JP5885973B2 - Low shrinkage explosion-resistant hydraulic hardened body - Google Patents

Low shrinkage explosion-resistant hydraulic hardened body Download PDF

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JP5885973B2
JP5885973B2 JP2011198144A JP2011198144A JP5885973B2 JP 5885973 B2 JP5885973 B2 JP 5885973B2 JP 2011198144 A JP2011198144 A JP 2011198144A JP 2011198144 A JP2011198144 A JP 2011198144A JP 5885973 B2 JP5885973 B2 JP 5885973B2
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宗訓 熊谷
宗訓 熊谷
恵美 八谷
恵美 八谷
大前 好信
好信 大前
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株式会社クラレ
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Description

  The present invention relates to a low-shrinkage type hydraulic hardened body that has high fluidity during construction, has excellent explosion resistance during a fire, and suppresses volumetric shrinkage of concrete during curing.
  A hydraulic hardened material that has been hardened by adding water to a composition containing cement, sand, and gravel as a main component, especially concrete, is known as a material with excellent fire resistance. Therefore, there is a demand for higher strength. However, because high-strength concrete is designed to have a denser structure than ordinary concrete, a phenomenon called “explosion” occurs in which concrete on the surface layer peels off due to the expansion of water vapor generated inside the concrete during a fire. May happen. Therefore, for such high-strength concrete, in order to suppress the explosion phenomenon, by mixing organic fibers such as polypropylene and polyvinyl alcohol into the concrete, before the concrete in the event of a fire, A method of controlling the explosion by forming a fine tunnel that serves as an escape route of the above has been studied (see, for example, Patent Documents 1 and 2).
  In addition, by using a fiber composed of an ethylene-vinyl alcohol copolymer having a melting point of 160 ° C. to 190 ° C., it was excellent in miscibility with base concrete, excellent in fluidity, and heated by a fire. In some cases, it has been reported that when the mixed ethylene-vinyl alcohol copolymer fiber melts, it becomes a passage for water vapor generated inside, and explosion can be suppressed (Patent Document 3).
  Moreover, since the high strength concrete has a small water / cement ratio, the self-shrinkage of the concrete accompanying the hydration reaction of the cement is large, so that cracking or cracking of the concrete is a problem. In order to solve this problem, if a method in which a swelling agent or shrinkage reducing agent is mixed is used, it is necessary to lengthen the mixing time in order to uniformly disperse these additives, and the strength of the concrete decreases. Therefore, by using porous fine aggregate with open pores that have absorbed moisture, the hydration reaction of concrete is delayed, the decrease in compressive strength of concrete is small, and the volume shrinkage of concrete can be suppressed (Patent Document 4).
Japanese Patent No. 2620910 JP 2000-143322 A Japanese Patent No. 4090762 JP 2007-246293 A
  As disclosed in Patent Documents 1 and 2 above, even when polypropylene fibers or polyvinyl alcohol fibers are used, the explosion prevention effect is not always sufficient. The method is not always effective when the thickness of the member is thin or the cover of the reinforcing bar is thin, and it is necessary to add a large amount of fibers. Moreover, in the high-strength concrete as described in patent document 1, since the structure | tissue is dense, it was necessary to mix a lot of fiber reinforcements, and there existed a problem that fluidity | liquidity worsened for that reason. Therefore, when casting is performed using this high-strength concrete, there is a problem that casting is difficult due to poor fluidity and compressive strength is reduced.
About the fall of said fluidity | liquidity and the fall of compressive strength, the fiber (henceforth abbreviated as EVA type fiber) which uses the ethylene-vinyl alcohol-type copolymer currently disclosed by patent document 3 as a component. Although it has been improved by the inclusion, the present inventors have noticed that there is a problem that the volume of concrete shrinks during curing.
  On the other hand, Patent Document 4 discloses a low-shrinking lightweight concrete using a porous fine aggregate having an open space, but the fine aggregate is ineffective in explosion resistance.
  Accordingly, an object of the present invention is to provide a low-shrinkage type explosion-proof explosion that has high fluidity during construction, and suppresses concrete explosion during fire, and further suppresses volumetric shrinkage of concrete during curing. It is providing a water-resistant hydraulic hardening body.
