JP2018108915A - Hydraulic compact and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic compact that has high strength and excellent appearance due to uniform dispersion of reinforcement fibers in a hydraulic compact, and a production method capable of efficiently obtaining the hydraulic compacts.SOLUTION: A hydraulic compact containing alkali-resistant fibers has a fluctuation range of specific gravity of each cut-off piece to an average specific gravity of 20 cut-off pieces equally cut out from an entirety or a part of the compact such that a length of each of vertical and horizontal lengths is 3 to 7 cm of 15% or smaller.SELECTED DRAWING: None

Description

  The present invention relates to a hydraulic molded body and a method for producing the same.

  Molded articles using hydraulic substances such as cement are generally widely used as building materials and civil engineering materials such as mortar and concrete. In a molded article using such a hydraulic substance, in order to improve the tensile strength, which is a weak point of the molded article, it is widely performed to mix reinforcing fibers at the time of molding. In particular, it has been studied to mix reinforcing fibers in secondary products that can be manufactured in factories, and various proposals have been made for more efficiently manufacturing molded products containing reinforcing fibers.

  For example, Patent Document 1 discloses a fiber-reinforced hydraulic property in which production efficiency is improved by omitting the kneading and extruding steps in the method of manufacturing a hydraulic inorganic molded body usually performed by a mixing-kneading-extrusion-pressing step. A method for producing an inorganic molded body is described. Patent Document 2 discloses a case where a hydraulic substance having a low fiber flow and low free water is used by using an alkali-resistant fiber having a predetermined fiber diameter and an aspect ratio and having a small buckling portion. Describes a hydraulic molded body having high strength and good appearance.

JP 2014-195957 A JP 2016-124709 A

  However, since the method for producing a hydraulic molded body as described in Patent Document 1 does not include a kneading step, it is difficult to disperse the fibers. For this reason, when the fiber addition amount is increased, the moldability is remarkably deteriorated, and it is difficult to obtain a molded product having both appearance and strength. Similarly, even in a hydraulic molded body as described in Patent Document 2, it is difficult to suppress fiber re-aggregation when the amount of added fibers is increased, and the moldability deteriorates. And it was not fully satisfactory in strength.

  Therefore, the present invention efficiently obtains a hydraulic molded body having high strength and excellent appearance, and the hydraulic molded body, because the reinforcing fibers are uniformly dispersed in the hydraulic molded body. It is an object of the present invention to provide a manufacturing method that can handle the above.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems. That is, the present invention provides the following preferred embodiments.
[1] A hydraulic molded body comprising alkali-resistant fibers,
The variation width of the specific gravity of each of the cut pieces is 15% with respect to the average specific gravity of 20 cut pieces that are equally cut from the whole or a part of the molded body so that the length and width are 3 to 7 cm, respectively. The following is a hydraulic molded body.
[2] The hydraulic molded body according to [1], wherein the number of buckling portions of the alkali-resistant fiber is 0.5 or less per 1 mm of fiber length.
[3] The hydraulic molded body according to [1] or [2], wherein the aspect ratio of the alkali-resistant fiber is 20 to 2000.
[4] Hydraulic property according to any one of [1] to [3], comprising 1.0 × 10 ^{5 to} 1.0 × 10 ¹³ alkali-resistant fibers per 1 m ^{3 of the} hydraulic molded body. Molded body.
[5] The hydraulic molded body according to any one of [1] to [4], wherein a bending strength as a cut piece of 5 × 16 cm is 6 N / mm ² or more.
[6] The alkali resistant fiber according to any one of [1] to [5], wherein the alkali resistant fiber is at least one selected from the group consisting of polyvinyl alcohol fiber, polyethylene fiber, polypropylene fiber, acrylic fiber, and aramid fiber. Hydraulic molded body.
[7] The hydraulic molding according to any one of [1] to [6], including stirring and mixing the hydraulic composition and the mixture containing water and the alkali-resistant fiber using a reciprocating rotary stirrer. Body manufacturing method.
[8] The method for producing a hydraulic molded article according to the above [7], wherein vertical convection is generated by a reciprocating rotary stirrer, and the mixture containing the hydraulic composition and water and the alkali-resistant fiber are stirred and mixed.
[9] The method for producing a hydraulic molded body according to [7] or [8], wherein the stirring blade of the reciprocating rotary stirrer is reciprocally rotated at a reciprocating rotational speed of 200 times / min to 1000 times / min.

  According to the present invention, since the reinforcing fibers are uniformly dispersed in the hydraulic molded body, it is possible to provide a hydraulic molded body that is excellent in performance such as appearance and strength, and the hydraulic molding described above. The manufacturing method which can obtain a body efficiently can also be provided.

  Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention.

<Hydraulic molded body>
The hydraulic molded body of the present invention contains alkali-resistant fibers, and usually contains hydraulic substances such as cement and gypsum in addition to the alkali-resistant fibers.
In the hydraulic molded body of the present invention, the average specific gravity (hereinafter referred to as “average specific gravity”) of 20 cut pieces equally cut from the whole or a part so that the length and width are 3 to 7 cm respectively. The fluctuation range (hereinafter also referred to as “specific gravity fluctuation range”) of the specific gravity (hereinafter also referred to as “local specific gravity”) of each of the cut pieces is 15% or less.

