JP2006143910A - Method for modifying muddy soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for modifying muddy soil, capable of preventing the powdery dust of powdery material of a solidifying agent from forming in modifying the muddy soil by mixing a new powdery dustless solidifying agent. <P>SOLUTION: This method for modifying the muddy soil is provided by putting a powdery dustless-solidifying agent obtained by calcining a molded material body obtained by molding a powdery material containing a raw material for cement clinker burning and gypsum at a temperature in a range of producing calcium alminate in its solid reaction and also without decomposing gypsum, into a muddy soil-storage container, agitating/mixing the solidifying agent with muddy soil while cracking the solidifying agent. In this method, since the powdery dustless solidifying agent maintaining the form as the molded material is used, the powdery dust is not formed in a working environment and it is possible to keep the environment extremely good state, and also since there is no need to perform the cracking separately, the solidifying agent is cracked at the same time with the mixing of the muddy soil by an agitator to progress a hydration reaction from crashed surfaces having a high activity quickly, it is possible to perform the modification of the muddy soil by exhibiting the performance of the solidifying agent well without sacrificing its initial strength-developing property. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mud reforming method, and more particularly, to an environmentally superior mud reforming method without generating dust.

Of the generated soil discharged during excavation work related to construction work, etc., soil that cannot be piled up on a standard dump or cannot be walked on it (cone index is approximately 200 kN / m ² or less or uniaxial compression) The strength of 50 kN / m ² is generally referred to as “mud”.
Mud is broadly divided into those that fall under dredging caused by dredging such as harbors and rivers, and construction sludge that is discharged during excavation work related to construction work other than dredging.
The latter construction sludge is handled as industrial waste in its original state, but it has been proposed that it can be used as a construction by-product by modifying its properties and converting it into useful materials. In the modification of mud, a method of modifying mud by mixing a cement-based solidifying material used for ground improvement into the mud and performing a stable treatment is known.
However, in this method, when the solidified material is agitated and mixed with the mud, the solidified material may be scattered as dust, which is environmentally undesirable and is a serious problem.

In order to suppress such dust generation, various methods relating to the solidifying material have been proposed.
For example, a method of adjusting the size of the solidified material particles has been proposed.
Japanese Laid-Open Patent Publication No. 7-305059 discloses a soil improver that is produced by sintering and pulverizing the cement, and having a specific surface area of 2500 cm ² / g or less. Specifically, the specific surface area of the cement is adjusted to a certain level or less by adjusting the pulverization process at the time of producing the cement to suppress scattering.

Furthermore, in JP-A-10-265777, organic sludge and limestone washing cake are mixed with at least one selected from the group consisting of aluminum-containing waste and coal ash, and the mixture is heated to 1000 to 1400 ° C. A ground improvement material is disclosed that is fired after granulating the prepared raw material to 1 to 10 mm. The content of free calcium oxide in the ground improvement material is 10 to 30% by weight. As minerals in the ground improvement material, calcium oxide (CaO), calcium aluminate (C ₁₂ A ₇ ), calcium silicate (β -C ₂ S), calcium aluminosilicate _(C 2 aS) have been described to be contained.

  However, although this method of adjusting the size of the solidified material particles is effective for dust control, the specific surface area of the solidified material particles becomes small, so the hydration reaction proceeds and the particles collapse. If it does not wait, internal hydration does not advance, and therefore it is difficult to exhibit the original performance of the solidified material particularly in terms of initial strength development.

  Japanese Patent No. 2514668 includes 5 to 95 parts by weight of a hydraulic composition composed of at least one of cement, slag, and gypsum, 5 to 95 parts by weight of quick lime or bitter lime or a mixture thereof, and further to the hydraulic composition. In addition, there is disclosed a molded body in which 0.5 to 1.5% by weight of a disintegration aid is mixed and pressed to form a briquette.

  Patent No. 2980752 discloses a low-viscosity liquid having a molecular weight of 1000 or less and composed of a saturated alkylene oxide having a low carbon number during the stirring / mixing step or grinding step of cement material containing fine particles of 10 μm or less. A method for producing a cement material sprayed with polyalkylene glycol is disclosed, and particulates that cause dust generation are trapped by polyalkylene glycol and adhered to other particles, or the fine particles are combined and compared. It is described that a product with low dust generation can be obtained by forming large particles.

