JP2010070439A - Concrete composition for plain concrete structure in port - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a concrete composition for a plain concrete structure in port in which bleeding is hard to occur without depending on temperature upon concrete structure production, and which has satisfactory workability as well in spite of the use of a large quantity of copper slag as a fine aggregate for increasing specific gravity. <P>SOLUTION: Regarding the blending ratio of the concrete composition for a plain concrete structure in port having a slump of 3 to 12 cm, under the unit water quantity of 140 to 165 kg/m<SP>3</SP>, cement is controlled to 250 to 350 kg/m<SP>3</SP>, fine aggregate is controlled to 900 to 1,100 kg/m<SP>3</SP>, coarse aggregate is controlled to 950 to 1,200 kg/m<SP>3</SP>and an admixture is controlled to 1.5 to 5.25 kg/m<SP>3</SP>, and the fine aggregate is composed of copper slag of 70 to 90 wt.%, limestone fine powder of 5 to 25 wt.% and natural sand of 5 to 25 wt.%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a concrete composition for an unreinforced concrete structure used in a harbor, for example, a wave-dissipating block, a covering block, a rooting block or the like.

  In an unreinforced concrete structure used in a harbor or the like, especially in the sea or on the coast, a concrete composition containing metal slag is often used to increase the specific gravity. In particular, copper slag has a higher specific gravity than blast furnace slag and the like, and is very suitable for blending into a concrete composition for harbor unreinforced concrete structures as fine aggregate.

As a method for producing concrete in which copper slag (high specific gravity sand) is mixed in large quantities as fine aggregate, copper slag (high specific gravity sand) is mixed at a ratio of 30 to 100% by weight in the total fine aggregate. There exists a manufacturing method of the high fluidity concrete whose slump flow is 45 cm or more characterized by doing (for example, refer to patent documents 1, claims 1-2). The high-fluidity concrete produced by this manufacturing method is a concrete that does not require compaction work because of its high fluidity. However, this high-fluidity concrete requires a large amount of water (175 kg / m ³ ) and a large amount of high-pressure concrete to increase the slump flow. Since a performance water reducing agent (10.3 kg / m ³ ) is blended (Patent Document 1, Paragraph No. 0023, Table 1), it is difficult to use such a blend for a concrete composition having general fluidity. .

  In addition, when the blending ratio of copper slag in fine aggregate is increased, copper slag has less fines, and since it is glassy and has a low water absorption rate, the unit water volume tends to increase and bleeding is increased. is there. When there is a lot of bleeding in this way, the porosity in the manufactured wave-dissipating block or coating block is increased, and the quality of the product is impaired. There is a problem that a water channel is formed by rising upward along the formwork, the black copper slag is exposed, a large number of black streaks are formed on the concrete surface, and the appearance is remarkably impaired. However, although the invention described in Patent Document 1 uses a large amount of water and bleeding becomes a problem, no investigation has been made on this point.

  In order to solve such a problem of bleeding, there is a cement using a fine aggregate containing blast furnace granulated slag fine aggregate and limestone crushed sand (see, for example, Patent Document 2, claims 1 and 5). In this invention, it is going to suppress bleeding by adding limestone crushed sand, but as the blending ratio, blast furnace granulated slag fine aggregate: limestone crushed sand = 5 parts by weight to 80 parts by weight: 95 parts by weight to 20 parts by weight is very much. A wide range is described (refer to claim 4 of Patent Document 2), and it is merely shown that any mixing ratio may be used.

  Also, when using copper slag, copper slag is not self-hardening like blast furnace granulated slag, and has the characteristics of glassy and low water absorption rate, so it should be the same blending ratio as blast furnace granulated slag Is difficult. Further, since crushed limestone contains a large amount of fine powder, the slump tends to be small, and simply adding crushed limestone sand to the blast furnace granulated slag fine aggregate has a problem that fluidity is lowered and workability is lowered.

