JPH07133146A - Installation method for concrete - Google Patents

Abstract

PURPOSE:To provide a concrete compd. which does not adversely affect the quality of ordinary concrete even if the underwater non-separable concrete and the ordinary concrete are kneaded and mixed by using the same mixer. CONSTITUTION:A welan gum is used as an underwater non-separable admixture at the time of using concrete for underwater placement compounded with the underwater non-separable admixture and the ordinary concrete not mixed with the, admixture for concrete installation by using the same kneading machine or the same transporting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete construction method for underwater pouring and aerial pouring.

[0002]

2. Description of the Related Art Conventionally, underwater construction has been performed in which concrete with a water-cement ratio of 50% or less and a unit cement amount of 370 kg / m ³ or more is placed from the underwater bottom using a tremie pipe. In recent years, underwater non-separable concrete has been developed with virtually no material separation in water, and it has been widely used in places where high quality is required and where environmental separation of concrete is not permitted.

As the underwater non-separable concrete,
In order to impart resistance to material separation in water, those using water-soluble cellulosic thickeners typified by methyl cellulose (MC), hydroxyethyl cellulose (HEC) and various dispersants have been put into practice.

[0004]

For example, the conventional non-separable underwater concrete using a water-soluble cellulosic thickener has a very high viscosity, so that if it adheres to the inside of a mixer or an agitator vehicle, its cleaning is difficult. There is.

Since the mixing in the plant mixer is performed in a batch system, it may be necessary to mix the ordinary concrete after the underwater non-separated concrete containing the thickener. In the case of agitator vehicles, it may be necessary to alternate between the two concrete types for transport. Depending on the construction site, both underwater non-separable concrete and ordinary concrete may be required.

[0006] When supplying the underwater non-separable concrete and the ordinary concrete by using the same mixing machine or the same conveying machine, if the former concrete is insufficiently washed, the quality of the latter concrete will be deteriorated. Have a bad effect. The former concrete has poor cleanability, and a great deal of work was required to completely clean it.

The present invention is intended to solve the above-mentioned problems associated with conventional underwater non-separable concrete construction.

[0008]

DISCLOSURE OF THE INVENTION The present invention relates to an underwater pouring concrete containing an underwater non-separable admixture, and an ordinary concrete containing no admixture, in the same kneading machine or the same conveying means. The present invention provides a concrete construction method characterized by using welan gum as the underwater non-separating admixture when using for the concrete construction.

In this case, the concrete for underwater casting is a concrete material consisting of cement, aggregate and water, and has a high content of 0.01 to 2.0% by weight per unit amount of welan gum and 0.1 to 4.0% by weight per unit amount of cement. Add a water reducing agent or a high performance AE water reducing agent to increase the slump flow to 40%.
Use concrete that is ~ 70 cm.

[0010]

[Function] When welan gum is used as an inseparable admixture in water, good underwater concrete that does not cause material separation in water is obtained as shown in the examples below, and this underwater concrete containing welan gum is
Since it does not adhere to the mixer as much as ordinary concrete, both concretes can be mixed continuously and alternately.

Particularly, in concrete mixing, 0.01 to 2.0% by weight of welan gum per unit amount of water and 0.1 to 4.0% by weight of high performance water reducing agent or high performance AE water reducing agent per unit amount of cement are added, Slump flow 40 ~
By making it 70 cm, it is possible to obtain an underwater concrete showing sufficient inseparability in water and maintaining good fluidity. This underwater concrete can be satisfactorily discharged from mixers and agitator cars in much the same way as ordinary concrete.

Detailed Description of the Invention The welan gum used in the present invention is, for example, K. Clare's CHEMSEC USA ■ 88 SYMPASI.
As described in the paper entitled APPLICATION OF NOVEL BIOGAMS submitted to UM, AT of Alcaligenes strains was described.
A polysaccharide (BIOGAM) of microbial origin produced by subjecting TC 31555 cells to aerobic fermentation under carefully controlled conditions, the general structure of which is shown in Chemical formula 1.

