JPH0559857B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for manufacturing centrifugally formed concrete products in which concrete is poured into a formwork using a filling method and compacted by centrifugal force to produce centrifugally formed concrete products. It was devised to reduce the amount of sludge generated during compaction as much as possible. <Conventional technology and its problems> When manufacturing hollow concrete products such as concrete piles, the conventional embedding centrifugal forming method involves placing kneaded hard 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 mixing water is squeezed out to obtain a solid concrete product. Here, the built-in type means that the formwork is divided into two and the assembled steel wire is inserted into one formwork, and hard concrete is poured into the 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. In addition, 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, concrete with a slump of 2 to 6 cm is used in the built-in type. Therefore, although the amount of sludge discharged by centrifugal molding is smaller than that by pump-feeding, it still generates 45 to 60 kg/m ³ .
On the other hand, the slump is less than 2cm (especially zero slump)
If this is done, the amount of sludge discharged can be significantly reduced, but problems will arise 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 reducer, and the material separation of the concrete increases 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 process at manufacturing plants. In view of the above-mentioned circumstances, the present invention uses concrete with a slump of 2 cm to 6 cm to maintain good workability and high strength of the product, while almost eliminating the amount of sludge discharged, thereby reducing the time and effort of sludge treatment. The purpose of the present invention is to provide a method for producing centrifugally formed concrete products that significantly reduces costs. <Means for Solving the Problems> A method for producing a centrifugally formed concrete product according to the present invention that achieves the above-mentioned object has the following features:
In the method of manufacturing centrifugally formed concrete products by placing concrete with a weight of 400 to 500 Kg/m ³ and a slump of 2 to 6 cm into a formwork and compacting it using centrifugal force, a high-performance water reducing agent is added and aggregate Concrete containing 0.2 to 1.2% of finely divided silica and 0.5 to 1.5% of clay based on the unit amount of cement is used as part of the concrete, or an air entraining agent is added in addition to the above composition. It is characterized by the use of concrete. The concrete used in the present invention has a slump of 2 to 6 cm, which is currently used in manufacturing plants, but the cement content per unit is 400 to 500 Kg/m 3 and the high performance water reducer is used in units of 400 to 500 kg/m ³ , similar to concrete with high performance water reducer added. Addition of 0.8 to 1.5% to the amount of cement and 0.7 to 2.7% of finely divided silica and clay to the amount of cement as part of the aggregate, or the specified amount of high performance water reducer and finely divided silica. and clay, and further added an air entraining agent to make the air content 2.0 to 4.0%. The water-cement ratio is 27.0 if no air entrainment agent is added.
~38.0%, ~26.5 with air entraining agent added
It is 37.5%. The high performance water reducing agent may be any of the conventionally used ones such as naphthalene sulfonate formalin high condensate, highly condensed triazine compound, sulfonated melamine condensate, etc. Commercially available products include Mighty 150 ( Manufactured by Kao Corporation, product name),
NL-4000 (manufactured by Pozoris Bussan Co., Ltd., trade name) can be mentioned. The amount of the high performance water reducing agent added is preferably 0.8 to 1.5% based on the unit amount of cement. In the present invention, it is essential to use fine silica powder and clay in combination (hereinafter, this combination will be referred to as "inorganic fine powder" in this specification). Here, it is particularly preferable to use fine powder silica having a fineness of 15 to 30 m ² /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),
Examples include Micropoz (manufactured by NORCEM, trade name). In addition, pentonite and other clays can be used as the clay, but the degree of swelling is 17 to 22.
(ACC method), the fineness is 0.4 in terms of Blaine specific surface area.
It is particularly preferable to use m ² /g or more. In addition, the degree of swelling by the ACC method in the present invention was determined by the following method. That is, 2.0 g of the sample was added in approximately 10 portions to a 100 ml graduated cylinder with a stopper containing 100 ml of purified water, and then the cylinder was stoppered. 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
After leaving it for 24 hours, read the apparent volume (ml) of the sample deposited in the container, and use this value as the method used in the present invention.
The degree of swelling is determined by the ACC method. The amounts of these finely divided silica and clay added are 0.2 to 1.2% and 0.5 to 1.5%, respectively, to the unit amount of cement.
