JP2010173897A - Method for producing concrete secondary product and the concrete secondary product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a concrete secondary product where, even if the amount of the material to be blended together with PFBC ash is small, proper compressive strength can be made to appear in the concrete product produced by the material, and further, demolding can be instantaneously performed in the production process, and to provide the concrete secondary product. <P>SOLUTION: In the method for producing a concrete secondary product, concrete containing PFBC ash and cement as a binder, wherein the content of the cement occupying in the binder is 20 to 40 mass%, is used as the raw material, to perform a metering stage S10 for the material, a kneading stage S20, a placing stage S30, a tamping stage S40, a demolding stage S50 and a curing stage S60. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a concrete secondary product and the concrete secondary product.

  Among the components of concrete, cement is usually used as a binder that generates substances that contribute to the development of concrete strength. Recently, however, from the viewpoint of promoting recycling, it is discharged as waste from steelworks and power plants. Attempts have been made to effectively use blast furnace slag fine powder and fly ash as binders.

  Blast-furnace slag fine powder is obtained by quenching molten blast-furnace slag that is generated simultaneously with pig iron in a blast furnace with water, drying and pulverizing it, or adding gypsum to this. Fly ash is ash that is collected by the dust collector from the combustion gas of the pulverized coal combustion boiler of a coal-fired power plant.

  Recently, as such a binder, concrete using PFBC ash discharged from a coal-fired power plant of a pressurized fluidized bed combined power generation (PFBC) system, which is a waste different from the above, has been proposed. (For example, Patent Document 1).

Japanese Patent Laid-Open No. 11-147747

  However, in the concrete described in Patent Document 1, PFBC ash is used in place of a part of cement, and the compressive strength of the produced concrete decreases with a decrease in the amount of cement.

  In addition, the concrete secondary product is manufactured by placing concrete on a formwork of the concrete secondary product and curing it, and then removing the mold from the formwork. There is no particular technique for shortening the time period up to.

  The present invention has been made in view of the above points, and even if the amount of cement blended with the PFBC ash is small, the concrete secondary product produced by the material exhibits appropriate compressive strength. An object of the present invention is to provide a method for producing a concrete secondary product that can be removed immediately in the production process and the concrete secondary product.

To achieve the above object, the present invention is a method for producing a concrete secondary product,
A concrete containing PFBC ash and cement as a binder and having a cement content of 20 to 40% by mass in the binder is blended so that the slump value is substantially zero,
Placing the blended concrete into a mold for molding the concrete secondary product;
Compacting the concrete placed in the formwork,
Without curing the concrete, remove the formwork of the compacted concrete,
The concrete from which the formwork has been removed is steam-cured.

According to the method for producing a concrete secondary product according to the present invention, by performing steam curing, the content ratio of the cement blended with PFBC ash is 20 to 20% compared to the concrete described in Patent Document 1. Even in a small amount of 40% by mass, an appropriate compressive strength can be expressed as a concrete secondary product.
Thus, the material cost can be reduced cement, reduces the CO ₂ generated during cement production, which contributes to reduce the environmental impact.

  Moreover, by performing steam curing, the compressive strength can be expressed in concrete at an early stage, and the production efficiency can be improved.

In the present invention, the slump value is substantially zero means that fresh concrete (unconsolidated concrete) is packed into a hollow steel cone with an inner diameter of the upper end of 10 cm, an inner diameter of the lower end of 20 cm, and a height of 30 cm. In the slump test (JIS A 1101) for measuring the displacement of how much the central portion of the top surface is lowered from the initial height after the cone is pulled out, this means that the displacement does not occur.
That is, according to the method for producing a concrete secondary product according to the present invention, the material is blended so that the slump value becomes substantially zero. However, since concrete does not deform, it retains its formed shape and becomes self-supporting, so it can be cured in a state in which the concrete is demolded. That is, since the usage time of the mold necessary for molding one product can be shortened, productivity can be improved.

  In the present invention, when the cement content in the binder is 40% by mass, the steam curing may be performed for at least 17 hours.

