Preparation method of mold bag concrete composition and mold bag concrete slurry

Abstract

The invention relates to a mold bag concrete composition and a preparation method of mold bag concrete slurry, and the mold bag concrete composition is prepared from, by weight, 15-35 parts of cement, 15-25 parts of superfine 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 carbon nanofibers and 3-4 parts of nano silicon dioxide which are independently placed. 1.5-2.5 parts of an anti-permeability agent, 1.5-2.0 parts of a water reducing agent and 0.2-0.4 part of an auxiliary dispersing agent; wherein the mass ratio of the superfine slag powder to the total mass of the superfine slag powder and the cement is 0.3-0.5; the water reducing rate of the water reducing agent is not less than 35%; the auxiliary dispersing agent is used for uniformly dispersing the modified carbon nanofibers; the anti-permeability agent and the modified carbon nanofibers can be subjected to dehydration condensation reaction. The mold bag concrete has the beneficial effects that the strength, the impermeability, the flowability and the durability of the mold bag concrete are comprehensively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of water conservancy projects, and particularly to a preparation method of a formwork bag concrete composition and a formwork bag concrete slurry. Background Art

[0002] Formwork bag concrete (also known as geotextile bag concrete or Geo-bag Concrete) is a structural material formed by pouring concrete into a specially made geotextile bag. This technology combines the advantages of geosynthetics and traditional concrete. Formwork bag concrete is mainly applied to the following water conservancy project scenarios: dam slope protection and anti-erosion, by directly laying the formwork bag on the slope to quickly form a high-strength protective layer; underwater repair and reinforcement: taking advantage of the self-compacting property of the formwork bag to directly pour underwater to repair leaking or damaged structures.

[0003] In the application of existing formwork bag concrete in water conservancy projects, there are generally problems of insufficient strength and poor impermeability, resulting in reduced structural stability and durability of water conservancy projects. In the face of water flow impact, wave action or other external loads, insufficient strength will cause deformation or even damage to the formwork bag concrete structure, thereby affecting the overall stability and safety of the project. At the same time, the formwork bag concrete in water conservancy projects needs to be frequently inspected and repaired, increasing the long-term maintenance cost. Summary of the Invention

[0004] I. Technical Problems to be Solved

[0005] In view of the above-mentioned disadvantages and deficiencies of the prior art, the present invention provides a preparation method of a formwork bag concrete composition and a formwork bag concrete slurry, which solves the technical problems of insufficient strength and poor impermeability existing when existing formwork bag concrete is applied to water conservancy projects.

[0006] II. Technical Solutions

[0007] To achieve the above object, the main technical solutions adopted by the present invention include:

[0008] In a first aspect, an embodiment of the present invention provides a formwork bag concrete composition, including, separately and independently placed 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 fiber, 3 - 4 parts of nano-silica, 1.5 - 2.5 parts of impermeability agent, 1.5 - 2.0 parts of water reducer, and 0.2 - 0.4 parts of auxiliary dispersant;

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

[0010] The water reduction rate of the water reducer ≥ 35%;

[0011] The auxiliary dispersant is used to uniformly disperse the modified nano-carbon fibers;

[0012] The impermeability agent can undergo a dehydration condensation reaction with the modified nano-carbon fibers.

[0013] As a preferred embodiment of the present invention, in the formwork bag concrete composition, the mass ratio of slag powder to the total mass of slag powder and cement 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 formwork bag concrete composition, the specific surface areas of the slag powder and the carbide slag are both ≥600 m² / kg; the specific surface area of the silica fume is ≥15000 m² / kg.

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

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

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

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

[0020] As a preferred embodiment of the present invention, in the formwork bag concrete composition, the impermeability agent is selected as a silane-based impermeability agent.

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

[0022] In a second aspect, an embodiment of the present invention provides a method for preparing a formwork bag concrete slurry, using the formwork bag concrete composition, which specifically includes the following steps:

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

[0024] Dry-mix and mix evenly the cement, slag powder, silica fume, carbide slag, and nano-silica to form a dry powder mixture;

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

[0026] S3. Mix the suspension prepared in S1 with the primary slurry evenly by stirring, and then add graded aggregate by stirring in the order from coarse to fine, and stir evenly to obtain a secondary slurry.

