JPH0244053A - Production of centrifugally formed concrete product - Google Patents

Abstract

PURPOSE:To reduce the amt. of sludge to be discharged while keeping excellent workability and strength by adding specified amts. of a high-performance water reducing agent and inorg. fine powder to concrete in the formation of concrete wherein the slump and unit cement amt. are controlled. CONSTITUTION:The concrete contg. 400-500kg/m<3> unit cement amt. and having 2-6cm slump is filled into a formwork, and centrifugally formed. In this case, 0.1-1.5% high-performance water reducing agent is added to the unit cement amt., and 0.7-2.7% inorg. fine powder is added to the unit cement to obtain concrete. An air-entraining agent is further added to keep the air content at 2.0-4.0%. Finely powdered silica and clay are jointly used as the inorg. powder, and their contents are preferably controlled respectively to 0.2-1.2% and 0.5-1.5%.

Description

[Detailed Description of the Invention] <Industrial Application> The present invention is a centrifugally formed concrete product in which concrete is poured into a formwork using a filling method and compacted by centrifugal force to produce a centrifugally formed concrete product. This manufacturing method is designed to reduce as much as possible the amount of sludge generated during compaction by centrifugal force.

<Conventional technology and its problems> When manufacturing hollow concrete products such as concrete piles, the embedding centrifugal force forming method, which has been conventionally used, involves placing hard mixed concrete into a half-split formwork. The concrete is introduced using a belt conveyor or screw conveyor, the formwork is rotated at high speed, the concrete is compacted by centrifugal force, and a part of the mixed water is squeezed out to obtain a solid concrete product.

Here, the built-in type means that the formwork is divided into two, the assembled steel wire is inserted into one formwork, and hard mixed concrete is poured into this formwork from a hopper using a belt conveyor, screw conveyor, etc. This is a method of centrifugally molding the mold by integrating it with the other mold.

Furthermore, unlike the pump-feeding type, in the built-in type, the unit water volume is significantly reduced in order to prevent the concrete poured into the formwork from flowing out and to reduce the amount of discharged sludge as much as possible. As a result, the built-in type is slump 2
~6cm of concrete is used.

Therefore, although the amount of sludge discharged by centrifugal molding is smaller than that by pump-feeding, it is still 45 to 60 k
g/m is generated. On the other hand, the slump was not WR by 2cm.
(Especially zero slump) can greatly reduce the amount of discharged sludge, but this poses a problem in terms of workability. Therefore, conventionally, the slump has been controlled at 2 to 6 cm from the viewpoint of workability.

By the way, in recent years, it has become possible to manufacture high-strength centrifugally formed concrete products by centrifugally forming concrete with a significantly reduced water-cement ratio using a high-performance water reducing agent, and now most manufacturing plants Concrete containing a high-performance water reducer is formed using centrifugal force.

However, in such cases, although a high-strength product can be obtained, on the other hand, the thixotropic properties of the concrete increase due to the addition of a high performance water reducing agent, and the material separation of the concrete becomes large due to centrifugal force and vibration, resulting in a large amount of sludge generation. There was a drawback.

Since the sludge generated in this way is strongly alkaline, it requires a lot of cost and effort to dispose of it at manufacturing plants.

In view of the above-mentioned circumstances, the present invention has a slump of 2 (2).
To provide a method for producing centrifugally formed concrete products using concrete with a thickness of 6 cm from 100 to 100 cm, which substantially eliminates sludge discharge while maintaining good workability and high product strength, and significantly reduces the labor and cost of sludge treatment. The purpose is to provide.

Means for Solving the Problems〉 The method for producing a centrifugally formed concrete product according to the present invention that achieves the above-mentioned object has a unit cement amount of 400 to 500
kg/rn', concrete with a slump of 2 to 6 cIT+ is poured into a formwork and compacted by centrifugal force to produce centrifugally formed concrete products. It is particularly important to use concrete to which inorganic fine powder has been added, or to use concrete to which high performance water reducing agent and inorganic fine powder as part of the aggregate have been added together with an air entraining agent.

The concrete used in the present invention has a slump of 2 to 6 yen, which is currently used in manufacturing plants, but the unit cement amount is 400 to 5 slump, similar to concrete with high performance water reducing agent added.
00 kg/m, a high performance water reducing agent is added in an amount of 0.8 to 1.5% per unit amount of cement, and inorganic fine powder is added as part of the aggregate at a rate of 0.7 to 2.7% per unit amount of cement. %, or the above specific amounts of a high performance water reducing agent and inorganic fine powder are added, and an air entraining agent is further added to make the air content 2.0 to 4.0%. The water-cement ratio is 27.0 when no air entrainment agent is added.
~38.0%, 26.5~ when air entraining agent is added
It is 37.5%.

