JP6440537B2 - Solidified material and method for producing the same - Google Patents

Description

  The present invention relates to a solidified material and a method for producing the same.

In recent years, the amount of municipal waste disposed of has declined due to the widespread use of sorting and recycling, so the remaining years in which the final disposal site can be used has been increasing slightly. However, how to deal with large amounts of municipal waste that continues to be generated in the future is an extremely important issue in Japan's sustainable economic development.
In addition, it is difficult to secure a new final disposal site around urban areas, which are a large source of municipal waste, due to stricter regulations. New social problems are occurring.

  Most of the collected municipal waste is incinerated for the main purpose of volume reduction. A part of the incineration ash (city waste incineration ash) generated by the incineration process is further reused as molten slag after further heat treatment. However, molten slag has problems such as difficulty in developing its use and the necessity of a large amount of energy for production. For this reason, most of the municipal waste incineration ash is finally disposed of.

Eco-cement can be cited as a technology for utilizing municipal waste incineration ash. Ecocement is a cement produced by using various wastes, mainly municipal waste incineration ash, as a raw material with a dry mass of 500 kg or more per ton of product.
Ecocement is used in the same way as Portland cement as a hydraulic material for ready-mixed concrete for concrete products and civil engineering. However, since waste such as municipal waste incineration ash is used as a raw material, the content of heavy metals (especially chromium) in eco-cement is higher than that in Portland cement. Ecocement was not suitable as a solidifying material for ground improvement soil because the amount of hexavalent chromium elution from ground improvement soil was regulated by the Soil Contamination Countermeasures Law and Water Pollution Control Law.

As a solidification material that uses a large amount of waste as a raw material and can reduce the elution amount of hexavalent chromium from the ground improvement soil, for example, Patent Document 1 contains cement and a chelate compound. A cement composition containing a hexavalent chromium elution reducing agent is described.
Patent Document 2 describes a ground improvement material comprising a cement-based solidifying material and a mixture of coal or lignite powder.
Furthermore, Patent Document 3 includes a hydraulic modulus (HM) of 2.20 to 2.45, a content of 3CaO · SiO ₂ of 61% by mass or more, and a content of 4CaO · Al ₂ O ₃ · Fe ₂ O _3. amount in 6-14 wt%, the half-value width of the peak of the X-ray diffraction angle of _{4CaO · Al 2 O 3 · Fe} 2 O 3 (2θ) is 12.1 ° is, 0.2 ° or more, 0.25 ° A cement clinker, wherein the b value in the Hunter Lab color system is 8.5 or more when pulverized so that the specific surface area of the brain is 3,000 to 4,500 cm ² / g, And a solidified material using the cement clinker.

JP 2002-60751 A JP 2001-139948 A JP 2010-64905 A

The solidified material using the cement clinker described in Patent Document 3 is excellent in strength development and the like and low in manufacturing cost.
However, the cement clinker exhibits the strength development property of the solidified material caused by decomposition of 3CaO.SiO ₂ (Alite; hereinafter also referred to as “C ₃ S”) when the raw material is fired in a reducing atmosphere. In order to prevent the decrease, the hydraulic modulus is set high (2.20 to 2.45).
Here, in order to increase the hydraulic modulus of the cement clinker, it is necessary to increase the amount of CaO in the raw material. For this reason, in the cement clinker described in Patent Document 3, it is difficult to increase the amount of waste (for example, municipal waste incineration ash) with a low CaO content as the raw material. Therefore, the upper limit of the total chromium amount in the cement clinker was 150 mg / kg, which was the same as that of a general Portland cement clinker.
The present invention can increase the amount of municipal waste incineration ash used as a raw material for cement clinker (hereinafter also referred to as “clinker raw material”), and even if the total chromium amount in the cement clinker is large, An object of the present invention is to provide a solidified material that can reduce the elution amount of hexavalent chromium from the ground improved soil using the solidified material containing the cement clinker, and further has excellent strength development.

