JP2001253749A - High-strength light weight cement hardened body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide lightweight concrete having high compressive strength and high flexural strength. SOLUTION: This high-strength lightweight cement hardened body consists of a hardened body formed from a mixture comprising at least cement, a pozzolanic fine powder, lightweight aggregate and a water reducing agent, wherein the high-strength lightweight cement hardened body also optionally contains metal fiber and/or organic fiber, or an inorganic powder and further, optionally contains fibrous particles or flaky particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength and lightweight cement hardened material.

[0002]

2. Description of the Related Art In recent years, in a high-rise building which has been actively constructed, in order to support the load of an upper structure which has been increased due to an increase in height, concrete of a lower structure has to be strengthened or its cross section has been enlarged. We have to do it. On the other hand, in order to reduce the weight of the upper structure, A
Lightweight concrete such as LC is being used.

[0003] However, in order to increase the strength of concrete, the unit cement amount increases, and the temperature cracks due to the heat of hydration of the cement and the cracks due to the self-shrinkage of the concrete tend to occur. In addition, the enlargement of the concrete section is often restricted in terms of the design of the building and economic efficiency.

[0004] On the other hand, if an attempt is made to reduce the weight of conventional concrete, the reduction in strength becomes remarkable. Therefore, there is a natural limitation in reducing the weight in view of the balance between weight reduction and strength reduction. Further, when the density of the concrete matrix decreases due to weight reduction, deterioration factors such as carbon dioxide and chloride easily enter from the outside, which promotes neutralization and salt damage, which is not preferable from the viewpoint of durability. However, the use of lightweight aggregates can reduce the weight of concrete while maintaining the same level of compressive strength without reducing the density of the matrix, but generally causes a problem that the flexural strength is reduced.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a lightweight concrete having a high compressive strength and a high bending strength (hereinafter referred to as a "hardened high-strength lightweight cement").

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above problems, and as a result, have found that at least a cured product of a compound containing cement, fine pozzolanic powder, lightweight aggregate, and a water reducing agent is obtained. The present inventors have found that a high-strength lightweight cement hardened body can solve the above-mentioned problems, and have completed the present invention. Also,
The hardened high-strength lightweight cement according to the present invention may contain metal fibers and / or organic fibers or inorganic powder, and may further contain fibrous particles or flaky particles.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The type of cement used in the present invention is not limited. Various portland cements such as ordinary Portland cement, early-strength Portland cement, medium heat Portland cement, low heat Portland cement, and mixed cements such as blast furnace cement and fly ash cement can be used.

In the present invention, it is preferable to use early-strength Portland cement when it is intended to improve the early strength of concrete, and to improve the fluidity of concrete, when it is desired to improve the fluidity of concrete. It is preferred to use

As the pozzolanic fine powder, silica fume, silica dust, fly ash, slag, volcanic ash,
Silica sol, precipitated silica and the like. Generally, in silica fume and silica dust, the average particle size is 1.
Since it is 0 μm or less and it is not necessary to grind, it is suitable as the pozzolanic fine powder of the present invention.

By blending pozzolanic fine powder,
Due to the microfiller effect and the cement dispersing effect, the concrete is densified and the compressive strength is improved. on the other hand,
When the amount of the pozzolanic fine powder increases, the unit water amount increases.
It is preferably 5 to 50 parts by weight based on parts by weight.

As the lightweight fine aggregate or lightweight coarse aggregate, a granulated type or a non-granulated type made of perlite, obsidian, shirasu, coal ash or ceramics can be used. Also,
The water content of each of them is preferably 25% or less in a water-absorbed state for 24 hours, more preferably 10% or less for lightweight fine aggregate, and more preferably 5% or less for lightweight coarse aggregate. The particle size of the lightweight fine aggregate is preferably 2 mm or less, more preferably 1.5 mm or less. The particle size of the lightweight coarse aggregate is 5 to 15 m.
m is preferred. The particle size of the aggregate is an 85% (weight) cumulative particle size. Further, the specific gravity of the lightweight fine aggregate and the lightweight coarse aggregate in the surface dry and saturated state (surface dry state) is 0.6 to 1.4.
It is more preferable that the specific gravity of both surfaces be 0.8 to 1.2.
The degree is preferred. Incidentally, in addition to the lightweight aggregate, ordinary aggregates such as crushed stone and fine sand may be used in combination.

As the water reducing agent, a lignin-based, naphthalene-sulfonic acid-based, melamine-based, polycarboxylic acid-based water reducing agent, a high performance water reducing agent or a high performance AE water reducing agent can be used. Among them, a high performance water reducing agent or a high performance AE water reducing agent is preferable. The amount of water reducing agent added depends on the fluidity and separation resistance of the concrete, the strength after hardening, and the cost.
With respect to 100 parts by weight of cement, 0.5
~ 4.0 parts by weight is preferred.

