JPH04317447A - Production of concrete and concrete admixture - Google Patents

Abstract

PURPOSE:To obtain a concrete admixture capable of improving the air entraining property and freezing and thawing resistance of the concrete mixed with fly ash by simultaneously using an air entraining agent and an emulsible defoaming agent consisting essentially of dimethylpolysiloxane in a specified ratio. CONSTITUTION:An air entraining agent (a) and an emulsible defoaming agent (b) consisting essentially of dimethylpolysiloxane are mixed in (a):(b)=95 to 99.8:0.2 to 5.0 (weight ratio of active components) to produce a concrete admixture which is incorporated into the concrete mixed with fly ash. A foamable anionic surfactant such as alkylbenzenesulfonates and alkylsulfonates or a foamable nonionic surfactant such as polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers is preferably used as the air entraining agent (a).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an admixture for concrete containing fly ash, and more particularly to an admixture that improves freeze-thaw resistance.

0002

BACKGROUND OF THE INVENTION It is known that the freezing and thawing properties of concrete can be improved by entraining air bubbles using an air entraining agent (AE agent). For example, when foaming anionic surfactants and foaming nonionic surfactants such as alkylbenzene sulfonates are added to concrete as air entraining agents (AE agents), air is entrained and freeze-thaw resistance is improved. There are many things. However, in the case of fly ash-containing concrete, it is generally known that simply adding a foaming surfactant to the concrete does not improve freeze-thaw resistance and entrain air.

The cause of this is that the carbon in the fly ash extinguishes the fine bubbles entrained in the concrete and turns them into coarse bubbles, and the water absorbed into the coarse bubbles freezes, reducing durability. It is speculated that it will cause

[0004] Therefore, fly ash-containing concrete compositions tend to have lower freeze-thaw resistance than fly ash powder-containing concrete, and it is desired to improve their durability.

[0005]

[Means for Solving the Problems] The present inventors have conducted intensive research on improving the freeze-thaw resistance of concrete mixed with fly ash. According to research by the present inventors, it is difficult to improve freeze-thaw resistance simply by adding a foaming surfactant to fly ash-containing concrete, so we investigated ways to improve this physical property. It is necessary to stably maintain fine bubbles, which are extremely effective for freeze-thaw resistance, even when mixed with fly ash. It was discovered that it has excellent effects.

That is, when an emulsifying antifoaming agent containing dimethylpolysiloxane as a main component is used in combination with an air entraining agent (AE agent), coarse foam can be extinguished and only fine foam can be left behind. That is, the above-mentioned problems can be solved by the combined use of antifoaming agents and AE agents, which are contradictory to each other.

[0007] The present inventors made various combinations of these substances and added them when producing fly ash-containing concrete, and succeeded in obtaining a quality concrete product with extremely excellent freeze-thaw resistance. The present invention has now been completed.

That is, the present invention provides an emulsified antifoaming agent (b) containing an air entraining agent (a) and dimethylpolysiloxane as main components.
(a):(b) =95~99.8:0.2~5
．． The present invention relates to a method for producing concrete mixed with fly ash, characterized in that it is used in combination at 0 (effective content, weight ratio). Further, the present invention provides an air entraining agent (a) and an emulsifying antifoaming agent (b) in a ratio of (a):(b) =95 to 99.8:
The present invention relates to a concrete admixture containing fly ash, characterized in that it contains fly ash in an amount of 0.2 to 5.0 (effective content, weight ratio).

The air entraining agent (AE agent) as component (a) used in the admixture of the present invention includes alkylbenzene sulfonates, alkyl sulfates, alkyl polyoxyethylene glycol sulfates, and alkylphenol polyoxyethylene glycol sulfates. salt, alkanesulfonate, alpha
- One or more foaming anionic surfactants selected from olefin sulfonates, rosin acids, salts of rosin derivatives, and alkyl sulfosuccinates, or polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl One or more foaming nonionic surfactants selected from ethers and alkylolamides are preferably used, with 95 to 99.8% by weight of the foaming nonionic surfactants and component (b) dimethylpolysiloxane as the main component. 0.2 to 5.0% by weight of an emulsifying antifoaming agent is used in combination. If the above-mentioned (a) component or (b) component of the present invention is less than or greater than the above range, excellent freeze-thaw resistance cannot be obtained, but exhibits extremely excellent freeze-thaw resistance within the above range. It is.

As the above-mentioned anionic or nonionic surfactant used as component (a) of the present invention, those generally used as air entraining agents can be used.
Particularly typical general formulas are shown below.

[0011]

[Chemical formula 1]

[0012] Component (b), an emulsifying antifoaming agent mainly composed of dimethylpolysiloxane, is, for example, Toshiba Silicone TSA770 [manufactured by Toshiba Silicone Co., Ltd.],
Shin-Etsu Silicone KM70 [manufactured by Shin-Etsu Silicone Co., Ltd.]
The general formula is shown below, but it is not limited thereto.

[0013]

[Case 2]

[0014] The fly ash-containing concrete to which the admixture based on the combination of component (a) and component (b) of the present invention is used includes, but is not particularly limited to, the mixing rate of fly ash. 2-1 per concrete
A range of 5 (volume %/m3) is preferable.

In the present invention, the fluidity of concrete is not particularly limited, and it can be used within the range of slump of 0 to 23 cm and slump flow of 30 to 70 cm.

