JP2002001397A - Modifier and process for solidifying and neutralizing muddy material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modifier for solidifying and neutralizing a muddy material, capable of surely solidifying and neutralizing the muddy material for a short time, producing a muddy material hardened body having high solidity with high-strength, and sufficiently inhibiting the elution of hexavalent chromium from the hardened body. SOLUTION: This modifier consists of: (A) hydraulic gypsum; (B) a solidifying agent; (C) porous inorganic particles; and (D) a pH-adjusting agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for solidifying muddy substances.
The present invention relates to an improvement material that neutralizes, and a method of solidifying and neutralizing a muddy substance using the improvement material.

[0002]

2. Description of the Related Art For example, mud generated at construction / construction sites such as tunnel work, water supply and sewerage work, excavation work, construction work, construction sites, etc., dredged mud at lakes, marshes, rivers, harbors, etc. Conventionally, activated sludge, sludge, sludge, etc. (hereinafter, collectively referred to as muddy substances) in a treatment plant are solidified at a muddy substance generation site or an industrial waste intermediate treatment plant. And then reclaimed, landfilled as industrial waste at a managed landfill, or reused as recycled soil in various applications. As the solidification treatment of such a muddy substance, a dry solidification treatment by sunlight, a dehydration solidification treatment by a filter press or a centrifugal separator, and a coagulation solidification treatment by cement or cement-based solidification material are generally performed.

[0003]

However, soil obtained by drying and dehydration and solidification by the sun produces turbid water when exposed to rainwater, and causes landfills and treatment sites to be turbid.
It causes soil pollution and natural destruction around the disposal site. Further, in the drying and solidifying treatment by the sun, a long time is required for drying, and it is easily affected by the weather. Further, the dehydration and solidification treatment requires a high cost for drying.

[0004] In addition, in the soil obtained by the coagulation and solidification treatment with cement or cement-based solidifying material, water in contact with the soil is discharged according to the drainage standard (pH 5.8-8.
Since it exhibits an alkalinity exceeding 6), the reuse of such soil and the treatment and disposal sites are limited and limited. In addition, when such soil is exposed to rainwater, turbid water is generated, which causes soil pollution and natural destruction in the vicinity of landfills, treatment sites, disposal sites, and the like. Further, the cone index (q _c ), which is the degree of solidification obtained based on the portable cone penetration test, is 200 kN.
/ M ² or more for the soil to exhibit strength
It takes more than 4 hours.

Here, the cone index is an index of trafficability. Trafficability refers to the traveling and workability of construction machinery. That is, the cone index is 300k
If it is N / m ² or more, a wetland bulldozer can run,
If the cone index is 200 kN / m ² or more, a super wetland bulldozer can run. The cone index is a value obtained by dividing the penetration resistance when a cone is penetrated into compacted soil by the bottom area of the cone, and is defined by the Japan Society of Geotechnical Engineers (JSF T
716). Various applications of the soil are determined according to the value of the cone index (unit: kN / m ² ) as shown in Table 1 below.

[Table 1] Cone index Use 200 or more Landfill 400 or more Landfill, residential land development, backfill material, river embankment, road body 800 or more Landfill, residential land development, backfill material, river embankment, road body, subgrade

Therefore, the present applicant has disclosed in Japanese Patent Application Laid-Open No. 10-147.
No. 781 proposes a mud dried and solidified material composed of a neutral water-soluble polymer agent and hemihydrate gypsum, and further, by adding a neutral water-soluble polymer agent and hemihydrate gypsum to the mud. A method of drying and solidifying mud by mixing and then curing is proposed.

[0008] However, there is room for improvement in the solidification rate of the mud, particularly in the consolidation property (agglomeration of particles) during mud treatment, the solidification degree of the consolidation soil (strength development), and the neutralization of the mud. It turned out to be. In addition, hexavalent chromium may be eluted from the soil obtained by the coagulation treatment with cement or cement-based solidifying material, but it is difficult to sufficiently suppress the elution of such hexavalent chromium.

Accordingly, an object of the present invention is to reliably solidify a muddy substance in a short time, and to solidify a solidified muddy substance (hereinafter, referred to as a solidified muddy substance) (strength development). To obtain a solidified muddy substance that shows high neutrality, and can sufficiently suppress the elution of hexavalent chromium from the solidified muddy substance. It is an object of the present invention to provide a material and a method for solidifying and neutralizing a muddy substance using the improved material.