  The fluctuation range of the specific gravity is an index indicating the dispersion state of the alkali-resistant fibers contained in the hydraulic molded body. That is, when the alkali-resistant fiber is present as a fiber aggregate (fiber ball) in the hydraulic molded body, the specific gravity of the fiber itself forming the fiber aggregate is very small relative to the hydraulic substance, and the fiber aggregate is air. Therefore, the bulk specific gravity of the molded body including the fiber aggregate is smaller than that of the molded body without the fiber aggregate. For this reason, the local specific gravity of the cut piece in which the fiber aggregate is present is smaller than the average specific gravity of the hydraulic molded body after cutting, and water is obtained by comparing the local specific gravity of each cut piece with the average specific gravity. The dispersion state of the fibers in the rigid molded body can be evaluated.

  When the alkali-resistant fiber is uniformly dispersed in the hydraulic molded body, the specific gravity variation range is reduced. Therefore, in the present invention, the specific gravity variation range is 15% or less, and 10% or less. It is preferably 8% or less, more preferably 6% or less. The ideal lower limit value of the fluctuation range is 0%, but may be 0.5% or more, for example. When the specific gravity fluctuation range exceeds 15%, a large number of fiber aggregates exist, and dispersion of the alkali-resistant fibers in the hydraulic molded body increases. Therefore, it is possible to obtain a hydraulic molded body having both high strength and appearance. It becomes difficult.

In the present invention, the measurement and calculation of the specific gravity fluctuation range can be performed, for example, according to the following procedure.
i) Production of cut piece The cut piece for measuring and calculating the specific gravity fluctuation range has a predetermined substantially the same size (volume) according to the size of the hydraulic molded body to be measured. It is carried out by cutting the hydraulic molded body into equal parts so that a cut piece is obtained. As long as 20 pieces of a predetermined approximately the same size can be obtained from a lump of hydraulic molded body, all of the hydraulic molded body may be cut out, or a part of the hydraulic molded body may be cut out. When a part of the hydraulic molded body is cut out, 20 cut pieces may be cut out continuously, or may be cut out from any part of the molded body. Further, the length and width of the cut surface of the cut piece are in the range of 3 to 7 cm, respectively, and the cut surface may be square or rectangular as long as it is within this range. The thickness of the cut piece is not particularly limited, but if there is a difference in thickness in the hydraulic molded body before cutting, the cut piece is cut so that the thickness of the 20 cut pieces is substantially the same. It is necessary to cut out so that the size (volume) of the 20 cut pieces becomes the same by adjusting the vertical and horizontal lengths. In addition, when 20 cut pieces cannot be cut out from a lump of hydraulic molded bodies, a total of 20 cut pieces are cut out from two or more hydraulic molded bodies that are the same product.
In an example which is an aspect of the present invention, a hydraulic molded body was cut so that each cut piece for measuring and calculating the specific gravity fluctuation range had a square cut surface of 5 cm square.

ii) Measurement of local specific gravity of each cut piece Next, the local specific gravity of each of the 20 cut pieces is measured, and the average value of the total local specific gravity is calculated as the average specific gravity of the hydraulic compact. The local specific gravity of the cut piece may be measured by a method conventionally used in the technical field. For example, it is easily measured using a specific gravity measurement kit (for example, a specific gravity measurement kit AD-1653 manufactured by A & D Corporation). can do.

iii) Calculation of specific gravity fluctuation range The local specific gravity of the 20 cut pieces measured and calculated by the above procedure is compared with the average specific gravity of the 20 cut pieces, and the local specific gravity having the largest specific gravity difference is The specific gravity fluctuation range (%) can be calculated by dividing by the average specific gravity according to the following formula.
Specific gravity fluctuation range (%) = local specific gravity / average specific gravity having maximum difference with respect to average specific gravity × 100

  From the viewpoint of ensuring sufficiently high strength and excellent appearance of the hydraulic molded body of the present invention, the number of buckling portions of the alkali-resistant fibers contained in the hydraulic molded body is 0.5 or less per 1 mm of fiber length. It is preferable that In the present invention, the “buckled portion” means a portion where the fiber is buckled, and means a defective portion of the fiber. For example, when a mixture containing a hydraulic substance such as cement and water and an alkali-resistant fiber are mixed together, the buckling part is mixed with a stirring factor (blade shape, stirring speed, stirring time, etc.) of the mixer, It is formed by physical impact due to aggregate factors (size, shape, specific gravity, hardness, etc.).

When the alkali-resistant fiber has a buckling portion, the tensile strength of the fiber is lowered. Therefore, even if a sufficient number of fibers are present in the hydraulic molded body, the strength of each fiber is weak and substantially In particular, the number of fibers contributing to the reinforcement of the molded body is also reduced. For this reason, it becomes difficult to obtain the reinforcing effect by the fibers. Further, since the fibers are bent around the buckling portion, the fibers are easily entangled, and the uniform dispersion of the fibers is inhibited. Therefore, in the present invention, the number of buckling portions of the alkali-resistant fiber is more preferably 0.4 or less per 1 mm of fiber length. If the number of buckling portions of the alkali-resistant fiber is 0.5 or less per 1 mm of fiber length, the reinforcing performance by the alkali-resistant fiber can be efficiently ensured, and the strength and appearance of the hydraulic molded body can be improved. Can be improved. Since it is ideal that the alkali-resistant fiber has no buckling part, the lower limit value of the number of buckling parts is usually 0 or more per 1 mm of fiber length.
In addition, the number of the buckling parts of a fiber can be quantified by the method described in the below-mentioned Example.

