WO2006016734A1

WO2006016734A1 - Frc reinforced by woven fabric coated with thermoset resin and preparation method thereof

Info

Publication number: WO2006016734A1
Application number: PCT/KR2004/002733
Authority: WO
Inventors: Joon-Seok Lee; Sangjin Hong; Hanyong Jeon
Original assignee: Pine Tex Co., Ltd.
Priority date: 2004-08-07
Filing date: 2004-10-28
Publication date: 2006-02-16
Also published as: KR20060013620A

Abstract

The present invention provides a fiber reinforced concrete (”FRC”) reinforced by the woven fabric out of yarns coated with thermoset resin and the preparation method thereof.

Description

FRC REINFORCED BY WOVEN FABRIC COATED WITH THERMOSET RESIN AND PREPARATION METHOD THEREOF

[Technical Field] The present invention relates to a fiber reinforced concrete ("FRC") reinforced by the woven fabric out of the yarns coated with thermoset resin and the preparation method thereof.

[Background Art] Fiber reinforced concrete ("FRC") is a new construction material obtained by dispersing short fibers having small cross sectional square measure into concrete. Non-reinforced cement or concrete shows low tensile strength and is easily broken when exposed to stress. In contrast, the FRC is known to have an improved toughness and ductility since the fibers resist the initiation and propagation of crack caused by impact or heat. Various FRCs made of steel, polyolefin, carbon, nylon, aramid or glass fibers have been suggested for such purpose.

In an article entitled "Flexural Characteristics of Steel Fiber and Polyethylene Fiber Hybrid-Reinforced Concrete," Kobayashi and Cho describe a FRC made by dispersing discontinuous steel and polyethylene fibers in a randomly oriented state into the concrete to provide it with both strength and toughness (K Kobayashi and R. Cho, Composites, Vol. 13 (Butterworth & Co. Ltd. 1982), pp. 164-168).

In World Patent Application WO 98/27022, J. Seewald discloses a high strength concrete of enhanced ductility comprising 30-200 kgf/m² of inorganic (e.g., steel) fibers (approximately 0.4-2.6 percent volume) along with a small amount of organic fibers of a low elasticity modulus.

Further, Korean Patent Publication No. 2001-80383 discloses a FRC having improved toughness and ductility, by employing fiber system comprising (A) a first component comprising fibers having a Young's modulus of at least 30 GigaPascals and having a width to thickness ratio of 10-200 and an average length of 5-50 mm (and more preferably 5-25 mm); and (B) a second component comprising fibers having a length to diameter ratio of 25-125 (diameter may be equivalent diameter, See ACI 544.1 R-5), an average length of 10-100 mm; the volume ratio of component A to B being at least 1 : 2.

[Disclosure] [Technical Problem]

However, portland cement, a major component of concrete is strongly alkalized up to pH 12.5 to 13 when exposed to water. Accordingly, unless fibers to be incorporated into FRC are resistant to alkali, the physical properties of the fibers may not be sufficiently manifested due to abrupt degradation of fibers in the alkaline environment. Further, even though the fibers are resistant to alkali, the fibers having high ratio of surface area to weight may face to abrupt surface degradation when exposed to the strong alkaline environment.

In addition, the self-aggregation of the fibers may prevent FRC from containing fibers in a large amount, and being uniformly reinforced throughout the FRC composition. Further, the aggregation of fibers itself may serve a weak point of FRC. Accordingly, there has been requested to develop reinforcing components for improving the toughness and ductility of FRC , which is resistant to alkali and self-aggregation.

[Technical Solution] Accordingly it is an object of the present invention to provide a

FRC composition having improved toughness and ductility, and the preparation method thereof.

Further, it is another object of the present invention to provide a FRC composition which is reinforced uniformly and along the selective direction, and the preparation method thereof.

In accordance with the aspects of the present invention, there is provided a FRC reinforced by the woven fabric out of yarns coated with thermoset resin and the preparation method thereof.

The term "concrete" refers to a composition containing a cement binder, usually with fine and course aggregates. As used hereinafter, however, the term means and refers to any cementetious material, such as cement, mortar cement, and masonry, into which fibers may be incorporated for purpose of reinforcing the material.

The present invention may employ conventional yarns without limited to particular yarns made of particular material. The yarn employed in the present invention may be glass yarn, acryl yarn, aramid yarn, carbon yarn, synthetic yarns such as nylon, polyester, polyethylene, polypropylene and polyvinyl alcohol (PVA) yarn, man-made yarns, or natural yarns such as sisal, elephant grass and Kraft pulp, and preferably PVA yarn.

Further, the yarn having fineness of 2 to 50 denier can effectively improve the homogeneity of FRC as well as toughness and ductility by splitting crack and absorbing fracture energy. The yarn having fineness of over 200 denier may not improve toughness and ductility of concrete due to low potentiality to resist propagation of crack caused by static or dynamic load. The present invention may employ the conventional woven fabric out of yarns coated with thermoset resin. However, a plain weave, a basket weave and a leno weave are preferable in view of durability.

