JP2001220204A - Covering concrete having ultra high strength - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide compounding for a covering concrete exhibiting function of an ultra high strength and a high durability in NTL construction. SOLUTION: A covering concrete containing at lest a cement, a pozzolanic fine powder, aggregates having particle diameters of <=2 mm, water and a water reducing agent. Further, the covering concrete may contain a metal fiber and/or an organic fiber, and an inorganic powder, fibrous particles or flaky particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-high-strength lining concrete to be used for supporting a tunnel.

[0002]

2. Description of the Related Art In the NATM construction method generally used as a mountain tunnel construction method, after excavating a ground, a support is carried out with concrete so that the ground does not collapse, a primary support is sprayed with concrete, and a secondary support is sprayed with concrete. Digging while doing each with lining concrete. In such a tunnel construction technology, the excavated cross section of the tunnel needs to be larger than the final designed cross section by the construction thickness of the spraying and the lining concrete. For this reason, the construction cost of the excavation work depends on the thickness of the shoring work, and the thickness of the shoring work becomes larger as the rock quality is poor or the tunnel has a large cross section, and the labor required for digging is enormous. It will be. In addition, since the shotcrete work and the lining concrete work are performed in different processes, the supporting work requires time and labor. As described above, there is a problem that the ratio of the construction cost from the excavation to the shoring is high in the total cost of the tunnel construction.

[0003] As a measure to solve this problem, the strength of shotcrete is increased to reduce the thickness of the concrete.
There is a method of making a single shell structure without performing secondary support. However, in the case of a single shell structure using only shotcrete, the finished surface is inevitably uneven, resulting in a poor appearance. For this reason, there is a visual sense of psychological anxiety for those who pass through the tunnel, and in the case of a road tunnel, there is a concern that it has a particularly adverse effect on safety.
Furthermore, since the shotcrete method has a large variation in quality, the probability of leaving a defect in a structure is higher than that of a normal concrete product, and there is a concern that long-term durability may be adversely affected. Recently, cases have been reported frequently in which the lining concrete of a tunnel constructed about 20 years ago has fallen due to lack of durability, and high durability performance has been strongly demanded. On the other hand, there is an NTL method in which a concrete having high fluidity is poured into a formwork together with a rapidly hardened material as a method of uniforming the quality of a hardened body, although the working speed is inferior to that of shotcrete. Since the use of the NTL method is expected to simplify and rationalize the construction of the tunnel support, it has begun to be considered by the Geoff Fronte Study Group.

[0004]

In the NTL method, since concrete is poured into a formwork to perform the work, it is first necessary that the base concrete has high fluidity without material separation. Also, to maintain the pot life so that it can be easily filled into the mold after being mixed with the hardened material, and to quickly develop strength after that,
Concrete is required to have high strength and high durability so that it can be used permanently as a single shell structure. Up to now, the composition of concrete used in the NTL method is almost the same as or close to that of conventional shotcrete. For this reason, a concrete composition which has high fluidity and high material non-separability, develops strength early, has high short-term strength and long-term strength, and satisfies all of high durability has not yet been obtained. Accordingly, an object of the present invention is to provide a blend of lining concrete exhibiting ultra-high strength and high durability performance for the NTL method.

[0005]

Means for Solving the Problems As a result of intensive research in view of the above-mentioned circumstances, at least, lining concrete containing cement, pozzolanic fine powder, aggregate having a particle size of 2 mm or less, water and a water reducing agent solves the above problems. The inventors have found that the present invention can be solved, and have completed the present invention. Further, the present invention may include metal fibers and / or organic fibers, and may further include inorganic powders, fibrous particles, or flaky particles.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The type of cement used in the present invention is not limited. Various portland cements such as ordinary Portland cement, early-strength Portland cement, medium heat Portland cement, low heat Portland cement, and mixed cements such as blast furnace cement and fly ash cement can be used.

[0007] In the present invention, it is preferable to use early-strength Portland cement in order to improve the early strength of concrete, and to improve the fluidity of concrete, it is preferable to use medium-heat Portland cement or low-heat Portland cement. It is preferred to use

[0008] Pozzolanic fine powder includes silica fume, silica dust, fly ash, slag, volcanic ash,
Silica sol, precipitated silica and the like. Generally, in silica fume and silica dust, the average particle size is 1.
Since it is 0 μm or less and it is not necessary to grind, it is suitable as the pozzolanic fine powder of the present invention.