[0010]

In order to achieve the above object, the present invention provides an improved material for solidifying and neutralizing a muddy substance.
It comprises (A) hydraulic gypsum, (B) a coagulant, (C) porous inorganic particles, and (D) a pH adjuster.

The improving material for solidifying and neutralizing the muddy substance of the present invention (hereinafter, simply referred to as the "improving material of the present invention") may be in a form in which the above-mentioned components are preliminarily mixed or in a separate state. And may be mixed at the time of use, or separately added to the muddy substance at the time of use.

In order to achieve the above object, the method for solidifying and neutralizing a muddy substance according to the present invention comprises: (A) a hydraulic gypsum, (B) a coagulant, and (C) a porous inorganic substance. Particles, and
(D) An additive comprising a pH adjuster is added and mixed.

In the method for solidifying and neutralizing the muddy substance of the present invention (hereinafter simply referred to as the method for solidifying and neutralizing the present invention), an improving material is added to 100 parts by weight of the muddy substance. It is desirable to add and mix 1 to 100 parts by weight, preferably 5 to 50 parts by weight, more preferably 10 to 50 parts by weight. However, more specifically, the proportion of the additive added is
What is necessary is just to determine suitably based on the property (for example, pH value and water content ratio) of a muddy substance.

In the solidification / neutralization method of the present invention, the method of adding the improving material of the present invention to the muddy substance is essentially arbitrary. That is, the improver obtained by previously mixing the constituents constituting the improver may be added to the muddy substance, or the respective components may be kept in separate states, mixed at the time of use, and added to the muddy substance. However, each component may be separately added to the slurry at the time of use.

The mixing of the muddy substance and the improving material of the present invention may be performed, for example, using a mixer. As a mixer,
Mortar mixer, cement mixer, whirl mixer, paddle mixer, screw mixer, kneader,
A line mixer (static mixer) can be exemplified. The mixer may be of a batch type (batch type) or a continuous type. The muddy substance inside the mixer may be heated or depressurized.

In the solidification / neutralization method of the present invention, the improving material of the present invention is added to a muddy substance and mixed to solidify and neutralize the muddy substance.
In addition to neutralization, it is necessary to add the improved material of the present invention to the muddy substance, mix and backfill, backfill, etc. with fluidity and material separation resistance suitable for the application A so-called fluidization treatment method is also included, in which the material is poured into a certain place or cast under water, or is subjected to underwater construction to solidify and neutralize in an appropriate curing state.

Here, as muddy substances, for example, mud generated at construction / construction sites such as tunnel works, waterworks and sewerage works, excavation works, building works, construction sites, etc., dredged muds at lakes, marshes, rivers, harbors, etc. Examples include mud in water treatment plants, activated sludge in sewage treatment plants, mud of industrial wastewater, sludge, spring water and muddy water at various construction sites, boring muddy water, waste bentonite muddy water, cement milk, and muddy water from aggregate production. In general, it refers to mud that remains after treatment of factory wastewater and mud that occurs in various manufacturing processes.It refers not only to mud mixed with a large amount of organic matter, but also to organic and inorganic mud. Including all of the things.

The water content ratio (w) of the muddy substance is 2 × 10
% To 2 × 10 ³ %. In some cases, the muddy substance having a high water content is previously mechanically dehydrated using a filter press, a belt press, a roller press, a drum press, an Oliver filter, or the like, and then the solidification / neutralization method of the present invention is performed. May be applied. Here, the water content ratio (w) of the muddy substance is, for example, JIS A1
Sample preparation was performed based on JIS A120
3 and can be obtained by drying the muddy substance to a constant mass at 110 ° C. and can be expressed by the following equation. The mass of the mud before drying is W ₁ , and the mass of the mud after drying is W ₂ .

[Equation 1] Water content (w) = (W ₁ −W ₂ ) / W ₂ × 100 (%)

In the improved material of the present invention or the solidification / neutralization method of the present invention (hereinafter, these may be collectively simply referred to as the present invention), the hydraulic gypsum is a hemihydrate gypsum. CaSO ₄ .1 / 2H ₂ O] and / or Type III anhydrous gypsum [Type III CaSO ₄ ]. It should be noted that there is no problem even if the hydraulic gypsum contains about 20% by weight or less of gypsum [CaSO ₄ .2H ₂ O] and / or type II anhydrous gypsum. Hereinafter, gypsum [CaSO ₄ · 2H ₂ O] and I
I-type anhydrous gypsum may be collectively referred to as dihydrate gypsum or the like. More specifically, hydraulic gypsum is hemihydrate gypsum, III
Anhydrous gypsum, a mixture of hemihydrate gypsum and type III anhydrous gypsum, a mixture of hemihydrate gypsum and dihydrate gypsum, a mixture of type III anhydrous gypsum and dihydrate gypsum, a hemihydrate gypsum, type III anhydrous gypsum and gypsum And the like. The composition of the hydraulic gypsum can be analyzed, for example, by X-ray diffraction. When Cu Kα radiation is used as the X-ray source, quantification can be achieved by measuring diffraction peaks at diffraction angles (2θ) as shown in Table 2 below.

