JP2002053352A - Concrete structure hardly causing crack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concrete structure in which cracks are hardly caused even when such a crack prevention procedure as reduction in unit water content, addition of a shrinkage reducing agent and expansive admixture, or increase in water-cement ratio is not performed. SOLUTION: This concrete structure is constructed by using, as a binder, a hydraulic composition consisting of gypsum and a fired material produced with at least one kind of municipal solid waste incineration ash and sewage sludge incineration ash, as a raw material, wherein the fired material comprises 10-25 wt.% C3A (3CaO.Al2O3), 10-20 wt.% C4AF (4CaO.Al2O3.Fe2O3), a 20-35 wt.% total content of C3A and C4AF and <=0.1 wt.% chlorine, and also contains at least either C3S (3CaO.SiO2) or C2S (2CaO.SiO2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete structure which is hardly cracked in the field of civil engineering and construction.

[0002]

2. Description of the Related Art In general, concrete has a low tensile strength and is liable to crack. In concrete constructions (buildings) in the field of construction, changes in the thickness of cross sections around openings such as walls and windows mainly due to drying shrinkage. Cracks are likely to occur in the places where they do. Further, in a concrete structure in the field of civil engineering, cracks are likely to occur in wall structures such as retaining walls and beams. Since these cracks lead to deterioration in aesthetics and durability, various means for suppressing or preventing cracks in concrete from the viewpoint of materials and construction have been conventionally studied. For example, for drying shrinkage of concrete, reduction of unit water amount, addition of a shrinkage reducing agent or an expanding agent, or curing has been performed for a sufficient time. In order to reduce the self-shrinkage of concrete, use of cement with low C ₃ A (for example, medium heat Portland cement, low heat Portland cement, etc.), addition of shrinkage reducing agents and expansion materials,
Methods such as increasing the water cement ratio have been employed. However, the reduction of the unit water amount has a limit in securing a predetermined slump, and the amount of water having a large heat capacity is small, so that the hydration heat inside the concrete is increased, and the temperature cracks are easily generated. In addition, the addition of shrinkage reducing agents and expanding materials increases the cost of concrete, and increasing the water-cement ratio to reduce autogenous shrinkage reduces design durability and reduces durability. Even another problem arises.

On the other hand, in recent years, cement (eco-cement) using waste as a main raw material has been manufactured, and chlorine has been reduced to 1%.
%, And two types of eco-cement, a hardened type eco-cement having a hardening property similar to that of ordinary cement, are being put into practical use. The applicant is Japanese Patent Application No. Hei 10
No. -39731 proposed a method of reducing the shrinkage of concrete by adding a shrinkage reducing agent to a quick-hardening eco-cement. However, fast-setting eco-cement contains 1.0% chlorine.
Contains degree, when using this concrete, chloride ion content in the per concrete 1 m ³ is JIS
Since there is a concern about the corrosion of reinforcing steel in concrete exceeding 0.30 kg specified in the standard, when using it as reinforced concrete for a wide range of applications, consideration must be given to corrosion of reinforcing steel such as the addition of rust preventives. Was. In addition, since the cement has a quick-setting property, when used for cast-in-place concrete, it was necessary to adjust a pot life by adding a retarder.

On the other hand, ordinary eco-cement uses chlorine.
Since it contains less than about 0.5%, it can be used in large quantities in reinforced concrete. However, according to the literature (“Concrete Engineering” Vol.37, No.8, pp. 26-30, 1999), ordinary eco-cement is used. Since the concrete used has almost the same drying shrinkage as concrete using ordinary cement or blast furnace cement, the frequency of occurrence of cracks is also the same, and reduction of cracks in concrete using ordinary eco-cement cannot be expected. Was considered.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a concrete structure which is less likely to be cracked without performing a method such as reducing the unit water amount, adding a shrinkage reducing agent or an expanding agent, or increasing the water-cement ratio. The purpose is to:

[0006]

