JPH11180757A - Fiber-reinforced lightweight cellular concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the effect of fiber reinforcement on the concrete (ALC (autoclaved lightweight concrete)) cured under conditions of high temp. and high pressure and also to enhance mechanical properties such as flexural strength of this concrete. SOLUTION: This concrete is produced by using powdery siliceous raw material, powdery calcareous raw material and cement as the main raw materials and mixing reinforcing para-aramide short fiber into these main raw materials. In the concrete, the fiber reinforcing para-aramide short fiber used has a fiber length that is >=2 times as long as the average cell diameter in the concrete and also <=50 mm. Of this fiber reinforcing para-aramide short fiber, the ratio of the amount of such short fiber that it has at least two ring-shaped projecting parts independent to each other, e.g. DL1, DL2 and DL3 in the figure, in the length direction, the maximum diameter of each of which projecting parts DL1, DL2 and D13 is >=1.1 times as long as the average diameter of small diameter parts DS1, DS2, DS3 and DS4 for connecting the projecting parts DL1, DL2 and DL3 to each other, to the total amount of the fiber reinforcing para-aramide short fiber is >=30 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lightweight cellular concrete excellent in bending strength and bending toughness.

[0002]

2. Description of the Related Art Light-weight cellular concrete (hereinafter sometimes referred to as ALC) is prepared by mixing water in a suitable material such as a silicate-based material such as silica stone, a calcareous material such as lime, and cement. After foaming to make it semi-plastic, it is cured in an autoclave under high temperature and high pressure (normally, a high temperature and high pressure curing method using steam is applied) to grow tobermorite crystals.

As a foaming agent used for foaming, aluminum metal powder is generally used. In general, a foaming agent is used during the kneading using a surfactant, or a foaming agent is used in advance. In recent years, a preform method of producing and mixing the same has been adopted.

[0004] The ALC produced in this manner has a characteristic that it has a low specific gravity and is lighter than water because it has a large number of air bubbles, but is very brittle and has a bending strength, a bending toughness,
There is a disadvantage that it is inferior in impact resistance and the like. Therefore, not only the product after the autoclave curing but also the strength of the foam molded product (green cake) before the autoclave curing is very weak, so that there is a problem that cracks and chips are easily generated in the manufacturing process.

It is widely known that the mixing of reinforcing fibers in ordinary cement mortars and concretes greatly improves mechanical properties, especially tensile strength, bending strength, toughness, etc. It has already been put to practical use as a cement mortar and fiber reinforced concrete material.

[0006] For lightweight cellular concrete, a method has been proposed in which fibers are mixed and reinforced as in the case of cement mortar or concrete in order to improve the above-mentioned disadvantages. Specifically, JP-A-56-37266 discloses
JP-A-56-84362, JP-A-57-1745
No. 8 discloses the use of meta-aramid fiber, stainless steel fiber, and asbestos fiber, respectively.

However, ALC is cured under high temperature and high pressure in an autoclave. Therefore, there is a problem that the meta-aramid fiber deteriorates due to heat and alkali and cannot obtain a sufficient reinforcing effect. However, there is a problem that the rust reduces the reinforcing effect in the long term even if rust prevention treatment is performed. Furthermore, asbestos fibers are currently difficult to use due to their carcinogenic problems.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 58-151363 discloses a cement concrete mixed with an aromatic polyetheramide fiber, but the cement concrete is premised on natural (normal temperature) curing. The problem of fiber degradation due to heat and alkali is not recognized.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the conventional method, improves the fiber reinforcing effect of ALC cured under high temperature and pressure, and improves the ALC with improved mechanical properties such as bending strength. The task is to provide.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a powdery siliceous raw material, calcareous raw material and ALC raw material mainly composed of cement are used for reinforcement. When a para-aramid short fiber having a specific fiber length and shape is mixed as a fiber, a desired ALC is used.
Was obtained.

