JP2000072516A - Cement for high-fluidity spray concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement for spray concrete that can stabilize the quality of the blown concrete. SOLUTION: This cement for high-fluidity spray concrete is a kind of cement that is prepared by adding an accelerator to a base concrete comprising a high-fluidity concrete and is used for spraying. This cement comprises a mixture of at least one selected from calcite powder with a Blaine specific surface area of >=3,000 cm2, a silica stone powder with a Blaine specific surface area of the same value and fly ash with the same Blaine specific surface area, with a normal portland cement or a high-early strength portland cement at a weight ratio of 1/9-5/5. The base concrete for the high-fluidity concrete has a slump flow of 450-750 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement for high-flow shotcrete suitable for a wet spraying method using high-flow concrete as a base concrete, and more particularly to a method of adding a quick-setting agent during pumping. The present invention also relates to a cement for high flow shotcrete that can stabilize the quality of shotcrete.

[0002]

2. Description of the Related Art In the construction work of an excavated tunnel or underground space, a method of spraying concrete on an exposed surface and lining the exposed surface to prevent the exposed surface from collapsing has been widely practiced. As a concrete spraying method, a dry method and a wet method are known, but the wet method is the mainstream of the spraying method because it has an advantage of generating less dust than the dry method.

[0003] In the wet method, the base concrete is pressure-fed through a transport pipe, blown out from a spray nozzle at the tip, and the excavated exposed surface is sprayed with concrete for lining. In addition, since quick-setting properties cannot be obtained by using only the base concrete, the quick-setting agent is added and mixed during the pressure feeding.

However, when a powder quick-setting agent mainly composed of a calcium aluminate-based mineral is added, the mixing and dispersing properties of the quick-setting agent in the base concrete are not stable, and stable quality (quick setting, strength, etc.) is obtained. Was difficult to obtain.

On the other hand, in recent years, the construction of tunnels with large cross sections and larger underground spaces has been increasing more and more. Along with this, the stabilization of the quality of shotcrete is further required. Therefore, the present invention generally provides a shotcrete cement capable of stabilizing the quality of shotcrete even with the use of the above-mentioned powder quick-setting admixture having poor mixing and dispersibility in base concrete. It is the purpose.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on various types of base concrete to solve the above-mentioned problems. As a result, the base concrete was made into a high-fluid concrete, and a specific inorganic powder was used as the cement. It has been found that the use of Portland cement or a mixture of Portland cement with a high-strength Portland cement in a specific ratio can stabilize the quality of shotcrete to which a quick-setting agent is added, thereby completing the present invention.

That is, the present invention relates to a cement used for performing a spraying operation by adding a quick-setting agent to a base concrete made of high-fluidity concrete, wherein the limestone powder has a Blaine specific surface area of 3000 cm ² / g or more. It consists of a mixture in which the weight ratio of one or more powders selected from silica powder having the same Blaine specific surface area, fly ash having the same Blaine specific surface area and ordinary Portland cement or early-strength Portland cement is 1: 9 to 5: 5. It is a cement for high fluidity shotcrete characterized by the above-mentioned (Claim 1). Further, the present invention is the cement for high flow shotcrete according to claim 1, wherein the slump flow of the base concrete of the high flow shot concrete is 450 to 750 mm (claim 2).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. First, the cement used in the present invention will be described. In the present invention, the Blaine specific surface area is 3000 cm ² / g or more, and in consideration of quick-setting property, the Blaine specific surface area is preferably
Limestone powder of 3500 cm ² / g or more, silica powder of the same Blaine specific surface area, fly ash of the same Blaine specific surface area, one or more powders (hereinafter referred to as inorganic powder) and ordinary Portland cement or early-strength Portland cement Preferably, a cement made of a mixture having a weight ratio of 1: 9 to 5: 5 and a strength development of 1: 9 to 4: 6 is used.
By using a mixture of these inorganic powders and ordinary Portland cement or early-strength Portland cement as a cement for high-flow shotcrete, compared to the case of using plain Portland cement plain containing no inorganic powder, the base concrete And the dispersibility of the quick setting agent in the high fluidity concrete is improved, and the quality of the shotcrete can be stabilized. If the Blaine specific surface area of the inorganic powder used in combination with the ordinary Portland cement or the early-strength Portland cement is less than 3000 cm ² / g, the fluctuation of the compressive strength tends to be large. That is, it is difficult to stabilize the quality of shotcrete, which is not preferable. In addition, the Blaine specific surface area is 10,000 cm ² / g
The fineness of more than 1000 is not practical because the labor required for the production is large and impractical.
It is preferably at most 0 cm ² / g.