The inventor of the present invention has conducted intensive studies to develop a concrete structure with less cracking without taking the above-described means for preventing cracking.
The present inventors have found that shrinkage cracks in concrete structures can be significantly reduced by using ordinary eco-cement as a binder for concrete, and completed the present invention.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The ordinary type eco-cement used in the present invention is a hydraulic composition manufactured using at least one of municipal waste incineration ash and sewage sludge incineration ash, and furthermore, at least one of municipal waste incineration ash and sewage sludge incineration ash. A fired product as a raw material, wherein C ₃ A is 10 to 25% by weight, C ₄ AF is 10 to 20% by weight and C ₃ A
And a C ₄ AF in a total amount of 20 to 35% by weight, chlorine of 0.1% by weight or less, and a calcined product containing one or more of C ₂ S or C ₃ S and a gypsum.

[0008] In addition, raw materials for ordinary eco-cement include municipal garbage incineration ash, sewage sludge incineration ash, sewage sludge dry powder in which quicklime is mixed with shells and sewage sludge, other general waste, and even ordinary cement. It may be a raw material whose components are adjusted by mixing with raw materials such as limestone, clay, silica, aluminum ash, bauxite, and iron. The clinker obtained by calcining such a raw material at 1200 to 1450 ° C. is pulverized, and then gypsum is added to the pulverized clinker, or clinker and gypsum are simultaneously pulverized to produce ecocement.

The clinker (calcined product) of ordinary ecocement has a C ₃ A content of 10 to 25% by weight, a C ₄ AF content of 10 to 20% by weight, and a total amount of C ₃ A and C ₄ AF of 20 to 35% by weight. % And chlorine is 0.1
It is preferable that the content is not more than% by weight. Since the aluminum source of this fired product is mainly derived from incinerated ash, C ₃ A
If less than 10% by weight, the amount of incinerated ash used will decrease,
It is not preferable from the viewpoint of effective use and recycling of waste, and if the amount of C ₃ A exceeds 25% by weight, it becomes difficult to secure the usable time due to the promotion of instantaneous setting and coagulation immediately after water injection, resulting in poor usability. . Moreover, C ₄ AF is much the amount of the C ₃ A is less than 10 wt%, usability is deteriorated becomes difficult to secure working life in the same manner as described above, the amount of C ₄ AF 20 wt% If the ratio exceeds the above range, physical properties such as setting time may be adversely affected. Moreover, because the total amount of C ₃ A and C ₄ AF is melt into the kiln tends to adhere in preparing the fired product exceeds 35 wt%, and C ₃ A in order to stably manufacture It is desirable that the total amount of C ₄ AF is 20 to 35% by weight. The chlorine content is 0.1% by weight
If the amount of cement exceeds the maximum, the Japanese Industrial Standards (JIS A 5308) and the Architectural Institute of Japan (JASS)
The weight of chlorine in the concrete 1 m ³ which is limited by 5) (the weight of Cl) may exceed the following 0.3 kg,
The chlorine content is desirably 0.1% by weight or less.

[0010] Gypsum to be used in the present invention, anhydrous gypsum, gypsum dihydrate, none of the hemihydrate gypsum can be used, plays a condensation adjustment and strength enhancement, the amount thereof in outer percentage converted to SO ₃
It is 1.5 to 6% by weight, preferably 3.5 to 5% by weight. If the amount is less than 1.5% by weight, the eco-cement may cause abnormal setting, and if it exceeds 6% by weight, the cured product may expand over a long period of time, resulting in reduced durability and dimensional stability.

The concrete structure using the ordinary eco-cement of the present invention can use aggregates, concrete admixtures for concrete, admixtures and the like used for ordinary concrete, and both kneading methods and curing methods are known. Can be applied.

[0012] Concrete structures using ordinary eco-cement satisfying the above-mentioned rules have reduced cracking, and in particular, concrete structures including concrete members whose shrinkage is restricted, and reinforced concrete members whose contraction is restricted. In a concrete structure, a concrete structure in which the thickness of a concrete member whose shrinkage is restricted is not uniform, or a concrete structure in which the concrete member whose contraction is restricted has an opening, the effect of reducing cracking is large.

[0013]

Examples of the present invention will be described below. In addition, these are illustrations and do not limit this invention.

