JP5143653B2 - Manufacturing method of concrete secondary product and concrete secondary product - Google Patents

Description

  The present invention relates to a method for producing a concrete secondary product that does not include cement in the material, and the concrete secondary product, and more particularly to a technique that allows immediate demolding in the production process.

  Concrete means a binder, water, aggregate, and an admixture added as necessary, and these are kneaded and mixed by other methods or hardened. Here, the admixing material is a material other than the binder, water, and aggregate, and is added as necessary before placing in order to give special properties to concrete and the like. The binding material is a material that reacts with water to generate a substance that contributes to the development of the strength of concrete, and includes, for example, cement, blast furnace slag fine powder, fly ash, and the like. Cement is a fine powder of mineral that hardens by reacting with water. The blast furnace slag fine powder is obtained by rapidly cooling a molten blast furnace slag produced simultaneously with pig iron in a blast furnace with water, drying and pulverizing it, and gypsum may be added thereto. Fly ash is ash collected by the dust collector from the combustion gas of the pulverized coal combustion boiler.

  Blast furnace slag fine powder discharged from the steelmaking process in steelworks and fly ash discharged from coal-fired power plants have been actively used as binders from the viewpoint of promoting the effective use of waste. . However, although concrete using these blast furnace slag fine powder or fly ash in combination with cement has been developed, a concrete composition containing no cement as a binder has not been developed. This is because blast furnace slag fine powder and fly ash are not hydraulic by themselves. However, fly ash reacts gradually with cement hydrate when used in combination with cement to form a hardened body (pozzolanic action). In addition, blast furnace slag fine powder has the property of exhibiting hydraulic properties using the alkaline component of cement as a stimulant (latent hydraulic property).

On the other hand, pressurized fluidized bed type combined cycle (Pressurized Fluidized Bed Combus t ion, PFBC) the PFBC ash discharged from coal fired power plant system, the concrete composition utilizing as a binder have been developed with the cement. Unlike general fly ash, PFBC ash is self-hardening, but the strength of the cured body when used alone as a binder is small, so even in concrete compositions using PFBC ash developed so far, There is no material that does not contain cement at all.

On the other hand, the present applicant has applied for a concrete composition not containing cement (Japanese Patent Application No. 2007-069 0 48). It is an object of the present invention to provide a method for producing a concrete secondary product that uses such a cement-free material and that can be instantly demolded during the production process, and the concrete secondary product.

In order to achieve the above object, the present invention provides:
A method for producing a secondary concrete product from concrete including fine aggregate, coarse aggregate, water, and a binder, wherein the binder comprises PFBC ash and blast furnace slag fine powder, and the slump value is substantially The concrete is mixed so that it becomes zero, and the mixed concrete is placed in a mold for molding the concrete secondary product, the concrete placed in the mold is compacted, and the concrete is Removing the mold of the compacted concrete without curing, subjecting the concrete from which the mold has been removed to precuring at 20 ° C. for at least 24 hours, and then steam curing the concrete It is characterized by.

  Here, the slump value is substantially zero. Concrete in an unconsolidated state is packed into a hollow steel cone having 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, and the cone is pulled out. Later, in the slump test (JIS A 1101) for measuring the displacement of how much the center of the top surface is lowered from the initial height, 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 removed. As described above, since the use time of the mold necessary for molding one product can be shortened, productivity can be improved. Moreover, since the steam curing is performed after performing the pre-curing for at least 24 hours, the strength of the concrete secondary product to be produced can be expressed more than a predetermined design standard strength.

In the present invention, the mixing ratio of the concrete is such that the water binder ratio, which is the mass ratio of the water to the binder containing the PFBC ash and blast furnace slag fine powder, is 40% or less, and the fine aggregate with respect to the total aggregate amount. The fine aggregate ratio that is the absolute volume ratio of the amount may be 50% or more. According to this configuration, the slump value can be made substantially zero by specifically blending the materials.

  In addition, since the water binder ratio is 40% or less, the ratio of water is less than usual, so that the strength is improved when consolidated.

