JP2002038153A - Water-reducing agent for soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-reducing agent which is used for soil, can reduce water, when the water is added to occurring soil or hydraulic substance-added occurring soil to impart flowability to the soil, and further has biodegradability. SOLUTION: This water-reducing agent for soil, characterized by containing a polymer which has carboxy group-based substituents and biodegradability, for example, at least one polymer selected from (1) alginic acid-based compounds, (2) acetal-based polymers having carboxy group-based substituents, and (3) polyamides having carboxy group-based substituents.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water reducing agent for soil used in, for example, improvement of soft ground and fluidization of generated soil by excavation or dredging.

[0002]

2. Description of the Related Art Conventionally, in the case of improving soft ground composed of hydrated soil, hydrated soil (generated soil) obtained by excavating and dredging the ground includes cement, lime, etc. (hydraulic material).
Is uniformly added and backfilled to harden the soft ground. In addition, a method has been adopted in which a hydraulic substance is uniformly added to generated soil discharged from a construction site and reused as landfill soil.

[0003] Further, as a method of use other than backfilling and landfilling on site, there is a method of once carrying the generated soil into a plant, adding a solidifying agent, processing it into sand or gravel, and reusing it as an improved material. Has been adopted.

[0004] By the way, in order to improve the soft ground by backfilling, and when reclaiming, in order to secure the strength of the ground after backfilling (or after reclamation), a hydraulic substance is uniformly added to the generated soil. In addition, it is required that the generated soil after the addition of the hydraulic substance is uniformly poured into the expected backfill site or the expected reclamation site so that no cavity is formed. Although depending on properties such as the initial moisture content of the generated soil, generally, a great effort is required to uniformly mix the hydraulic substance and the generated soil. In addition, since the fluidity of the generated soil to which the hydraulic substance is added is considerably low and the workability is not good, there is a problem that it is necessary to perform measures such as leveling and compaction to achieve uniformity.

[0005]

In order to avoid such a problem, a method of securing fluidity by adding water to the above-mentioned generated soil or generated soil to which a hydraulic substance has been added is also adopted. However, the work space is limited due to the nature that the water treatment is performed on site, and it is necessary to avoid an increase in the volume of the generated soil due to the water addition. In addition, there is no guarantee that a large amount of water or muddy water is always available near the site. In other words, it is required to reduce the amount of water or mud provided for the water treatment as much as possible.

Therefore, for example, a method of using a water reducing agent to impart desired fluidity to the above-mentioned generated soil or the generated soil to which a hydraulic substance is added with a smaller amount of water is adopted. However, all of the conventional water reducing agents have little biodegradability, and although they have the effect of reducing the amount of water added, they have a problem that the environmental load becomes extremely large.

More specifically, generated soil to which a water reducing agent has been added is used, for example, for backfilling or landfilling, or is transported to another place and discarded. Components may leak from the soil, causing contamination of the surrounding soil and pollution of rivers and groundwater veins. Since conventional water reducing agents have little biodegradability,
Once the water reducing agent leaks into the surrounding environment, it becomes a major factor in environmental load.

In order to prevent the leakage of the water reducing agent into the surrounding environment, the generated soil to which the water reducing agent has been added is subjected to a filter press or the like to separate the generated soil from the water containing the water reducing agent. Although a method of returning only the generated soil to the surrounding environment can be adopted, an additional operation is required, resulting in an increase in cost.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to be suitably used for imparting fluidity to the above-mentioned generated soil or the generated soil to which a hydraulic substance has been added. A biodegradable soil water reducing agent.

[0010]

Means for Solving the Problems The inventors of the present invention can reduce the amount of water added to the generated soil when imparting fluidity to the generated soil and the like, and can reduce the environmental load compared to the conventional one. Studied diligently to provide a small soil water reducer. As a result, they have found that a specific compound (polymer compound) having a carboxyl group-based substituent can be suitably used as the water reducing agent for soil, and have completed the present invention.

That is, in order to solve the above problems, the soil water reducing agent according to the present invention is characterized by comprising a polymer having a carboxyl group-based substituent and having biodegradability. I have. Here, the term “biodegradability” refers to the modified MITI described on pages 1281 to 1286 of the OECD guidelines.
The evaluation is based on the biodegradation rate measured according to the test (I) method, and “having biodegradability” means that the biodegradation rate is 30% or more. MIT
Method I is a method using activated sludge.

[0012] The soil water reducing agent according to the present invention is characterized in that, in the above constitution, the polymer is an acetal-based polymer having a carboxyl-based substituent.