According to this structure, the compressive strength at the age of 7 days of the concrete secondary product to be manufactured can be expressed to be equal to or higher than the compressive strength (22.5 N / mm ² ) required for the building block. This compressive strength is obtained by multiplying the safety standard 1.25 by 18N / mm ² which is the design standard strength of the block type retaining wall of the unreinforced concrete secondary product specified in JIS A 5371. .
The safety factor is used to ensure that the compressive strength of the concrete secondary product does not become too small relative to the required design standard strength, because the compressive strength of the concrete secondary product varies considerably from lot to lot. .

  In the present invention, when the content of the cement in the binder is 20 to 30% by mass, pre-curing is performed for at least 24 hours before the steam curing, and then the steam curing is performed for at least 24 hours. Also good.

According to this configuration, the compressive strength of the manufactured concrete secondary product at the age of 7 days can be expressed to a compressive strength (22.5 N / mm ² ) or more required for the stacking block.

  In the present invention, as the binder, blast furnace slag fine powder may be used together with the PFBC ash and the cement. According to this configuration, the blast furnace slag fine powder has the property of exhibiting hydraulic properties using the alkaline component of cement as a stimulant (latent hydraulic property), and therefore can be used together with PFBC ash and cement as a binder. It can contribute to the effective use of waste.

  In this invention, it is good also considering the content rate of the said blast furnace slag fine powder which occupies for the said binder as 30 mass%.

  The present invention is a concrete secondary product, comprising PFBC ash and cement as a binder, and having a cement content of 20 to 40% by mass in the binder, and having a slump value substantially Formulated to be zero, the blended concrete is placed in a mold for molding the concrete secondary product, the concrete placed in the mold is compacted, without curing the concrete, The formwork of the compacted concrete is removed, and the concrete from which the formwork has been removed is steam-cured.

  According to the present invention, even if the amount of cement blended with the PFBC ash is small, the concrete secondary product produced by the material can exhibit appropriate compressive strength, and immediately in the manufacturing process. It is possible to provide a method for producing a concrete secondary product that can be demolded and the concrete secondary product.

It is process drawing which shows the manufacturing process of the concrete secondary product which concerns on this embodiment. It is a graph which shows the temperature history by the steam heating of curing process S60. It is a table | surface which shows the specification of the material of the concrete specimen used for this examination. It is a table | surface which shows the compounding conditions of the material of the concrete test body used for this examination. It is the table | surface which put together the measurement graph of the temperature history which shows the curing condition 1, and the measurement result of the compressive strength at the time of the predetermined material age of the test body produced by the curing condition 1. FIG. It is the table | surface which put together the measurement graph of the temperature history which shows the curing condition 2, and the measurement result of the compressive strength at the time of the predetermined material age of the specimen produced by the curing condition 2. It is the table | surface which put together the measurement graph of the temperature history which shows the curing conditions 3, and the measurement result of the compressive strength at the time of the predetermined material age of the test piece produced by the curing conditions 3. It is the table | surface which put together the measurement graph of the temperature history which shows the curing condition 4, and the measurement result of the compressive strength at the time of the predetermined material age of the specimen produced by the curing condition 4.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a process diagram showing a manufacturing process of a concrete secondary product according to this embodiment. The concrete secondary product as used herein means a member / product manufactured by a manufacturing facility of a factory, and examples thereof include blocks, sleepers, or unreinforced concrete pipes.

  As shown in FIG. 1, the concrete secondary product is manufactured by carrying out a material measuring step S10, a kneading step S20, a driving step S30, a compacting step S40, a demolding step S50, and a curing step S60. .

  In the material measurement step S10, fine aggregate, coarse aggregate, water, and a binder are appropriately mixed depending on the type, shape, and size of the concrete secondary product.

  Coarse aggregate is an aggregate that remains 85% or more by mass on a 5 mm mesh screen, but is not particularly limited, such as crushed stone and artificial aggregate. Further, the fine aggregate is an aggregate that passes through a 10 mm mesh screen and passes through a 5 mm mesh screen by 85% or more, but is not particularly limited, such as river sand and crushed sand.

  In addition, a binder produces | generates the substance which contributes to the strength expression of concrete among the constituent materials of concrete, and PFBC ash, blast furnace slag fine powder, and cement are used in this embodiment.

