JPH0567583B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a novel hume tube concrete composition and a method for producing a centrifugal concrete hume tube using the same. Prior art and its problems When manufacturing centrifugal concrete molded bodies (huum tubes, poles, piles, etc.), excellent formability, that is, shortened manufacturing time, and good internal compaction properties are required. Due to material separation due to centrifugal force during manufacturing, the cross section of a centrifugal concrete molded body can generally be divided into a concrete layer, a mortar layer, and a paste layer from the outside to the inside, and each layer of a good product can be divided into a concrete layer, a mortar layer, and a paste layer. are strongly integrated with each other. However, if the material is compacted due to insufficient dehydration during manufacturing, water remains near the interface between the mortar layer and the paste layer. This residual water migrates to the bottom of the hollow article after molding and pushes up the paste layer, thereby creating a so-called "float". In addition, inner surface peeling of hollow products also occurs when centrifugal concrete molded bodies that have not been sufficiently dehydrated are subjected to steam curing. In centrifugal concrete molded bodies, especially hume pipes, in which the formability of the inner surface is important, the occurrence of floating and inner surface peeling is a fatal defect, and a great deal of effort is put into repairing it. Conventionally, the following measures have been taken to prevent the occurrence of lifting, inner surface peeling, etc., but satisfactorily results have not been obtained. (1) In order to reduce the unit water content of concrete, the slump should be made as small as possible,
The use of high performance water reducing agents has been practiced. However, there is a limit to the reduction in unit water volume. Therefore, unless a vibrating centrifugal molding machine that can mold even in a no-slump state is used, it is difficult to say that this is an effective countermeasure. (2) During centrifugal forming, the number of compaction layers is increased, that is, the tube thickness is divided into several layers. Although this method is effective in preventing the occurrence of floating, it is not practical because it significantly lengthens the production time of the molded body. Means for Solving the Problems As a result of extensive research in view of the current state of technology as described above, the present inventor has discovered that when polyethylene glycol of a specific molecular weight is added to ready-mixed concrete as a hume pipe material, It was discovered that during centrifugal molding, water movement is significantly smoother and dehydration is promoted, thereby preventing floating, inner surface peeling, etc., and significantly shortening centrifugal molding time. That is, the present invention provides the following compositions and methods. Polyethylene glycol with a molecular weight of 400 to 3800 0.005 to 100 parts by weight of Portland cement
A concrete composition for humid pipes containing 5 parts by weight. Polyethylene glycol with a molecular weight of 400 to 3800 0.005 to 100 parts by weight of Portland cement
A method for producing a centrifugal concrete hume pipe, comprising centrifugally forming a concrete composition containing 5 parts by weight. The Portland cement used in the present invention is not particularly limited, and may be any of ordinary, early-strength and ultra-early-strength Portland cements. The polyethylene glycol used in the present invention has a molecular weight of 400 or more and about 3,800. When the molecular weight exceeds 3800, polyethylene glycol acts as a setting retarder, increasing the amount of air mixed into the molded product, and reducing the compressive strength due to the voids formed. The amount of polyethylene glycol used is approximately 0.005 to 5.0 parts by weight per 100 parts by weight of cement. The amount of polyethylene glycol
If the amount is less than 0.005 parts by weight, the effect of the blending will hardly be exhibited, whereas if it exceeds 5.0 parts by weight, the viscosity during preparation of the concrete composition will increase and workability will decrease. Considering economic efficiency, it is more preferable that the amount of polyethylene glycol used is about 0.03 to 0.3 parts by weight per 100 parts by weight of cement. Generally, when polyethylene glycol is added to concrete compositions, the air content increases,
Fine pores may be formed on the outer surface of the centrifugal molded body, resulting in a poor finished surface or a decrease in the strength of the molded body. To prevent this, antifoaming agents can be added, if necessary. The antifoaming agent is not particularly limited, and silicone-based antifoaming agents (for example, the antifoaming agent manufactured by San Nopco Co., Ltd. under the trade name "SN-Defoamer") are not particularly limited.
14HP", trade name "SN-Defoamer 305", trade name "Nopco 8034L", etc.) Nonionic surfactant type: Known ones such as higher alcohol type such as octyl alcohol and siloxhexanol. It can be used.The amount of antifoaming agent added is usually about 0.005 to 0.5% of the weight of cement.The amount of antifoaming agent added to cement is
If it is less than 0.005%, the effect will not be sufficiently exhibited, and 0.5%
If it exceeds %, there is little improvement in the effect, and on the contrary, the physical properties of the centrifugal molded product may deteriorate. In addition, in the present invention, according to a conventional method,
Known additives may also be blended. Examples of such additives include cement admixtures (slag powder, fly ash, silica fume, limestone powder, silica powder, etc.), expansive agents for concrete (for example, "Denka CSA", Denki Kagaku Kogyo Co., Ltd.; ”, Onoda Cement Co., Ltd.), high-strength admixtures for steam curing (for example, ``Nonclave'', Osaka Cement Co., Ltd., ``Asano Super Mix'', Nippon Cement Co., Ltd.; ``Denka Σ1000”, sold by Denki Kagaku Kogyo Co., Ltd., etc.), colorants,
Examples include polymers for cement (SBR, EVA, PVA, etc.). Furthermore, admixtures such as AE agents, water reducing agents, high-performance water reducing agents, shrinkage control agents, condensation/hardening time control agents, rust preventive agents, waterproofing agents, etc. should be used within the range that does not cause floating of the hume tube or internal peeling. You can also. In the present invention, a raw material mixture consisting of Portland cement, polyethylene glycol, fine aggregate, coarse aggregate and, if necessary, other additives is kneaded in the presence of water. The viscosity of fine aggregate and coarse aggregate, the amount used, the kneading method, etc. are no different from known methods. The concrete thus obtained is centrifugally formed and steam cured in a conventional manner to form a humid pipe product. Effects of the Invention According to the present invention, dehydration during centrifugal molding is significantly promoted, so molding time is significantly shortened.
Furthermore, since the obtained hume tube is prevented from floating and from peeling off its inner surface, repair work, which conventionally required a great deal of labor, is no longer necessary. The manufacturing costs of the hume tube are therefore significantly reduced. Furthermore, as a result of the improvement in fluidity due to the combination of polyethylene glycol, even if the water:cement ratio during kneading is reduced by about 0.5 to 3% compared to the known method, the same slump as in the known method can be obtained. Therefore, the strength of the centrifugal molded product finally obtained is improved. Furthermore, the problem of difficulty in discharging concrete from the charging hopper due to low slump, which was seen when the water:cement ratio was conventionally reduced, does not occur. Furthermore, conventionally, if an admixture other than the concrete forming substance is used, the strength of the concrete molded body generally decreases depending on the amount used.
However, in the present invention, by using polyethylene glycol of a specific molecular weight, plain concrete can be obtained without a decrease in strength. Examples Examples will be shown below to further clarify the features of the present invention. Example 1 A coarse aggregate consisting of 100 parts by weight of ordinary Portland cement and crushed stone from Takatsuki with a maximum dimension of 13 mm (G in Table 1)
A concrete material with a slump value of 3 (cm) was made by uniformly mixing fine aggregate made of river sand from the Ibi River (shown as S in Table 1) and water (shown as W in Table 1). . Table 1 shows the blending ratio (parts by weight). Five types of polyethylene glycol (PEG) having different molecular weights shown in Table 2 were used, and the blending ratio was 0.034% based on the weight of cement. or,
Silicone defoamer (trade name “SN-Defoamer”)
14HP”, manufactured by San Nopco Co., Ltd.) of cement weight.
Added 0.017%. In Table 1, W/C is water-cement ratio (%)
and S/a respectively indicate the S/S+G ratio (%).

