Soil conditioner and soil containing the same

Abstract

To provide a soil conditioner and soil containing the same that are capable of reducing freeze and dust generation in outdoor sports grounds.SOLUTION: A soil conditioner comprises an aggregate, asphalt, and a plasticizer, where the plasticizer contains a fatty acid-based compound. The soil comprises a parent material for the soil and the soil conditioner.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a soil improver and a soil containing the same. [Background technology]

[0002] Soil is used as the surface layer in various outdoor athletic fields such as baseball fields, schoolyards, parks, etc. The surface layer of soil can generate dust due to the effects of wind and the impact of athletes' shoes.

[0003] Therefore, dust suppressants are sometimes used for these soils. For example, Patent Document 1 discloses a dust suppressant for outdoor sports grounds that contains a polybutene emulsion.

[0004] Moreover, Patent Document 2 discloses a soil conditioner for outdoor sports grounds, which contains aggregate, asphalt, and polybutene. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-67841 A [Patent Document 2] Patent Publication No. 2021-88871 Summary of the Invention [Problem to be solved by the invention]

[0006] The soil of outdoor playgrounds, especially in cold regions, freezes in winter and frost pillars form. When frost pillars form, even if the soil is compacted afterwards, the surface becomes loose. Then, in early spring, the loose surface makes it easier for dust to rise.

[0007] Therefore, the present invention provides a soil conditioner and soil containing the same that can reduce freezing and dust generation in outdoor playgrounds. [Means for solving the problem]

[0008] The present inventors have discovered that a soil conditioner having the following features and soil containing the same can reduce freezing in outdoor playgrounds and the resulting generation of dust.

[0009] That is, the present invention has the following aspects: Aspect 1 A soil conditioner comprising aggregate, asphalt, and a plasticizer, the plasticizer comprising a fatty acid-based compound. Aspect 2 2. The soil conditioner according to claim 1, wherein the fatty acid compound is a fatty acid alkyl ester compound. Aspect 3 The soil conditioner according to aspect 2, wherein the fatty acid alkyl ester compound is a compound represented by the following formula (1): R1-CO-(AO)m-OR2...General formula (1) (In the formula, R1 represents a linear or branched hydrocarbon group having 15 to 19 carbon atoms; R2 represents either hydrogen or a linear or branched hydrocarbon group having 1 to 18 carbon atoms; AO represents a linear or branched alkylene oxide unit having 2 to 4 carbon atoms; and m represents the average number of moles added and is a number from 0 to 30.) Aspect 4 The soil conditioner according to aspect 1, wherein the aggregate content is 90 to 99 mass%, the total content of the asphalt and the plasticizer is 1 to 10 mass%, and the plasticizer content is 5 to 50 parts by mass per 100 parts by mass of the asphalt. Aspect 5 A soil comprising a soil base material and the soil improver according to any one of aspects 1 to 4. Aspect 6 6. The soil of claim 5, wherein the soil base material comprises red soil and mountain sand. Aspect 7 6. The soil according to aspect 5, wherein the soil base material has a content of 50 to 90 volume %, and the soil improver has a content of 10 to 50 volume %. Aspect 8 6. An outdoor playground comprising the soil according to embodiment 5 in a surface layer. Effect of the Invention

[0010] According to the present invention, it is possible to provide a soil conditioner and soil containing the same that can reduce freezing in outdoor playgrounds and the resulting generation of dust. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 shows the results of the freeze-thaw test in Experiment 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Soil conditioner> The soil conditioner of the present invention includes aggregate, asphalt, and a plasticizer, and the plasticizer includes a fatty acid compound. The inventors have found that when a fatty acid compound is used as a plasticizer for asphalt in the soil conditioner, freezing and dust generation in outdoor athletic fields can be reduced. This is thought to be because the plasticizer effectively plasticizes the asphalt and firmly attaches the asphalt to the aggregate, making it difficult for moisture to penetrate between the aggregates, thereby suppressing freezing. It is also thought that the asphalt binds the soil particles together, suppressing the generation of dust.

