Fluidized solidified soil suitable for underwater forming and preparation method thereof

Abstract

The invention discloses flow-state solidified soil suitable for underwater forming. The flow-state solidified soil is prepared from the following raw materials in parts by weight: 3-10 parts of magnesium slag, 3-10 parts of mineral powder, 0.5-1 part of calcium sulfate, 0.02-0.06 part of sodium polyacrylate, 0.01-0.03 part of phosphoric acid, 30 parts of water and 50 parts of soil. The preparation method comprises the following steps: 1, weighing magnesium slag, mineral powder, calcium sulfate, sodium polyacrylate and soil, and uniformly mixing to obtain dry powder; and 2, adding mixing water prepared from phosphoric acid and water into the dry powder, and stirring. According to the fluid-state solidified soil, the sodium polyacrylate is added and dissolved to form a colloidal structure, the water retention capacity of the fluid-state solidified soil is improved, the sodium polyacrylate and metal ions with the valence being two or more are cross-linked to form insoluble salt, a compact hydrophobic layer is formed on the surface, the fluid-state solidified soil is formed in deep accumulated water, dispersion is avoided, and the fluid-state solidified soil has high strength; the large fluidity characteristic is not changed, the workability and durability are ensured, and meanwhile, the utilization of solid waste resources is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to fluidized solidified soil suitable for underwater molding and a preparation method thereof. Background Art

[0002] Fluidized solidified soil is a backfill material suitable for a variety of applications, including civil air defense backfill, foundation backfill, and water-stop curtains. Its raw materials often use harmless industrial solid waste instead of traditional cementitious materials such as cement and lime. Its cost is lower than traditional backfill materials such as foamed concrete and graded sand and gravel. It offers advantages such as high fluidity, low energy consumption, and low carbon emissions.

[0003] However, in actual application scenarios, it's often difficult to avoid some water accumulation, typically static water or low-velocity dynamic water. Existing fluidized soil can only be formed with minimal static water accumulation. If water accumulation exceeds 30cm, it tends to disperse before forming, making construction impossible. Furthermore, when only a small amount of water is present, the water content in the fluidized soil mix must be reduced during construction, sacrificing workability, reducing construction efficiency, and increasing construction costs.

[0004] The soil solidifier raw materials in the patent "Soil Solidifier for Highly Fluid Solidified Soil" with authorization announcement number CN112142406B are composed of a gelling material, an active mixed material, a micro-expansion material, an activator, a dispersant, hydrophobic nano-silica, an inorganic polyphosphate, a polyquaternary ammonium salt, and its derivatives. By adding some hydrophobic nano-silica and mixing it with the gelling material and the active mixed material through a conical twin-screw spiral mixer, it is preferentially adsorbed on the surface of the gelling material and the active mixed material particles, giving the surface a hydrophobic property, thereby reducing water adsorption and reducing the amount of dispersant used, thereby achieving the effect of improving the fluidity of the fluidized solidified soil and forming a synergistic effect with the dispersant. At the same time, the hydrophobic silica is greatly helpful in improving the strength of the solidified soil itself. However, the raw materials used in this patent are inorganic materials and cannot form a hydrophobic sedimentation layer. There is no description of underwater use. In addition, the dispersion of the nanomaterial is difficult and the cost is relatively high. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the above-mentioned prior art and provide a fluidized solidified soil suitable for underwater molding. This fluidized solidified soil improves its water retention by adding sodium polyacrylate, which dissolves to form a colloidal structure. Furthermore, the sodium polyacrylate is cross-linked with divalent or higher metal ions to form an insoluble salt, forming a dense hydrophobic layer on the surface of the fluidized solidified soil. This allows the fluidized solidified soil to be formed in deeper water without dispersion and to have high strength without changing its high fluidity characteristics, thus ensuring its workability and durability. This solves the problem that existing fluidized solidified soils are difficult to mold in the presence of water or low-flow water.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a fluidized solidified soil suitable for underwater molding, characterized in that it is made of the following raw materials in parts by weight: 3 to 10 parts of magnesium slag, 3 to 10 parts of mineral powder, 0.5 to 1 part of calcium sulfate, 0.02 to 0.06 parts of sodium polyacrylate, 0.01 to 0.03 parts of phosphoric acid, 30 parts of water, and 50 parts of soil.