Thus, according to the present invention, there is provided (1) a lightweight aerated concrete comprising a powdery siliceous raw material, calcareous raw material and cement as main raw materials, and reinforcing para-aramid short fibers mixed therein; The short fibers have a fiber length of not less than twice the average cell diameter in the lightweight cellular concrete and not more than 50 mm, and in the reinforcing para-aramid short fibers, at least two independent fibers are provided in the length direction. Para-aramid short fibers having an annular projection and having a maximum diameter of 1.1 times or more the average diameter of the small diameter portion connecting these annular projections occupy 30% by weight or more. (2) The fiber-reinforced lightweight cellular concrete according to (1), wherein the annular protrusions are present at both ends of the short fiber; Aramid short fibers, co polyparaphenylene-3,4'-diphenylene-Terefutaramido said a short fiber (1) or (2) fiber reinforced lightweight concrete according is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The reinforcing fibers to be mixed when producing the ALC of the present invention are para-aramid fibers, such as polyparaphenylene terephthalamide fibers, copolyparaphenylene / 3,4'-oxydiphenylene. -Terephthalamide fibers and the like can be mentioned. In meta-aramid fiber,
The heat-resistant alkali resistance is not sufficient, and the desired reinforcing effect cannot be obtained. Among them, copolyparaphenylene containing terephthalic acid as an acid component and paraphenylenediamine and 3,4′-oxydiphenylenediamine as amine components.
Fibers made of a 3,4'-oxydiphenylene-terephthalamide polymer are preferred because they show a good reinforcing effect.
The copolymerization molar ratio of paraphenylenediamine to 3,4'-oxydiphenylenediamine is preferably 1: 3 to 3: 1, particularly preferably about 1: 1.

Even if such para-aramid fibers are exposed to a strong alkaline atmosphere at a high temperature and a high pressure for a long time, the fiber physical properties are hardly deteriorated (in a saturated steam at 150 ° C.).
(A strong retention rate of 60% or more when treated at 10 ° C. for 10 hours), so that steam curing under high temperature and high pressure, which is often employed in the production of ALC, for example, at a temperature of 180 ° C. and a pressure of 10 kg / c
It has a high strength retention even in curing with saturated steam of m ² .

The fiber length of the reinforcing fiber must be at least twice the average cell diameter of ALC and not more than 50 mm. Here, the average cell diameter of ALC is a value obtained from bubbles existing in a compression direction cross section of a test piece for bending test described later, and when the cells of ALC are flat, the maximum diameter and the minimum diameter of the bubbles are determined. The average value is defined as the average cell diameter.

In ALC, a large number of air bubbles are present in a matrix, and for effective fiber reinforcement, it is necessary for fibers to reinforce the matrix across the air bubbles.
If the fiber length of the reinforcing fiber is less than twice the average cell diameter of the lightweight cellular concrete, it cannot be reinforced across the cells, so the mechanical properties of ALC, that is, bending strength, impact strength, toughness, etc. Is difficult to sufficiently increase.

As the fiber length of the reinforcing fiber increases, the mechanical properties such as the bending strength of the fiber reinforced ALC improve. However, when the fiber length exceeds 50 mm, the fibers are mixed with each other when mixing and stirring with the ALC raw material. The fibers are apt to be entangled and the state of dispersion of the fibers is significantly deteriorated. The average cell diameter of the lightweight cellular concrete is usually about 0.2 to 2.0 mm.

Further, the reinforcing short fiber used in the present invention has at least two annular projections independent from each other in the longitudinal direction, and the maximum diameter of each annular projection is determined by the maximum diameter of these annular projections. It is necessary that the para-aramid short fibers having an average diameter of 1.1 times or more of the connecting small diameter portion account for 30% by weight or more.

That is, there are many bubbles in ALC,
Since the bubble portion is not reinforced, the fiber reinforcing effect is smaller than that of ordinary mortar, concrete, or the like. Therefore,
In ALC, in order to obtain a sufficient fiber reinforcing effect,
The adhesion between the reinforcing fiber and the ALC is very important, and in order to sufficiently bond between the reinforcing fiber and the ALC, the reinforcing fiber has at least two annular projections, and the maximum diameter of each annular projection is It is effective to use a para-aramid short fiber having an average diameter of 1.1 times or more the small diameter portion connecting these annular projections. That is, compared with the short fiber having a uniform thickness, the short fiber having at least two annular protrusions described above is ALC
Since the pullout resistance of the fiber inside increases significantly, the reinforcing effect is greatly improved.

