JP6726941B2 - COMPOSITION FOR CONCRETE HAVING IMPROVED FROZE DAMAGE, MOLDED ARTICLE FORMED THEREOF, MANUFACTURING METHOD THEREOF, AND QUALITY CONTROL METHOD - Google Patents

Description

The present invention relates to a technique for improving frost damage resistance of concrete using blast furnace slag fine aggregate, and in particular, a composition for concrete having improved frost damage resistance, a molded article formed by molding the same, a method for producing the same, and It relates to a quality control method.

Blast furnace slag fine aggregate is one of the by-products generated in the process of producing pig iron from iron ore. By using this blast furnace slag fine aggregate, it is possible to produce concrete having high frost damage resistance (freeze-thaw resistance) without using an AE agent (for example, see Patent Documents 1 and 2). ..

JP, 2014-159354, A JP, 2005-074603, A

However, even concrete using blast furnace slag fine aggregate may not be able to obtain sufficient frost damage resistance depending on the casting height and the composition. For example, FIG. 1 shows the freezing and thawing test results of a core specimen taken from a box culvert specimen with a height of 2150 mm (100% blast furnace slag fine aggregate used, water cement ratio (W/C)=35%). Is. Salt water is used as frozen water. As shown in this figure, the samples taken from below have higher relative dynamic elastic modulus, that is, frost damage resistance, but in all cases, the relative dynamic elastic modulus is less than 60% by 150 freeze-thaw cycles. It can be seen that the effect of improving the frost damage resistance by using the material has not appeared.

FIG. 2 shows the results of a bleeding test of concrete that was kneaded in an actual machine. As shown in this figure, the concrete with water cement ratio (W/C) of 35% and blast furnace slag fine aggregate 100% has crushed sand and water cement ratio (W/C) of 25%. It was found that the amount of bleeding was considerably higher than that of the concrete, and it is speculated that the bleeding of concrete impedes freeze-thaw resistance.

In order to study the effect of bleeding of concrete on freeze-thaw resistance, the concrete content was changed with the water-cement ratio (W/C) kept constant at 35% and the unit water amount (W) varied between 155 and 195 kg/m ^3. A bleeding test and a freeze-thaw test were performed on the sample. Table 1 shows the mix of concrete test pieces (specimen numbers 1 to 5).

Here, in the formulation of Table 1, the cement (C) is early-strength Portland cement (density: 3.13 g/cm ³ , Blaine value: 4600 cm ² /g), and the fine aggregate (S) is blast furnace. Slag fine aggregate (surface dry density: 2.72 g/cm ³ , water absorption rate: 1.12%), and coarse aggregate (G) as hard sandstone crushed stone (maximum size: 20 mm, surface dry density: 2. 74 g/cm ³ , water absorption rate: 0.60%) were used. Further, the amount of air, the fine aggregate ratio (s/a), and the amount of the high-performance water reducing agent used were as shown in Table 1. The fine aggregate ratio (s/a) in Table 1 is the fine aggregate ratio (s/a)=fine aggregate (S)/(fine aggregate (S)+coarse aggregate (G))×100 Calculated using the formula (%). However, the fine aggregate ratio is the absolute volume ratio of the amount of fine aggregate to the total amount of aggregate in concrete expressed as a percentage. Each specimen was prepared by steam curing and then underwater curing until the material age was 7 days. The maximum temperature of steam curing was 50° C., and the maximum temperature holding time of steam curing was 5 hours. Regarding the value of the compressive strength, the strength test value of the one which was cured in air after being demolded after steam curing was adopted. The compressive strength of each specimen is 41.4~42.4N / mm ² at an age of 18 hours, a 54.5~59.5N / mm ² at an age of 7 days, the compressive strength of each specimen is It is almost the same.

