JP2009073698A - High-strength concrete composition for centrifugal force molding and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a concrete composition for centrifugal force molding exerting high strength in regard to centrifugally molded concrete secondary products such as a pile, a pole or a Hume pipe and the like. <P>SOLUTION: In the high-strength concrete composition for centrifugal force molding containing early-strength portland cement, a high-strength additive, a dispersant, an aggregate and water, the containing ratio of gypsum hemihydrate in gypsum is 10-90 mass% and the unit quantity of cement is 490-640 kg/m<SP>3</SP>in the early-strength portland cement, the mass ratio of water to the early-strength portland cement is 20.0-25.5 mass%, the high-strength additive contains anhydrous gypsum and noncrystalline silica wherein the mass ratio of anhydrous gypsum/noncrystalline silica is 15/85-90/10 and the dispersant is a naphthalene-based dispersant. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a concrete composition suitable for concrete forming such as piles, poles, and fume pipes manufactured using centrifugal force, and a method for manufacturing a concrete secondary product using the same. In particular, the present invention relates to a centrifugal molding concrete composition having an extremely high strength of 130 N / mm ² after steam curing and subsequent air curing without using special aggregates or fiber reinforcements.

  Conventionally, a forming method using centrifugal force is generally employed for manufacturing a columnar or cylindrical concrete secondary product such as a pile, a pole, or a fume tube. In this method, concrete is placed in a formwork with reinforcing bars and molded by centrifugal force, precured at room temperature for a predetermined time, steam-cured at normal pressure, demolded after cooling, and aired for several weeks. Shipped with medium curing.

Recently, concrete secondary products such as concrete piles tend to be required to have higher support. In order to satisfy these requirements, methods are used to optimize the materials used, the mix of concrete, centrifugal molding conditions, pre-curing conditions, and the addition of atmospheric steam curing conditions and high-temperature high-pressure curing. However, the present situation is that the stable high-strength cured body has not necessarily been obtained. Incidentally, when using ordinary concrete material, the high intensity regions such as the design strength (compressive strength) 130N / mm ² level centrifugal molding concrete composition is close to a limit to technical, high strength that It is said that it is extremely difficult to ensure (see Patent Documents 1 to 3).
Japanese Patent No. 2887561 JP 2005-263567 A JP 2005-179149 A

As described above, in view of the fact that it has been difficult to satisfy the design standard strength (compressive strength) of 130 N / mm ² or more in the conventional centrifugally molded concrete cured body, Concrete composition for forming a centrifugal force that has a demolding compression strength of about 115 N / mm ² or more after steam curing and a high strength of 130 N / mm ² after subsequent air curing (after 1 to 2 weeks) The purpose is to provide.

  The present invention also clarifies the optimum conditions of concrete material, blending, kneading, filling into molds, centrifugal force forming, pre-curing and steam curing, and manufacturing the above-described high-strength centrifugal force forming products. The purpose is to provide a method to do.

As a result of intensive studies to achieve high strength of centrifugal force molding products, the present inventors have found that high strength centrifugal force molding containing early strength Portland cement, high strength admixture, dispersant, aggregate and water. It is a concrete composition, and the ratio of hemihydrate gypsum in gypsum of early-strength Portland cement is 10 to 90 mass%, the unit cement amount is 490 to 640 kg / m ³ , and the water / early strength Portland cement mass ratio is 20.0. 25.5% by mass, the high-strength admixture contains anhydrous gypsum and amorphous silica, the mass ratio of anhydrous gypsum / amorphous silica is 15/85 to 90/10, and the dispersant is naphthalene-based. It came to invent the high-strength centrifugal force molding concrete composition which is a dispersing agent.

  In the high-strength centrifugal molding concrete composition of the present invention, the amorphous silica in the high-strength admixture is preferably silica fume, and the high-strength admixture is obtained by mixing and crushing anhydrous gypsum and silica fume. preferable. Furthermore, it is more preferable that 6 to 25 parts by mass of the high-strength admixture and 1.0 to 5.5 parts by mass of the dispersant are included on an aqueous solution basis with respect to 100 parts by mass of the early strong Portland cement.

