Fluidified solidified soil suitable for underwater forming and method for preparing same

Abstract

The application discloses a kind of flow state solidified soil suitable for underwater forming, which is made of the following raw materials by weight fraction: magnesium slag 3-10 parts, mineral powder 3-10 parts, calcium sulfate 0.5-1 part, polyacrylic acid sodium salt 0.02-0.06 part, phosphoric acid 0.01-0.03 part, water 30 parts, and soil 50 parts. The preparation method comprises the following steps: I. Mix magnesium slag, mineral powder, calcium sulfate, polyacrylic acid sodium salt and soil to obtain dry powder; II. Add the mixing water prepared from phosphoric acid and water to the dry powder and stir. The flow state solidified soil of the application improves its water retention performance by adding polyacrylic acid sodium salt to form a gel-like structure, and forms an insoluble salt by cross-linking polyacrylic acid sodium salt with divalent or higher metal ions to form a dense hydrophobic layer on the surface, so that the flow state solidified soil can form in deep water and avoid dispersion with high strength, without changing its high fluidity characteristics, ensuring its workability and durability, and realizing the utilization of solid waste resources.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of building materials, and particularly relates to a flowable solidified soil suitable for underwater forming and a preparation method thereof. BACKGROUND

[0002] The flowable solidified soil is a backfill material suitable for various application scenarios such as civil air defense backfill, foundation backfill, and water stop curtain, and the raw material thereof often uses harmless industrial solid waste instead of traditional cementitious materials such as cement and lime, and has a lower use cost than traditional backfill materials such as foamed concrete and graded sandstone. The flowable solidified soil has the advantages of large fluidity, low energy consumption, and low carbon emission.

[0003] However, in actual application scenarios, it is often difficult to avoid some water accumulation problems, which are generally static water and low-flow dynamic water. The existing flowable solidified soil can only be formed under a small amount of static water, and is prone to dispersion before forming when the water accumulation is more than 30 cm, which cannot be constructed. Moreover, under the premise of a small amount of water, the water content in the flowable solidified soil needs to be reduced during construction, which sacrifices the workability, reduces the construction efficiency, and increases the construction cost.

[0004] The soil solidifying agent in the patent with the authorized announcement number CN112142406B is composed of cementitious materials, active mixed materials, micro-expansion materials, activators, dispersants, hydrophobic nano-silicon oxide, inorganic polyphosphates, and polyquaternary ammonium salts and their derivatives. By adding part of hydrophobic nano-silicon oxide and mixing it with cementitious materials and active mixed materials through a conical twin-screw spiral mixer, the hydrophobic nano-silicon oxide is preferentially adsorbed on the surface of the cementitious materials and active mixed materials, making the surface have hydrophobic properties, thereby reducing the adsorption of water and the amount of dispersant, improving the fluidity of the flowable solidified soil, and forming synergy with the dispersant. Meanwhile, the hydrophobic silicon oxide helps to improve the strength of the solidified soil. However, the raw materials used in the patent are inorganic materials, which cannot form a hydrophobic precipitation layer, and it is not mentioned that the flowable solidified soil can be used underwater. Moreover, the dispersion of nano materials is difficult, and the cost is high. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a flowable solidified soil suitable for underwater forming in view of the deficiencies of the prior art. The flowable solidified soil adds sodium polyacrylate, uses the gel structure formed by the dissolution of sodium polyacrylate to improve the water retention performance of the flowable solidified soil, and uses the cross-linking of sodium polyacrylate and divalent metal ions to form insoluble salts, thereby forming a dense hydrophobic layer on the surface of the flowable solidified soil. The flowable solidified soil can be formed in deep water accumulation to avoid dispersion and has high strength without changing its large fluidity characteristics, ensuring its workability and durability, and solving the problem that the existing flowable solidified soil is difficult to form in the presence of water accumulation and low-flow water.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a flow state solidified soil suitable for underwater forming, characterized by being made of raw materials including the following components by weight: magnesium slag 3-10 parts, mineral powder 3-10 parts, calcium sulfate 0.5-1 part, polyacrylic acid sodium salt 0.02-0.06 part, phosphoric acid 0.01-0.03 part, water 30 parts, and soil 50 parts.

