Solidification material

Abstract

To provide a solidification material that achieves sufficient reduction in pH.SOLUTION: A solidification material contains hydraulic alumina, and at least one of inorganic water-soluble sodium salt and inorganic water-soluble magnesium salt.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a solidification material that can be used in high-pressure jet mixing methods, chemical injection methods, and the like. [Background technology]

[0002] As a ground improvement method, there is a method of construction using a slurry-like solidification material. Also, as a solidification material, for example, there is a cement-based solidification material mainly composed of cement. However, although the cement-based solidification material is suitable for making the ground strong, the pH of the ground tends to be high due to the alkali of the cement itself. Therefore, "in the solidification treatment using a solidification material for water-containing soil, it is intended to provide a neutral solidification material that is neutral and has excellent solidification strength, and to provide a method for solidification improvement of water-containing soil using said solidification material", and "a neutral solidification material for water-containing soil consisting of 85 to 99 mass % hydraulic alumina and 1 to 15 mass % lithium carbonate" has been proposed. In addition, the proposal states that "a neutral solidification material for water-containing soil consisting of 65 to 98 mass % hydraulic alumina, 1 to 15 mass % lithium carbonate, and 1 to 20 mass % calcium carbonate" is more preferable. The proposal states, "We discovered that when hydraulic alumina is used as a soil solidification material, lithium carbonate acts as an excellent solidification aid (solidification strength enhancer), and furthermore, that by using this in combination with calcium carbonate, high strength comparable to that of cement-based solidification materials can be obtained in the neutral range, leading to the completion of this invention."

[0003] However, according to this proposal, the solidification material slurry has a short solidification time, and is not suitable for the high-pressure injection mixing method, and may not be suitable for the chemical injection method. In addition, the present inventor recognizes that the pH cannot be sufficiently controlled according to this proposal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4462853 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a solidification material capable of sufficiently suppressing pH, and more preferably, to provide a solidification material having a solidification time that can be used in a high-pressure injection mixing method or the like. [Means for solving the problem]

[0006] The means for solving the above problems are as follows.

[0007] (Means described in claim 1) 20-80% hydraulic alumina and inorganic water-soluble sodium Salt 0 .1 to 10 mass% and 、 Sodium chloride is blended as the inorganic water-soluble sodium salt. A solidification material characterized by:

[0008] (Means described in claim 2) At least one of an oxycarboxylic acid and an oxycarboxylic acid condensate is blended in an amount of 0.1 to 5 mass %. The solidification material according to claim 1.

[0009] (Means described in claim 3) As the oxycarboxylic acid, gluconic acid is blended. The solidification material according to claim 2.

[0010] (Means described in claim 4) Glucono δ-lactone is blended as the oxycarboxylic acid condensate. The solidification material according to claim 2.

[0011]

[0012] (Claim 5 (Means described in The inorganic water-soluble sodium Salt It is obtained from seawater be, The solidification material according to claim 1. Effect of the Invention

[0013] According to the invention, a solidification material is obtained that can sufficiently suppress the pH. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Next, an embodiment of the present invention will be described. Note that the embodiment is an example of the present invention. The scope of the present invention is not limited to the scope of the embodiment.

[0015] The solidification material of this embodiment is blended with hydraulic alumina and at least one of an inorganic water-soluble sodium salt and an inorganic water-soluble magnesium salt. Preferably, at least one of an oxycarboxylic acid and an oxycarboxylic acid condensate is further blended. The following describes each of the materials in order. The solidification material of this embodiment is usually blended with a liquid such as water to form a slurry. The term "slurry" refers to a suspension of a liquid and solid particles, and the solid particles are usually in the form of fine powder. Hereinafter, the solidification material will also be referred to as a solidification material slurry.

[0016] (hydraulic alumina) This form of solidification material slurry contains hydraulic alumina. When water is added to hydraulic alumina, it undergoes a rehydration reaction, and the particles aggregate and harden. Hydraulic alumina is composed mainly of Al2O3, and further contains Fe2O3, SiO2, Na2O, etc. Hydraulic alumina can be produced from ρ-alumina, a type of intermediate alumina. ρ-alumina can be produced by dehydrating gypsum (α-Al2O3·3H2O) and bayerite (β-Al2O3·3H2O) at low temperatures in a vacuum. Unlike alumina cement, ρ-alumina does not contain CaO, so it does not have the problems associated with CaO.

