KR20000007951A - Method of manufacturing light strong board for double floor using cement concrete compound with enforcing fiber - Google Patents

Abstract

PURPOSE: Glass fiber, imported so far, is chemically unstable, gets weak through use, and is not suitable for high temperature curing. Asbestos fiber has low shock strength, generates heavy dust and harms the human body, so that the asbestos fiber is seldom used. Polypropylene fiber is not suitable for intensifying the strength of cement concrete compound because of its low elasticity, which promises neither stability nor reliability. CONSTITUTION: With 0.6mmx36MM, both-end-hook type, specific gravity of 7.85, aspect ratio of 60, and tensile strength of 110kg/cm¬3, the carbon fiber is made from both coal and petroleum pitch, by firing at a low temperature, it has the tensile elasticity of 50GPa, and 12 micro-meter¯20 micro-meter diameter. On the surface of the fiber are used both the pitch carbon fiber which is oxidized to have the atomic ratio of oxygen to carbon of 0.1¯0.6dl and the polyacrylonitrile carbon fiber which has the tensile elasticity of 200¯400GPa with 6.5¯7.0 micrometer diameter. The board for double floor is light, very strong, and endurable, also contributing to recycling, saving energy and saving foreign currency due to its substitution effect for import.

Description

Manufacturing method of fiber reinforced cement concrete composite and double floor top plate

The present invention is a hook-type steel fiber and PAN (polyacrylonitrile) as a part of the development and application of the manufacturing technology of light weight, high strength fiber reinforced cement concrete composite for the reduction of enormous imported lightweight materials and steel materials used in various structures A method of manufacturing fiber-reinforced cement concrete composites using silica-based and pitch-based carbon fibers and fine powder silica powder as aggregate, and to develop structural members having excellent mechanical performance using the composites. It is related with the manufacturing method of the light weight, high strength, and stress-resistant double-floor top plate.

Among the fiber-reinforced materials of conventional fiber-reinforced cement-concrete composites, the glass fibers that have been imported and used for some time are chemically unstable, which inevitably leads to a decrease in strength after a long time, and vulnerable to high temperature curing. Asbestos fibers have low impact strength and dust Due to severe pollution and harmful to the human body, its use is suppressed, and polypropylene fiber has a low elastic modulus, which is a problem in increasing the strength of the cement concrete composite, and thus it was unable to improve stability and reliability.

The present invention is to solve the drawbacks of the conventional manufacturing method of the fiber-reinforced cement-concrete composite, and the mechanical properties, heat resistance and chemical stability, etc. are superior to other fibers and have a balance performance that is not in these fibers and It is aimed at the development of lightweight, high strength and high strength reliable building materials using both ends of hook-type steel fiber and strength reinforcing mesh which have excellent mechanical performance.

The present invention, by reinforcing both ends of the hook-type steel fiber and PAN-based and pitch-based carbon fiber, as well as excellent mechanical performance, durability, watertightness, good aesthetics can be produced slender member and a large weight Since the air can be shortened greatly by the reduction, it is possible to use it as an industrial material and to manufacture high value-added secondary products for the construction industry.

1 is a detailed view of the apparatus for measuring the bending strength of the plate specimen of the present invention

Figure 2 is a detailed view of the upper plate specimen of the present invention

Figure 3 is a detailed view of the mesh (mesh) for reinforcing the matrix of the present invention

Figure 4 is a detailed view of the type and specification of the anchor (anchor) installed in the mesh (mesh) of the present invention

Figure 5 is a detailed view of the reinforcing both ends hook-type steel fiber of the present invention

