JP2001316156A - Hydraulic paste and fiber-reinforced cured body using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a fiber-reinforced hydraulic hardened body with toughness and aseismaticity and a hydraulic paste as a base material of the hardened body. SOLUTION: The paste contains at least a hydraulic material, water and a reinforcing fiber whose part is a polyvinyl alcohol fiber with thickness of >=8 dtex and <55 dtex and strength of >=8 cN/dtex. Compression strength of the standard hardened body is 45-70 MPa.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber-reinforced hydraulically cured product having high toughness and excellent earthquake resistance, a hydraulic paste capable of providing the cured product, and a method for producing the fiber-reinforced hydraulically cured product.

[0002]

2. Description of the Related Art Conventionally, hydraulic materials such as cement and gypsum have low tensile strength and are fragile, and thus have been reinforced with reinforcing fibers such as metal fibers, rock fibers, glass fibers, and organic fibers. . Above all, polyvinyl alcohol (PVA) fibers are widely used as reinforcing materials for hydraulic materials because they have excellent mechanical performance and high affinity with hydraulic materials.

[0003]

However, in the conventional hydraulically cured product, cracking when an external stress is applied is effectively suppressed by incorporating reinforcing fibers, and as a result, excellent bending strength is obtained. However, once cracks occur, individual breakage of single fibers occurs in a chain reaction, and there is a problem that the toughness of the molded article is significantly reduced and brittle fracture occurs. In view of the above, in recent years, studies have been made on hydraulically molded articles having excellent seismic resistance so that the toughness does not decrease even after the occurrence of cracks (JP-A-10-36150 and JP-A-10-236831). It is an object of the present invention to reduce toughness even after cracking, toughness and
An object of the present invention is to provide a hydraulic cured product having excellent impact resistance, a paste capable of providing the cured product, and a method for producing the hydraulic cured product.

[0004]

According to the present invention, there is provided (1) a paste containing at least a hydraulic material, reinforcing fibers and water, wherein at least a part of the reinforcing fibers has a fineness of 8 dte.
(2) (1) A hydraulic paste characterized by being a polyvinyl alcohol-based fiber having a strength of 8 cN / dtex or more and a compressive strength of 45 to 70 MPa of a standard molded body obtained from the paste. )
And (3) a method for producing a fiber-reinforced hydraulically cured product obtained by curing the paste described in (1).

[0005]

First, in the present invention, it is necessary to use a specific PVA-based fiber (fiber A) as a reinforcing fiber. Unless such fibers are used, it is difficult to obtain a hydraulically cured product having excellent toughness. First, it is necessary to set the fineness of the fiber A to 8 dtex or more, preferably 10 dtex or more from the viewpoint of ensuring uniform dispersion of the fiber. If the fineness is too small, a fiber ball or the like is likely to be generated, and the flexural strength and toughness of the cured product become insufficient. In addition, from the viewpoint of ensuring sufficient adhesiveness with a hydraulic material and efficiently transmitting an external stress to obtain a cured product having high toughness, the fineness of fineness A needs to be less than 55 dtex, preferably 52 dtex or less. There is. It is preferable that the fineness is large from the viewpoint of obtaining a sufficient reinforcing effect by increasing the uniform dispersibility of the fiber, but when the fineness is too large, the external stress is efficiently transmitted,
In addition, it is difficult to efficiently suppress the expansion of cracks, and it is difficult to obtain a cured product having high toughness. From the above, it is preferable that the fineness of the fiber A be in the above range.
The fiber length of the fiber may be set according to the fineness, the composition of the paste, etc., but from the viewpoint of uniform dispersibility, the fiber length is preferably 100 mm or less, particularly preferably 50 mm or less, and more preferably 30 mm or less, in view of bridging effect and the like. From, the fiber length is 3
mm or more, particularly preferably 5 mm or more, more preferably 8 mm or more.

