JP2000335950A - Concrete for structure of civil engineering and construction for recycling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject concrete which can wholly be used as a reclaimed aggregate, has a largely unchanged slump and good adhesivity, and enables the recycling of the resource, by specifying a unit binder content and the compression strength of a cured concrete product. SOLUTION: This concrete of civil engineering and construction structure for recycling has a unit binder content of 200 to 500 kg/mm3 and a cured product compression strength of >=50 N/mm2. When the concrete having the maximum size of >40 mm is used, the strength of the concrete is controlled by forming test pieces from 40 mm-sieved concrete. The binder includes various Portland cements and mixed cements mixed with blast furnace slag and flied ash. In order to enhance the strength of the concrete, 2 to 15 wt.% of II type anhydrous gypsum or 2 to 20 wt.% of a silica-containing substance is added to the binder. On the production of the recycling concrete, the maximum diameter of virgin aggregate is desirably >=25 mm, more desirably >=40 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete of a civil engineering building structure for recycling, which is reused as an aggregate of concrete used for construction of a civil engineering building structure and production of concrete products.

[0002]

2. Description of the Related Art Conventionally, construction waste materials after demolishing civil engineering and building structures have been landfilled at industrial sites as industrial waste. However, in recent years, disposal sites are becoming full, and construction of new disposal sites is likely to cause pollution problems such as contamination of groundwater.

Under such circumstances, the industry has been studying a method of recycling construction waste generated at the present time and a study of recycling concrete to be used in civil engineering and building structures on the assumption that it will be reused in the future. Is coming to be done.

[0004] The former study shows that the design strength of concrete that has been used in civil engineering until now is 18 to 27 N / mm.
^Since it is small, it is difficult to use it as aggregate for concrete, so it is a general study to use it as a roadbed material or to recycle it for backfilling or filling in structures.
In addition, a water-permeable water-base material (Japanese Patent Laid-Open No. 9-77548) in which waste concrete is crushed and the particle size is adjusted, and the mixture is further mixed with cement, water, and the like to further agglomerate the material is proposed. Have been. In addition, the crushing of construction waste material is not good in grain shape (small volume ratio and angular), and also generates a lot of fine particles with high water absorption, so the unit water volume increases for use in ordinary concrete. In order to solve the above-mentioned problems, there has been proposed a method (U.S. Pat. No. 5,085,086) for utilizing concrete for compaction concrete which originally has a small amount of water by super-hardening.

[0005] In the latter case, for example, when limestone is entirely used as aggregate for concrete in the future and this concrete is to be reused as construction waste material, the entire construction waste material is crushed and uniform in particle size and used as fine and coarse aggregate. However, it is a study of complete recycling to return the fine powder that cannot be used as aggregate to cement raw material.

[0006] However, in any case, in the recycling of construction waste materials, since the design strength of current general civil engineering and building structures is low, when such concrete is crushed, many small parts that cannot be used as aggregates are often produced. It has a problem that it occurs and it is difficult to use the whole amount as aggregate as it is.

The present inventors have conducted intensive studies on concrete of a civil engineering building structure for recycling to be used as aggregate in the future, with the aim of solving the above-mentioned problems in the latter case. The present invention was completed by finding out the concrete mixing conditions and strength conditions that cause little generation of parts and can be fully recycled and do not greatly deviate from the standard particle size range of the Japan Society of Civil Engineers.

[0008]

That is, the present invention provides a recycle material characterized in that the unit binder amount is 200 to 500 kg / m ³ and the cured product has a compressive strength of 50 N / mm ² or more. Concrete for civil engineering and building structures.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The unit binder amount of concrete of the civil engineering building structure for recycling of the present invention is 200 to 500 kg / m ³ . As the unit binder amount is smaller, a sound recycled aggregate having a smaller water absorption can be obtained. However, if the unit binder amount is less than 200 kg / m ³ , the strength is low even if the admixture described below is mixed, so that many fine portions are crushed when crushed. It is difficult to use all of the generated and crushed material as it is as aggregate. 500 kg / m ³
In concrete containing a large amount of binder beyond the limit, the particle size distribution tends to be biased to both extremes of fine parts and coarse parts,
A single crushing cannot make the particle size distribution appropriate. Preferred unit binder amount is 250-450 kg
/ M ³ , more preferably 300 to 400 kg /
m is ^3.

