JP5611795B2 - Quick setting agent for spraying, sprayed concrete using the same, and spraying method - Google Patents

Description

  The present invention relates to a rapid setting agent for spraying used for spraying concrete, sprayed concrete using the same, and a spraying method.

In order to prevent the collapse of exposed ground such as tunnel excavation, a spraying method for quick setting sprayed concrete in which a quick setting agent is mixed with concrete is performed. (See Patent Document 1)
In this method, spray concrete is usually made at a cement, aggregate, and water metering and mixing plant installed at the excavation site, transported by an agitator car, pumped by a concrete pump, and joined at a midway. It is a construction method in which a pipe is mixed with a quick-setting agent pumped from the other side and sprayed to the ground surface as a quick setting sprayed concrete to a predetermined thickness.

  In this method, the rebound rate, which is the ratio of the amount that falls without being attached to the ground and the amount that is sprayed, is as large as 15 to 30% by weight, and a method that requires little rebound is required. There is no spraying material or spraying method, and improvements are strongly desired.

  In recent years, spraying speed per unit time has increased compared to before due to economic considerations and improved performance of construction machines. In particular, when excavating large-section tunnels, it is important to reduce the construction time and excavation cycle in consideration of economic efficiency and work efficiency.

  However, with the increase in the spraying speed, the shotcrete will take a large weight in a short time, and the previous initial strength development performance may not be able to support its own weight and may peel off and increase the rebound, Since danger increases, improvement of initial strength development is desired.

  So far, as a method to improve the strength development properties of shotcrete, a wet spray method using a quick setting agent made by mixing a mixture of calcium aluminate and anhydrous gypsum, etc. Has been proposed. (See Patent Document 2).

Japanese Patent No. 1312600 Japanese Patent No. 4248455

In the wet spray method using a quick-setting agent made by mixing calcium aluminate and anhydrous gypsum etc., strength development can be improved, but gypsum must be mixed with cement, and the batch for producing ready-mixed concrete at the construction site. Char plant requires equipment to store and meter gypsum. Thus, there has been a demand for sprayed concrete having both economic efficiency and strength development.
As a result of repeated investigations to solve the above problems, the present inventors use a specific gypsum whose particle size is adjusted for the spray setting agent, thereby improving the adhesion and strength development of sprayed concrete. As a result, the present invention was completed.

  That is, the present invention includes (1) calcium aluminate, 5% or less of particles having a particle size of 1 μm or less, 80% or more of particles of 10 μm or less, and an average particle size of 2 to 6 μm, Spraying agent containing alkali metal aluminate and / or alkali metal carbonate, (2) Spraying agent containing 5 to 15 parts of spraying agent of (1) for 100 parts of cement A spraying method using the sprayed concrete of (3) and (2).

  By using the rapid setting agent for spraying of the present invention, the setting and hardening performance of the shotcrete is improved, the adhesion to the ground and rock is improved, and the rebound of the material immediately after spraying is reduced. In addition, since the initial strength development is greatly improved, the phenomenon of peeling and peeling is reduced even under spraying conditions in which a large weight is applied in a short time, and the rebound is reduced and the safety of work can be ensured. .

Hereinafter, the present invention will be described in detail.
In the present invention, “parts” and “%” are based on mass unless otherwise specified.
The concrete referred to in the present invention is a general term for cement paste, mortar, and concrete.

As the cement used in the present invention, various Portland cements such as early strength and various mixed cements obtained by mixing blast furnace slag, fly ash, etc. with these Portland cements can be used, and they can be properly used depending on required requirements. it can.
The cement amount of the concrete used in the present invention is preferably 360 to 600 kg / m ³ from the viewpoints of workability, viscosity, and economy.

Calcium aluminate used in the present invention improves initial coagulation and strength development. A mixture of CaO raw material or Al ₂ O ₃ raw material is baked in a kiln or melted in an electric furnace. This is a quick-setting component that causes agglomeration of cement concrete in the initial stage.
As a mineral component of calcium aluminate, when CaO is C and Al ₂ O ₃ is A, a pulverized calcium aluminate heat treatment product represented by C ₃ A, C ₁₂ A ₇ , CA, CA ₂ or the like Is mentioned. Furthermore, as other components, calcium aluminosilicate containing SiO ₂ , C ₁₁ A ₇ · CaX ₂ (X is a halogen such as fluorine) in which one CaO of C ₁₂ A ₇ is replaced with a halide such as CaF ₂ , C ₄ A ₃ · SO ₃ containing SO ₃ component, calcium aluminate in which alkali metals such as sodium, potassium and lithium are partly dissolved, and the like can be used. One or more of these can be used. is there.
Among these, amorphous calcium aluminate obtained by quenching the heat-treated product corresponding to the C ₁₂ A ₇ composition is preferable in terms of reaction activity.
The particle size of the calcium aluminate, from the viewpoint of quick-setting property or development of strength, preferably 3000 cm ² / g or more in Blaine value, 4000 cm ² / g or more is more preferable.

