JP6083810B2 - Cement-based solidifying material additive, additive-containing solidifying material, and method for producing improved soil - Google Patents

Description

  The present invention relates to an additive for increasing the strength development of a cement-based solidified material (hereinafter referred to as “solidified material”), a solidified material containing the additive, and a method for producing improved soil obtained by solidification using the solidified material. About.

  Currently, solidifying materials, Portland cement, mixed cement and the like are used for solidifying soil. And most of the solidifying materials mainly contain cement and various auxiliary materials. For example, the solidified material described in Patent Document 1 is mainly composed of cement clinker powder, and includes gypsum powder, blast furnace slag powder, and limestone powder.

As for the solidifying material, the optimum blending of cement and auxiliary materials can be selected according to uses such as shallow layer improvement, foundation foundation improvement, deep layer improvement, and generated soil improvement, which is an advantage not found in Portland cement and the like. Among these aids, gypsum is the main one. Gypsum reacts with clay minerals such as allophane in the soil to produce ettringite and the like, and has the effect of increasing the strength of the improved soil.
However, since the clay mineral content varies depending on the soil, the amount of gypsum required also varies. When the amount of gypsum is small, strength development is low, and when it is excessive, unreacted gypsum remaining in the improved soil reacts with rain water and the improved soil expands. In order to prevent such troubles in the field, the optimum compounding is confirmed by conducting an indoor compounding test. In most cases, the compounding determined there is a compounding amount of the solidified material having a predetermined composition with respect to the soil, and cement. It does not determine the optimal composition of materials and aids.
On the other hand, when the optimum blending of cement and auxiliary materials is determined by an indoor blending test, the solidified material is manufactured in a custom-made manner for each construction property, which causes a heavy burden on the solidified material production site.
Therefore, if there is an additive for the solidifying material that does not affect the quality of the improved soil, it becomes possible to change the composition of the solidifying material by adding it to the solidifying material having a predetermined composition. Can be close to manufacturing. Further, if the additive is less expensive than the solidified material, the cost of the solidified material can be reduced.

JP 2012-046704 A

  Therefore, an object of the present invention is to provide a solidifying material additive capable of maintaining a state of high strength development even when added externally, a solidifying material containing the additive, and the like.

Therefore, the present inventors have examined the solidifying material variously, and found that when a solidifying material containing the following additive is used for a specific target soil, the strength of the improved soil is high, and the present invention has been completed. . That is, the present invention is a solidifying material additive having the following constitution. In the present invention, the solidifying material is a concept including a cement (for example, cement such as blast furnace cement) used for solidifying soil.
[1] Cement-based solidifying material for sandy soil or additive used for cement, and the passing mass percentage of the sieve is 100% with a nominal size of 600 μm, and over 90% with a nominal size of 150 μm. And an additive for solidifying material comprising limestone powder of 70% or more with a sieve having a nominal size of 75 μm.
[2] to cement solidifying material or cement 100 parts by targeted soil sandy soil, the additive material containing solidifying material comprising 1 to 20 parts by weight of solidifying material for the additive material according to [1].
[3] The additive-containing solidified material according to [2], wherein the additive-containing solidified material contains 20 to 70% by mass of blast furnace slag powder.
[4] The additive-containing solidified material according to [2] or [3], wherein the additive-containing solidified material further contains 12% by mass or less of gypsum powder.
[5] A method for producing improved soil in which 100 to 500 kg of the additive-containing solidifying material according to any one of [2] to [4] is added and mixed per 1 m ^{3 of} sandy soil.

  The additive for solidifying material of the present invention has a high effect of improving the strength development of the solidifying material and cement when sandy soil is the target soil. Therefore, it can be added to the solidifying material and cement, and it is possible to change the composition in the direction of diluting the cement amount and gypsum amount of the solidifying material having a predetermined composition, especially by reducing the amount of gypsum in the solidifying material. The cost of the solidifying material can be reduced.

It is a figure which shows the uniaxial compressive strength of the improvement soil formed by mixing the additive-containing solidification material and sandy soil of this invention. It is a figure which shows the uniaxial compressive strength of the improved soil formed by mixing the additive-containing solidifying material and viscous soil of the present invention.

Below, the manufacturing method of the additive for solidification material of this invention, an additive-containing solidification material, and improved soil is demonstrated in detail.
1. Additive for solidifying material As described above, the additive is an additive used for solidifying material or cement with sandy soil as a target soil, and the passing mass percentage of the sieve is 100% on a sieve having a nominal size of 600 μm, It consists of limestone powder that is 90% or more on a sieve with a nominal size of 150 μm and 70% or more on a sieve with a nominal size of 75 μm. When the passing mass percentage of the sieve is within the above range, the effect of improving the strength development of the solidifying material or cement is high. The passing mass percentage of the sieve is preferably 95% or more and 80% or more, more preferably 100% or 85% or more, respectively, in a sieve having a nominal size of 150 μm and a sieve having a nominal size of 75 μm. Is 90% or more, particularly preferably 95% or more, with a sieve having a nominal size of 75 μm.
The content of calcium carbonate in the limestone powder is preferably 90% by mass or more. When the value is less than 90% by mass, the effect of improving the strength development of the solidified material is low. In addition, this value becomes like this. More preferably, it is 95 mass% or more, More preferably, it is 97 mass% or more.
As shown in FIG. 1 described later, the solidified material or cement to which the additive of the present invention is added has high strength of the obtained improved soil when sandy soil is used as the target soil.

