JP2000109832A - Solidifying material for moisture-containing soil and improvement of solidification of moisture-containing soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition, which comprises, as its essential components, specified amounts of a slug, aluminium sulfate and/or iron sulfate and a lithium salt, and the balance alumina cement, thereby improving the solidification-improving property of moisture-containing soil. SOLUTION: The amount of a slug in the solidifying material ranges 10 to 50 pts.wt. per 100 pts.wt. of the essential components, that of aluminium sulfate and/or iron sulfate ranges 10 to 30 pts.wt. per 100 pts.wt. of the essential components, and the amount of the lithium salt ranges 2.5 pts.wt. to 5 pts.wt. per 100 pts.wt. of the essential components. The most preferred lithium salt is lithium carbonate. The solidifying material may further comprise an inorganic porous moisture-absorbing material and/or an organic polymer moisture-absorbing material, so that the uniaxial compression strength of the soil obtained after improvement in solidification can further be improved, with the soil after the addition of the solidifying material suffering little variation in the pH value. The inorganic porous moisture-absorbing material preferably includes perlite or the like, and the organic polymer moisture-absorbing material preferably includes synthetic polymers such as polyacrylamide or the like, or a natural material such as waste paper or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a solidifying material for hydrous soil and a method for improving solidification of hydrous soil using the same.

[0002]

2. Description of the Related Art To improve the soil quality of soft soil, a solidification treatment using a solidifying material is performed. In addition, when carrying out hydrous residual soil generated due to civil engineering work in that area, instead of using it in soft soil areas, it is difficult to transport it as it is because of its high fluidity. After solidification treatment, it is necessary to carry it out. For any purpose, the solidified material must be such that the soil after solidification has sufficient strength for the purpose, has an appropriate solidification rate, and the solidified material is chemically stable. Although properties such as harmful substances are not required to be eluted, many techniques have already been disclosed as a solidifying material that requires a plurality of functions. These can be broadly classified into cement-based and gypsum-based, depending on the type of hydraulic component included, although gypsum-based systems are unlikely to cause alkali pollution due to alkali elution,
What has not been able to give sufficient strength to the soil after solidification has not been obtained.

[0003] On the other hand, cement-based solidified materials may cause alkaline pollution because the cement itself is a strong alkali, but since the soil after solidification has no problem in strength, it is possible to reduce alkali pollution while taking advantage of strength. Many attempts have been made to suppress it. For example, JP-A-61-2278
No. 99 discloses a solidified material obtained by adding a sulfate of aluminum or iron as a neutralizing agent to cement, and JP-A-5-78664 discloses a solidified material obtained by adding a sulfuric acid band to a cement as a neutralizing agent. Is disclosed. Japanese Patent Publication No. 57-19716 discloses a solidified material obtained by adding aluminum sulfate, an alkali metal carbonate and an oxide of an alkaline earth metal to cement. These are
The target soil, the amount of solidified material added, the evaluation method, etc. are different from each other, so it is not possible to compare and evaluate as solidified material, but it is true that further improvement is required for solidified material,
In addition, there is a demand for a solidified material prepared according to the purpose of use of the soil after the improvement, without increasing the strength.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solidified material having excellent performance in improving the solidification of hydrous soil and to provide a method for improving the solidification of hydrous soil. Specifically, the pH value is in a range of 10 or less at which the pH value drop due to the buffer capacity of the soil occurs relatively quickly, and the unconfined compressive strength is 0.5 kgf, which is a measure that a person can walk on.
An object of the present invention is to provide a solidified material that gives an improved soil having a density of not less than / cm ² or more, and to provide a method for improving the solidification of hydrous soil using the solidified material.

[0005]

Means for Solving the Problems The present inventors have found that a composition comprising a specific ratio of alumina cement, slag, aluminum sulfate and / or iron sulfate, and a lithium salt serves as the above-mentioned solidified material. Thus, the present invention has been completed. That is, the present invention provides a composition comprising 10 to 50 parts by weight of slag, 10 to 25 parts by weight of aluminum sulfate and / or iron sulfate, 2.5 to 5 parts by weight of a lithium salt, and the balance being alumina cement. A solidified material for hydrous soil, comprising Further, the present invention relates to a method for improving solidification of hydrous soil, wherein the solidifying material for hydrous soil is added in an amount of 50 to 400 kg per 1 m ^{3 of} hydrous soil. Hereinafter, the present invention will be described.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A solidified material containing cement as a component gives an improved solidified soil in terms of strength. However, cement itself is a strong alkali, and when cement is used as a component of a solidified material. It is necessary to pay attention to the suppression of alkali elution. In the present invention, a pH is reduced by using a cement by using a hydraulic component obtained by adding slag to a relatively low alkali alumina cement among cements, and adding aluminum sulfate and / or iron sulfate as a neutralizing agent. We are trying to control the rise.

[0007] Several types of alumina cements having different compositions are commercially available as the main component of the solidifying material of the present invention, and all of them can be used without any trouble.