[0007] The present invention uses soil as raw material, magnesium slag and mineral powder as gelling materials, calcium sulfate as activator, polyacrylate sodium salt and phosphoric acid as admixtures. After adding water, the main hydration product of magnesium slag is calcium silicate hydrate (CSH) gel. The silicate glass structure of mineral powder is dense, and the hydration reaction is slow after contacting water. It is necessary to break the glass network structure in an alkaline environment to release active ions. Mg is generated during the initial hydration process of magnesium slag. 2+ , Ca 2+ and OH − The pH value of the whole system rises rapidly to above 11, which destroys the Si-O-Al bond on the surface of the mineral powder silicate glass and accelerates the dissolution of active SiO2 and Al2O3. On the other hand, it is conducive to the dissolution of calcium sulfate in an alkaline environment and releases SO4 2- ions, and Al in the mineral powder 3+ The reaction generates ettringite (AFt, 3CaO・Al2O3・3CaSO4・32H2O), forming early strength. At this time, the hydration reaction proceeds in the positive direction, and a large amount of divalent or higher metal ions (such as Ca 2+ Mg 2+ 、Al 3+ 、Fe 2+ 、Zn 2+ ) is produced, which rapidly reacts with sodium polyacrylate to form insoluble salts that partially encapsulate the cementitious material particles and affect the subsequent hydration reaction. The added phosphoric acid, on the one hand, regulates the system's pH, thereby slowing the reaction rate in the initial hydration reaction and reducing the dissolution of divalent or higher-valent metal ions. This controls the amount of insoluble salts formed by the reaction of divalent or higher-valent metal ions with sodium polyacrylate, ensuring that the sodium polyacrylate can fully dissolve in the system to form a colloidal structure. Furthermore, phosphoric acid reacts with magnesium slag and mineral powder to form phosphates, which fill the pores of the fluidized solidified soil and increase its density. As the hydration reaction continues, the magnesium slag and mineral powder hydrate to produce a large amount of CSH gel. AFt crystals generated by calcium sulfate and mineral powder are interspersed in the CSH gel, forming a dense network structure that effectively improves the strength, density, and impermeability of the fluidized solidified soil.

[0008] The sodium polyacrylate salt, an admixture used in the raw materials of the fluidized solidified soil of the present invention, is easily soluble in alkaline aqueous solution. In alkaline aqueous solution, as the number of divalent or higher metal ions increases, it first dissolves and then precipitates, and when the sodium polyacrylate salt is fully dissolved, a colloidal structure is formed. Therefore, the present invention controls the amount of precipitate generated by adding phosphoric acid to ensure that the sodium polyacrylate salt is fully dissolved to form a colloidal structure. On the one hand, the colloidal structure is used to absorb part of the water in the fluidized solidified soil, which is beneficial to improving the water retention performance of the fluidized solidified soil, effectively reducing the water loss of the fluidized solidified soil during mixing, transportation and pouring, maintaining the workability of the fluidized solidified soil, and improving construction efficiency. On the other hand, the colloidal structure is used to effectively disperse stress and improve the mechanical properties of the fluidized solidified soil. At the same time, the colloidal structure is used to fill the microscopic pores of the fluidized solidified soil, significantly improving the anti-seepage performance of the fluidized solidified soil, reducing the penetration of water and harmful ions, and thus extending the service life of the fluidized solidified soil. As magnesium slag and mineral powder continue to dissolve, phosphoric acid is consumed in large quantities due to the reaction with magnesium slag and mineral powder to form phosphates. The concentration of divalent or higher metal ions in the system increases, and the carboxyl functional groups contained in sodium polyacrylate form insoluble salts with divalent or higher metal ions, causing molecular cross-linking and gelation precipitation to form a dense hydrophobic layer. In particular, the soil contains a large amount of aluminum ions and iron ions, which are adsorbed on the interface layer between the fluidized solidified soil and water, protecting the unsolidified fluidized solidified soil. As shown in the following reaction formula (1), sodium polyacrylate reacts with calcium ions due to charge adsorption to produce chelation and generate insoluble salts, forming gel properties, thereby isolating the accumulated water from the internal cementitious materials of the fluidized solidified soil, ensuring the subsequent strength growth of the fluidized solidified soil in a water-logged environment.

