JP4865643B2 - Method for producing hardened cementitious body - Google Patents

Description

The present invention relates to a method for producing a cementitious cured body capable of preventing the occurrence of uneven color on the surface in the production of a cementitious cured body that exhibits an ultrahigh strength with a compressive strength of 100 N / mm ² or more.

In recent years, a cemented hardened body that has a compressive strength of 100 N / mm ² or more and that can reduce the thickness of members (wall materials, floor materials, ceiling materials, etc.) of ordinary houses and buildings has been proposed. (Patent Document 1). The cementitious hardened body described in Patent Document 1 is a hardened body of a mixture containing cement, pozzolanic fine powder, fine aggregate, water and water reducing agent, and further, if necessary, metal fiber and inorganic powder. It will be.

The above-mentioned high-strength hardened cementitious material is cement, pozzolanic fine powder, fine aggregate, water, water reducing agent, and if necessary, a compound containing metal fiber, inorganic powder, etc., is molded and primarily cured, After demolding, the molded body is produced by steam curing (secondary curing) at 60 to 90 ° C. for about 3 to 48 hours. Color unevenness may occur and the appearance may deteriorate.
JP 2001-270756 A

  Accordingly, the present invention provides a method for producing a hardened cementitious material that can prevent the occurrence of uneven color on the surface of a hardened cementitious material that exhibits ultra-high strength obtained by secondary curing. With the goal.

As a result of intensive studies to solve the above problems, the inventors of the present invention have a cementitious cured body that exhibits ultra-high strength obtained by secondary curing. A large amount of cement minerals and calcium hydroxide, and some of the unreacted cement minerals and calcium hydroxide on the surface of the hardened body react with water and carbon dioxide, resulting in calcium hydroxide, calcium carbonate and hydrogen carbonate. Color unevenness occurs when calcium, etc. occur, and secondary curing is carried out in a carbon dioxide gas atmosphere of a specific concentration under predetermined conditions to form a thin layer of calcium carbonate on the surface of the cured body Thus, the inventors have found that surface unevenness can be prevented and the present invention has been completed.
That is, the present invention provides the following [1 ] .
[1] (A) At least a cement, a fine powder having a BET specific surface area of 5 to ²⁰ m ² / g , a fine aggregate, a water reducing agent, and water, and having a water / cement ratio of 10 to 24% by mass A molding step of kneading a certain compound and pouring the kneaded compound into a mold to form an uncured molded body; and (B) a primary curing of the uncured molded body to obtain a cured molded body. A curing process comprising: a curing process; and (C) a secondary curing process in which the cured molded body is demolded, and the molded body is subjected to secondary curing to obtain a cementitious cured body , and the compressive strength is 100 N / mm ² or more. A method for producing a cured product, wherein the secondary curing step is performed at a temperature increase rate of 20 ° C./min or less, after steam curing at 70 to 95 ° C. for 10 to 48 hours, and at a temperature decrease rate of 20 ° C./min or less. until done by cooling, and secondary curing from the start temperature increase of 2 to 12 hours step or all steps of the carbon dioxide concentration is from 0.1 to 10% carbon dioxide gas cut A method for producing a hardened cementitious material, which is performed in an atmosphere .

According to the method for producing a hardened cementitious material of the present invention, it is possible to prevent the occurrence of uneven color on the surface of the hardened cementitious material obtained after secondary curing.
Moreover, according to the manufacturing method of the hardened cementitious material of the present invention, it is possible to manufacture a hardened cementitious material that is excellent in a high-class feeling and heavy feeling.
Furthermore, since the hardened cementitious material obtained in the present invention exhibits an ultra-high strength of 100 N / mm ² or more, by using the hardened cementitious material, members (wall materials, flooring materials, ceiling materials, etc.) By reducing the thickness, the weight can be reduced, and the precast member can be easily constructed.

