WO2018003612A1

WO2018003612A1 - Fiber-reinforced carbonated cement molded product and method for producing same

Info

Publication number: WO2018003612A1
Application number: PCT/JP2017/022749
Authority: WO
Inventors: 祥徳人見; 彰今川; 真也稲田; 嘉宏岩崎; 宏明乗竹; 三郎羽田; 樋口　隆行; 泰一郎森; 拓海前田
Original assignee: 株式会社クラレ; デンカ株式会社
Priority date: 2016-06-30
Filing date: 2017-06-20
Publication date: 2018-01-04
Also published as: JPWO2018003612A1; JP6898926B2

Abstract

Provided is a fiber-reinforced carbonated cement molded product comprising a cement component, inorganic needles, and fibers, the inorganic needles each having a length of 1 mm or less and an aspect ratio of 20 or more.

Description

Fiber-reinforced carbonated cement molding and method for producing the same

The present invention relates to a fiber-reinforced carbonated cement molded article having a high bending strength and a small dimensional change rate, and a method for producing the same.

Cement moldings are building materials that are widely used all over the world for various applications such as slate. Cement moldings are required to improve lightness while ensuring strength from the viewpoints of reduction in structure strength and earthquake resistance. For example, there is a technique in which reinforcing fibers are added to a cement molded product.

Since the tensile strength can be complemented by adding reinforcing fibers, fiber reinforced cement molded products are used in a wide range of fields. However, unlike conventional concrete, such fiber reinforced cement moldings are thin and have a low specific gravity, so there is a tendency for the dimensional change rate of dry and wet to be large, so that cracking occurs under restraint, and installation is difficult. It may get worse. For this reason, the technique which carbonizes a fiber reinforced cement molding is developed (patent document 1).

International Publication No. 2015/068704 Pamphlet

When such a fiber reinforced cement molded product is carbonated, it is possible to obtain a fiber reinforced carbonated cement molded product having a high bulk specific gravity, a high bending strength, and at the same time a small dimensional change rate. The low dimensional change rate of this fiber-reinforced carbonated cement molding is that after pre-curing, the calcium hydroxide and belite containing carbon dioxide react with carbon dioxide to expand their volume, and the molding becomes dense. Due to being.

However, for example, when the pre-curing time is short, the bending strength of the molded product is insufficient only with the pre-curing, and the molded product itself does not withstand volume expansion due to carbonation, and the specific gravity does not increase. In some cases, cracks are induced, resulting in a decrease in the bending strength of the molded product. Therefore, there is still room for improvement regarding the bending strength and the dimensional change rate of the molded product.

Therefore, an object of the present invention is to provide a fiber-reinforced carbonated cement molded article having a high bending strength and a small dimensional change rate, and a method for producing the same.

In order to solve the above-mentioned problems, the present inventor arrived at the present invention as a result of detailed studies on a fiber-reinforced carbonated cement molding and a method for producing the same.

That is, the present invention includes the following preferred embodiments.
[1] A fiber-reinforced carbonated cement molding containing a cement component, inorganic needles and fibers,
The inorganic needle-like product is a fiber-reinforced carbonated cement molded product having a length of 1 mm or less and an aspect ratio of 20 or more.
[2] The fiber-reinforced carbonated cement molded article according to [1], wherein the carbonation reaction rate is 30% or more.
[3] The fiber-reinforced carbonated cement molding according to [1] or [2], wherein the fiber is a polyvinyl alcohol fiber.
[4] The fiber-reinforced carbonated cement molded article according to any one of [1] to [3], wherein the inorganic needles are made of calcium carbonate or potassium titanate.
[5] The ^{composition according} to any one of [1] to [4], wherein 2 × 10 ⁻² to 1000 × 10 ^{−2 of the} inorganic needles are contained per 1 μm ² of the fiber-reinforced carbonated cement molding. Fiber reinforced carbonated cement molding.
[6] The fiber-reinforced carbonated cement molded article according to any one of [1] to [5], wherein the cement component contains 18% by mass or more of belite.
[7] The fiber-reinforced carbonated cement molded article according to any one of [1] to [6], further comprising pulp.
[8] A fiber-reinforced cement molded article containing a cement component, inorganic needles and fibers,
The inorganic needle-like article is a fiber-reinforced cement molded article having a length of 1 mm or less and an aspect ratio of 20 or more.
[9] A mixing step of obtaining a curable composition by mixing cement components, inorganic needles, fibers, and water,
A molding step for obtaining a molded body by molding the hydraulic composition;
[1] to [7], including a pre-curing step for pre-curing the molded body to obtain a cured body, and a carbonation-curing step for obtaining a fiber-reinforced carbonated cement molding by carbonizing and curing the cured body. A method for producing the fiber-reinforced carbonated cement molding according to any one of the above.
[10] The method according to [9], wherein the curing time in the pre-curing step is within 12 hours.

According to the present invention, it is possible to provide a fiber-reinforced carbonated cement molded article having a high bending strength and a small dimensional change rate, and a method for producing the same.

It is a photograph which shows the coloring condition when a phenolphthalein solution is sprayed on the cross section of the fiber reinforced carbonated cement molding in one embodiment (Example 1) of this invention. It is a photograph which shows the coloring condition when the phenolphthalein solution is sprayed on the cross section of the fiber reinforced carbonated cement molding in Comparative Example 1.

The fiber-reinforced carbonated cement molding which is one embodiment of the present invention includes a cement component, inorganic needles and fibers.

(Cement component)
Examples of the cement component contained in the fiber-reinforced carbonated cement molding include various Portland cements such as ordinary cement, early-strength cement, and ultra-early-strength cement. In one embodiment of the present invention, the cement component may be various mixed cements obtained by blending blast furnace slag, fly ash or silica with these Portland cements, moderately heated cement, alumina cement, or the like.

Usually, the cement, alite: 3CaO · SiO ₂ (composition formula _C 3 S), belite: 2CaO · SiO ₂ (composition formula _C 2 S), aluminate: _Al 2 _{O 3} (composition formula _C 3 A) Ferrite: Cement minerals such as 4CaO.Al ₂ O ₃ .Fe ₂ O ₃ (composition formula C ₄ AF) are included. Belite is a kind of dicalcium silicate containing CaO and SiO ₂ as main components, and there are α-type, α′-type, β-type, and γ-type, each having a different crystal structure and density. Of these, α-type, α′-type and β-type react with water and exhibit hydraulic properties. However, the γ-type does not exhibit hydraulic properties and has the property of reacting with carbon dioxide. Ordinary cements such as Portland cement basically contain almost no γ-type belite (γ belite). In one embodiment of the present invention, the cement component is subjected to carbonation treatment after pre-curing, and therefore, commercially available belite cement or cement obtained by mixing belite cement with various cements may be used. Of the α type, α ′ type, β type, and γ type, β type and γ type are preferable.

In one embodiment of the present invention, the cement component preferably has a belite content of 18% by mass or more, more preferably 20% by mass or more, and further preferably 22% by mass or more, preferably 60% by mass or less. More preferably, it has a belite content of 58% by mass or less. If the belite content of the cement component is greater than or equal to the above lower limit value, the fiber reinforced carbonated cement exhibits a high densification effect by belite, good dimensional stability and water resistance, and excellent paintability. A molded product can be obtained. Moreover, when the belite content of the cement component is not more than the above upper limit, the amount of the hydraulic component serving as a binder is sufficient, and a fiber-reinforced carbonated cement molded product having high bending strength can be obtained. .

Also, the reaction rate of belite is preferably 70% or more. When belite also undergoes a hydration reaction, it produces a C—S—H gel similar to alite and is effective as a binder. However, because belite has a slower hydration reaction than alite, At such timing, the reaction rate is still low and the binder effect is insufficient. On the other hand, according to one embodiment of the present invention, not only the hydration reaction but also the carbonation reaction occur at the same time. Therefore, a reaction rate of 70% or higher of belite can be secured at an early stage, the bending strength is high, and the dimensional change rate is high. It is possible to supply a low product. The reaction rate of belite is more preferably 75% or more, and further preferably 80% or more.