[0027] S4. Add an anti-seepage agent to the secondary slurry and stir evenly to obtain a formwork 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] III. Beneficial effects

[0031] The beneficial effects of the present invention are as follows: For a formwork bag concrete composition and a preparation method of formwork bag concrete slurry of the present invention, blast furnace slag powder and silica fume undergo pozzolanic reaction under the excitation of carbide slag. A solid waste system is used to partially replace cement in proportion. While ensuring the concrete strength, it is beneficial to control the increase in porosity caused by cement hydration heat. Blast furnace slag powder undergoes secondary hydration in the later stage of cement hydration, further filling the pores. Finally, the prepared formwork bag concrete is denser and has better anti-seepage performance. Using blast furnace slag powder, silica fume and carbide slag for solid waste recycling reduces the amount of cement used, which is green and environmentally friendly. The anti-seepage agent can react directionally with modified nano-carbon fibers, promoting the uniform distribution of modified nano-carbon fibers. The dispersion rate of nano-carbon fibers ≥ 90%, realizing three-dimensional toughening of formwork bag concrete, and overall improving the strength of formwork bag concrete. The 28-day compressive strength is 62 MPa, and ≥ 70 MPa at 90 days. At the same time, it ensures the balance between the enhancement and anti-seepage performance of concrete. Nano-silica fills the micropores of the material, synergistically with the secondary hydration reaction of the solid waste system, reducing shrinkage and also improving the early strength of concrete; nano-silica and the anti-seepage agent jointly fill the gaps and micropores of the concrete, improving the anti-seepage property of the concrete. At the same time, nano-silica can also improve the early strength of the concrete. Optimized aggregate gradation and high-performance water reducer can improve the fluidity of the slurry, facilitating the formwork bag pumping requirement and reducing the risk of pipe blockage; the slurry spread ≥ 600 mm, and the formwork bag concrete has no segregation during underwater pumping, and the underwater formwork bag is filled densely. At the same time, the appropriate fluidity is conducive to the uniform dispersion of modified nano-carbon fibers, nano-silica and the anti-seepage agent, thereby assisting in improving the anti-seepage performance of the concrete. Compared with the prior art, this formwork bag concrete takes into account the comprehensive improvement of strength, anti-seepage property, fluidity and durability, breaking through the technical barrier in the prior art that can only enhance a certain performance of formwork bag concrete singly, and has wide application value in the field of water conservancy projects, while taking into account environmental protection and economy.

[0032] The silanol groups on the surface silane coupling agent-modified nanofibers react with the silane of the impermeability agent to form Si-O-Si bonds, preventing the impermeability agent from competitively adsorbing onto the nanofibers. The impermeability agent can directionally block the capillary pores between the nanofibers and the matrix. This achieves a comprehensive improvement in impermeability, durability, and compatibility with nanofibers. Its composite design is particularly suitable for scenarios with high impermeability and high durability requirements in water conservancy projects, such as tidal gates and subsea tunnels. The chloride ion diffusion coefficient is reduced to below 0.5×10⁻¹² m² / s, and the impermeability grade is W14.

[0033] In the preparation method of the slurry, the modified nanofibers are pre-dispersed and then mixed with other materials through stepwise stirring to avoid agglomeration. The impermeability agent is added last, and rapid stirring is used to ensure its uniform distribution.

[0034] The aggregate gradation is optimized, with the proportion of fine aggregate increased to more than 40%. With the addition of a carboxylic acid water reducer, the slump of the concrete slurry reaches 250 mm without segregation.

[0035] The water-binder ratio is controlled between 0.26 - 0.30 and adjusted with a water reducer to balance low porosity and high fluidity. Specific Embodiments

[0036] To better explain the present invention for easy understanding, the following provides a detailed description of the present invention through specific embodiments.

