JP2021160973A - Hardened body - Google Patents

Abstract

To provide a hardened body that can reduce manufacturing cost and improve strength.SOLUTION: A hardened body containing a sodium and potassium-containing coal ash and an alkali activation agent has, setting sodium and potassium in coal ash as x (mass%) and y (mass%) as the contained amount in terms of sodium oxide and potassium oxide, respectively, a total alkali A defined by the following equation (1) A=x+0.658y ... (1) of 1.2 mass% or more, and a mass ratio of sodium and potassium derived from alkali activation agent in terms of respective sodium oxide and potassium oxide to coal ash of 0.01 to 0.6.SELECTED DRAWING: None

Description

The present disclosure relates to a cured product.

Patent Document 1 describes a geopolymer cured product composed of fly ash, an alkaline aqueous solution, and an aggregate.

Japanese Patent No. 6096674

As the fly ash used for the geopolymer cured product of Patent Document 1, grade F fly ash and grade C fly ash are mentioned, but according to the amount of alkali contained in these fly ash, the geopolymer cured product is produced. The amount of alkali added at the time of doing this will increase to some extent. Then, there is a problem that the raw material cost of the cured geopolymer is increased. Insufficient mixing of fly ash, aggregate and alkali in the manufacturing process of the cured geopolymer may cause a decrease in strength due to inhomogenization of the cured geopolymer.

In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a cured product capable of reducing manufacturing costs and improving strength.

In order to achieve the above object, the cured product according to the present disclosure is a cured product containing sodium and potassium-containing coal ash and an alkali activator, and the sodium and potassium in the coal ash are mixed with sodium oxide and potassium oxide. When x (mass%) and y (mass%) are used as the content based on potassium oxide, the following formula (1)
A = x + 0.658y ・ ・ ・ (1)
The total alkali A defined in is 1.2% by mass or more, and the mass ratio of sodium and potassium derived from the alkali activator to the coal ash based on sodium oxide and potassium oxide is 0.01 to 0. It is 6.

Further, the cured product according to the present disclosure is a cured product containing coal ash containing sodium and potassium, an alkali activator, and a carbon fiber composite material, and sodium derived from the alkali activator with respect to the coal ash. The carbon fiber composite material has a mass ratio of 0.01 to 0.6 based on sodium oxide and potassium oxide, respectively, and the carbon fiber composite material with respect to the mixture containing the coal ash, the alkali activator, and the carbon fiber composite material. The mass ratio of is 1 to 50.

According to the cured product of the present disclosure, the amount of the alkali activator to be added can be reduced by applying sodium and potassium excessively contained in the coal ash to the formation reaction of the cured product to impart strength, and thus the raw material cost. The manufacturing cost can be reduced by reducing the amount. In addition, as sodium and potassium applied to the formation reaction of the cured product, those derived from the alkali activator added during the manufacturing process of the cured product are reduced, and sodium and potassium existing inside or on the surface of the coal ash particles are reduced. By utilizing the above, the dispersibility of sodium and potassium in the mixture of coal ash and the alkali activator is improved, so that the cured product is homogenized and the strength can be improved.

According to the cured product of the present disclosure, by including a carbon fiber composite material having strong alkali resistance, strength and durability can be enhanced, and toughness can be improved by a bridging effect when cracks occur. Further, when a resin reinforced with carbon fibers is used as the carbon fiber composite material, the surface of the carbon fibers is covered with the resin, so that the carbon fibers have undulations, and the physical strength can be improved by the anchor effect. Further, by effectively utilizing an inexpensive waste carbon fiber composite material as the carbon fiber composite material, the strength of the cured product can be improved while reducing the weight and cost.

Hereinafter, the cured product according to the embodiment of the present disclosure will be described. Such an embodiment shows one aspect of the present disclosure, does not limit the disclosure, and can be arbitrarily modified within the scope of the technical idea of the present disclosure.

