JPH10324555A - Cement admixture and method for placing jointed concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of placing a jointed concrete reduced in cracking and excellent in packing property, adhesion to existing concrete, usage and workability. SOLUTION: This cement admixture contains an expanding material, dry- shrinkage reducing agent, water reducing agent and aq. polymer dispersion. When a jointed concrete is placed, the joint of existing concrete is covered with the aq. polymer dispersion, and the jointed concrete contg. the cement, expanding material, dry-shrinkage reducing agent and water reducing agent and having >=30 cm packing property by the U-shaped packing test method is placed on the lower face and/or the side face of the existing concrete.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement admixture which is a cast-in-place concrete having a good adhesion to existing concrete, and a method of placing the cast-in concrete, particularly for use in a reverse-casting method. The present invention relates to a method of placing cast concrete having good adhesion to existing concrete such as slab lower surface concrete.

[0002]

2. Description of the Related Art In a reinforced concrete structure, it is impossible to pour a large amount of concrete continuously, and it is necessary to transfer new concrete to existing concrete or to reinforce existing concrete. For example, when casting new concrete for repair
There is a seam between the existing concrete and the newly cast concrete. Therefore, the adhesive force between the existing concrete and the newly cast concrete at that location is a problem, and if the adhesive force is not obtained, the appearance, strength, durability, etc. of the structure may be impaired. And other issues.

On the other hand, in an urban area or the like, the underground floor is large in order to make effective use of the land, for example, it is often used just before the boundary. The construction of the ground floor can be carried out at the same time, and the upside-down concrete method has been adopted to improve work safety, reduce noise and vibration, and improve productivity. Is used.

[0004] In addition, it has been noted that the repair and reinforcement of the lower part of the existing slab concrete is filled with a slab lower surface reinforced concrete that can be constructed without interrupting traffic, because it does not cause traffic congestion.

[0005] In order to improve the adhesion between the existing concrete and the newly cast concrete, the existing concrete surface is roughened, water-absorbed, or a paste is applied to the interface. It is possible.
The usual joint is the upper surface or the upper surface and the side surface of the existing concrete, and by the treatment of the existing concrete surface, a good adhesive force is obtained even with mortar or concrete that is usually used. However, in the case of reverse-casting concrete or floor slab bottom reinforced concrete, the adhesive force between the existing concrete and the newly cast concrete is obtained from the lower surface or the lower surface and the side surface of the existing concrete. However, there is a problem that bleeding and settlement of concrete are apt to occur, so that it is difficult to obtain the adhesive force.

Therefore, metal gas is used in combination with a water reducing agent, an inorganic fine powder, a thickening agent, a separation preventing agent, and the like to generate hydrogen gas, thereby compensating for a decrease in volume and ensuring adhesion to an existing concrete surface. However, the method of compensating for volume by hydrogen gas using metal aluminum in back-casting concrete is a chemical reaction, so the reaction depends on the season and day temperature, cement type, admixture, and alkali metals in the water reducing agent. In some cases, it was difficult to control the amount of swelling because the speed was changed and the reaction was terminated during transportation. In particular, since the amount of metallic aluminum used is usually as small as several tens of grams per 1 m ³ , it is difficult to uniformly disperse the metal aluminum. As described above, it is difficult to control the amount of expansion by using aluminum metal, and if the amount of expansion is too large, the compressive strength is reduced by as much as 5% with a volume increase of 1%. there were.

[0007] Further, the grouting material used in the back-casting method or the like has a risk of cracking due to heat of hydration or cracking due to drying shrinkage in a large amount of construction, which may be high in cost. .

The inventor of the present invention has obtained the knowledge that can solve the above-mentioned problems by using a specific material, and has completed the present invention.

[0009]

That is, the present invention is a cement admixture containing an expanding material, a drying shrinkage reducing agent, a water reducing agent, and an aqueous polymer dispersion. A U-type filling test, which is a method of placing cast concrete, characterized by covering a polymer dispersion with a cast concrete containing a cement, an expanding material, a drying shrinkage reducing agent, and a water reducing agent. This is a method of casting cast concrete having a fillability exceeding 30 cm by a method, and casting the cast concrete on the lower surface and / or side surface of existing concrete.

Hereinafter, the present invention will be described in detail.

As the cement used in the present invention, various portland cements such as ordinary, fast and super fast,
Various mixed cements obtained by mixing blast furnace slag or fly ash with these Portland cements, and low heat-generating cements such as high belite cements and the like can be mentioned.
Unit amount of cement, preferably 300 ~900kg / m ^3. 300k
may a less than g / m ³ bonding strength can not be obtained, 900 kg /
sometimes cracking occurs due to the drying shrinkage and heat of hydration greater than m ^3.

