JP2011094063A - Soil stabilizer and method of soil stabilization using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil stabilizer that controls increase in pH of surplus soil from construction and stabilizes and reinforces the soil and a method of soil stabilization using the soil stabilizer. <P>SOLUTION: The soil stabilizer includes a coagulant containing polyaluminum chloride and sulfates and a calcium-containing compound containing at least either of unslaked lime or slaked lime, includes ≥50 pts.mass of the coagulant to 100 pts.mass of the total aggregate of the soil stabilizer. The coagulant contains 0.1-20 mass% of the sulfates based on the total aggregate mass of the coagulant. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a soil stabilization treatment material applicable to the ground improvement field or the ground environment field and a soil stabilization treatment method using the same.

Conventionally, construction generated soil has been used as a bank embankment material and a backfill material from the viewpoint of reducing environmental burden and cost. Construction soil generated from sediment-like ones, over state range to that of a high water content ratio represented by the shield mud, applications are determined based primarily on the cone index q _C. According to the Construction Sludge Treatment Soil Utilization Technical Standard (August 2006, Ministry of Land, Infrastructure, Transport and Tourism), when the generated soil is used effectively, the corn index needs to be over 200 kN / m ² .

  In addition, substances that are eluted from the treated soil and affect the surrounding pH are beginning to be recognized as environmental load factors. The ministerial ordinance on water quality standards (May 2003, Ministry of Health, Labor and Welfare) stipulates that the pH of tap water should be in the neutral range (5.8 to 8.6). Increasing cases are imposed.

  Under such circumstances, many soil modifiers aimed at improving the corn index of construction-generated soil and neutralizing pH have been studied (see Patent Documents 1 to 5). Patent Documents 1 and 2 describe a solidified material mainly composed of cement or magnesium oxide. Patent Document 3 describes a solidifying material mainly composed of gypsum. Patent Document 4 describes an improved material mainly composed of paper sludge. Patent Document 5 describes a solidified material using polyaluminum chloride (PAC) and other materials in combination.

JP-A-10-273660 JP 2003-147359 A JP 2005-306939 A JP 2005-288338 A JP 2006-219547 A

  By the way, the treatment material using cement, magnesium oxide, paper sludge or the like as the main material is considered to increase the pH of the treated soil, and may not satisfy the above-mentioned ministerial ordinance regarding water quality standards. Further, in order to keep the treated soil in a neutral region, it is necessary to add a large amount of other materials. In this case, the amount of the modifying material becomes enormous, so there is room for improvement in terms of handling.

  The conventional treatment material using gypsum as a main material does not necessarily improve the strength of the generated soil, and may not satisfy the conditions stipulated in the construction sludge treatment soil utilization technical standards. In addition, the treatment material using both polyaluminum chloride and other materials can maintain the pH of the generated soil and the strength of the generated soil by adding how much polyaluminum chloride even if the pH of the treated soil can be maintained in a neutral range. It is not clear whether the conditions can be satisfied.

  This invention is made | formed in view of the said situation, and it aims at providing the soil stabilization processing material which can fully suppress the pH raise of construction generation | occurrence | production soil, and the soil stabilization processing method using the same.

  The soil stabilization treatment material according to the present invention contains a flocculant containing polyaluminum chloride and sulfate, and a calcium-containing compound containing at least one of quick lime and slaked lime, and the total mass of the soil stabilization treatment material is 100. The flocculant is contained in an amount of 50 parts by mass or more based on part by mass, and the flocculant has a sulfate content of 0.1 to 20% by mass based on the total mass of the flocculant. .

Since the treatment material according to the present invention has a smaller amount of calcium-containing compound (for example, cement composition) and a larger amount of flocculant than conventional ones, it is possible to suppress an increase in pH of the treated soil. Moreover, the processing material which concerns on this invention can improve the intensity | strength of processing soil by mix | blending the flocculant containing a predetermined amount of sulfate. That is, aluminum hydroxide gel and dihydrate gypsum are produced by the coexistence of SO ₄ ²⁻ , calcium, polyaluminum chloride, and water generated from sulfate. It is inferred that high strength is expressed by the columnar gypsum dispersed in the aluminum hydroxide gel (see FIG. 5).

