JP2002068804A - Concrete composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concrete composition containing coal ash in relatively large quantities, excellent in fluidity and having high compressive strength and superior resistance to neutralization. SOLUTION: The concrete composition uses eco-cement comprising a hydraulic composition consisting essentially of gypsum and a calcined body obtained from ash of municipal garbage and/or ash of sewage sludge as raw material and containing calcium silicate and 10-40 wt.% one or more selected from calcium chloroaluminate, calcium fluoroaluminate and calcium aluminate and also uses coal ash as part of an aggregate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a concrete composition in which eco-cement is used for cement and coal ash is used as a part of aggregate to increase initial strength and long-term strength and to reuse waste. About things.

[0002]

2. Description of the Related Art In recent years, general waste such as municipal waste and sewage sludge, or industrial waste has increased remarkably, and as a countermeasure, attempts have been made in various fields to recycle and effectively utilize them. As one example, cement (eco-cement) using municipal garbage incineration ash or sewage sludge incineration ash as a main raw material has been developed, and has begun to be used as a concrete material.

On the other hand, coal ash discharged from coal-fired power plants in large quantities as combustion ash is partially used as fly ash in cement admixtures, but most of it is landfilled. Effective reuse is demanded because of tight times. By the way, fly ash used as a cement admixture has smooth and spherical particles, so by adding an appropriate amount to concrete, it improves workability, increases long-term strength by densifying the concrete structure, increases water tightness and chemicals. Various effects can be obtained, such as an improvement in resistance to water, etc., as well as a reduction in the heat of hydration of the cement to suppress cracks in the temperature and also to an effect of suppressing the alkali-aggregate reaction.

[0004] However, if the amount of fly ash is too large, problems such as a delay in setting, a decrease in initial strength, and a delay in strength development in a low-temperature environment are caused, and thus the amount of fly ash is limited. According to the JIS standard, the replacement ratio of fly ash to cement for fly ash cement is limited to a maximum of 30%. As described above, at present, fly ash discharged from thermal power plants is rarely used in large quantities.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a concrete composition using eco-cement, in which coal ash is used as a part of the aggregate to effectively utilize the coal ash.
In addition, a concrete composition that improves the fluidity of fresh concrete by blending coal ash, further densifies the structure to increase compressive strength, and suppresses the intrusion of carbon dioxide gas in the atmosphere to prevent neutralization of concrete. It provides things. According to the present invention, such a combination of eco-cement and coal ash enhances the compressive strength and durability of a concrete composition using eco-cement,
Workability is improved.

[0006]

Means for Solving the Problems The present invention relates to a concrete composition having the following constitution. Note that the present invention refers to a concrete composition including mortar. (1) A concrete composition obtained by mixing cement and aggregate with water, wherein at least one of municipal waste incineration ash and sewage sludge incineration ash is used as a raw material, and calcium chloroaluminate, calcium fluoroaluminate, and calcium aluminate are used. A concrete composition characterized by using a calcined product containing 10 to 40 wt% of at least one of calcium silicate and a hydraulic composition mainly composed of gypsum as cement, and using coal ash as a part of aggregate. . (2) The concrete composition according to the above (1), wherein the mixing ratio of coal ash is 5 to 60 vol% with respect to the total amount of fine aggregate and coal ash. (3) The particle size of the coal ash is at least 1,000 cm ² / g,
(1) or wherein the 45 μm sieve residue is 85% by weight or less.
(2) The concrete composition. (4) The concrete composition according to the above (1), (2) or (3), wherein the SiO ₂ content of the coal ash is 35% by weight or more and the ignition loss is 9.0% or less. (5) The concrete composition according to any one of (1) to (4), wherein the coal ash is discharged from a coal-fired power plant.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. The concrete composition of the present invention comprises, as a raw material, at least one of municipal waste incineration ash and sewage sludge incineration ash, and contains 10 to 40% by weight of at least one of calcium chloroaluminate, calcium fluoroaluminate, and calcium aluminate and calcium silicate. The present invention is characterized in that a hydraulic composition mainly composed of a calcined product and gypsum (this hydraulic composition is called ecocement) is used as cement, and coal ash is used as a part of the aggregate.

