JP7374926B2 - Ground injection material, its cured product, ground improvement method, and powder material for ground injection - Google Patents

Description

The present invention relates to a ground injection material, a cured product thereof, a ground improvement method, and a powder material for ground injection.

As a type of ground improvement method, a chemical injection method in which a hardening agent is injected into the ground is known. Additionally, various ground injection materials are known for use in this construction method.
Unlike the jet grouting method, which disturbs the ground using a high-pressure jet, the chemical injection method using ground injection materials has the advantages of being able to perform improvements without disturbing the ground as much as possible, and having compact equipment. has. Therefore, there are many achievements.

Up to now, various ground injection materials have been known. For example, a technique is known in which two specific liquids (one of which contains cement) are mixed to form a mixture, and the mixture is injected into the ground as a ground injection material.

As one example, Patent Document 1 describes a two-component type ground injection agent consisting of a rapidly hardened material slurry and a cement slurry. Here, the quick hardening agent slurry contains SiO ₂ and MgO as chemical components, the content molar ratio of Al ₂ O ₃ and MgO (Al ₂ O ₃ /MgO) is 17 to 60, and the content of SiO ₂ and MgO is 17 to 60. It contains calcium aluminate, gypsum, alkali metal carbonate, sodium aluminate, set retarder and water with a molar ratio (SiO ₂ /MgO) of 2.0 to 7.5. Further, the cement slurry contains cement and water.

As another example, Patent Document 2 describes that aqueous slurry A and aqueous slurry B are mixed to form a ground injection material. Here, the aqueous slurry A includes 100 parts by mass of calcium aluminate, 20 to 300 parts by mass of gypsum, and 0.5 to 15 parts by mass of one or more selected from the group of alkali metal carbonates, hydrogen carbonates, or sulfates. , 0.5 to 15 parts by weight of sodium aluminate, and 0.1 to 10 parts by weight of a setting retarder. Furthermore, aqueous slurry B contains 100 to 2200 parts by mass of cement per 100 parts by mass of calcium aluminate in aqueous slurry A.

Japanese Patent Application Publication No. 2017-154948 Japanese Patent Application Publication No. 2014-109012

In the "two-component type" ground injection material described in the above patent document, each component usually has sufficient fluidity before mixing the two components, but quickly hardens after the two components are mixed. It is designed with the intention of advancing.

However, according to the findings of the present inventors, when a ground injection material is conventionally designed with priority given to rapid hardening after mixing two liquids, as a trade-off, at least one of the two liquids is Pot life tended to be short. For example, in conventional two-part type ground injection materials, at least one of the two parts tends to gel or harden in a relatively short period of time before being mixed with the other part. .

Therefore, the present inventors set out to provide a new two-component type ground injection material that exhibits a soil improvement effect immediately after being poured into the ground, and which can ensure a sufficient pot life before being poured into the ground. As one of our objectives, we conducted various studies.

As a result of intensive studies, the present inventors completed the invention provided below and solved the above problems.

That is, according to the present invention,
Two liquids, including liquid A, which is a mixed slurry of powder material A containing calcium aluminate and carboxylic acid salt, and water, and liquid B, which is a mixed slurry of powder material B containing cement, and water. A type of ground injection material,
A ground injection material whose gel time measured by the following steps (1) to (5) when mixing the A liquid and the B liquid is 1 second or more and 30 seconds or less,
is provided.

[procedure]
(1) After mixing liquid A and liquid B to obtain a mixture, at least a portion of the obtained mixture is collected into a truncated conical paper cup placed on a horizontal surface. The amount to be collected should be 70% or less of the capacity of the paper cup. The paper cup used has a bottom inner diameter of 5.3 cm, a top inner diameter of 7.5 cm, and a height of 8.8 cm.
(2) After the operation in (1) above, hold the paper cup in a state where the line connecting the center of the bottom surface and the center of the top surface of the paper cup is inclined at 60 degrees with respect to the vertical plane, so that the interface between the mixture and the air is It is determined whether the interface is flowing and changing, or whether the interface is immobile.
(3) After confirming the above (2), place the paper cup on a horizontal surface again.
(4) Repeat (2) and (3) above until the interface becomes immobile in (2) above.
(5) The time required for the interface to reach an immobile state in (2) above is defined as gel time.

Further, according to the present invention,
A cured product obtained by mixing the A liquid and the B liquid in the ground injection material,
is provided.

Further, according to the present invention,
A ground improvement method for improving the ground using the cured product;
is provided.

Further, according to the present invention,
A powder material for ground injection, consisting of the powder material A and the powder material B;
is provided.

According to the present invention, there is provided a new two-component type ground injection material that exhibits a soil improvement effect immediately after being poured into the ground, and which can ensure a sufficient pot life before the ground injection.

Embodiments of the present invention will be described in detail below.
In this specification, unless otherwise specified, values that may vary depending on temperature conditions are assumed to be values under the condition of 20°C.

<Ground injection material>
The ground injection material of this embodiment is a mixed slurry of liquid A, which is a mixed slurry of powder material A containing calcium aluminate and carboxylic acid salt, and water, and a mixed slurry of powder material B, containing cement, and water. It is a two-component type product containing a certain B solution.