[0021]

Examples of hemihydrate gypsum include natural gypsum, flue gas desulfurization gypsum, phosphate gypsum which is a by-product in the production of phosphoric acid, medical treatment such as precision casting, dentistry and surgery, art and craft, and waste which is a waste in the production of ceramics. Hemihydrate gypsum (β-type hemihydrate gypsum) obtained by calcining dihydrate gypsum such as gypsum mold and waste gypsum in a gypsum board manufacturing plant in a batch or continuous manner, for example, α-type half which is a by-product of phosphoric acid production Water gypsum can be mentioned. Type III anhydrous gypsum can be obtained by setting the firing temperature of dihydrate gypsum to be higher than that for firing β type hemihydrate gypsum. Further, the obtained hemihydrate gypsum or type III anhydrous gypsum may be pulverized as required to adjust the particle size. By adjusting the particle size, some control of the setting (hydration) time of hemihydrate gypsum or type III anhydrous gypsum can be achieved. In some cases, waste gypsum board at a gypsum board manufacturing plant or construction site is crushed and separated into paper and dihydrate gypsum, and hemihydrate gypsum obtained by firing such gypsum in a batch or continuous manner and / Or I
Mix Type II anhydrous gypsum and paper from waste gypsum board,
It may be used as a raw material for the improved material of the present invention.

In the present invention, by using hydraulic gypsum as one of the components constituting the improving material, it is possible to dry the sun,
The muddy substance can be solidified in a shorter time than the coagulation and solidification treatment using cement or a cement-based solidifying material, and a predetermined strength can be quickly developed in the solidified muddy substance. In particular, the use of hydraulic gypsum can improve the cone index or the uniaxial compressive strength of the solidified muddy substance. Incidentally, the cone index of the solidified mud substance is 200 kN / m ² or more, or JIS A1
Uniaxial compressive strength measured according to 216T is 4.9 × 1
It is preferably at least 0 ⁴ Pa (0.5 kgf / cm ² ). Furthermore, using a pH meter specified in JIS Z8002, the pH of the solidified mud is 5.8 to 8.6 in the pH measurement result based on JSF-T7T.
In the measurement results based on the soil particle size test of IS A1204, it is preferable that fine particles (silt, clay) of 74 μm or less do not exist in the solidified mud.

In the present invention, a coagulant is used as a dissociation group such as a carboxyl group (—COO ⁻ ) or a sulfone group (—S
It is preferable to select from an anionic polymer coagulant having O ₃ ⁻ ) or an inorganic coagulant, specifically, a metal acrylate / acrylamide copolymer (eg, sodium acrylate / acrylamide copolymer) , Anionic polyacrylamide polymer, polyacrylamide partial hydrolyzate, acrylic acid / vinyl alcohol copolymer, partially sulfomethylated polyacrylamide (eg, polysulfomethylated polyacrylamide), sodium alginate, carboxymethyl cellulose (C
MC) and inorganic coagulants (eg, aluminum sulfate or polyaluminum chloride (PAC), ferric sulfate, ferrous sulfate, ferric chloride, zinc chloride, titanium tetrachloride, sodium aluminate) At least one selected from the group
Preference is given to a type of coagulant. The improving material may be constituted by one kind of these coagulants or a combination of two or more kinds.

In general, agglomeration refers to the action of assembling fine particles suspended in water to increase the apparent particle size and facilitate solid-liquid separation.
And flocculation. The coagulant in the present invention not only has these effects but also a substance (-O) that increases the alkali concentration (pH) in the muddy substance.
H, Ca, etc.). Therefore, the composition of the coagulant itself in the present invention can be the same as the composition of a known coagulant,
Called coagulant.