FIG. 3 shows the effect of the unit water amount (W) on the bleeding of concrete, and FIG. 4 shows the effect of the unit water amount (W) on the freeze-thaw resistance. Here, the bleeding test is performed in accordance with JIS A 1123:2012 using a lightweight mold of φ150×300 mm. The freeze-thaw test is performed in accordance with the underwater freeze-thaw test method (method A) defined in JIS A 1148:2010. However, as the solution for immersing the sample, 10% by weight of salt water (10% by weight concentration of sodium chloride aqueous solution) is used so that the deterioration due to the freeze-thaw action is promoted. As the test piece, a cylindrical test piece of φ100×200 mm and a prismatic test piece of 100×100×400 mm are used.

As shown in FIG. 3, it can be seen that the bleeding amount increases as the unit water amount (W) increases. Further, as shown in FIG. 4, it can be seen that the more bleeding concrete, the lower the freeze-thaw resistance.

In particular, as shown in FIG. 4 and Table 1, even if the water-cement ratio (W/C) is the same and the strengths are almost the same, if the unit water content (W) is large, the freeze-thaw cycle number is less than 300 times. May lead to destruction. In the example of FIG. 4, when the unit water content (W) is 155 or 165 kg/m ³ , the relative dynamic elastic modulus is 90% or more at 300 freeze/thaw cycles, and the frost damage resistance is excellent, but the unit water content (W ) Of 175 kg/m ³ or more, the relative dynamic elastic modulus is reduced to 60% or less at an early stage, leading to destruction.

As described above, in the concrete using the blast furnace slag fine aggregate, the more the bleeding is, the lower the frost damage resistance (freeze-thaw resistance) tends to be. Therefore, there has been a demand for a technique capable of improving frost damage resistance even when there is a large amount of bleeding.

The present invention has been made in view of the above, and an object thereof is to provide a composition for concrete having improved frost damage resistance, a molded article formed by molding the same, a method for producing the same, and a quality control method. ..

In order to solve the above problems and achieve the object, the composition for concrete according to the present invention is a fine aggregate containing blast furnace slag fine aggregate, a binder containing cement, water, and coarse aggregate. Which is a composition for concrete which suppresses bleeding, and is a relative ratio of 300 freeze-thaw cycles in a freeze-thaw test based on the method A described in JIS A 1148 for a concrete specimen produced by the concrete composition. It has a kinetic elastic modulus of 60% or more and is excellent in freeze-thaw resistance.

Further, another composition for concrete according to the present invention is characterized in that, in the above-mentioned invention, the unit water amount is reduced to 165 kg/m ³ or less without adding a thickening agent or a separation reducing agent to suppress bleeding. And

Further, another concrete composition according to the present invention is characterized in that, in the above-mentioned invention, a thickener or a separation reducing agent is added to suppress bleeding.

Further, another concrete composition according to the present invention is characterized in that, in the above-mentioned invention, the addition amount of the thickening agent or the separation reducing agent to the binder is 0.04% or more.

Further, another composition for concrete according to the present invention is characterized in that, in the above-mentioned invention, a unit water amount is 195 kg/m ³ or less.

Further, another composition for concrete according to the present invention is characterized in that, in the above-mentioned invention, a mass ratio of the blast furnace slag fine aggregate to the fine aggregate is 0.33 to 1.0.

Further, another concrete composition according to the present invention is characterized in that, in the above-mentioned invention, a mass ratio of water to the binder is 0.25 to 0.50.

Further, another composition for concrete according to the present invention is characterized in that, in the above-mentioned invention, it does not contain an agent entraining air.

In addition, another composition for concrete according to the present invention, in the above-mentioned invention, freeze-thaw even if the concentration of the solution for immersing the concrete specimen used in the freeze-thaw test is 10% by mass of salt water. It is characterized by excellent resistance.

Further, another composition for concrete according to the present invention is characterized in that, in the above-mentioned invention, a molded article obtained by molding the composition for concrete has excellent freeze-thaw resistance.

The molded product according to the present invention is a molded product obtained by molding the above-mentioned concrete composition.

