JPH0414520A - Method for spraying concrete - Google Patents

Abstract

PURPOSE:To improve the workability and economy of the title method by feeding a mixture of pulverized cement, foamable agent, and sagging preventing agent with a pressure and spraying the mixture upon a slope. CONSTITUTION:The concrete to be used for this concrete spraying method is prepared by mixing 0.05-0.3pts.wt. of a foamable agent, 0.1-3.0pts.wt. of a sagging preventing agent, and 30-60pts.wt. of water with 100pts.wt. of pulverized cement and stirring the mixture after adding 15-40 volume % of air into the mixture. The mixture prepared in such way is fed through a hose with a pressure and sprayed up a slope.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a slope frame using the cast-in-place frame construction method for protecting cut slopes, embankment slopes, or slopes that are at risk of collapsing or collapsing. Concrete spraying in etc. is related to construction methods.

[Conventional technology]

In recent years, cast-in-place frame construction methods such as free frame construction methods have been attracting attention as slope stabilization construction methods that provide both durability and aesthetic appeal.

The free frame construction method is a construction method in which a wire mesh formwork is installed along the ground, reinforcing bars are built into the wire mesh formwork, anchors are taken into the ground, and mortar or concrete is directly sprayed to construct the method frame. Since the slope and the ground are integrated and the slope is formed continuously, it has high strength and durability, and economical cross sections and dimensions can be freely selected depending on the ground conditions. . In addition, the bare ground within the frame can be covered with bagged soil and vegetation, sprayed with soil for vegetation, or sprayed with mortar and concrete for environmental conservation and disaster prevention.

On the other hand, concrete spraying is a construction method in which concrete is sprayed onto a slope, for example, at high pressure and high speed using a machine using compressed air, and there are two methods: wet method and dry method. The former wet method 1 is a construction method in which all the materials to be sprayed are mixed in advance in a spraying machine, and the materials are forced to the construction site using compressed air and then sprayed from a nozzle. On the other hand, in the latter dry method 1, aggregate and cement are mixed and sprayed into a spraying machine, which is then pumped with compressed air, and mixed with water pumped through a separate route at the nozzle. , is a spraying method. In general, it is used for primary lining of tunnels, etc., in addition to the above-mentioned construction of legal frameworks.

On the other hand, in ordinary concrete, an AE agent (anionic or nonionic surfactant) is often added to improve the workability or durability of the concrete. The AE agent is an admixture that distributes fine closed cells in concrete in a -like manner, and the action of these fine cells improves the sliding between concrete particles and improves fluidity. Usually, the amount of AE agent added is CX0.02-0.05
The amount of air at that time is approximately 3 to 5% by volume.

As an application technology of the bubble-forming concrete to which the above-mentioned AE agent, foaming agent, etc. have been added, for example, air mortar with a large amount of foaming agent added to the air content of 40 to 60% is sprayed for backfilling of tunnels. Construction may take place. In addition,
The 28-day compressive strength of this air mortar is σ = 20k
It is about gf/cn+2. In addition, as another example of application, a large amount of air bubbles may be formed in a building member to reduce its weight.

[Problem to be solved by the invention]

In the concrete spraying method, there is a risk that rebound will create honeycomb-shaped pockets in the concrete and form a layer of weak strength.
It is necessary to take measures such as removing rebound solids in advance to prevent them from getting mixed in. However, in the case of downward spraying, such as in the case of concrete for framing, it is impossible to completely remove rebound, and therefore measures must be taken to reduce rebound as much as possible.

Normally, in order to reduce the rebound rate, based on past experience and tests, it is necessary to increase the unit cement amount, water-cement ratio, and fine aggregate ratio, that is, increase the mortar content.
It is effective to use concrete with a high moisture content.

However, if the amount of cement increases, the cement paste in the mortar material will adhere to the inside of the hose, causing the hose to become clogged, and material separation will occur, causing variations in the quality of concrete. On the other hand, if the concrete has a high water-cement ratio and is highly fluid, when spraying it into a wire mesh frame installed on a slope, as in the case of a legal framework, dripping may occur outside the frame, making construction difficult. Due to the physical properties of concrete, spraying is not desirable.

In addition, in the case of wet spraying concrete, it is generally difficult to make the concrete material flow in a constant state within the hose, and it is sent in a pulsating state due to the influence of aggregate particle size, water-cement ratio, air pressure, etc. This often causes the nozzle to vibrate greatly, making it impossible for the nozzleman to hold the nozzle in the proper direction, which not only makes it difficult to spray concrete, but also causes a lot of rebound, which impairs the quality of the concrete. Not only is the yield low, but the rebound rate is high, making it uneconomical. but,
At present, methods and devices for efficiently pumping concrete with a hose have not yet been developed for spraying with a small water-cement ratio and therefore a small slump.

