JP5484798B2 - Spraying method - Google Patents

Description

The present invention relates to, for example, a tunnel, such as a road, a railway, and a waterway, and a spraying quick-setting agent and spraying material used when spraying fast-setting concrete on an exposed natural ground surface in a slope. , Sprayed concrete, and a spraying method using the same.
Moreover, the cement concrete as used in this invention is a general term for cement paste, mortar, and concrete.

  2. Description of the Related Art Conventionally, in order to prevent collapse of exposed ground in tunnel excavation work or the like, a method of spraying quick setting concrete in which a powder quick setting agent is mixed with concrete is used. Known quick setting agents include calcium aluminates, sulfates, alkali metal aluminates, and mixtures thereof with alkali carbonates (see Patent Documents 1 to 2).

  Recently, from the viewpoint of durability, rapid-setting agents that do not contain alkalis have been developed to improve long-term strength development.In addition, as an application for permanent structures, alkali aggregate reaction of aluminum sulfate and calcium aluminate is performed. The quick setting agent which suppresses is proposed (refer patent document 3-patent document 6).

JP-A-11-130497 JP-A-11-199287 JP-A-8-48553 JP-A-10-265247 JP 10-330147 A JP-A-11-199286

  When the quick-setting agent containing no alkali is used, there are cases where the rebound rate at the time of spraying is high and the cost is high, and furthermore, there is a problem that the environmental load is increased due to the increase in materials used. In addition, there are cases where the amount of dust is large and the work environment deteriorates. For this reason, development of the quick setting agent which is excellent in quick setting property and intensity | strength development property and can provide high durability, reducing the usage-amount of an alkali is awaited.

  In view of the above situation, the present inventors use the spray setting agent and spray material of the present invention, so that even if the amount of alkali used is smaller than that of conventional quick setting agents, The present invention was completed by obtaining the knowledge that the strength was excellent.

That is, (1) cement concrete containing 100 parts by mass of cement, (2) 100 parts by mass of amorphous calcium aluminate , 50 to 150 parts by mass of anhydrous gypsum, R ₂ O / Al ₂ O ₃ molar ratio ( R is alkali metal) 1 to 5 parts by weight of powdered alkali metal aluminate with 0.8 to 1.2, 10 to 20 parts by weight of powdered anhydrous aluminum sulfate, 0.2 to 1 part by weight of oxycarboxylic acids Te becomes, and for spraying quick-setting admixture 7-15 parts by weight, wherein R _{2 O} in Kyuyuizai is 1% or less, a spraying method comprising mixing amorphous calcium are those aluminate was quenched Cook corresponding to 12CaO · 7Al ₂ O ₃ composition, the alkali metal aluminate is sodium aluminate, oxycarboxylic acids are citric acid, quick-setting for spraying Usage is a該吹with method is 10 to 12 parts per 100 parts of cement, the blowing, characterized in that blowing joins mixed with cement concrete the quick-setting admixture for spraying in the discharge port tip It is an attachment method.

  By using the quick setting agent for spraying and the spray material of the present invention, effects such as excellent quick setting and strength development can be obtained even if the amount of alkali used is smaller than that of conventional quick setting agents.

Hereinafter, the present invention will be described in detail.
In the present invention, “parts” and “%” are based on mass unless otherwise specified.

Calcium aluminate used in the present invention is a mixture of a raw material containing calcia and a raw material containing alumina, calcined in a kiln, heat treated such as melting in an electric furnace, and CaO obtained by pulverization Although it is mainly composed of Al ₂ O ₃ , it is also possible to contain SiO ₂ , CaF ₂ , Mg, Si and the like.

As a mineral form of calcium aluminate, crystalline or amorphous exists, but in the present invention, amorphous calcium aluminate is preferable in terms of reaction activity, and corresponds to a 12CaO · 7Al ₂ O ₃ composition. An amorphous calcium aluminate obtained by quenching the heat-treated product is more preferable.

The molar ratio of CaO to Al ₂ O _{3 in} the calcium aluminate is preferably 1.7 to 3.0 and more preferably 1.9 to 2.5 in terms of the CaO / Al ₂ O ₃ molar ratio. If the molar ratio is outside this range, excellent quick setting may not be obtained.

The particle size of the calcium aluminate is preferably 4000 cm ² / g or more in Blaine value in terms of quick-setting property, 6000 cm ² / g or more is more preferable.