  The present invention is further mixed with the above-mentioned high-strength centrifugal force molding concrete composition, filled into a cylindrical formwork with reinforcing bars, and then subjected to centrifugal force molding, precured, then steam cured and then demolded, A method for producing a high-strength centrifugal force molding product that is then cured in air is provided.

By the method for producing a centrifugal force molding product of the present invention, a high strength centrifugal force molding product having a design standard strength of 130 N / mm ² can be produced. For this reason, in the case of a pile, since a supporting force can be taken largely, the number of construction can be reduced and there exists an effect that it is economical. Moreover, since the structure of the high-strength centrifugal force forming concrete composition becomes dense, it also has an effect of contributing to improvement in durability.

The present invention is described in detail below.
First, the preferable characteristic of the material used for a concrete composition is as follows.

  The cement used in the high-strength centrifugal molding concrete composition of the present invention is early-strength Portland cement, and the proportion of hemihydrate gypsum in the gypsum of early-strength Portland cement is 10 to 90% by mass, preferably 20 to 80% by mass. %. The amount of hemihydrate gypsum in gypsum of early-strength Portland cement is determined by centrifugal force formability (consolidation, homogeneity (inhibition of undulation on the inner surface), suppression of generation of sludge), and strength development after steam curing. Therefore, the mass ratio of the amount of hemihydrate gypsum to the total amount of dihydrate gypsum and hemihydrate gypsum in the gypsum of cement measured by the differential thermogravimetric analysis method described later is In the above-mentioned range of 10 to 90% by mass, it is one of the essential essential requirements.

Furthermore, the hydraulic strength (HM) of early strong Portland cement is 2.20 to 2.30, more preferably 2.23 to 2.28, and the amount of SO _{3 in} the cement is 2.5 to 3.5. The thing of the mass%, More preferably, the thing of 2.8-3.1 mass% can be used. The particle size of the early strong Portland cement is not particularly limited, and the fineness (Blaine specific surface area) is 4200 to 4800 cm ² / g, and the 32 μm sieve residue by air jet sieve is 3.0 to 8.0 mass. %, Volume content by laser diffraction particle size distribution measuring device (manufactured by Seishin Enterprise, LMS-30 (Laser Micro Sizer)) is 50% passage diameter 6-16 μm, more preferably 8-12 μm, 90% passage diameter / The 10% passage diameter ratio is 5 to 15, and the n value (particle size distribution uniform number, particle size target range 4 to 32 μm) in the Rosen-Rammler diagram is 1.10 to 1.40, preferably 1.15 to 1.35. Can be used satisfactorily.

The high-strength admixture used in the high-strength centrifugal force molding concrete composition of the present invention is one of the indispensable materials for producing a high-strength centrifugal force-forming product, and contains anhydrous gypsum and amorphous silica. It is a waste. As the amorphous silica, silica fume, fine powder fly ash (average particle size of 10 μm or less) and the like can be used. In particular, silica fume having a silica content of 90% by mass or more is more preferable, and the primary particles are aggregated or sintered. It is preferable that the secondary particles formed by the above are sufficiently crushed and dispersed. As a method for realizing this, it is also effective to pulverize anhydrous gypsum and silica fume. The preferable content ratio (anhydrous gypsum / amorphous silica mass ratio) of anhydrous gypsum and amorphous silica in the high-strength admixture is 15/85 to 90/10, more preferably 20/80 to 65/35. The fineness (brain specific surface area) of the high-strength admixture is influenced by the ratio of the constituent components or particularly the dispersed state of the amorphous silica particles, but in a more preferable blending ratio, it is 4000 to 15000 cm ² / g, preferably It is the range of 5000-13000 cm < ² > / g.

  The high-strength admixture is more preferably a mixture obtained by mixing and grinding anhydrous gypsum and amorphous silica. Since amorphous silica is exposed to a high temperature state during production, primary particles form agglomerated secondary particles, which are peptized by mixing and pulverization, and the dispersion state when used in concrete is improved. Moreover, what is generally marketed as an admixture for steam curing can also be used conveniently. Examples include Denka Σ1000, Denka Σ2000 (manufactured by Denki Kagaku Kogyo Co., Ltd.), nonclave, super nonclave (manufactured by Sumitomo Osaka Cement Co., Ltd.), die mix (manufactured by Showa KDE Co., Ltd.), Taiheiyo Ultra Supermix. (Manufactured by Taiheiyo Material Co., Ltd.). Among these, use of Denka Σ2000 and super nonclave is more preferable.