As a result of intensive studies to solve the above problems, the inventor has a hydraulic modulus (HM) of 2.00 to 2.10, an amount of free lime of 0.1 to 1.0% by mass, A cemented clinker pulverized product having a chromium content of 200 ppm or more and a ratio of water-soluble hexavalent chromium in the total chromium content of 3% by mass or less, and a solidified material containing gypsum, the SO in the solidified material According to the solidified material having a ratio of ₃ of 3.5 to 15% by mass, the inventors have found that the object of the present invention can be achieved and completed the present invention.
That is, the present invention provides the following [1] to [7].
[1] Hydraulic modulus (HM) of 2.00 to 2.10, free lime content of 0.1 to 1.0% by mass, total chromium content of 200 ppm or more, and water content in the total chromium content A cement clinker pulverized product having a ratio of functional hexavalent chromium of 3% by mass or less and a solidified material containing gypsum, wherein the ratio of SO _{3 in} the solidified material is 3.5 to 15% by mass. Solidified material characterized by that.
[2] The solidified material according to [1], including fine blast furnace slag powder in an amount of 10 to 150 parts by mass per 100 parts by mass of the cement clinker pulverized product.
[3] The above cement clinker is obtained by reduction firing, and the b ^* value in the Hunter L ^* a ^* b ^* color system is 8.5 or more. ] The solidification material as described in.

[4] A method for producing the solidified material according to any one of [1] to [3], wherein (a) clinker raw material containing municipal waste incineration ash is reduced and calcined in the presence of a reducing agent. A clinker preparation step for obtaining a cement clinker, (b) a cement preparation step for mixing and pulverizing the cement clinker and gypsum to obtain a cement, and (c) mixing the cement and gypsum to obtain a solidified material. A method for producing a solidified material, comprising a step of preparing a solidified material to be obtained.
[5] The method for producing a solidified material according to [4], wherein in the step (a), municipal waste incineration ash is used in an amount of 250 kg or more per 1 ton of cement clinker.
[6] Between step (a) and step (b), (a ′) for the cement clinker obtained in the clinker preparation step, measure the b ^* value in the Hunter L ^* a ^* b ^* color system, Only the cement clinker having a b ^* value of 8.5 or more is described in the above [4] or [5] including the reduction degree confirmation step used in the step (b), assuming that the reduction calcination has been sufficiently performed. Method for producing solidified material.
[7] A ground improvement method using the solidified material according to any one of [1] to [3], wherein the ratio of humic acid and fulvic acid is 5% by mass or more (converted value in dry soil) soil improvement wherein soil 1 m ³ per admixing was added in an amount of 50~400kg the solidifying material comprising at.

According to the solidified material of the present invention, the amount of municipal waste incineration ash used in the raw material of cement clinker used for the solidified material can be increased.
Further, according to the solidified material of the present invention, even if the total amount of chromium in the cement clinker is large, the elution amount of hexavalent chromium from the ground improvement soil using the solidified material containing the cement clinker can be reduced. .
Furthermore, the solidified material of the present invention is excellent in strength development.

The solidified material of the present invention has a hydraulic modulus (HM) of 2.00 to 2.10, a free lime content of 0.1 to 1.0% by mass, a total chromium content of 200 ppm or more, and a total chromium. A cement clinker pulverized product in which the amount of water-soluble hexavalent chromium in the amount is 3% by mass or less, and a solidified material containing gypsum, wherein the ratio of SO _{3 in} the solidified material is 3.5 to 15 % By mass.
The hydraulic modulus is 2.00 to 2.10, preferably 2.01 to 2.08, more preferably 2.02 to 2.06. When the value is less than 2.00, the strength development property of the solidified material is lowered. If the value exceeds 2.10, it becomes difficult to increase the amount of waste (in particular, municipal waste incineration ash with a low CaO content).

  The silicic acid ratio (SM) of the cement clinker used in the present invention is preferably 1.30 to 1.90, more preferably 1.40 to 1.80. When the value is 1.30 or more, the amount of liquid phase is not large, and therefore the cement clinker can be manufactured more easily. When the value is 1.90 or less, the amount of waste used can be further increased.

  The iron ratio (IM) of the cement clinker used in the present invention is preferably 1.50 to 2.10, more preferably 1.60 to 1.90. When the value is 1.50 or more, the grindability of the cement clinker becomes better and the manufacturing cost is reduced. When the value is 2.10 or less, the amount of gypsum necessary for ensuring the quality of the solidified material is small, and thus the manufacturing cost is reduced.

  The amount of free lime of the cement clinker used in the present invention is 0.1 to 1.0% by mass, preferably 0.2 to 0.8% by mass, and more preferably 0.3 to 0.6% by mass. When the value is less than 0.1% by mass, the amount of heat required for producing a clinker by firing increases. When this value exceeds 1.0 mass%, the strength development property of a solidification material will fall.

