JPH10236861A - Hydraulic hardened body and hydraulic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hydraulic hardened body which not only hardly produces first cracks but shows high stress even when first racks are produced by using a fiber having proper adhesion property to the matrix and having high tensile strength thereby reinforcing a hydraulic hardened body. SOLUTION: This hydraulic hardened body is reinforced by a fiber and has such properties that when the body shows Amm deflection under Bkgf bending stress in the production of first cracks, the body shows 5×Amm deflection under >=0.8×Bkgf bending stress. In order to suppress production of cracks and to obtain a high bridging effect after production of cracks, a fiber having proper adhesion property to the matrix and tensile strength is preferably used. Considering these, a polyvinyl alcohol fiber having 5 to 500 denier is preferably used. It is preferable that the fiber has about 3 to 10mm length and about 50 to 300 aspect ratio, and that the fiber is compounded by 0.2 to 10wt.% in the hydraulic hardened body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic cured product and a hydraulic composition reinforced by fibers.

[0002]

2. Description of the Related Art Hydraulic materials such as cement are widely used as cement paste, cement, mortar, cement concrete and the like in the field of civil engineering and construction, and are regarded as important building materials. These have high compressive strength but low tensile strength and are brittle. In general, it is known that reinforcing agents, steel frames, and in special cases, asbestos are mixed in to cover the brittleness and reinforce the tensile strength. In recent years, fibrous materials such as organic fibers are used as reinforcing materials. It is also being considered.

When a hydraulic material is reinforced with a fibrous material, the strength of the cured product is predicted by the sum of the product of the volume fraction of both the matrix and the fibrous material and their modulus (composite rule). Such a composite rule is based on the premise that a sufficient interfacial bonding force between the reinforcing material and the matrix exists. From the above, it has been studied to increase the strength of the reinforcing fiber and to improve the adhesiveness with a hydraulic substance.

[0004]

However, if the adhesive strength between the reinforcing material and the matrix is too high, the reinforcing material is firmly fixed to the matrix when a crack or the like occurs in the cured product due to external stress. The stress is concentrated only at the local portion of the bridging single fiber (bridging fiber) existing in the crack portion, and the stress cannot be dispersed inside the fiber. The bridging fiber will break before dispersion takes place. As a result, cracks and individual fiber breaks occur in a chain reaction, and only one
It is expected from the model that catastrophic breakage is caused by the occurrence of cracks at several places.

[0005] Under such circumstances, although the reinforcing fibers having high modulus and high adhesiveness have a deterrent effect on the occurrence of cracks, the reinforcing effect after the occurrence of cracks is considered to be insufficient. In view of the above problems, the present invention has been studied only to increase the strength of the reinforcing fiber and the adhesion to the matrix to suppress the generation of cracks (to increase the stress at which the first cracks are generated). It has been found that not only the first crack is hardly generated but also a high stress is required after the first crack is generated in order to obtain an excellent hydraulically cured product.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a hydraulically hardened material reinforced with fibers, wherein the deflection when the first crack occurs is Amm, and the bending stress at this time is Bkgf, 5 × Amm A hydraulically cured product having a bending stress of 0.8 × Bkgf or more when exhibiting flexure, and a hydraulic composition containing fibers. The specimen was manufactured to have a deflection of Amm when the first crack occurred, and a bending stress at this time of B.
The present invention relates to a hydraulic composition having a bending stress of 0.8 × Bkgf or more when exhibiting a deflection of 5 × Amm when the weight is set to kgf.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The deflection at the time of the first crack occurrence is represented by A
mm, when the bending stress at this time is Bkgf, 5 ×
Bending stress when exhibiting Amm deflection is 0.8 × Bk
gf or more is required, preferably 1.0 × Bkgf or more, more preferably 1.3 × Bkgf or more. Since such a cured body has a sufficient bridging effect even after the first crack is generated, the bending load is not rapidly reduced, and the cured body exhibits high toughness. If the bending stress when exhibiting 5 × Amm deflection is small, the adhesion between the fiber and the matrix is too high and the degree of freedom of the fiber is small, so that the fiber breaks in a chain and a sufficient reinforcing effect is obtained. Absent. Conversely, if the adhesiveness between the fiber and the matrix is too small, a sufficient bridging effect cannot be obtained after the first crack occurs, resulting in "absence" and reduced bending stress.