In order to enhance the reinforcing effect and obtain a sufficient bridging effect, the fiber A has a strength of at least 8 cN / dtex, preferably at least 10 cN / dtex, more preferably at least 1 cN / dtex.
It is necessary to be 1 cN / dtex or more. If the strength of the fiber is too low, not only the bending strength of the obtained cured product becomes small, but also the bridging fiber that suppresses crack expansion easily breaks, resulting in poor toughness. In addition,
Since the frictional resistance generated when stress is applied to the cured body is generated in proportion to the surface area of the fiber, the tensile force (frictional resistance) applied to the fiber having a smaller fineness increases. Therefore, it is preferable that the thinner the fiber, the higher the strength. The upper limit of the strength of the fiber A is not particularly limited, but is generally 100 cN / dtex or less. In some cases, a hydrophobic substance such as an epoxy resin, a polyolefin-based resin, a polyethylene oxide resin, or a fluorine-based compound may be added or coated to reduce the affinity for the matrix, and PVA modified with a hydrophobic group may be applied to the surface. You may give. At this time, it is preferable that the adhesion rate to the fiber is about 0.1 to 10% by mass.

Of course, a fiber other than the fiber A may be blended as a reinforcing fiber as long as the effect of the present invention is not impaired. For example, PVA fiber other than fiber A, polyolefin fiber (polypropylene fiber, polyethylene fiber, etc.), acrylic fiber, polyamide fiber (including aramid fiber), polyester fiber (molten liquid crystalline polyester, polyethylene Naphthalate)
Polybenzoxazole fibers, rayon fibers (polynosic rayon fibers, solvent-spun rayon fibers, etc.) and inorganic fibers (glass fibers, steel fibers, etc.) can be used.
Wood pulp or the like can also be used. However, from the viewpoint of efficiently obtaining the effects of the present invention, it is preferable that the main component of the reinforcing fiber to be mixed is the fiber A, specifically, 60% by mass or more, particularly 70% by mass or more, and further 90% by mass or more. Is preferably the fiber A. The amount of the reinforcing fiber is not particularly limited, but from the viewpoint of sufficiently obtaining the reinforcing effect, 0.1% by volume or more, particularly 0.5% by volume or more, more preferably 0.8% by volume or more. From the viewpoint of ensuring uniform dispersion of the reinforcing fibers and sufficiently exhibiting the reinforcing effect, the volume is preferably 5% by volume or less / formed body, particularly preferably 3% by volume or less / formed body.

[0008] A hydraulic paste may be prepared using at least the reinforcing fiber, hydraulic material and water. However, in order to obtain a hydraulic cured product having not only a high bending strength but also a high toughness, it is necessary to use a hydraulic paste in which the compression strength of the standard molded product is 45 to 70 MPa. Heretofore, it has been considered that a hydraulically hardened body having high compressive strength is preferable from the viewpoint of durability and the like of the hydraulically hardened body.However, the present inventors have proposed to improve the toughness and earthquake resistance of the hydraulically hardened body. It has been found that it is necessary to use a specific reinforcing fiber and to reduce the compressive strength of the standard molded body. Specifically, it is necessary that the compressive strength of the standard molded body obtained from the paste is 70 MPa or less. That is, in the compact having a small compressive strength, the first crack is easily generated by the external stress, but the stress generated when the first crack is generated is small. Therefore, even if a crack occurs, the bridging (crosslinking) effect of the reinforcing fiber is exerted, and the crack is prevented from further expanding,
Furthermore, since the external stress is transmitted to other fibers before the bridging fiber breaks, the external stress can be shared by a large number of fibers. Therefore, even after the first crack has occurred, the molded body has excellent toughness and earthquake resistance without significantly lowering toughness.

The above fact can be confirmed from the fact that a large number of cracks (multi-cracks) occur in the fracture surface of the cured product when a bending test is performed on the molded product. When the first crack occurs, a bridging (cross-linking) effect by the reinforcing fiber is exerted to suppress the expansion of the crack. Further, a new crack is generated near the first crack, and the bridging effect by the reinforcing fiber also occurs in the crack. Is played. As described above, one crack induces the occurrence of another crack, and the bridging effect of the reinforcing fiber is exerted at each crack, so that the brittle fracture of the hardened body is suppressed, and the crack is excellent in toughness and earthquake resistance. Become. In the cured product with low compressive strength, the cracks formed are very small in width and do not cause fatal damage to the molded product,
Further, since the stress generated in the crack is reduced, the crack expansion can be suppressed by the reinforcing fiber.