2. Solidifying Material The additive-containing solidifying material of the present invention contains 1 to 20 parts by mass of the solidifying material additive with respect to 100 parts by mass of the solidifying material or the cement. If this value is within the above range, the strength development of the solidified material is high. In addition, this value becomes like this. Preferably it is 2-15 mass parts, More preferably, it is 2-12 mass parts.
The solidifying material is not particularly limited, and a commercially available solidifying material can be used. The cement is not particularly limited, and includes ordinary Portland cement, early-strength Portland cement, ultra-early strong Portland cement, medium heat Portland cement, low heat Portland cement, and portland cement such as sulfate-resistant Portland cement, blast furnace cement. Examples thereof include one or more selected from blast furnace slag-containing cement, coal ash-containing cement including fly ash cement, mixed cement such as silica cement, and eco-cement.

The additive-containing solidified material of the present invention further contains 20 to 70% by mass of blast furnace slag powder. If this value is within the above range, elution of hexavalent chromium from the improved soil can be suppressed. In addition, this value becomes like this. More preferably, it is 30-70 mass%, More preferably, it is 40-70 mass%.
Examples of the blast furnace slag powder include pulverized granulated slag obtained by quenching and crushing molten slag produced as a by-product when producing pig iron in a blast furnace with water, and more preferably stipulated in JIS A 6206. It is blast furnace granulated slag.

The branes specific surface area of the blast furnace slag powder is preferably 3000 cm ² / g or more. When the value is less than 3000 cm ² / g, the initial strength development of the solidified material may be low. Incidentally, that value is more preferably 4000 cm ² / g or more, further preferably 4500cm ² / g or more. Moreover, the upper limit of this value is 10,000 cm < ² > / g from the point of a grinding | pulverization cost. The blast furnace slag powder can be obtained by pulverization with a pulverizer such as a ball mill or a jet mill.
The basicity of the blast furnace slag powder is preferably 1.6 or more. If the value is less than 1.6, the strength development property of the solidified material may be lowered. The value is more preferably 1.8 or more, and still more preferably 1.9 or more. In addition, the upper limit of the value is 3.0 because of easy availability. The basicity is calculated using the following formula.
Basicity = [(CaO + MgO + Al ₂ O ₃ ) / SiO ₂ ]
However, the chemical formula in the formula represents the content (% by mass) of the compound represented by the chemical formula in the blast furnace slag powder.

The additive-containing solidifying material of the present invention more preferably contains 12% by mass or less of gypsum powder.
If the value is within the above range, the strength development of the solidified material is good and the risk of expansion of the improved soil is low. In addition, this value becomes like this. Preferably it is 11 mass parts or less, More preferably, it is 10 mass parts or less.
The gypsum powder is not particularly limited, and examples thereof include one or more selected from dihydrate gypsum, flue gas desulfurization gypsum, phosphate gypsum, titanium gypsum, hydrofluoric gypsum, refined gypsum, hemihydrate gypsum, and anhydrous gypsum. . Among these, anhydrous gypsum is preferable in terms of high strength development, and not only natural products, but also anhydrous gypsum obtained by heating dihydrate gypsum recovered from gypsum waste with a heating device can be used.
Moreover, the brane specific surface area of the gypsum powder is preferably 2000 to 12000 cm ² / g. If the value is out of the range, the strength development property of the solidified material may be lowered. In addition, this value becomes like this. More preferably, it is 3000-8000 cm < ² > / g, More preferably, it is 4000-6000 cm < ² > / g, Most preferably, it is 4500-5500 cm < ² > / g.

  The additive-containing solidified material of the present invention may contain silica fume, silica powder, steelmaking slag powder, clinker dust, and the like as other optional components as long as the strength development property of the solidified material is not impaired. Here, the clinker dust is dust generated by extracting a part of the combustion gas from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the bottom cyclone, and cooling the extracted combustion gas. The dust includes chlorine bypass dust recovered from the combustion gas by a chlorine bypass device attached to the cement kiln. Clinker dust has the effect of improving the early strength development of the solidified material.

The fineness of the additive-containing solidified material of the present invention is a Blaine specific surface area, preferably 2000 to 10000 cm ² / g. If this value is in the range of 2000 to 10000 cm ² / g, the solidified material is excellent in strength development and workability. In addition, this value becomes like this. More preferably, it is 2500-8000 cm < ² > / g, More preferably, it is 3000-6000 cm < ² > / g.

