JP7680817B2 - Plastic grout material and construction method using same - Google Patents

Description

The present invention relates to a plastic grout material suitable for underwater application and a method for injecting such a grout material into an underwater application area.

The term "plasticity" in the plastic grout material means the property of exhibiting fluidity when a shear force is applied, and not exhibiting fluidity unless a shear force is applied.
The plastic grout material is considered to correspond to Bingham fluid in terms of rheological properties, and has non-segregation properties underwater and low shrinkage properties. The plastic grout material is used, for example, as an injection material to be injected into voids, joints, cracks in the ground or structures, or gaps between the ground and structures, or as a filling material in the back cavity of the tunnel lining of an existing tunnel (see, for example, Patent Document 1).
Plastic grout materials are sometimes used to fill gaps between boulders such as rubble mounds constructed as foundations for revetments, for example, to improve a limited area of a rubble mound for seismic reinforcement of revetments.

When filling the gaps between boulders with plastic grout material, it is ideal for the plastic grout material to spread concentrically (or spherically) from the outlet of the injection pipe to fill the gaps. By spreading the grout material concentrically (or spherically) from the outlet of the injection pipe to fill the gaps, it becomes possible to, for example, limit the filling to the improvement range required for seismic reinforcement, and prevent the filling of unnecessary areas (outside the improvement range required).

When filling the gaps between boulders underwater, if a grout material that spreads concentrically (or spherically) from the discharge port is used, a weak defective part 3 may occur in the lower region 2 of the improved body generally indicated by reference number 1 in Figure 1.

The applicant has conducted various researches and experiments on the cause of the defective portion 3.
When filling gaps between boulders underwater, as the grout material spreads concentrically from the discharge outlet, if some of the grout material spreading downward is pushed through a relatively narrow gap into a wider gap, the pressure of the water between the boulders acts to tear off some of the pushed-out grout material, causing that part to break off under its own weight and fall downward.
Some of the fallen grout material absorbs and contains (mixes with) the water present between the gravel, improving its fluidity and making it easier to move downward by gravity, and then moves further downward (falls). Therefore, it is presumed that the lower region 2 of the improved body 1 contains a lot of torn, water-rich, and highly fluid grout material, resulting in defective parts 3. This highly fluid grout material contains a lot of water, so its strength decreases, and it may not be possible to obtain the required strength.
In other words, the reason why defective parts 3 occur is that, for example, part of the grout material present in the relatively large gaps between the gravel is torn off and falls due to the pressure of the water between the gravel, absorbs water, becomes defective grout material, becomes easily fluid, and moves downward.
No plastic grout material or injection method has been proposed to address these problems.

Patent No. 5697228

The present invention was proposed in consideration of the problems with the conventional technology described above, and aims to provide a plastic grout material that can prevent defects from being created in the lower area of an improved body constructed underwater, and a construction method using the same.

The inventors conducted various studies on whether it is possible to prevent the grout material from tearing when applied underwater. In this study, they noticed that if the grout material is applied in air (air) rather than underwater, the water pressure will not act to tear off parts of the grout material, and the torn grout material will not absorb water and become more fluid, so the inconvenience shown in Figure 1 (the inconvenience of a defective part 3 occurring in the lower region 2 of the improved body 1) will not occur. They then came to the conclusion that if the grout material is not easily torn underwater, such inconvenience will not occur.
The present invention was created based on such findings.
The plastic grout material of the present invention comprises water and a powder,
The powder contains cement and silica fume.
The water-powder ratio (W/(C+SF)×100%) of the powder to the water is 40 to 65% by mass,
Contains bentonite, sodium aluminate , thickener, water reducer ,
The ratio of the silica fume in the powder (SF/(C+SF)×100%) is 5 to 20 mass %,
The amount of the bentonite mixed is 2 to 8 mass% of the cement,
The amount of the inorganic sodium aluminate mixed is 0.4 to 1.0 mass % of the cement,
The amount of the thickener mixed is 0.2 to 1.0% by mass of the water,
The mixing amount of the water reducing agent is 0.2 to 3.0 mass % of the cement .