[0009] Reaction (1) In addition, sodium polyacrylate can also act on the soil part of the fluidized solidified soil, effectively improving the soil structure, increasing the number of large soil aggregates, and maintaining the stability of soil particles and pore structure; sodium polyacrylate has good hydrophilicity under alkaline conditions, and after dissolving, it absorbs water to form a colloidal structure that forms units that can slowly release water molecules inside the fluidized solidified soil, helping the cementitious materials in the fluidized solidified soil to fully react with free water to form strong hydration products, thereby improving the later strength.

[0010] The above-mentioned fluidized solidified soil suitable for underwater molding is characterized in that it is made of raw materials including the following parts by weight: 6 to 10 parts of magnesium slag, 3 to 6 parts of mineral powder, 0.7 to 1 part of calcium sulfate, 0.02 to 0.04 parts of sodium polyacrylate, 0.01 to 0.02 parts of phosphoric acid, 30 parts of water, and 50 parts of soil.

[0011] In addition, the present invention also discloses a method for preparing the fluidized solidified soil suitable for underwater forming as described above, characterized in that the method comprises the following steps: Step 1: According to the designed proportion of the target product, fluidized solidified soil, slag, mineral powder, calcium sulfate, sodium polyacrylate and soil are weighed respectively, and the mixture is put into a blender and stirred to obtain a dry powder; Step 2: Add the weighed mixing water prepared by phosphoric acid and water to the dry powder in step 1 and stir at a low speed to obtain fluidized solidified soil suitable for underwater molding.

[0012] The above method is characterized in that the stirring and mixing time in step 1 is 30 seconds.

[0013] The above method is characterized in that the time of low-speed stirring in step 2 is 120s.

[0014] The above method is characterized in that the specimen forming process of the fluidized solidified soil described in step 2 is: placing the test mold with the opening facing upward in a water tank, injecting an appropriate amount of water into the water tank so that the water level is 5 cm to 10 cm higher than the top of the test mold, and then directly pouring the fluidized solidified soil into the test mold to form a small hill shape at the upper end of the test mold opening, and each test mold is filled within 60 seconds. After the fluidized solidified soil is initially solidified, the excess part of the upper end of the test mold is scraped off with a scraper, and then the mold is removed after curing in water for 1 day. The test block obtained after demolding is continued to be placed in water for curing until 28 days to test the compressive strength.

[0015] Compared with the prior art, the present invention has the following advantages: 1. Sodium polyacrylate is added to the fluidized solidified soil of the present invention. Utilizing the characteristics of sodium polyacrylate being easily soluble in alkaline aqueous solutions and first dissolving and then precipitating, the pH of the system is controlled by phosphoric acid, so that the sodium polyacrylate is first fully dissolved to form a colloidal structure to absorb water in the fluidized solidified soil, thereby improving the water retention performance of the fluidized solidified soil. Then, the carboxyl functional groups contained in the sodium polyacrylate react with divalent or higher metal ions to form insoluble salts, causing molecular cross-linking and gelation precipitation to form a hydrophobic layer, thereby isolating the accumulated water from the cementitious material inside the fluidized solidified soil, ensuring smooth construction and molding of the fluidized solidified soil, and being suitable for underwater molding.

[0016] 2. In the fluidized solidified soil of the present invention, magnesium slag and mineral powder are added to hydrate and produce a large amount of CSH gel. Calcium sulfate and mineral powder are added to generate AFt crystals that are interspersed in the CSH gel to form a dense network structure, effectively improving the strength of the fluidized solidified soil, especially the early strength, density, and impermeability. Phosphoric acid is added to react with magnesium slag and mineral powder to generate phosphates, which fill the pores of the fluidized solidified soil and increase its density, thereby ensuring the overall strength of the solid fluidized solidified soil. There is no need to reduce the water content to avoid reducing the strength of the solid fluidized solidified soil and thus reducing its fluidity. That is, the subsequent strength of the fluidized solidified soil is improved while ensuring its fluidity, thereby improving construction efficiency and reducing construction costs.