[0037] To better understand the above technical solutions, the 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 described 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 example provides a method for preparing a formwork bag concrete slurry, which includes the following steps:

[0040] (1) Prepare mixing water according to a water-binder ratio of 0.28. Mix 0.8 parts (by mass, the same hereinafter) of surface silane coupling agent-modified nanofibers (modification ratio ≤ 1.5%) and 0.2 parts of non-ionic polyvinylpyrrolidone with 50% of the mixing water by volume and disperse them for 30 min using 40 kHz ultrasonic waves to form a stable suspension; wherein, the water-binder ratio is the ratio of water to the total mass of cement, granulated blast furnace slag powder, silica fume, and carbide slag, and the mixing water here is the total water consumption excluding the water consumption required for auxiliary dissolution in other steps;

[0041] (2) Mix 23 parts of cement, 15 parts of slag powder, 5 parts of silica fume, 2 parts of carbide slag, and 3 parts of nano-silica in a concrete mixer at 30 rpm for 3 - 5 min to form a dry powder mixture; the specific surface area of both slag powder and carbide slag is ≥600 m² / kg, and the specific surface area of silica fume is ≥15000 m² / kg.

[0042] (3) Mix 1.5 parts of polycarboxylate superplasticizer with the remaining volume of mixing water, then add it to the dry powder mixture and stir to mix evenly to prepare a primary slurry.

[0043] (4) Slowly add the suspension prepared in (1) to the primary slurry multiple times and stir at 60 rpm for 3 - 5 min to mix evenly; then add the graded aggregates in the order of coarser first and finer later, with a stirring rate of 120 rpm. After adding each type of aggregate, stir for 2 min before adding the other type to ensure that the aggregates are fully wrapped by the slurry; after adding all the aggregates and stirring to mix evenly, prepare a secondary slurry; among them, the graded aggregates include 23 parts of basalt coarse aggregates with a particle size of 5 - 15 mm and 17 parts of quartz sand fine aggregates with a particle size of 0.3 - 1.2 mm, and the particle size ranges of the coarse and fine aggregates are continuously distributed.

[0044] (5) Add the pre-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 min until evenly mixed to obtain the formwork concrete slurry.

[0045] (6) Pour the formwork concrete slurry into the formwork under water environment. After pouring the formwork, apply a pressure of 5 - 10 kPa to discharge air bubbles, improve the compactness, and cure at room temperature under water for 7 - 28 days to prepare concrete test blocks.

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

[0047] Table 1

[0048]

[0049] Conduct the following performance tests on the formwork concrete slurry or test blocks:

[0050] 1) Refer to GB / T 50081 - 2002 "Standard Test Method for Compressive Strength of Concrete": Conduct compressive strength tests on the concrete test blocks, and the results are shown in Table 2 in detail;

[0051] 2) Refer to GB / T 50082 - 2009 "Standard Test Method for Durability of Concrete": Conduct water permeability resistance tests (step-by-step pressure method) and chloride ion penetration tests on the concrete test blocks, and the results are shown in Table 2 in detail;

[0052] 3) Refer to GB / T 50080-2016 "Standard Test Method for Properties of Ordinary Concrete Mixtures": The slump and spread of the concrete slurry were tested, and the results are shown in Table 2;

[0053] 4) Refer to GB / T 50082-2024, the chemical erosion resistance of the concrete specimens was tested: 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 shown in Table 2;

[0054] 5) Refer to GB / T 50082 and "Specifications for Water Conservancy Projects" to test the erosion resistance of the concrete specimens: The rotating water flow erosion test was adopted to simulate the wear rate under actual working conditions, and the surface spalling depth was measured and recorded. The results are shown in Table 2;

[0055] 6) Observe the distribution of nano-carbon fibers on the surface of the concrete specimens by SEM.

[0056] Example 2

[0057] This example provides a preparation method of the formwork bag concrete slurry. The difference between this example and Example 1 is as follows:

[0058] (1) Prepare mixing water according to the water-binder ratio of 0.30. Mix 1.2 parts (by mass, the same below) of nano-carbon fibers modified with surface silane coupling agent (modification ratio ≤ 1.5%) and 0.4 part of non-ionic polyvinylpyrrolidone with 50% volume of the mixing water, and disperse them by 40 kHz ultrasonic wave for 30 min to form a stable suspension;

[0059] (2) Put 20 parts of cement, 20 parts of slag powder, 8 parts of silica fume, 3 parts of carbide slag and 3 parts of nano-silica into a concrete mixer and stir at 30 rpm for 3 - 5 min to mix them into dry powder;

[0060] (3) Mix 2.0 parts of polycarboxylate superplasticizer with the remaining volume of the mixing water, then add it to the dry powder and stir evenly to prepare the primary slurry.

