JPH07115910B2 - Method for producing concrete composition and centrifugal force concrete molding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel concrete composition and a method for producing a centrifugal force concrete molded body using the same.

Prior art and its problems Centrifugal concrete compacts (fume pipes, poles, piles, etc.) are required to have excellent moldability, that is, shortening of the manufacturing time and good compaction of the inner surface during manufacturing. The product is required to have high strength. Furthermore, it is also important that the milky white liquid waste called soybean paste or paste is less produced and the disposal thereof is easy.

Conventionally, in order to improve the strength of a centrifugal force concrete molded body, it has been proposed to mix various additives into the concrete material. Specifically, for example, (a) by using a water reducing agent to reduce the W / C ratio, (b) by using type II anhydrous anhydrous gypsum or an admixture containing this as a main component,
There are known methods for improving strength, (C) using (A) and (B) in combination, and the like. In particular, in the case of a propulsion pipe that requires a concrete strength of 700 kgf / cm ² or more, a method of using the above (a) and (b) together is performed.

However, according to these methods, although the purpose of improving the strength is achieved for the time being, the addition of additives causes
There are new problems such that the compaction property of the inner surface during centrifugal molding is lowered and the molding time is prolonged, and a soft paste layer remains on the inner surface of the molded body, which requires a long time for the treatment.

Furthermore, in the case of concrete that does not use high-strength admixtures such as type II anhydrous gypsum (hereinafter referred to as plain concrete), it is necessary to secure the required standard strength without impairing other properties.

Also, by adding a coagulation accelerator to the slag (corresponding to the above-mentioned soft paste layer) that accumulates on the inner surface of the molded body during centrifugal molding, the amount of slag produced is reduced and the solid content ratio in the slag is reduced. A method of reducing the amount has been proposed (Japanese Patent Laid-Open No. 56-161108). According to this method, it is said that the precipitation treatment step of wastewater after the recovery of roe is simplified. However, this method requires a new operation of adding a coagulation accelerator at the time of centrifugal molding, which complicates the production process and does not improve the strength itself of the molded body.

Means for Solving the Problems The present inventor has conducted various studies in view of the current state of the art as described above, and in the case of using a type II anhydrous gypsum-based admixture, a water reducing agent, polyethylene glycol and a defoaming agent in combination. Have found that the problems of the prior art can be substantially or largely eliminated.

That is, the present invention provides the following compositions and methods (hereinafter, the inventions of and are collectively referred to as the first invention of the present application): Portland cement 100 parts by weight, type II anhydrous gypsum as a main component A concrete composition containing 5 to 10 parts by weight of an admixture, 0.1 to 2.0 parts by weight of a water reducing agent, 0.05 to 0.5 parts by weight of a defoaming agent, and 0.5 to 10% by weight of the admixture of polyethylene glycol having a molecular weight of 8000 or less. , And 100 parts by weight of Portland cement, 5 to 10 parts by weight of admixture mainly composed of type II anhydrous gypsum, 0.1 to 2.0 parts by weight of water reducing agent, 0.05 to 0.5 parts by weight of defoaming agent, and polyethylene glycol having a molecular weight of 8,000 or less are mixed. A method for producing a centrifugal force concrete molding, which comprises centrifuging a concrete composition containing 0.5 to 10% of the weight of the material.

Furthermore, in the subsequent research, if the strength of the concrete molded body is not particularly required to be 700 kg f / cm ² or more, the type II anhydrous gypsum is not used, and the molecular weight is
It was found that by using polyethylene glycol of 190 or more and less than 4000, the amount of slag produced can be reduced and the centrifugal molding time can be shortened without lowering the strength of the molded body.

That is, the present invention further provides the following composition and method (hereinafter, the inventions of and are collectively referred to as the second invention of the present application): 100 parts by weight of Portland cement, 0.1 to 2.0 parts by weight of water reducing agent Parts, a defoaming agent 0.05 to 0.5 part by weight and a polyethylene composition 0.025 to 1.0 part by weight of polyethylene glycol having a molecular weight of 190 or more and less than 4000, and 100 parts by weight of Portland cement, a water reducing agent 0.1 to 2.0 parts by weight, a defoaming agent 0.05 to A method for producing a centrifugal force concrete molding, which comprises centrifuging a concrete composition comprising 0.5 part by weight and 0.025 to 1.0 part by weight of polyethylene glycol having a molecular weight of 190 or more and less than 4000.