3. Manufacturing method of improved soil The manufacturing method is a method of manufacturing improved soil by adding and mixing 100 to 500 kg of the additive-containing solidifying material per 1 m ^{3 of} sandy soil. If the added amount is less than 100 kg, the strength of the improved soil is low, and if it exceeds 500 kg, the strength of the improved soil tends to be saturated. In addition, this value becomes like this. Preferably it is 200-400 kg, More preferably, it is 250-350 kg.
Further, the mixing of the additive-containing solidifying material and the sandy soil may be either a method of adding the solidifying material as a slurry or a method of adding it in a powder form.
As shown in FIG. 1 to be described later, the strength of the improved soil manufactured by the improved soil manufacturing method of the present invention increases as the curing temperature increases, and the elongation of the strength increases remarkably in an environment of 30 ° C. .

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to this Example.
1. Materials used (1) Limestone powder (manufactured by Taiheiyo Cement)
The passing mass percentage of the sieve is 100% for a sieve with a nominal size of 600 μm, 97.4% for a sieve with a nominal size of 150 μm, and 77.1% for a sieve with a nominal size of 75 μm.
The content of calcium carbonate is 99.3% by mass.
(2) Ordinary Portland cement (manufactured by Taiheiyo Cement)
Blaine specific surface area 3250 cm ² / g, gypsum content (in terms of SO ₃ ) 2.1 mass%. However, a small amount of mixed components (cement mixture) such as limestone fine powder is not included.
(3) Blast furnace slag powder (Sement Kanto)
Blaine specific surface area 4680 cm ² / g, SO ₃ content 1.9% by mass
(4) Anhydrous gypsum (Nacord)
SO ₃ content 54.8% by mass
(5) Blast furnace cement type B (manufactured by Taiheiyo Cement)
(6) Cement-based solidifying material (manufactured by Taiheiyo Cement)

2. Production of solidified material According to the formulation shown in Table 1, the cement, blast furnace slag powder, anhydrous gypsum powder, and limestone powder were mixed to produce a solidified material (Examples 1 to 6). Further, as a solidifying material for comparison, blast furnace cement type B (Comparative Example 1) and a commercially available cement-based solidifying material (Comparative Example 2) were used.

3. Preparation of improved soil The improved soil was prepared according to JGS 0821-2008 “Method for preparing specimen without compaction of stabilized soil”. Specifically, using the soil shown in Table 2 as the target soil, 300 kg of the additive-containing solidifying material per 1 m ^{3 of the} soil was added in a powder state, and then mixed with a soil mixer for 3 minutes. The obtained mixture was packed in a mold having an inner diameter of 3.5 cm and a height of 7 cm, and sealed at 20 ° C. to prepare a specimen of improved soil. The strength of the improved soil was measured in accordance with JIS A 1216 “Soil uniaxial compression test method”. The results are shown in Table 3.

As shown in Table 3 and FIG. 1, the additive-containing solidified material (Examples 1 to 6) to which the solidifying material additive of the present invention is added is a blast furnace cement type B (Comparative Example 1) or a commercially available cement-based solidified material. Compared with the material (Comparative Example 2), the curing temperature is 5 ° C., 20 ° C., and 30 ° C., and exhibits a strength expression equal to or higher than that. In addition, when the target soil is sandy soil, the strength development is significantly higher than that of the viscous soil of FIG. 2, and the strength increase is particularly large at the age of 28 days.
In addition, the additive-containing solidified material containing no anhydrous gypsum (Examples 1 to 3) exhibits higher strength than the additive-containing solidified material containing anhydrous gypsum (Examples 4 to 6). This can be said to be an excellent effect unique to the present invention.
From the above, the additive for solidifying material of the present invention, when sandy soil is used as the target soil, is highly effective in improving the strength development of the solidifying material in each stage, and accordingly, the amount of gypsum in the solidifying material is increased. The risk of expansion of the improved soil and the cost of the solidified material can be reduced.

Claims (5)

  A cement-based solidifying material or an additive used for cement with sandy soil as the target soil, and the passing mass percentage of the sieve is 100% for a sieve having a nominal size of 600 μm, 90% or more for a sieve having a nominal size of 150 μm, and a nominal size An additive for cement-based solidifying material made of limestone powder having a size of 75 μm and 70% or more. To cement solidifying material or cement 100 parts by targeted soil sandy soil,
An additive-containing solidifying material comprising 1 to 20 parts by mass of the cement-based solidifying material additive according to claim 1 .   The additive-containing solidified material according to claim 2, wherein the additive-containing solidified material contains 20 to 70 mass% of blast furnace slag powder.   The additive-containing solidified material according to claim 2 or 3, wherein the additive-containing solidified material further contains 12% by mass or less of gypsum powder. Sandy soils 1 m ³ per method of improved soil mixing by 100~500kg adding additive material containing solidifying material according to any one of claims 2-4.

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