Solution A contains calcium aluminate and carboxylate. Further, the gel time when liquid A and liquid B are mixed is 1 second or more and 30 seconds or less. By injecting such a two-component type ground injection material into the ground, it is possible to immediately obtain a soil improvement effect immediately after the ground injection, and at the same time, it improves the usable life of liquid A before mixing with liquid B. can be done.
Even if liquid A contains calcium aluminate and carboxylate, if the gel time is less than 1 second, it will hinder the actual ground injection work. Moreover, if the gel time is more than 30 seconds, it becomes difficult to obtain an early ground improvement effect as a ground injection material.
Further, even if the gel time is 1 second or more and 30 seconds or less, for example, if the A liquid does not contain a carboxylate salt, the pot life of the A liquid tends to be short, which is not desirable in practice.
As described above, the ground injection material of this embodiment is a two-liquid system containing specific liquids A and B, and has an excellent gel time when mixed with liquids A and B. It has the following effects.

The present inventors have found that, in particular, as a carboxylate salt, a salt of a carboxylic acid having a relatively small number of carbon atoms (such as a metal salt), which will be described later, may be included in the A liquid, and that the carboxylic acid in the A liquid may be By appropriately adjusting the amount of salt, it is easy to design the gel time after mixing liquids A and B to 30 seconds or less. As a result, the usable life of liquid A can be easily extended. Furthermore, although it is not an essential component, by adding an appropriate amount of alum to the B solution, it is easy to design the gel time after mixing the A and B solutions to an appropriate value.

(gel time)
The gel time in the ground injection material of this embodiment refers to the time when when liquid A and liquid B are mixed to form a mixture, the mixture thickens significantly and becomes difficult to flow starting from the start of mixing (t=0). It means the time it takes to become

Specifically, gel time is determined based on the following procedure.
[procedure]
(1) After mixing liquid A and liquid B to obtain a mixture, at least a portion of the obtained mixture is collected into a truncated conical paper cup placed on a horizontal surface. The amount to be collected should be 70% or less of the capacity of the paper cup. The paper cup used has a bottom inner diameter of 5.3 cm, a top inner diameter of 7.5 cm, and a height of 8.8 cm.
(2) After the operation in (1) above, hold the paper cup in a state where the line connecting the center of the bottom and the center of the top surface of the paper cup is inclined at 60 degrees with respect to the vertical plane, so that the interface between the mixture and the air flows. Determine whether the interface changes or the interface remains unchanged.
(3) After confirming the above (2), place the paper cup on a horizontal surface again.
(4) Repeat (2) and (3) above until the interface becomes immobile in (2) above.
(5) The gel time is the time from the start of mixing of liquids A and B in (1) above until the interface reaches a state of immobility in (2) above.

In addition, in the above (1), the mixing ratio of liquid A and liquid B is usually set to equal volumes of 500 mL each.
In addition, in order to measure the gel time more accurately, for example, (i) conduct a preliminary experiment to understand the approximate gel time and then perform the main test, (ii) measure using only one paper cup. Instead, the mixture may be sampled in multiple paper cups in (1) above, and a new paper cup containing the mixture may be tilted every second.

The gel time is 1 second or more and 30 seconds or less, preferably 3 seconds or more and 20 seconds or less. By keeping the gel time appropriately short, it is possible to better improve the soft and easily deformed ground. In addition, since the gel time is appropriately long, there is more work time when injecting the mixture of liquids A and B into the ground, making it easier to perform soil improvement work.

The ground injection material of this embodiment tends to have a high gel strength and initial strength after mixing the A liquid and the B liquid. Here, high gel strength means that even when the mixture obtained by mixing liquids A and B has not yet sufficiently hardened and still has fluidity, it is less deformed by external forces and This means that it can adequately counter the
In particular, ground injection materials with high gel strength and high initial strength can be preferably used, for example, for improving soft ground that contains a lot of water.

(Powder material A, liquid A)
As mentioned above, powder material A includes calcium aluminate and carboxylate. Powder material A preferably further contains gypsum, a setting modifier, and the like. In addition, liquid A is a slurry obtained by mixing this powder material A with water.
The components constituting powder material A or A liquid, the properties of A liquid, etc. will be explained below.

・Carboxylate A carboxylate is a compound in which the proton of the carboxy group of a carboxylic acid is replaced with a cation. In other words, a carboxylic acid salt can be obtained, for example, by preparing a carboxylic acid as a starting material and reacting it with an appropriate basic substance (neutralization reaction).