A mineral component contained in ecocement, for example, calcium chloroaluminate is 11CaO · 7A.
l ₂ O ₃ .CaCl ₂ (abbreviated as C ₁₁ A ₇ CaCl ₂ ), and calcium fluoroaluminate is 11 CaO.7 Al ₂ O ₃ .Ca
F ₂ (abbreviated as C ₁₁ A ₇ CaF ₂ ), calcium aluminate is 3
CaO.Al ₂ O ₃ (abbreviated as C ₂ A). Calcium silicate is 2CaO.SiO ₂ (abbreviated as C ₂ S),
3CaO.SiO2 (abbreviated as C ₃ S). Preferably, calcium aluminate, such as _{C 11 A 7 CaCl 2, C} 11 A 7 CaF 2, C 2 A containing 10 to 40 wt%, C ₂
More than one kind of calcium silicate of S or C ₃ S
Contains 40 wt%. The chloride ion content is 0.1% by weight or less for ordinary type eco-cement and 0.5 to 1.5% by weight for quick-setting type eco-cement.

Ecocement is manufactured using calcined ash such as sewage sludge dry powder obtained by mixing quicklime with shells and sewage sludge, and other general waste and industrial waste. Also. Limestone, clay, silica, aluminum ash, which is a common cement raw material,
A raw material whose components are adjusted by mixing bauxite and iron powder may be used. Clinker obtained by calcining these raw materials at 1200 to 1500 ° C. is pulverized, and if necessary, gypsum is added at the time of pulverization or after pulverization to produce ecocement.

[0010] The clinker aluminum source is mainly derived from the raw incineration ash. Therefore, C ₁₁ A ₇ CaCl ₂ , C ₁₁
If the content of aluminum compounds such as A ₇ CaF ₂ and C ₃ A is less than 10% by weight, the amount of incinerated ash used is reduced, which is not preferable from the viewpoint of effective use of waste and recycling. On the other hand, if the amount exceeds 40% by weight, the hardened cement body may be excessively expanded due to the progress of hydration, which is not appropriate.

Gypsum to be added to clinker is anhydrous gypsum,
Both gypsum and hemihydrate gypsum may be used. From the strength development, the addition amount of gypsum is 1 to 3 per 100 parts by weight of clinker.
0 parts by weight is preferred.

The amount of the ecocement obtained as described above is desirably 1 to 80 parts by weight of the ecocement based on 100 parts by weight of the concrete composition. Here, the concrete composition weight refers to the total amount of the basic components of eco-cement and water and further containing other hydraulic composition, mineral fine powder, admixture material, fine aggregate or coarse aggregate. Ecocement content is the amount of ecocement based on the total weight of the concrete composition. If the amount of ecocement is less than 1 part by weight, a predetermined strength cannot be obtained. On the other hand, if the amount of the ecocement is more than 80 parts by weight, the desired fluidity cannot be obtained, and the workability is remarkably reduced, which may result in poor construction.

The concrete composition of the present invention uses coal ash as a part of the aggregate. As coal ash, those discharged from coal-fired power plants are mainly used. Coal ash is not limited to fly ash specified by the standard (JIS), and a wide range of coal ash including fly ash called raw powder and cinder ash can be used. By using coal ash for a part of the fine aggregate, fine coal ash is filled between the fine aggregates, the denseness of the structure is increased, and the strength can be increased. In addition, the fluidity of the fresh concrete is improved by the bearing effect.

The coal ash preferably has a density of 1.8 or more, a specific surface area of the brane of 1,000 cm ² / g or more, and a 45 μm sieve residue of 85% or less. Those having a specific surface area and a sieve residue outside these ranges are not preferred because the particle size is large and the compactness of the composition is reduced when blended into a concrete composition, which adversely affects the initial strength and durability. The coal ash preferably has a SiO ₂ content of 35% by weight or more and a loss on ignition of 9.0% or less. If the ignition loss is larger than this, it is difficult to obtain a target air amount. By the way, the amount of air is 3.0-
6.0 vol% is appropriate.

Since coal ash has a particle size in the range of fine aggregate, it is used in place of fine aggregate. The mixing amount of coal ash is appropriately 5 to 60 vol%, preferably 20 to 50 vol%, based on the total volume of fine aggregate and coal ash. If the amount of coal ash is less than 5 vol%, the effect is not recognized, while
When the content is more than ol%, the initial strength of the concrete composition decreases, and the age required for obtaining the target strength increases.
Also, a decrease in the initial strength causes a decrease in durability.

The type of fine aggregate is not limited. Common aggregates such as sand and crushed sand used in ordinary concrete can be widely used. In particular, in the present invention, coal ash is used as a part of the aggregate because fine aggregates are not suitable as ordinary concrete aggregate due to lack of fine particles in the particle size distribution of the fine aggregate. The fine parts of the aggregate can be supplemented, and such fine aggregate can be used. The amount of fine aggregate is 7 in total with coal ash.
100 to 1000 kg / m ³ is appropriate.