In the present invention, the aspect ratio of the alkali-resistant fiber is preferably 20 to 2000. When the aspect ratio of the alkali-resistant fiber is within the above range, the fibers are hardly entangled with each other, and it becomes easy to uniformly disperse the fiber in a mixture containing a hydraulic substance and water. A hydraulic molded body can be obtained. In the present invention, the aspect ratio of the alkali-resistant fiber is more preferably 25 to 1900, and further preferably 30 to 1800.
Moreover, it is also a preferable aspect that the aspect ratio of the alkali-resistant fiber is 50 to 2000, which may be 55 to 1900 or 60 to 1800.
The aspect ratio means the ratio (L / D) between the fiber length (L) and the fiber diameter (D). In the present invention, the aspect ratio can be calculated by calculating the average fiber length according to JIS L1015 “Chemical Fiber Staple Test Method (8.5.1)” and calculating the fiber aspect ratio by the ratio to the average fiber diameter. it can.

The number of alkali-resistant fibers in the present invention can be appropriately set according to the type of fiber used, fiber diameter, aspect ratio, etc., but 1.0 × 10 ⁵ to 1.0 per 1 m ^{3 of the} hydraulic molded body. X10 It is preferable that ¹³ alkali-resistant fibers are included. Since the hydraulic molded body of the present invention contains a large amount of fibers in a state of being uniformly dispersed in the molded body as compared with the conventional hydraulic molded body, a higher reinforcing effect by the alkali-resistant fibers can be obtained. , Has high strength. From the viewpoint of both the reinforcing effect and uniform dispersibility obtained, the number of alkali-resistant fibers is more preferably 1.0 × 10 ^{6 to} 1.0 × 10 ¹² per 1 m ^{3 of} hydraulic molded body, More preferably, the number is 1.0 × 10 ^{7 to} 1.0 × 10 ¹¹ .

In the present invention, the average fiber strength of the alkali-resistant fiber is not particularly limited, but is preferably 5 cN / dtex or more, more preferably 6 cN / dtex or more, and further preferably 7 cN / dtex or more. When the average fiber strength of the alkali-resistant fiber is equal to or higher than the lower limit, a molded body having excellent bending strength can be obtained. The upper limit of the average fiber strength of the alkali-resistant fiber in the present invention is appropriately set according to the type of fiber, and is, for example, 30 cN / dtex or less.
In addition, average fiber strength can be measured by the method described in the Example mentioned later.

  The alkali-resistant fiber in the present invention may be an organic fiber or an inorganic fiber as long as it has chemical durability against cement alkali. Examples of the alkali-resistant inorganic fibers include alkali-resistant glass fibers, steel fibers (steel fibers), stainless fibers, carbon fibers, ceramic fibers, and asbestos fibers. Examples of alkali-resistant organic fibers include polyvinyl alcohol (hereinafter also referred to as “PVA”) fibers (such as vinylon fibers), polyolefin fibers (such as polyethylene fibers, polypropylene fibers, ethylene / propylene copolymer fibers), and ultrahigh molecular weight polyethylene. Fiber, polyamide fiber (polyamide 6, polyamide 6,6, polyamide 6,10, etc.), aramid fiber (especially para-aramid fiber), polyparaphenylenebenzobisoxazole fiber (PBO fiber), acrylic fiber, rayon fiber (polynosic) Fiber, solvent-spun cellulose fiber, etc.), polyphenylene sulfide fiber (PPS fiber), and polyether ether ketone fiber (PEEK fiber). These alkali resistant fibers may be used alone or in combination of two or more. The addition amount of the alkali-resistant fiber is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, and further preferably 0.5 to 2 parts by mass with respect to 100 parts by mass of the hydraulic molded body. is there.

  Among these, as the alkali-resistant fiber, from the viewpoint of being able to be produced at low cost while having the reinforcing performance of the hydraulic molded body, alkali-resistant glass fiber, carbon fiber, polyvinyl alcohol fiber (such as vinylon fiber), polyolefin-based fiber It is preferably at least one selected from the group consisting of fibers (polyethylene fibers, polypropylene fibers, ethylene / propylene copolymer fibers, etc.), acrylic fibers and aramid fibers, polyvinyl alcohol fibers, polyethylene fibers, polypropylene fibers, More preferably, it is at least one selected from the group consisting of acrylic fibers and aramid fibers, and even more preferably polyvinyl alcohol fibers. 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 hydraulic molded body of the present invention contains a hydraulic substance in addition to the alkali-resistant fibers, and includes aggregates and various admixtures (admixtures / admixtures) as necessary.

  In the present invention, examples of the hydraulic substance include cement and gypsum, and preferably contain cement. Examples of the cement include ordinary Portland cement, early-strength Portland cement, ultra-early strong Portland cement, and medium-heated Portland cement, such as Portland cement, alumina cement, blast furnace cement, silica cement, and fly ash cement. Examples of gypsum include dihydrate gypsum, α-type or β-type hemihydrate gypsum, and anhydrous gypsum. These hydraulic substances may be used alone or in combination of two or more.

  In the present invention, examples of the aggregate include fine aggregate, lightweight aggregate, and coarse aggregate. These aggregates may be used alone or in combination of two or more.