The content of the cement component in the fiber-reinforced carbonated cement molding is usually 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, based on the total mass of the fiber-reinforced carbonated cement molding. More preferably 80% by weight or more, particularly preferably 85% by weight or more, particularly preferably 90% by weight or more, very preferably 92% by weight or more, preferably 99% by weight or less, more preferably 98% by weight or less. More preferably, it is 97 mass% or less.

(fiber)
The fiber-reinforced carbonated cement molding can obtain a reinforcing effect by containing fibers. The fiber contained in the fiber-reinforced carbonated cement molding may be an inorganic fiber or an organic fiber. Examples of inorganic fibers include alkali-resistant glass fibers, steel fibers (steel fibers), stainless fibers, carbon fibers, ceramic fibers, and asbestos fibers. Organic fibers include recycled fibers such as rayon fibers (polynosic fibers, solvent-spun cellulose fibers, etc.); polyvinyl alcohol fibers (polyvinyl alcohol fibers, vinylon, etc.), polyolefin fibers (polyethylene fibers, polypropylene fibers, ethylene / propylene) Copolymer fibers, etc.), ultrahigh molecular weight polyethylene fibers, polyamide fibers (polyamide 6, polyamide 6,6, polyamide 6,10 etc.), aramid fibers (particularly para-aramid fibers), polyparaphenylene benzobisoxazole fibers (PBO) Fiber), polyester fiber (PET, PBT, etc.), acrylonitrile fiber, polyurethane fiber, acrylic fiber, polyphenylene sulfide fiber (PPS fiber), polyether ether ketone fiber (PEEK fiber), etc. Synthetic resin fibers. These alkali resistant fibers may be used alone or in combination of two or more.

Of these, organic fibers, particularly synthetic resin fibers, are preferable from the viewpoint of improving the bending strength and reducing the weight of the fiber-reinforced carbonated cement molding. Among the synthetic resin fibers, alkali-resistant synthetic resin fibers are preferable from the viewpoint of chemical durability against cement alkali in the fiber-reinforced carbonated cement molding. Alkali-resistant synthetic resin fibers include polyvinyl alcohol fibers (polyvinyl alcohol fibers, vinylon, etc.), polyolefin fibers (from the viewpoint that the fiber-reinforced carbonated cement molding has high bending strength and can be manufactured at low cost. Polyethylene fibers, polypropylene fibers, ethylene / propylene copolymer fibers, etc.), acrylic fibers and aramid fibers are preferred, polyvinyl alcohol fibers, polyethylene fibers, polypropylene fibers, acrylic fibers and aramid fibers are more preferred, and polyvinyl alcohol fibers are further preferred. preferable. The said fiber can be manufactured by a conventionally well-known method. The polyvinyl alcohol fiber may be spun by a wet, dry-wet or dry method using a spinning stock solution in which a polyvinyl alcohol polymer is dissolved in a solvent.

The aspect ratio of the fibers contained in the fiber-reinforced carbonated cement molding is preferably 30 or more, more preferably 50 or more, still more preferably 70 or more, particularly 90 or more, and particularly preferably 100 or more. Is preferably 1000 or less, more preferably 900 or less, still more preferably 800 or less, particularly preferably 700 or less, and particularly preferably 600 or less. When the aspect ratio of the fiber is not less than the above lower limit value, the adhesive force of the fiber to the cement component is increased, and a high toughness imparting effect to the fiber-reinforced carbonated cement molded product is exhibited. When the aspect ratio of the fiber is not more than the above upper limit value, the fibers are less likely to get entangled, and the fiber is not easily broken or damaged due to the fiber following the expansion and contraction of the molded body. It can be even higher.

The fibers contained in the fiber-reinforced carbonated cement molding preferably have an average fiber diameter of 1 to 200 μm, and more preferably 2 to 100 μm. If the average fiber diameter is equal to or greater than the lower limit value, the fibers can be uniformly dispersed. If the average fiber diameter is equal to or smaller than the upper limit value, the number of fibers per unit volume in the fiber-reinforced carbonated cement molded product is increased, resulting in a high reinforcing effect. Is demonstrated.

The fiber content in the fiber-reinforced carbonated cement molding is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and still more preferably, based on the total mass of the fiber-reinforced carbonated cement molding. 0.5% by mass or more, particularly preferably 0.7% by mass or more, particularly preferably 1% by mass or more, preferably 5% by mass or less, more preferably 4% by mass or less, still more preferably 3% by mass or less, Especially preferably, it is 2 mass% or less. When the fiber content in the fiber-reinforced carbonated cement molded product is equal to or higher than the lower limit, the reinforcing effect of the fiber-reinforced carbonated cement molded product by the fibers can be further enhanced, and further, the fiber-reinforced carbonated cement molded product. As a result, the carbonation reaction rate can be increased, and the reinforcing effect of the fiber-reinforced carbonated cement molding can be further enhanced. If the fiber content in the fiber-reinforced carbonated cement molding is not more than the above upper limit value, the fiber dispersibility in the fiber-reinforced carbonated cement molding is good. Can be reinforced.

When the fiber is a polyvinyl alcohol fiber, the polyvinyl alcohol fiber may be a composite fiber of a polyvinyl alcohol polymer and another polymer, or may be a sea-island fiber. The polyvinyl alcohol-based polymer is composed of vinyl alcohol, and may be a copolymer with other monomers other than vinyl alcohol as long as the effects of the present invention are not impaired, or may be modified. From the viewpoints of fiber mechanical strength and alkali resistance, the ratio of the modified unit in the polyvinyl alcohol polymer is preferably 30 mol% or less, more preferably 10 mol% or less. Further, from the viewpoints of fiber mechanical strength, alkali resistance, etc., the average degree of polymerization of the polyvinyl alcohol polymer determined by the viscosity method in an aqueous solution at 30 ° C. is preferably 1000 or more, more preferably 1500 or more, and the production cost, etc. From the above point, it is preferably 10,000 or less, more preferably 5000 or less, and still more preferably 3000 or less. Further, from the viewpoint of heat resistance, durability and dimensional stability (low dimensional change rate), the saponification degree of the polyvinyl alcohol polymer is preferably 99 mol% or more, more preferably 99.8 mol% or more. 100 mol% or less.

Polyvinyl alcohol fiber can be produced, for example, by the following method. A polyvinyl alcohol-based polymer is dissolved in water at a concentration of 10 to 60% by mass, and wet spinning is performed in a coagulation bath containing sodium hydroxide and bow glass using the obtained prevention stock solution. Then, a polyvinyl alcohol fiber can be obtained by performing roller stretching, neutralization, wet heat stretching, washing with water and drying. Stretching is usually performed at a stretching temperature of 200 to 250 ° C., preferably 220 to 240 ° C. The draw ratio is usually 5 times or more, preferably 6 times or more. Thereafter, the polyvinyl alcohol fiber is cut into a desired fiber length within the above range.