The method of the present invention is a method for injecting or filling a plastic grout material into water or an area below the groundwater level, comprising the steps of:
The plastic grout material comprises:
Contains water and powder,
The powder contains cement and silica fume.
The water-powder ratio (W/(C+SF)×100%) of the powder to the water is 40 to 65% by mass,
Contains bentonite, sodium aluminate, thickener, water reducer,
the powder comprises cement and silica fume;
The ratio of the silica fume in the powder (SF/(C+SF)×100%) is 5 to 20 mass %,
The amount of the bentonite mixed is 2 to 8 mass% of the cement ,
The amount of sodium aluminate mixed is 0.4 to 1.0 mass% of the cement ,
The amount of the thickener mixed is 0.2 to 1.0% by mass of the water ,
The mixing amount of the water reducing agent is 0.2 to 3.0 mass % of the cement .

In the method for injecting or filling a plastic grout material according to the present invention, the plastic grout material is preferably injected or filled into a ground containing granular matter having a 10% particle size of 50 mm or more, where the 10% particle size means a particle size at which the passing mass percentage in a particle size accumulation curve is 10%.

According to the plastic grout material of the present invention having the above-mentioned configuration, the plastic grout material contains water and powder,
The powder contains cement and silica fume, as well as bentonite, inorganic plasticizer, thickener, and water reducing agent, and therefore has a large size and weight (underwater extrusion length in Experimental Example 3) before it is torn off under its own weight in water, and has the property of being difficult to tear off even when loaded with its own weight (large underwater tensile strength in Experimental Example 3), so that some of it will tear off in water, absorb water, become more fluid, and be prevented from moving downward due to gravity. Therefore, even if it is filled or injected underwater, the grout material containing a lot of water is prevented from moving below the improved body, and it is possible to prevent the generation of defective parts in the lower area of the constructed improved body.

FIG. 1 is an explanatory diagram showing a disadvantage in the conventional technology. FIG. 2 is an explanatory diagram showing why the inconvenience shown in FIG. 1 occurs; FIG. 13 is an explanatory diagram of an experimental apparatus used in Experimental Example 3. FIG. 13 is a table showing the experimental results of Experimental Examples 1 to 4. FIG. 1 is a relationship diagram showing the correlation between flow value and vane shear strength. FIG. 1 is a diagram showing the relationship between air tensile strength and vane shear strength. FIG. 1 is a diagram showing the relationship between underwater tensile strength and vane shear strength. FIG. 8 is a diagram showing FIG. 7 differentiated by the amount of silica fume mixed in. FIG. 8 is a diagram showing FIG. 7 classified according to the amount of bentonite mixed. FIG. 1 is a diagram showing the relationship between the extrusion length in air and the extrusion length in water.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
First, the cause of the defective portion 3 shown in FIG. 1 will be described with reference to FIG.
In Fig. 2, the reference numeral 21 denotes gravel in the water. There is no problem with the grout material 25A (grout material present in a large space) present at the top of Fig. 2. However, when filling the gaps between the boulders 21, as the grout material spreads concentrically, a part of the grout material 25A spreading downward is pushed out through the relatively narrow gap SN into the wide gap SW, and the pressure of the water present between the gravel 21 acts to tear off a part of the pushed-out grout material, which is torn off by its own weight and falls downward (grout material 25B in Fig. 2).
The fallen grout material 25B absorbs (mixes with) the water present between the gravel 21, improving its fluidity, and is therefore more likely to move downward by gravity, and moves further downward (falls) (grout material 25C in FIG. 2). As a result, it is presumed that the lower region 2 (FIG. 1) of the improved body 1 (FIG. 1) contains a large amount of torn, water-rich, and highly fluid grout materials 25B, 25C, resulting in defective portions 3. The highly fluid grout materials 25B, 25C contain a large amount of water, reducing their strength, and may not be able to obtain the required strength (18 N/mm ² ).

That is, as explained with reference to Fig. 2, a part of the grout material 25A present in the relatively large gap between the gravel 21 is torn off by the water pressure, falls by its own weight, and becomes water-absorbed defective grout material 25B, 25C. The water-absorbed defective grout material 25B, 25C is easily fluidized, so it moves downward, and a defective part 3 is generated in the lower region 2 of the improved body 1.
Here, if it is possible to prevent a portion of the grout material from being torn off by water pressure and dropping under its own weight, the problem described with reference to FIG. 2 will not occur.
As a result of extensive research, the inventor has created a plastic grout material that is difficult to tear apart in water and difficult to fall under its own weight.