Coarse aggregates include various types of aggregates such as ordinary aggregates such as gravel and crushed stone used in ordinary concrete, as well as artificial aggregates mainly composed of iron, anti-firestone, expanded shale and the like. can do. Furthermore, an artificial lightweight aggregate made of a non-expandable fly ash granulated sintered body can be used as a coarse aggregate, and the reuse of waste can be further promoted by using such an artificial lightweight aggregate together. it can. Incidentally, the average particle size is 5 mm or more, the density is 1.8 or more, and the water absorption is 3.0.
%, An artificial lightweight aggregate made of a non-foamable fly ash granulated sintered body having a compressive strength of 40 N / mm ² or more (product of Taiheiyo Cement Corporation: E-SPHERES, etc.) is known.

The amount of coarse aggregate (unit coarse aggregate amount) is suitably 550 liters or less, preferably 400 liters or less per m ³ of concrete. If the amount of the coarse aggregate is larger than this, the engagement of the aggregate becomes remarkable, and even when a good cement paste is prepared, the upper part of the slump collapses.

A high-performance water reducing agent can be used in the concrete composition of the present invention. As a high performance water reducing agent,
Any of conventionally used alkylallyl-based, naphthalene-based, melamine-based, and polycarboxylate-based admixtures can be used. Preferably, a polycarboxylate-based admixture is good. In addition, a high-performance AE water reducing agent or AE agent having air entrainment performance can also be used. The amount of these high-performance water reducing agents is adjusted in consideration of the materials to be used and the required water reducing effect. Generally, 0.05 to 10% by weight is appropriate for 100 parts by weight of cement. If it is less than 0.1% by weight, the water reducing effect is practically negligible, and if it exceeds 10% by weight, the effect of improving water reducing and fluidity levels off.

The concrete composition of the present invention includes:
In addition to the above, various concrete admixture materials such as quick-hardening agents or quick-setting agents, high-strength admixtures, hydration accelerators, setting modifiers, etc. which are usually used in concrete, or various fibers or steels as reinforcing materials are also included Can be used. In addition, in the concrete composition of the present invention, the method of mixing and kneading the components is not limited, as long as they can be uniformly kneaded, and the order of adding the components is not limited.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples. In addition, these are illustrations and do not limit this invention.

[Production of eco-cement] A hydraulic composition a (normal type eco-cement) having a small amount of chloride ions and a hydraulic composition b (a quick-setting type eco-cement) having a large amount of chloride ions produced as follows. Cement). Production of hydraulic composition (a): Dry municipal waste incineration ash
(a) 35.8 wt%, limestone powder 57.1 wt%, clay 0.2 wt
%, And 3.5 wt% of an iron raw material, which was calcined at 1300-1450 ° C. in a rotary kiln to obtain clinker. This clinker is crushed by a vertical mill to have a Blaine specific surface area of 40.
Crushed to 00 cm ² / g. 8.4 parts by weight of gypsum dihydrate and 3.6 parts by weight of gypsum hemihydrate were added to 100 parts by weight of this calcined product to produce a normal type ecocement having a specific surface area of Blaine of 4700 cm ² / g. Production of hydraulic composition (b) : Dry municipal waste incineration ash
(b) 51.9 wt%, limestone powder 47.2 wt%, aluminum ash 0.
6 wt% and 0.3 wt% of calcium chloride were used as raw materials, which were fired at 1300 to 1450 ° C. in a rotary kiln to obtain clinker. This clinker was ground with a vertical mill to a Blaine specific surface area of 4000 cm ² / g. This fired product 100
12 parts by weight of anhydrous gypsum was added to the parts by weight to produce a quick-setting ecocement having a specific surface area of the brane of 4700 cm ² / g. Incineration ash a, b, limestone powder, clay,
The components of aluminum ash and fluorite are shown in Table 1. Tables 2 and 3 show the mineral and chemical compositions of the hydraulically baked products a and b.
It was shown to.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[Production of concrete composition] Concrete compositions were prepared according to the mixing ratios shown in Table 5 using eco-cements (hydraulic compositions) a and b shown in Table 3 and coal ash (CA1 to CA5) shown in Table 4. Was manufactured. A fresh property test was performed on this concrete composition, and the results are shown in Table 6. In addition, accelerated neutralization tests were conducted in accordance with the guidelines for design and construction of highly durable reinforced concrete structures (draft) and the explanation “Concrete neutralization test method (draft)”. Standardized compression strength test (JIS
A 1108). The results of the compression strength test are shown in Table 6, and the results of the neutralization test are shown in Table 7.