It is preferable that 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, if fine silica exceeds 1.2% of the unit cement amount or clay exceeds 1.5% of the unit cement amount,
The viscosity of concrete increases significantly. Also,
The slump drop of the mixed concrete becomes large, which is undesirable because it causes problems in the work and causes blockage of the hopper. The method of the present invention exhibits even more remarkable effects when finely divided silica and clay are used in combination as inorganic fine powders, and an air entraining agent is used to adjust the air content to 2.0 to 4.0%. The air entraining agent used here may be any of the conventionally used agents such as natural resin acids, higher alcohol sulfuric esters, polyoxyethylene alkyl allyl ethers, and polyoxyoctyl phenol ethers. Examples thereof include Sokagakusha Co., Ltd., trade name), Hiform (Onoda Co., Ltd., trade name), and Chupol C (Takemoto Yushi Co., Ltd., trade name). By using such an air entraining agent and changing the amount added, the air content of concrete can be reduced to 2.0.
~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. The cement used for concrete mixing is
Although any of various portland cements or mixed cements can be used, ordinary portland cement is usually used. To carry out the method of the present invention, the unit amount of cement is 400.
Concrete with ~500Kg/m ³ and a slump of 2-6cm, to which specific amounts of high-performance water reducing agent and inorganic fine powder have been added, is poured into a half-split formwork using a belt conveyor or screw conveyor, and then the other formwork is The formwork can be rotated to perform centrifugal force forming, or the cement amount per unit is 400 to 500 kg/m ³ ,
Concrete with a slump of 2 to 6 cm is added with a specific amount of high performance water reducing agent and inorganic fine powder, and the concrete is made to have an air content of 2.0 to 4.0% using an air entraining agent, and then centrifugally formed. It is preferable that the centrifugal force is a maximum of 30G, for example, an initial velocity of 1~
1-4 minutes on 5G, 1-6 minutes on medium speed 5-15G, high speed
It is best to use 15-30G for 1-4 minutes. When centrifugal force forming is carried out in this way, a 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 in the hollow part of the concrete molded body. It sticks evenly to the inner 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 active shaving cream-like sludge is deposited in the hollow of the concrete molding. It exhibits the effect of uniformly adhering to the inner circumferential surface of the concrete, and after curing, it exhibits a remarkable effect in strengthening the cream-like sludge adhering to the inner circumferential surface and strengthening the adhesion with concrete. The high-performance water reducing agent, inorganic fine powder, and air entraining agent used as additives in the present invention may be added to concrete separately as shown in the examples below, but the present invention is not limited to this. A mixture of two or more may 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. <Examples> Hereinafter, the present invention will be described in detail based on Examples. Examples 1 to 15 The cement used is ordinary Portland cement, the fine aggregate is sand from Ogasa, the coarse aggregate is crushed stone from Iwase (maximum size 20 mm), and the high-performance water reducing agent is Mighty.
150 (manufactured by Kao Corporation, trade name), silica hume (Japan Heavy Chemical Industry, trade name) with Blaine specific surface area of 20 m ² /g as fine powder silica, swelling degree (AC