On the other hand, when the compression strength of the molded article is too high,
Although cracks due to external stress are unlikely to occur, a first crack is generated when an external stress of a certain value or more is applied, and the stress generated when the first crack is generated increases. Therefore, the bridging fiber present in the crack portion breaks before transmitting the external stress to other fibers, and therefore, even when the above-described fiber A is used, the toughness after the first crack occurs is significantly reduced. It becomes a molded body with low toughness and earthquake resistance. In such a molded article, the width of the first crack is much larger than that of the above-mentioned molded article, and in the molded article, substantially only the first crack is generated and the above-described multi-crack is not generated. In addition, fibers other than PVA-based fibers have low affinity with hydraulic materials, so that "leaving out" easily occurs, a sufficient bridging effect is not exerted, and external stress cannot be transmitted effectively. In addition, even if the PVA fiber is a fiber other than the fiber A specified above, the surface area per fiber is too large or too small, so that the balance between the adhesive force at the contact interface with the matrix and the frictional resistance is lost. In addition, since the bridging effect is easily broken, the ability to transmit external stress becomes insufficient, and a cured product having high toughness cannot be obtained. Therefore, it is necessary to use the fiber A in order to obtain a cured product having high toughness. Therefore, it is possible to use a reinforcing fiber other than the fiber A in combination for the purpose of increasing the mechanical performance (bending strength and the like) of the cured body and for suppressing the drying shrinkage crack, but it increases the toughness of the molded body. Therefore, it is necessary to use the fiber A.

However, if the compressive strength is too low, the matrix itself will be broken before the bridging effect is exerted by the reinforcing fibers, so that a molded article having high toughness cannot be obtained. Therefore, the compressive strength of the standard molded body needs to be 45 MPa or more, preferably 50 MPa or more. Incidentally, the compressive strength of the standard molded body according to the present invention,
It refers to the compressive strength of a hydraulic molded body obtained by the method described in the examples using a sample paste. By using a paste in which the compressive strength of the standard molded product falls within the above range, a high-performance hydraulically cured product can be obtained. The compressive strength of the standard molded body can be adjusted by changing the type and amount of the hydraulic material, water, reinforcing fiber, aggregate, and other additives. Further, from the viewpoint of making it difficult to suppress the generation of the first crack, the bending strength (MOR) of the standard molded body is 12 MPa or more, and furthermore, 13 MPa.
As described above, a paste of 14 MPa or more is more preferable.

[0012] The paste of the present invention comprises a hydraulic material, a reinforcing fiber.
It can be prepared by kneading fibers and water at least.
The hydraulic material that can be used in the present invention is not particularly limited.
Ko, gypsum slag, magnesia and the like,
Cement, especially Portland cement, even ordinary por
Strand cement can be suitably used. Above all, C _Three
A (calcium aluminate) with a lower amount
It is preferable from the viewpoint of increasing the fluidity of the paste. Of hydraulic material
The blending amount should be adjusted to increase the mechanical performance of the cured product.
800 kg / m^ThreeAbove, especially 900 kg / m^Three
More than 1000kg / m^ThreeAbove and 11
00kg / m^ThreePreferably, the flow rate of the paste
To reduce the dynamics and the compressive strength of the cured product moderately
Are 1500kg / m^ThreeBelow, especially 1400 kg / m^Three
Below, 1300kg / m^ThreePreferably
No.

