JP2002029803A - Cement admixture, concrete containing the same and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement admixture and concrete containing the same which can be applied without the separation of raw materials even in a place where water is present and also satisfactorily applied even in a place where voids such as cracks are present and to provide the manufacturing method thereof. SOLUTION: The cement admixture consists of an alkali thickening type polymer emulsion obtained by copolymerizing an unsaturated carboxylic acid with an ethylenic unsaturated compound, and bentonite. The concrete contains the admixture and is manufactured by forcibly sending concrete containing bentonite, and the alkali thickening type polymer emulsion separately, and mixing with each other at the tip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement admixture used in the fields of civil engineering and construction, concrete containing the same, and a method for producing the same. The concrete in the present invention is a general term for cement paste, mortar and concrete. In the present invention, the unit of “part” or “%” represents a mass unit unless otherwise specified.

[0002]

2. Description of the Related Art Heretofore, a method for reducing the rebanding of shotcrete, a method for preventing a gap from filling underground or the back of a tunnel, and preventing flow such as cracks, and a material for using these in a place where water exists. As a method for preventing the separation, it is effective to lower the fluidity as much as possible. As a method for adding the silicate, it is known to add a silicate, an aluminate, a chloride and an aluminum salt.

[0003]

However, these additives are effective in terms of instantaneously lowering the fluidity of concrete and preventing runoff (limited injection). There is a problem that the solidified state is obtained in about 60 minutes to 60 minutes, and the filling property of the concrete is deteriorated.

[0004] In addition, cement-bentonite-based injection materials have been conventionally known. When preparing a slurry, cement is first charged into a mixer and then bentonite is charged. The bentonite did not sufficiently swell due to the adsorption on the surface of the surface of the sample, so that a thickening effect was recognized but the effect was insufficient.

Therefore, a method of first preparing a bentonite slurry, sufficiently swelling the bentonite, and then mixing the slurry with the cement has been adopted. When the length is short, calcium ions in the cement are adsorbed to the bentonite particles before the swelling of the bentonite progresses, so that the subsequent swelling is hindered and a sufficient thickening effect cannot be obtained in many cases.

Therefore, in the on-site construction management, it is necessary to carefully consider the order in which cement and bentonite are charged, and the time interval between the charging of bentonite and the charging of cement, and strict process control has to be performed.

As a result of various studies, the present inventors have found that by using a specific production method for a specific cement admixture and a concrete containing the same, a good plastic concrete can be obtained. The inventors have found that the present invention can be solved, and have completed the present invention.

[0008]

That is, the present invention provides a cement admixture comprising an alkali-thickened polymer emulsion obtained by copolymerizing an unsaturated carboxylic acid and an ethylenically unsaturated compound, and bentonite. Concrete containing a cement admixture, concrete containing bentonite, and an alkali-thickened polymer emulsion are separately pumped separately, and are mixed and mixed at the tip thereof. is there.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The alkali thickening type polymer emulsion used in the cement admixture of the present invention is a polymer emulsion obtained by copolymerizing an unsaturated carboxylic acid and an ethylenically unsaturated compound and having a self-thickening property.
As a polymerization method, it is obtained by copolymerizing an unsaturated carboxylic acid and an ethylenically unsaturated compound copolymerizable therewith by a method such as emulsion polymerization, suspension polymerization, solution polymerization, or bulk polymerization.

Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, aconitic acid, crotonic acid and the like. These anhydrides include maleic anhydride, And citraconic anhydride. Also, as a half ester,
Monomethyl itaconate, monobutyl itaconate, monoethyl maleate and the like can be mentioned. Among them, acrylic acid,
Methacrylic acid is preferred because it exhibits more excellent effects.

Examples of the ethylenically unsaturated compound copolymerizable with the unsaturated carboxylic acid include cyanovinyl monomers such as ethylene, acrylonitrile and methacrylonitrile, methyl acrylate, ethyl acrylate and the like.
Acrylic ester monomers such as butyl acrylate, hexyl acrylate, cyclohexyl acrylate, octyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate, and glycidyl acrylate; methacrylic esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, and glycidyl methacrylate Monomer, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl stearate, vinyl octylate, VEOBA 10 (trade name: Shell Japan)
Vinyl esters of C _3-18 aliphatic carboxylic acids such as, vinyl aromatic carboxylate monomers such as vinyl benzoate, styrene, vinyl toluene, α-methylstyrene, aromatic vinyl monomers such as N-vinylpyrrolidone, methyl vinyl ether, Ethyl vinyl ether, butyl vinyl ether,
Vinyl ether monomers such as phenyl vinyl ether,
Amide monomers such as acrylamide and methacrylamide, maleimide monomers such as maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-phenylmaleimide and N-toluylmaleimide, and halogens such as vinyl chloride and vinylidene chloride Olefin monomer, divinylbenzene, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, propylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, triallyl cyanurate , Triallyl isocyanurate, trimethylolpropane trimethacrylate, allyl acrylate, allyl Polyfunctional vinyl monomers such as methacrylate and the like.