As the expanding material used in the present invention, there are calcium-sulfoaluminate-based expanding material and lime-based expanding material, and any of hydration heat suppression type for mascon and normal type can be used. The particle size of the expansive material is not particularly limited, but is usually preferably 2,000 to 4,000 cm ² / g. 2,
If it is less than 000 cm ² / g, unreacted substances may remain for a long period of time and the durability may be reduced. If it exceeds 4,000 cm ² / g, the hydration reaction may be too fast and the desired expansion may not be obtained. The amount of the expanding material to be used is preferably 3 to 15 parts by weight, more preferably 5 to 13 parts by weight, based on 100 parts by weight of cement. If the amount is less than 3 parts by weight, the effect of reducing shrinkage may be small, and if it exceeds 15 parts by weight, the amount of expansion may be too large to lower the strength.

The drying shrinkage reducing agent used in the present invention is a kind of nonionic surfactant and is usually a liquid having a pure content of 99% or more, and has a function of dissolving in water to lower its surface tension. Things. Its basic structure has a polyoxyalkylene polymer, and a terminal is added with a lower alcohol, a phenol, an amino bond and the like. Specifically, polypropylene glycol, ethylene oxide methanol adduct, ethylene oxide / propylene oxide block polymer, ethylene oxide / propylene oxide random polymer, cycloalkyl group adduct of glycol, adduct of methyl group added to both ends of glycol,
A phenyl group adduct of glycol, a block polymer obtained by adding a methylphenyl group to glycol, an adduct obtained by adding ethylene oxide methanol to both ends of glycol, and an adduct obtained by adding dimethylamine to glycol can be used. The drying shrinkage reducing agent acts in a strong alkaline aqueous solution of cement without being adsorbed by cement particles, has low volatility, and does not have an abnormally large amount of air entrainment,
It does not hinder the hydration of cement and has a lower molecular weight than the water reducing agent. The drying shrinkage reducing agent is preferably used in place of part or all of the kneading water. The amount of the drying shrinkage reducing agent to be used is preferably 1 to 12 parts by weight, more preferably 2 to 8 parts by weight, based on 100 parts by weight of cement. If the amount is less than 1 part by weight, the effect of reducing shrinkage may be small, and if it exceeds 12 parts by weight, setting delay may occur and the fluidity may decrease.

The water reducing agent used in the present invention is used to improve the fluidity of concrete and to reduce the unit water volume, and high-performance AE water reducing agents, high-performance water reducing agents, AE water reducing agents, and the like can be used. . Specifically, formalin condensate of naphthalene sulfonate, formalin condensate of melamine sulfonate, polystyrene sulfonate, hydroxypolyacrylate, copolymer of α, β-unsaturated dicarboxylic acid and olefin, polyethylene glycol mono Copolymers derived from alkenyl ethers and maleic or methacrylic monomers, styrene-acrylate-maleic copolymers, modified lignin sulfonic acid compounds, aromatic amino sulfonic acid compounds, etc. can be used It is.
Further, a polymer that is partially polymerized by a cross-linking reaction or a partially esterified maleic acid can be used, and one or more of these can be used. The amount of the water reducing agent used is preferably 0.01 to 4 parts by weight in terms of solid content, and
Parts by weight are more preferred. If the amount is less than 0.01 part by weight, it may be difficult to obtain a predetermined fluidity, and if it exceeds 4 parts by weight, separation or setting delay may occur.

The aqueous polymer dispersion (hereinafter referred to as "aqueous polymer") used in the present invention contains 0.05% of water in water.
Fine particles of a polymer of 5 μm are uniformly dispersed. When the fine particles are rubber, they are called latex, and when they are resin, they are called emulsion. Examples of the latex include chloroprene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, and methyl methacrylate butadiene rubber. Examples of the emulsion include polyacrylate, ethylene vinyl acetate, and epoxy resin.

The method of coating the aqueous polymer may be, for example, a method of diluting the aqueous polymer with water and applying it to the existing concrete surface or spraying. Is preferred. In addition, it is also possible to use a method in which an aqueous polymer is mixed with a cement, an expanding material, a drying shrinkage reducing agent, and a water reducing agent, and a method in which a mixture obtained by kneading an aqueous polymer in a mortar or paste is applied to an existing concrete surface. It is.
The method of mixing the expanding material, the drying shrinkage reducing agent, the cement, the water reducing agent, and the aqueous polymer is not particularly limited as long as it can be uniformly mixed.

