JP6399405B2 - Plastic injection material - Google Patents

Description

  The present invention relates to a plastic injection material.

An injection material containing cement such as cement milk is known as an injection material for repairing and strengthening by injecting into a cavity or gap of a civil engineering structure. As such an injection material, there is a plastic injection material in which a component imparting plasticity such as bentonite is blended so as not to flow out from the injection site to the surrounding immediately after injection.
For example, Patent Document 1 describes a plastic injection material containing cement, bentonite, and water. Such a plastic injection material is a so-called plastic injection material obtained immediately before use by preparing cement as a hardening component and bentonite as a plasticizing component as separate liquids and kneading the two liquids immediately before injection. It is a two-component plastic injection material.

Reference 2 describes a one-component plastic injection material that can be used with simpler injection equipment than a two-component plastic injection material.
Such a one-pack type plastic injection material is prepared in advance by kneading all components such as cement, bentonite, water and a dispersant, and the plastic injection material is transferred to the vicinity of the injection site and injected into the site. is there. In Patent Document 2, in order to facilitate pumping with a pump or the like, the plastic injection material is adjusted so that the flow value immediately after the adjustment is 140 mm or more and the relatively high fluidity is 120 mm or more 20 minutes after the adjustment. Is described.

However, the plastic injection material having high fluidity has a problem in that the strength of the cured product varies after curing, and stable repair and reinforcement cannot be performed. In order to suppress such variation in strength after curing, it may be possible to lengthen the kneading time after adding water when preparing the injection material, but it takes time to adjust the plastic injection material. There's a problem.
In addition, although the plastic injection material having high fluidity can be easily transferred, there are cases where the plasticity cannot be sufficiently exhibited during use. In particular, when a plastic injection material is produced near the injection site and injection is performed in a relatively short time after the production, the plastic injection material cannot be sufficiently exhibited at the time of injection, and the plastic injection material tends to flow out around the injection site. There is a problem.

Japanese Patent No. 3378501 JP 2002-155277 A

  Therefore, in view of the conventional problems as described above, the present invention provides a plastic injection material that can be produced in a relatively short time, and at the same time, can obtain plasticity in a short time after production and can suppress variation in strength after curing. The issue is to provide.

The plastic injection material according to the present invention is made by kneading a mixture containing cement, bentonite, and water, the swelling power of the bentonite is 30 or more, and the mass ratio of the water to the bentonite is 8.2 or less. When the mass ratio of the cement to the bentonite is 0.15 or more and 0.25 or less and the kneading time of the mixture is 3 minutes or less, the flow value is 120 mm or less.

  According to the present invention, a mixture containing cement, bentonite, and water is kneaded, the swelling power of the bentonite is 30 or more, the mass ratio of the water to the bentonite is 8.2 or less, and the mixture When the kneading time is 3 minutes or less, the flow value is configured to be 120 mm or less, so that it can be produced in a short time, and plasticity is obtained in a short time after production, and the strength after curing is high. A plastic injection material capable of suppressing variations can be obtained.

In addition, the flow value in this invention is a flow value measured according to Japan Highway Public Corporation Standard JHS-A-313-1992 "Testing method of air mortar and air milk, consistency test of injecting material by cylinder method".
The swelling force in the present invention is the swelling force (ml / 2g) determined by the bentonite (powder) swelling test method (JBAS-104) of the Japan Bentonite Industry Association.

In the present invention, the mass ratio of the cement to said bentonite is 0.15 to 0.25.

  When the mass ratio of the cement to the bentonite is 0.15 or more and 0.25 or less, there is less variation in strength after curing, and plasticity can be exhibited in a shorter time.

In the present invention, but without a dispersant, or it may include 0 kg / ^{m 3} beyond less than 0.15 kg / ^{m 3.}

  By not containing the dispersant or in the above range, there is less variation in strength after curing, and plasticity can be exhibited in a shorter time.

  As described above, according to the present invention, it is possible to obtain a plastic injection material capable of obtaining plasticity in a relatively short time and suppressing variation in strength after curing.

  Below, one Embodiment of the plastic injection material concerning this invention is described.