[0010] Further, the compressive strength of concrete of the civil engineering building structure for recycling of the present invention is such that the concrete strength in use is 50 N / mm ² or more. If it is less than 50 N / mm ² , the strength is small, and fine portions are increased at the time of crushing, which is not preferable, and the concrete strength when reused as aggregate is also reduced. Preferably at 60N / mm ² or more, more preferably 70N / mm ² or more.
The higher the compressive strength is, the more preferable. However, when the unit binder amount exceeds 500 kg / m ³ , even if the strength is high, when crushed, the regenerated coarse aggregate shifts to a coarser one and easily falls out of the standard particle size range. The fine aggregate portion shifts to a finer portion, and the fine powder portion also increases. In the present invention, in the case where concrete having a maximum dimension of concrete exceeding 40 mm is used, the strength is controlled by preparing a specimen using concrete under a 40 mm sieve.

The binder of the present invention is a mixture of various portland cements such as ordinary, fast, moderate heat, ultra-fast, sulfate-resistant, white, and high belite, and mixed blast furnace slag and fly ash. is there.

Further, these various portland cements and mixed cements are used to increase concrete strength.
An appropriate amount of type-II anhydrous gypsum and / or an admixture of one or more silica-containing substances of aluminosilicate compounds such as amorphous silica and metakaolin having high hydration activity such as calcined ash of silica fume and silicified wood It was done.

[0013] The type II anhydrous gypsum is preferably used in an amount of 2 to 15% by weight in the binder, regardless of whether it is used in combination with the silica-containing substance. If it is less than 2% by weight, the strength effect is small, and if it exceeds 15% by weight, the elongation of strength is stagnated, which is not preferable. More preferably, it is 3 to 10% by weight.

The silica-containing substance is used in an amount of 2 to 20% by weight in the binder, regardless of whether it is used in combination with the type II anhydrous gypsum or not, regardless of the curing method. If it is less than 2% by weight, the strength effect is small, and if it exceeds 20% by weight, no further increase in strength can be expected. A more preferred range is 4 to 15% by weight.

[0015] It should be noted that the combined use of the type II anhydrous gypsum and the silica-containing substance in the above-mentioned range allows a higher strength to be exhibited with a smaller amount of the unit binder, so that a high quality recycled aggregate can be obtained. Most preferred as concrete for recycling civil engineering construction structures.

In producing the concrete of the civil engineering building structure for recycling according to the present invention, the maximum size of the virgin aggregate is preferably 25 mm or more, more preferably 40 mm or more. In the case of the same composition, the smaller the maximum size of the virgin aggregate, the higher the compressive strength. However, if the maximum size is less than 25 mm, the size of the coarse aggregate in the recycled aggregate is reduced by crushing, and the size of the virgin coarse aggregate is reduced. In the observation of the concrete cut surface when reused, the area of the coarse aggregate occupying the cut surface was remarkably reduced, and the cut surface without coarse aggregate such as mortar, the elastic modulus decreased This is because it is difficult to obtain healthy concrete. Therefore,
As the maximum aggregate size of the virgin aggregate is 25 mm or more, a sound recycled aggregate can be obtained.

It is preferable to add various water reducing agents in the usual manner when producing the concrete of the civil engineering and building structure for recycling according to the present invention, and in particular, a high performance water reducing agent or a high performance AE having a large water reduction rate. The use of a water reducing agent is more preferable, and the amount of use is not limited as long as curing failure does not occur.