[0017] 3. The raw materials used in the fluidized solidified soil of the present invention are environmentally friendly. The cementitious materials magnesium slag and slag are both industrial solid wastes with low cost and wide sources, which realizes the effective utilization of solid waste resources, is environmentally friendly, and has outstanding environmental protection properties. It also effectively ensures the workability and strength of the fluidized solidified soil and reduces construction costs.

[0018] 4. The preparation process of the fluidized solidified soil suitable for underwater molding of the present invention is simple and convenient. The dry materials are first mixed evenly, and then mixing water is added and stirred evenly. No additional construction equipment is required, and the process is easy to implement and suitable for promotion.

[0019] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a diagram showing the process of forming the fluidized solidified soil specimen of the present invention. DETAILED DESCRIPTION

[0021] Example 1 The fluidized solidified soil suitable for underwater molding in this embodiment is made of the following raw materials in parts by weight: 3 parts of magnesium slag, 10 parts of mineral powder, 0.8 parts of calcium sulfate, 0.04 parts of sodium polyacrylate, 0.01 parts of phosphoric acid, 30 parts of water, and 50 parts of soil.

[0022] The preparation method of fluidized solidified soil for underwater forming in this embodiment includes the following steps: Step 1: According to the designed proportion of the target product, fluidized solidified soil, slag, mineral powder, calcium sulfate, sodium polyacrylate and soil were weighed respectively, and the mixture was put into a blender and stirred at a low speed of 60 r / min for 30 seconds to obtain a dry powder; Step 2: Add the weighed mixing water prepared by phosphoric acid and water to the dry powder in step 1 and stir at a low speed of 60 r / min for 120 s to obtain fluidized solidified soil suitable for underwater molding.

[0023] Example 2 The difference between this embodiment and Example 1 is that the fluidized solidified soil suitable for underwater molding is made of the following raw materials in parts by weight: 10 parts of magnesium slag, 3 parts of mineral powder, 0.8 parts of calcium sulfate, 0.04 parts of sodium polyacrylate, 0.01 parts of phosphoric acid, 30 parts of water, and 50 parts of soil.

[0024] Example 3 The difference between this embodiment and Example 1 is that the fluidized solidified soil suitable for underwater molding is made of the following raw materials in parts by weight: 7 parts of magnesium slag, 6 parts of mineral powder, 0.8 parts of calcium sulfate, 0.04 parts of sodium polyacrylate, 0.01 parts of phosphoric acid, 30 parts of water, and 50 parts of soil.

[0025] Example 4 The difference between this embodiment and Example 1 is that the fluidized solidified soil suitable for underwater molding is made of the following raw materials in parts by weight: 7 parts of magnesium slag, 6 parts of mineral powder, 0.5 parts of calcium sulfate, 0.04 parts of sodium polyacrylate, 0.01 parts of phosphoric acid, 30 parts of water, and 50 parts of soil.

[0026] Example 5 The difference between this embodiment and Example 1 is that the fluidized solidified soil suitable for underwater molding is made of raw materials including the following parts by weight: 7 parts of magnesium slag, 6 parts of mineral powder, 1.0 part of calcium sulfate, 0.04 parts of sodium polyacrylate, 0.01 parts of phosphoric acid, 30 parts of water, and 50 parts of soil.

[0027] Example 6 The difference between this embodiment and Example 1 is that the fluidized solidified soil suitable for underwater molding is made of raw materials including the following parts by weight: 7 parts of magnesium slag, 6 parts of mineral powder, 1.0 part of calcium sulfate, 0.02 parts of sodium polyacrylate, 0.01 parts of phosphoric acid, 30 parts of water, and 50 parts of soil.

[0028] Example 7 The difference between this embodiment and Example 1 is that the fluidized solidified soil suitable for underwater molding is made of the following raw materials in parts by weight: 7 parts of magnesium slag, 6 parts of mineral powder, 1.0 part of calcium sulfate, 0.06 parts of sodium polyacrylate, 0.01 parts of phosphoric acid, 30 parts of water, and 50 parts of soil.