Here, the term "the maximum diameter is 1.1 times or more the average diameter of the small diameter portion connecting these annular projections" refers to DS1, DS2, DS3 and D in FIG.
DL1 having a diameter of 1.1 times or more the average diameter of S4,
Mean DL2 and DL3.

At this time, even if there is an annular projection, the maximum diameter of the annular projection is 1.10 of the average diameter of the small diameter portion connecting the annular projections.
If it is not one or more times, it will not be included in the annular projection in the present invention.

The short fiber according to the present invention may have at least two annular projections in its length direction. In particular, both ends of the fiber (see FIG. 2) or its vicinity (see FIG. 3). )
It is preferable to have an annular projection because the resistance to pulling out the fiber is further increased and a good reinforcing effect is obtained. Here, the vicinity of both ends means a portion where the distance L1 from the end portion E is within 20% of the total length L of the short fiber in FIG. 3, and it is desirable that the annular projection portion DL exists in this portion.

Further, in the present invention, it is necessary that the short fibers having at least two annular projections as described above occupy 30% by weight or more of the whole reinforcing short fibers. If the amount of the short fibers is less than 30% by weight, a sufficient reinforcing effect cannot be obtained.

The short fibers used in the present invention and having at least two annular projections in the longitudinal direction as described above may be prepared by, for example, spinning and drawing conditions (for example, discharge amount during spinning, spinning tension, draw ratio, etc.). ) Can be easily manufactured by intermittently changing or cutting into short fibers by cutting while applying tension and forming an annular projection using snapback at the time of cutting. it can.

The mixing amount of the reinforcing fibers has an optimum value depending on the matrix material as the ALC raw material, and is not particularly limited. However, if the mixing amount of the reinforcing fibers is too small, the reinforcing effect is reduced. It is difficult to obtain sufficiently satisfactory mechanical properties. On the contrary, if it is too large, the fibers tend to be entangled with each other at the time of mixing and stirring with the ALC raw material,
As a result, fiber balls are easily formed, and the dispersion state is deteriorated. As a result, not only the reinforcing effect is reduced, but also the cost is increased.

In general, the fiber weight is preferably 0.05% to 3.0%, more preferably 0.1% to 2.0%, particularly preferably 0.1% to 3.0% of the solid weight of the matrix material. 2 to 1.0%.

The ALC of the present invention comprises a siliceous raw material, a calcareous raw material and a cement as a main raw material, a foaming agent mixed with the main raw material, and foaming. It is produced by curing under the conditions and growing tobermorite crystals.

The tobermorite crystal has a great influence on the strength of ALC, and it is necessary that this crystal is sufficiently grown to obtain high strength. In order to sufficiently grow tobermorite crystals, it is appropriate to carry out steam curing under high temperature and high pressure in an autoclave.
C. to 220C, preferably 160C to 200C, most preferably 170C to 190C. The optimal curing time depends on the curing temperature, but at 175 ° C,
6 hours to 20 hours, preferably 7 hours to 15 hours, most preferably 8 hours to 12 hours.

When ALC is fiber-reinforced, even if a fiber having sufficiently excellent wet heat resistance is used, the fiber gradually deteriorates under curing conditions, that is, under high temperature and high alkalinity conditions. The shorter the better. Therefore, the preferable curing condition is such that the tobermorite crystal grows sufficiently and the deterioration of the reinforcing fiber is minimized.

As described above, by curing under high temperature and high pressure, tobermorite crystals gradually grow, but in the process, Ca (OH) ₂ in the matrix gradually decreases. When the X-ray analysis is performed, the Ca
The peak intensity of the (001) ₂ plane of (OH) ₂ decreases, and the peak intensity of the 002 plane of the tobermorite crystal increases. And
The peak intensity of the 002 plane of the tobermorite crystal is Ca (O
If greater than 30% of the peak intensity of H) ₂ 001 side, is sufficiently cured it can be determined that the tobermorite crystals grow well and this time, excellent mechanical properties ALC Can be obtained. The peak of the 002 plane of the tobermorite crystal was 2θ = about 7.8 °, Ca
The peak of (OH) ₂ is at 2θ = about 18.1 °.

