JP6868079B2 - Manufacturing method of hardened cementum - Google Patents

Description

The present invention relates to a method for producing a hardened cementum.

In recent years, various hardened cementums having high compressive strength have been proposed.
For example, Patent Document 1 describes (A) cement, (B) ^{fine powder having a BET specific surface area of 5 to 25 m 2} / g, and (C) inorganic powder having a brain specific surface area of 3,500 to 10,000 cm ² / g. , (D) Fine Aggregate, (E) Water Reducer, and (F) Water. The fine aggregate is 2CaO · SiO ₂ and 2CaO · Al ₂ O ₃ · containing SiO _2, relative to 2CaO · _SiO 2 100 parts by weight of a total amount of _{2CaO · Al 2 O 3 · SiO} 2 and _{4CaO · Al 2 O 3 · Fe} 2 O 3 is 10 to 100 parts by weight Cement compositions characterized by containing certain calcined products have been described.
The hardened cementaceous product obtained by curing the cement composition has a high compressive strength exceeding ^{250 N / mm 2} when the calcined product contained in the fine aggregate is used in an absolutely dry state, and the fine aggregate is said to be fine. When the calcined product contained in the aggregate is used in a surface dry state, it ^{has a high compressive strength of 200 N / mm 2} or more and a small self-shrinkage rate.

JP-A-2009-227574

An object of the present invention is to provide a method for producing a hardened cementum, which can obtain a hardened cementum having high compressive strength.

As a result of diligent studies to solve the above problems, the present inventor has carried out a molding step of placing at least a cement composition containing cement, water and a water reducing agent, and an uncured molded product at 10 to 40 ° C. A primary curing step of removing the mold after sealing or aerial curing for an hour or longer, a water absorption step of allowing the cured molded body to absorb water, and a secondary curing step of curing the absorbed molded product at 15 ° C. or higher. The present invention has been completed by finding that the above object can be achieved by the method for producing a hardened cementaceous product.

That is, the present invention provides the following [1] to [7].
[1] A method for producing a hardened cement material having a compressive strength of 80 N / mm ² or more, wherein a cement composition containing at least cement, water and a water reducing agent is cast in a mold to form an uncured molded product. And the primary curing step of obtaining a cured molded product by removing the mold from the mold after sealing or aerial curing the uncured molded product at 10 to 40 ° C. for 10 hours or more. A method for producing a hardened cement material, which comprises a water absorption step of causing the cured molded body to absorb water and a secondary curing step of curing the water-absorbed molded body at 15 ° C. or higher.
[2] The method for producing a hardened cementum according to the above [1], wherein in the water absorption step, the hardened molded product is immersed in water.
[3] The method for producing a cementum-cured product according to the above [2], wherein in the water absorption step, the cured molded product is immersed in water under reduced pressure.
[4] The above-mentioned [2], wherein in the water absorption step, the cured molded product is immersed in water at 90 ° C. or higher, and then the water temperature is cooled to 40 ° C. or lower while the molded product is immersed. How to manufacture a hardened cementum.

[5] In the primary curing step, when the cured molded product develops ^{a compressive strength of 5 to 100 N / mm 2} , the cured molded product is removed from the mold, and the cured products are removed from the mold [1] to [4]. ]. The method for producing a hardened cementaceous product according to any one of.
[6] The cementum hardening according to any one of [1] to [5], wherein in the secondary curing step, the water-absorbed molded product is steam-cured or warm-water-cured at 50 to 98 ° C. for 1 hour or longer. How to make a body.
[7] The method for producing a hardened cementum according to the above [6], wherein in the secondary curing step, the molded product after steam curing or hot water curing is heated at 100 to 200 ° C. for 1 hour or more.
The applicant has previously filed Japanese Patent Application No. 2015-34112 and Japanese Patent Application No. 2015-104920 (hereinafter referred to as "prior application") in connection with the present invention. By stating the application number of the prior application here, the content of the invention of the prior application shall be included in this application.

According to the method for producing a hardened cementum of the present invention, a hardened cementum having high compressive strength can be obtained.