In this embodiment, the "carboxylic acid" in the carboxylic acid salt (in other words, the carboxylic acid as the above-mentioned "starting material") preferably has a relatively small number of carbon atoms. The present inventors have found that when the number of carbon atoms in the carboxylic acid in the carboxylic acid salt is relatively small, it is easier to lengthen the pot life of the A liquid, and the curing progress after mixing the A liquid and the B liquid is further inhibited. Easy to hurry.
Specifically, the carboxylic acid salt is preferably a salt of a carboxylic acid having 10 or less carbon atoms, that is, a compound in which the proton of the carboxy group of the carboxylic acid having 10 or less carbon atoms is substituted with a cation. The number of carbon atoms here is more preferably 1 or more and 10 or less, still more preferably 1 or more and 8 or less, particularly preferably 1 or more and 5 or less, particularly preferably 1 or more and 3 or less, and most preferably 1 or 2.

The "carboxylic acid" in the carboxylic acid salt may be a monocarboxylic acid or a polycarboxylic acid (eg, dicarboxylic acid or tricarboxylic acid). From the viewpoint of cost etc., monocarboxylic acids are preferred.

Examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, lauric acid, palmitic acid, stearic acid, oxalic acid, succinic acid, adipic acid, hydroxycarboxylic acid (carboxylic acid having a hydroxyl group), etc. I can do it.
Among these, formic acid or acetic acid is preferable as the carboxylic acid in view of availability, cost, effectiveness, and the like. That is, the carboxylic acid "salt" preferably includes an acetate and/or a formate.
In addition, in terms of obtaining a more remarkable effect, it is preferable that the carboxylic acid is not a hydroxycarboxylic acid (carboxylic acid having a hydroxy group).

Preferably, the carboxylic acid salt includes a carboxylic acid metal salt. Specifically, the carboxylic acid salt can be a lithium, sodium, potassium, magnesium, calcium, barium, or the like carboxylic acid salt.
More preferably, the carboxylic acid salt includes a carboxylic acid calcium salt.

The amount of carboxylic acid salt in powder material A may be adjusted as appropriate in consideration of the balance such as the desired pot life of liquid A and the speed of curing after mixing with liquid B.
The amount of carboxylate in powder material A is, for example, 0.01% by mass or more and 3% by mass or less, preferably 0.03% by mass or more and 2% by mass or less, more preferably 0.05% by mass or more and 1% by mass. It is as follows.

In powder material A, the amount of carboxylate relative to calcium aluminate is preferably 0.1 parts by mass or more and 50 parts by mass or less, more preferably 0.1 parts by mass or more and 25 parts by mass, based on 100 parts by mass of calcium aluminate. part or less, more preferably 0.15 parts by mass or more and 10 parts by mass or less.
By appropriately adjusting the amount of carboxylic acid salt, it is possible to achieve a better balance between the pot life of liquid A before mixing with liquid B and the speed of curing after mixing with liquid B. can.

Powder material A may contain only one type of carboxylic acid salt, or may contain two or more types of carboxylate. In the latter case, it is preferable that the total amount of all carboxylic acid salts is within the above numerical range.

・Calcium aluminate Calcium aluminate, in the technical field of hydraulic materials, is a general term for substances that contain aluminum oxide (Al ₂ O ₃ ) and calcium oxide (CaO) as main components and have hydration activity. . Here, "main component" means that the total content of aluminum oxide and calcium oxide in the entire calcium aluminate is, for example, 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more. means.

Calcium aluminate is typically produced by mixing aluminum oxide (Al ₂ O ₃ ), calcium oxide (CaO), and in some cases silica (SiO ₂ ) to form a mixture, and then firing and/or melting the mixture. It can be obtained by cooling it.
A rotary kiln, an electric furnace, or the like can be used for firing/melting.
Examples of the CaO raw material include calcium carbonate such as limestone and shells, calcium hydroxide such as slaked lime, and calcium oxide such as quicklime.
Examples of the Al ₂ O ₃ raw material include bauxite, an industrial byproduct called aluminum residual ash, and aluminum powder.

Both crystalline and amorphous calcium aluminates can be used. From the viewpoint of further enhancing the curability after mixing the A liquid with the B liquid, an amorphous material, for example, an amorphous calcium aluminate produced by rapidly cooling after melting is preferable.

The CaO/Al ₂ O ₃ molar ratio in the calcium aluminate is preferably 1.0 or more and 3.0 or less, more preferably 1.7 or more and 2.5 or less. By appropriately adjusting this molar ratio, it is possible to further accelerate the curing after mixing liquid A with liquid B, and it is also possible to obtain the soil improvement effect at an early stage.

The content of impurities (components other than CaO and Al ₂ O ₃ ) in the calcium aluminate is preferably 15% by mass or less, more preferably 10% by mass or less. When the impurity content is 15% by mass or less, the curing after mixing the liquid A with the liquid B can be further accelerated, and the soil improvement effect can be obtained more quickly.
Here, typical impurities include silicon oxide, magnesium oxide, sulfur oxide, and the like. In addition, organic substances, alkali metal oxides, alkaline earth metal oxides, titanium oxide, iron oxide, alkali metal halides, alkaline earth metal halides, alkali metal sulfates, and these are some of CaO and Al ₂ O ₃ Substituted or solid-dissolved substances are also included as impurities. Of course, impurities are not limited to these.

