JPH0755849B2 - Dust reducing agent for concrete spraying method - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a dust-reducing agent that reduces dust and rebound and improves working environment in a concrete or mortar spraying method.

[Prior art]

The concrete spraying method is a method to prevent collapse of the ground by sealing the wall surface with thin concrete before the loosening of the surrounding ground occurs during tunnel excavation, without using special equipment such as wall frames. , Concrete of desired thickness can be constructed in a short time regardless of the shape of various rock planes. There are many construction examples due to such simple construction workability. The spray concrete method includes a dry method and a wet method. In the dry construction method, air is transported by a spraying device while mixing a quick-setting agent into dry-mix concrete in which aggregate and cement are mixed by a mixer. It is a method of spraying this dry mix concrete onto the tunnel rock while adding water in the pipe before the spray nozzle. In this method, aggregate and cement are separated during pumping, and the mixing time with water is short, and mixing is likely to be incomplete, so that rebound and dust are generated on the surface of the sprayed rock mass. As described above, the dry method has problems such as dust and rebound, but there are many construction examples because the feeding distance can be increased and the hose is less likely to be clogged when the material is fed. In the wet method, materials such as aggregate, cement and water are kneaded by a mixer, then pressure-fed by a spraying device, and sprayed while adding a quick-setting agent in a pipe in front of the nozzle. This method has the advantages that it is completely mixed except for the quick-setting admixture, and that water is not mixed at the nozzle, so uniform concrete is sprayed and there is little dust and rebound. However, in order to transfer the cement containing water,
The pumping distance cannot be long, and it has drawbacks such as blocking of material in the hose and short usable time. In order to prevent splashing and dust generation during construction in the spraying method, a method is known in which a water-soluble polymer such as a cellulose derivative or polyethylene oxide is mixed as an aqueous solution into concrete in the wet method. Similarly, as a dust reducing agent in the wet method, JP
-102852 discloses that an aqueous solution of polyacrylamide is effective, and JP-A-59-174554 discloses that an aqueous solution of partially hydrolyzed polyacrylamide is effective.

[Problems to be Solved by the Invention]

As described above, the dry method has an advantage that long-distance pressure feeding is possible and the hose is unlikely to be blocked, but has a drawback that a large amount of rebound and dust is generated on the blown rock surface. If a high-molecular-weight water-soluble polymer is added to prevent this, the fluidity of the concrete deteriorates, which causes workability deterioration such as pulsation or blockage of the hose when air is transferred through the hose. An object of the present invention is to provide a blockage-reducing agent that improves the working environment without causing pulsation or blockage of a hose in a concrete spraying method by a dry method.

[Means for solving problems]

The present invention is configured as follows to achieve the above object. That is, the present invention is a dust reducing agent to be used by mixing dry mix concrete into the dry mix concrete in a concrete spraying method (so-called dry method) in which water is added under pressure through a hose and water is added immediately before spraying. , 5 to 50% by weight of sodium 2-acrylamido-2-methylpropanesulfonate and 50 to 95% by weight of acrylamide are used as water-soluble polymer powder and calcium lignin sulfonate powder at 4: 1 to 1: 1. It is a dust reducing agent for the concrete spraying method, characterized by being contained in the range of. When the copolymerization ratio of the polymer is outside the above range, the thickening effect of concrete is insufficient and the dust reducing effect is low. Further, the higher the degree of polymerization of the polymer, the better the effect of reducing dust, and the reduced viscosity η _{SP / C at} a concentration of 0.1% in 1N saline solution at 25 ° C. is preferably 10 or more. The particle size of the polymer powder is preferably 0.3 mm or less, and the amount of the polymer powder added to concrete is 0.05 to 0.5% based on the cement.

[Action]

