JP2005154239A - Dust reducing agent and shotcrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dust reducing agent for blasting process with which the occurrence of dust originating from concrete in blasting is decreased even in the small addition to the shotcrete and the shotcrete employing the dust reducing agent. <P>SOLUTION: The dust reducing agent for the blasting process contains 70-100 wt.% water-soluble cellulose ether having 55,000-100,000 Pa×s viscosity in 2 wt.% aqueous solution at 20°C, 0 to <30 wt.% polycarboxylic acid-based polymer and 0-10 wt.% defoaming agent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a dust reducing agent for a spraying method capable of obtaining a concrete that generates less dust derived from concrete during concrete spraying construction, and a shotcrete using the same that generates less dust.

The shotcrete method is often used for tunnels, especially mountain tunnels using the NATM method. However, because of the compressed air used when spraying concrete, dust derived from concrete is generated during spraying. The dust is highly alkaline and may adversely affect the human body. Recently, dust reducing agents that suppress the generation of dust have been proposed (Patent Documents 1 and 2).
However, conventional dust reducing agents sometimes have insufficient dust reduction.
Japanese Patent Laid-Open No. 5-105493 JP 62-59560 A

  An object of the present invention is to provide a dust reducing agent for a spraying method that reduces the generation of dust derived from concrete at the time of concrete spraying, and a shotcrete using the same, even if the amount added to the shotcrete is small. Is to provide.

  The inventors of the present invention have intensively studied a dust reducing agent for spraying method that can suppress the generation of dust derived from concrete during concrete spraying. When water-soluble cellulose ether having a specific viscosity range is used, the dust is reduced. A shotcrete with less generation was obtained, and furthermore, the addition of a polycarboxylic acid polymer and / or an antifoaming agent found that dust suppression was more effective and completed the present invention.

That is, the present invention relates to a water-soluble cellulose ether of 70 to 100% by weight, a polycarboxylic acid polymer of 0 to less than 30% by weight and an antifoaming agent of 0 to less than 5 to 100000 mPa · s at 20 ° C. The present invention provides a dust reducing agent for spraying method containing 10% by weight.
Further, the present invention includes 0.04 to 0.5 parts by weight of the dust reducing agent for spraying method and 50 to 70 parts by weight of water with respect to 100 parts by weight of cement, and the fine aggregate ratio is 55 to 75 parts. % Of shotcrete.

  The dust reducing agent for spraying method of the present invention can suppress the generation of dust derived from concrete at the time of concrete spraying even if the amount added to the sprayed concrete is small. The sprayed concrete using the dust reducing agent for the spraying method has less dust generated during construction, so the hygiene environment of the construction worker is improved. Moreover, the shotcrete using the dust reducing agent for the spraying method of the present invention can be suitably used for the construction of a tunnel using the wet spraying method using the powder rapid setting agent or the NATM method. Furthermore, it can be suitably used for mortar spraying work performed in the construction of a TBM tunnel or the like.

  The water-soluble cellulose ether used for the dust reducing agent for spraying method of the present invention (hereinafter sometimes simply referred to as dust reducing agent) has a viscosity of 25,000% aqueous solution of 55,000 to 100,000 mPa · s at 20 ° C. When the viscosity is less than 55000 mPa · s, it is necessary to add a lot of dust reducing agent in order to suppress dust. In addition, when the viscosity exceeds 100,000 mPa · s, there are cases where the amount of dust is large because the dissolution rate in water becomes small. From the viewpoint of the effect of suppressing dust and the compressive strength of the sprayed concrete, it is preferably 75000 to 100000 mPa · s. The viscosity of the aqueous solution of water-soluble cellulose ether is measured using a B-type viscometer.

Examples of the water-soluble cellulose ether include hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), hydroxymethyl cellulose (HMC), hydroxyethyl methyl cellulose (HEMC), hydroxypropyl methyl cellulose (HPMC), and hydroxyethyl ethyl cellulose (HEEC). . Hydroxyethyl methylcellulose and hydroxypropylmethylcellulose are preferred.
The water-soluble cellulose ether may be used alone or in combination of two or more. In the case of combining, the viscosity when the combined product is a 2% by weight aqueous solution may be 55,000 to 100,000 mPa · s at 20 ° C.