Examples of the gypsum used in the present invention include anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum, and one or more of these can be used. Of these, anhydrous gypsum is preferred from the standpoint of strength development.
In the present invention, the particle size of gypsum is 5% or less for particles having a particle size of 1 μm or less, 80% or more for particles having a particle size of 10 μm or less, and an average particle size adjusted to 2 to 6 μm. The method for adjusting the particle size is not particularly limited, and for example, it is carried out by pulverization and classification.
When particles with a particle size of 1 μm or less are contained in excess of 5%, it is difficult to obtain the effect of improving the adhesion and strength development, and the storage stability of the powder quick-setting agent itself may be deteriorated. If it is less than 80%, the effect of improving adhesion and strength development cannot be obtained.
The amount of gypsum used is preferably 10 to 150 parts, more preferably 40 to 120 parts, relative to 100 parts of calcium aluminate. If it is less than 10 parts, it is difficult to improve adhesion and strength development, and if it exceeds 150 parts, it is difficult to improve adhesion and strength development and may expand for a long time.

  In the spray setting agent of the present invention, an alkali metal aluminate and / or an alkali metal carbonate is used as an aid for promoting the initial setting.

The alkali metal aluminate used in the present invention is, for example, one obtained by mixing and melting aluminum hydroxide and an alkali metal hydroxide and drying to obtain a powder, which promotes very early condensation. Examples thereof include lithium aluminate, sodium aluminate, and potassium aluminate, and one or more of these can be used. Among these, sodium aluminate is preferable in terms of setting properties.
The amount of alkali metal aluminate used is preferably 1 to 20 parts and more preferably 2 to 15 parts with respect to 100 parts of calcium aluminate from the standpoints of early setting and long-term strength.

  The alkali metal carbonate used in the present invention assists in increasing the initial strength, and includes sodium carbonate, potassium carbonate, sodium bicarbonate and the like, and one or more of these can be used. is there. The amount of alkali metal carbonate used is preferably 1 to 50 parts, more preferably 3 to 20 parts, per 100 parts of calcium aluminate. If it is less than 1 part, there is no effect, and if it exceeds 50 parts, the setting performance may be lowered.

  The amount of the rapid setting agent for spraying of the present invention is preferably 5 to 15 parts with respect to 100 parts of cement from the viewpoints of initial setting property, initial strength development and workability. If it is less than 5 parts, proper rapid setting performance cannot be obtained, and if it is added in excess of 15 parts, the piping may be clogged and it is not economical.

In this invention, it is possible to use a water reducing agent for shotcrete as needed. A water reducing agent means what is used in order to improve the fluidity | liquidity of concrete, and both a liquid and a powdery thing can be used and a high performance water reducing agent is preferable. Formalin condensates of alkyl allyl sulfonate, naphthalene sulfonate, and melamine sulfonate, polycarboxylic acid polymer compounds, and the like can be used, and one or more of these can be used.
What is necessary is just to set the usage-amount of a water reducing agent in the surface of the fluidity | liquidity to require and strength expression.

  Furthermore, in this invention, in order to improve the impact resistance and toughness of shotcrete, it is possible to use a fiber substance together.

In the present invention, both inorganic fibers and organic fibers can be used, which has the effect of improving the impact resistance and toughness of shotcrete.
The length of the fiber material is preferably 70 mm or less, more preferably 0.5 to 60 mm in terms of concrete pumpability and mixing properties, in terms of pumpability.
Examples of the inorganic fiber include glass fiber, carbon fiber, and metal fiber, and examples of the organic fiber include vinylon fiber, PET recycled fiber, and polypropylene fiber. One or more of these can be used. Among these, metal fiber and polypropylene fiber are preferable in terms of economy.
The amount of the fiber material used is preferably 0.1 to 2% by volume, more preferably 0.3 to 1.5% by volume of the shotcrete, from the viewpoints of impact resistance, toughness, fluidity, and pumpability.

  The amount of water used in the production of shotcrete is preferably 30 to 65 parts, more preferably 40 to 60 parts with respect to 100 parts of cement, from the viewpoints of economy, pumpability and strength development.

The aggregate such as fine aggregate and coarse aggregate used in the shotcrete of the present invention preferably has a low water absorption rate and a high strength of the aggregate itself, but is not particularly limited.
The fine aggregate is preferably one having a maximum dimension of 5 mm or less, and examples thereof include river sand, mountain sand, and lime sand. As the coarse aggregate, those having a maximum dimension of 15 mm or less are preferable.

  The fluidity of the shotcrete used in the present invention is not particularly limited, and may be a value that provides appropriate workability and adhesion.