  Also, since the fine aggregate ratio, which is the absolute volume ratio of the fine aggregate amount to the total aggregate amount, is 50% or more, the concrete has more voids than usual, so a porous block having water retention and water permeability. Suitable as

  In the present invention, a mass ratio between the PFBC ash and the blast furnace slag fine powder may be set to 25:75 to 75:25.

  In the present invention, the content of the fine blast furnace slag powder in the binder containing the PFBC ash and fine blast furnace slag powder may be 50% by mass or less.

  In the present invention, an admixture may be further added to the concrete.

Moreover, this invention is a concrete secondary product manufactured with the manufacturing method of the concrete secondary product of any one of Claim 1 to 5 .

  ADVANTAGE OF THE INVENTION According to this invention, while using the material which does not contain cement, the manufacturing method of the concrete secondary product which can be demolded immediately in a manufacturing process, and its concrete secondary product can be provided.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
The concrete secondary product according to the present embodiment includes fine aggregate, coarse aggregate, water, and a binder as materials.

  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. 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.

As described above, the binder is a material that reacts with water to generate a substance that contributes to the development of the strength of concrete, and generally includes cement, but in the concrete secondary product according to the present embodiment, As the binder, a material composed of PFBC ash and blast furnace slag fine powder is used.

  Here, PFBC ash refers to ash discharged from a pressurized fluidized bed combined power generation (PFBC) type coal-fired power plant. Moreover, the blast furnace slag fine powder means a product obtained by rapidly cooling a molten blast furnace slag generated simultaneously with pig iron in a blast furnace with water, and drying and pulverizing it.

  The material of these concrete secondary products is blended so as to be substantially zero slump. Zero slump means that a displacement amount (slump value) by a slump test becomes 0 cm. In the slump test, unconsolidated 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. This is a test for measuring the displacement of how much the height falls (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, the water binder ratio is preferably 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 preferably 50% or more. Here, the water binder ratio is the ratio of water and binder in the fresh concrete composition. Moreover, it is preferable that the mass ratio of PFBC ash and blast furnace slag fine powder is 25: 75-75: 25, and the content rate of the said blast furnace slag fine powder which occupies for a binder is 50 mass% or less.

  Next, the manufacturing method of the concrete secondary product which consists of such a material is demonstrated. In addition, as a concrete secondary product which consists of the said material, blocks, a sleeper, or an unreinforced concrete pipe etc. are mentioned, for example.

  As shown in FIG. 1, the concrete secondary product manufacturing method includes a material measuring step S10, a kneading step S20, a driving step S30, a compacting step S40, a demolding step S50, and a steam curing step S60.

  In the material measurement step S10, the material is mixed so as to be suitable for the kind, shape, size, etc. of the concrete secondary product under the above-described mixing conditions.

  In the kneading step S20, the blended materials are kneaded uniformly to obtain high-quality concrete. For kneading, for example, a forced kneading mixer suitable for kneading ultra-high kneaded concrete with a rich blend as described above is used.

  In the placing step S30, the concrete kneaded in the kneading step S20 is placed on the formwork. 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 formwork into the corners of the formwork 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 a form into which concrete has been 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 steam 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 the heat history of steam curing.
As shown in FIG. 2, steam curing is performed in a cycle of a pre-curing period, a temperature rising period, an isothermal curing period, and a slow cooling period.

  For steam curing, concrete heating may be caused by rapid heating, excessively high maximum temperature, or rapid cooling. ] (1) Put in the curing room to raise the temperature evenly, (2) After mixing, heat for 2 to 3 hours before curing, (3) In the temperature rising period, the temperature rising rate is 20 ° C (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.

  And finally, the concrete secondary product which does not contain cement is manufactured by taking out the concrete after steam curing from the curing room. After steam curing, post-curing may be performed as necessary.

  Next, as a concrete secondary product not containing cement, a block was actually manufactured according to the above manufacturing method and its strength was measured. The details will be described below.