  PFBC ash is ash discharged from a pressurized fluidized bed combined power generation (PFBC) type coal-fired power plant, and blast furnace slag fine powder is a molten blast furnace generated simultaneously with pig iron in a blast furnace. The slag is quenched with water, dried and crushed.

  As a cement, a kind can be used according to a use, for example, normal Portland cement, early-strength cement, and moderately hot cement are mentioned.

  And these constituent materials of concrete are mix | blended so that it may become a zero slump substantially. Zero slump means that a displacement amount (slump value) by a slump test becomes 0 cm. In the slump test, fresh concrete is packed into a steel hollow cone with an inner diameter of the upper end of 10 cm, an inner diameter of the lower end of 20 cm, and a height of 30 cm. After the cone is pulled out, the center of the top surface starts from the initial height. This is a test to measure how much the displacement is lowered (JIS A 1101). Therefore, zero slump means that even after the cone is pulled out, the concrete remains in its shape and does not deform.

  As specific blending conditions, for example, the water binder ratio is 40% by mass or less, and the fine aggregate ratio representing the absolute volume ratio of the fine aggregate amount to the total aggregate amount is 50% or more. Here, the water binder ratio is the ratio of water and binder in the fresh concrete composition.

Moreover, the content rate of the cement which occupies for a binder is 20-40 mass%.
Moreover, it is preferable that the content rate of the blast furnace slag fine powder which occupies for a binder is 30 mass%. Since the blast furnace slag fine powder has the property of exhibiting hydraulic properties (latent hydraulic properties) using the alkaline component of cement as a stimulant, it can be used together with PFBC ash and cement as a binder.

  In addition, an admixture may be included as a material for the concrete secondary product, for example, a high-performance water reducing agent is used. A high-performance water reducing agent is, for example, an admixture mainly composed of polycarboxylic acid-based, naphthalene-based, melamine-based, and aminosulfonic acid-based surfactants, and provides high water reducing performance and good slump retention performance to concrete. Used to give.

  In the kneading step S20, the blended materials are kneaded uniformly in order to obtain high-quality concrete. For the kneading, for example, a forced kneading mixer suitable for kneading the super-mixed kneaded concrete having the above-described blend is used.

  In the placing step S30, the concrete mixed in the mixing step S20 is placed on the mold. The mold is desired to be made of a material that is firm and does not cause a deviation in shape and dimensions even when vibration, pressure, heat, and the like are repeatedly applied during manufacturing. For example, a steel mold is used. Moreover, it is preferable that a formwork is attachable to the molding machine used in order to implement a subsequent process (S40). The concrete is placed into the mold using, for example, a hopper, a concrete pump, or an automatic material feeder.

  The compacting step S40 is a process for filling the concrete that has been driven into the mold into every corner of the mold by vibration or pressurization, or a combination thereof, so that the concrete becomes dense, For example, it is performed using a vibrator, a pressure molding machine, a centrifugal molding machine, a tamping machine, or the like to which the formwork in which the concrete is placed in the placing step S30 can be attached.

  In the demolding step S50, after the concrete is compacted in S40, the mold is removed immediately (for example, after about 5 seconds). As described above, since the material is blended so that the concrete becomes zero slump, even if the mold is removed immediately, the concrete does not deform after being removed.

  In the curing step S60, curing is promoted by heating the concrete after demolding with steam. Specifically, the demolded concrete is placed in a curing room to which steam generated by a boiler is supplied and cured for a predetermined time.

FIG. 2 is a graph showing a temperature history due to steam heating in the curing step S60.
As shown in FIG. 2, curing is performed in a cycle of a pre-curing period, a temperature rising period, an isothermal curing period, and a slow cooling period.
With regard to such curing, there are cases in which cracking and reduction in the strength of expression may occur due to rapid heating, excessively high maximum temperatures, or rapid cooling. (1) After molding, put in the curing room to raise the temperature evenly, (2) After mixing, heat for 2 to 3 hours before curing, and (3) In the temperature rising period, the temperature rising rate is 20 (4) The maximum temperature is set to 65 ° C during the isothermal curing period, (5) The temperature is gradually decreased during the slow cooling period, and the product is taken out with no significant difference from room temperature. .