  Examples of the fine aggregate include fine particles having an average particle diameter of 5 mm or less, for example, 0.1 to 5 mm. Specifically, for example, sand having a particle size of 5 mm or less; fine aggregate obtained by pulverizing or granulating inorganic materials such as silica, fly ash, blast furnace slag, volcanic ash-based shirasu, various sludges, and rock minerals Etc. Examples of the sands include river sand, mountain sand, sea sand, crushed sand, quartz sand, slag, glass sand, iron sand, ash sand, calcium carbonate, artificial sand, and the like.

  Examples of the lightweight aggregate 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, and shirasu balloon.

  Examples of the coarse aggregate include various gravels, artificial aggregates, recycled aggregates and the like in which particles having a particle diameter of 5 mm or more are contained by 85% or more by weight.

  The ratio of the aggregate with respect to the hydraulic substance (cement) in a hydraulic composition is 0.1-10 in the weight ratio of S (aggregate) / C (cement), for example, Preferably it is 0.5-5. 0.

  The hydraulic molded body of the present invention 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, Examples thereof include setting retarders. Admixtures may be used alone or in combination of two or more.

  The hydraulic molded body of the present invention 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.

Since the hydraulic molded body of the present invention contains alkali-resistant fibers in a sufficiently uniform dispersed state, it has excellent bending strength. For this reason, the bending strength as a 5 cm × 16 cm cut piece of the hydraulic molded body of the present invention is preferably 6 N / mm ² or more, more preferably 6.5 N / mm ² or more, and even more preferably 7 N / mm ² or more, particularly preferably 7.5 N / mm ² or more. Moreover, the lower limit value of the bending strength as a cut piece of 5 cm × 16 cm is not particularly limited, and is usually 25 N / mm ² or less.
In addition, bending strength can be measured by the method described in the Example mentioned later.

<Method for producing hydraulic molded body>
The hydraulic molded body of the present invention includes a hydraulic composition such as cement and a hydraulic composition containing various admixtures and the like as long as the above-described aggregate and the effect of the present invention are not impaired as necessary. It can be produced by stirring and mixing the mixture and alkali-resistant fiber and curing the mixture. Among them, since the hydraulic molded article of the present invention containing alkali-resistant fibers in a sufficiently uniform dispersed state and excellent in strength and appearance can be efficiently produced, the production method of the present invention comprises a hydraulic composition and It is preferable to include stirring and mixing the mixture containing water and the alkali-resistant fiber using a reciprocating rotary stirrer (hereinafter also referred to as “mixing step”).

  In the mixing step, the alkali-resistant fiber is obtained by stirring and mixing a hydraulic composition and a mixture containing water (hereinafter also referred to as “water mixture of hydraulic composition”) and alkali-resistant fiber using a reciprocating rotary stirrer. To disperse. In the mixing step of the production method of the present invention, the agitation and mixing of the alkali-resistant fibers may be performed after the alkali-resistant fibers are collectively added to the water mixture of the hydraulic composition, and the alkali resistance in the water mixture of the hydraulic composition. You may carry out adding a fiber.

  The water mixture of the hydraulic composition usually includes all components other than the alkali-resistant fiber, and includes at least a hydraulic substance and water, and the hydraulic molded body includes aggregates and various admixtures. Is contained in the above mixture. The order of adding and / or mixing the hydraulic substance, water, and aggregate is not particularly limited. The total amount to be used, such as hydraulic substance, water, and aggregate, may be included from the beginning, or a part thereof may be included. For example, if the mixture includes some hydraulic material, water, aggregate, etc., the remainder may be added during and / or after dispersion of the alkali resistant fibers. For mixing, for example, a hydraulic substance, water and aggregate may be mixed using a stirrer or the like conventionally used in the field. For example, after mixing a hydraulic substance and aggregate in a dry process, May be added and mixed.

  The water content in the water mixture of the hydraulic composition may be appropriately adjusted according to the composition of the mixture, but the mixing ratio of water and hydraulic substance (cement) in the mixture [water / cement ratio (W / C)] is, for example, 20 to 70% by weight, preferably 25 to 60% by weight, and more preferably 30 to 50% by weight.

  Next, a hydraulic molding material can be obtained by adding and dispersing alkali-resistant fibers to the mixture. The reciprocating rotary stirrer used in the mixing step of the production method of the present invention means a stirrer having a function in which the stirring shaft provided with the stirring blades is not rotated in one direction but reversed every specific rotation angle. As such a reciprocating rotary stirrer, for example, a reciprocating rotary stirrer agitator manufactured by Shimazaki Engineering Co., Ltd. can be used.