JP 7-166705 A JP 2000-302499 A

  In view of the above-mentioned problems, the present invention hardly causes bleeding regardless of the temperature at the time of manufacturing a concrete structure, despite the fact that a large amount of copper slag is used as a fine aggregate in order to increase the specific gravity, and has good workability. It aims at providing the concrete composition for harbor unreinforced concrete structures.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor found that a copper slag having a larger specific gravity than a blast furnace slag or the like as a metal slag is blended in a fine aggregate by 70 to 90% by weight. It can be a concrete composition with high specific gravity suitable for blocks, and copper slag is low in fine powder, so if mixed in large quantities, the bleeding will increase and the quality of the product will be impaired or water will be formed and it will be black Although there is a problem that copper slag is exposed and the appearance is impaired, bleeding can be suppressed if limestone fine powder containing a lot of fine fine powder is blended as a fine aggregate in an amount of 5 to 25% by weight. This limestone fine powder has the effect of suppressing heat generation due to the hydration reaction, so it prevents cracking due to heat generation when mass concrete such as wave-dissipating blocks are produced. On the other hand, the limestone fine powder is a fine fine powder, so the slump tends to be remarkably low and the workability may be lowered. However, if natural sand such as land sand is blended in an amount of 5 to 25% by weight, The present invention has been completed by investigating that workability is not lowered.

That is, the present invention relates to a concrete composition for a harbor unreinforced concrete structure having a slump of ^{3 to} 12 cm, a cement of 250 to 350 kg / m ³ under a unit water volume of 140 to 165 kg / m ³ , a fine aggregate It consists of 900-1,100 kg / m ³ , coarse aggregate 950-1,200 kg / m ³ and admixture 1.5-5.25 kg / m ³ , fine aggregate 70-90% by weight copper slag, limestone fine It is a concrete composition for harbor unreinforced concrete structure characterized by being comprised from 5 to 25 weight% of powder and 5 to 25 weight% of natural sand.

Concrete composition according to the present invention, the slump is a concrete composition for harbor unreinforced concrete structure is 3～12Cm, under unit water 140~165kg / ^{m 3,} a cement 250~350kg / ^{m 3} , Consisting of fine aggregate 900-1,100 kg / m ³ , coarse aggregate 950-1,200 kg / m ³ and admixture 1.5-5.25 kg / m ³ , and high specific gravity copper slag in the fine aggregate 70-90% by weight is added to the concrete composition so that it can be made into a concrete composition with high specific gravity suitable for wave-dissipating blocks and coating blocks, and copper slag has a small amount of fine powder, so when mixed in large quantities, there is much bleeding. However, there is a problem that the quality of the product is impaired or the appearance of the copper slag that is black is exposed due to the formation of a water channel, and the appearance is impaired. Since 5 to 25% by weight of limestone fine powder containing a large amount is blended as fine aggregate, bleeding can be suppressed and this limestone fine powder has an effect of suppressing heat generation due to hydration reaction. It is possible to prevent cracking due to heat generation when producing mass concrete such as limestone, while limestone fine powder is a fine fine powder, so slump tends to be extremely low, and workability may be reduced, Since natural sand such as land sand is blended in an amount of 5 to 25% by weight, workability is not lowered.

  In the concrete composition for a harbor unreinforced concrete structure according to the present invention, the copper slag contained in the fine aggregate is 70 to 90% by weight when the copper slag is less than 70% by weight. It is difficult to obtain a concrete composition having a large specific gravity suitable for a block or a covering block, and when it exceeds 90% by weight, bleeding is increased and a water channel is formed in the produced wave-dissipating block or covering block, resulting in a dense structure. The quality of the product deteriorates due to the decrease in actuality and the concrete subsidence also causes subsidence cracks, and due to a significant increase in bleeding, liberated water with low specific gravity is released along the formwork during curing. As a result, the water channel is formed, the black copper slag is exposed, many black streaks are formed on the concrete surface, and the appearance is notably impaired. This is because even delayed bleeding end time, splicing out of the concrete, the finishing of the concrete surface, workability is deteriorated impact like mold demolding further reduced frost resistance of concrete.