<Description of the symbols for the main parts of the drawings>

1 steel bar 2 specimen

3: support 4: displacement measuring instrument

5: universal test machine 10: mesh

20: hook type steel fiber

Steel fiber used in the present invention is a product manufactured in Korea with a hook type of both ends of the size Ø0.6mm × 36mm specific gravity 7.85, aspect ratio (ℓ / d) 60, tensile strength 110kg / ㎠, carbon fiber is coal-based and Pitch system oxidized to a tensile modulus of 50 GPa or more produced by firing at a relatively low temperature using a petroleum pitch as a raw material and having a carbon fiber diameter of 12 µm to 20 µm and an oxygen-to-carbon atomic ratio of 0.1 to 0.6 at the surface layer of the fiber. Carbon fiber and polyacrylonitrile (PAN) carbon fiber with tensile modulus of 200-400 GPa and a fiber diameter of 6.5-7.0 μm were used. The optimum length for the production of the present invention was 3 mm-20 mm, and the cement had a specific gravity of 3.14. The crude steel portland cement was used, and the aggregate used was silica powder having a specific gravity of 2.7 and a particle size of 0 to 80 µm. At a rate of 1%, methylcellulose as a thickener and antifoam as an antifoaming agent were used at a ratio of 0.5 and 1% of the cement weight, respectively.

The formulation used in the present invention is mixed with a test method through a test mixture to ensure proper walkablity while uniformly dispersing the fibers in the matrix so that the fibers and the matrix do not separate and do not produce fiber balls in the composite preparation. Formulation conditions were selected.

The cement matrix is composed of PAN CF short fibers (CF length: 5, 10, 20 mm) and pitch CF short fibers (CF length: 3, 6, 10, 20 mm), respectively. V _f = 0, 1, 2 , 3% was mixed, and the mixing example is as shown in Table (1) below, in the case of high strength reinforcement plate was mixed 0.2 to 0.4 Vol.% Of both ends hook-type steel fiber (20) .

Mixing used high-performance Omni-Mixer for fiber dispersion for random uniform dispersion in the cement matrix of the fiber, and the beam time was: a) Dry blend (cement, dispersing agent and silica powder): 30 seconds, b) Primary blend ( Add water and admixtures): 3-5 minutes, c) Secondary blend (Add carbon fiber): 4.5-6.5 minutes, total 10 minutes to produce a homogeneous fiber reinforced cement concrete composite Can be.

In the present invention, when mixing with the Omni-Mixer for fiber dispersion, a good mixing condition in which uniform dispersion is achieved is up to 3% by volume ratio for fiber lengths of 3 to 5 mm, up to 2% by volume ratio for 6 to 10 mm, and 11 In the case of the length of -20 mm, it is 1% of mixing ratio by volume ratio.

Formulation of fiber reinforced cement concrete composite Type of CF CFContent (vol.%) Mix.No. W / C (%) CFLength (mm) Unit Weight (kg / m ³ ) Cement Water Silicapowder CF Admixture SP ^* M.C. A.F. PAN-basedCF One One 75 3 843 632 253 17.8 8.43 4.22 8.43 2 75 3 759 632 253 17.8 8.43 4.22 8.43 3 75 3 674 632 253 17.8 8.43 4.22 8.43 4 75 3 590 632 253 17.8 8.43 4.22 8.43 2 5 75 3 843 632 253 35.6 8.43 4.22 8.43 6 75 3 759 632 253 35.6 8.43 4.22 8.43 7 75 3 674 632 253 35.6 8.43 4.22 8.43 8 75 3 590 632 253 35.6 8.43 4.22 8.43 3 9 75 3 843 632 253 53.4 8.43 4.22 8.43 10 75 3 759 632 253 53.4 8.43 4.22 8.43 11 75 3 674 632 253 53.4 8.43 4.22 8.43 12 75 3 590 632 253 53.4 8.43 4.22 8.43 Pitch-basedCF One 13 75 3 843 632 253 16.3 8.43 4.22 8.43 14 75 3 759 632 253 16.3 8.43 4.22 8.43 15 75 3 674 632 253 16.3 8.43 4.22 8.43 16 75 3 590 632 253 16.3 8.43 4.22 8.43 2 17 75 3 843 632 253 32.6 8.43 4.22 8.43 18 75 3 759 632 253 32.6 8.43 4.22 8.43 19 75 3 674 632 253 32.6 8.43 4.22 8.43 20 75 3 590 632 253 32.6 8.43 4.22 8.43 3 21 75 3 843 632 253 48.9 8.43 4.22 8.43 22 75 3 759 632 253 48.9 8.43 4.22 8.43 23 75 3 674 632 253 48.9 8.43 4.22 8.43 24 75 3 590 632 253 48.9 8.43 4.22 8.43