The specific value of the bending stress varies depending on the form, size, composition, etc. of the cured product, but the donor is produced in the same manner as in the example except that the same hydraulic composition as the cured product is used. In this case, the stress at the time of occurrence of the first crack is preferably 10 kgf or more, particularly preferably 15 kgf or more, and 5 × A
A bending stress of 10 mmf or more, especially 20 kgf or more when exhibiting a deflection of mm is preferable. Note that, when the first crack occurs in the present invention, when a deflection-stress curve is created, the deflection and the stress have a substantially proportional relationship and show the maximum deflection. In the case where a flexure-bending stress curve of the cured product cannot be prepared, a donor is prepared in the same manner as in the example except that the same hydraulic composition as that of the cured product is used, and the donor may be measured.

Further, the toughness index I ₂₀ is preferably 15 or more, particularly preferably 20 or more. The toughness index referred to in the present invention is to first create a flexure-bending stress curve of the cured body,
When the deflection at the time of the first crack occurrence is A, the deflection is 0.
The area under the flexure-bending stress curve (= toughness) corresponding to 10.5 × A from (1) is divided by the area under the flexure-bending stress curve between flexure 0 and flexure A (= toughness). Value. It can be said that the larger the toughness index, the stronger the external stress, and the higher the stress after the first crack. When the toughness index of the cured product cannot be measured, a specimen similar to the example may be manufactured and measured except that the same cured composition as the cured product is used.

When a fibrous material is used as a reinforcing material, the higher the modulus of the fibrous material, the better the reinforcing effect can be obtained, as described in the composite rule described above. However, such a composite rule is applied. A region where the matrix forms an extremely small strain due to bending stress (proportional limit strength LOP: Limit of
Proportionality). Therefore, although it is expected that the LOP is increased (the crack is hardly generated) by using the fiber having a high modulus, if the adhesive force between the matrix and the fiber is too high, the strain of the matrix is increased and the crack after the crack is generated. Sufficient effects cannot be obtained in terms of improving strength and maintaining strength (improving toughness).

In order to suppress the occurrence of cracks and to obtain a high bridging effect after the occurrence of cracks, the fibers and the matrix must have not only an appropriate adhesive property but also a high tensile strength. Is preferred. Specifically, it is preferably at least 4 g / d, more preferably at least 5 g / d.

In order to obtain the effect of the present invention, the reinforcing material has an appropriate degree of freedom and a sufficient degree of freedom so that the bridging fiber is stress-dispersed inside the fiber and many other fibers after the occurrence of a crack. In order to exhibit a bridging effect, it is necessary to have an appropriate bonding force to the matrix.
The fiber having an appropriate adhesive strength is not particularly limited. For example, when a fiber having a high adhesiveness to a hydraulic substance such as a PVA-based fiber is used, if a fiber having a fineness is used, the adhesive strength is increased, so that a relatively thick fiber is used. It is preferable to use fibers having a diameter of, for example, 3d or more and 10000d or less, particularly 4d or more and 500d or less, and more preferably 5d or more and 200d or less. The fiber length is preferably about 3 to 10 mm, and the aspect ratio is preferably about 50 to 300.
The aspect ratio is obtained by dividing the fiber length by the diameter of a circle having the same area as the area of the fiber cross section.

A hydrophobic substance such as an epoxy resin, a polyolefin resin or a fluorine compound may be provided or coated to control the affinity for the matrix. Conversely, when using a fiber having a low affinity with the hydraulically hardened material such as polyethylene fiber or polypropylene fiber, use a fiber having a fineness and a high aspect ratio, or activate the fiber surface by low-temperature plasma treatment. To increase the affinity to the matrix by forming, etching, etc., indenting (pressing) or bending into a hook shape,
There is a method of performing processing such as attaching a web.