As described above, according to a technique for suppressing dust by separately treating the fine powder contained in the solidified material, it is possible to suppress the dust without affecting the initial strength development of the solidified material.
However, in order to produce such a solidified material, it requires more processing steps for dust control, such as a pressure forming step and a step of spraying polyalkylene glycol. It was time consuming.

Japanese Patent Laid-Open No. 7-305059 JP-A-10-265777 Japanese Patent No. 2514668 Japanese Patent No. 2980752

  The object of the present invention is to solve the above problems, use a novel dust-free solidified material that is easy to manufacture and does not impair the initial strength, and solidifies the mud during the mud reforming by mixing the solidified material. An object of the present invention is to provide a method for modifying mud that makes it possible to reliably prevent generation of dust in powder.

  The inventors of the present invention use a ball mill or the like, unlike a general cement clinker, which is obtained by firing a specific material at a low temperature under specific conditions, unlike a hard cemented clinker. Finding that it can be easily pulverized without pulverization, and if the fired body is used as a solidifying material without pulverization, the shape during molding is maintained before use and the generation of dust in the solidifying material is suppressed. In addition, the present invention obtains the knowledge that a high activity fracture surface appears by easily crushing at the time of use, and the performance as a solidifying material can be exhibited by the rapid progress of the hydration reaction. Reached.

In the method for modifying mud according to the present invention, the calcium aluminate is solid-phased into a molding material obtained by storing mud in a storage tank and then molding a powder material containing a cement clinker firing raw material and gypsum. The dust-free solidified material produced by the reaction and calcined at a temperature where gypsum does not decompose is charged into the storage tank, and the solidified material and mud are stirred and mixed while crushing the solidified material with a stirrer. It is characterized by doing.
Preferably, in the method for modifying mud according to the present invention, the firing temperature of the dust-free solidified material is 600 to 1200 ° C.

  The method for modifying mud according to the present invention uses a dust-free solidified material obtained by firing a molding material body and maintaining the shape of the molding body, so that no dust is generated in the working environment and the environment is extremely good. In addition, it is not necessary to pulverize separately, and the solidified material is crushed simultaneously with mixing with mud using a stirrer, and the hydration reaction proceeds quickly from a highly active fracture surface. It is possible to easily modify the mud that has satisfactorily demonstrated the performance of the solidified material without sacrificing expression.

  The mud modification method of the present invention uses a non-dust solidifying material containing a large amount of calcium aluminate. It also exhibits good solidification performance for modification and can realize effective strength development.

The present invention is illustrated by the following preferred examples, but is not limited thereto.
1. Non-dust solidifying material used in the present invention The non-dust solidifying material used in the present invention is a molding material obtained by molding a powder material containing a cement clinker firing raw material and gypsum, and calcium aluminate by solid phase reaction. It is formed by firing at a temperature at which it is produced and the gypsum does not decompose.
Portland cement generally used as a solidifying material is manufactured by firing cement clinker and then mixing and crushing cement clinker and gypsum. In the dust-free solidifying material used in the present invention, the raw material for cement clinker firing Since the material in which gypsum is added in advance is fired, the fired body (cement clinker) itself contains gypsum.

Further, since calcium aluminate is generated by a solid phase reaction, it can be fired at a lower temperature than ordinary portland cement clinker and the like, and firing at a low temperature at which gypsum is not decomposed can be realized.
Further, the non-dusting solidifying material, at a temperature at which the gypsum does not decompose, calcium aluminate, those with little need _{4CaO · Al 2 O 3 · Fe} 2 O 3 or the like melt phase to produce a solid phase reaction It is. In such firing, the reaction does not proceed rapidly as in, for example, ordinary Portland cement clinker firing, and a macroscopically heterogeneous fired body is obtained.

  Furthermore, since the reaction of the entire system also reacts relatively slowly, the pores generated by the decomposition and desorption of carbon dioxide from the calcium carbonate inevitably contained in the raw material or the dehydration remain as it is. The fired body, that is, the solidified material, becomes porous.

The cement clinker firing raw material used in the production of the dust-free solidified material essentially includes a calcium raw material and an aluminum raw material, which may contain a small amount of a silica raw material and an iron raw material. be able to.
The composition of the raw material for firing the cement clinker may be determined by adjusting the ratio of the calcium raw material and the aluminum raw material so as to match the mineral composition of the calcium aluminate to be generated by firing. For example, Japanese Patent No. 2872867, Japanese Patent No. 3179702 In addition, the same composition as that described in JP-A-8-169734, alumina cement clinker, and Irwin cement clinker firing raw material composition can be used.