The total chromium amount in the cement clinker used in the present invention is 200 ppm or more, more preferably 300 ppm or more, and particularly preferably 400 ppm or more. In the present invention, even if the value is 200 ppm or more, since the elution amount of hexavalent chromium from the ground improvement soil using the solidified material containing the cement clinker is low, the waste in the raw material of the cement clinker Can be increased (especially municipal waste incineration ash). The upper limit of the value is not particularly limited, but the elution amount of hexavalent chromium from the ground improved soil is reduced (for example, below the reference value of the elution amount of hexavalent chromium in the Soil Contamination Countermeasures Law (0.05 mg / liter or less)) From the viewpoint, it is preferably 900 ppm or less, more preferably 800 ppm or less.
In the present specification, the “total chromium amount in the cement clinker” means the total amount of hexavalent chromium and trivalent chromium in the cement clinker. “Ppm” is based on mass.

  The proportion of water-soluble hexavalent chromium in the total chromium amount is 3% by mass or less, preferably 2.7% by mass or less, more preferably 2.4% by mass or less. When this ratio exceeds 3 mass%, the elution amount of hexavalent chromium from the ground improvement soil increases.

As the raw material of the cement clinker used in the present invention, a general raw material used for the production of Portland cement clinker can be used. Specifically, CaO raw materials such as limestone, quicklime and slaked lime; SiO ₂ raw materials such as silica and clay; Al ₂ O ₃ raw materials such as clay; Fe ₂ O ₃ raw materials such as iron cake and iron cake may be used. it can.

Further, in addition to the raw material, waste can be used as a part of the raw material.
Here, in this specification, “waste” refers to industrial waste or general waste.
Industrial waste refers to waste generated from business activities. Examples of industrial waste include raw consludge, various sludges (eg, sewage sludge, purified water sludge, steelmaking sludge, etc.), building wastes, concrete wastes, and various incineration ash (eg, coal ash, incineration fly ash, molten fly ash, etc.) ), Foundry sand, rock wool, waste glass, blast furnace secondary ash, construction generated soil (sediment generated secondary to construction work (for example, boring waste soil generated by excavating the ground), and construction sludge (for example, A mixture of cement milk and excavated soil)), etc., produced by ground improvement work.
General waste refers to waste other than industrial waste.
Examples of general waste include municipal waste incineration ash, sewage sludge dry powder, and shells.
These may be used individually by 1 type and may be used in combination of 2 or more type.
In the present invention, it is desirable to use municipal waste incineration ash as part of the raw material from the viewpoint of using waste that has not been recycled.

The amount of the waste used is preferably 400 kg or more, more preferably 500 kg or more per ton of cement clinker from the viewpoint of promoting effective utilization of the waste. In addition, the upper limit of the amount of waste used is preferably 800 kg, more preferably 700 kg, from the viewpoint of strength development of the solidified material.
In addition, among the wastes used as raw materials, the amount of municipal waste incineration ash used is preferably 250 kg or more, more preferably 350 kg or more from the viewpoint of promoting the use of municipal waste incineration ash per ton of cement clinker. . Moreover, the upper limit of the usage amount of the municipal waste incineration ash is preferably 650 kg, more preferably 550 kg, from the viewpoint of strength development of the solidified material.
In addition, the usage-amount (mass) of the said waste is a dry mass.

The cement clinker used in the present invention can be obtained by reduction firing. As an example of the method for producing the cement clinker, there is a method in which a clinker raw material containing municipal waste incineration ash is calcined in the presence of a reducing agent so that the amount of free lime is 0.1 to 1.0% by mass. It is done.
The above clinker raw materials are reduced and fired after mixing the respective raw materials so as to obtain a cement clinker having a desired hydraulic modulus (2.00 to 2.10) and the like. The method of mixing each raw material is not particularly limited, and can be performed using a conventional apparatus or the like.