(Inorganic needles)
The inorganic needle-like material contained in the fiber-reinforced carbonated cement molding has a length of 1 mm or less, preferably 0.8 mm or less, more preferably 0.6 mm or less, still more preferably 0.4 mm or less, particularly preferably 0.8 mm. Needle-like inorganic crystals of 2 mm or less, particularly preferably 0.1 mm or less, very preferably 0.05 mm or less, particularly 0.03 mm or less. Due to the needle-like shape of the inorganic crystals, the dispersibility of the inorganic crystals in the fiber-reinforced carbonated cement molding is better and the mechanical strength such as bending strength is less uneven than the shape of thin plate or scale. Furthermore, since the fiber-reinforced carbonated cement molded article is rich in inorganic crystal filling properties, a fiber-reinforced carbonated cement molded article having high mechanical strength can be obtained. When the length of the inorganic needles is equal to or less than the above upper limit value, the dispersibility of the inorganic needles in the fiber-reinforced carbonated cement molded article is good, so there is little unevenness in mechanical strength such as bending strength, Since the fiber-reinforced carbonated cement molded article is rich in inorganic needle-like filling, a fiber-reinforced carbonated cement molded article having high mechanical strength can be obtained. In general, it is known that when the length of the filler is 1 mm or less, the elastic modulus can be improved, but the influence on the mechanical strength is low. According to one embodiment of the present invention, a fiber-reinforced carbonated cement molding having a high bending strength and a low dimensional change rate can be obtained by using an inorganic needle having the predetermined length and aspect ratio. At the same time, since the length of the inorganic needles is short, the dispersibility in the fiber-reinforced carbonated cement molding is high, and the unevenness of the mechanical strength can be suppressed to a low level. In one embodiment of the present invention, the length of the inorganic needle is usually 0.002 mm or more. The length of the inorganic needles is the average of the lengths of the inorganic needles that are confirmed in the field of view by dividing a part of the fiber-reinforced carbonated cement molding and observing the fracture surface with an electron microscope. For example, at 10 arbitrary positions on the fracture surface of the fiber-reinforced carbonated cement molding, 60 μm × 90 μm cross-sectional enlarged images were obtained by an electron microscope, and the 10 cross-sectional enlarged images were obtained. The length of the inorganic needles can be calculated by arbitrarily selecting 50 from the inorganic needles observed inside and calculating the average value of the lengths as N number 50.

The inorganic needles contained in the fiber-reinforced carbonated cement molding have an aspect ratio of 20 or more, preferably 25 or more, more preferably 30 or more, and even more preferably 33 or more. When the aspect ratio of the inorganic needle-shaped material is not less than the above lower limit, the dimensional change rate of the fiber-reinforced carbonated cement molded product is small, cracks can be suppressed, and the mechanical strength of the fiber-reinforced carbonated cement molded product is further reduced. Can be improved. In one embodiment of the present invention, the aspect ratio of the inorganic needles is usually 1000 or less, especially 500 or less, especially 300 or less, more preferably 100 or less, for example 50 or less. In addition, the aspect ratio of the inorganic needles is a part of the fiber-reinforced carbonated cement molded product, and the inorganic needles of the fracture surface are observed with an electron microscope and confirmed in the field of view. Can be calculated by taking the average of the width and length (average width and average length) and dividing the average length by the average width, for example, any of the fracture surfaces of the fiber-reinforced carbonated cement molding In each of the 10 locations, an enlarged cross-sectional image of 60 μm × 90 μm was obtained with an electron microscope, and 50 arbitrarily selected from the inorganic needles observed in the 10 cross-sectional enlarged images, The average value of length (average width and average length) is calculated, and the average length can be calculated by dividing the average length by the average width.

Examples of the inorganic needles include calcium carbonate, titanium oxide, potassium titanate, basic magnesium sulfate, aluminum hydroxide, aluminum borate, calcium silicate, gypsum fiber, glass fiber, sepiolite, zonolite, wollastonite, Examples include kaolinite and kapiolite, and mixtures thereof. From the viewpoint of manufacturability and expansion resistance in carbonation, the inorganic needles are preferably made of calcium carbonate, potassium titanate or aluminum borate, more preferably calcium carbonate or potassium titanate, More preferably, it consists of calcium.

In one embodiment of the present invention, the fiber-reinforced carbonated cement molded product preferably has 2 × 10 ⁻² to 1000 × 10 ⁻² inorganic needles per 1 μm ² of fiber-reinforced carbonated cement molded product. More preferably 3 × 10 ⁻² to 900 × 10 ⁻² , still more preferably 4 × 10 ⁻² to 800 × 10 ⁻² , particularly preferably 5 × 10 ⁻² to 700 × 10 ⁻² , especially Preferably 10 × 10 ⁻² to 600 × 10 ⁻² , very preferably 20 × 10 ⁻² to 500 × 10 ⁻² , especially 30 × 10 ⁻² to 400 × 10 ⁻² , especially 40 × 10 ^-2 to 300 × 10 ⁻² , for example, 50 × 10 ⁻² to 200 × 10 ⁻² . When the number per 1 μm ^{2 of the} inorganic needles in the fiber-reinforced carbonated cement molded product is equal to or higher than the lower limit, the bending strength of the fiber-reinforced carbonated cement molded product can be further increased. When the number per 1 μm ^{2 of the} inorganic needle-like material in the fiber-reinforced carbonated cement molded product is equal to or less than the upper limit, moldability and dispersibility are good. The number per unit is divided into 10 μm × 10 μm sections in a 20 μm × 30 μm cross-sectional enlarged image obtained by dividing a part of the fiber reinforced carbonated cement molding and observing the fracture surface with an electron microscope. 10 places, and the number of inorganic needles that can be confirmed in these sections is counted and converted into the number per 1 μm ² .
In one embodiment of the present invention, as described above, the standard deviation of the number of inorganic needles that can be confirmed in 10 arbitrarily selected 10 μm × 10 μm sections is preferably 15 or less, more preferably 14 This is less than this, more preferably 13 or less, and usually 3 or more. When the standard deviation is less than or equal to the above upper limit, the dispersibility of inorganic needles in the fiber-reinforced carbonated cement molding is high, so there is little unevenness in mechanical strength such as bending strength, and fiber-reinforced carbonation with high mechanical strength. A cement molding can be obtained. In addition, the said standard deviation can measure the number of the inorganic needle-like objects which can be confirmed in a 10 micrometer x 10 micrometer division about 10 places, respectively, and can calculate it based on the measured value.

In one embodiment of the present invention, the content of the inorganic needles in the fiber-reinforced carbonated cement molding depends on the type of inorganic needles and the amount and type of other components such as fibers, pulp and aggregates. Based on the total mass of the fiber-reinforced carbonated cement molding, preferably 0.1 to 10% by mass, more preferably 0.3 to 8% by mass, still more preferably 0.6 to 6% by mass, particularly preferably 0.8 to 4% by mass, particularly preferably 1 to 3% by mass. When the content of the inorganic needle-like material in the fiber-reinforced carbonated cement molded product is equal to or higher than the lower limit, the bending strength of the fiber-reinforced carbonated cement molded product can be further increased. When the content of the inorganic needle-like material in the fiber-reinforced carbonated cement molded product is equal to or less than the upper limit, moldability and dispersibility are good. The content of the inorganic needles in the fiber-reinforced carbonated cement molding can be calculated from, for example, the amount of inorganic needles added, and when the inorganic needles are made of potassium titanate or the like. It can also be measured by quantifying elements such as titanium by elemental analysis or the like.

(pulp)
It is preferable that the fiber-reinforced carbonated cement molding further includes pulp. The pulp may be natural pulp or synthetic pulp. Natural pulp includes unbleached and bleached pulp from conifers or hardwoods, specifically pulp obtained from straw, bamboo, cotton, hemp, ramie, ridge, honey or eucalyptus. . In addition, recovered waste paper obtained from newspapers, paper bags, cardboard boxes, and the like is also included. Examples of the synthetic pulp include polyolefin-based pulp and polyaramid-based pulp. The synthetic pulp may be anything as long as it is a fibrillar substance having a shape similar to these.

The above pulp may be beaten. The CSF (Canadian Standard Freeness) representing the degree of beating is preferably 30 to 750 ml, more preferably 50 to 300 ml. In the present invention, CSF can be measured according to JIS P 8121 “Pulp Freeness Test Method”. The pulp can be beaten with a beater such as a refiner or beater.