By blending pozzolanic fine powder,
Due to the microfiller effect and the cement dispersing effect, the concrete is densified and the compressive strength is improved. on the other hand,
When the amount of the pozzolanic fine powder increases, the unit water amount increases.
It is preferably 5 to 50 parts by weight based on parts by weight.

In the present invention, an aggregate having a particle size of 2 mm or less is used. Here, the particle size of the aggregate is 85% (weight).
It is a cumulative particle size (an aggregate larger than 2 mm may be included). If the particle size of the aggregate exceeds 2 mm, the strength decreases. It is preferable to use an aggregate having a maximum particle size of 2 mm or less, more preferably an aggregate having a maximum particle size of 1.5 mm or less, from the viewpoint of the separation resistance of the concrete, the strength after hardening, and the like.

[0011] Aggregates include river sand, land sand, sea sand, crushed sand,
Silica sand and mixtures thereof can be used. The amount of the aggregate is determined based on the workability and separation resistance of the concrete, the strength after hardening and the resistance to cracks, etc.
50 to 250 parts by weight, preferably 8 parts by weight,
0 to 180 parts by weight is more preferred.

As the water reducing agent, a lignin type, naphthalene sulfonic acid type, melamine type or polycarboxylic acid type water reducing agent, an AE water reducing agent, a high performance water reducing agent or a high performance AE water reducing agent can be used. Among them, it is preferable to use a high performance water reducing agent or a high performance AE water reducing agent. The amount of the water reducing agent to be added is 0.5 to 4.0 parts by weight in terms of solid content with respect to 100 parts by weight of cement in view of the fluidity and separation resistance of concrete, the strength after hardening, and the cost. preferable.

In the present invention, the water / cement ratio is preferably from 10 to 30%, more preferably from 15 to 25%, in view of the fluidity and separation resistance of the concrete, the strength and durability of the cured product, and the like.

The type of the hardened material used in the present invention is not particularly limited. Commonly hardened materials include cement minerals and inorganic salts. The rapidly hardened material usually used in the NTL method is a cement mineral powder, and is generally slurried and added to and mixed with the base concrete. The cement-hardened rapid hardening material is mainly composed of calcium aluminate or calcium sulfoaluminate as a main component, and is often used in combination with a setting retarder such as citric acid or oxycarboxylate as appropriate. Recently, liquid quick-hardened materials having no self-hardening properties have been developed, and it is expected that quality control accompanying powder slurrying can be simplified. The amount of the hardened material varies depending on the working conditions such as the environmental temperature and the materials used. However, in the case of a rapidly hardened material, the solid content is usually about 10 to 15% of the cement mass, For hardwoods, it is about 8-15%.

In the present invention, from the viewpoint of enhancing the flexural strength and flexural toughness of the cured product, it is preferable that the composition contains metal fibers and / or organic fibers. Examples of the metal fiber include a steel fiber and an amorphous fiber. Among them, the steel fiber is excellent in strength, and is preferable from the viewpoint of cost and availability. The metal fiber preferably has a diameter of 0.01 to 1.0 mm and a length of 2 to 30 mm. If the diameter is less than 0.01 mm, the strength of the fiber itself is insufficient, and the fiber tends to be cut when subjected to tension. 1.0mm in diameter
If the number exceeds the number, the number of pieces with the same compounding amount decreases, and the flexural strength of concrete decreases. If the length exceeds 30 mm, fiber balls tend to be formed during kneading. If the length is less than 2 mm, the adhesive strength to the matrix is reduced and the bending strength is reduced.

The amount of the metal fibers is preferably less than 4%, more preferably less than 3.5% of the concrete volume after setting. The content of the metal fiber is determined from the viewpoint of fluidity and bending strength of the cured product. In general, as the content of the metal fiber increases, the bending strength improves, but on the other hand, the unit water amount also increases in order to secure fluidity. Therefore, the content of the metal fiber is preferably the above-mentioned amount.

