JPH08277150A - Concrete composition - Google Patents

Abstract

PURPOSE: To obtain a concrete composition excellent in development of strength in spite of use of a large amount of fly ash by properly determining a concrete mixing. CONSTITUTION: This concrete composition comprises a cement (C), a fine aggregate (S), a coarse, aggregate (G), fly ash (F) and water (W). The unit amount of the cement is 250-350kg/m<3> , that of the fly ash is 150-300kg/m<3> and the weight ratio (S/G) of the fine aggregate (S) to the coarse aggregate (G) is 0.35-0.55.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete composition which utilizes fly ash in a large amount and exhibits good strength.

[0002]

2. Description of the Related Art Fly ash, which is produced in large quantities as a by-product from a pulverized coal combustion boiler of a thermal power plant, is effectively used as a cement admixture, but most of it is discarded as landfill. There is. Fly ash used as a cement admixture has improved workability of concrete because the fly ash particles are smooth and spherical, and the concrete structure is densified to increase the long-term strength, watertightness, resistance to chemicals, etc. It is suitable for mass concrete structure where temperature crack due to self-heating is a problem because the heat of hydration of cement is mitigated by the mixture of fly ash, and it also has an inhibitory effect on alkali-aggregate reaction. It has many excellent properties as concrete, such as being present.

[0003]

On the other hand, when fly ash is mixed with concrete in a large amount, delay of setting,
There are problems such as a decrease in initial strength and a delay in strength development in a low temperature environment, and the amount of the mixture is naturally limited. For example, the fly ash cement stipulated in JIS standard limits the replacement ratio of fly ash to cement to 30% at the maximum, and is not currently associated with the large use of fly ash.

Accordingly, the object of the present invention is to solve the above-mentioned drawbacks and to provide a concrete composition exhibiting good strength by appropriately defining the concrete composition, even though a large amount of fly ash is used. And

[0005]

In order to achieve the above-mentioned object, according to the concrete composition of the present invention, cement (C), fine aggregate (S), coarse aggregate (G), fly ash ( F) and a concrete composition containing water (W), wherein the unit cement amount is 250 to 350 kg / m ³ , the unit fly ash amount is 150 to 300 kg / m ³ , and
Weight ratio of fine aggregate (S) to coarse aggregate (G) (S /
G) is 0.35 to 0.55 (Claim 1), the water cement ratio (W / C) is 50% by weight or more (Claim 2), and the slump value of concrete is 8 to 22 cm. (Claim 3), a high-performance water reducing agent is further included (Claim 4), and the cement is ordinary Portland cement or early-strength Portland cement (Claim 5). Hereinafter, the present invention will be described in detail.

As the cement used in the present invention, various kinds of portland cement such as normal, early strength, ultra-early strength, moderate heat, sulfate resistance, white color, etc. can all be used, but it is great for improving initial and long-term strength development. To be effective,
Preferably, normal Portland cement or early-strength Portland cement is used. The amount of cement used is 250 to 350 kg / m ³ per unit amount of cement in concrete.
Range. When the unit cement content is less than 250 kg / m ³ , strength development, particularly initial strength, is lowered, which is not preferable. On the other hand, if it exceeds 350 kg / m ³ , it is not preferable because the mixing of concrete becomes difficult in the mass use of fly ash which is the object of the present invention.

[0007] Next, as fly ash, of course, fly ash specified by JIS is used, and fly ash usually called raw powder and cinder ash are generally used, and so-called general coal ash in a broad sense is used. You can The amount of fly ash used is such that the amount of unit fly ash in concrete is in the range of 150 to 300 kg / m ³ . If the unit fly ash amount is less than 150 kg / m ³ , it does not meet the purpose of mass use of fly ash, which is the object of the present invention, and the strength development is not sufficient, and the aggregate to be described later, in particular, the particle size balance It is not preferable because the use of bad fine aggregate is restricted. Also, if this exceeds 300 kg / m ³ ,
It is not preferable because the fluidity of concrete is lost and it is difficult to mix and mix.

[0008] Next, as the aggregate, ordinary aggregates such as sand, gravel, and crushed stone which are used for ordinary concrete can be used without regard to various kinds of aggregates. Even for those that are considered unsuitable as normal aggregate for concrete because the particle size distribution of the aggregate is unbalanced, the flowability of concrete is secured by the large amount of fly ash mentioned above and the appropriate mix of concrete accordingly. It can be preferably used as the aggregate of the present invention.

The use weight ratio (S / G) of the fine aggregate (S) to the coarse aggregate (G) in this aggregate is 0.35 to 0.55.
Range. If it is less than 0.35, the amount of fine aggregate used is extremely small, the fluidity of concrete is lost, and mixing is difficult, which is not preferable. On the other hand, if this range exceeds 0.55, the amount of coarse aggregate is reduced, which is not preferable for securing a so-called concrete required slump value of 8 to 22 cm.

Next, the present invention can eliminate defects such as a decrease in initial strength and an increase in drying shrinkage due to an increase in the amount of unit water by using a high-performance water-reducing agent together, and at the same time, it can be applied to concrete of fly ash. It is possible to achieve a large amount of mixing, and it is also possible to realize the production of concrete with good initial and long-term strength development even by mixing a large amount of fly ash.