  The gypsum that can be used for producing the dust-free solidified material is not particularly limited, and examples thereof include dihydrate gypsum, hemihydrate gypsum, anhydrous gypsum, and gypsum waste materials. Here, the gypsum waste material means recovered gypsum in gypsum waste, and any waste material containing gypsum can be used without limitation, for example, when a building is newly constructed or demolished It is possible to use gypsum board that has been collected from gypsum board to be used or waste material from the production of gypsum board.

Blaine specific surface area of such gypsum, 1000~15000cm ² / g, it is desirable that preferably 2500~7000cm ² / g. If it is less than 1000 cm ² / g, the dissolution rate is slow, and the supply of sulfate ions contained in gypsum is insufficient. On the other hand, if it exceeds 15000 cm ² / g, it is difficult to mix and handle because of the fine powder. Because it becomes.

  The dust-free solidifying material used in the present invention is obtained by firing a molding material body molded using the above-mentioned raw material for cement clinker firing and the above-mentioned powder raw material made of gypsum.

The temperature at which a molding material body obtained by molding a powder material containing cement clinker firing raw material and gypsum is calcined is kept in a state where calcium aluminate is generated by a solid-phase reaction and contained gypsum is not decomposed. The temperature needs to be within a possible range, preferably 600 to 1200 ° C, more preferably 700 to 1000 ° C.
Thus, since it bakes at low temperature, a liquid phase will hardly be produced | generated. In addition, the reaction proceeds slowly, and pores due to decomposition and desorption of carbon dioxide and dehydration are easily generated from calcium carbonate contained in the molding material body, and a macroscopically heterogeneous porous fired body, that is, a porous body. A dust-free solidified material is obtained. Thereby, the obtained fired body can be easily crushed.

As the reaction, when the firing temperature is raised, first, the adhering water and crystallization water contained in the molded body material are scattered, and then the iron content contained in a small amount in the molded body material is melted to cause a trace amount of liquid. A phase is generated, the contained calcium carbonate is decomposed, and a reaction occurs in which a calcium aluminate phase is generated.
When the firing temperature is less than 600 ° C., the formation reaction of the calcium aluminate phase may be insufficient, which is not preferable.
On the other hand, when the firing temperature exceeds 1200 ° C., the gypsum is decomposed, and the reaction proceeds so much that it becomes a strong sintered body and may not be easily crushed.

The fired body thus obtained, that is, the dust-free solidified material, is mainly composed of calcium aluminate and gypsum.
The calcium aluminate to be contained is preferably contained in the obtained fired body in an amount of 20% by weight or more, more preferably in an amount of 24% by weight or more.
This is because by setting the amount to 20% by weight or more, a necessary strength can be secured when used as a mud modifier.

Moreover, it is preferable that content of gypsum is 5 to 50 weight% in the sintered body obtained, Preferably it is 30 to 40 weight%.
If the amount of gypsum is less than 5% by weight, the amount of ettringite produced during the hydration reaction of the solidified material is reduced, so that it is difficult to obtain good strength development, and the crushability of the solidified material is lowered, which is not preferable. .
On the other hand, if it exceeds 50% by weight, it is difficult to obtain sufficient strength when used as a mud modifier, which is not preferable.
The gypsum added with the above content reacts with calcium aluminate when using the solidifying material to produce abundant ettringite. Since the produced ettringite has a high moisture trapping effect, it has a function of quickly and stably treating mud containing a large amount of water to realize early strength development.

The calcium aluminate phase as a solid phase is one in which the calcium aluminate is present as a crystal phase in the solidified material, and the type thereof is not particularly limited. For example, 11CaO · 7Al ₂ O ₃ · CaF _{2 , 11CaO · 7Al 2 O 3 ·} CaCl 2, 3CaO · Al 2 O 3, 12CaO · 7Al 2 O 3, CaO · Al 2 O 3, CaO · 2Al 2 O 3, 4CaO · 3Al 2 O 3 · SO 3 etc. Can be mentioned.

Preferably, 12CaO · 7Al ₂ O ₃ based calcium aluminate is desirable for stable production and excellent hydration properties.
12CaO · _7Al 2 _{O 3} based calcium aluminate, 12CaO · _7Al 2 _{O 3} and _{11CaO · 7Al 2 O 3 · CaX} 2 with the addition of halogen (wherein, X is fluorine, chlorine, bromine, a halogen element iodine (Shown) alone or a mixture of 11CaO · 7Al ₂ O ₃ · CaX ₂ and 12CaO · 7Al ₂ O ₃ is preferred.
Further, such _{4CaO · Al 2 O 3 · Fe} 2 O 3 may coexist as a melt phase.