The dispersant used in the concrete composition for high strength centrifugal force molding according to the present invention is a high performance water reducing agent having a high water reduction rate that is not delayed and does not entrain air even when added in a relatively large amount. As the high-performance water reducing agent, one having a polyalkylallyl sulfonate or aromatic amino sulfonate as a main component can be used. More preferred is a polyalkylallyl sulfonate high-performance water reducing agent. Examples thereof include methyl naphthalene sulfonic acid formalin condensate, naphthalene sulfonic acid formalin condensate and anthracene sulfonic acid formalin condensate. As the form, either powdered or aqueous solution type can be used, but the latter (aqueous solution) is more preferable from the viewpoint of ease of handling. The solid content (solute content) in the aqueous solution is often in the range of about 25 to 45% by mass. Since the water content of the dispersant is added to the kneaded water in the concrete blending design, it is necessary to obtain the water content in advance for its use. Specific examples of marketed dispersants are Mighty HS (manufactured by Kao Corporation), Mighty 150 (manufactured by Kao Corporation), Cellflow (Daiichi Kogyo Seiyaku Co., Ltd.), Leo Build 8000H (BASF Pozzolith Co., Ltd.) Product), Pole Fine 510-AN (manufactured by Takemoto Yushi Co., Ltd.), Floric PS (manufactured by Floric Co., Ltd.), and the like.
FIG. 1 shows an infrared absorption spectrum of a typical polyalkylallyl sulfonate dispersant. The infrared absorption spectrum of the dispersant was measured using FT / IR-4000 (measurement accuracy: 4 cm ⁻¹ ) manufactured by JASCO Corporation. The dispersant was applied as it was on the NaCl plate, dried at 110 ° C., and measured by the transmission method. The measurement range was 400 to 4000 cm ⁻¹ and the number of integrations was 16 times.

  The type of the aggregate used in the high-strength centrifugal force molding concrete composition of the present invention is not particularly limited, and those usually used in centrifugal force molding products can be used. The maximum size of the coarse aggregate is more preferably 15 mm, and the fine aggregate rate (s / a) is selected from the range of 30 to 45% by mass.

Next, the concrete composition in the high strength centrifugal molding concrete composition of the present invention is as follows.
First, the unit amount of early strong Portland cement is preferably 490 to 640 kg / m ³ . If the unit amount of early-strength Portland cement is less than 490 kg / m ³ , sufficient strength cannot be obtained, and if it exceeds 640 kg / m ³ , the water-cement ratio can be reduced, but the volume ratio of cement paste to the gap between aggregates is excessive. Thus, compaction by centrifugal molding becomes insufficient, and as a result, high strength cannot be obtained.

  The high-strength admixture is preferably 6 to 25 parts by mass and more preferably 8 to 20 parts by mass with respect to 100 parts by mass of the early strong Portland cement. If the content of the high-strength admixture is less than 6 parts by mass, an effect of improving the strength cannot be expected, and if it exceeds 25 parts by mass, the centrifugal force moldability is lowered and the strength may be lowered.

  The naphthalene-based dispersant is preferably 1.0 to 5.5 parts by mass on the basis of an aqueous solution with respect to 100 parts by mass of early strong Portland cement, and more preferably 2.0 to 4.5 parts by mass in view of economy. preferable. That is, when the dispersant is less than 1.0 part by mass on the basis of the aqueous solution, water reduction is insufficient, and even if added over 5.5 parts by mass, the water reduction effect reaches its peak, and the water reduction is large enough to meet the increased amount. It is uneconomical because it is difficult to obtain the effect.

  Further, the high strength of the centrifugal force-forming concrete composition of the present invention can be achieved while the interaction between the high-strength admixture and the dispersant occurs, and these admixtures (agents) are simply used. It is not a good thing if there is much, but there exists a proper addition amount.