Further, the method for producing a molded article according to the present invention, a fine aggregate containing blast furnace slag fine aggregate, a binder containing cement, water, and a concrete composition containing coarse aggregate, a predetermined amount A method for producing a molded article having freeze-thaw resistance, which suppresses bleeding of the concrete composition, wherein the composition for concrete in which bleeding is suppressed is frozen based on the A method according to JIS A 1148. It is characterized in that a molded article having a freeze-thaw resistance with a relative dynamic elastic modulus of 60% or more after 300 freeze-thaw cycles in a melting test is produced.

Further, the method for producing another molded article according to the present invention, in the above-mentioned invention, when the bleeding amount obtained by a bleeding test for the concrete composition is a predetermined amount or more, the composition for concrete is increased. By suppressing the bleeding of the concrete composition by adding a viscous agent or a separation reducing agent, from the concrete composition with suppressed bleeding, to produce a molded article having a predetermined freeze-thaw resistance, To do.

Further, another method for producing a molded article according to the present invention, in the above-mentioned invention, suppresses the bleeding of the concrete composition containing no air-entraining agent, and a molded article having a predetermined freeze-thaw resistance. It is characterized by being manufactured.

Further, the quality control method according to the present invention is a molded product produced from a concrete composition containing fine aggregate containing blast furnace slag fine aggregate, binder containing cement, water, and coarse aggregate. A method for controlling the freeze-thaw resistance of a concrete composition, wherein the bleeding of the concrete composition is suppressed, and the freeze-thaw resistance of a molded article produced from the concrete composition in which the bleeding is suppressed is determined according to JIS A In the freeze-thawing test based on the method A described in 1148, the relative dynamic elastic modulus after 300 freeze-thawing cycles is controlled to be 60% or more.

Further, another quality control method according to the present invention, in the above-mentioned invention, when the bleeding amount obtained by the bleeding test for the concrete composition is a predetermined amount or more, a thickener for the concrete composition. Alternatively, it is characterized in that bleeding of the concrete composition is suppressed by adding a separation reducing agent, and freeze-thaw resistance of a molded article produced from the concrete composition in which bleeding is suppressed is controlled.

Further, another quality control method according to the present invention, in the above-mentioned invention, suppresses bleeding of the concrete composition that does not contain an agent that entrains air, and is manufactured from the concrete composition in which bleeding is suppressed. It is characterized by controlling freeze-thaw resistance of a molded article.

According to the concrete composition of the present invention, a fine aggregate containing blast-furnace slag fine aggregate, a binder containing cement, water, and a coarse aggregate, and containing concrete composition for suppressing bleeding In the freeze-thaw test based on the method A described in JIS A 1148, the relative dynamic elastic modulus in the freeze-thaw cycle of 300 times is 60% or more, and the freeze-thaw is performed on the concrete specimen produced by the composition for concrete. It has excellent resistance. Therefore, it is possible to provide a composition for concrete having excellent frost resistance, a molded product obtained by molding the composition, a method for producing the same, and a quality control method.

FIG. 1 is a diagram showing the relationship between the driving height and freeze-thaw resistance. FIG. 2 is a diagram showing the relationship between the time from driving and the bleeding amount. FIG. 3 is a diagram showing the relationship between the unit water amount and the bleeding amount. FIG. 4 is a diagram showing the effect of a unit water amount on freeze-thaw resistance. FIG. 5: is a figure which shows the influence which a thickener has on freeze-thaw resistance. FIG. 6 is a diagram showing the influence of the thickener on the bleeding amount. FIG. 7: is a figure which illustrates the mass ratio of blast furnace slag fine aggregate with respect to fine aggregate, and the relationship of freeze-thaw resistance.

Embodiments of a concrete composition, a molded article obtained by molding the same, a method for producing the same, and a quality control method according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments.