In the present invention, the porous inorganic particles are preferably at least one kind of porous inorganic particles selected from the group consisting of silica, zeolite, porous silica, and silica powder. Alternatively, as porous inorganic particles, perlite, vermiculite, diatomaceous earth, kaolin, activated clay, silica sand, quartzite, bentonite mainly containing montmorillonite, silica mainly, alumina, iron oxide, calcium oxide are used. Fly ash or the like can also be used. Substances in muddy substances (substances containing -OH, Ca, etc.) that increase the alkali concentration (pH) due to the presence of porous inorganic particles
Is adsorbed on the porous inorganic particles, neutralization of the muddy substance is promoted, and functions as a so-called aggregate in the solidified muddy substance. The porous inorganic particles are 1 × 10 ^{2 to} 1 × 10 ⁴ m ²
/ G, preferably 5 × 10 ^{2 to} 8 × 10 ³ m ² / g. here,
The specific surface area can be measured by the BET method.

Further, according to the present invention, the content of the muddy substance
Substances (-OH, Ca, etc.) that increase the concentration of lukari (pH)
PH adjusting agent for neutralizing silicate is a silicate
It is desirable to contain a compound, such a pH adjuster
Is, for example, SiO_Two, Al_TwoO _Three, K_TwoO, Na_TwoO, F
e_TwoO_Three, SO_Three, CaO, C
And a kind of clay contained in the lime layer. pH adjustment
Other agents include FeSO _FourSuch as sulfate and FeCl_Threeetc
Can be mentioned. Furthermore, with a pH adjuster
And the intercalated porous interlayer
(Layered crystal or ion-exchanged layered crystal)
it can. Here, the molecular layered crystal is a neutral two-dimensional crystal.
The layers are weakly interconnected, such as van der Waals forces or hydrogen bonds.
It has a structure stacked on each other by action, graphite,
Transition metal dichalcogen compounds (eg, TiS_Two, Nb
Se_Two, MoS_Two), Divalent metal phosphorus chalcogen compounds (eg
For example, MPS_Three, MPSe_Three, Ta_TwoS_TwoC), oxides (examples)
For example, MoO_Three, V_TwoO_Five), Oxyhalides (eg
For example, FeOCl, VOCl, CrOCl), halogenated halogen
(Eg, ZrNCl, ZrNBr), hydroxide
(For example, Zn (OH)_Two, Cu (OH)_Two), Silicate
(For example, kaolinite, halloysite, H_TwoSi
_TwoO_Five, H_TwoSi₁₄O₂₉・ 5H_TwoO), others (Ni (C
N)_Two, VOSO_Four, Ag_TwoC_TwoO)
You. In an ion-exchange layered crystal, each crystal layer is electrically
Instead of being charged, the oppositely charged
Ions are present between the layers. Cation exchange ion exchange
As exchangeable layered crystals, silicates (for example, montmorillona
, Vermiculite, beidellite), phosphate
(For example, Zr (HPO_Four)_Two・ NH_TwoO, Ti (HP
O_Four)_Four・ NH_TwoO, Na (UO_TwoPO_Four) · NH_TwoO), j
Tanoates (e.g., Na_TwoTi_ThreeO₇, KTiNbO_Five, R
b_xMn_xTi_2-xO_Four), Uranates (eg, Na_TwoU_Two
O₇, K_TwoU_TwoO₇), Vanadates (eg, KV_ThreeO₈,
K_ThreeV_FiveO₁₄, CaV₆O₁₆・ NH_TwoO, Na (UO_TwoV_ThreeO
₉) · NH_TwoO), niobate (eg, KNb)_ThreeO₈, K
_FourNb₆O₁₇, KCa_TwoNb_ThreeO_Ten), Tungstate
(Na_TwoW_FourO₁₃, Ag₆W_TenO₃₃), Molybdate
(Mg_TwoMo_FiveO₁₇, Cs_TwoMo_FiveO₁₆, Cs_TwoMo₇O_{twenty two},
Ag₆Mo_TenO₃₃). In addition, mud
If the solidified material is cured in the air, the acid in the solidified mud
Calcium iodide (CaO) reacts with carbon dioxide in air
And the pH of the solidified mud becomes more neutral (pH 5.8).
~ 8.6). Curing is, for example, 24 hours (1 day)
Or it may be more. In addition, as described above,
Hexavalent chromium in the solidified mud
Becomes trivalent chromium and is rendered harmless.
Keeps the pH of the compound neutral (pH 5.8 to 8.6)
Therefore, trivalent chromium in the solidified mud is stable.
Continue to be.

As the compounding ratio of the improving material in the present invention,
The coagulant is used in an amount of 0.1 to 30 parts by weight, preferably 0.2 to 20 parts by weight, and the porous inorganic particles is 5 to 200 parts by weight, preferably 10 to 100 parts by weight, based on 100 parts by weight of the hydraulic gypsum. And a pH adjuster in an amount of 0.1 to 110 parts by weight, preferably 0.5 to 30 parts by weight. However, more specifically, the addition ratio of the improving material may be appropriately determined based on the properties (for example, pH value and water content ratio) of the muddy substance.

