JP5807824B2 - Manufacturing method of high strength centrifugal molded concrete pipe - Google Patents

Description

The present invention relates to a method for producing a high-strength centrifugal molded concrete pipe with a compressive strength of 100 N / mm 2 or more.

Conventionally, compression strength are many manufacturing high strength concrete products exceeding 100 N / mm @ 2, often, as a unit powder weight is 650 kg / m ³ or more, such as silicon oxide, aluminum oxide calcium oxide wherein, as a powder to a hydration reaction in an alkaline under cement mainly silica powder and blast furnace slag, fly ash (coal ash), limestone, high strength for concrete, such as rice hull ash is added, and water flour Concrete blended so that the body ratio is 21% or less is used.

However, when trying to manufacture centrifugally formed concrete tubes (hereinafter referred to as fume tubes) using concrete with a unit powder amount of 650 kg / m ³ or more and a water powder ratio of 21% or less. However, the centrifugal moldability is remarkably deteriorated. This is particularly noticeable when fine particles such as silica fume are frequently used to increase the strength of centrifugally formed concrete (for example, Patent Document 1).

  This is because fine particles increase the strength of the concrete, but easily accumulate on the inner surface of the cylinder during centrifugal molding, and this remains as a fragile layer without being compacted by centrifugal force. Even if an inner finishing tool such as a brush or spatula is used. This is because the inner surface is not finished and the centrifugal moldability is remarkably deteriorated.

  In order to solve this problem, a method of adding a sludge reducing agent to concrete has been proposed (for example, Patent Documents 2 and 3).

  In addition, there has been proposed a method in which sludge is not generated by adjusting the centrifugal molding method to reduce high-speed centrifugation G without using a sludge reducing agent (for example, Patent Document 4).

  Furthermore, in general, a method of applying strong vibration using hard concrete has been proposed in order to improve the finish of the inner surface of a centrifugally formed concrete pipe (hereinafter referred to as a fume pipe) (for example, Patent Document 5).

  Other non-patent documents 1 to 4 have papers on high-strength concrete piles and on-site high-strength concrete.

JP 2010-1000050 A Japanese Patent Laid-Open No. 2002-60258 Japanese Patent Laid-Open No. 10-217228 JP 2005-169814 A Japanese Patent Laid-Open No. 06-254831

Annual report of concrete engineering Vol. No. 28 1,2006 "The effect of curing method on long-term physical properties of centrifugally formed high-strength concrete" Annual report of concrete engineering Vol. 31 No. 2,2009 "Repeated compression property of RC column using super high strength concrete" Annual report of concrete engineering Vol. 32 No. 1,2010 "Basic properties of ultra-high-strength concrete" Annual report of concrete engineering Vol. 31 No. 1,2009 “Paper: Strength development of ultra-high-strength concrete with different silica fume substitution rates”

  The production of high-strength concrete products by conventional centrifugal molding that lowers the sludge reducing agent and high-speed centrifugal G described above is mainly used only for piles that do not finish the inner surface, and is used for fume pipes that require an inner surface finish. It has not been.

  The reason is that, in the case of the above method, a soft layer that is not compacted so that a finger can be inserted into the inner surface of the tube after centrifugal molding is formed, so that finishing such as a brush or a spatula is required as an inner surface finish. This is because the inner surface of the fume tube cannot be finished and the formation of the smooth surface is extremely poor.

  For this reason, it can be used only for concrete piles that do not require an inner surface finish, and even if a high-strength concrete pile with a compressive strength exceeding 130 N / mm 2 can be realized, only a product with a compressive strength of about 90 N / mm 2 can be produced with a fume pipe. There was a problem.

  In addition, the method of applying strong vibration using hard concrete for improving the inner surface finish of the fume tube is an effective method for a normal fume tube having a water powder ratio of 30% or more. When the water powder ratio is small and the total amount of powder is large, it is difficult to knead as homogeneous concrete, and it takes a long time to knead. In addition, there is a problem that a weak layer remains, strong vibration not only causes noise problems, but the centrifugal molding equipment is easily painful, and it is difficult to control the hardened concrete.