The Portland cement used in the first invention of the present application and the second invention of the present application is not particularly limited, and may be either normal, early strength or ultra-early strength Portland cement.

As the admixture mainly composed of type II anhydrous gypsum used in the first invention of the present application, a normal type II anhydrous gypsum content of 80 to 10
About 0% by weight of powder is used. The specific surface area of the powder is usually about 2000 ~ 8000 cm ² / g, 6000 ~ 7500c
About m ² / g is more preferable. Such admixtures are commercially available, for example, under the trade names of "Nonclave" {Osaka Cement Co., Ltd.}, "Asano Supermix" {Nippon Cement Co., Ltd.}, "Denka Σ1000" {Denki Kagaku Co., Ltd., etc. It is marketed in. The compounding amount of the admixture mainly composed of type II anhydrous gypsum is about 5 to 10 parts by weight with respect to 100 parts by weight of cement. When the amount of the admixture is less than 5 parts by weight, the strength of the concrete molded body is insufficient. On the other hand, when it exceeds 10 parts by weight, the strength of the concrete molded body decreases and the centrifugal formability decreases. As a result, the thickness of the soft paste layer remaining on the inner surface of the molded body increases, which is not preferable.

The water reducing agent used in the first invention of the present application and the second invention of the present application,
There is no particular limitation, and known materials can be used as they are. For example, those containing a salt of a formalin condensate of naphthalene sulfonic acid as a main component {Trade name "Mighty 100", "Mighty 150" manufactured by Kao Corporation, "Pole Fine" trade name manufactured by Takemoto Yushi Co., Ltd., Trade name "Sanflow PS", "Sunflow PSP100", etc. manufactured by Sanyo Kokusaku Pulp Co., Ltd .; Mainly composed of water-soluble polymer obtained by condensation of trimethylolmelamine monosulfonate salt {Showa Denko KK) Specific examples include the trade name "Melment F-10" manufactured by the company.

Polyethylene glycol used in the first invention of the present application {HO
(CH ₂ CH ₂ O) _n } usually has a molecular weight of 9000 or less, more preferably about 2000 to 8000. When the molecular weight is more than 9,000, the water solubility is lowered and the desired effect is not sufficiently achieved. When the molecular weight is less than 2000, it exhibits a liquid or waxy form and is slightly inferior in workability. When polyethylene glycol having a molecular weight of 4000 or more is used, voids are formed during molding, but ettringite, which is produced in a large amount in the presence of the type II anhydrous gypsum used in combination, is filled in the voids. A molded product having a sufficient strength of more than 10 is obtained. The amount of polyethylene glycol used is usually about 0.5 to 10% by weight of the admixture. The amount used
If it is less than 0.5%, the effect of the composition is hardly exerted, while if it exceeds 10%, the viscosity at the time of preparation of the concrete composition becomes high and the workability deteriorates. Considering the economic efficiency, the amount of polyethylene glycol used is more preferably about 0.5 to 10% of the weight of the admixture.

The polyethylene glycol used in the second invention of the present application containing no type II anhydrite-based admixture is 19
Use one that is 0 or more and less than 4000. When the molecular weight is 4,000 or more, polyethylene glycol acts as a setting retarder to increase the amount of air entrained in the molded body and reduce the compressive strength due to the voids formed. That is, unlike the case of the first invention of the present application, a large amount of ettringite derived from type II anhydrous gypsum is not generated, so that voids remain and the strength is reduced. The amount of polyethylene glycol used is 0.025 to 1 per 100 parts by weight of cement.
It is about 0 parts by weight. The amount of polyethylene glycol is 0.0
If it is less than 25 parts by weight, the effect of the compounding is hardly exhibited, whereas if it exceeds 1.0 part by weight, the viscosity at the time of preparation of the concrete composition becomes high and the workability is deteriorated. Considering the economic efficiency, the amount of polyethylene glycol used is 0.04 to 100 parts by weight of cement.
More preferably, it is about 0.3 part by weight.

