JP2004091324A - Heavyweight concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heavyweight concrete of which the cost is reduced by using only one kind of heavyweight aggregate and which decreases the time required for formulation designing, prevents the aggregate segregation, meets required quality, workability, etc., and has a superior resistance to freezing and thawing. <P>SOLUTION: One kind of heavyweight aggregate with a specific gravity ≥4 is selected, used, and mixed with a thickener (e.g. a water-soluble methylcellulose polymer) and an AE water reducing agent to form the heavyweight concrete with a specific gravity ≥2.4. <P>COPYRIGHT: (C)2004,JPO

Description

(4) The present invention relates to a concrete with a specific gravity of 2.4 or more, which contains a thickener, and has excellent physical strength and chemical stability.

For heavy concrete, various technologies have been proposed and used in many fields, such as radiation shielding, balance weights for ships and heavy machinery, and foundations for buildings, rotary presses, and tower structures. Block, concrete, etc. for rivers, marine works, etc.

The main raw materials for heavy aggregates include iron ore such as magnetite, hematite, and iron sulfide, and high specific gravity aggregates such as titanium ore, barite, olivine, iron-based dust, and punch dust. Used.

The heavy concrete is usually prepared by appropriately mixing cement, water, heavy coarse aggregate, heavy fine aggregate, ordinary coarse aggregate, ordinary fine aggregate and an admixture. The use of aggregates has the following problems.

That is, since two or more types of heavy aggregates are used, handling is complicated and workability is extremely poor, and extra stock costs such as transportation costs and securing yards are required, resulting in high costs. Further, as the number of types of aggregates used increases, it becomes more difficult to design and mix heavy concrete to achieve required quality and workability, and it takes extra time.

The mix design of heavy concrete is basically the same as that of ordinary concrete, and the proportion of each material is adjusted so that the required unit volume, strength, durability, watertightness and workability suitable for workability can be obtained economically. To select, it is actually quite difficult to design the mix as compared to ordinary concrete.

In addition, in factories where the processing system for coarse and fine aggregates is few in terms of equipment, if concrete and coarse aggregates are not completely replaced in the storage bins or cumulative measurement of coarse and fine aggregates is not performed, ordinary concrete will not be used. Cannot be balanced. And in some cases, factory equipment must be improved.

Further, when the specific gravity of the heavy concrete to be manufactured is high, the separation phenomenon of the aggregate is liable to occur, and as a result, the workability is deteriorated, and it is difficult to obtain the desired concrete.
JP-A-62-158181

The present invention reduces cost by selecting one type of heavy aggregate to be used, shortens the time required for the blending design, and prevents the separation of the aggregate to reduce the required quality and workability. It is intended to propose a heavy-duty concrete which satisfies and has excellent resistance to freezing and thawing.

The present invention satisfies the required qualities such as workability, characterized in that coarse aggregate / fine aggregate and one kind of heavy aggregate are selected and used as an aggregate and a thickener is blended as an admixture. The present invention also provides heavy concrete having a specific gravity of 2.4 or more, which is excellent in resistance to freezing and thawing.

That is, the present invention is a concrete with a specific gravity of 2.4 or more obtained by mixing a thickener as an admixture. In the present invention, the particle size distribution of 0.15 mm or less is substantially 15 to 25% by weight, It is preferable to mix a weight aggregate having a particle size of 10 mm or less and a specific gravity of 4 or more, and it is preferable that the thickener is a water-soluble methylcellulose-based polymer.

Next, the reasons for limiting each component of the heavy concrete according to the present invention will be described.
A: Specific gravity of heavy aggregate.
If the specific gravity of the heavy aggregate is less than 4, it is not possible to manufacture heavy concrete satisfying the specific gravity required for the application, and the amount of heavy aggregate must be increased to satisfy the required specific gravity, which is uneconomical. It is a target. Therefore, the specific gravity of the heavy aggregate was set to 4 or more.

B: Particle size of heavy aggregate.
One of the features of the heavy concrete according to the present invention is that a thickener is compounded to produce a high-quality heavy concrete having excellent physical strength and chemical stability using one kind of aggregate. Therefore, if the particle size range of the heavy aggregate is too wide, it is difficult to obtain an ideal particle size distribution. Therefore, the particle size of the heavy aggregate is set to 10 mm or less.

C: Particle size distribution of fine powder of heavy aggregate.
When the particle size distribution of the heavy aggregate of 0.15 mm or less is less than 15% by weight, bleeding increases, the separation resistance decreases, and the viscosity of the cement paste and the fluidity of the concrete decrease. On the other hand, when the particle size distribution of 0.15 mm or less exceeds 25% by weight, the fine aggregate ratio increases, the mortar content in the concrete becomes excessive, and the workability cannot be improved by blending. In addition, when the mortar content in the concrete increases, the amount of air with respect to the mortar decreases even if the amount of air per m 3 is the same, and the resistance to freeze-thaw decreases. Therefore, the particle size distribution of 0.15 mm or less in the weight aggregate is set in the range of 15 to 25% by weight.

Since the present invention is configured as described above, it is possible to reduce the cost by selecting one type of heavy aggregate to be used, shorten the time required for the blending design, and prevent the aggregate separation, It is possible to provide heavy-duty concrete that satisfies the required quality, workability, etc., and has excellent resistance to freezing and thawing relatively inexpensively.