As the high-performance water-reducing agent, any one having a chemical composition conventionally used as an admixture for concrete, for example, an alkylylallyl-based, naphthalene-based, melamine-based, or triazine-based compound can be used.
Desirably, a polycarboxylic acid salt-based admixture is preferable. Of course, it is possible to apply a high-performance AE water reducing agent having air entrainment performance. As this type of admixture, commercially available products include Reobuild SP-8S (manufactured by NMB, trade name), Mighty 2000 WHS (manufactured by Kao, trade name) Chupole HP-8 (manufactured by Takemoto Yushi Co., Ltd.), etc. Can be mentioned. While increasing the amount of the fly ash while maintaining the unit amount of cement per 1 m ^{3 of} concrete at a predetermined amount, the volume occupied by fine powder in the concrete increases and the fluidity of the concrete is impaired. It is possible to obtain a predetermined softness (slump value) in concrete by appropriately adjusting the amount of the agent added. The amount of the high-performance water reducing agent added is adjusted in consideration of the water reducing effect of Portland cement, aggregate, fly ash, and the like to be used, but generally 0.1 to 100 parts by weight of Portland cement is used. Add 10% by weight.
If it is less than 0.1% by weight, the water-reducing effect is substantially absent, and if it is added in excess of 10% by weight, the effects of improving the water-reducing property and the fluidity reach a ceiling.

In the present invention, the air entraining agent has a chemical composition conventionally used as an air entraining agent for concrete, for example, nonionic type, anionic type, oxyethylene type, higher fatty acid salt type, natural resin acid salt type chemical composition. Any thing can be used. For example, AE-775S (manufactured by NMB, Inc., product name) containing an alkylcarboxylic acid compound as a main component, Vinsol (manufactured by Yamamune Chemical, product name) of natural resin acid, Seeker AER (Nippon Seeker of the Alkylphenol system). , Product name) and the like. In the present invention, it is desirable to adjust the addition ratio of the air entraining agent to adjust the air entraining amount of concrete to 4.5 to 5.5%.

In addition to the above-described components, the present invention is also generally used in concrete for rapid hardening / hardening.
Various concrete admixture materials such as quick-setting admixtures, high-strength admixtures, hydration accelerators, setting regulators, and various fibers as reinforcing materials,
Steel or the like can also be used.

There is no limitation on the mixing and kneading method of each of the above components, as long as they can be uniformly mixed and kneaded, and the order of addition of the blended components is not particularly limited, but the water content is
The water cement ratio (W / C) is adjusted to be 50% by weight or more. If this content is less than 50% by weight, it is not preferable for securing the required slump value of 8 to 22 cm which is preferable for concrete construction.

For the curing after the concrete is poured, various curing methods can be applied, and any of normal temperature curing, high temperature curing, normal pressure steam curing and high temperature and high pressure curing can be adopted. Can be combined to obtain a higher strength concrete hardened body.

[0016]

The concrete according to the present invention, by appropriately adjusting the concrete mix as described above, does not impair the excellent characteristics of the fly ash as concrete, even if a large amount of fly ash is used. However, rather, these properties can be exerted synergistically, and a concrete having good initial strength and long-term strength development can be obtained.

[0017]

[Examples] Concrete was prepared by mixing the materials shown below and the concrete shown in Table 1 with JIS A
The compressive strength was measured according to 1108. 20 ℃
Underwater curing. The results are shown in Table 1. As shown in Table 1, in each of the examples of the present invention, excellent initial and long-term strength characteristics were exhibited. In the table, blank indicates that mixing of concrete is impossible. (Materials used) Cement CN: Ordinary Portland cement made by Chichibu Onoda Cement Fly Ash F A: Specific gravity 2.23, Blaine specific surface area 3340 cm ² / g B: Specific gravity 2.23, Blaine specific surface area 3700 cm ² / g Fine aggregate : Land sand (Shizuoka) specific gravity 2.59, FM 2.75 Coarse aggregate: Crushed stone (Ibaraki) maximum size 20mm, specific gravity 2.6
4, GFM6.66 High-performance AE water reducing agent: NMB, Rheobuild SP-8S Air entraining agent: NMB, AE-77
5S

[0018]

[Table 1]

[0019]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain concrete having good strength development in the initial and long term, and it is possible to effectively utilize fly ash, which is an industrial by-product, in large quantities.

Claims (5)

[Claims] 1. A concrete composition containing cement (C), fine aggregate (S), coarse aggregate (G), fly ash (F), and water (W), the unit cement amount of which is 250 to
350kg / m ³ , unit fly ash amount is 150-300
A concrete composition characterized in that the weight ratio (S / G) of the fine aggregate (S) to the coarse aggregate (G) is 0.35 to 0.55 in kg / m ³ . 2. A concrete composition having a water-cement ratio (W / C) of 50% by weight or more. 3. The slump value of concrete is 8 to 22 cm.
It shows that it is characterized by the above-mentioned.
The concrete composition described. 4. The concrete composition according to claim 1, further comprising a high-performance water reducing agent. 5. The concrete composition according to claim 1, wherein the cement is ordinary Portland cement or early-strength Portland cement.