JPH0978063A - Soil-improving agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a soil-improving agent for grouping which is excellent in permeability through soil, keeps its strength for appropriately long time by formulating a fine-particle powder having a specific CaO content and a Blaine value and mostly comprising a glassy material. SOLUTION: This soil-improver, excellent in permeation through soil, holding its strength for an appropriately long time is produced by formulating (A) a fine-particle powder which comprises water-granulated blast-furnace slag or the like, contains 20-50wt.% of calcium oxide where more than 90% of the inner structure is glassy (amorphous) and has a Blaine value of 5,000cm<2> /g, (B) an alkali stimulant comprising one or more of sodium hydroxide, potassium hydroxide, sodium aluminate, sodium carbonate, potassium carbonate and a non-colloidal and ionicaly activated water glass with a molar ratio SiO2 /Na2 O of <=2.5 and (C) calcium carbonate so that they become 35-90wt.% to the fine particles of calcium carbonate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground improvement agent for grouting and the like.

[0002]

2. Description of the Related Art Various kinds of grout injection agents for improving the ground have been conventionally used. Most of the present days are mostly water glass or cement.

Looking back on the history of grouting agents in Japan, in the 1960s, Mr. Higuchi showed that unstable water glass grout (LW) with a short gel time, which was a combination of cement suspension and dilute water glass solution, and later on this LW. With improvements
Unstable water glass grout (C-LW), which is a combination of fine particle blast furnace colloid cement and water glass diluting solution with low molar ratio, has high gel time of ten and high strength and high durability,
Furthermore, a relatively long gel time grout (MS) in which the mixing ratio of granulated blast furnace slag and Portland cement is changed and water glass diluted solution of each molar ratio is combined is the basis.

At present, for the purpose of permeation, there are many solution-type ones in which water glass and a curing agent are combined.

On the other hand, a suspension type or a semi-suspension type is generally used for the purpose of obtaining high strength.

[0006]

When an alkali is added to a calcium-containing compound such as granulated blast furnace slag, hydrolysis occurs and the latent hydraulic property of granulated blast furnace slag is developed. Utilizing this property, the present applicant has previously utilized the excellent hydraulic properties of calcium-containing substances such as granulated blast furnace slag in Japanese Patent Application Laid-Open No. 4-293994, as well as penetrability and long-term aging. As a ground improvement agent with excellent strength, the content of calcium oxide is 20 to 50% by weight.
90% or more of the internal structure is vitreous, fine powder having a Blaine value of 5000 cm ² / g or more, sodium hydroxide or potassium hydroxide, and BET surface area of 40 m ² /
A ground improvement agent containing at least g of white carbon as a main material was proposed.

In this case, the strength increases with the passage of time, as will be made clear later in Examples. For example, 2
The compressive strength on the 8th becomes about 50 kgf / cm ² .

However, it is usually preferable that the strength is high, but the ground improvement by the grout injection is often used as a temporary construction work, and thereafter, the ground which has been strengthened once may be excavated by this construction work. In such an application, it is not preferable that the strength increases unitarily or linearly with time, and after a certain time, the strength does not further increase or even if the strength increases, the gradient is gentle. desired.

Therefore, the object of the present invention is to ensure that the strength is practically sufficient, and that the strength does not increase so much with the lapse of time.

To solve this problem, the applicant of the present invention has disclosed in Japanese Patent Laid-Open No.
No. 41533, an admixture which is a mixture of fine powder of limestone and clay is added to the material system,
The one that suppresses the development of strength was previously proposed.

However, since the clay component of the admixture is obtained through a special process, it not only causes a cost increase but also cannot be easily or universally obtained.

[0012] Therefore, the main object of the present invention is to solve the above-mentioned premised problem while using a material that suppresses the development of strength, which is easily and inexpensively available.

[0013]

The ground improvement agent of the present invention, which has solved the above-mentioned problems, has a calcium oxide content of 20-5.
0% by weight, 90% or more of the internal structure is vitreous, and fine powder having a Blaine value of 5000 cm ² / g or more, an alkali stimulant, and calcium carbonate as main materials, and the calcium carbonate is It is characterized by being 35 to 90% by weight with respect to the powder.

