JP2002128556A - Sprayed cement concrete, quick-setting sprayed cement concrete and spraying method using the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a sprayed cement concrete or a quick-set sprayed concrete capable of reducing rebound and improving setting properties and strength. A sprayed cement concrete containing rebound concrete. The rebound concrete may contain a quick setting agent. A quick-setting sprayed cement concrete containing the sprayed cement concrete and a quick-setting agent. Calcium aluminates, alkali metal aluminates, and alkali metal carbonates may be contained as a quick setting agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates mainly to shotcrete for tunnels used in the civil engineering and construction industries. In the present invention, mortar and concrete are collectively called cement concrete.

[0002]

2. Description of the Related Art For example, in the excavation of a mountain tunnel, the NATM method is mainly used in which a rock bolt inserted into the ground and a shotcrete added with a quick-setting agent, which is constructed along the excavation wall surface, are used as main support members. Has become.

The NATM method is, for example, a method in which a tunnel is excavated, and a concrete to which a quick-setting agent is added is sequentially sprayed on a surface of the excavated ground by a spraying machine or the like to perform primary lining. Say.

[0004]

However, in the NATM method, there is a problem in that concrete rebounds, that is, a so-called "rebound" occurs, and about 20% of the total amount of sprayed concrete is rebounded. Was.

[0005] Therefore, the NATM method is not economically preferable because cement and concrete are used more than necessary.
In addition, since the rebound concrete was discarded without being effectively used, there was a problem that it was not preferable for recycling.

The inventor of the present invention found that the use of rebound concrete for quick-setting sprayed cement concrete used in the NATM method for tunnels can significantly reduce rebound and promote setting and hardening. It was completed.

[0007]

That is, the present invention relates to a sprayed cement concrete containing rebound concrete, and a sprayed cement concrete in which the rebound concrete contains a quick setting agent. And, it is a quick setting spraying cement concrete containing the spraying cement concrete and the quick setting agent, the quick setting spraying concrete containing the calcium aluminate as the quick setting agent, and The quick-setting sprayed cement concrete according to claim 3 or 4, wherein the binder contains an alkali metal aluminate and / or an alkali metal carbonate. Further, a spraying method using the quick-setting spraying cement concrete.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

[0009] The sprayed cement concrete of the present invention contains cement and rebound concrete.

[0010] As the cement of the present invention, ordinary, early strength,
Examples include various portland cements having extremely high strength, low heat, and moderate heat, and various mixed cements obtained by mixing a pozzolanic substance such as silica or blast furnace slag with these portland cements.

The aggregate of the present invention is not particularly limited as long as it can be sprayed, but preferably has high aggregate strength. The aggregate includes fine aggregate and coarse aggregate. As fine aggregate, river sand, mountain sand, lime sand, silica sand and the like can be used, and as coarse aggregate, river gravel, mountain gravel, lime gravel and the like can be used.

The rebound concrete of the present invention refers to concrete that has rebounded when the shot concrete is sprayed on the ground.

The rebound concrete contains fine aggregate, coarse aggregate, quick setting agent, moisture, cement hydrate and the like.
In rebound concrete, initial setting is easy,
Rebound concrete containing a quick-setting agent is preferred in that the effect of reducing rebound is sufficient. As a quick setting agent,
The following quick setting agents are mentioned.

When the rebound concrete is reused, the rebound concrete is crushed and the particle size is reduced to 0.15.
mm and not more than 5 mm (hereinafter referred to as rebound concrete fine aggregate) are used as a part of fine aggregate,
mm (hereinafter referred to as rebound concrete coarse aggregate) is used as a part of the coarse aggregate. Also, 0.15
Those having a diameter of less than mm may be used as fine powder.

[0015] After the rebound concrete is sprayed, it is preferable to reuse it after 1 to 28 days of age, and more preferably 3 to 7 days after its age. Age 1
If it is less than a day, it is difficult to recycle because the rebound concrete does not harden sufficiently, and it is not economically advantageous to store it for more than 28 days.

[0016] The amount of the rebound concrete of the present invention is not particularly limited. Usually, a part or all of the aggregate can be used.
% Is preferably replaced with rebound concrete, and more preferably 10-30% is replaced with rebound concrete. If it is less than 5%, it is difficult to set initially,
The effect of reducing rebound may not be sufficient,
%, The slump loss may increase.

[0017] The quick-setting sprayed cement concrete of the present invention contains sprayed cement concrete and a quick-setting agent.

The quick-setting agent of the present invention is used for accelerating the initial setting, and is not particularly limited as long as it can be mixed with the sprayed cement concrete. Examples of the quick setting agent include cement minerals such as calcium aluminates. Among these, the setting properties such as quick setting and hardening of quick-setting sprayed cement concrete are excellent, and in terms of good strength development, the use of cement mineral quick-setting agents is preferable, and calcium aluminates are more preferable. .