Generally, when a concrete composition is mixed with the above admixture and polyethylene glycol, the air content is increased, fine pores are generated on the outer surface of the centrifugal molded body, and the finished surface is deteriorated or the molded body is deteriorated. The strength may decrease.
In order to prevent this, in the first invention of the present application and the second invention of the present application, an antifoaming agent is added in an amount of 0.05 to 0.5% of the cement weight. The defoaming agent is not particularly limited, and is silicone-based {for example, trade name "SN-Defoamer from San Nopco Ltd.
14HP ", trade name" SN-Defoamer 305 ", trade name" Nopco
Commercially available products such as 8034L "}: nonionic surfactant system: known compounds such as higher alcohol systems such as octyl alcohol and cyclohexanol can be used.
If the amount of the defoaming agent added to the cement is less than 0.05%, the effect is not sufficiently exhibited, and if it exceeds 0.5%, the effect is hardly improved and the physical properties of the centrifugally molded product are deteriorated.

In addition, in the present invention, known additives may be further added according to a conventional method. As such an additive, there is silica fume fine powder or the like. This improves the compactness of the centrifugal compact.

In the present invention, a raw material mixture consisting of Portland cement, an admixture (only in the case of the first invention of the present application), polyethylene glycol, an antifoaming agent, a fine aggregate, a coarse aggregate and, if necessary, other additives is water. Kneading in the presence of. The particle size of fine aggregate and coarse aggregate, the amount used, the kneading method and the like are not different from known methods. The concrete thus obtained is centrifugally molded according to a conventional method and steam-cured to obtain a product.

EFFECTS OF THE INVENTION According to the present invention, as a result of the improvement of the fluidity due to the combined use of type II anhydrous gypsum and polyethylene glycol, the water: cement ratio during kneading is reduced by about 0.5 to 3% as compared with the known method. Even so, a slump equal to that in the known method is obtained, so that the strength of the finally obtained centrifugal molded body is improved. In addition, the problem of difficulty in discharging concrete from the input hopper due to the low slump, which has been observed when the water: cement ratio is reduced, does not occur. Further, when the admixture was used conventionally, it was necessary to extend the molding time, but in the present invention, the molding can be completed within a short time as in the case where the admixture is not used. Furthermore,
The amount of paste or paste layer produced during centrifugal molding is not small. The amount of flaking that occurs after steam curing is also significantly reduced.

Furthermore, conventionally, when an admixture other than a concrete molding substance is used, the strength of the concrete molded body is generally lowered depending on the amount used. However, in the second invention of the present application, by using polyethylene glycol having a specific molecular weight, it is possible to obtain plain concrete without lowering the strength.

Examples Examples will be shown below to further clarify the features of the present invention.

Example 1 100 parts by weight of ordinary Portland cement, 1.5 parts by weight of a water reducing agent trademark (“Mighty 150”, manufactured by Kao Co., Ltd.), coarse aggregate made of crushed stone from Takatsuki having a maximum dimension of 13 mm (shown as G in Table 1) , Evenly mixed with fine aggregate made of river sand from Ibigawa (shown as S in Table 1), type II anhydrous gypsum-based mixed material (shown as K in Table 1) and water (shown as W in Table 1) Then, a concrete material having a slump value of 7 ± 1 (cm) was obtained.

Table 1 shows the compounding ratio (parts by weight) other than the cement and the water reducing agent. In addition, to sample Nos. 5 to 7, 4% by weight of the admixture, polyethylene glycol (molecular weight 6000) was added. Sample 2
As the admixture of No. 7, "nonclave" manufactured by Osaka Cement Co., Ltd. was used. Further, to Sample Nos. 5, 6, and 7, a silicon-based defoaming agent (trade name "SN-Defoamer 14HP", manufactured by San Nopco Ltd.) was added at 0.1% of the weight of cement.

In Table 1, W / C is the water cement ratio (%), S / a is S /
The S + G ratio (%) is shown.

Then, using the concrete obtained above, a diameter of 20 cm
A centrifugal molded body test piece having a height of 30 cm and a thickness of 40 cm was obtained. The concrete weight per one mold was 15 kg, and the centrifugal molding was performed under the conditions of 6 G for 4 minutes, 12 G for 3 minutes, and 30 G for 10 minutes. After pre-curing the molded test piece in humid air at 20 ° C for 4 hours, raise the temperature at a rate of 20 ° C / hour, steam-cure at 70 ° C for 4 hours, demold after natural air cooling, and at 20 ° C. It was damp air cured for 2 hours.