The alkali stimulant may be selected from the group consisting of one or more selected from the following group. (1) Sodium hydroxide (2) Potassium hydroxide (3) Sodium aluminate (4) At least one of carbonates consisting of sodium carbonate, potassium carbonate, and sodium-potassium carbonate (5) SiO ₂ / Na ₂ O molar ratio Non-colloidal and ionic activated water glass having a value of 2.5 or less Furthermore, as the calcium carbonate, one having the following composition can be used. _{Ig.loss: 43.0 ~45.0% SiO 2:} 1.0% or less Al ₂ O _3: 0.2% or less Fe ₂ O _3: 0.3% or less CaO: 54.5 ~55.5% MgO: 0.5 % or less also further, BET surface area of 40 m ² / G or more of white carbon can be contained.

Specifically, the fine powder is 20
0-500 kg / m ³ , 10-% concentration of sodium hydroxide 200-500 liters / m ³ , white carbon 1
It is 0.01 to 1.0% by weight with respect to a 0% sodium hydroxide solution, and the calcium carbonate can be 50 to 90% with respect to the fine powder.

The white carbon is silicic acid anhydride,
One or more selected from the group of hydrous silicic acid, hydrous calcium silicate and hydrous aluminum silicate can be used.

[0017]

The blast furnace (water granulated) slag fine powder can be used as the fine powder according to the present invention.

The slag particles are stimulated by an alkali stimulant such as sodium hydroxide, and CaO-MgO-Al ₂ O
_A hydration product of _3- nH ₂ O is formed. Further, calcium carbonate reacts with alkali as follows. CaCO ₃ + NaOH → Ca (OH) ₂ + Na ₂ CO ₃ takes place in a chain, and the calcium silicate particles produced by the pozzolan reaction effectively intervene between the slag particles to guarantee the strength. .

On the other hand, if it is not desired to increase the strength as described above, the amount of slag may be reduced, but the amount of slag is set to 1 m ³ of soil when the porosity is 40%. When it is set to 350 kg / m ³ , the void filling rate is 59% and the 28-day compressive strength is 50 kgf / m ³ , whereas when the slag amount is set to 200 kg / m ³ , for example, the void filling rate is set to 200 kg / m ^3. Is 34% and 28 days compressive strength is 0-4kgf
/ M ^{3 which} is extremely low and not suitable for practical use. Therefore, with the improved material proposed in Japanese Patent Laid-Open No. 4-293994, only high strength materials can be obtained. This is the same as the fact that the cement water ratio (W / C) of the cement paste determines the strength.

However, when calcium carbonate is used in accordance with the present invention, the strength is developed to the extent that practicality is satisfied, and an excessive increase in long-term strength can be suppressed. Moreover, according to JP-A-6-41533,
Compared with the case of adding an admixture which is a mixture of fine powder of limestone and clay, it is possible to secure an equivalent strength suppressing effect and required strength.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. In the present invention, the content of calcium oxide is 20 to 5
0% by weight, 90% or more of the internal structure is vitreous, and a fine powder having a Blaine value of 5000 cm ² / g or more is used. As a typical example of this, fine powder of granulated blast furnace slag can be mentioned. Other metallurgical slags can also be used. The content of calcium oxide in the fine powder is more preferably 25 to 35% by weight. The Blaine value is more preferably 8000 to 16000 cm ² / g in terms of permeability.
It is. Coarse particles have poor permeability to the ground. Although the Blaine value can be used up to about 20000 cm ² / g, even if the Blaine value is higher than this value, the improvement of the permeability cannot be expected so much and the cost required for pulverization increases.

An alkaline stimulant is added to this type of slag. As the alkali, sodium hydroxide is preferable, but potassium hydroxide can be used except for the cost, and it has been confirmed that the effect is basically the same. Further, at least one of carbonates consisting of sodium aluminate, sodium carbonate, potassium carbonate, and sodium / potassium carbonate, the SiO ₂ / Na ₂ O molar ratio is 2.5 or less, and more preferably 1.45 or less. Non-colloidal and ionic activated water glasses of can also be used.