  According to the present invention, it is possible to sufficiently suppress an increase in pH of construction-generated soil. Moreover, the intensity | strength of soil fully improves in about 24 hours by mixing the soil stabilization processing material and soil which contain the said flocculent by a predetermined | prescribed ratio.

(A) is a SEM image of the gel-like substance produced by mixing ordinary Portland cement and a flocculant, and (b) is a graph showing the EDS analysis result of this gel-like substance. (A) is a SEM image of the gel-like substance produced by mixing the blast furnace cement B type and the flocculant, and (b) is a graph showing the EDS analysis result of this gel-like substance. (A) is a SEM image of the columnar substance produced | generated by mixing normal Portland cement and a flocculant, (b) is a graph which shows the EDS analysis result of this columnar substance. (A) is a SEM image of the columnar substance produced | generated by mixing blast furnace cement B type | mold and a flocculant, (b) is a graph which shows the EDS analysis result of this columnar substance. It is a SEM image which shows a mode that the lump of gel-like substances is connected by the columnar substance.

<Soil stabilization material>
The stabilization processing material which concerns on this embodiment contains the coagulant | flocculant containing polyaluminum chloride and a sulfate, and a cement composition (calcium containing compound). As the cement composition, for example, ordinary Portland cement or blast furnace cement B type can be used.

  The flocculant contains polyaluminum chloride and sulfate. The content of sulfate based on the total mass of the flocculant is 0.1 to 20% by mass, preferably 0.1 to 9.3% by mass, and 8.4 to It is more preferable that it is 8.7 mass%. If the sulfate content is less than 0.1% by mass, the soil strength is insufficiently improved. On the other hand, if the sulfate content exceeds 20% by mass, the effect of improving the soil strength is saturated.

As sulfates, aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), potassium aluminum sulfate (AlK (SO ₄ ) ₂ · 12HO), ammonium sulfate ((NH ₄ ) ₂ SO ₄ ), potassium sulfate (K ₂ SO ₄ ) Etc. can be illustrated.

  The soil stabilization processing material which concerns on this embodiment contains the said flocculent 50 mass parts or more with respect to 100 mass parts of total mass of the said processing material. When the content of the flocculant is less than 50 parts by mass, the increase in the content of the cement composition increases the pH of the soil, making it difficult to maintain the neutral range. Although depending on the type of soil to be treated and the water content ratio, the content of the flocculant is preferably 60 to 90 parts by mass from the viewpoint of achieving high soil strength while maintaining the pH of the soil in a neutral range. 70 to 80 parts by mass is more preferable. The soil of the treated soil is preferably maintained in a neutral range of pH 5.8 to 8.6 from the viewpoint of reducing the load on the environment.

<Treatment method of construction waste soil>
The soil stabilization method according to the present embodiment includes a step of mixing the stabilization treatment material and the construction generated soil (treated soil). The method of mixing both is not specifically limited, For example, in order to mix on-site, a processing material should be sprinkled on to-be-processed soil and mixed using heavy machinery, such as a backhoe. When the soil to be treated has fluidity, it may be mixed by adding a treatment material to the soil to be treated and stirring.