The method for producing a hardened cement material of the present invention is a method for producing a hardened cement material having a compressive strength of 80 N / mm ² or more, and a cement composition containing at least cement, water and a water reducing agent is poured into a mold. A molding step of setting to obtain an uncured molded body, and a molding in which the uncured molded body is sealed or cured in the air at 10 to 40 ° C. for 10 hours or more, and then removed from the mold and cured. It includes a primary curing step of obtaining a body, a water absorbing step of causing a cured molded body to absorb water, and a secondary curing step of curing the absorbed molded body at 15 ° C. or higher.
Hereinafter, each step will be described in detail.

[Molding process]
This step is a step of casting a cement composition containing at least cement, water and a water reducing agent into a mold to obtain an uncured molded product.
The cement composition used in the present invention may be any paste, mortar, or concrete as long as it contains at least cement, water, and a water reducing agent.
Further, the raw materials of the cement composition used in the present invention and the composition thereof are particularly limited as long as the compressive strength of the cementum cured product obtained by the production method of the present invention is 80 N / mm ^{2 or more.} It's not a thing. When raw materials and formulations such that the compressive strength of the cementitious cured product is ^{less than 80 N / mm 2} are adopted, the effect of improving the compressive strength by performing the water absorption step in the production method of the present invention is reduced, and the effect of improving the compressive strength of the present invention is reduced. It becomes difficult to achieve the purpose.

The type of cement is not particularly limited, and for example, various Portland cements such as ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, moderate heat Portland cement, sulfate-resistant Portland cement, and low heat Portland cement can be used. Can be used.
The amount of cement is preferably the ratio of cement in the binder (powder raw material consisting of cement and an inorganic powder other than cement which is optionally blended) from the viewpoint of further increasing the compressive strength of the hardened cement material. It is 30% by mass or more, more preferably 40% by mass or more, still more preferably 60% by mass or more, and particularly preferably 80% by mass or more.

As water, tap water or the like can be used.
The ratio of water to binder (mass ratio of water / binder) is preferably 0.35 or less, more preferably 0.33 or less, and particularly preferably 0., from the viewpoint of further increasing the compressive strength of the cementum cured product. It is 30 or less.

As the water reducing agent, a water reducing agent such as naphthalene sulfonic acid type, melamine type, polycarboxylic acid type, AE water reducing agent, high performance water reducing agent or high performance AE water reducing agent can be used. Among them, a naphthalene sulfonic acid-based or polycarboxylic acid-based high-performance water reducing agent or a high-performance AE water reducing agent is preferable from the viewpoint of improving the fluidity of the cement composition and increasing the compressive strength of the cementum cured product.
The blending amount of the water reducing agent is preferably 0.4 to 4.0 parts by mass, more preferably 0.6 to 3.5 parts by mass, and further preferably 0.7 to 3.% by mass with respect to 100 parts by mass of the binder. It is 0 parts by mass, particularly preferably 0.8 to 2.5 parts by mass. When the amount is 0.4 parts by mass or more, the water reduction performance is improved and the fluidity of the cement composition is improved. When the amount is 4.0 parts by mass or less, the compressive strength of the cementum cured product becomes higher.

If necessary, other raw materials may be added to the cement composition used in the present invention as long as the object of the present invention is not impaired. Examples of other raw materials to be blended as needed include binders other than cement, aggregates, fibers, antifoaming agents, shrinkage reducing agents and the like.
Examples of binders other than cement include silica fume, quartz powder (silica stone powder), volcanic ash, fly ash, blast furnace slag powder, limestone powder, plasters (anhydrous plaster, etc.), and expansion materials. These may be used individually by 1 type, and may be used in combination of 2 or more type.

Unit binder amount of cement composition used in the present invention (the amount of the binder per unit volume) is preferably from 400 kg / ^{m 3} or more, more preferably 450 kg / ^{m 3} or more, particularly preferably 500 kg / ^{m 3} That is all. When the amount is 400 kg / m ³ or more, the compressive strength of the cementum cured product becomes higher.

