JP2002047489A - Low hexavalent chromium grout - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low hexavalent chromium grout which can decrease the amount of hexavalent chromium eluted therefrom, is excellent in permeation properties, and decreases the amount of hexavalent chromium eluted from a fine-particle cement excellent in strength development. SOLUTION: This grout comprises a fine-particle cement, a fine-particle slag, and calcium aluminate and may further contain a reducing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low hexavalent chromium injection material for reducing elution of hexavalent chromium contained in fine particle cement. The parts and percentages in the present invention are based on mass unless otherwise specified.

[0002]

2. Description of the Related Art Injectable materials currently used in the field of civil engineering and construction are roughly classified into water glass-based injectable materials and cement-based injectable materials. Although the permeability of the water glass-based injection material is better than that of the cement-based injection material, there is a problem that the durability is poor. In addition, the silt layer and the clay layer have poor permeability even when a water glass-based injection material is used, and the water glass-based injection material enters a wedge shape into the silt layer or the clay layer due to liquid pressure, which is a so-called split injection mode. Become. However,
Since the water glass-based injection material has a low compressive strength (homogel strength) itself, there are cases where the reinforcement of the ground and the water stopping effect cannot be obtained.

[0003] In recent years, an injection material has been developed in which cement particles have been made into fine particles to improve the permeability of the cement-based injection material. Can be obtained.

On the other hand, the cement industry is expected to treat various types of industrial waste, and the use of industrial waste such as sewage sludge and old tires for the production of cement has been continued. Its usage is expected to increase. Accordingly, there is a concern that the content of harmful components contained in cement, in particular, hexavalent chromium, may increase.

In order to fix hexavalent chromium,
A method of adding blast furnace slag or adding ferrous sulfate has been studied (JP-A-2000-086322). However, in order to improve the permeability by this method, when the cement is micronized, the specific surface area increases, the amount of hexavalent chromium eluted increases, and since the time until hardening is several hours, groundwater is hardened before hardening. For example, the diffusion of hexavalent chromium cannot be improved, and there is a problem that a sufficient effect cannot be obtained.

The present inventor has found that the use of a specific material can reduce the amount of hexavalent chromium eluted when fine particle cement is used, and has completed the present invention.

[0007]

That is, the present invention relates to a low hexavalent chromium injecting material containing fine particle cement, fine particle slag, and calcium aluminate, and further comprising a reducing agent. Hexavalent chromium injection material.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

As the fine particle cement used in the present invention, various kinds of Portland cements, such as ordinary, early-strength, and ultra-high-strength cements, are used.
Cement mixed with fly ash, limestone, silica sand, or the like, which is finely divided to m ² / g or more, may be used. The particle size of the fine particle cement is preferably 5,000 cm ² / g or more, more preferably 8,000 cm ² / g or more, and most preferably 12,000 cm ² / g or more in terms of Blaine value. If it is less than 5,000 cm ² / g, the permeability may be poor.

The fine particle slag used in the present invention is obtained by making blast furnace slag or converter slag into fine particles.
Among these, the blast furnace slag that has been rapidly cooled and made into fine particles is preferable from the viewpoint of strength development. The particle size of the fine particle slag is preferably 5,000 cm ² / g or more in terms of Blaine value,
8,000cm more preferably at least ² / g, ^{12,000cm 2} / g or more it is most preferred. If it is less than 5,000 cm ² / g, the permeability may be poor. The amount of fine particle slag used is 100 fine particle cement.
The amount is preferably from 50 to 1,000 parts, more preferably from 200 to 500 parts, per part. If the amount is less than 50 parts, the fixation ratio of hexavalent chromium may decrease, and if it exceeds 1,000 parts, the initial strength may decrease.