[0013] <aggregate> The type of aggregate is not particularly limited, but aggregates in the range of particle sizes typically used in outdoor athletic fields can be used. Examples of such aggregates include fine aggregates.

[0014] Examples of fine aggregates include fine aggregates in which 70% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more have a particle size of 2.36 mm or less. Examples of fine aggregates include river sand, dune sand, mountain sand, sea sand, crushed sand, fine sand, screenings, crushed stone dust, silica sand, artificial sand, glass cullet, and casting sand. In addition, as an aggregate, coarse aggregate with a particle size of 2.36 mm or more, for example, crushed stone No. 7 with a particle size range of 2.36 mm or more and less than 4.75 mm, can be mixed with the fine aggregate. Here, the particle size in this specification refers to a value measured in accordance with JIS A1102:2014.

[0015] The content of aggregate in the soil conditioner may be 80% by mass or more, 85% by mass or more, 90% by mass or more, 92% by mass or more, 94% by mass or more, or 96% by mass or more, or 99% by mass or less, 97% by mass or less, 95% by mass or less, 93% by mass or less, or 90% by mass or less, in terms of dried mass. The content of aggregate in the soil conditioner may be, for example, 90% by mass or more and 99% by mass or less, or 94% by mass or more and 97% by mass or less.

[0016] <asphalt> The soil modifier includes asphalt. This imparts adhesion to the aggregate and prevents dust generation. The type of asphalt is not particularly limited, but ordinary petroleum asphalt can be used. Examples of asphalt include straight asphalt, which is petroleum asphalt for paving, and modified asphalt. Examples of modified asphalt include blown asphalt; asphalt modified with polymeric materials such as thermoplastic elastomers and thermoplastic resins.

[0017] The total content of asphalt and plasticizer in the soil conditioner may be 1.0% by mass or more, 2.0% by mass or more, 3.0% by mass or more, 4.0% by mass or more, or 5.0% by mass or more, and may be 10.0% by mass or less, 8.0% by mass or less, 6.0% by mass or less, 5.0% by mass or less, or 4.0% by mass or less. The total content of asphalt and plasticizer in the soil conditioner can be, for example, 1.0% by mass or more and 10.0% by mass or less, or 3.0% by mass or more and 6.0% by mass or less.

[0018] <Plasticizer> The soil conditioner may contain a fatty acid compound as a plasticizer, which can reduce freezing and the resulting dust generation in outdoor playgrounds.

[0019] As the fatty acid compound, for example, a fatty acid compound having an iodine value of 50 to 110 can be used. The plasticizer may be a combination of a plurality of fatty acid compounds, and in this case, the above iodine value refers to the value of the fatty acid compound in which a plurality of compounds are combined. The iodine value of the fatty acid compound is the iodine value measured in accordance with JIS K0070-1992.

[0020] Examples of the fatty acid-based compound include fatty acids and fatty acid alkyl esters, fatty acid polyoxyalkylene alkyl esters, and polyoxyalkylene fatty acid esters. These can be used alone or in combination of two or more selected from these.

[0021] Specifically, the fatty acid compound may be a compound represented by the following general formula (1): R1-CO-(AO)m-OR2...General formula (1) (In the formula, R1 represents a linear or branched hydrocarbon group having 15 to 19 carbon atoms; R2 represents either hydrogen or a linear or branched hydrocarbon group having 1 to 18 carbon atoms; AO represents a linear or branched alkylene oxide unit having 2 to 4 carbon atoms; m represents the average number of moles added; and is a number from 0 to 30.)

[0022] The molecular weight (g / mol) of the fatty acid compound may be, for example, 100 or more, 150 or more, 200 or more, 250 or more, 270 or more, or 280 or more, or 500 or less, 450 or less, 400 or less, 350 or less, 330 or less, or 320 or less. When the fatty acid compound is used in combination with multiple compounds, these molecular weights may be weight average molecular weights.

[0023] Here, R1 can be a linear or branched alkyl group having 15 to 17 carbon atoms and a linear or branched alkenyl group having 15 to 17 carbon atoms. R2 can be hydrogen or a methyl group. AO can be an ethylene oxide unit. m can be 0 to 15. The iodine value of the fatty acid compound can be 60 to 100 (g / 100 mg), or 70 to 85 (g / 100 mg). In the present invention, the "alkenyl group" refers to a hydrocarbon group containing 1 to 3 double bonds.