Hereinafter, the present invention will be described in detail.
The material and preferred blending ratio of the cementitious cured body obtained by the production method of the present invention will be described.
The cementitious hardened body obtained by the production method of the present invention, cement, fine powder, fine aggregate, Ru der those cured formulations comprising water and water reducing agents.
The type of cement is not particularly limited. For example, 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, when trying to improve the early strength of the cured body, it is preferable to use early-strength Portland cement, and when trying to improve the fluidity of the blend, It is preferred to use low heat Portland cement.

Examples of the fine powder include silica fume, silica dust, fly ash, slag, volcanic ash, silica sol, and precipitated silica.
In the present invention, fine powder, a blend of fluidity and curing after development of strength and denseness, etc., a BET specific surface area of ^{5~20m 2 / g, 8~15m 2 /} g virtuous preferable. In general, silica fume and silica dust have a BET specific surface area of 5 to ²⁰ m ² / g, and do not need to be crushed. By adding silica fume and silica dust, dark and deep color development can be achieved. It is suitable as the fine powder of the present invention because it can improve the sense of quality and solidity of the cured body.
By blending the fine powder, the micro filler effect and the cement dispersing effect are exhibited, the hardened body is densified, and the compressive strength is improved. On the other hand, if the amount of fine powder added is too large, the amount of unit water will increase, and the strength development and compactness after curing will decrease, so the amount of fine powder added will be 5-50 with respect to 100 parts by weight of cement. A mass part is preferable and 10-40 mass parts is more preferable.

As the fine aggregate, river sand, land sand, sea sand, crushed sand, silica sand or a mixture thereof can be used. In the present invention, from the viewpoint of workability and separation resistance of the blend, crack resistance after curing, etc., it is preferable to use a fine aggregate having a 85% mass cumulative particle size of 2.5 mm or less. In view of strength development after hardening and the like, it is more preferable to use a fine aggregate having a maximum particle size of 2.5 mm or less, and it is particularly preferable to use a fine aggregate having a maximum particle size of 2.0 mm or less.
The amount of fine aggregate blended is preferably 50 to 250 parts by weight with respect to 100 parts by weight of cement, from the viewpoint of workability and separation resistance of the blend, strength after curing, denseness, impact resistance, etc. -180 mass parts is more preferable.

As the water reducing agent, a lignin-based, naphthalenesulfonic acid-based, melamine-based, or polycarboxylic acid-based water reducing agent, an AE water reducing agent, a high-performance water reducing agent, or a high-performance AE water reducing agent can be used. Among these, it is preferable to use a polycarboxylic acid-based high-performance water reducing agent or high-performance AE water reducing agent from the viewpoint of fluidity of the blend, strength development after curing, and compactness. By mix | blending a water reducing agent, the fluidity | liquidity and separation resistance of a compound, the denseness after hardening, intensity | strength, etc. improve.
The blending amount of the water reducing agent is preferably 0.1 to 4.0 parts by mass in terms of solid content with respect to 100 parts by mass of cement, from the aspects of fluidity and separation resistance of the formulation, denseness and strength after curing, cost, etc. 0.1-1.5 mass parts is more preferable.

As water, tap water or the like can be used.
In the present invention, the water / cement ratio is 10 to 24% by mass . When the water / cement ratio exceeds 24% by mass, there is almost no unreacted cement mineral or calcium hydroxide on the surface of the hardened body at the end of the secondary curing. There is almost no unevenness and there is little need to apply the present invention.
In the present invention, the water / cement ratio, fluidity and separation resistance of the formulation, the strength of the cured product, durability, terms such as denseness and impact resistance, preferable 1 5 to 23 wt% is good .