In the present invention, if the weight ratio of the inorganic powder in the mixture of the inorganic powder and the ordinary Portland cement or the early Portland cement is less than 10%, the fluctuation of the compressive strength tends to increase, which is not preferable. On the other hand, if the weight ratio of the inorganic powder exceeds 50%, the quick-setting property is undesirably reduced.

As the ordinary Portland cement or the early-strength Portland cement, commercially available ones can be used. As long as the inorganic powder also has a predetermined Blaine specific surface area, commercially available ones may be used,
You may use what was ground. The method for mixing the inorganic powder and the ordinary Portland cement or the early-strength Portland cement is not particularly limited. For example, the inorganic powder and the ordinary Portland cement (or the early-strength Portland cement) are previously mixed at a predetermined ratio, This may be used at the time of concrete production, or may be measured and put into a mixer at the time of concrete production. Commercially available mixtures having a predetermined weight ratio include fly ash cements B and C.
Species, silica cement B and C types.

Materials other than cement used for the base concrete will be described. Examples of the high performance water reducing agent include alkyl allyl sulfonic acid type, naphthalene sulfonic acid type, melamine sulfonic acid type, and polycarboxylic acid type high performance water reducing agents (including high performance AE water reducing agents). Either can be used. Fine aggregates include river sand, sea sand, mountain sand, crushed sand and mixtures thereof. Coarse aggregates include river gravel, sea gravel, crushed stone and mixtures thereof. If necessary, an acrylic or cellulose thickener may be used.

In the present invention, the quick-setting agent to be used is not particularly limited either. A quick-setting agent obtained by combining calcium aluminate and gypsum or a quick-setting agent obtained by combining calcium aluminate and gypsum with alkali aluminate; Furthermore, a quick setting agent combining calcium aluminate and alkali aluminate and / or alkali carbonate can be used. The addition amount of the quick setting agent is 3 to 10% by weight based on the cement in consideration of quick setting property and cost.
Is preferred. The shotcrete in the present invention is obtained by adding a quick-setting agent to the base concrete, and the high-flow shotcrete is the slump flow of the base concrete among the shotcrete.
Shotcrete of 400mm or more.

Next, a base concrete to which the cement of the present invention can be applied will be described. In the cement of the present invention, the slump flow is 400 m as the base concrete.
m of high-fluidity concrete must be used. Naturally, the high-fluidity concrete is practical concrete that does not cause material separation in a slump flow test. Preferably, the slump flow is 450-7
50mm high fluid concrete. Slump flow is 40
Concrete with a thickness of less than 0 mm is not preferred because the fluctuation of the compressive strength tends to increase. Slump flow is 75
If it exceeds 0 mm, the rebound rate tends to increase,
Since the amount of the quick-setting admixture also increases, it is not very preferable in terms of cost and the like.

As the high-fluid concrete, any of so-called "powder-based high-fluid concrete" and "thickener-based high-fluid concrete" can be used as long as the slump flow is within the above range. The composition of these high fluidity concretes is not particularly limited, but the amount of cement is
450~700kg / m ^3, unit water amount 160~200kg / m ^3, water / cement ratio is 28 to 40 wt%, coarse aggregate amount 0.20~0.26m ³ / m ^3, fine aggregate ratio of 55 to 65 % By volume, 2 ~ 8kg when using thickener
/ m ³ is preferable from the viewpoint of pumping performance and the like. If necessary, an admixture such as anhydrous gypsum or an admixture such as a shrinkage reducing agent or an expanding agent may be added as long as the stability of quality is not lost.

The method for preparing the base concrete is not particularly limited, and may be mixed by a conventional mixer. Regarding the construction method of shotcrete,
The usual wet method can be arbitrarily applied. A conventionally used device can also be applied to the spraying device.