The calcium aluminates of the present invention include:
Mixing a raw material containing calcia and a raw material containing alumina, and calcining in a kiln or performing a heat treatment such as melting in an electric furnace, CaO and Al ₂ O ₃ as main components,
It is a general term for substances having hydration activity, and a part of CaO and / or Al ₂ O ₃ is alkali metal oxide, alkaline earth metal oxide, silicon oxide, titanium oxide, iron oxide, alkali metal halide, Alkaline earth metal halides,
It is a compound obtained by dissolving a small amount of a compound substituted with an alkali metal sulfate, an alkaline earth metal sulfate, or the like, or a compound containing CaO and Al ₂ O ₃ as main components. The mineral form may be either crystalline or amorphous.

Of these, calcium aluminate is preferable in terms of reaction activity, and 12CaO · 7Al ₂ O ₃
A mixture containing amorphous calcium aluminate obtained by quenching a heat-treated product corresponding to a composition (hereinafter referred to as C ₁₂ A ₇ ) is more preferable.

The particle size of calcium aluminates is determined by the reaction
In terms of sex, 3000cm in Brain value^Two/ G or more is preferred
4000cm^Two/ G or more is more preferable. 300
0cm ^Two/ G, the reactivity is low and sufficient effect is achieved.
May not be able to volatilize.

Further, an alkali metal aluminate and / or an alkali metal carbonate may be used in combination with the quick-setting agent of the present invention. The alkali metal aluminate of the present invention (hereinafter referred to as aluminate) promotes initial setting and reduces rebound.

Examples of the aluminate include lithium aluminate, sodium aluminate and potassium aluminate, and one or more of these can be used.
Among these, sodium aluminate is preferred from the viewpoint of promoting initial setting and reducing rebound.

The amount of the aluminate used is preferably from 10 to 100 parts by mass, more preferably from 20 to 80 parts by mass, based on 100 parts by mass of the calcium aluminates. If the amount is less than 10 parts by mass, initial setting is difficult, and rebound may increase. If the amount exceeds 100 parts by mass, long-term strength development may be impaired.

The alkali metal carbonate (hereinafter referred to as carbonate) of the present invention promotes initial setting, reduces rebound and improves initial strength development.

Examples of the carbonate include sodium carbonate, potassium carbonate, and sodium bicarbonate, and one or more of these can be used. Among them, sodium carbonate is preferred in terms of promoting initial setting, reducing rebound, and improving initial strength development.

The amount of the carbonate used is preferably from 10 to 100 parts by mass, more preferably from 20 to 80 parts by mass, based on 100 parts by mass of the calcium aluminates. If the amount is less than 10 parts by mass, the initial setting is difficult, the rebound increases, and there is a possibility that the initial strength manifestation may be impaired.

The quick-setting agent of the present invention is preferably used in combination with calcium aluminates, aluminates, and carbonates in order to promote initial setting, reduce rebound, and improve initial strength development.

The amount of the quick setting agent used is preferably 3 to 15 parts by mass, more preferably 5 to 10 parts by mass, based on 100 parts by mass of cement. If it is less than 3 parts by mass, it is difficult for the initial setting to occur,
Rebound may increase, and if it exceeds 15 parts by mass, long-term strength development may be impaired.

The water / cement ratio of the sprayed cement concrete of the present invention is preferably 25-70%, more preferably 40-60.
% Is more preferred. If it is less than 25%, the pumpability may be deteriorated, and if it exceeds 70%, the coagulation properties and the strength expression may be deteriorated.

In the spraying method of the present invention, it is possible to spray as quick setting cement concrete in terms of required physical properties, economy and workability. As the spraying method of the present invention, any of a dry spraying method and a wet spraying method can be used. As a dry spraying method, there is a method of mixing cement, aggregate including rebound concrete, and a quick-setting admixture, pneumatically feeding, for example, adding water from one side of a Y-tube, and spraying in a wet state. No. As a wet spraying method, cement, aggregate including rebound concrete, and water are mixed and kneaded, air-pneumatically fed, and, for example, a method of adding a quick-setting agent from one of the Y-shaped pipes and spraying the mixture. Is mentioned.

In the spraying method of the present invention, conventional spraying equipment can be used. The spraying equipment is not particularly limited as long as the spraying is sufficiently performed. For example, Aliver 280 (trade name) is used for pumping cement concrete, and a quick-setting agent pumping apparatus is used for pumping a quick-setting agent. "Natom Cleat" can be used.

In the present invention, zeolite, hydrotalcite, hydrocalumite, reinforcing fiber material, water reducing agent,
High-performance water reducing agent, high-performance AE water reducing agent, thickener, cement expander, rust inhibitor, anti-freezing agent, clay minerals such as bentonite and montmorillonite, gypsum, limestone fine powder, blast furnace slag fine powder, silica fume, and fly Ash and the like may be used together within a range that does not substantially inhibit the object of the present invention.

