JP3889946B2 - Fiber for preventing concrete explosion and explosion-resistant concrete containing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a concrete explosion-preventing fiber for preventing explosion of a concrete body at the time of a fire in a concrete building and the like, and a explosion-resistant concrete body in which the explosion-preventing fiber is mixed.
[0002]
[Prior art]
A concrete building has a so-called concrete explosion phenomenon in which a crack occurs on the surface in the event of a fire, causing a scaly explosion and peeling. This is thought to be due to the rapid expansion of the moisture inside the concrete body into water vapor due to the heat of the fire. It is known that this phenomenon is particularly remarkable in high-strength concrete bodies in which the compressive strength is increased by increasing the blending amount of a binder such as cement and silica that reacts with water when molding the concrete body. In order to prevent such explosion of the concrete body, conventionally, heat-melting synthetic fiber is mixed in the concrete body in advance, and the synthetic fiber is melted by the high temperature generated in the event of a fire, and the inside is formed from the space formed in the trace. A method of preventing the explosion by releasing the water vapor generated in the gas and avoiding an increase in internal pressure is known as follows. For example, JP-A-6-321606 describes a method of mixing polypropylene fiber or polyester fiber together with an air entraining agent. Japanese Patent Application Laid-Open No. 8-189080 describes a method of mixing polypropylene fibers into a precast concrete driving frame. Japanese Patent Application Laid-Open No. 11-256818 discloses a method in which synthetic fibers are attached to the inner surface of a mold with an adhesive and the synthetic fibers that are peeled off when the concrete is placed are mixed with concrete. Japanese Patent Application Laid-Open No. 11-303245 describes a method of setting the type, size, and amount of fiber to be mixed, assuming the explosion depth in advance in consideration of the difference in concrete strength. Japanese Patent Application Laid-Open No. 2000-143322 describes a method of mixing polypropylene fiber or vinylon fiber having a weight residual ratio of 30% or less when heated at 500 ° C.
[0003]
[Problems to be solved by the invention]
However, as described above, many proposals have been made to prevent high-strength concrete bodies from exploding at the time of fire, but there is no example of more effective explosion prevention by paying attention to the melting behavior of the mixed synthetic fibers, The reality is that no more suitable fibers for explosion prevention have been pursued. The present inventors pay attention to the elution of alkali content of concrete, and at the time of curing the concrete, a single fiber or composite comprising at least an alkali-soluble resin that can form a void for preventing explosion in the concrete. As soon as the present invention has been found, it has been found that fibers are effective in preventing explosion of high-strength concrete. In particular, with the recent increase in strength of concrete, voids in the cement matrix have decreased, and the conventional explosion-proofing fiber cannot absorb the expansion pressure of water vapor at the beginning of the fire, causing the problem of explosion. To try to solve.
[0004]
[Means for Solving the Invention]
The fiber for preventing concrete explosion according to the present invention is a composite fiber in which at least one component is made of an alkali-soluble resin and the other component is made of an alkali hardly soluble or insoluble resin. Resin having an alkali weight loss rate of 50% or more when subjected to an alkali weight loss treatment in a 1% aqueous sodium hydroxide solution at -100 ° C. for 30 minutes, and an alkali-soluble residue of an alkali-soluble resin with respect to an alkali hardly soluble or insoluble resin with a composite fiber weight ratio is 1.3 or more, Ru der intended to solve the above problems. Also, the composite fiber is a core-sheath composite fiber, the core portion of the core-sheath composite yarn is formed from an alkali-soluble resin, the sheath portion is formed from alkali-soluble or Hi溶resin It is not preferred. Also, it is preferable that the alkali-soluble resin is a copolyester resin.