The plastic grout material according to the embodiment of the present invention contains water and a powder, and the water-powder ratio of the powder to water (W/(C+SF)×100%) is 40 to 65 mass%,
The powder contains cement and silica fume, and the ratio of the silica fume in the powder (SF/(C+SF)×100%) is 5 to 20 mass %,
It contains bentonite, and the amount of bentonite mixed is 2 to 8 mass % of the cement.
Contains an inorganic plasticizer, and the amount of the inorganic plasticizer mixed is 0.4 to 1.0 mass% of the cement;
A thickener is included, and the amount of the thickener mixed is 0.2 to 1.0% by mass of water;
The mixture contains a water reducing agent in an amount of 0.2 to 3.0 mass % of the cement.

Here, in the above materials in the formulation according to the embodiment,
The cement used was a commercially available product (manufactured by Pacific Cement Corporation under the trade name "ordinary Portland cement").
Silica fume was also used as a commercially available product (product name "SILICA FUME SILICIUM" sold by SKW East Asia Co., Ltd.).
The polymer plasticizer used was a commercially available product ("Parfait Hard" sold by Midori Kosan Co., Ltd.).
The bentonite used was a commercially available product (manufactured by Kunimine Kogyo Co., Ltd. under the trade name "Kunigel V1").
The inorganic plasticizer used was a commercially available product (manufactured by Asada Chemical Industry Co., Ltd. under the trade name "sodium aluminate").
The thickener used was a commercially available product (trade name "HECELLOSE" sold by Tomoe Engineering Co., Ltd.).
A commercially available water reducing agent (product name "Master Glenium SP8SV" manufactured by Pozzolith Solutions Co., Ltd.) was used.
Tap water was used.

According to experiments conducted by the inventors using several types of cement and silica fume, including the above-mentioned commercially available products, in addition to the experimental examples described below, mixing becomes difficult when the water-powder ratio (W/(C+SF) x 100%) of the powder consisting of cement and silica fume is less than 40 mass%, and when it exceeds 65 mass%, the target strength (18 N/ ^mm2 ) may not be obtained.
In other words, for the multiple types of cement and silica fume (including the above-mentioned commercially available products) that the inventors experimented with, if the water-powder ratio (W/(C+SF) x 100%) of the powder consisting of cement and silica fume was 40 to 65 mass%, mixing was possible and the target strength (18 N/mm ² ) was achieved.

According to experiments conducted by the inventors on several types of silica fume, including the above-mentioned commercially available products, in addition to the experimental examples described below, if the proportion of silica fume in the powder (SF/(C+SF)×100%) is less than 5% by mass, it is not possible to prevent the grout material from breaking apart and falling in water due to its own weight, and if it exceeds 20% by mass, the viscosity of the grout material becomes too high, making it difficult to mix.
In addition, with respect to the multiple types of silica fume (including the above-mentioned commercially available products) that the inventors have experimented with, if the ratio of silica fume in the powder (SF/(C+SF)×100%) is 5 to 20 mass %, it is possible to prevent the grout material from breaking apart and falling in water due to its own weight, and it is possible to knead the grout material without the viscosity becoming too high.

According to experiments conducted by the inventors on several types of bentonite, including the above-mentioned commercially available products, in addition to the experimental examples described below, when the amount of bentonite was less than 2% by mass of cement, it was not possible to prevent the grout material from breaking apart and falling in water due to its own weight, and when the amount of bentonite was more than 8% by mass of cement, the viscosity of the grout material became too high, making mixing difficult in some cases.
The inventors have experimented with several types of bentonite (including the above-mentioned commercially available products), and found that when the bentonite was present at 2 to 8 mass % of cement, it was possible to prevent the grout material from breaking apart and falling in water due to its own weight, and also to mix the grout material without the viscosity becoming too high.

According to experiments conducted by the inventors other than the experimental examples described below on several types of inorganic plasticizers, including the above-mentioned commercially available products, if the amount of inorganic plasticizer mixed is less than 0.4 mass% of the cement, it is not possible to obtain the flow value (155 mm or less) required for a plastic grout material, and if the amount exceeds 1.0 mass% of the cement, the hardening speed becomes too fast, resulting in reduced workability.
In contrast, with respect to the multiple types of inorganic plasticizers (including the above-mentioned commercially available products) that the inventors have experimented with, if the amount of inorganic plasticizer mixed is 0.4 to 1.0 mass % of the cement, it is possible to obtain the flow value (155 mm or less) required for a plastic grout material, and further, the hardening speed does not become too fast, so that workability does not decrease.