  The plastic injection material of the present embodiment is a mixture of cement, bentonite, and water, the swelling power of the bentonite is 30 or more, and the mass ratio of the water to the bentonite is 8.2 or less. The plastic injection material is configured so that the flow value becomes 120 mm or less when the kneading time of the mixture is within 3 minutes. This will be specifically described below.

(cement)
The cement used in this embodiment is not particularly limited.
For example, normal Portland cement, early-strength Portland cement, ultra-high-strength Portland cement, moderately hot Portland cement, sulfate-resistant Portland cement, white Portland cement and other Portland cements, ultrafast cement, alumina cement and the like can be mentioned. Also, various kneaded cements obtained by kneading fly ash, blast furnace slag, etc. with Portland cement can be used.
Of these, ordinary Portland cement is preferred.

(Bentonite)
The bentonite used in the present embodiment is not particularly limited as long as the swelling power is 30 or more.
The swelling power of bentonite is 30 or more, preferably 35 or more.
When the swelling power of bentonite is the above value, sufficient plasticity can be imparted to the plastic injection material, and at the same time, plasticity can be exhibited immediately after kneading even in a relatively short time. Furthermore, it is possible to suppress the occurrence of variation in strength after the plastic injection material is cured.

(water)
In this embodiment, water is blended so that the mass ratio with respect to bentonite in the plastic injection material is 8.2 or less, and preferably 8.0 or less.
When the mass ratio of water to bentonite is the above value, sufficient plasticity can be imparted to the plastic injection material, and at the same time, plasticity can be exhibited even in a short time of kneading. Furthermore, after the plastic injection material is hardened, it is possible to suppress the occurrence of variation in strength.

(Other ingredients)
The plastic injection material of this embodiment may further contain another component as necessary. Other components include admixtures, aggregates such as fine aggregates, water reducing agents, retarders, dispersants and the like.
Examples of the admixture include blast furnace slag, fly ash, silica fume, gypsum, limestone fine powder, and quicklime fine powder.
As the admixture, blast furnace slag is particularly preferable from the viewpoint of strength development.

Plastic injection material of the present embodiment preferably contains no dispersing agent is preferably less than 0.15 kg / ^{m 3} greater than 0 kg / ^{m 3} in the case of containing. By containing no dispersant or the amount within the above range, plasticity can be exhibited even in a short time of kneading, and it is possible to further suppress the occurrence of variation in strength after the plastic injection material is cured.
The dispersant referred to in the present embodiment is not particularly limited as long as it is used as an admixture for concrete and has an action of enhancing the dispersibility of the cement composition. For example, among the chemical admixtures for concrete described in JIS A 6204, those capable of exhibiting a dispersing action such as a high performance water reducing agent, a water reducing agent, an AE water reducing agent, a high performance AE water reducing agent, a fluidizing agent, and the like. . More specifically, phosphoric acid, naphthalene sulfonic acid, melamine sulfonic acid, lignin sulfonic acid, polycarboxylic acid-based dispersant and the like can be mentioned.

Although content of each component in the plastic injection material of this embodiment is not specifically limited, For example, content as follows is mentioned.
The cement content is preferably such that the mass ratio of cement to bentonite is 0.15 or more and 0.25 or less, preferably 0.16 or more and 0.22 or less.
When the mass ratio of the cement to bentonite is within the above range, a plastic injection material with less variation in strength after curing can be obtained in a relatively short time.

  More specifically, bentonite is, for example, 8 mass% to 16 mass%, preferably 8.9 mass% to 10.4 mass%. In this case, it is mentioned that cement is 0.8 mass% or more and 2.0 mass% or less, for example, Preferably it is 1.7 mass% or more and 1.9 mass% or less.

In the plastic injection material of the present embodiment, when an admixture is contained in addition to cement, the content of the admixture is, for example, 12% by mass or more and 25% by mass or less, preferably 15% by mass or more and 20% by mass. The following may be mentioned.
Further, the total mass ratio of cement and admixture to bentonite is, for example, 1.5 or more and 2.5 or less, preferably 1.6 or more and 2.0 or less, more preferably 1.6 or more and 1.9 or less. It is preferable that
When the total mass ratio of cement and admixture with respect to bentonite is in the above range, it is preferable because variation in strength after curing is more easily suppressed.