The content of the water-soluble cellulose ether in the dust reducing agent of the present invention is 70 to 100% by weight. If the amount is less than 70% by weight, the effect of reducing dust is reduced because the concrete viscosity cannot be sufficiently secured when the unit cement amount is less than 400 kg / m ³ . Preferably it is 75 to 95 weight%.
The content of each component excluding the optional component in the dust reducing agent of the present invention is a proportion of the total amount of the water-soluble cellulose ether and the polycarboxylic acid polymer and / or antifoaming agent added as necessary ( (% By weight).

It is preferable to include a polycarboxylic acid polymer in the dust reducing agent of the present invention because the dust suppressing effect is further improved and the fluidity retention time of the shotcrete is increased.
Examples of polycarboxylic acid polymers include maleic anhydride, maleic acid, maleate, maleate, and other maleic acid compounds; acrylic acid, methacrylic acid, acrylate, methacrylate, acrylate, methacrylic acid Examples include (meth) acrylic acid compounds such as esters; and polymers of monomers such as unsaturated (poly) alkylene glycol ether monomers having a carboxyl group. The polymer may be a homopolymer of one kind of monomer or two or more kinds of copolymers. Also, one or more of these monomers and one or more of other vinyl monomers such as unsaturated (poly) alkylene glycol ether monomers having no styrene or carboxyl group A copolymer may be used. Here, (poly) alkylene glycol is preferably (poly) ethylene glycol ether. As the polycarboxylic acid polymer, a polycarboxylic acid polymer having a polyalkylene glycol chain, particularly a polyethylene glycol ether chain, is preferable because the fluidity retention time of the shotcrete is particularly long.

The content of the polycarboxylic acid polymer in the dust reducing agent of the present invention is 0 to less than 30% by weight. If it is 30% by weight or more, the dust suppressing effect may not be sufficiently exhibited when the unit cement amount is less than 400 kg / m ³ . Moreover, 4-24 weight% is preferable at the point of fluidity | liquidity retention time of shotcrete, and the suppression of dust.

When the antifoaming agent is contained in the dust reducing agent of the present invention, the dust suppressing effect is further improved and the compressive strength of the shotcrete is increased, which is preferable. Although the content of the antifoaming agent in the dust reducing agent of the present invention is 0 to 10% by weight, it is preferably 1 to 10% by weight in terms of the compressive strength of the shotcrete.
As the defoaming agent used here, in addition to a commercially available defoaming agent for cement, a commercially available defoaming agent for cement mortar, or a commercially available defoaming agent for concrete, polydimethylsiloxane or polyoxyalkylene alkyl ether-based nonionic surface activity Agents. An antifoamer may be used alone or in combination of two or more.

  The dust reducing agent of the present invention may contain optional components other than the water-soluble cellulose ether, polycarboxylic acid polymer, and antifoaming agent as necessary within the range not detracting from the effects of the present invention. . Examples of the optional component include a setting adjuster, an extender, an expansion material, a rust preventive, a shrinkage reducing agent, a pigment, a fiber, a water repellent, and a whitening prevention agent. These optional components may be used alone or in combination of two or more.

  The shotcrete of the present invention contains 0.04 to 0.5 parts by weight of the dust reducing agent for spraying method and 50 to 70 parts by weight of water with respect to 100 parts by weight of cement. The material ratio is 55 to 75%. If the dust reducing agent is less than 0.04 parts by weight with respect to 100 parts by weight of cement, the effect of suppressing the generation of dust may not be sufficient. On the other hand, when the amount is more than 0.5 parts by weight, pulsation occurs when the concrete is fed and a lot of dust is generated, which is not preferable. The amount is preferably 0.08 to 0.3 parts by weight in terms of suppressing dust generation.

  As the cement used in the shotcrete of the present invention, various portland cements such as normal, early strength, ultra-early strength, low heat and moderate heat, as well as fly ash, blast furnace slag, silica or limestone fine powder, etc. Various mixed cements mixed with Ordinary Portland cement or early-strength Portland cement is preferred in terms of compressive strength at the age of 28 days and fluidity retention of the shotcrete.