  As a result of intensive studies to solve the above problems, the present inventors have at least an ethylene-vinyl alcohol copolymer having an ethylene content of 25 to 70 mol% as a component, a cross-section having a hollow shape, and a hollowness ratio. Is obtained by obtaining a low-shrinkage type explosion-resistant hydraulic cured body containing a fiber (hereinafter sometimes abbreviated as EVA hollow fiber) in a range of 0.1 to 50%. It has been found that this has been achieved, and the present invention has been completed.
Especially, it is preferable that the said hollow fiber satisfies following (1)-(4).
(1) The fiber fineness is 0.1 to 100 dtex,
(2) The hollow ratio is 1 to 45%,
(3) The fiber length is 1 to 30 mm,
(4) 0.05 to 5.0 volume% is contained with respect to 100 volume% of the hydraulic cured body.
  According to the present invention, when polypropylene fibers or polyvinyl alcohol fibers are blended by dispersing EVA hollow fibers having a hollow cross section and a hollow ratio in the range of 0.1 to 50% in the concrete. Compared to, the slump value (indicating the fluidity of the hydraulic composition, the higher the value, the higher the fluidity) is reduced and the fluidity is maintained. Excellent in properties.
  According to the present invention, EVA hollow fibers having a hollow cross section and a hollow ratio in the range of 0.1 to 50% are dispersed in concrete, and are shown in Examples and Comparative Examples described later. As shown, in the fire resistance test, the main body of the test specimen was compared with polypropylene (hollow) fiber, polyvinyl alcohol (non-hollow) fiber, EVA non-hollow fiber, and EVA hollow fiber having a hollow ratio outside the above range. The result that the survival rate after the explosion was high was obtained. This means that the hollow structure of the EVA hollow fiber having a hollow ratio within a predetermined range can serve as an escape route for water vapor against rapid volume expansion of moisture in the early stage of fire occurrence, When exposed to 160 ° C. or higher in the temperature raising process, the void size is increased by dissolution of the EVA hollow fibers, and a space for further relaxing the expansion pressure generated in the concrete can be secured. Conceivable. Therefore, it is considered that the explosion suppression effect can be exhibited in all stages from the initial stage at the time of fire occurrence to the subsequent temperature increase.
  Furthermore, according to the present invention, the volumetric shrinkage during curing is changed by dispersing EVA hollow fibers having a hollow cross section and a hollow ratio in the range of 0.1 to 50% in the concrete. Thus, a low-shrinkage hydraulic hardened body that does not have the problem of cracking of the concrete can be obtained. This is considered to be because the water retained in the hollow portion of the hollow fiber makes the hydration reaction gentle, so that self-shrinkage can be suppressed.
Hereinafter, the present invention will be described in detail. The present invention is a low shrinkage type explosion-resistant hydraulic hardened body containing EVA hollow fibers having a hollow ratio in the range of 0.1 to 50%. In the present invention, hydraulic means the property that cement, lime, and the like are cured by reaction with water, and the hydraulic cured body is a composition mainly composed of a material having hydraulic properties. It refers to the formed solid or molded body. The explosion resistance means the property of suppressing the explosion phenomenon as described above, and the low shrinkage is a value obtained by measuring the volume shrinkage of the hydraulic cured body according to JIS A112 9-3 is 100. When it is less than × 10 −6 , this hydraulic cured body is referred to as a low shrinkage type hydraulic cured body.
(Hydraulic composition)
In the present invention, a hydraulic composition for producing a hydraulic cured body is an EVA-based hollow having a hollow ratio within a predetermined range in a normal component composed of a binder such as cement, an aggregate, a water reducing agent, and the like. It is adjusted by adding fiber and adding water to this.
(Binder)
Examples of the binder used in the present invention include gypsum, gypsum slag, and magnesia. Among them, cement is preferably used. Portland cement is a typical example, but blast furnace cement, fly ash cement, alumina cement or the like may be used, or these may be used in combination.
In the present invention, when the ratio of water and cement is high, when the hardened body breaks due to stress, the number of cases where the fibers come out more than the case where the fibers break at the fracture surface tends to increase. Therefore, the water / cement (mass ratio) is preferably 0.5 or less, particularly 0.45 or less.
(aggregate)
In the present invention, fine aggregates, coarse aggregates, or a mixture thereof exemplified below can be used as the aggregates. As fine aggregates, for example, river, sea, land sand, broken sand, silica, silica fume, blast furnace slag, fly ash, etc. with a size of about 0.1 to 0.5 mm are used, and coarse aggregates are large. A rubble of about 10 to 40 mm can be used.