  In addition, when the grain size of copper slag changes greatly, it becomes difficult to make the concrete of a predetermined quality. Therefore, when copper slag having a grain size division of 0.3 to 5.0 mm is used, the quality of the concrete composition is reduced. This is preferable because it is easy to maintain. In addition, in JIS A 5011-3, which defines the particle size classification of copper slag, not only the particle size but also the chemical composition and physical / chemical properties are required to satisfy certain conditions. It is more preferable that the copper slag conforms to the JIS standard.

In the concrete composition for harbor unreinforced concrete structure according to the present invention, the amount of fine limestone powder contained in the fine aggregate is 5 to 25% by weight. It cannot be sufficiently suppressed, and heat generation due to hydration reaction cannot be sufficiently suppressed, so that cracking due to heat generation when mass concrete such as a wave-dissipating block is easily generated, and limestone fine powder is 25 This is because, if the weight percentage is exceeded, the fine limestone powder is a fine fine powder, so that the slump becomes extremely low and the workability is lowered. Moreover, it is because there is a risk that the concrete surface is likely to be dried during concrete pouring and a cold joint is generated. As such limestone fine powder, those having a specific surface area of about 2,500 to 10,000 cm ² / g can be preferably used.

  In addition, in order to prevent the slump from becoming too small due to limestone fine powder containing a lot of very fine fine powder, in the concrete composition for harbor unreinforced concrete structure according to the present invention, natural sand is used as fine aggregate. Use 5-25% by weight. The reason why the amount of natural sand contained in the fine aggregate is 5 to 25% by weight is that if it is less than 5% by weight, it is not possible to prevent the slump from being reduced by the fine limestone powder and the fluidity from being lowered. When the natural sand contained in the aggregate exceeds 25% by weight, the proportion of copper slag in the fine aggregate is relatively lowered, and a concrete composition having a sufficiently high specific gravity cannot be obtained. is there. Moreover, land sand etc. can be utilized as such natural sand.

  Further, the mixing ratio of such copper slag, fine limestone powder and natural sand in the fine aggregate is set to 80 to 90% by weight of copper slag, 5 to 10% by weight of fine limestone powder and 5 to 10% by weight of natural sand. For example, a concrete composition having a high specific gravity suitable for a wave-dissipating block can be obtained, which is preferable.

  As the coarse aggregate used in the concrete composition according to the present invention, those having a maximum dimension of about 40 mm can be more preferably used. This is because the concrete composition according to the present invention is a concrete composition used for unreinforced concrete, so that a relatively large coarse aggregate can be used and a larger maximum dimension in the coarse aggregate provides the same slump. This is because the amount of unit water required for this can be reduced. In addition, since the workability is lowered when the particle size distribution of the coarse aggregate is discontinuous, it is preferable to use those defined by JIS, for example, using crushed stone 4020 or crushed stone 4005 defined by JIS A 5005. Or what added the crushed stone 2505, the crushed stone 2005, and the crushed stone 1505 to these can be used.

Further, the respective the unit amount for the fine aggregate and coarse aggregate was 900~1,100kg / ^{m 3} and 950~1,200kg / ^{m 3,} the unit amount of coarse aggregate is less than 950 kg / ^{m 3} In this case, the fine aggregate unit amount must be more than 1,100 kg / m ³ , and as a result, the fine aggregate rate becomes too large. As a result of worsening and lowering workability, bleeding also increases and adversely affects the strength of the concrete after hardening. Further, if the unit amount of coarse aggregate is more than 1,200 kg / m ³ , the unit amount of fine aggregate must be less than 900 kg / m ³ , so that the fine aggregate rate becomes too small. This is because the concrete becomes rough and material separation is likely to occur, resulting in a decrease in workability.

The concrete composition for harbor unreinforced concrete structure according to the present invention, under the unit water 140~165kg / ^{m 3,} the cement 250~350kg / ^{m 3} and admixtures 1.5~5.25kg / ^{m 3} As a result, the water-cement ratio is about 40-65%. The reason for this blending ratio is that when the water-cement ratio exceeds 65%, durability and strength are easily lowered, and when it is less than 40%, workability is lowered.