<Explanation of the cured product according to the first embodiment of the present disclosure>
As the cured product according to the first embodiment of the present disclosure, a solidified product obtained by putting a raw material (mixture described later) into a geopolymer concrete or a frame body having various shapes and curing it at room temperature or heating to remove the frame is used. Can be mentioned. Such a cured product contains coal ash containing sodium and potassium and an alkali activator, and may further contain aggregate if necessary. Further, in the formation of the cured product according to the present disclosure, the amorphous alumina and silica in the coal ash are eluted by mixing the coal ash and the alkaline aqueous solution, and the intervening sodium or potassium is involved in the formation of the cured product together with the alumina. It occurs when silica is condensed and polymerized to grow an alkaline aluminosilicate hydrate gel.

As the coal ash, for example, various fly ash can be used. In the first embodiment, when sodium and potassium in coal ash are defined as x (mass%) and y (mass%) as the contents based on sodium oxide and potassium oxide, respectively, the following formula (1) is used.
A = x + 0.658y ・ ・ ・ (1)
The total alkali A defined in is 1.2% by mass or more, preferably 1.5% by mass or more.

As the alkali activator, for example, water glass (sodium silicate aqueous solution or potassium silicate aqueous solution), an aqueous solution of alkali metal or alkaline earth metal silicate, carbonate, or hydroxide can be used. can. When producing a cured product, such an alkali activator contains sodium and potassium as alkaline components, but in the cured product according to this embodiment, sodium derived from the alkali activator for coal ash and sodium and potassium. The mass ratio of sodium oxide and potassium oxide standard for potassium is 0.01 to 0.6.

As the aggregate, for example, one or more known gravel, sand, etc. can be used. In the first embodiment, when a mixture for obtaining a cured product (a mixture containing at least coal ash and an alkali activator and the cured product contains aggregate, coal ash, an alkali activator and an aggregate) The mass ratio of the aggregate to (the mixture containing and) is 0 to 0.8.

In the cured product according to the first embodiment, fly ash having a high content of sodium and potassium, which cannot normally be used for cement, can be used as coal ash. Therefore, by applying sodium and potassium excessively contained in coal ash to the formation reaction of the cured product, the amount of the alkali activator to be added can be reduced, so that the production cost can be reduced by reducing the raw material cost. be able to. In addition, as sodium and potassium applied to the formation reaction of the cured product, those derived from the alkali activator added during the manufacturing process of the cured product are reduced, and sodium and potassium existing inside or on the surface of the coal ash particles are reduced. By utilizing the above, the dispersibility of sodium and potassium in the mixture of coal ash and the alkali activator is improved, so that the cured product is homogenized and the strength can be improved. The specific action and effect of improving the strength will be described in Examples described later.

<Explanation of the cured product according to the second embodiment of the present disclosure>
The cured product according to the second embodiment of the present disclosure uses coal ash further containing 6% by mass to 12% by mass of calcium as a calcium oxide standard with respect to the cured product according to the first embodiment. In the presence of calcium in the cured product formed as a condensed polymer of silica and alumina, CSH (calcium silicate hydrate) gel is formed, and the tissue structure is densified in an appropriate amount to increase the strength and strength. Durability is improved. Therefore, usually, a calcium raw material such as blast furnace slag is added. However, according to the cured product according to the second embodiment, by using coal ash containing a high concentration of calcium, it is not necessary to add a calcium-based raw material such as blast furnace slag, so that CSH gel is produced. As a result, the strength can be expected to increase, and the amount of the cured product can be reduced and the cost can be reduced. The specific action and effect of the strength development associated with the formation of the CSH gel will be described in Examples described later.

<Explanation of the cured product according to the third embodiment of the present disclosure>
The cured product according to the third embodiment of the present disclosure is a cured product containing coal ash containing sodium and potassium, an alkali activator, and a carbon fiber composite material, and is sodium derived from an alkali activator for coal ash. The mass ratio of sodium oxide and potassium oxide to each of sodium oxide and potassium oxide is 0.01 to 0.6, and the mass ratio of the carbon fiber composite material to the mixture for obtaining a cured product is 1 to 50. All of the cured products according to the second and third embodiments may contain an aggregate if necessary, and the mass ratio of the aggregate to the mixture is the same as that of the first embodiment.