[0005]
By mixing 0.01 to 5.0 vol% of the explosion-preventing fiber of the present invention with respect to the concrete body, at least one of the alkali-soluble resin components of the fiber by elution of the alkali content in the concrete during curing of the concrete. The part melts and the volume decreases, and as a result, an explosion-proof concrete body in which voids are formed in the concrete in advance is obtained. Such a concrete body in which voids are formed in advance effectively acts to absorb the expansion pressure of water vapor in the early stage of fire and contributes to prevention of explosion of the concrete body.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
The concrete explosion preventing fiber of the present invention is applied as a composite short fiber or the like in which at least one component is made of an alkali-soluble resin and the other component is made of an alkali hardly soluble or insoluble resin . The alkali-soluble resin in the present invention means a volume reduction tends resin by dissolving or decomposing the alkali content of the concrete in the concrete curing, alkali reduction of more than a predetermined value at a particular condition as described below It is a resin showing the rate . Alkali-soluble or contrast and is Hi溶resins is that the resin does not reduce the volume by volume reduction difficult resin or alkali content, by alkali content of the concrete in the concrete curing. The alkali-溶樹fat is a melt-spinnable polymers or copolymers, a resin which can reduce the volume by dissolving or decomposing at alkaline, 1 percent of 98-100 ° C. more specifically a resin 1g alkali reduction rate when the caustic treatment 30 minutes in aqueous sodium hydroxide is 50% or more resins. As the alkali-soluble resin, a copolyester resin that is easily soluble even with a weak alkali is particularly preferable. As the copolyester, for example, a known copolyester resin such as polyethylene terephthalate obtained by copolymerizing one or two dicarboxylic acids other than terephthalic acid having a polyalkylene glycol or a sulfonate group can be applied. Also, the alkali hardly soluble or insoluble resin is not particularly limited, but for example, polyethylene, polypropylene, polymethylpentene, polybutene or a copolymer thereof, polyamide, polybutylene terephthalate, polyethylene terephthalate, polystyrene. Polyacetal, polycarbonate, polyphenylene sulfide, vinylon and the like can be applied. As alkali-soluble or Hi溶resin, considering the explosion prevention materially preferably more higher thermal melting decomposition during fire, for example, polypropylene or copolymers thereof, polyacetal and the like are more preferable.
[0007]
Examples of the cross-sectional shape of the composite short fiber include a parallel type, a core-sheath type, a sea-island type, a petal-like divided type, and other shapes other than a circular shape, a hollow shape, etc. Considering the dissolution by the alkali and the securing of voids after volume reduction, it is a core-sheath type composite fiber, the core part of the core-sheath type composite fiber is formed from an alkali-soluble resin, and the sheath part is hardly soluble in alkali. Or it is preferable to form from insoluble resin. Moreover, although the length dimension and diameter of a fiber are not specifically limited, 3-30 mm and 1-20 dtex are respectively preferable. By using the fiber of such form and configuration, it remains in the form of composite short fiber at the time of concrete enforcement, and maintains a state in which the fiber is not easily crushed against compression at the time of construction. After the concrete has hardened to the extent that it does not flow, the alkali-soluble resin in the core gradually dissolves from both ends of the fiber due to the alkali content of the concrete, the volume decreases, and the core of the composite fiber becomes hollow. It becomes a hollow fiber and becomes a composite short fiber that easily forms a void for preventing explosion with this hollow portion.
[0008]
In the present invention, the main purpose is to previously provide a void for preventing explosion in the concrete body, and even if there is a difference in dissolution time due to the influence of alkali content, the hardly alkaline resin is also dissolved to form a void. May be.
[0009]
Further, alkali-soluble or Ru der alkali dissolution residual mass ratio of the alkali-soluble resin to Hi溶resin 1.3 or more. Here, the alkali-dissolved residual mass ratio is each after 1 g of alkali hardly soluble or insoluble resin and 1 g of alkali-soluble resin in a 1% sodium hydroxide aqueous solution at 98 to 100 ° C. for 30 minutes. The mass of the alkali-soluble or insoluble resin after the alkali weight loss treatment is divided by the mass of the alkali-soluble resin after the alkali weight loss treatment. The alkali dissolution residual mass ratio is more preferably 2.0 or more, and still more preferably 4.0 or more. By setting the alkali-dissolved residual mass ratio to 1.3 or more, when the composite fiber is mixed into concrete, the alkali-soluble resin in the core is gradually removed from both ends of the fiber due to the alkali content of the concrete during concrete curing. As the volume of the composite fiber is reduced, the core portion of the composite fiber is hollowed out to form a hollow fiber, and this hollow portion becomes a composite fiber that easily forms a void for preventing explosion in advance. When the alkali dissolution residual mass ratio is less than 1.3, the concrete is sufficiently dissolved by the alkali content, and the concrete is neutralized before the volume is reduced, and it becomes difficult to form voids due to the dissolution of the composite fiber in advance. It is inferior in expression of the prevention effect.