32.0% by weight of dried municipal waste incineration ash shown in Table 1, 64.2% by weight of limestone, 2.4% by weight of iron raw material, and 1.4% by weight of soda ash (containing 99.6% by weight of sodium carbonate: manufactured by Central Glass Company) The raw material whose components were adjusted was fired at 1300 to 1450 ° C. using a rotary kiln. The obtained fired product was pulverized with a vertical mill, and then added and mixed with hemihydrate gypsum in terms of SO ₃ of 2.1% by weight to produce ecocement. The fineness of this ecocement is 42
00 cm ² / g. Table 2 shows the mineral composition of the obtained fired product.

[0015]

[Table 1]

[0016]

[Table 2]

(Test Method) The eco-cement and the materials shown in Table 3 were blended at the weight ratio shown in Table 4 and the concrete was kneaded, and the mold described in the JIS draft "Dry shrinkage cracking test method for concrete (draft)" was prepared. The concrete was poured into a frame, demolded after 7 days of wet curing, and three specimens were prepared. Immediately after demolding, the test specimen was subjected to a crack test in a state where shrinkage was restrained in accordance with the same plan. Table 5 shows the number of days required from the start of drying to the occurrence of cracks. In addition, as shown in FIG. 1, in a flat plate form having a 50 cm × 50 cm opening in the center and having a length of 200 cm × width 200 cm × thickness 10 cm, the cover thickness was set to strengthen the constraint of concrete.
At a position of 5 cm, three D16 rebars are arranged on one side, and the above concrete is poured, and after 7 days of moist curing, the concrete is removed from the mold.
% In a constant temperature / humidity chamber for 3 months, and then the presence or absence of cracks in the corners of the concrete was visually observed. Table 6 shows the results.

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

[Table 6]

From Table 5, it can be seen that in the concrete of the comparative example, cracks occurred in all the examples by 45 days except for the comparative example 3 in which the shrinkage reducing agent was added, whereas in the concrete of the example, cracks occurred. It takes an average of 56 to 76 days, and it can be seen that cracks are unlikely to occur as much as concrete (Comparative Example 3) to which a shrinkage reducing agent has been added. In addition, when compared at the same water cement ratio (Example 1 and Comparative Example 1,
2, 5, or 6. Comparative Example 3 is excluded. ), The number of days of cracking of concrete using ordinary eco-cement is much longer than that of concrete using other Portland cements. It is found that it is effective.

From Table 6, it can be seen from Table 6 that the concrete using ordinary eco-cement had no cracks at the corners even in the simulated wall member assuming an opening such as a window frame (Example 1). It can be seen that the effect of suppressing the occurrence of cracks is high also in the portion.

[0024]

As described above, the concrete structure using the normal type eco-cement of the present invention is less likely to crack and has high durability under the condition of restraint of shrinkage.
Further, according to the present invention, effective use and recycling of waste can be achieved through expansion of uses of ecocement manufactured from waste.

[Brief description of the drawings]

FIG. 1 is a perspective view of concrete having an opening.
The unit of the numerical value in the figure is cm.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C04B 22:14) C04B 22:14) B

Claims (5)

[Claims] [Claim 1] A fired product produced from at least one of municipal solid waste incineration ash and sewage sludge incineration ash, wherein C ₃ A is 10
25 wt%, C ₄ 10 to 20 wt% of AF and C ₃ A and C ₄ total amount 20 to 35 wt% of AF, chlorine 0.1 wt% or less, and C ₃ S
Alternatively, a concrete structure using, as a binder, a hydraulic composition composed of a calcined product containing at least one C ₂ S and gypsum. 2. The concrete structure according to claim 1, comprising a concrete member whose shrinkage is restrained. 3. The concrete structure according to claim 2, wherein the concrete member whose shrinkage is restricted is a reinforced concrete member. 4. The concrete structure according to claim 2, wherein the concrete member whose shrinkage is restricted is not uniform in thickness. 5. The concrete structure according to claim 2, wherein the concrete member whose shrinkage is restricted has an opening.