JP5981969B2 - Method for producing concrete member - Google Patents

Description

The present invention relates to a method of manufacturing a concrete member.

  High-strength concrete is obtained by increasing the compressive strength by reducing the weight ratio of water to the binder (water binder ratio) and densifying the concrete structure after hardening.

  High strength concrete before hardening is required to have high fluidity in order to fill the formwork densely. However, if the fluidity is excessively increased, the aggregate and the cement paste are separated.

Therefore, conventionally, it is intended to produce high-quality high-strength concrete by appropriately using a water-reducing agent (high-performance water-reducing agent, AE water-reducing agent, high-performance AE water-reducing agent and the like in JIS A 6204).
For example, in Non-Patent Document 1, for the purpose of providing high-strength concrete having a design standard strength of 150 to 200 N / mm ² , cement, two types of special polycarboxylic acid-based high-performance water reducing agents, fine aggregates, And a mixture of coarse aggregate, polypropylene fiber, and steel fiber is disclosed.

In Patent Document 1, as an ultra-high strength, high fluidity concrete design strength is 200 N / mm ^2, and the hydraulic binder of 300~400L / ^{m 3,} the coarse aggregate 250~350L / ^{m 3,} Containing 100-200 L / m ³ artificial high-density fine aggregate and 0.5-4.0 wt% chemical admixture (polycarboxylic acid-based high performance AE water reducing agent) of hydraulic binder Is disclosed.

JP 2009-51682 A

Kenro Mitsui, Masao Kojima, Toshio Yonezawa, Masahiro Hamada, Hirozo Mitsuhashi, Architectural Institute of Japan Vol. 16 No. 32 “Development of design standard strength 150-200N / mm2 ultra high strength fiber reinforced concrete and application to actual building Application ", Architectural Institute of Japan, February 20, 2010, pp. 21-26

  By adopting such ultra-high-strength concrete for a concrete structure, it is possible to increase the height of the concrete structure and reduce the cross-section of the member for improving the degree of freedom of space. Therefore, in recent years, concrete with higher strength is being demanded for the purpose of further increasing the height of concrete structures.

Therefore, the present invention is, without reducing the workability, compressive strength and to provide a method for manufacturing a can with the concrete member to build a concrete member of more than 200 N / mm ^2.

In order to solve the above problems, the production method of the concrete member of the invention, a pouring step of pouring high strength concrete, the high strength concrete and a first curing step for autoclave curing, after the first curing step And a second curing step of performing dry heating curing at 200 ° C.
Here, wherein the high-strength concrete, 1 m ³ and the low thermal cement is added in the range of per 260～310L, fly ash or silica flour is added in the range of 1 m ³ per 120~170L, 1m ³ per and silica fume, which is added in the range of 70～100L, and fine aggregate was added in a range of 1 m ³ per 150~250L material, and coarse aggregate that are added in the range of 1 m ³ per 90～120L, wherein A concrete mixture formed by mixing low heat cement and water added so that the weight ratio to the binder containing the fly ash or silica stone powder and the silica fume is 11 to 13%, and the concrete mixture Steel fibers added to the outer volume ratio of 0.5 to 2%, and polygonal cross-section and twisted polyp And pyrene fibers, using what was included.

According to such a method for producing a concrete member, a concrete member having a compressive strength of 230 N / mm ² or more can be produced.

According to the production method of concrete member of the invention, without reducing the workability, compressive strength it is possible to construct a concrete member of more than 200 N / mm ^2.

It is a graph which shows the relationship between Ca / Si ratio of the high strength concrete which concerns on this embodiment, and compressive strength.

Hereinafter, preferred embodiments of the present invention will be described.
The high-strength concrete according to the present embodiment is composed of a mixture including at least a binder, water, fine aggregate, and coarse aggregate.

The binder includes low heat cement and fly ash or silica powder and silica fume. As the binder, a premixed product previously mixed in a predetermined composition may be used, or may be mixed during concrete production. Each powder contains Ca (calcium) and Si (silicon), and the optimum mixing balance of each powder considered from the chemical composition may vary depending on the curing temperature. According to this, as shown in FIG. 1, a compressive strength of 230 N / mm ² or more can be ensured.