As the water used in the present invention, for example, tap water, river water and the like may be used, and the unit water amount in the paste is preferably 300 kg / m ³ or more, particularly preferably 320 kg / m ³ or more. By increasing the unit water amount, the fluidity and workability of the paste can be improved. Generally, it is considered that increasing the unit water amount of the paste is not preferable because the strength and the like of the hydraulic hardened body is reduced. However, in the present invention, it is sufficient to increase the unit water amount because the unit is reinforced by the specific fiber A. Mechanical properties, and by increasing the unit water amount, the compressive strength of the cured product is appropriately reduced, so that a favorable effect can be obtained from the viewpoint of toughness. However, the preferred unit water amount varies depending on the configuration of the hydraulic material, the reinforcing fibers, and the like constituting the paste. Therefore, it is preferable to appropriately set the unit water amount in accordance with the compressive strength and fluidity of the standard molded body. From the point of workability, the flow value of the paste is 120m
m or more, particularly preferably 130 mm or more, particularly 140 mm or more, and from the viewpoint of cured body performance, it is preferably 300 mm or less, particularly 170 mm or less. From the viewpoint that the compressive strength and bending strength of the cured body are not unnecessarily reduced, the unit water amount of the paste is set to 600 kg / m ^3.
Not more than 500 kg / m ³ , especially 450 kg / m ³
m ³ or less. From the same point, it is preferable to set the water / hydraulic material ratio (mass ratio) in the paste. From the viewpoint of appropriately reducing the compressive strength of the cured product and increasing the fluidity of the paste, it is 0.25 or more. In particular, it is preferably at least 0.28, and from the viewpoint that the compressive strength, bending strength and the like of the hardened body are not reduced more than necessary, 0.42
Hereinafter, it is particularly preferable to set it to 0.40 or less.

Further, an aggregate may be further added. However, it is not preferable to mix coarse aggregate, and it is preferable to use fine aggregate from the viewpoint of effectively transmitting stress by the reinforcing fiber to obtain a hardened body having high toughness.
As described above, increasing the proportion of water in the slurry improves the fluidity, and tends to reduce the compressive strength of the cured body. However, by appropriately blending fine aggregate, the compressibility is improved while improving the fluidity. A decrease in strength can be suppressed, and an excellent effect can be obtained. The blending amount of the fine aggregate is preferably about 10 to 50% by mass of the hydraulic material, particularly preferably 20 to 40% by mass.
kg / m ³ or more, further 200 kg / m ³ or more, especially 30
It is preferably at least 0 kg / m ^{3, and} more preferably at most 600 kg / m ³ from the viewpoint of fluidity and the like.

Further, other additives may be added.
From the viewpoint of increasing the mechanical performance of the hydraulic molded body without impairing the fluidity of the paste, it is preferable to add a water reducing agent, especially a high-performance AE water reducing agent. The applicable water reducing agent is not particularly limited, and examples thereof include high-performance AE water reducing agents such as polycarboxylic acid type, lignin sulfonic acid type, naphthalene sulfonic acid type, and melamine sulfonic acid type. When the amount of water is increased in order to reduce the compressive strength of the cured product or increase the fluidity, a remarkable effect can be obtained by adding such a high-performance AE water reducing agent. Among them, when a polycarboxylic acid-based high-performance AE water reducing agent is used, the dispersibility of the fiber A is remarkably improved, so that the fiber A can be used more preferably. Although the reason for improving the dispersibility of the fiber A is not clear, it is presumed that the linear structure of the water reducing agent improves the dispersion state by bonding the water reducing agent and the fiber by hydrogen bonding with the PVA-based fiber. . Polycarboxylic acid-based high-performance AE
Specific examples of the water reducing agent include, for example, “Tupole” manufactured by Takemoto Yushi, “Darlex Super” manufactured by Denka Grace, “Leo Build” manufactured by NMB, “Parick” manufactured by Fujisawa Pharmaceutical, “Mayty” manufactured by Kao, and “Suntory” manufactured by Sunflow. Flow "and the like. The addition amount of the water reducing agent may be appropriately set depending on other compounding materials and the like. Usually, about 0.2 to 1% by mass is required for the hydraulic material,
Add more than about 2 times in excess, specifically 0.5-3% by mass
It is preferable to add a certain amount. Specifically, 1 kg / m ³ or more, particularly preferably formulated 3 kg / m ³ or more, preferably set to 30kg / m ³ or less from the viewpoint of the cured product performance.