The thermoset resin used in the present invention may comprise conventional thermoset resin including epoxy, vinyl ester, unsaturated polyesters, phenolic resins or a mixture thereof.

The present invention further provides the method for preparing

FRC comprising following steps: (1 ) coating the yarns with thermoset resin; (2) weaving fabric out of the coated yarns with thermoset resin; and

(3) mixing the woven fabric out of the yarns coated with thermoset resin with concrete composition.

(1 ) the step of coating the yarns with thermoset resin

The method for coating the yarn with thermoset resin is partially modified from the method for sizing warp threads for weaving or the method of prepreging for forming composite material.

The yarn of the present invention, preferably polyvinyl alcohol yarn is dipped in the thermoset resin, and the excessive thermoset resin is removed by passing the yarn through a squeezing roller under an appropriated pressure, for example 10 to 15 kg/cm. The thermoset resin absorbed into the yarn is stiffened in a heating chamber optionally with a hardening agent. The production rate of the yarns coated with the thermoset resin depends on the kind of the thermoset resin and hardening agent used, the temperature of heating chamber and the heating time.

One of the most important factors in coating the yarn with the thermoset resin is the amount of the thermoset resin used. When the thermoset resin is used in a small amount as in sizing the warp threads, i.e., 2 to 5 weight percent, the yarn is not sufficiently mixed with concrete to avoid self-aggregation and thus the FRC cannot contain the yarn in a large amount. In contrast, when the thermoset resin is used in an excessive amount as in prepreging for composite materials, i.e., 40 to 45 weight percent, the yarn may lose the ability to absorb the fracture energy. Accordingly, the thermoset resin is preferably used in the present invention in an amount of 5 to 20 weight percent, more preferably 10 to 15 weight percent based on the weight of yarn.

Further, the yarn absorbing the thermoset resin should be heated at a temperature that the thermoset resin is sufficiently stiffened. For instance, vinyl ester is stiffened at a temperature of about 130 ^°C and epoxy resin is preferably stiffened at a temperature of about 160 ⁰C . The complete stiffening of the thermoset resin provides the FRC with resistance to alkaline environment.

(2) the step of weaving fabric out of yarns coated with thermoset resin In order to maintain the shape of fabric, the coated yarn should be warped by side-withdrawal or direct withdrawal from a creel for preventing a wrench and removing torque with considering its thickness of 200 to 500 denier. Further, a rapier or projectile weaving machine may be preferably used for weaving the present fabric out of the coated weft which is thick and strong.

The plain weave, a basket weave and a leno weave are preferable in view of durability.

(3) the step of mixing the woven fabric out of yarns coated with thermoset resin with concrete composition

The FRC of the present invention can be obtained by layering the woven fabric on concrete composition which is evenly spread, followed by spreading concrete composition thereon. The process can be repeated to obtain the FRC of desirable toughness and ductility. Further, the FRC of the present invention can be reinforced along the selective direction by designing the direction of layering the woven fabric of the present invention. In a conventional FRC comprising the fibers which are not coated with the thermoset resin, it is difficult to incorporate the fiber in an amount of 1 weight % since the physical properties of the FRC may be deteriorated due to the self-aggregation of the fiber. However, the FRC of the present invention can comprise the coated yarn in an amount of up to 2 weight % based on the weight of the concrete composition and the physical properties of the FRC such as toughness, ductility and ability of absorbing fracture energy are continuously enhanced in proportion to the amount of yarn incorporated, since the FRC of the present invention may completely prevent the self-aggregation of the fibers. Accordingly, the FRC of the present invention can comprise a large amount of woven fabric out of the yarn coated with the thermoset resin and has an improved toughness and ductility owing to the resistance of the yarn coated with the thermoset resin to degradation in alkaline environment and self-aggregation. Further, the FRC of the present invention has a uniformly improved toughness and ductility throughout the composition and can be reinforced along the selective direction. The directional selectiveness permits the significant improvement of the physical properties with a small amount of the coated yarn.

The present invention is further described in the following Examples which are given for the purpose of illustration only, and are not intended to limit the scope of the invention.

Example 1 : The preparation of the yarn coated with thermoset resin

Polyvinyl alcohol yarn (the fineness of monofilament: 2 denier, the fineness of whole fibers: 200 denier, Kuray, Japan) was dipped in 15 weight % of vinyl ester (Korea Chemical, Co.) based on the weight of the yarn for 10 seconds, followed by passed through a squeezing roller under a pressure of 10 kg/cm. Then the vinyl ester was stiffened in heating chamber at 130 ⁰C to obtain polyvinyl alcohol yarn coated with vinyl ester. Example 2: The preparation of FRC comprising the fiber coated with thermoset resin

A plain mesh fabric of 60 cm width, 10/cm warp and 10/cm weft density was woven out of the polyvinyl alcohol yarn obtained in Example 1 by employing a rapier weaving machine at a weaving rate of 50 ppm (picks per minute). The obtained fabric was mixed with concrete composition (portland concrete, Hanil Cement) in an amount of 1 weight % based on the weight of the concrete composition in a layer by layer manner, followed by solidifying at room temperature for 28 days, to obtain the FRC comprising the woven fabric out of yarn coated with thermoset resin of the present invention.