High performance water reducing agents are the same as those traditionally used.
Any of naphthalene sulfonate formalin high condensates, high condensed triazine compounds, sulfonated melamine condensates, etc. may be used, and commercially available products include Mighty 150.
(manufactured by Kao Corporation, trade name) and NL-4000 (manufactured by Hozoris Bussan Co., Ltd., trade name). The amount of the high performance water reducing agent added is preferably 0.8 to 1.5% based on the unit amount of cement.

The amount of inorganic fine powder added is 0.7 to 0.7 to the unit amount of cement.
It is preferable to set it to 2.7%.

As this inorganic fine powder, it is particularly preferable to use finely divided silica and clay in combination. Here, it is particularly preferable to use fine powder silica having a particle size of 15 to 30 m'/g in terms of Blaine specific surface area. This is usually called silica hume, and commercially available products include, for example, silica hume (manufactured by Japan Heavy Chemical Industry Co., Ltd., trade name), Micropoz (NORCE
Manufactured by M Company, product name), etc. In addition, bentonite and others can be used as the clay, but III! It is particularly preferable to use a powder having a moisture content of 17 to 22 (A, C, C, method) and a particle size of 0.4 m''76 or more in terms of Blaine specific surface area.

In addition, the degree of swelling according to the A, C, C method in the present invention was determined by the following method. That is, 2.0 g of sample was mixed with 10 g of purified water.
Add 0 ml to a 100 mj graduated cylinder with a stopper in approximately 10 portions, and then stopper it. However, the amount added at each time should be adjusted so that the sample added earlier does not stick to the inner wall and is deposited smoothly on the bottom of the cylinder, and the next sample is added only after most of the sample added earlier has settled. . After adding the sample, leave it for 24 hours, read the apparent volume (mj) of the sample deposited in the container, and calculate this value as l! according to the A, C, C, method of the present invention. ! Moisture.

The amounts of these finely divided silica and clay added are preferably 0.2 to 1.2% and 0.5 to 1.5%, respectively, based on the unit amount of cement.

As can be seen from the Examples described below, the effect of the present invention is not significant when the amount of fine silica is less than 0.2% based on the amount of cement per unit, or when the amount of clay is less than 0.5% based on the amount of cement. On the other hand, fine powder silica is 1% per unit amount of cement.
．． If the clay content exceeds 2%, or if the clay content exceeds 1.5% based on the unit amount of cement, the viscosity of the concrete will increase significantly. In addition, the slump drop of the mixed concrete becomes large, which is undesirable because it causes blockage of the nine hoppers, which causes problems in the work.

The method of the present invention uses finely divided silica and clay as inorganic fine powders and an air entraining agent to reduce the air content to 2.0 to 4.
．． When it is set to 0%, an even more remarkable effect is exhibited.

The air entraining agent used here may be any of those conventionally used such as natural resin acids, higher alcohol sulfuric esters, polyoxyethylene alkyl allyl ethers, and polyoxyoctylphenol ethers. Examples include Hyform (manufactured by Koshoda Co., Ltd., trade name), Chewpol C (manufactured by Takemoto Yushi Co., Ltd., trade name).

By using such an air entraining agent and changing the amount added, the air content of concrete is adjusted to 2.0 to 4.0%. If the air content of the concrete exceeds 4%, air will remain in the specimen after centrifugal forming, resulting in a weakened compressive strength.

Incidentally, as the cement used for the concrete mixed line, any of various types of Portland cement and 8 types of mixed cement can be used, but ordinary Portland cement is usually used.

To carry out the method of the present invention, the unit amount of cement is 400 to 50.
0 kg/m and a slump of 2 to 6 cm, concrete to which specific amounts of a high performance water reducing agent and inorganic fine powder have been added is poured into a formwork that has been roasted in half using a belt conveyor or screw conveyor, and then mixed with the other formwork. Integrate and rotate this formwork to perform centrifugal force forming, or unit cement amount 400-500 kg/m", slump 2-6c
m of concrete by adding a specific amount of high performance water reducing agent and inorganic fine powder, and reducing the air content to 2 by using an air entraining agent.
．． Concrete with a concentration of 0 to 4.0% is poured and centrifugally formed. The centrifugal force is preferably 30G at maximum, for example, 1 to 4 minutes at an initial speed of 1 to 5G, 1 to 6 minutes at a medium speed of 5 to 15G, and 1 to 4 minutes at a high speed of 15 to 30G.

