JP2007186371A - Explosive fracture-resistant cement hardened body and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an explosive fracture-resistant cement hardened body which has excellent explosive fracture resistance, whose strength designing is easily carried out, since it exhibits ≥30 N/mm<SP>2</SP>practical strength, and which is hardly affected by inherent water. <P>SOLUTION: The explosive fracture-resistant cement hardened body is formed by carbonation-treating a part or the whole of the cement hardened body and contains cement composed essentially of calcium aluminate and a method of producing the same is provided. The explosive fracture-resistant cement hardened body contains a latent hydraulic compound and/or a pozzolan compound, is adjusted to have 40-60% water/binder ratio and can contain an organic fiber having ≤3 mm fiber length. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention mainly relates to an explosion-resistant cement hardened body used in the civil engineering and construction industry and a method for producing the same.
In addition, the cement hardened body in this invention is a general term for a paste hardened body, a mortar hardened body, and a concrete hardened body.

  In a structure affected by a fire such as a tunnel or a building, explosion of a hardened cement body at the time of a fire is regarded as a problem. This is because the hardened cement body is scattered by explosion, and humans may be seriously damaged such as being injured or killed. The reason why the hardened cement body explodes at the time of fire is that the water present in the hardened cement body causes a steam explosion as the temperature rises. Therefore, in order to suppress the explosion of the hardened cement body, it is considered important to efficiently release the moisture in the hardened cement body to the outside of the hardened body.

From the above viewpoint, various methods for obtaining an explosion-resistant cement hardened body have been studied. As a method for suppressing the explosion of the hardened cement body, there is a method of covering with a hardened cement body having a high porosity and low strength (Patent Document 1). This is based on the fact that, in a porous cement hardened body, the inherent moisture deviates rapidly from the hardened body, so that explosion does not easily occur.
Japanese Unexamined Patent Publication No. 09-13531

Moreover, the method (patent documents 2-5) which mix | blends an organic fiber is also proposed. This is because the blended organic fiber burns with a rise in temperature to form voids, which serve as an inherent moisture path and suppress explosion.
Japanese Patent Publication No.57-20126 JP-A-11-79807 Japanese Patent Laid-Open No. 11-303245 JP 2000-143322 A

However, the method of covering with a cement hardened body having a high porosity and low strength is not useful from the viewpoint of strength design, and has problems such as an increase in the size of a structure and a reduction in available space.
Moreover, the method using an organic fiber had the subject that the explosion suppression effect fluctuate | varies greatly with the moisture content of a cement hardening body. That is, when the moisture content of the hardened cement body is high, a sufficient explosion suppressing effect may not be obtained. Furthermore, the conventional organic fiber has a fiber length of 5 mm or more, and it has become clear that the path forming ability is not sufficient when such a fiber is used. That is, according to the experimental results found by the present inventors through various experiments, the fiber continuity (path forming ability) when a long fiber having a fiber length of 5 mm or more is used even at the same addition rate. It has become clear that the fiber length is inferior to the ability to form a path when a short fiber length of less than 5 mm is used.

On the other hand, in order to raise the intensity | strength of a cement hardening body, it is also well-known to carbonize a cement hardening body (for example, patent documents 6-9).
Japanese Patent Laid-Open No. 10-194798 JP-A-11-228253 JP-A-11-246283 JP 2000-203964 A

  However, Patent Documents 6 to 9 do not disclose the technical idea of obtaining a hardened explosive-resistant cement, and suggest that alumina cement can be used as the cement (Patent Document 6, paragraph [0007], (Patent Document 7, Paragraph [0008], Patent Document 8, Paragraph [0009], and Patent Document 9, Paragraph [0006]). Specifically, a hardened cement body containing alumina cement is carbonized to make it explosive resistant. It has not been shown to obtain an excellent cement cured body.

The present invention provides an explosive-resistant cement hardened body that is excellent in explosive resistance, has an actual strength of 30 N / mm ² or more, is easy to design, and is hardly affected by the moisture contained in the hardened cement body. The task is to do.