The mixing ratio of the aggregate with respect to the binder is appropriately selected within the range of 100 to 600 parts by mass of the aggregate with respect to 100 parts by mass of the binder.
(Water reducing agent)
Examples of water reducing agents include polyacrylates, polymethacrylates, copolymers of acrylic acid and allyl ether, copolymers of α-olefin and ethylenically unsaturated dicarboxylic acid, partially esterified products, partially amidated products, and partially imidized products. Examples of water-soluble salts such as those such as SP-8 series manufactured by BASF Pozzolith, HP-11 series manufactured by Takemoto Yushi Co., Ltd., and Nippon Zeon Co., Ltd. A workpiece 500 manufactured by Denka Grace Co., Ltd., 100PHX, and the like are preferably used, but are not limited thereto. The blending amount of the water reducing agent is preferably appropriately selected within the range of 0.1 to 4.0 parts by weight of the water reducing agent with respect to 100 parts by weight of the total amount of the binder and the aggregate.
(EVA hollow fiber)
The EVA hollow fiber added to the hydraulic composition in the present invention is a fiber containing a saponified product of a copolymer of ethylene and vinyl acetate as a component, and the amount of ethylene contained in the copolymer is 25 to 25. 70 mol% is used. Preferably it is 30-50 mol%. When the ethylene content is lower than 25 mol%, the obtained EVA hollow fiber has a property of being easily dissolved in water, so that sticking occurs between the fibers and the dispersibility is reduced in the hydraulic composition. Is likely to occur. On the other hand, when the ethylene content is higher than 70 mol%, a low melting point fiber having a melting point of 120 ° C. or lower is formed, so that the fiber is easily melted by heat of hydration before curing in the hydraulic composition. Prone. By adjusting the ethylene content, an EVA hollow fiber having a melting point of 200 ° C. or lower can be produced.
  The EVA hollow fiber used in the present invention can be produced by melt spinning an ethylene-vinyl alcohol copolymer. Various conditions such as spinning temperature, take-up speed, drawing temperature, draw ratio, heat treatment temperature, etc. can be appropriately selected and set according to the physical properties of the raw cotton such as the desired fineness, hollowness, shrinkage, etc. For example, an ethylene-vinyl alcohol copolymer can be melted with an extruder, and the melt can be produced by spinning with a melt spinning apparatus using a spin pack equipped with a die for forming a hollow section. it can. A spinning temperature in the range of 200 to 300 ° C. is employed. About the process after spinning, it may be stretched as necessary after spinning, and various conditions such as stretching temperature, stretching ratio, heat treatment temperature, etc. are set according to the desired fineness, strength, elongation characteristics, etc. It is desirable to set appropriately.
  In the present invention, the average fineness of the EVA hollow fibers is preferably in the range of 0.1 to 100 dtex, and more preferably 0.5 to 80 dtex. If the fineness is less than 0.1 dtex, the water retention ability is reduced, so that it is difficult to exert an effect on shrinkage suppression. If the fineness exceeds 100 dtex, the void size after heating and melting becomes too large, and the compression strength after heating is reduced. It tends to be unfavorable.
In the present invention, the EVA hollow fiber needs to have a hollow ratio of 0.1 to 50% represented by the following formula (1), more preferably 1 to 45%, and still more preferably 5 ~ 40%. When the hollow ratio is less than 0.1%, the water retention ability is reduced, so that the effect of suppressing shrinkage is hardly exhibited, and the problem that the explosion suppressing effect at the initial stage of fire occurrence is not sufficiently exhibited occurs. On the other hand, if it exceeds 50%, the hollow part tends to be crushed and clogged when concrete is kneaded, so that it is not used in the present invention.
Hollow ratio (%) = <A/(A+B)> × 100 (1)
However, A: Cross-sectional area of hollow part, B: Cross-sectional area of non-hollow part
  In the present invention, the fiber length of the EVA hollow fiber is preferably in the range of 1 to 30 mm, and more preferably in the range of 5 to 25 mm. When the fiber length is less than 1 mm, the space into which the water vapor generated before the fiber dissolves becomes small, which is not preferable because the effect of suppressing explosion in the initial stage of fire tends to be small. Moreover, when the fiber length exceeds 30 mm, the fibers are entangled during kneading into concrete, dispersibility is deteriorated, and fluidity is easily deteriorated, which is not preferable.
