JP3488975B2 - Composition for soil stabilization treatment - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition used for soil stabilization treatment of soft ground. In particular, the present invention provides a composition for stabilizing soil, which is effective for solidifying soil such as soft soil having a high water content and sludge.

[0002]

2. Description of the Related Art The composition used for soil stabilization is
When added to soft ground, it causes ion exchange reaction with soil particles, pozzolanic reaction, etc., and improves mechanical and hydraulic properties of soil. Cement-based compositions are mainly used for silt and sandy soil. Further, in the above composition, a large amount of addition is required for high organic soil or sludge having a high water content, and in some cases, it may not be suitable for practical use. In such a case, quick lime or cement, granulated blast furnace slag, bozolan material such as fly ash, gypsum, composite composition of a mixture of cement hydration stimulants such as sodium sulphate, or a fired fired material (3C
_{aO · 3Al 2 O 3 · CaSO} 4) or special cementitious composition mainly containing strength enhancing material alumina cement-based compounds have been used.

[0003] However, the Auin composition or the special cement composition containing an alumina cement compound as a main component is necessarily expensive because the Auin composition and the alumina cement are produced by high temperature firing. It has drawbacks that cannot be obtained. Also in terms of construction, when adopting the wet mixing method in the deep layer mixing method or the surface layer mixing, the hain compound exhibits rapid hardening in the presence of water, so that gelation occurs during mixing with soil and workability is improved. Deterioration and poor mixing. A method of adding a setting retarder to compensate for these defects has been adopted, but it requires a complicated operation to set the amount of addition and causes a cost increase.

[0004]

DISCLOSURE OF THE INVENTION The present invention does not use expensive hain-based compounds or alumina cement-based compounds, and is more suitable for soft soil with a high water content and sludge than ordinary cement, quicklime, and slaked lime. It is an object to provide an inexpensive composition having a stable effect.

[0005]

The composition for soil stabilization according to the present invention is 3CaO.Al ₂ O ₃ .6H ₂ O.
(Hereinafter abbreviated as C ₃ AH ₆ ) is characterized by being a mixture of a product obtained by thermally decomposing at 300 ° C. or higher and quick lime.

It is known that when C ₃ AH ₆ is decomposed at 300 ° C. or higher, 12CaO.7Al ₂ O ₃ .H ₂ O (hereinafter abbreviated as C ₁₂ A ₇ H) and some free lime are formed. As a result of repeated studies paying attention to the fact that C ₁₂ A ₇ H is rehydrated when mixed with water to form C ₃ AH _6, as a result of adding and mixing quick lime to the thermal decomposition product of C ₃ AH ₆ , and mixing it The present invention has been completed by finding that it exhibits an excellent strength developing effect as a composition for treating soft soil having a water content ratio and sludge. The present invention will be described in detail below.

First, the synthesis of C ₃ AH ₆ will be described, and then the thermal decomposition reaction of C ₃ AH ₆ will be described. C ₃ A
H ₆ can be easily synthesized by adding water to Al (OH) ₃ and CaO or Ca (OH) ₂ and mixing them. The reaction formula is 2Al (OH) ₃ + 3CaO + 3H ₂ O → 3CaO · A
l ₂ O ₃ · 6H ₂ O or 2Al (OH) ₃ + 3Ca (OH) ₂ → 3CaO · Al
A ₂ O ₃ · 6H ₂ O. Next, the obtained C ₃ AH ₆ is heated to 300 ° C. or higher and decomposed into C ₁₂ A ₇ H and CaO or Ca (OH) ₂ . The reaction formula is 300 to 500 ° C., 7C ₃ AH ₆ → C ₁₂ A ₇ H + 9Ca (OH) ₂ + 32H
₂ O ↑ Above 500 ° C, C ₁₂ A ₇ H + 9Ca (OH) ₂ → C ₁₂ A ₇ H + 9CaO
+ 9H ₂ O ↑, and according to these reaction formulas, C ₁₂ A ₇ H and Ca
It is possible to obtain a mixture with O or Ca (OH) ₂ .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum hydroxide used as the Al source is not particularly limited as long as it contains aluminum in the form of aluminum hydroxide, but aluminum sludge is most suitable because it is inexpensive and available in large quantities. Is. Aluminum sludge is a sludge produced as a by-product when neutralizing and draining a waste liquid containing a large amount of aluminum salts formed mainly in the surface treatment process of aluminum products,
It contains a large amount of aluminum hydroxide, mostly in gel form. Therefore, some impurities are included in addition to aluminum hydroxide, so some of them are used as ceramic raw materials such as cement, but most of them are currently landfilled as industrial wastes, and development of applications is desired. ing. As the CaO or Ca (OH) ₂ source, commercially available quicklime or slaked lime can be used as a raw material.