The structure constructed of concrete of the civil engineering structure for recycling according to the present invention is demolished when it reaches the end of its useful life or purpose of use and becomes construction waste. This can be crushed by a suitable crusher such as a jaw crusher. At this time, the maximum aggregate size is arbitrarily changed by changing the clearance of the crusher. In the scope of the present invention, the number of times of crushing is one, and it is not necessary to perform a plurality of times of crushing to control the particle size distribution, and the crushed material is used in its entirety as recycled aggregate for concrete. However, concrete is manufactured by adding virgin aggregate to the insufficient fine and coarse aggregates.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0020]

EXAMPLE 1 Using a binder consisting of ordinary Portland cement alone or a binder obtained by blending type II anhydrous gypsum or a silica-containing substance with ordinary Portland cement and a high-performance water reducing agent, as shown in Table 1, unit binding was carried out. Specimens were prepared by kneading concrete with different material amounts. In addition, slump is 5-18cm
(Because the unit water amount is not changed in the case of the same unit binder amount,
The amount of air varied within the range of 2 ± 0.5%, depending on the type of admixture and the amount of admixture). The particle size distribution of the aggregate was adjusted to be within the standard particle size range of the Japan Society of Civil Engineers. For measurement of compressive strength, concrete with a maximum aggregate size of 40 mm or less is molded into a cylinder of φ15 × 30 cm, and concrete with a maximum aggregate size of more than 40 mm is converted into a cylinder of φ15 × 30 cm using concrete under a 40 mm sieve. The molded specimens were subjected to standard curing for 91 days before conducting.

Further, if the maximum aggregate size is 40 mm or less, a cylinder of φ15 × 30 cm, the maximum aggregate size is 40 m
For concrete over m, a block with a thickness of 2.5 times the maximum aggregate size, a width of 4 times and a length of 6 times is separately manufactured, and the maximum aggregate size is 25 mm with a jaw crusher. The crusher was adjusted once so as to be crushed once. Tables 2 and 3 show the results of measuring the particle size distribution separately for 5 mm above (coarse aggregate) and below (fine aggregate), together with the compressive strength.

<Materials Used> “Aggregate” Coarse aggregate: gravel with a maximum dimension of 25 mm, Himekawa, Niigata, ratio
Weight 2.68: Gravel with a maximum dimension of 40 mm, from Himekawa, Niigata Prefecture, specific gravity 2.6
7: Gravel with a maximum dimension of 80 mm, from Himekawa, Niigata Prefecture, specific gravity 2.7
0: Gravel with a maximum size of 15 mm, from Himekawa, Niigata Prefecture, specific gravity 2.6
6 ・ Fine aggregate: River sand from Himekawa, Niigata Prefecture, specific gravity 2.62 “Cement” Ordinary Portland cement: Brake made by Denki Kagaku Kogyo Co., Ltd.
Value 3200cm^Two/ g, specific gravity 3.16 “Admixture material” a. Type II anhydrous gypsum: manufactured by Morita Chemical Co., hydrofluoric acid generated by-product stone
Plaster, Brain value 6000cm^Two/ g, specific gravity 2.96 b. Silica fume: manufactured by Elchem, specific surface area 24m^Two/ g,
Specific gravity 2.39 c. Rice baked ash: specific surface area 20m^Two/ g, specific gravity 2.40 d. Metakaolin: Fired clay at 800 ° C and ground
Object, specific surface area 8500cm^{Two / g}, Specific gravity 2.40 "water reducer" High-performance water reducer: manufactured by Daiichi Kogyo Chemical Co., Ltd., naphthalene-based, powder
type

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

As shown in Tables 2 and 3, when the strength is less than 50 N / mm ² even if the amount of the unit binder is small, the particle size distribution of the coarse aggregate portion does not greatly deviate from the standard particle size range of the Japan Society of Civil Engineers. The particle size becomes extremely fine and deviates from the standard particle size range (formulation No. 1). When the strength is increased by increasing the amount of the unit binder, the particle size distribution of the fine aggregate comes closer to the standard particle size range of the Japan Society of Civil Engineers, and finally comes into the range (formulation No. 2 to No.22). However, when the amount of the unit binder is further increased and the strength is increased, the particle size distribution of the coarse aggregate becomes coarse, and when the unit binder amount exceeds 500 kg / m ³ , the standard particle size range is deviated, and the fine aggregate The particle size distribution also tends to shift to a finer one, and at the same time the fine powder portion tends to increase.