Here, as the siliceous raw material which is one of the main raw materials of ALC, silica stone, silica sand, blast furnace slag, fly ash and the like can be used.

At this time, the average particle size of the siliceous raw material is 10 μm
When the content is below, the reaction rate during curing increases, and the conditions (temperature and time) for curing the autoclave can be relaxed. Therefore, deterioration of fibers is remarkably reduced, and a larger reinforcing effect is obtained, which is preferable.

That is, when foamed concrete is cured under high temperature and high pressure, tobermorite crystals which greatly affect the strength grow, but when a siliceous raw material having a small average particle size is used, the tobermorite crystals are grown. Since the growth rate is increased, the curing temperature and time of the autoclave can be relaxed, and foam concrete having sufficient strength can be obtained.

As a calcareous raw material which is another main raw material of ALC, quick lime, slaked lime and the like can be used.

As the cement, any cement can be used as long as it is hydraulic. For example, Portland cement, hydraulic lime, Roman cement, natural cement and the like are preferable. In addition, there are many types of Portland cement, for example, ordinary Portland cement, moderate heat Portland cement, early-strength Portland cement, low-heat Portland cement, etc. are exemplified.In the present invention, any of them may be used. it can.

The foaming agent and foaming method used for ALC are as follows:
Although not particularly limited, for example, an aluminum foaming method using aluminum metal powder is generally used. In the preform system and the mix foam system, a commonly used foaming agent such as a surfactant is used.

For mixing and stirring of the fiber and the raw material mixture, a commonly used stirrer such as a paddle mixer, a propeller mixer, and a pot mixer can be used.

In order to uniformly disperse the reinforcing fibers, the fibers may be subjected to a surface treatment with a substance such as a surfactant in advance, or
Alternatively, it can be added to the raw material blend as needed.

Curing after foam molding is usually carried out in an autoclave under saturated steam pressure conditions at about 180 ° C. for 8 to 15 hours. However, any apparatus capable of curing at high temperature and high pressure is particularly limited to this method. Not something.

The lightweight cellular concrete obtained by the above method has a specific gravity of 0.4 or more and less than 1.4, and is excellent in bending strength and bending toughness.

[0040]

The present invention will be described below in detail with reference to examples. In addition, the manufacturing method and the evaluation method of the test piece used in the Example are as follows.

(1) Method of preparing test piece Silica stone, quicklime, cement, gypsum, aluminum powder (foaming agent), reinforcing fiber and water were mixed with an omni mixer (GAR).
(BRO, model: OM-10-E, volume: 10 L) and kneaded at a stirring speed of 400 rpm for about 3 minutes to obtain a uniform slurry.

Next, this slurry is poured into a mold,
In a state where water does not evaporate, the mixture is foamed by holding at about 40 ° C. for 4 hours, and then autoclaved (175 ° C. × 9 hours).
To obtain a fiber-reinforced ALC.

The ALC main raw material was mixed with 60% silica.
Parts by weight, 19 parts by weight of quicklime, 19 parts by weight of cement,
Gypsum was 2 parts by weight, the amount of water used was 65% by weight based on the solid content, and the blending amount of reinforcing fibers was 1% by weight based on the weight of the solid content.

From about the center of the foaming direction of the ALC, the compression direction at the time of measuring the bending strength is set to be the foaming direction.
A 4 cm × 4 cm × 16 cm sample was cut out to obtain a test piece.

(2) Method of Measuring Bending Strength The test piece was adjusted so that the water content was 10% ± 2%, and measured according to a three-point bending measurement method. That is, a 10-ton tensile compression tester (TOYO BALDW)
UNIVERSAL TESTING IN
Using Strument Model UTM 10t), the center of the fulcrum distance of 10 cm was compressed at a speed of 2 mm / min, and the bending strength was determined from the highest point of the stress.