The type of fibrous material to be used is not particularly limited. However, metal fibers such as steel fibers have rust-generating properties and have a specific gravity of 7 to 8 which is problematic in terms of weight reduction. It is preferable to use an organic fiber having a specific gravity as low as 0.9 to 1.5 as a reinforcing material. For example, high polymerization degree polyethylene fiber, aramid fiber, carbon fiber, polyarylene
High-strength and high-modulus fibers such as fiber, but these have low affinity for water and are difficult to impart appropriate adhesion to the matrix, and therefore have high affinity for water and high strength. It is preferable to use a polyvinyl alcohol-based fiber or an acrylic fiber, which has high weather resistance and alkali resistance and is advantageous in terms of cost, particularly a polyvinyl alcohol-based fiber. A feature of the present invention is that the "adhesion" with the matrix, which has been set to be higher as high as before, is not excessively enhanced,
The characteristics of the present invention are further exhibited when the A-based fiber is used.

The hydraulic material used in the present invention is not particularly limited, but cement is preferred. Portland cement is a typical example. Blast furnace cement, fly ash cement, alumina cement and the like can be used. May be used in combination. Further, it can be used as a mortar or concrete in which these cements are mixed with sand or gravel. Other hydraulic materials include gypsum, gypsum slag, magnesia and the like. In addition, auxiliary agents such as mica, sepiolite, attapulgite, and pulp can be used. The method for producing the hydraulic molded product is also not particularly limited. For example, in the case of a thin plate, a long-mesh papermaking method or a Hatschek method can be employed. In the case of mortar, concrete, or the like, casting, spray molding, injection molding, or the like may be employed as the on-site molding method, and vibration molding, centrifugal force molding, extrusion molding, or the like may be used as the factory molding method. . The compounding ratio of the fibrous material in the hydraulic cured product is 0.2 to
It is preferably 10% by weight, particularly preferably 1 to 5% by weight.

The state of occurrence of cracks after the bending test is preferably such that many cracks (multi-cracks) occur on the surface on the tensile side. When the stress concentrates locally on the bridging fiber and the reinforcing material breaks, or when the bridging effect is insufficient because the fiber strength or frictional resistance is too low, only a monocrack occurs. Therefore, if only a monocrack is generated, the cured product has insufficient toughness. That is, when a bending stress is applied to the cured product, even if a crack occurs, the stress is dispersed in the bridging fiber, and the crack width is widened before the bridging fiber is cut. The fibers also exhibit a bridging effect to disperse the stress, and the reinforcing material has high strength and frictional resistance, so that an excellent reinforcing effect can be obtained even after cracks occur. Although there is a limit to the strength of a single fiber, the improvement of a large number of integral strengths having a distribution of deformation strain hinders the progress of the first crack, and cracks are generated in other parts of the matrix. Cracks will occur. Those that follow such a destruction process have excellent toughness of the cured product.

The hydraulically cured product of the present invention can be used for all products such as slates, pipes, wall panels, floor panels, shingles, partitions, road pavements, tunnel linings, slope protection, and concrete improvement products. Cement, concrete moldings and 2
It can be used for the following products.

[0018]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. [Apparent fineness Dr] The obtained fibrous material was measured for a certain test length, and the apparent fineness was measured at n = 5 or more, and the average value was obtained. 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 g / d] In an atmosphere of a temperature of 20 ° C. and a relative humidity of 65%, a test length of 20 cm (a fineness measured by a vibroscope is 2 cm), and a tensile speed of 1
The modulus was measured by an Instron tester at 0 cm / min, and the modulus was determined from its extension / load curve. When the fiber length of the sample is short, the sample length is measured as the grip length.