Therefore, the object of the present invention is to make it possible to efficiently pump concrete by stirring and mixing it into a hose, and also to make it possible to spray concrete without forming air pockets due to its fluidity immediately after the nozzle blows out. Another object of the present invention is to provide a concrete spraying method that can eliminate sag outside the wire mesh frame by having thixotropic properties that rapidly gel immediately after spraying and increase shear resistance.

[Means to solve the problem]

The above problem was solved using fine powder cement C and foaming agent (:
×0.3% by weight is mixed, and an anti-sag agent is added to CX0.
．． 1 to 3.0% by weight, and further water-cement ratio W/C
This can be solved by stirring and mixing the air content to 30 to 60%, adjusting the amount of air to 15 to 40% by volume, and then spraying by pressure feeding through a hose.

Also, especially for cement, fine aggregate and water reducers.
15-70% by weight of cement with a particle size of 100 μm or less, 85-30% by weight of blast furnace quenched slag powder with a particle size of 15 μm or less
A cement part consisting of 20 to 70 parts by weight, and 80 to 70 parts by weight of blast furnace slag with a particle size of 70 μm to 5.0 mm as fine aggregate.
It is also possible to use a water reducing agent with a solid content of 30 parts by weight and 4% by weight or less based on the cement part.

[Effect]

In the present invention, the cement used is a finely powdered cement, specifically, cement mixed with blast furnace quenched slag powder, blast furnace cement, fly ash cement, high-strength cement, etc., and the foaming agent is added to CX0.05. ~0.3
% by weight and an anti-sag agent of CX of 0.1 to 3.0% by weight are mixed, and the water-cement ratio W/C is set to 30 to 60%, and the air content is adjusted to 15 to 40% by volume. Note that as the foaming agent, an AE agent, a foaming agent, a foaming agent, etc. can be used. Further, as the anti-sag agent, natural fiber minerals, steel fibers, organic fibers such as nylon, etc. can be used.

Therefore, when concrete is pumped, fine air bubbles defoam and change into water droplets at the contact area between the mortar and the inner wall of the pipe, reducing the pumping resistance of the concrete lead mortar, and the mortar itself contains a foaming agent and By incorporating an anti-sagging agent, good thixotropic properties can be obtained.

Therefore, immediately after stirring, the shear resistance force τ3,
Since it has excellent fluidity of about 0g/cm2, it can be efficiently pumped through the hose. Further, immediately after the nozzle blows out, the mortar exhibits high thixotropy and low viscosity as described above, so rebound can be prevented and air pockets generated in the mortar can be eliminated. After that, the concrete that is sprayed and left to stand still increases its shear resistance rapidly and exhibits high viscosity, so it does not sag even on slopes and has good workability.

On the other hand, as a cement material, Portland cement (N
In the case of PC), the shear resistance force τ immediately after kneading is large, and the shear resistance force increases as the standing time elapses, and the shear resistance force increases as the standing time elapses. Since it is susceptible to thixotropy, fine powder cement is used.

Regarding cement, fine aggregate and water reducing agent, particle size 10 is disclosed in JP-A-61-281057.
15-70% by weight of cement below 0 μm, particle size 15 μm
20 to 70 parts by weight of cement part consisting of 85 to 30% by weight of the following pulverized blast furnace quenched slag powder, 80 to 30 parts by weight of quenched blast furnace slag with a particle size of 70 μOI to 5.0 mm as fine aggregate, and cement part When formulated with a water-reducing agent of 4% by weight or less in terms of solid content, chemical bonding in particular can increase strength and reduce drying shrinkage, as well as abrasion resistance, frost damage resistance, chemical resistance, and salt resistance. Effects such as permeability can be obtained, and the adhesion strength of the joining part is increased, and the inclusion of fine closed cells absorbs stress and suppresses the occurrence of cracks. In addition, the above-mentioned Japanese Patent Application Laid-Open No. 61-2
The mortar disclosed in Publication No. 81057 is sold by Nippon Steel Cement Co., Ltd. under the product name rNEM-FJ.
can be easily obtained. Moreover, the special fine aggregate is also sold as "rNEM-G" at the same time.