FIG. 3 is a table showing specifications of block materials.
As shown in FIG. 3, water (Water, W), PFBC ash (PFBC coal ash, P), blast furnace slag fine powder (ground granulated blast-furnace slag, BF), fine aggregate (sand, S), coarse aggregate (gravel, G), and admixture were used. Specifically, tap water is used for water, raw powder (100% Wambo) for PFBC ash, fine slag powder 4000 for blast furnace slag fine powder, crushed sand and blast furnace slag fine aggregate, coarse bone for fine aggregate Crushed stone was used for the material, and bipress concrete was used for the admixture. FIG. 4 is a table showing the chemical composition ratio of PFBC ash and blast furnace slag fine powder.

  In addition, the concrete secondary product which concerns on this invention may also contain an admixture as a material. Bi-press concrete is an admixture that is manufactured and sold by Yuken Chemical Co., Ltd. and contains a nonionic surfactant and a special chemical synthesis product. By blending this, it is possible to improve the filling properties of super hard kneaded concrete and the like, as well as to improve aesthetics, product uniformity, and concrete strength. The admixture is not particularly limited to bipress concrete.

FIG. 5 is a table showing the blending conditions of the block material.
As shown in FIG. 5, 30% water binder ratio (W / B), which is a mass ratio of water (water, W) to binder (binder, B; total amount of PFBC ash and blast furnace slag fine powder) The content of blast furnace slag fine powder (BF / B) in the material is 30%, the unit water amount (W) representing the amount of water used when making 1 m ³ of concrete is 90 kg / m ³ , and the total amount of aggregate is fine. The fine aggregate ratio (sand / aggregate, s / a) representing the absolute volume ratio of the aggregate amount is 57%, the ratio of the admixture to the binder (SP) is 1.5%, and the fine aggregate ratio The fine aggregate mixing ratio, which is the ratio between the crushed sand S1 and the blast furnace slag fine aggregate S2, was set to 2.2: 1.0.

  The concrete with the above composition is kneaded so as to be uniform, and is poured into a steel block formwork. The concrete is then squeezed by vibration and pressure, and the block formwork is removed immediately (about 5 seconds). Then, the concrete from which the formwork was removed was installed in the curing room and steam curing was performed.

FIG. 6 is a graph showing the temperature history of steam curing used in this study.
As shown in FIG. 6, the temperature is set to 20 ° C., the pre-curing period is 2 hours (elapsed time: 0 to 2 hours), and the room temperature is increased to 65 ° C. at a temperature increase rate of 22.5 ° C./h. (Elapsed time: 2 to 4 hours), held at that room temperature for 3 hours (elapsed time: 4 to 7 hours), and then gradually cooled to 20 ° C. at a cooling rate of 15 ° C./h (elapsed time: 7 to 11 hours) ).
After performing the steam curing under the conditions as described above, the block was manufactured by performing the air curing for a while at 20 ° C. and then removing the concrete from the curing room.
And the compressive strength at the time of a predetermined age was measured with respect to this manufactured block (JIS A 1108).

FIG. 7 is a table summarizing the relationship between the age of the manufactured blocks and the compressive strength.
As shown in FIG. 7, block expresses compressive strength of 11.3N / mm ² at 1 day age of approximately equal compressive strength 11.8 N / mm ² and wood age 1 day thereafter ages 7 days The result was expressed.

  As described above, according to the method for producing a cement-free concrete secondary product according to the present embodiment, as a material, coarse aggregate, fine aggregate, water, and a binder containing PFBC ash and blast furnace slag fine powder. In addition to using it, the material was blended so that it would become zero slump, so in the manufacturing process of the product, after the material was driven into a mold and compacted, the concrete would not be deformed even if it was removed immediately. Since it is self-supporting with its shape, it can be cured in a demolded state. That is, since the usage time of the mold necessary for molding one product can be shortened, productivity can be improved.

  In addition, according to the method for producing a cement-free concrete secondary product according to the present embodiment, the blending that becomes the zero slump specifically has a water binder ratio of 40% by mass or less and a fine amount with respect to the total aggregate amount. This can be realized by setting the fine aggregate ratio representing the absolute volume ratio of the aggregate amount to 50% or more. Here, by setting the water binder ratio to 40% or less, the concrete has a smaller proportion of water than usual, so that the effect of improving the strength during consolidation is obtained. Also, by setting the fine aggregate ratio, which is the absolute volume ratio of the fine aggregate amount to the total aggregate amount, to 50% or more, the concrete has more voids than usual, so a porous block having water retention and water permeability. Will be suitable as.