  Conventionally, for stirring and mixing water mixture of hydraulic composition and fiber, mortar mixer, Eirich mixer, Nauta mixer, rotary type, which is a general rotary stirrer that rotates propeller type and screw type blades in one direction A stirrer, pan mixer, planetary mixer, etc. are widely used. In such a general rotary stirrer, only the rotation in a fixed direction is given to the contents to be stirred and mixed. On the other hand, by using a reciprocating rotary stirrer, complicated vertical convection can be generated for the contents to be stirred and mixed in the stirring tank. For this reason, it can suppress that the fiber contained in the water mixture of a hydraulic composition settles / stagnates in the lower layer part of a stirring tank, or floats / stays in the upper layer part of a stirring tank. By vertical convection, the fibers can be dispersed not only in a part of the water mixture of the hydraulic composition in the stirring tank but also in the whole. As a result, it is possible to disperse a relatively large amount of alkali-resistant fibers in a sufficiently uniform state in the molded body, which is difficult to disperse uniformly in the conventional method, and as a result, has high strength. In addition, the hydraulic molded body of the present invention having excellent appearance can be obtained. In addition, since the stirring flow is more complicated than in the case of stirring and mixing by rotation in a certain direction, the fibers can be dispersed in the water mixture of the hydraulic composition in a shorter time, and the water of the present invention can be efficiently used. A rigid molded body can be obtained.

  Conventionally, in a hydraulic molded body, it is common to use fibers having a relatively small aspect ratio from the viewpoint of improving the dispersibility and moldability of the fibers. In this case, the specific surface area of the fibers is reduced. Therefore, the adhesiveness of the fiber to the hydraulic composition is low and the reinforcing performance is inferior. On the other hand, it is preferable to increase the fiber aspect ratio in order to increase the adhesion of the fiber and enhance the reinforcement performance. However, in this case, the dispersion of the fiber into the water mixture of the hydraulic composition is difficult, and the mixing is forcibly mixed. Attempts to damage the fiber will eventually lead to a reduction in reinforcement performance. Thus, the reinforcing performance and the fiber dispersibility are in a trade-off relationship. On the other hand, in the production method of the present invention, by using a reciprocating rotary stirrer, complex vertical convection is generated in the water mixture of the hydraulic composition as described above, and it has been considered difficult in the past. It becomes possible to uniformly disperse a relatively large amount of alkali-resistant fiber having a relatively large ratio in the mixture.

  In the mixing step, the reciprocating rotation speed of the reciprocating stirring blade is appropriately adjusted according to the components constituting the water mixture of the hydraulic composition, the addition amount and addition speed of the alkali-resistant fiber, the reversing angle of the stirring blade, etc. However, in the present invention, the reciprocating rotational speed of the reciprocating rotary stirrer is preferably 200 times / minute or more, more preferably 250 times / minute or more, and 300 times / minute or more. More preferably, it is preferably 1000 times / minute or less, more preferably 900 times / minute or less, and still more preferably 800 times / minute or less. When the reciprocating rotational speed is equal to or higher than the above lower limit value, the alkali-resistant fiber can be blended in a sufficiently uniform dispersed state in the water mixture of the hydraulic composition, and thus water having high strength and excellent appearance. A rigid molded body can be obtained. Further, when the reciprocating rotational speed is equal to or lower than the above upper limit value, the alkali resistant fibers are hardly entangled during the fiber agitation and mixing step, the generation of fiber aggregates can be suppressed, and defects in the alkali resistant fibers (buckling) Part) is difficult to occur. If the reciprocating rotational speed is too slow, it becomes difficult to uniformly disperse the alkali resistant fibers in the water mixture of the hydraulic composition, and if the reciprocating rotational speed is too fast, the alkali resistant fibers are likely to be damaged. The number of buckling portions per 1 mm of fiber length tends to increase, and it is difficult to ensure the strength of the hydraulic molded body obtained in any case. Note that the reciprocating rotational speed means a speed required when the stirring blade starts rotating from the rotation start point and reverses and returns to the rotation start point as one rotation.

  The stirring time of the alkali-resistant fiber and the water mixture of the hydraulic composition is appropriately determined according to the components constituting the water mixture of the hydraulic composition, the addition amount and addition speed of the alkali-resistant fiber, the reversing angle of the stirring blade, and the like. Just decide. In the production method of the present invention, by using a reciprocating rotary stirrer, a complicated stirring flow is generated in the stirring tank, so that the fibers can be uniformly dispersed in the water mixture of the hydraulic composition in a shorter time. it can. Therefore, in the production method of the present invention, the stirring time of the alkali-resistant fiber and the water mixture of the hydraulic composition can be, for example, about 30 to 600 seconds, or 40 to 300 seconds.

  What is necessary is just to select suitably the rotation angle of the rotary blade of a reciprocating rotary stirrer according to the component which comprises the water mixture of a hydraulic composition, the addition amount of an alkali-resistant fiber, an addition speed, etc. Here, in the present invention, the rotation angle means a rotation angle until the stirring blade is reversed, for example, 90 ° (1/4 rotation), 180 ° (1/2 rotation), or 360 ° (1 rotation). Any of these may be used.

  When stirring and mixing while adding alkali-resistant fibers, the charging speed may be appropriately determined according to the components constituting the water mixture of the hydraulic composition, the amount of alkali-resistant fibers added, and the like. The addition rate of the alkali-resistant fiber may be, for example, 6.0 kg / second or less, preferably 4.5 kg / second or less, more preferably 4 kg / second or less per 1000 kg of the solid content in the water mixture of the hydraulic composition. 0.0 kg / second or less. When the alkali-resistant fiber is added to the hydraulic composition mixture at an addition rate within the above range, the uniform dispersibility of the fiber is further improved, so that the formation of fiber aggregates is suppressed, and as a result, the strength of the hydraulic molded body and Appearance can be sufficiently improved. In addition, “per 1000 kg of solid content of the mixture” means that the addition rate changes according to the amount of the solid content of the mixture. For example, the addition rate is set smaller as the solid content of the mixture is smaller.