The concrete composition according to the present invention is a concrete composition containing fine aggregate containing blast furnace slag fine aggregate, a binder containing cement, water, and coarse aggregate, and suppressing bleeding. Then, the relative dynamic elastic modulus at the freeze-thaw cycle of 300 times in the freeze-thaw test based on the method A of JIS A 1148 for the concrete specimen produced by the concrete composition is 60% or more, and the freeze-thaw resistance is Is excellent.

Here, in the above-mentioned freeze-thaw test, 10% by mass of salt water (10% by mass concentration of sodium chloride aqueous solution) may be used as a solution for immersing the specimen. Generally, a freeze-thaw test using salt water is a test under more severe conditions than a test using fresh water.

As a method for suppressing bleeding of the concrete composition, for example, a method of reducing the unit water content (W) of the concrete composition, a method of increasing the fine aggregate ratio (s/a), and a thickening of the concrete composition Although a method of adding an agent or a separation reducing agent can be used, in the following description, the case of adding a thickener to a concrete composition will be described as an example.

The thickener serves to reduce the separation of water in the material of the concrete composition and to generate a stickiness. As such a thickener, for example, a high-performance special thickener "Viscotop" (registered trademark) manufactured by Kao Corporation can be used. Alternatively, instead of or in addition to the thickening agent, a separation reducing agent having a function of reducing the separation of the material may be contained. The separation reducing agent exerts the same effect as that of the thickener, thereby suppressing the bleeding of concrete and contributing to the improvement of freeze-thaw resistance.

FIG. 5 shows the effect of the addition amount of the thickener on the freeze-thaw resistance for the test piece (test piece No. 5 in Table 1) in which the unit water amount (W) with an extremely large bleeding amount is 195 kg/m ^3. This is what I examined. The addition amount of the thickener was set to 0.00, 0.04% and 0.08% with respect to cement (C) which is a binder. As the thickener, the above-mentioned highly functional special thickener was used. As shown in this figure, by adding a thickener and suppressing the amount of bleeding, the freeze-thaw resistance of concrete is significantly improved. Even with concrete having a unit water content (W) of 195 kg/m ³ , if the bleeding is suppressed by using a thickener, the relative dynamic elastic modulus at 300 cycles can be maintained at 90% or more, and high frost resistance. It can be seen that

FIG. 6 is a graph showing the effect of the added amount of the thickener on the bleeding amount of concrete in a sample (Unit No. 5 in Table 1) having a unit water amount (W) of 195 kg/m ³ . As in the case of FIG. 5, the addition amount of the thickener was set to three types of 0.00, 0.04% and 0.08% with respect to the cement (C) which is the binder, and the approximate curve based on each plot was used. I am adding. As shown in this figure, it is understood that the bleeding amount decreases exponentially when the thickener is added.

As for the addition amount (content) of the thickener, the standard use amount set in the product is sufficient. That is, if the added amount of the thickener is at least this standard amount, the bleeding amount can be suppressed to a state where there is almost no bleeding and the freeze-thaw resistance of concrete is improved. For example, the standard amount of use when the above-mentioned high-performance special thickener is used is about 1.0 to 10% with respect to the unit water amount (W). This is about 0.35 to 3.5% when converted to the cement (C) when the water cement ratio (W/C) is 35%.

Conventionally, when 100% of blast furnace slag fine aggregate was used as fine aggregate, if the amount of bleeding was large, the desired frost damage resistance could not be obtained in some cases. On the other hand, according to the present embodiment, it is possible to easily obtain concrete with high frost damage resistance simply by adding a thickening agent (or a separation reducing agent) without performing processing such as reducing the unit water amount. There is an effect that can be. Thus, by using a thickener, it is possible to use concrete with a water-cement ratio of about 35%, which can be produced with the same production efficiency as ordinary concrete, in applications where frost damage resistance is required. Become. As described above, in the present invention, it is of course possible to suppress the bleeding by reducing the unit water amount or increasing the fine aggregate ratio without using the thickener. By doing so, it becomes possible to more reliably exert the effect of improving the frost damage resistance by using the blast furnace slag fine aggregate.