  The present invention has been made for the purpose of producing a high-strength fume tube having a compressive strength of 100 N / mm 2 or more without using a sludge reducing agent or lowering the high-speed centrifugation G in view of the conventional problems as described above. .

The feature of the invention described in claim 1 for solving the conventional problems as described above is that the coarse aggregate, the fine aggregate, the fine granular admixture for strengthening, the water reducing agent and the cement are mixed with water. A method for producing a high-strength centrifugal molded concrete pipe, in which a concrete pipe is formed by centrifugal molding, wherein the fine particulate admixture contains 50 kg / m ³ or more of silica fume , and the cement or the fine particulate admixture with cement the total powder weight consisting of wood is at 650 kg / m ³ or more, the ratio of water to said total powder weight (water powder ratio) is 21% (wt%, hereinafter the same) or less, fine bone to the total aggregate volume The ratio of aggregate volume (fine aggregate ratio s / a) is 45% or less, the paste fine aggregate ratio α indicating the filling ratio of the cement paste to the fine aggregate voids is 2.0 <α <3.0, and the coarse mortar Mortar coarse aggregate ratio showing the filling rate to the aggregate gap There is a 2.5 <β <3.6, there slump flow value by adjusting the amount of the water reducing agent 400Mm～800mm, to 50cm slump flow time of 15 seconds or more, to.

The feature of the invention described in claim 2 is that, in addition to the structure of claim 1, the water powder ratio is 16% to 21%.

  The feature of the invention described in claim 3 is that, in addition to the configuration of claim 1 or 2, the fine aggregate ratio is 35% to 45%.

In the present invention, the silica fume to the particulate admixture comprises 50 kg / ^{m 3} or more, cement or is in total powder weight consisting of cement and fine particulate admixture is 650 kg / ^{m 3} or more, with respect to said total powder weight The ratio of water (water powder ratio) is 21% (weight%, the same shall apply hereinafter) or less, and the ratio of fine aggregate volume to the total aggregate volume (fine aggregate ratio s / a) is 45% or less. The paste fine aggregate ratio α indicating the filling ratio with respect to the aggregate gap is 2.0 <α <3.0, and the mortar coarse aggregate ratio β indicating the filling ratio with respect to the coarse aggregate gap of the mortar is 2.5 <β <3. The slump flow value is set to 400 mm to 800 mm and the 50 cm slump flow time is set to 15 seconds or longer by adjusting the amount of the water reducing agent added, thereby reducing the use of the sludge reducing agent and the high speed centrifugation G. Without compression strength of 10 A high-strength fume tube having a good moldability that can be finished smoothly without leaving a fragile layer on the inner surface at 0 N / mm 2 or more could be produced.

Graph of the relationship between paste fine aggregate ratio (α) and mortar coarse aggregate ratio (β) and moldability for the formulation examples in Table 2

Next, embodiments of the present invention will be described.
Examples Materials used Cement (C): Ordinary Portland cement Coarse aggregate (a): Crushed stone 2005
Fine aggregate (S): Crushed sand Admixture (Add): Fine granular admixture for strengthening (Product name: Cerapower CPS, manufactured by D Shi Co., Ltd.)
Water reducing agent (PX): High performance AE water reducing agent (Product name: Leo Build 8000S BASF Pozzolith Co., Ltd.)

Formulation examples are shown in Table 1.

Table 1

Kneading condition: empty kneading (coarse aggregate + fine aggregate + cement + admixture) 30 seconds after water injection (water + water reducing agent) 360 seconds kneading Centrifugal force (G): low speed (5G) 1 minute, medium speed (15G ) 1 minute, high-speed (35G) 7-minute curing conditions: steam curing, preliminarily 4 hours-temperature rise (20 ° C / hour)-maximum temperature 70 ° C-6 hours hold-natural cooling, after mold removal, air curing

  As a result of manufacturing the fume tube in accordance with the above conditions, it was possible to form an internal brush finish with a good shape and to manufacture a high-strength fume tube having a compressive strength of 100 N / mm 2 or more.

