concrete. Bagged concrete is primarily used in water conservancy projects, including embankment slope protection and scour prevention. The bags are laid directly on the slope surface to quickly form a high-strength protective layer. Underwater repair and reinforcement utilizes the self-compacting properties of the bags to allow for direct underwater pouring to repair leaking or damaged structures.

[0003] Existing bagged concrete used in hydraulic projects generally suffers from insufficient strength and poor impermeability, which reduces the stability and durability of the structures. This lack of strength can cause deformation or even failure of the bagged concrete structures when subjected to water flow, wave action, or other external loads, compromising the overall stability and safety of the project. Furthermore, bagged concrete in hydraulic projects requires frequent inspection and repair, increasing long-term maintenance costs. Summary of the Invention

[0004] 1. Technical Problems to be Solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a bagged concrete composition and a method for preparing bagged concrete slurry, which solve the technical problems of insufficient strength and poor impermeability of the existing bagged concrete when applied to water conservancy projects.

[0006] 2. Technical Solution

[0007] In order to achieve the above objectives, the main technical solutions adopted by the present invention include:

[0008] In a first aspect, an embodiment of the present invention provides a bagged concrete composition, comprising, separately and in parts by weight: 15-35 parts of cement, 15-25 parts of slag powder, 5-10 parts of silica fume, 2-4 parts of carbide slag, 35-40 parts of graded aggregate, 0.8-1.2 parts of modified nano-carbon fibers, 3-4 parts of nano-silicon dioxide, 1.5-2.5 parts of an anti-seepage agent, 1.5-2.0 parts of a water reducer, and 0.2-0.4 parts of an auxiliary dispersant;

[0009] The mass ratio of slag powder to the total mass of slag powder and cement is 0.3-0.5;

[0010] The water reducing rate of the water reducing agent is ≥35%;

[0011] Auxiliary dispersant is used to uniformly disperse the modified carbon nanofibers;

[0012] The anti-seepage agent and the modified nano-carbon fiber can undergo a dehydration condensation reaction.

[0013] As a preferred embodiment of the present invention, the mass ratio of the slag powder to the total mass of the slag powder and cement in the bagged concrete composition is 0.4-0.5;

[0014] 15-20 parts of slag powder, 5-8 parts of silica fume, and 2-3 parts of carbide slag.

[0015] As a preferred embodiment of the present invention, in the bagged concrete composition, the specific surface areas of the slag powder and the carbide slag are both ≥600 m² / kg; and the specific surface area of ​​the silica fume is ≥15,000 m² / kg.

[0016] As a preferred embodiment of the present invention, the mold bag concrete composition, the graded aggregate includes coarse aggregate and fine aggregate;

[0017] Among them, the particle size of coarse aggregate is 5-15mm, and the particle size of fine aggregate is 0.3-1.2mm;

[0018] The mass ratio of coarse aggregate to fine aggregate is 55-60:40-45.

[0019] As a preferred embodiment of the present invention, the modified nano-carbon fibers in the mold bag concrete composition are nano-carbon fibers modified with a surface silane coupling agent, with a modification ratio of ≤1.5%; and the auxiliary dispersant is non-ionic polyvinyl pyrrolidone.

[0020] As a preferred embodiment of the present invention, the anti-seepage agent of the mold bag concrete composition is a silane-based anti-seepage agent.

[0021] As a preferred embodiment of the present invention, the water reducer in the mold bag concrete composition is a polycarboxylate water reducer.

[0022] In a second aspect, an embodiment of the present invention provides a method for preparing a bagged concrete slurry, using the bagged concrete composition, and specifically comprising the following steps:

[0023] S1. Prepare mixing water according to a water-binder ratio of 0.26-0.30, mix and disperse the modified nanocarbon fibers and the auxiliary dispersant with 30-50% volume of mixing water to form a stable suspension;

[0024] Dry-mix cement, slag powder, silica fume, carbide slag and nano-silicon dioxide to form dry powder;

[0025] S2. Mix the water reducer and the remaining volume of mixing water, then add it to the dry powder, stir and mix, and prepare a primary slurry;

[0026] S3, stirring and mixing the suspension prepared in S1 and the primary slurry, then adding the graded aggregate in the order of coarse first and fine later, stirring and mixing to prepare the secondary slurry;

[0027] S4. Add the anti-seepage agent to the secondary slurry, stir and mix well to prepare the mold bag concrete slurry.