In the present invention, it is preferable to include an inorganic powder in the blend from the viewpoint of improving the fluidity of the blend, the strength development and denseness after curing, and further improving the high-grade and profound feeling of the cured body. Examples of the inorganic powder include slag, limestone powder, feldspar, mullite, alumina powder, quartz powder, fly ash, volcanic ash, silica sol, carbide powder, and nitride powder. Among them, slag, limestone powder, and quartz powder are preferable from the viewpoint of cost and quality stability after curing, and especially by adding quartz powder, gloss is generated and the high-class feeling and profound feeling of the cured body are improved. Can be made.
In the present invention, the inorganic powder, strength development after fluidity and hardening of the formulation, of a dense, etc., preferably Blaine specific surface area is ^{4000~10000cm 2 / g, 4500~9000cm 2 /} g is more preferable.
By blending the inorganic powder, the fluidity of the blend is improved, and the cementitious hardened body is further densified. On the other hand, if the amount of inorganic powder added is too large, the amount of unit water will increase, and the strength development and compactness after curing will decrease, so the amount of inorganic powder added will be 5 to 50 parts per 100 parts by mass of cement. A mass part is preferable and 10-40 mass parts is more preferable.

  In the present invention, in order to improve the bending strength and fracture energy after curing, it is preferable to include one or more fibers selected from metal fibers, organic fibers and carbon fibers in the blend. Examples of the metal fibers include steel fibers and amorphous fibers, among which steel fibers are excellent in strength and are preferable from the viewpoint of cost and availability. The metal fiber preferably has a diameter of 0.01 to 1.0 mm and a length of 2 to 30 mm. When the diameter is less than 0.01 mm, the proof stress of the fiber itself is insufficient, and it is easy to break when subjected to tension. When the diameter exceeds 1.0 mm, the number of the same compounding amount decreases, and the effect of improving the bending strength decreases. If the length exceeds 30 mm, fiber balls are likely to occur during kneading. If the length is less than 2 mm, the effect of improving the bending strength decreases. The blending amount of the metal fibers is preferably less than 4.0% of the volume of the blend, and more preferably 0.5 to 3.0%. When the content of the metal fiber is increased, the unit water amount is also increased in order to ensure workability at the time of kneading. Therefore, the amount of the metal fiber is preferably the above amount.

As the organic fiber, vinylon fiber, polypropylene fiber, polyethylene fiber, aramid fiber, or the like can be used. Among these, vinylon fibers are preferable from the viewpoint of strength, cost, availability, and the like. As the carbon fiber, a PAN-based carbon fiber or a pitch-based carbon fiber can be used.
The organic fiber or carbon fiber preferably has a diameter of 0.005 to 1.0 mm and a length of 2 to 30 mm. When the diameter is less than 0.005 mm, the proof stress of the fiber itself is insufficient, and it is easy to break when subjected to tension. When the diameter exceeds 1.0 mm, the number of the same compounding amount decreases, and the effect of improving the breaking energy of the cured body is lowered. If the length is less than 2 mm, the adhesive force with the matrix is reduced, and the effect of improving the fracture energy and the like is reduced. If the length exceeds 30 mm, fiber balls are likely to occur during kneading. The amount of the organic fiber or carbon fiber is preferably 10% or less, more preferably 1.0 to 7.0% of the volume of the blend. The blending amount of the fiber is determined from the viewpoint of fluidity and breaking energy of the cured body. That is, in general, when the fiber content is increased, the breaking energy is improved, but the unit water amount is increased to ensure fluidity. Therefore, the blending amount of the organic fiber or carbon fiber is preferably within the above numerical range.

In the present invention, fibrous particles or flaky particles can be included in the blend in order to improve the toughness after curing. Examples of the fibrous particles include wollastonite, bauxite, and mullite, and examples of the flaky particles include mica flakes, talc flakes, vermiculite flakes, and alumina flakes.
The average particle size of the fibrous particles or flaky particles is preferably 1 mm or less. The toughness of the cured product is improved by blending fibrous particles or flaky particles having the above particle sizes. When the average particle size exceeds 1 mm, the fluidity of the blend, the strength of the cured product, and the like are not preferable. In addition, the particle size of the particle | grains in this invention is the magnitude | size of the maximum dimension (especially the length in fibrous particle | grains).
The blending amount of the fibrous particles or flaky particles is preferably 35 parts by weight or less, more preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of cement, from the viewpoint of fluidity of the blend, strength and toughness after curing. preferable.
In addition, it is preferable to use a fibrous particle having a needle-like degree represented by a ratio of length / diameter of 3 or more from the viewpoint of increasing toughness after curing.