As described above, the unit binder amount is 200 kg / m ³ or more and the strength is 50 N / mm ^{2 based on} the particle size distribution of the aggregate as the concrete of the civil engineering building structure for recycling.
(Formulation No. 2) or more, 60 N / mm ² or more (No. 3), 70 N /
mm ² or more (No. 6), it approaches the standard particle size range of fine aggregate (coarse aggregate is within the standard particle size range), and 110N
At around / mm ² (Nos. 20 to 22), it is shown that both coarse aggregate and fine aggregate fall within the standard particle size range. The unit binder amount is preferably 500 kg / m ³ or less, and more preferably 250 to 450 kg / m ^3.
more preferably ^{kg / m 3, 300~400kg / m} 3 indicates the most favorable particle size distribution. Even if the particle size distribution of fine aggregate does not fall within the standard particle size range due to crushing, the amount of fine aggregate generated is smaller than that of coarse aggregate if it moves parallel to the particle size distribution curve. The virgin fine aggregate at the time can be adjusted sufficiently.

Example 2 Using the recycled aggregates shown in Tables 2 and 3, 30 liters of concrete were mixed and mixed with the concrete shown in Table 4 to obtain φ10 ×
Table 5 shows the results of measuring the compressive strength and the static elastic modulus of a 28-day-old specimen that was molded and molded as a 20 cm specimen and standard-cured. The recycled aggregate was used at a ratio of 5 mm above (coarse aggregate) / below (fine aggregate), and virgin fine aggregate was replenished in terms of volume for insufficient aggregate. As an example, Formulation No. 1
In the case of No. 6, the recycled coarse aggregate was 75.8%, which was 92%.
Equivalent to 5 kg. On the other hand, the amount of recycled fine aggregate is 24.2%, which is calculated to be 295 kg. In addition, the volume of the recycled fine aggregate is 686 / 2.62 = 262 liters, and 295 / 2.49 = 118 liters, and the replenishment amount of the virgin fine aggregates is 262-118 = 144 liters. Similarly, the formulation No. The replenishment of virgin fine aggregate of 1-28 was determined. Further, the particle size distribution was not corrected due to the difference in the particle size distribution of the recycled aggregate, and the resulting slump variation was not corrected and recorded.
It described in.

[0029]

[Table 4]

[0030]

[Table 5]

[0031] From Table 5, the concrete strength and static elastic modulus using recycled aggregate is then corresponds with concrete strength of the original which was produced recycled aggregate, fine aggregate portion strength less than 50 N / mm ² When the amount of unit binder is extremely small and the unit binder amount is less than 200 kg / m ³ or when the unit binder amount exceeds 500 kg / m ³ and deviates from the standard particle size range even if the strength is high, the slump becomes small and the same slump is obtained. In such a case, the strength decreases with an increase in the unit water amount, which is not preferable (formulation Nos. 1 and 28). In the examples, when the unit binder amount is 450 to 500 kg / m ³ , the strength of the concrete using the recycled aggregate is reduced although the strength is high. This seems to be due to the fact that the concrete becomes an acute angle and acts to tear the mortar when the concrete receives compressive stress (No. 25, No. 26). In addition, when the maximum size of the recycled aggregate is less than 25 mm, the static elastic modulus is lowered even if the compressive strength is high, which is not preferable (No. 27). In addition, even in the recycled aggregate, the slump decrease is small within the proper range of the present embodiment, and when the strength of the recycled aggregate is high, the strength is higher than that of the virgin aggregate in connection with the good adhesiveness.

[0032]

The following effects can be obtained by crushing concrete of a civil engineering building for recycling according to the present invention and using it as concrete as recycled aggregate. (1) The whole amount can be used as recycled aggregate without greatly deviating from the standard particle size range by one crushing. (2) When used as recycled aggregate, the coefficient of static elasticity with respect to compressive strength is lower than when virgin aggregate is used, but within the scope of the present invention, the slump does not change much and has good adhesion. Therefore, the strength is higher than that of the virgin aggregate, and there is no practical problem. (3) Resources can be used, and industrial waste can be used effectively.

Claims (1)

[Claims] 1. A unit binder amount of 200 to 500 kg / m
^3. The concrete of a civil engineering building structure for recycling, wherein the cured product has a compressive strength of 50 N / mm ² or more.