JP4516530B2 - Explosion resistant hardened cement and method for producing the same - Google Patents

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 water vapor 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 Japanese Patent Laid-Open No. 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 a hardened explosive-resistant cement, and cement hardening that is superior in explosive resistance by forcibly carbonizing a combination of specific materials. Getting a body 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 of combining specific materials, the carbonated cement cured body is excellent in explosion resistance, and further, an organic material having a specific fiber length. It has been found that a hardened cement body having excellent explosion resistance can be obtained by blending fibers, 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 subjecting a part or all of the hardened cement to forced carbonation treatment , containing cement and an ettringite-generating admixture, and having a water / binder ratio of 40-60%. it is resistant explosion cement hardened body, characterized in Rukoto using cement kneaded product.
(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 explosion-resistant cement hardened body according to any one of (1) to ( 3 ), wherein the fiber contains organic fibers having a fiber length of 3 mm or less.
( 5 ) The explosion-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 cement hardened body in which a cement kneaded material is prepared by blending at least water with the cement composition, poured into a mold and cured, and the molded body obtained by demolding after hardening is forcibly carbonized. in the method of manufacturing, the cement composition contains the cement and formation of ettringite-based admixture, the cement kneaded product, water / binder ratio is characterized Rukoto prepared in a range of 40% to 60% It is a manufacturing method of an explosion-resistant cement hardened body.
( 7 ) The method for producing an explosion-resistant cement hardened body according to ( 6 ), wherein the cement is a blast furnace cement.
( 8 ) The explosive-resistant cement hardened body according to (6) or (7 ) above, wherein the ettringite-forming admixture is at least one selected from an expanding material, a rapid hardening material, and a high-strength material. It is a manufacturing method.
( 9 ) Manufacture of the explosion-resistant cement hardened | cured body as described in any one of said (6)-(8) characterized by the said cement kneaded material mix | blending the organic fiber whose fiber length is 3 mm or less. Is the method.
(10) said cement kneaded product, fine aggregate, or fine aggregate and any one anti explosion resistant cement of above, wherein the coarse aggregate is obtained by blending (6) - (9) 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 cement of the present invention includes various portland cements such as normal, early strength, super 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 that, like amorphous compounds composed mainly of CaO and Al ₂ O ₃ component. 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, but you change the mixing ratio of the purpose and application and the materials used are 40% to 60% water binder ratio, is good preferable 40-55%. 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, part or all of the hardened cement body is subjected to forced carbonation treatment . Although the method of forced carbonation process is not particularly limited, and specific examples thereof, for example, a method of contacting with carbonate components. 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 forced carbonation treatment. Also, the temperature is preferably 20 ° C. or higher, more preferably 30 ° C. or higher.

The timing of the forced 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 forced 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 forced 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. Conversely, if it exceeds 40 N / mm ² , a long time is required for the forced carbonation treatment, which is not preferable from the viewpoint of productivity.

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

Curing up to the forced carbonation treatment (hereinafter referred to as pre-curing) 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 the respective materials 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, from the age 24 hours, more forcibly starts carbonation, allowed to fully carbonated to the inside cured body. 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 condition of forced carbonation process was a carbon dioxide concentration of 20% and a relative humidity of 60% and temperature 40 ℃. 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.

Table 2 shows that even when blast furnace cement is used as the cement, the hardened cement bodies of Examples No. 2-2 to No. 2-10 that contain cement and an ettringite-generating admixture produce 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 forced carbonation processing period and having changed carbonation depth as shown in Table 5. The results are also shown in Table 5.

From Table 5, experiments treated forced carbonation Nanba5-2～nanba5-6, hardened cement embodiment of No.4-4 are experiments No.5-1 untreated forced carbonation 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. 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)

Cement kneaded material containing a cement and an ettringite-forming admixture and having a water / binder ratio in the range of 40 to 60%, in a cemented hardened body obtained by subjecting a part or all of the hardened cement to forced carbonation treatment Explosion-resistant cement hardened body characterized by using   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 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. A method for producing a hardened cement body, comprising preparing a cement kneaded material by blending at least water with a cement composition, pouring it into a mold, curing it, and demolding it after curing, forcibly carbonizing the molded body In the above, the cement composition contains cement and an ettringite-forming admixture, and the cement kneaded material is prepared in a water / binder ratio of 40 to 60%. A method for producing a hardened cement body.   The method for producing a hardened explosion-resistant cement according to claim 6, wherein the cement is a blast furnace cement.   The method for producing a hardened explosion-resistant cement according to claim 6 or 7, 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 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.