When centrifugal force forming is performed in this way, shaving cream-like sludge, which is a combination of the inorganic fine powder in the concrete squeezed out by centrifugal force and a part of the sludge, is formed around the inner periphery of the hollow part of the concrete molded body. It sticks evenly to the surface. As a result, almost no sludge is discharged after centrifugal force forming. Here, inorganic fine powder, especially fine silica and clay, have a strong adsorption effect on the fine particles and water squeezed out by centrifugal force, and the extremely viscous shaving cream-like sludge is transferred to the hollow part of the concrete molding. It exhibits the effect of uniformly adhering to the inner circumferential surface, and after curing, it exhibits a remarkable effect in strengthening the creamy sludge adhering to the inner circumferential surface and strengthening its adhesion to concrete.

High performance water reducing agent used as an additive in the present invention, no 8
1. The mold powder and the air entrainment agent may be added to concrete separately as shown in the examples below, but the invention is not limited to this, and a mixture of two or more of these additives may also be used. .

It should be noted that curing of the centrifugally formed concrete of the present invention is not particularly limited as long as normal curing may be employed, and underwater curing, steam curing, autoclave curing, etc. may be employed.

Practical example Hereinafter, the present invention will be explained in detail based on examples.

Examples 1 to 15 The cement used was ordinary Portland cement, the fine aggregate was sand from Ogasa, and the coarse aggregate was crushed stone from Iwase (maximum size 20 m).
), Mighty 150 (manufactured by Kao Corporation,
Product name), Blaine specific surface area as fine silica: 201
T1''/g silica hume (Japan Heavy Chemical Industry, trade name), clay with swelling degree (A, C, C, method) of 20,
Bentonite Hotaka seal (manufactured by Kanto Bentonite Co., Ltd., trade name) with a fineness of Blaine specific surface MI 0.5 m”/g,
Vinsol (manufactured by Nuke Kagaku Co., Ltd., trade name) as an air entraining agent
were mixed in the proportions shown in Table 1 so that the slump of the concrete would be 2 to 6c+n, and kneaded for 70 seconds using a forced stirring mixer. The slump and air-containing MA of the concrete obtained by kneading were measured. The results are shown in Table 1.

Next, concrete was filled and poured into the half-cut formwork, and the inner diameter of the formwork was 20cm, which was integrated with the other formwork by tightening bolts.
A cylindrical test centrifugal molding form with a length of 30 cm is centrifugally compacted at an initial speed of 2G for 1 minute, at a medium speed of 15G for 4 minutes, and at a high speed of 30G for 2 minutes, and is discharged at the end of compaction. The amount of sludge was measured. Thereafter, the product was left in a room for 3 hours, and then steam-cured, demolded, and autoclaved in order, and the compressive strength of the product was measured. The steam curing conditions were a temperature increase of 20°C/h, a maximum temperature of 65°C, a holding time of 3 hours, a temperature drop of 20°C/h, and the product was left until it reached room temperature. Autoclave curing is performed at a temperature increase of 60°C/h.

Maximum temperature 180℃, holding time 4 hours, drop temperature 60℃/
h. Leave it until it reaches room temperature. Table 1 shows the amount of discharged sludge and compressive strength.

Comparative Example 1 is an example in which only a high performance water reducing agent was used in a formulation widely used in the production of concrete pile products;
Examples 1 to 15 are examples using a high performance water reducing agent and fine inorganic powder such as fine silica or clay, or using a high performance water reducing agent and an empty 9
ic2! ! Finely divided silica and clay are used as the additive and inorganic fine powder to reduce the air content of concrete to 2.0 to 4.0%.
This is an example. Comparative Examples 2 to 8 are examples in which the slump of concrete is in the range of 2 to 6 cm, but the content of fine silica, clay, or air exceeds the range of the present invention. The amount added is within the scope of the present invention, but the slump or air content is an example where either the content is beyond the scope of the present invention.