  Examples of anhydrous gypsum used in the present invention include hydrofluoric acid byproduct anhydrous gypsum and natural anhydrous gypsum. The pH when the gypsum is immersed in water is preferably from a weak alkali having a pH of 8 or less to acidic. When the pH is high, the solubility of the gypsum component becomes high, which may inhibit the initial strength development. The pH here is a value obtained by measuring the pH of the diluted slurry at 20 ° C. of gypsum / ion exchange water = 1 g / 100 g using an ion exchange electrode or the like.

The particle size of the anhydrite is preferably 3000 cm ² / g or more in Blaine value from the viewpoint of strength development, 5000 cm ² / g or more is more preferable.

  The amount of anhydrous gypsum used is preferably 50 to 150 parts with respect to 100 parts of calcium aluminate. If it is less than 50 parts, long-term strength development may be impaired, and if it exceeds 150 parts, excellent quick setting may not be obtained.

The powder alkali metal aluminate used in the present invention is obtained by mixing and reacting an alumina raw material and an alkali metal raw material, and examples of the alkali metal include lithium, sodium, and potassium. The molar ratio of alkali metal aluminate R ₂ O (R is an alkali metal element) and Al ₂ O ₃ is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. If it is less than 0.8, excellent rapid setting properties may not be obtained, and if it exceeds 1.2, long-term strength development may be impaired.

  The particle size of the powdered alkali metal aluminate is preferably equal to or greater than that of calcium aluminate or gypsum from the viewpoint of improving quick setting.

The amount of powdered alkali metal aluminate used is preferably 1 to 5 parts per 100 parts of calcium aluminate. If it is less than 1 part, it may not be possible to obtain excellent quick setting properties. If it exceeds 5 parts, R ₂ O exceeds 1%, so that strength development may be impaired and long-term strength development may be inferior. May also decrease.

As the powdered aluminum sulfate used in the present invention, commonly used powdered aluminum sulfate can be used, and it is not affected by impurities usually contained.
Some powdered aluminum sulfate contains anhydrous salt and crystal water, but any of them can be used as it is and is not affected by the amount of crystal water.

The particle size of the powdered aluminum sulfate is preferably 2000 to 5000 cm ² / g in terms of Blaine value. If it is less than 2000 cm ² / g, good quick setting may not be obtained, and even if it exceeds 5000 cm ² / g, further effects cannot be expected.

  The amount of powdered aluminum sulfate used is preferably 10 to 20 parts per 100 parts of calcium aluminate. If it is less than 10 parts, excellent quick setting may not be obtained, and if it exceeds 20 parts, strength development may be impaired.

  Examples of the oxycarboxylic acids used in the present invention include gluconic acid, tartaric acid, citric acid, malic acid, salicylic acid, lactic acid, and salts thereof. Examples of the salt include alkali metal salts such as sodium and potassium. Of these, citric acid is preferred from the standpoint of increasing initial strength and not increasing the amount of alkali.

  As for the usage-amount of oxycarboxylic acid, 0.2-1 part is preferable with respect to 100 parts of calcium aluminates. If it is less than 0.2 part, the setting property and initial strength development of the quick setting spray cement concrete may be hindered, the viscosity of the quick setting slurry may be increased, and the workability of the quick setting spray cement concrete may be lowered. If it exceeds 1 part, the coagulability and strength development may be inhibited.

  The rapid setting agent used in the present invention can contain alkali metal carbonate, alkali metal sulfate, quicklime, slaked lime, aluminum hydroxide and the like in addition to these materials.

The cement used in the present invention is not particularly limited, but preferably has a 3CaO.Al ₂ O ₃ content of 5 parts or more in 100 parts of cement, which is one of the minerals constituting the cement. If it is less than 5 parts, sufficient quick setting may not be obtained.

  Furthermore, in the present invention, addition of a pH adjuster, a dispersant, a stabilizer, an antifreeze agent, a water solubility promoter, an AE agent, a water reducing agent, an AE water reducing agent, a set retarder, a thickener, a fiber, a fine powder, and the like An agent can be used in combination as long as the object of the present invention is not substantially inhibited.

  The amount of the quick setting agent used in the present invention is preferably 7 to 15 parts with respect to 100 parts of cement. If the amount used is less than 7 parts, excellent quick setting may not be obtained, and if it exceeds 15 parts, the construction cost increases, which is not preferable.