Occurrence rate of slag during centrifugal molding (percentage of discharged liquid slag to 15kg of concrete), solid content ratio of slag (percentage of solids obtained by drying liquid slag to 100kg of concrete to 100kg) and soft paste layer Thickness (uncompressed paste thickness attached to the inner surface of the molded body, mm) and compressive strength of the obtained test piece (kg f / c
m ² ) is shown in Table 2.

Also, using the concrete obtained above, after obtaining a vibration compaction cylindrical test piece of 10 cm in diameter × 20 cm in height, steam curing is performed under the same conditions as the centrifugally molded test piece, and at 20 ° C. for a predetermined period of time. Wet air was cured.

Table 3 shows the compressive strength (kg f / cm ² ) of the obtained test pieces.

As is clear from the results shown in Tables 2 and 3, the sample No. 2 in which the admixture alone was mixed at 5% of the cement weight had a softer paste layer than the sample No. 1 in which the admixture was not added. The thickness increases, and the formability decreases. 7.5 admixtures each
% And 10% in the sample Nos. 3 and 4, the thickness of the soft paste layer was further increased, and the moldability was further reduced.
As a result, the compression strength of the centrifugally molded product also decreases.

On the other hand, in Sample Nos. 5 and 6 in which the admixture and polyethylene glycol are used in combination, the thickness of the soft paste layer is relatively small, the moldability is extremely good, and the compressive strength is high. In particular, in Sample No. 6 in which the admixture of 7.5% by weight of cement and polyethylene glycol are used together, a remarkable improvement in compressive strength is observed. In Sample 7 in which the admixture of 10% of the cement weight and polyethylene glycol are used together, the thickness of the soft paste layer is increased. Therefore, when centrifugal moldability is important, the amount of admixture used is 10% of the cement weight, even if polyethylene glycol is used together.
Is preferably the upper limit.

Example 2 A test was conducted according to the method of Example 1 except that the amount of polyethylene glycol used was changed variously. The amount of defoaming agent (same as in Example 1) used was 0.1% of the cement weight.
And

The composition of concrete is shown in Table 4, and the test results are shown in Table 5 (centrifugal molded body) and Table 6 (cylindrical body).

In Table 4, sample Nos. 1, 3 and 6 have the same composition as sample Nos. 1, 3 and 6 in Table 1.

In the composition shown in Table 4, when an admixture of 7.5% by weight of cement is used and the amount of polyethylene glycol is increased, the centrifugal moldability is improved as the amount is increased. A significant improvement in strength is observed in both the centrifugally molded body and the columnar body as compared with the case where polyethylene glycol is not added.

Regarding the concrete composition shown in Table 4, the best moldability was obtained when polyethylene glycol was 4% of the admixture weight, and the highest strength was achieved when it was 2%.

Example 3 Using concrete having the same composition as the sample No. 6 of Example 1, (a) 6G × 4 minutes, 12G × 3 minutes, 30G × 10 minutes,
(B) 6G x 4 minutes, 12G x 3 minutes, 30G x 5 minutes and (d) 6G x
Centrifugal molding was carried out under the respective molding conditions of 2 minutes, 12 G × 1.5 minutes and 30 G × 5 minutes. The dimensions of the molded body are the same as in Example 1.

Table 7 shows the condition of slag during molding and the compression strength of the molded body. The result of (a) is the same as that of the sample No. 6 of Example 1.

As is clear from the results shown in Table 7, according to the present invention, even when the time for medium-speed and high-speed rotation is shortened {(b) and (c)}, the operation (a) Moldability and compressive strength equivalent to () are obtained.

Example 4 Defoaming agent for 100 parts by weight of cement (same as Example 1)
(D) 0, (e) 0.05 parts by weight and (f) 0.1
A concrete having the same composition as that of Sample No. 6 of Example 1 was prepared except that the parts by weight were used, and the respective slumps and air contents were examined. Also, a centrifugal molded body was manufactured in the same manner as in Example 1 using each concrete. Eighth of these results
Shown in the table.

As is clear from the results shown in Table 8, the use of the defoaming agent reduces the amount of air in the concrete, effectively prevents the formation of voids on the surface of the molded body, and increases the strength of the molded body by 10%. Improve.