[0007] The present application uses soil as raw material, magnesium slag and mineral powder as cementing materials, calcium sulfate as an activator, and polyacrylic acid sodium salt and phosphoric acid as additives. 2+ , Ca 2+ and OH − , etc., so that the pH of the whole system rapidly increases to above 11, on the one hand, breaking the Si-O-Al bond on the surface of the silicate glass body of the mineral powder and accelerating the dissolution of active SiO2 and Al2O3, and on the other hand, facilitating the dissolution of calcium sulfate in the alkaline environment and releasing SO4 2- ions to react with Al 3+ in the mineral powder to generate ettringite (AFt, 3CaO・Al2O3・3CaSO4・32H2O) to form early strength. 2+ , Mg 2+ , Al 3+ , Fe 2+ , Zn 2+ , etc., are generated, which rapidly react with the polyacrylic acid sodium salt to generate insoluble salt, partially wrapping the cementing material particles and affecting the later hydration reaction, while the added phosphoric acid, on the one hand, plays a role in adjusting the pH of the system, thereby delaying the reaction rate in the initial stage of the hydration reaction, reducing the dissolution amount of the divalent or more metal ions in the initial stage of the hydration reaction, and controlling the generation amount of the insoluble salt generated by the reaction of the divalent or more metal ions with the polyacrylic acid sodium salt in the initial stage of the hydration reaction, so as to ensure that the polyacrylic acid sodium salt can be fully dissolved in the system to form a gel structure, and on the other hand, the phosphoric acid reacts with the magnesium slag and the mineral powder to generate phosphate, which fills the pores of the flow state solidified soil and improves its compactness.

[0008] The polyacrylic acid sodium salt used in the raw material of the flow state solidified soil is easy to dissolve in alkaline aqueous solution, and with the increase of the number of divalent metal ions in the alkaline aqueous solution, it is dissolved first and then precipitated, and when the polyacrylic acid sodium salt is fully dissolved, a gel structure is formed. Therefore, the present application controls the amount of precipitation by adding phosphoric acid to ensure that the polyacrylic acid sodium salt is fully dissolved to form a gel structure. On the one hand, the gel structure absorbs part of the water in the flow state solidified soil, which is beneficial to improve the water retention performance of the flow state solidified soil, effectively reduces the water loss of the flow state solidified soil in the process of stirring, transportation and pouring, maintains the workability of the flow state solidified soil, improves the construction efficiency, on the other hand, the gel structure effectively disperses the stress, improves the mechanical properties of the flow state solidified soil, at the same time, the gel structure fills the micro-pores of the flow state solidified soil, significantly improves the impermeability of the flow state solidified soil, reduces the penetration of water and harmful ions, thereby prolongs the service life of the flow state solidified soil. With the continuous dissolution of magnesium slag and mineral powder, phosphoric acid is consumed in large quantities due to the reaction with magnesium slag and mineral powder to form phosphate, the concentration of divalent metal ions in the system increases, the carboxyl functional group contained in the polyacrylic acid sodium salt forms an insoluble salt with the divalent metal ion, causing molecular crosslinking and gelation precipitation to form a dense hydrophobic layer, especially the soil contains a large amount of aluminum ions and iron ions, which are adsorbed on the interface layer between the flow state solidified soil and water, protecting the un-solidified flow state solidified soil, such as the following reaction formula (1), the polyacrylic acid sodium salt reacts with calcium ions to form an insoluble salt due to the chelation effect caused by the charge adsorption, forming a gel property, thereby isolating the accumulated water from the internal cementing material of the flow state solidified soil, ensuring the subsequent strength growth of the flow state solidified soil in the accumulated water environment.