[0010]
Further, the amount of explosion preventing fibers mixed in the concrete is preferably 0.01 to 5.0 vol%. More preferably, it is 0.05-3.5 vol%. If it is less than 0.01 vol%, the effect of preventing explosion is inferior, and if it exceeds 5.0 vol%, the concrete strength is lowered, which is not preferable. The amount of the mixed fibers is preferably increased because the cement matrix voids decrease as the concrete compressive strength increases. For example, 0.1 to 3.5 vol% is preferable for high-strength concrete of 80 N / mm ² or more.
[0011]
The explosion-preventing fiber of the present invention is preferably mixed in high-strength concrete, preferably 80 N / mm ² or more, more preferably 120 N / mm ² or more, and it is more effective when applied to high-strength concrete having a small cement matrix void. Is.
[0012]
The concrete explosion-proof fiber of the present invention dissolves and reduces the volume of the alkali-soluble resin due to the alkali content of the concrete during the curing of the concrete. Suppress and prevent. Moreover, in the composite fiber with the alkali hardly soluble or insoluble resin, the volume formed by the void formed in advance is reduced by the thermal dissolution or thermal decomposition of the alkali hardly soluble or insoluble resin during fire, and further increased. A void is formed, so that a concrete explosion during a fire is prevented by providing a void in the concrete in two stages.
[0013]
More specifically, in the high-strength concrete having a strength of 80 N / mm ² or more, since the voids of the cement matrix are reduced compared to normal concrete, for example, when the concrete surface during a fire is heated, In the early stage of the fire (temperature range up to about 200 ° C), the moisture in the concrete is vaporized and the expansion pressure causes a vapor explosion, which easily causes the first stage explosion, and then the high temperature when the temperature rises further. In the region, strain pressure is generated due to the temperature difference between the concrete surface and the interior, and the second stage explosion is likely to occur. The conventional concrete body absorbs these internal pressures because of the large number of matrix voids. The explosion-preventing fiber of the present invention compensates for the matrix deficiency peculiar to high-strength concrete by forming voids in advance during concrete curing as described above. In particular, the composite fiber for explosion prevention mixed in the concrete of the present invention intends to suppress and prevent the explosion by providing a gap in two stages to cope with the explosion phenomenon in two stages due to the steam explosion and concrete distortion. It is. Conventional explosion-proof fibers made of a single component such as polypropylene have been difficult to contribute to such an initial steam explosion.
[0014]
【Example】
(Example 1) Copolymerized polyester resin (product name: ALKALI SOLUBLE Super-BR, manufactured by Kanebo Gosei Co., Ltd.) which is an alkali-soluble resin as a core component, and copolymerized polypropylene resin (which is an alkali-insoluble resin as a sheath component) Using a product name: XK1167, manufactured by Nippon Polychem Co., Ltd., melt spinning was carried out at 300/285 ° C. to obtain 44 dtex undrawn yarn. The undrawn yarn was wet-drawn 2.7 times at 80 ° C., and after giving an alkyl phosphate potassium salt, it was cut to obtain 17 dtex × 10 mm core-sheath type composite short fiber for concrete explosion prevention of the present invention. The composite fiber was added in an amount of 1 vol% with respect to the concrete in which cement and aggregate were mixed at a weight ratio of 4: 1, and a concrete block having a height of 40 cm and 80 cm was prepared by inserting a reinforcing bar in the center. After the concrete block thus prepared was naturally cured for 60 days, the state of the conjugate fiber in the block was confirmed. As a result, the core portion of the conjugate fiber was dissolved and a cavity portion was formed. The concrete block was heated according to JIS-A-1304 and burned at 1100 ° C. for 5 hours. As a result, the surface of the concrete block remained a clean surface without explosion. In addition, when 1 g of each of the resin of the core component and the sheath component was alkali reduced in a 1% sodium hydroxide aqueous solution at 98 to 100 ° C. for 30 minutes, each residual mass was 0.24 g and 1 g, The residual alkali dissolution mass ratio was 1 / 0.24≈4.2.