The amount of cement used in the shotcrete of the present invention is preferably 330 to 500 kg / m ³ , and the water cement ratio is preferably 40 to 65%. Moreover, it does not specifically limit regarding the slump and slump flow of shotcrete.

  The aggregate used in the present invention preferably has a low water supply rate and high aggregate strength. The maximum size of the aggregate is not particularly limited as long as it can be sprayed. As the fine aggregate, river sand, mountain sand, lime sand, quartz sand and the like can be used, and as the coarse aggregate, river gravel, mountain gravel, lime gravel and the like can be used.

In the spraying method of the present invention, conventional spraying equipment can be used. The spraying pressure is not particularly limited, and the spraying speed of the sprayed concrete is usually 1.5 to 20 m ³ / h, and the amount of spraying air is not particularly limited.

  The spraying equipment is not particularly limited as long as the spraying is sufficiently performed. For the concrete pumping, the Arriver brand name "Aliver 280", Shintech "MKW-25SMT" and squeeze pumps can be used. It is. In addition, a rapid setting agent pumping device “NATM cleat” can be used for pumping the powder admixture.

  In the spraying method of the present invention, it is possible to construct a dry spraying method, but since there is a possibility of increasing the amount of dust, before using the quick setting agent, water is added to the concrete side in advance and kneaded. It is preferable to use a spraying method.

  As a wet spraying method, cement, fine aggregate, coarse aggregate, and water are added to prepare concrete, and then transported to a Y-shaped pipe with a piston-type concrete pump or pneumatic feeding method, where a rapid setting agent Is added to the concrete and sprayed from the nozzle as sprayed concrete.

  As a method of mixing the quick setting agent of the present invention with sprayed concrete, it is preferable to mix it immediately before spraying using a Y-shaped tube or the like. Specifically, it is preferable that the rapid setting agent is added to the concrete that has been pumped and the time until the sprayed concrete is discharged is within 10 seconds, and more preferably within 2 seconds.

  Moreover, it is also possible to spray this shotcrete directly on the slope ground, or on the place where the frame skeleton is arranged, in addition to the tunnel ground. Here, the frame skeleton is a structure in which a wire mesh, a reinforcing bar, a steel frame, and the like are combined and fixed to a wall surface.

  Hereinafter, the present invention will be described in more detail based on experimental examples.

Experimental example 1
A mortar having a cement / sand ratio = 1/3 and a water / cement ratio = 50% was blended with 1.0% of a polycarboxylic acid-based water reducing agent in 100 parts of cement to prepare a mortar. The quick setting agent containing anhydrous gypsum, powdered alkali metal aluminate salt, powdered aluminum sulfate, and oxycarboxylic acids shown in Table 1 with respect to 100 parts of calcium aluminate is added to 10 parts of mortar with respect to 100 parts of cement. Blended and measured for Procter penetration resistance and compressive strength. The test environment temperature is 20 ° C. The results are also shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement, Blaine 3200 cm ² / g, Denki Kagaku Kogyo Co., Ltd. Calcium aluminate: obtained by mixing calcia raw material and alumina raw material at a predetermined ratio and melting at 1600 ° C. in an electric furnace, 12CaO · 7Al ₂ O Corresponding to ₃ compositions, amorphous, brane 5500 cm ² / g
Anhydrous gypsum: natural anhydrous gypsum, brain 5000 cm ² / g
Powder alkali metal aluminate: sodium aluminate, Na ₂ O / Al ₂ O ₃ molar ratio 1.0, Na ₂ O = 40%
Powdered aluminum sulfate: Anhydrous aluminum sulfate, commercial product, Daimei Chemical Co., Ltd. Oxycarboxylic acids: Citric acid, Reagent primary water: Tap water reducing agent: Polycarboxylic acid-based water reducing agent Fine aggregate: Niigata Himekawa production river sand, density 2.62g / Cm ³

<Measurement method>
Proctor penetration resistance (condensation properties): Conforms to ASTM C 403 "Concrete setting time test method by penetration resistance". The setting property was evaluated for 1 minute and 3 minutes after mixing the quick setting agent in the mortar.
Compressive strength: Tested with a 4 cm × 4 cm × 16 cm prism specimen. Age 24 hours, 28 days

  From Table 1, it can be seen that even if the amount of alkali used is small, the effect of excellent quick setting and strength development is obtained.