[0009] Reaction formula (1)

[0010] In addition, the polyacrylic acid sodium salt can also act on the soil part of the flow state solidified soil, effectively improving the soil structure, increasing the number of soil macro-aggregates, and keeping the soil particles and pore structure stable; the polyacrylic acid sodium salt has good hydrophilicity under alkaline conditions, and the gel structure formed by absorbing water after dissolution forms a unit that can slowly release water molecules inside the flow state solidified soil, helping the cementing material in the flow state solidified soil to fully react with free water to form hydrated products with strength, and improving the late strength.

[0011] The above-mentioned flow state solidified soil suitable for underwater forming is characterized by being made of raw materials including the following components in the following proportions: magnesium slag 6-10 parts, mineral powder 3-6 parts, calcium sulfate 0.7-1 part, polyacrylic acid sodium salt 0.02-0.04 part, phosphoric acid 0.01-0.02 part, water 30 parts, and soil 50 parts.

[0012] In addition, the present application also discloses a method for preparing the flow state solidified soil suitable for underwater forming as described above, characterized by comprising the following steps:

[0013] Step one, according to the design ratio of the target product flow state solidified soil, the slag, the mineral powder, the calcium sulfate, the sodium polyacrylate and the soil are respectively weighed and put into the blender to be stirred and mixed uniformly to obtain the dry powder material;

[0014] Step two, the mixed water prepared by the phosphoric acid and water is added into the dry powder material in step one to be stirred at low speed to obtain the flow state solidified soil suitable for underwater forming.

[0015] The method has the characteristics that the stirring and mixing time in step one is 30s.

[0016] The method has the characteristics that the stirring time at low speed in step two is 120s.

[0017] The method has the characteristics that the flow state solidified soil in step two is formed by the following process: the test mold is opened upwardly and placed in the water tank, an appropriate amount of water is injected into the water tank to make the water surface higher than the top end of the test mold by 5cm~10cm, then the flow state solidified soil is directly poured 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 60s, after the flow state solidified soil is initially set, the excess part at the upper end of the test mold is scraped off with a spatula, then the test mold is removed after curing in water for 1d, and the test block obtained after the test mold is removed is continuously placed in water for curing until 28d to test the compressive strength.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] 1. In the flow state solidified soil of the present application, the sodium polyacrylate is added, which is easily dissolved in alkaline aqueous solution and precipitated after dissolution. By controlling the pH of the system with phosphoric acid, the sodium polyacrylate is first fully dissolved to form a gel structure to absorb water in the flow state solidified soil, improving the water retention performance of the flow state solidified soil. Then, the sodium polyacrylate contains carboxyl functional groups which form insoluble salts with divalent metal ions, causing molecular crosslinking and gelation precipitation to form a hydrophobic layer, thereby isolating the accumulated water from the internal cementing material of the flow state solidified soil, ensuring the smooth construction and forming of the flow state solidified soil, and being suitable for underwater forming.

[0020] 2. In the flow state solidified soil of the present application, magnesium slag and mineral powder are added to produce a large amount of C-S-H gel through hydration, calcium sulfate is added to generate AFt crystals which are interpenetrated in the C-S-H gel to form a dense network structure, effectively improving the strength, especially the early strength, density and impermeability of the flow state solidified soil. Phosphoric acid is added to react with magnesium slag and mineral powder to generate phosphate, which fills the pores of the flow state solidified soil to improve its density, thereby ensuring the overall strength of the solid flow state solidified soil. Without reducing the water content to avoid the reduction of the flowability of the solid flow state solidified soil due to the reduction of its strength, the subsequent strength of the flow state solidified soil is improved under the premise of ensuring its flowability, improving the construction efficiency and reducing the construction cost.

[0021] 3、The raw materials used in the flow state solidified soil of the present application are environmentally friendly, wherein the cementing materials, magnesium slag and slag, are industrial solid wastes, low in cost, widely available, effectively utilize solid waste resources, are environmentally friendly, have outstanding environmental protection performance, and effectively ensure the workability and strength of the flow state solidified soil and reduce construction cost.