The plastic injection material of this embodiment is configured such that the flow value is 120 mm or less, preferably 100 mm or less when the kneading time for kneading the mixture containing cement, bentonite, and water is within 3 minutes.
When the flow value when the kneading time of the mixture is 3 minutes or less is in the above range, variation in strength after curing can be suppressed.
In addition, the flow value when the mixing time of the mixture is within 3 minutes is 120 mm or less, which means that the flow value is 120 mm or less from the start of mixing until 3 minutes have passed. It means that it should be.

  The flow value referred to in this embodiment is measured by the cylinder method of the consistency test method defined in the Japan Highway Public Corporation Standard “Testing Method for Air Mortar and Air Milk (JHS A-313-1992)”. Specifically, the plastic injection material after kneading is filled in a cylindrical cylinder having a diameter of 80 mm and a height of 80 mm placed on a smooth board, and is measured as the diameter of the expanded grout material when the cylinder is pulled up. Is.

  As a method of configuring the plastic injection material of the present embodiment so as to have the above flow value, the content of each component, the swelling power of bentonite to be used, the mass ratio of bentonite and water, the cement of the cement with respect to bentonite For example, the mass ratio, the total mass ratio of cement and admixture with respect to bentonite, and the like may be appropriately adjusted.

  Next, a method for producing the plastic injection material of this embodiment will be described.

First, cement and bentonite are mixed to prepare a powder mixture. When other powder components are blended in the plastic injection material, the powder mixture may be prepared by kneading other powder components together with cement and bentonite.
The mixing method in producing the powder mixture is not particularly limited, and for example, using a powder mixing apparatus such as a V-type mixer, a nauter mixer, a pan-type mixer, a ribbon-type mixer, For example, mixing at 35 ° C. for about 10 minutes can be mentioned.

Next, a powder mixture prepared as described above is mixed with water so that the mass ratio of water to bentonite is 8.2 or less, and the mixture is further kneaded, and plastic injection is performed. Make the material.
The kneading in the present embodiment means not only simply mixing (mixing) the materials but also kneading so that the materials are mixed.
In this embodiment, the kneading time for kneading the mixture containing cement, bentonite, and water is, for example, 1 minute or more and 5 minutes or less, preferably more than 1 minute and 3 minutes or less.
In the case of the kneading time, sufficient plasticity can be exhibited in a relatively short time after kneading. Moreover, the dispersion | variation in the intensity | strength after hardening can be suppressed.

In this embodiment, the method of kneading the mixture is not particularly limited, and examples thereof include kneading at 5 to 35 ° C. using a kneading apparatus such as a hand mixer and a mortar mixer.
In addition, as a method of mixing the mixture in order to measure the flow value, for example, at a temperature of 20 ° C., using a power mixer, setting the rotation speed of the mixer to 750 rpm to 1250 rpm and mixing for a predetermined time. Can be mentioned.

The plastic injection material of this embodiment can be used, for example, as a one-component plastic injection material that is produced by kneading a mixture containing cement, bentonite, and water and then transported to the injection site.
In particular, the plastic injection material of the present embodiment is suitable for a small-scale construction using a relatively small amount. When a two-component type plastic injection material is adopted for such a small-scale construction, there is a problem that a mixing facility is installed at two locations and a facility for transferring two liquids is required, which makes the injection facility large. Therefore, in small-scale construction, a one-pack type plastic injection material that can inject the injection material with simple equipment is suitable. When using a one-pack type plastic injection material in such small-scale construction, a small amount of plastic injection material can be produced near the injection site, and the transfer distance is relatively short. It will be injected in a relatively short time after production. Thus, even when inject | pouring in a comparatively short time after manufacture, since the plastic injection material of this embodiment can exhibit sufficient plasticity, it is used suitably.

  Even when the plastic injection material of the present embodiment is manufactured in a relatively short time, since the strength after curing is good and there is little variation in strength, a stable strength can be obtained at the location where the plastic injection material is injected. Therefore, stable repair and strengthening can be performed.