  In the present invention, the method for producing shotcrete is not particularly limited. Any method may be used as long as a predetermined kneading property can be obtained by a predetermined blending.

In the spraying method of the present invention, the spraying operation is performed as dry cement mortar containing cement, cement mortar containing cement and water, or a paste or concrete thereof from the required physical properties, economy, workability, and the like. Either a dry spraying method or a wet spraying method can be used.
As a dry spraying method, cement, quick-setting agent, aggregate, etc. are mixed, pneumatically fed, water is added from the addition pipe on the way, and sprayed in a wet state, or cement and aggregate are mixed. Examples include a method of pneumatically feeding, adding a quick setting agent and water in the middle, and spraying in a wet state.
Examples of the wet spraying method include a method in which cement, water, aggregate, etc. are mixed and kneaded, pneumatically fed, and the quick setting agent of the present invention is added and sprayed from one side of the Y-tube in the middle. .

In the present invention, conventionally used spraying equipment or the like can be used, the spraying pressure is not particularly limited, and the discharge amount of sprayed concrete is usually 1.5 to 20 m ³ / h, The amount of blowing air is not particularly limited.
The spraying equipment is not particularly limited as long as the spraying is sufficiently performed. For example, for the spraying of sprayed concrete, Arriba trade name “Aliver 280”, Shintech “MKW-25 SMT”, PET “ A “G4 pump”, a squeeze pump, or the like can be used. In addition, a quick-setting agent pumping device “Natom Cleat” can be used for pumping the powder quick-setting agent.

  Hereinafter, the present invention will be described in more detail based on experimental examples, but the present invention is not limited thereto.

"Experiment 1"
The unit quantity of each material cement 360 kg / ^{m 3,} fine aggregates 1053kg / ^{m 3,} the coarse aggregate 717kg / ^{m 3,} and water 216 kg / ^{m 3,} and the shotcrete.
This was pumped with a hose provided with two Y-shaped pipes on the way using a concrete pump “Shintech MKW-25SMT”. Of the two Y-tubes, air is injected from the Y-tube on the pump side, and from the other Y-tube on the tip side of the hose, 100 parts of calcium aluminate, 5 parts of alkali metal aluminate, 10 parts of alkali carbonate The quick setting agent for spraying, which is mixed with gypsum in the amount shown in Table 1, is pumped together with air so as to be 7 parts per 100 parts of cement by the quick setting agent addition machine “Denkatom Cleat”, combined and mixed And made into shotcrete.
This sprayed concrete 1 m ³ was sprayed under the condition of a spray speed of 10 m ³ / h to measure the rebound rate and the compressive strength of each material age. The results are shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement, commercially available fine aggregate: Himekawa water sand from Itoigawa, Niigata Prefecture, surface dry density 2.62
Coarse aggregate: No. 6 crushed stone from Itoigawa, Niigata Prefecture, maximum size 15 mm, surface dry density 2.68
Calcium aluminate: A heat-treated product corresponding to a C ₁₂ A ₇ composition, which is an amorphous material quenched with a brane value of 5,900 cm ² / g
Gypsum: Anhydrous gypsum (natural product), 2% of particles with a particle size of 1 μm or less and 99% of particles with a particle size of 10 μm or less, adjusted to a particle size of 3 μm by pulverization and classification Alkali metal aluminate : Sodium aluminate, commercial product alkali metal carbonate: Sodium carbonate, commercial product

<Measurement method>
Compressive strength: The prepared shotcrete was sprayed on a 25 cm wide × 25 cm pullout mold and a 50 cm wide × 50 cm long × 20 cm thick mold. Within one day of age, measurement was performed using a specimen of a pull-out formwork. Cover the pin from the surface of the pullout formwork with sprayed concrete, pull out the pin from the back side of the formwork, determine the pullout strength at that time, and calculate from the formula (compression strength) = (pullout strength) x 4 / (surface area of the specimen) The compressive strength was calculated.
After the first day of age, the compression strength of a specimen having a diameter of 5.5 cm and a length of 11 cm collected from a mold having a width of 50 cm, a length of 50 cm, and a thickness of 20 cm was determined using a 200 KN pressure machine.
Rebound ratio: the shotcrete was 1 m ³ spray after spraying ends, the amount of shotcrete dropped to vinyl sheet lined on the floor without adhering to measure, not adhere during the rebound rate = (spraying Calculated from the formula: (Mass of shotcrete dropped on) / (total amount of shotcrete used for spraying) × 100 (%).

  From the results of Table 1, it can be seen that the examples according to the present invention are excellent in adhesion and exhibit good strength development. Experiment No. 1-1 conducted as a comparative example has a large rebound rate and lower strength development than the examples.