In addition, in the said Example, a flow value is based on JIS A1150 "the slump flow test method of concrete."
Comparative test example

As shown in Table 2, blending Nos. With different water powder ratio, fine aggregate ratio, admixture addition amount, and flow value were different. While comparing the tests of formability and compressive strength for 1-30, the blended examples of centrifugally formed high-strength concrete piles and cast-in-place concrete shown in the papers of Non-Patent Documents 1 to 4 were tested as reference examples. In addition, the compounding of the Example of Table 1 is test example No. 2 in Table 2. 13 is shown. The moldability shown in Table 2 means that the fragile layer can be finished smoothly without leaving the inner surface, ◯ indicates good, Δ indicates slightly poor, and x indicates poor.

  Reference Example 1 is a combination of centrifugal high-strength concrete piles shown in Non-Patent Document 1, Reference Example 2 is a combination of ultra-high-strength concrete RC columns shown in Non-Patent Document 2, Reference Example 3 Is a blend of ultra-high strength concrete shown in Non-Patent Document 3, and Reference Examples 4 to 6 are blends of ultra-high-strength concrete using silica fume shown in Non-Patent Document 4.

Table 2

ここに，
α：ペースト細骨材比
β：モルタル粗骨材比
Ｗ：単位水量 ｋｇ／ｍ3
Ｃ：単位セメント（粉体）量 ｋｇ／ｍ3
Ｓ：単位細骨材量 ｋｇ／ｍ3
Ｇ：単位粗骨材量 ｋｇ／ｍ3
WS,WG：表乾状態の細骨材，粗骨材の単位容積質量
VS，VG：表乾状態の細骨材，粗骨材の空隙率
ρc，ρs：セメント，細骨材の密度 The calculation of the paste fine aggregate ratio (α) and the mortar coarse aggregate ratio (β) in Table 2 is based on the following formula.

here,
α: Paste fine aggregate ratio β: Mortar coarse aggregate ratio W: Unit amount of water kg / m 3
C: Unit cement (powder) amount kg / m3
S: Unit fine aggregate amount kg / m3
G: Unit coarse aggregate kg / m3
WS, WG: Unit volume mass of fine and coarse aggregates in the dry state
VS, VG: Porosity of fine aggregate and coarse aggregate ρc, ρs: Density of cement and fine aggregate

  FIG. 1 is a graph showing the relationship between the paste fine aggregate ratio (α) and the mortar coarse aggregate ratio (β) and the formability of the blending examples and reference examples in Table 2.

  From this result, when the paste fine aggregate ratio α is in the range of 2.0 <α <3.0 and the mortar coarse aggregate ratio β is in the range of 2.5 <β <3.6, the moldability is good. It has been found.

  In addition, in FIG. 1, the paste fine aggregate ratio α and the mortar coarse aggregate ratio β and the relationship between the quality of the moldability and the water powder ratio of 22% or more are indicated by white circles. In Examples with a water powder ratio of 21% or less, those with good moldability are indicated by black circles, and those with poor moldability are indicated by black triangles. The examples of high-strength concrete on-site casting and the composition of high-strength piles are shown in black diamonds.

  As seen from this, those having good moldability have a paste fine aggregate ratio α of 2.0 <α <3.0 and a mortar coarse aggregate ratio β of 2.5 <β <3.6. I understand. Those within the range but having poor moldability have a slump flow value of less than 400. All of the reference examples were poor in centrifugal formability, and were outside the above ranges of α and β.

When the water powder ratio was 21% or less and the fine aggregate ratio was 35 to 45% and the flow value was 400 or more, the moldability was good, but the fine aggregate ratio was 50%. In the above case (Formulation No. 18), the moldability was not preferable.