Next, the manufacturing method of the cementitious hardening body of this invention is demonstrated.
[(A) Molding process]
This step includes kneading a mixture containing at least cement, fine powder, fine aggregate, a water reducing agent, and water and having a water / cement ratio of 10 to 24% by mass. It is a step of pouring into a mold to form an uncured molded body .
The method of kneading the blend is not particularly limited. For example, (1) materials other than water and water reducing agent are mixed in advance (premix), and the premix, water, and water reducing agent are charged into the mixer. And knead. (2) Materials other than water are mixed in advance (premix, except that the water reducing agent is a powder type), and the premix and water are put into a mixer and kneaded. (3) Each material is individually put into a mixer and kneaded. And the like.
Moreover, 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.
The molding method for molding the kneaded compound is not particularly limited, and a conventional molding method such as casting can be employed. For example, the blend is poured into a predetermined mold to form an uncured molded body. In addition, the compound obtained by kneading the above materials is the flow value measured without performing the falling motion 15 times in the method described in “JIS R 5201 (Cement physical test method) 11. Flow test”. However, it is excellent in fluidity of 230 mm or more and excellent in workability such as pouring into a mold.

[(B) Primary curing process]
This step is a step of obtaining a cured molded body by first curing the uncured molded body formed in the molding step (A).
Examples of the primary curing include a method in which an uncured molded body is left in a mold and left at room temperature (for example, 20 ° C.) for a predetermined time (about 4 to 200 hours).
The compression strength of the molded body in this step is preferably 10 to 100 N / mm ² , more preferably 10 to 80 N / mm ² , and particularly preferably 15 to 60 N / mm ² . When the compression strength of the molded body is less than 10 N / mm ^2, it is difficult to remove the mold in the next step (C). When the compression strength of the molded body exceeds 100 N / mm ² , the need for secondary curing becomes poor. In addition, when secondary curing is not performed, color unevenness may occur on the surface, which is not preferable.

[(C) Secondary curing process]
In this step, (B) the molded body cured in the primary curing step is removed from the mold and subjected to secondary curing in a carbon dioxide gas atmosphere having a carbon dioxide gas concentration of 0.1 to 10% to obtain a cementitious cured body.
The secondary curing, steam curing is used, in the present invention, the productivity of the cost and the cured body, the strength development and denseness like after curing, heating rate 20 ° C. / min or less (more preferably 1 ~ 15 ° C / min), after 10-48 hours steam curing at 70-95 ° C, a curing method to cool down to room temperature at a temperature drop rate of 20 ° C / min or less (more preferably 0.1-15 ° C / min) Used .

Carbon dioxide concentration in the secondary curing step, Ri 0.1% to 10% der, it is good Mashiku or more and less than 0.15% 5.0%, more preferably less than 0.2% or more 3.0%, with 0.3 to 2.5% It is particularly preferred. When the carbon dioxide gas concentration is less than 0.1%, color unevenness may occur on the surface of the obtained cementitious cured body. Moreover, since the high-class feeling and profound feeling of a hardening body may fall, it is unpreferable. Even if the carbon dioxide gas concentration is 10% or more, color unevenness may occur on the surface of the obtained cementitious cured body. Moreover, since it becomes the hue which the whole hardening body faded and the high-class feeling and profound feeling of a hardening body fall, it is unpreferable.
Incidentally, the secondary curing, the total process may be carried out in a carbon dioxide atmosphere, but from the viewpoint of prevention uneven color development of reduction and hardened surface of the carbon dioxide gas usage, 2-12 hours from the start Atsushi Nobori This step may be performed in a carbon dioxide atmosphere.
The method for supplying carbon dioxide is not particularly limited, and examples thereof include a method of supplying from a carbon dioxide cylinder and a method of supplying by dry ice sublimation.