(3) Measurement method of specific gravity A test piece (4 cm × 4 cm ×
16 cm) was placed in a dryer at 60 ° C. for 24 hours to make it completely dry, and then the specific gravity (mass / volume) was determined by measuring the mass of the test piece.

Examples 1 to 5 and Comparative Examples 1 and 2 Copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fiber ("Technola T-20" manufactured by Teijin Limited)
0 ") was cut using a rotary cutter so as to have a fiber length shown in Table 1. At this time, by applying tension to the fiber and cutting the fiber, as shown in FIG. 2, annular projections (the maximum diameter of which is 1.36 of the average diameter of the small diameter portion) are formed at both ends.
Times).

The obtained short fibers (single yarn fineness: 1.5 denier (single yarn diameter: 12 μm), strength: 28.0 g / de, elongation: 4.6%) were used as reinforcing fibers, and the above fiber reinforcement was performed. ALC
Was obtained. The average cell diameter of the obtained fiber-reinforced ALC was 0.8 mm. Further, the X-ray diffraction intensity ratio (peak intensity of 002 face of tobermorite crystal / Ca (OH) ₂
Of the 001 plane) was 10.4, and it was determined that the tobermorite crystal was sufficiently grown. Table 1 shows the results of evaluating the specific gravity and bending strength of the obtained test pieces.

[0049]

[Table 1]

As is evident from Table 1, the fiber has an annular protrusion at both ends, and the fiber length is ALC average cell diameter (0.8 mm).
In the case where para-aramid fibers having a diameter twice (1.6 mm) to 50 mm (Examples 1 to 5) were used, a good reinforcing effect was obtained, but the average cell diameter of the ALC fibers (0. 8
mm) (less than 1.6 mm) (Comparative Example 1)
In the case of (2), when the reinforcing effect was extremely small, and when it exceeded 50 mm (Comparative Example 2), it was difficult to disperse the fibers in the ALC raw material, and a satisfactory reinforcing effect was not obtained.

Example 6, Comparative Example 3 In Example 3, the maximum diameter of the annular projections at both ends (the average diameter of the small diameter portion) was changed by changing the tension applied to the fiber when cutting the fiber. Was changed as shown in Table 2.
The evaluation results are as shown in Table 2. When the maximum diameter of the annular projection exceeds 1.1 times the average diameter of the small diameter portion (Example 6), a good reinforcing effect was obtained. When the ratio was less than 1.1 times (Comparative Example 3), a sufficient reinforcing effect was not obtained.

[0052]

[Table 2]

Examples 7 to 10 and Comparative Examples 4 to 6 In Example 3, the spinning and drawing conditions of copolyparaphenylene / 3,4'-oxydiphenylene / terephthalamide fiber were changed intermittently to The fiber in which the annular protrusions were intermittently formed in the length direction was cut into a fiber length of 12 mm, and as shown in Table 3, short reinforcing fibers having different numbers of annular protrusions and different positions were obtained. . The maximum diameter of the annular projection was about 1.3 times the average diameter of the small diameter portion, and the single fiber fineness, strength and elongation of the short fibers were adjusted to be almost the same as in Example 3. . In Comparative Example 4, for comparison,
Fibers having a uniform diameter in the length direction without forming an annular protrusion were used. Using these reinforcing fibers, test pieces were prepared in the same manner as in Example 3, and specific gravity and bending strength were evaluated.

The results are as shown in Table 3. In the case where the reinforcing short fiber has at least two annular projections in its length direction (Examples 7 to 10), good reinforcement was obtained. An effect was exhibited, and in particular, a remarkable reinforcing effect was exhibited when annular projections were provided at both ends (Examples 7 and 8).

On the other hand, when there is no annular projection (Comparative Example 4)
Or when there is only one annular protrusion (Comparative Examples 5 and 6)
Had a poor reinforcing effect. .

[0056]

[Table 3]

[Examples 11 to 12, Comparative Example 7] Example 3
And the short fibers for reinforcement (having annular projections at both ends) and the short fibers for reinforcement of Comparative Example 4 (having a uniform diameter with no annular projections) were used by mixing at a ratio shown in Table 4. A test piece was prepared in the same manner as in Example 3 under the other conditions, and the specific gravity and the bending strength were evaluated.