Examples of the reducing agent include flammable substances such as coke, activated carbon, waste wood, waste plastic, heavy oil sludge, and solid waste lump obtained by compressing and solidifying waste such as municipal waste.
Here, “reduction firing” in this specification means firing in a reducing atmosphere.
By producing cement clinker by reduction firing, it is possible to suppress the formation of hexavalent chromium that is likely to occur in an oxidizing atmosphere even if chromium is contained in the raw material waste. Further, in the step of heating (firing) the waste, even if the waste is temporarily heated in an oxidizing atmosphere to produce hexavalent chromium, heating (firing) is then performed in a reducing atmosphere. As a result, hexavalent chromium is reduced to trivalent chromium, so the amount of hexavalent chromium in the cement clinker can be reduced.
According to the method of firing the clinker raw material in the presence of the reducing agent, the amount of hexavalent chromium in the resulting cement clinker can be further reduced, and the ratio of hexavalent chromium in the total chromium amount can be further reduced. .

The method for firing the raw material is not particularly limited, and for example, a conventional apparatus such as a rotary kiln can be used.
The reduction firing is preferably performed so that the flame of the burner for firing directly hits the cement clinker before the firing is finished (hereinafter also referred to as “flame film firing”).
By combining firing in the presence of a reducing agent and flame film firing, the proportion of hexavalent chromium in the total amount of chromium contained in the obtained cement clinker can be further reduced.

Hereinafter, a case where a rotary kiln is used will be described as an example of reduction firing.
Examples of the fuel used for calcination include heavy oil, natural gas, and fuel alternative waste (for example, waste oil, waste tire, and waste plastic) in addition to coal as a main fuel.
The firing temperature is preferably 1,300 to 1,600 ° C., and the firing time is preferably 10 to 120 minutes, more preferably 20 to 100 minutes.
As a method of performing flame film firing using a rotary kiln, (a) a method in which an angle is given to the direction of the flame from the main burner and the flame is heated (fired) so as to lick the cement clinker, (b) By shifting the installation position from the center position, a method of heating (firing) so that the flame licks the cement clinker, (c) By installing an auxiliary burner in addition to the main burner, the shape of the flame can be easily controlled And a method of heating (firing) so that the flame licks the cement clinker.

Examples of the method for firing the cement clinker in the presence of the reducing agent include a method of supplying the reducing agent into the rotary kiln.
The reducing agent is preferably supplied from the rotary kiln outlet side or in the middle of the rotary kiln. The reducing agent preferably has a slower combustion rate than the main fuel for the rotary kiln, or has a combustion rate similar to that of the main fuel and is coarser than the main fuel.

  The particle size of the reducing agent is preferably 0.1 to 20 mm. If the particle size is 0.1 mm or more, the reducing agent will not burn out at the very initial stage of firing, so the amount of hexavalent chromium in the cement clinker can be reduced, and from the ground improved soil The amount of elution of hexavalent chromium can be reduced. When the particle size is 20 mm or less, it is difficult for the unburned reducing agent to remain in the cement clinker, so that the strength development of the solidified material is improved.

  The amount of the reducing agent used is preferably 5 to 20 parts by mass, more preferably 10 to 20 parts by mass, per 100 parts by mass of the clinker raw material fed into the rotary kiln. When the amount is 5 parts by mass or more, the amount of hexavalent chromium in the cement clinker can be further reduced. When the amount is 20 parts by mass or less, an excessive amount (exceeding the amount for making the hexavalent chromium amount zero) can be omitted, which is economical.

After firing, the obtained cement clinker is preferably cooled at a cooling rate of 40 ° C./min or more until the temperature of the cement clinker becomes 400 ° C. or less. When the cooling rate is 40 ° C./min or more, trivalent chromium in the cement clinker can be prevented from being oxidized to hexavalent chromium by oxygen in the air.
Further, when the temperature of the cement clinker is 400 ° C. or lower, the possibility that trivalent chromium in the cement clinker is oxidized to hexavalent chromium by oxygen in the air becomes extremely small.
In addition, the cooling rate of the baked product after the temperature of the cement clinker is cooled to 400 ° C. or lower is not particularly limited.

  As a method of cooling the cement clinker at a cooling rate of 40 ° C./min or more, a method of cooling using an air quenching cooler, a method of cooling by putting the cement clinker into water, and watering and cooling the cement clinker And the like.

The b ^* value in the Hunter L ^* a ^* b ^* color system of the cement clinker obtained by the above method is preferably 8.5 or more, more preferably 8.6 or more. If this value is 8.5 or more, the elution amount of hexavalent chromium from the ground improved soil can be further reduced.
In addition, the b ^* value in the Hunter L ^* a ^* b ^* color system can be used as an index for confirming whether the cement clinker has been sufficiently reduced and fired.
The b ^* value can be measured using a commercially available spectral color difference meter (for example, trade name “CP6R-2000DP” manufactured by Nippon Denshoku Co., Ltd.).

