JPS63134543A - Manufacture of concrete hollow moldings - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing concrete hollow molded products using a centrifugal molding method, and more specifically, the present invention relates to a method for producing concrete hollow molded products using a centrifugal molding method. The present invention relates to a method for manufacturing concrete hollow molded products with substantially no decrease in strength.

[Conventional technology] Concrete hollow circular products such as concrete piles and concrete pipes are generally manufactured by pouring concrete into a formwork, then rotating the formwork and compacting the concrete using the centrifugal force. Manufactured by centrifugal molding. This method has the feature that excess water in the concrete pipe is efficiently discharged outside the molded product, making it possible to obtain a hollow concrete product with excellent strength and durability.

However, when centrifugal molding is carried out using the normal method, a suspension called slag containing a large amount of fine particles such as cement and aggregate is discharged, and if this slag is disposed of as is, it causes problems such as environmental pollution, resulting in large losses. It is necessary to carry out solid-liquid separation treatment of slag, which requires a large amount of equipment and costs a huge amount of money.

There is a strong demand for reducing the solid content in slag from the perspective of reducing costs and labor in slag treatment, and one way to do this is to add water-soluble polymers such as polyacrylamide in the centrifugation process ( JP-A-59-102854) has been proposed.

[Problems to be Solved by the Invention] However, although this method of adding a polyacrylamide polymer is effective in reducing the solid content in slag, it does not reduce the strength of the resulting concrete molded product, especially the compressive strength. There is a problem that the amount decreases.

In view of this situation, the present inventors have arrived at the present invention as a result of intensive study on a forming method that does not have the above-mentioned problems, and the purpose of the present invention is to reduce the strength of concrete molded products. An object of the present invention is to provide a method for producing a concrete molded product that significantly reduces the solid content in slag.

[Means for Solving the Problems] The gist of the present invention is that in centrifugal molding of concrete hollow molded products, water-soluble acrylic acid represented by the following general formula is A method for producing a concrete hollow molded article, which comprises adding a hydrazide polymer to concrete.

CON HN H2 However, in the formula, R represents a hydrogen atom or a methyl group, A represents one vinyl monomer unit copolymerizable with acrylic acid hydrazide, m% n each represents mol%, 4≦m≦1oo (2)
m+n”100 (3)
The relationship is as follows.

In the present invention, a water-soluble acrylic acid hydrazide polymer represented by general formula (1) is used.

This polymer may be a homopolymer of acrylic hydrazide, or it may be a copolymer of acrylic hydrazide and a copolymerizable vinyl monomer as long as it maintains water solubility.In the case of a copolymer, acrylic hydrazide The unit must be contained in an amount of 4 mol% or more. If the acrylic acid hydrazide unit is less than 4 mol%, the solid content in the slag will be reduced, but the compressive strength of the concrete molded product will be lowered, which is not preferable. (meth)acrylamide, (meth)acrylic acid, alkyl esters of (meth)acrylic acid such as methyl, ethyl, butyl, and 2-ethylhexyl, aminoalkyls such as dimethylaminoethyl (meth)acrylate and dimethylaminoethyl (meth)acrylate. (meth)acrylate or its tertiary or quaternary salt, aminoalkyl (meth)acrylamide or its tertiary or quaternary salt such as dimethylaminopropyl (meth)acrylamide, vinyl acetate, vinyl chloride,
Vinylidene chloride, styrene, acrylonitrile, maleic anhydride, etc. may be mentioned. One or more of these vinyl monomers can be used as a copolymerization component within a range where water solubility is maintained in the combination.

Among these vinyl monomers, (meth)acrylamide and (meth)acrylic acid are more preferably used.

This copolymer may be a random copolymer, a block or an alternating copolymer.

The acrylic acid hydrazide polymer used in the present invention can be obtained by various conventionally known methods, for example, acrylic acid hydrazide and vinyl monomer A.
A copolymer with can be obtained according to the method described in Japanese Patent Publication No. 60-45205 and Japanese Patent Application Laid-open No. 55-144004.

In the method of the present invention, only the acrylic acid hydrazide polymer may be added, but other water-soluble polymers may also be added together with it. However, in this case as well, the amount of one acrylic hydrazide monomer unit in the acrylic hydrazide polymer must be 4 mol% or more, and preferably the total amount of the acrylic hydrazide polymer and other water-soluble polymers is 4 mol% or more. The content of one unit of acrylic acid hydrazide monomer is adjusted to be 4 mol % or more. Water-soluble polymers other than this acrylic acid hydrazide polymer include polyacrylamide, partial hydrolyzate of polyacrylamide,
Examples include polyacrylic acid, copolymers of acrylamide and acrylic acid, and salts of these (co)polymers.

In the present invention, the acrylic acid hydrazide polymer may be added at any stage before the end of centrifugal molding, and the method of addition is not particularly limited. For example, after the polymer is dissolved as an aqueous solution in a mixer for preparing concrete components, the concrete components may be added, and during mixing of the concrete components in the mixer,
The polymer may be added as a powder or as an aqueous solution when pouring the mixed concrete into the formwork or during the centrifugal forming process of the concrete. In addition, when adding during the centrifugal molding process, it can be added at any time before the centrifugal molding process ends, such as during low speed rotation, medium speed rotation, high speed rotation, etc., to prevent slag. It may be added to the slag while it is forming.

In addition, when adding the polymer aqueous solution etc. at the time of mixing concrete components, it is preferable to adjust the amount of water added so as to maintain the water/cement ratio in this system at a predetermined value.

