JP3433081B2 - Fiber reinforced lightweight cellular concrete - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lightweight cellular concrete having excellent bending strength and bending toughness.

[0002]

2. Description of the Related Art Light-weight cellular concrete (hereinafter sometimes abbreviated as ALC) is prepared by mixing water in an appropriate ratio with a siliceous raw material such as silica stone, a calcareous raw material such as lime, and a mixture material such as cement. After foaming to a semi-plastic state, it is cured by autoclave under high temperature and high pressure (usually a high temperature and high pressure curing method using steam is applied) to grow tobermorite crystals.

As the foaming agent used for foaming, it is common to use aluminum metal powder, but a foaming agent used for foaming during kneading using a surfactant, or a foaming agent in advance. Recently, a preform method of manufacturing and mixing is also adopted.

Since the ALC thus produced has a large number of bubbles, it has a characteristic that it has a low specific gravity and is lighter than water, but on the other hand, it is very brittle and has a high bending strength, bending toughness, and
It has the drawback of being inferior in impact resistance. Therefore, not only the product after curing in the autoclave but also the foamed molded product (green cake) before curing in the autoclave has a very weak strength, and thus cracks and chips easily occur in the manufacturing process, which is a problem.

It is widely known that, in ordinary cement mortar and concrete, mechanical properties, especially tensile strength, bending strength, toughness, etc. are greatly improved by mixing reinforcing fibers, and it is widely known that fiber reinforcement It has already been put to practical use as a cement mortar and fiber reinforced concrete material.

For lightweight cellular concrete, for the purpose of improving the above-mentioned drawbacks, a method has been proposed in which fibers are mixed and reinforced as in the case of cement mortar or concrete. Specifically, JP-A-56-37266,
JP-A-56-84362, JP-A-57-1745
It is disclosed in Japanese Patent Publication No. 8 and it is proposed to use meta-aramid fiber, stainless fiber and asbestos fiber, respectively.

However, since ALC is aged in an autoclave under high temperature and high pressure, meta-aramid fiber has a problem that the fiber is deteriorated by heat and alkali and a sufficient reinforcing effect cannot be obtained, and in stainless fiber, ALC is used. However, even if rust-proofing is applied, there is a problem that the reinforcing effect is reduced due to rust in the long term. Moreover, 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 aromatic polyether amide fiber. The cement concrete is premised on natural (normal temperature) curing. The problem of fiber degradation due to heat and alkali is not recognized.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of the conventional method, improves the fiber reinforcing effect of ALC that is cured under high temperature and high pressure, and improves mechanical properties such as bending strength. The challenge 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, a calcareous raw material and an ALC raw material containing cement as a main raw material are used for reinforcement. When para-aramid short fibers having a specific fiber length and shape are mixed as fibers, the desired ALC
It was determined that

Thus, according to the present invention, (1) in a lightweight cellular concrete obtained by mixing powdery siliceous raw material, calcareous raw material and cement as main raw materials and reinforcing para-aramid short fibers, the para-aramid for reinforcing. short fibers, more than twice the average cell diameter in said light weight cellular concrete, having the following fiber length 50 mm, and is in said reinforcing para-aramid short fibers, the lengthwise, cut into short fibers
Generated by cutting while applying tension when performing
Has at least two annular protrusions that are independent of each other and is formed by utilizing a snapback, and the maximum diameter of each annular protrusion is 1.1 of the average diameter of the small diameter portions connecting these annular protrusions. Fiber reinforced lightweight cellular concrete characterized by containing 30% by weight or more of para-aramid short fibers that are double or more times, (2) The annular projections are present at both ends of the short fibers (1). Fiber-reinforced lightweight cellular concrete of (3), and (3) para-aramid short fibers are copolyparaphenylene.3,4'-oxydiphenylene terephthalamide short fibers, (1) or (2) above. Concrete provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The reinforcing fibers to be mixed when manufacturing the ALC of the present invention are para-aramid fibers, such as polyparaphenylene terephthalamide fibers, copolyparaphenylene.3,4'-oxydiphenylene. -Terephthalamide fiber etc. can be mentioned. In the meta-aramid fiber,
Insufficient heat resistance and alkalinity prevent desired reinforcement effect. Among them, copolyparaphenylene containing terephthalic acid as an acid component and paraphenylenediamine and 3,4′-oxydiphenylenediamine as an amine component.
A fiber made of a 3,4′-oxydiphenylene terephthalamide polymer is preferable because it exhibits a good reinforcing effect.
The copolymerization molar ratio of para-phenylenediamine and 3,4'-oxydiphenylenediamine is 1: 3 to 3: 1, preferably about 1: 1.