Next, a method for producing the dust-free solidified material used in the present invention will be described in detail.
In order to produce the dust-free solidified material used in the present invention, a cement clinker firing raw material and gypsum are mixed to prepare a powder material, then the powder material is molded, and the resulting molded product is decomposed by gypsum. And calcining at a temperature in the above range where calcium aluminate is produced by solid phase reaction.
Specifically, first, the cement clinker firing raw material, which is a raw material used for the non-dust solidifying material, and the gypsum are pulverized and powdered, and mixed at a predetermined mixing ratio to prepare a powder material. As a preparation method, a mixed powder may be obtained by simultaneously pulverizing the cement clinker firing raw material and gypsum, or the cement clinker firing raw material and gypsum may be separately pulverized and mixed. good.

When the cement clinker firing raw material and gypsum are pulverized at the same time, the fineness of the obtained mixed powder is preferably the same as the above-mentioned suitable conditions for the fineness of gypsum.
When the cement clinker firing raw material and gypsum are separately pulverized, the cement clinker firing raw material has a fineness of brane specific surface area of 1000 to 3000 cm ² / g (average powder diameter of 200 μm or less, more preferably 90 μm or less), gypsum powder The degree is preferably set to the above-described suitable condition. The fineness of the cement clinker firing raw material does not particularly affect the ease with which the dust-free solidified material is crushed after firing.
Moreover, the mixing method is not specified, and as long as it can mix uniformly, you may mix using a well-known arbitrary method.

Next, the obtained mixed powder material body is molded. This is to prevent the dust of the solidified material from scattering during use and to facilitate handling by forming a molded body.
Specifically, a pressure molding method can be used as the molding method, but the molding method is not limited to these, and any known molding method can be used.

When pressure molding is used as the molding method, the mixture of the obtained cement clinker firing raw material and gypsum, that is, the mixed powder material, is used as a tool for molding, for example, a material conveying screw or die part of an extrusion molding machine. Alternatively, it is put into a mold of a press machine or the like, and is extruded with a molding pressure of, for example, about 5000 kg / cm ² or less to make a mold and solidify to obtain a molded body. In addition, the pressure at the time of shaping | molding does not affect especially the ease of crushing of the dust-free solidification material after baking.

Next, the obtained molded body is fired, and as described above, the temperature is within a range in which calcium aluminate is generated in a solid-phase reaction and the gypsum contained therein can be maintained in a non-decomposed state, preferably It is 600-1200 degreeC, More preferably, it is 700-1000 degreeC, and it bakes at low temperature. Thereby, the non-dust solidifying material used in the present invention as described above can be obtained.
As a method for firing, in addition to a manufacturing method using a rotary kiln, a manufacturing method using an infrared heating furnace, a reflection furnace, an electric furnace, a tunnel kiln, a gas furnace, or the like can also be used.

2. The mud reforming method of the present invention The mud reforming method of the present invention stores mud in a storage tank, then puts the above-mentioned dust-free solidified material into the storage tank, and crushes the solidified material with a stirrer. In this way, the solidified material and the mud are sufficiently stirred and mixed.
The method uses the above-mentioned non-dust solidifying material as the solidification material when the mud is generated at the site where the mud is generated, or when the generated mud is carried out to the mud reforming plant and performed at the reforming plant. Thus, the effects of the present invention can be obtained.
The dust-free solidified material does not need to be separately pulverized, and the solidified material is easily crushed simultaneously with mixing with mud using a stirrer.

The dust-free solidifying material used in the present invention described above is very effective for the modification of mud because calcium aluminate and gypsum react to generate ettringite and capture a large amount of moisture. .
The dust-free solidified material is easily crushed by the stirrer, and the hydration reaction proceeds rapidly by exposing a highly active fracture surface, so the performance of the solidified material is good without sacrificing initial strength development. It is possible to easily modify the mud soil exhibited in the above.
Moreover, since the non-dust solidifying material is used while maintaining the shape as the molded body, dust is not generated in the working environment, and the environment can be maintained extremely well.