[0013] The soil water reducing agent according to the present invention is also characterized in that, in the above structure, the polymer is a polyamide having a carboxyl group-based substituent.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The "soil" in which the soil water reducing agent according to the present invention is used includes not only generated soil obtained by excavation and dredging (for example, soft clay and construction residual soil), but also soil. The concept includes a soil composition in which a solidifying agent (a hydraulic substance) such as cement or lime is added to the generated soil.
The above-mentioned generated soil refers to all the soil generated by construction on the ground, and more preferably one having a relatively small particle size constituent unit such as gravel, sand, silt, and clay as a main component.
In particular, secondary particles (natural structural units, that is, pedds) can be easily formed by adding water or stirring after adding water.
Further, those which can be loosened to the size of the primary particles are preferable. In addition, the generated soil includes generated soil (secondary generated soil) such as muddy residual soil generated “secondarily” by adopting a muddy water shield method or the like. In addition, the "secondary generated soil" referred to here means not only the ground excavated or the like, but also the generated soil generated by excavation or the like with further secondary processing such as water addition.

[0015] These "soils" are basically based on the premise that water is added to impart fluidity, but the soil water reducing agent according to the present invention provides the soil with fluidity. It can reduce the amount of added water (the amount of water added) necessary for application, and in some cases, can be reduced to zero, and additionally has biodegradability. Hereinafter, the soil water reducing agent according to the present invention will be described in detail.

The soil water reducing agent according to the present invention comprises a polymer having a carboxyl group-based substituent and having biodegradability. In the present invention, the “carboxyl group-based substituent” is defined by the following general formula (1) —COOM ¹ or —COOM ² OOC— (1) (where M ¹ is a hydrogen atom, an alkali metal Atom, an ammonium group, or an organic amine group, and M ² represents an alkaline earth metal atom).

The polymer is preferably hydrophilic. In this case, the polymer adsorbs small particles such as secondary particles and primary particles that constitute soil, and due to its own hydrophilicity, the polymer adsorbs water on the small particles. (Water added to impart fluidity) to improve dispersibility. Although the mechanism of action is not necessarily clear, it is presumed that the polymer adsorbs small particles constituting soil by its carboxyl group-based substituent.

Therefore, it is sufficient that at least one of the carboxyl group-based substituents is present in one molecule of the polymer, but it is more preferable that a large number of the carboxyl group-based substituents be present.
Specifically, it is more preferable that the polymer has an acid value of 50 mgKOH / g (polymer) or more. If such a polymer is used, the soil can be more favorably adsorbed and dispersed. On the other hand, the upper limit of the acid value of the polymer is determined by the number of carboxyl group-based substituents that the polymer may have per unit weight. May be set to an optimum value according to the environment in which may leak.

When the polymer adsorbs small particles mainly by the carboxyl group-substituent, the polymer may be adsorbed between the carboxyl group-substituent and the anion exchange group of the soil (small particles). It is presumed that the chemical adsorption has occurred. Among clay minerals and humus, which are the main ion exchangers constituting soil, representatives having anion exchange groups include allophane, imogolite, 1: 1 type mineral, and 2: 1 type to 2: Examples include 1: 1 type intermediate species minerals, gibbsite, iron oxide minerals, and the like, and it is generally known that their anion exchange capacity increases with a decrease in pH. Therefore, in some cases, the combined use of the soil water reducing agent and the acidic substance according to the present invention is expected to further improve the dispersibility of soil in added water.

In the present invention, “biodegradable” refers to
Evaluation shall be based on the biodegradation rate measured according to the modified MITI test (I) method described on pages 1281 to 1286 of the OECD guidelines, and “with biodegradability” means that the biodegradation rate is 30% or more. And its value is 6
Those having 0% or more are more preferable. The biodegradation rate indicates the rate of degradation of a polymer per unit time by a microorganism. When the value is 30% or more, it is generally used as an index for determining that the polymer has biodegradability.

The weight-average molecular weight of the polymer contained in the soil water reducing agent of the present invention is not particularly limited, but from the viewpoint of dispersibility of the soil, it is 500 to 100,000.
Is more preferably in the range of 2,000 to 10
It is particularly preferred that it is in the range of 0.000. In addition,
In the present invention, the “weight average molecular weight” is a value in terms of polyethylene glycol obtained by a gel permeation (GPC) method.