The water content ω of the soil to be treated is preferably 5 to 1000% and more preferably 25 to 1000% from the viewpoint of obtaining treated soil with high strength. The water content ratio ω (%) is defined by the following formula (1). In the formula, W _W is the mass of water contained in the soil, W _S is the mass of the solid content contained in the soil, respectively.
ω = (W _W / W _S ) × 100 (1)

What is necessary is just to adjust suitably the quantity of the processing material added to a to-be-processed soil according to the characteristic of a to-be-processed soil, the use of a treated soil, or required performance. For example, when the construction-generated soil is effectively used, it is preferable to add a treatment material so that the cone index exceeds 200 kN / m ² . Specifically, it is preferable to add about 100 to 200 kg of treatment material to 1 m ^{3 of the} soil to be treated. In addition, in the case where the construction generated soil to be discarded is simply transported, a smaller addition amount may be used as compared with the above.

The mechanism by which the soil cone index is increased by the treatment material according to this embodiment is presumed as follows. That is, according to a scanning electron microscope observation result, by mixing ordinary Portland cement or blast furnace cement B type and the above-mentioned flocculant, the gel-like substance shown in FIG. 1A or FIG. The columnar substance shown in (a) or FIG. The EDS component analysis was performed about these substances (refer the graph (b) of FIGS. 1-4). As a result, it was found that the gel-like substance was an aluminum hydroxide gel mainly containing Al, Cl, Ca and Si and incorporating Ca ²⁺ from its form and components. On the other hand, it was found that the columnar substance mainly contains Ca and S and is gypsum from its form and components. As shown in FIG. 5, columnar gypsum is dispersed in the aluminum hydroxide gel, and the columnar gypsum connects the lumps of aluminum hydroxide gel. In the SEM image, “Agel” means aluminum hydroxide gel, “Gyp” means gypsum, and “EDS” means the position where component analysis was performed.

In order to confirm the effect of the soil stabilization treatment material according to the present invention, a plurality of types of treatment materials were prepared, and a soil treatment test was performed using them. The following cement and flocculant were used. The sulfate contained in the following flocculant was 8.5% by mass based on the total mass of the flocculant.
Normal Portland cement (OPC): Taiheiyo Cement
Blast furnace cement type B (BB): Taiheiyo Cement Co., Ltd.
Flocculant: TAIPACK (trade name) manufactured by Daimei Chemical Industry Co., Ltd.

(Examples 1-5)
Five types of treatment materials were prepared using ordinary Portland cement (OPC) and a flocculant. Table 1 shows the blending ratio of each flocculant. On the other hand, simulated soil having a water content ω of 42% was prepared using silty clay. The silty clay has a liquidity limit ω _L of 35%, and when the water content ratio ω is 42%, it exhibits a fluid sludge shape.

150 kg of treatment material was added to 1 m ^{3 of} simulated soil, stirred for 1 minute with a Hobart mixer, and then allowed to stand. After 24 hours, a portable corn penetration test (JGS1228-2000) and a pH test (JGS0211-2000) were performed on the treated simulated soil. Table 1 shows the results.

(Examples 6 to 10)
Except for using Blast Furnace Cement B (BB) instead of ordinary Portland Cement (OPC), five types of treatment materials were prepared in the same manner as in Examples 1 to 5, and using these, Processed. Moreover, the measurement of the corn index and pH of the soil after a process was also performed similarly to Examples 1-5. Table 2 shows the results.

(Examples 11 to 13)
The treatment material according to Example 3 was used to treat Kanto Loam (water content ratio: 140%). The amount of treatment material added was 100 kg, 150 kg, and 200 kg with respect to 1 m ^{3 of} soil. The corn index and pH of the treated soil were measured in the same manner as in Examples 1-5. Table 3 shows the results.

Claims (2)

A flocculant comprising polyaluminum chloride and sulfate;
A calcium-containing compound containing at least one of quicklime and slaked lime;
A soil stabilization treatment material containing
The flocculant is contained in an amount of 50 parts by mass or more with respect to 100 parts by mass of the total mass of the soil stabilization treatment material, and the flocculant has a sulfate content of 0.1 to 20 based on the total mass of the flocculant. A soil-stabilized material characterized by being mass%.   A soil stabilization method comprising a step of mixing the soil stabilization material according to claim 1 and the soil to be treated.