Experimental example 2
Experiment No. The experiment was conducted in the same manner as in Experimental Example 1 except that the rapid setting agent shown in 1-4 was used and the molar ratio of R ₂ O and Al ₂ O _{3 in} the powdered alkali metal aluminate shown in Table 2 was changed. The results are also shown in Table 2.

<Materials used>
Powder alkali metal aluminate: sodium aluminate, prototype synthesized by changing the mixing ratio of NaOH and Al (OH) ₃ , Na ₂ O / Al ₂ O ₃ molar ratio 0.7-1.3

From Table 2, by using a quick setting agent containing powdered alkali metal aluminate having a proper molar ratio of R ₂ O and Al ₂ O ₃ , the effect of excellent quick setting and strength development is achieved. I understand.

Experimental example 3
The unit quantity of each material, cement 400 kg / ^{m 3,} fine aggregates 1,058kg / ^{m 3,} the shotcrete was prepared as coarse aggregate 711kg / ^{m 3,} and water 200 kg / ^{m 3,} Shintech concrete pumping machine It pumped by the speed | rate of 10 m < ³ > / h by "MKW-25SMT". Compressed air is inserted from a Y-tube attached after a 10-inch long 3 inch pressure-resistant hose, sprayed concrete is conveyed by air using a 2.5-inch material hose of 10 m in length, and a Y-tube attached to the tip No. No. 1 was used for the experiment No. The quick setting agent shown in 1-4 is transported and mixed with concrete to form quick setting spray concrete so that the added amount shown in Table 3 is added to 100 parts of cement in the concrete, and sprayed from the nozzle for 3 minutes. It was. The results are also shown in Table 3.

<Materials used>
Cement: Ordinary Portland cement, commercially available, Blaine value 3,200 cm ² / g, specific gravity 3.15
Fine aggregate: Niigata Prefecture Itoigawa city Himekawa production river sand, surface dry state, specific gravity 2.62
Coarse aggregate: Himekawa Sakegawa gravel, Itoigawa city, Niigata prefecture, surface dry condition, specific gravity 2.62, maximum dimension 15mm

<Evaluation method>
Blowing state: evaluated as ○ when the rise to the pull-out form is good, Δ when the rise is not, and × when the dull.
Strength for 24 hours: Cover the pin installed in the pullout formwork 25cm wide x 25cm long with the quick setting spray concrete from the surface of the pullout formwork, pull out the pin from the back side of the formwork, and obtain the pullout strength at that time , (24 hour strength) = (pullout strength) × 4 / (test specimen contact area).
28 days strength: Measured with a test specimen in which concrete sprayed on a mold having a width of 40 cm, a length of 40 cm, and a depth of 30 cm was cored to φ50 mm × length 100 mm.

  From Table 3, it can be seen that by using an appropriate amount of the quick setting agent, the spraying surface is good and the quick setting and strength development properties are excellent.

  INDUSTRIAL APPLICABILITY The present invention can be used, for example, when tunnels such as roads, railways, and conduits, and slopes, are sprayed with rapidly setting concrete on exposed ground surfaces.

Claims (3)

(1) Cement concrete containing 100 parts by mass of cement, (2) 100 parts by mass of amorphous calcium aluminate , 50 to 150 parts by mass of anhydrous gypsum, R ₂ O / Al ₂ O ₃ molar ratio (R is 1 to 5 parts by weight of powdered alkali metal aluminate having an alkali metal) of 0.8 to 1.2, 10 to 20 parts by weight of powdered anhydrous aluminum sulfate, and 0.2 to 1 part by weight of oxycarboxylic acids. A spraying method formed by mixing 7 to 15 parts by mass of a rapid setting agent for spraying, wherein R ₂ O in the rapid setting agent is 1% or less. Amorphous calcium aluminate is 12CaO ・ 7Al ₂ O ₃ The heat-treated product corresponding to the composition is rapidly cooled, the alkali metal aluminate is sodium aluminate, the oxycarboxylic acid is citric acid, and the amount of spray setting agent used is 100 parts of cement. The spraying method according to claim 1, which is 10 to 12 parts. The spraying method according to claim 1 or 2, wherein the spray setting agent is mixed and mixed with cement concrete at the tip of the discharge port .