In the present invention, the improving material may further contain a solidification promoting material. Here, solidification promoting material includes aluminum oxide, than this aluminate is a salt resulting from a strong metal oxides basicity also [general formula: xM ₂ ^I O · y
It is preferable to contain Al ₂ O ₃ .ZH ₂ O (provided that z = 0 is included). The solidification accelerator may be an aluminate, or may be an inorganic or mineral containing an aluminate. Aluminates can be classified into hydrous metaaluminates, hydrooxoaluminates, and anhydrous aluminates (including spinel-type compounds and non-spinel-type compounds that are alkali metal salts and divalent metal salts).
Aluminates in this category can be used. As the aluminate, specifically, calcium aluminate (having a composition such as CaO.Al ₂ O ₃ , 3CaO.Al ₂ O ₃ ), sodium aluminate, potassium aluminate,
Examples include strontium aluminate, barium aluminate, and magnesium aluminate. When the solidification accelerator is composed of calcium aluminate, examples of the solidification accelerator of such a composition include alumina cement, high alumina slag, blast furnace slag, converter slag, electric furnace slag, or a mixture thereof. . The average particle size may be about 0.1 to 100 μm, preferably about 1 to 50 μm. The ratio of the solidification promoting material in the improving material depends on the pH of the muddy substance, the properties of the muddy substance (for example, silt content, clay content, colloid content, etc.), and the properties (for example, corn The index may be determined as appropriate, but it is desirable that the solidification accelerator is contained in an amount of 1 to 400 parts by weight, preferably 3 to 50 parts by weight, based on 100 parts by weight of the hydraulic gypsum. For example, as a result of the reaction of calcium aluminate and calcium sulfate to form ettringite, a kind of solidified muddy substance (netting) can be achieved.

In the present invention, the improving material may further include clinker ash. Since clinker ash absorbs and retains water, drying and solidification are promoted even for a muddy substance having a high water content. Clinker ash is obtained by crushing porous massive coal ash formed by coal coal ash particles generated by burning coal in a boiler of a thermal power plant. . The main components are SiO ₂ and Al ₂ O ₃ . Generally, the particle size is adjusted during crushing, most of which are fine gravel and coarse sand,
Shows a particle size close to that of sand. Although three types of 5-20 mm, 5 mm under and 3 mm under are commercially available, it is preferable to use 3 mm under with a large surface area. Clinker ash has a pore structure in which a large number of fine pores having a diameter of 0.2 to 20 μm are present, and thus is excellent in water absorption and water retention. Therefore, by further containing clinker ash in the improving material, it becomes possible to dry and solidify a muddy substance having a high water content in a short time. In addition, the compressive strength is high, which contributes to the improvement of the cone index. In addition, 2.9 × 10 ⁶ Pa (3
It is preferable to use clinker ash having a compressive strength of 0 kgf / cm ² or more.

In the present invention, the modifier may further include a setting retarder (retarder) for delaying the setting (hydration) time of the hydraulic gypsum.
As a setting retarder, gelatin, degraded keratin, casein, casein calcium, albumin, γ-globulin, zein, pepsin, pectin, papain, starch, colloidal or high molecular material such as tannin, sucrose,
Hexametaphosphate, ethylenediaminetetraacetate,
Examples thereof include citric acid, carboxylate such as citric acid, gluconic acid, and acetic acid, borate such as borax, alkaline carbonate, and sulfates of Fe ³⁺ , Cr ³⁺ , and Al ³⁺ . By adding a setting retarder to the improving material and adding and mixing the improving material to the muddy substance, the setting (hydration) of hydraulic gypsum is delayed, and the mixture of the muddy substance and the improving material is In a muddy state, it can be transferred to a desired location using, for example, a pump and piping.

In the present invention, the improving material may further include a superabsorbent polymer (eg, a crosslinked polyacrylate material, an isobutylene / maleate material, a starch / polyacrylate material, an acrylic fiber). (Cross-linked polyvinyl alcohol-based material, cross-linked carboxy-methyl-cellulose-based material).

The solidified mud obtained by the solidification / neutralization method of the present invention includes, for example, embankment material, underwater embankment material, backfill material, backfill material, roadbed material, embankment material, land preparation material , Abandoned concrete substitute material, vegetation soil,
It can be used as aggregate for concrete.