Examples of the aggregate include only fine aggregate or a combination of fine aggregate and coarse aggregate.
Examples of the fine aggregate include river sand, land sand, mountain sand, sea sand, crushed sand, silica sand, artificial fine aggregate, slag fine aggregate or a mixture thereof. Examples of the coarse aggregate include river gravel, land gravel, mountain gravel, sea gravel, crushed stone, artificial coarse aggregate, slag coarse aggregate or a mixture thereof.
The proportion of aggregate (total of fine aggregate and coarse aggregate) in the cement composition used in the present invention is preferably 65% by volume or less, more preferably 60% by volume or less, and particularly preferably 55% by volume or less. is there. When the ratio is 65% by volume or less, the compressive strength of the cementum cured product becomes higher.

Examples of the fiber include one or more selected from the group consisting of metal fiber, organic fiber and carbon fiber. When the cement composition contains fibers, it is possible to improve the bending strength, fracture energy, etc. of the cementum hardened body.
The dimensions of the fibers are preferably 0.05 to 0.5 mm in diameter and 5 to 25 mm in length, more preferably 0.1 to 0.3 mm in diameter and 8 to 20 mm in length.
The fiber aspect ratio (fiber length / fiber diameter) is preferably 20-200, more preferably 40-150, and particularly preferably 50-100.
The proportion of fibers in the cement composition used in the present invention is preferably 4% by volume or less, more preferably 3% by volume or less.

Commercially available products can be used as the defoaming agent, shrinkage reducing agent and the like.
The amount of the defoaming agent to be blended is preferably 0.001 to 0.1 parts by mass, more preferably 0.01 to 0.07 parts by mass, and particularly preferably 0.01 to 0, based on 100 parts by mass of the binder. It is 0.05 parts by mass. When the amount is 0.001 part by mass or more, the compressive strength of the cementum cured product is high. When the amount exceeds 0.1 parts by mass, the effect of improving the compressive strength of the cementum cured product reaches a plateau.
The blending amount of the shrinkage reducing agent is preferably 3 parts by mass or less, more preferably 0.3 to 2.5 parts by mass, and particularly preferably 0.5 to 2 parts by mass with respect to 100 parts by mass of the binder. When the amount is 3 parts by mass or less, the compressive strength of the cementum cured product becomes higher.

In this step, the method of kneading the cement composition before placing the cement composition is not particularly limited. Further, 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. Further, the casting (molding) method is not particularly limited.

[Primary curing process]
In this step, the uncured molded product obtained in the previous step is sealed or cured in the air at 10 to 40 ° C. for 10 hours or more, and then removed from the mold to obtain a cured molded product. is there.
The curing temperature is 10 to 40 ° C, preferably 15 to 30 ° C. When the temperature is 10 ° C. or higher, the curing time can be shortened. When the temperature is 40 ° C. or lower, the compressive strength of the cementum cured product becomes higher.
The curing time is 10 hours or more, preferably 12 to 72 hours, more preferably 18 to 54 hours, and particularly preferably 24 to 48 hours. If the time is 10 hours or more, defects such as chips and cracks are less likely to occur in the cured molded product during demolding.

Further, in this step, it is preferable to remove the cured molded product from the mold when the cured molded product exhibits a compressive strength of 5 to ^{100 N / mm 2.} If the compressive strength is 5 N / mm ² or more (more preferably 10 N / mm ² or more, particularly preferably 20 N / mm ² or more), the cured molded product has defects such as chips and cracks during demolding. It is less likely to occur. When the compressive strength is 100 N / mm ² or less (more preferably 80 N / mm ² or less, particularly preferably 60 N / mm ² or less), the cured molded product is allowed to absorb water with less effort in the water absorption step described later. Can be done.
Further, if the compressive strength is preferably 5 to 30 N / mm ² , more preferably 5 to 25 N / mm ² , and particularly preferably 5 to 20 N / mm ² , the water is not boiled in the water absorption step described later. When immersed in, the water absorption rate can be increased.