The reaction between the two may be carried out at room temperature according to the reaction formula, but in order to accelerate the reaction, 50
A method of heating to about 100 ° C is desirable. Also, since aluminum sludge is usually produced in a state of containing 20 to 100% (external ratio) of water, it is possible to add quick lime for a reaction that also serves as dehydration, and to add more water to aluminum sludge. Alternatively, a method in which slaked lime or quick lime is added after forming a slurry to complete the reaction quickly can be considered.

Next, the thermal decomposition reaction of C ₃ AH ₆ obtained by the reaction will be described. According to the above reaction formula, C ₃ AH ₆ becomes C ₁₂ A ₇ H and Ca (OH) _{2 when} it exceeds 300 ° C.
Moreover, when the temperature exceeds 500 ° C., Ca (OH) ₂ is easily decomposed into CaO. Below 300 ° C., the decomposition reaction of C ₃ AH ₆ does not proceed, so the decomposition product used in the present invention cannot be obtained. Further, even if the temperature exceeds 500 ° C., the state does not change up to around 1000 ° C. at which the decomposition reaction of C ₁₂ A ₇ H starts.

The thermal decomposition product of C ₃ AH ₆ reacts with water to quickly return to C ₃ AH ₆ to exhibit dehydration and strength development effects, so that the performance as a soil stabilization composition is excellent even in this state. (See Comparative Example 1 below). However, as a result of continuing the research for further improving the performance, the inventors of the present invention obtained a composition for soil stabilization treatment of soft soil, sludge, etc. by adding and mixing an appropriate amount of quicklime to the thermal decomposition product of C ₃ AH _6. It has been discovered that the strength development of is much better. In this case, the amount of quick lime added is 10 to 100 parts by weight of the thermal decomposition product of C ₃ AH _6.
An appropriate amount is 200 parts by weight, preferably 20 to 150 parts by weight, which is suitable for most soil types. If the addition amount is 10 parts by weight or less, the addition effect is small, and if the addition amount is 200 parts by weight or more, the soil stabilization treatment performance of the thermal decomposition product of C ₃ AH ₆ cannot be exhibited well. Furthermore, in actual use,
It is also possible to add fly ash, stone powder, a water-soluble polymer, a highly water-absorbent resin, sewage sludge incineration ash, etc. to the soil stabilization composition of the present invention to improve the dehydration property and adjust the solidification rate. . The addition amount of the composition of the present invention is appropriately in the range of 20 to 200 kg per 1 cubic meter (m ³ ) of the target soil. The following will describe specific examples of the composition of the present invention and the effects thereof by examples, but the present invention is not limited to the following examples.

[0012]

[Comparative Example 1] Aluminum sludge of the components shown in Table 1 was added to a stainless reactor equipped with an agitator (capacity: 30 L).
3kg, quicklime (CaO content 92.3%) 6.14k
g and 20 L of fresh water were added and the reaction was carried out at 50 ° C. for 24 hours with stirring. When the composition after the reaction was examined by powder X-ray diffraction, formation of C ₃ AH ₆ was confirmed. After dehydrating the reaction product, it was heated in an electric furnace at 350 ° C. for 3 hours to be thermally decomposed, and a mixture of C ₁₂ A ₇ H and Ca (OH) ₂ 10.0 kg
Got The resulting mixture of C ₁₂ A ₇ H and Ca (OH) ₂ was crushed by a disc mill and passed through a 1 mm sieve, 0.6 mm
Sample A was adjusted to have a particle size of 74.8% through a sieve and 56.3% through a 0.15 mm sieve.

[0013]

[Table 1]

[0014]

[Example 1] Quick lime (CaO content 9
(2.3%) 200 g was added to and mixed with the composition to prepare Sample B.

[0015]

[Comparative Example 2] Slaked lime (industrial slaked lime J
A composition in which 200 g of IS1 product) was added and mixed was manufactured to be a sample C.

[0016]

[Comparative Example 3] A sample A was prepared by mixing 200 g of ordinary Portland cement with 800 g of sample A to prepare a sample D.

[0017]

[Comparative Example 4] A sample E was prepared by adding 200 g of gypsum dihydrate to 800 g of sample A to prepare a composition.

[0018]

[Comparative Example 5] Slaked lime (industrial slaked lime JIS No. 1 product), which is a known soil stabilization composition, was used as Sample F.