The outline of the solidification and neutralization mechanism of the muddy substance by the improved material of the present invention will be described below. When the improving agent is added to the muddy substance, the coagulant in the improving agent will be soluble in water since the spatial structure has a hydrophilic ionic group (for example, a carboxyl group ion) having a three-dimensional structure. And begin to spread. At the same time, based on the osmotic pressure generated by the ion concentration inside the coagulant being higher than the external water, water starts to enter the coagulant and negative ionic groups (for example, carboxyl group ions) repel each other,
Further spreading is promoted. However, the coagulant has 3
Since it has a dimensional bridge structure, it cannot be expanded beyond a certain extent, and it is just as if the fishing net had been expanded.
Then, water is taken into each of the meshes. As described above, the interaction between the action of spreading to dissolve and the action of suppressing the spread by the crosslinked structure causes the coagulant to coagulate and absorb water. For example, most of the mud-like substances exhibit alkalinity due to concrete pouring or chemical injection, and in the course of such a change of the coagulant, a substance (-OH,
Ca, etc.) are insolubilized and immobilized. Further, as for the properties, the coagulant is dissolved by the water in the muddy substance, becomes a paste, adheres to the muddy substance surface (for example, the surface of the soil particles), and binds the muddy substances (the soil particles). Let it. However, the effect of such a coagulant is to change the consistency of the muddy substance, such as water absorption and coagulation, to make it close to a lump, and to change the consistency to a granular state, thereby increasing the solidification strength of the muddy substance itself. It does not make it.

Next, the water contained in the muddy substance reacts with the hydraulic gypsum, and the hydraulic gypsum becomes dihydrate gypsum, whereby the granular muddy substance exhibits strength. Gypsum is a state in which needle-like crystals and hexagonal plate-like crystals are entangled with each other, so that most muddy substances do not re-mudify,
Entrapment, stabilization, and solidification of mud are formed (generated).

Since the improving material contains porous inorganic particles, a substance (-O) for increasing the alkali concentration (pH) is used.
H, Ca and the like) are adsorbed on the porous inorganic particles, and furthermore, since the modifier contains a pH adjuster, neutralization is promoted. In addition, since the coagulant is entangled in a paste form, the surface potential is neutralized, and no alkalinity as pH is exhibited. In the drying process of the solidified mud, the solidified mud easily absorbs carbon dioxide (CO ₂ ) in the air, and the carbon dioxide and calcium oxide (CaO) in the solidified mud are easily absorbed. The reaction produces calcium carbonate, a neutral substance. Such a phenomenon occurs remarkably when the solidified mud is cured, for example, for 24 hours. As a result, the pH of the solidified mud further approaches neutrality (pH 5.8 to 8.6). In addition, the solidified mud is converted into a solid with reduced odor (odor concentration measurement according to the Notification of the Environment Agency, No. 63, 1995), for example, a solid with less generation of H ₂ S.

When the solidifying accelerator containing aluminate is further included in the modifier, the solidification (reaction) process of the hydraulic gypsum is based on the hydration reaction of hemihydrate gypsum or type III anhydrous gypsum. At the same time, and over time, hemihydrate gypsum and II
A reaction occurs between the type I anhydrous gypsum and the aluminate (aluminate layer) contained in the solidification accelerator, for example, ettringite (3CaO.Al ₂ O ₃ .3CaSO ₄ .3)
(Having a composition of 2H ₂ O or the like), and a solid net (net-like) of the solidified muddy substance can be achieved.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on preferred embodiments.

(Example 1) Muddy substance generated at a construction site
(Moisture content w = 110%, pH = 12.4
Including cement that comes out after ground improvement based on the RJP method
Set in the following Table 3 for 100 parts by weight
Mixing (stirring) was performed by adding 20 parts by weight of
Was. The composition of the hydraulic gypsum is such that the β-type hemihydrate gypsum is about 90%.
% By weight, about 2% by weight of type III anhydrous gypsum, the rest is dihydrate
It was a plaster. In addition, as a coagulant, metal acrylate
Acrylamide copolymer (specifically, sodium acrylate
Lium-acrylamide copolymer)
Using porous silica as the mechanical particles, a pH adjuster and
And SiO_Two, Al_TwoO_Three, K_TwoO, Na_TwoO, Fe
_TwoO _Three, SO_Three, CaO and C are used as a mixture.
Was.