The carbon fiber composite material is, for example, a resin reinforced with carbon fibers, and examples of the resin include epoxy resin, phenol resin, polyester resin, vinyl ester resin, cyanate ester resin, polyimide resin, polyamide resin, polycarbonate resin, and polyphenylene. Examples thereof include sulfide resin and polyether ether ketone resin. As the resin reinforced with such fibers, for example, carbon fiber reinforced plastic (CFRP), glass fiber reinforced plastic (GFRP), boron fiber reinforced plastic, aramid fiber reinforced plastic, polyethylene fiber reinforced plastic and the like can be used. can. In addition, a fiber reinforced metal or the like can be used as the carbon fiber composite material.

Generally, the bending strength of the carbon fiber composite material increases as the aspect ratio increases, but the dispersibility deteriorates as the fiber length increases, and the effect of improving the strength of the cured product decreases. Therefore, the appropriate aspect ratio of the carbon fiber composite material is 30 to 200. As a result, the length of the maximum side of the carbon fiber composite material is preferably 2 mm to 60 mm. Here, the length of the maximum side corresponds to the length of the longest straight line among the straight lines connecting any two vertices when the carbon fiber composite material has a polyhedron shape, and the carbon fiber composite material has a cylindrical shape. In the case, it corresponds to the length of the longest straight line connecting any position on both end faces, and the carbon fiber composite material has a spherical shape (including an elliptical body and an incomplete elliptical body instead of a perfect sphere). Corresponds to the length of the longest straight line connecting any two positions on the surface.

By containing the carbon fiber composite material in each of the cured products according to the third embodiment of the present disclosure, the strength and durability can be enhanced, and the toughness can be improved by the bridging effect when cracks occur. Further, when a resin reinforced with carbon fibers is used as the carbon fiber composite material, the surface of the carbon fibers is covered with the resin, so that the carbon fibers have undulations, and the physical strength can be improved by the anchor effect. Further, by effectively utilizing an inexpensive waste carbon fiber composite material as the carbon fiber composite material, the strength of the cured product can be improved while reducing the weight and cost. The specific action and effect of improving the strength will be described in Examples described later.

<Examples of a cured product according to each embodiment of the present disclosure>
In order to clarify the action and effect of improving the strength of the cured product according to the first embodiment of the present disclosure, each index value regarding the strength of the cured product prepared under the conditions of Examples 1 to 4 and Comparative Examples 1 and 2 is obtained. (Compliant with JIS R5201). Table 1 summarizes the composition of each cured product and each index value regarding the strength of each cured product. As the alkaline aqueous solution in each Example and each Comparative Example, water glass, sodium hydroxide, potassium hydroxide, or a mixture thereof diluted with water can be used.

In Examples 1 to 3 in which the total alkalinity is larger than that of Comparative Example 1, the compressive strength and the bending strength are increased as compared with Comparative Example 1, and it can be seen that the larger the total alkalinity, the higher the strength of the cured product. The reason for this is that the larger the total alkali in the fly ash, the more all or part of the sodium and potassium in the fly ash is utilized for the formation of the alkaline aluminosilicate hydrate gel, which is higher than the case where the alkaline aqueous solution is simply added. It is considered that this is because the formation proceeds uniformly and uniformly, and the more sodium and potassium are present, the larger the amount of alkaline aluminosilicate gel is formed and the strength of the cured product is improved.

By utilizing all or part of sodium and potassium in fly ash for the production of alkaline aluminosilicate hydrate gel, the total alkali derived from the alkaline aqueous solution can be reduced, so that the production cost is reduced due to the reduction in raw material cost. be able to. This is because Example 4 reduced the total alkali derived from the alkaline aqueous solution with respect to fly ash as compared with Comparative Example 1 (the latter was 13% by mass, while the former was 11% by mass). It can be confirmed that the compressive strength and the bending strength of the above are the same. Further, comparing Example 2 in which the total alkali derived from the alkaline aqueous solution with respect to fly ash was increased from 13% by mass to 16% by mass with respect to Comparative Example 1, it was found that the total alkali in the fly ash was large. Since the same strength can be obtained even if the total alkali derived from the alkaline aqueous solution with respect to fly ash is small, it was confirmed that the production cost can be reduced by reducing the raw material cost while suppressing the decrease in the strength of the cured product.