The vitrification rate of calcium aluminate is preferably 70% or more, more preferably 90% or more in terms of reaction activity. By setting this value appropriately, it is easier to obtain the ground improvement effect earlier.
The vitrification rate is determined by measuring the main peak area S of the crystalline mineral in advance for the measurement sample by powder X-ray diffraction method, then heating it at 1000°C for 2 hours, and then slowly cooling it at a cooling rate of (1 to 10°C)/min. Then, the main peak area S ₀ of the crystalline mineral after heating is determined by powder X-ray diffraction method, and using these values of S ₀ and S, the vitrification rate χ is calculated using the following formula.
Vitrification rate χ (%) = 100 x (1-S/S ₀ )

The particle size of the calcium aluminate is preferably a Blaine specific surface area value of 3000 cm ² /g or more, more preferably 5000 cm ² /g or more in terms of initial strength development. The upper limit is, for example, 9000 cm ² /g or less. By appropriately increasing this value, it is possible to further accelerate the curing after mixing liquid A with liquid B, and it is easier to obtain the soil improvement effect earlier. Furthermore, by appropriately reducing this value, the usable life of liquid A can be further extended.

A specific example of calcium aluminate is alumina cement. That is, commercially available alumina cement or the like may be used as a calcium aluminate raw material for producing liquid A.
Specific examples of alumina cement include alumina cement No. 1, alumina cement No. 2, and the like. These can be purchased from Denka Co., Ltd. and AGC Co., Ltd.

Powder material A may contain only one type of calcium aluminate, or may contain two or more types of calcium aluminate having different properties/physical properties.
The amount of calcium aluminate in powder material A is, for example, 10% by mass or more and 80% by mass or less, preferably 20% by mass or more and 75% by mass or less, more preferably 25% by mass or more and 70% by mass or less. By appropriately adjusting the amount of calcium aluminate, it is possible to achieve a better balance between the pot life of liquid A before mixing with liquid B and the speed of curing after mixing with liquid B. In addition, it is easier to obtain early ground improvement effects.

- Gypsum The powder material A preferably further contains gypsum. By including gypsum, it is easy to design a longer pot life for liquid A before mixing with liquid B.

There are no particular limitations on the type of plaster that can be used. Furthermore, it is not excluded to use different types of plaster together.
Examples of gypsum include gypsum hemihydrate and gypsum anhydrite. Anhydrite is preferred in terms of strength development. More specific examples of anhydrite include hydrofluoric acid by-product anhydrite and natural anhydrite.
Regarding the pH when gypsum is immersed in water, it is preferably a weakly alkaline to acidic pH of 8 or less. When this pH is appropriately low, the solubility of the gypsum component can be lowered, and the initial strength development can be further improved. Note that the pH here is the pH of a diluted slurry of gypsum/ion-exchanged water=1 g/100 g at 20° C., measured using an ion-exchange electrode or the like. The pH is more preferably 3 or more and 8 or less, and even more preferably 5 or more and 7 or less.

The particle size of the gypsum is preferably 3000 cm ² /g or more in Blaine specific surface area value, and 5000 cm ² /g or more from the viewpoint of initial strength development after mixing liquids A and B and a longer pot life of liquid A. More preferred. Moreover, from the viewpoint of a longer pot life, this value is preferably 30,000 cm ² /g or less, more preferably 20,000 cm ² /g or less.

The amount of gypsum in powder material A is 10% by mass or more and 80% by mass or less, preferably 20% by mass or more and 75% by mass or less, more preferably 25% by mass or more and 70% by mass or less.
As another point of view, the amount of gypsum relative to calcium aluminate in powder material A is preferably 50 parts by mass or more and 250 parts by mass or less, more preferably 70 parts by mass or more and 200 parts by mass, based on 100 parts by mass of calcium aluminate. It is as follows.
By appropriately increasing the amount of gypsum, a longer pot life of liquid A can be obtained. Moreover, by appropriately reducing the amount of gypsum, the initial strength of the cured product obtained by mixing liquid A and liquid B can be increased. In other words, it is easier to obtain the ground improvement effect earlier.

・Coagulation regulator
Powder material A and/or liquid A may contain a coagulation modifier for the purpose of adjusting the pot life of liquid A, adjusting the curability when mixed with liquid B, and the like.
In particular, the setting regulator may be included in the powder material A in advance, or may be prepared separately from the powder material A and added when preparing the A liquid.

As coagulation modifiers, aluminates such as sodium aluminate and potassium aluminate, carbonates such as sodium carbonate and potassium carbonate, hydroxides such as sodium hydroxide and potassium hydroxide, aluminum sulfate, iron (III) sulfate, etc. , silicates such as sodium silicate and potassium silicate, phosphates such as sodium phosphate, calcium phosphate, and magnesium phosphate, inorganic salts such as borates such as lithium borate and sodium borate, and sugars. It will be done.

As the setting modifier, commercially available products may be used. Examples of commercially available products include Denka Setter D-100 and D-300 manufactured by Denka Corporation.