According to the experiments conducted by the inventors using several types of thickeners, including the above-mentioned commercially available products, in addition to the experimental examples described below, when the amount of thickener mixed was less than 0.2% by mass of water, the anti-separation property in water was low and the cement particles were sometimes diffused in water. And when the amount of thickener mixed exceeded 1.0% by mass of water, the viscosity of the grout material became too high and mixing was sometimes difficult.
Regarding the multiple types of thickeners (including the above-mentioned commercially available products) that the inventors experimented with, when the amount of thickener mixed was 0.2 to 10.0 mass % of water, the anti-separation property in water was high, so that the cement particles did not diffuse in the water, and the viscosity of the grout material did not become too high, making it possible to knead it.

According to experiments conducted by the inventors other than the experimental examples described below on several types of water reducing agents, including the commercially available products mentioned above, if the amount of water reducing agent mixed is less than 0.2% by mass of cement, the fluidity when the materials are mixed is low and pumping of the grout material is difficult, and even if the amount exceeds 3.0% by mass of cement, the fluidity when the materials are mixed is not improved, and the pumping performance of the material is not improved, and there are cases where adding the water reducing agent is ineffective.
The inventors experimented with several types of water-reducing agents (including the commercially available products mentioned above). When the amount of water-reducing agent mixed was 0.2 to 3.0 mass% of the cement, the fluidity of the materials when mixed was improved and the pumpability of the grout material was also improved. As the amount of water-reducing agent mixed increased, the fluidity of the materials when mixed and the pumpability of the materials improved.
In the illustrated embodiment, no polymer plasticizer (PA) is included. Although the basic formulation "Prototype" shown in Table 1 below includes a polymer plasticizer, this basic formulation "Prototype" was selected as a comparative example to demonstrate the effects of the present invention. In that sense, no upper and lower limits of the polymer plasticizer are mentioned.

As described above, the plastic grout material according to the embodiment is injected into voids, joints, cracks in the ground or structures, and gaps between the ground and structures, filled into the back cavity of the lining of an existing tunnel, and used to fill gaps between boulders such as rubble mounds constructed as the foundation of a revetment.
The plastic grout material according to the embodiment has a property of being difficult to break in water and difficult to fall under its own weight. The plastic grout according to the embodiment shown in the figure exerts its effect in a ground containing granular matter with a 10% particle size of 50 mm or more, which is underwater or located below the groundwater level, and in which the gaps between the particles with a 10% particle size of 50 mm or more are filled with water.
The plastic grout material according to the embodiment is injected or filled underwater or at a position lower than the groundwater level, for example, in a ground containing granular matter with 10% particle size of 50 mm or more.
Here, the filling speed of the grout material is assumed to be, for example, 50 liters per minute. However, it has been confirmed by another experiment by the inventor, not described in the experimental examples, that the present invention is applicable even if the filling speed is not 50 liters per minute.
As for the injection or filling method, known techniques can be applied.

Next, experimental examples of the present invention will be described.
First, the specimens used in the experimental examples will be described.
A specimen of a grout material not applicable to the present invention is shown as a basic mix "Prototype."
The grout material specimens applicable to the present invention were produced by varying the water-powder ratio "W/(C+SF) x 100%", the proportion of silica fume in the powder "SF/(C+SF) x 100%, bentonite "BN" (C x %), polymer plasticizer "PA" (C x %), inorganic plasticizer "PB" (C x %), thickener "VA" (W x %), and water reducer "SP" (C x %) to prepare samples according to 17 types of blends (including the basic blend) shown in Table 1 below.
Table 1

Here, the water-to-powder ratio, the proportion of silica fume in the powder, the amounts of bentonite, polymeric plasticizer, inorganic plasticizer, and water-reducing agent are expressed as mass % relative to the cement (expressed as "C x %), and the amount of thickener is expressed as mass % relative to the water ("W x %).
As shown in Table 1, only the basic formulation "Prototype" contains the polymer plasticizer "PA", and the 16 types of samples according to the experimental examples of the present invention do not contain the polymer plasticizer "PA".
For each sample shown in Table 1, 80% of the total mixing amount of water was added to the mixer, and the water-reducing agent "SP" and a mixture of cement or powder (excluding the thickener) were added to the mixer and mixed at a low speed (139 rpm) for 3 minutes (material A).
Next, 20% of the total mixing amount of water and thickener "VA" were mixed for 30 seconds with another mixer (hand mixer), and then polymer-based plasticizer "PA" (basic formulation "Prototype" only) and inorganic plasticizer "PB" were added and mixed for 60 seconds (material B).
Then, material B was added to the mixer in which material A was being mixed, and the mixture was mixed at low speed for one minute to prepare a test specimen. All samples shown in Table 1 were used to prepare test specimens in the same manner.