[Water absorption process]
This step is a step of allowing the cured molded product obtained in the previous step to absorb water.
Examples of the method of allowing the cured molded product to absorb water include a method of immersing the molded product in water.
Further, in the method of immersing the molded body in water, from the viewpoint of increasing the amount of water absorption in a short time and increasing the compressive strength of the cementified cured product, (1) the molded body is placed in water under reduced pressure. Method of dipping, (2) After immersing the molded body in water of 90 ° C. or higher (preferably boiling water), the water temperature is lowered to 40 ° C. or lower while the molded body is immersed. Method of lowering, or (3) After immersing the molded product in water at 90 ° C. or higher (preferably boiling water), the molded product is immersed in water at 90 ° C. or higher (preferably boiling). A method of removing the water from the water and then immersing it in water at 40 ° C. or lower is preferable.

Examples of the method of immersing the molded product in water under reduced pressure include a method of using equipment such as a vacuum pump and a large decompressing container.
Examples of the method of immersing the molded body in boiling water include a method of using equipment such as a high-temperature and high-pressure container and a hot / hot water tank (a water tank containing hot water or hot water).
The time for immersing the cured molded product in water under reduced pressure or water at 90 ° C. or higher is preferably 3 minutes or longer, more preferably 8 minutes or longer, and particularly preferably 20 minutes or longer from the viewpoint of increasing the water absorption rate. More than a minute. The upper limit of the time is not particularly limited, but is preferably 60 minutes, more preferably 45 minutes from the viewpoint of increasing the compressive strength of the cementum cured product.

When the cement composition is a paste or mortar, the water absorption rate in the water absorption step is preferably 0.2% by volume or more, more preferably 0.3, as a ratio of water to 100% by volume of the cured compact having a diameter of 50 × 100 mm. ~ 2.0% by volume, more preferably 0.35 to 1.7% by volume, still more preferably 0.35 to 1.2% by volume, still more preferably 0.35 to 0.8% by volume, still more preferably 0. .35 to 0.6% by volume, particularly preferably 0.35 to 0.5% by volume, and when the cement composition is concrete, the ratio of water to 100% by volume of the cured compact of φ100 × 200 mm is It is preferably 0.2% by volume or more, more preferably 0.3 to 2.0% by volume, still more preferably 0.35 to 1.7% by volume, still more preferably 0.35 to 1.2% by volume, still more preferably. Is 0.35 to 0.8% by volume, more preferably 0.35 to 0.6% by volume, and particularly preferably 0.35 to 0.5% by volume.
Regardless of whether the cement composition is paste, mortar, or concrete, the compressive strength of the hardened cementum can be further increased if the water absorption rate is 0.2% by volume or more.
When the water absorption rate is 0.2% by volume or less, it becomes easy to select a material for obtaining a cementum cured product having ^{a compressive strength of 80 N / mm 2 or more.}

[Secondary curing process]
This step is a step of curing the water-absorbed molded product obtained in the previous step at 15 ° C. or higher.
The curing temperature is 15 ° C. or higher, preferably 50 to 98 ° C., more preferably 70 to 95 ° C. When the temperature is 15 ° C. or higher, the curing time can be shortened. When the curing temperature is 98 ° C. or lower, the compressive strength of the cementum cured product becomes higher.
The curing time is preferably 1 hour or more, more preferably 2 to 72 hours, and particularly preferably 3 to 48 hours. When the time is 1 hour or more, the compressive strength of the cementum hardened product becomes higher.

The curing method is not particularly limited, and examples thereof include steam curing, hot water curing, underwater curing, aerial curing, and wet air curing.
Above all, from the viewpoint of shortening the curing time and increasing the compressive strength of the hardened cementum, the temperature is 50 to 98 ° C. (preferably 60 to 95 ° C., more preferably 70 to 95 ° C.) for 1 hour or more (preferably 2 to 72 ° C.). Time, more preferably 3 to 48 hours, still more preferably 10 to 48 hours, particularly preferably 18 to 48 hours), steam curing or hot water curing is preferred.