C. method) is 20, and the fineness is Blaine specific surface area 0.5.
m ² /g of bentonite Hodakajirushi (manufactured by Kanto Bentonite Co., Ltd., trade name) and Vinsol (manufactured by Yamasou Kagaku Co., Ltd., trade name) as an air entraining agent, using Table 1 so that the slump of the concrete is 2 to 6 cm. They were mixed in the proportions shown in , and kneaded for 70 seconds using a forced stirring mixer. The slump and air content of the mixed concrete were measured. The results are shown in Table 1. Next, concrete was poured into the half-split formwork, and a cylindrical test centrifugal force forming form with an inner diameter of 20cm and a length of 30cm, which was integrated with the other formwork by bolting, was heated at an initial speed of 2G for 1 minute at a medium speed. Centrifugal compaction was performed at 15G for 4 minutes and at high speed 30G for 2 minutes, and the amount of sludge discharged at the end of compaction 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. Steam curing conditions are temperature rise 20
°C/h, maximum temperature 65 °C, holding time 3 hours, drop temperature 20 °C/h, and leave until room temperature. Autoclave curing: temperature rise 60℃/h, maximum temperature 180℃, holding time 4 hours, fall temperature 60℃/h, leave until room temperature. Table 1 shows the amount of sludge discharged and the compressive strength. Comparative Example 1 is an example in which only a high-performance water reducing agent is used in a formulation widely used in the production of concrete pile products, and Examples 1 to 15 are examples in which a high-performance water reducing agent and finely divided silica and clay are used as inorganic fine powders. This is an example in which a high-performance water reducing agent, an air-entraining agent, and finely powdered silica or clay are used as inorganic fine powder, and the air content of the concrete is set to 2.0 to 4.0%. Comparative Examples 2 to 8 are examples in which the concrete slump 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, Comparative Examples 9 to 15
This is an example in which the amounts of fine silica and clay added are within the scope of the present invention, but either the slump or air content is beyond the scope of the present invention.

【table】

[Table] 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 was 54 kg per 1 m ³ of concrete. However, Examples 1 to 15 of concrete using a high performance water reducing agent and inorganic fine powder, or concrete using a high performance water reducing agent, inorganic fine powder, and an air entraining agent with an air content of 2.0 to 4.0%. In this case, the amount of discharged sludge is 0 to 3 kg per 1 m ³ of concrete, which is 94 to 100% lower than the amount of discharged sludge in Comparative Example 1.
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, in Comparative Examples 2 to 8, in which the slump was 2 to 6 cm and the content of fine silica, clay, or air exceeded the range of the present invention, the amount of sludge discharged was 25 to 46 kg per 1 m ³ of concrete. 15 of the amount of Comparative Example 1
Only ~54% was reduced. In addition, in Comparative Examples 9 to 15, in which the amounts of finely divided 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 was 1 m ³ of concrete. 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 cement amount and the amount of high-performance water reducing agent added are the same, and the slump is 2 to 6 cm, fine silica or clay is used as the inorganic fine powder,
In Comparative Examples 4 and 6 to 8, in which fine powder silica was used in large amounts exceeding 1.2% and clay exceeded 1.5% relative to the cement weight, the compressive strength was lower than that of the Examples within the scope of the present invention. It has decreased significantly. This is because the unit water volume increases significantly. As mentioned above, the reason why Examples 1 to 15 have an extremely smaller amount of discharged sludge and a higher compressive strength than Comparative Examples 1 and 2 to 15 is because the high performance water reducing agent and inorganic fine powder were used, respectively. This is based on the synergistic effect of adding specific amounts of high-performance water reducer and inorganic fine powder, as well as adding an air entraining agent to bring the air content of concrete to 2.0 to 4.0%. It is. <Effects of the Invention> As described above in detail with the examples, the method for producing centrifugally formed concrete products according to the present invention does not require complicated steps,
By adopting the same charging format as the conventional centrifugal molding 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. Unit cement amount 400-500Kg/m ³ , slump 2
In the method of manufacturing centrifugally formed concrete products by placing ~6 cm of concrete into a formwork and compacting the concrete by centrifugal force, high-performance water reducer is added at 0.8 to 1.5% based on the unit amount of cement.
Centrifugally formed concrete characterized by using concrete to which 0.2 to 1.2% of finely powdered silica and 0.5 to 1.5% of clay are added to the unit amount of cement as part of the aggregate. How the product is manufactured. 2 The water-cement ratio of concrete is 27.0 to 38.0.
%. The method for producing a centrifugally formed concrete product according to claim 1. 3 Unit cement amount 400-500Kg/ ^m3 , slump 2
In the method of manufacturing centrifugally formed concrete products by placing ~6 cm of concrete into a formwork and compacting the concrete by centrifugal force, high-performance water reducer is added at 0.8 to 1.5% based on the unit amount of cement.
In addition, as part of the aggregate, 0.2 to 1.2% of finely divided silica and 0.5 to 1.5% of clay are added to the unit amount of cement, and
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 air entraining agent. 4 The water-cement ratio of concrete is 26.5 to 37.5.
%. The method for producing a centrifugally formed concrete product according to claim 3.