In the present invention, the water / cement ratio is preferably from 10 to 30%, more preferably from 15 to 25%, in view of the fluidity and separation resistance of the concrete, the strength and durability of the cured product, and the like.

In the present invention, from the viewpoint of increasing the bending strength of the cured product, it is preferable that the composition contains metal fibers and / or organic fibers. As metal fiber, steel fiber,
Amorphous fibers and the like can be mentioned, and among them, steel fibers are excellent in strength, and are preferable in terms of cost and availability. Metal fibers have a diameter of 0.01 to 1.0
mm and a length of 2 to 30 mm are preferable. Diameter 0.0
If it is less than 1 mm, the strength of the fiber itself is insufficient, and the fiber is apt to break when subjected to tension. If the diameter exceeds 1.0 mm, the number of pieces with the same blending amount decreases, and the flexural strength of concrete decreases. If the length exceeds 30 mm, fiber balls tend to be formed during kneading. If the length is less than 2 mm, the adhesive strength to the matrix is reduced and the bending strength is reduced.

The amount of the metal fibers is preferably less than 4%, more preferably less than 3.5% of the concrete volume after setting. The content of the metal fiber is determined from the viewpoint of fluidity and bending strength of the cured product. In general, as the content of the metal fiber increases, the bending strength improves, but on the other hand, the unit water amount also increases in order to secure fluidity. Therefore, the content of the metal fiber is preferably the above-mentioned amount.

The organic fibers include vinylon fiber, polypropylene fiber, polyethylene fiber, aramid fiber, carbon fiber and the like. The organic fiber has a diameter of 0.005 to 1.
Those having a length of 0 mm and a length of 2 to 30 mm are preferable. The content of the organic fibers is preferably less than 10% of the concrete volume after setting, more preferably less than 7%. In the present invention, a combination of metal fibers and organic fibers may be used.

In the present invention, from the viewpoint of increasing the packing density of the cured product, it is preferable to include an inorganic powder having an average particle size of 3 to 20 μm, more preferably 4 to 10 μm. As the inorganic powder, quartz powder, limestone powder, Al
Oxide powder such as ₂ O ₃ , carbide powder such as SiC, SiN
And the like, and among them, quartz powder is preferable in terms of cost and quality stability of the cured product. Examples of the quartz powder include quartz, amorphous quartz, and opal and cristobalite silica-containing powders. The amount of the inorganic powder is preferably 50 parts by weight or less, more preferably 20 to 35 parts by weight, based on 100 parts by weight of cement, from the viewpoint of the fluidity of the concrete, the strength of the hardened body, and the like.

In the present invention, from the viewpoint of increasing the toughness of the cured product, it is preferable to include fibrous particles or flaky particles having an average particle size of 1 mm or less. Here, the particle size of a particle is the size of its maximum dimension (in particular, its length for fibrous particles). Examples of the fibrous particles include wollastonite, bauxite, and mullite, and examples of the flaky particles include mica flake, talc flake, vermiculite flake, and alumina flake. The blending amount of the fibrous particles or flaky particles is preferably 35 parts by weight or less, more preferably 10 to 25 parts by weight, based on 100 parts by weight of cement, from the viewpoint of the fluidity of the concrete, the strength and the toughness of the cured product. From the viewpoint of enhancing the toughness of the cured product, it is preferable to use fibrous particles having a needleiness expressed by a length / diameter ratio of 3 or more.

In the present invention, the method for kneading concrete is not particularly limited. The apparatus used for kneading is not particularly limited, and a conventional mixer such as an omni mixer, a pan-type mixer, a biaxial kneading mixer, and a tilting mixer can be used.

By molding, curing and hardening the kneaded concrete, the high-strength lightweight cement hardened product of the present invention can be manufactured. The molding method is not particularly limited, and can be performed by a conventional molding method such as cast molding. Also, the method of curing the concrete is not particularly limited, and may be room temperature curing, steam curing, or the like.

[0021]

The present invention will be described below with reference to examples. The materials and test methods used in the following examples and comparative examples are as follows. (Materials used) 1) Cement; Low heat Portland cement (commercially available) 2) Pozzolanic fine powder; Silica fume (average particle size 0.7 μm) 3) Aggregate: 2: 1 of silica sand No. 4 and silica sand No. 5 (weight ratio) ) Mixed product 4) Lightweight fine aggregate; average particle size 1.2 mm, surface dry specific gravity 1.2, water absorption rate after 24 hours 6.5%, granulation type 5) Lightweight coarse aggregate; Asano Super Light ( Taiheiyo Cement Co., Ltd.), average particle size 10 mm, surface dry specific gravity 0.8, water absorption after 24 hours 4.4%, granulation type 6) Metal fiber; steel fiber (diameter: 0.2 mm, length: 15) 7) Organic fiber; Vinylon fiber (diameter: 0.6 mm, length: 15 mm) 8) High-performance AE water reducing agent; Polycarboxylic acid-based high-performance AE water reducing agent 9) Water; tap water 10) Quartz powder (average) 11) Fibrous particles; wollastonite (average length of 0. 3mm, length / diameter ratio 4)