Here, the composition for concrete according to the present invention contains blast furnace slag fine aggregate. Blast furnace slag is a by-product of pig iron production in a blast furnace, and its main components are CaO, SiO ₂ , Al ₂ O ₃ , and MgO. This blast furnace slag can be used in the form of blast furnace slag fine powder or blast furnace slag fine aggregate. In this case, the blast furnace slag fine powder is used as a binder, and the blast furnace slag fine aggregate is used as a fine aggregate.

The blast furnace slag fine aggregate is an amorphous blast furnace slag fine aggregate. As the amorphous blast-furnace slag fine aggregate, for example, one obtained by lightly crushing granulated blast-furnace slag obtained by rapidly cooling blast-furnace slag with water and adding an anti-caking agent can be used. The temperature of the molten blast furnace slag immediately before being rapidly cooled in the production of granulated blast furnace slag is 1400°C to 1500°C, and by quenching, it consolidates without atomic arrangement to the crystals and is vitreous (amorphous). Becomes The quality of blast furnace slag fine aggregate is specified in JIS A 5011-1.

Examples of the cement used in the present invention include ordinary Portland cement, early strength Portland cement, super early strength Portland cement, moderate heat Portland cement, low heat Portland cement and the like.

The composition for concrete of the present invention contains fine aggregates containing blast furnace slag fine aggregate, a binder containing cement, and water, and is composed of cement (C) and binder (B). The mass ratio (C/B) is preferably 0.3 to 1.0.

FIG. 7 illustrates the relationship between the mass ratio (BFS/S) of blast furnace slag fine aggregate (BFS) to fine aggregate (S) and freeze-thaw resistance. In this figure, the binder (B) is composed of ordinary Portland cement (C) and blast furnace slag fine powder (GGBF), and the mass ratio (W/B) of water to the binder (B) is 40%, and the binder ( The mass ratio (GGBF/B) of blast furnace slag fine powder (GGBF) to B) was set to 60%, and the freeze-thaw resistance of concrete produced through steam curing without adding an AE agent (nonAE) is shown. .. As shown in this figure, the blast furnace slag fine aggregate of 33% or more used as the fine aggregate has a relative dynamic elastic modulus of 60% or more after 300 freeze-thaw cycles. It can be seen that the relative dynamic elastic modulus of the blast furnace slag fine aggregate using 67% or more is 98% or more, and all of them have excellent freeze-thaw resistance. From this, the mass ratio (BFS/S) of the blast furnace slag fine aggregate (BFS) to the fine aggregate (S) is preferably 0.33 to 1.0. In addition to the blast furnace slag fine aggregate, a general fine aggregate such as crushed sandstone can be used as the fine aggregate.

The composition for concrete of the present invention usually further contains coarse aggregate, and the composition for concrete is cured to obtain concrete. As the coarse aggregate, for example, general coarse aggregate such as crushed sandstone can be used. The amount of the coarse aggregate used in the concrete composition is preferably 100 to 500 parts by mass of the coarse aggregate (G) with respect to 100 parts by mass of the binder (B).

Moreover, the mass ratio (W/B) of water to the binder (B) in the composition for concrete is 0.25 to 0.50, that is, water is 25 parts with respect to 100 parts by mass of the binder (B). It is preferably ˜50 parts by mass. When the binder (B) consists only of cement (C), the water cement ratio (W/C) is preferably 0.25 to 0.50. Further, the concrete composition of the present invention may further contain other components as long as the effects of the present invention are not impaired.

The unit water content (W) in the concrete composition is preferably 195 kg/m ³ or less when the bleeding is reduced by using a thickener (or a separation reducing agent). When the bleeding is reduced only by reducing the unit amount of water without using a thickener (or a separation reducing agent), it is preferably 165 kg/m ³ or less.