[0017] As the hydraulic alumina, for example, BK-112 manufactured by Sumitomo Chemical Co., Ltd. can be used.

[0018] The mixing ratio of hydraulic alumina to the total amount of the solidification material slurry is preferably 20 to 80 mass%, more preferably 30 to 70 mass%, and particularly preferably 40 to 60 mass%. If the mixing ratio is less than 20 mass%, aluminum may be excessively hydrated to become a water-containing substance, and strength may not be obtained. On the other hand, if the mixing ratio is more than 80 mass%, the slurry may become highly viscous, making it difficult to pump.

[0019] (Inorganic water-soluble salts) In the solidification material slurry of this embodiment, at least one of inorganic water-soluble sodium salt and inorganic water-soluble magnesium salt (hereinafter, simply referred to as "inorganic water-soluble salt") is blended together with hydraulic alumina. When an inorganic water-soluble salt is blended, the dissociation equilibrium of alumina is shifted by the electrolytic ions of the salt, and the pH of the suspension (solidification material) and solidified matter (improved soil) can be suppressed. In particular, according to this embodiment, the pH of the solidification material slurry is suppressed to 9 or less (preferably pH 5.8 to 8.6), which is within the range of the Water Pollution Prevention Act and the pH of marine drainage.

[0020] Furthermore, if the pH of the solidification material slurry is high, when the solidification material (suspension) is pumped into the ground using high-pressure jet mixing or chemical injection methods, etc., and the suspension leaks out onto the ground surface, it may cause alkaline contamination of the surrounding area. In addition, when ground improvement work is carried out underwater, such as on the seabed, it may have an impact on the surrounding ecosystem.

[0021] The mixing ratio of the inorganic water-soluble salt to the total amount of the solidification material slurry is preferably 0.1 to 10 mass%, more preferably 0.2 to 7 mass%, and particularly preferably 0.3 to 5 mass%. If the mixing ratio is less than 0.1 mass%, the dissociation equilibrium shift is small, and the effect of lowering the pH level may not be sufficiently obtained. On the other hand, if the mixing ratio is more than 10 mass%, the aluminum on the surface may not become hydration active, and strength may not be obtained.

[0022] Of the inorganic water-soluble salts, it is preferable to use sodium chloride as the inorganic water-soluble sodium salt, since sodium chloride has high solubility in water and is easy to prepare an aqueous solution of, and is low in toxicity and therefore highly safe.

[0023] As the inorganic water-soluble sodium salt, it is preferable to use seawater, which is water containing sodium ions and magnesium ions. If seawater is used, the process of dissolving salt on-site can be omitted, and in construction near the sea, seawater can be easily obtained, so the amount of clean water used can be reduced.

[0024] In addition, even when seawater is used, it is not necessary that all of the inorganic water-soluble sodium salt is supplied by seawater, and a part of the inorganic water-soluble sodium salt may be obtained from seawater. Furthermore, seawater can be used as the inorganic water-soluble sodium salt after being appropriately treated, and in this case, seawater can be said to be a supply source of the inorganic water-soluble sodium salt.

[0025] (Hydroxycarboxylic acid condensation products) The solidification material slurry of this embodiment is preferably blended with at least one of oxycarboxylic acid and oxycarboxylic acid condensate (hereinafter, simply referred to as "oxycarboxylic acid"). Blending with oxycarboxylic acid can reduce the viscosity of the slurry and effectively extend the hardening (solidification) time.

[0026] The mixing ratio of the oxycarboxylic acid to the total amount of the solidification material slurry is preferably 0.1 to 5 mass%, more preferably 0.2 to 3 mass%, and particularly preferably 0.3 to 2 mass%. If the mixing ratio is less than 0.1 mass%, the viscosity reducing effect and hardening retardation effect may not be obtained. On the other hand, if the mixing ratio is more than 10 mass%, the alumina surface may be blocked, resulting in poor hardening.