The solidifying material of the present invention includes the above-mentioned cement clinker pulverized product and gypsum.
The brane specific surface area of the solidified material is preferably from 2,500 to 5,000 cm ² / g, more preferably from the viewpoints of the strength development property of the solidified material, the cost related to production, and the durability of the ground improvement soil. Is 3,000 to 4,500 cm ² / g.
Examples of the gypsum include anhydrous gypsum, hemihydrate gypsum, dihydrate gypsum, and mixtures thereof.
And SO ₃ ratio (in cement SO ₃ in the solidifying material, contained in the SO ₃ in the gypsum to be added later separately from the preparation of cement, blast furnace slag or the like described later can be blended in any other The ratio of the total amount of SO ₃ is 3.5 to 15% by mass, preferably 4 to 10% by mass, more preferably 6 to 9% by mass. When the ratio is less than 3.5% by mass, when preparing a slurry containing a solidifying material, the viscosity of the slurry becomes high, workability is inferior, and strength development is reduced. When this ratio exceeds 15 mass%, the strength development property of a solidification material will fall and the hardening of the soil which applied the solidification material will be delayed.

The solidified material of the present invention may contain blast furnace slag fine powder from the viewpoint of strength development (uniaxial compressive strength) and the like. The blending amount of the blast furnace slag fine powder is preferably 10 to 150 parts by mass, more preferably 20 to 100 parts by mass, and particularly preferably 40 to 80 parts by mass per 100 parts by mass of the crushed cement clinker. When the blending amount is 10 parts by mass or more, the strength development property (particularly, uniaxial compressive strength) of the solidified material is improved. When the blending ratio is 150 parts by mass or less, a decrease in long-term strength development can be suppressed.
Further, as a material of the solidifying material, fly ash, silica stone powder, limestone powder and the like may be further included.

The method for producing a solidified material according to the present invention includes: (a) a clinker preparation step of obtaining a cement clinker by reducing and firing a clinker raw material containing municipal waste incineration ash in the presence of a reducing agent; and (b) the cement clinker A cement preparation step of mixing and crushing gypsum to obtain cement;
(C) A solidifying material preparation step of mixing the cement and gypsum to obtain a solidified material.
In the step (a), the method for obtaining the cement clinker by reduction firing is as described above.
In the case where blast furnace slag fine powder, fly ash, silica stone powder, limestone powder, or the like is further used as a raw material for the solidifying material, these powders may be appropriately added and mixed in the step (c).

Between step (a) and step (b), (a ′) the b ^* value in the Hunter L ^* a ^* b ^* color system is measured for the cement clinker obtained in the clinker preparation step, and the b ^* Only the cement clinker having a value of 8.5 or more may include a reduction degree confirmation step used in step (b), assuming that the reduction calcination has been sufficiently performed.
By including the step (a ′), the solidified material of the present invention that satisfies the above-described various conditions (such as the ratio of water-soluble hexavalent chromium in the total chromium content) can be obtained more reliably.

The ground improvement method using the solidification material of the present invention includes 1) dry addition in which the solidification material is added to the ground improvement target soil in powder form, and 2) a slurry obtained by mixing the solidification material and water. Addition of slurry to be added to and mixed with soil to be ground improved.
When slurry addition is performed, the mass ratio of water and the solidifying material (water / solidifying material ratio) is preferably 0.5 to 1.5, more preferably 0.6 to 1.0.
The amount of the solidifying material of the present invention used for soil improvement target soil is preferably 50 to 500 kg, more preferably 1 m ^{3 of} soil, although it depends on the properties and construction conditions of the target soil and the required strength of the solidified soil. 60-200 kg.
In the present invention, the soil to be ground improvement is not particularly limited, but from the viewpoint that excellent strength development can be expected, humic acid and fulvic acid in total, preferably 5% by mass or more, More preferably, a material (generally referred to as “humus soil”) containing 10% by mass or more (converted value in dry soil) is suitable.