[0019]

[Comparative Example 6] Quick lime (CaO content 92.3%), which is a known soil stabilization composition, was used as Sample F.

[0020]

[Test Example 1] Each of Samples A to G has a water content ratio of 109%.
A soil stabilization treatment was carried out by adding 100 kg / m ³ to Kanto loam. Soil stabilization is evaluated by "Test method of stabilized soil with cement composition" according to 1
The uniaxial compressive strength was measured after 3 days and 7 days. The results are shown in Table 2.

[0021]

[Table 2]

As is clear from Table 2, as compared with the case where the thermal decomposition product of C ₃ AH ₆ (particle size adjusted product) alone (Sample A) or quick lime alone (Sample F) is used, Sample A and quick lime are used. When the sample B (Example 1) which is the mixture (mixing weight ratio 8: 2) is used, the uniaxial compressive strength is improved, and the excellent soil stabilization treatment effect is exhibited. Moreover, the effect of adding quick lime as an additive is clear compared to the cases of slaked lime (Sample C), cement (Sample D), and gypsum dihydrate (Sample E).

[0023]

Comparative Example 7 A stainless beaker having a capacity of 5 L was charged with 1.9 kg of aluminum sludge having the components shown in Table 3 and quick lime (Ca).
O content 92.3%) 1.2 kg and 50 L of warm water 3 L
Is added to form a slurry, and the mixture is kept at 50 ° C with a stirrer to
Mixed for hours. After the completion of mixing, the mixture was left standing at room temperature for 24 hours, the solid content was separated by suction filtration, and the separated solid content was dried in a dryer at 110 ° C. for 3 hours to obtain a C ₃ AH ₆ -containing material 2.7.
I got kg. Further, this was heated in an electric furnace at 550 ° C. for 3 hours for thermal decomposition, and a mixture of C ₁₂ A ₇ H and CaO 2.
0 kg was obtained. The obtained mixture of C ₁₂ A ₇ H and CaO was crushed by a vibration mill, and then passed through a 1 mm sieve, 0.6 mm
Sample H was prepared by adjusting the particle size so that it passes 75.7% of the sieve and 58.5% of the 0.15 mm sieve.

[0024]

[Table 3]

[0025]

[Example 2] Quick lime (CaO content 9
(2.3%) 500 g was added and mixed to prepare a composition, which was designated as Sample I.

[0026]

[Comparative Example 8] Sample J was prepared by preparing a composition in which 500 g of ordinary Portland cement was added and mixed with 500 g of sample H.

[0027]

[Comparative Example 9] Slaked lime (industrial slaked lime J
A composition in which 500 g of IS1 product) was added and mixed was manufactured to be a sample K.

[0028]

Test Example 2 Samples H to K were added to a volcanic ash construction sludge having a water content of 135% at a rate of 120 kg / m ³ to perform soil stabilization treatment. As for the evaluation of the soil stabilization treatment, the uniaxial compressive strength after 1 day, 3 days, and 7 days was measured by the “test method for stabilized soil with cement composition” as in Test Example 1. The results are shown in Table 4.

[0029]

[Table 4]

As is clear from Table 4, when the thermal decomposition product of C ₃ AH ₆ (particle size adjusted product) alone (Sample H) or cement (Sample J) or slaked lime (Sample K) was used as an additive. Compared with the above, the soil stabilization treatment effect of the composition (Sample I) to which quick lime was added and mixed is clear.

[0031]

EFFECTS OF THE INVENTION It is possible to obtain a superior stabilizing effect to soft soil and sludge having a high water content ratio than the conventionally used soil stabilizing composition, and to reduce the addition amount of the composition for construction. The economic effect of is expected.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C09K 17/06 C09K 17/06 P 17/10 17/10 P // C09K 103: 00 103: 00 (58) Fields investigated ( Int.Cl. ⁷ , DB name) C09K 17/08 C01F 7/16 C04B 7/32 C04B 7/34 C09K 17/02 C09K 17/06 C09K 17/10

Claims (2)

(57) [Claims] 1. 30% of 3CaO.Al ₂ O ₃ .6H ₂ O
A composition for soil stabilization, which is a mixture of a product pyrolyzed at 0 ° C or higher and quicklime. _2. 30% of 3CaO.Al ₂ O ₃ .6H ₂ O
100 parts by weight of product pyrolyzed at 0 ° C. or higher and quick lime 10
The composition for soil stabilization according to claim 1, which is a mixture of about 200 parts by weight.