When the fiber-reinforced carbonated cement molded product contains pulp, the content of the pulp is preferably 1 to 10% by mass, more preferably 2 to 6% by mass with respect to the fiber-reinforced carbonated cement molded product. . When the content of the pulp in the fiber-reinforced carbonated cement molded product is equal to or higher than the lower limit, the trapping property of the particulate matter is improved. When the pulp content in the fiber-reinforced carbonated cement molding is less than or equal to the above upper limit, the uniformity of dispersion becomes good, delamination is suppressed, and higher flame retardancy can be obtained.

In a preferred embodiment of the invention, the fiber reinforced carbonated cement molding comprises pulp. When the fiber-reinforced carbonated cement molded product contains pulp, the dispersibility of fibers in the fiber-reinforced carbonated cement molded product is improved, air permeability control is facilitated, and the reinforcing effect can be contributed. . In the case where pulp is present, the production is facilitated in the case of producing a fiber-reinforced carbonated cement molding by a papermaking method. Papermaking means that a slurry-like curable composition in which a cement component or the like is suspended in an aqueous medium is filtered and molded into a mesh. The papermaking plate (papermaking body) refers to a molding plate (molded product) formed by the papermaking.

(aggregate)
The fiber reinforced carbonated cement molding may include aggregate. As the aggregate, various aggregates can be used as necessary. Examples of the aggregate include fine aggregate, lightweight aggregate, and coarse aggregate. Aggregates may be used alone or in combination of two or more.

The fine aggregate may be a fine aggregate having a particle size of 5 mm or less, such as sands having a particle size of 5 mm or less; silica stone, fly ash, blast furnace slag, volcanic ash-based shirasu, various sludges, rock minerals, etc. Fine aggregate obtained by pulverizing or granulating the inorganic material. These fine aggregates may be used alone or in combination of two or more. Examples of sands include sands such as river sand, mountain sand, sea sand, crushed sand, quartz sand, slag, glass sand, iron sand, ash sand, calcium carbonate, and artificial sand. These fine aggregates may be used alone or in combination of two or more.

The coarse aggregate is an aggregate containing 85% by mass or more of particles having a particle size of 5 mm or more. The coarse aggregate may be composed of particles having a particle size of more than 5 mm. Examples of the coarse aggregate include various types of gravel, artificial aggregate (eg, blast furnace slag), recycled aggregate (eg, recycled aggregate of building waste), and the like. These coarse aggregates may be used alone or in combination of two or more.

Lightweight aggregates include natural lightweight aggregates such as volcanic gravel, expanded slag and charcoal, and artificial lightweight aggregates such as foamed pearlite, foamed perlite, foamed black stone, vermiculite, shirasu balloons and fly ash microballoons. Can be mentioned. These lightweight aggregates may be used alone or in combination of two or more. Since the fiber-reinforced carbonated cement molded product can maintain mechanical strength even when it is thinned, it is possible to reduce the weight while reducing the amount of lightweight aggregate that is easily pulverized during the manufacturing process. Therefore, the proportion of the lightweight aggregate in the total aggregate can be reduced to preferably 10% by mass or less, more preferably 5% by mass or less.

Further, the fiber-reinforced carbonated cement molding may include a functional aggregate. Here, functional aggregates include colored aggregates, hard aggregates, aggregates having elasticity, aggregates having a specific shape, and the like. Specifically, layered silicates (for example, , Mica, talc, kaolin), alumina, silica and the like. The ratio of the functional aggregate to the aggregate can be appropriately set according to each type. For example, the mass ratio of the aggregate to the functional aggregate (aggregate / functional aggregate) is 99/1 to 70/30, preferably 98/2 to 75/25, more preferably 97/3 to 80/20. These functional aggregates may be used alone or in combination of two or more.

When the fiber-reinforced carbonated cement molding includes aggregate, the mass ratio of aggregate (S) to cement component (C) (aggregate (S) / cement component (C)) is preferably 1 / It may be 20 to 100/1, more preferably 1/10 to 50/1, still more preferably 1/6 to 3/1.

In a preferred embodiment of the present invention, the fiber reinforced carbonated cement molding comprises aggregate. When the fiber-reinforced carbonated cement molding includes the aggregate, not only the reinforcing effect by the aggregate but also the coexistence of the aggregate and the fiber can increase the carbonation reaction rate and increase the mechanical strength. Although this mechanism is not clear, it becomes easier for carbon dioxide to pass through the fiber and aggregate through the fiber reinforced carbonated cement molding, and in the carbonation curing process, the carbon dioxide ventilation rate is improved and carbonation is improved. It is conceivable that the reaction rate increases.

The above-mentioned fiber-reinforced carbonated cement molding may contain various admixtures as necessary. Examples of the admixture include AE agent, fluidizing agent, water reducing agent, high performance water reducing agent, AE water reducing agent, high performance AE water reducing agent, thickener, water retention agent, water repellent, swelling agent, curing accelerator, A carbonation accelerator, a setting retarder, etc. are mentioned. The admixture may be contained alone or in combination of two or more.

The above-mentioned fiber-reinforced carbonated cement molding may also contain a water-soluble polymer substance as necessary. Examples of the water-soluble polymer substance include cellulose ethers such as methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and hydroxypropyl methyl cellulose, polyvinyl alcohol, polyacrylic acid, and lignin sulfonate. The water-soluble polymer substance may be used alone or in combination of two or more.

The above-mentioned fiber reinforced carbonated cement molding may contain a hardening accelerator (a cement ingredient) as necessary. Examples of the curing accelerator include calcium chloride, aluminum chloride, iron chloride, sodium chloride, magnesium chloride, alkali sulfate, alkali carbonate, sodium silicate, and calcium sulfate (such as gypsum).

Further, the fiber-reinforced carbonated cement molding may contain a carbonation accelerator as necessary. Examples of the carbonation accelerator include water-based polymer dispersions, thermoplastic emulsions such as polyacrylic acid esters, polyvinyl acetate, and ethylene-vinyl acetate copolymers, and synthetic rubber latexes such as styrene-butadiene rubber. . Examples of the re-emulsifying powder resin (powder emulsion) include ethylene-vinyl acetate copolymer and vinyl acetate vinyl versatate (VAVeoVa).

Further, the fiber-reinforced carbonated cement molding may contain a chemical having a high affinity for carbon dioxide gas. Examples of drugs having high affinity include amine drugs such as monoethanolamine, diethanolamine, and triethanolamine, and gels on which they are immobilized, without particular limitation. In addition, you may use these individually or in combination of 2 or more types.

The fiber-reinforced carbonated cement molding is carbonated. Carbonation means that Ca (OH) ₂ generated by a hydration reaction of a cement component and belite, which is a cement component, react with carbon dioxide gas to generate CaCO ₃ . The carbonation reaction rate of the fiber-reinforced carbonated cement molded product is preferably 30% or more, more preferably 40% or more, still more preferably 50% or more, particularly preferably 60% or more, and particularly preferably 70% or more. Is preferably 80% or more, and most preferably 90% or more. If the carbonation reaction rate of the fiber reinforced carbonated cement molding is equal to or higher than the above lower limit, the fiber reinforced carbonated cement molding has a higher mechanical strength (bending strength, etc.) because the inside of the fiber reinforced carbonated cement molding becomes more dense. A carbonated cement molding can be obtained. The upper limit of the carbonation reaction rate of the fiber-reinforced carbonated cement molded product is not particularly limited, but is usually 99% or less, such as 98% or less, and particularly 95% or less. The carbonation reaction rate of the fiber-reinforced carbonated cement molding can be measured by the method described later.

The fiber-reinforced carbonated cement molded article is excellent in mechanical strength and can be thinned. For example, the thickness of the thinnest part in the fiber-reinforced carbonated cement molded article is preferably 8 to 100 mm, more preferably 10 mm. It is ˜95 mm, more preferably 15 to 90 mm.