[0027] As the oxycarboxylic acid, one or more of aqueous solutions of gluconic acid, lactic acid, citric acid, etc. can be selected and used. However, it is preferable to use gluconic acid as the oxycarboxylic acid. When a small amount of gluconic acid is added, it is possible to effectively reduce viscosity and retard hardening.

[0028] As the oxycarboxylic acid condensate, it is preferable to use glucono-δ-lactone. When glucono-δ-lactone is used, the amount of glucono-δ-lactone added can be reduced because it does not contain water, and since it is a powder, there is no risk of corrosion of the storage container due to acid.

[0029] (Application) The solidification material slurry of this embodiment can be used in a ground improvement method with a solidification time of, for example, 10 to 3000 minutes (preferably 30 to 300 minutes). When the solidification material slurry of this embodiment is used in a high-pressure injection mixing method or a chemical injection method, the outflow of the solidification material can be suppressed by allowing a solidification time of about several tens of minutes even when the groundwater flow is fast. In addition, in the case of column pile lap construction using the high-pressure injection method, the lap part can be reliably connected by allowing a long solidification time of about 2 days.

[0030] The high-pressure jet mixing method is a method of creating an improved body by injecting a solidification material into the ground at high pressure. More specifically, the high-pressure jet mixing method has, for example, a drilling process and a subsequent construction process. In the drilling process, a hole is drilled in the ground with a self-drilling injection pipe with a bit at the tip, and the injection pipe is inserted into the ground. In the construction process, the injection pipe inserted into the ground is pulled up while rotating around its axis, and during this pulling process, the solidification material is high-pressure injected into the ground to create an improved body. The high-pressure jet mixing method is sometimes called the high-pressure jet injection method. High-pressure jet mixing methods are widely used for ground improvement, and in the past, there were methods such as the CCP method (chemical mixing pile method), but in recent years, due to the diversification of requirements for this method, various methods have come into existence, such as the CJG method (column jet grout method), cross jet method, super jet grout method, super midi jet grout method, JSG method, and RJP method (rosin jet pile method). EXAMPLES

[0031] Next, an embodiment of the present invention will be described. A solidification material (suspension) was prepared with the blending amounts shown in Table 1, and various tests were carried out. The suspension was prepared by first adding water and inorganic water-soluble salt, stirring and dissolving them in a chemical mixer, and then adding alumina powder and stirring. Note that lithium carbonate is water-insoluble, so it was added to the water at the same time as the alumina.

[0032] [Table 1]

[0033] The pH of the suspension, bleeding, homogeneous strength at 7 and 28 days, and pH of the solidified material are shown in Table 2.

[0034] [Table 2]

[0035] Next, tests were conducted to clarify the effects of adding inorganic water-soluble salts and hydroxycarboxylic acids. A suspension was prepared by first adding water, inorganic water-soluble salts, and hydroxycarboxylic acids in the amounts shown in Table 3, and then dissolving them by stirring in a chemical mixer, and then adding alumina powder and stirring. The solidification time, bleeding, pH, homogeneous strength at 28 days, and viscosity are also shown in the same table. For comparison, the results for a cement-based solidification material slurry are shown in Table 4.

[0036] [Table 3]

[0037] [Table 4] [Industrial Applicability]

[0038] INDUSTRIAL APPLICABILITY The present invention can be used as a solidification material that can be used in high-pressure jet mixing methods, chemical injection methods, and the like.

Claims

1. 20 to 80% by mass of hydraulic alumina and 0.1 to 10% by mass of an inorganic water-soluble sodium salt are blended, Sodium chloride is blended as the inorganic water-soluble sodium salt. A solidification material characterized by:

2. At least one of an oxycarboxylic acid and an oxycarboxylic acid condensate is blended in an amount of 0.1 to 5 mass %. The solidification material according to claim 1 .

3. As the oxycarboxylic acid, gluconic acid is blended. The solidification material according to claim 2.

4. Glucono δ-lactone is blended as the oxycarboxylic acid condensate. The solidification material according to claim 2.

5. The inorganic water-soluble sodium salt is obtained from seawater. The solidification material according to claim 1 .

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