[0013]

[Chemical 1]

That is, the main chain of this BIOGAM has two D
-Glucose, 1 D-glucuronic acid and 1 L
-Rhamnose, the side chain is composed of one rhamnose or one mannose.

Such welan gum is available as a dry powder product, but if this welan gum powder is added to a concrete mixing system in an extremely small amount, it exhibits remarkable pseudoplasticity and exhibits a suspension stabilizing effect of fine particles. For this reason, the material separation of the concrete is suppressed during the hardening until the fluidity is sacrificed. Further, the effect of preventing separation is almost independent of temperature.

When welan gum is added to the concrete mixture, it is preferable to add it in an amount of 0.01 to 2.0% by weight per unit amount of water. If it is less than 0.01% by weight, a sufficient separation preventing effect cannot be obtained. On the other hand, if it is added in an amount of more than 2.0% by weight, the viscosity sharply rises and the fluidity decreases, making it difficult to secure the fluidity intended by the present invention. The preferable range of addition of welan gum is 0.3 to 1.0% by weight per unit amount of water.

It is possible to improve the fluidity and filling property of concrete by adding a dispersant which imparts fluidity to a concrete composition whose viscosity is increased by adding welan gum, for example, a high performance water reducing agent or a high performance AE water reducing agent. Preferred are naphthalene sulfonate, melamine sulfonate, polycarboxylate and amino sulfonate.

The amount of such a high-performance water-reducing agent or high-performance AE water-reducing agent added to a concrete mixture has a proper range depending on its type, but in general, a unit cement amount (other than cement) is used. If fine powder is also present in the powder, the slump flow is adjusted to 50 to 70 cm by setting the range to 0.1 to 4.0% by weight based on the total unit powder amount). If it is less than 0.1% by weight, the effect of imparting fluidity is small and the fluidity intended in the present invention cannot be secured. On the other hand, the effect is saturated even if added in excess of 4.0% by weight, which is uneconomical.

[0019]

EXAMPLES The effects of the present invention will be shown by the following test examples. [In-water non-separation test] Basic composition of the following materials, namely cement 450 kg / m ³ fine aggregate 695 kg / m ³ coarse aggregate 950 kg / m ³ water cement ratio 45% to unit water content of welan gum powder 0.7% by weight, and 3.0% by weight of a high-performance water reducing agent per unit amount of cement were added and mixed, and a slump flow of 60 to 70 cm was obtained. The high-performance water reducing agent is Mighty 150 manufactured by Kao Co., Ltd., which is of the naphthalene sulfonate type.

For comparison, with respect to the above basic composition,
Without adding welan gum, an AE water reducing agent was added in an amount of 0.25% by weight based on the amount of cement, and a slump with a diameter of 18 cm was obtained. The AE water reducing agent used is Reozilt No. 8 under the trade name of Pozzolis, which is based on lignin sulfonate.

The underwater inseparability test of these concretes was conducted as follows. That is, concrete that has not solidified yet is placed in a cylindrical container with an inner diameter of 15 cm and a height of 30 cm, and an iron plate with a diameter of 10 cm and a thickness of 0.5 mm is placed on the upper surface of
Pour water from CC slowly into the container, and after 5 minutes and 60
After a minute, the supernatant water was collected in a cup and its pH was measured.

As a result, in the concrete of the comparative example without addition of welan gum, the pH of the supernatant after 5 minutes was 10.4, while that of the case with addition of welan gum was 7.1. In addition, after 60 minutes, the pH of the concrete without addition of welan gum was 10.6, whereas that of the case with addition of welan gum was 7.1.

In this test, the fact that the pH value of the supernatant did not rise means that the alkaline component in the concrete mix did not diffuse into the supernatant. That is, even if welan gum-added concrete is cast in water, the cement components remain trapped in the mix for a long time and the inseparability in water is extremely good.