The activated water glass will be described. Ordinary water glass, for example, No. 3 water glass defined by JIS, is colloidal and nonionic. On the other hand, activated water is obtained by bringing water glass and sodium hydroxide into contact with each other and contacting and activating them according to formulas (1) and (2) on page 2 of Japanese Patent Publication No. 36155/1990. It is glass.

When activated water glass liquid is added to the fine powder of granulated blast furnace slag, the latent hydraulic property is exhibited by the sodium. In this case, even if the vitrification rate of the fine powder of granulated blast furnace slag is low, unlike ordinary water glass or other alkali that has not been activated, Ca ²⁺ from the granulated blast furnace slag It can be pulled out and hardened by setting. Moreover, it exhibits extremely excellent permeability.

Further, in the present invention, fine white carbon may be added. As the fine white carbon, one kind or two or more kinds selected from the group of silicic acid anhydride, hydrous silicic acid, hydrous calcium silicate and hydrous aluminum silicate can be used. BET surface area is 40 m ² / g or more, preferably 50 to 30
Those of 0 m ² / g can be preferably used. Also, hydrous calcium silicate is desirable because it delays the rate of hydrolysis of slag particles by an alkaline solution, which facilitates the adjustment of gel time.

Further, as the calcium carbonate in the present invention, one having the above composition can be used. In this case, the average particle size of calcium carbonate is 1 to 5 μm.
m, max. 15 μm (5000-50000 cm ² /
The fine powder of g) is preferred.

The preferred composition of the ground improvement agent according to the present invention is:
Fine powder containing calcium oxide is 200-500 kg / m ³ , 1
Sodium hydroxide is 200 to 500 liters / m ^{3 on} the basis of 0% concentration, white carbon is 0.01 to 1.0% by weight with respect to 10% sodium hydroxide solution, and the calcium carbonate is based on fine powder. 35-90% by weight
(Particularly preferably 50 to 80% by weight).

The fine powder causes a curing reaction even with a small amount of an alkali stimulant, but it is necessary to add a required amount of the alkali stimulant in terms of early development of strength, and sodium hydroxide is added at 200% on the basis of 10% concentration. It is preferable to contain liter / m ³ or more. On the other hand, if sodium hydroxide is excessive, alkali remains in the ground, which may cause a factor that impairs the living environment. The addition amount can be adjusted in a linearly inversely proportional manner depending on the concentration of sodium hydroxide. For example, at a concentration of 5%, 400 to 1000 liters /
the m ^3. The white carbon fine particles are preferably added in an amount of 0.01% by weight or more in order to exert the effect. On the contrary, if the amount added is too large, the gel time becomes short and the permeability is impaired. The calcium carbonate content is preferably 35% by weight or more based on the fine powder.
If it is less than 35% by weight, the strength tends to be excessive. 8
If it exceeds 5% by weight, the desired strength cannot be obtained.

In the ground improvement agent according to the present invention, 25 kg of 7,000 to 10,000 cm ² / g of cement is further added.
It can be blended in the range of / m ³ or less. This cement formulation has the function of ensuring a solidification throughout the permeation area.

The ground improvement agent according to the present invention can be prepared by mixing each material in advance and applying it to the target ground with one liquid, for example, it can be injected into the ground through an injection pipe. The suspension and the alkaline stimulant, eg sodium hydroxide solution, can be fed separately to the injection tube and combined by mixing in the injection tube or in the ground. in this case,
White carbon can be added to one liquid side. Furthermore, the ground improvement agent according to the present invention can be used not only for grout injection but also for other methods such as a stirring and mixing method.

[0031]

EXAMPLES The effects of the present invention will be clarified by showing examples below. (Comparative Examples 1 and 2, Examples 1-6) relative to the chemical 1 m ^3, the fine powder of granulated blast furnace slag (Blaine value 15000 cm ² /
g: Calcium oxide content is 20 to 50% by weight, and 90% or more of the internal structure is vitreous) 350 kg /
m ^3, and sodium hydroxide 10% concentration was used as a basic formulation of 350 l / m ^3, 28 days compressive strength were examined penetration distance by the time change in viscosity and penetration test (Comparative Example 1). In the experiment, the kneading time was set to 10 minutes,
Mold filled with Toyoura standard sand with an injection tube (diameter 5 m
(mφ × 100 mm in length), one liquid was injected at an injection pressure of 1 kg / cm ² .