Next, in order to clarify the action and effect (improvement of strength and durability) of the cured product according to the second embodiment of the present disclosure, the cured product prepared under the conditions according to Examples 5 and 6 and Comparative Examples 3 and 4. Each index value regarding the strength of was obtained. Table 2 summarizes the composition of each cured product and each index value regarding the strength of each cured product.

In Examples 5 and 6 corresponding to the cured product according to the second embodiment obtained by using coal ash containing 6% by mass and 12% by mass of calcium as the calcium oxide standard, 3% by mass and 16 by mass as the calcium oxide standard. Compared with Comparative Examples 3 and 4 in which coal ash containing mass% calcium was used, the compressive strength and bending strength were increased. Therefore, as a calcium oxide standard, coal containing 6% by mass to 12% by mass of calcium. It was confirmed that the use of ash improves the strength and durability of the cured product.

Next, in order to clarify the action and effect of improving the strength of the cured product according to the third embodiment of the present disclosure, each index relating to the strength of the cured product prepared under the conditions of Examples 7 to 10 and Comparative Examples 5 and 6. Got a value. Table 3 summarizes the composition of each cured product and each index value regarding the strength of each cured product. CFRP was used as the carbon fiber composite material in each Example and each Comparative Example. Further, the CFRP having a maximum side length of 15 mm was used.

Comparing the compressive strength and bending strength of Examples 7 to 10 with the compressive strength and bending strength of Comparative Examples 5 and 6, the former is higher than any of the indexes. The strength (particularly the bending strength) is improved by including CFRP, but when the CFRP compounding ratio is 60% by mass, the dispersibility deteriorates, the flow value decreases, and the strength also decreases. Therefore, it was confirmed that the effect of improving the strength of the cured product can be obtained by including CFRP as a carbon fiber composite material having a blending ratio in the range of 1 to 50 with respect to the mixture for obtaining the cured product.

The contents described in each of the above embodiments are grasped as follows, for example.

[1] The cured product according to one aspect is
With coal ash containing sodium and potassium,
A cured product containing an alkali activator,
When sodium and potassium in the coal ash are defined as x (mass%) and y (mass%) as the contents based on sodium oxide and potassium oxide, respectively, the following formula (1)
A = x + 0.658y ・ ・ ・ (1)
The total alkali A defined in is 1.2% by mass or more,
The mass ratio of sodium oxide and potassium oxide derived from the alkali activator to the coal ash is 0.01 to 0.6, respectively.

According to the cured product of the present disclosure, the amount of the alkali activator to be added can be reduced by applying sodium and potassium excessively contained in the coal ash to the formation reaction of the cured product to impart strength, and thus the raw material cost. The manufacturing cost can be reduced by reducing the amount. In addition, as sodium and potassium applied to the formation reaction of the cured product, those derived from the alkali activator added during the manufacturing process of the cured product are reduced, and sodium and potassium existing inside or on the surface of the coal ash particles are reduced. By utilizing the above, the dispersibility of sodium and potassium in the mixture of coal ash and the alkali activator is improved, so that the cured product is homogenized and the strength can be improved.

[2] The cured product according to another aspect is the cured product according to [1].
The coal ash further contains 6% by mass to 12% by mass of calcium based on calcium oxide.

According to such a configuration, by using coal ash containing a high concentration of calcium, it is not necessary to add a calcium-based raw material such as blast furnace slag, so that strength development accompanying the formation of CSH gel is expected. It is possible to reduce the weight and cost of the cured product.

[3] The cured product according to still another aspect is the cured product according to [1] or [2].
The cured product further contains a carbon fiber composite material, and the cured product further contains a carbon fiber composite material.
The mass ratio of the carbon fiber composite to the mixture containing the coal ash, the alkali activator and the carbon fiber composite is 1 to 50.