When the powder material A and/or the A liquid contains a setting modifier, the amount thereof may be adjusted as appropriate based on the desired pot life of the A liquid, the curability after mixing with the B liquid, and the like.
Specifically, the amount of the setting modifier is, for example, 0.01% by mass or more and 2% by mass or less, preferably 0.03% by mass or more and 1.5% by mass or less, based on all components other than water of liquid A. It is preferably used in an amount of 0.05% by mass or more and 1% by mass or less. That is, when a setting modifier is included in the powder material A in advance, the amount of the setting modifier relative to the entire powder material A is preferably within the above range. In addition, when preparing a setting modifier separately from powder material A, it is preferable that the amount of the setting modifier in the entire powder material A and the setting modifier be about the above level.

- Water As mentioned above, liquid A is a slurry of powder material A mixed with water. In addition, it is considered that at least a part of the carboxylic acid salt in liquid A is dissolved in water.
The amount of water when mixing powder material A with water to form liquid A may be adjusted as appropriate depending on desired fluidity, pumpability, injectability into the ground, etc. The amount of water can be adjusted to be, for example, 50% by mass or more and 95% by mass or less, preferably 60% by mass or more and 90% by mass or less, based on the entire A liquid.

・Pot life/solid content of liquid A As mentioned above, before mixing liquid A with liquid B, liquid A has a relatively long pot life (ensure sufficient pot life before pouring into the ground). can). Although the A liquid contains hydraulic calcium aluminate, by using it together with the carboxylate, the A liquid itself is difficult to generate solid content.

Here, the long pot life of liquid A, specifically the fact that it is difficult to generate solid content, means that when mixing powder material A and water to obtain liquid A, The liquid A, which has been left for a certain period of time with the start of mixing with water as 0 minutes, is passed through a sieve with an opening of 4.0 mm, and evaluation can be made by determining whether there is any solid content that cannot pass through the sieve.
Specifically, when mixing powder material A and water to obtain liquid A, the mesh opening is set to 4.0, preferably 30 minutes, more preferably 45 minutes, and still more preferably 60 minutes after mixing. The sieve residue through a 0 mm sieve is 0.1% by mass or less based on the total amount of powder material A.

In addition, when evaluating the pot life of the entire liquid A containing water in the evaluation using the above-mentioned sieve, the mixing ratio of the powder material A and water can be set arbitrarily. That is, it is possible to prepare liquid A by mixing powder material and water at the mixing ratio used during actual ground injection, and evaluate the pot life of liquid A as described above.
On the other hand, for example, if you want to evaluate the length of pot life when mixed with water as a property of powder material A itself, more specifically, which of powder materials A1 and A2 with different compositions is longer? If you want to evaluate whether it has a visible time based on a uniform standard, the amount of water is, for example, 50% by mass or more and 95% by mass or less, preferably 60% by mass or more and 90% by mass or less in the entire A liquid. The pot life of the liquid A obtained by mixing as described above can be evaluated as described above. Alternatively, if the powder material is commercially available and a recommended mixing ratio with water is indicated, the amount of water may be adjusted accordingly.

-Production method of liquid A The method for producing liquid A is not particularly limited. It may be prepared by adding powder material A to water and mixing.
For production stability and prevention of unintentional coagulation or gelation, if part A contains a coagulation modifier, first add the coagulation modifier to the water, then add other ingredients to the water. It is preferable to obtain liquid A in this order.
For mixing, various mixers and the like known in the technical field can be used.

(Powder material B, B liquid)
Powder material B contains cement, as described above. Powder material B may preferably further contain alum or the like. In addition, liquid B is a slurry obtained by mixing this powder material B with water.
Liquid B usually exists in a state where it is not in contact with or mixed with liquid A until immediately before use.
The components constituting powder material B or liquid B will be explained below.

- Cement The cement that can be used is not particularly limited. Specifically, various types of Portland cement such as normal, early-strength, ultra-early-strength, low-heat or medium-heat, various mixed cements made by mixing these cements with blast furnace slag, fly ash, silica fume, etc., blast furnace cement, and municipal waste incineration. Examples include environmentally friendly cement (ecocement) manufactured using ash and sewage sludge incineration ash, and commercially available fine particle cement (alumina cement, which means calcium aluminate, is preferably used here). (excluded from cement).

Various cements and various mixed cements may be used after being pulverized. Further, cements prepared by increasing or decreasing the amount of components (eg, gypsum, etc.) normally used in cement can also be used.
Cement may be used alone or in combination of two or more types. Among these, blast furnace cement is preferred because it has a low hexavalent chromium content.

- Alum Powder material B or liquid B preferably contains alum. As the present inventors have found, when powder material B or B liquid contains alum, the curing after mixing of A liquid and B liquid can be accelerated. In addition, the soil improvement effect can be obtained more quickly.

Alum that can be used is not particularly limited. Examples include various alums such as potassium alum, chromium alum, and iron alum.
Alum stone can also be mentioned. Here, alumite is a natural product having a component range of [(K, Na) (Al, Fe) ₃ (SO ₄ ) ₂ (OH) ₆ ]. Furthermore, it is also possible to use raw alum stone powder obtained by pulverizing alum stone, and calcined alum stone powder obtained by calcining alum stone at a temperature of 800° C. or lower and pulverizing it.
As the alum, it is preferable to use commercially available potassium alum or calcined alumite powder. Additionally, some alums contain anhydrous salt or crystallized water, and any of them can be used as is.