[0024] The fatty acid compounds (b) represented by the general formula (1) include fatty acids: R1COOH, fatty acid methyl esters: R1COOCH3, and fatty acid (poly)oxyethylene methyl esters: R1COO(CH2CH2O). m CH3, (poly)oxyethylene fatty acid ester: R1COO(CH2CH2O) mH, and specific examples thereof include palmitic acid, palmitic acid methyl ester, palmitic acid (poly)oxyethylene methyl ester (average number of moles added: 1 to 15), (poly)oxyethylene palmitic acid ester (average number of moles added: 1 to 15), stearic acid, stearic acid methyl ester, stearic acid (poly)oxyethylene methyl ester (average number of moles added: 1 to 15), (poly)oxyethylene stearate ester (average number of moles added: 1 to 15), oleic acid, oleic acid methyl ester, oleic acid (poly)oxyethylene methyl oleic acid ester (average number of moles added: 1 to 15), (poly)oxyethylene oleic acid ester (average number of moles added: 1 to 15), linoleic acid, linoleic acid methyl ester, linoleic acid (poly)oxyethylene methyl ester (average number of moles added: 1 to 15), (poly)oxyethylene linoleic acid ester (average number of moles added: 1 to 15), linolenic acid, linolenic acid methyl ester, linolenic acid (poly)oxyethylene methyl ester (average number of moles added: 1 to 15), (poly)oxyethylene linolenic acid ester (average number of moles added: 1 to 15).

[0025] Among these, a fatty acid methyl ester mixture containing 75 to 95 mass% of oleic acid methyl ester and having an iodine value of 50 to 110 (g / 100 mg) or a polyoxyethylene fatty acid ester having 16 to 18 carbon atoms (average number of moles added: 3 to 15) can be used.

[0026] The content of the plasticizer in the soil conditioner may be 5 parts by mass or more, 10 parts by mass or more, 15 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, or 30 parts by mass or more, and 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, 35 parts by mass or less, 30 parts by mass or less, or 25 parts by mass or less, relative to 100 parts by mass of asphalt. For example, the content of the plasticizer in the soil conditioner may be 5 parts by mass or more and 50 parts by mass or less, or 10 parts by mass or more and 30 parts by mass or less, relative to 100 parts by mass of asphalt. If it is within the range, even if the soil conditioner is mixed with the soil base material, the advantageous effects of the present invention can be obtained, and the occurrence of stickiness and the like is small.

[0027] The content of the plasticizer in the soil conditioner may be 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 1.0% by mass or more, or 1.5% by mass or more, or 5.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, 1.5% by mass or less, 1.0% by mass or less, or 0.8% by mass or less. For example, the content of the plasticizer in the soil conditioner may be 0.1% by mass or more and 5.0% by mass or less, or 0.5% by mass or more and 1.5% by mass or less.

[0028] <others> The soil conditioner may not contain any other components than aggregate, asphalt, and plasticizer. For example, the soil conditioner may contain 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, 1% by mass or less, or 0.1% by mass or less of other components.

[0029] "soil" The soil of the present invention includes a soil base material and the above-mentioned soil improver. This soil can be used as the surface layer of an outdoor sports field.

[0030] <Base material for soil> The soil base material is not particularly limited, but examples thereof include the above-mentioned aggregate, mountain sand, red soil, and pitted ash.

[0031] The soil base material may contain, for example, 5 to 45 mass%, 10 to 40 mass%, or 15 to 35 mass% of soil particles with a particle size of 0.075 mm or less, 50 to 95 mass%, 55 to 90 mass%, or 60 to 85 mass% of soil particles with a particle size of more than 0.075 mm and not more than 2.0 mm, and 0 to 30 mass%, 0 to 20 mass%, or 5 to 15 mass% of soil particles with a particle size of more than 2.0 mm and not more than 4.75 mm.