  For example, in order to improve the dispersibility of the alkali-resistant fiber, the alkali-resistant fiber may be supplied in a fixed amount, or the fiber in an unraveled state may be added, or these methods may be performed alone or in combination. Good.

  When the fiber is supplied in a fixed amount, it is not particularly limited as long as the alkali-resistant fiber can be continuously fed in a predetermined amount range. For example, various quantitative supply devices (for example, a vibration feeder, a screw feeder, a belt feeder, etc.) can be used as an apparatus for supplying while controlling the input amount and / or input speed of the alkali-resistant fiber.

  When unraveling the fibers, for example, the fiber aggregates can be unraveled to a smaller fiber aggregate unit by a predetermined disaggregation means or the like to the extent that generation of fiber aggregates can be suppressed. When the fiber aggregate is unraveled, from the viewpoint of maintaining the fiber strength, it is preferable to carry out within a range in which fiber fibrillation, fiber pulverization, and buckling portion formation do not occur.

  The fiber aggregate can be usually solved by various methods in a dry process. For example, fiber agglomerates (fiber veil, coarse fiber fiber defibrated material, shortcut fiber bundles, etc.) may be unwound by hooking the fibers on a roll having protrusions and passed between opposing rotating gears. It may be solved by a shearing force of a rotating disk having a groove, or by a collision force of airflow. You may perform these methods individually or in combination of 2 or more types. For example, the fiber aggregates (such as a short-cut fiber lump cut to a predetermined length) may be unraveled in a dry manner to separate the fibers, thereby unraveling the fiber aggregates.

  It is preferable that the alkali-resistant fiber is subjected to a disaggregation treatment prior to addition to the mixture from the viewpoint of further suppressing the formation of fiber aggregates. The disaggregation treatment is a treatment for separating the fibers and separating the fibers to promote the formation of single fibers.

  The disaggregation treatment can be usually performed by various methods under a dry process. For example, a process of unraveling the fiber by passing between opposing rotating gears, a process of unraveling the fiber by hooking it onto a roll having protrusions, a process of unraveling the fiber by the shearing force of a rotating disk with grooves, and an airflow impinging force And one or more treatments selected from the group consisting of treatments for unraveling fibers. Preferably, the fiber is unwound by passing between opposed rotating gears.

  In the process of unwinding the fibers by passing between the opposing rotating gears, the alkali-resistant fibers are unwound by the rotational force of the gears when the fibers pass through the clearance between the gears.

  In the process of unraveling the fibers by hooking the fibers on the roll having the protrusions, the fibers can be unwound by hooking the fibers with the protrusions of the rotating roll and rolling them.

  In the process of unwinding the fiber by the shearing force of the rotating disk having the groove, the fiber can be defibrated while being drafted in the bias direction by the interaction of the sawtooth blade between the rotor having the groove and the stator.

  In the process of unwinding the fiber by the impact force of the airflow, the fiber can be unwound by applying compressed air with an air nozzle when the fiber is introduced. Air is not particularly limited as long as it is applied from at least one direction.

  In the production method of the present invention, a hydraulic molding material obtained by stirring and mixing alkali-resistant fibers can be put into a mold and molded. At this time, vibration may be applied as necessary. The vibration is usually performed by vibrating the formwork. By applying vibration, the hydraulic molding material can be more evenly distributed inside the mold.

  The vibration frequency when vibrating is preferably 10 to 1000 Hz, more preferably 20 to 900 Hz, and still more preferably 30 to 800 Hz. The amplitude is preferably 0.1 to 20 μm, more preferably 0.5 to 18 μm, and still more preferably 1 to 15 μm.

You may press the hydraulic molding material thrown into the mold with a press using an upper surface shaping | molding die, a roll, etc.
The pressure at the time of pressing can be appropriately set depending on the state of the kneaded hydraulic molding material, the form of the mold, etc., but is preferably 10 to 150 MPa, more preferably 20 to 140 MPa, and still more preferably 30 to 130 MPa. By pressing with the pressure in the above range, it is possible to integrate the alkali-resistant fibers contained in the hydraulic molding material without damaging them.

  The pressing may be performed while heating as necessary. As heating temperature, about 40-90 degreeC is preferable, More preferably, it is 45-85 degreeC, More preferably, it is 50-80 degreeC.

  After molding into a predetermined shape, a hydraulic molded body can be obtained by curing the hydraulic molding material by curing in an atmosphere of 100 ° C. or lower.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

  The average fiber strength, the aspect ratio, the number of buckling portions, the specific gravity fluctuation range, and the bending strength of the cut piece in the hydraulic molded body were measured according to the following measurement methods.

[Average fiber diameter (μm) and aspect ratio]
The average fiber length was calculated according to JIS L1015 “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.

[Average fiber strength]
In accordance with JIS L1015 “Chemical Fiber Staple Test Method (8.5.1)”, the fiber was left to stand for 5 days in an atmosphere of a temperature of 20 ° C. and a relative humidity of 65%, and then the single fiber was tested. Fiber strength was measured with FAFEGRAPH M (manufactured by Texttechno) at a tension rate of 60 mm / min, and the strength was calculated by dividing this strength by the fineness. Fiber strength was measured for 10 or more randomly selected fibers, and the average value was taken as the average fiber strength.

