JP7554065B2 - Composite fiber material for concrete production, its manufacturing method, and method for manufacturing ultra-high strength concrete - Google Patents

Description

The present invention relates to a composite fiber material used in producing ultra-high strength concrete, a method for producing the composite fiber material, and a method for producing ultra-high strength concrete using the composite fiber material.

High-strength concrete exceeding 70N/ ^mm2 may cause spalling when heated, causing the covering of the component to crack and spall off, potentially making it impossible to ensure sufficient evacuation time in the event of a fire. Furthermore, with ultra-high-strength concrete exceeding 150N/ ^mm2 , if a column component is subjected to a strong earthquake force, the base of the column may collapse, causing the covering to spall off.

Conventional countermeasures for fire resistance against explosion phenomena during fires and structural performance against collapse phenomena during earthquakes include the following.
(1) Covering with fire-resistant finishing materials The most common fire-resistance method that relates to evacuation time is to cover with a finishing material that has fire-resistant properties, such as calcium silicate board. If the thickness of calcium silicate board is 25 mm, sufficient fire resistance is obtained, and since the finishing thickness is applied with adhesive, it is only the thickness of the fire-resistant board, and the impact on the effective room area is small.

(2) Combination of steel fiber and synthetic fiber This is the most common method for providing structural and fire resistance properties in a composite manner. In order to avoid the collapse phenomenon during an earthquake, it is necessary to mix highly rigid reinforcing factors such as steel fiber, knead it uniformly to produce ultra-high strength concrete, and apply it to column members. In addition, since the required fire resistance must also be imparted, factors that enhance fire resistance must be further mixed in. In the case of such ultra-high strength concrete, the most common combination is to mix in the required amount of steel fiber to ensure the required structural performance, and polypropylene (PP) fiber to ensure the required fire resistance.

Patent Document 1 discloses high-strength, explosion-resistant concrete that contains cement, water, fine powder admixtures, aggregates, and chemical admixtures, and further contains required organic fibers and inorganic fibers such as metal fibers and carbon fibers in a specified content ratio, in order to provide high-strength, explosion-resistant concrete that can effectively suppress explosion during a fire without reducing the fluidity even in concrete with an extremely low water-binder ratio.

Patent Document 2 discloses that in order to provide ultra-high-strength precast concrete with a compressive strength of 150 N/mm2 or ^more and capable of preventing spalling, fresh concrete containing synthetic resin fibers is poured, demolded, and subjected to high-temperature hysteresis curing, and then cured in a drying furnace at a temperature equal to or higher than the melting point of the synthetic resin fibers, so that the molten synthetic resin is absorbed into the minute voids in the concrete during curing, and part of the space occupied by the synthetic resin is converted into a cavity in the hardened cement body, thereby suppressing spalling.

Patent Document 3 discloses a concrete composition that contains water, cement, fine aggregate, and a specified volume of coarse aggregate, and further contains deformed steel fibers with deformed portions and straight steel fibers without deformed portions in a specified content ratio, in order to provide a hardened concrete body that has excellent compressive strength, flexural strength, and explosion resistance.

JP 2003-306366 A JP 2012-153539 A JP 2019-38721 A

Achieving fire resistance by covering with a fire-resistant finish is the most economical method, and the only option for structural performance is to use steel fibers, but design issues remain.

When using steel fiber and synthetic resin fiber together, it takes a lot of time and effort to mix both types of fibers into the concrete, by adding 50% of the steel fiber in order of difficulty of mixing, stirring and mixing for a certain period of time, then adding the remaining 50% and stirring and mixing for a certain period of time, then adding 50% of the synthetic resin fiber and stirring and mixing for a certain period of time, then adding the remaining 50% and stirring and mixing for a certain period of time. If the required amounts of both fibers are mixed in sequentially, it is difficult to maintain the fluidity and fresh properties over time, and if fresh properties are prioritized, the structural performance and fire resistance will not reach the required levels. Conversely, if the required structural performance and fire resistance are prioritized, the required fresh properties will not be obtained, and the actual construction will be far from being achieved. In other words, depending on the type and brand, steel fibers should be mixed into the concrete at about 1.0% of the volume, and synthetic resin fibers at about 0.25-0.30% of the volume; however, both are close to the upper limit when mixed alone, so mixing them together places a great strain on the concrete, and the fresh properties of the concrete are often far from the required range, far from being suitable for actual construction, so some kind of action is required.

Furthermore, previous experimental results indicate that PP (polypropylene) fibers, which are expected to have fire-resistant properties, also contribute somewhat to structural performance, and it is hoped that both properties may be achieved using synthetic resin fibers alone. However, no synthetic resin fibers have been reported to date that demonstrate structural performance that exceeds that of steel fibers.