In Comparative Example 1, a part of the amount of the fine powder was replaced with calcium carbonate having the above composition, and the same characteristics were examined (Comparative Example 2 and Examples 1 to 6). The results are shown in Table 1, FIG. 1 and FIG.

[0033]

[Table 1]

From these results, the viscosity and the permeability are not so different, but the strength is remarkably changed by the addition of calcium carbonate. Generally, when used for temporary construction, the compression strength for 28 days is 20 kgf / cm.
² below (optionally up to about up to 25 kgf / cm ² may be allowed), and is preferably 15 kgf / cm ^2. If the strength is excessively low, the desired ground will not be strengthened. Therefore, it is understood that the blending amount of calcium carbonate is preferably 35 to 90% by weight, particularly 50 to 80% by weight.

(Examples 7 to 11) 1 of the fine powder of Example 3 was used.
The 28-day compressive strength was examined by changing the type of the alkali stimulant based on the combination of 75 kg / m ³ and calcium carbonate 175 kg / m ³ , and the results shown in Table 2 were obtained. Table 2 also shows the results of Example 3.

[0036]

[Table 2]

According to Table 2, similar curing can be achieved with the listed alkali stimulants. Although the permeation distance is not shown, the permeation distance is substantially the same as in Example 3 and shows excellent permeation.

(Examples 12 to 16 and Reference Example) White carbon (hydrous silicic acid) and cement (9000 cm ² / g) were added to the composition of Example 3 to examine the effect of the addition. Further, the Blaine value of the fine powder of Example 3 was changed to examine the influence of the Blaine value. The results are shown in Table 3.

[0039]

[Table 3]

From this result, the addition of white carbon brings about an improvement in permeability and strength. It can be seen that although the addition of cement tends to deteriorate the permeability, the effect of improving the strength is enhanced.

[0041]

As described above, according to the present invention, it is possible to utilize the excellent hydraulic properties of calcium-containing substances such as granulated blast furnace slag, and to improve the permeability and the strength after a long period of time. Can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing changes in viscosity with time due to differences in the amount of alkali stimulant added.

FIG. 2 is a bar graph showing the results of investigation of permeability by adding an alkali stimulant.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Daniel Gvano France 92110 Clichy Allegambetta 1 (72) Inventor Uber Batmont France 92000 Wattaire Avenue, Nanterre City 6 Sortansie Enterprise

Claims (5)

[Claims] 1. A fine powder having a calcium oxide content of 20 to 50% by weight, 90% or more of the internal structure being glassy, and a Blaine value of 5000 cm ² / g or more, an alkali stimulant, and carbonic acid. A ground improvement agent comprising calcium as a main material and the calcium carbonate content of 35 to 90% by weight relative to the fine powder. 2. The ground improvement agent according to claim 1, wherein the alkali stimulant is one or more selected from the following group. (1) Sodium hydroxide (2) Potassium hydroxide (3) Sodium aluminate (4) At least one of carbonates consisting of sodium carbonate, potassium carbonate, and sodium-potassium carbonate (5) SiO ₂ / Na ₂ O molar ratio Water glass with non-colloidal and ionic properties of 2.5 or less 3. The ground improvement agent according to claim 1, wherein the calcium carbonate has the following composition. Ig.loss: 43.0-45.0% SiO ₂ : 1.0% or less Al ₂ O ₃ : 0.2% or less Fe ₂ O ₃ : 0.3% or less CaO: 54.5-55.5% MgO: 0.5% or less 4. The ground improvement agent according to claim 1, further comprising white carbon having a BET surface area of 40 m ² / g or more. 5. The fine powder is 200 to 500 kg / m ³ , 10
The concentration of sodium hydroxide is 200 to 500 liters / m ³ , white carbon is 0.01 to 1.0% by weight with respect to a 10% sodium hydroxide solution, and the admixture is 50 with respect to fine powder. The ground improvement agent according to claim 1, which is -80% by weight.