  On the other hand, in the case where the water powder ratio is 30% or more, there is not enough cement paste to sufficiently cover the aggregate, so when the flow value increases, the aggregate and cement paste are separated and centrifuged. Aggregate is exposed on the inner surface, and the moldability deteriorates. (Formulation Nos. 3 and 6) In this case, the 50 cm slump flow time was 15 seconds or less. The 50 cm slump flow time is the time until the slump flow reaches 50 cm, and the shorter this time is, the more the separation of the aggregate and the cement paste is.

In the case where the water powder ratio having a target strength of a compressive strength of 100 N / mm 2 or more is 21% or less and the total powder amount is 650 kg / m ³ or more, the formulation number of Example As shown in 13, 15-17, 19-23, and 26-30, the centrifugal moldability is improved by increasing the flow value.

That is, the concrete in which this flow value can be realized is added with 50 kg / m ³ or more of silica fume for increasing the strength and has a high separation resistance, for example, a silica fume premix cement manufactured by Taiheiyo Cement Co., Ltd. It is preferable to use a high-strength admixture (trade name: Cerapower CPS, manufactured by Daishi Co., Ltd.) as an admixture.

  Further, as the water reducing agent, a polycarboxylic acid-based dispersant having a high dispersion effect in a small amount and excellent in long-term dispersion stability is used, and preferably Leo Build 8000S manufactured by BASF Pozzolith Co., Ltd. is preferably used.

  In the relationship between the paste fine aggregate ratio α and the mortar coarse aggregate ratio β and the centrifugal moldability shown in Table 2, when the water powder ratio is 21% or less, No. 17 has a paste fine aggregate ratio α of 2.06 and a mortar coarse aggregate ratio β of 3.16. No. 18 had a paste fine aggregate ratio α of 2.23 and a mortar coarse aggregate ratio β of 4.03, and the centrifugal moldability was not good.

  In addition, blending No. In No. 23, the paste fine aggregate ratio α is 2.87, the mortar coarse aggregate ratio β is 3.13, and the centrifugal moldability is good. No. 24 had a paste fine aggregate ratio α of 3.43 and a mortar coarse aggregate ratio β of 2.84, and the centrifugal moldability was not good.

  The reason for this is that mortar enters the voids of the coarse aggregate by centrifugal molding, and cement paste enters the mortar. In No. 18, the fine aggregate ratio was too high, and the mortar coarse aggregate ratio β was 4.03, and the excess mortar was too large with respect to the voids in the coarse aggregate. No. 24 is considered to be unable to be molded because the paste fine aggregate ratio α is 3.43 and the excess paste is too large for the fine aggregate gap.

From these results, it was found that the paste fine aggregate ratio α is appropriate in the range of 2.0 <α <3.0 and the mortar coarse aggregate ratio β is in the range of 2.5 <β <3.6.

Claims (3)

Coarse aggregate, fine aggregate, fine granular admixture for strengthening, water reducing agent and cement, add water and knead,
A method for producing a high-strength centrifugal molded concrete pipe that forms a concrete pipe by centrifugal molding,
Wherein comprises a silica fume to particulate admixture 50 kg / m ³ or more, and the cement or is in total powder weight consisting of cement and fine particulate admixture is 650 kg / m ³ or more, of water to the said total powder weight The ratio (water powder ratio) is 21% (weight%, the same shall apply hereinafter) or less, the ratio of the fine aggregate volume to the total aggregate volume (fine aggregate ratio s / a) is 45% or less, and the fine aggregate of cement paste The paste fine aggregate ratio α indicating the filling ratio with respect to the gap is 2.0 <α <3.0, and the mortar coarse aggregate ratio β indicating the filling ratio with respect to the coarse aggregate gap of the mortar is 2.5 <β <3.6. And a slump flow value of 400 mm to 800 mm and a 50 cm slump flow time of 15 seconds or more by adjusting the amount of the water reducing agent added. The method for producing a high-strength centrifugal molded concrete pipe according to claim 1, wherein the water powder ratio is 16% to 21%.   The method for producing a high-strength centrifugal molded concrete pipe according to claim 1 or 2, wherein the fine aggregate ratio is 35% to 45%.

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