  In the hydraulic cured body produced by adding EVA hollow fibers to the hydraulic composition, the EVA hollow fibers are contained in an amount of 0.05 to 5.0% by volume with respect to 100% by volume of the hydraulic cured body. It is preferable that 0.08 to 3.0% by volume is contained. When the content is less than 0.05% by volume, the effect of suppressing explosion is reduced. Conversely, when the content exceeds 5.0% by volume, the kneadability tends to deteriorate.
(Additives added to hydraulic composition)
In addition to the above binder, aggregate, water reducing agent, EVA hollow fiber, the hydraulic cured body of the present invention includes conventional additives such as AE agents, setting / curing modifiers, rust preventives, foaming agents, It may contain foaming agents, polymer admixtures, natural or artificial siliceous admixtures, cement admixtures such as expansion materials, synthetic fibers other than EVA hollow fibers, steel fibers, etc. An additive can be used individually or in combination of 2 or more types.
  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by an Example. In addition, the physical property of each fiber in this invention and the physical property of the obtained hydraulic hardening body and evaluation of explosion resistance mean what was measured with the following method.
[Fiber fineness dtex]
Evaluation was made according to JIS L1015 “Testing method for chemical fiber staples (8.5.1)”.
[Fiber length mm]
Evaluation was made according to JIS L1015 “Testing method for chemical fiber staples (8.4.1)”.
[Hollow%]
The cross-sectional area (A) of the hollow part and the cross-sectional area (A + B) in the outer periphery of the fiber were obtained from the cross-sectional photograph of the fiber, and calculated by the above formula (1).
[Concrete slump value mm]
In accordance with the concrete slump test method according to JIS A1101, fill the cone (upper side diameter 10 cm, lower side diameter 20 cm, height 30 cm) with fresh concrete according to the prescribed procedure, pull up the cone and lower the collapsed fresh concrete on the upper side. Was measured.
[Volume shrinkage]
JIS A 112 9-3 "mortars and length change measuring method of the concrete Part 3 dial gauge method" were evaluated according to. However, the dimension of the specimen was a cylindrical specimen having a diameter of 20 cm and a height of 420 cm, and the change in length up to the age of 8 days in a temperature 20 ° C. atmosphere was measured. The volume shrinkage is displayed as −800 × 10 −6 when a hydraulic cured body having a length of 1 m shrinks by 0.8 mm, for example. When the volume shrinkage is a positive (+) value, the concrete expands, and when the volume shrinkage is a negative value, the concrete shrinks.
[Compressive strength of hydraulic cured body MPa]
A cylindrical body having a diameter of 10 cm and a height of 20 cm was formed as a sample, and a load was applied at an increasing rate of 0.25 MPa per second, and measurement was performed according to the JIS A1108-1993 test method.
[Evaluation of explosion resistance]
A fire-resistant cured sample (cylinder with a diameter of 10 cm and a height of 20 cm) is 3 m wide, 1 m high and 50 cm deep, and has a total of nine LPG burner flame jets on one wall. It was set in a brick heater and heated to conduct an explosion test. The heating program of the refractory brick heater was implemented according to the ISO834 test method, and reached 700 ° C. 15 minutes after the start of heating and reached 830 ° C. 30 minutes after the heating. And after heating temperature reached 830 degreeC, gas supply was interrupted | blocked and it cooled until it became room temperature. After further natural cooling for about 4 hours, the explosion resistance of each cylindrical specimen after the explosion test was measured. The mass of the specimen before and after the explosion was measured, and the residual ratio of the specimen was obtained by the following equation (2). The explosion prevention property was evaluated.
<Main body mass after fire resistance test / Main body mass before fire resistance test> × 100 (2)
[Examples 1-4, Comparative Examples 1-4]
Hydraulic cured bodies containing EVA hollow fibers according to the present invention (Examples 1 to 6), for comparison, hydraulic cured bodies not containing fibers (Comparative Example 1), EVA fibers (non-hollow) Hydraulic cured body containing (Comparative Example 2), Hydraulic cured body containing polyvinyl alcohol (PVA) fiber (non-hollow) (Comparative Example 3), Hydraulic cured body containing polypropylene (PP) fiber (hollow) (Comparative example 4) The hydraulic hardening body (comparative example 5) containing EVA type | system | group hollow fiber (hollow rate 60%) was produced, and the performance of the hydraulic hardening body was evaluated.