In Patent Document 1, organic fibers and inorganic fibers such as metal fibers and carbon fibers are individually mixed in a specified amount. In Patent Document 2, high-temperature history curing after demolding and curing at a temperature above the melting point of the synthetic resin fibers mixed into the concrete in a drying furnace are required. In Patent Document 3, deformed steel fibers with deformed parts and straight steel fibers without deformed parts are individually mixed with organic fibers such as PP fibers.

There are two theories, or a combination of the two, proposed for the mechanism behind the spalling phenomenon when high-strength concrete is heated. One theory is the thermal stress theory, which states that when heated, a temperature difference occurs toward the inside of the component, which in turn causes stress differences at various positions, leading to destruction. The other theory is the water vapor pressure theory, which states that when heated, the water contained within the concrete evaporates, generating internal pressure and leading to destruction. PP fiber is a material that is attributed to the latter water vapor pressure theory, and due to its low melting point (approximately 170°C), it melts early on when heated, and it is believed that the resulting voids relieve the water vapor pressure generated inside the concrete.

As mentioned above, in the case of ultra-high strength concrete of 150N/mm2 or ^more , in order to impart the required structural and fire resistance properties, it is necessary to mix steel fibers and synthetic fibers such as PP fibers up to their respective upper limits. However, mixing fibers to that extent results in concrete that is far from the fresh properties that can withstand actual manufacturing and construction.

The present invention aims to provide a composite fiber material for concrete production that can provide fresh properties sufficient to withstand practical construction when producing ultra-high strength concrete of 150 N/mm2 or ^more , and the required structural performance and fire resistance after hardening , a method for producing the same, and a method for producing ultra-high strength concrete.

To achieve the above-mentioned objective, a composite fiber material for concrete production is a composite fiber material that is mixed with other materials when producing ultra-high strength concrete, in which inorganic fibers for imparting structural performance to the ultra-high strength concrete and synthetic fibers for imparting fire resistance performance are integrated, and at least a portion of the inorganic fibers are exposed from the synthetic fibers for adhesion to the ultra-high strength concrete.

According to this composite fiber material for concrete production, the total number of fibers is significantly reduced by integrating inorganic fibers and synthetic fibers, and mixing is easier than when the two fibers are stirred and mixed in sequence during the production of ultra-high strength concrete, and the required fresh properties can be secured and the required structural performance and fire resistance can be imparted to the ultra-high strength concrete. In this case, ultra-high strength concrete refers to concrete with a compressive strength of 150 N/mm2 or ^more . Inorganic fibers include metal fibers such as steel fibers and stainless steel fibers, and ceramic fibers such as glass fibers and carbon fibers. Synthetic fibers include PP fibers, polyvinyl alcohol fibers, vinylidene fibers, polylactic acid fibers, etc.

The method for producing a composite fiber material for concrete production to achieve the above object is a method for producing a composite fiber material to be mixed with other materials in the production of ultra-high strength concrete, in which a synthetic fiber sheet made of synthetic fibers is wrapped around a part of the inorganic fibers to integrate the inorganic fibers with the synthetic fibers (however, this does not include a method for producing the inorganic fibers by impregnating the inorganic fibers with a polymer coating) . For example, the synthetic fiber sheet can be wrapped around the center or both ends in the direction in which the inorganic fibers extend. The wrapped synthetic fiber sheet can also be bonded with an adhesive.

Another method for producing a composite fiber material for concrete production to achieve the above object is a method for producing a composite fiber material to be mixed with other materials in the production of ultra-high strength concrete, in which the inorganic fiber and the synthetic fiber are integrated by welding the synthetic fiber to a part of the inorganic fiber (however, this does not include the method of impregnating the inorganic fiber with a polymer coating) . For example, the synthetic fiber is welded to the center or both ends of the inorganic fiber in the extending direction.

Another composite fiber material for concrete production to achieve the above object is a composite fiber material to be mixed with other materials in the production of ultra-high strength concrete, in which the inorganic fiber and the synthetic fiber are integrated by the presence of the synthetic fiber in the internal cavity of the inorganic fiber. For example , the synthetic fiber can be filled in the internal cavity of the inorganic fiber.

In order to achieve the above-mentioned objective, a method for producing ultra-high strength concrete involves mixing the above-mentioned composite fiber material for concrete production, or the composite fiber material for concrete production produced by the above-mentioned production method, to produce ultra-high strength concrete.

According to this method for producing ultra-high strength concrete, by using a composite fiber material for producing concrete in which inorganic fibers and synthetic fibers are integrated, the total number of fibers is significantly reduced, making mixing easier than when mixing the two fibers separately when producing ultra-high strength concrete, ensuring the required fresh properties, and imparting the required structural and fire resistance properties to the ultra-high strength concrete.