  The appropriate mass ratio of water / early strength Portland cement varies depending on the various concrete materials used and the unit amount (formulation), but is in the range of 20.0-25.5% by mass, preferably 21-23% by mass. . If the amount is less than 20.0% by mass, the viscosity of the concrete increases, the handling property is deteriorated, and it is too hard to be put into the formwork. If the amount exceeds 25.5% by mass, the concrete is fluidized and tightened by centrifugal force. This is not preferable because the hardening is insufficient and high strength is difficult to obtain.

In addition, when manufacturing a high intensity | strength steel pipe pile by centrifugal force shaping | molding, it is preferable to use an expansion material together with a high intensity | strength admixture as said concrete mixing | blending. The expansion material is of Awin-lime-gypsum system or lime-gypsum system, and is used within 18 parts by mass based on the total amount of the expansion material and high-strength admixture with respect to 100 parts by mass of early-strength Portland cement. Is preferred. In this case, as the expansion material, commercially available Denka CSA ^# 20 (manufactured by Denki Kagaku Kogyo Co., Ltd.), Taiheiyo Expan or Taiheiyo Gypcal (Pacific Material Co., Ltd.) can be used. Approximately 5 to 8 parts by mass is preferable.

  There are no particular limitations on the order in which the concrete materials are used, the mixer to be used, the kneading time, etc., and the conditions normally used in the production of centrifugal force forming products can be employed. The fluidity of the proper mixed concrete is 10 cm or less, preferably 1 to 4 cm with slump, and about 6 to 12 cm with steel pipe pile. This concrete is placed in a placed formwork, homogenizing the concrete in the axial direction of the formwork (1-4G), and attaching to the inner surface of the formwork (low speed 5-14G) , High speed 15 to 20G), centrifugal molding is performed in four steps (20G or more) in which the coarse aggregate is concentrated and compacted toward the inner surface of the mold. Each centrifugal force application time is selected in the range of 1 to 5 minutes.

  The molded body formed by centrifugal force is precured for 4 to 6 hours at room temperature, for example, a temperature range of 5 to 35 ° C., and then steam-cured. Steam curing is performed at a temperature rising rate of 15 to 22 ° C./h, a maximum temperature of 60 to 100 ° C., preferably 70 to 90 ° C., held at the maximum temperature for 3 to 6 hours, and then cooled for 8 to 12 hours. To do. After cooling, the mold is removed, and curing is performed in the air for one week or longer.

[Materials used]
[1] Early strong Portland cement (HC):
The early strength Portland cement has a hydraulic modulus (HM) of 2.23 to 2.28, an amount of SO _{3 in} the cement of 2.80 to 3.11% by mass, and a fineness (Brain specific surface area) of 4450. ˜4640 cm ² / g, 32 μm sieve residue by air jet sieve is 5.1 to 7.7% by mass, Rosin by laser diffraction type particle size distribution measuring device (manufactured by Seishin Enterprise, LMS-30 (Laser Micro Sizer)) -As shown in Table 1, the n value (particle size distribution equal number, particle size target range 4 to 32 μm) in the Rammel diagram is 1.16 to 1.35, and the proportion of hemihydrate gypsum (% by mass) is different. Used the type.

The amount of SO _{3 of} early strong Portland cement was measured by JIS R 5202: 1999 “Chemical analysis method of Portland cement” and JIS R 5204: 2002 “Fluorescent X-ray analysis method of cement”.