The manufacturing method of the said fiber reinforced carbonated cement molding is not specifically limited. In a preferred embodiment of the present invention,
A mixing step of mixing the cement component, inorganic needles, fibers and water to obtain a curable composition;
A molding step for obtaining a molded body by molding the hydraulic composition;
A fiber reinforced carbonated cement molding is obtained by a method including a pre-curing step for precuring a molded body to obtain a cured body, and a carbonation curing step for obtaining a fiber-reinforced carbonated cement molding by carbonizing and curing the cured body. Can be manufactured.

(Mixing process)
The above-mentioned cement component, fiber and water, and if necessary, pulp, aggregate and / or various admixtures are mixed by mixing means such as a known or conventional mixer to obtain a slurry-like curable composition. be able to. In addition, when a curable composition contains a pulp, it is preferable from a viewpoint of the dispersibility of each component to mix a pulp and water and to mix a pulp in water, and to add another component after mixing.
In mixing, the mixing order is not particularly limited, but preferably, when the curable composition contains pulp, the pulp and water are mixed and the pulp is dispersed in water, and then other components such as cement components and admixtures are used. It is more preferable from the viewpoint of the dispersibility of each component to add and mix the inorganic needles together with the additives, and finally add the fibers.

The inorganic needles themselves may be added to the above mixture, or a compound that is a raw material for the inorganic needles may be added to form the inorganic needles in situ in the mixture. When adding the compound used as the raw material of the inorganic needle-like material, the inorganic needle-like material may be formed in the fiber-reinforced carbonated cement molding after passing through the pre-curing step and the carbonation-curing step.

The fiber dispersion method can be performed by various methods. For example, a mixer or kneader having high stirring performance can be used. Examples of the mixer and kneader having high stirring performance include, for example, a vertical mixer, a screw mixer, a double-arm kneader, a pressure kneader, and an Eirich used in papermaking. Examples thereof include a mixer, a super mixer, a planetary mixer, a Banbury mixer, a continuous mixer, and a continuous kneader.

The water contained in the hydraulic composition may have, for example, a water / cement component ratio (W / C) of 20 to 80% by mass, preferably 25 to 70% by mass, more preferably 30 to 60% by mass. %.

(Molding process)
In the molding step, a molded body can be obtained by molding the slurry-like curable composition prepared as described above. For example, the curable composition is molded as follows. The above curable composition is fed into a plurality of bats of a wet papermaking machine, is made into a cake on the cylinder surface by the rotation of a mesh cylinder of internal negative pressure in the bat, is transported to a making roll, and is a single layer Or it is laminated | stacked and it cut | disconnects from a winding roll by making predetermined thickness. The separated plate-like molded product in a wet state is pressure-molded with a press if necessary, then cured (pre-curing and carbonation curing), and then dried as necessary to form a desired hydraulic inorganic molding. A board is manufactured. As mentioned above, although the case using a Hatschek paper machine was described, the molding method of the hydraulic composition is not particularly limited, and a general fiber-reinforced concrete or cement molding method can also be used. For example, it is easily desired by a method such as long net paper making method molding such as single paper making, casting molding, press molding, extrusion molding, or a flow-on method that obtains a desired thickness once or several times using slurry. It is possible to mold a molded body of the shape.

(Pre-curing process)
The pre-curing step is preferably performed to such an extent that the entire molded body molded into a desired shape is cured. If the whole is not cured, not only the molded body may be damaged during handling to deplate or mold and move to the subsequent process, but also mass increase due to CaCO ₃ generated by carbonation described later (that is, volume increase) ), The molded body is entangled and expands, so that the densification effect is hardly exhibited. Therefore, it is preferable to perform the pre-curing at least in a high-humidity atmosphere in which moisture in the molded body does not evaporate. Curing is due to the hydration reaction (condensation reaction) of the cement component, but if the moisture in the molded body evaporates, the hydration reaction of the cement component is inhibited, and curing may not proceed until the molded body can be handled. . The relative humidity is preferably 30 to 100%, more preferably 50 to 100%, still more preferably 65 to 100%, even more preferably 80 to 100%, particularly preferably 90 to 100%, particularly preferably 100%. A pre-curing process is performed in an atmosphere. In addition, in such a high humidity atmosphere, the molded body is put into a container or bag that does not allow moisture to pass, a plastic plate or plastic film (polyethylene sheet, etc.), a method of sandwiching the molded body between metal plates, etc. Curing may be performed by a method that can prevent evaporation of moisture in the molded body. The curing temperature in the pre-curing process is not particularly limited, but is, for example, 30 to 120 ° C, preferably 50 to 110 ° C. When the pre-curing step is performed at a temperature of 100 ° C. or higher, an autoclave treatment may be performed. In addition, when using a polyvinyl alcohol-type fiber as a fiber, it is preferable to perform a pre-curing process at the temperature of 120 degrees C or less from a heat-and-moisture-resistant viewpoint of the fiber. The maturity necessary for curing (curing temperature ° C. × curing time hr) is preferably 200 to 2000, more preferably 250 to 1500, and still more preferably 300 to 1000.

According to one embodiment of the present invention, since the molded body can include the inorganic needles, the mechanical strength of the molded body can be increased, so that the cured body can be removed from the mold even if the curing time in the pre-curing process is short. It can be cured to any extent, and even if the curing time in the precuring process is short, the expansion of the cured body can be suppressed in the carbonation curing process, and the fiber reinforcement has high bending strength and low dimensional change rate. Since a carbonated cement molding can be obtained, it is industrially advantageous. In a preferred embodiment of the present invention, the curing time in the pre-curing step depends on the curing temperature, but is preferably within 12 hours, more preferably within 10 hours, even more preferably within 8 hours, particularly preferably within 6 hours, especially Preferably it is within 5 hours. The curing time is usually 1 hour or longer, particularly 2 hours or longer, especially 3 hours or longer.

The curing atmosphere gas in the pre-curing step is not particularly limited, and other than air, carbon dioxide, nitrogen, oxygen, water vapor, helium or argon having a concentration lower than the concentration in carbonation curing, or a mixed gas thereof is used in the present invention. Can be used in a range that does not impede the purpose.

The hydraulic composition preferably contains pulp and / or aggregate. When the hydraulic composition contains pulp and / or aggregate, the air permeability of the cured product obtained in the pre-curing process can be increased. The increase in the air permeability facilitates the subsequent carbonation reaction. The air permeability of the cured body is, for example, increasing the content of pulp and / or aggregate in the hydraulic composition, partially using lightweight aggregate as the aggregate, adjusting the press pressure, etc. Can be adjusted.

According to another embodiment of the present invention, there is provided a fiber-reinforced cement molded article comprising the above cement component, inorganic needles and fibers, wherein the inorganic needles have a length of 1 mm or less and an aspect ratio. Also provided are fiber reinforced cement moldings having a ≧ 20. The fiber-reinforced cement molded product is not carbonized, that is, a cured product after the pre-curing step. The fiber-reinforced cement molding can achieve high bending strength and low dimensional change rate by undergoing carbonation. The carbonation reaction rate of the fiber-reinforced cement molded article is preferably 5% or less, more preferably 3% or less, still more preferably 1% or less, and usually 0% or more.