From the viewpoint of increasing the compressive strength of the hardened cementum, it is preferable to further heat the molded product cured by the above-mentioned curing method at 100 to 200 ° C. for 1 hour or more.
The heating temperature is preferably 100 to 200 ° C, more preferably 150 to 190 ° C, and particularly preferably 170 to 180 ° C. When the heating temperature is 100 ° C. or higher, the heating time can be shortened. When the heating temperature is 200 ° C. or lower, the compressive strength of the cementum cured product becomes higher.
The heating time is preferably 1 hour or longer, more preferably 24-72 hours, and particularly preferably 36-48 hours. If the heating time is 1 hour or more, the compressive strength of the cementum cured product becomes higher.

The hardened cementum obtained by the production method of the present invention is compressed as compared with the hardened cementum obtained by the conventional production method even if the component composition (blending of raw materials) of the cement composition is the same. The strength is higher.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.
[Material used]
The materials used are as shown below.
(1) Cement A (low-grade Portland cement; manufactured by Taiheiyo Cement)
(2) Cement B (Silica Fume Premix Cement; manufactured by Taiheiyo Cement Co., Ltd.)
(3) Cement C (Blast furnace cement type B; manufactured by Taiheiyo Cement Co., Ltd.)
(4) Silica fume (BET specific surface area: 17 m ² / g)
(5) Silica stone powder (50% cumulative particle size: 7 μm, maximum particle size: 67 μm, 95% cumulative particle size: 27 μm)
(6) Fine aggregate A (silica sand, maximum particle size: 1.0 mm, particle size of 0.6 mm or less: 98% by mass, particle size of 0.3 mm or less: 45% by mass, 0.15 mm or less Particle size: 3% by mass)
(7) Fine aggregate B (crushed sand, coarse grain ratio: 2.79, surface dry density: 2.62 g / cm ³ )
(8) Coarse aggregate (crushed stone, coarse grain ratio: 6.72, surface dry density: 2.62 g / cm ³ )
(9) Polycarboxylic acid-based high-performance water reducing agent A (manufactured by Floric, trade name "Floric SF500U")
(10) Polycarboxylic acid-based high-performance water reducing agent B (manufactured by BASF Japan, trade name "Master Grenium SP8 series")
(11) Defoamer (manufactured by BASF Japan, trade name "Master Air 404")
(12) Water (tap water)

[Example 1]
Cement A, silica fume, and silica stone powder were mixed according to the formulation shown in Table 1. The obtained mixture and fine aggregate A were put into an omnimixer and kneaded for 15 seconds.
Next, water, a polycarboxylic acid-based high-performance water reducing agent A, and a defoaming agent were added to the omnimixer and kneaded for 2 minutes.
After kneading, the kneaded material adhering to the side wall in the omnimixer was scraped off, and kneading was further carried out for 4 minutes.

The obtained kneaded product was cast into a cylindrical mold having a diameter of 50 × 100 mm to obtain an uncured molded product. After casting, the uncured molded product was sealed and cured at 20 ° C. for 48 hours, and then demolded to obtain a cured molded product.
The molded product was immersed in boiling water (water temperature: 100 ° C.) for 30 minutes, and then cooled while the molded product was immersed in water until the water temperature became 30 ° C. or lower. The mass of the molded product before and after immersion was measured, and the water absorption rate was calculated from the obtained measured values.
After the immersion, the molded product was steam-cured at 90 ° C. for 48 hours to obtain a cementum cured product.
The compressive strength of the cured molded product at the time of demolding and the compressive strength of the obtained cementic cured product were measured according to "JIS A 1108 (compressive strength test method for concrete)".

[Example 2]
The molded product after being immersed in water was steam-cured at 90 ° C. for 48 hours and then heated at 180 ° C. for 48 hours in the same manner as in Example 1 to obtain a cementum cured product.
The compressive strength of the obtained hardened cementum was measured in the same manner as in Example 1.