  The present inventor has made various efforts to solve the above problems, and as a result, the cemented hardened body subjected to carbonation curing using a specific cement is excellent in explosion resistance. It has been found that a cement hardened body excellent in explosion resistance can be obtained by blending a long organic fiber, and the present invention has been completed.

The present invention employs the following means in order to solve the above problems.
(1) A hardened cement obtained by carbonizing a part or all of a hardened cement, and containing a cement containing calcium aluminate as a main component.
(2) The explosion-resistant cement hardened body according to (1) above, which contains a latent hydraulic substance and / or a pozzolanic substance.
(3) The explosive-resistant cement hardened body according to (1) or (2), wherein the water / binder ratio is adjusted in the range of 40 to 60%.
(4) The explosion-resistant cement hardened body according to any one of (1) to (3), wherein the fiber contains an organic fiber having a fiber length of 3 mm or less.
(5) The explosive-resistant cement hardened body according to any one of (1) to (4), wherein the compressive strength is 30 N / mm ² or more.
(6) A method for producing a hardened cement body comprising preparing a cement kneaded product by blending at least water with cement, pouring the cement kneaded material into a mold, curing the molded body obtained by demolding after curing, and carbonizing curing In the above, the cement is a cement mainly composed of calcium aluminate.
(7) The method according to (6), wherein the cement kneaded material is a mixture of a latent hydraulic substance and / or a pozzolanic substance.
(8) The method according to (6) or (7), wherein the water / binder ratio is adjusted in the range of 40 to 60%.
(9) Manufacture of the explosion-resistant cement hardened | cured material as described in any one of said (6)-(8) characterized by the above-mentioned cement kneaded material mix | blending the organic fiber whose fiber length is 3 mm or less. Is the method.
(10) The explosion-resistant cement according to any one of (6) to (9), wherein the cement kneaded material is a fine aggregate or a mixture of fine aggregate and coarse aggregate. It is a manufacturing method of a hardening body.
(11) The method for producing a hardened explosion-resistant cement according to any one of (6) to (10), wherein the cement kneaded material is a mixture of a cement admixture.
In the present invention, “parts” and “%” are based on mass unless otherwise specified.

According to the present invention, an explosion-resistant cement hardened body that is excellent in explosion resistance, has an actual strength of 30 N / mm ² or more, is easy in strength design, and is not easily affected by the moisture contained in the cement hardened body. Can be obtained.

The calcium aluminate referred to in the present invention is a general term for compounds mainly composed of CaO and Al ₂ O ₃ and is not particularly limited. Specific examples _{thereof, CaO · 2Al 2 O 3,} CaO · Al 2 O 3, 12CaO · 7Al 2 O 3, 11CaO · 7Al 2 O 3 · CaF 2, 3CaO · Al 2 O 3, 3CaO · 3Al 2 Examples thereof include crystalline calcium aluminates represented as O ₃ · CaSO ₄ , and amorphous compounds mainly composed of CaO and Al ₂ O ₃ components. Among these, it is possible to select a CaO / Al ₂ O ₃ molar ratio in the range of 0.5 to 2.0, from the viewpoint of securing a moderate pot life, and also from the viewpoint of the explosion resistance suppressing effect. It is preferable to select one having a CaO / Al ₂ O ₃ molar ratio in the range of 0.75 to 1.25. Commercially available alumina cement can be used as a cement mainly composed of such calcium aluminate.
Even if a hardened cement using only Portland cement containing no calcium aluminate as a main component is carbonized, the effect of improving explosion resistance is not sufficient.