[Strain-Bending Stress Curve] The composition of the cured product used in the test is as follows. Specifically, ordinary Portland cement (Normal Portland cement manufactured by Chichibu Onoda) and silica (Silica # 400 manufactured by Keiwa Filter Materials)
0: specific surface area 4274 cm ² / g), a thickener (Shin-Etsu Silicon High Metroz 90SH30000), and a high-performance water reducing agent (Kao Mighty 150). Cement 100 parts by weight Silica 100 parts by weight Thickener 1.5 parts by weight PVA fiber 6.4 parts by weight Water 40 parts by weight High performance water reducing agent 2 parts by weight

These are mixed and kneaded by using a mixer (DALTON's functional mixing stirrer), and the mixture is molded by using an extruder (Honda Iron Co., Ltd. vacuum extruder HDE-3) to obtain a composite. Was. After a sheet for preventing drying was stuck and left at room temperature for 24 hours, curing was carried out in water for 28 days. A donor having a width of 25 mm and a thickness of 5 mm was prepared and subjected to a three-point bending test with a span length of 50 mm using an autograph manufactured by Shimadzu to produce a bending-bending stress curve. When the deflection and the bending stress are substantially proportional to each other and the point having the maximum deflection is defined as the first crack occurrence, the deflection A and the stress B at this time are read from the curve, and when the deflection of 5 × A is exhibited. The stress was read as well.

[Toughness index I ₂₀ ] First, a flexure-bending stress curve of the cured body is created, and when the flexure at the time of the first crack occurrence is A, the flexure is a flexure corresponding to a flexure from 0 to 10.5 × A. -The area under the bending stress curve (= toughness) was determined by dividing the area between the deflection 0 and the deflection A-the area under the bending stress curve (= toughness). [Crack state] At the time of matrix breakage in the bending test, the state of occurrence of cracks on the surface on the tensile side was observed, and it was visually judged whether it was a monocrack (mono) or a multicrack (multi).

Examples 1-4, Comparative Examples 1-3 Various P
A cured product was produced using a VA-based fiber (manufactured by Kuraray Co., Ltd.). Table 1 shows the results. In addition, FIGS. 1 to 7 show flexure-bending stress curves of the hydraulic hardened bodies obtained in the respective Examples and Comparative Examples.

[0024]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a diagram showing a flexure-bending stress curve of a hydraulic cured product obtained in Example 1.

FIG. 2 is a view showing a flexure-bending stress curve of a hydraulic cured product obtained in Example 2.

FIG. 3 is a view showing a flexure-bending stress curve of a hydraulic cured product obtained in Example 3.

FIG. 4 is a view showing a flexure-bending stress curve of a hydraulic cured product obtained in Example 4.

FIG. 5 is a diagram showing a flexure-bending stress curve of a hydraulic cured product obtained in Comparative Example 1.

FIG. 6 is a diagram showing a flexure-bending stress curve of a hydraulic cured product obtained in Comparative Example 2.

FIG. 7 is a view showing a flexure-bending stress curve of a hydraulic cured product obtained in Comparative Example 3.

Claims (3)

[Claims] 1. A hydraulically hardened body reinforced by fibers, wherein a bending when a first crack occurs is Amm, and a bending stress at this time is Bkgf, and a bending stress when exhibiting a bending of 5 × Amm. Is 0.8 × Bkgf or more. 2. A hydraulic composition containing fibers, comprising:
Using the hydraulic composition to produce a test hydraulic cured product,
Hydraulic composition wherein the bending stress at the time of the first crack generation of the specimen is Amm and the bending stress at this time is Bkgf, and the bending stress at the time of exhibiting 5 × Amm bending is 0.8 × Bkgf or more. 3. A hydraulically hardened body reinforced with 5 to 500 d of polyvinyl alcohol-based fiber, wherein the deflection when the first crack occurs is A mm, and the bending stress at this time is B.
A hydraulically hardened body having a bending stress of 0.8 × Bkgf or more when exhibiting a deflection of 5 × Amm, where kgf.