JP2546385B2 - Centrifugal compaction slag reduction method for concrete - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for reducing slag by centrifugal compaction of concrete, and particularly in centrifugal molding of concrete, efficiently reduces the solid content in the slag during molding. The present invention relates to a centrifugal compaction method for reducing slag, which improves product quality as well as workability and productivity.

[Prior Art] A centrifugal compaction molding method in which a concrete-filled formwork is rotated at high speed and the concrete is compacted by centrifugal force is
Conventionally, it is mainly used for forming hollow cylindrical products such as piles, poles, and fume tubes. Centrifugal compaction reaches a maximum centrifugal force of 30 to 40 G, so most of the surplus water is drained and the unit volume weight of tubular concrete is 2500 kg / m ³
It is an excellent molding method that can produce a concrete product with high durability, high physical strength, and high watertightness.

By the way, fine particles in the cement and fine particles in the aggregate are simultaneously released into the surplus water released during the centrifugal compaction, and these are discharged as a slurry.
A slurry containing such effluent is commonly referred to as Noro. This slag is usually treated by solid-liquid separation by coagulation treatment, natural sedimentation, etc., and the solid content is discarded. However, since the cost of such a slag treatment is great, it has been eagerly desired to reduce the volume of the slag produced in the past.

Conventionally, as a method for reducing slag in a centrifugal compaction molding method, a method of adding a water-soluble polymer to a molding material (Japanese Patent Application Laid-Open No. S60-12065)
56-161108, JP-B-62-18507, and JP-A-59-11211).

[Problems to be Solved by the Invention] In the conventional method for reducing slag, many of them use an aggregating agent or the like as an active ingredient, and there is a drawback that workability and inner surface finish of the product are poor.

Incidentally, among the conventional methods, JP-A-59-11211 describes that sodium polyacrylate and polyacrylamide have no effect, and JP-B-62-18507 discloses a molecular weight without using a water reducing agent. The use of 8,000 to 70,000 acrylamide / sodium acrylate copolymer is said to be effective.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and provide a method for reducing the centrifugal compaction slag of concrete which can improve the inner surface finishability, workability and productivity of the product.

[Means for Solving the Problems] The method of reducing the centrifugal force of concrete according to the present invention reduces
A method of adding a water-soluble polymer and a water-reducing agent to concrete and performing centrifugal molding, wherein the water-soluble polymer has a molecular weight of 500,000 to 1,000,000 and a hydrolysis rate of 5 to 50 mol%. Or a partially hydrolyzed polymethacrylamide, or 50 to 95 mol% of acrylamide or methacrylamide having a molecular weight of 500,000 to 1,000,000 and acrylic acid or methacrylic acid 5
It is characterized in that a salt of a copolymer with about 50 mol% is used.

That is, the inventors of the present invention have earnestly studied to reduce the solid content of the noro solid matter during the centrifugal compaction molding and improve the inner surface finish of the product molding pipe, and as a result, the fine components of concrete do not separate on the surface. It was found that the molding material should be appropriately thickened to such an extent that workability is not affected. Therefore, by using a water-soluble polymer for thickening, a water-reducing agent is used in combination to increase fluidity and improve workability, thereby achieving the object of the present invention. When using together agents,
The inventors have found that a polymer having a larger molecular weight than the polymer disclosed in -18507 is effective in reducing slag, and completed the present invention.

 Hereinafter, the present invention will be described in detail.

The water-soluble polymer used in the present invention is a polyacrylamide or polymethacrylamide partially hydrolyzed product having the following or, namely, a molecular weight of 500,000 to 1,000,000 and a hydrolysis rate of 5 to 50 mol%.

A salt of a copolymer of 50 to 95 mol% of acrylamide or methacrylamide and 5 to 50 mol% of acrylic acid or methacrylic acid having a molecular weight of 500,000 to 1,000,000.

Is.

When the molecular weight of such a water-soluble polymer is less than 500,000, there is almost no thickening effect, and there is no effect of reducing the solid content of slag. On the other hand, when the molecular weight exceeds 1,000,000, the aggregating action becomes remarkable, which adversely affects the workability of concrete and reduces the formability and productivity.

When the hydrolysis rate of the above partial hydrolyzate is less than 5 mol%, the thickening action is low, and when it exceeds 50 mol%, the reaction with Ca ²⁺ ions in the concrete causes a decrease in the thickening action. Such a partial hydrolyzate can be easily produced by subjecting polyacrylamide or polymethacrylamide to alkaline hydrolysis according to a conventional method.