[0028] As a preferred embodiment of the present invention, in the preparation method, in S3, the stirring and mixing rate is 60-120 rpm.

[0029] As a preferred embodiment of the present invention, in the preparation method, in S4, the stirring and mixing rate is 100-120 rpm.

[0030] 3. Beneficial Effects

[0031] The beneficial effects of the present invention are as follows: a method for preparing a bagged concrete composition and bagged concrete slurry of the present invention, slag powder and silica fume undergo a pozzolanic reaction under the stimulation of carbide slag, and a solid waste system is used to partially replace cement in proportion, which ensures the strength of the concrete while helping to control the increase in porosity caused by the heat of cement hydration. The slag powder undergoes secondary hydration in the later stage of cement hydration, further filling the pores, and the bagged concrete finally prepared is denser and has better anti-seepage performance. Slag powder, silica fume and carbide slag are used as solid waste for recycling, which reduces the amount of cement used and is green and environmentally friendly. The anti-seepage agent can react with the modified nano-carbon fibers in a directional manner to promote the uniform distribution of the modified nano-carbon fibers. The dispersion rate of the nano-carbon fibers is ≥90%, which realizes the three-dimensional toughening of the bagged concrete and improves the strength of the bagged concrete as a whole. The compressive strength is 62 MPa after 28 days and ≥70 MPa after 90 days. At the same time, it ensures that the reinforcement and anti-seepage performance of the concrete are balanced. Nanosilica fills the micropores of the material, synergizing with the secondary hydration reaction of the solid waste system to reduce shrinkage and improve the concrete's early strength. Nanosilica and an anti-seepage agent jointly fill the gaps and micropores in the concrete, enhancing its impermeability. Nanosilica also improves its early strength. Optimized aggregate grading and a high-performance water-reducing agent enhance slurry fluidity, facilitating pumping of the bagged concrete and reducing the risk of pipe blockage. With a slurry expansion of ≥600 mm, the bagged concrete can be pumped underwater without segregation, ensuring dense filling of the bagged concrete. Furthermore, the optimal fluidity facilitates the uniform dispersion of the modified nanocarbon fibers, nanosilica, and anti-seepage agent, further enhancing the concrete's impermeability. Compared to existing technologies, this bagged concrete achieves comprehensive improvements in strength, impermeability, fluidity, and durability, breaking through the technical barriers of existing technologies that only enhance a single property of bagged concrete. It has broad application value in water conservancy projects while maintaining both environmental and economic benefits.

[0032] The silanol groups on the nanocarbon fibers modified with a silane coupling agent react with the silane of the anti-seepage agent to form Si-O-Si bonds. This prevents the anti-seepage agent from competing with the nanocarbon fibers for adsorption, and the anti-seepage agent can then block the capillaries between the nanocarbon fibers and the matrix. This achieves comprehensive improvements in impermeability, durability, and compatibility with the nanofibers. This composite design is particularly suitable for water conservancy projects requiring high impermeability and durability, such as tidal gates and submarine tunnels. The chloride ion diffusion coefficient is reduced to below 0.5×10⁻¹²m² / s, achieving an impermeability rating of W14.

[0033] In the slurry preparation method, the modified nanofibers are pre-dispersed and then mixed with the other materials through step-by-step stirring to prevent agglomeration. The anti-seepage agent is added last and is also stirred rapidly to ensure its uniform distribution.

[0034] Aggregate grading is optimized, the proportion of fine aggregate is increased to more than 40%, and combined with carboxylic acid water reducer, the slump of concrete slurry reaches 250 mm without segregation.

[0035] The water-cement ratio is controlled at 0.26-0.30 and adjusted by water reducer to achieve both low porosity and high fluidity. DETAILED DESCRIPTION

[0036] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods.

[0037] In order to better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0038] Example 1

[0039] This embodiment provides a method for preparing a mold bag concrete slurry, comprising the following steps:

[0040] (1) Prepare mixing water according to a water-binder ratio of 0.28, mix and disperse 0.8 parts (by mass, the same below) of surface silane coupling agent-modified nanocarbon fibers (modification ratio ≤ 1.5%) and 0.2 parts of non-ionic polyvinyl pyrrolidone with 50% volume of mixing water, and disperse them under 40 kHz ultrasonic wave for 30 min to form a stable suspension; wherein, the water-binder ratio is the ratio of water to the total mass of cement, slag powder, silica fume and carbide slag, and the mixing water here is the total water used minus the water required for auxiliary dissolution in other steps;

[0041] (2) Stir 23 parts of cement, 15 parts of slag powder, 5 parts of silica fume, 2 parts of carbide slag and 3 parts of nano-silicon dioxide in a concrete mixer at 30 rpm for 3-5 minutes to form a dry powder; the specific surface area of ​​the slag powder and carbide slag is ≥600 m² / kg, and the specific surface area of ​​the silica fume is ≥15,000 m² / kg.