* Superplasticizer: Mighty 150 V

In addition, the curing of the specimens was a cure (23 ± 2 ℃, 60 ± 5% RH), underwater curing (23 ± 2 ℃) and autoclave curing after demoulding the specimen, autoclave curing was the highest temperature After curing was completed at 180 ° C. (10 atm) for 5 hours, air curing was again performed at 23 ± 2 ° C. and 60 ± 5% RH. Test age was somewhat different depending on the type of specimen, but averaged 7 days.

The test method for fiber reinforced cement concrete composites is carried out in accordance with KS L 5105 and KS F 2409 for the flow test and unit volume weight test, respectively. The compressive strength test is performed in accordance with KS L 5105 5.08cm × 5.08cm × 5.08 A cubic specimen of cm was fabricated and measured, and a ø5 × 10 cm cylindrical specimen was fabricated to determine the compressive stress-strain relationship, and a strain was measured by attaching a wire strain gage (length 30 mm) to the center of the specimen. . Bending strength and bending stress-deflection measurements were made in 4cm × 4cm × 16cm square specimens in accordance with JIS R 5201. Crosshead speed 0.5mm by 3-point bending load test method using a 25ton Computer Controlled Universal Testing Machine (Autograph). The bending test was carried out by the displacement control method of / min, and the load-deflection curve at this time was obtained by an XY recorder. In order to measure the flexural load capacity, the specimens of 50 × 50 × (2.0∼3.5) cm of specimens were prepared and subjected to wet curing for 1 day, followed by autoclave curing (curing for 5 hours under conditions of 10 ℃). When the specimen was manufactured, the mesh was reinforced, and in the case of the high strength reinforcing plate, the hook-type steel fibers 20 were reinforced instead of the mesh. The flexural load measurement of the specimens was carried out by placing four edges of the specimens (2) on the ø25mm support (3) using a 100ton universal testing machine (5) as shown in FIG. ) And loaded on it, and the deflection of the center point at the time of loading until the breakage was measured by using the displacement measuring instrument (4).

As a result of searching for the optimum blend through the test as described above, the relationship between the fiber mixing rate and the flow value considering the workability is significantly increased with the increase of the fiber mixing rate so that the mixed water adheres to the surface. In order to ensure proper workability, the fiber mixing ratio is 1 to 3%, and the PAN-based CF has a relatively large specific gravity compared to the pitch-based CF but the fiber diameter is so small that the aspect ratio (ℓ / d) is very large. Even at the same CF mixing rate, since the number of mixed fibers is much larger, the Flow value is significantly lowered. In addition, the workability of the matrix is greatly affected by the change in the water cement ratio. The workability of the fiber reinforced cement concrete matrix is good at the water cement ratio of 70 to 110%.

The unit volume weight of fiber-reinforced cement-concrete matrix was slightly lower in calculation if the fiber mixing ratio was increased due to the difference between matrix and fiber specific gravity, but in reality, the decrease rate was larger than the theoretical value. This tendency becomes more prominent in the curing of Si and autoclave, which is caused by the increase of porosity due to the increase of the volume of the fiber, and the unit volume weight is decreased up to 3% of the fiber content but the unit volume weight is increased in the case of 4%. In terms of weight reduction of the matrix, the fiber content is preferably 4% or less. In addition, as the length of the CF short fibers increases to 3, 6, 10 mm, the flow value is significantly reduced to about 30%, so the length of the fiber is preferably 3 to 6 mm.