The calcium aluminate used in the present invention is obtained by mixing a raw material containing calcia and a raw material containing alumina and subjecting them to a heat treatment such as firing in a kiln or melting in an electric furnace. And Al ₂ O ₃ as main components,
A general term for substances having hydration activity, which are CaO and / or A
Compounds in which part of l ₂ O ₃ has been replaced with an alkali metal oxide, an alkaline earth metal oxide, an alkali metal halide, an alkaline earth metal halide, an alkali metal sulfate, an alkaline earth metal sulfate, or the like. Or CaO and Al ₂ O ₃
Is a substance in which these are dissolved in a substance mainly composed of The mineral form may be either crystalline or amorphous. Among them, amorphous calcium aluminate is preferable in terms of reaction activity, and 12CaO · 7Al ₂ O ₃ (C ₁₂ A
₇ ) An amorphous calcium aluminate obtained by quenching a heat-treated product corresponding to the composition is more preferable. The particle size of the calcium aluminate is preferably 5,000 cm ² / g or more in Blaine value, 8,000cm ² / g or more is more preferable. If it is less than 5,000 cm ² / g, the permeability may be poor. The amount of calcium aluminate used is 1 to 300 parts per 100 parts of fine particle cement.
Parts are preferred, and 20 to 100 parts is more preferred. If the amount is less than 1 part, the fixation ratio of hexavalent chromium may decrease,
Even if it exceeds 0 parts, a further improvement in the fixation ratio of hexavalent chromium cannot be expected.

The reducing agent used in the present invention is iron sulfate
Sulfates such as divalent iron salts such as (II) and trivalent titanium salts such as titanium (III) sulfate; sulfites such as sodium sulfite, potassium sulfite and calcium sulfite; sodium bisulfite and potassium bisulfite Such as bisulfites, sulfides such as sodium sulfide, potassium sulfide, calcium sulfide, and ammonium sulfide; thiosulfates such as sodium thiosulfate and potassium thiosulfate; sulfur dioxide and sulfur; and peat and lignite. Of these, iron (II) sulfate,
The use of sodium thiosulphate or potassium thiosulphate is preferred. The amount of the reducing agent used is preferably 0.01 to 50 parts, more preferably 0.1 to 5 parts, based on 100 parts of the fine particle cement. If the amount is less than 0.01 part, the immobilization rate of hexavalent chromium may be small, and even if it exceeds 50 parts, the immobilization rate of hexavalent chromium may not change.

Furthermore, in the present invention, it is preferable to use a coagulation modifier together to adjust the composition so that the required curing time is obtained. Specific examples of the setting regulator include aluminates such as sodium aluminate and potassium aluminate, carbonates such as sodium carbonate and potassium carbonate, sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide. Hydroxides, such as aluminum sulfate, iron (III) sulfate, and alum; silicates such as sodium silicate, potassium silicate, and lithium silicate; and silicon fluoride such as sodium silicate and magnesium silicate fluoride. , Phosphates such as sodium phosphate, calcium phosphate, and magnesium phosphate; inorganic salts such as borate such as lithium borate and sodium borate; and organic acids such as citric acid, gluconic acid, tartaric acid, and malic acid. Or its sodium, potassium, lithium and calcium salts, and Kind, and the like. The amount of the setting modifier used is not particularly limited since it is adjusted according to the curing time, but is preferably 0.01 to 50 parts with respect to 100 parts of the fine particle cement.

Further, in order to improve the permeability, it is preferable to use a dispersant in combination. As dispersants, naphthalene sulfonic acid formalin condensate salt type, lignin sulfonate type, melamine sulfonic acid formalin condensate salt type,
Polycarboxylate and polyether dispersants are preferred. The amount of the dispersant to be used is preferably 0.01 to 10 parts, more preferably 0.1 to 3 parts, per 100 parts of the fine particle cement. If it is less than 0.01 part, the permeability may be poor, and if it exceeds 10 parts, the initial strength may be reduced.

The low hexavalent chromium injection material of the present invention (hereinafter referred to as the present injection material) contains fine cement, fine slag, calcium aluminate and, if necessary, a reducing agent. Mix water to make a suspension,
It can be injected into the ground or the like. The amount of this infused material varies depending on the type of soil, water content, and required strength, etc., and is not determined uniformly.
Generally, it is preferably 5 to 300 kg, more preferably 50 to 150 kg, per 1 m3 of soil. If it is less than 5 kg, the solidification strength may be low, and if it exceeds 300 kg, the solidification strength may be too large.

The amount of water when the present injection material is used as a suspension is not particularly limited as long as the suspension has a viscosity that can be pumped by a pump. For example, 100 to 1,000 parts is preferable, and 200 to 500 parts is more preferable, based on a total of 100 parts of the fine particle cement, the fine particle slag, the calcium aluminate, and the reducing agent. If it is less than 100 parts, the viscosity may be too high, and if it exceeds 1,000 parts, the solidification strength may decrease.

