KR20070062916A - Soil hardening material - Google Patents

Abstract

A soil hardening material is provided to have a higher soil hardening ability than the conventional magnesium oxide-containing soil hardening material and to reduce environmental load because the amount of magnesium oxide added to soft soil is reduced. The soil hardening material contains 20-60% by mass of magnesium oxide, 1-50% by mass of a sulfate salt of magnesium, calcium, and/or aluminum, 0.1-10% by mass of a phosphate salt, and 10-60% by mass of calcium carbonate. The magnesium has an average periclase crystallite diameter of 10-50 nanometers, a BET specific surface area of 5-20m^2/g, an average particle size of 1-5 micrometers, less than 10vol% of particles with a particle size larger than 10 micrometers, and an apparent density of 0.3-0.8g/cm^3.

Description

SOIL HARDENING MATERIAL}

BRIEF DESCRIPTION OF THE DRAWINGS In the soil solidification process of Example 1 and the comparative example 1, it is a graph which shows the relationship of the quantity of the alkaline material added to the soil, and the cone index of solidification process soil.

2 is a graph showing the relationship between the amount of alkaline material added to the soil and the cone index of the solidified soil in the soil solidification treatment of Example 2 and Comparative Example 2. FIG.

3 is a graph showing the relationship between the amount of alkaline materials added to the soil and the cone index of the solidified soil in the soil solidification treatment of Example 3 and Comparative Example 3. FIG.

4 is a graph showing the relationship between the amount of alkaline material added to the soil and the cone index of the solidified soil in the soil solidification treatment of Example 4 and Comparative Example 4. FIG.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2003-193050

[Patent Document 2] Japanese Unexamined Patent Publication No. 2003-193462

The present invention relates to soil solidification materials, and more particularly, to soil solidification materials useful for solidifying soft soils. One use of magnesium oxide is as a solidifying material for soft soils. Magnesium oxide has the advantage of being less alkaline, in view of being slightly alkaline compared to calcium oxide, which is equally used as soil solidifying material. However, magnesium oxide has a problem that the solidification reaction rate is slow and the solidification capacity of the soil is slightly inferior to calcium oxide. For this reason, the improvement of soil solidification capability is examined by adding sulfate etc. to magnesium oxide as a reaction acceleration | stimulation material of soil solidification.

Patent Document 1 discloses a magnesium oxide-containing soil solidifying material using sulfate as a reaction accelerator. In this patent document, examples of the sulfate salt include calcium sulfate and magnesium sulfate.

Patent Document 2 discloses a magnesium oxide-containing soil solidifying material using any one or more of phosphate, sulfate, carbonate and organic acid as a reaction accelerator. Examples of phosphates include superphosphate lime, superphosphate lime, soluble phosphorus, calcined phosphorus, anhydrous gypsum, dihydrate gypsum, potassium sulfate, aluminum sulfate, ammonium sulfate, kalilum, sodium alum, carbonate Examples of sodium carbonate, sodium hydrogen carbonate and organic acids include citric acid, tartaric acid, lactic acid and oxalic acid, respectively.

Although magnesium oxide is weak alkali compared with calcium oxide, considering the load on the environment after the solidification treatment, it is preferable that the amount of magnesium oxide added for solidification of the soil is small.

Accordingly, an object of the present invention is to develop a soil solidifying material having a higher solidification capacity of soil than a conventional magnesium oxide-containing soil solidifying material, so that the effect of high soil solidification can be obtained by adding a small amount of magnesium oxide as much as possible.

Means to solve the problem

MEANS TO SOLVE THE PROBLEM As a result of carrying out examination about the soil solidification material containing magnesium oxide and a sulfate containing magnesium oxide, it was found that by adding a predetermined amount of phosphate and calcium carbonate further, it becomes possible to further improve the solidification capacity of the soil. .

The present invention is a soil solidified material containing 20 to 60% by mass of magnesium oxide, 1 to 50% by mass of sulfate of magnesium, calcium and / or aluminum, 0.1 to 10% by mass of phosphate, and 10 to 60% by mass of calcium carbonate. Is in.

Preferred embodiments of the present invention are as follows.

(1) Furthermore, calcium oxide and / or light dolomite are contained in the range of 1-90 mass parts with respect to magnesium oxide and 100 mass parts.

(2) Magnesium, calcium and / or aluminum sulfate is contained in the range of 1 / 50-1 mass times of magnesium oxide.

(3) The phosphate salt is contained in the range of 1 / 100-1 / 10 mass times of magnesium oxide.

(4) Calcium carbonate is contained in 1/3 to 3 mass times of magnesium oxide.

