JP2007186372A - 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 explosion 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 and an ettringite producing admixture and a method of producing the same is provided. In the explosive fracture-resistant cement hardened body, the cement is blast furnace cement, the ettringite producing admixture is one or more kinds selected from an expanding material, a quick hardening material and a high strength material, the water/binder ratio is adjusted to 35-60% and the explosive fracture-resistant cement hardened body 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 6-11).
Japanese Patent Laid-Open No. 10-194798 JP-A-11-228253 JP-A-11-246283 JP 2000-203964 A Japanese Patent Laid-Open No. 2003-176160 JP 2003-335567 A

  However, Patent Documents 6 to 11 do not disclose the technical idea of obtaining an explosion-proof hardened cement body, and obtain a cement hardened body excellent in explosion resistance by carbonizing a combination of specific materials. That is not shown.

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 hardened cement body subjected to carbonation curing in combination with specific materials is excellent in explosion resistance, and further has a specific fiber length. It has been found that a cement hardened body excellent in explosion resistance can be obtained by blending organic fibers having the above, and the present invention has been completed.

The present invention employs the following means in order to solve the above problems.
(1) An explosive-resistant cement-cured body characterized in that a cement-cured body obtained by carbonizing a part or all of the cement-cured body contains cement and an ettringite-generating admixture.
(2) The explosion-resistant cement hardened body according to (1), wherein the cement is a blast furnace cement.
(3) The explosive-resistant cement hardened body according to (1) or (2), wherein the ettringite-forming admixture is at least one selected from an expanded material, a hardened material, and a high-strength material. is there.
(4) The explosive-resistant cement hardened body according to any one of (1) to (3), wherein the water / binder ratio is adjusted in a range of 35 to 60%.
(5) The explosive-resistant cement hardened body according to any one of (1) to (4) above, wherein the fiber contains organic fibers having a fiber length of 3 mm or less.
(6) The explosive-resistant cement hardened body according to any one of (1) to (5) above, wherein the compressive strength is 30 N / mm ² or more.
(7) A cement hardened body prepared by blending at least water with a cement composition, preparing a cement kneaded product, pouring it into a mold, curing it, and demolding it after curing. In the production method, the cement composition contains a cement and an ettringite-forming admixture, and is a method for producing an explosion-resistant hardened cement body.
(8) The method according to (7), wherein the cement is a blast furnace cement.
(9) The explosive-resistant cement hardened body according to (7) or (8) above, wherein the ettringite-forming admixture is at least one selected from an expanded material, a hardened material, and a high-strength material. It is a manufacturing method.
(10) The method for producing a hardened explosion-resistant cement according to any one of (7) to (9), wherein the water / binder ratio is adjusted in a range of 35 to 60%.
(11) The method for producing a hardened explosion-resistant cement according to any one of (7) to (10), wherein the cement kneaded material is a blend of organic fibers having a fiber length of 3 mm or less. Is the method.
(12) The explosion-resistant cement according to any one of (7) to (11), wherein the cement kneaded material is a fine aggregate or a mixture of a fine aggregate and a coarse aggregate. It is a manufacturing method of a hardening body.
(13) The method according to any one of (7) to (12), 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 cement according to the present invention is usually various early Portland cements such as early strength, very early strength, low heat, and moderate heat, various mixed cements obtained by mixing these Portland cements with blast furnace slag, fly ash, or silica, and limestone. Examples include filler cement mixed with powder and blast furnace slow-cooled slag fine powder, environmentally friendly cement manufactured using various industrial wastes as the main raw material, so-called eco-cement, etc., one or more of these It is. Among them, it is preferable to select a blast furnace cement from the viewpoint of improving explosion resistance.

The ettringite-forming admixture referred to in the present invention is a generic term for admixtures that are mixed with cement to produce ettringite (3CaO.Al ₂ O ₃ .3CaSO ₄ .32H ₂ O), and is particularly limited. It is not a thing. In general, admixtures called expansion materials, rapid hardening materials, and high-strength materials can be used. Specific examples thereof include, for example, “Denka CSA” and “Denka Power CSA” (trademarks of Denki Kagaku Kogyo Co., Ltd., the same as those having “Denka” at the beginning). It is done. Examples of the quick-hardening material include a mixture of various calcium aluminates and inorganic sulfates. Calcium aluminate, expressed as _{CaO · 2Al 2 O 3, CaO} · Al 2 O 3, 12CaO · 7Al 2 O 3, 11CaO · 7Al 2 O 3 · CaF 2, 3CaO · 3Al 2 O 3 · CaSO 4 , etc. Crystalline calcium aluminates, and amorphous compounds mainly composed of CaO and Al ₂ O ₃ components. Examples of inorganic sulfates include gypsum, aluminum sulfate, and alum. Examples of commercially available quick-hard materials include “Denka Cosmic”, “Denka ES”, “Denkabi Foam”, “Denka Super Cement”, “Jet Cement” (Sumitomo Osaka Cement Co., Ltd., Taiheiyo Cement Co., Ltd.) Trademark), “Coca Ace” (trademark of Mitsubishi Materials Corporation), and the like. In addition, examples of the high-strength material include those mainly composed of inorganic sulfate, and if necessary blended with a pozzolanic substance. Examples of commercially available high-strength materials are “Denka Σ1000”, “Denka Σ2000”, “Denka Σ80N”, “Nonclave” (trademark of Sumitomo Osaka Cement Co., Ltd.), “Supermix” (Pacific Cement Co., Ltd.) Trademark).