  The shotcrete of the present invention contains 50 to 70 parts by weight of water with respect to 100 parts by weight of cement. If it is less than 50 parts by weight, the flowability of the shotcrete is low and a lot of dust may be generated. Moreover, when it exceeds 70 weight part, sufficient intensity | strength may not be obtained. It is more preferable that it is 55-65 weight part at a point with less dust generation amount.

The shotcrete of the present invention contains fine aggregate, but the fine aggregate ratio is 55 to 75%. A fine aggregate ratio of less than 55% is not preferable because much dust is generated. On the other hand, when the fine aggregate ratio is more than 75%, the unit water amount for obtaining a predetermined fluidity increases, and the compressive strength of the shotcrete decreases, which is not preferable. It is more preferable that the fine aggregate ratio is 60 to 70% in terms of the amount of dust generated and the compressive strength. Here, the fine aggregate ratio is the volume content of the fine aggregate in the total aggregate.
The fine aggregate is an aggregate through which 85% by weight passes through a 5 mm sieve, and is not particularly limited. For example, commercially available fine aggregates such as sand, quartz sand, and crushed lime sand are used.

In shotcrete of the present invention may contain a coarse aggregate, but the volume of the total aggregate combined fine aggregate and coarse aggregate are occupied in the shotcrete 1 m ³ of the present invention, 0.6 ˜0.7 m ³ is preferable in terms of compressibility of concrete and reduction of rebound of shotcrete.

  The shotcrete of the present invention further includes a quick setting agent, a high-performance water reducing agent, a high-performance AE water reducing agent, an AE water reducing agent and a fluidizing agent, as necessary, within a range that does not impair the effects of the present invention. One or two types of water reducing agent, expansion agent, curing accelerator, curing retarder, polymer for cement, foaming agent, waterproofing agent, rust preventive agent, shrinkage reducing agent, pigment, fiber, water repellent, anti-whitening agent, etc. You may use the above together.

  When a water reducing agent is used in combination, it is preferable to use 0.1 to 3 parts by weight of a polycarboxylic acid-based water reducing agent with respect to 100 parts by weight of cement in terms of dust generation amount and compressive strength. If the amount is less than 0.1 parts by weight, the flowability of the mortar may not be improved even if a water reducing agent is added. When the amount exceeds 3 parts by weight, the material separation of concrete and the compressive strength at the initial age may be reduced. Examples of the polycarboxylic acid-based water reducing agent include a polycarboxylic acid-based water reducing agent, a polycarboxylic acid-based AE water reducing agent, a polycarboxylic acid-based high-performance water reducing agent, and a polycarboxylic acid-based high-performance AE water reducing agent. These may be commercially available, for example, trade names NT-1000 (manufactured by NM), NT-1000S (manufactured by NM), NT-1000H (manufactured by NM), Leo Build SP8N (manufactured by NM), and Pozoris. 15H (manufactured by NM), FTN-30 (manufactured by Grace Chemicals), Super 300 (manufactured by Grace Chemicals), Yamaso-02NL (manufactured by Yamasou Chemical), Mighty 3000H (manufactured by Kao Corporation), Tupole HP-11 (Made by Takemoto Yushi Co., Ltd.).

  When using a quick setting agent together, the usage-amount of 5-15 weight part is preferable with respect to 100 weight part of cement. If it is less than 5 parts by weight, the strength is insufficient for a short time, and therefore, it is not preferable because it may peel off when sprayed on the ceiling of the tunnel. If it exceeds 15 parts by weight, a lot of dust may be generated. The quick setting agent is not particularly limited, and a commercially available quick setting agent can be used. For example, calcium quickeners, calcium sulfoaluminate quicksets, calcium sodium aluminate quicksets and aluminate powder quicksets, and aluminate Liquid quick setting agents such as liquid quick setting agents and water-soluble aluminum salt liquid quick setting agents are listed.

  The shotcrete of the present invention is produced, for example, by adding the dust reducing agent of the present invention to a concrete mixer together with other materials at the time of concrete production. Moreover, the dust reducing agent of the present invention is added from a hopper of a truck agitator loaded with concrete, and the mixture is manufactured, for example, by stirring at high speed for about 2 minutes. As a method of adding the dust reducing agent, a fixed amount supply device may be used, or a necessary amount may be added to a container dissolved or dispersed with water and added together. Since there is no need to install a fixed amount supply device, it is preferable to add the required amount in a container that is dissolved or dispersed with water and add it together.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples.