The para-aramid fiber is hardly deteriorated in its physical properties even after being exposed to a strong alkaline atmosphere under high temperature and high pressure for a long time (150 ° C. in saturated steam).
Since the tenacity retention rate after treatment for 10 hours at 60% or more), steam curing under high temperature and high pressure that is often adopted when producing ALC, for example, temperature 180 ° C, pressure 10 Kg / c
It has a high strength retention rate even during 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 at most 50 mm. Here, the average bubble diameter of ALC is a value obtained from the bubbles present in the cross section in the compression direction of the bending test specimen described later, and when the bubbles of ALC are flat, the maximum and minimum diameters of the bubbles are Let the average value be the average bubble diameter.

In ALC, a large number of air bubbles are present in the matrix, and in order to effectively reinforce the fibers, it is necessary for the 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. It will be difficult to raise sufficiently.

The longer the fiber length of the reinforcing fiber, the better the mechanical properties such as the bending strength of the fiber reinforced ALC. However, when the fiber length exceeds 50 mm, the fibers are mixed with each other during mixing and stirring with the ALC raw material. Entanglement is likely to occur, and the dispersed state of the fibers is significantly deteriorated. As a result, the reinforcing effect is reduced, which is not suitable. The average cell diameter of the lightweight cellular concrete is usually about 0.2 to 2.0 mm.

Furthermore, the short fibers in the reinforcement used in the present invention
It is granted its lengthwise, the tension when cutting the short fibers
While snapping back caused by cutting
It has at least two mutually independent annular protrusions formed by utilizing, and the maximum diameter of each annular protrusion is 1.1 times or more of the average diameter of the small diameter portion connecting these annular protrusions. It contains para-aramid short fibers 30% by weight or more, such as
It is necessary that.

That is, many bubbles are present in ALC,
Since this bubble portion is not reinforced, the fiber reinforcing effect is smaller than that of ordinary mortar, concrete and the like. Therefore,
In order to obtain a sufficient fiber reinforcement effect in ALC,
The adhesion between the reinforcing fiber and the ALC is very important, and in order to sufficiently bond the reinforcing fiber and the ALC, at least two annular protrusions are provided, and the maximum diameter of each annular protrusion is It is effective to use the para-aramid short fibers whose average diameter is 1.1 times or more of the small diameter portion connecting these annular protrusions. That is, in comparison with short fibers having a uniform thickness, the short fibers having at least two annular protrusions described above have ALC
Since the pulling-out resistance of the fibers inside is significantly increased, the reinforcing effect is greatly improved.

Here, the term "the maximum diameter is 1.1 times or more of the average diameter of the small-diameter portions connecting these annular protrusions" means that DS1, DS2, DS3 and D in FIG.
DL1 having a diameter of 1.1 times or more the average diameter of S4,
It means DL2 and DL3.

At this time, even if the annular protrusions are present, the maximum diameter is 1. The average diameter of the small diameter portions connecting the annular protrusions is 1.
If it is not more than 1 time, it is not included in the annular projection portion in the present invention.

The short fibers in the present invention may have two or more annular projections in the length direction thereof, and in particular, both ends of the fiber (see FIG. 2) or the vicinity thereof (see FIG. 3). )
It is preferable to have an annular protrusion on the fiber because the fiber pullout resistance is further increased and a good reinforcing effect can be obtained. Here, the vicinity of both ends means a portion in which the distance L1 from the end portion E is within 20% of the total length L of the short fibers in FIG. 3, and it is desirable that the annular protrusion portion DL exists in this portion.

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

[0023] As used in the present invention, short fibers having at least two annular projections in the longitudinal direction as described above, when cutting the short fibers, cut while imparting a tension at the time of cutting
Can be readily prepared by way utilizing the snapback occurs that causes <br/> the annular protrusion formed of.

The amount of the reinforcing fibers mixed is not particularly limited because there is an optimum value depending on the matrix material which is the ALC raw material, but if the amount of the reinforcing fibers mixed is too small, the reinforcing effect is reduced. And it is difficult to obtain sufficiently satisfactory mechanical properties. On the contrary, if the amount is too large, the fibers are easily entangled with each other during mixing and stirring with the ALC raw material,
As a result of facilitating the formation of fiber balls and deteriorating the dispersed state, not only the reinforcing effect is lowered, but also the cost is increased.

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

As has been conventionally known, the ALC of the present invention comprises siliceous raw materials, calcareous raw materials and cement as main raw materials, and a foaming agent is mixed into the raw materials to foam the mixture, which is then heated in an autoclave at high temperature and high pressure. It is manufactured by curing underneath and growing tobermorite crystals.

The tobermorite crystal has a great influence on the strength of ALC, and it is necessary that the crystal is sufficiently grown in order to obtain high strength. In order to sufficiently grow the tobermorite crystals, it is appropriate to perform steam curing under high temperature and high pressure in an autoclave, and the curing temperature is 150.
C to 220 C, preferably 160 to 200 C, most preferably 170 to 190 C. The optimum curing time depends on the curing temperature, but in the case of 175 ° C,
It is 6 hours to 20 hours, preferably 7 hours to 15 hours, and most preferably 8 hours to 12 hours.