Experimental Example 1 : The test on the physical properties of FRC of the present invention

Polyvinyl alcohol yarn (the fineness of monofilament: 2 denier, the fineness of the yarn: 200, Kuray, Japan) was coated with 15 weight % of vinyl ester (Korea Chemicals, Co., Ltd.) based on the weight of yarn by the method of Example 1. A plain mesh fabric of 10 warp and 10 weft per cm was woven from the coated yarn. The fabric was mixed with concrete in the amount of 0.75 weight % based on the weight of concrete composition by the method identical to Example 2 to obtain the FRC of the present invention. A control FRC was prepared by mixing the uncoated stapled fiber of 20 mm long with the concrete composition in the same amount as the present FRC. Flexural, tensile, compressive and shear strength of the present and control FRC were measured by using a universal test machine (Heung-Jin Precision Machine), and the result is shown in Table 1. The compressive strength (KSF 2405) was measured using a cylindrical specimen of 10 cm in diameter and 20 cm in length at a cross head speed of 0.03 mm/sec. The tensile strength (KS F 2423) was indirectly tested by loading a cylindrical specimen of 10 cm in diameter and 20 cm in length until the specimen is broken at a right angle to the loading direction. Further, flexural strength (KS F2408) was measured by using a beam- shaped specimen of 10 cm in width and thickness and 40 cm in length. [Table 1 ]

According to the result, the present FRC shows superior physical properties, i.e., flexural, tensile, compressive and shear strength to the control FRC.

Experimental Example 2: The test on the physical properties of FRC according to the amount of fiber to be incorporated

Polyvinyl alcohol fiber (the fineness of monofilament: 2 denier, the fineness of the yarn: 200, Kuray, Japan) was coated with 15 weight % of vinyl ester (Korea Chemicals, Co., Ltd.) based on the weight of yarn by the method of Example 1. A plain mesh fabric of 10 warp and 10 weft per cm was woven from the coated yarn. The fabric was mixed with concrete in the amount as indicated in Table 2 by the method identical to Example 2 to obtain the FRC groups of the present invention. Control FRC groups were prepared by mixing the uncoated stapled fiber of 20 mm long with the concrete composition in the amount as indicated in Table 2. Flexural, tensile, compressive and shear strength of the present and control FRC were measured by using a universal test machine (Heung-Jin Precision Machine), and the result is shown in Table 2. [Table 2]

According to the result, the physical properties of the present FRC was improved up to 2.00 wt/wt % of coated fiber being incorporated. However, those of the control FRC were deteriorated when fiber was added in an amount of more than 1.0 wt/wt %, and it was inferred to be due to the aggregation of fiber. Accordingly, it is believed that the present FRC efficiently prevents the self-aggregation of fiber in the FRC.

[Industrial Applicability]

The FRC of the present invention is usefully applicable to the material for construction or civil engineering, i.e., building or bridge.

While the invention has been described with respect to the above specific embodiments, it should be recognized that various modifications and changes may be made to the invention by those skilled in the art which also fall within the scope of the invention as defined by the appended claims.

Claims

[CLAIMS] [Claim 1 ]

A fiber reinforced concrete ("FRC") reinforced by a woven fabric out of yarns coated with thermoset resin. [Claim 2]

A FRC of claim 1 , wherein the yarn is coated with thermoset resin in the amount of 5 to 20 weight % based on the weight of yarn. [Claim 3]

A FRC of claim 1 , wherein the woven fabric out of the yarn coated with the thermoset resin is a plain weave, a basket weave or a leno weave. [Claim 4]

A FRC of claim 1 comprising woven fabric out of the yarn coated with thermoset resin in the amount of at least 1 weight % based on the weight of concrete composition. [Claim 5]

A preparing method of a FRC of claim 1 comprising following steps: (1 ) coating the yarns with thermoset resin; (2) weaving fabric out of the coated yarns with thermoset resin; and (3) mixing the woven fabric out of the yarns coated with thermoset resin with concrete composition. [Claim 6]

A method of claim 5, wherein the yarn is coated with the thermoset resin in the amount of 5 to 20 weight % based on the weight of the yarn in the step (1 ). [Claim 7] A method of claim 5, wherein the woven fabric out of the coated yarn is mixed with concrete in the amount of at least 1 weight % based on the weight of concrete composition in the step (3).