[0032] The content of the soil base material in the soil may be 10% by volume or more, 20% by volume or more, 30% by volume or more, 40% by volume or more, 50% by volume or more, or 60% by volume or more, or 90% by volume or less, 85% by volume or less, 80% by volume or less, 75% by volume or less, or 70% by volume or less. The content of the soil base material in the soil may be, for example, 10% by volume or more and 90% by volume or less, or 40% by volume or more and 80% by volume or less.

[0033] The content of the soil modifier in the soil may be 10% by volume or more, 20% by volume or more, 30% by volume or more, 40% by volume or more, or 50% by volume or more, or 80% by volume or less, 70% by volume or less, 60% by volume or less, 50% by volume or less, or 40% by volume or less. The content of the soil modifier in the soil may be, for example, 10% by volume or more and 80% by volume or less, or 20% by volume or more and 60% by volume or less.

[0034] The soil may not contain any other components than the soil base material and the soil improver. For example, the soil may contain 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, 1% by mass or less, or 0.1% by mass or less of other components.

[0035] <<Soil conditioner and soil manufacturing method>> The method for producing a soil conditioner includes mixing asphalt, aggregate, and plasticizer. Here, for each component of the method for producing a soil conditioner, reference can be made to each component described for the soil conditioner of the present invention. That is, for the types and amounts of asphalt, aggregate, plasticizer, etc., reference can be made to the above types and contents.

[0036] The method for producing the soil conditioner can include a step of mixing asphalt and aggregate to obtain a first mixture, and a step of adding and mixing a plasticizer to the first mixture to obtain the soil conditioner. Here, the aggregate can be heated to, for example, about 180°C and dried before mixing, and can be heated to about 150°C to 170°C and mixed during each mixing.

[0037] The soil conditioner thus obtained can be cured to reduce its temperature and then mixed with the soil base material. If the soil base material contains a large amount of water, the water content can be reduced by aeration or the like before mixing with the soil base material and the soil conditioner.

[0038] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. EXAMPLES

[0039] Experiment 1: Experiment on the mixture ratio of soil conditioner and soil base material Example of production The following seven types of plasticizers were prepared: [Table 1]

[0040] The fine sand aggregate was heated to 185°C and mixed with asphalt (straight asphalt 60 / 80) heated to 160°C. 20 seconds after mixing the fine sand and asphalt, plasticizer 1 was added and mixed to obtain a soil conditioner. At this time, the fine sand and asphalt were mixed in a mass ratio of 94:6, and 22 parts by mass of plasticizer were mixed with 100 parts by mass of asphalt. In other words, this soil conditioner contained 92.8% by mass of fine sand, 5.9% by mass of asphalt, and 1.3% by mass of plasticizer. This soil conditioner was cured overnight, and when the temperature dropped to about 60°C, it was loosened with a shovel.

[0041] After that, the soil modifier was transported to a test site in a cold region, and the soil base materials of red soil and mountain sand were mixed with the soil modifier by a backhoe for about an hour. In the soil of Example 1, the red soil, mountain sand, and soil modifier were mixed at 40 volume%, 30 volume%, and 30 volume%, respectively, and in the soil of Example 2, they were mixed at 40 volume%, 10 volume%, and 50 volume%, respectively. In addition, as the soil of Comparative Example 1, the red soil and mountain sand were mixed at 40 volume% and 60 volume%, respectively. Then, these soils were spread evenly as the surface layer in three adjacent construction areas of an outdoor playground and compacted.

[0042] The particle size distribution, unit volume mass, and water content of the soil conditioner, red soil, and mountain sand used are as shown in the table below. [Table 2]

[0043] The particle size distribution of the soil obtained for each example was as follows: [Table 3]

[0044] Test Method <Permeability test> A permeability test was conducted to evaluate the drainage of the soil of the playground. The test was conducted according to the method described in F010 of the "Pavement Survey and Testing Method Handbook."

[0045] <Proctor Needle Penetration Test> The Proctor needle penetration test was conducted to evaluate the cushioning properties of the soil of the playground. The test was conducted in accordance with the method described in the "Construction Guidelines for Outdoor Sports Facilities."