  In addition, in the manufacturing method of the concrete secondary product of this embodiment, it is preferable to change curing conditions with the content rate of the cement which occupies for a binder.

  For example, when the cement content in the binder is 40% by mass, the total period of the temperature increase period and the isothermal curing period (hereinafter referred to as the steam curing period) is performed for at least 17 hours. When the content ratio of cement is 20 to 30% by mass, it is preferable to perform precuring for at least 24 hours before steam curing, and then perform steam curing for at least 24 hours.

  And after performing curing in this way, what has appropriate compressive strength as a concrete secondary product is manufactured by taking out concrete after steam curing from a curing room. After steam curing, post-curing may be performed as necessary.

  Next, in setting the conditions for the above-mentioned concrete secondary product manufacturing method, we made several concrete specimens by changing the concrete composition and curing conditions, and examined them by measuring the compression strength. The details will be described below.

FIG. 3 is a table showing the material specifications of the concrete specimen used in this study.
As shown in FIG. 3, the secondary concrete materials are water (W), cement (C), PFBC ash (P), blast furnace slag fine powder (BF), fine aggregate (S and BS), coarse bone A high performance water reducing agent (SP1) was used as a material (G1 and G2) and an admixture.

FIG. 4 is a table showing the mixing conditions of the concrete specimen materials used in this study.
As shown in FIG. 4, concrete specimens of six types of blending (blending conditions 1 to 6) were produced in this study.

These all blends (blending conditions 1 to 6) have 30% water binder ratio (W / B), which is a mass ratio of water (W) to binder (B), and total aggregate amount (a ) The fine aggregate ratio (s / a) representing the absolute volume ratio of the fine aggregate amount (s) to 57) is 57%, and the content of the blast furnace slag fine powder (BF) in the binder (B) (BF / B) Was 30%, and the amount of water used to make 1 m ³ of concrete was 90 kg / m ³ .
Moreover, the compounding quantity of the blast furnace slag fine powder (BF) was mix | blended so that it might become the same quantity (90 g / m < ³ >) with each compounding condition among binders (B).
In addition, the fine aggregate (S), fine aggregate (BS), coarse aggregate (G1), and coarse aggregate (G2) are almost the same ratios (S: 752 to 759 kg / m ³ ) for each blending condition. , BS: 346 to 349 kg / m ³ , G1: 338 to 341 kg / m ³ , G2: 507 to 512 kg / m ³ ).

On the other hand, the amount of PFBC ash (P) and cement (C) in the binder (B) was changed according to each blending condition. Specifically, the contents of the cement (C) to total binder (B), the blending conditions 1 3.5 wt% (11kg ^{/ m} 3), the blending conditions 2 7 wt% (21kg ^{/ m} 3) 10% by weight (30 kg / m ³ ) in blending condition 3, 20% by weight (60 kg / m ³ ) in blending condition 4, 30% by weight (90 kg / m ³ ) in blending condition 5 and 40% by weight in blending condition 6 (120 kg / m ³ ). Here, the binder (B) was adjusted so as to have the same amount (300 kg / m ³ ) for each blending condition. That is, the blending ratio is such that the content of PFBC ash (P) in the binder (B) decreases as the content of cement (C) in the binder (B) increases.

  Moreover, in each compounding condition, in order to make fresh concrete become a zero slump, the high performance water reducing agent (SP1) is supplementarily added.

  The material consisting of the above blending conditions 1 to 6 is prepared by first kneading the aggregate (a) and the binder (B) for 30 seconds, and then adding water to which the admixture has been added in advance. And kneaded for 4 minutes. Thereafter, the kneaded material was placed in a mold and compacted with a rod-shaped vibrator. In addition, the shape (Φ100 × 200 mm) defined as a specimen for measuring the compressive strength of concrete was used as the mold.