The particle size of the formation of ettringite-based admixture of the present invention, but are not particularly limited, is preferably 2500~9000cm ² / g in Blaine specific surface area, 4000~8000cm ² / g is more preferable. Outside the above range, sufficient explosion resistance may not be obtained.

  The use ratio of the ettringite-forming admixture is not particularly limited, but is usually preferably 5 to 50 parts, more preferably 10 to 30 parts, out of a total of 100 parts of cement and ettringite-forming admixture. If it is less than 5 parts, sufficient explosion resistance may not be obtained, and if it exceeds 50 parts, further enhancement of the effect cannot be expected.

  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. Usually, the water binder ratio is preferably in the range of 35-60%, and 40-55%. Is more preferable. If the water binder ratio is less than 35%, 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 when it is sufficiently cured and does not reach a very high strength. Specifically, it is 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 . 10-30 N / mm < ² > is more preferable. Outside this range, the explosion resistance effect may not be sufficiently obtained. 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 blending ratio of the organic fibers can be used in the range of 0.1 to 3 parts, more preferably 0.5 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, limestone fine powder, blast furnace slow-cooled slag fine powder, sewage sludge incineration ash and its molten slag, admixture materials such as municipal waste incineration ash and its molten slag, pulp sludge incineration ash, water reducing agent, AE water reducing agent, high Performance water reducing agent, high performance AE water reducing agent, antifoaming agent, thickening agent, rust preventive agent, antifreeze agent, shrinkage reducing agent, cement admixture such as polymer, setting modifier, clay mineral such as bentonite, and hydrotal One or two or more of anion exchangers such as sites can be used as long as the object of the present invention is not substantially inhibited.

  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.

Cement and an ettringite-forming admixture were blended in the proportions shown in Table 1 to prepare 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 and left for 5 hours before steam curing to prepare a cylindrical specimen having a diameter of 15 cm and a height of 30 cm. After steam curing, carbonation curing was further forcibly started from the age of 24 hours, and the inside of the cured body was completely carbonated. Steam curing conditions were set at 65 ° C. for 4 hours. In addition, when the compressive strength of the hardening body at the time of starting carbonation (material age 24 hours) was confirmed, all were the range of 10-30 N / mm < ² >. 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>
Cement (I): Commercially available ordinary Portland cement, specific gravity 3.16, Blaine specific surface area 3300 cm ² / g.
Admixture A: Commercially available expansion material, “Denka CSA # 20”, Blaine specific surface area 2500 cm ² / g.
Admixture B: Commercially available rapid hardwood, “Denka Cosmic”, Blaine specific surface area of 6000 cm ² / g.
Admixture C: Commercially available high strength material, “Denka Σ1000”, Blaine specific surface area 5000 cm ² / g.
Admixture D: Mixture of equal amounts of Admixture A and Admixture C.
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.
Explosion test: The hardened cement body was put in a furnace, heated to 1200 ° C. in 1 hour, and the presence or absence of explosion was observed. Out of 12 specimens, if 6 or more explosions are observed, ×, if 3 or more and 5 or less, △, if 1-2, ○, if no explosion is observed ◎.

  From Table 1, it can be seen from Experiment No.1-2 to No.1-10 that contain cement and an ettringite-producing system admixture. It can be seen that it is superior in explosion resistance (see the result of the explosion test) as compared with the hardened cement body of Comparative Example -1. In particular, the use ratio of the admixture is 15 to 50 parts (experiment No.1-2 to No.1-5, No.1-8 to No.1-10) of the total 100 parts of cement and admixture. By doing so, the explosion resistance is improved.

  The same procedure as in Example 1 was performed except that blast furnace cement was used as the cement. The results are also shown in Table 2.

<Materials used>
Cement (b): Commercially available blast furnace cement type B, specific gravity 3.06, Blaine specific surface area 3500 cm ² / g.