In addition, in the examples of this specification, when conducting a test using the mortar, the names NEM-F and NEM-G are simply used.

On the other hand, the numerical limits for the foaming agent and anti-sagging agent are based on the findings from the examples described later, and on the other hand, the upper limit of the water-cement ratio W/C is set at 60% in consideration of durability and watertightness. This is because, as the water-cement ratio W/C increases, the air content decreases inversely to it, making it difficult to secure an air content of 15%. Regarding the amount of air, the lower limit is set at 15% by volume based on the above water-cement ratio W/C, and the upper limit is set at 40% by volume based on the relationship with the foaming agent content and strength. %.

In this specification, "Shotcrete J" includes both mortar mixed with only fine aggregate and concrete further mixed with coarse aggregate.

[Specific configuration of the invention]

Hereinafter, the present invention will be clarified by examples.

(Example 1) In Example 1, tests were conducted on the relationship between the amount of foaming agent added and shear resistance force τ, and the difference in shear resistance force τ depending on the type of foam material, and the test results are shown in Figures 1 and 2. shows.

FIG. 1 is a diagram showing the relationship between the amount of foaming agent added and shearing resistance, and FIG. 2 is a diagram showing the relationship between the type of foaming agent and shearing resistance. In both FIGS. 1 and 2, the vertical axis shows the shear resistance force τ (gf/cm2), and the horizontal axis shows the standing time (sin) after kneading.

First, in Figure 1, the mortar composition is NEM-F 68.
9g, NEM-G 1378g, anti-sagging agent CX1.
5%, the water-cement ratio is 55%, the Ll line shows the case where the foaming agent is mixed with CX 0.1%, the L2 line shows the case where the foaming agent is mixed with CX 0.2%, and the L3 line shows the case where the foaming agent is mixed with CX 0.2%.
The line shows the case where no foaming agent is added. In addition,
As the foaming agent, an AE agent is used.

From FIG. 1, the τ value of the L2 line increases rapidly from 0 to 5 akin, indicating high thixotropy. On the other hand, the LL line remains flat after 2a+in, but the τ value rapidly increases from 0 to 2m1n, and exhibits high chicken tropism during this period.

On the other hand, the L3 line to which no foaming agent was added remained flat from the beginning of standing, and was found to lack thixotropy. In addition, the amount of air contained at this time (Air value)
is 30% by volume in the L1 line, 35% by volume in the L2 line,
It is 5% by volume in the L3 line.

By the way, there are different types of foaming agents, such as protein-based agents and surfactants.The former protein-based agents include, for example, non-toxic hydrolyzed proteins, which have excellent foaming action and the foam is stable. . The latter surfactants include, for example, higher alkyl ether sulfate salts.
Excellent bubble action. In the test shown in FIG. 2, two types of surfactants were tested: an anionic surfactant and a protein-based surfactant. In addition, the mortar composition is NEM-F 689g,
NEM-G1378 g, foaming agent CX 0.2%, anti-sagging agent CX 1.5%, water-cement ratio 55%, the L1 line shows the case where the foaming agent is an anionic surfactant, and the L2 line shows the foaming agent. The case where is made into a protein system is shown. Figure 2 shows that for line 1 using an anionic surfactant, the τ value increases linearly with a constant slope, and for line L2 using a protein-based foaming agent, it increases once 3 minutes have elapsed. It has remained at the same level, and it has been found that anionic surfactants are more effective. Further, as for the case where an AE agent is used as a foaming agent, as shown in FIG. 1, the above-mentioned anionic surfactant is slightly more effective, but the effect is greater.

In addition, as the anionic surfactant, PARIC
#100 was used.

(Example 2) In Example 2, tests were conducted on the relationship between the amount of anti-sag agent added and the τ value, and the relationship between the type of anti-sag agent and the τ value, and the test results are shown in Figures 3 and 4. shows.

FIG. 3 is a diagram showing the relationship between the amount of anti-sagging agent added and shear resistance force τ, and FIG. 4 is a diagram showing the relationship between the type of anti-sag agent and shear resistance force τ. In both FIGS. 3 and 4, the vertical axis shows the shear resistance force τ (gf/C2), and the horizontal axis shows the standing time (1n) after kneading.

First, in Figure 3, the mortar composition is NEM-F 68.
9g, N) iM-G 1378g, air foaming agent (AE) C
xO, 2%, water-cement ratio 55%, the Ll line shows the case where no anti-sag agent is mixed, the L2 line shows the case where the anti-sag agent is mixed with Cxl, 5%, and the L3 line shows the case where the anti-sag agent is mixed with CX3. The case where .0% is mixed is shown.