(Testing Method) After being batch-poured into a horizontal biaxial forced kneading mixer and kneaded, a specimen for compressive strength test was subjected to a J-shape using a mold having a diameter of 100 mm and a height of 200 mm.
In accordance with IS A 1132 "How to make a specimen for concrete strength test", concrete was poured into a mold in two layers, and each layer was compacted for 10 seconds using an internal vibrator.
The specimen for bending strength test was 100 mm long and 1 mm wide.
JIS A using a formwork of 00 mm and height of 400 mm
According to 1132, concrete was poured into the formwork in one layer and compacted for 10 seconds using an internal vibrator. Each specimen was pre-cured at 20 ° C. for 48 hours and then steam-cured at 90 ° C. for 48 hours. After completion of each curing, the mold was removed and a strength test was performed. The compression strength test is JIS A 1108 "Compression test method for concrete", and the bending strength test is JIS A
The test was performed in accordance with 1106 "Method of Concrete Bending Test".

Example 1 (Blending conditions) Low heat Portland cement; 100 parts by weight Silica fume; 32.5 parts by weight Light fine aggregate; 30 parts by weight Light coarse aggregate; 10 parts by weight High-performance AE water reducing agent: 0.5 parts by weight Part (in terms of solid content) Water / cement ratio: 22% Using these materials, the compressive strength and the flexural strength were measured in accordance with the test method described above. The results of these measurements are shown in Table 1.

Example 2 (Blending conditions) Low heat Portland cement; 100 parts by weight Silica fume; 32.5 parts by weight Aggregate: 30 parts by weight Light fine aggregate: 30 parts by weight High-performance AE water reducing agent: 1.0 part by weight ( Solids) Water / cement ratio; 22% steel fiber; 2% of volume in concrete Using these materials, the compressive strength and flexural strength were measured according to the test method described above. The results of these measurements are shown in Table 1.

Example 3 (Blending conditions) Low heat Portland cement; 100 parts by weight Silica fume; 32.5 parts by weight Aggregate: 30 parts by weight Light fine aggregate: 30 parts by weight Quartz powder: 30 parts by weight Wollastonite: 24 parts by weight Part High-performance AE water reducing agent; 1.0 part by weight (solid content) water / cement ratio; 22% steel fiber; 2% of the volume in concrete Using these materials, compressive strength and bending were determined according to the test method described above. The strength was measured. The results of these measurements are shown in Table 1.

Comparative Example (Blending conditions) Low heat Portland cement; 100 parts by weight Aggregate; 30 parts by weight Light fine aggregate; 30 parts by weight High-performance AE water reducing agent; 1.0 part by weight (solid content) Water / cement ratio; 22% Compressive strength and flexural strength were measured using these materials according to the test method described above. The results of these measurements are shown in Table 1.

[0027]

[Table 1]

As can be seen from Table 1, Examples 1 to 3
As compared with the comparative example, both the compressive strength and the bending strength are remarkably improved, and particularly, the bending strength is more than doubled.

[0029]

As described above, the high-strength lightweight cement cured product of the present invention
Since it has high compressive strength and bending strength while being lightweight, it is effective in reducing the load particularly when used for the superstructure of a high-rise building.

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Claims (6)

[Claims] 1. A high-strength, lightweight, hardened cement comprising at least a cured product of a compound containing cement, pozzolanic fine powder, lightweight aggregate, and a water reducing agent. 2. The high-strength lightweight cement cured product according to claim 1, wherein the composition contains metal fibers and / or organic fibers. 3. The metal fiber has a diameter of 0.01 mm to 1.0 m.
The high-strength lightweight cement cured product according to claim 2, which is a steel fiber having a length of 2 to 30 mm. 4. An organic fiber having a diameter of 0.005 mm to 1.0 mm.
The high-strength lightweight cement cured product according to claim 2, wherein the cured cement is one or more fibers selected from vinylon fibers, polypropylene fibers, polyethylene fibers, aramid fibers, and carbon fibers having a length of 2 to 30 mm. 5. The high-strength lightweight cement cured product according to claim 1, wherein the composition contains an inorganic powder having an average particle size of 3 to 20 μm. 6. The high-strength lightweight cement cured product according to claim 1, wherein the composition contains fibrous particles or flaky particles having an average particle size of 1 mm or less.