  In the manufacturing process of the concrete secondary product according to the present embodiment, the curing of the concrete is a steam curing. However, the present invention is not limited to this, and a normal curing (for example, in water or in the air) may be performed.

  Moreover, in the manufacturing method of the concrete secondary product which concerns on this embodiment, although the pre-curing period was put for 2 to 3 hours or more after mixing, it is not restricted to this, You may leave the pre-curing period for 24 hours or more. Since the test which examines the strength expression effect of the concrete secondary product by the difference in curing conditions was done, the details are explained below.

  FIG. 8 is a table showing the constituent materials of the test body of the concrete secondary product used in the test relating to the curing conditions and the blending thereof.

As shown in FIG. 8, PFBC ash, blast furnace slag fine powder, fine aggregate, coarse aggregate, and an admixture are used as constituent materials for concrete secondary product specimens in tests related to curing conditions. The water binder ratio (W / B) is 30%, the fine aggregate ratio (s / a) representing the absolute volume ratio of the fine aggregate amount to the total aggregate amount is 57%, and the binder (B) The content (BF / B) of blast furnace slag fine powder (BF) occupying 30% was mixed at ³⁰ kg, and the unit water amount (W) representing the amount of water used when making 1 m ³ of concrete was blended at 90 kg / m ³ .

  In addition, only PFBC ash (P) and blast furnace slag fine powder (BF) were used for the binder (B), and the mass ratio of the PFBC ash to the blast furnace slag fine powder was 70:30. In order to adjust the slump value (JIS A 1101) to be substantially zero, a high-performance water reducing agent was used as an admixture, and 1.5% by weight was added to the binder (B).

  Then, in preparing the concrete of the test body, the water in which the high-performance water reducing agent was added in advance was added to the one in which the aggregate and the binder were kneaded for 30 seconds, and the mixture was further mixed for 4 minutes. Produce fresh concrete, then cast the fresh concrete into a mold (φ100mm × 200mm), compact with a rod-shaped vibrator, then immediately remove the formwork, and then perform curing to produce multiple specimens did.

FIG. 9 is a graph showing the temperature history of steam curing of each specimen.
As shown in FIG. 9, in this test, the curing condition No. The curing of 1-3 was performed.

  Curing conditions No. In 1, without increasing the pre-curing period, the room temperature is increased to 65 ° C. at a temperature increase rate of 22.5 ° C./h (elapsed time: 0 to 2 hours), and then the isothermal curing period of 65 ° C. is 19 hours. Taken (elapsed time: 2 to 21 hours), and then allowed to cool naturally. That is, curing condition No. In 1, the pre-curing is performed for 0 hours and the steam curing is performed for 21 hours.

  In addition, Condition No. 2, the pre-curing period was taken at 20 ° C. for 4 hours (elapsed time: 0 to 4 hours), and then the temperature was increased to 50 ° C. at a rate of 15 ° C./h (elapsed time: 4 to 6 hours). Thereafter, the temperature was maintained at room temperature for 4 hours (elapsed time: 6 to 10 hours), and then further increased to 65 ° C. at 15 ° C./h (elapsed time: 10 to 11 hours). Then, an isothermal curing period of 65 ° C. was taken for 17 hours (elapsed time: 11 to 28 hours), and then allowed to cool naturally. That is, curing condition No. In 2, the pre-curing is performed for 4 hours and the steam curing is performed for 24 hours.

  In addition, curing conditions No. 3, the pre-curing period is taken at 20 ° C. for 24 hours (elapsed time: 0 to 24 hours), and then the room temperature is increased to 50 ° C. at a temperature increase rate of 15 ° C./h (elapsed time: 24 to 26 hours). Thereafter, the temperature was kept at room temperature for 4 hours (elapsed time: 26 to 30 hours), and then further increased to 65 ° C. at 15 ° C./h (elapsed time: 30 to 31 hours). And the isothermal curing period of 65 degreeC was taken for 17 hours (elapsed time: 31-48 hours), and it was allowed to cool naturally after that. That is, curing condition No. In No. 3, pre-curing is performed for 24 hours, and steam curing is performed for 24 hours.