When the ALC is reinforced with fibers, even if fibers having sufficiently excellent heat and humidity resistance are used, they gradually deteriorate under curing conditions, that is, under high temperature and high alkaline conditions. The shorter the better. Therefore, a curing condition is preferred in which the tobermorite crystals grow sufficiently and the deterioration of the reinforcing fiber is minimized.

As described above, by performing curing at high temperature and high pressure, tobermorite crystals gradually grow, but in the process, Ca (OH) ₂ in the matrix gradually decreases. When X-ray analysis is performed, Ca
The peak intensity of (001) plane of (OH) ₂ decreases and the peak intensity of 002 plane of the tobermorite crystal increases. And
The peak intensity of the 002 plane of the tobermorite crystal is Ca (O
H) ₂ of more than 30% of the peak intensity on the 001 plane, it can be judged that it has been sufficiently aged and the tobermorite crystals have grown sufficiently. At this time, ALC with excellent mechanical properties was obtained. Can be obtained. The peak of the 002 plane of the tobermorite crystal is 2θ = about 7.8 °, Ca
The peak of (OH) ₂ is 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.
The following is preferable because the reaction rate during curing is increased and the autoclave curing conditions (temperature, time) can be relaxed, so that deterioration of the fiber is significantly reduced and a greater reinforcing effect is obtained.

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

As the calcareous raw material which is the other 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 preferably exemplified. Incidentally, there are many types of Portland cement, for example, ordinary Portland cement, moderate heat Portland cement, early strength Portland cement, low heat Portland cement and the like are exemplified, but any of them can be used in the present invention. 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 general. In the preform method and the mixed foam method, a generally used foaming agent such as a surfactant is used.

For mixing and stirring 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 optionally used.

For the purpose of uniformly dispersing the reinforcing fiber, the surface of the fiber is previously treated with a substance such as a surfactant, or
Alternatively, it can be added to the raw material mixture 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, but any method capable of high temperature and high pressure curing is particularly limited to this method. Not a thing.

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]

EXAMPLES The present invention will be specifically described below with reference to examples. The method for producing the test pieces used in the examples and the evaluation method are as follows.

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

Next, this slurry is cast into a mold,
Keeping water at a temperature of 40 ° C for 4 hours without foaming to foam, and then autoclave cure (175 ° C x 9 hours)
Was performed to obtain a fiber reinforced ALC.

The main ingredient of the ALC is 60 silica.
Parts by weight, quicklime 19 parts by weight, cement 19 parts by weight,
The amount of gypsum was 2 parts by weight, the amount of water used was 65% by weight based on the solid content, and the amount of the reinforcing fiber was 1% by weight based on the weight of the solid content.

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

(2) Bending strength measuring method The above test pieces were adjusted so that the water content was 10% ± 2%, and the bending strength was measured according to the three-point bending measuring method. That is, a tensile / compression tester for 10 tons (TOYO BALDW
Made by IN, UNIVERSAL TESTING IN
Using a STRUMENT MODEL UTM 10t), the center with a 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 stress.

(3) Method of measuring specific gravity A test piece (4 cm × 4 cm ×) for use in the above bending test.
(16 cm) was placed in a dryer at 60 ° C. for 24 hours to be in an absolutely dry state, and then the mass of the test piece was measured to determine the specific gravity (mass / volume).

[Examples 1 to 5, Comparative Examples 1 and 2] Copolyparaphenylene.3,4'-oxydiphenylene.terephthalamide fiber ("Technora T-" manufactured by Teijin Ltd.)
200 ") was cut into a fiber length shown in Table 1 by using a rotary cutter. At this time, by applying tension to the fibers and cutting the fibers, as shown in FIG. 2, annular protrusions (the maximum diameter of which is 1.
36 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 carried out. ALC
The test piece of 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 plane of tobermorite crystal / Ca (OH) ₂
The peak intensity on the 001 plane) was 10.4, and it was judged that the tobermorite crystal was sufficiently grown.

Table 1 shows the results of evaluation of specific gravity and bending strength of the obtained test pieces.

[0050]

[Table 1]

As is apparent from Table 1, the average bubble diameter (0.8 mm) having annular projections at both ends and a fiber length of ALC was used.
In the case of using para-aramid fiber having a size of 2 times (1.6 mm) to 50 mm (Examples 1 to 5), good reinforcing effect was obtained, but the average cell diameter (0. 8
mm) less than twice (1.6 mm) (Comparative Example 1)
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 and Comparative Example 3] In Example 3, the maximum diameter of the annular protrusions at both ends (the average diameter of the small diameter portion) was changed by changing the tension applied to the fiber when the fiber was cut. (Indicated by multiples) was changed as shown in Table 2.