[Continuous kneading test] The basic composition of the following materials, that is, cement 450 kg / m ³ fine aggregate 695 kg / m ³ coarse aggregate 950 kg / m ³ water cement ratio 45% to 45% water cement ratio Add 0.7% by weight to the unit amount of water and 3.0% by weight of the high-performance water reducing agent to the amount of the unit cement, and knead the mixture with a slump flow of 60 cm in an actual mixer. The high-performance water reducing agent used is Reovirt NL4000 under the trade name of Pozzolis, which is based on melamine sulfonate.

For comparison, with respect to the basic composition,
1.15% by weight of methylcellulose-based thickening agent per unit amount of water, 3.5% by weight of the same melamine sulfonate-based high-performance water reducing agent (trade name Reovirt NL4000 manufactured by Pozzolis Co., Ltd.) per unit of cement amount, Knead a slump flow of 60 cm with an actual mixer. The methylcellulose-based thickening agent used is a product name U manufactured by Mitsui Petrochemical Co., Ltd.
It is WB. This comparative example is a typical mix example of a conventional underwater non-separable concrete.

As an actual mixer, the kneading capacity is
Using a 3.0 m ³ forced twin-screw type plant mixer, 1
The kneading amount per batch is 2.5 m ³ . In the test, the effects on the quality of ordinary concrete were examined by alternately mixing the water-separable concrete of the present invention example containing welan gum and the comparative example containing methylcellulose, and ordinary concrete.

The ordinary concrete used in the test has a unit cement amount: 260 kg / m ³ , fine aggregate amount: 833 kg / m ³ , coarse aggregate amount: 1050 kg / m ³ , water cement ratio: 60%, and slump Value 8c
m ± 2.5 cm Target. The evaluation of the test is as follows: first mix the normal concrete in the first batch, discharge it from the mixer, then immediately mix the underwater non-separable concrete (second batch), and immediately discharge the underwater non-separable concrete. The concrete was kneaded (third batch), and the slump value of the ordinary concrete obtained in the third batch was used. The results are shown in Table 1.

[0028]

[Table 1]

As can be seen from the results in Table 1, in the case of the conventional underwater non-separable concrete of the comparative example, the slump value of the ordinary concrete which was subsequently mixed was lowered to 4.0 cm, whereas In the case of the example, the slump value is 7.5.
Since cm is maintained, it can be seen that the quality of ordinary concrete is hardly affected.

[0030]

As described above, according to the present invention,
It is possible to produce underwater non-separable concrete and ordinary concrete with the same mixer, which can greatly contribute to the construction of underwater non-separable concrete. In the test, an example of a twin-screw mixer was shown, but the same effect can be obtained with an agitator vehicle, so that the work can be rationalized in terms of transportation and dispatch.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Shigematsu 2-1-1, Tobita-yari, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Masayoshi Minami 1-29 Kitahamahigashi, Chuo-ku, Osaka-shi, Osaka Sansan Co., Ltd. (72) Inventor Masato Yoshizaki 1-29 Kitahamahigashi, Chuo-ku, Osaka-shi, Osaka Sanaki Co., Ltd.

Claims (3)

[Claims] 1. A concrete for underwater pouring containing an underwater non-separable admixture and a normal concrete containing no admixture for use in concrete construction using the same kneading machine or the same conveying means. A concrete construction method characterized by using welan gum as the water-separable admixture. 2. The underwater pouring concrete is cement,
A concrete material consisting of aggregate and water is blended with 0.01 to 2.0 wt% of welan gum per unit amount of water and 0.1 to 4.0 wt% of high performance water reducing agent or high performance AE water reducing agent per unit amount of cement, and slump flow is performed. The concrete construction method according to claim 1, wherein the concrete has a length of 40 to 70 cm. 3. Welan gum is a strain of Alcaligenes strains.
The concrete construction method according to claim 1 or 2, which is a dry powder composed of a polysaccharide of microbial origin produced by aerobically fermenting ATTC 31555 cells.