[0046] <Freeze-thaw test> A freeze-thaw test was conducted to evaluate the effects of freezing the soil in the playground. The test was conducted in accordance with the method described in the Wet and Dry Cyclic Test Method in the "Construction Sludge Recycling Manual." The test specimens were prepared using the method described in Method F007-A in the "Pavement Survey and Test Method Handbook." The test specimens were placed in a freezer at -10°C for one day, and then the frozen specimens were immersed in water at 20°C for one day. This cycle was repeated three times, and the dry mass was measured before and after the test to confirm the residual rate.

[0047] Dust generation test After winter, in early spring, a dust generation test was conducted in the abovementioned playground. The test was conducted by enclosing the playground in a hemispherical container with soil on the bottom, blowing air into the container from the top, and measuring the amount of dust generated inside the container with a digital dust meter.

[0048] "result" The test results are shown in the table below: [Table 4]

[0049] The permeability of the soil of Examples 1 and 2 was lower than that of the soil of Comparative Example 1, but was sufficient for a playground. In addition, the Proctor needle penetration test revealed that the soil of Examples 1 and 2 had high cushioning properties and moderate hardness. Furthermore, it was found that the soil of Comparative Example 1 completely loses its shape before freezing when thawed after freezing, whereas the soil of Examples 1 and 2 is very little affected by freezing. And, it was found that the generation of dust is greatly reduced in the soil of Examples 1 and 2 compared to the soil of Comparative Example 1 after wintering.

[0050] In addition, some clumps of asphalt mortar were confirmed in the soil of Example 2 compared to the soil of Example 1. In addition, in Example 1, the plasticizer 1 was changed to each of Plasticizers 2 to 7, and the test results were roughly the same.

[0051] Experiment 2: Experiment on the amount of plasticizer in soil conditioner The soil conditioners of Examples 3 to 5 were produced in the same manner as in Experiment 1, except that the amount of plasticizer per 100 parts by mass of asphalt was changed to 10 parts by mass, 20 parts by mass, and 30 parts by mass. Each soil was obtained by mixing 30% by volume of these soil conditioners with 70% by volume of the same soil base material. In addition, using the soil conditioner of Example 4, test specimens were also produced in which the amount of soil base material was changed from 0% by volume to 100% by volume.

[0052] A freeze-thaw test was carried out on each soil in the same manner as in Experiment 1. The results are shown in Figure 1.

[0053] Comparing Example 3 with Example 4, it can be seen that the freeze-thaw property worsens when the amount of plasticizer is reduced. On the other hand, comparing Example 4 with Example 5, it was found that the freeze-thaw property worsens to some extent even when the amount of plasticizer is increased. In addition, the soil of Example 5 felt a little sticky when touched with the hand.

Claims

1. A soil conditioner comprising aggregate, asphalt, and a plasticizer, the plasticizer comprising a fatty acid-based compound.

2. The soil conditioner according to claim 1 , wherein the fatty acid compound is a fatty acid alkyl ester compound.

3. The soil conditioner according to claim 2, wherein the fatty acid alkyl ester compound is a compound represented by the following formula (1): R １ -CO-(AO)m-OR ２ ・・・General formula (1) (In the formula, R １ represents a linear or branched hydrocarbon group having 15 to 19 carbon atoms; R ２ represents either hydrogen or a linear or branched hydrocarbon group having 1 to 18 carbon atoms; AO represents a linear or branched alkylene oxide unit having 2 to 4 carbon atoms; and m represents the average number of moles added and is a number from 0 to 30.

4. The content of the aggregate is 90 to 99% by mass, the total content of the asphalt and the plasticizer is 1 to 10% by mass, and the content of the plasticizer is 5 to 50 parts by mass relative to 100 parts by mass of the asphalt. The soil conditioner according to claim 1.

5. A soil comprising a soil base material and the soil improver according to any one of claims 1 to 4.

6. The soil according to claim 5 , wherein the soil base material comprises red soil and mountain sand.

7. The soil according to claim 5, wherein the content of the soil base material is 50 to 90% by volume, and the content of the soil modifier is 10 to 50% by volume.

8. An outdoor playground comprising the soil according to claim 5 in its surface layer.

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