Fibers having the specifications shown in Table 2 were added to the hydraulic compositions having the compositions shown in Table 1 (the fibers were not added in Comparative Example 1), and hydraulic cured bodies were produced as follows. In addition, the ethylene content of the ethylene-vinyl alcohol copolymer constituting the EVA fibers of Examples 1 to 6 and Comparative Examples 2 and 5 is 44 mol%, and the melting point is 170 ° C. The melting point of polyvinyl alcohol is 228 ° C., and the melting point of polypropylene is 165 ° C.
Normal Portland cement (manufactured by Taiheiyo Cement), fine aggregate (river sand), coarse aggregate (maximum particle size 20 mm) and high-performance AE water reducing agent (SP) (Pozoris SP-8N) in the proportions shown in Table 1, 100 Using a liter capacity twin screw mixer, mixing was performed as follows. First, mix cement and sand for 1 minute, then add water and knead for 2 minutes. Next, the fibers were added at a blending ratio shown in Table 2 (1.0% by volume with respect to the hydraulic composition shown in Table 1), kneaded for 1 minute, scraped off once and kneaded again for 1 minute. Next, it was discharged and turned over, and kneaded again for 2 minutes to prepare.
The obtained hydraulic composition was cast in a mold for a cylindrical specimen having a diameter of 10 cm and a height of 20 cm, and four were prepared for each example and each comparative example. The prepared cylindrical specimen was cured in air in a room at 20 ° C. and 65% RH for 24 hours, immediately demolded, placed in 20 ° C. water, and cured in water for 28 days. Thereafter, two of the above four were removed from the water and the compressive strength was measured after 5 hours. The remaining two pieces were dried in a hot air dryer at 105 ° C. for 7 days and then subjected to an explosion test.
Separately from this, a slump value indicating the degree of fluidity of fresh concrete was measured. Moreover, about Examples 1-6 and Comparative Examples 2-5 to the hydraulic composition of Table 1, a fiber was added and the composition was adjusted, and the form for cylindrical specimens having a diameter of 20 cm and a height of 420 cm 3 pieces were prepared for each example or comparative example. The specimen was placed on a measuring table, and the change in length in the longitudinal direction of the specimen was measured with a dial gauge. The measuring device was left in a test room at a temperature of 20 ± 2 ° C., and the length change until the age of 8 days was measured to obtain the volume shrinkage.
Table 2 shows the measurement results of the slump value, the volume shrinkage, the compressive strength, and the residual ratio of the specimen after the explosion test (after heating).
(Slump value)
As is apparent from Table 2, the slump value of the cured product (Examples 1 to 6) to which fibers were added tends to be equal to or lower than the slump value of the cured product to which fibers are not added (Comparative Example 1). However, the slump value of the specimens (Examples 1 to 6) to which the EVA fibers were added was less reduced than the slump value of the specimen (Comparative Example 4) to which the polypropylene fibers were added, that is, the EVA series. It can be seen that the test specimen to which the fiber was added had better fluidity and better workability than the test specimen to which the polypropylene fiber was added.
  Further, since the PVA fiber is a fiber rich in hydrophilicity, when the PVA fiber is added to the hydraulic composition, the fluidity is impaired (Comparative Example 3), whereas the EVA hollow fiber is more hydrophobic than the PVA fiber. Therefore, it has a feature that it has better fluidity than PVA fibers (Examples 1 to 6).
(Volume shrinkage)
From the results of Table 2, none of the test specimens of Examples 1 to 4 according to the present invention caused volume shrinkage, and in the test specimen of Example 5 according to the present invention, the hollow ratio of the EVA-based hollow fiber Is as low as 5%, and in the specimen of Example 6, the EVA hollow fiber content is as low as 0.1%, but even in that case the volume shrinkage is small. On the other hand, all of the test samples of the comparative examples caused a large shrinkage of 100 × 10 −6 or more. In the test body of the present invention, since moisture is retained inside the EVA hollow fiber, it is considered that the progress of the hydration reaction is slow and self-shrinkage is suppressed. In particular, while the hydraulic cured body containing the EVA non-hollow fiber of Comparative Example 2 contracts, the hydraulic hardening containing the EVA hollow fiber (hollow rate 0.1 to 50%) according to the present invention. It is noteworthy that the body has low volume shrinkage. In addition, when EVA type | system | group hollow fiber whose hollow rate is 60% is mix | blended (comparative example 5), volume shrinkage is large, but this is because the hollow rate of EVA type | mold hollow fiber is too high, and a hydraulic composition. It is considered that the hollow portion of the hollow fiber is crushed when adjusting the object.