[0008] The slag not only has a hardened body strength of alumina cement, but also has a function of suppressing a decrease in strength due to a transition of alumina cement hydrate.
The same effect is exhibited when coexisting with alumina cement as one component of the solidifying material for hydrous soil. If the amount of the slag is too small, the effect of adding the slag is not sufficiently exhibited, and if the amount is too large, the strength of the slag is reduced.

Both aluminum sulfate and iron sulfate in the form of ferrous sulfate or ferric sulfate, which are added as a neutralizing agent, are inexpensive and easily available materials, and have high performance as neutralizing agents. However, use of aluminum sulfate is preferred in terms of effect. These can be added alone or as a mixture of sulfates. However, since aluminum sulfate and iron sulfate also act as a setting retarder for alumina cement, the amount of addition is limited,
By setting the proportion of aluminum sulfate or iron sulfate, or a mixture thereof, in the solidified material of the present invention to 10 to 25 parts by weight of the entire solidified material essential component, a solidified material giving favorable results can be obtained. .

[0010] The solidifying material of the present invention comprises alumina cement,
A lithium salt is further added to a component composed of slag and a metal sulfate of aluminum sulfate and / or iron sulfate to improve the curing speed. It is known that lithium ions act as a hardening accelerator for alumina cement. Addition of a lithium salt compensates for delay in hardening of alumina cement due to the addition of aluminum sulfate or iron sulfate as a neutralizing agent, and provides sufficient solidification as a solidifying material. A solidified material having a speed can be obtained. Examples of the lithium salt used in the solidifying material of the present invention include inorganic salts such as lithium carbonate, lithium chloride and lithium nitrate, or organic salts such as lithium acetate and lithium formate. The use of lithium carbonate is most preferred because of its availability.

The addition amount of the lithium salt is preferably 2.5 to 5 parts by weight based on the whole essential components of the solidifying material. When the amount is less than this range, the effect of addition is not sufficiently exhibited, and when the amount is too large, it is not only uneconomical, but also increases the pH of the soil after solidification, which is not preferable.

As described above, the solidified material of the present invention can sufficiently exhibit its performance by mixing alumina cement, slag, aluminum sulfate and / or iron sulfate, and lithium salt, which are essential components, in an appropriate amount. By adding the porous material water-absorbing material and / or the water-absorbing organic substance, the uniaxial compressive strength of the soil after the solidification can be further improved without substantially changing the pH value of the soil after the addition of the solidifying material. The water-absorbing material is combined and immobilized with the free water existing in the soil,
Since it has the function of reducing the amount of free water contained, the use of a solidified material with the addition of a water-absorbing material is the same as the improvement of solidification of hydrous soil with a low water content, and the uniaxial compressive strength of the soil after the addition of the solidified material Is thought to be higher. Therefore, the addition of a water absorbing material is particularly effective in improving the solidification of soil having a high water content.

Examples of the water-absorbing organic substances usable in the present invention include synthetic polymers such as polyacrylamide, polymethacrylamide, polyvinyl alcohol, and polyacrylate, and natural organic polymers such as waste paper and pulp. However, among them, a suitable means such as a shredder etc.
The addition of waste paper cut to a length of several tens of mm gives a solidified material that is excellent both in performance and cost.

On the other hand, examples of the inorganic porous water-absorbing material that can be used in the present invention include pearlite, zeolite, silica, bottom ash and the like. Among them, pearlite is preferred in terms of water absorption performance, chemical stability, and price. Is the most preferred material.

The amount of the water-absorbing material added per 100 parts by weight of the solidifying material essential component is 0.1 to 5 parts by weight in the case of a synthetic organic polymer, and in the case of a natural organic polymer such as waste paper and an inorganic porous material. The content is preferably 5 to 60 parts by weight. In both organic and inorganic systems, if the amount is less than the respective ranges, the effect of addition may not be sufficiently exhibited, while if the amount is too large, it may not be economical or the compressive strength of the soil after solidification improvement may be reduced. Since the improvement of the solidified material in terms of compressive strength leads to a reduction in the amount of solidified material required for solidification improvement, the amount of water-absorbing material added to the solidified material achieves the water content ratio of the soil to be improved and the target strength It is determined appropriately in consideration of the necessary amount of the solidifying material necessary to perform the heat treatment.

Since the solidified material of the present invention is a mere mixture of the constituent components, special equipment is required for its preparation.
No means is required, and a known method using a known solid mixing device such as a mixer can be applied.

When the solidified material of the present invention is used to improve hydrated soil, it is preferable to mix the solid in a solid state from the viewpoint that excess water is not added to the soil. At that time, a mixer mixing method of mixing with a target soil using a mixer and a shallow layer treatment method using a stabilizer can be effectively used. The amount of the water-containing soil, the characteristics of the water-containing soil, especially by water content, water content soil 1 m ³ per 5
By adding 0 to 400 kg, the desired material age 7
An improved soil having a uniaxial compressive strength of 0.5 kgf / cm ² or more after one day can be obtained. Needless to say, by increasing the amount of the solidifying material added as necessary, it is possible to further increase the uniaxial compressive strength of the soil without causing a large increase in the pH value, and the amount to be added is appropriately selected according to the purpose and economy. Will be. Hereinafter, the present invention will be described in more detail with reference to specific examples.