The amount of alum in powder material B or liquid B is, for example, 0.3 parts by mass or more and 10 parts by mass or less, preferably 0.5 parts by mass or more and 5 parts by mass or less, based on 100 parts by mass of cement. By using a suitably large amount of alum, the curing after mixing of liquids A and B can be accelerated. Furthermore, by using a suitably small amount of alum, it is possible to suppress unintended changes in the B liquid over time (for example, a decrease in fluidity or hardening before mixing with the A liquid).

-Production method of liquid B/water, water content Liquid B can be obtained by mixing powder material B with water (kneading powder material B with water). When using alum, alum may be included in powder material B in advance, or alum may be added as a separate material from powder material B when preparing liquid B.
For mixing, various mixers and the like known in the technical field can be used.

The amount of water may be adjusted as appropriate depending on the type of cement in the powder material B, hardenability of the cement, desired hardness, pumpability, injectability into the ground, etc. As an example, the amount of water is, for example, about 100 parts by mass to 500 parts by mass, preferably about 100 parts by mass to 300 parts by mass, based on 100 parts by mass of powder material B.

It should be noted that the powder material B or liquid B may contain other components other than cement, water, and alum as long as the effects of the invention are not excessively diminished. Examples of "other components" include carbonates, heavy metal carbonates, calcium hydroxide, magnesium hydroxide, alkali hydroxides, sulfates, and sulfites.
However, powder material B or liquid B preferably does not contain carboxylate or calcium aluminate.

<Cured product, ground improvement method>
A cured product can be obtained by mixing the above-mentioned liquid A and the above-mentioned liquid B. In addition, the hardened material can improve the ground.

The method of mixing liquids A and B and the specific procedure for improving the ground with liquids A and B are not particularly limited, and various methods known in the technical field of ground improvement can be applied.
For example, (i) the so-called two-shot method in which liquids A and B are mixed at the tip using a double pipe and injected into the ground, (ii) liquids A and B are transferred from an injection pump to an injection pipe. A so-called 1.5-shot method in which the liquids are mixed and poured during the injection, and (iii) a one-shot method in which liquids A and B are mixed in a mixing tank such as a mixer, etc. can be adopted. When implementing these methods, a known injection pump or the like can be used.

In other words, (1) Liquids A and B may be mixed together to form a mixture before injection into the ground, and the mixture may be injected into the ground, or (2) Liquids A and B may be pumped separately. , the two may be mixed in the ground at the moment of injection into the ground or after injection into the ground.

The mixing ratio of liquid A and liquid B may be adjusted as appropriate depending on the desired speed of curing, pumpability, etc. The mixing ratio of liquid A: liquid B is typically about 20:80 to 80:20, preferably about 30:70 to 70:30, by volume.

Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and the present invention includes modifications, improvements, etc. within a range that can achieve the purpose of the present invention.
Reference embodiments of the present invention are additionally described below.
1.
Two liquids, including liquid A, which is a mixed slurry of powder material A containing calcium aluminate and carboxylic acid salt, and water, and liquid B, which is a mixed slurry of powder material B containing cement, and water. A type of ground injection material,
A ground injection material having a gel time of 1 second or more and 30 seconds or less as measured by the following steps (1) to (5) when the liquid A and the liquid B are mixed.
[procedure]
(1) After mixing liquid A and liquid B to obtain a mixture, at least a portion of the obtained mixture is collected into a truncated conical paper cup placed on a horizontal surface. The amount to be collected should be 70% or less of the capacity of the paper cup. The paper cup used has a bottom inner diameter of 5.3 cm, a top inner diameter of 7.5 cm, and a height of 8.8 cm.
(2) After the operation in (1) above, hold the paper cup in a state where the line connecting the center of the bottom surface and the center of the top surface of the paper cup is inclined at 60 degrees with respect to the vertical plane, so that the interface between the mixture and the air is It is determined whether the interface is flowing and changing, or whether the interface is immobile.
(3) After confirming the above (2), place the paper cup on a horizontal surface again.
(4) Repeat (2) and (3) above until the interface becomes immobile in (2) above.
(5) The gel time is the time from the start of mixing of liquids A and B in (1) above until the interface reaches a state of immobility in (2) above.
2.
1. The ground injection material described in
When mixing the powder material A and water to obtain the liquid A, the sieve residue through a sieve with a mesh opening of 4.0 mm after 30 minutes has passed after mixing the powder material A and water is as follows. A ground injection material that is 0.1% by mass or less based on the total amount of powder material A.
3.
1. or 2. The ground injection material described in
A ground injection material in which the CaO/Al ₂ O ₃ molar ratio in the calcium aluminate is 1.0 or more and 3.0 or less.
4.
1. From 3. The ground injection material according to any one of
A ground injection material in which the powder material A further contains gypsum.
5.
1. From 4. The ground injection material according to any one of
A ground injection material in which the liquid A further contains a coagulation regulator.
6.
1. From 5. The ground injection material according to any one of
A ground injection material in which the powder material B further contains alum.
7.
1. From 6. The ground injection material according to any one of
A ground injection material in which the carboxylic acid salt includes a carboxylic acid metal salt.
8.
1. From 7. The ground injection material according to any one of
A ground injection material in which the carboxylic acid salt includes a carboxylic acid calcium salt.
9.
1. From 8. The ground injection material according to any one of
A ground injection material in which the carboxylic acid salt includes a salt of a carboxylic acid having 1 or more and 5 or less carbon atoms.
10.
1. From 9. The ground injection material according to any one of
A ground injection material in which the carboxylate salt contains at least one compound selected from the group consisting of acetates and formates.
11.
1. From 10. The ground injection material according to any one of
A ground injection material in which the amount of the carboxylate salt in the A liquid is 0.1 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the calcium aluminate.
12.
1. From 11. A cured product obtained by mixing the A liquid and the B liquid in the ground injection material according to any one of the above.
13.
12. A ground improvement method for improving the ground using the hardened material described in .
14.
1. From 13. A powder material for ground injection consisting of powder material A and powder material B in any one of the above.