(5) Magnesium oxide is in the range of 10-50 nm of average pericle crystallite diameter, BET specific surface area is in the range of 5-20 m <2> / g, and average particle diameter is in the range of 1-5 micrometers, The proportion of the particles having a particle diameter exceeding 10 μm does not exceed 10% by volume, and the apparent density is in the range of 0.3 to 0.8 g / cm 3.

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The soil solidifying material of the present invention is composed of four essential components, sulfate, phosphate and calcium carbonate, which are one or two or more metals selected from the group consisting of magnesium oxide, magnesium, calcium and aluminum.

Content of magnesium oxide exists in the range of 20-60 mass% with respect to the total amount of an essential component, Preferably it exists in the range of 25-60 mass%. If the content of magnesium oxide is less than the above range, the solidification capacity of the soil is lowered.

Sulfates, phosphates and calcium carbonates of magnesium, calcium and aluminum serve as reaction promoters of magnesium oxide. Moreover, sulfates of magnesium, calcium, and aluminum are weakly acidic, and also have an effect of suppressing a rise in pH of the soil after the solidification treatment. Since calcium carbonate is slightly alkaline than magnesium oxide, there is less load on the soil after the solidification treatment.

Content of a sulfate is in the range of 1-50 mass% with respect to the total amount of an essential component, Preferably it exists in the range of 10-30 mass%. Moreover, it is preferable to exist in the range of 1 / 50-1 mass times of magnesium oxide, and, as for content of sulfate, it is more preferable to exist in the range of 1 / 10-3 / 4 mass times.

The content of the phosphate salt is in the range of 0.1 to 10% by mass, preferably 0.5 to 5% by mass, based on the total amount of the essential components. Moreover, it is preferable to exist in the range of 1 / 100-1 / 10 mass times of magnesium oxide, and, as for content of a phosphate, it is more preferable to exist in the range which is 1/50-1/20 mass times.

Content of calcium carbonate exists in the range of 10-60 mass% with respect to the total amount of an essential component, Preferably it exists in the range of 20-60 mass%. Moreover, it is preferable to exist in the range of 1 / 3-3 mass times of magnesium oxide, and, as for content of calcium carbonate, it is more preferable to exist in the range of 1 / 3-2 mass times.

When content of sulfate, phosphate, and calcium carbonate is less than the said range, the effect as a reaction promoter will become inadequate.

It is preferable that the magnesium oxide used in the soil solidification material of this invention is light magnesium oxide. Particularly preferred magnesium oxide is in the range of 10-50 nm of average pericle crystallite diameter, in the range of 5-20 m 2 / g of BET specific surface area, in the range of 1-5 μm of average particle diameter, It is magnesium oxide in the ratio of the particle | grains whose diameter exceeds 10 micrometers does not exceed 10 volume%, and an apparent density is 0.3-0.8 g / cm <3>.

The average pericle crystallite diameter of magnesium oxide is in the range of 10 to 50 nm, preferably in the range of 20 to 40 nm. The average pericles crystallite diameter is the average diameter of the crystallites that form the magnesium oxide particles. The average pericle crystallite diameter is one of the indicators of the reactivity of magnesium oxide. When the average pericle crystallite diameter is in the above range, the reactivity of magnesium oxide is increased, and the expression of soil solidification is accelerated.

The BET specific surface area of magnesium oxide is 5-20 m <2> / g, Preferably it is 10-20 m <2> / g. The BET specific surface area is one of the indicators of the reactivity of magnesium oxide. When the BET specific surface area is in the above range, the reactivity of magnesium oxide is increased, and the expression of soil solidification is accelerated.

The average particle diameter of magnesium oxide is the range of 1-5 micrometers. An average particle diameter becomes one of the indexes which show the dispersibility and handling property of magnesium oxide. When the average particle diameter is in the above range, the magnesium oxide is easily dispersed in the soil to be solidified, and the handling property is improved.

The ratio of the particle | grains whose particle diameter of magnesium oxide exceeds 10 micrometers is less than 10 volume%. The distribution of the particle diameter of magnesium oxide becomes one of the indicators of dispersibility. When the ratio of the particle | grains whose particle diameter exceeds 10 micrometers exists in the said range, it will be easy to disperse | distribute magnesium oxide to the soil to solidify, and handling property will improve.

The apparent density of magnesium oxide is in the range of 0.3 to 0.8 g / cm 3, preferably in the range of 0.5 to 0.8 g / cm 3. The apparent density becomes one of the indicators of dispersibility and handling properties of magnesium oxide. When the apparent density is in the above range, the magnesium oxide is easily dispersed in the soil to be solidified, and the handling property is improved.