Hereinafter, "having a carboxyl group-based substituent,
The "polymer having biodegradability" will be described with reference to specific examples. Specific examples of such a polymer include 1) alginic acid and a salt thereof, 2) an acetal polymer having a carboxyl group-based substituent, and 3) a polyamide having a carboxyl group-based substituent. However, the present invention is not particularly limited to these.

In the present invention, "alginic acid and salts thereof" specifically refers to alginic acid and alkali metal salts, alkaline earth metal salts, ammonium salts, or amine salts of alginic acid. In these alginic acid-based compounds, it is considered that the carboxyl group-based substituent mainly affects the adsorptivity to soil and the dispersibility in water. In alginic acid-based compounds, the repeating units are linked by polysaccharide ether bonds, and are easily decomposed by microorganisms even if they leak to the surrounding environment.

The alginic acid-based compound can be obtained by a commonly used method. For example, a dried product of a brown alga of the genus Phaeophycese is extracted with an aqueous solution of sodium carbonate, and the extract is treated with an acid to obtain alginic acid.

The term "acetal polymer having a carboxyl group substituent (hereinafter simply referred to as acetal polymer)" refers to an oxymethylene unit, ie, -CH
_In a polyacetal compound having ₂ O- as a repeating unit, it refers to a compound in which one or two of the hydrogen atoms of at least one oxymethylene unit is the above-mentioned carboxyl group-based substituent. In the acetal-based polymer, the bonds between the repeating units are based on polysaccharide ether bonds, and are easily decomposed by microorganisms even if they leak to the surrounding environment. Particularly preferred examples of such an acetal-based polymer include, for example, sodium polyglyoxylate; polyglyoxylic acid / polyethylene glycol block copolymer; oxide of polysaccharide; and the like.

All of the acetal polymers exemplified above can be obtained by a commonly used method. For example, sodium polyglyoxylate is obtained by polymerizing glyoxylate in the presence of a suitable polymerization initiator to obtain an acetal ester polymer, stabilizing the acetal ester polymer by adding a terminal group for stabilization,
Subsequently, the stabilized acetal ester polymer may be saponified with sodium hydroxide. Further, if the acetal ester polymer adjusted to a desired degree of polymerization and polyethylene glycol are polymerized using a polymerization initiator as needed, a polyglyoxylic acid / polyethylene glycol block copolymer can be obtained. it can.

Further, the above-mentioned oxide of the polysaccharide is, for example,
It can be easily obtained by partially oxidizing the corresponding polysaccharide with nitric acid or the like.

"Polyamide having a carboxyl group-based substituent (hereinafter, simply referred to as polyamide)" is a compound having a main chain having a repeating structure of an amide bond and having at least one carboxyl group-based substituent. Point to. In the above polyamide, the bond between the repeating units conforms to the peptide bond of the protein, and is easily decomposed by microorganisms even when leaked to the surrounding environment. Particularly preferred examples of such polyamides include, for example, sodium polyaspartate; sodium polyglutamate; and the like. In addition, any of the above-mentioned polyamides can be easily synthesized by a commonly used biotechnological technique or chemical engineering technique.

The soil water reducing agent according to the present invention may contain only one kind of the above-mentioned "polymer having a carboxyl group-based substituent and having biodegradability". Two or more types may be included. Hereinafter, the specific usage of the soil water reducing agent according to the present invention will be described, but the usage is not particularly limited to the following specific examples.

In the case where the "soil" of the present invention is transported to, for example, a plant or a cultivation material near the site, or when it is reused for backfilling or landfill, it is necessary to improve the workability. Is required to have a desired fluidity. That is, if the desired fluidity is imparted to the soil, 1) pipe transportation becomes easy, 2) uniform mixing of the composition by stirring becomes easy,
3) When backfilling or reclaiming land, it is easy to work the soil uniformly and without voids. In general, the fluidity to be imparted to the soil is preferably such that the flow value measured by the method described in the following example is in the range of 70 or more, and more preferably in the range of 90 or more. It is said.

The soil water reducing agent according to the present invention is used for the above-mentioned "soil", and can reduce the amount of water added to impart fluidity to the soil, and in some cases, can reduce it to zero. It is. That is, the use of the above-mentioned soil water reducing agent makes it possible to add a small amount of water, or to impart desired fluidity to the soil without adding moisture. Can be minimized. In addition, the amount of water to be secured for the fluidity imparting process can be significantly reduced (or can be reduced to zero). In addition, since the polymer contained in the soil water reducing agent has biodegradability, even if the polymer leaks from the soil to the surrounding environment after the fluidity-imparting treatment, the polymer is a microorganism or the like. Is easily decomposed and does not cause environmental pollution.