  Further, since the concrete composition according to the present invention is used as harbor concrete or mass concrete, the cement used is preferably a blast furnace cement that can suppress heat of hydration and prevent cracking, etc. Low heat Portland cement, fly ash cement, or the like that can be suppressed can be used, and ordinary Portland cement that is easily available may be used. Moreover, as an admixture used for the concrete composition which concerns on this invention, AE water reducing agent, a high performance AE water reducing agent, etc. can be used.

  Although the concrete composition according to the present invention uses a large amount of copper slag as a fine aggregate in order to increase the specific gravity, bleeding hardly occurs regardless of the temperature at the time of manufacturing the concrete structure, and the workability is good. It is a concrete composition for harbor unreinforced concrete structures. Therefore, with respect to a general concrete composition not containing copper slag and having little bleeding and the concrete composition according to the present invention, when the temperature at the time of manufacturing the concrete structure is summer and winter, bleeding and bleeding occurrence time (start To the end time), the concrete composition according to the present invention shows less bleeding than a general concrete composition. Even if there is little bleeding, if the occurrence time of bleeding is long, the development of concrete strength will be slow, water will be generated on the concrete surface, the quality will deteriorate, and it will take time to finish the concrete surface and remove the formwork. Sex is reduced.

In each example and each comparative example, blast furnace cement type B (manufactured by Mitsubishi Materials Corporation) marketed as cement was used. In addition, copper slag in fine aggregate is copper slag (manufactured by Onahama Smelting Co., Ltd.) with a particle size classification of 0.3 to 5.0 mm and a density of about 3.5 mm. 10,000 cm ² / g (trade name: MC-100, manufactured by Asahi Mine Company) or specific surface area of about 7,500 cm ² / g (product name: MC75, manufactured by Asahi Matter Company) or specific surface area of about 6,360 cm ² / g ( Asahi-Kou Suesha brand name: O-4400) was used. Further, as natural sand (land sand), land sand having a particle size of 5 mm or less (from Kashima, Ibaraki) and crushed sand having a particle size of 5 mm or less (from Kasama, Ibaraki) were used. In addition, crushed stone 4020 and crushed stone 2005 (both from Kasama, Ibaraki) are used for the coarse aggregate, tap water is used for the water, respectively, and the AE water reducing agent (No. 70 and No. 78P manufactured by BASF Pozzolith Co., Ltd.) is used for the admixture. ) Was added to the extent that adequate slump and air volume could be secured.

Since Comparative Example 1 and Comparative Example 2 of concrete generally not containing copper slag and Examples 1 to 3 and Examples 4 to 5 containing a large amount of copper slag differ greatly from each other, the nominal strength Comparison was made between the amount of bleeding of concrete and the time of occurrence of bleeding when blended so as to be 21 N / mm ² , target slump 8 cm, and target air amount 4%. The comparison was performed in Comparative Example 1 and Examples 1 to 3 when the room temperature was high (about 25 ° C.), and Comparative Example 2 and Examples 4 to 5 when the room temperature was low (around 10 ° C.). When the concrete temperature after kneading, which is closely related to room temperature, is high, the amount of bleeding decreases and the bleeding occurrence time is shortened. When the concrete temperature is low, the amount of bleeding increases and bleeding occurs. This is because time tends to be longer.

Comparative Example 1 is a general concrete composition containing no copper slag having a nominal strength of 21 N / mm ² , a target slump of 8 cm, and a target air amount of 4% in summer (room temperature 25 ° C.). When the concrete was kneaded, the slump was 7.5 cm, the air content was 3.6%, the concrete temperature was 25.0 ° C., the bleeding amount was 0.17 cm ³ / cm ² , and the bleeding occurrence time was 210 minutes. . On the other hand, Example 1 is a concrete composition with a target slump of 8 cm and a copper slag weight mixing ratio of 84% with a target air amount of 4%. When the concrete is kneaded, the slump is 7.0 cm, the amount of air is 3.3%, the concrete temperature is 25.0 ° C., and the concrete composition can obtain substantially the same strength and workability as Comparative Example 1. In Example 1, although the unit water amount was larger than that in Comparative Example 1, the bleeding amount was 0.15 cm ³ / cm ² , and the bleeding amount was smaller than that in Comparative Example. In addition, the bleeding occurrence time was a little longer as 270 minutes, but the workability was satisfactory.