Example 1
The dust reducing agent shown in Table 1 was produced.
The following materials were used.
<Materials used>
Water-soluble cellulose ether A: hydroxyethyl methylcellulose (trade name; Metroles SNB60T, manufactured by Shin-Etsu Chemical Co., Ltd.). Viscosity (20 ° C.) of 2% by weight aqueous solution 60000 mPa · s.
Water-soluble cellulose ether B: Hydroxypropyl methylcellulose (trade name; hi Metroles 90SH100000, manufactured by Shin-Etsu Chemical Co., Ltd.). Viscosity of 2% by weight aqueous solution (20 ° C.) 100000 mPa · s.
Water-soluble cellulose ether C: hydroxypropyl methylcellulose (trade name; Marporose 90EMP-75000, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.). Viscosity of 2% by weight aqueous solution (20 ° C.) 75000 mPa · s.
Water-soluble cellulose ether D: Hydroxypropyl methylcellulose (trade name; hi Metroles 90SH30000, manufactured by Shin-Etsu Chemical Co., Ltd.). Viscosity of 2% by weight aqueous solution (20 ° C.) 30000 mPa · s.
Polycarboxylic acid polymer: sodium methacrylate 54 mol%, sodium methallylsulfonate 7 mol%, methyl acrylate 8 mol%, methoxypoly (n = 40) ethylene glycol methacrylate 16 mol% and methoxypoly (n = 23) ethylene To 800 g each of a 45% solid solution containing a polymer compound having an average molecular weight of 11900 obtained by polymerizing 15 mol% of glycol methacrylate, 75.2 g of a 10 wt% sodium hydroxide aqueous solution as a pH adjuster. The mixture was stirred at room temperature for about 3 minutes, and then 0.5 parts by weight of sodium sulfite and triethanolamine were added to 100 parts by weight of the solid content of the polymer compound and stirred for 3 minutes. This was put into a kneader-type kneader / stirrer having a treatment volume of 1 L, and concentrated and dried while kneading at a temperature of 90 ° C. under a reduced pressure of 4 kPa. The obtained granular material was pulverized by a pulverizer and classified to produce a polycarboxylic acid polymer powder having a particle size of 50 to 500 μm. The water content of the powder was 2.2% by weight.
Antifoaming agent E: Commercially available antifoaming agent (trade name; SN deformer 14HP, manufactured by San Nopco).
Antifoaming agent F: Commercially available antifoaming agent (trade name; Adecanate B-107, manufactured by Asahi Denka Kogyo Co., Ltd.).

  Mortar was manufactured using each dust reducing agent of Table 1, and the spray test, the dust amount measurement, and the air amount measurement were performed. The test results are shown in Table 2.

The material and composition of the mortar and the test methods and conditions were as follows.
<Material and formulation>
Cement: Ordinary Portland cement (manufactured by Taiheiyo Cement, density: 3.16 g / cm ³ ) 5.00 kg
Fine aggregate: quartz sand (FM; 3.20, density; 2.63 g / cm ³ ) 7.00 kg
Limestone crushed sand (FM; 2.95, density; 2.64 g / cm ³ ) 3.00 kg
Dust reducing agent: amount shown in Table 2 with respect to 100 parts by weight of cement (parts by weight)
Water: Tap water 3.00kg

<Method for producing mortar>
The dust reducing agent was premixed in a dry mortar with a sand: cement weight ratio of 1: 2, and water was added thereto, followed by stirring with a hand mixer for 60 seconds.

<Air volume measurement method>
The amount of air of the mortar produced using the above production method was measured based on JIS A 1128-1999 using a mortar air meter C13-S manufactured by Maruto Seisakusho.
<Blowing test>
Cement mineral powder rapid setting agent (“Shot Master” manufactured by Taiheiyo Materials Co., Ltd.) is mixed with mortar produced using the above manufacturing method at a ratio of 7 parts by weight with respect to 100 parts by weight of cement. A caustic spray mortar was prepared. The quick setting sprayed mortar was sprayed at a spraying rate of 20 kg / min for 2 minutes and 30 seconds with the inside of a simple tent of 2.0 m × 2.4 m × 4.8 m sealed, and dust measurement was performed.
<Dust measurement method>
In the sealed tent, the amount of dust is measured with a light scattering digital dust meter (Model 3411 made by Nippon Kanomax Co., Ltd.) at a position 3 m from the spraying place at intervals of 15 seconds, and the measured value (count number) during the measurement time is measured. The average value (measurement result / measurement time (minutes)) was shown as CPM, and the relative value when the count number in the case where no dust reducing agent was added (Comparative 1-4) was 100 was shown as the relative ratio.