[0042] (3) Mix 1.5 parts of polycarboxylate water reducer with the remaining volume of mixing water, then add it to the dry powder and stir to prepare a first-level slurry;

[0043] (4) Slowly add the suspension prepared in (1) to the first-stage slurry several times, and stir at 60 rpm for 3-5 minutes to mix thoroughly; then add the graded aggregate in the order of coarse first and fine later, with a stirring rate of 120 rpm. Stir for 2 minutes after adding one type of aggregate each time before adding another type to ensure that the aggregate is fully coated by the slurry; stir and mix thoroughly after adding the aggregates to prepare the second-stage slurry; wherein, the graded aggregate includes 23 parts of basalt coarse aggregate with a particle size of 5-15 mm and 17 parts of quartz sand fine aggregate with a particle size of 0.3-1.2 mm, and the particle size range of the coarse aggregate and the fine aggregate is continuously distributed;

[0044] (5) Add the previously prepared anti-seepage agent solution (1.5 parts of isobutyltriethoxysilane dissolved in 10 times the volume of 5% ethanol) to the secondary slurry and stir at 120 rpm for 3-5 minutes until mixed to obtain the mold bag concrete slurry;

[0045] (6) Pour the bagged concrete slurry into the bag under water. After the bag is filled, apply a pressure of 5-10 kPa to expel bubbles and improve the density. The bag is then cured underwater at room temperature for 7-28 days to prepare a concrete test block.

[0046] The main chemical components of slag powder, silica fume and carbide slag in this embodiment are shown in Table 1:

[0047] Table 1

[0048]

[0049] The following performance tests are conducted on the bagged concrete slurry or test blocks:

[0050] 1) Refer to GB / T 50081-2002 "Standard for Test Methods of Compressive Strength of Concrete": Compressive strength tests were conducted on concrete specimens. The results are detailed in Table 2.

[0051] 2) Referring to GB / T 50082-2009, "Standard for Test Methods of Concrete Durability": concrete specimens were subjected to water penetration resistance tests (step-by-step pressure method) and chloride ion penetration tests. The results are detailed in Table 2.

[0052] 3) According to GB / T 50080-2016, Standard Test Methods for Performance of Ordinary Concrete Mixtures, the slump and expansion of the concrete paste were tested. The results are shown in Table 2.

[0053] 4) Chemical corrosion resistance test was conducted on concrete specimens according to GB / T 50082-2024: the specimens were immersed in 5% Na2SO4 solution, and the mass loss rate and strength loss rate of the specimens were recorded. The results are detailed in Table 2.

[0054] 5) Concrete specimens were tested for scour resistance in accordance with GB / T 50082 and the "Water Conservancy Engineering Code": a rotating water flow scour test was used to simulate the wear rate under actual working conditions, and the surface spalling depth was recorded and measured. The results are detailed in Table 2.

[0055] 6) The distribution of carbon nanofibers on the surface of concrete specimens was observed by SEM.

[0056] Example 2

[0057] This embodiment provides a method for preparing a mold bag concrete slurry. The difference between this embodiment and Example 1 is that:

[0058] (1) Prepare mixing water according to a water-binder ratio of 0.30, mix and disperse 1.2 parts (by mass, the same below) of surface silane coupling agent-modified nanocarbon fibers (modification ratio ≤ 1.5%) and 0.4 parts of non-ionic polyvinyl pyrrolidone in 50% volume of mixing water, and disperse them under 40 kHz ultrasonic dispersion for 30 min to form a stable suspension;

[0059] (2) Mix 20 parts of cement, 20 parts of slag powder, 8 parts of silica fume, 3 parts of carbide slag and 3 parts of nano-silicon dioxide in a concrete mixer at 30 rpm for 3-5 minutes to form a dry powder;

[0060] (3) Mix 2.0 parts of polycarboxylic acid water reducer with the remaining volume of mixing water, then add it to the dry powder and stir to prepare a first-level slurry.