The concrete of each blending condition placed in the mold in this way is removed from the mold immediately after the casting in about 5 seconds, and then placed in the curing room to perform steam curing. Was made. In addition, preparation of the said concrete specimen was performed based on JISA1132.
Then, the compressive strength was measured for these specimens at a predetermined age (JIS A 1108).

  FIG. 5 to FIG. 8 are tables summarizing graphs of temperature history indicating curing conditions and measurement results of compressive strength at the time of a predetermined age of specimens prepared under the curing conditions. As shown in FIG. 5 to FIG. 8, curing was performed under four different curing conditions (curing conditions 1 to 4) in preparing the specimen.

  In the curing condition 1 (see the graph of FIG. 5), the specimen consisting of the blending condition 1 and the blending condition 2 is set at a temperature increase rate of 22.5 ° C / h from 20 ° C to 65 ° C without providing a pre-curing period The room temperature was raised (elapsed time: 0 to 2 hours), then cured at that room temperature for 6 hours at an isothermal temperature (elapsed time: 2 to 8 hours), and then allowed to cool naturally. That is, under the curing condition 1, pre-curing is not performed (0 hour), and steam curing is performed for 8 hours.

  Curing condition 2 (see the graph of FIG. 6) is a case where the steam curing period in curing condition 1 is extended. Specifically, the temperature increase rate is 22.5 ° C./h without providing a pre-curing period. The room temperature was raised from 20 ° C. to 65 ° C. (elapsed time: 0 to 2 hours), and then cured at the room temperature for 19 hours at an isothermal temperature (elapsed time: 2 to 21 hours). That is, under curing condition 2, pre-curing is not performed (0 hours), and steam curing is performed for 21 hours.

  In the curing condition 3 (see the graph of FIG. 7), the specimen consisting of the blending conditions 3 to 6 was taken at 20 ° C. for a pre-curing period of 4 hours (elapsed time: 0 to 4 hours). The room temperature was raised to 65 ° C. at 5 ° C./h (elapsed time: 4 to 6 hours), then cured at the room temperature for 15 hours (isolated time: 6 to 21 hours), and then allowed to cool naturally. That is, under the curing condition 3, the pre-curing is performed for 4 hours and the steam curing is performed for 17 hours.

  Curing condition 4 is a case where the specimen consisting of blending condition 4 and blending condition 5 is cured by extending the pre-curing period and steam curing period in curing condition 3, and specifically, pre-curing at 20 ° C. The period is 24 hours (elapsed time: 0 to 24 hours), and then the temperature is increased at a rate of 22.5 ° C./h to 65 ° C. (elapsed time: 24 to 26 hours). It was cured with time isothermal (elapsed time: 26 to 48 hours), and then allowed to cool naturally (see the graph of FIG. 8). That is, under curing condition 4, pre-curing is performed for 24 hours and steam curing is performed for 24 hours.

  According to the measurement results of the compressive strength of the specimens prepared under the curing conditions 1 to 4, when curing specimens having the same blending conditions, the longer the period of steam curing, the more compressive strength of the specimens prepared. It can be seen that it is improved at any age. In particular, the difference appears remarkably in the compressive strength at the time of demolding, and concrete develops the compressive strength early due to the extension of the steam curing period.

  Moreover, the compression strength of the produced specimen is improving, so that the content rate of the cement (C) which occupies for a binder (B) among compounding conditions is high.

  Furthermore, among the curing conditions, the compression strength of the specimen prepared as the pre-curing period is increased is improved.

When manufacturing a concrete secondary product, in general, (i) it can be demolded in one day after being placed in a mold, (ii) the compressive strength at the time of demolding is 10 N / mm ² or more, ( iii) Conditions are required such that the compressive strength at the age of 7 (date of product shipment) has a value equal to or higher than the required design standard strength multiplied by a safety factor.
The safety factor is used to ensure that the compressive strength of the concrete secondary product does not become too small relative to the required design standard strength, because the compressive strength of the concrete secondary product varies considerably from lot to lot. .
With regard to the condition (iii), for example, when applied to an unreinforced concrete secondary product of a stacked block of retaining walls, it is required that the compressive strength at the age of 7 is 22.5 N / mm ² or more. The This compressive strength is obtained by multiplying a safety factor of 1.25 by 18 N / mm ² which is the design standard strength of the boundary block of the unreinforced concrete secondary product defined in JIS A 5371.