Embodiments of the present invention will be described in detail based on Examples and Comparative Examples. Note that the present invention is not limited to the examples.

<Examples 1-1 to 1-4 and Comparative Example 1>
(Preparation of powder material A and liquid A)
First, each component shown in the "Powder material A" column of Table 1 below was mixed using a Proshare mixer (WB type, manufactured by Taiheiyo Kiko Co., Ltd.) to prepare powder material A. .
Thereafter, a setting modifier (manufactured by Denka Corporation, Denka Setter D-100) and the above powder material A were added in this order into water and thoroughly kneaded to obtain a liquid A.
The amounts of each component in Solution A are as listed in Table 1.

(Preparation of powder material B and liquid B)
Each component shown in the "Liquid B" column of Table 1 below was mixed in the amounts shown in Table 1 to obtain Solution B.

(Measurement of gel time after mixing liquid A and liquid B)
It was measured using the following procedure.
(1) A mixture was obtained by mixing equal amounts of liquid A and liquid B, each having a volume of 500 mL. Thereafter, 60 mL of the resulting mixture was collected into a frustum-shaped paper cup placed on a horizontal surface. The paper cup used had a bottom inner diameter of 5.3 cm, a top inner diameter of 7.5 cm, and a height of 8.8 cm.
(2) After the operation in (1) above, hold the paper cup in a state where the line connecting the center of the bottom and the center of the top surface of the paper cup is inclined at 60 degrees with respect to the vertical plane, so that the interface between the mixture and the air flows. It was determined whether the interface changes or the interface remains unchanged.
(3) After confirming the above (2), the paper cup was placed on a horizontal surface again.
(4) The above (2) and (3) were repeated until the interface became immobile in the above (2).
(5) Starting from the start of mixing of liquids A and B in (1) above, the gel time was defined as the time until the interface reached the immobile state in (2) above.

(Evaluation of pot life of liquid A)
Solution A was left for 30 minutes after preparation, starting from the time when powder material A was added to water (0 minutes). Thereafter, the liquid A was passed through a sieve with an opening of 4.0 mm, and the amount of solid content (coarse particles) that could not pass through the sieve was determined.
Based on the total amount of powder material A, if the amount of solids that cannot pass through the sieve is 0.1% by mass or less, there is no sieve residue, otherwise there is sieve residue. And so.

(gel strength)
The cement composition immediately after mixing liquids A and B was poured into a mold measuring 4 cm long x 4 cm wide x 16 cm high. Then, the strength was measured by touch at a stage where curing had not yet progressed sufficiently. Then, evaluation was made on the following four levels.
◎ (Excellent): The shape did not collapse even when the mold was removed, and the cement composition did not become dented even when pressed with a finger.
○ (Good): The shape did not collapse even when the mold was removed, but when the cement composition was pressed with a finger, it was slightly depressed.
Δ (Acceptable): The shape did not collapse even when the mold was removed, but the cement composition was dented when pressed with a finger.
× (unacceptable): The shape would collapse when the mold was removed.

(Initial strength)
The strength was measured according to JIS R 5201. Specifically, a test specimen measuring 4 cm in length x 4 cm in width x 16 cm in height was prepared using the composition of liquids A and B, and 30 minutes, 1 hour, and 1 hour after mixing liquids A and B were prepared. The compressive strength after 1 day was measured.

The compositions of liquid A and powder material A, liquid B and powder material B, the above measurement/evaluation results, etc. are summarized in Tables 1 and 2.

In the above table, calcium aluminate has a CaO/Al ₂ O ₃ molar ratio of calcium carbonate and aluminum oxide of 2.2, silica is added, and is melted at 1650°C and rapidly cooled to achieve a vitrification rate of 97%. The material used was pulverized to a Blaine specific surface area value of 5000 cm ² /g.
Furthermore, as the gypsum, natural anhydrite with a Blaine specific surface area value of 5000 cm ² /g was used.
Further, as the Portland cement, ordinary Portland cement (manufactured by Denka Corporation) was used.