/ / As shown in Table 1, in the formulation used for manufacturing centrifugally formed concrete products such as piles in Comparative Example 1, the amount of sludge discharged after centrifugally forming is 1 m of concrete.
However, concrete using a high performance water reducing agent and fine inorganic powder, or concrete using a high performance water reducing agent, fine inorganic powder, and an air entrainment agent, has an air content of 2.0 to 4.
．． In Examples 1 to 15 where the concrete was 0%, the amount of discharged sludge was 0 to 3 kg per 1rr1' of concrete.
The amount of discharged sludge in Comparative Example 1 was reduced by 94 to 100%. Note that the compressive strengths of Examples 1 to 12 are approximately the same as or greater than Comparative Example 1.

On the other hand, Comparative Examples 2 to 3 have a slump of 2 to 6 cm, and any of fine silica, clay, and air content exceeds the range of the present invention.
The amount of discharged sludge in Example 8 was 25 to 46 kg per 1rr1'' of concrete, which was only 15 to 54% of the amount in Comparative Example 1.

Furthermore, in Comparative Examples 9 to 15, in which the amounts of fine silica and clay added were within the range of the present invention, and either slump or air content exceeded the range of the present invention, the amount of discharged sludge per concrete was On the other hand, it was 18 to 40 kg, which was only 26 to 67% of the amount in Comparative Example 1.

Even if the unit amount of cement and high-performance water reducing agent are the same and the inorganic fine powder is within the range of the present invention, if the slump exceeds 6 cm, the unit amount of water increases significantly and a large amount of sludge is discharged. Moreover, if the air content exceeds 4%, air will remain in the aggregate portion even after centrifugal force forming, and the compressive strength will drop significantly.

When the unit amount of cement and the amount of high-performance water reducing agent added are the same, and the slump is 2 to 6 cm, fine silica and clay are used as the inorganic fine powder, and the amount of fine silica is 1.2% with respect to the unit amount of cement. Clay is 1.0% by weight of cement.
In Comparative Examples 4 and 6 to 8, in which a large amount exceeding 5% was used, the compressive strength was significantly decreased compared to each of the Examples within the scope of the present invention. This is because the unit water volume increases significantly.

As mentioned above, Examples 1 to 15 are Comparative Example 1 and Comparative Example 2.
The reason why the amount of discharged sludge is extremely small and the compressive strength of the product is higher than that of No. 15 is due to the addition of specific amounts of a high performance water reducing agent and inorganic fine powder. By adding a specific amount of each and adding an air entraining agent, the air content of concrete can be increased from 2.0 to 2.0.
This is based on the synergistic effect of setting the amount to 4.0%.

<Effects of the Invention> As specifically explained above along with the examples, the method for producing centrifugally formed concrete products according to the present invention does not require complicated steps and can be performed in the same way as the conventional centrifugal forming method. By adopting a feed-in method, it is possible to significantly reduce the amount of discharged sludge while maintaining high production efficiency. Moreover, the strength of the manufactured product is equivalent to that of conventional products. As a result, the effort and cost for treating discharged sludge can be significantly reduced, and the effect is tremendous.

Claims (1)

[Claims] 1) A method of producing a centrifugally formed concrete product by filling concrete with a unit cement amount of 400 to 500 kg/m^3 and a slump of 2 to 6 cm into a formwork, and compacting the concrete by centrifugal force. , high-performance water reducing agent is added at 0.8 to 1.5% based on the unit cement amount, and inorganic fine powder is added at 0.7 to 2.7% based on the unit cement amount as part of the aggregate. A method for manufacturing a centrifugally formed concrete product, characterized by using concrete that has been formed by centrifugal force. 2) In the method of producing centrifugally formed concrete products by placing concrete with a unit cement amount of 400 to 500 kg/m^3 and a slump of 2 to 6 cm into a formwork and compacting it by centrifugal force, a high-performance water reducing agent is used. is added in an amount of 0.8 to 1.5% based on the amount of cement per unit, and fine inorganic powder is added as part of the aggregate in an amount of 0.7 to 2.7% based on the amount of cement. A method for producing a centrifugally formed concrete product, characterized by using concrete with an air content of 2.0 to 4.0% by adding an agent. 3) The water-cement ratio of concrete is 27.0 to 38.
2. The method for producing a centrifugally formed concrete product according to claim 1, wherein the centrifugal force forming concrete product is 0%. 4) The water-cement ratio of concrete is 26.5 to 37.
The method for producing a centrifugally formed concrete product according to claim 2, wherein the content is 5%. 5) Use of concrete in which 0.2 to 1.2% of finely divided silica and 0.5 to 1.5% of clay are added to each unit of cement as the inorganic fine powder, The method for producing a centrifugally formed concrete product according to 2, 3 or 4.