[0061] The remaining steps are the same.

[0062] Example 3

[0063] This example provides a preparation method of the formwork bag concrete slurry. The difference between this example and Example 1 is as follows:

[0064] In (2), put 35 parts of cement, 15 parts of slag powder, 5 parts of silica fume, 2 parts of carbide slag and 3 parts of nano-silica into a concrete mixer and stir at 30 rpm for 3 - 5 min to mix them into dry powder;

[0065] The remaining steps are the same.

[0066] Example 4

[0067] This example provides a method for preparing a flexible concrete slurry. The difference between this example and Example 1 is as follows:

[0068] (5) Add the previously prepared impermeability 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 flexible concrete slurry. The difference between this comparative example and Example 1 is as follows:

[0071] Replace the surface silane coupling agent-modified nanofibers in (1) with ordinary nanofibers; the remaining steps are the same.

[0072] Comparative Example 2

[0073] This comparative example provides a method for preparing a flexible concrete slurry. The difference between this comparative example and Example 1 is as follows:

[0074] The graded aggregate in (4) 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 remaining steps are the same.

[0075] Comparative Example 3

[0076] This comparative example provides a method for preparing a flexible concrete slurry. The difference between this comparative example and Example 1 is as follows:

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

[0078] Comparative Example 4

[0079] This comparative example provides a method for preparing a flexible concrete slurry. The difference between this comparative example and Example 1 is as follows:

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

[0081] Table 2

[0082]

[0083] Based on the above examples and comparative examples, the analysis is as follows with reference to the table:

[0084] Example 1, as the optimal example, the prepared concrete-filled flexible bag specimens have the highest 28-day compressive strength and 90-day compressive strength, the best impermeability grade, chemical erosion resistance and surface spalling depth; the slump and spread of the corresponding slurry are also relatively excellent, and the comprehensive performance is the best. The chloride ion diffusion coefficient is the smallest, and the concrete-filled flexible bag specimens are the densest.

[0085] In the SEM results of the concrete specimens prepared in Examples 1 to 4, the monofilament dispersion rate of the nanofibrous carbon is greater than 90%, and there are no aggregates with a diameter > 50 μm.

[0086] It can be seen from the comparison between Example 2 and Example 1 that on the basis of Example 1, increasing the dosage of ground granulated blast-furnace slag can increase the slump and spread of the slurry, improve the fluidity of the slurry, facilitate the pumping requirements of the concrete-filled flexible bag, reduce the risk of pipe blockage, and there is no segregation in the underwater pumping of the concrete-filled flexible bag, and the underwater concrete-filled flexible bag is filled densely.

[0087] It can be seen from the comparison between Example 3 and Example 1 that on the basis of Example 1, reducing the dosage of ground granulated blast-furnace slag reduces the slump and spread of the slurry; at the same time, the compressive strength is also affected.

[0088] It can be seen from the comparison between Example 4 and Example 1 that on the basis of Example 1, increasing the dosage of the impermeability agent can effectively inhibit the chloride ion diffusion.

[0089] It can be seen from the comparison between Comparative Example 1 and Example 1 that on the basis of Example 1, the surface silane coupling agent-modified nanofibrous carbon is replaced with ordinary nanofibrous carbon. The SEM results show that the ordinary nanofibrous carbon is prone to agglomeration, which affects the compressive strength of the concrete specimen, increases the chloride ion diffusion, and reduces the chemical erosion resistance. The agglomerated nanofibrous carbon increases the porosity between the fiber and the matrix interface, and the impermeability grade decreases significantly, and the durability of the concrete decreases.

[0090] It can be seen from the comparison between Comparative Example 2 and Example 1 that on the basis of Example 1, the amount of coarse aggregate in the graded aggregate is too much, the porosity of the concrete specimen increases, which will lead to a decrease in compressive strength, an increase in chloride ion diffusion, a significant decrease in impermeability grade, and a decrease in the durability of the concrete.