In addition, the hemihydrate gypsum ratio was calculated | required with the following method.
First, the amount of hemihydrate gypsum and the amount of dihydrate gypsum were quantified by differential thermogravimetric analysis (TG-DTA). Specifically, using a differential thermothermal gravimetric analyzer TG-DTA6200 (manufactured by Seiko Instruments Inc.), about 30 mg of the sample is put into a cell (made of aluminum) having a hole of 20 μm in diameter and having a capacity of 30 μL. The temperature was raised from room temperature to 300 ° C. at a rate of 5 ° C./min. As shown in FIG. 2, first, from the curve (DTG in FIG. 2) obtained by differentiating the weight loss curve (TG in FIG. 2), the DTG peak A rising temperature (about 125 ° C.), DTG accompanying dehydration of hemihydrate gypsum The rise temperature of peak B (about 155 ° C.) and the end point of peak B (about 195 ° C.) were determined. Next, the weight loss around 125 to 155 ° C. due to dehydration of dihydrate gypsum (a mass%) and the weight loss near 155 to 195 ° C. due to dehydration of hemihydrate gypsum (b mass%) are obtained, and the formula (1) And the amount of dihydrate gypsum (mass%) and the amount of hemihydrate gypsum (mass%) in the gypsum of cement were computed using Formula (2). From these, the ratio (mass%) of hemihydrate gypsum was computed using Formula (3). An aluminum plate was used as a reference.

Dihydrate gypsum amount (mass%) = weight loss a (mass%) × 172 (molecular weight of dihydrate gypsum) ÷ (1.5 × 18 (molecular weight of H ₂ O)) (1) hemihydrate gypsum amount (mass%) = (Weight loss b (mass%)-weight loss a (mass%) ÷ 3) x 145 (molecular weight of hemihydrate gypsum) ÷ (0.5 x 18 (molecular weight of H ₂ O)) (2) hemihydrate gypsum ratio ( (Mass%) = hemihydrate gypsum amount ÷ (hemihydrate gypsum amount + dihydrate gypsum amount) x 100 (3)

[2] High strength admixture (A):
Preparation: Type II anhydrous gypsum powder (hydrofluoric acid anhydrous gypsum) and silica fume (manufactured by Elchem Co.) were mixed at a ratio of gypsum / silica fume mass ratio of 10/90, 20/80, 30/70, 65/35, It changed into 80/20 and 95/5, and mixed and pulverized by a test ball mill (Φ30 × 30 cm) so that the specific surface area of the brain was 5500 to 11000 cm ² / g. Further, when the mass ratio of anhydrous gypsum / silica fume was 20/80, a mixture obtained by simply mixing anhydrous gypsum powder and silica fume with a V-type mixer was used without mixing and grinding.

As commercial products, Denka Σ2000 (anhydrous gypsum / amorphous silica mass ratio: 20/80, manufactured by Denki Kagaku Kogyo Co., Ltd.), Dymix (anhydrous gypsum / amorphous silica mass ratio: 60/40, Showa KDE), super nonclave (anhydrous gypsum / amorphous silica mass ratio: 50/50, manufactured by Sumitomo Osaka Cement Co., Ltd.), nonclave (anhydrous gypsum / amorphous silica mass ratio: 98/1), Sumitomo Osaka Cement Co., Ltd.) was used. The mass ratio of anhydrous gypsum / amorphous silica described was determined according to JIS M8852: 1998 “Chemical analysis method of high siliceous raw material for ceramics”, and SO ₃ and SiO ₂ were quantified, and the amount of SO ₃ was CaSO ₄ In terms of (anhydrous gypsum), the amount of SiO ₂ was regarded as the amount of amorphous silica.

[3] Dispersant:
A commercially available naphthalene-based high-performance water reducing agent Mighty HS (manufactured by Kao Corporation) was used.

[4] Aggregate Coarse aggregate is classified into hard sandstone crushed stone (JIS A 5005: 1993 “crushed stone for concrete and crushed sand” is classified according to the size of the crushed stone 1505, JIS A 1110: 1999 “rough aggregate density and water absorption. The density according to “rate test method” was 2.70 g / cm ^{3, the} water absorption was 0.50%, and the coarse particle rate according to JIS A 1102: 1999 “aggregate screening test method” was 6.67).

The fine aggregate is crushed sand (JIS A 1109: 1999 “Density and water absorption test method of fine aggregate”, the density is 2.66 g / cm ³ and the water absorption is 1.20%, JIS A 1102: 1999 “ The coarse particle ratio according to “Aggregate screening test method” was 2.80).