The compressive strength of the cementitious cured body obtained by the production method of the present invention is preferably 100 N / mm ² or more, more preferably 120 N / mm ² or more. A hardened cementitious material having a compressive strength of 100 N / mm ² or more is extremely dense and has excellent freeze-thaw resistance, abrasion resistance, water permeability, durability, and the like. In the cementitious hardened body of compressive strength less than 100 N / mm ^2, two in order curing end, because the cement minerals and calcium hydroxide unreacted surface there is little, the cured surface at the time of a secondary curing End Therefore, there is little need to apply the present invention.

Hereinafter, the present invention will be described by way of examples.
1. Materials Used for Formulation The materials shown below were used for the cementitious cured body.
(1) Cement; Low heat Portland cement (manufactured by Taiheiyo Cement)
(2) Fine powder; silica fume (BET specific surface area 14m ² / g)
(3) Inorganic powder; quartz powder (Blaine specific surface area 7000cm ² / g)
(4) Fine aggregate; quartz sand No. 5 (5) water reducing agent; polycarboxylic acid-based high-performance water reducing agent (6) water; tap water (7) metal fiber; steel fiber (diameter: 0.2 mm, length: 15 mm)

2. Test 1
Low heat Portland cement 100 parts by weight, silica fume 32 parts by weight, quartz powder 35 parts by weight, fine aggregate 105 parts by weight, water reducing agent 0.8 parts by weight (in terms of solid content), water 22 parts by weight and steel fiber (total volume in the formulation) 2%) was put into a biaxial kneader and kneaded to obtain a blend. The blend was poured into a mold having a length of 70 mm, a width of 70 mm, and a thickness of 20 mm to form an uncured molded body ((A) molding step). The uncured molded body was left as a primary curing at 20 ° C. for 24 hours to obtain a cured molded body ((B) primary curing process).
The molded body was demolded (the compression strength of the molded body at the time of demolding was 20 to 25 N / mm ² ), and secondary curing was performed under the conditions of the carbon dioxide gas atmosphere shown in Table 1 ((C) Secondary curing process ). The secondary curing was performed by raising the temperature to 90 ° C. at a rate of temperature increase of 15 ° C./min, and after steam curing at 90 ° C. for 48 hours, the temperature was decreased to 40 ° C. at a rate of temperature decrease of 15 ° C./min. Carbon dioxide was supplied from a carbon dioxide cylinder into the curing device.
Ten cementitious hardened bodies were obtained under the conditions of each carbon dioxide gas atmosphere shown in Table 1. The surface of the 10 cemented hardened bodies was visually observed to check for the occurrence of uneven color, and a sense of quality and profoundness. Moreover, the brightness of the cementitious hardened body surface was measured using a color difference meter (CR-210, manufactured by Minolta). Further, Ry of the hardened cementitious material was measured using a surface roughness meter based on “JIS B 0601-1994”.
The results are shown in Table 2.

As shown in Table 2, in the cementitious cured bodies (Nos. 1 and 2) obtained by the production method of the present invention, no uneven color was observed on the surface. Further, the cured body was glossy and excellent in a high-class feeling and a heavy feeling. Moreover, about the cementitious hardened body (Nos. 1 and 2), after a certain time (6 months) had elapsed, the surface of the cementitious hardened body was again visually observed. However, no uneven color or fading was observed.
On the other hand, in the cementitious cured body (No. 3) that was not cured in a carbon dioxide atmosphere, the occurrence of uneven color was observed in some of the cured bodies. Also, the luxury and profound feeling were poor.
Further, even in a cementitious cured body (No. 4) cured in a carbon dioxide atmosphere in which the carbon dioxide concentration exceeds the provisions of the present invention, color unevenness was observed in some of the cured bodies. Also, the luxury and profound feeling were poor.

3. Test 2
The properties (compressive strength, bending strength, water permeability, freeze-thaw resistance) of the hardened cementitious material obtained by the production method of the present invention were examined.
(1) Compressive strength test of hardened cementitious material The composition used in Test 1 above was poured into a 50mm x 100mm mold, pre-set at 20 ° C for 24 hours (primary curing), demolded and cured Got the body. The molded body was secondarily cured under the same conditions as in Test 1 (the conditions in the carbon dioxide atmosphere were the conditions in Table 1) to obtain hardened cementitious bodies (three pieces). The compressive strength (average value of 3 pieces) of the hardened cementitious body was 230 N / mm ² .