[Table 3] Hydraulic gypsum 100 parts by weight Coagulant 2 parts by weight Porous inorganic particles 20 parts by weight pH adjuster 0.5 parts by weight

The improving material obtained by previously mixing the components constituting the improving material was added to the muddy substance. The cement was mixed (stirred) for 3 minutes using a cement mortar mixer to mix the improving material and the muddy substance. Then, the solidified slurry obtained after mixing is discharged from the cement mortar mixer, left in a constant temperature chamber, and after adding the improving material, the cone index, pH, and water content of the solidified slurry obtained after 24 days have passed. The ratio (w) and the condition of the effluent were tested. In addition, addition, mixing, discharge, standing, and measurement were all performed in a constant temperature room (temperature 20 ° C, relative humidity 60).
%). Here, the outflow water was observed by visual observation. Further, the analysis of the hexavalent chromium content (unit: milligram / liter) in the solidified mud obtained 24 days after the start of mixing was performed according to JIS K-0.
102. Table 5 shows the measurement results. In Table 5, the unit of the cone index is kN / m ² . Also,
The pH is based on JSF T-211. Distilled water having a mass of 2 to 3 times the mass of the solidified mud after drying is added to the solidified mud (or the solidified pulverized mud) based on JSF T-211 and sufficiently stirred. , For 30 minutes or more and within 3 hours. Similar results can be obtained by keeping each component of the improving material in a separate state and mixing it at the time of use and adding it to the muddy material, or adding each component separately at the time of use to the muddy material. Was done.

Also, as Comparative Example 1, mixing, discharging, and standing were performed under the same conditions as in Example 1 without adding any improving material, and the mud-like solid obtained 24 days after the start of mixing. Was measured in the same manner as in Example 1.

Example 2 Mud which is a muddy substance generated at a construction site (mud containing bentonite with a water content of w = 101%, pH = 8.9, and produced by a shield method at the construction site) An improving material having the composition shown in Table 4 (the components are the same as in Example 1) was added to 100 parts by weight of
5 parts by weight were added in the same manner as in Example 1 and mixed (stirred). Then, in the same manner as in Example 1, the physical properties of the solidified muddy substance were measured. Table 5 shows the results. Here, unlike Example 1, the solidified muddy substance obtained 12 hours after the start of mixing was measured in the same manner as in Example 1. Further, unlike the first embodiment, a solidification accelerator made of calcium aluminate is added to the improved material. It should be noted that the same results were obtained when the components of the improving material were kept separately and mixed at the time of use and added to the muddy material, or when each component was separately added to the muddy material at the time of use. was gotten.

Further, as Comparative Example 2, mixing, discharging, and standing were performed under the same conditions as in Example 2 without adding any improving material, and the solidified mud obtained 12 hours after the start of mixing. Was measured in the same manner as in Example 1.

[Table 4] Hydraulic gypsum 100 parts by weight Coagulant 2 parts by weight Porous inorganic particles 10 parts by weight pH adjuster 0.5 parts by weight Solidification accelerator 10 parts by weight

[Table 5] Cone index pH Water content (%) Effluent Hexavalent Cr Example 1 1500 or more 7.9 41 Clear water 0.05 or less Example 2 810 7.5 30 Clear water 0.05 or less Compare Example 1 1500 or more 12.4 41 Translucent water 0.15 Comparative Example 2 8.9 90 Turbid water 0.09

As is clear from Table 5, in Examples 1 and 2, the solidified mud has a high cone index, its pH is neutral, and the effluent is clear water. And hexavalent chromium was less than 0.05 milligram / liter. In Example 1, the cone index of the solidified mud material obtained 15 minutes after the start of mixing was also measured. As a result, 630 kN / m ² was obtained. On the other hand, in Comparative Example 1, since the muddy substance contained cement, the corn index after 24 days was about the same as in Example 1, but the pH was strong alkali, and the effluent was It was translucent water, and hexavalent chromium was 0.15 mg / liter. Further, in Comparative Example 2, the solidified mud obtained 12 hours after the start of mixing,
Almost the same properties as the original muddy material.

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. The muddy substances used in the examples are examples. Further, the composition and the mixing ratio of the improving material are also examples, and can be appropriately changed. Furthermore, the method of adding the improving material and the method of mixing (stirring) described in the examples are also examples, and can be appropriately changed.