[Mixing concrete]
Cement, admixture, fine aggregate and coarse aggregate are put into a biaxial forced kneading mixer (capacity: 50 liters), stirred for 30 seconds, then mixed with water and admixture, mixed for 4 minutes, concrete Was made. Of these, the amount of water derived from the dispersant (aqueous solution type) is added to the amount of mixing water (tap water).

[Preparation of specimen]
The strength test column specimen was filled with concrete in a mold having an inner diameter of Φ10 × length of 20 cm, and subjected to vibration compaction by a table vibrator. On the other hand, the centrifugal force molded body (outer diameter Φ20 × length 30 × thickness 4 cm) is charged with a predetermined amount of concrete into the mold, and the conditions are 2G-3min, 10G-1min, 20G-1min and 30G-5min. Was subjected to centrifugal force molding.
The molding condition is judged by the compaction properties in the cross section of the specimen, the smoothness of the inner surface of the cavity (cylindrical) (eg, the presence or absence of undulations), the sludge generation situation, etc., and the compressive strength test of some centrifugally molded specimens It was used for.

[Pre-curing and steam curing]
The cylindrical specimen for strength test and the centrifugal molded specimen were pre-cured at 20 ° C. for 4 hours, heated to 80 ° C. at a heating rate of 20 ° C./h (3 hours), and held at 80 ° C. for 3 hours. After that, it was cooled at a temperature drop rate of 10 ° C./h (6 hours).

[Compressive strength test]
JIS A 1108: 1999 “Compression strength test method for concrete” is used for the strength test column specimens immediately after demolding and subsequently for 7 days in the air. Centrifugal force molding specimens are JIS A 1136: 1993 “centrifugal compacted concrete. The compressive strength test was performed according to the “compression test method”.

Unless otherwise specified, the following conditions were used as reference conditions. In addition, Table 3 shows concrete composition unit amounts (kg / m ³ ) of Examples and Comparative Examples.

[1] Early strength Portland cement (3): density 3.14 g / cm ³ , Blaine specific surface area 4580 cm ² / g, hemihydrate gypsum ratio 51% by mass
[2] High-strength admixture (A): Denka Σ2000 (anhydrous gypsum / amorphous silica mass ratio: 20/80, manufactured by Denki Kagaku Kogyo KK, Blaine specific surface area 4900 cm ² / g)
[3] Dispersant: Mighty HS (manufactured by Kao Corporation, solid content 35.5% by mass)
[4] Aggregate: Maximum size of coarse aggregate (G _MAX ) 15 mm, fine aggregate rate (s / a) 35% by mass
[5] Formulation (unit amount): unit water amount 125 kg / m ³ , early strength Portland cement 550 kg / m ³ , high strength admixture 55 kg / m ³

[Examples 1-7, Comparative Examples 1-3]
Table 3 shows the compressive strength and centrifugal moldability of the vibration molded product when using early-strength Portland cement and a commercially available high-strength admixture and changing the unit amount. In this case, the addition ratio of the high-strength admixture was also changed, and the relationship with the required water / cement mass ratio (W / C) was also evaluated.

Comparative Example 1 (unit cement amount: 480 kg / m ³ , water / cement mass ratio: 26.0%) is not preferable because the strength development of the vibration compacted molded product is low. Further, in Comparative Example 4 (unit cement amount 650 kg / m ³ , water / cement mass ratio 18.5%), although the strength development of the vibration compacted molded article is good, the moldability of the centrifugal molded specimen is not preferable.
Comparative Example 2 (unit water amount 110 kg / m ³ , unit cement amount 560 kg / m ³ , water / cement mass ratio 19.6%) is inferior in slump development even when the dispersant is added more than the standard addition amount. Centrifugal molding specimen could not be molded.
Further, by increasing the addition ratio (A / C) of the high strength admixture, the water / binder ratio (W / (C + A)) could be reduced, and the strength expression of the centrifugal molded specimen increased. In Comparative Example 3, the compression strength of the vibration compacted molded product and the centrifugal molded product did not reach 130 N / mm ² because A / C was small. (Examples 3 to 6, Comparative Example 3).
In Example 7 (unit water amount 120 kg / m ³ , unit cement amount 600 kg / m ³ , water / cement mass ratio 20.0%), although the dispersant is the upper limit of the standard addition amount, The strength development is also good, and it is possible to mold a centrifugal molded specimen.
In Comparative Example 3 (unit water amount 120 kg / m ³ , unit cement amount 650 kg / m ³ , water / cement mass ratio 18.5%), although the strength development of the vibration compacted molded article is good, the molding of the centrifugal molding specimen is performed. Sex is not preferred.