Examples of the organic fibers include vinylon fibers, polypropylene fibers, polyethylene fibers, aramid fibers, and carbon fibers. Organic fibers have a diameter of 0.005 to
Those having a length of 1.0 mm and a length of 2 to 30 mm are preferred. Organic fiber content is 10% of concrete volume after setting
Is preferably less than 7%, more preferably less than 7%. In the present invention, it is possible to use metal fibers and organic fibers in combination.

In the present invention, from the viewpoint of increasing the packing density of the cured product, it is preferable to include an inorganic powder having an average particle size of 3 to 20 μm, more preferably 4 to 10 μm. As the inorganic powder, quartz powder, limestone powder, Al
Oxide powder such as ₂ O ₃ , carbide powder such as SiC, SiN
And the like, and among them, quartz powder is preferable in terms of cost and quality stability of the cured product. Examples of the quartz powder include quartz and amorphous quartz, and opal and cristobalite silica-containing powders. The amount of the inorganic powder is preferably 50 parts by weight or less, more preferably 20 to 35 parts by weight, based on 100 parts by weight of cement, from the viewpoint of the fluidity of the concrete, the strength of the hardened body, and the like.

In the present invention, from the viewpoint of increasing the toughness of the cured product, it is preferable to include fibrous particles or flaky particles having an average particle size of 1 mm or less. Here, the particle size of a particle is the size of its maximum dimension (in particular, its length for fibrous particles). Examples of the fibrous particles include wollastonite, bauxite, and mullite, and examples of the flaky particles include mica flake, talc flake, vermiculite flake, and alumina flake. The blending amount of the fibrous particles or flaky particles is preferably 35 parts by weight or less, more preferably 10 to 25 parts by weight, based on 100 parts by weight of cement, from the viewpoint of the fluidity of the concrete, the strength and the toughness of the cured product. From the viewpoint of enhancing the toughness of the cured product, it is preferable to use fibrous particles having a needleiness expressed by a length / diameter ratio of 3 or more.

In the present invention, the method for kneading concrete is not particularly limited. The apparatus used for kneading is not particularly limited, and a conventional mixer such as an omni mixer, a pan-type mixer, a biaxial kneading mixer, and a tilting mixer can be used.

The above kneaded concrete is cast by the NTL method, mixed with a rapidly hardened material, cured and hardened, whereby the ultra high strength lining concrete of the present invention can be manufactured. In addition, the concrete placement method by the NTL method includes a blowing method, a blowing pressure bonding method, a pouring method,
There are a pouring and pressure bonding method and a coating method, but in the present invention, any of them can be used and is not particularly limited.

[0022]

The present invention will be described below with reference to examples. In this embodiment, the physical properties targeted by the present invention can be used for a normal NTL method in which a form is installed on a face immediately after cross-section excavation, and a single-shell structure with an ultra-high-strength and high-durability permanent structure. Pot time 1
5 minutes or more (the slump flow of concrete after 15 minutes from the addition and kneading of the quick setting agent is 350 mm or more), the compressive strength is 0.5 MPa or more 30 minutes after casting, and 5 MPa or more at 6 hours of age. The pressure was 80 MPa or more at the age of 28 days. In terms of flexural strength, 15 days at the age of 28 days
MPa or more. The casting method used was a pouring method.

Materials used in this example 1) Cement; Low heat Portland cement (manufactured by Taiheiyo Cement) Early-strength Portland cement (manufactured by Taiheiyo Cement) 2) Pozzolanic fine powder; Silica fume (average particle size 0.7 μm) 3 ) Aggregate; 2: 1 (weight ratio) mixture of silica sand No. 4 and silica sand No. 5 4) Metal fiber: steel fiber (diameter: 0.2 mm, length: 15 mm) Organic fiber: vinylon fiber (diameter: 0) 0.6 mm, length: 15 mm) 5) High-performance AE water reducing agent; polycarboxylic acid-based high-performance AE water reducing agent 6) Water; tap water 7) Quartz powder (average particle diameter 7 μm) 8) Fibrous particles; Wollastonite (Average length 0.3 mm, length / diameter ratio 4) 9) Rapid hardened material; trade name "Asano Super Natom" (powder made by Asano Co., Ltd.) trade name "RHOCA Jet" (made by Onoda Co., Ltd.) Liquid) 10) Setting regulator; citric acid