In carrying out the present invention, a high performance water reducing agent,
For example, one or two methylolated products or sulfonated products of naphthalene, melamine, phenol, and aniline.
More than one type of formalin monocondensate or cocondensate may be used in combination with the admixture of the present invention. One example is naphthalene sulfonate formalin condensate [e.g. Mighty 150;
manufactured by Kao Corporation], melamine sulfonate formalin condensate [e.g. Mighty 150V-2; manufactured by Kao Corporation]
, phenolsulfonate formalin cocondensate (e.g. Patent No. 1097647), phenolsulfanilate formalin cocondensate (e.g. JP-A-1-1134)
19), phenol-melamine methylolated sulfonate co-condensate (for example, JP-A-56-13674), etc. can be used in combination.

In addition to fly ash, the fly ash-containing concrete of the present invention contains various admixtures (agents) such as blast furnace slag, silica fume, expanding agents, water reducing agents, thickeners, water retaining agents, water-soluble highly It is also possible to contain molecules etc. as necessary. Further, according to the present invention, highly fluid and non-separable concrete using fly ash and blast furnace slag can be produced. The total usage ratio of (a) component and (b) component is 0.01 to 0.1 w to cement.
t%, but it is not particularly limited depending on the mixing rate of fly ash used, admixtures used together, etc.

The admixture of the present invention can be used by mixing the (a) component and (b) component and adding them simultaneously to the kneading water, or by adding the (a) component first to the kneading water ( b)
There are two ways to use the ingredients, one is to add the ingredients after the concrete has been mixed, and either method can be effective, and the addition method is not limited.

[0019]

[Examples] The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 The materials used in the examples are shown below.

[0021] Cement; manufactured by Chuo Cement Co., Ltd. Specific gravity = 3.16 Fine aggregate; River sand from Kinokawa Specific gravity = 2.57 FM = 2.89 Coarse aggregate; Crushed stone from Takarazuka
Specific gravity = 2.60 FM = 6.57 Fly ash; manufactured by Kansai Electric Power Company Specific gravity = 2.
No. 23 fly ash concrete was prepared under the following mixing conditions. The weight of the materials used is kg per 1 m2.

[0022] Ordinary Portland cement (C) 370k
g, fly ash 230 kg (22 volume%), kneading water (W) 178 kg, river sand (S) 627 kg, gravel (G) 853 kg, W/C=48%, S/(S+G)
+ fly ash) = 36.7%, 5.5% of Mighty 150 [manufactured by Kao Corporation] was added as a high-performance water reducing agent to the kneading water.
5 kg was added, and further admixtures of the present invention and comparative admixtures shown in Table 1 were adjusted so that the concrete air content was 4 to 6%. The above mixture is kneaded for 3 minutes using a forced stirring mixer.

Slump and slump flow measurement test J
It was carried out according to the ISA 1101 method. Furthermore, after filling the mixed concrete into the formwork, steam curing is performed. Steam curing conditions are 2 hours preheating time, 20°C to 6°C.
The temperature was raised to 0°C in 2 hours, maintained at 60°C for 1 hour, and then naturally cooled. Immediately after steam curing, demolding was performed.

Freeze-thaw resistance was determined according to ASTM C512. Measurement of degree of air bubbles is based on ASTM C 45
It was carried out according to 7.

[0025]

[Table 1]

(1): TSA770 (manufactured by Toshiba Silicone Co., Ltd.) (2): KM70 (manufactured by Shin-Etsu Silicone Co., Ltd.) Example 2 According to Example 1, the concrete conditions in Table 2 were applied. A performance test of the invention admixture was conducted. The results are shown in Table 3.

[0027]

[Table 2]

C: Cement, FA: Fly Ash, W
: Water, S: Sand, G: Gravel

[0029]

[Table 3]

Table 4 summarizes the performance test results when the admixture and water reducing agent were added.

[0031]

[Table 4]

Water reducing agent used (a) Naphthalene sulfonate formalin condensate [for example, Mighty 150; manufactured by Kao Corporation] (b) Melamine sulfonate formalin condensate [for example, Mighty 150]
V-2; Manufactured by Kao Corporation] From the results in Table 3 when only the admixture was used and Table 4 when the admixture and water reducing agent were used together, the admixture of the present invention was superior to the comparative product. It can be seen that the freeze-thaw resistance (durability index) is superior in comparison.

[0033]

[Effect of the invention] When the admixture of the present invention is used in concrete mixed with fly ash, air entrainment and freeze-thaw resistance (durability index) can be improved, and durability can be improved. becomes possible.

Claims (3)

[Claims] [Claim 1] An air entraining agent (a) and an emulsifying antifoaming agent (b) containing dimethylpolysiloxane as the main components (a)
:(b) =95-99.8: A method for producing concrete mixed with fly ash, characterized in that it is used in combination at a ratio of 0.2 to 5.0 (effective content, weight ratio). [Claim 2] An air entraining agent (a) and an emulsifying antifoaming agent (
b) Mix and simultaneously add to the kneading water or (a)
2. The method for producing concrete mixed with fly ash according to claim 1, wherein (b) is added after the concrete has been mixed. [Claim 3] An air entraining agent (a) and an emulsifying antifoaming agent (
b) and (a):(b) =95~99.8:0.2
A concrete admixture containing fly ash, characterized in that it contains fly ash in an amount of ~5.0 (effective content, weight ratio).