The appropriate amount of polymer to be added to the total amount of ordinary concrete constituents such as water, cement, and aggregate (hereinafter referred to as "concrete charge amount") depends on the composition of concrete and the amount of acrylic acid hydrazide monomer per unit in the polymer. Although it varies depending on the content etc., it is approximately 0.0001 to 0.2% by weight, preferably 0.001 to 0.1% by weight.

If the amount of polymer added is less than the above lower limit, it will be difficult to sufficiently reduce the solid content in the slag, and if it is more than the above upper limit, the flocs will be redispersed, making it impossible to sufficiently reduce the solid content in the slag. If the polymer is added as an aqueous solution, it is preferably used as an aqueous solution with a concentration of about 0.05 to 2% by weight, more preferably about 0.1 to 1% by weight.

The concrete components used in the present invention may contain additives such as reinforcing agents, extenders, hardening accelerators, hardening retarders, water reducing agents, and fluidizing agents, as required.

[Example] The present invention will be further explained below using Examples.

Examples 1 to 11 Ordinary Portland cement 11.4 kg, fine aggregate 19.
5kg, crushed stone 32kg, cement, dispersant Mighty 1
In the process of mixing 0.8 kg of 50 (registered trademark, manufactured by Kao ■) and water, the polymer having the composition shown in Table 1 was made into an aqueous solution of 0.51 i% by weight, and the second
Add at the rate listed in the table to make the total water content 5.7kgk:
Adjust and mix everything.

16 kg of the concrete mixed in this way was placed in a centrifugal molding test mold with an inner diameter of 200 mm and a length of 300 mm, and was heated at a low speed of 150 rpw for 2 minutes, followed by 4 minutes.
00 rpm medium speed rotation for 2 minutes, finally 1l100r
The concrete was compacted by rotating for 10 minutes at a high speed of 40 mm to form a hollow concrete pile with a wall thickness of 40 mm. After the rotation was stopped, the slag in the centrifugal mold was collected, and the amount of slag and the solid content in the slag were measured. The compressive strength of the obtained concrete pile was also measured. The solid content of this slag was determined from the evaporation by heating at 110° C. for 6 hours. Furthermore, the inner surfaces of the molded products obtained in these Examples were extremely smooth.

The test results are shown in Table 2.

Comparative Examples 1 to 4 Hollow concrete piles were formed in the same manner as in Example 1, except that the type and amount of polymer added were as shown in Table 2, and the results shown in Table 2 were obtained. In these examples, it was possible to reduce the solid content in the slag, but the compressive strength of the concrete was significantly reduced.Also, in these comparative examples, the amount of water used was adjusted to be the same. Nevertheless, the amount of slag produced was smaller than in the example, and it is presumed that this is because more water was incorporated into the concrete molding.

Although the inner surfaces of the molded products obtained in these comparative examples were smoother than in the case where no water-soluble polymer was added, the smoothness was inferior to that obtained in the above examples.

Comparative Example 5 A concrete pile was formed in the same manner as in Example 1 except that no water-soluble polymer was added.

The results are shown in Table 2.

Table 1 Examples 12-21 Ordinary Portland cement 11.4 kg, fine aggregate 19.
5kg, crushed stone 32kg, cement dispersant Mighty 15
0 (registered trade name, manufactured by Kao ■) 0.8 kg and water 5.7 kg
were mixed in a mixer, 8 kg of this was placed in the mold used in Example 1, and then 0.0 kg of the polymer shown in Table 3 was mixed.
．． Add 5% by weight aqueous solution to 16kg of concrete.
After adding in the proportions shown in the table, 8 kg of the mixed concrete was further charged. Subsequently, centrifugal molding was performed in the same manner as in Example 1, and the results shown in Table 3 were obtained. Furthermore, the inner surfaces of the molded products obtained in these Examples were extremely smooth.

Comparative Examples 6 to 9 Hollow concrete piles were formed in the same manner as in Example 12, except that the type and amount of the water-soluble polymer to be added were as shown in the specified sections of Table 3. The results are shown in Table 3 together with the results of Examples 12 to 21.
Although the inner surfaces of the molded products obtained in these comparative examples were smoother than in the case where no water-soluble polymer was added, the smoothness was inferior to that obtained in Example 1 above.

Table 3 [Effects of the Invention] As described above, the method of the present invention can significantly reduce the solid content in slag by adding a water-soluble polymer with a specific composition, and Since it does not exhibit the conventional problem of a decrease in the compressive strength of concrete due to addition of water-soluble polymers, it has the characteristic that it can provide molded products with the same strength as molded products obtained by normal methods that do not add water-soluble polymers. ing. Therefore, this provides an excellent industrial advantage in that the enormous amount of equipment and labor associated with slag treatment can be reduced without deteriorating the quality of the molded product. Furthermore, since the molded product obtained by this method has a very smooth hollow inner surface, conventional products may not be used in the method of burying piles, etc. while draining soil from the hollow part, which is used when driving piles, etc. This also has the effect of making soil removal easier.

Claims (1)

[Scope of Claims] 1) In centrifugal molding of concrete hollow moldings, a water-soluble acrylic acid hydrazide polymer represented by the following general formula is added to the concrete at any stage from the preparation of concrete for molding to the completion of centrifugal molding. A method for manufacturing a concrete hollow molded article, characterized by: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (1) However, in the formula, R represents a hydrogen atom or a methyl group, A represents a vinyl monomer unit copolymerizable with acrylic acid hydrazide, and m and n each represent mol%. It has the following relationship: 4≦m≦100(2) m+n=100(3).