JPH0228533B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing concrete columns using centrifugal force. To manufacture concrete columns such as concrete poles and piles, concrete is poured into a forming form with the cylindrical core on its side, and the forming form is rotated at high speed to compact it using centrifugal force. During high-speed rotation, excess water and fine particles in the concrete are separated from the concrete by the action of centrifugal force, pushed out to the inner surface of the product, and discharged as slurry. However, this slurry must be treated in accordance with the Water Pollution Control Act and waste treatment regulations, and it is also difficult to secure a place to dump the treated material. As a method for preventing the generation of such slurry, Japanese Patent Publication No. 57-60124 etc. discloses that slurry containing 85% by weight or more of soluble Sio ₂ with a Blaine value of 15,000~
By mixing 20 to 35% by weight of ultrafine particles as a water absorbing agent with a density of 25,000cm ² /g to a mixture of ordinary Portland cement and ultrafine particles, the centrifugal force is 35%.
By compacting at ~50G and high-speed rotation for 2 to 15 minutes, the ultrafine particles absorb excess water in the slurry that is being separated from the concrete, preventing the slurry from flowing out. What it does is known. However, it requires a considerable mixing ratio of 20 to 35% by weight of expensive ultrafine particles, which is economically disadvantageous, and it is not suitable as a strength member when forming concrete columns. Injecting a large amount of such ultrafine particles that cannot contribute is wasteful in terms of strength, and it is necessary to devise ways to use as small a quantity as possible.
In addition, this known technique has many restrictive conditions, such as the magnitude of centrifugal force, and is difficult to implement. Therefore, as a result of further research and repeated experiments on the method of using such water-absorbing agents, the applicant of the present application has found that ultrafine particles with a specific surface area of about 10 times or more compared to those described in the above-mentioned publication have a By using a small amount of 1, it was possible to suppress the generation of slurry, and it was possible to obtain a product with no slurry and a smooth inner surface of the concrete column with a good finish. This invention has the same technical idea as described in the above-mentioned publication, in which ultrafine particles containing soluble SiO ₂ are added to a concrete material consisting of ordinary Portland cement, a water reducing agent, fine aggregate, coarse aggregate, and water. The general concept of the present invention is a method of mixing and centrifugally compacting concrete columns, and ultrafine particles containing 90% by weight or more of the soluble SiO ₂ and having a fineness of 150,000 to 300,000 ^{cm 2} /g. To provide a method for manufacturing concrete columns using centrifugal force, which comprises mixing 2 to 5% by weight of a mixture of ordinary Portland cement and ultrafine particles, and compacting the mixture using centrifugal force. It is something to do. An embodiment of the method of the present invention will be described below. a Materials used: Γcement…Ordinary Portland cement manufactured by O Company
Specific gravity: 3.17 Γ Fine aggregate...Natural sand from Kinugawa Specific gravity: 2.59 Γ Coarse aggregate: Jade crushed stone from Kinugawa Specific gravity: 2.61 Γ Water reducing agent: Polyalkylaryl sulfonate based manufactured by K Company Γ Ultra-fine particles: Made by Company N, commonly known as silica flower or ferrosilicon duct (a) Chemical analysis value...Table 1 (b) Specific surface area...283200cm ² /g (measured by BET method) (c) Specific gravity...2.23 (d) PH...5.49 (dispersed with water) ) (e) Usage amount…0, 0.5, 1.0, 1.5, 2.5, 3.0,
4.0, 5.0% by weight (divided within the total with cement)

[Table] The formulation is as shown in Table 2, and in Examples 1 to 4, the total of cement + ultrafine particles was 470Kg/
^m3 ,

【table】

[Table] In Examples 5 to 9, the amount was 500 Kg/m ³ , and in Examples 10 to 16, it was 530 Kg/m ³ . b Method for manufacturing specimens Concrete with the above-mentioned composition was poured into a formwork for centrifugal force specimens (outer diameter 20 cm x inner diameter 10 cm x length 30 cm) as shown in Table 3.

[Table] Centrifugal compaction was performed under centrifugal compaction conditions. c Test results (a) Amount of slurry The weight of the slurry flowing out onto the inner surface of the specimen was measured. (b) Inner surface finish condition of specimen The following judgments were made by visual inspection. Γ...Smooth. Δ...Slightly small wave shape. ×...The height of the waveform is large and the number of waves is large. The test results are shown in Table 4, and the relationship between the mixing ratio of ultrafine particles and the amount of discharged slurry (weight ratio) is shown in the figure.

【table】

[Table] From these experimental results, the following was found. (1) The mixing ratio of ultrafine particles necessary to prevent slurry discharge is 2% or more, but the most preferable range is 2.0 to 5.0%.In other words, the above mixing ratio without slurry discharge is Example ³ when the unit cement amount is 470Kg/m3
When the unit cement amount was 500Kg/ ^m3 , it was 2.5% (Example 8), and when the unit cement amount was 530Kg/ ^m3 , it was 2.0% (Example 14). Contrary to the increase in quantity, the required mixing ratio of ultrafine particles is decreasing. (2) The finished state of the inner surface of the specimen was also generally good for the examples without slurry discharge. In other words, during centrifugal compaction work, due to the small gaps between the tires of the forming form and the grooves of the wheels that support them, left and right reciprocating vibrations occur in the longitudinal direction of the forming form. However, when slurry is generated, the inner surface of the specimen becomes wavy due to this left-right reciprocating vibration, and when compaction is completed, the inner surface finish is not smooth but has a wavy shape. It is. However, when no slurry is generated, the inner surface of the specimen remains smooth even when subjected to left and right reciprocating vibrations. (3) When the mixing ratio of ultrafine particles exceeds 5%, slurry generation is completely eliminated, but (a) the compressive strength of the specimen after autoclave curing decreases, and contrary to the increase in the mixing ratio, the compression The decrease in strength increases. (b) We want to minimize the amount of expensive ultrafine particles used. Therefore, in practical terms, the preferred mixing ratio is 2 to 5% as described above. As mentioned above, according to the method of this invention,
Since ultrafine particles with a powder degree of 150,000 to 300,000 cm ² /g are used as the water absorbing agent, the Blaine value of 15,000 to 15,000, which is used in the conventional method described above, is used.
Due to its extremely fine characteristics and large specific surface area, which is approximately 10 times larger than that of ultrafine particles of 25000cm ² /g,
The water absorption effect has been significantly increased, and as a result, the weight percentage required to inhibit slurry has increased significantly.
While the conventional method requires a large amount of 20 to 35%, this invention uses only 2 to 5%, which is about one-tenth of the amount required. The present invention has excellent effects in terms of reducing the manufacturing cost of the column and maintaining strength.

[Brief explanation of drawings]

The figure is a characteristic diagram showing the relationship between the mixing ratio of ultrafine particles and the amount of discharged slurry.

Claims (1)

[Claims] 1 Concrete material consisting of ordinary Portland cement, water reducing agent, fine aggregate, coarse aggregate and water,
In the method of manufacturing concrete columns by centrifugal compaction by mixing ultrafine particles containing soluble SiO ₂ , the ultrafine particles containing 90% by weight or more of soluble SiO ₂ and having a fineness of 150,000 to 3,000,000 cm ² /g are used. A method for manufacturing concrete columns using centrifugal force, characterized by mixing ultrafine particles in an amount of 2 to 5% by weight with respect to a mixture of ordinary Portland cement and ultrafine particles, and compacting the mixture using centrifugal force. .