As shown in Table 2, no solid content was observed 30 minutes after the preparation of liquid A. That is, the pot life of liquid A was long. Incidentally, when we continued to observe the formation of solids (components that cannot pass through the sieve) even after 30 minutes from preparation, we observed that a certain amount of solids had been formed only after about 130 minutes.
That is, among the ground injection materials of this embodiment, it was shown that especially liquid A had a long pot life before being mixed with liquid B.

In addition, as shown in Table 2, a ground injection material that contains two specific liquids, liquid A and liquid B, and whose gel time after mixing liquid A and liquid B is 1 second or more and 30 seconds or less, has a gel strength. The results were good, and the initial strength (for example, 1-day strength) was sufficiently high. In other words, it was confirmed that the material exhibited favorable performance as a ground injection material.

<Examples 2-1 to 2-10, Comparative Example 2>
Additional examples further demonstrate the utility of the ground injection material of this embodiment.

(Preparation of powder material A and liquid A)
First, each component shown in the "Powder material A" column of Table 3 below was mixed using a Proshare mixer (WB type, manufactured by Taiheiyo Kiko Co., Ltd.) to obtain a mixture.
Thereafter, a setting modifier (manufactured by Denka Corporation, Denka Setter D-100) and the above powder material A were added in this order into water and thoroughly kneaded to obtain a liquid A.
The amounts of each component in Solution A are as listed in Table 3.

(Preparation of powder material B and liquid B)
Each component shown in the "Liquid B" column of Table 3 below was mixed in the amount shown in Table 2 to obtain Solution B.

(Measurement of gel time after mixing liquid A and liquid B) and (evaluation of pot life of liquid A)
It was measured in the same manner as in Example 1-1.

The above is summarized in Table 3.
Note that in Table 3, calcium aluminate, gypsum, and Portland cement are the same as those in Table 1.
As shown in Table 3, in Examples 2-1 to 2-10, the pot life of liquid A was good.

The gel strength and initial strength of the ground injection materials of Examples 2-1 to 2-10 were also evaluated. The results were as good as Examples 1-1 to 1-4.

This application claims priority based on Japanese Patent Application No. 2018-231152 filed on December 10, 2018, and the entire disclosure thereof is incorporated herein.

Claims (9)

Two liquids, including liquid A, which is a mixed slurry of powder material A containing calcium aluminate and carboxylic acid salt, and water, and liquid B, which is a mixed slurry of powder material B containing cement, and water. A type of ground injection material,
The carboxylate salt contains at least one compound selected from the group consisting of acetate and formate,
A ground injection material having a gel time of 1 second or more and 30 seconds or less as measured by the following steps (1) to (5) when the liquid A and the liquid B are mixed.
[procedure]
(1) After obtaining a mixture by mixing 500 mL each of liquid A and liquid B, at least a portion of the obtained mixture is collected into a truncated cone-shaped paper cup placed on a horizontal surface. The amount to be collected should be 70% or less of the capacity of the paper cup. The paper cup used has a bottom inner diameter of 5.3 cm, a top inner diameter of 7.5 cm, and a height of 8.8 cm.
(2) After the operation in (1) above, hold the paper cup in a state where the line connecting the center of the bottom surface and the center of the top surface of the paper cup is inclined at 60 degrees with respect to the vertical plane, so that the interface between the mixture and the air is It is determined whether the interface is flowing and changing, or whether the interface is immobile.
(3) After confirming the above (2), place the paper cup on a horizontal surface again.
(4) Repeat (2) and (3) above until the interface becomes immobile in (2) above.
(5) The gel time is the time from the start of mixing of liquids A and B in (1) above until the interface reaches a state of immobility in (2) above. The ground injection material according to claim 1,
When mixing the powder material A and water to obtain the liquid A, the sieve residue through a sieve with a mesh opening of 4.0 mm after 30 minutes has passed after mixing the powder material A and water is as follows. A ground injection material that is 0.1% by mass or less based on the total amount of powder material A. The ground injection material according to claim 1 or 2,
A ground injection material in which the CaO/Al ₂ O ₃ molar ratio in the calcium aluminate is 1.0 or more and 3.0 or less. The ground injection material according to any one of claims 1 to 3,
A ground injection material in which the powder material A further contains gypsum. The ground injection material according to any one of claims 1 to 4,
A ground injection material in which the liquid A further contains a coagulation regulator. The ground injection material according to any one of claims 1 to 5,
A ground injection material in which the powder material B further contains alum. The ground injection material according to any one of claims 1 to 6,
A ground injection material in which the carboxylic acid salt includes a carboxylic acid metal salt. The ground injection material according to any one of claims 1 to 7,
A ground injection material in which the carboxylic acid salt includes a carboxylic acid calcium salt. The ground injection material according to any one of claims 1 to 8 ,
A ground injection material in which the amount of the carboxylate salt in the liquid A is 0.1 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the calcium aluminate.