Examples of a method for obtaining calcium aluminate include a method in which a CaO raw material and an Al ₂ O ₃ raw material are heat-treated with a rotary kiln or an electric furnace.
Examples of the CaO raw material for producing calcium aluminate include calcium carbonate such as limestone and shells, calcium hydroxide such as slaked lime, and calcium oxide such as quick lime. Examples of the Al ₂ O ₃ raw material include industrial by-products called bauxite and aluminum residual ash, and aluminum powder.
When calcium aluminate is obtained industrially, impurities may be contained. Specific examples _{thereof, SiO 2, Fe 2 O 3} , MgO, TiO 2, MnO, Na 2 O, K 2 O, Li 2 O, S, like P ₂ O _5, and F or the like. The presence of these impurities is not particularly problematic as long as the object of the present invention is not substantially impaired. Specifically, there is no particular problem if the total of these impurities is in the range of 10% or less.

The compound other than calcium aluminate of the above, such as _{4CaO · Al 2 O 3 · Fe} 2 O 3, 6CaO · 2Al 2 O 3 · Fe 2 O 3, 6CaO · Al 2 O 3 · 2Fe 2 O 3 Calcium aluminoferrite, calcium ferrite such as 2CaO · Fe ₂ O ₃ and CaO · Fe ₂ O ₃ , calcium aluminosilicate such as galenite 2CaO · Al ₂ O ₃ · SiO ₂ , anorthite CaO · Al ₂ O ₃ · 2SiO ₂ , Merubinaito 3CaO · MgO · 2SiO _2, Akerumanaito 2CaO · MgO · 2SiO _2, Monte calcium magnesium silicate, such as celite CaO · MgO · SiO _2, tri-calcium silicate 3CaO · SiO _2, dicalcium silicate 2CaO · SiO _2, rankinite night 3CaO · 2SiO ₂ Which may include calcium silicates such as wollastonite CaO · SiO _2, calcium titanate CaO · TiO _2, free lime, leucite _{(K 2 O, Na 2 O} ) a · Al ₂ O ₃ · SiO ₂ or the like. In the present invention, these crystalline or amorphous materials may be mixed.

The particle size of the calcium aluminate of the present invention is not particularly limited, but is usually in the range of 3000 to 9000 cm ² / g as a Blaine specific surface area value, and more preferably about 4000 to 8000 cm ² / g. If it is less than 3000 cm ² / g, strength development may not be sufficient, and if it exceeds 9000 cm ² / g, handling may be difficult.

In the present invention, it is preferable to use a latent hydraulic substance or a pozzolanic substance together with calcium aluminate from the viewpoint of improving explosion resistance. An example of the latent hydraulic material is blast furnace slag fine powder. Examples of pozzolanic substances include fly ash, silica fume, pulp sludge incineration ash, sewage sludge incineration ash, and waste glass powder. Among these, use of fly ash or silica fume is preferable. The fineness of fly ash and silica fume is not particularly limited. Usually, fly ash has a brain specific surface area of about 3000 to 9000 cm ² / g, and silica fume has a BET specific surface area. It is in the range of about ^{2 to 20} m ² / g.

  The latent hydraulic substance or pozzolanic substance is preferably used within a range of 70 parts or less, more preferably within a range of 10 to 50 parts, by replacing with calcium aluminate. If it exceeds 70 parts, it may be difficult to obtain sufficient strength to facilitate strength design.

  The amount of water used is not particularly limited because it varies depending on the purpose / use of use and the blending ratio of each material, but it is usually preferably in the range of 40-60% in terms of the water binder ratio, 45-55%. Is more preferable. If the water binder ratio is less than 40%, it may be difficult to obtain sufficient explosion resistance, and if it exceeds 60%, it may be difficult to obtain sufficient strength that facilitates strength design.

In the present invention, a part or all of the hardened cement body is carbonized. The method of carbonation treatment is not particularly limited, and specific examples thereof include a method of contacting with a carbonic acid component. The carbonic acid component referred to in the present invention is a generic term for substances capable of supplying a CO ₂ component, CO ₃ ²⁻ , HCO ₃ ^−, etc., and is not particularly limited. Specific examples thereof include, for example, carbon dioxide, supercritical carbon dioxide, dry ice, carbonates such as sodium carbonate, potassium carbonate and iron carbonate, bicarbonates such as sodium bicarbonate, potassium bicarbonate and iron bicarbonate, and Examples include carbonated water. In addition, an appropriate moisture is required for the carbonation treatment. The temperature is also preferably 20 ° C. or higher, more preferably 30 ° C. or higher.