[0029] Example 8 The difference between this embodiment and Example 1 is that the fluidized solidified soil suitable for underwater molding is made of the following raw materials in parts by weight: 7 parts of magnesium slag, 6 parts of mineral powder, 1.0 part of calcium sulfate, 0.04 parts of sodium polyacrylate, 0.02 parts of phosphoric acid, 30 parts of water, and 50 parts of soil.

[0030] Example 9 The difference between this embodiment and Example 1 is that the fluidized solidified soil suitable for underwater molding is made of raw materials including the following parts by weight: 7 parts of magnesium slag, 6 parts of mineral powder, 1.0 part of calcium sulfate, 0.04 parts of sodium polyacrylate, 0.03 parts of phosphoric acid, 30 parts of water, and 50 parts of soil.

[0031] The fluidized solidified soil in Examples 1 to 9 of the present invention was molded into test pieces, and the molding process is as follows: Figure 1As shown in Figure 1, the process is as follows: place the test mold with the opening facing upward in a water tank, inject an appropriate amount of water into the water tank so that the water level is 5cm~10cm higher than the top of the test mold, and then pour the fluidized solidified soil directly into the test mold until a small hill is formed at the upper end of the test mold opening. Each test mold is poured within 60s. After the fluidized solidified soil is initially solidified, use a scraper to scrape off the excess part of the upper end of the test mold, then cure in water for 1d before removing the mold. The test block obtained after demolding is continued to be placed in water for curing until 28d to test the compressive strength, and the initial setting time and expansion are recorded. The results are shown in Table 1 below.

[0032] Table 1

[0033] As can be seen from Table 1, among the raw materials of the fluidized solidified soil of the present invention, the mineral powder has a greater effect on the 28d compressive strength of the underwater formed fluidized solidified soil than the magnesium slag, and the higher the mineral powder content, the higher the 28d compressive strength of the underwater formed fluidized solidified soil; magnesium slag greatly improves the expansion of the underwater formed fluidized solidified soil, which is beneficial to improving its construction performance; the content of the admixture sodium polyacrylate needs to be adjusted according to the strength of the matrix. Generally, the lower the matrix strength, the more sodium polyacrylate is required.

[0034] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A fluidized solidified soil suitable for underwater forming, characterized in that: The invention is prepared from the following raw materials in parts by weight: 3-10 parts of magnesium slag, 3-10 parts of mineral powder, 0.5-1 part of calcium sulfate, 0.02-0.06 parts of sodium polyacrylate, 0.01-0.03 parts of phosphoric acid, 30 parts of water and 50 parts of soil.

2. The fluidized solidified soil suitable for underwater forming according to claim 1, characterized in that: The invention is prepared from the following raw materials in parts by weight: 6-10 parts of magnesium slag, 3-6 parts of mineral powder, 0.7-1 part of calcium sulfate, 0.02-0.04 parts of sodium polyacrylate, 0.01-0.02 parts of phosphoric acid, 30 parts of water and 50 parts of soil.

3. A method for preparing fluidized solidified soil suitable for underwater forming as claimed in claim 1 or 2, characterized in that: The method comprises the following steps: Step 1: According to the designed proportion of the target product, fluidized solidified soil, slag, mineral powder, calcium sulfate, sodium polyacrylate and soil are weighed respectively, and the mixture is put into a blender and stirred to obtain a dry powder; Step 2: Add the weighed mixing water prepared by phosphoric acid and water to the dry powder material in step 1 and stir at a low speed to obtain fluidized solidified soil suitable for underwater molding.

4. The method according to claim 3, characterized in that The stirring and mixing time in step 1 is 30s.

5. The method according to claim 3, characterized in that The low-speed stirring time in step 2 is 120s.

6. The method according to claim 3, characterized in that The specimen forming process of the fluidized solidified soil described in step 2 is as follows: place the test mold with the opening facing upward in a water tank, inject an appropriate amount of water into the water tank so that the water level is 5 cm to 10 cm higher than the top of the test mold, and then pour the fluidized solidified soil directly into the test mold to form a small hill shape at the upper end of the test mold opening, and each test mold is filled within 60 seconds. After the fluidized solidified soil is initially solidified, use a scraper to scrape off the excess part of the upper end of the test mold, then cure in water for 1 day and then remove the mold. The test block obtained after demolding is continued to be placed in water for curing until 28 days to test the compressive strength.

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