The said magnesium oxide can be manufactured by baking the magnesium hydroxide particle | grains produced by adding alkali, such as calcium hydroxide, to seawater at the temperature of 650-900 degreeC, Preferably it is 680-900 degreeC. Magnesium hydroxide particles obtained from seawater are injected with sulfate sulfate in seawater, and magnesium oxide particles obtained by firing these magnesium hydroxide particles in the above temperature range are usually contained in an amount in the range of 0.5 to 2.5% by mass. do. The firing time differs depending on factors such as firing temperature and magnesium hydroxide particle size, but is generally 10 to 120 minutes.

The sulfates of magnesium, calcium and aluminum used in the soil solidifying material of the present invention may be anhydrous salts or salt-containing salts. Sulfate component sulfate (SO ₄ ^{2 -)} is preferred to contain not less than 35% by mass. Examples of the sulfate include anhydrous magnesium sulfate, magnesium sulfate and 7 hydrate, anhydrous calcium sulfate (anhydrous gypsum), calcium sulfate and 0.5 hydrate (half gypsum), calcium sulfate and dihydrate, anhydrous aluminum sulfate, aluminum sulfate and 18 The well-known sulfate used for the soil solidification materials, such as hydrate salt, is mentioned. Sulfate may be used individually by 1 type, and may use 2 or more types together. As the sulfate, it is preferable to use sulfates of magnesium and calcium.

The phosphate used for the soil solidifying material of the present invention contains orthophosphate, condensed phosphate, and mixtures thereof. Examples of the phosphate include sodium phosphate, sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate, lime superphosphate, lime superphosphate, dissolved phosphorus ratio and calcined phosphorus ratio. Phosphate may be used individually by 1 type, and may use 2 or more types together. As a phosphate, it is preferable to use sodium hexametaphosphate.

In the soil solidifying material of the present invention, ordinary powdered or particulate calcium carbonate can be used as the calcium carbonate. The particle size of the calcium carbonate is preferably 50 mass% or more, more preferably 80 mass% or more, having passed through 100 mesh sieve.

In the soil solidifying material of the present invention, magnesium oxide and calcium oxide obtained by calcining calcium oxide and / or small dolomite (dolomite (magnesium and calcium bicarbonate)) in order to improve the soil solidification effect and speed up the soil solidification. Complex] may be added. Since calcium oxide and light dolomite are strongly alkaline compared to magnesium oxide, the amount of calcium oxide and / or light dolomite added is in the range of 1 to 90 parts by mass with respect to 100 parts by mass of magnesium oxide in consideration of the load on the environment after the solidification treatment. It is desirable to have. In particular, when calcium oxide and / or light dolomite are added to the soil solidification material, the total content of alkaline materials (magnesium oxide, calcium oxide and light dolomite) in the soil solidification material is preferably in the range of 25 to 80 mass%. Do.

The soil solidifying material of the present invention can be produced by, for example, mixing each of the above components using a known mixing device such as a mixer.

The soil solidifying material of the present invention may be added in the form of a powder to the soft soil to be solidified or in the form of a suspension dispersed in water. The amount of solidified soil added to the soft soil cannot be determined uniformly because it varies with the softness and moisture content of the soil, but is usually in the range of 20 to 150 kg per 1 m 3 of soil.

Example

The soil solidified material was prepared using the following material.

(1) magnesium oxide A

The calcium hydroxide suspension of 15 mass% concentration was added to seawater so that it might become 0.9 in molar ratio as the amount of calcium with respect to the amount of magnesium in seawater, and the magnesium hydroxide particle | grains were produced | generated, and the magnesium hydroxide suspension was obtained. The obtained magnesium hydroxide suspension was concentrated so that solid content concentration might be 35 mass%. The concentrated magnesium hydroxide suspension was washed with industrial water, filtered and dried to obtain magnesium hydroxide. The average particle diameter of the obtained magnesium hydroxide was 3.3 micrometers. This magnesium hydroxide was calcined for 30 minutes at a temperature of 700 ° C. in a rotary kiln calcining furnace to obtain magnesium oxide.

The obtained magnesium oxide had a ratio of particles having a pericle crystallite diameter of 31 nm, a BET specific surface area of 15.8 m 2 / g, an average particle diameter of 3.3 μm, a particle diameter of more than 10 μm, 7 vol%, and an apparent density of 0.66 g. / Cm <3>, the purity was 95.88 mass% and the content of the sulfuric acid root was 1.82 mass%. In addition, magnesium oxide pericles crystallite diameter, average particle diameter, the ratio of the particle | grains whose particle diameter exceeds 10 micrometers, and apparent density were measured by the following method.