It is preferable to add a viscosity agent from the viewpoint of uniformly dispersing the components and suppressing the breathing. By adding such a viscosity agent, the viscosity of the paste increases, and the shearing force between the fibers or between the fibers and the matrix increases, so that the fibers tend to be separated into single fibers, so that an excellent effect is obtained. In particular, when the amount of water is increased in order to reduce the compressive strength of the molded body, the dispersibility of each material is increased, but the fibers are difficult to be formed into a single fiber. Dispersibility can be significantly improved. The usable viscosity agent is not particularly limited, but a cellulose compound, particularly a cellulose compound having an alkoxy group (among others, one or more cellulose compounds selected from methylcellulose, propylmethylcellulose and hydroxyethylmethylcellulose) is preferably used. You. Among them, a methoxy group, an ethoxy group, a propoxy group, a hydroxypropoxy group, a cellulose compound substituted with one or more alkoxy groups selected from hydroxyethoxy groups is preferably used, and a glucose ring unit is preferably used. 1.
What substituted 5 to 2.5 hydroxyl groups with an alkoxy group can be used more suitably.

The amount of the viscous agent added depends on the fluidity of the paste,
What is necessary is just to determine suitably according to the dispersibility of a fiber, etc. In general, as the degree of polymerization of the viscosity agent increases, the viscosity of the paste increases with a small amount of addition.
000mPa · s or more, sometimes 100000m
Those having a pressure of about Pa · s are widely used. Although it is possible to use such a viscosity agent in the present invention,
In the present invention, 2000 to 8000 mPa · s, particularly 3 mPa · s
A more excellent effect can be obtained when the viscosity agent is used at 000 to 5000 mPa · s. The amount of addition is 0.1 to 1% by mass relative to the water constituting the paste, particularly 0.3 to 0.5%.
It is preferable to set it to about mass%. Specifically, 0.1 to
It is preferable to add about 10 kg / m ³ .

Such a material may be uniformly mixed to prepare a hydraulic paste. The method of adding the material, the order of addition, and the kneading method are not particularly limited. Next, the obtained paste is molded as required, and then cured to produce a cured product. The method for producing the cured product of the present invention is not particularly limited, and examples thereof include a spray molding method, an injection molding method, a pressure molding method, a vibration molding method, a combined vibration and pressure molding method, a centrifugal molding method, and a winding molding method. , Vacuum molding, and extrusion molding can be used. Of course, the present invention also includes an article (molded body) obtained by painting as a plastering material. In the present invention, a remarkable effect is obtained particularly when kneading and molding are performed. Note that kneading molding according to the present invention refers to a method of uniformly kneading a muddy matrix and fibers in a system in which water is present, and then molding the mixture into a desired shape by the molding method described above. It is clearly distinguished from the conventional papermaking method. What is necessary is just to shape | mold by the said method and to cure | harden as needed. The curing method and the curing period are not particularly limited, and may be performed by a desired method such as room temperature curing, autoclave curing, steam curing, and underwater curing. The cured product obtained according to the present invention is excellent in toughness, for example, when a bending test is performed on a standard molded product obtained from the paste of the present invention, the flexure at the time of bending strength development is 10 mm or more,
Furthermore, it becomes 11 mm or more, especially 13 mm or more. This is equivalent to several tens of times when reinforced with steel fibers.

The molded article of the present invention can be any product, for example, pier reinforcement, pier beam, building column, formwork, underground wall, deep building material, marine / underwater structure, high altitude building All cement, concrete moldings and secondary products such as articles, manholes, slate boards, pipes, wall panels, floor panels, roofing panels, partitions, road pavement, tunnel lining, slope protection, concrete factory products, etc. Can be used for products. Further, the present invention is not limited to the above-mentioned cement products, and can be applied to structures other than these, interior and exterior members of buildings, and civil engineering materials. Further, it may be used as a plastering mortar, a machine base, a reactor pressure vessel, a container for liquefied natural gas, or the like. Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited to the examples.