[Production of cement clinker A]
The raw material for eco-cement was used as a raw material for clinker (clinker raw material). The amount of waste in the clinker raw material is 1 ton of cement clinker,
It was 517 kg. The amount of municipal waste incineration ash contained in the waste was 356 kg per ton of cement clinker.
About the said clinker raw material, the chemical composition was measured based on "Cement Association standard test method JCAS I-14 (Chemical analysis method of the raw material for cement manufacture)." The results are shown in Table 1.

Cement clinker A was produced by firing the clinker raw material using a rotary kiln by the following method.
A rotary kiln with an auxiliary burner added to the main burner was used. The size and shape of the burner frame were changed by changing the operating conditions of the auxiliary burner while keeping the operating conditions (combustion type, soot amount (coal consumption per hour)) of the rotary kiln main burner fixed.
Coal was used as the main fuel for the rotary kiln. The amount of free lime in the cement clinker after calcination was adjusted to 0.1 to 1.0% by mass by adjusting the soot amount of the coal on the auxiliary burner side.
As the reducing agent, coke (manufactured by Tokai Sanko Co., Ltd .; particle size: 3 mm or less; fixed carbon content: 99% by mass or more) was used. The reducing agent was blown from the auxiliary burner side. The amount of the reducing agent used was 18 parts by mass with respect to 100 parts by mass of the clinker raw material fed into the rotary kiln.
Moreover, the flame film baking was performed by changing the size and shape of the flame of the auxiliary burner so that the flame of the burner directly hits the cement clinker before the completion of the baking.
As firing conditions, the firing time was 40 minutes.
An air quenching cooler was used to cool the cement clinker after firing. The cooling rate was adjusted to 40 ° C./min or more.
[Production of cement clinker BF]
Cement clinker B to F were obtained in the same manner as in the production of cement clinker A except that the firing was performed under the firing conditions shown in Table 2 and the amount of reducing agent used.

The obtained cement clinkers A to F are subjected to chemical analysis in accordance with “JIS R 5204 (cement fluorescent X-ray analysis method)”, and the hydraulic rate, silicic acid rate, iron rate, C ₃ S according to the Borg formula are used. (Alite; 3CaO · SiO ₂ ), C ₂ S (Belite; 2CaO · SiO ₂ ), C ₃ A (aluminate phase; 3CaO · Al ₂ O ₃ ), and C ₄ AF (ferrite phase; 4CaO · Al ₂ O ₃ · Fe ₂ O ₃ ) content was calculated.
Further, the amount of free lime of the cement clinker was measured in accordance with “Cement Association Standard Test Method JCAS I01 (Quantitative Method for Free Calcium Oxide)”. The results are shown in Table 2.

Moreover, the b ^* value in the hunter L ^* a ^* b ^* color system of the cement clinker was measured using a spectral color difference meter (trade name “CP6R-2000DP” manufactured by Nippon Denshoku Co., Ltd.).
Furthermore, in accordance with “Cement Association Standard Test Method JCAS I-51 (Method for Quantifying Trace Components in Cement and Cement Raw Materials)”, the total chromium content in cement clinker (hexavalent chromium and trivalent chromium in cement clinker) Total amount), and the amount of water-soluble hexavalent chromium.
From the obtained total chromium amount and water-soluble hexavalent chromium amount, the ratio of water-soluble hexavalent chromium in the total chromium amount was calculated. The results are shown in Table 3.

[Production of cement 1 to 6]
Cement clinker A to F and gypsum (exhausted and dihydrated gypsum made by Kashima Steel Works, Nippon Steel & Sumitomo Metal Corporation) were simultaneously pulverized using a ball mill, so that the specific surface area of branes and gypsum content shown in Table 4 were obtained. Cement 1-6 having was produced. In the grinding, 200 ppm of diethylene glycol was used as a grinding aid.

[Example 1]
Blast furnace slag fine powder (manufactured by Esmento Kanto Co., Ltd .; trade name: ESMENT 4000; brane specific surface area: 4,350 cm ² / g; SO ₃ content: 1.8% by mass) and anhydrous gypsum (Thailand) Domestic natural anhydrous gypsum; Blaine specific surface area: 3,700 cm ² / g; SO ₃ content: 55% by mass) were mixed in the formulations shown in Tables 5 and 6 to obtain a solidified material.