[0034]

Hereinafter, the present invention will be described in detail with reference to experimental examples.

Reference Example 1 Unit cement amount 360 kg, unit water amount 198 kg, S /
a = 46% sprayed concrete, and a quick setting agent consisting of 100 parts by mass of calcium aluminates, 20 parts by mass of aluminate, and 30 parts by mass of carbonate were added to cement 100
The quick-setting sprayed concrete obtained by mixing 7 parts by mass with respect to the parts by mass was sprayed into a simulated tunnel by a wet method. Rebound concrete generated at the time of spraying was collected, crushed after a predetermined age by a crusher, and the following experiment was immediately performed. In addition, the particle size is 0.15 mm or more and 5 m.
m or less was defined as rebound concrete fine aggregate, and those having a particle size exceeding 5 mm were defined as rebound concrete coarse aggregate.

Experimental Example 1 Rebound concrete coarse aggregate and rebound concrete fine aggregate were respectively replaced with coarse aggregate and fine aggregate at the ratios shown in Table 1, and the unit cement amount was 360 kg / m ³ and the unit water amount was 198 kg / m ^3. , S / a = 46% sprayed concrete was prepared. A quick setting spray concrete obtained by mixing 7 parts by mass of 100 parts by mass of calcium aluminate, 20 parts by mass of aluminate, and 30 parts by mass of carbonate with this sprayed concrete with respect to 100 parts by mass of cement. Was sprayed on a simulated tunnel by a wet method. The setting time, rebound rate, and slump loss of the obtained quick-setting spray concrete were measured.
Table 1 shows the results.

<Materials used> Rebound concrete coarse aggregate: 7 days old, specific gravity 2.55 Rebound concrete fine aggregate: 7 days old, specific gravity 2.45 Cement: ordinary Portland cement, commercially available calcium Aluminates: main component C ₁₂ A ₇ , amorphous,
Blaine specific surface area 5900 cm ² / g Aluminate: sodium aluminate, commercial product Carbonate: sodium carbonate, commercial product Coarse aggregate: from Himekawa, Niigata prefecture, crushed stone, specific gravity 2.64 Fine aggregate: from Himekawa, Niigata prefecture, specific gravity 2.62 water: tap water

<Measurement Method> Setting time: Fine aggregate and rebound concrete fine aggregate were used as sand without using coarse aggregate and rebound concrete coarse aggregate. A quick-setting mortar having a water / cement ratio of 60% and a cement-sand ratio of 1: 3 was prepared, and the setting time was measured. The setting time is ASTM C 403
The values were indicated by the proctor penetration resistance values measured according to the above. Rebound rate: Measure the ratio of the mass of rebounded concrete to the mass of quick-setting concrete sprayed, and
Indicated by Slump loss: A value obtained by subtracting the slump value after 90 minutes from the slump value immediately after kneading was defined and evaluated as slump loss. Regarding slump, the slump value of shotcrete containing no quick-setting agent was determined according to JIS A11.
01 was measured.

[0039]

[Table 1]

EXPERIMENTAL EXAMPLE 2 Sprayed concrete was prepared by replacing 20% of the rebound concrete coarse aggregate and 20% of the rebound concrete fine aggregate with the rebound concrete coarse aggregate and the rebound concrete fine aggregate, respectively. The setting was performed in the same manner as in Experimental Example 1 except that the quick-setting agent shown in Table 2 was mixed to prepare a quick-setting sprayable concrete, and the setting time, the rebound rate, and the compressive strength were measured. Table 2 shows the results.

<Measurement Method> Compressive strength: A specimen was cored from a simulated tunnel sprayed with quick-setting sprayed concrete, and subjected to JIS A1.
It measured according to 108.

[0042]

[Table 2]

[0043]

The rebound can be reduced by using the quick-setting sprayed cement concrete of the present invention.
Since the setting property and the strength development can be improved, it is possible to perform the spraying with good economic efficiency and low environmental load.
Further, since the quick-setting sprayed cement concrete of the present invention uses rebound concrete, recycling of the cement concrete is promoted, which is also useful for reducing environmental load.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 22:08 C04B 22:08 Z 22:10) 22:10)

Claims (6)

[Claims] 1. A sprayed cement concrete containing rebound concrete. 2. A sprayed cement concrete in which the rebound concrete contains a quick setting agent. 3. A quick-setting sprayed cement concrete comprising the sprayed cement concrete according to claim 1 and a quick-setting agent. 4. The quick-setting sprayed cement concrete according to claim 3, wherein the quick-setting agent contains calcium aluminates. 5. The quick-setting sprayed concrete according to claim 3, wherein the quick-setting agent further comprises an alkali metal aluminate and / or an alkali metal carbonate. 6. A spraying method using the quick-setting sprayable cement concrete according to any one of claims 3 to 5.