[0020]

[Example] [Fineness dtex] The apparent fineness was measured at n = 5 or more by measuring the weight of a given test length of the obtained fibrous material.
The average was determined. In addition, the fineness could not be measured by measuring the weight of a certain yarn length (fine denier fiber) was measured by a vibroscope.

[Fiber strength cN / dtex] Temperature 20 in advance
The fibers were allowed to stand for 24 hours in an atmosphere of 65 ° C. and a relative humidity of 65% to adjust the humidity.
The fiber strength was measured in cm / min using an Instron tester “Autograph manufactured by Shimadzu Corporation”. The fiber length is 20
If it is shorter than cm, the maximum length of the sample within the possible range is measured as the grip length.

[Flow value mm] A cast iron cylinder having an upper side diameter of 7 cm, a lower side diameter of 10 cm, and a height of 6 cm has a diameter of 30 cm.
cm of the cast iron disk, and the cylinder was gently stripped vertically after filling the cylinder with hydraulic paste and the paste was allowed to flow onto the disk. Then, after the disk is hit 15 times, the diameter of the paste spread by the hit or the like is measured in mm. If the spread does not become circular, the average value of the maximum diameter and the minimum diameter is used as the flow value.

[Standard molded body] A hydraulic paste is poured into a predetermined mold, and the surface is lightly rubbed with a hand four to five times.
After wrapping in a polyethylene sheet at 65 ° C. and standing for 24 hours, it was demolded and cured in water at 20 ± 1 ° C. for 27 days to produce a standard specimen. [Compressive strength MPa] A cylindrical body (standard molded body) having a diameter of 5 cm and a height of 10 cm was molded into a sample, and 0.25 N / sec.
/ By applying a load at an increased speed of mm ² JIS A1108
-Measured according to 1993. [Bending strength MPa, deflection mm] A three-point bending test was performed using a standard molded body under the following conditions, and the bending stress when the maximum load occurred was defined as the bending strength, and the deflection when the bending strength was developed was read and evaluated. . Apparatus Shimadzu Autograph AG5000-B Sample Thickness 10 mm, width 60 mm, length 240 mm (standard molded body) Test speed 0.5 mm / min, 3 equally divided bending spans 180 mm

Examples 1 to 6, Comparative Examples 1 to 6 Ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.), Toyoura standard sand, and methylcellulose as a viscosifying agent (“High-Metroze 90SH400” manufactured by Shin-Etsu Chemical Co., Ltd.)
0 ") was added and kneaded for 1 minute, and water and a high-performance AE water reducing agent (" Reobuild SP-8N "manufactured by NMB Co.) were added and kneaded for 30 seconds. Then, after kneading, kneading was further performed for 90 seconds, reinforcing fibers were added, kneading was performed for 30 seconds, followed by scraping, and kneading was further performed for 90 seconds to prepare a hydraulic paste having the composition shown in Table 1. A standard molded body was manufactured from the obtained hydraulic paste, and the performance was evaluated. Table 1 shows the results. The blending amount of each material other than the fibers in Table 1 is the blending kg per 1 m ³ .

[0025]

[Table 1]

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hisashi Suemori 1-2-1, Kaigandori, Okayama City Inside Kuraray Co., Ltd. (72) Inventor Hideki Hojo 1-12-13 Umeda, Kita-ku, Osaka Co., Ltd. F term in Kuraray (reference) 4G012 PA04 PA24 PB40 PC02 PC03 PC08 PC12

Claims (3)

[Claims] 1. A paste containing at least a hydraulic material, reinforcing fibers and water, wherein at least a part of the reinforcing fibers has a fineness of 8 dtex or more and less than 55 dtex, and a strength of 8 c.
A hydraulic paste comprising polyvinyl alcohol-based fibers of N / dtex or more, and a standard molded body obtained from the paste having a compression strength of 45 to 70 MPa. 2. A fiber-reinforced hydraulically cured product obtained by curing the paste according to claim 1. 3. A method for producing a fiber-reinforced hydraulically cured product, comprising curing the paste according to claim 1.