(2) Bending strength test of hardened cementitious material The composition used in the above test 1 was poured into a 4 x 4 x 16 cm formwork, placed at 20 ° C for 24 hours (primary curing), demolded, and hardened. A molded body was obtained. The molded body was secondarily cured under the same conditions as in Test 1 (the conditions in the carbon dioxide atmosphere were the conditions in Table 1) to obtain hardened cementitious bodies (three pieces). The bending strength (average value of three pieces) of the hardened cementitious material was 47 N / mm ² .

(3) Water permeability test The compound used in the above test 1 was poured into a mold having a diameter of 50 x 100 mm, pre-set at 20 ° C for 24 hours (primary curing), and then demolded to obtain a cured molded body. The molded body was secondarily cured under the same conditions as in Test 1 (the conditions in the carbon dioxide atmosphere were the conditions in Table 1) to obtain hardened cementitious bodies (three pieces). The water permeability coefficient of the hardened cementitious material was measured by a variable water permeability test method according to “JIS A 1404 (test method for building cement waterproofing agent)”. As a result, no water penetration was observed, and the penetration depth was zero.

(4) Freezing and thawing test The composition used in the above test 1 was poured into a 10 × 10 × 40 cm formwork, placed at 20 ° C. for 24 hours (primary curing), and then demolded to obtain a cured molded body. It was. The molded body was secondarily cured under the same conditions as in Test 1 (the conditions in the carbon dioxide atmosphere were the conditions in Table 1) to obtain hardened cementitious bodies (three pieces). The durability index in the freeze-thaw test of the hardened cementitious material was measured according to “JIS A 1148 (method for freeze-thaw test of concrete)”. As a result, the durability index (average value of 3 pieces) was 99.8.
From the results of the above tests (1) to (4), the hardened cementitious material obtained by the production method of the present invention has high compressive strength and bending strength, and is excellent in water permeability and freeze-thaw resistance. I understood that.

4). Test 3
100 parts by mass of low heat Portland cement, 32 parts by mass of silica fume, 35 parts by mass of quartz powder, 105 parts by mass of fine aggregate, 0.8 parts by mass of water reducing agent (in terms of solid content) and 22 parts by mass of water are put into a biaxial kneader and kneaded. To obtain a formulation. The blend was subjected to molding, primary curing, and secondary curing (the conditions of the carbon dioxide atmosphere were the conditions of 2 in Table 1) in the same manner as in Test 1 to obtain 10 cemented hardened bodies.
When these 10 cemented hardened bodies were visually observed, no color unevenness was observed in all 10 sheets, and they were glossy and excellent in a high-class feeling and profound feeling. The cemented cured body had a lightness of 50.2 and Ry of 25 μm.

Claims (1)

(A) A composition comprising at least cement, a fine powder having a BET specific surface area of 5 to ²⁰ m ² / g , a fine aggregate, a water reducing agent, and water, and having a water / cement ratio of 10 to 24% by mass . A molding step in which the kneaded mixture is poured into a mold to form an uncured molded body,
(B) a primary curing step of primary curing the uncured molded body to obtain a cured molded body;
(C) Production of a cementitious cured body having a compressive strength of 100 N / mm ² or more, including a secondary curing step in which the cured molded body is demolded and the molded body is secondarily cured to obtain a cementitious cured body. In the secondary curing process, the temperature is raised at a rate of temperature rise of 20 ° C / min or less, and after steam curing at 70 to 95 ° C for 10 to 48 hours, the temperature is lowered to room temperature at a temperature drop rate of 20 ° C / min or less. And the process for 2 to 12 hours from the start of the temperature raising of the secondary curing or the whole process is carried out in a carbon dioxide gas atmosphere having a carbon dioxide concentration of 0.1 to 10%. .