From FIG. 3, it is clear that the L2 line in which 1.5% of CX was mixed with the anti-sagging agent had the greatest effect, showed a high shear resistance force τ value in a short time with the passage of time, and had high thixotropy.

By the way, as the anti-sagging agent, for example, Milcon J, which is a product of Showa Mining Co., Ltd. and which is specially processed from natural fibrous clay minerals, can be used.

The aforementioned Milcon shows a thickening effect when stirred in water or resin, and when measured with a rotational viscometer, the viscosity becomes low when the shear force is large due to the entanglement of the single fibers contained in Milcon. , conversely, when it is small, it has thixotropic characteristics showing high viscosity. Moreover, according to this millcon, it is possible to improve the adsorption property of mortar and concrete spraying.

The above-mentioned milcon includes long fiber type LS, fine powder type SP, medium fiber type ε type, etc. depending on the fiber shape, and tests were conducted to determine the difference in effectiveness of these three types. In other examples, the former LS type is used as the anti-sagging agent.

Mortar composition is NEM-F 689g, NEM-G
1378 g, air foaming agent (AE) CX 0.2%, anti-sagging agent CX 1.5%, water-cement ratio 55% are fixed, and the case where Milcon LS type is used as the anti-sagging agent is shown by the L1 line, SPε The case where the type is used is shown by the L2 line, and the case where the ε type is used is shown by the L3 line.

From Figure 4, it is clear that the anti-sagging agent is most effective when using the long fiber LS type, and there is no significant difference between the fine powder SPε type and the medium fiber ε type. .

(Example 3) In Example 3, a test was conducted on the relationship between cement type and τ value, and the test results are shown in FIG.

In FIG. 5, the vertical axis shows the shear resistance force τ (gf/c+a2), and the horizontal axis shows the standing time (win) after kneading.

Mortar mix: 689g of cement, NEM-G 13
78g, foaming agent (AE) CX 0.2%, anti-sag agent CX
I, 5%, water-cement ratio 55%, and two types of cement were used: ordinary Portland cement (NPC) and NEM-F.

In FIG. 5, the ordinary portland cement (NP
The case where C) is used is shown in line 1.1, and NE
The case where MF is used is shown by the L2 line.

From FIG. 5, it can be seen that in the case of ordinary Portland cement (NPC), the shear resistance value τ immediately after stirring is large, and it lacks fluidity. In addition, the thixotropic property leveled off after 1 minute of standing time, and the τ value did not increase, indicating that the thixotropic property was weak, and the concrete spraying of the present invention was found to be unsuitable for practical use. On the other hand, NEM
- When using F, the τ value immediately after kneading is 3 g7
It has been found that the τ value is as low as 0.3 cm, and then increases steeply as the standing time elapses, indicating high thixotropy.

The amount of air (Air) was 28% in the case of ordinary Portland cement (NPC) and 35% in the case of NEM-F.

(Example 4) In Example 4, a test was conducted on the relationship between the water-cement ratio, the shear resistance value τ value, and the amount of air, and the test results are shown in FIG. Figure 6 shows the shear resistance force τ (lrf/cm) on the vertical axis.
2), and the horizontal axis shows the standing time (1n) after kneading.

Mortar composition is NEM-F 689g, NEM-G
1378g, air foaming agent (AE) CX 0.2%, anti-sagging agent CX 1.5%, water-cement ratio is 53%,
Tests were conducted on three types: 55% and 58%.

In FIG. 6, the LLε type is shown when the water-cement ratio is 53%, the L2 line is when the water-cement ratio is 55%, and the L3 line is when the water-cement ratio is 58%.

From FIG. 6, the case of W/C=55% shows the highest thixotropy, and the τ value after 5 minutes of standing time is the highest. On the other hand, the case where W/C=58% showed the lowest τ value. However, there is not an extreme difference in the τ value between W/C=53% and 58%. However, there is a noticeable difference in the amount of air (Air value) at that time. W/C
= 53.55%, the air amount was Air = 35%, whereas when W/C = 58%, Air = 15%.
%, and it is found that as the water-cement ratio increases, the bubble content decreases and the foaming effect due to the addition of a foaming agent weakens.

(Example 5) In Example 5, a test was conducted regarding the relationship between air content and mortar compressive strength, and the test results are shown in FIG. In FIG. 7, the vertical axis shows compressive strength σ (kg/am''), and the horizontal axis shows material age (days).