The results are as shown in Table 4, wherein the short fibers having at least two annular projections account for 30% by weight or more of the whole reinforcing short fibers (Examples 11 and 1).
In 2), a good reinforcing effect was recognized, but when it was less than 30% by weight (Comparative Example 7), the reinforcing effect was inferior.

[0059]

[Table 4]

Example 13 and Comparative Examples 8 to 10
In place of copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fiber, polyparaphenylene terephthalamide (PPTA) fiber having a single fiber fineness of 1.5 denier (manufactured by Toray DuPont Kevlar Co., Ltd. Kevlar K-29 type), polyester fiber with a single yarn fineness of 6 denier (Tetron, manufactured by Teijin Limited), vinylon fiber with a single yarn fineness of 1.6 denier (MEWLON TYPE AA, manufactured by Unitika Ltd.), single yarn fineness Was carried out in the same manner as in Example 3 except that 2.0 denier meta-type aramid fiber (manufactured by Teijin Limited, Conex) was used as a reinforcing fiber, and the fiber length and blending amount were changed as shown in Table 5. In addition, these short fibers give tension at the time of cutting, and the both ends have 1.2 mm of the average diameter of the small diameter portion.
An annular projection having a maximum diameter of 0 to 1.35 times was formed. Table 5 shows the results of evaluation of specific gravity and bending strength of the obtained test pieces.

[0061]

[Table 5]

As is apparent from Table 5, when the polyester fibers (Comparative Example 9), vinylon fibers (Comparative Example 9), and meta-type aramid fibers (Comparative Example 10) were used as the reinforcing fibers, the autoclave curing was performed. Moisture and heat resistance in the process (1)
(Strength retention after treatment in saturated steam at 50 ° C. for 10 hours) was as low as 55% or less, and fiber deterioration was severe. Therefore, almost no reinforcing effect was observed.

On the other hand, para-aramid fiber P
When PTA fiber was used (Example 13), the degradation of the fiber in the autoclave curing step was similar to the case where copolyparaphenylene / 3,4′-oxydiphenylene / terephthalamide short fiber was used as the reinforcing fiber. Since it is almost eliminated, an ALC having excellent mechanical properties can be obtained.

[0064]

The lightweight cellular concrete of the present invention uses para-aramid short fibers having a specific fiber length and shape as reinforcing fibers. It has excellent mechanical properties such as strength and is industrially highly useful, for example, as a lightweight material for construction.

[Brief description of the drawings]

FIG. 1 is an enlarged side view for explaining the shape of a reinforcing short fiber used in the present invention.

FIG. 2 is an enlarged side view showing an example of a reinforcing short fiber used in the present invention.

FIG. 3 is an enlarged side view showing another example of a reinforcing short fiber used in the present invention.

[Explanation of symbols]

 DL1, DL2, DL3, DL annular protrusion Ds1, DS2, DS3, DS4 small diameter portion E end of short fiber L1 distance from end to annular protrusion

Claims (3)

[Claims] 1. A lightweight cellular concrete comprising a powdery siliceous raw material, calcareous raw material, and cement as main raw materials, and reinforcing para-aramid short fibers mixed therein, wherein the reinforcing para-aramid short fibers comprise the lightweight cellular concrete. Having a fiber length of not less than twice the average cell diameter in the medium and not more than 50 mm, and in the reinforcing para-aramid short fiber, in the length direction thereof, having at least two annular projections independent of each other; Fiber reinforced lightweight cellular concrete characterized in that para-aramid short fibers whose maximum diameter of the annular projections is 1.1 times or more the average diameter of the small diameter portions connecting these annular projections occupy 30% by weight or more. . 2. The fiber-reinforced lightweight cellular concrete according to claim 1, wherein the annular annular projections are present at both ends of the short fiber. 3. The fiber-reinforced lightweight cellular concrete according to claim 1, wherein the para-aramid short fibers are copolyparaphenylene / 3,4′-oxydiphenylene / terephthalamide short fibers.