The dry weight of the matrix according to the fiber mixing amount does not show a significant influence on the increase of the CF mixing rate, and the PAN system shows a slightly higher value than the pitch system depending on the type of fiber. This is because the specific gravity of the fiber itself is large in the PAN system, and when weight reduction is the main purpose, water and cement are 70% to 110%, aggregate / cement ratio is 0.3 to 0.5, and carbon fiber content is 1 to 3%. When cellulose is used in a proportion of 0.5 to 1.5% by weight of cement, it has the characteristics of producing a fiber-reinforced cement concrete composite of 1.41 to 1.65.

As the amount of CF short fiber increases, the change in compressive strength is not so large, but slightly decreases. This is due to the increase in pore size and compaction due to the increase of fiber content as well as the relationship between fiber content and unit volume weight. The fiber mixing rate was 3% or less, and the mixing of PAN-based carbon fiber showed somewhat higher strength than the mixing of Pitch-based carbon fiber. This is because the number of fibers is mixed because of the small size, and the strength of the fibers themselves is high. The compressive strength of the carbon fiber reinforced cement concrete composite is made by using silica powder, so that the uniform dispersion, fluidity and formability of the fiber are good, and the weight of the member and the reaction product by the fine powder of silica powder during autoclave curing are reduced to the voids in the matrix. It was found that the tissue was sealed and the autoclave curing showed 7 to 20% higher strength than the air curing.

The relationship between the mixing rate and the bending strength of the CF short fibers showed a tendency to increase the bending strength significantly with the increase of the mixing amount of the CF short fibers, which improved the dispersibility of CF by silica powder and at the same time This is because the reinforcing effect is increased by improving the adhesion. In addition, the PAN-based carbon fibers showed somewhat higher strength than that of the pitch-based carbon fibers, because the fibers themselves had significantly higher tensile strength and higher elasticity than the PAN-based carbon fibers.

In order to check the relationship between bending stress and deflection amount of CFRC subjected to bending stress, when V _f = 0, 1, 2, and 3% of PAN-based CF short fibers were mixed, the bending stress-sag relation with increasing fiber mixing rate was V _f In the case of plain = 0%, the linear drop decreased, whereas CFRC showed a remarkable non-linearity and showed a ductile characteristic without sharp drop even after showing the maximum bending stress. It can be seen that the deformation performance increases greatly with the increase of the bending stress as the CF mixing rate increases. In particular, the bending toughness (absorption energy) tends to increase rapidly.

In addition, the autoclave curing showed excellent flexural deformation characteristics, because the matrix itself was strengthened and the adhesion between the fibers and the matrix was significantly increased, resulting in a decrease in the number of fibers from the matrix and an increase in fracture fibers.

When manufacturing the fiber-reinforced cement-concrete composite, if the silica powder / cement ratio is 30%, it is possible to uniformly disperse the short fibers up to 3% of fiber in the cement matrix without the occurrence of fiber balls due to the dispersion and thickening effect of the silica powder. The optimum mixing condition for obtaining light weight and high strength is that the silica powder / cement ratio is 30%, the carbon fiber mixing ratio is 3% or less, and the fiber length is 3 to 6 mm.

As described above, according to the optimum mixing conditions developed in consideration of the mechanical properties and economic aspects in the present invention was prepared a specimen specimen 2 as shown in Figure 2 to measure the flexural strength.

Here, the stress state of the upper specimen 2 is evaluated as follows. The maximum bending moment M generated when P kg is loaded at the center of the square upper plate specimen 2 of 4 corner support within the elastic range is approximately

(One)

Where a is the length of one side of the specimen,

u is the length of one side of the square plate,

In terms of the u value,

(2)

(c: radius of loading steel)

Represented by.