Further, the concrete composition of the present invention suppresses bleeding by the above-mentioned method without containing an admixture having air entrainment such as an AE agent, thereby making it possible to obtain a concrete using a blast furnace slag fine aggregate. The effect of improving frost damage resistance can be effectively exerted.

The composition for concrete of the present invention is excellent in freeze-thaw resistance, that is, frost damage resistance. Therefore, the concrete composition of the present invention is effective as a material for a concrete structure in a cold region where frost damage resistance is required.

The concrete composition of the present invention is also excellent in resistance to salt damage. Therefore, it is particularly effective for construction such as a structure requiring salt damage resistance, and a place where a combination of frost damage, salt damage and fatigue may occur, such as a highway in a mountainous area where snow melting agents are sprayed in winter. In addition to these applications, for example, in sites where frost resistance, fatigue resistance and salt damage resistance of coastal structures, marine structures, waterway structures, road structures and retaining wall structures in cold regions are required. It is preferably used. At this time, the composition for concrete of the present invention may be molded in advance and applied as a molded product (precast concrete product).

Further, according to the concrete product using the molded product of the present invention, not only frost damage resistance but also salt damage resistance is exhibited. Therefore, for example, when the present invention is applied to a structure under an environment in which there is a possibility of being frost-damaged and salt-damaged, such as a coastal/marine structure in a cold region, excellent frost-damage resistance performance and salt damage resistance performance are exhibited Therefore, the service life of the structure can be extended as compared with the case where the structure is usually made of mortar or concrete.

Further, the method for producing a molded article according to the present invention suppresses the bleeding of the concrete composition by the above method, and from the concrete composition in which this bleeding is suppressed, relative in freeze-thaw cycle 300 times in the freeze-thaw test. It is intended to produce a molded article having freeze-thaw resistance with a dynamic elastic modulus of 60% or more. According to the method for producing a molded article according to the present invention, concrete having excellent freeze-thaw resistance can be stably obtained by suppressing bleeding. Here, when the bleeding amount obtained by the bleeding test for the concrete composition is equal to or more than a preset predetermined amount, a thickener (or a separation reducing agent) is added to the concrete composition to suppress bleeding. As a result, the above-mentioned molded article having freeze-thaw resistance can be produced. A unit water amount (W) may be used instead of the bleeding amount as a criterion for adding the thickening agent (or the separation reducing agent). This is because there is a correlation between the bleeding amount and the unit water amount (W). For example, in the case of FIG. 3, the thickener (or separation reducing agent) may be added when the bleeding amount of the concrete composition is 0.010 (cm ³ /cm ² ) or more, and It may be added when the amount of water (W) is 175 kg/m ³ or more.

Further, the quality control method according to the present invention suppresses bleeding of the concrete composition by the above method, and freeze-thaw resistance of a molded article produced from the concrete composition in which this bleeding is suppressed, a freeze-thaw test. It is controlled so that the relative dynamic elastic modulus is 300% or more after 300 freeze-thaw cycles. According to the quality control method of the present invention, concrete having excellent freeze-thaw resistance can be stably obtained by suppressing bleeding. As a method for suppressing bleeding, the same method as the above-described method for manufacturing a molded product can be applied.

As described above, according to the composition for concrete according to the present invention, fine aggregate containing blast furnace slag fine aggregate, binder containing cement, water, and coarse aggregate are contained, and bleeding is performed. A composition for concrete which is suppressed, wherein a relative dynamic elastic modulus at a freeze-thaw cycle of 300 times in a freeze-thaw test based on a method A described in JIS A 1148 for a concrete specimen produced by the concrete composition is 60%. Above, it is excellent in freeze-thaw resistance. Therefore, it is possible to provide a composition for concrete having excellent frost resistance, a molded product obtained by molding the composition, a method for producing the same, and a quality control method.