Example 2
Spray concrete was produced using the dust reducing agent of the present invention product 5 of Example 1, and a fluidity test (slump), an air amount measurement, a spray test, a dust amount measurement, and a compressive strength test were performed. Table 3 shows the composition of concrete, and Table 4 shows the test results.

At this time, materials, test methods and conditions were as follows.
<Materials used>
Cement: Ordinary Portland cement (manufactured by Taiheiyo Cement, density: 3.16 g / cm ³ )
Fine aggregate: mountain sand (FM; 2.88, density; 2.60 g / cm ³ )
Coarse aggregate: Crushed stone (maximum aggregate particle size: 13 mm, density: 2.63 g / cm ³ )
Dust reducing agent: Dust reducing agent of Invention product 5 of Example 1 Water: Tap water high-performance water reducing agent: Polycarboxylic acid-based high-performance water reducing agent (trade name; NT-1000, manufactured by NM Corp., main component: polycarboxylic acid Complex of acid ether compound and intermolecular cross-linked polymer)

<Concrete production method>
The above materials were kneaded with the formulation shown in Table 3. For mixing, a 100 L pan-type forced mixing mixer was used, and the mixing amount of one batch was 75 L.

<Fresh properties of concrete>
About concrete which knead | mixed the said material with the mixing | blending shown in Table 3, according to JIS A 1101-1998 "the slump test method of concrete" and JIS A 1118-1997 "the test method by the volume of the air quantity of fresh concrete", slump and air amount Was measured.
<Blowing test>
The concrete obtained above was pumped using a concrete pumping machine “Ariba 260” manufactured by Fuji Bussan Co., Ltd. From one of the merging and mixing sections provided on the way, cement mineral powder quick setting agent ("Shot Master" manufactured by Taiheiyo Materials Co., Ltd.) is pumped by the quick setting agent addition device "Q Gun" manufactured by Japan Private Co. A rapid setting shot concrete was prepared by mixing in the merging and mixing part at a ratio of 7 parts by weight to the part. This quick setting sprayed concrete was sprayed for 3 minutes at a spraying amount of 3 m ³ / h to a simulated tunnel having a height of 3 m and a width of 5 m.
<Dust measurement method>
The simulated tunnel is sealed with a sheet, and the dust amount is measured with a light scattering digital dust meter (model 3411 manufactured by Nippon Kanomax Co., Ltd.) at a position 3 m from the spraying location every minute, and the measured value during the measurement time (counting) Number) average value (measurement result / measurement time (minutes)) is shown as CPM, and the relative value when the count number is 100 when no dust reducing agent is added (Comparative 2-1) is shown as the relative ratio. It was.
<Compressive strength>
Three specimens having a diameter of 5 cm and a height of 10 cm were prepared by spraying spray concrete onto a formwork having a width of 50 cm, a length of 50 cm, and a height of 20 cm, and collecting the core by core removal. After the specimen was exposed outdoors until the age of 28 days, the compressive strength was measured according to JIS A 1108-1999 “Concrete compression test method”.

  From the above results, it was confirmed that the shot concrete of the present invention product 5 of Example 1 of the present invention product 5 produced less dust even with a small addition amount.

Claims (2)

  Contains 70 to 100% by weight of water-soluble cellulose ether having a viscosity of 55,000 to 100,000 mPa · s at 20 ° C., 0 to less than 30% by weight of a polycarboxylic acid polymer, and 0 to 10% by weight of an antifoaming agent. Dust reducing agent for spraying method.   Shotcrete containing 0.04 to 0.5 parts by weight of the dust reducing agent according to claim 1 and 50 to 70 parts by weight of water and having a fine aggregate ratio of 55 to 75% with respect to 100 parts by weight of cement .