(Carbonation curing process)
The cured body obtained by the pre-curing step is preferably cured as a whole so that it can be taken out from the mold. A carbonation curing process is performed using this hardening body. Here, in the carbonation curing process of the hardened body, calcium hydroxide generated by hydration reaction of the cement component: Ca (OH) ₂ [see the following formula (1)], and carbon dioxide gas that has permeated: CO ₂ React to produce calcium carbonate: CaCO ₃ and water as shown in the following formula (2). At this time, since the cured body shifts from highly alkaline to neutral side, it is possible to easily confirm the carbonation reaction rate by applying a phenolphthalein solution to the cut surface of the cured body and observing the coloration state. it can.
CaO.SiO ₂ + H ₂ O → Ca (OH) ₂ + SiO ₂ (1)
Ca (OH) ₂ + CO ₂ → CaCO ₃ + H ₂ O (2)

The carbonation curing step is preferably performed in an atmosphere having a high carbon dioxide gas concentration. The carbonation curing step is preferably performed in a carbon dioxide gas atmosphere having a concentration of 5% or more, more preferably 8% or more, preferably 30% or less, more preferably 20% or less. When the carbon dioxide concentration is not less than the above lower limit, carbonation is further promoted, the mechanical strength of the fiber-reinforced carbonated cement molding is improved, and the selectivity of the paint is further expanded. Further, when the carbon dioxide concentration is less than or equal to the above upper limit, the danger due to excessive increase of the carbon dioxide concentration is reduced, and it is economically advantageous. As the atmospheric gas, in addition to carbon dioxide gas, a gas such as air, nitrogen, oxygen, water vapor, helium, or argon can be mixed and used within a range that does not impair the object of the present invention. Carbonation in a high-pressure vessel containing carbon dioxide gas is also effective from the viewpoint of improving productivity. On the other hand, the carbonation temperature is not particularly limited, but the higher the temperature, the faster the carbonation reaction. For example, 0 ° C. or higher, preferably 20 ° C. or higher, more preferably 30 ° C. or higher, and still more preferably 40 ° C. C. or higher, particularly preferably 50 ° C. or higher, particularly preferably 60 ° C. or higher. In addition, when using a polyvinyl alcohol-type fiber as a fiber, it is preferable to perform a carbonation curing process at the temperature of 120 degrees C or less from a heat-and-moisture-resistant viewpoint of the fiber. The time for the carbonation curing process varies depending on the time for the carbonation curing process and the concentration of carbon dioxide gas, but is usually 8 to 48 hours.

In one embodiment of the present invention, as the carbonation reaction requires water as in the above formula (1), the carbonation curing step is preferably performed at a constant humidity. The relative humidity in the carbonation curing process is preferably 30 to 95%, more preferably 35 to 90%, and still more preferably 40 to 85%. When the relative humidity in the carbonation curing step is not less than the above lower limit value, the carbonation reaction and the hydration reaction of the cement component can be further promoted. Further, when the relative humidity in the carbonation curing process is not more than the above upper limit value, the generation of condensed water on the surface of the cured body is suppressed, and the carbon dioxide gas easily enters the inside of the cured body, and the surface of the cured body due to the condensed water. Since the erosion of the product is suppressed, the appearance of the product is improved.

The hardened body obtained in the pre-curing process can be densified uniformly throughout the hardened body as the carbonation reaction proceeds not only to the surface of the hardened body but also to the inside by the carbonation curing. In the case of a hardened cement containing belite, densification is more likely to proceed with carbon dioxide gas. There are many unclear points about the mechanism, but it is thought to be as follows. When a normal hardened cement body is carbonated (neutralized), as shown in the above formulas (1) and (2), Ca (OH) ₂ generated by the hydration reaction of cement is converted to carbon dioxide gas. Although it reacts to become CaCO ₃ , if a large amount of belite exists in the hardened cement, the belite does not hydrate and reacts directly with carbon dioxide gas to generate a large amount of CaCO ₃ and SiO ₂ . At the same time, the C—S—H gel produced by the hydration reaction reacts with carbon dioxide gas to produce CaCO ₃ and SiO ₂ in the same manner. Furthermore, Ca (OH) ₂ generated by the cement hydration reaction also reacts with carbon dioxide to become CaCO ₃ . For this reason, it is considered that a large amount of reaction product is generated at an early stage as compared with a normal hardened cement body, which fills voids in the hardened cement body and densifies it. In fact, the carbonized cured body has an increased specific gravity, a reduced water absorption, a reduced total pore volume, and a reduced dimensional change rate. It is understood that organization densification is occurring. The total pore volume can be grasped from the pore distribution measurement by mercury porosimetry. Note that there are three types of CaCO ₃ crystal forms: calcite, aragonite, and vaterite. In any case, it is preferable in terms of densification, but aragonite and vaterite are particularly preferable. Aragonite is an acicular crystal having an aspect ratio of less than 20 mm, but can slightly contribute to the improvement of the bending strength of the fiber-reinforced carbonated cement molding. Vaterite has a lower specific gravity than calcite and aragonite. Therefore, when the same mass of CaCO ₃ is present in the hardened cement body, the occupied volume becomes larger in the vaterite, which is more effective and preferable for densification. In addition, calcite is easily generated from Ca (OH) ₂ , whereas aragonite and vaterite are easily generated from belite and C—S—H gel. This is also one of the major features of the present invention in that aragonite and vaterite effective for densification are generated at an early stage. Such densification by carbonation is preferable in that it can be densified more efficiently than a method of mechanically increasing specific gravity and reducing voids by applying a press or the like before curing. For example, the dimensional change rate is associated with expansion / contraction during water absorption / evaporation, and the rate of change can be suppressed by increasing the specific gravity. However, at the same specific gravity, the specific gravity is increased by pressing. In comparison, a fiber-reinforced carbonated cement molding having a lower dimensional change rate per specific gravity is obtained when densified by carbonation.

The fiber-reinforced carbonated cement molded product according to one embodiment of the present invention is a carbonic acid having a high reaction rate by performing the carbonation curing process after the entire molded body is cured to the extent that it can be removed from the mold by the precuring process. Because of the advancement of densification, the hydration reaction of hydraulic components, which have a slower reaction rate than carbonation, is incomplete, and in a short time the bending strength is high and the dimensional change rate per specific gravity is high. It is possible to obtain a fiber-reinforced carbonated cement molding that is small, excellent in water permeability, and excellent in paintability.

Moreover, according to one embodiment of the present invention, the cured body contains inorganic needles, whereby the mechanical strength of the cured body is increased, and expansion of the cured body to the outside due to CaCO ₃ generated by carbonation. Can be suppressed. Therefore, most or all of the increased amount of CaCO ₃ produced by carbonation contributes to further densification. According to one embodiment of the present invention, when the cured body contains inorganic needles, the densification effect by the carbonation curing can be enhanced.
Furthermore, due to the densification effect resulting from such inorganic needles, the adhesion between the cement component and the fibers inside the cured body is increased, and the mechanical strength such as the bending strength of the fiber-reinforced carbonated cement molding is further increased, The dimensional change rate can be lowered.

Thus, since the fiber-reinforced carbonated cement molding includes fibers and inorganic needles and is manufactured through carbonation curing, the dimensional change rate per specific gravity is very low, preferably 0.1%. In the following, it is more preferably 0.09% or less, further preferably 0.08% or less, particularly preferably 0.075% or less, and a fiber-reinforced carbonated cement molding having a low dimensional change rate can be obtained. In addition, the dimensional change rate per specific gravity of the fiber reinforced carbonated cement molding is usually 0% or more.

The carbonation curing process can be carried out without any particular limitation. For example, the carbonized curing process can be performed by putting the cured product obtained in the pre-curing process into a rack or the like and introducing it into a curing tank, followed by curing under predetermined conditions. it can. On the other hand, when the contact of carbon dioxide gas with the cured body is suppressed and reaction spots are generated in the cured body, problems such as warping of the cured body may occur. Therefore, in order to eliminate reaction spots, spacers are used to circulate the gas in the curing tank, spray carbon dioxide uniformly from the top and bottom of the cured body, and prevent the cured bodies from overlapping each other when loading the cured bodies on the rack. It is particularly preferable to devise so that the carbon dioxide gas can be brought into uniform contact with the cured body, for example, by providing a hard disk or by placing the cured body vertically.