[0061] The rest of the steps are the same.

[0062] Example 3

[0063] This embodiment provides a method for preparing a mold bag concrete slurry. The difference between this embodiment and Example 1 is that:

[0064] (2) 35 parts of cement, 15 parts of slag powder, 5 parts of silica fume, 2 parts of carbide slag and 3 parts of nano-silicon dioxide were stirred in a concrete mixer at 30 rpm for 3-5 minutes to form a dry powder;

[0065] The rest of the steps are the same.

[0066] Example 4

[0067] This embodiment provides a method for preparing a mold bag concrete slurry. The difference between this embodiment and Example 1 is that:

[0068] (5) Add the previously prepared anti-seepage agent solution (2.0 parts of isobutyltriethoxysilane dissolved in 10 times the volume of 5% ethanol) to the secondary slurry; the remaining steps are the same.

[0069] Comparative Example 1

[0070] This comparative example provides a method for preparing a mold bag concrete slurry. The difference between this comparative example and Example 1 is that:

[0071] The surface silane coupling agent-modified nanocarbon fibers in (1) are replaced with ordinary nanocarbon fibers; the remaining steps are the same.

[0072] Comparative Example 2

[0073] This comparative example provides a method for preparing a mold bag concrete slurry. The difference between this comparative example and Example 1 is that:

[0074] (4) The medium-graded aggregate includes 26 parts of basalt coarse aggregate with a particle size of 5-15 mm and 14 parts of quartz sand fine aggregate with a particle size of 0.3-1.2 mm; the rest of the steps are the same.

[0075] Comparative Example 3

[0076] This comparative example provides a method for preparing a mold bag concrete slurry. The difference between this comparative example and Example 1 is that:

[0077] In (2), 10 parts of cement, 35 parts of slag powder, 12 parts of silica fume, 5 parts of carbide slag and 3 parts of nano-silicon dioxide were stirred in a concrete mixer at 30 rpm for 3-5 minutes to form a dry powder; the remaining steps were the same.

[0078] Comparative Example 4

[0079] This comparative example provides a method for preparing a mold bag concrete slurry. The difference between this comparative example and Example 1 is that:

[0080] In (2), 35 parts of cement, 10 parts of slag powder, 4 parts of silica fume, 2 parts of carbide slag and 3 parts of nano-silicon dioxide were stirred in a concrete mixer at 30 rpm for 3-5 minutes to form a dry powder; the remaining steps were the same.

[0081] Table 2

[0082]

[0083] According to the above embodiments and comparative examples, the analysis is as follows:

[0084] As the best example, the bagged concrete sample prepared in Example 1 exhibited the highest 28-day and 90-day compressive strengths, the best impermeability rating, chemical corrosion resistance, and surface spalling depth. The corresponding slurry also exhibited excellent slump and spread, resulting in the best overall performance. The chloride ion diffusion coefficient was minimized, and the bagged concrete sample was the densest.

[0085] In the electron microscope scanning results of the concrete test blocks prepared in Examples 1 to 4, the single fiber dispersion rate of the nano-carbon fibers was greater than 90%, and there were no agglomerates with a diameter greater than 50 μm.

[0086] Comparing Example 2 with Example 1, it can be seen that, on the basis of Example 1, increasing the amount of slag powder can increase the slump and expansion of the slurry, improve the fluidity of the slurry, facilitate the pumping requirements of the mold bag, reduce the risk of pipe blockage, and the mold bag concrete can be pumped underwater without segregation, and the underwater mold bag is densely filled.

[0087] Comparing Example 3 with Example 1, it can be seen that, on the basis of Example 1, reducing the amount of slag powder used reduces the slump and expansion of the slurry; at the same time, the compressive strength is also affected.

[0088] Comparing Example 4 with Example 1, it can be seen that, on the basis of Example 1, increasing the amount of the anti-seepage agent can effectively inhibit the diffusion of chloride ions.

[0089] Comparison between Comparative Example 1 and Example 1 shows that, based on Example 1, the surface silane coupling agent-modified nanocarbon fibers are replaced with ordinary nanocarbon fibers. The electron microscope scanning results show that ordinary nanocarbon fibers are prone to agglomeration, which affects the compressive strength of the concrete sample, increases chloride ion diffusion, and reduces resistance to chemical corrosion. The agglomerated nanocarbon fibers increase the porosity between the fiber and matrix interface, significantly reduce the impermeability grade, and reduce the durability of the concrete.