Mortar mixture is NEM-F 689g, foaming agent (AE)
Appropriate amount to adjust air volume, anti-sag agent Cx1.5%
, NEM-G 1378g with a water-cement ratio of 55%
and in the case of NEM-62067g, that is, C/S
Two types of tests were conducted: a case of 1/2 and a case of 1/3.

In addition, regarding the amount of air at that time, Air = 20 to 35%
The amount of foaming agent was adjusted appropriately so that it was within the range of .

By the way, since the mortar using NEM-F has blast furnace slag as its base, a dense hydrate is formed by the hydration reaction of the slag, and if the water-cement ratio is 30-35
%, the strength is 1000 to 110l10 after 28 days of age.
It shows a compressive strength of 0 (/cm2) and a water-cement ratio of 4
In the case of about 2%, the strength at 28 days of age is 750 (kgf/
cm2).

On the other hand, when the amount of air is generally increased by mixing a foaming agent or an AE agent, the compressive strength decreases as the amount of air increases. Therefore, in the present invention, in addition to using fine powder cement to obtain high thixotropy as described above, it also contains a large amount of air to ensure fluidity within the hose. This causes the problem of a decrease in compressive strength, but this problem is solved by using a finely powdered cement that exhibits high compressive strength.

As shown in Figure 7, C/S = 1/2 and C/S1
There was no noticeable difference in compressive strength between the materials of /3 and both materials were able to secure a high compressive strength of about 300 (kgf/c+a2) at 28 days of age.

〔Effect of the invention〕

As explained in detail above, according to the present invention, it is possible to impart high thixotropy to the concrete when constructing concrete for concrete frames, and when it is pumped with a hose, it has high fluidity and pumping performance, and the air bubbles caused by the addition of a foaming agent This dual effect reduces the frictional resistance between the material and the material, allowing for efficient pressure feeding. In addition, when the nozzle blows out the concrete, it has a low viscosity due to its high thixotropic properties, so concrete can be sprayed without creating air pockets, and it rapidly gels afterwards, increasing the shear resistance value, which prevents sagging and improves workability. It is also possible to improve economic efficiency.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the amount of foaming agent added and shearing resistance τ, Figure 2 is a diagram showing the relationship between the type of foaming agent and shearing resistance τ, and Figure 3 is a diagram showing the relationship between the amount of anti-sagging agent added and τ Figure 4 is a diagram showing the relationship between the type of anti-sagging agent and the τ value, Figure 5 is a diagram showing the relationship between the type of cement and the τ value, and Figure 6 is a diagram showing the relationship between the type of cement and the τ value.
The figure shows the water-cement ratio, shear resistance value τ, and air amount Air.
FIG. 7 is a diagram showing the relationship between air amount and mortar compressive strength. Patent applicant: Wright Kogyo Co., Ltd. Agent, Patent attorney: Yoshihisa Nagai Teriji connects death grip, runs through life, Sakaki Seki (min + figure sootsu λ) use, reduces Aoi Kyohite's sha-kei challenge practice 4 &, nl'? 1saki IVi + rrun + figure 2 with sagging Me II, after kneading the kakukan hunting diagram with Yafu Sengagabi dket time (min). E, Training J1 #1 Fuma fmin)

Claims (2)

[Claims] (1) Using fine powder cement C, add foaming agent C x 0.0
In addition to mixing 5 to 0.3% by weight, an anti-sagging agent is added to Cx.
0.1 to 3.0% by weight is mixed, and the water-cement ratio W/
Stir and mix C at 30-60%, and adjust the amount of air to 15-40%.
A concrete spraying method that is characterized by making the volume % and then spraying by pumping the inside of a hose. (2) 15 to 70% by weight of cement with a particle size of 100 μm or less
, blast furnace quenched slag fine powder with a particle size of 15 μm or less 85-30
20 to 70 parts by weight of the cement part, 80 to 30 parts by weight of quenched blast furnace slag with a particle size of 70 μm to 5.0 mm as fine aggregate, and a water reduction of 4% by weight or less in terms of solid content to the cement part. Using a mortar consisting of a foaming agent, mix C x 0.05 to 0.3% by weight, and mix an anti-sagging agent C x 0.1 to 3.0% by weight, and further increase the water-cement ratio W/C. A concrete spraying method characterized in that the concrete is mixed by stirring at a concentration of 30 to 60%, the amount of air is adjusted to 15 to 40% by volume, and then the concrete is sprayed by pumping through a hose.