[Experimental Example 1]
A flow test was carried out in accordance with JIS R 5201 for specimens prepared from each sample shown in Table 1. However, instead of a flow cone, a cylinder (inner diameter 80 mm, height 80 mm) described in NEXCO Test Method 313 "Test Method for Air Mortar and Air Milk" was used.
The "strike flow value", which is the spread after 15 strikes, and the "static flow value", which is the spread before the strikes were applied, were measured.

[Experimental Example 2]
For the test specimens prepared from each sample shown in Table 1, the JGS1411 "In-situ vane test method" was performed, and the vane shear strength of the grout material in the fresh state (before solidification) of the composition shown in Table 1 was measured.
However, a small vane blade (width 20 mm, height 40 mm) was used.
The fluidity of plastic grout materials is generally evaluated by a flow test, but the static flow values are concentrated in a narrow range of about 90 to 110 mm, so the sensitivity of the measurement is not high. Therefore, an evaluation by vane shear strength (Experimental Example 2), which has a high measurement sensitivity, was performed in addition to the flow test of Experimental Example 1.

[Experimental Example 3]
In order to evaluate the tensile strength in a fresh state (before solidification) of the specimens prepared from each sample shown in Table 1, the tip of a commercially available synthetic resin syringe 12 (e.g., capacity 100 cc) was opened and fixed to a housing C, as shown in Fig. 3. The syringe 12 was filled with a sample (reference numeral 14) shown in Table 1, and a transparent beaker 16 (e.g., capacity 500 cc) was placed below the syringe 12 in the housing C.
The beaker 16 can be filled with water, and is provided with a scale (not shown) at intervals of, for example, 1 cm.
As shown in Fig. 3, the plunger 18 of the syringe 12 is pressed in the direction of the arrow A until the sample 14 is cut by its own weight, and the sample 14 (grout material) in the syringe 12 is pushed out into the beaker 16. The manner in which the plunger 18 is pressed in the direction of the arrow A and the sample 14 is pushed out into the beaker 16 is captured by a video camera (not shown). From the video camera image, the length from the lower tip of the syringe 12 in Fig. 3 to the tip of the sample 14 at the moment when the sample 14 is cut is measured as the "push-out length".
Experimental example 3 was performed both when the beaker 16 was filled with water (measurement of the extrusion length in water) and when it was not filled with water (measurement of the extrusion length in air).
The extrusion length when the beaker was not filled with water was multiplied by the density of Sample 14 (grout material) and the gravitational acceleration g to obtain the tensile strength in air in a fresh state.
The extrusion length when the beaker is filled with water was multiplied by the density of sample 14 (grout material) and the gravitational acceleration g, and the buoyancy acting on the sample for the extrusion length was subtracted from this to obtain the tensile strength in water in a fresh state.

[Experimental Example 4]
The compressive strength of the specimens prepared from each sample shown in Table 1 was measured in accordance with JIS A1108 "Concrete Compressive Strength Test Method". The specimens were cylindrical specimens with dimensions of φ50×100 mm, which were demolded after 1 day of age and then cured in water until the material reached the test age.
The experimental results of Experimental Examples 1 to 4 are shown collectively in the table of FIG.
In FIG. 4, the compressive strength (uniaxial compressive strength) is not shown for sample "50-00-4" (water powder ratio 50%, silica fume amount 0%, bentonite amount 4%), sample "55-00-4" (water powder ratio 55%, silica fume amount 0%, bentonite amount 4%), sample "55-05-4" (water powder ratio 55%, silica fume amount 5%, bentonite amount 4%), sample "55-05-6" (water powder ratio 55%, silica fume amount 5%, bentonite amount 6%), sample "60-5-4" (water powder ratio 60%, silica fume amount 5%, bentonite amount 4%), and sample "65-10-4" (water powder ratio 65%, silica fume amount 10%, bentonite amount 4%). This is because the compressive strength test in Experimental Example 4 was conducted only on samples (mixtures) that were considered to be representative. Also, as is clear from FIG. 4, all samples (mixtures) whose compressive strengths were measured exceeded the target strength (18 N/mm2 ⁾ , and it is estimated that the samples whose compressive strengths were not measured also exceeded the target strength.