From Table 2, even when blast furnace cement is used as the cement, the hardened cement bodies of Examples No. 2-2 to No. 2-10, which contain cement and an ettringite-generating admixture, generate ettringite only with cement. It can be seen that it is superior in explosion resistance (see the result of the explosion test) as compared with the cement hardened body of Comparative Example No. 2-1 which does not contain a system admixture. In particular, the proportion of admixture used is 10 to 30 parts (experiment No.2-2 to No.2-5, No.2-7 to No.2-9) out of 100 parts of cement and admixture. By doing so, the explosion resistance is improved.
In addition, it is clear from comparison of Experiment No. 1-7 in Table 1 and Experiment No. 2-7 in Table 2, Experiment No. 1-9 in Table 1 and Experiment No. 2-9 in Table 2. As the blast furnace cement, the explosion resistance is superior to the case of using ordinary Portland cement.

  The same procedure as in Example 2 was carried out except that a binder comprising 80 parts of cement (b) and 20 parts of admixture B was used and concrete was prepared by changing the water / binder ratio as shown in Table 3. The results are also shown in Table 3.

As shown in Experiments No. 2-8 and No. 3-1 to No. 3-5 in Table 3, by adjusting the water / binder ratio in the range of 35-60%, 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 / binder ratio to 40% or more (Experiment No. 2-8, No. 3-2 to No. 3-5), 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 a binder consisting of 80 parts of cement (b) and 20 parts of admixture B, organic fiber is blended as shown in Table 4 with respect to 100 parts of the binder, and the unit binder amount is 400 kg / m ³ , water / Concrete having a binder ratio of 40%, s / a of 46%, and air amount of 3 ± 1.0% was prepared. Other than that was carried out similarly to Example 2. The results are also shown in Table 4.

<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. 4-1 to No. 4-9 in Table 4, by blending 0.1 to 3.0 parts of organic fiber having a fiber length of 3 mm or less with respect to 100 parts of the binder. It can be seen that a hardened cement body having excellent explosion resistance (see the result of the explosion test) can be obtained.

A binder consisting of 80 parts of cement (B) and 20 parts of admixture B is used. 1.0 part of organic fiber a is blended with 100 parts of binder, the amount of unit binder is 400 kg / m ³ , and water / bonding. Concrete having a material ratio of 40%, s / a of 46%, and air amount of 3 ± 1.0% was prepared. And it carried out like Example 2 except having adjusted the carbonation curing period and having changed carbonation depth as shown in Table 5. The results are also shown in Table 5.

  From Table 5, the hardened cement bodies of Examples No. 5-2 to No. 5-6 and No. 4-4 subjected to carbonation treatment are comparative examples of Experiment No. 5-1 not subjected to 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 (13)

  An explosive-resistant cement hardened body comprising a cement hardened body obtained by carbonizing a part or all of the cement hardened body and containing cement and an ettringite-forming admixture.   The explosion-resistant cement hardened body according to claim 1, wherein the cement is a blast furnace cement.   The explosive-resistant cement hardened body according to claim 1 or 2, wherein the ettringite-generating admixture is at least one selected from an expanded material, a hardened material, and a high-strength material.   The explosion-resistant cement hardened body according to any one of claims 1 to 3, wherein the water / binder ratio is adjusted in a range of 35 to 60%.   The hardened explosion-proof cement according to any one of claims 1 to 4, comprising an organic fiber having a fiber length of 3 mm or less. Compressive strength is 30 N / mm < ² > or more, The explosion-resistant cement hardening body as described in any one of Claims 1-5 characterized by the above-mentioned.   In a method for producing a hardened cement body, a cement kneaded material is prepared by blending at least water with a cement composition, poured into a mold, cured, and demolded after curing, and then carbonized and cured. The method for producing a hardened explosion-resistant cement, wherein the cement composition contains cement and an ettringite-forming admixture.   The method for producing a hardened explosion-resistant cement according to claim 7, wherein the cement is a blast furnace cement.   The method for producing a hardened explosion-resistant cement according to claim 7 or 8, wherein the ettringite-generating admixture is at least one selected from an expanding material, a rapid hardening material, and a high-strength material.   The method for producing a hardened explosion-resistant cement according to any one of claims 7 to 9, wherein the water / binder ratio is adjusted in a range of 35 to 60%.   The method for producing a hardened explosion-resistant cement according to any one of claims 7 to 10, 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 7-11 characterized by the above-mentioned. Method. The method for producing a hardened explosion-resistant cement according to any one of claims 7 to 12, wherein the cement kneaded material is a mixture of a cement admixture.