[Mean Periclese Determinant Diameter]

Using an X-ray diffraction apparatus, the X-ray diffraction pattern of the surface of the magnesium peroxide crystallite 200 is measured under the condition of a tube voltage of 40 kV and a tube current of 20 mA, and the average pericle crystallite diameter is determined. Silicon is used for standard samples.

[Average particle diameter, the ratio of the particle | grains whose particle diameter exceeds 10 micrometers]

Magnesium oxide was added to ion-exchanged water, and ultrasonic dispersion treatment was performed for 30 seconds, and then the particle size distribution was measured using a laser diffraction particle size distribution measuring device (SK Laser LMS-30, manufactured by Seishin Co., Ltd.) The ratio of the particle | grains whose diameter and particle diameter exceed 10 micrometers is calculated | required.

[Apparent density]

Magnesium oxide is slowly added slowly to the 50 cm3 mark of the measuring cylinder, and then the mass of magnesium oxide in the measuring cylinder is weighed, and the apparent density is calculated by the following formula.

Apparent density (g / cm 3) = mass of magnesium oxide (g) / 50 (cm 3)

(2) magnesium oxide B

58 nm pericle crystallite, 12.9 m2 / g BET specific surface area, 15.8 m average particle diameter, 67 vol% of particles having a particle diameter exceeding 10 m, and an apparent density of 0.68 g / cm3. Magnesium minor magnesium oxide having a content of 96.94% by mass and a sulfate content of 0.03% by mass

(3) magnesium sulfate and 7 hydrate

(4) calcium sulfate (anhydrous gypsum)

(5) sodium hexametaphosphate

(6) Calcium Carbonate (manufactured by Ube Materials, Inc.)

Particle Diameter: 100 Mesh Sieve 90 Mass% Pass

(7) Calcium Oxide (manufactured by Ube Materials, Inc.)

Particle Diameter: 200 Mesh Sieve 95 Mass% Pass

[Examples 1-4, Comparative Examples 1-4]

The said raw material was mixed by the mass ratio shown to following Table 1 and Table 2, and the soil solidified material was prepared. In Table 1 and Table 2, alkali component content (mass%) is a weight percentage of the alkaline material (magnesium oxide, calcium oxide) contained in soil solidification material.

Example 1 Comparative Example 1 Example 2 Comparative Example 2 Magnesium oxide A 30 30 45 45 Magnesium sulfate, 7 hydrated salt 15 15 5 5 Calcium sulfate 5 5 10 10 Hexametaphosphate One - One - Calcium carbonate 49 - 34 - Calcium oxide - - 5 5 Alkali component content (mass%) 30.0 60.0 50.0 76.9

Example 3 Comparative Example 3 Example 4 Comparative Example 4 Magnesium oxide A 40 40 - - Magnesium oxide B - - 40 40 Calcium sulfate 10 10 10 10 Hexametaphosphate One One One One Calcium carbonate 19 - 19 - Calcium oxide 30 30 30 30 Alkali component content (mass%) 70.0 86.4 70.0 86.4

[Soil solidification treatment]

The soil solidified material obtained above in the soft soil (cantolom, water content: 133 mass%, wet density: 1.331 g / cm 3, dry density: 0.797 g / cm 3, pH6.5) 1 m 3 was respectively shown in Tables 3 and 4 below. It added and mixed in the ratio of 30 kg / m <3>, 70 kg / m <3>, 100 kg / m <3> shown to, and prepared the solidified soil. In Tables 3 and 4, the amount of alkaline material (kg / m 3) added to the soil is the amount of alkaline material (magnesium oxide and calcium oxide) contained in the soil solidifying material added to the soil. The evaluation results of the strength and pH of this solidified soil are shown in Tables 3 and 4. Soil strength was assessed by the cone index. Cone index and pH were measured by the following method.

[Measurement method of cone index]

JGS-0716 prepared test specimen according to the Cone Index Test Method for Compressed Soil, stored in a sealed container and stored in a constant temperature and humidity chamber (20 ° C, 80% RH). (kN / m 2) was measured. Higher cone index values indicate higher soil strength.

[measurement method of pH]

The sample obtained by the non-drying method by storing the solidified soil in an airtight container, storing it in a constant temperature and humidity chamber (20 degreeC, 80% RH), and 14 days after age, according to JGS-0211 "The pH test method of the earth suspension." 10 g was poured into 50 g of pure water, stirred for 1 hour, and then left to stand for 1 hour, and the pH of the water was measured.