According to the present invention, it is possible to provide a composite fiber material for concrete production that can provide fresh properties sufficient to withstand actual construction when producing ultra-high strength concrete of 150 N/ ^mm2 or more, and the required structural performance and fire resistance after hardening , a manufacturing method thereof, and a manufacturing method for ultra-high strength concrete.

1A and 1B are a front view and a side view, respectively, showing a composite fiber material for concrete production in which PP fiber is wrapped around the central portion of steel fiber according to this embodiment. 1A and 1B are a front view and a side view, respectively, showing a composite fiber material for concrete production in which PP fibers are wrapped around both ends of steel fibers according to this embodiment. 1A and 1B are a front view and a side view, respectively, showing a composite fiber material for concrete production in which PP fibers are stuffed into the hollows of steel fibers according to this embodiment.

The following describes the embodiment of the present invention with reference to the drawings. Figure 1 is a front view (a) and a side view (b) showing a composite fiber material for concrete production in which PP fiber is wrapped around the center of steel fibers according to this embodiment. Figure 2 is a front view (a) and a side view (b) showing a composite fiber material for concrete production in which PP fiber is wrapped around both ends of steel fibers according to this embodiment. Figure 3 is a front view (a) and a side view (b) showing a composite fiber material for concrete production in which PP fiber is packed into the hollows of steel fibers according to this embodiment.

1(a) and (b), a PP fiber sheet 12 is wrapped around the center 11a of the steel fibers 11 in the extending direction and attached with an adhesive, integrating the steel fibers 11 and the PP fiber sheet 12. The PP fiber sheet 12 is made of PP fibers in the form of a single sheet. For example, a sheet of 41 μm (0.041 mm) PP fibers can be used.

In the composite fiber material for concrete production shown in Figures 2(a) and (b), the steel fibers 11 and the PP fiber sheet 12 are integrated by wrapping the PP fiber sheet 12 around both end portions 11b of the steel fibers 11 in the extension direction and attaching them with an adhesive.

In Figures 1 and 2, the steel fibers 11 may have a length of, for example, about 5 to 40 mm and a diameter of about 0.05 to 2 mm, but are not limited to these and can be changed as appropriate, and the length and shape may be straight, wavy, or hooked, and it is preferable that they are zinc-plated to prevent rust. The cross-sectional shape of the steel fibers may be other than circular, and may be oval, square, pentagonal, hexagonal, octagonal, etc.

In the composite fiber material for concrete manufacturing shown in Figures 1 and 2, the steel fibers 11 and the PP fiber sheet 12 are integrated, so the total number of fibers is greatly reduced, and by mixing such composite fiber material for concrete manufacturing with cement, water, aggregate, admixtures, etc. when manufacturing ultra-high strength concrete of 150 N/ ^mm2 or more, the mixing time is reduced and mixing is made easier than when the two fibers are mixed and mixed in order, and the required fresh properties can be secured. The mixing properties of both steel fibers and PP fibers are highly dependent on the amount of each fiber, and the amount of fiber in mixing is not the volume or capacity but the number of fibers, and the total surface area of the fibers is correlated with the difficulty of mixing, so that the integration of the two fibers greatly reduces the number of fibers (total surface area of the fibers), making mixing easier.

In addition, the steel fibers 11 at both ends 11b or at the center 11a exhibit their integrity due to their adhesion to the concrete, improving their strength and preventing the collapse of the column base and the peeling of the covering during an earthquake. The PP fiber sheets 12 at the center 11a or both ends 11b of the steel fibers 11 do not contribute to the adhesion to the concrete, but melt when heated to form voids, which guide and relieve the vapor pressure generated inside the concrete to the voids and prevent the occurrence of the explosion phenomenon during a fire. In this way, the required structural performance and fire resistance can be imparted to the ultra-high strength concrete.

The composite fiber material for concrete manufacturing shown in Figures 3(a) and (b) is made by packing PP fibers 14 into the internal cavity of steel fibers 13, which are formed into a cylindrical shape from a large number of steel fibers, so that the steel fibers 13 and PP fibers 14 are integrated.

The composite fiber material for concrete manufacturing shown in Figures 3(a) and (b) can be manufactured by placing PP fiber 14 in the center of a plate-shaped steel fiber, rolling it into a cylindrical shape, and cutting it to a specified length. Alternatively, PP fiber 14 may be inserted into the internal cavity of the cylindrical steel fiber 13 and then cut to a specified length.

