JP2769239B2 - Admixture for concrete - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the surface beauty of concrete blocks, concrete plates, concrete pipes, and other instantly demolded concrete products manufactured by vibration and pressure molding using hardened concrete. It relates to an admixture for concrete that can be improved.

[Conventional technology and its problems]

As concrete technology advances, stiffened or ultra-hardened concrete is pressure-formed while performing external vibration compaction by a machine, and immediately released from the mold (immediate removal)
Concrete products can be obtained by steam curing.

However, the stiff concrete used in the instant deconstruction method is a concrete in a dry state such as wet soil, which causes insufficient filling even under strong vibration, and causes a lack of corners, bean boards, and soot on the concrete surface. Voids are easily formed, and the surface appearance is a problem. In addition, reducing the amount of cement paste so as not to cause the product to lose its shape, deformation, sagging, etc. after molding also causes the deterioration of the surface appearance.

Since the mixing of hardened concrete basically reduces the amount of cement paste to prevent mold collapse after molding, the amount of cement paste filling between aggregate particles is insufficient. Therefore, the surface appearance of the cement paste is improved by increasing the lubricating properties of the cement paste by increasing the vibration and press pressure of the molding machine or by adding an admixture, but these methods have not been able to provide sufficient effects. It is.

[Means for solving the problem]

The present inventors have conducted intensive studies in order to solve the above problems, and found that when a concrete product is obtained by press-molding hardened concrete, a concrete containing a specific anionic surfactant, dextrin and alkylamine oxide is obtained. The present inventors have found that the use of the admixture for the present invention significantly improves the surface appearance of concrete products, and has completed the present invention.

That is, in the present invention, the surface tension of a 1% aqueous solution is 40 dyne / c.
The present invention provides an admixture for concrete containing m or less of an anionic surfactant, dextrin and alkylamine oxide.

The hard kneading concrete in the present invention comprises water from 90 to 140 in the concrete 1 m ^3, slump refers to the 1cm or less.

The admixture of the present invention basically focuses on a small amount of cement paste and attempts to increase the amount of paste by entraining bubbles.

In general, entrainment of bubbles in hardened concrete is difficult to occur due to a small amount of water. Further, if the bubbles are entrained, the strength is reduced. In view of these, the admixture of the present invention facilitates entrainment of bubbles during concrete production and increases the amount of paste. After molding, the paste effectively covers the interface between the mold and the concrete, and acts to break bubbles after molding. is there.

The admixture of the present invention is an anionic surfactant as described above,
A concrete admixture containing dextrin and an alkylamine oxide, which, when combined with these three components, has an excellent effect on improving the surface appearance of concrete products and can be an admixture with less decrease in concrete strength. The above-mentioned performance cannot be obtained by using an anionic surfactant alone or in a blended system of two components with dextrin or alkylamine oxide.

The anionic surfactant used in the present invention does not limit the structure and the like, and the surface tension of a 1% aqueous solution is 40 dyne.
Any anionic surfactant of not more than / cm may be used. If the surface tension of the 1% aqueous solution is greater than 40 dyne / cm, the foaming power is undesirably reduced. The lower the surface tension, the greater the foaming power, and a surface tension of 40 dyne / cm or less is required. Examples of anionic surfactants include alkyl fatty acid salts, alkyl sulfate salts, alkyl sulfosuccinates, alkylbenzene sulfonates, alkyl phosphates, polyoxyethylene alkyl ether sulfates, rosinates and the like. One or more kinds are used.

The alkylamine oxide used in the present invention is suitably a mono-long chain alkyldimethylamine oxide,
The carbon number of the alkyl group is preferably from 8 to 18, particularly preferably 12.

Further, the dextrin used in the present invention is not particularly limited, and those usually used can be used.

In the present invention, the weight ratio of anionic surfactant, dextrin and alkylamine oxide is preferably anionic surfactant: dextrin: alkylamine oxide = 45 to 80:45 to 15: 5 to 10.