When the aqueous polymer is diluted with water and applied to existing concrete to form a film, the amount of the aqueous polymer applied is preferably from 10 to 500 g / m ^{2 in} terms of solid content. Is the coating amount of less than 10 g / m ² may high adhesion can not be obtained, 50
Even if it exceeds 0 g / m ² , improvement of the coating effect cannot be expected. When applying a mixture kneaded in cement mortar or paste, the amount of the aqueous polymer applied is
The amount is preferably 2 to 30 parts by weight in terms of solid content based on 00 parts by weight. If the amount is less than 2 parts by weight, a high adhesive force cannot be obtained,
Even if it exceeds 30 parts by weight, no improvement in the effect of addition can be expected.

The amount of water used in the present invention is not particularly limited, but is preferably from 20 to 100 parts by weight, more preferably from 25 to 70 parts by weight, based on 100 parts by weight of the total of cement and expansive material. . If the amount is less than 20 parts by weight, the expansion may be significantly delayed. If the amount exceeds 100 parts by weight, bleeding and material separation may be increased.

The aggregate used in the present invention is not particularly limited, and crushed stone, crushed sand, river sand, limestone and the like which are usually used can be used. The amount of the aggregate is preferably 100 to 800 parts by weight based on 100 parts by weight of the total of the cement and the expanding material. If the amount is less than 100 parts by weight, heat generation and shrinkage are so large that cracks may occur. If the amount is more than 800 parts by weight, fluidity may decrease.

In the present invention, the mortar or the high-concentration mortar
In the case of a reed, prevention of material separation and improvement of plastic deformation capacity
From the viewpoint, it is possible to use stone powder such as calcium carbonate powder.
preferable. In particular, the total unit amount of cement and expansive material is 50
0kg / m^ThreeIf less, it is preferable to use stone powder. stone
The particle size of the powder is not particularly limited, but the Blaine value
In 3,000-10,000cm ^Two/ g is preferred. The amount of stone powder used is
80 parts by weight for the total of 100 parts by weight of cement and expander
The following is preferred. In particular, the total unit of cement and expansive material
500kg / m^ThreeLess than cement, intumescent, and stone
Total unit weight of powder is 500kg / m^ThreeAdd the stone powder so that
Is preferably obtained. Combination of cement, expansive material and stone powder
Total unit weight is 500kg / m^ThreeIf less than, the filling property is poor and bleeden
May occur.

Furthermore, in the present invention, water-soluble polymers such as cellulose derivatives, starch derivatives, polyvinyl alcohol, polyethylene oxide, polyacrylamide, and biopolymers; powdered cellulose such as cellulose; inorganic fine powders such as silica fume; It is possible to use a separation inhibitor having an effect of preventing bleeding of clay minerals such as sepiolite and the like. In addition to the water-based polymer used to coat the existing concrete, low-molecular-weight polymerizable polymers or prepolymers, such as unsaturated polyester or epoxy resin, which are liquid polymers, such as ethylene vinyl acetate, which is a re-emulsifying powder resin, and a curing agent, etc. It is possible.
It is also possible to adjust the time from coating to casting by using an aqueous polymer together with a film forming time regulator.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Example 1 A unit amount of cement A was 500 kg / m ^3, and 6 parts by weight of an expanding material α, 152 parts by weight of fine aggregate,
And 158 parts by weight of coarse aggregate were put into a mixer, kneaded at a low speed for 30 seconds, and 0.36 parts by weight of water, 1.0 part by weight of a water reducing agent in terms of solid content, and 4 parts by weight of a drying shrinkage reducing agent were added, Concrete mixed for 150 seconds was prepared. Slump flow of prepared concrete is 65cm, U-shaped filling test result is 30.5c
m, air volume was 4.5%. Treat the lower surface of the existing concrete with a water jet with a discharge pressure of 2,300 kgf / cm ² ,
Three days after the aqueous polymer was applied as shown in Table 1 and the film was sufficiently formed, a mold was set under the existing concrete,
The prepared concrete was poured. On the 28th day after curing, coring was performed to measure the adhesive strength. Table 1 shows the results.