[0016]

Test Examples Hereinafter, the present invention will be described with reference to test examples. 1. Materials used Cement: Ordinary Portland cement (manufactured by Nippon Cement Co., Ltd.) Early strength Portland cement (manufactured by Nippon Cement Co., Ltd.) Limestone powder: A: Pulverized limestone produced in bird form (Brain specific surface area: 3700 cm ² / g) B: Pulverized limestone from bird shape (Brain specific surface area 2500 cm ² / g) Fly ash; manufactured by Techno Resource Co., Ltd. (Brain specific surface area 5000 cm ² / g) Silica powder; “Micro silica 3500” (Brain) Specific surface area: 3500cm ² / g) High-performance water reducing agent; "NT-1000S" (manufactured by NMB Corporation) Thickener: "Asano HF" (manufactured by Nippon Cement Co., Ltd.) Fine aggregate: Kokura Minami-ku, Kitakyushu Crushed sand (specific gravity: 2.69): Offshore sea sand (specific gravity: 2.59) = 3: 7 (weight ratio) mixture of coarse sand, coarse aggregate; Crushed stone from Kajiku, Moji-ku, Kitakyushu (specific gravity: 2.80) Water; Tap water quick-setting agent; A: "Asano Super Natomu "(manufactured by Nippon cement (Ltd.)) B:" Den Kanat Mick Type-5 "(manufactured by Denki Kagaku Kogyo Co.)

Table 1 shows the composition of the base concrete.
The base concrete was kneaded for 90 seconds using a biaxial forced kneading mixer (0.1 m ³ ).

[0018]

[Table 1]

The type and amount of the quick setting agent shown in Table 2 were added to the above base concrete, and concrete was sprayed on a box culvert of width 2.5 × depth 3.0 × height 3.0 m with a lath boat stuck inside. In addition, the amount of one spray
It was 0.15m ^3. MEYCO Equipment as spraying equipment
MEYCO Suprema manufactured by Japan Privlico Co., Ltd. was used as a quick-setting agent supply device.

The following characteristics 1) to 3) were measured for the base concrete and the shotcrete. 1) Slump flow: After raising the slump cone of the base concrete immediately after kneading according to "JIS A 1101 (Slump test method for concrete)", the length of the maximum diameter of the expanded concrete and the length in the direction perpendicular thereto are measured. Then, the average value was calculated. 2) Quick setting: The state of the concrete immediately after spraying was examined by finger touch. 3) Compressive strength and its variation; Concrete is sprayed on a wooden box of 30 × 40 × 20 cm, a specimen of φ5 × 10 cm is collected, and cured in humid air at 20 ° C. (Material age: 3 hours and 28 days)
Thereafter, the compressive strength was measured according to "JISA 1108 (test method for compressive strength of concrete)". In addition, the compressive strength in each material age was the average value of three specimens. Regarding the variation in the compressive strength, the coefficient of variation (the index indicating the variation in the compressive strength) of the compressive strength of the three specimens at each material age was determined. Table 2 shows the results.

[0021]

[Table 2]

As is clear from Table 2, in the wet spraying method using high fluidity concrete as the base concrete, in Test Examples 1 to 21 using the cement specified in the present invention, the coefficient of variation of the compressive strength was small. And the stability of quality was excellent. In contrast, Test Examples 22 to 26 using cements other than those specified in the present invention
In this case, the coefficient of variation of the compressive strength was inferior and the quick-setting property was poor as compared with the test examples. On the other hand, in Test Examples 27 to 28 in which concrete having a slump flow of less than 400 mm was used as the base concrete, the coefficient of variation in compressive strength was large and the stability of quality was low.

[0023]

As described above in detail, in the present invention, high fluidity concrete is used as a base concrete of shotcrete in wet spraying using a quick-setting agent, and cement used for the base concrete is used in the present invention. By using the prescribed cement for high fluidity shotcrete, the mixing and dispersibility in the base concrete with respect to various quick-setting agents is improved, and the quality of the shotcrete can be stabilized.

Claims (2)

[Claims] 1. A cement for use in spraying by adding a quick-setting agent to a base concrete made of high-fluidity concrete, wherein the limestone powder has a specific surface area of 3000 cm ² / g or more. Silica powder, characterized in that the weight ratio of one or more powders selected from fly ash of the same brane specific surface area and ordinary Portland cement or early-strength Portland cement is 1: 9 to 5: 5, characterized by comprising a mixture. High fluidity shotcrete for cement. 2. The slump flow of the base concrete of high flow shotcrete is 450 to 750 mm.
A cement for high flow shotcrete as described.