[Comparative Example 1]
A cementum hardened product was obtained in the same manner as in Example 1 except that the molded product after demolding was steam-cured at 90 ° C. for 48 hours.
The compressive strength of the obtained hardened cementum was measured in the same manner as in Example 1.
[Comparative Example 2]
A hardened cementum was obtained in the same manner as in Example 2 except that the molded product after demolding was steam-cured at 90 ° C. for 48 hours and further heated at 180 ° C. for 48 hours.
The compressive strength of the obtained hardened cementum was measured in the same manner as in Example 1.

[Example 3]
According to the formulation shown in Table 1, cement B and fine aggregate B are kneaded for 30 seconds using a biaxial forced kneading mixer, and then water, a high-performance water reducing agent B, and a defoaming agent are added to the mixer. Kneaded for 3 minutes. Then, the coarse aggregate was put into the mixer and kneaded for 3 minutes. After allowing to stand for 5 minutes, it was kneaded for another 30 seconds.
The obtained kneaded product was cast into a cylindrical mold having a diameter of 100 × 200 mm to obtain an uncured molded product. After casting, the uncured molded product was sealed and cured at 20 ° C. for 24 hours, and then demolded to obtain a cured molded product.

After immersing the molded product in boiling water, the molded product was cooled while being immersed in water until the water temperature became 30 ° C. or lower.
After the immersion, the molded product was cured in water at 20 ° C. until the material age reached 28 days to obtain a cementum cured product.
The water absorption rate was calculated, the compressive strength of the cured molded product at the time of demolding, and the compressive strength of the obtained cementum cured product were measured in the same manner as in Example 1.

[Example 4]
A cementum cured product was obtained in the same manner as in Example 3 except that the cured molded product was immersed in water in a depressurized desiccator instead of being immersed in boiling water. The depressurization was performed using "Aspirator (AS-01)" manufactured by AS ONE Corporation.
The water absorption rate was calculated, the compressive strength of the cured molded product at the time of demolding, and the compressive strength of the obtained cementum cured product were measured in the same manner as in Example 1.
[Example 5]
The molded product after being immersed in water was cured in water at 20 ° C. until the age of the material reached 28 days, and then heated at 180 ° C. for 48 hours in the same manner as in Example 3. A quality cured product was obtained.
The compressive strength of the obtained hardened cementum was measured in the same manner as in Example 1.

[Comparative Example 3]
A hardened cementum was obtained in the same manner as in Example 3 except that the molded product after demolding was cured in water at 20 ° C. until the material age was 28 days.
The compressive strength of the obtained hardened cementum was measured in the same manner as in Example 1.
[Comparative Example 4]
The molded product after demolding was cemented in the same manner as in Example 3 except that it was cured in water at 20 ° C. and then heated at 180 ° C. for 48 hours until the material age was 28 days. A cured product was obtained.
The compressive strength of the obtained hardened cementum was measured in the same manner as in Example 1.

[Example 6]
According to the formulation shown in Table 1, cement B and fine aggregate B are kneaded for 30 seconds using a biaxial forced kneading mixer, and then water, a high-performance water reducing agent B, and a defoaming agent are added to the mixer. And kneaded for 2 minutes. Then, the coarse aggregate was put into the mixer and kneaded for 2 minutes. After allowing to stand for 5 minutes, it was kneaded for another 30 seconds.
The obtained kneaded product was cast into a cylindrical mold having a diameter of 100 × 200 mm to obtain an uncured molded product. After casting, the uncured molded product was sealed and cured at 20 ° C. for 24 hours, and then demolded to obtain a cured molded product.
After immersing the molded product in boiling water, the molded product was taken out of boiling water and then immersed in water at 20 ° C. for cooling.
After the immersion, the molded product was steam-cured at 55 ° C. for 24 hours.
The water absorption rate was calculated, the compressive strength of the cured molded product at the time of demolding, and the compressive strength of the obtained cementum cured product were measured in the same manner as in Example 1.

[Comparative Example 5]
A hardened cementum was obtained in the same manner as in Example 6 except that the molded product after demolding was steam-cured at 55 ° C. for 24 hours.
The compressive strength of the obtained hardened cementum was measured in the same manner as in Example 1.