The experimental results will be described with reference to FIGS.
From FIG. 4, it was found that each sample in Table 1 may have inferior tensile strength in air compared to the basic formulation "Prototype", but has stronger tensile strength in water than the basic formulation "Prototype".
It was also revealed that each sample in Table 1 had a compressive strength equal to or greater than that of the basic mix "Prototype."
In Fig. 4, light grey indicates data for extrusion lengths longer than the limit of extrusion length measurable by the test device in Experimental Example 3 described with reference to Fig. 3 (80 mm in the test device created by the inventors). In other words, the samples marked with light grey in Fig. 4 (for example, 50-05-6 in air) have tensile strengths greater than the values shown in Fig. 4.

The relationship between the vane shear strength (Experimental Example 2) and the flow value (static flow value and impact flow value) will be described with reference to FIG.
In Fig. 5, the flow values (static flow value and impact flow value) of each sample in Table 1 are plotted on the vertical axis and the vane shear strength on the horizontal axis. The plots of static flow value and vane shear strength are indicated by "◯", and the plots of impact flow value and vane shear strength are indicated by "●".
As is clear from Fig. 5, for each sample in Table 1, both the static flow value and the impact flow value are correlated with the vane shear strength. Therefore, as described in Experimental Example 2, it can be said that it is appropriate to perform the evaluation by vane shear strength (Experimental Example 2) in addition to the flow test (Experimental Example 1). In Fig. 5, there are multiple plots where the static flow value is around 90 mm and the impact flow value is around 140 mm, and the vane shear strength is significantly different despite the same flow value, indicating that the vane shear test is more sensitive than the flow test. In the following, the tensile strength in a fresh state will be evaluated with a focus on the vane shear strength.
From Figure 5, no difference can be seen between the samples containing silica fume and bentonite and the basic mix.

In Fig. 6, the vertical axis represents the tensile strength in air and the horizontal axis represents the vane shear strength of each sample in Table 1. In Fig. 6, the plots marked with "●" indicate extrusion lengths exceeding 80 mm (plots exceeding the measurement limit of the experimental device in Experimental Example 3), and the plots marked with "◯" indicate extrusion lengths of 80 mm or less.
As is clear from FIG. 6, there is a strong correlation between the vane shear strength and the tensile strength in air in a fresh state.
Also in Figure 6, no difference is observed between the samples containing silica fume and bentonite and the basic mix.

In Fig. 7, the tensile strength in water of each sample in Table 1 is plotted on the vertical axis, and the vane shear strength is plotted on the horizontal axis. In Fig. 6, the plots marked with "●" indicate extrusion lengths exceeding 80 mm (plots exceeding the measurement limit of the experimental device in Experimental Example 3), and the plots marked with "◯" indicate extrusion lengths of 80 mm or less.
6 and 7, the tensile strength of the fresh samples is lower in water than in air, and the tensile strength of each sample varies widely. In particular, when the vane shear strength is in the range of 0.3 to 0.7 kN/ ^m2 , the tensile strength in water varies by about three times (the variation is large).
Here, in Fig. 7, the "prototype" has a very low underwater tensile strength. This clearly shows that the addition of silica fume and bentonite improves the tensile strength in the fresh state.

In Fig. 8, the relationship between the tensile strength in water and the vane shear strength shown in Fig. 7 is shown by dividing the plots by the amount of silica fume mixed in. In Fig. 8, the plots indicated by "◯" are those with a silica fume mixed in amount of 0% (proportion of silica fume in the powder: SF/(C+SF) x 100%), the plots indicated by "●" are those with a silica fume mixed in amount of 5%, the plots indicated by "□" are those with a silica fume mixed in amount of 10%, and the plots indicated by "■" are those with a silica fume mixed in amount of 15%. The plots with an upward arrow are those where the extrusion length exceeded 80 mm.
It is clear from Fig. 8 that the samples containing 10% or 15% silica fume tend to have stronger underwater tensile strength than the samples containing 0% or 5% silica fume. This shows that adding at least 10% silica fume (mass percent of powder) improves underwater tensile strength.