On the other hand, the salt of the copolymer can be easily produced by copolymerizing a predetermined amount of acrylamide or methacrylamide with acrylic acid or methacrylic acid in the presence of a radical initiator according to a conventional method.

Such a water-soluble polymer is preferably added in an amount of 0.005 to 1% by weight, particularly 0.01 to 0.5% by weight, based on cement.

On the other hand, as the water reducing agent, a generally used one can be applied, for example, a condensate of (alkyl) naphthalene sulfonic acid and formalin, or a condensate of methylolated melamine sulfonic acid and formalin, or A high-performance water reducing agent containing these salts as a main component can be used.

Such a water reducing agent is preferably added so that the weight ratio of the water-soluble polymer to the water reducing agent is in the range of 1:10 to 30. If the ratio of the water-soluble polymer to the water-reducing agent exceeds the above range, the workability is lowered,
On the other hand, if the amount is too small, the thickening effect decreases, and the solid content in the roe cannot be sufficiently reduced.

In the present invention, the type of cement in the concrete mix is not particularly limited, Portland cement,
In addition, early-strength cement, blast furnace cement, fly ash cement and the like can be used, and there is no particular limitation on the water cement ratio and the like. It goes without saying that a swelling agent or the like may be added to the concrete composition components, if necessary.

[Action] By using a water-reducing agent and a specific water-soluble high-molecular polymer in combination, it is possible to reduce slag, workability, productivity, and
The improvement of the inner surface finish of the product forming pipe is achieved.

That is, by dispersing cement with a water-reducing agent and increasing the viscosity with a water-soluble polymer to retain fine-grained components in concrete, surplus water with a low solid content of noro is released under centrifugal force.

In addition, excess water is reduced, and the finish of the inner surface of the product forming pipe is improved.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

Examples 1 to 5 and Comparative Examples 1 to 5 Water-soluble high-molecular weight polymers shown in Table 2 and high-performance water-reducing agents were dissolved in water in predetermined amounts, and concrete having a composition shown in Table 1 was kneaded with a forced kneading mixer. After mixing, 15 kg of a centrifuge sample having an inner diameter of 20 cm and a height of 30 cm was filled. After completion of the charging, the mixture was compacted under centrifugal molding conditions of low speed (5G) for 2 minutes, medium speed (12G) for 30 seconds, and high speed (30G) for 6 minutes. After the completion of compaction, the amount of slag produced and the amount of solids in the slag were measured, and the inner surface finish of the specimen was visually determined. Then, pre-positioning time 3 hours, heating rate 20 ℃
/ Hr, maximum temperature of 65 ° C., steam curing was performed for 4 hours, and the compressive strength after demolding was measured. The results are shown in Table 2.

From Table 1, according to the method of the present invention, the slump value is good and the workability is excellent, the amount of slag and the solid content in the slag are both reduced, and the inner surface finish of the product forming pipe is also improved. Moreover, it is clear that the strength of the resulting product is also significantly higher.

[Effects of the Invention] As described in detail above, according to the method for reducing slag by concentrating centrifugal force on concrete according to the present invention, the amount of slag produced is reduced and the amount of solid content in the slag is also reduced.

 As a result, the slag processing cost is significantly reduced.

The inner surface finish of the product forming tube is improved, and a good product free from floating, sagging, cracks, etc. can be obtained.

 Various properties such as product strength are also improved.

 Workability is extremely good and productivity is high.

It is possible to manufacture high quality products at low cost and high production efficiency.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Arimitsu 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd. (56) Reference JP-A-56-161108 (JP, A) Kosho 48-30330 (JP, B1)

Claims (1)

(57) [Claims] 1. A method of adding a water-soluble polymer and a water-reducing agent to concrete and performing centrifugal molding, wherein the water-soluble polymer has a molecular weight of 500,000 to 1,000,000 and a hydrolysis rate of 5 to 50. Mol% polyacrylamide or polymethacrylamide partial hydrolyzate, or 50 to 95 mol% acrylamide or methacrylamide having a molecular weight of 500,000 to 1,000,000 and acrylic acid or methacrylic acid 5 to 5
A method for reducing the centrifugal compaction slag by using a salt of a copolymer with 50 mol%.