When the present injection material is mixed with water to form a suspension, fine cement, fine slag, calcium aluminate, and water, and if necessary, a reducing agent are blended and mixed with a mixer. It may be injected into the ground in one shot, injecting with a pump. In this case, since the present injection material may be cured by a mixer, a pump, a hose, or the like, it is necessary to secure a curing time of at least 30 minutes or more. Therefore, for example, a suspension composed of fine-particle cement, fine-particle slag, and water and a suspension composed of calcium aluminate and a reducing agent are separately prepared, and the two kinds of suspensions are mixed with a Y-tube. So-called 1.
The injection method of 5 shots is also such that the two suspensions are separately pumped and mixed and injected at the tip of a double injection tube.
It is more preferable to inject into the ground in so-called two shots.

Further, the injection material includes a material separation resistance material such as bentonite, allophane, methylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, and polyvinyl alcohol; a foaming agent such as gelatin, casein, and metallic aluminum; It is also possible to use an antifoaming agent such as silicone in combination.

The injection material is used in injection methods currently used, such as a single pipe rod method, a single pipe strainer method, a double pipe single phase method, a double pipe double phase method, and a double pipe double packer method. It is possible to

[0020]

EXAMPLES Hereinafter, the present invention will be further described with reference to experimental examples of the present invention, but the present invention is not limited thereto.

Experimental Example 1 Fine particles slag and calcium aluminate shown in Table 1 were mixed with 100 parts of fine particle cement to prepare an injection material. A suspension was prepared by mixing 100 parts of the prepared injection material and 300 parts of water, and the curing time, compressive strength, and hexavalent chromium elution amount of the injection material were measured. The results are also shown in Table 1.

<Materials Used> Fine particle cement: Finely pulverized ordinary Portland cement,
Blaine value 12,500cm ² / g Fine particle slag: Rapidly cooled blast furnace slag finely pulverized product, Blaine value 1
3,000cm ² / g Calcium aluminate: Glass with C ₁₂ A ₇ composition, Blaine value 8,500cm ² / g

<Test Method> Curing time: Time until the suspension does not flow even if the suspension is put in a cup and tilted Compressive strength: Measured in accordance with JIS R 5201;
28 days Hexavalent chromium elution amount: Measured according to the Notification of the Environment Agency No. 46, 1 and 28 days old

[0024]

[Table 1]

Experimental Example 2 The same procedure as in Experimental Example 1 was conducted except that 400 parts of fine particle slag, 50 parts of calcium aluminate and a reducing agent shown in Table 2 were mixed with 100 parts of fine particle cement. Table 2 shows the results
It is described together.

<Materials used> Reducing agent a: Iron (II) sulfate, commercially available reducing agent A: sodium sulfite, commercially available reducing agent C: sodium bisulfite, commercially available reducing agent D: sodium sulfide, commercially available reducing agent e : Sodium thiosulfate, commercial product Reducing agent f: Potassium thiosulfate, commercial product Reducing agent key: Sulfur, commercial product

[0027]

[Table 2]

Experimental Example 3 No. 7 silica sand was placed in a polyethylene tube having a diameter of 5 cm and a length of 30 cm until the height became 20 cm. On the other hand, fine particle cement 10
0 parts, 400 parts of fine particle slag, 50 parts of calcium aluminate
Parts, 1 part of the setting modifier shown in Table 3 and 1 part of a polyether-based dispersant were mixed to prepare the present injection material. Main injection material 100
Part of water and 300 parts of water to prepare a suspension, gently pour the suspension into a polyethylene tube containing sand, and determine the penetration length into sand, compressive strength, and the amount of hexavalent chromium eluted. It was measured. The results are also shown in Table 3.

<Materials used> Setting regulator A: sodium fluorosilicate, reagent Setting regulator B: citric acid, reagent Setting regulator C: sodium tartrate, reagent Setting regulator D: malic acid, reagent Dispersant: powder type commercially available Goods

<Measurement method> Penetration length in sand: After one day, the cured product was taken out of the polyethylene tube, and the length of the cured product was defined as the penetration length.

[0031]

[Table 3]

[0032]

As described above, by using the low hexavalent chromium injection material of the present invention, (1) the elution amount of hexavalent chromium can be reduced. (2) Excellent permeability. (3) Excellent strength development. And so on.

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Claims (2)

[Claims] 1. A low hexavalent chromium injection material containing fine particle cement, fine particle slag, and calcium aluminate. 2. The method according to claim 1, further comprising a reducing agent.
A low hexavalent chromium injection material as described above.