[0022] 4、The preparation process of the flow state solidified soil suitable for underwater molding is simple and convenient, the dry materials are first mixed uniformly, then the mixed water prepared from phosphoric acid and water is added and stirred uniformly, without the need for more construction equipment, easy to implement, and suitable for promotion.

[0023] The technical solutions of the present application are described in further detail below through the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Process diagram for molding of the flow state solidified soil test piece of the present application. DETAILED DESCRIPTION

[0025] Example 1

[0026] The flow state solidified soil suitable for underwater molding of this example is made from the following raw materials by weight fraction: magnesium slag 3 parts, mineral powder 10 parts, calcium sulfate 0.8 parts, polyacrylic acid sodium salt 0.04 parts, phosphoric acid 0.01 parts, water 30 parts, and soil 50 parts.

[0027] The preparation method of the flow state solidified soil suitable for underwater molding of this example includes the following steps:

[0028] Step one, the slag, mineral powder, calcium sulfate, polyacrylic acid sodium salt, and soil are respectively weighed according to the design ratio of the target product, flow state solidified soil, put into a stirrer, and stirred at a low speed of 60 r / min for 30 s to mix uniformly, to obtain dry powder;

[0029] Step two, the mixed water prepared from the weighed phosphoric acid and water is added to the dry powder in step one and stirred at a low speed of 60 r / min for 120 s, to obtain the flow state solidified soil suitable for underwater molding.

[0030] Example 2

[0031] The difference between this example and example 1 is that the flow state solidified soil suitable for underwater molding is made from the following raw materials by weight fraction: magnesium slag 10 parts, mineral powder 3 parts, calcium sulfate 0.8 parts, polyacrylic acid sodium salt 0.04 parts, phosphoric acid 0.01 parts, water 30 parts, and soil 50 parts.

[0032] Example 3

[0033] The difference between this example and Example 1 is that the fluidified solidified soil suitable for underwater molding is made from raw materials including the following parts by weight: magnesium slag 7 parts, mineral powder 6 parts, calcium sulfate 0.5 parts, polyacrylic acid sodium salt 0.04 parts, phosphoric acid 0.01 parts, water 30 parts, soil 50 parts.

[0034] Example 4

[0035] The difference between this example and Example 1 is that the fluidified solidified soil suitable for underwater molding is made from raw materials including the following parts by weight: magnesium slag 7 parts, mineral powder 6 parts, calcium sulfate 0.5 parts, polyacrylic acid sodium salt 0.04 parts, phosphoric acid 0.01 parts, water 30 parts, soil 50 parts.

[0036] Example 5

[0037] The difference between this example and Example 1 is that the fluidified solidified soil suitable for underwater molding is made from raw materials including the following parts by weight: magnesium slag 7 parts, mineral powder 6 parts, calcium sulfate 1.0 parts, polyacrylic acid sodium salt 0.04 parts, phosphoric acid 0.01 parts, water 30 parts, soil 50 parts.

[0038] Example 6

[0039] The difference between this example and Example 1 is that the fluidified solidified soil suitable for underwater molding is made from raw materials including the following parts by weight: magnesium slag 7 parts, mineral powder 6 parts, calcium sulfate 1.0 parts, polyacrylic acid sodium salt 0.02 parts, phosphoric acid 0.01 parts, water 30 parts, soil 50 parts.

[0040] Example 7

[0041] The difference between this example and Example 1 is that the fluidified solidified soil suitable for underwater molding is made from raw materials including the following parts by weight: magnesium slag 7 parts, mineral powder 6 parts, calcium sulfate 1.0 parts, polyacrylic acid sodium salt 0.06 parts, phosphoric acid 0.01 parts, water 30 parts, soil 50 parts.

[0042] Example 8

[0043] The difference between this example and Example 1 is that the fluidified solidified soil suitable for underwater molding is made from raw materials including the following parts by weight: magnesium slag 7 parts, mineral powder 6 parts, calcium sulfate 1.0 parts, polyacrylic acid sodium salt 0.04 parts, phosphoric acid 0.02 parts, water 30 parts, soil 50 parts.