Strength of the plastic injection material of the present embodiment, for example, be a uniaxial compressive strength measured in JIS A 1216 "uniaxial compression test soil" is 300 kN / ^{m 2} or more 5000kN / ^{m 2} or less, and the uniaxial compression The coefficient of variation calculated by the following method of strength is 20% or less, preferably 15% or less. This coefficient of variation indicates that the smaller the value, the less the variation in uniaxial compression strength.
The coefficient of variation is calculated by dividing the standard deviation of the uniaxial compressive strength value by the average value and multiplying by 100 to express the percentage.

  In addition, although the plastic injection material concerning this embodiment is as above, it should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  Examples The plastic injection material according to the present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples.

  The following materials were used as the plastic injection material.

Cement (symbol NC): Normal Portland cement (manufactured by Sumitomo Osaka Cement)
Blast furnace slag (symbol S): ESMENT (manufactured by ESMENT Kanto)
Bentonite (symbol B): swelling power 30, trade name Super Clay (manufactured by Hojun Co.), swelling power 36, trade name Western Gel (manufactured by Mitsubishi Corporation), swelling power 5, trade name Akagi (manufactured by Hojun Co.)
Water (symbol W): tap water

The plastic injection materials of Examples and Comparative Examples were prepared using the above materials in the formulations shown in Table 1.
In Table 1, the mass ratio of water to bentonite is W / B, the mass ratio of cement to bentonite is NC / B, the total mass ratio of cement and admixture to bentonite is (S + NC) / B, blast furnace slag The mass ratio of cement to is shown as NC / S.
The production method of each plastic injection material is as follows.
Cement, slag and bentonite in the material were kneaded for 10 minutes with a mixing device (device name: V-type mixer, manufactured by Dalton) to prepare a powder mixture.
This powder mixture and water were put into a Toslon can as a kneading container and kneaded by a kneading apparatus (device name: Power Mixer PM-1011, manufactured by Ryobi Co., Ltd.) to produce the plastic injection materials of Examples and Comparative Examples.
The mixing conditions were a temperature of 20 ° C. and a mixer rotation speed of 1000 rpm.
In addition, each plastic injection material measured the flow value and the uniaxial compressive strength about what knead | mixed for each kneading | mixing time shown in Table 1.

<Measurement of flow value>
The flow values of the kneading times of each Example and Comparative Example were measured according to Japan Highway Public Corporation Standard JHS-A-313-1992, “Testing Method of Air Mortar and Air Milk, Consistency Test of Injection Material by Cylinder Method”.
The results are shown in Table 1.

<Measurement of uniaxial compressive strength and calculation of coefficient of variation>
The plastic injection material kneaded for each kneading time of each example and comparative example was taken out to prepare a specimen (diameter 5 cm, height 10 cm).
The measuring method measured the uniaxial compressive strength with the uniaxial compression tester (made by Sekensha).
The standard deviation of each uniaxial compressive strength value was divided by the average value of each value and multiplied by 100 to calculate the coefficient of variation (%).
The results are shown in Table 1.

As shown in Table 1, each example had a low flow value of 120 mm or less when kneaded for 3 minutes. That is, it is clear that the plasticity was exhibited within the kneading time within 3 minutes.
Further, the coefficient of variation (%) of the uniaxial compressive strength in each example was less than 15% in the case of kneading for 3 minutes or more.
On the other hand, each comparative example had a high flow value when kneaded for 3 minutes, that is, the plasticity could not be exhibited by kneading for 3 minutes. In each comparative example, the coefficient of variation of uniaxial compressive strength exceeded 20% in the kneading for 3 minutes, or the material was separated and the uniaxial compressive strength could not be measured. That is, variation in strength after curing could not be suppressed by short-time kneading.

Claims (2)

A mixture containing cement, bentonite and water is kneaded,
The swelling power of the bentonite is 30 or more,
The water mass ratio to the bentonite is 8.2 or less,
The mass ratio of the cement to the bentonite is 0.15 or more and 0.25 or less,
A plastic injection material configured to have a flow value of 120 mm or less when the kneading time of the mixture is within 3 minutes. But without a dispersant, or plastic injection material according to claim 1, a dispersing agent 0 kg / ^{m 3} beyond containing less than 0.15 kg / ^{m 3.}