Example 1 (Blending conditions) Low heat Portland cement; 100 parts by weight Silica fume; 32.5 parts by weight Aggregate: 120 parts by weight High-performance AE water reducing agent: 1.0 parts by weight (solid content) water / cement ratio; 22% Asano Super Natom; 5 parts by weight Setting regulator; 1.0 part by weight based on 100 parts by weight of cement

(Test Method and Results) Cement, silica fume, aggregate, high-performance AE water reducing agent and water were collectively charged into a biaxial kneading mixer and kneaded. After kneading, citric acid and a quick hardener were added thereto, and kneading was performed again. afterwards,
Change in pot life over time, and age 30 minutes, 6 hours and 2
The compressive strength on day 8 was measured, and the results are shown in Table 1.

[0026]

[Table 1]

Example 2 (Blending conditions) Early strength Portland cement; 100 parts by weight Silica fume; 32.5 parts by weight Aggregate: 120 parts by weight High-performance AE water reducing agent: 2.0 parts by weight (solid content) Water / cement ratio 22% RHOCA Jet; 7 parts by weight setting regulator; 1.2 parts by weight per 100 parts by weight of steel fiber; 2% of volume in concrete

(Kneading method) Cement is added to a biaxial kneading mixer.
Water was added to a mixture in which silica fume, aggregate, high-performance AE water reducing agent, and steel fiber were previously mixed and kneaded. Thereafter, a setting modifier and a hardened material were added and kneading was performed again. Temporal change of pot life after adding hardened wood, age 30 minutes,
The compressive strength at 6 hours and 28 days and the bending strength at 28 days of material age were measured, and the results are shown in Table 2.

[0029]

[Table 2]

Example 3 (Blending conditions) Early-strength Portland cement; 100 parts by weight Silica fume; 32.5 parts by weight Aggregate: 120 parts by weight Quartz powder; 30 parts by weight Wollastonite; 24 parts by weight High-performance AE water reducing agent; 2.0 parts by weight (solid content) Water / cement ratio; 22% RHOCA Jet; 7 parts by weight Setting modifier; 1.2 parts by weight with respect to 100 parts by weight of steel fiber; 2% of volume in concrete

(Kneading method) Cement is added to a biaxial kneading mixer.
Silica fume, aggregate, quartz powder, wollastonite,
A high-performance AE water reducing agent, steel fiber and water were added at once and kneaded. Thereafter, a setting modifier and a hardened material were added and kneading was performed again. The time-dependent change in the pot life after the addition of the hardened material, the compressive strength at the age of 30 minutes, 6 hours and 28 days, and the bending strength at the age of 28 days were measured. The results are shown in Table 3.

[0032]

[Table 3]

As can be seen from the above Tables 1 to 3, in all the examples, the pot life shows a slump flow value of 350 mm or more up to 15 minutes, and the compressive strength shows an age of 30 years.
0.5MPa or more that can remove the formwork in minutes,
5 MPa or more at a material age of 6 hours, 80 MPa or more at a material age of 28 days, and a bending strength of 15 MPa or more at a material age of 28 days.

[0034]

According to the present invention, it is possible to provide a lining concrete having ultra-high strength and high durability performance for the NTL method.

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Claims (6)

[Claims] 1. An ultra-high-strength lining concrete comprising at least a cement, a pozzolanic fine powder, an aggregate having a particle diameter of 2 mm or less, a cured product of a compound containing water and a water reducing agent. 2. The high-strength lining concrete according to claim 1, wherein the composition contains metal fibers and / or organic fibers. 3. The metal fiber has a diameter of 0.01 to 1.0 mm,
The ultra-high-strength lining concrete according to claim 2, which is a steel fiber having a length of 2 to 30 mm. 4. The organic fiber has a diameter of 0.005 to 1.0 m.
The ultra-high-strength lining concrete according to claim 2, which is at least one fiber selected from vinylon fiber, polypropylene fiber, polyethylene fiber, aramid fiber, and carbon fiber having a length of 2 to 30 mm. 5. The ultra-high-strength lining concrete according to claim 1, wherein the composition contains an inorganic powder having an average particle size of 3 to 20 μm. 6. The ultra-high-strength lining concrete according to claim 1, wherein the composition contains fibrous particles or flaky particles having an average particle size of 1 mm or less.