As a more specific advantage, 1) a large space (cultivation material) even when the soil is once cured at the site.
2) Fluidity-imparting treatment is possible even at sites where it is difficult to secure water. 3) Work time can be shortened. 4) The burden on the environment is small, that is, an environment-friendly type. Reuse and disposal of generated soil is possible.

As a form of the soil to which fluidity is given, for example, a mixture A consisting of 1) generated soil + soil water reducing agent + added water, and 2) generated soil + soil water reducing agent + added Water + solidifying agent such as cement (hydraulic substance),
And a mortar-like mixture B (generally treated fluidized soil). Usually, a mortar-like mixture B is obtained and reused on site (such as backfill for ground improvement). If necessary, a hardening accelerator such as calcium chloride, triethanolamine, or calcium thiocyanate may be added to the mortar-like mixture B. When the mixture A is prepared, the mixture A may be added and stirred while transporting the mixture A or after transporting the mixture A to a predetermined treatment plant.

The “moisture” used for preparing the above-mentioned mixtures A and B may be water alone, or may be a water mixture such as adjusted muddy water. Then, as shown in the following examples, particularly when the soil water reducing agent according to the present invention is used in the preparation of the mixture B, it is necessary to impart desired fluidity as compared with the case where it is not used. The amount of the "moisture" can be significantly reduced.

The order in which the generated soil, the water reducing agent for soil, the moisture, and the solidifying agent such as cement (when preparing the above mixture B) is added, and the method of uniformly mixing them are not particularly limited. . Generally, a water-reducing agent dispersion (or aqueous solution of a water-reducing agent) is prepared by uniformly dispersing or dissolving a water-reducing agent for soil in the above-mentioned water, and the generated soil or the generated soil to which a solidifying agent is added (the present invention Soil) and the water reducing agent dispersion, and uniformly stirring and mixing with a stirring means such as a mortar mixer.

In addition, the above-mentioned water reducing agent for soil, moisture, and solidifying agent for a predetermined amount of generated soil (in the case of the above-mentioned mixture B)
May be determined depending on the quality (initial water content, composition, etc.) of the generated soil and the desired degree of fluidity, and are not particularly limited. Generally, it is more preferable to add the soil water reducing agent in the range of 0.6 to 36 g, and more preferably in the range of 1.2 to 9.6 g, as the amount of the polymer, based on 1200 g of the generated soil. More preferably, In addition, when ordinary Portland cement is used as a solidifying agent, 1 g of the generated soil is
It is more preferable to add within the range of 2 to 360 g,
More preferably, it is added in the range of 36 to 240 g. If the soil water reducing agent to be added is in the range of the above value as the amount of the polymer, saccharides and amino acids generated by biodegradation of the polymer cause eutrophication of the surrounding environment. There is little fear.

By the way, as described above, in order to impart fluidity to soil, even if the soil water reducing agent of the present invention is used,
Basically, water addition is required. For example, when solidified material such as cement is added to muddy residual soil (secondary generated soil) generated by the muddy water shield method, etc. Is, by using the soil water reducing agent of the present invention,
In some cases, the addition of the water is not necessary. As an example,
If the solidified material is added to the muddy residual soil, its fluidity is reduced, and it may be necessary to add water to secure the desired fluidity. In such a case, the soil water reducing agent according to the present invention is first added to the muddy residual soil to sufficiently disperse the soil components, and then the solidified product is added. Liquidity can be secured.

Further, although the initial moisture content of the soil is extremely large,
Even if the desired fluidity is not reached as it is, the soil water reducing agent of the present invention is added to the soil and stirred to sufficiently disperse the soil components, so that the desired water content can be obtained without further adding moisture. It may be possible to ensure liquidity.

[0039]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited thereto. In Examples and Comparative Examples, “%” refers to “% by weight” unless otherwise specified.
(% By mass) ".

First, the generated soil and soil used in the following Examples and Comparative Examples, and a method for evaluating the fluidity of the soil will be described.

As the generated soil, one having a water content of 48% generated by general civil engineering work in the Kanto region was used. The particle size composition of the generated soil was 20% for sand, 50% for silt, and 30% for clay. Then, 100 g of ordinary Portland cement (solidifying agent, hydraulic substance) is added to 1200 g of the generated soil, and the mixture is kneaded with a mortar mixer at low speed for 30 seconds to obtain a test soil (soil in the present invention). Was prepared.