  Then, after curing under such curing conditions, the compressive strength (JIS A 1108) at a predetermined age in the air exposure state was measured for each specimen.

  FIG. 10 shows the result of the compressive strength at the time of the predetermined age of each test body, FIG. 10 (a) is a table summarizing the results, and FIG. 10 (b) is a graph. In addition, the compressive strength of each test body was measured immediately after completion of curing, at the age of 7 days and at the age of 28 days.

As shown in FIG. 10, the difference in the compressive strength of each specimen clearly appears immediately after the end of curing. It turns out that it becomes large in order of 1-3. This is because the longer the pre-curing period, the more the CaO and SO ₃ contained in the PFBC ash, which occupies 70% of the binder, the hydration reaction proceeds, and Ca (OH) ₂ and ettringite are generated. This is considered to be due to the fact that the hardness is exhibited and the produced Ca (OH) ₂ acts as a stimulant to promote the hydration reaction of the blast furnace slag and further promote hardening (latent hydraulic).

Each specimen gradually increased in compressive strength as the age of the material passed, and the compressive strength at the age of 28 days was determined as the curing condition No. 1 is 14.3 N / mm ² , and curing condition No. 2 is 17.3 N / mm ² , and curing condition No. 3 is 21.7 N / mm ² .

Here, in the building construction standard specification and the explanation JASS5, the required concrete strength (durability design standard strength) to be secured in the durability design is 18 N / mm ² , which is a general one with a service limit period of 30 years. It has established. On the other hand, according to the test results, the concrete secondary product was No. When manufactured under the curing condition 3, the general durability design standard strength is satisfied.

  That is, in producing the concrete secondary product according to the present embodiment, a general design standard strength can be expressed in the concrete secondary product by setting the pre-curing period for 24 hours or more.

It is process drawing which shows the manufacturing process of the concrete secondary product which does not contain cement based on this embodiment. It is a graph which shows the heat history of steam curing. It is a table | surface which shows the specification of the material of a block. It is a table | surface which shows the chemical composition ratio of PFBC ash and blast furnace slag fine powder. It is a table | surface which shows the compounding conditions of the material of a block. It is a graph which shows the temperature history of the steam curing used by this examination. It is the table | surface which put together the relationship between the age of the manufactured block, and compressive strength. It is a table | surface which shows the structural material of the test body of the concrete secondary product used in the test which concerns on curing conditions, and its mixture. It is a graph which shows the temperature history of the steam curing of each test body. The result of the compressive strength at the time of the predetermined material age of each test body is shown, The figure (a) is a table | surface which put together the result, and the figure (b) is a graph.

Explanation of symbols

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

Claims (6)

A method for producing a secondary concrete product from concrete comprising fine aggregate, coarse aggregate, water, and binder,
The binder is made of PFBC ash and blast furnace slag fine powder ,
Mixing the concrete so that the slump value is substantially zero,
Placing the mixed 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 secondary concrete product, comprising subjecting the concrete from which the formwork has been removed to precuring at 20 ° C. for at least 24 hours and then steam curing the concrete. The blending of the concrete is such that the water binder ratio, which is the mass ratio of the water to the binder containing the PFBC ash and blast furnace slag fine powder, is 40% or less, and the absolute volume of the fine aggregate amount relative to the total aggregate amount The method for producing a concrete secondary product according to claim 1, wherein the ratio of fine aggregate as a ratio is 50% or more.   3. The method for producing a concrete secondary product according to claim 1, wherein a mass ratio of the PFBC ash to the blast furnace slag fine powder is 25:75 to 75:25. Method for manufacturing a concrete secondary product according to claim 1 or 2 content of the blast furnace slag occupied in the binder, characterized in that 50 mass% or less.   The method for producing a concrete secondary product according to any one of claims 1 to 4, further comprising blending an admixture with the concrete. A concrete secondary product produced by the method for producing a concrete secondary product according to any one of claims 1 to 5 .

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