[0018]

EXAMPLES (1) Raw materials used Alumina cement: Blaine specific surface area 3,000 cm ² / g Al ₂ O ₃ content 52% by weight Slag: Blast furnace slag, commercial product Aluminum sulfate: anhydrous, commercial product Lithium carbonate: dihydrate Salt, commercially available waste paper: shredder cutting waste, width of about 5 mm × length of about 20 mm perlite: particle size: 1.2 mm or less, unit volume mass: 0.20 kg / l, commercial product

(2) Preparation of solidified material A predetermined amount of alumina cement, slag, aluminum sulfate and lithium carbonate, and if necessary, a material to which waste paper cuttings or pearlite are added are mixed for 3 minutes by a Hobart mixer to solidify the solidified material. I got

(3) Improvement of soil The soil to be treated has a water content of 62% and a density of 1.752.
g / cm ³ viscous soil. The solidified material prepared in the above (2) was added at a rate of 100 kg per 1 m ^{3 of the} soil to be treated, and then mixed with a Hobart mixer for 3 minutes to prepare an improved soil. After mixing, the soil is 5cm in diameter and 10 in height.
cm of steel cylindrical mold, temperature 20 ℃,
After curing for 7 days and 28 days in a constant temperature and humidity chamber with a relative humidity of 96%, the specimens were demolded to obtain two kinds of test specimens having different material ages.

(4) Evaluation of Soil after Improvement: Uniaxial Compressive Strength The specimen obtained in (3) above was subjected to JIS A12
The unconfined compressive strength was measured by a method according to No. 16. still,
For uniaxial compressive strength, the target soil 1m ³ per 100
The addition of kg gave good soil having an unconfined compressive strength of 0.5 kgf / cm ² or more, which is a strength that allows a person to walk on after 7 days of age. (5) Evaluation of soil after improvement: pH measurement The soil before molding obtained in (3) above was measured for the pH of the improved soil in accordance with the Japan Society of Soil Engineering Standards JSFT 211-1990. Regarding the pH value, those having a pH of 10 or less were regarded as good.

Examples 1 to 4 and Comparative Examples 1 to 3 Table 1 shows the results when the mixing ratio of alumina cement, slag, aluminum sulfate and lithium carbonate was variously changed. When a solidified material having a composition falling within the range of the present invention is used, the pH value of the soil after solidification improvement is 10 or less, and the uniaxial compressive strength after 7 days of material age is 0.5 kgf / cm ^2.
That is all, and the target standard was cleared. On the other hand, in the case of a solidified material having a composition outside the range of the present invention, the pH value or the unconfined compressive strength of the soil after solidification improvement does not reach the intended standard, which indicates that it is unsuitable as a solidified material.

[0023]

[Table 1]

Examples 5 to 8 Here, examples are shown in which waste paper or pearlite is further added as a water absorbing material to a composition comprising alumina cement, slag, aluminum sulfate and lithium carbonate. The results are shown in Table 2, which shows that the addition of the water-absorbing material improves the uniaxial compressive strength after 7 days of material age.

[0025]

[Table 2]

[0026]

The unconfined compressive strength of the soil after improvement using the solidified material of the present invention after 7 days has a uniaxial compressive strength of 0.5 kgf / cm ² or more. Not only work becomes possible, but also the pH value is within 10 or less, where the pH value drop due to the soil buffer capacity is likely to occur quickly, and the possibility of causing alkaline pollution is low, and as a solidification improving material for hydrous soil, High utility value.

Continued on the front page F term (reference) 2D040 AB07 AB11 AC00 BA12 CA04 CA10 4H026 CA01 CA05 CB02 CB05 CB07 CB08

Claims (5)

[Claims] (1) 10 to 50 parts by weight of slag;
1. parts by weight of aluminum sulfate and / or iron sulfate;
A solidifying material for hydrous soil, comprising, as essential components, a composition comprising 5 to 5 parts by weight of a lithium salt and the balance being alumina cement. 2. A solidifying material for hydrous soil, further comprising 0.1 to 5 parts by weight of an organic synthetic polymer water absorbing material per 100 parts by weight of the solidifying material essential component according to claim 1. 3. A solidified material for hydrous soil, further comprising 5 to 60 parts by weight of waste paper per 100 parts by weight of the solidified material essential component according to claim 1. 4. A solidified material for hydrous soil, further comprising 5 to 60 parts by weight of an inorganic porous water-absorbing material per 100 parts by weight of the solidified material essential component according to claim 1. 5. The water-containing soil solidifying material according to claim 1, wherein the solidified material for water-containing soil is 50 to 400 k / m ^{3 of} water-containing soil.
g, a method for improving solidification of hydrous soil.