The low heat cement is so-called low heat Portland cement. Low heat Portland cement has the characteristics that the calorific value of hydration is small and the long-term strength is large as compared with medium heat Portland cement.
In this embodiment, the low heat cement is added within a range of 260 (more preferably 290) to 310 L (liter) per m ^{3 of} the concrete mixture excluding fine aggregate and coarse aggregate.
Here, when the addition amount of the low heat cement is out of the range of 260 to 310 L / m ³ , the balance of the chemical composition and the particle size distribution of each powder (low heat cement, fly ash or quartzite powder, silica fume) is lost. The strength may not be achieved.

As fly ash, JIS standard type II so-called concrete fly ash is used. In the present embodiment, fly ash (silica fine powder) is added within a range of 120 (more preferably 150) to 170 L per 1 m ^{3 of} the concrete mixture. In place of fly ash, fine silica powder (cumulative 50% particle diameter of about 10 μm or less) may be used.
Here, when the addition amount of fly ash is out of the range of 120 to 170 L / m ³ , the balance of the chemical composition and the particle size distribution of each powder (low heat cement, fly ash or quartzite powder, silica fume) is lost, and high The strength may not be achieved.

As the silica fume, powdery so-called concrete silica fume is used.
In this embodiment, silica fume is added within a range of 70 (more preferably 80) to 100 L per 1 m ^{3 of} the concrete mixture.
Here, when the addition amount of silica fume is out of the range of 70 to 100 L / m ³ , the balance of the chemical composition and particle size distribution of each powder (low heat cement, fly ash or silica stone powder, silica fume) is lost, and the high strength is obtained. May not be achieved.

Water is added to the binder containing low heat cement, fly ash (silica stone powder) and silica fume so that the weight ratio is 11 to 13%.
Here, if the weight ratio of water to the binder is less than 11%, kneading may not be possible. On the other hand, if the weight ratio of water to the binder is greater than 13%, high strength may not be achieved.

As the fine aggregate, silica sand No. 6 is used in the present embodiment, but the material constituting the fine aggregate is not limited as long as the particle diameter is 0.5 to 0.6 mm or less, for example, Natural aggregates such as river sand and mountain sand, crushed sand, blast furnace slag fine aggregate, etc. can also be used.
In this embodiment, fine aggregate is added within a range of 150 to 250 (more preferably 200) L per 1 m ^{3 of} the concrete mixture.
Here, if the amount of fine aggregate added is less than 150 L / m ^{3, the} amount of coarse aggregate that is replaced from the fine aggregate in a compounded manner becomes too large, and good fluidity can be obtained by interference with steel fibers. There is a risk of disappearing. On the other hand, if the amount of fine aggregate added is greater than 250 L / m ³ , shrinkage as concrete may increase.

Gravel or crushed stone is used for coarse aggregate. In this embodiment, crushed stone (Otsuki crushed stone) is used, and is added within a range of 90 (more preferably 100) to 120 L per 1 m ^{3 of} the concrete mixture.
Here, if the amount of coarse aggregate added is less than 90 L / m ³ , shrinkage as concrete may increase. On the other hand, when the addition amount of coarse aggregate is larger than 120 L / m ³ , there is a possibility that good fluidity cannot be obtained due to interference with steel fibers and the like.

The steel fiber is mixed with the concrete mixture so that the outer volume ratio is about 0.5 to 2%.
In this embodiment, the length is 13 ± 2 mm, the diameter is 0.16 mm, the cross-sectional area is 0.020 m ² , and the mass is 204.1 mg ± 15% per 100 pieces. In addition, the shape dimension of steel fiber is not limited, For example, you may use a length of 6 +/- 2mm.
Here, if the volume ratio of the steel fibers is less than 0.5%, the reinforcing effect of the fibers decreases, and there is a possibility that the strength cannot be obtained satisfactorily. On the other hand, if the volume ratio of the steel fibers is larger than 2%, the fluidity of the concrete may be greatly reduced.
Steel fibers are added for the purpose of supplementing strength reduction due to the addition of polypropylene fibers described later.

In this embodiment, the steel fiber is appropriately selected from known steel fibers such as high-tensile steel fibers having a tensile strength of 2000 N / mm ² or more, amorphous steel fibers, and stainless steel fibers.
The shape of the steel fiber is not limited, and it is possible to use a deformed cross-sectional diameter shape in addition to a deformed cross section such as a circular cross section, a rectangular cross section, or a polygonal cross section.