The present invention is a dust reducing agent in which a water-soluble polymer powder having a specific composition and calcium lignin sulfonate powder are mixed, and the dust reducing agent reduces the generation of dust without causing pulsation of a hose in a dry concrete spraying method. Can be made. In the dry method, dry mix concrete and added water are sprayed onto the rock surface in a very short time immediately before spraying, while being uniformly kneaded by friction with the wall surface of the hose. When the water-soluble polymer is added to the shotcrete, the pulsation of the hose due to the adhesion of concrete to the wall surface of the hose easily occurs due to the thickening action of the water-soluble polymer. However, in order to reduce the generation of dust and rebound, it is necessary to enhance the adhesion action of concrete or the collision energy absorption action on the sprayed surface by the thickening effect of the water-soluble polymer. In order to reduce dust on the spray surface while preventing pulsation of the hose, it is desirable that the water-soluble polymer be uniformly dispersed and dissolved in concrete on the spray surface without excessive thickening in the hose. . The role of calcium lignin sulfonate in the present invention is to coat the powder surface so that the water-soluble polymer powder is uniformly dispersed in the dry mix concrete, and to slightly delay the thickening due to the dissolution of the water-soluble polymer powder in concrete. It is possible to prevent local thickening at a stage where the kneading is uneven, and to prevent mutual adhesion of particles in concrete or adhesion to a hose by a dispersing action by electric repulsion. On the other hand, the water-soluble polymer used in the present invention has good dispersibility in concrete, and needs to be rapidly dissolved on the sprayed surface in order to absorb collision energy. A water-soluble polymer having a carboxyl group such as a partially hydrolyzed polyacrylamide easily reacts with calcium ions in cement to form an inactive calcium salt, and a nonionic polyacrylamide has a high dissolution rate. The sodium 2-acrylamide-2-methylpropanesulfonic acid / acrylamide copolymer of the present invention has a high dissolution rate and does not react with calcium ions to be insolubilized.
For this reason, the thickening effect effective for absorbing the collision energy on the sprayed surface also occurs promptly. By thus using a water-soluble polymer having good solubility in combination with calcium lignin sulfonate, excessive thickening can be suppressed and pulsation of the hose can be prevented in the dry concrete spraying method. (Example) Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto. (Synthesis example) At a weight ratio shown in the table below, 30 g of the monomer is dissolved in 270 g of ion-exchanged water, and the temperature is kept at 40 ° C, and the bubbling is continued with nitrogen gas. After 5 minutes, 6 mg of ammonium persulfate,
After adding 6 mg of oxalic acid and 0.15 mg of ferrous sulfate as an aqueous solution and starting the polymerization reaction, the inflow of nitrogen gas is stopped and the container is sealed. After 1 hour, the temperature was raised to 60 ° C and the reaction was continued for 2 hours. The viscosity of a 0.5% pure aqueous solution of the obtained sample was measured by a Brookfield viscometer. As described above, the charged amount of 2-acrylamido-2-methylpropanesulfonic acid soda was 5 with respect to the total monomer weight.
It has a high aqueous solution viscosity at wt% to 50 wt%. For the purpose of dust reduction, concrete has a high thickening effect,
A polymer having a high viscosity in an aqueous solution is required, and thus a polymer in the above range is effective. (Construction example) spraying location is a framework steel支保Engineering, affixed keystone plate on its outer periphery, an empty section, simulated tunnel 14m ² inner pitched wooden sheet piles to the inner surface. The length of this tunnel is
At 22 m, both sides are closed with steel gates to block the effects of natural ventilation and prevent the dilution of dust. For the spraying, an appropriate amount of the powder quick-setting admixture is added to the spraying machine while the dry mix concrete in which the dust reducing agent is mixed and stirred using a twin-screw forced kneading mixer is supplied to the spraying machine via a belt conveyor. This dry mix concrete is pneumatically transported by high-pressure air connected to a spraying machine (Aliver 280), and water is added per unit concrete during spraying and sprayed. The dust concentration was measured using a digital dust meter (P-5L2 manufactured by Shibata Kagakuki) at a height of about 5 m behind the nozzle and 1.2 m above the ground surface. The bounce rate was measured by placing a blue sheet under the spraying area, measuring the weight of the material bounced on the sheet, and then expressing the bounce rate relative to the total spray rate. The compressive strength is 15 × 15 × 55 cm. It is sprayed on the formwork without the side plate of the concrete bending test formwork, and demolded at the required age.
A compressive strength test was conducted. This method is generally called a dry method. The nominal formulation is shown in Table 2. The composition of the sample (dust reducing agent) used in the test is shown in Table 3, and the experimental result is shown in Table 4. The meaning of the display is as follows. Ca / RS: Calcium lignin sulfonate AAM: Acrylamide AMPS: 2-Acrylamido-2-methylpropanesulfonic acid soda AAC: Sodium acrylate PAAM: Polyacrylamide Methylcellulose: Dow Chemical Co., Ltd. Methocel K1
5M η _{SP / C} : Solvent 1N saline solution, polymer concentration 0.1%, reduced viscosity at temperature 25 ° C All composition ratios in the table are wt%, the addition amount in Table 4 is reduction of dust per cement The amount of addition of the agent is expressed in% by weight.

【The invention's effect】

The present invention relates to a dust reducing agent for a concrete spraying method, and by using a dust reducing agent in which a water-soluble polymer powder having a specific composition and calcium lignin sulfonate powder are mixed, dry mix concrete is pumped over a long distance. In the dry concrete spraying method, the generation of dust can be reduced without causing pulsation of the hose. As a result, the working environment is improved, the worker can continue working for a long time without fear of blockage of the hose, and workability is significantly improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Masuda 3-7-14 Kiyomi, Fukuoka City, Saitama (72) Inventor Kozo Katayama 561 Waseda Tsurumakicho, Shinjuku-ku, Tokyo (72) Inventor Hideyuki Watanabe Tokyo 5-4 Higashigoken-cho, Shinjuku-ku (72) Inventor Kaoru Kaneko 690 Shinmaruko, Nakahara-ku, Kawasaki-shi, Kanagawa (56) Reference JP-A-62-17057 (JP, A)

Claims (1)

[Claims] 1. A dust reducing agent, which is used by being mixed into dry mix concrete in a concrete spraying method in which water is added to the hose by high-pressure air and water is added immediately before spraying, the content being 5 to 50% by weight. 2-
Acrylamide-2-methyl propane sulfonate and 50-95 wt% acrylamide copolymerized water-soluble polymer powder and calcium lignin sulfonate powder
A dust reducing agent for a concrete spraying method, characterized by being contained in a weight ratio of 4: 1 to 1: 1.