(Compressive strength)
From the result of Table 2, the hydraulic hardening body (Examples 1-6) which mix | blended EVA type | system | group hollow fiber (hollow rate: 0.1-50%) based on this invention does not contain a fiber (comparative example 1). ), When the EVA-based non-hollow fiber is blended (Comparative Example 2), compared with the case where the polypropylene fiber is blended (Comparative Example 4), it is almost the same level in terms of compressive strength. : 60%) is better than that of Comparative Example 5 (Comparative Example 5).
(Explosion resistance)
From the results in Table 2, it is clear that the hydraulic hardened bodies (Examples 1 to 6) containing the EVA hollow fibers according to the present invention have excellent explosion resistance. Particularly, the hydraulic curing of the EVA-based hollow fiber blends of Examples 1 to 6 rather than the hydraulic cured body blended with the EVA-based non-hollow fiber of Comparative Example 2 and the EVA hollow fiber of 60% hollow ratio of Comparative Example 5. It is noteworthy that the body has better explosion resistance.
  Polyvinyl alcohol fiber (hereinafter sometimes abbreviated as “vinylon fiber”), which is added to prevent explosion when preparing a conventional hydraulic composition such as concrete or mortar, decomposes while melting at a high temperature of 200 ° C. or higher. However, the EVA hollow fiber used in the present invention has a melting point lower than 200 ° C. by controlling the ethylene content as described above. Therefore, when the hydraulic cured body to which EVA hollow fibers are added is heated by a fire or the like, the EVA hollow fibers are rapidly melted and decomposed compared to the hydraulic cured bodies to which vinylon fibers are added, and the escape route of water vapor. Therefore, it is considered that the hydraulic hardened body to which EVA hollow fibers are added gives a result that is superior in explosion prevention property to the hydraulic hardened body to which vinylon fibers are added.
  Furthermore, in the present invention, the adhesion between the fiber and the hydraulic cured body is also an important factor to be considered. When the hydraulic hardened body is heated with a sudden rise in temperature such as a fire, the moisture present in the voids vaporizes and the vapor pressure increases, so the surrounding matrix has a stress that tries to destroy it. Be loaded. If the fiber is not present in the hydraulic hardened body, the matrix is easily destroyed, resulting in an explosion. When fibers are present, cross-linking by the fibers is formed in the matrix to be cut, and attempts to prevent destruction of the matrix. Thereafter, the fiber is melted and decomposed by further temperature rise, so that a fine tunnel serving as an escape route for water vapor is formed, and explosion prevention is considered to be achieved.
  Conventionally, it is known that vinylon fiber is excellent in adhesiveness with a hydraulic cured body, whereas polypropylene fiber is known to have low adhesiveness with a hydraulic cured body. When a hydraulic hardened body to which vinylon fiber is added is heated with a rapid temperature rise such as a fire, vinylon fiber has high adhesiveness to the matrix, so the presence of vinylon fiber causes water vaporization during heating. It tries to prevent the destruction of the matrix against the increase in vapor pressure, but once the matrix breaks down before the fiber melts or decomposes due to further temperature and vapor pressure increase, the fibers are firmly fixed to the matrix. This may lead to a large explosion. Polypropylene fibers, on the other hand, have low adhesion to the matrix and weak crosslinks formed by the fibers before they melt, so they cannot resist the increase in vapor pressure due to moisture vaporization during heating and easily explode. There is a case.
EVA-based hollow fibers have fewer hydroxyl groups than vinylon fibers, so the adhesion to hydraulic cured bodies is lower than vinylon fibers, but on the other hand, the adhesion is higher than polypropylene fibers,
That is, it has moderate adhesiveness to prevent matrix destruction. In the case of a hydraulic hardened body to which EVA hollow fiber is added, the EVA hollow fiber melts the matrix to be divided by the increase in vapor pressure due to vaporization of water during heating when heating is accompanied by a rapid temperature rise such as a fire. Crosslinks are formed before heating, and when heated, they are rapidly melted and decomposed at a temperature of 200 ° C. or less to form fine tunnels that serve as escape routes for water vapor. Therefore, EVA hollow fibers are formed by the formation of crosslinks in the matrix to prevent explosions before the fibers melt when the vapor pressure increases due to heating, and the fine tunneling caused by the fibers melting and decomposing due to further temperature rise. Since the production proceeds more smoothly than vinylon fiber or polypropylene fiber, it is considered that the explosion-proof performance is superior to that of vinylon fiber or polypropylene fiber.