Polypropylene fiber is mixed so that it may become 0.1%-0.6% by the volume ratio of outer division with respect to a concrete mixture.
In this embodiment, a polypropylene fiber having a diameter of 48 μm and a length of 20 mm is used, but the polypropylene fiber is not limited in size, for example, having a diameter of 18 μm and a length of 10 mm.
Here, if the volume ratio of the polypropylene fiber is less than 0.1%, the effect of the refractory fiber is reduced, and the explosion suppressing effect at the time of fire may not be obtained. On the other hand, when the volume ratio of the polypropylene fibers is larger than 0.6%, the fluidity of the concrete is greatly lowered and high strength may not be obtained. In addition, when 0.55% polypropylene fiber is added in an externally divided volume ratio, a decrease in compressive strength of about 30 N / mm ² occurs.

  The shape of the polypropylene fiber is not limited, and it is possible to use a deformed cross-sectional shape in addition to a deformed cross section such as a circular cross section, a rectangular cross section, or a polygon cross section. For example, for the purpose of improving the adhesion between the fiber and the concrete mixture, the fiber is twisted, deformed into a corrugated shape, or has a hook or hook at the end. The thing and the edge part may be crushed and what is called a dog horn shape may be sufficient.

Next, the manufacturing method of the concrete member of this embodiment is demonstrated.
In this embodiment, a concrete member is manufactured by a kneading process, a placing process, a mold curing process, a first curing process, and a second curing process.

  The kneading step is a step in which steel fibers and polypropylene fibers are kneaded into a concrete mixture produced by cement, fly ash, silica fume, fine aggregate, coarse aggregate, and water.

  The kneading step of the present embodiment includes dry kneading in which the powder portion of the concrete mixture is kneaded, wet kneading in which the liquid portion is added to the powder portion kneaded by dry kneading, and kneading by wet kneading. And fiber kneading in which fibers (steel fibers and polypropylene fibers) are put into the concrete mixture and kneaded.

  Here, in dry kneading, cement, fly ash, silica fume, fine aggregate, and coarse aggregate are kneaded in a dry state. At this stage, polypropylene fibers may be kneaded together. The method and means for kneading each material in dry kneading are not limited, and may be appropriately performed.

  In the wet kneading, after the kneading of the powder portion is completed, water is added and kneaded to cause the concrete mixture to exhibit a predetermined fluidity. In addition, the kneading method and means in the wet kneading are not limited and may be appropriately performed.

  In fiber kneading, fibers are mixed into a concrete mixture having a predetermined fluidity obtained by wet kneading and further kneaded. In addition, the kneading method and means in fiber kneading are not limited, and may be appropriately performed.

The placing step is a step of placing a concrete mixture (high-strength concrete) containing fibers kneaded by the kneading step by a known means.
High-strength concrete is placed in a mold formed in a shape corresponding to the shape of the concrete structure.

The mold curing process is a process for curing the high-strength concrete placed by the placing process.
In the present embodiment, high-strength concrete placed on the mold is performed at room temperature (about 20 ° C.) until a predetermined strength is exhibited (about 1-2 days).

  The first curing process is a process in which high-strength concrete having a predetermined strength is removed from the mold curing process and cured by either steam curing, autoclave curing, or a combination thereof.

In the first curing process, concrete is cured at a temperature higher than normal temperature to build a basic structure. The curing method is performed by high temperature curing at about 90 ° C. using a steam curing tank or by maintaining an isothermal isobaric state at about 180 ° C. and about 10 atm using an autoclave tank for about 3 hours. In addition, when performing curing using the heat of hydration of cement by adiabatic curing at the stage of the mold curing process, this corresponds to the first curing process.
The curing temperature, atmospheric pressure, and holding time in the first curing step are not limited to the above conditions, and may be set as appropriate. Moreover, when it is judged that a basic structure can fully be constructed | assembled in a formwork curing process, you may abbreviate | omit a 1st curing process. In addition, heat insulation curing may be performed in the mold curing process, and further, a first curing process by high temperature curing or high temperature high pressure curing may be performed.

A 2nd curing process is a process of performing dry heating curing to the high-strength concrete after a mold curing process or a 1st curing process.
In the second curing step of the present embodiment, dry heating curing is performed for 3 hours or more in a temperature environment of about 200 ° C.

As mentioned above, according to the manufacturing method of the high-strength concrete and concrete member of this embodiment, it is possible to provide ultra-high-strength concrete whose design standard strength exceeds 200 N / mm ² for the concrete containing the coarse aggregate. Become. Moreover, since the water binder ratio is ensured by 11 to 13% by weight, the fluidity is not lowered as compared with the conventional high-strength concrete, and the workability is not lowered.