[0049]

According to the present invention, the solidification and neutralization of muddy substances can be promptly carried out by forming the improving material from hydraulic gypsum, a coagulant, porous inorganic particles, and a pH adjuster. It can be performed, and the solidified mud exhibits sufficient strength. In addition, the solidified mud is converted into a solidified substance with reduced odor, and furthermore, the elution of hexavalent chromium can be suppressed. Therefore, it is possible to easily convert the muddy substance generated at the construction site, for example, to improved soil at the site, and to prevent muddy water from being generated even when the solidified muddy substance is exposed to running water or rainwater. Can be suppressed. In addition, the treatment of the muddy substance can be performed by a simple plant, so that the treatment cost can be reduced and the muddy substance can be efficiently and effectively recycled. By further including the solidification promoting material in the improving material, a solid net of the solidified mud can be achieved (reticulation), and the strength of the solidified mud can be further increased in a short time. Can be planned.

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Claims (19)

[Claims] 1. An improving material for solidifying and neutralizing a muddy substance, comprising (A) a hydraulic gypsum, (B) a coagulant, (C) a porous inorganic particle, and (D) a pH adjuster. An improved material characterized by comprising: 2. Hydraulic gypsum is hemihydrate gypsum and / or III
The improved material according to claim 1, which is a type of anhydrous gypsum. 3. An anionic polymer coagulant having a carboxyl group or a sulfone group as a dissociating group,
The improvement material according to claim 1 or 2, wherein the improvement material is made of an inorganic coagulant. 4. The coagulant includes metal acrylate / acrylamide copolymer, anionic polyacrylamide polymer, partially hydrolyzed polyacrylamide, acrylic acid
The improvement according to claim 3, wherein the at least one coagulant is selected from the group consisting of a vinyl alcohol copolymer and an inorganic coagulant. 5. The method according to claim 1, wherein the porous inorganic particles are at least one kind of porous inorganic particles selected from the group consisting of activated silica, zeolite, porous silica, and silica powder. Any one of item 4
The improved material described in the item. 6. The improved material according to claim 1, wherein the pH adjuster contains a silicate compound. 7. The mixing ratio of the modifier is (A) 100 parts by weight of hydraulic gypsum, (B) 0.1 to 30 parts by weight of a coagulant, and (C) 5 to 200 parts by weight of porous inorganic particles. And (D) 0.1 to 110 parts by weight of a pH adjuster, The improving material according to any one of claims 1 to 6, characterized in that: 8. The improved material according to claim 1, further comprising a solidification accelerating material. 9. The improvement according to claim 8, wherein the solidification accelerator contains an aluminate. 10. Mud-like substances include (A) hydraulic gypsum, and (B)
A method for solidifying and neutralizing a muddy substance, comprising adding and mixing a coagulant, (C) a porous inorganic particle, and (D) a modifier comprising a pH adjuster. 11. The method for solidifying and neutralizing a muddy substance according to claim 10, wherein 1 to 100 parts by weight of an improving material is added to 100 parts by weight of the muddy substance and mixed. . 12. Hydraulic gypsum is hemihydrate gypsum and / or II.
The method for solidifying and neutralizing a muddy substance according to claim 10 or 11, wherein the method is type I anhydrous gypsum. 13. The coagulant according to claim 10, wherein the coagulant comprises an anionic polymer coagulant having a carboxyl group or a sulfone group as a dissociating group, or an inorganic coagulant. The method for solidifying and neutralizing a muddy substance according to claim 1. 14. A coagulant comprising a metal acrylate / acrylamide copolymer, an anionic polyacrylamide polymer, a partially hydrolyzed polyacrylamide, acrylic acid
14. The method for solidifying and neutralizing a muddy substance according to claim 13, wherein the method is at least one coagulant selected from the group consisting of a vinyl alcohol copolymer and an inorganic coagulant. 15. The method according to claim 10, wherein the porous inorganic particles are at least one kind of porous inorganic particles selected from the group consisting of activated silica, zeolite, porous silica, and silica powder. Item 15. The method for solidifying and neutralizing a muddy substance according to any one of Item 14. 16. The method for solidifying and neutralizing a muddy substance according to claim 10, wherein the pH adjuster contains a silicate compound. 17. The mixing ratio of the modifier is (A) 100 parts by weight of hydraulic gypsum, (B) 0.1 to 30 parts by weight of a coagulant, and (C) 5 to 200 parts by weight of porous inorganic particles. The method for solidifying and neutralizing a muddy substance according to any one of claims 10 to 16, wherein: (D) 0.1 to 110 parts by weight of a pH adjuster. 18. The method for solidifying and neutralizing a muddy substance according to claim 10, wherein the improving material further contains a solidification promoting material. 19. The method for solidifying and neutralizing a muddy substance according to claim 18, wherein the solidification promoting material contains an aluminate.