The evaluation results are shown in Table 2. When the maximum diameter of the annular protrusions exceeds 1.1 times the average diameter of the small diameter portions (Example 6), good reinforcing effect is obtained. But
In the case of less than 1.1 times (Comparative Example 3), a sufficient reinforcing effect was not obtained.

[0054]

[Table 2]

[Examples 7 to 8 and Comparative Example 4 ] The reinforcing short fibers of Example 3 (having annular protrusions at both ends
No) and an annular protrusion are not formed, and the diameter is uniform in the length direction.
And used in a mixture at a ratio shown in Table 3,
Other conditions were the same as in Example 3 to prepare a test piece.
Then, the specific gravity and bending strength were evaluated.

The result is a tableThreeAs shown inAnnular protrusion
Short fibers having at least two parts are all reinforcing short fibers.
If it occupies more than 30% by weight of the body(Example7,8)
Has a good reinforcing effectIs recognized, but less than 30% by weight
(Comparative exampleFour)ThenThe reinforcing effect was inferior.

[0057]

[Table 3]

[Example 9 and Comparative Examples 5 to 7 ] In Example 3, copolyparaphenylene.3,4'-
Instead of oxydiphenylene terephthalamide fiber, polyparaphenylene terephthalamide (PPTA) fiber (Kevlar K-29 type manufactured by Toray DuPont Kevlar Co., Ltd.) with a single yarn fineness of 1.5 denier, single yarn fineness 6
Denier polyester fiber (Tetoron Co., Tetron), single fiber fineness vinylon fiber (Unitika Co., MEWLON TYPE PE AA), single fiber fineness 2.0 denier meta type aramid fiber (Teijin) Conex, manufactured by Co., Ltd.) was used as each reinforcing fiber, and the same procedure as in Example 3 was performed except that the fiber length and the compounding amount were changed as shown in Table 5. In addition, these short fibers,
At the time of cutting, tension was applied to form an annular protrusion having a maximum diameter of 1.20 to 1.35 times the average diameter of the small diameter portion at both ends.

Table 4 shows the results of evaluation of specific gravity and bending strength of the obtained test pieces.

[0060]

[Table 4]

As is apparent from Table 4 , when polyester fibers (Comparative Example 5 ), vinylon fibers (Comparative Example 6 ) and meta-aramid fibers (Comparative Example 7 ) were used as reinforcing fibers, autoclave curing was performed. Moisture and heat resistance in the process of (15
The strength retention after treatment for 10 hours in saturated steam at 0 ° C.) was as low as 55% or less, and fiber deterioration was severe, so almost no reinforcing effect was recognized.

On the other hand, the para-aramid fiber P
When PTA fibers were used (Example 9 ), as in the case where copolyparaphenylene.3,4'-oxydiphenylene terephthalamide short fibers were used as reinforcing fibers,
Since there is almost no deterioration of fibers in the autoclave curing step, ALC having excellent mechanical properties can be obtained.

[0063]

The lightweight cellular concrete of the present invention uses para-aramid short fibers having a specific fiber length and shape as the reinforcing fibers, so that even if it is cured at high temperature and high pressure, the deterioration of the fibers is small and the bending It has excellent mechanical properties such as strength and is industrially highly useful as a lightweight material for construction, for example.

[Brief description of drawings]

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

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

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

[Explanation of symbols]

DL1, DL2, DL3, DL annular protrusion D S1 , DS2, DS3, DS4 small diameter portion E short fiber end L1 distance from end to annular protrusion

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-3-153554 (JP, A) JP-A-9-295877 (JP, A) JP-A-58-145655 (JP, A) JP-A-56- 100162 (JP, A) JP 55-85457 (JP, A) JP 55-10423 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C04B 16/06 D01F 6 / 60

Claims (3)

(57) [Claims] 1. A lightweight cellular concrete comprising a powdery siliceous raw material, a calcareous raw material and cement as main raw materials and reinforcing para-aramid short fibers mixed therein, wherein the reinforcing para-aramid short fibers are the lightweight cellular concrete. the average cell diameter twice or more in, had the following fiber length 50 mm, and is in said reinforcing para-aramid short fibers, the lengthwise, switching while applying tension when cutting the short fibers
Use snapback generated by disconnection
Made a, such that at least two has an annular protrusion, 1.1 times the average diameter of the largest diameter thin portion connecting these annular protrusion of the annular projection are independent from each other para-aramid Fiber-reinforced lightweight cellular concrete characterized by containing 30% by weight or more of short fibers. 2. A ring Jo突 electromotive unit, according to claim 1 wherein present in both ends of the short fiber fiber reinforced lightweight concrete. 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.