<Materials Used> Cement A: Ordinary Portland cement, expanded material manufactured by Nippon Cement Co. α: Calcium sulfoaluminate-based expanded material,
Commercial product Drying shrinkage reducing agent A: Copolymer of ethylene oxide and propylene oxide Water reducing agent: High-performance AE water reducing agent, composite of polycarboxylic acid ether and crosslinked polymer Fine aggregate: River sand, 5 mm below, specific gravity 2.56 coarse Aggregate: crushed stone, Gmax = 20 mm, specific gravity 2.65 Aqueous polymer a: ethylene vinyl acetate emulsion, specific gravity 1.06 aqueous polymer b: styrene butadiene rubber latex,
Specific gravity 1.06 Aqueous polymer c: polyacrylate emulsion, specific gravity 1.05

<Measurement method> Slump flow: Measured according to JSCE-F503 Fillability: High fluidity concrete committee “U”
Air filling: Measured according to JIS A 1128 Adhesion: After hardening of concrete, coring, φ
Prepare a 5cm specimen, grind the upper and lower surfaces, adhere to the jig for tensile test, measure the adhesive force of 28 days old

[0026]

[Table 1]

Example 2 The unit amount of cement B was 315 kg / m ^3, and based on 100 parts by weight of cement B, 11 parts by weight of expander α, 77 parts by weight of stone powder, 280 parts by weight of fine aggregate, and 230 parts of coarse aggregate Parts by weight into a mixer and knead at low speed for 30 seconds, then add 47 parts by weight of water, 0.7 parts by weight of water reducing agent in terms of solid content, and 7 parts by weight of drying shrinkage reducing agent a and knead for 150 seconds. It carried out like Example 1 except having produced concrete. Table 2 shows the results. The produced concrete had a slump flow of 67 cm, a U-shaped filling test result of 31 cm, and an air volume of 4.3%.

<Materials used> Cement B: Early strength Portland cement, manufactured by Sumitomo Osaka Cement Co., Ltd. Stone powder: Calcium carbonate powder, specific gravity 2.70, Blaine value 5,000 cm ² / g

[0029]

[Table 2]

Example 3 Cement shown in Table 3 and 100 parts by weight of cement were used in the amounts shown in Table 3 for the amount of the expanding material, drying shrinkage reducing agent, stone powder and water 15
0 kg / m ^3, fine aggregates 865~875kg / m ^3, as well as coarse aggregate 731～
Blended 741kg / m ^3, slump flow value of concrete
Fill the water reducing agent with cement,
It was blended in a range of 0.38 to 0.42 parts by weight in terms of solid content with respect to a total of 100 parts by weight of the expanding material and the stone powder. The air volume was also adjusted to be 4.5 ± 0.5%. The concrete surface is treated with a water jet with a discharge pressure of 1,800 kg / cm ² ,
The procedure was performed in the same manner as in Example 1 except that the aqueous polymer b was applied at 150 g / m ² to form a film. The results are also shown in Table 3.

<Materials used> Cement C: high belite cement, expander manufactured by Chichibu Onoda Co., Ltd. β: lime-based expander, commercially available drying shrinkage reducing agent b: lower alcohol alkylene oxide adduct

[0032]

[Table 3]

Example 4 Using a unit amount of cement B shown in Table 4, and using 100 parts by weight of cement, an expanding agent α shown in Table 4, a water reducing agent in terms of solid content, fine aggregate, coarse aggregate, water , And 4 parts by weight of a drying shrinkage reducing agent A, and the same procedure as in Example 2 was carried out, except that a concrete in which the amount of air was adjusted to 4.5% was prepared. The results are also shown in Table 4.

[0034]

[Table 4]

Example 5 The procedure of Example 2 was repeated, except that 0.6 parts by weight, in terms of solids, of an expanding agent α, a drying shrinkage reducing agent and a water reducing agent were added to 100 parts by weight of cement B, as shown in Table 5. went. The results are also shown in Table 5.

<Materials> Water reducing agent: High-performance AE water reducing agent, maleic anhydride, copolymer of methoxypolyethylene glycol-acrylate and styrene

[0037]

[Table 5]

[0038]

The cast-in-place concrete of the present invention has an excellent filling property, has little cracking and self-shrinkage due to drying shrinkage, and has good adhesion to existing concrete. The effect of improving workability and improving workability without traffic congestion is achieved by placing concrete under the floor slab reinforced concrete.

Claims (4)

[Claims] 1. A cement admixture comprising an expanding material, a drying shrinkage reducing agent, a water reducing agent, and an aqueous polymer dispersion. 2. A casting method comprising coating a joint surface of existing concrete with an aqueous polymer dispersion, and joining a joint concrete containing a cement, an expanding agent, a drying shrinkage reducing agent, and a water reducing agent. How to put joint concrete. 3. The method according to claim 2, wherein the cast concrete is a concrete having a filling property exceeding 30 cm in a U-type filling test method. 4. The method according to claim 2, wherein the cast concrete is joined to a lower surface and / or a side surface of the existing concrete.