In carrying out the method for reforming mud according to the present invention, for example, when it is carried out at the site of occurrence, excavation of the ground or formation of a tank-like stockyard using the landform of the site in advance is generated. This can be achieved by storing the muddy soil in the stock yard, adding a dust-free solidifying material, and stirring and mixing with an earthwork machine such as a backhoe or a clamshell.
Or, for example, when the mud reforming method of the present invention is carried out in a reforming plant, the generated mud is transported to the reforming plant, and the mud is stored in a storage tank equipped with a stirrer in the reforming plant. Then, it can also be achieved by adding a non-dust solidifying material and stirring and mixing with a stirrer.

Further, the addition amount of the mud dust-free solidifying material used in the present invention, 50～600Kg about per mud 1 m ³ is preferred.

The invention is illustrated by the following examples, comparative examples and test examples.
Example 1
After mixing 5 g of the raw material powder prepared in the formulation shown in Table 1 and 5 g of dihydrate gypsum, it was molded using a uniaxial compression molding machine at a pressure of 10 t / cm ² to obtain a pellet-shaped molded body having a diameter of 30 mm. It was. The pellet was fired at 1000 ° C. for 1 hour to obtain a dust-free solidified material.

Comparative Example 1
The solidified material was obtained by firing under the same conditions as in Example 1 except that the firing temperature was 1300 ° C.

Comparative Example 2
The raw material for firing ordinary Portland cement clinker was fired under the same conditions as in Example 1 to obtain a solidified material.

Test example 1
The solidified material obtained in Example 1 and Comparative Example 1 was placed in a “meal container” having a diameter of 100 mm and a height of 100 mm, together with four “agate balls” having a diameter of 100 mm, and a planetary ball mill device (Flitch). (Manufactured by (Fritch)) for 10 minutes at 200 rpm.
In the case of the dust-free solidified material obtained in Example 1, the obtained powder had a passing rate of 100% through a 1 mm sieve.
In the case of the solidified material obtained in Comparative Example 1, even after the pulverization treatment, the solidified material was hardly pulverized, and the passage rate of the 1-mm sieve was less than 1%.
Since the fired body of Comparative Example 2 was very brittle and would collapse when pinched with a finger, the above test was not performed.

Test example 2
As sample soil, dredged soil (wet density; 1.194 g / cm ³ , water content ratio: 250.4%, Ig.loss; 14.9%, Nara Prefecture) and highly organic soil (wet density; 1.189 g / cm ³ , water content ratio: 279.0%, Ig.loss; 29.1%, produced in Kochi Prefecture).
300 kg of the solidified material obtained in Example 1 and Comparative Example 2 is added to 1 m ³ of the sample soil, and the sample soil is reformed by thoroughly mixing with a stirrer. I got the soil. Even with this mixing treatment, no dust was generated because the solidified material was a molded body.
The strength of each modified soil at the age of 7 days was measured. The results are shown in Table 2.
However, the strength was measured in accordance with a uniaxial compression test: JIS A 1216 “Soil uniaxial compression test method”.

  From the above results, since the non-dust solidifying material used in the mud reforming method of the present invention is a molded body, it can be mixed and used as a molded body for the modification of mud, and even when mixed with mud, It can be seen that there is no occurrence and it is environmentally favorable. In addition, the method for modifying mud according to the present invention allows the dust-free solidified material to be easily crushed, so that a hydration reaction can be rapidly advanced by exposing a highly active fracture surface, and thus a good initial stage. Strength development can be obtained, and the mud can be easily modified so that the performance of the solidifying material can be exhibited well. Moreover, it turns out that a favorable solidification performance can be demonstrated and effective strength expression can be implement | achieved also with respect to a highly hydrous mud and a highly organic mud.

The mud reforming method of the present invention is applied to dredged soil accompanying dredging such as harbors and rivers, and construction sludge discharged from excavation work related to construction work other than dredging. It is used for reforming. In particular, it can be effectively applied to highly hydrous mud and highly organic mud and can be used as an effective reforming method.

Claims (2)

  A range in which calcium aluminate is produced by solid-phase reaction and gypsum is not decomposed by storing muddy soil in a storage tank and then molding a powder material containing cement clinker firing raw material and gypsum The dust-free solidified material obtained by firing at a temperature of 10% is charged into the storage tank, and the solidified material and the mud are stirred and mixed while the solidified material is crushed by a stirrer. Method. The method according to claim 1, wherein the dust-free solidifying material has a firing temperature of 600 to 1200 ° C.