[0091] It can be seen from the comparison between Comparative Example 3 and Example 1 that on the basis of Example 1, the dosage of ground granulated blast-furnace slag is too much, the impermeability grade of the concrete specimen decreases significantly, the chloride ion diffusion increases, and the chemical erosion resistance decreases, and the durability of the concrete decreases significantly. The reason is that the risk of temperature difference cracks caused by the peak value of cement hydration heat increases, and the shrinkage rate of the concrete increases, exacerbating the surface micro-cracks.

[0092] Comparing Comparative Example 4 with Example 1, it can be seen that on the basis of Example 1, when the dosage of ground granulated blast-furnace slag is too small, the early compressive strength of the concrete specimen decreases significantly, the impermeability grade drops significantly, and the durability of the concrete decreases. The reason is that the secondary hydration of ground granulated blast-furnace slag weakens, and the alleviation of the heat of hydration of cement by ground granulated blast-furnace slag is limited, resulting in a decrease in the compactness of the concrete specimen. When the dosage of ground granulated blast-furnace slag is too small, the lubrication effect of ground granulated blast-furnace slag weakens, and the slump of the concrete paste is the lowest.

[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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and 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 concrete filled flexible mattress composition, characterized in that, Comprising separately and independently placed components by weight parts: 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 silica, 1.5 - 2.5 parts of impermeability agent, 1.5 - 2.0 parts of water reducing agent, and 0.2 - 0.4 parts of auxiliary dispersant; Among them, 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 ≥ 35%; The auxiliary dispersant is used to uniformly disperse the modified nano carbon fiber; The impermeability agent and the modified nano carbon fiber can undergo a dehydration condensation reaction.

2. The concrete filled flexible mattress 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, 2 - 3 parts of carbide slag.

3. The concrete-filled flexible bag composition according to claim 1, wherein The specific surface areas of both slag powder and carbide slag are ≥ 600 m² / kg; the specific surface area of silica fume ≥ 15000 m² / kg.

4. The concrete filled flexible bag composition according to claim 1, wherein The graded aggregate includes coarse aggregate and fine aggregate; Among them, the particle size of the coarse aggregate is 5 - 15 mm, and the particle size of the fine aggregate is 0.3 - 1.2 mm; The mass ratio of the coarse aggregate to the fine aggregate is 55 - 60:40 - 45.

5. The formwork bag concrete composition according to claim 1, characterized in that The modified nano carbon fiber is a nano carbon fiber modified by a surface silane coupling agent, and the modification ratio ≤ 1.5%; the auxiliary dispersant is selected as non-ionic polyvinylpyrrolidone.

6. The concrete filled flexible bag composition according to claim 5, wherein The impermeability agent is selected as a silane-based impermeability agent.

7. The concrete filled flexible bag composition according to claim 1, wherein The water reducing agent is a polycarboxylate water reducing agent.

8. A preparation method of a formwork bag concrete slurry, characterized in that, Using the flexible bag concrete composition described in any one of claims 1 - 7, specifically including the following steps: S1. Prepare mixing water according to a water-binder ratio of 0.26 - 0.30, and mix and disperse the modified nano carbon fiber and the auxiliary dispersant with 30 - 50% volume of the mixing water to form a stable suspension; Dry mix and uniformly mix cement, slag powder, silica fume, carbide slag, and nano silica into dry powder; S2. Mix the water reducing agent with the remaining volume of the mixing water evenly, then add it to the dry powder, and stir and mix evenly to prepare a primary slurry; S3. Stir and mix evenly the suspension prepared in S1 with the primary slurry, and then stir and add the graded aggregate in the order of first coarse and then fine, and stir and mix evenly to prepare a secondary slurry; S4. Add the impermeability agent to the secondary slurry, and stir and mix evenly to obtain the flexible bag concrete slurry.

9. The preparation method according to claim 8, wherein, In S3, the stirring and mixing rate is 60 - 120 rpm.

10. The preparation method according to claim 8, characterized in that, In S4, the stirring and mixing rate is 100 - 120 rpm.

Images