In the carbonation curing step, the cured product obtained in the pre-curing step has a carbonation reaction rate of preferably 30% or more, more preferably 40% or more, further preferably 50% or more, particularly preferably 60% or more, especially Preferably it is carbonated to 70% or more, very preferably 80% or more, most preferably 90% or more. When the carbonation reaction rate is equal to or higher than the lower limit, densification (densification) easily proceeds inside the fiber-reinforced carbonated cement molded article, and a fiber-reinforced carbonated cement molded article having high mechanical strength can be obtained. it can. The upper limit value of the carbonation reaction rate is not particularly limited, but is usually 99% or less, for example 98% or less, particularly 95% or less.

The surface of the fiber-reinforced carbonated cement molded product after the carbonation curing process may be painted using a paint as necessary. The paint is not particularly limited, and is a phenol resin paint, synthetic resin blend paint, alkyd resin paint, phthalic acid resin paint, acrylic alkyd resin paint, amino alkyd resin paint, melamine baked resin paint, epoxy resin paint, modified Epoxy resin paint, tar epoxy resin paint, polyurethane resin paint, moisture-curing polyurethane resin paint, acrylic urethane resin paint, polyester urethane resin paint, alkyd modified silicone resin paint, acrylic silicone resin paint, silicone resin paint, chlorinated rubber resin paint, Examples thereof include vinyl acetate emulsion paint, acrylic resin paint, acrylic emulsion resin paint, NAD acrylic resin paint, vinyl chloride resin paint, fluororesin paint, and lacquer paint. The above-mentioned fiber-reinforced carbonated cement molded article has high density and is becoming neutralized. Therefore, it is not necessary to select an alkali-resistant paint necessary for ordinary cement-based materials, and is economically superior.

The fiber-reinforced carbonated cement molding which is one embodiment of the present invention is useful as a building material. Examples of building materials include moldings such as slate, tiles, wall panels, ceiling materials, floor panels, roof materials, and partition walls, and secondary products.

In another embodiment of the present invention, a method for using and using the above-mentioned fiber reinforced carbonated cement molding, particularly a method for using and using as a building material, is also provided.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

(Average fiber diameter (μm) and aspect ratio)
The average fiber length was calculated according to JIS L 1015 “Testing method for chemical fiber staples (8.5.1)”, and the aspect ratio of the fiber was evaluated based on the ratio to the average fiber diameter. In addition, about the average fiber diameter, 100 fibers were taken out at random, the fiber diameter in the center part of the length direction of each fiber was measured with the optical microscope, and the average value was made into the average fiber diameter (mm).

(Length (mm) and aspect ratio of inorganic needles)
The length of the inorganic needles was determined by dividing a part of the fiber-reinforced carbonated cement molding and observing the fracture surface with a scanning electron microscope S-3400N (manufactured by Hitachi High-Technologies Corporation, Scanning Electron Microscope). It was calculated by taking the average length of inorganic needles confirmed in the visual field. Observation was performed at any 10 locations on the fractured surface of the fiber-reinforced carbonated cement molding, and after obtaining a 60 μm × 90 μm cross-sectional enlarged image with the above-mentioned scanning electron microscope, observations were made in these 10 cross-sectional enlarged images. 50 inorganic needles were arbitrarily selected, and the average values of the length and width (average length and average width) were calculated. This average length was taken as the length of the inorganic needles. Further, the aspect ratio was calculated by dividing the average length by the average width.

(Measurement of the number of inorganic needles per 1 μm ² of fiber-reinforced carbonated cement molding)
A part of the fiber reinforced carbonated cement molding was divided, and the fracture surface was observed with a scanning electron microscope S-3400N (manufactured by Hitachi High-Technologies Corporation, Scanning Electron Microscope). The resulting cross section of 20 μm × 30 μm was obtained. In the enlarged image, 10 sections of 10 μm × 10 μm are arbitrarily selected, the number of inorganic needles confirmed in these sections is counted, converted to the number per 1 μm ² , and 1 μm of fiber reinforced carbonated cement molding. The number of inorganic needles per ² was determined.
In addition, the standard deviation of the number of inorganic needles was calculated based on the number of inorganic needles that can be confirmed in the 10 μm × 10 μm compartments at the 10 locations.

(Measurement of carbonation reaction rate)
Apply a 1.0 w / v% phenolphthalein ethanol (90) solution manufactured by Wako Pure Chemical Industries, Ltd. to the cross section of the cured body before and after the carbonation curing process, and after 1 minute, I took a picture. After that, for the cross-sectional photograph after the carbonation curing process, the total area of the part with the same color as that dyed with phenolphthalein before the carbonation curing process is image analysis software (free software IMAGE-J) The carbonation reaction rate (%) was calculated by the following formula.
Carbonation reaction rate (%) = {(cross-sectional area−dyed area) / (cross-sectional area)} × 100

(Method for measuring bulk specific gravity)
In accordance with JIS A 5430, the fiber-reinforced carbonated cement molding was put into an air dryer equipped with a stirrer, and the bulk specific gravity (g / cm ³ ) was determined from the mass and volume after drying at 105 ° C. ± 5 ° C. for 24 hours. .

(Measurement of bending strength)
From the fiber-reinforced carbonated cement molded product, three pieces cut into strips having a length of about 150 mm and a width of about 50 mm were cut out for each fiber-reinforced carbonated cement molded product. Then, in order to adjust the moisture content at the time of measurement of a cut piece uniformly, the cut piece was dried for 72 hours with the dryer adjusted to 40 degreeC. The measuring method of bending strength (N / mm ² ) was measured according to JIS A 1408. A three-point bending load test was performed on an autograph AG5000-B manufactured by Shimadzu Corporation with a test speed (loading head speed) of 2 mm / min, a center loading method and a bending span of 100 mm.

(Measurement of dimensional change rate per specific gravity)
In accordance with JIS A 5430, the test specimen was put in a dryer equipped with a stirrer, the temperature was kept at 60 ± 3 ° C., taken out after 24 hours, put into a desiccator conditioned with silica gel, and room temperature (20 ± 1. (5 ° C). Next, a piece of glass is attached to the specimen, and the marked line is engraved so that the distance between the marked lines is about 140 mm. The length between the marked lines is measured by a comparator having an accuracy of 1/500 mm, It was. Next, the length direction of the test body was raised horizontally and immersed in water at 20 ° C. ± 1.5 ° C. so as to be about 30 mm below the water surface. After 24 hours, the water was removed from the water and adhered to the surface, and the length between the marked lines was measured again. The rate of change in length due to water absorption was determined by (length between marked lines during water absorption−length between marked lines during drying) / length during drying × 100. Further, the obtained rate of change in length was divided by the bulk specific gravity to determine the dimensional change rate (%) per specific gravity.

In the examples and comparative examples, the following components were used.

(fiber)
A completely saponified polyvinyl alcohol having a polymerization degree of 1700 was dissolved in water at a concentration of 16.5% by mass, and 1.6% by mass of boric acid was added to the polyvinyl alcohol to obtain a spinning dope. This spinning dope is wet-spun into a coagulation bath at 70 ° C. consisting of sodium hydroxide 11 g / L and bow glass 350 g / L, followed by roller drawing, neutralization, wet heat drawing, washing with water, and drying, followed by fiber production. In the heat treatment process in the process, the film was wound by dry heat drawing at 235 ° C. so that the total draw ratio was 19 times. The obtained fiber had an average fiber diameter of 7 μm. This was cut into a fiber length of 4 mm (aspect ratio: 571) to obtain a PVA fiber.