The load-deflection relationship of the specimens according to the anchor shape is an index of stiffness. The deflection, maximum load, and stiffness ratios of 300 kg loads with linear load and deflection are shown in Table (2).

When the influence of the anchor shape is evaluated by the ratio of stiffness, which is the inverse ratio of deflection, A and C in Fig. 4 become 0.88 and 0.93 of B. When deflection performance is compared, A deflection at maximum load is small, The load suddenly drops. On the other hand, B and C have sag at maximum load 1.4 times and 1.5 times A, respectively. In this case, since A resists the sliding (activity) deformation between CFRC and the mesh 10 at the front of the upper plate, the rigidity decrease to the maximum load is small, but the sudden drop in load is caused because the mesh 10 peels from the CFRC at the same time as the fracture. Occurs. On the other hand, B and C resist the sliding deformation of the anchor near the center of the specimen with high stress, and B is the compression plastic deformation of CFRC mainly, and C is the tensile plastic deformation of the anchor. I think this becomes big. In addition, even after the maximum load, the mesh 10 is less likely to peel off from the CFRC, and the load reduction is alleviated.

Strength Characteristics and Maximum Bending Moment According to Anchor Shape Sign Deflection (300kg) Maximum Load MaximumBendingMoment (kg mm) mm RelativeStiffness kg Ratio A2 ^* 0.80 0.88 1260 0.84 300 B2 0.70 1.00 1500 1.00 358 C2 0.75 0.93 1700 1.13 405

* A2: Anchor Shape A, CF = 2vol.%

The load-deflection relationship was tested for the case where the anchor shape was B and the distance between the anchors was 30, 60, 90, and 120 mm for the two cases of thickness 30mm and 35mm of the specimen (2). The same, the smaller the interval between the anchor interval 60mm, the more the number of anchors, the smaller the force burdened by one anchor, the higher the maximum load, but 30mm and 60mm is mostly the same. This is because the increase in the number of anchors has a limit in the improvement of strength, and in the form of failure, the anchor spacing reaches 90 and 120 mm in flexural failure, and the anchor spacing 30 and 60 mm in the lower shear shear failure. The difference between them is that the smaller the distance is, the smaller the force exerted by one anchor on the sliding (activity) or peeling force of the mesh 10 and the CFRC is. That is, because the flexural strength is greater and the shear strength is higher, shear failure occurs first, so the anchor interval of 60mm or less is appropriate.

Strength Characteristics and Maximum Bending Moment with Anchor Spacing Sign Deflection (300kg) Maximum Load MaximumBendingMoment (kg mm) mm RelativeStiffness kg Ratio T30 30 0.70 1.00 1500 1.00 358 60 0.71 0.99 1440 0.96 343 90 0.84 0.83 1140 0.76 272 120 0.95 0.74 850 0.57 203 T35 30 0.57 1.23 1740 1.16 415 60 0.57 1.23 1680 1.12 401 90 0.78 0.90 1360 0.91 324 120 1.01 0.69 1050 0.70 250

Strength Characteristics and Maximum Bending Moment According to the Thickness of the Upper Plate Specimen Sign Deflection (300kg) Maximum Load MaximumBendingMoment (kg mm) mm RelativeStiffness kg Ratio T20 1.02 0.69 890 0.59 355 T25 0.85 0.82 1350 0.90 538 T30 0.70 1.00 1500 1.00 598 T35 0.57 1.23 1740 1.16 693

When the shape of the anchor is B and the thickness of the upper plate specimen 2 is 20, 25, 30, and 35 mm, respectively, the deflection, the maximum load, and the stiffness ratio at 300 kg are shown in Table (4). In this case, if the reciprocal ratio of deflection according to the thickness of the upper specimen is represented by the ratio of stiffness, when the thickness of the upper specimen is 20, 25, 30, and 35 mm, the thickness is 0.69, 0.82, 1.0, and 1.23, respectively. Flexural failure and 35mm thickness has shear failure in the lower part.