The timing of the carbonation treatment is preferably performed after sufficient curing. Specifically, it is more preferable to perform the carbonation treatment when the compressive strength of the hardened cement body is in the range of about 5 to 40 N / mm ² . If the carbonation treatment is performed when the compressive strength of the hardened cement does not reach 5 N / mm ² or more, cracking is likely to occur, and sufficient strength that facilitates strength design is difficult to obtain. On the contrary, if it exceeds 40 N / mm ² , a long time is required for the carbonation treatment, which is not preferable from the viewpoint of productivity.

  In the present invention, part or all of the hardened cement body is carbonated. When the hardened cement body includes a reinforcing bar, the carbonation treatment is performed within the range of the thickness up to the reinforcing bar, that is, the cover thickness. This is important from the viewpoint of corrosion prevention of reinforcing bars.

  Curing until the carbonation treatment (hereinafter referred to as precuring) is not particularly limited. Examples include underwater curing, air drying curing, steam curing, and autoclave curing, and one or more of these may be combined. From the viewpoint of efficiently producing a secondary product, it is preferable to select steam curing.

  In the present invention, organic fibers can be used in combination. Organic fiber plays a role of further improving explosion resistance. The organic fiber is not particularly limited, but specific examples thereof include polypropylene fiber, vinylon fiber, cellulose fiber, acrylic fiber, and pulp fiber. The compounding ratio of the organic fiber can be used in the range of 0.1 to 3 parts, more preferably 0.3 to 2 parts, with respect to 100 parts of the binder. If it is less than 0.1 part, the effect of improving the explosion resistance may not be obtained. Conversely, even if it is used in excess of 3 parts, further improvement of the effect cannot be expected, and the fluidity is deteriorated. There is a case.

In the present invention, it is important to use a fiber having a short fiber length in order to efficiently introduce the moisture contained in the hardened cement body to the outside of the hardened cement body. The fiber length of the organic fiber is preferably less than 5 mm, and more preferably 3 mm or less. If the fiber length of the organic fiber is 5 mm or more, the effect of sufficiently improving the explosion resistance may not be obtained.
In addition, the thickness of a fiber is not specifically limited, Usually, it exists in the range of 10-750 micrometers.

  In the present invention, admixtures such as limestone fine powder and blast furnace slow-cooled slag fine powder, water reducing agent, AE water reducing agent, high performance water reducing agent, high performance AE water reducing agent, antifoaming agent, thickener, rust preventive agent, antifreeze The object of the present invention is to use one kind or two or more kinds of a cement admixture such as an agent, a shrinkage reducing agent, a polymer and a setting modifier, a clay mineral such as bentonite, and an anion exchanger such as hydrotalcite. It is possible to use in the range which does not inhibit substantially.

  In the present invention, the mixing method of each material is not particularly limited, and each material may be mixed at the time of construction, or a part or all of them may be mixed in advance.

  Any existing device can be used as the mixing device, and for example, a tilting barrel mixer, an omni mixer, a Henschel mixer, a V-type mixer, and a Nauta mixer can be used.

A calcium aluminate as shown in Table 1 and a latent hydraulic substance or pozzolanic substance were blended to form a binder. Using this binder, concrete having a unit binder amount of 400 kg / m ³ , a water / binder ratio of 40%, s / a of 46%, and an air amount of 3 ± 1.0% was prepared. A polycarboxylic acid-based high-performance AE water reducing agent was added so that the concrete slump would be 18 ± 2.5 cm. This concrete was packed in a mold to prepare a cylindrical specimen having a diameter of 15 cm and a height of 30 cm. It was demolded at a material age of 24 hours, was subjected to water curing at 20 ° C. for 6 days until the material age was 7 days, and was further forced to start carbonation curing, so that the inside of the cured body was completely carbonated. Carbonation was confirmed by the phenolphthalein method. The conditions for forced carbonation were carbon dioxide concentration 20%, relative humidity 60%, and temperature 40 ° C. While measuring the compressive strength of the obtained hardened cement body, an explosion test was performed. The results are also shown in Table 1.