[0090] Comparison between Comparative Example 2 and Example 1 shows that, based on Example 1, excessive use of coarse aggregate in the graded aggregate increases the porosity of the concrete sample, which leads to reduced compressive strength, increased chloride ion diffusion, a significant decrease in impermeability grade, and reduced durability of the concrete.

[0091] Comparing Comparative Example 3 with Example 1 shows that, compared to Example 1, the excessive amount of slag powder used significantly reduced the concrete sample's impermeability, increased chloride ion diffusion, decreased chemical corrosion resistance, and significantly decreased concrete durability. This is because the risk of cracking increases due to the peak temperature difference in cement hydration heat, and the increased shrinkage of concrete exacerbates surface microcracks.

[0092] Comparing Comparative Example 4 with Example 1 shows that, compared to Example 1, the use of too little slag powder significantly reduced the early compressive strength of the concrete specimens, significantly decreased the impermeability rating, and reduced the durability of the concrete. This is due to the weakened secondary hydration of the slag powder and its limited ability to alleviate the heat of cement hydration, resulting in reduced density of the concrete specimens. When the slag powder is used too little, its lubricating effect is weakened, resulting in the lowest slump of the concrete paste.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 bagged concrete composition, characterized in that: The composition comprises the following components, which are placed separately and calculated by weight: 15-35 parts of cement, 15-25 parts of slag powder, 5-10 parts of silica fume, 2-4 parts of carbide slag, 35-40 parts of graded aggregate, 0.8-1.2 parts of modified nano-carbon fiber, 3-4 parts of nano-silicon dioxide, 1.5-2.5 parts of anti-seepage agent, 1.5-2.0 parts of water reducing agent, and 0.2-0.4 parts of auxiliary dispersant; The mass ratio of slag powder to the total mass of slag powder and cement is 0.3-0.5; The water reducing rate of the water reducing agent is ≥35%; Auxiliary dispersant is used to uniformly disperse the modified carbon nanofibers; The anti-seepage agent and the modified carbon nanofiber can undergo a dehydration condensation reaction; The modified nano-carbon fibers are nano-carbon fibers modified with a surface silane coupling agent, and the anti-seepage agent is a silane-based anti-seepage agent; Graded aggregates include coarse aggregate and fine aggregate; Among them, the particle size of coarse aggregate is 5-15mm, and the particle size of fine aggregate is 0.3-1.2mm; The mass ratio of coarse aggregate to fine aggregate is 55-57.5:42.5-45.

2. The bagged concrete composition according to claim 1, wherein The mass ratio of slag powder to the total mass of slag powder and cement is 0.4-0.5; 15-20 parts of slag powder, 5-8 parts of silica fume, and 2-3 parts of carbide slag.

3. The bagged concrete composition according to claim 1, wherein The specific surface area of ​​slag powder and carbide slag is ≥600 m² / kg; the specific surface area of ​​silica fume is ≥15,000 m² / kg.

4. The bagged concrete composition according to claim 1, wherein The modification ratio of the nano-carbon fibers modified with the surface silane coupling agent is ≤1.5%; the auxiliary dispersant is non-ionic polyvinyl pyrrolidone.

5. The bagged concrete composition according to claim 1, wherein The water reducer is a polycarboxylic acid water reducer.

6. A method for preparing a mold bag concrete slurry, characterized in that: The mold bag concrete composition according to any one of claims 1 to 5 specifically comprises the following steps: S1. Prepare mixing water according to a water-binder ratio of 0.26-0.30, mix and disperse the modified nanocarbon fibers and the auxiliary dispersant with 30-50% volume of mixing water to form a stable suspension; Dry-mix cement, slag powder, silica fume, carbide slag and nano-silicon dioxide to form dry powder; S2. Mix the water reducer and the remaining volume of mixing water, then add it to the dry powder, stir and mix, and prepare a primary slurry; S3, stirring and mixing the suspension prepared in S1 and the primary slurry, then adding the graded aggregate in the order of coarse first and fine later, stirring and mixing to prepare the secondary slurry; S4. Add the anti-seepage agent to the secondary slurry, stir and mix well to prepare the mold bag concrete slurry.

7. The preparation method according to claim 6, wherein In S3, the stirring and mixing speed is 60-120 rpm.

8. The preparation method according to claim 6, wherein In S4, the stirring and mixing speed is 100-120 rpm.

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