To the test soil, water, a soil water reducing agent, and a comparative soil water reducing agent were added in accordance with the description of each Example / Comparative Example to impart fluidity. Was evaluated by its flow value (expanded). More specifically, a diameter of 55 mm placed on a horizontal table surface,
A hollow cylindrical container having a height of 50 mm is tightly packed with an object to be measured for flow value (soil provided with fluidity: fluidized soil), and then the container is vertically lifted to a height exceeding 50 mm. Then, the maximum diameter of the measurement object spread on the table surface was measured in two directions, and the average value was defined as a flow value (unit: mm). The higher the flow value, the higher the fluidity of the measurement object, and the flow value of 55 mm
This indicates that the measurement object has almost no fluidity.

As described above, the biodegradability of each of the polymers constituting the soil water reducer and the comparative soil water reducer was measured according to the modified MITI test (I) described in the OECD guidelines. Evaluated by biodegradation rate.

Example 1 First, a crude methyl glyoxylate polymer was added to 200 Torr (2.66 × 10 6
Distillation was performed under the conditions of ⁴ Pa) and 86 ° C. to obtain a methyl glyoxylate monomer (hereinafter, simply referred to as methyl glyoxylate), which was used in the following operations.

A glass reaction vessel equipped with a stirrer, thermometer, condenser and dropping funnel was charged with 500 m of methylene chloride.
1, 2.0 ml of water as a polymerization initiator, and 0.20 ml of triethylamine as a polymerization catalyst were supplied. The freshly distilled methyl glyoxylate 238
A mixture of 9 g and 500 ml of methylene chloride was dropped from the dropping funnel in two portions to obtain a reaction mixture. Each dropping operation takes 30 to 35 minutes, and the reaction temperature is controlled to a maximum of about 40 ° C., and there is a 90-minute waiting time between the two dropping operations to wait for the distillation of methyl glyoxylate. Was.

Subsequently, the reaction mixture was cooled to 25 ° C., and thereto was added dropwise 10 ml of a 25% hexane solution of diethylaluminum chloride, and the mixture was stirred for 15 minutes to be completely mixed and dissolved. Then, ethyl vinyl ether 90
g and 90 ml of methylene chloride were added dropwise over 35 minutes while maintaining the reaction temperature at about 30 ° C., and the mixture was further stirred for about 90 minutes while maintaining the reaction temperature.

Here, a mixture of 1.0 ml of methyl alcohol and 10 ml of methylene chloride was further added and stirred for 10 minutes. Next, a mixture of 30 g of ethyl vinyl ether and 30 ml of methylene chloride was added dropwise over 15 minutes, and stirring was continued for 15 minutes to obtain a solution of a stabilized ester polymer (a stabilized acetal ester polymer). Note that all of the above operations were performed under the replacement with clean nitrogen gas, that is, while preventing the invasion of air.

A glass reaction vessel equipped with two new dropping funnels, a stirrer, a thermometer and a distillate discharge port was prepared.
A 50% aqueous sodium hydroxide solution 3328 is added to the reaction vessel.
g. Next, after heating the aqueous sodium hydroxide solution to 45 ° C., a solution of the stabilized ester polymer (diluted with water to 3000 ml) and 5
2535 g of a 0% aqueous sodium hydroxide solution was dropped into the reaction vessel over 3 hours from separate dropping funnels to perform a saponification reaction of the stabilized ester polymer. The saponification reaction was carried out while maintaining the reaction temperature at a maximum of 60 ° C., and the methylene chloride was discharged out of the reaction vessel by boiling.

At the end of the saponification reaction of the stabilized ester polymer, the dropping funnel and the reaction vessel are washed with methylene chloride,
The reaction system (saponified phase) to which the washing liquid was added was stirred for 1 hour. Then, the solution containing the saponification reaction product is added for about 25 minutes.
C. and additional methyl alcohol was added to completely precipitate the product. Next, the saponification reaction product (solid product) is collected by centrifugation, washed with an equal volume mixture of methyl alcohol and water, and dried at 40 to 45 ° C. under atmospheric pressure to remove sodium polyglyoxylate. Obtained.

The obtained sodium polyglyoxylate had a weight average molecular weight of 16,000, a biodegradation rate of 62%, and an acid value per unit weight of 520 mg KOH / mg in an aqueous potassium hydroxide solution. Was. Sodium polyglyoxylate is equivalent to the `` acetal polymer having a carboxyl group-based substituent '' described in the embodiment, and is used as the soil water reducing agent according to the present invention. Was added.