The alkali-thickening polymer emulsion used in the cement admixture of the present invention is characterized in that the alkali in the cement neutralizes and dissociates the carboxyl groups of the emulsion particles and swells or dissolves the surface layer or the whole of the emulsion particles. As the viscosity of the system increases, the viscosity increases.
It is also possible to use another emulsion blended with the alkali thickened polymer emulsion.

In the present invention, concrete has thixotropic properties (thixotropic) due to these thickening effects, and becomes a material suitable for pouring into a limited range.

The solid content of the alkali-thickened polymer emulsion is not particularly limited, but is preferably as high as possible. Usually, the solid content concentration is 20 to
About 60% is preferable, and 30 to 50% is more preferable.

The amount of the alkali thickening type polymer emulsion to be used is 0.1 to 100 parts by weight based on 100 parts of cement.
10 parts is preferable, 0.2 to 5 parts is more preferable, and 0.1 part is preferable.
3 to 3 parts are more preferred. If the amount is less than 0.1 part, the thickening effect may be small, and if it exceeds 10 parts, the initial strength expression may be poor.

The bentonite used in the cement admixture of the present invention is effective in further increasing the viscosity.
The type of bentonite is not particularly limited,
Montmorillonite clay minerals such as ordinary sodium bentonite and calcium bentonite are used.

The amount of bentonite used varies depending on the type, but usually 10 to 10 parts of cement is used.
150 parts is preferable and 20 to 100 parts is more preferable.
If the amount is less than 10 parts, the thickening effect may be small, and
If it exceeds 0 parts, the initial strength expression may be deteriorated.

The larger the swelling power of bentonite, the higher the viscosity and the smaller the amount of addition. The specific swelling power is preferably 6 ml / 2 g or more, more preferably 9 ml / g.
2 g or more is more preferable. If it is less than 6 ml / 2 g, the thickening effect may not be obtained.

Here, the swelling force is measured by the following method. 2.00 g of bentonite is gently added in small portions to a 100 ml measuring cylinder with a stopper, and the amount added at a time is adjusted so that the previously added bentonite does not adhere to the inner wall of the cylinder and deposits smoothly on the bottom of the cylinder. I do. After most of the previously added sample has settled, the next sample is added. After the addition of the entire amount is completed, the container is stoppered, and after standing for 24 hours, the apparent volume of the sample deposited in the container is read and calculated.

[0021] The cement used in the present invention is not particularly limited, and ordinary cement can be used.
More specifically, ordinary, high strength, ultra-high strength, low heat, etc. various Portland cements and these Portland cements,
It is possible to use various mixed cements mixed with silica, slag, fly ash or the like.

In addition, various cement admixtures and cement admixtures can be used for the cement in addition to aggregates such as sand and gravel.

The water used in the present invention is not particularly limited, but usually, fresh water is used. The amount of water used is
Although not particularly limited, usually, cement 100
40 to 250 parts per part is preferred. If the amount is less than 40 parts, the fluidity may be poor, and if it exceeds 250 parts, the strength may be delayed.

By mixing the cement admixture of the present invention into concrete, plastic concrete can be obtained.
Here, the plasticity refers to a state in which the fluidity is small when left at rest, but easily flows when pressurized.

In the present invention, when concrete mixed with water and a cement admixture are mixed, the fluidity is reduced within a few seconds after mixing. Therefore, when the pumping distance is lengthened or the workability is considered, the cement admixture is reduced. It is preferable that the agent, water, and the kneaded concrete are separately fed under pressure, and the application is performed while being joined and mixed at the tip.

As a method of merging and mixing, a method of using a mixing tube such as a Y-shaped tube, a method of using a double tube, a method of using an inlet piece for merging and mixing a cement admixture liquid in a shower shape, and the like are used. is there. Further, a method in which a spiral mixer is set in the tube after the combined mixing and further mixing is also possible. If the cement admixture and the concrete are sufficiently mixed, the adhesiveness and plasticity will come out and the workability will be improved, and if the mixing is insufficient, there will be some fluidization, making it difficult to complete the work. May be.

In the case of filling the gap in the underground or the back of the tunnel, it is sufficient to simply pour it in. However, in the case of spraying a place where water is present or a place where the flow to a crack or the like is prevented, a squeezing method is used. Blowing with air is also useful. The location where compressed air is introduced is not particularly limited, but is preferably introduced into the mixing tube.

[0028]

The present invention will be further described below with reference to embodiments.

Example 1 100 parts of cement, 100 parts of bentonite and 250 parts of water were kneaded with a mixer and mixed with cement bentonite milk (A
Liquid). On the other hand, an alkali thickening type polymer emulsion (solution B) having a solid concentration of 30% was prepared. Solution A is pumped at a flow rate of 20 liters per minute by a squeeze pump, and Solution B is cemented by a spiral pump.
For 0 parts, the flow rate is adjusted so that the alkali thickening type polymer emulsion has the compounding amount shown in Table 2 in terms of solid content and separately pumped to a mixing tube, and continuously plasticized while mixing with a non-driven line mixer. Concrete was manufactured. The flow value of the produced plastic concrete, the filling property of the mold, and the presence or absence of material separation when poured into water were confirmed. The results are also shown in Table 2. For comparison, a similar experiment was performed using a system without using a cement admixture and a polymer emulsion system having no alkali thickening. The results are also shown in Table 2.