Example 5 A concrete having the same composition as that of the sample No. 6 of Example 1 was prepared except that polyethylene glycol having a molecular weight of 8,000 and 10,000 was used, and the slump was measured, whereas the former was 7.4 cm. In the latter case, the polyethylene glycol swelled without being dissolved and the viscosity was increased, so that the measurement was impossible.

Example 6 100 parts by weight of ordinary Portland cement, 1.5 parts by weight of a water reducing agent (trademark "Mighty 150", manufactured by Kao Corporation), maximum dimension 1
Coarse aggregate made of 3 mm Takatsuki crushed stone (shown as G in Table 9), fine aggregate made of river sand from Ibigawa (shown as S in Table 9), polyethylene glycol (shown as PEG in Table 9) 0.14 Parts by weight, silicone-based defoamer (trade name "SN-
Defoamer 14HP ", manufactured by San Nopco Ltd., 0.1 part by weight and water (shown as W in Table 9) were uniformly mixed to obtain a concrete material having a slump value of 7 ± 1 (cm).

Table 9 shows the compounding ratio (parts by weight) of water, coarse aggregate and fine aggregate and the average molecular weight of polyethylene glycol. All S / a {S / S + G ratio (%)} is 43.

Then, using the concrete obtained above, a diameter of 20 cm
A centrifugal molded body test piece having a height of 30 cm and a thickness of 4 cm was obtained. The concrete weight per one mold was 15 kg, and the centrifugal molding was performed under the conditions of 6 G for 4 minutes, 12 G for 3 minutes, and 30 G for 10 minutes. After pre-curing the molded test piece in humid air at 20 ° C for 4 hours, raise the temperature at a rate of 20 ° C / hour, steam-cure at 70 ° C for 4 hours, demold after natural air cooling, and at 20 ° C. It was cured in wet air for 2 weeks.

Occurrence rate of slag during centrifugal molding (percentage of discharged liquid slag with respect to 15 kg of concrete), solid content ratio of slag (percentage of solids obtained by drying liquid slag with respect to 15 kg of concrete at 100 ° C) and soft paste layer Table 10 shows the thickness (thickness of uncompacted paste attached to the inner surface of the compact, mm) and the air entrainment rate (%) of fresh concrete.

Also, using the concrete obtained above, after obtaining a vibration compaction cylindrical body test piece with a diameter of 10 cm × height of 20 cm, steam curing is performed under the same conditions as the centrifugal molded body test piece, and at 20 ° C. Wet and cured for a period of time.

Table 11 shows the compressive strength (kg f / cm ² ) of the obtained test pieces.

As is clear from the results shown in Tables 10 and 11, the compressive strength does not decrease when the average molecular weight of polyethylene glycol is less than 4000 (Nos. 2 and 3).

On the other hand, the average molecular weight of polyethylene glycol is
When it becomes higher, this acts as a setting retarder, increasing the air entrainment rate in the molded body and lowering the compressive strength.

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Claims (4)

[Claims] 1. Portland cement 100 parts by weight, admixture mainly composed of type II anhydrous gypsum 5 to 10 parts by weight, water reducing agent 0.1
~ 2.0 parts by weight, antifoaming agent 0.05 to 0.5 parts by weight and polyethylene glycol having a molecular weight of 8,000 or less 0.5 to 10% of the admixture weight
The concrete composition contained in the ratio of. 2. 100 parts by weight of Portland cement, 5 to 10 parts by weight of an admixture mainly composed of type II anhydrous gypsum, and a water reducing agent of 0.1.
~ 2.0 parts by weight, antifoaming agent 0.05 to 0.5 parts by weight and polyethylene glycol having a molecular weight of 8,000 or less 0.5 to 10% of the admixture weight
A method for producing a centrifugal force concrete molded product, which comprises centrifuging a concrete composition contained at a ratio of. 3. Portland cement 100 parts by weight, water reducing agent
0.1-2.0 parts by weight, antifoaming agent 0.05-0.5 parts by weight and molecular weight 190
A concrete composition comprising 0.025 to 1.0 part by weight of polyethylene glycol of 4000 or more and less than 4000. 4. Portland cement 100 parts by weight, water reducing agent
0.1-2.0 parts by weight, antifoaming agent 0.05-0.5 parts by weight and molecular weight 190
A method for producing a centrifugal force concrete molded product, which comprises centrifugally molding a concrete composition comprising 0.025 to 1.0 part by weight of polyethylene glycol having a content of at least 4000.