"Experimental example 2"
The composition of the quick setting agent for spraying is 100 parts of calcium aluminate, 60 parts of gypsum, 5 parts of alkali metal aluminate and 10 parts of alkali metal carbonate. The test was conducted in the same manner as in Experimental Example 1 by changing the particle size and the average particle size.

  From the results of Table 2, it can be seen that by using the quick setting agent according to the present invention, the quick setting property is excellent and the good strength development property is obtained.

"Experiment 3"
The composition of the spray setting agent is 60 parts of gypsum with respect to 100 parts of calcium aluminate, and the spray setting agent is a mixture of alkali metal aluminate and alkali metal carbonate shown in Table 3. The test was carried out in the same manner as in Experimental Example 1. The results are shown in Table 3.

  From the results in Table 3, it can be seen that by using the spray quick setting agent of the present invention, the quick setting property is excellent and good strength development is obtained.

"Experimental example 4"
As a quick setting agent for spraying, 100 parts of calcium aluminate is mixed with 60 parts of gypsum, 5 parts of alkali metal aluminate and 10 parts of alkali metal carbonate as shown in Table 4. The test was carried out in the same manner as in Experimental Example 1 by changing the amount of the quick setting agent for spraying to 100 parts of cement. The results are shown in Table 4.

  From the results of Table 4, it can be seen that if the amount of spraying agent for spraying is small, the effect of improving adhesion and initial strength development is small, and if the amount is large, the strength development is good but the rebound rate is large.

“Experimental Example 5”
As a quick setting agent for spraying, a mixture of 60 parts of gypsum, 5 parts of alkali metal aluminate and 10 parts of alkali metal carbonate with respect to 100 parts of calcium aluminate, The test was carried out in the same manner as in Experimental Example 1 using the concrete blending shown in Table 5. For formulations with a large amount of cement, a water reducing agent was used during concrete production. The results are shown in Table 5.

<Materials used>
Water reducing agent: High performance water reducing agent, polycarboxylic acid polymer compound, liquid water reducing agent, commercial product

  From the results in Table 5, the greater the W / C, the lower the adhesion and strength development. Concrete with good condition could be obtained by mixing and producing concrete using a water reducing agent with a small blend of W / C (Experiment No. 5-1 and 5-2).

"Experimental example 6"
Fiber material shown in Table 6 is blended with sprayed concrete with a unit cement amount of 450 kg / m ³ , a unit water amount of 203 kg / m ³ (including a unit water reducing agent amount of 5.4 kg), and a fine aggregate ratio of 60%. And kneaded to prepare shotcrete. The quick setting agent for spraying is a mixture of 60 parts of plaster, 5 parts of alkali metal aluminate and 10 parts of alkali metal carbonate with respect to 100 parts of cement. The same procedure as in Experimental Example 1 was performed except that the addition was performed so as to be part. The results are also shown in Table 6.

<Materials used>
Fiber material: Steel fiber, fiber length 30mm, commercial product

From the results shown in Table 6, it can be seen that, even if a fiber material is mixed, the use of the spray setting agent of the present invention provides excellent adhesion and good strength development.

"Experimental example 7"
The dry concrete mixed as the unit amount of the concrete material excluding water was the same as in Experimental Example 1, and was pumped by a concrete pump (trade name “Aliver 280”, manufactured by Arriver).
Two Y-shaped pipes are installed in the middle of the concrete pumping pipe, quick setting agent and air are inserted from the Y-shaped pipe on the pump side, and 45 parts of water from the other Y-shaped pipe on the tip side of the hose to 100 parts of cement. It added so that it might become, and dry-type spraying construction was implemented.
The quick setting agent for spraying is a mixture of 60 parts of plaster, 5 parts of alkali metal aluminate and 10 parts of alkali metal carbonate with respect to 100 parts of cement. It added so that it might become a part.
As a result, it was possible to carry out spraying without trouble such as blockage of piping. Compressive strength at the age of 10 minutes 28 at that time are respectively 2.0 N / mm ^2, was 50.6N / mm ^2.

  The quick setting agent for spraying of the present invention, the shotcrete using the same, and the spraying method can be used when spraying on exposed ground surfaces in tunnel construction such as roads, railways, and waterways, for example. Besides these, it is also applicable to natural ground exposed during excavation of deep foundation piles and slope spraying.

Claims (3)

Calcium aluminate, gypsum having a particle diameter of 1 μm or less of 5% by mass or less and 10 μm or less of particles of 80% by mass or more and an average particle diameter of 2 to 6 μm, an alkali metal aluminate and / or Or the quick setting agent for spraying containing alkali metal carbonate. A shotcrete characterized in that it contains 5 to 15 parts by mass of the spray setting agent according to claim 1 with respect to 100 parts by mass of cement. A spraying method using the shotcrete according to claim 2.