According to such a configuration, by including the carbon fiber composite material having strong alkali resistance, the strength and durability can be enhanced, and the toughness can be improved by the bridging effect at the time of crack occurrence. Further, when a resin reinforced with carbon fibers is used as the carbon fiber composite material, the surface of the carbon fibers is covered with the resin, so that the carbon fibers have undulations, and the physical strength can be improved by the anchor effect. Further, by effectively utilizing an inexpensive waste carbon fiber composite material as the carbon fiber composite material, the strength of the cured product can be improved while reducing the weight and cost.

[4] The cured product according to one aspect is
With coal ash containing sodium and potassium,
Alkali activator and
A cured product containing a carbon fiber composite material.
The mass ratio of sodium oxide and potassium derived from the alkali activator to the coal ash based on sodium oxide and potassium oxide is 0.01 to 0.6, respectively, and the coal ash, the alkali activator, and the carbon fiber are used. The mass ratio of the carbon fiber composite material to the mixture containing the composite material is 1 to 50.

According to the cured product of the present disclosure, by including a carbon fiber composite material having strong alkali resistance, strength and durability can be enhanced, and toughness can be improved by a bridging effect when cracks occur. Further, when a resin reinforced with carbon fibers is used as the carbon fiber composite material, the surface of the carbon fibers is covered with the resin, so that the carbon fibers have undulations, and the physical strength can be improved by the anchor effect. Further, by effectively utilizing an inexpensive waste carbon fiber composite material as the carbon fiber composite material, the strength of the cured product can be improved while reducing the weight and cost.

[5] The cured product according to still another aspect is the cured product of [3] or [4].
The maximum side length of the carbon fiber composite material is 2 mm to 60 mm.

Generally, the bending strength of the carbon fiber composite material increases as the aspect ratio increases, but the dispersibility deteriorates as the fiber length increases, and the effect of improving the strength of the cured product decreases. On the other hand, according to the configuration of [5], deterioration of the dispersibility of the carbon fiber composite material can be suppressed, so that the effect of improving the strength of the cured product can be appropriately obtained.

[6] The cured product according to still another aspect is any of the cured products [1] to [5].
The cured product is geopolymer concrete.

According to such a configuration, it is possible to provide a geopolymer concrete capable of reducing the manufacturing cost and improving the strength.

Claims (6)

With coal ash containing sodium and potassium,
A cured product containing an alkali activator,
When sodium and potassium in the coal ash are defined as x (mass%) and y (mass%) as the contents based on sodium oxide and potassium oxide, respectively, the following formula (1)
A = x + 0.658y ・ ・ ・ (1)
The total alkali A defined in is 1.2% by mass or more,
A cured product in which the mass ratio of sodium oxide and potassium oxide derived from the alkali activator to the coal ash is 0.01 to 0.6, respectively, based on sodium oxide and potassium oxide. The cured product according to claim 1, wherein the coal ash further contains 6% by mass to 12% by mass of calcium as a calcium oxide standard. The cured product further contains a carbon fiber composite material, and the cured product further contains a carbon fiber composite material.
The cured product according to claim 1 or 2, wherein the mass ratio of the carbon fiber composite material to the mixture containing the coal ash, the alkali activator and the carbon fiber composite material is 1 to 50. With coal ash containing sodium and potassium,
Alkali activator and
A cured product containing a carbon fiber composite material.
The mass ratio of sodium oxide and potassium derived from the alkali activator to the coal ash based on sodium oxide and potassium oxide is 0.01 to 0.6, respectively, and the coal ash, the alkali activator, and the carbon fiber are used. A cured product in which the mass ratio of the carbon fiber composite material to the mixture containing the composite material is 1 to 50. The cured product according to claim 3 or 4, wherein the length of the maximum side of the carbon fiber composite material is 2 mm to 60 mm. The cured product according to any one of claims 1 to 5, wherein the cured product is geopolymer concrete.