<Materials used>
Calcium aluminate A: Commercially available alumina cement, CaO / Al ₂ O ₃ molar ratio is 1.0, CaO · Al ₂ O ₃ as a main component, specific gravity 2.96, Blaine specific surface area 5000 cm ² / g.
Calcium aluminate B: Commercially available alumina cement, CaO / Al ₂ O ₃ molar ratio of 0.75, mainly composed of CaO · 2Al ₂ O ₃ and CaO · Al ₂ O ₃ , specific gravity 2.75, brain specific surface area 5000 cm ² / g.
Calcium aluminate C: commercially available alumina cement, CaO / Al ₂ O ₃ molar ratio of 1.25, mainly composed of 12CaO · 7Al ₂ O ₃ and CaO · Al ₂ O ₃ , specific gravity 3.06, Blaine specific surface area 5000 cm ² / g.
Latent hydraulic material: Commercial blast furnace slag fine powder (BFS), Blaine specific surface area 4000 cm ² / g.
Pozzolanic substance A: Commercially available fly ash (FA), Blaine specific surface area 4000 cm ² / g.
Pozzolanic material B: commercially available silica fume (SF), BET specific surface area 15 m ² / g.
Water: Tap water fine aggregate: From Himekawa, Niigata Prefecture, crushed sand, 5mm below, FM 2.82, specific gravity 2.64.
Coarse aggregate: from Himekawa, Niigata Prefecture, crushed stone, G _max 25 mm, specific gravity 2.62.
Polycarboxylic acid-based high-performance AE water reducing agent: Trade name Mighty 3000 manufactured by Kao Corporation

<Measurement method>
Compressive strength: Measured at 91 days of age according to JIS A 1108.
Explosive test: A cemented body was put in a furnace, heated to 1200 ° C. in 1 hour, and the presence or absence of an explosion was observed. Out of 12 specimens, 9 or more explosions were detected, x was 6 or more and 8 or less *, 3 or more was 5 or less, Δ was 1 to 2 ◯ for cases, and ◎ for cases where no explosion was observed.

From Table 1, the cement hardened bodies of Examples No. 1-1 to No. 1-11 containing cement containing calcium aluminate as a main component are those of Experiment No. 1-12 containing ordinary Portland cement. It turns out that it is excellent in the explosion resistance (refer to a blast test result) compared with the cement hardening body of a comparative example.
Further, as shown in Experiments No. 1-5 to No. 1-11, the explosion resistance is further improved by containing a certain amount or more of a latent hydraulic substance or a pozzolanic substance.

  The same procedure as in Example 1 was conducted except that calcium aluminate A was used and concrete was prepared by changing the water / cement ratio as shown in Table 2. The results are also shown in Table 2.

As shown in Experiments No. 1-1 and No. 2-2 to No. 2-5 in Table 2, by adjusting the water / binder ratio in the range of 40 to 60%, explosion resistance (explosion) It can be seen that a hardened cement body excellent in the test results is obtained. In particular, by setting the water / binding material ratio to 45% or more (Experiment No. 2-2 to No. 2-5), the explosion resistance is improved.
Further, by setting the water / binder ratio to 60% or less, a hardened cement body having a compressive strength of 30 N / mm ² or more was obtained.

Using calcium aluminate A, 100 parts of binder is mixed with organic fibers as shown in Table 3, unit cement amount 400 kg / m ³ , water / cement ratio 40%, s / a 46%, air volume 3 ± 1.0% concrete was prepared. Other than that was carried out in the same manner as in Example 1. The results are also shown in Table 3.