[0027]

[Table 4]

[0028]

[Table 5]

[Fresh property test] The fresh property of the concrete composition was evaluated in four steps (流動: especially good, ○: good,
Δ: normal, ×: bad). A good fluidity indicates good slump test and workability, and a good air content indicates that a small amount of AE agent used to obtain a target air amount is sufficient. As shown in Table 6, the fluidity of concrete when coal ash is mixed is the case without mixing
(Nos. 12 to 14), but the effect is small in the case of coarse ash (Nos. 18 and 19). The fluidity is 20% to 45% of the total amount of fine aggregate and coal ash used.
Vol% (No.5 to No.10) is the largest. The amount of air in concrete when coal ash is mixed is when the amount of coal ash is small
(No.3,4) is slightly better, but in other cases (No.1,2,5-14)
Not much different. When the amount of coal ash is increased (No. 15), the amount of the AE auxiliary agent required for obtaining the air amount is significantly increased, which is not practical. When the ignition loss in coal ash is large (No.
17) is the same.

[Compressive strength test] As shown in Table 6, when the compressive strength was compared at the same water cement ratio, the one in which coal ash was mixed in concrete was compared with the one in which no coal ash was mixed (No. No. 12 for No. 12, No. 3 to 7 for No. 13, No. 9 to 11 for No. 14) Improvement in strength from early age is observed, The tendency became remarkable.
Also, as the mixing ratio of coal ash increases, the improvement in strength increases, but when the mixing ratio exceeds 45 vol% (No. 11), the strength increase decreases, and when the mixing ratio exceeds 60 vol% (No. 15), , The strength development at the initial age is almost the same as in the case of no mixing (No. 13). The one using a fast-setting eco-cement with a high chloride ion content (composition b) (No. 6) improves the compressive strength due to the incorporation of coal ash, but has a low chloride ion content.
Its effect is smaller than that of the composition (a) (No. 5).

[Neutralization test] As shown in Table 7, (No.
2 is No.12, No.3-7 is No.13, No.9-11
(Compared to No. 14) Carbonized ash is more neutralized than non-contaminated ones. The effect increases as the amount of coal ash increases up to 45 vol%, but the effect increases when the amount of coal ash exceeds 60 vol% (N
o.15), due to the non-uniformity of fine aggregate particle size, neutralization progresses from the young age, and it is almost the same as in the case of no contamination (No. 13).
In addition, the one using a fast-setting eco-cement (composition b) with a high chloride ion content (No. 6) uses a normal-type eco-cement (composition a) with a low chloride ion content at the initial age. Although the depth of the neutralization was smaller than that of No.5 (No.5), the difference gradually became smaller as the material age progressed. Was small and the incorporation of coal ash was effective.

[0032]

[Table 6]

[0033]

[Table 7]

[0034]

The concrete composition of the present invention improves the fluidity of fresh concrete by using coal ash as a part of the aggregate. Furthermore, the compressive strength increases from the initial age, and the long-term strength greatly increases due to the effect of the pozzolanic reaction. Further, since the structure can be densified, neutralization is also suppressed. Furthermore, construction by-products and general waste are produced by using eco-cement produced from municipal waste incineration ash and sewage sludge incineration ash as a main raw material, and using a large amount of coal ash produced as a by-product from pulverized coal combustion boilers at thermal power plants. It is possible to promote the reuse of waste such as goods and industrial waste. It should be noted that even those having a particle size distribution that is not suitable as ordinary aggregate for concrete can be used in combination with coal ash, which helps to secure high-quality aggregate resources that are gradually becoming difficult to obtain. Further, if artificial fine aggregate produced using industrial by-products such as blast furnace slag and ferronickel slag as a raw material is used in combination with coal ash, the effective use of industrial by-products can be further promoted.

Claims (5)

[Claims] 1. A concrete composition comprising water mixed with cement and aggregate, wherein at least one of municipal waste incineration ash and sewage sludge incineration ash is used as a raw material, and calcium chloroaluminate, calcium fluoroaluminate, calcium Concrete characterized by using a calcined material containing 10 to 40% by weight of at least one aluminate and calcium silicate and a hydraulic composition mainly composed of gypsum as cement, and using coal ash as a part of aggregate. Composition. 2. The concrete composition according to claim 1, wherein the mixing ratio of coal ash is 5 to 60 vol% based on the total amount of fine aggregate and coal ash. 3. The coal ash has a specific particle size of 1000 cm ² / g.
The concrete composition according to claim 1 or 2, wherein the 45 µm sieve residue is 85 wt% or less. 4. The coal ash according to claim 1, wherein the SiO ₂ content is at least 35 wt% and the ignition loss is at most 9.0%.
Concrete composition. 5. The concrete composition according to claim 1, wherein the coal ash is discharged from a coal-fired power plant.