[Number of buckling parts present in the fiber]
The molded body was immersed in a 5% by mass hydrochloric acid aqueous solution at 20 ° C. to dissolve the cement, and then 20 fibers were taken out with tweezers. The fiber was immersed in warm water at 80 ° C. in which a blue dye was dissolved for 30 minutes, spread on a slide glass so as not to overlap as much as possible, and then a cover glass was placed thereon to obtain an evaluation sample. This evaluation sample was magnified and observed with a video microscope manufactured by Keyence Corporation, the length of each fiber was measured, and the number of dyed portions of buckling portions present in all fibers was counted. Thereafter, the number of buckling portions per 1 mm of fiber was calculated by the following formula.
Number of buckling portions present per 1 mm of fiber (pieces / mm) = total number of buckling portions counted (pieces) / total length of 20 fibers (mm)

[Specific gravity fluctuation range]
Twenty pieces of 5 cm square were cut out from the hydraulic molded body, and the specific gravity (local specific gravity) of each piece was measured using a specific gravity measurement kit AD-1653 manufactured by A & D. Then, after calculating the average value of the local specific gravity of the 20 cut pieces as the average specific gravity of the hydraulic molded body, the local specific gravity and the average specific gravity of the 20 cut pieces are compared, and the specific gravity having the largest difference is calculated. The range of fluctuation was calculated by dividing the difference by the average specific gravity.
Specific gravity fluctuation range (%) = local specific gravity / average specific gravity having maximum difference with respect to average specific gravity × 100

[Bending strength of cut piece]
From the hydraulic molded body, six cut pieces were cut into strips of 5 cm width and 16 cm length, and the cut pieces were dried at 40 ° C. in order to adjust the moisture content at the time of measurement of the cut pieces. Dry for 72 hours on a machine. The measuring method of bending strength was measured according to JIS A1408, and an average value was calculated from the obtained results to obtain bending strength. The bending strength was measured using an autograph AG5000-B manufactured by Shimadzu Corporation with a test speed (loading head speed) of 2 mm / min and a bending load span of 146 mm using the central loading method.

[Bending strength fluctuation range]
Similarly to the above, six cut pieces were cut out and the bending strength was measured according to JIS A1408. Thereafter, an average value was calculated from the bending strength result of the hydraulic molded body to obtain an average bending strength, and the fluctuation range was calculated by dividing the bending strength difference having the largest difference by the average bending strength.
Bending strength fluctuation width (%) = cut piece bending strength having maximum difference with respect to average bending strength / average bending strength × 100

[Impact strength test method]
Similarly to the above, six cut pieces were cut out and Charpy impact strength was measured in accordance with Charpy impact test method JIS K7111 No. 1. An average value was calculated from the obtained results and defined as Charpy impact strength.

[Charpy impact strength fluctuation range]
Similarly to the above, six pieces were cut out and Charpy impact strength was measured according to JIS K7111 No. 1. Thereafter, an average value was calculated from the Charpy impact strength results of the hydraulic molded body to obtain an average Charpy impact strength, and the fluctuation range was calculated by dividing the Charpy impact strength difference having the largest difference by the average Charpy impact strength.
Bending strength fluctuation width (%) = cut piece bending strength having maximum difference with respect to average bending strength / average bending strength × 100
In the examples and comparative examples, the following components were used.
(fiber)
PVA1: polyvinyl alcohol fiber (vinylon), average fiber diameter 7 μm, manufactured by Kuraray Co., Ltd. PP: polypropylene fiber, average fiber diameter 14 μm
PVA2: polyvinyl alcohol fiber (vinylon), average fiber diameter 27 μm, manufactured by Kuraray Co., Ltd. PVA3: polyvinyl alcohol fiber (vinylon), average fiber diameter 39 μm, manufactured by Kuraray Co., Ltd. It cut | disconnected and used so that it might have a predetermined aspect ratio in an Example and a comparative example.
(cement)
・ Normal Portland cement: Taiheiyo Cement (aggregate)
・ No. 6 silica sand: Toyo Materan

[Example 1]
<Kneading process>
In a container charged with 28 parts by mass of water so that the water / cement ratio (W / C) is 45% by mass, a reciprocating agitator [reciprocating agitator agitator, revolving angle: 90 ° 1/4 turn), manufactured by Shimazaki Engineering Co., Ltd., 62 parts by weight of ordinary Portland cement and 37.5 parts by weight of No. 6 silica sand were put into a container and kneaded for 60 seconds. Next, 0.5 parts by mass of PVA1 was charged, and a reciprocating rotary stirrer (reciprocating rotary stirrer agitator, rotation angle: 90 ° (1/4 rotation), manufactured by Shimazaki Engineering Co., Ltd.) was used 400 times / minute. Kneading at a reciprocating rotational speed of 90 seconds.

<Molding process>
The kneaded material obtained by the kneading step was poured into a mold having a width of 50 cm and a length of 180 cm, and then filled with a target thickness of 10 mm.
The kneaded material filled in the mold was pressed using a vibration press machine while applying a vibration of 200 Hz and an amplitude of 1 μm at a pressure of 40 MPa. Subsequently, it was kept for 24 hours at a temperature of 50 ° C. and a humidity of 98% for primary curing. Thereafter, for secondary curing, the molded body after the primary curing was wrapped in a compress and cured for 28 days in an environment of a temperature of 20 ° C. and a humidity of 60%.
Table 1 shows the characteristics of the obtained hydraulic molded body. In addition, the number of fibers in the hydraulic molded body described in the table is a value calculated by dividing the added fiber weight by the specific gravity of the fiber and further dividing by the volume per fiber.