<Materials used>
Organic fiber a: Vinylon fiber, fiber length 3 mm, fiber diameter 100 μm.
Organic fiber b: acrylic fiber, fiber length 3 mm, fiber diameter 100 μm.
Organic fiber c: cellulose fiber, fiber length 3 mm, fiber diameter 50 μm.
Organic fiber d: Polypropylene fiber, fiber length 3 mm, fiber diameter 100 μm.
Organic fiber e: Vinylon fiber, fiber length 6 mm, fiber diameter 100 μm.

  As shown in Experiments No.3-1 to No.3-9 in Table 3, cement hardening with excellent explosion resistance (see explosion test results) by blending organic fibers with a fiber length of 3 mm or less It turns out that a body is obtained. In particular, by adding 0.3 parts or more (experiment No. 3-2 to No. 3-9) of organic fibers with a fiber length of 3 mm or less to 100 parts of the binder, the explosion resistance is remarkably improved. To do.

Calcium aluminate A is used, 1.0 part of organic fiber a is blended with 100 parts of cement, unit cement amount is 400 kg / m ³ , water / cement ratio is 40%, s / a is 46%, air amount is 3 ± 1.0% concrete was prepared. And it carried out like Example 1 except having adjusted the carbonation curing period and changing carbonation depth as shown in Table 4. The results are also shown in Table 4.

  From Table 4, the hardened cement bodies of Examples No. 4-2 to No. 4-6 and No. 3-4 subjected to carbonation treatment are comparative examples of Experiment No. 4-1 which are not carbonation treatment. It can be seen that it is superior in explosion resistance (refer to the explosion test result) as compared with the hardened cementitious material. In particular, the explosion resistance is further improved as the carbonation depth increases.

The explosive-resistant cement hardened body of the present invention is excellent in explosive resistance, has an actual strength of 30 N / mm ² or more, is easy to design for strength, and is not easily affected by moisture contained in the hardened cement body. It can be widely applied to tunnels, civil engineering and building structures.

Claims (11)

  An explosive-resistant cement-cured body comprising a cement-cured body obtained by carbonizing a part or all of the cement-cured body, the cement containing calcium aluminate as a main component.   The explosion-resistant cement hardened body according to claim 1, comprising a latent hydraulic substance and / or a pozzolanic substance.   The explosion-resistant cement hardened body according to claim 1 or 2, wherein the water / binder ratio is adjusted in a range of 40 to 60%.   The explosion-resistant cement hardened body according to any one of claims 1 to 3, wherein the fiber contains an organic fiber having a fiber length of 3 mm or less. Compressive strength is 30 N / mm < ² > or more, The explosion-proof cement hardening body as described in any one of Claims 1-4 characterized by the above-mentioned.   In the method for producing a hardened cement body, the cement kneaded material is prepared by blending at least water with cement, poured into a mold and cured, and the molded body obtained by demolding after curing is carbonized and cured. A method for producing a hardened explosion-resistant cement, wherein the cement is a cement mainly composed of calcium aluminate.   The method for producing a hardened explosion-resistant cement according to claim 6, wherein the cement kneaded material is a mixture of a latent hydraulic substance and / or a pozzolanic substance.   The method for producing a hardened explosion-resistant cement according to claim 6 or 7, wherein the water / binder ratio is adjusted in a range of 40 to 60%.   The method for producing a hardened explosion-resistant cement according to any one of claims 6 to 8, wherein the cement kneaded material is a mixture of organic fibers having a fiber length of 3 mm or less.   The said cement kneaded material is what mix | blended the fine aggregate or the fine aggregate and the coarse aggregate, The manufacture of the explosion-proof cement hardening body as described in any one of Claims 6-9 characterized by the above-mentioned. Method. The said cement kneaded material mix | blends the cement admixture, The manufacturing method of the explosion-resistant cement hardened | cured material as described in any one of Claims 6-10 characterized by the above-mentioned.