The admixture for concrete of the present invention is used when producing a vibration pressure molded product using hardened concrete, and does not limit the concrete product or the molding machine.

As the concrete composition, materials other than cements of the hydraulic composition, for example, blast furnace slag, fly ash,
It is also possible to use the composition containing silica fume, expanding material, lightweight aggregate, inorganic fiber, organic fiber and the like.

〔Example〕

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 Using the concrete materials shown in Table 1 and adding the admixtures shown in Table 3 by mixing the concrete shown in Table 2, FIG.
Concrete blocks having the following shapes were molded.

Concrete block is 3900 ~ 4000rpm
At a vibration frequency of 1.3 to 1.5 mm and a vibration acceleration of 10.2 to 12 G for 3 seconds, and press-molded with a press pressure of 1 kg / cm ² for 5 seconds. The concrete filling amount is about 45 kg per one block.

Immediately after the block molding, the mold is released, the temperature is raised from 20 to 60 ° C. in 2 hours, and the temperature is kept at 60 ° C. for 2 hours and naturally cooled.

The dimension retention was determined by measuring the surface portion and the retaining portion, and determining the percentage of expansion and contraction relative to the original dimensions. In addition, the surface aesthetics was viewed from the surface, the conservative finished state and the smoothness. Furthermore, compressive strength is φ10cm
The core was cut out with a diamond cutter and cut to a height of 10 cm.

 Table 4 shows the results.

Example 2 Using the concrete materials shown in Table 5 and adding the admixture shown in Table 3 according to the concrete blending shown in Table 6, FIG.
Concrete pipes having the shapes shown in FIG.

For concrete pipes, using a hydraulic vibration immediate de-pipe making machine, at a frequency of 3800-4200 rpm, amplitude 0.5-0.9 mm,
It was molded in 3 minutes and 30 seconds while filling concrete with a vibration acceleration of 4.45 to 8.02G.

Immediately after the pipe is formed, remove it from the mold.
The temperature is raised to 60 ° C. in 2 hours, kept at 60 ° C. for 3 hours, and allowed to cool naturally.

The dimension retention was determined from the percentage of expansion and contraction of the pipe length and the inner diameter with respect to the original dimensions. In addition, the surface appearance was viewed from the finished state and smoothness of the inner and outer surfaces of the pipe. Furthermore, the compressive strength is φ
Cut out the core with a 5cm diamond cutter, height 5cm
The measurement was performed with the sample cut into pieces.

 Table 7 shows the results.

[Effects of the Invention] As is clear from the results of Tables 4 and 7, the admixture of the present invention exhibits an excellent effect of improving the surface appearance of concrete products. Concrete products using the admixture of the present invention have less strength reduction than those using the conventional admixture, and have excellent dimensional stability. It can be used.

[Brief description of the drawings]

FIG. 1A is a plan view of a concrete block manufactured in Example 1, FIG. 1B is a cross-sectional view taken along line AA in FIG.
FIG. 2A is a plan view of the concrete pipe produced in Example 2, and FIG. 2B is a cross-sectional view. The unit of the dimension in the drawing is mm.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C04B 24/20 C04B 24/34 24/34 24/38 Z 24/38 B28B 1/08 // C04B 103: 40 (58) Survey Field (Int.Cl. ⁶ , DB name) C04B 28/02 C04B 24/08 C04B 24:08 C04B 24/16 C04B 24:16 C04B 24/34 C04B 24:34 C04B 24/38 C04B 24:38 C04B 24 / 12 C04B 24:12 C04B 103: 40 B28B 3/00-3/02 B28B 1/08

Claims (2)

(57) [Claims] 1. A concrete admixture comprising an anionic surfactant having a surface tension of a 1% aqueous solution of 40 dyne / cm or less, dextrin and alkylamine oxide. 2. The weight ratio of anionic surfactant, dextrin and alkylamine oxide is as follows: anionic surfactant: dextrin: alkylamine oxide = 45.
The admixture for concrete according to claim 1, wherein the ratio is from 80:45 to 15: 5 to 10.