[Example 2]
A hydraulic molded body was obtained in the same manner as in Example 1 except that PVA1 was changed to 1.5 parts by mass. Table 1 shows the characteristics of the obtained hydraulic molded body.

[Example 3]
A hydraulic molded body was obtained in the same manner as in Example 1 except that 0.5 part by mass of polypropylene fiber was used as the alkali-resistant fiber. Table 1 shows the characteristics of the obtained hydraulic molded body.

[Example 4]
A hydraulic molded body was obtained in the same manner as in Example 2 except that the rotational speed of the reciprocating rotary stirrer was 1200 times / minute. Table 1 shows the characteristics of the obtained hydraulic molded body.

[Example 5]
A hydraulic molded body was obtained in the same manner as in Example 1 except that 2.0 parts by mass of PVA2 was used as the alkali-resistant fiber. Table 1 shows the characteristics of the obtained hydraulic molded body.

[Example 6]
A hydraulic molded body was obtained in the same manner as in Example 1 except that 2.0 parts by mass of PVA3 was used as the alkali-resistant fiber. Table 1 shows the characteristics of the obtained hydraulic molded body.

[Comparative Example 1]
A hydraulic molded body was obtained in the same manner as in Example 1 except that the alkali-resistant fiber was not used. Table 1 shows the characteristics of the obtained hydraulic molded body.

[Comparative Example 2]
A hydraulic molded body was obtained in the same manner as in Example 2 except that a mortar mixer (manufactured by Nikko Co., Ltd., Model No. TMM-1) was used as the stirrer, and the rotation speed was 200 times / minute. Table 1 shows the characteristics of the obtained hydraulic molded body.

[Comparative Example 3]
A hydraulic molded body was obtained in the same manner as in Example 2 except that an Eirich mixer (manufactured by Nihon Eirich, model number R08) was used as a stirrer. Table 1 shows the characteristics of the obtained hydraulic molded body.

[Comparative Example 4]
A hydraulic molded body was obtained in the same manner as in Example 2 except that a Nauta mixer (manufactured by Hosokawa Micron Corporation, model number VN-5) was used as a stirrer, and the rotation speed was 200 times / minute. Table 1 shows the characteristics of the obtained hydraulic molded body.

  In the hydraulic molded body of the present invention having a specific gravity fluctuation range of 15% or less (Example 2), the same number of the same PVA fibers is used as compared with the hydraulic molded body having a specific gravity fluctuation range exceeding 15%. Also, it was shown that the bending strength is remarkably high and the reinforcing performance is excellent. By using a reciprocating rotary stirrer, a hydraulic compact with a small specific gravity fluctuation range (that is, excellent in uniform dispersibility) can be obtained. By controlling the stirring conditions, hydraulic properties can be obtained without damaging the fibers. It was confirmed that the fibers can be uniformly dispersed in the molded body, and a hydraulic molded body having high strength can be obtained. Further, in the hydraulic molded body of the present invention having a specific gravity fluctuation range of 15% or less, the bending strength and Charpy impact strength are high, the strength is excellent, and the fiber is uniformly dispersed, whereby the bending strength is increased. It was also confirmed that the fluctuation range of the Charpy impact strength was small.

Claims (9)

A hydraulic molded body comprising alkali-resistant fibers,
The variation width of the specific gravity of each of the cut pieces is 15% with respect to the average specific gravity of 20 cut pieces that are equally cut from the whole or a part of the molded body so that the length and width are 3 to 7 cm, respectively. The following is a hydraulic molded body.   The hydraulic molded body according to claim 1, wherein the number of buckling portions of the alkali-resistant fiber is 0.5 or less per 1 mm of fiber length.   The hydraulic molded body according to claim 1 or 2, wherein the alkali-resistant fiber has an aspect ratio of 20 to 2,000. Hydraulic moldings 1 m ³ per, 1.0 × ¹⁰ 5 to 1.0 comprising a × ^{10 13} present alkali-resistant fibers, hydraulic molding according to any one of claims 1 to 3. The hydraulic molded body according to any one of claims 1 to 4, wherein a bending strength as a cut piece of 5 x 16 cm is 6 N / mm ² or more.   The hydraulic molded body according to any one of claims 1 to 5, wherein the alkali-resistant fiber is at least one selected from the group consisting of polyvinyl alcohol fiber, polyethylene fiber, polypropylene fiber, acrylic fiber and aramid fiber.   The manufacturing method of the hydraulic molded object in any one of Claims 1-6 which stirs and mixes the hydraulic composition and the mixture containing water, and an alkali-resistant fiber using a reciprocating rotary stirrer.   The method for producing a hydraulic molded body according to claim 7, wherein vertical convection is generated by a reciprocating rotary stirrer, and the mixture containing the hydraulic composition and water and the alkali-resistant fiber are stirred and mixed.   The method for producing a hydraulic molded body according to claim 7 or 8, wherein the stirring blade of the reciprocating rotary stirrer is reciprocated at a reciprocating rotational speed of 200 times / min to 1000 times / min.