In Fig. 9, the relationship between the tensile strength in water and the vane shear strength shown in Fig. 7 is shown by dividing the plots by the amount of bentonite mixed in. In Fig. 8, the plots shown with "◯" are those with a bentonite mixed amount (mass % relative to cement) of 4%, the plots shown with "●" are those with a bentonite mixed amount of 6%, the plots shown with "□" are those with the "basic mix", and the plots with an upward arrow are those with an extrusion length exceeding 80 mm.
In Figure 9, no significant difference is observed between the bentonite content of 4% and 6%. The reason why no significant difference is observed is presumably because the effect of the silica fume content cannot be eliminated.
However, when comparing the plot "□" of the basic mix with the plot "◯" of the mix with 4% bentonite in Figure 9, or when comparing the "basic mix" with mix "50-00-4" in Figure 3 (a mix with no silica fume but 4% bentonite: the mix just below the prototype in Figure 3), there are several mixes in which the basic mix is stronger in vane shear strength (plot "□"), but the plot "◯" of the mix with 4% bentonite is superior in underwater tensile strength (for example, mix "50-00-4": underwater tensile strength of basic mix = 0.14 kN/ ^m2 : underwater tensile strength of mix "50-00-4" = 0.17 kN/ ^m2 ).
Considering this, it is believed that the addition of bentonite improves the underwater tensile strength and makes the plastic grout material less likely to break apart in water. It is also clear that the addition of bentonite can provide the property required for the plastic grout material of the present invention (the property of making a part of the grout material less likely to break apart in water).

Figure 10 shows the relationship between the extrusion length in water and the extrusion length in air for each sample in Table 1. In Figure 10, the plots indicated with "◯" are those with 0% silica fume content, those indicated with "●" are those with 5% silica fume content, those indicated with "□" are those with 10% silica fume content, and those indicated with "■" are those with 15% silica fume content. The plots with an upward or rightward arrow are those with an extrusion length exceeding 80 mm.
As described above by comparing Figures 6 and 7, the fresh samples have a lower tensile strength in water than in air. However, as shown in Figure 10, the samples with 10% and 15% silica fume mixed amount have a longer extrusion length in water than in air. Considering that the present invention prevents a part of the grout material from tearing off in water, Figure 10 shows that the required property of the plastic grout material of the present invention (the property of preventing a part of the grout material from tearing off in water) can be obtained by mixing silica fume.

Please note that the illustrated embodiments are merely examples and are not intended to limit the technical scope of the present invention.

1...Improved body 2...Improved body lower region 3...Defective part of improved body 12...Syringe 14...Sample (plastic grout material)
C...Housing 16...Beaker 18...Plunger 21...Grubble 25A, 25B, 25C...Grout material (plastic grout material)

Claims (3)

Contains water and powder,
the powder comprises cement and silica fume;
The water-powder ratio of the powder to the water is 40 to 65% by mass,
Contains bentonite, sodium aluminate , thickener, water reducer ,
The proportion of the silica fume in the powder is 5 to 20 mass %,
The amount of the bentonite mixed is 2 to 8 mass% of the cement,
The amount of sodium aluminate mixed is 0.4 to 1.0 mass% of the cement,
The amount of the thickener mixed is 0.2 to 1.0% by mass of the water,
A plastic grout material characterized in that the amount of the water reducing agent mixed is 0.2 to 3.0 mass % of the cement . 1. A method for injecting or filling a plastic grout material into water or into an area below the groundwater level, comprising:
The plastic grout material comprises:
Contains water and powder,
the powder comprises cement and silica fume;
The water -powder ratio of the powder to the water is 40 to 65% by mass,
Contains bentonite, sodium aluminate, thickener, water reducer,
The proportion of the silica fume in the powder is 5 to 20 mass %,
The amount of the bentonite mixed is 2 to 8 mass% of the cement ,
The amount of sodium aluminate mixed is 0.4 to 1.0 mass% of the cement ,
The amount of the thickener mixed is 0.2 to 1.0% by mass of the water ,
A method for injecting or filling a plastic grout material , characterized in that the amount of the water reducing agent mixed is 0.2 to 3.0 mass % of the cement . 3. The method for injecting or filling a plastic grout material according to claim 2, wherein the plastic grout material is injected or filled into ground containing granular matter with a particle size of 50 mm or more for 10%.

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