[0044] Example 9

[0045] The difference between this example and Example 1 is that the fluidified solidified soil suitable for underwater molding is made from raw materials including the following parts by weight: magnesium slag 7 parts, mineral powder 6 parts, calcium sulfate 1.0 parts, polyacrylic acid sodium salt 0.04 parts, phosphoric acid 0.03 parts, water 30 parts, soil 50 parts.

[0046] The fluidified solidified soil in the embodiments 1-9 of the present application is formed into a test piece, and the forming process is as shown in the figure, and the process is as follows: the test mold opening is placed upward in the water tank, an appropriate amount of water is injected into the water tank, the water surface is higher than the top end of the test mold by 5-10 cm, then the fluidified solidified soil is directly poured 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 in 60 s, after the fluidified solidified soil is initially cured, the excess part at the upper end of the test mold is scraped off with a scraper, then the mold is removed after curing in water for 1 d, the test block obtained after the mold is removed is continuously placed in water for curing until 28 d for testing the compressive strength, and the initial curing time and the spread are recorded, and the results are shown in Table 1. Figure 1

[0047] Table 1

[0048]

[0049] From Table 1, it can be seen that in the raw materials of the fluidified solidified soil of the present application, the influence of the mineral powder on the 28d compressive strength of the underwater formed fluidified solidified soil is greater than that of the magnesium slag, and the higher the mineral powder content, the higher the 28d compressive strength of the underwater formed fluidified solidified soil; the magnesium slag can well improve the spread of the underwater formed fluidified solidified soil, which is beneficial to improve the construction performance; the dosage of the additive polyacrylic acid sodium salt needs to be adjusted according to the matrix strength, and generally the lower the matrix strength, the more the amount of polyacrylic acid sodium salt required.

[0050] The above is only a preferred embodiment of the present application, and does not limit the present application. Any simple modification, change and equivalent change made according to the technical essence of the present application to the above embodiment are still within the protection scope of the technical solution of the present application.​

Claims

1. A fluidified soil suitable for underwater forming, characterized in that, The raw materials include the following components in parts by weight: magnesium slag 3-10 parts, mineral powder 3-10 parts, calcium sulfate 0.5-1 part, polyacrylic acid sodium salt 0.02-0.06 part, phosphoric acid 0.01-0.03 part, water 30 parts, and soil 50 parts.

2. A fluidified soil suitable for underwater forming according to claim 1, characterized in that, The raw materials include the following components in parts by weight: magnesium slag 6-10 parts, mineral powder 3-6 parts, calcium sulfate 0.7-1 part, polyacrylic acid sodium salt 0.02-0.04 part, phosphoric acid 0.01-0.02 part, water 30 parts, and soil 50 parts.

3. A method of preparing a fluidified soil suitable for underwater forming according to claim 1 or 2, characterised in that, The method comprises the following steps: Step one, magnesium slag, mineral powder, calcium sulfate, polyacrylic acid sodium salt and soil are weighed according to the design ratio of the target product, and are stirred and mixed in a blender to obtain dry powder; Step two, the mixed water prepared from the weighed phosphoric acid and water is added to the dry powder in step one and is stirred at low speed to obtain a fluid solidified soil suitable for underwater forming.

4. The method of claim 3, wherein, The stirring and mixing time in step one is 30 seconds.

5. The method of claim 3, wherein, The low-speed stirring time in step two is 120 seconds.

6. The method of claim 3, wherein, The test piece forming process of the fluid solidified soil in step two is as follows: the test mold is placed in the water tank with the opening facing upward, an appropriate amount of water is injected into the water tank so that the water surface is higher than the top end of the test mold by 5-10 cm, then the fluid solidified soil is directly poured into the test mold to form a small hill at the upper end of the test mold opening, and each test mold is filled within 60 seconds, after the fluid solidified soil is initially set, the excess part at the upper end of the test mold is scraped off with a spatula, then the mold is removed after 1 day of curing in water, and the test block obtained after the mold is removed is further cured in water for 28 days to test the compressive strength.

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