Therefore, according to the present invention, since one kind of heavy aggregate is selected and used without using a plurality of heavy aggregates, heavy concrete disturbed by various qualities, which is difficult with the prior art, can be obtained with simple equipment. It can be manufactured inexpensively and provided for a variety of uses.

Next, the constituent elements of the present invention will be described.
1. Mixing design Same as ordinary concrete, but it is necessary to consider the following (1), (2) and (3).
(1) Mass per unit volume: 2.4 t / m3 or more.
(2) Strength: The design standard strength of the structure is set to 210 kgf / cm2, and strength is guaranteed according to JISA5308.
(3) Durability: Considering concrete exposed to a severe natural environment as a prerequisite, in order to ensure durability against freezing and thawing, the air volume shall be 4% specified in JIS A5308-1989 and the allowable range ± 1%. . In addition, the water cement ratio is set to 65% or less.

2. Regarding the materials The following (1), (2), (3) and (4) are listed as cement, heavy aggregate, ordinary aggregate and thickener used as the material of the heavy concrete according to the present invention. .

(1) Cement: Blast furnace cement B (which has a blast furnace slag content of 30 to 60% by weight, manufactured by Nippon Cement Co., Ltd.) which rapidly develops latent hydraulicity and hardens firmly is preferable.

(2) Heavy aggregate: Magnetite (Fe3O4) or the like, which has a large specific gravity and is chemically stable, is preferable.

(3) Ordinary aggregate:
a) Fine aggregate: sand used for ordinary concrete is preferable, coarse sand is weathered granite processed sand, fine sand is, for example, old Izumo sand dune sand, and the mixing ratio depends on the unit mass of concrete. Change.
b) Coarse aggregate: A crushed stone used for ordinary concrete, for example, a coarse aggregate obtained by mixing crushed stone 2005 and crushed stone 4020 in a ratio of 1: 1 is preferable.

(4) Thickener: Used to suppress separation and bleeding of heavy aggregate and increase the viscosity of cement paste. The main component is a water-soluble methylcellulose-based polymer (for example, trade name: Marine Keep manufactured by Tokuyama). Preferably, the following AE water reducing agent is blended, whereby the characteristics can be further improved.

(5) AE water reducing agent: An AE agent that uniformly distributes a large number of fine and independent air bubbles in concrete to improve workability and frost damage resistance, and a unit water amount necessary to obtain a required slump. A high-performance AE water reducing agent which has both effects of the water reducing agent used for reducing the water is used to minimize the unit water volume. The main component of the AE water reducing agent is a polycarboxylic acid ether-based complex (for example, trade name: Reobuild SP-8N). Next, examples of the present invention will be described.

Table 1 shows a composition example of a heavy concrete for a wave-dissipating block based on 210-8-40-BB, in which crushed magnetite sand was used as a heavy aggregate. Among them, 210 is the strength, 8 is the slump, 40 is the maximum size of the coarse aggregate, and BB is the cement symbol indicating blast furnace cement B type.

The materials used in this example are as follows.
1. Cement: Blast furnace cement B type manufactured by Nippon Cement Co., Ltd.
2. Heavy aggregate: One type of crushed magnetite sand. (See Tables 4 and 5)
3. Fine aggregate: Weathered granite processed sand was used as coarse sand, and old Izumo dune sand was used as fine sand, and the mixing ratio was changed according to the unit mass of concrete.
4. Coarse aggregate: Crushed stone used for ordinary concrete in the Matsue area, which is a 1: 1 mixture of crushed stone 2005 and crushed stone 4020.
5. Thickener: Trade name: Marine keep made by Tokuyama.
6. AE water reducing agent: Trade name: Leobuild SP-8N.

The above materials were blended in the proportions shown in Table 1 as follows. The mixer used for the compounding was a three-cut inclined cylinder type, and was kneaded for 3 minutes after charging by the simultaneous charging method for all materials, and the volume per batch was 40 l.

(4) The concrete discharged from the mixer was turned over on a watertight kneading plate, and then slump, unit mass, air volume and workability were measured.

Trial kneading to check the characteristic values of heavy concrete such as compressive strength and bending strength was made into 4 batches each, and the 4 batches were transferred to a kneading boat and cut back sufficiently. Was done.

First, Table 2 shows the results of measurement tests of slump, air volume, compressive strength, bending strength and workability.

か ら From the results in Table 2, the compressive strength is quite high, and the design strength: 210 kgf / cm2 (28 days) can be sufficiently guaranteed. Next, the results of the freeze-thaw test are shown in Table 3.

The sample used in this test was 210-8-40-BB, W / C = 60%, and heavy concrete using magnetite crushed sand as a heavy aggregate. Test Method for Resistance of Specimen ".

Regarding the freeze-thaw test, it is generally considered that a concrete product having good durability is obtained when the relative dynamic elastic modulus of the test result is 60% or more in 300 cycles. According to the results shown in Table 3, at the end of 300 cycles, the relative dynamic elastic modulus was 85% or more and the air content was entrained at 4% or more. . Table 4 shows an example of the quality of the heavy aggregate used in the present embodiment, and Table 5 shows an example of the particle size distribution.

Claims (2)

A heavy-weight concrete containing a thickener and having a specific gravity of 2.4 or more. The heavy concrete according to claim 1, wherein the thickener is a water-soluble methylcellulose-based polymer.