Based on the conditions required for manufacturing the secondary concrete product, the measurement results show that the ones that satisfy the conditions (i) to (iii) are cured under the curing conditions 3 Among the specimens composed of the blending conditions 6 and the specimens cured under the curing conditions 4, these are specimens composed of the blending conditions 4 and 5.
As described above, the concrete having a content of 20 to 40% by mass in the binder (B) of the cement (C) blended with the PFBC ash (P) is subjected to steam curing under a predetermined condition. It was confirmed that appropriate compressive strength can be developed as the next product.

  As mentioned above, according to the manufacturing method of the concrete secondary product which concerns on this embodiment, the content rate which occupies for the binder of the cement mix | blended with PFBC ash by performing steam curing in a manufacture process is the concrete of patent document 1. Even if it is a small amount of 20 to 40% by mass as compared with the above, an appropriate compressive strength can be developed as a concrete secondary product.

Specifically, when the cement content in the binder is 40% by mass, steam curing is performed for at least 17 hours, so that the compressive strength of the concrete secondary product to be manufactured at the age of 7 days is 22. it can be expressed in 5N / mm ² or more.

Further, when the cement content in the binder is 20 to 30% by mass, the pre-curing is performed for at least 24 hours before steam curing, and then the steam curing is performed for at least 24 hours. The compressive strength of the next product at the age of 7 days can be expressed to 22.5 N / mm ² or more.

Thus, the material cost can be reduced cement, reduces the CO ₂ generated during cement production, which contributes to reduce the environmental impact.

  Moreover, since the compressive strength can be expressed early in concrete by performing steam curing, it is possible to improve the production efficiency.

  According to the method for producing a concrete secondary product according to the present embodiment, since the material is blended so that the slump value is substantially zero, the material is driven into a formwork and compacted, and then immediately demolded. However, since concrete does not deform and retains its formed shape and becomes self-supporting, it can be cured in a state in which the concrete is demolded. That is, since the usage time of the mold necessary for molding one product can be shortened, productivity can be improved.

  Moreover, according to the manufacturing method of the concrete secondary product which concerns on this embodiment, since a blast furnace slag fine powder is included as a binder with PFBC ash and cement, it can contribute to the effective utilization of waste with PFBC ash. .

S10 Material measurement process S20 Mixing process S30 Driving process S40 Compaction process S50 Demolding process S60 Curing process

Claims (6)

A method for producing a concrete secondary product, comprising:
A concrete containing PFBC ash and cement as a binder and having a cement content of 20 to 40% by mass in the binder is blended so that the slump value is substantially zero,
Placing the blended concrete into a mold for molding the concrete secondary product;
Compacting the concrete placed in the formwork,
Without curing the concrete, remove the formwork of the compacted concrete,
A method for producing a concrete secondary product, comprising steam curing the concrete from which the formwork has been removed.   The method for producing a concrete secondary product according to claim 1, wherein when the cement content in the binder is 40% by mass, the steam curing is performed for at least 17 hours.   When the content of the cement in the binder is 20 to 30% by mass, the precuring is performed for at least 24 hours before the steam curing, and then the steam curing is performed for at least 24 hours. Item 3. A method for producing a secondary concrete product according to Item 1 or 2.   The method for producing a secondary concrete product according to any one of claims 1 to 3, wherein fine powder of blast furnace slag is also used as the binder together with the PFBC ash and the cement.   The content rate of the said blast furnace slag fine powder which occupies for the said binder is 30 mass%, The manufacturing method of the concrete secondary product in any one of Claims 1-4 characterized by the above-mentioned. Concrete secondary products,
A concrete containing PFBC ash and cement as a binder and having a cement content of 20 to 40% by mass in the binder is blended so that the slump value is substantially zero,
Placing the blended concrete into a mold for molding the concrete secondary product;
Compacting the concrete placed in the formwork,
Without curing the concrete, remove the formwork of the compacted concrete,
A concrete secondary product obtained by steam curing the concrete from which the formwork has been removed.

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