[Examples 8 to 10, Comparative Examples 4 and 5]
Table 4 shows the compressive strength and centrifugal moldability of the specimens when cements having different half-waterification ratios in gypsum of early-strength Portland cement are used.
In Comparative Example 4 (hemihydrate gypsum ratio is 5% by mass), both the vibration compaction molding and the centrifugal force molded product have low strength development. In contrast, in Comparative Example 5 (semihydrogypsum ratio is 95% by mass or more), compaction is achieved. Both properties and compressive strength decreased.

[Examples 11 to 15, Comparative Examples 6 and 7]
Table 5 shows the compression strength of the vibration molded article when the ratio of the high strength admixture type II anhydrous gypsum (AH) and silica fume (SF) was changed and mixed and pulverized. Example 15 is a case where II type anhydrous gypsum powder (3840 cm ² / g) and silica fume (BET specific surface area: 16 m ² / g) are mixed with a V type mixer and are not mixed and pulverized. .

  In Comparative Examples 6 and 7 in which the mass ratio of anhydrous gypsum to silica fume is 10/90 or 95/5, the compressive strength is low, and the appropriate range of the mass ratio of anhydrous gypsum and silica fume of high strength admixture is 15 / It turns out that it is 85-90 / 10. In addition, this mass ratio in the range of 20/80 to 65/35 was able to increase the compressive strength. In Example 15, since the mass ratio of anhydrous gypsum and silica fume is 20/80, it is not mixed and pulverized, so the compressive strength is slightly lower than Example 11 that was mixed and pulverized.

[Examples 16 to 18, Comparative Example 8]
Table 6 shows the compressive strength of the vibration molded specimen when a commercially available high-strength admixture is used. As the high-strength admixture brand, Denka Σ2000, super nonclave and die mix (Examples 16 to 18) are preferable. In other words, an anhydrous gypsum / amorphous silica mass ratio that is too large (Comparative Example 8) is preferable. There wasn't.

It is a figure which shows the infrared absorption spectrum of a typical dispersing agent. It is a figure which shows the differential thermogravimetric analysis result of the amount of hemihydrate gypsum and the amount of dihydrate gypsum.

Claims (5)

A high-strength centrifugal force molding concrete composition comprising early-strength Portland cement, high-strength admixture, dispersant, aggregate and water,
The ratio of hemihydrate gypsum in the gypsum of early strong Portland cement is 10 to 90% by mass, the unit cement amount is 490 to 640 kg / m ³ , and the water / early strong Portland cement mass ratio is 20.0 to 25.5% by mass. ,
The high-strength admixture contains anhydrous gypsum and amorphous silica, and the mass ratio of anhydrous gypsum / amorphous silica is 15/85 to 90/10,
A high-strength centrifugal molding concrete composition, wherein the dispersant is a naphthalene-based dispersant.   The high-strength centrifugal force molding concrete composition according to claim 1, wherein the amorphous silica in the high-strength admixture is silica fume.   The concrete composition for high-strength centrifugal force molding according to claim 1 or 2, wherein the high-strength admixture is obtained by mixing and crushing anhydrous gypsum and silica fume.   The high-strength admixture is contained in an amount of 6 to 25 parts by mass and the dispersant is contained in an amount of 1.0 to 5.5 parts by mass on the basis of an aqueous solution with respect to 100 parts by mass of early-strength Portland cement. The concrete composition for high-strength centrifugal force forming as described.   The concrete composition for high-strength centrifugal force molding according to any one of claims 1 to 4 is mixed, filled into a cylindrical formwork with reinforcing bars, and then subjected to centrifugal force molding, followed by pre-curing and subsequent steam curing. A method for producing a high-strength centrifugal force molding concrete composition which is subsequently demolded and then cured in the air.

Images