Test results of specimens according to the reinforcement type No. Thickness (mm) Reinforcement form Deflection by each load (mm) 100 kg 200 kg 300 kg 400 kg One Nil 0.28 0.84 1.56 3.18 2 30 mesh reinforcement 0.22 0.69 1.31 2.21 3 Steel fiber reinforcement 0.15 0.32 0.90 1.42

In addition, in order to find out the strength of the upper specimen (2) according to the reinforcement form, the upper specimen (2) having a thickness of 30mm is manufactured and not reinforced by the internal reinforcement and mesh (10), hooks at both ends instead of the mesh (10) Table 5 compares the deflection for each load when reinforced with the shape steel fiber 20. At this time, when the reinforcement with the mesh 10 than the internal reinforcement was less than about 30% deflection, when the reinforcement with both ends hook-type steel fiber 20, about 55% deflection was found.

In the case of the high strength reinforcing plate in which 0.2-0.4 Vol.% Of the both ends hook type steel fibers 20 are mixed in the matrix instead of the reinforcing mesh 10, both ends of the hook type steel fibers 20 act as anchors in the matrix. By restraining the breakage of the matrix, even after reaching the maximum stress, the fibers are stretched without being pulled out to increase the resistance after cracking during flexural behavior, thereby solving the problem of sudden load drop due to peeling when the mesh 10 is used.

As such, the present invention utilizes fiber reinforced cement concrete composites using both ends of hook-type steel fibers and carbon fiber, which is an industrial by-product, and to develop a rational structural member that combines cement concrete, fibers, and mesh to compensate for the weaknesses of the weak concrete. It is an invention that it is possible to manufacture a lightweight, high strength and strength double floor floor plate, which has great practical value in terms of recycling of resources, and that the effect of saving foreign currency due to energy saving and import substitution is expected to be very large.

Claims (2)

PAN-based carbon fibers with a diameter of 6.5 to 20 µm, specific gravity of 1.60 to 1.80, tensile strength of 7,500 to 38,000 kg / cm 2, elastic modulus of 3.5 to 25.0 × 10 ⁵ kg / cm 2, fiber length of 3 to 20 mm, and mixing amount of 1.0 to 3.0% Pitch carbon fiber and crude steel portland cement with a specific gravity of 3.14, silica powder with a specific gravity of 2.7 and a particle size of 0 to 80 µm are used as aggregates. Rose and antifoaming agent are formed by mixing antifoam together in slurry state, and the specific gravity is 1.4-1.7, compressive strength is 190-260 ㎏ / ㎠, flexural strength is 65-120 ㎏ / ㎠, and the flexural toughness of cement motor is usually 50-80 times light weight, high strength, excellent heat and fire resistance, and a method of producing a fiber-reinforced cement concrete composite characterized by excellent durability and water tightness. PAN-based carbon fibers with a diameter of 6.5 to 20 µm, specific gravity of 1.60 to 1.80, tensile strength of 7,500 to 38,000 kg / cm 2, elastic modulus of 3.5 to 25.0 × 10 ⁵ kg / cm 2, fiber length of 3 to 20 mm, and mixing amount of 1.0 to 3.0% Pitch carbon fiber and crude steel portland cement with a specific gravity of 3.14, silica powder with a specific gravity of 2.7 and a particle size of 0 to 80 µm are used as aggregates. Rose, antifoaming agent is a mesh of 2.5mm diameter, Ø0.6mm × 36mm, specific gravity 7.85, aspect ratio (ℓ / d) 60, using fiber reinforced cement concrete composite formed by mixing antifoam together in slurry. A method of manufacturing a lightweight, high strength and strength double floor top plate, a reasonable structural member that combines concrete, fiber, and mesh that compensates for the weakness of concrete that is weak in tension by using hook type steel fibers having a tensile strength of 110㎏ / ㎠.