[Table] Next, using the concrete obtained above,
A centrifugal compact test piece with a diameter of 20 cm, a height of 30 cm, and a thickness of 4 cm was obtained. The weight of concrete per formwork is
The weight is 15Kg, and centrifugal molding takes 4 minutes at 6G and 1.5 minutes at 12G.
The test was carried out at 30G for 5 minutes. After pre-curing the molded test piece in a humid atmosphere at 20℃ for 4 hours,
The temperature was raised at a rate of °C/hour, steam curing was carried out at 70 °C for 4 hours, the mold was demolded after natural air cooling, and the mold was subjected to two cycles of humid air curing at 20 °C. Slag generation rate during centrifugal molding (percentage of discharged liquid slag per 15 kg of concrete),
Solid content of slag (percentage of solid content obtained by drying liquid slag at 100℃ for 15 kg of concrete) and soft paste layer thickness (thickness of uncompacted paste attached to the inner surface of the molded body,
mm) and compressive strength of the obtained test piece (Kgf/cm ² )
are shown in Table 2. Also, using the concrete obtained above, the diameter
After obtaining a vibration-compacted cylindrical test piece measuring 10 cm x 20 cm in height, it was steam-cured under the same conditions as the centrifugally formed test piece, and then cured in humid air at 20°C for a predetermined period of time. Compressive strength (Kgf/
cm ² ) are shown in Table 2.

[Table] As is clear from the results shown in Table 2, in sample No. 1 to which polyethylene glycol was not added, the thickness of the slag was large and it was necessary to extend the centrifugal molding time. On the other hand, in samples No. 2, 3, and 4 to which polyethylene glycol with a molecular weight of 3800 or less was added,
The thickness of the slag was small and the centrifugal formability was good. In particular, sample No. 4, which uses polyethylene glycol with a molecular weight of 2,600 to 3,800, shows extremely excellent results in terms of centrifugal moldability and strength. On the other hand, the molecular weight of polyethylene glycol is 6000
If it exceeds the range, the moldability is actually reduced. Example 2 In the winter season (December and January), when inner surface peeling and floating tend to occur, the composition shown in Table 3 is used, and polyethylene glycol with the molecular weight shown in Table 4 and an antifoaming agent are added to it. In addition, a Huum tube with an outer diameter of 900 mm was manufactured.

【table】

【table】

[Table] In Table 4, the antifoaming agents are those of Example 1.
The antifoaming agent is an ester type antifoaming agent (trademark "LG145", manufactured by Asahi Denka Kogyo Co., Ltd.).
(manufactured by). Table 5 shows the results of observing the inner surface condition of each product after steam curing. The evaluation shown in Table 5 was performed according to the criteria shown in Table 6.

【table】

[Table] Sample No. 17 without adding polyethylene glycol
In this case, inner surface peeling and lifting were significant, and a great deal of effort was required to repair them. On the other hand, in samples No. 11 to 16 according to the present invention,
Excellent results have been obtained in terms of centrifugal formability, prevention of internal peeling, prevention of floating, appearance, and ease of handling. On the other hand, in samples Nos. 7 to 10 using polyethylene glycol with a large molecular weight, internal peeling and lifting were observed in some parts. Furthermore, the centrifugal moldability was inferior to that of the present invention, and the color of the product became whitish.

Claims (1)

[Claims] 1. 0.005 to 5 polyethylene glycol with a molecular weight of 400 to 3,800 per 100 parts by weight of Portland cement.
A concrete composition for humid pipes containing parts by weight. 2 Polyethylene glycol with a molecular weight of 400 to 3800 0.005 to 5 per 100 parts by weight of Portland cement
1. A method for producing a centrifugal concrete hume pipe, comprising centrifugally forming a concrete composition containing parts by weight.