High-strength concrete can provide a concrete member having a compressive strength of 200 N / mm ² or more by curing at a temperature higher than room temperature (first curing step).
Furthermore, a concrete member having a compressive strength of 230 N / mm ² or more can be produced by performing dry heat curing at 200 ° C.

  Therefore, for example, if it is used as a pillar of a high-rise concrete building, it becomes possible to reduce the cross section without reducing the strength as a pillar, so that the use space can be liberalized. In addition, since the entire structure can be reduced in weight, the overall cost can be reduced.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and the above-described constituent elements can be appropriately changed without departing from the spirit of the present invention.

  Further, in the above embodiment, as the kneading step of the concrete mixture, only the powder material is kneaded, then the liquid material is added, and the kneaded fiber is kneaded after the predetermined fluidity is expressed. However, the order in which the materials are charged in the kneading step is not limited, and may be set as appropriate.

  In the above embodiment, a predetermined amount of polypropylene fibers having the same shape is added, but polypropylene fibers having different shapes may be added. For example, one having a diameter of 48 μm and a length of 20 mm and one having a diameter of 18 μm and a length of 10 mm may be used by 50% each. Similarly, steel fibers may be added in combination with different materials and shapes.

Hereinafter, the result of the experiment 1 performed in order to confirm the effectiveness of the high strength concrete which concerns on this embodiment is shown.
In Experiment 1, with respect to high-strength concrete, sample A which was subjected to 90 ° C. curing after 20 ° C. air curing, sample B which was subjected to autoclave curing (180 ° C. and 10 atm) after 20 ° C. air curing, and 20 ° C. Sample C, which was cured at 90 ° C. after being cured in air and heated at 200 ° C., and Sample D which was cured at 200 ° C. after being cured in air at 20 ° C. , Compression strength was measured.

  Table 1 shows the composition of the concrete used in Experiment 1.

  Table 2 shows the physical property values of the low heat cement used in this experiment.

  Table 3 shows the physical properties of fly ash used in this experiment.

  Table 4 shows the physical properties of the silica fume used in this experiment.

  Table 5 shows the physical properties of the fine aggregate used in this experiment.

The results of the experiment, the compressive strength of the sample A is 207n / mm ^2, compression strength of Sample B 231N / mm ^2, compression strength of Sample C is 235N / mm ^2, compression strength of Sample D was a 255N / mm ² . Therefore, it was demonstrated that the high-strength concrete of the present embodiment can provide a concrete member having a compressive strength of 200 N / mm ² or more by curing at a temperature higher than room temperature (first curing step). . Furthermore, it was demonstrated that a concrete member having a compressive strength of 230 N / mm ² or more can be produced by performing drying and heating curing at 200 ° C.

Further, as Experiment 2, high strength concrete having a PP fiber amount of 2.5 kg / m ³ in Table 1 was cured at 20 ° C. in air and then cured by using the heat of hydration of cement in the mold curing process. The compressive strength was measured about the sample E which gave the temperature higher than normal temperature of about degree C, and performed heat curing at 200 degreeC. As a result of the experiment, the compressive strength of Sample E was 249 N / mm ² . Therefore, a concrete member having a compressive strength of 230 N / mm ² or more can be produced by performing drying and heating curing at 200 ° C. after curing using the heat of hydration of cement in the mold curing process of the present embodiment. Has been demonstrated.

Therefore, a concrete member having a compressive strength exceeding 200 N / mm ² can be provided by the method for producing high-strength concrete and concrete member according to the present embodiment.

Claims (1)

A placing process for placing high- strength concrete;
A first curing process for curing the high-strength concrete in an autoclave ;
A second curing step of performing a dry heating curing at 200 ° C. after the first curing step ,
In the high-strength concrete,
Low heat cement added in the range of 260-310 L / m ³ ;
Fly ash or quartzite powder added in the range of 120-170 L / m ³ ;
Silica fume added in the range of 70-100 L / m ³ ;
Fine aggregate added in the range of 150-250 L per m ³ ;
And coarse aggregate that are added in the range of 1 m ³ per 90～120L,
A concrete mixture obtained by mixing the low heat cement and water added so that the weight ratio to the binder containing the fly ash or silica stone powder and the silica fume is 11 to 13%;
Steel fibers added so as to be 0.5 to 2% in an external volume ratio with respect to the concrete mixture,
A method for producing a concrete member, comprising a polypropylene fiber having a polygonal cross section and a twisted shape .

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