(Cement component)
-Ordinary Portland cement: Belite content 18% by mass, made by Taiheiyo Cement

(Inorganic needles and inorganic substances)
・ Acicular calcium carbonate: length 0.02mm, aspect ratio 40
Potassium titanate whisker: length 0.015 mm, aspect ratio 33
・ Calcium carbonate (calcite): length 0.007mm, aspect ratio 1
Calcium carbonate (Aragonite): length 0.001 mm, aspect ratio 10
・ Glass fiber: Length 3mm, aspect ratio 230

(pulp)
-NUKP: Hyogo Pulp Co., Ltd. cello fiber, CSF = 115 ml

Example 1
Pulp (NUKP) 3% by mass using a checkered papermaking machine, acicular calcium carbonate (length: 0.02 mm, aspect ratio: 40) 1% by mass as inorganic needles, ordinary Portland cement (β Belite) Content: 27% by mass) 94.5% by mass, and 1.5% by mass of PVA fibers as fibers and water were mixed to obtain a hydraulic composition. The obtained hydraulic composition was molded to obtain a papermaking plate (size: 30 cm × 45 cm × 6 mm). The water content in the hydraulic composition was water / cement component (W / C) = 40% by mass. Moreover, the added amount of pulp, inorganic needles, ordinary Portland cement and fiber is a numerical value based on the ratio to the total solid content.

Thereafter, the resulting papermaking sheet (molded body) was wrapped in a polyethylene sheet, and a precuring process was performed at 100% relative humidity and 50 ° C. for 6 hours to obtain a cured body.

Next, the obtained cured product is put into an Asahi Scientific Co., Ltd. Asahi neutralization test apparatus ACT-250, and a carbonation curing process is performed for 24 hours at a carbon dioxide concentration of 20%, a relative humidity of 60%, and a temperature of 60 ° C. It was. A fiber-reinforced carbonated cement molding (1) was thus obtained. Table 2 shows the physical properties of the fiber-reinforced carbonated cement molding (1).

Example 2
The amount of inorganic needles added was changed to 3% by mass instead of 1% by mass, and ordinary Portland cement (β belite content: 27% by mass) was changed to 92.5% by mass instead of 94.5% by mass. Produced a fiber-reinforced carbonated cement molding (2) in the same manner as in Example 1. Table 2 shows the physical properties of the fiber-reinforced carbonated cement molding (2).

Example 3
Fiber reinforced carbonated cement molding was carried out in the same manner as in Example 1 except that potassium titanate whiskers (length: 0.015 mm, aspect ratio: 33) were used as inorganic needles instead of acicular calcium carbonate. A product (3) was obtained. Table 2 shows the physical properties of the fiber-reinforced carbonated cement molding (3).

Comparative Example 1
A fiber-reinforced carbonated cement molded article (4) was obtained in the same manner as in Example 1 except that the inorganic needles were not added and the carbonation curing process was not performed. Table 2 shows the physical properties of the fiber-reinforced carbonated cement molding (4).

Comparative Example 2
A fiber-reinforced carbonated cement molded article (5) was obtained in the same manner as in Example 1 except that the inorganic needles were not added. Table 2 shows the physical properties of the fiber-reinforced carbonated cement molding (5).

Comparative Example 3
Fiber reinforced carbonated cement in the same manner as in Example 1 except that particulate calcium carbonate (calcite, length: 0.007 mm, aspect ratio: 1) was used instead of acicular calcium carbonate as the inorganic substance. A molded product (6) was obtained. Table 2 shows the physical properties of the fiber-reinforced carbonated cement molding (6).

Comparative Example 4
Fiber reinforced carbonated cement molding in the same manner as in Example 1 except that calcium carbonate (aragonite, length: 0.001 mm, aspect ratio: 10) was used instead of acicular calcium carbonate as the inorganic needle. A product (7) was obtained. Table 2 shows the physical properties of the fiber-reinforced carbonated cement molding (7).

Comparative Example 5
A fiber-reinforced carbonated cement molded article (8) in the same manner as in Example 1 except that glass fibers (length: 3 mm, aspect ratio: 230) were used as inorganic needles instead of acicular calcium carbonate. Got. Table 2 shows the physical properties of the fiber-reinforced carbonated cement molding (8).

Comparative Example 6
A fiber-reinforced carbonated cement molding (9) was obtained in the same manner as in Example 1 except that no PVA fiber was added. Table 2 shows the physical properties of the fiber-reinforced carbonated cement molding (9).

Comparative Example 7
A fiber-reinforced carbonated cement molding (10) was obtained in the same manner as in Example 1 except that the carbonation curing process was not performed. Table 2 shows the physical properties of the fiber-reinforced carbonated cement molding (10).

From the results shown in Table 2, the fiber-reinforced carbonated cement moldings (1) to (3) obtained in Examples 1 to 3 had a high bending strength and a low dimensional change rate. It can also be seen that the specific gravity is high and densification is achieved.
On the other hand, in Comparative Example 1, the inorganic needle-like material was not used and the carbonation curing process was not performed, so that the dimensional change rate was high and the bending strength was low. Further, in Comparative Example 2 in which no inorganic needles are used, the specific gravity is low and the dimensional change rate is also lower than those of the fiber-reinforced carbonated cement molded products (1) to (3) obtained in Examples 1 to 3. Since it was higher, the degree of densification was lower and the bending strength was lower. Similarly, in the comparative examples 3 to 5 using the inorganic material having an aspect ratio of 1, an inorganic needle material having an aspect ratio of 10, or an inorganic needle material having a length of 3 mm, the degree of densification is similarly reduced. In addition, the bending strength was low. In Comparative Example 6 in which no polyvinyl alcohol fiber was used, although the specific gravity was relatively high, the bending strength was low. This is presumably because the expansion effect to the outside of the cured body by the inorganic needles was suppressed in the carbonation curing process, but the reinforcing effect by the polyvinyl alcohol fiber was not obtained. In Comparative Example 7 where carbonation curing was not performed, the specific gravity was low and the dimensional change rate was high.

Since the fiber-reinforced carbonated cement molding according to the present invention has both high bending strength and a small dimensional change rate, it is a building material, particularly slate, tile, wall panel, ceiling material, floor panel, roofing material, partition wall, etc. Can be suitably used.

Claims

A fiber reinforced carbonated cement molding comprising a cement component, inorganic needles and fibers,
The inorganic needle-like product is a fiber-reinforced carbonated cement molded product having a length of 1 mm or less and an aspect ratio of 20 or more.
The fiber-reinforced carbonated cement molding according to claim 1, wherein the carbonation reaction rate is 30% or more.
The fiber-reinforced carbonated cement molding according to claim 1 or 2, wherein the fiber is a polyvinyl alcohol fiber.
The fiber-reinforced carbonated cement molded product according to any one of claims 1 to 3, wherein the inorganic needle-shaped material is made of calcium carbonate or potassium titanate.
5. The fiber-reinforced carbonated cement molding according to claim 1, wherein 2 × 10 −2 to 1000 × 10 −2 inorganic needles are contained per 1 μm 2 of the fiber-reinforced carbonated cement molding. object.
The fiber-reinforced carbonated cement molding according to any one of claims 1 to 5, wherein the cement component contains 18% by mass or more of belite.
The fiber-reinforced carbonated cement molded article according to any one of claims 1 to 6, further comprising pulp.
A fiber reinforced cement molding comprising a cement component, inorganic needles and fibers,
The inorganic needle-like article is a fiber-reinforced cement molded article having a length of 1 mm or less and an aspect ratio of 20 or more.
A mixing step of mixing a cement component, inorganic needles, fibers, and water to obtain a curable composition;
A molding step for obtaining a molded body by molding the hydraulic composition;
8. A pre-curing step for pre-curing the molded body to obtain a cured body, and a carbonation curing step for obtaining a fiber-reinforced carbonated cement molding by carbonizing and curing the cured body. A method for producing the fiber-reinforced carbonated cement molding according to claim 1.
The method according to claim 9, wherein the curing time in the pre-curing step is within 12 hours.