More specifically, 100 g of ordinary Portland cement was added to 1200 g of the generated soil, and the 20% aqueous solution of the above sodium polyglyoxylate was added to the test soil obtained by kneading with a mortar mixer at low speed for 30 seconds. Was added thereto and kneaded with the mortar mixer at a high speed for 3 minutes to obtain a fluidized soil. That is,
The amount of sodium polyglyoxylate solids added to the generated soil is 0.3%. Then, the flow value was measured using the fluidized soil.

The acid value (unit: mgKOH / mg), the biodegradation rate (unit:%) of the sodium polyglyoxylate,
Moisture content (unit weight (mass)%) based on generated soil,
In addition, the measurement results of the flow values are summarized in Table 1 below.

Example 2 Poly (sodium L-aspartate) manufactured by Sigma, which is a "polyamide having a carboxyl group-based substituent" was used as a soil water reducing agent according to the present invention. The poly (sodium L-aspartate) had a weight-average molecular weight of 9,900, a biodegradability of 74%, and an acid value per unit weight of 398 mgKOH / mg in an aqueous potassium hydroxide solution. .

A fluidized soil was obtained according to the method described in Example 1 except that 18 g of a 20% aqueous solution of poly (sodium L-aspartate) was used instead of the aqueous solution of sodium polyglyoxylate. The flow value of the fluidized soil was measured. That is, the addition amount of the solid poly (sodium L-aspartate) to the generated soil is 0.3%.

The measurement results of the acid value, the biodegradation rate, the amount of water added to the generated soil, and the flow value of the poly (sodium L-aspartate) are summarized in Table 1 below.

[Comparative Example 1] Water was added to the above-mentioned test soil at a rate of 1
4.4 g was charged, and the mixture was kneaded with the above mortar mixer at high speed for 3 minutes to obtain a fluidized soil, and the flow value of the fluidized soil was measured. The measurement results of the amount of water added to the generated soil and the flow value are summarized in Table 1 below.

Comparative Example 2 Example 1 was repeated except that 18 g of a 20% aqueous solution of sodium polyacrylate (weight average molecular weight: 11,000), which was commercially available as a soil water reducing agent, was added to the test soil. The fluidized soil was obtained according to the method described in (1), and the flow value of the fluidized soil was measured.
That is, the addition amount of the sodium polyacrylate solid content to the generated soil is 0.3%.

Table 1 below shows the measurement results of the acid value, the biodegradation rate, the amount of water added to the generated soil, and the flow value of the sodium polyacrylate.

[0059]

[Table 1]

As apparent from Table 1, the fluidized soil of Comparative Example 1 has almost no fluidity. On the other hand, Comparative Example 1
In Examples 1 and 2 in which the same amount of water was added as in Comparative Example 1,
The flow value is greatly improved as compared with the result. That is, if the water reducing agent for soil according to the present invention is used, it is possible to give the soil a larger flow value (fluidity) by adding the same amount of water. In other words, it is possible to greatly reduce the amount of added water necessary for providing the soil with a desired flow value, as compared with the case where the soil water reducing agent is not used.

Although the fluidized soil of Comparative Example 2 was excellent in fluidity, the added sodium polyacrylate (conventional soil water reducing agent) had no biodegradability, There is a concern about the adverse effects of leakage to the surrounding environment.
On the other hand, it can be seen that the fluidized soils of Examples 1 and 2 are excellent in fluidity, and the added water reducing agents for soil are all excellent in biodegradability and have a small load on the environment.

[0062]

According to the soil water reducing agent of the present invention,
It is possible to reduce the amount of water added to impart predetermined fluidity to soil, or to reduce it to zero. In addition, since the polymer contained in the soil water reducing agent has biodegradability, even if the polymer leaks from the soil to the surrounding environment after the fluidity-imparting treatment, the polymer is a microorganism or the like. Therefore, it is easily decomposed and does not cause environmental pollution.

As a more specific advantage, 1) a large space (cultivation material) even when the soil is once cured at the site.
2) Fluidity-imparting treatment is possible even at sites where it is difficult to secure water. 3) Work time can be shortened. 4) Environmentally friendly soil generated with less impact on the environment. Can be reused and disposed of.

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Claims (3)

[Claims] 1. A water reducing agent for soil comprising a polymer having a carboxyl group-based substituent and having biodegradability. 2. The soil water reducing agent according to claim 1, wherein the polymer is an acetal polymer having a carboxyl group substituent. 3. The soil water reducing agent according to claim 1, wherein the polymer is a polyamide having a carboxyl group-based substituent.