In the composite fiber material for concrete manufacturing shown in Fig. 3(a) and (b), the steel fiber 13 and the PP fiber ¹⁴ are integrated, so that the total number of fibers is significantly reduced. By mixing such composite fiber material for concrete manufacturing with cement, water, aggregate, admixture, etc., when manufacturing ultra-high strength concrete of 150 N/mm2 or more, the stirring and mixing time is reduced and mixing is made easier than when the two fibers are stirred and mixed in order, and the required fresh properties can be secured. In addition, the cylindrical steel fiber 13 can exhibit integration with the concrete due to adhesion to the concrete like normal steel fibers, improving the strength and preventing the occurrence of crushing phenomenon during earthquakes. In addition, the PP fiber 14 in the internal cavity of the steel fiber 13 melts when heated by fire, etc., and the inside of the steel fiber 13 becomes a void, and the steam pressure generated inside the concrete is guided to the void and relaxed, preventing the occurrence of explosive spalling phenomenon during fire. In this way, the required structural performance and fire resistance can be imparted to the ultra-high strength concrete.

In the composite fiber material for concrete manufacturing shown in Figures 1 to 3, the ratio of steel fiber to PP fiber, in volume ratio, is preferably, for example, steel fiber:PP fiber = approximately 1:0.3, but this is not limited to this and can be changed as necessary.

In addition, the composite fiber materials for concrete manufacturing shown in Figures 1 to 3 can be manufactured using similar technologies, as nanotechnology can be used to produce smaller composite materials.

It is preferable to determine the dimensions, shape, volume, etc. of each fiber appropriately based on the results of a mixing test in which the two fibers are mixed separately. It is also preferable to carry out tests of bending, bending toughness, and bending toughness for structural performance, and finally, a load-bearing fire test using a full-scale column specimen for fire resistance, and to quantify the performance based on the results of each test.

Although the embodiments for carrying out the present invention have been described above, the present invention is not limited to these, and various modifications are possible within the scope of the technical concept of the present invention. For example, in the composite fiber material for concrete production according to this embodiment, the steel fibers may be replaced with stainless steel fibers, carbon fibers, glass fibers, etc., and the PP fibers may be replaced with polyvinyl alcohol fibers, vinylidene fibers, polylactic acid fibers, etc.

In addition, the lengths of both ends 11b wrapped with the PP fiber sheet 12 in Fig. 2(a) or the volume amounts of the steel fibers do not have to be uniform, and may be long or short, large or small, as long as the exposed length of the steel fibers 11 for adhesion to concrete is secured. In addition, after securing the exposed length of the steel fibers 11 in Fig. 2(a), the PP fiber sheet 12 may be wrapped around only one end of the steel fibers 11, rather than both ends.

According to the present invention, by mixing the composite fiber material for concrete production of the present invention with cement, water, aggregate, admixtures, etc. when producing ultra-high strength concrete of 150 N/ ^mm2 or more, mixing becomes easier than when inorganic fibers and synthetic fibers are mixed separately, and the required fresh properties can be ensured, thereby improving the productivity of ultra-high strength concrete and imparting the required structural performance and fire resistance to the hardened ultra-high strength concrete.

11. Steel fiber (inorganic fiber)
11a central portion 11b both ends 12 PP fiber sheet (synthetic fiber)
13 Cylindrical steel fibers (inorganic fibers)
14 PP fiber (synthetic fiber)

Claims (5)

A composite fiber material that is mixed with other materials in the production of ultra-high strength concrete,
A composite fiber material for concrete manufacturing, in which inorganic fibers for imparting structural performance to the ultra-high strength concrete and synthetic fibers for imparting fire resistance performance are integrated, and at least a portion of the inorganic fibers are exposed from the synthetic fibers for adhesion to the ultra-high strength concrete. A composite fiber material that is mixed with other materials in the production of ultra-high strength concrete,
A composite fiber material for concrete production, in which the inorganic fibers and the synthetic fibers are integrated together by the presence of the synthetic fibers in the internal cavities of the inorganic fibers. 1. A method for producing a composite fiber material to be mixed with other materials in the production of ultra-high strength concrete, comprising the steps of:
A method for manufacturing a composite fiber material for concrete production, which comprises wrapping a synthetic fiber sheet made of synthetic fibers around a portion of the inorganic fibers to integrate the inorganic fibers with the synthetic fibers (excluding a method for manufacturing the material by impregnating the inorganic fibers with a polymer coating). 1. A method for producing a composite fiber material to be mixed with other materials in the production of ultra-high strength concrete, comprising the steps of:
A method for manufacturing a composite fiber material for concrete production, in which a synthetic fiber is fused to a portion of an inorganic fiber to integrate the inorganic fiber with the synthetic fiber (excluding a method for manufacturing the material by impregnating the inorganic fiber with a polymer coating). A method for producing ultra- high strength concrete, comprising mixing the composite fiber material for concrete production according to claim 1 or 2, or the composite fiber material for concrete production produced by the production method according to claim 3 or 4.

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