Example 1 Comparative Example 1 Example 2 Comparative Example 2 Amount of Soil Solidified Material to Soil: 30㎏ / ㎥ Amount of Alkaline Material Added to Soil (㎏ / ㎥) Cone Index (kN / ㎡) pH (-)  9.0 100 9.0  18.0 512 8.9  15.0 526 8.6  23.1 625 8.9 Soil solidified amount: 70㎏ / ㎥ Amount of alkaline material added to soil (㎏ / ㎥) Cone index (kN / ㎡) pH (-)  21.0 1195 9.1  42.0 2311 8.8  35.0 3302 9.1  53.9 4129 9.0 Soil solidified amount: 100㎏ / ㎥ Amount of alkaline material added to soil (㎏ / ㎥) Cone index (kN / ㎡) pH (-)  30.0 2138 9.0  60.0 3620 8.9  50.0 5172 9.1  76.9 6662 9.2

Example 3 Comparative Example 3 Example 4 Comparative Example 4 Amount of Soil Solidified Material to Soil: 30㎏ / ㎥ Amount of Alkaline Material Added to Soil (㎏ / ㎥) Cone Index (kN / ㎡) pH (-)  21.0 596 9.3  25.9 701 9.5  21.0 590 9.5  25.9 613 9.7 Soil solidified amount: 70㎏ / ㎥ Amount of alkaline material added to soil (㎏ / ㎥) Cone index (kN / ㎡) pH (-)  49.0 2256 10.4  60.5 2536 11.0  49.0 1510 10.5  60.5 1239 11.0 Soil solidified amount: 100㎏ / ㎥ Amount of alkaline material added to soil (㎏ / ㎥) Cone index (kN / ㎡) pH (-)  70.0 4705 11.1  86.4 3659 11.5  70.0 2174 11.3  86.4 1987 11.4

In the soil solidification process of Example 1 and Comparative Example 1 in FIG. 1, the relationship between the quantity of the alkaline material added to the soil and the cone index of the solidified soil is shown in a graph. In FIG. 2, in the soil solidification treatment of Example 2 and Comparative Example 2, the graph shows the relationship between the amount of alkaline material added to the soil and the cone index of the solidified soil. In the soil solidification process of Example 3 and Comparative Example 3 in FIG. 3, the relationship between the quantity of the alkaline material added to the soil and the cone index of the solidified soil is shown in a graph. In the soil solidification process of Example 4 and Comparative Example 4 in FIG. 4, the relationship between the quantity of the alkaline material added to the soil and the cone index of the solidified soil is shown in a graph.

As is clear from the graphs of Figs. 1 to 4, the solidified soil to which the soil solidifying material containing both phosphate and calcium carbonate (Examples 1 to 4) is added does not contain both the phosphate and calcium carbonate. Compared with the solidified soil which added (Comparative Examples 1-4), it turns out that the cone index with respect to the quantity of the alkaline material added to the soil tends to show a high value.

The soil solidifying material of the present invention has a higher soil solidifying ability than the conventional magnesium oxide-containing soil solidifying material. For this reason, the amount of magnesium oxide added to the soft soil can be reduced by using the soil solidifying material of the present invention, so that the load on the environment can be reduced.

Claims (6)

A soil solidifying material containing 20 to 60% by mass of magnesium oxide, 1 to 50% by mass of sulfates of magnesium, calcium and / or aluminum, 0.1 to 10% by mass of phosphate, and 10 to 60% by mass of calcium carbonate. The method of claim 1, Furthermore, the soil solidifying material containing calcium oxide and / or light dolomite in the range of 1-90 mass parts with respect to 100 mass parts of magnesium oxides. The method of claim 1, A soil solidifying material containing the sulfate of magnesium, calcium, and / or aluminum in the range of 1 / 50-1 mass times of magnesium oxide. The method of claim 1, A soil solidifying material containing phosphate in the range of 1/100 to 1/10 mass times of magnesium oxide. The method of claim 1, Soil solidifying material which contains calcium carbonate in the range of 1/3 to 3 mass times of magnesium oxide. The method of claim 1, Magnesium oxide is in the range of 10-50 nm of average pericle crystallite diameter, BET specific surface area is in the range of 5-20 m <2> / g, average particle diameter is in the range of 1-5 micrometers, and particle diameter is A soil solidifying material having a proportion of particles exceeding 10 μm not exceeding 10 volume% and having an apparent density in the range of 0.3 to 0.8 g / cm 3.

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