As soil for soil improvement, Kanto Loam (Saitama City, Saitama; water content: 73.1%; wet density: 1.69 g / cm ³ ; humic acid content: 7.4 mass%; fulvic acid content : 5.5% by mass).
Here, the water content is a 110 ° C. constant weight value obtained in accordance with “JIS A 1203 (Soil water content test method)”. The wet density is a value obtained in accordance with “JIS A 1210 (Method for testing soil compaction by tamping)”. The contents of humic acid and fulvic acid are each in accordance with the method described in “Study on Hydration Delayed Action of Cement by Peat (I)” (Okada, Onoda Research Report No. 32, pp 11-24, 1980). It is the conversion value in dry soil obtained.
The obtained solidified material and water were mixed so that the mass ratio of water and solidified material (ratio of water / solidified material) was 1.0 to obtain a slurry, and then the soil for soil improvement and the slurry were mixed. The ground improved soil was obtained by mixing for 3 minutes using a Hobart mixer.
Incidentally, the amount of solidifying material, was an amount to be ground improvement target soil 1 m ³ per 70 kg.
The uniaxial compressive strength of the obtained ground-improved soil at the age of 7 days was measured in accordance with “JIS A 1216 (uniaxial compressive test method for soil)”.
In addition, a hexavalent chromium elution test was conducted on soil improvement soil on the age of 7 days in accordance with Ministry of the Environment Notification No. 18, and in accordance with “JIS K 0102 (factory drainage test method)”. The elution amount of hexavalent chromium was measured. The results are shown in Table 6.

[Examples 2 to 5, Comparative Examples 1 to 5]
Soil improved soil was obtained in the same manner as in Example 1 except that the solidified material mixed in the formulations shown in Tables 5 and 6 was used.
The uniaxial compressive strength of the obtained ground improved soil and the elution amount of hexavalent chromium from the ground improved soil were measured in the same manner as in Example 1. The results are shown in Table 6.

The cement clinker (Examples 1 to 5) used in the solidifying material of the present invention is a large amount of 356 kg of municipal waste incineration ash.
Further, from Table 6, it can be seen that even when the solidified material contains cement clinker having a total chromium amount of 393 ppm or more, the elution amount of hexavalent chromium from the ground improvement soil is low (0.02 mg / liter or less) ( Examples 1-5).
Moreover, when Examples 3-5 and Comparative Examples 1-2 are compared, it turns out that the solidification material of this invention is excellent in strength expression.

Claims (7)

Hydraulic modulus (HM) of 2.00 to 2.10, free lime content of 0.1 to 1.0% by mass, total chromium content of 200 ppm or more, and water-soluble hexavalent in the total chromium content A cement clinker pulverized product having a chromium content of 3% by mass or less and a solidified material containing gypsum, wherein the SO ₃ content in the solidified material is 3.5 to 15% by mass. Solidified material.   The solidified material according to claim 1, comprising blast furnace slag fine powder in an amount of 10 to 150 parts by mass per 100 parts by mass of the cement clinker pulverized product. The solidified material according to claim 1 or 2, wherein the cement clinker is obtained by reduction firing and has a b ^* value of 8.5 or more in the Hunter L ^* a ^* b ^* color system. . A method for producing the solidified material according to any one of claims 1 to 3,
(A) a clinker preparation step of obtaining a cement clinker by reducing and firing a clinker raw material containing municipal waste incineration ash in the presence of a reducing agent;
(B) a cement preparation step of mixing and pulverizing the cement clinker and gypsum to obtain a cement;
(C) a solidifying material preparation step of mixing the cement and gypsum to obtain a solidified material;
The manufacturing method of the solidification material characterized by including.   The method for producing a solidified material according to claim 4, wherein in the step (a), municipal waste incineration ash is used in an amount of 250 kg or more per ton of cement clinker. Between step (a) and step (b), (a ′) the b ^* value in the Hunter L ^* a ^* b ^* color system is measured for the cement clinker obtained in the clinker preparation step, and the b ^* The method for producing a solidified material according to claim 4 or 5, comprising a reduction degree confirmation step used in step (b), assuming that only cement clinker having a value of 8.5 or more is sufficiently reduced and fired. . It is the ground improvement method using the solidification material of any one of Claims 1-3, Comprising: 1m of soil which contains a humic acid and a fulvic acid in the ratio of 5 mass% or more (equivalent value in dry soil) in total ^The ground improvement method characterized by adding the said solidification material in the quantity of 50-400 kg per ³ , and mixing.