Next, compared with Example 1, Example 2 increases the amount of natural sand by reducing the amount of fine limestone powder to about half. Also in this case, the bleeding amount was 0.16 cm ³ / cm ² which was substantially the same as in Comparative Example 1, and the bleeding occurrence time was 280 minutes, which was substantially the same as in Comparative Example 1.

In addition, Example 3 has a mixing ratio almost the same as that of Example 1 in which the type of limestone fine powder is changed, and the type of limestone fine powder varies from a specific surface area of about 7,500 cm ² / g to a specific surface area of 6,360 cm ² / g. It has been changed to. Although the slump is larger than that in Example 1 due to the increase in the unit water amount, the bleeding amount is 0.15 cm ³ / cm ² as in Example 1, and the bleeding occurrence time can be shortened to 240 minutes, which is almost the same as in Comparative Example 1. It was about the same.

Comparative Example 2 is a general concrete composition containing no copper slag having a nominal strength of 21 N / mm ² , a target slump of 8 cm, and a target air amount of 4% in winter (room temperature 7 ° C.). When the concrete was kneaded, the slump was 9.0 cm, the air amount was 4.7%, the concrete temperature was 9.0 ° C., the bleeding amount was 0.29 cm ³ / cm ² , and the bleeding occurrence time was 550 minutes. On the other hand, Example 4 is a concrete composition including the same room temperature as Comparative Example 2 and the same mixing ratio as Example 1, and a target slump of 8 cm and a target air amount of 4% and a copper slag weight mixing ratio of 84%. When the concrete is kneaded, the slump is 9.0 cm, the amount of air is 4.8%, the concrete temperature is 9.0 ° C., and it is a concrete composition that can obtain substantially the same strength and workability as Comparative Example 2. In Example 4, although the unit water amount was larger than that in Comparative Example 2 containing no copper slag, the bleeding amount was 0.24 cm ³ / cm ² , and the bleeding amount was smaller than that in Comparative Example 2. Moreover, although the bleeding occurrence time was slightly increased to 650 minutes, the workability was satisfactory.

Next, Example 5 is a mixing ratio almost the same as that of Example 4 in which the type of limestone fine powder was changed, and the type of limestone fine powder was changed from a specific surface area of about 7,500 cm ² / g to a specific surface area of 10,000 cm ² / g. It has been changed to. The slump was smaller than in Example 4, the bleeding amount was 0.13 cm ³ / cm ² , the bleeding occurrence time was 360 minutes, and the bleeding amount was smaller than in Comparative Example 2, and the bleeding occurrence time was also shortened. This is the concrete temperature at room temperature of 15 ° C. When compared with Comparative Example 1 at room temperature of 25 ° C., the amount of bleeding was reduced, but the bleeding occurrence time was increased.

  Thus, the concrete composition according to the present invention is a concrete composition for harbor unreinforced concrete structures used for wave-dissipating blocks, covering blocks, rooting blocks, and the like, and is used to increase specific gravity. In spite of the use of a large amount of copper slag, bleeding is unlikely to occur, and workability is not impaired because it is formulated so as to form a predetermined slump.

Claims (1)

A concrete composition for a harbor unreinforced concrete structure having a slump of 3 to 12 cm, with a unit water volume of 140 to 165 kg / m ³ , a cement of 250 to 350 kg / m ³ and a fine aggregate of 900 to 1,100 kg. / M ³ , coarse aggregate 950-1,200 kg / m ³ and admixture 1.5-5.25 kg / m ³ ,
A concrete composition for harbor unreinforced concrete structures, wherein the fine aggregate is composed of 70 to 90% by weight of copper slag, 5 to 25% by weight of fine limestone powder, and 5 to 25% by weight of natural sand.