[Example 7]
According to the formulation shown in Table 1, cement C and fine aggregate B are kneaded for 30 seconds using a biaxial forced kneading mixer, and then water, a high-performance water reducing agent B, and a defoaming agent are added to the mixer. And kneaded for 2 minutes. Then, the coarse aggregate was put into the mixer and kneaded for 1.5 minutes. After allowing to stand for 5 minutes, it was kneaded for another 20 seconds. A cementum hardened product was obtained in the same manner as in Example 3 except that the kneaded product obtained by the kneading was used.
The water absorption rate was calculated, the compressive strength of the cured molded product at the time of demolding, and the compressive strength of the obtained cementum cured product were measured in the same manner as in Example 1.

[Comparative Example 6]
A hardened cementum was obtained in the same manner as in Example 7 except that the molded product after demolding was cured in water at 20 ° C. until the material age was 28 days.
The compressive strength of the obtained hardened cementum was measured in the same manner as in Example 1.

[Example 8]
A hardened cementum was obtained in the same manner as in Example 7 except that cement A was used instead of cement C and the molded product after being immersed in water was steam-cured at 55 ° C. for 24 hours. ..
The water absorption rate was calculated, the compressive strength of the cured molded product at the time of demolding, and the compressive strength of the obtained cementum cured product were measured in the same manner as in Example 1.

[Comparative Example 7]
The molded product after demolding was steam-cured at 55 ° C. for 24 hours to obtain a cementum-cured product in the same manner as in Example 8 except that a cementum-cured product was obtained.
The compressive strength of the obtained hardened cementum was measured in the same manner as in Example 1.
The results are shown in Table 2.

From Table 2, the cementum cured product (Examples 1 to 8) obtained by the production method of the present invention is compared with the cementum cured product (Comparative Examples 1 to 7) obtained by the production method without the water absorption step. It can be seen that the compressive strength is improved.
Specifically, the hardened cementum in Example 1 has the same composition (blending of raw materials) as the hardened cementum in Comparative Example 1, except that a water absorption step is performed. production method and although those prepared in a similar manner, it can be seen that having a larger compressive strength than compressive strength of Comparative example ^{1 (202N / mm 3) (} 238N / mm 3).

The above-mentioned findings (difference between Example 1 and Comparative Example 1) by including the water absorption step are found in Example 2 (compressive strength: 357 N / mm ³ ) and Comparative Example 2 (compressive strength: 290 N / mm ³ ). 3 (compressive strength: 167 N / mm ³ ) and Comparative Example 3 (compressive strength: 143 N / mm ³ ), Example 5 (compressive strength: 235 N / mm ³ ) and Comparative Example 4 (compressive strength: 197 N / mm ³ ), example 6 (compressive strength: 132N / mm ³⁾ and Comparative example 5 (compressive strength: 115N / ^mm 3), example 7 (compressive strength: 102N / mm ³⁾ and Comparative example 6 (compressive strength: 92N / mm ³ ), or example 8 (compressive strength: 102N / mm ³⁾ and Comparative example 7 (compressive strength: the 90 N / mm ^3), respectively, even when compared, observed in the same manner.

Claims (3)

A method for producing a hardened cementum having a compressive strength of 80 N / mm ^{2 or more.}
A molding process in which a cement composition containing at least cement, water, and a water reducing agent is cast into a mold to obtain an uncured molded product.
The uncured molded product is sealed or cured in the air at 10 to 40 ° C. for 10 hours or more, and then removed from the mold to obtain a cured molded product.
A water absorption step of immersing the cured molded product in water under reduced pressure to cause the cured molded product to absorb water.
A method for producing a hardened cementum, which comprises a secondary curing step of curing the water-absorbed molded product at 15 ° C. or higher (excluding the case of immersing the molded product in water under reduced pressure). The cementic cured product according to claim 1, wherein in the primary curing step, when the cured molded product exhibits a compressive strength of 5 to ^{100 N / mm 2, the cured molded product is removed from the mold.} Manufacturing method. The method for producing a hardened cementum according to claim 1 or 2, wherein the secondary curing step is performed by curing the water-absorbed molded product in water.