As described above, the composition for concrete according to the present invention, a molded article obtained by molding the same, the manufacturing method and the quality control method are useful for concrete containing a large amount of blast furnace slag fine aggregate, and particularly Due to its excellent frost resistance, it is suitable for concrete products used in coastal areas and cold areas where there is a risk of frost damage.

Claims (15)

A fine aggregate containing blast furnace slag fine aggregate, a binder containing cement, water, and a coarse aggregate, a concrete composition containing a thickener or a separation reducing agent,
The relative dynamic elastic modulus at 300 freeze-thaw cycles in the freeze-thaw test based on the method A described in JIS A 1148 for the concrete specimen produced from the concrete composition is 60% or more, and the freeze-thaw resistance is excellent. A composition for concrete characterized by the above. The composition for concrete according to claim 1 , wherein the addition amount of the thickening agent or the separation reducing agent to the binder is 0.04% or more. The composition for concrete according to claim 1 or 2 , wherein the unit water amount is 195 kg/m ³ or less. The mass ratio of the blast furnace slag fine aggregate to the fine aggregate is 0.33 to 1.0, and the composition for concrete according to any one of claims 1 to 5 . Concrete composition according to any one of claims 1-4 in which the weight ratio of water to said binder is characterized in that 0.25 to 0.50. Concrete composition according to any one of claims 1-5, characterized in that it does not contain the agent to entrain air. Claim 1-6 concentration of the solution is immersed the concrete specimen to be used for the freeze-thaw test even 10% of water at a mass ratio, which is characterized by excellent resistance to freezing and thawing The composition for concrete as described in 1. The molded product obtained by molding the composition for concrete has excellent freeze-thaw resistance, and the composition for concrete according to any one of claims 1 to 8 . Molded article obtained by molding the concrete composition according to any one of claims 1-8. Manufacturing method for producing a molded article having a predetermined freeze-thaw resistance from a concrete composition containing fine aggregate including blast furnace slag fine aggregate, cement-containing binder, water, and coarse aggregate And
Bleeding of the concrete composition was suppressed by adding a thickener or a separation reducing agent, and from the composition for concrete in which the bleeding was suppressed, freeze-thawing in a freeze-thaw test based on the method A described in JIS A 1148. A method for producing a molded article, comprising producing a molded article having freeze-thaw resistance with a relative dynamic elastic modulus of 60% or more after 300 cycles. When the bleeding amount obtained by the bleeding test for the concrete composition is a predetermined amount or more, the bleeding of the concrete composition is suppressed by adding a thickener or a separation reducing agent to the concrete composition. The method for producing a molded article according to claim 10 , wherein a molded article having a predetermined freeze-thaw resistance is produced from the composition for concrete in which bleeding is suppressed. The method for producing a molded article according to claim 10 or 11 , wherein bleeding of the concrete composition containing no air-entraining agent is suppressed to produce a molded article having a predetermined freeze-thaw resistance. .. Quality control method for controlling freeze-thaw resistance of a molded article produced from a composition for concrete containing fine aggregate containing blast furnace slag fine aggregate, binder containing cement, water, and coarse aggregate And
Bleeding of the concrete composition is suppressed by adding a thickener or a separation reducing agent, and freeze-thaw resistance of a molded article produced from the concrete composition in which the bleeding is suppressed is described in JIS A 1148. The quality control method is characterized in that the relative dynamic elastic modulus is controlled to be 60% or more in 300 freeze-thaw cycles in the freeze-thaw test based on Method A. When the bleeding amount obtained by the bleeding test for the concrete composition is a predetermined amount or more, the bleeding of the concrete composition is suppressed by adding a thickener or a separation reducing agent to the concrete composition. The quality control method according to claim 13 , wherein the freeze-thaw resistance of a molded product produced from the composition for concrete in which bleeding is suppressed is controlled. Claim suppressing bleeding of the concrete composition without the agent to entrain air, characterized in that managing the freeze-thaw resistance of moldings produced from the concrete composition with suppressed bleeding 13 Or the quality control method described in 14 .

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