[0015]
(Example 2) A single short fiber for preventing concrete explosion of the present invention was obtained in the same manner as in Example 1 except that only the above-mentioned copolymerized polyester resin was used. A concrete block to which this was added was prepared in the same manner as in Example 1, and after this concrete block was naturally cured for 60 days, the state of single fibers in the block was confirmed. Part was formed. This concrete block was similarly heated according to JIS-A-1304 and burned at 1100 ° C. for 5 hours. As a result, no concrete explosion phenomenon was confirmed. When 1 g of the copolyester resin was subjected to alkali weight reduction treatment in a 1% aqueous sodium hydroxide solution at 98 to 100 ° C. for 30 minutes, the alkali weight loss rate was 76%.
[0016]
Comparative Example 1 A concrete block was prepared in the same manner as in Example 1 except that no fiber was added, and the same combustion test was performed. As a result, the surface part of the concrete block was peeled off due to the explosion, and the central reinforcing bar was exposed.
[0017]
(Comparative example 2) The core-sheath-type composite fiber was obtained like Example 1 except having used the polyethylene terephthalate resin which is an alkali poorly soluble resin for a core component. A concrete block to which this was added in the same manner as in Example 1 was naturally cured for 60 days, and then the state of the composite fiber in the block was confirmed. It was not melt | dissolved and the cavity part was not formed. This concrete block was similarly heated according to JIS-A-1304 and burned at 1100 ° C. for 5 hours. As a result, a scale-like steam explosion was confirmed on the surface of the concrete block. In addition, when 1 g of each of the resin of the core component and the sheath component was alkali reduced in a 1% sodium hydroxide aqueous solution at 98 to 100 ° C. for 30 minutes, the respective remaining masses were 0.98 g and 1 g, respectively. The alkali dissolution residual mass ratio was 1 / 0.98≈1.0.
[0018]
【The invention's effect】
The explosion-preventing fiber of the present invention is particularly effective for high-strength concrete with a small cement matrix void, and is dissolved and reduced in volume by alkali during the concrete curing after placing the concrete, and the matrix is insufficient. It can contribute to prevention of water vapor explosion at the beginning of fire.
In particular, the composite fiber for explosion prevention of the present invention can suppress and prevent explosion by providing a gap in two stages to cope with the explosion phenomenon in two stages due to steam explosion and concrete distortion.

Claims (5)

At least one component is made of an alkali-soluble resin, and the other component is a composite fiber made of an alkali hardly soluble or insoluble resin ,
The alkali-soluble resin is a resin having an alkali weight loss rate of 50% or more when 1 g of resin is subjected to alkali weight loss treatment in 1% aqueous sodium hydroxide solution at 98 to 100 ° C. for 30 minutes,
The following alkali dissolution residual mass ratio of the alkali-soluble resin to the hardly-soluble or insoluble resin is 1.3 or more,
It you wherein, concrete explosion prevention fibers.
[Alkali-dissolved residual mass ratio: 1 g of hardly soluble or insoluble resin and 1 g of alkali-soluble resin are each subjected to alkali weight loss treatment in 1% aqueous sodium hydroxide at 98 to 100 ° C. The value obtained by dividing the mass of the molten resin after the alkali reduction treatment by the mass of the alkali-soluble resin after the alkali reduction treatment. ] The composite fiber is a core-sheath type composite fiber, wherein the core part of the core-sheath type composite fiber is formed from an alkali-soluble resin, and the sheath part is formed from an alkali hardly soluble or insoluble resin. The fiber for preventing concrete explosion according to claim 1 . The fiber for preventing concrete explosion according to claim 1 or 2 , wherein the alkali-soluble resin comprises a copolymerized polyester resin. The alkali hardly soluble or insoluble resin is polyethylene, polypropylene, polymethylpentene, polybutene or a copolymer thereof, polyamide, polybutylene terephthalate, polyethylene terephthalate, polystyrene, polyacetal, polycarbonate, polyphenylene sulfide, or vinylon. The fiber for concrete explosion prevention of any one of 1-3. Concrete explosion prevention fiber according to any one of claims 1 to 4 are mixed 0.01～5.0Vol% relative concrete bodies, and at least a portion of the entrained fibers decreased volume Explosion-resistant concrete body characterized in that a void is formed.