  Furthermore, the adhesion between the fiber and the matrix is small in a matrix with a large amount of cement (low sand), such as high-strength concrete or high-strength mortar, and a matrix with a small amount of cement (high sand), such as ordinary concrete or normal It is generally said that it is large in mortar. Therefore, if it is intended to obtain an appropriate adhesion with a matrix with a large amount of cement, a vinylon fiber excellent in adhesiveness with the matrix is suitable. On the other hand, if an attempt is made to obtain an appropriate adhesion with a matrix with a small amount of cement. Polypropylene fibers having low adhesion to the matrix are preferred. As described above, the EVA hollow fiber has lower adhesion to the matrix than the vinylon fiber, but higher than the polypropylene fiber, and the adhesiveness can be adjusted by controlling the ethylene content in the copolymer. It is suitable for the use of concrete and mortar with a wide range of physical properties from ordinary concrete and ordinary mortar to high strength concrete and high strength mortar. Here, high strength concrete and high strength mortar are concrete and mortar having a compressive strength of 60 MPa or more, and ordinary concrete and normal mortar are concrete and mortar of 20 MPa or more and less than 60 MPa.
  The hydraulic hardened body containing EVA hollow fibers according to the present invention is from ordinary concrete, ordinary mortar, etc. to high-strength concrete, high-strength mortar, etc., compared to conventional hardened bodies containing vinylon fiber or polypropylene fiber. Since it is excellent in explosion prevention performance in a hydraulic hardened body having a wide range of compressive strength, it can be used as a concrete member constituting a floor, wall, column, beam or the like of a building. In addition, because thin-walled members such as handrails tend to explode due to a rapid increase in temperature because of their large surface area, in the case of using conventional vinylon fibers or polypropylene fibers, it is not easy to impart explosion resistance, If the EVA hollow fiber according to the present invention is used, explosion resistance can be imparted even to a thin member.
  Furthermore, in comparison with polypropylene fiber, polypropylene fiber has a specific gravity of 0.9, so when polypropylene fiber is added to the hydraulic composition, the fiber floats on the surface, and the fiber is uniformly mixed in the composition Whereas it is difficult to do so, EVA hollow fibers have a specific gravity of about 1.1 to 1.2. Therefore, EVA hollow fibers have an advantage that uniform mixing is easy in the composition. Uniform mixing of the fiber into the composition is an important factor for obtaining excellent anti-explosion performance.
  In particular, the hydraulic cured body containing EVA hollow fibers having a hollow ratio in the range of 0.1 to 50% according to the present invention is compared with the hydraulic cured body containing EVA non-hollow fibers as described above. And since water | moisture content is hold | maintained inside EVA type | system | group hollow fiber, since advancing of a hydration reaction becomes loose | gentle and self-shrinkage is suppressed, it is remarkably excellent in volume shrinkage.
  The hydraulic hardened body containing EVA hollow fibers according to the present invention is higher than conventional hydraulic hardened bodies containing vinylon fibers or polypropylene fibers, high-strength concrete made of ordinary concrete, ordinary mortar, etc., high-strength mortar, etc. Since a wide range of hydraulic hardened bodies having various compressive strengths are excellent in explosion prevention performance, they can be widely used as concrete members constituting floors, walls, columns, beams, etc. of buildings.
  Although the preferred embodiments of the present invention have been described above by way of example, those skilled in the art can make various modifications, additions and substitutions without departing from the scope and spirit of the present invention disclosed in the claims. It will be understandable.

Claims (1)

  1. A fiber comprising at least an ethylene-vinyl alcohol copolymer having an ethylene content of 25 to 70 mol% as a component and having a hollow cross section and satisfying the following (1) to (3) is hydraulically cured. The volume shrinkage is -50 × 10 −6 or more and less than 100 × 10 −6 contained by 0.05 to 5.0% by volume with respect to 100% by volume of the body and measured by JIS test method (JIS A1129-3) A low shrinkage explosion-resistant hydraulic hardened body.
    (1) The fiber fineness is 0.1 to 100 dtex,
    (2) The hollow ratio is 1 to 45%,
    (3) The fiber length is 1 to 30 mm.
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