The criteria for judging the presence or absence of material separation when the plastic concrete was poured into water are shown in Table 1.

[0031]

[Table 1]

<Materials used> Cement: ordinary Portland cement, commercially available water: tap water Bentonite: swelling power 9.9 ml / 2 g, commercially available alkaline thickening type polymer emulsion A: ethyl acrylate / methacrylic acid copolymer emulsion (polymer Composition "mass ratio"; ethyl acrylate: methacrylic acid = 50:50) Non-alkali thickening type polymer emulsion B: styrene /
2-Ethylhexyl acrylate copolymer emulsion (polymer composition "mass ratio"; styrene: 2-ethylhexyl acrylate = 45:55)

<Measurement method> Flow value: Spreading after placing plastic concrete in a flow cone having an inner diameter of 80 mm and a height of 80 mm and extracting the cone. Measurement after 2 minutes. Material separation: Suspension of water when poured in water. Visual judgment of condition Fillability: Filling a mold (15 cm × 15 cm × 55 cm), curing and removing the frame, and visually determining the presence or absence of voids (unfilled portion) on the side and bottom surfaces of the mold.

[0034]

[Table 2]

Table 2 shows that the concrete produced by mixing the cement admixture of the present invention has a good filling property and no material separation in water.

Example 2 Cement milk (Solution A) was produced by changing the amount of bentonite to 100 parts of cement so as to obtain the composition shown in Table 2, adding 250 parts of water and kneading with a mixer. On the other hand, an alkali thickening type polymer emulsion C having a solid concentration of 50%
(Solution B) was added to 100 parts of cement so as to have a solid content of 5%. Solution A is pumped at a flow rate of 20 liters per minute by a squeeze pump, and Solution B is flowed by a spiral pump so that the alkali thickening type polymer emulsion becomes 5% in solid content with respect to 100 parts of cement. Was adjusted and separately fed to a mixing pipe, and plastic concrete was continuously produced while mixing with a non-driven line mixer. The flow value of the produced plastic concrete, the filling property of the mold, and the presence or absence of material separation when poured into water were confirmed in the same manner as in Example 1. The results are also shown in Table 3.

<Materials used> Cement: ordinary Portland cement, commercially available bentonite A: swelling power 24.0 ml / 2 g, commercially available bentonite B: swelling power 9.9 ml / 2 g, commercially available water: tap water Alkaline thickening polymer Emulsion C: Ethyl acrylate / acrylic acid copolymer emulsion (polymer composition “weight ratio”; ethyl acrylate: acrylic acid = 50: 50) and ethylene / vinyl acetate copolymer polymer emulsion (polymer composition “weight ratio”; ethylene: acetic acid) (Ethyl acrylate / methacrylic acid copolymer emulsion: Ethylene / vinyl acetate copolymer emulsion = 70: 30)

[0038]

[Table 3]

From Table 3, it can be seen that the concrete produced by mixing the cement admixture of the present invention has a good filling property and almost no material separation in water.

[0040]

The use of the cement admixture of the present invention makes it possible to produce good plastic concrete.
The construction can be performed without reducing the rebound of the sprayed concrete or in the place where water is present, without separating the material, and can be sufficiently constructed even in a place having a void such as a crack. In addition, by separately feeding the cement admixture and the cement concrete separately and mixing and mixing them at the nozzle tip, it becomes possible to efficiently produce good plastic concrete efficiently and to quickly construct it.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 14/10 C04B 14/10 Z 28/02 28/02 C08K 3/34 C08K 3/34 C08L 33/02 C08L 33/02 35/00 35/00 // C04B 103: 44 C04B 103: 44 (72) Inventor Tomohiro Kaneko F-term in Denki Kagaku Kogyo Co., Ltd. 1-4-1, Yurakucho, Chiyoda-ku, Tokyo 4G012 PA06 PB16 PB30 PB31 PB32 4G056 AA07 CC31 CC39 CD55 4J002 BB081 BB091 BC021 BF011 BF021 BG002 BG011 BG041 BG051 BG061 BG071 BG101 BH021 CD191 DJ036 DM007 FD016 FD332 GL332GL

Claims (3)

[Claims] 1. A cement admixture comprising an alkali-thickened polymer emulsion obtained by copolymerization of an unsaturated carboxylic acid and an ethylenically unsaturated compound, and bentonite. 2. A concrete containing the cement admixture according to claim 1. 3. The method for producing concrete according to claim 2, wherein the concrete containing bentonite and the alkali-thickened polymer emulsion are separately fed under pressure and mixed and mixed at the tip.