• International Journal of Highway Engineering
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• v.12 no.1
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• pp.47-54
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• 2010

This study had a focus on investigating technical validity of Two-Lift Concrete Pavements which had never been constructed in Korea in order to olve the problem of existing concrete pavements. This study found out the application of Steel Fiber Reinforced Concrete (SFRC) which was one of ew techniques. Also, optimal steel fiber contents and pavement thickness were determined. This study also measured compressive strengths, lexural strengths, toughness indexes, tensile strengths and fatigue strengths to estimate the performance of SFRC of according to results of aboratory experiments, slumps and air contents of concrete specimens the standards satisfied and compressive strengths to open traffic. At bending ests, Toughness Index of SFRC increased but flexural strength didn’'t increase as compared with non-steel fiber concretes. And, energy absorption of SFRC was very good and SFRC showed improvement in freezing and thawing resistances. To complete this research, we will evaluate the pplication methods and performance of SFRC at field section.

• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.109-116
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• 2014

The flexural behavior test of UHPC segmental box girder which has 160 MPa compressive strength and 15.4 m length was carried out. The effect of steel fibers in combination with reinforcing bars on improving the ductile performance of UHPC box girder was evaluated by comparing the flexural behavior of the UHPC segmental box girders made by the two kinds of mixing portion. The test variables are volume fraction of steel fibers and the arrangement of reinforcing bars. The behavior of UHPC box girder BF2 composed of 1% volume fraction of steel fibers and longitudinal reinforcing bars in web and upper flange with stirrup showed the similar ductile behavior with the girder BF1 composed of 2% volume fraction without stirrup in elastic stress region. But BF1 had the better stiffness and showed the more ductile behavior in inelastic stress region. Segmental interfaces of UHPC box girder have not any crack and slide until the final flexural collapse load.

• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.573-581
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• 2013

In this paper, an experimental investigation of bond properties between steel fiber reinforced concrete and glass fiber reinforced polymer reinforcements was performed. The experimental variables were diameter of reinforcements, volume fraction of steel fiber, cover thickness and compressive strength of concrete. Bond failure mainly occurred with splitting of concrete cover. Main factor for splitting of concrete is tension force occurred by the displacement difference between reinforcements and concrete. Therefore, in order to prevent the bond failure between reinforcements and concrete, capacity of tensile strength of concrete cover should be upgraded. As a results of test, volume fraction of steel fiber significantly increases the bond strength. Cover thickness changes the failure mode. Diameter of reinforcements also changes the failure mode. Generally, diameter of reinforcement also affects the bond properties but this effect is not significant as volume fraction of fiber. Increase of compressive strength increases the bond strength between concrete and reinforcement because compressive strength of concrete directly affects the tensile strength of concrete.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.76-82
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• 2002

The rapid-set cement concrete causes high hydration temperature and nay result in a high drying shrinkage and shrinkage-induced cracking. This problem may be fixed by incorporating polypropylene fibers in rapid-set cement concrete, because of increased toughness, resistance to impact, corrosion, fatigue, and durability. A series of concrete drving shrinkage tests was peformed in order to investigate the shrinkage properties of polypropylene fiber reinforced concrete with experimental variables such as concrete types, fiber reinforcement, W/C ratio, with and without restraint. Uni-axially restrained bar specimens were used for the restrained shrinkage tests. The results were as follows; The dry shrinkage of rapid-set cement concrete was much lessor than that oi OPC, probably because of smaller weight reduction rate by early hydration and strength development. The constraint and bridging effects caused by polypropylene fibers were great for the rapid-setting cement concrete when compared with that of plain concrete, and this resulted In increased resistance against tensile stress and cracking.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.311-321
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• 2021

Many studies have been performed on hybrid fiber reinforced concrete for years, which is to improve some of the weak material properties of concrete. Studies on characteristics of hybrid fiber reinforced concrete using amorphous steel fiber and organic fiber, however, yet remain to be done. The purpose of this research is to evaluate the compressive and tensile behaviors and then propose a material model of high performance hybrid fiber reinforced concrete using amorphous steel fiber and polyamide fiber. For this purpose, the high performance hybrid fiber reinforced concretes were made according to their total volume fraction of 1.0% for target compressive strength of 40MPa and 60MPa, respectively, and then the compressive and tensile behaviors of those were evaluated. Also, based on the experimental results of the high performance hybrid fiber reinforced concrete and mortar, each material model for the compressive and tensile behavior was suggested. It was found that the experimental results and the proposed models corresponded relatively well.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.79-86
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• 2012

Though steel reinforcing bars are the most widely used tensile reinforcement, corrosion problems are encountered due to the exposure to aggressive environments. As an alternative material to steel, the fiber reinforced polymers have been used as reinforcement in concrete structures. However, bond strength of FRP rebar is relatively low compared to steel rebar. It has been reported that fibers in matrix can resist crack growth, propagation and finally result in an increase of toughness. In this study, high-strength concrete reinforced with structural fibers was produced to enhance interfacial bond behavior between FRP rebar and concrete matrix. The interfacial bond-behaviors were investigated from a direct pullout test. The test variables were surface conditions of GFRP bars and fiber types. Total of 54 pullout specimens with three different types of bars were cast for bond strength tests. The bond strength-slip responses and resistance of the bond failure were evaluated. The test results showed that the bond strength and toughness increased according to the increased fiber volume.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.483-489
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• 2014

In this study, the flexural test of amorphous steel fiber-reinforced concrete was performed according to ASTM C 1609 to investigate its flexural performances. The amorphous steel fibers have different configurations from conventional steel fibers : thinner sections and coarser surfaces. Primary test parameters are fiber type (amorphous and conventional steel fibers), concrete compressive strength (27 and 50 MPa), and fiber volume fraction (0.25, 0.50, and 0.75%). Based on the test results, flexural strength and flexural toughness of the amorphous and conventional steel fiber-reinforced concrete were investigated. The results showed that the addition of the amorphous steel fibers into concrete could enhance both flexural strength and toughness while the addition of the conventional steel fibers into concrete was mainly effective to increase the flexural toughness.

• Magazine of the Korea Concrete Institute
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• v.3 no.1
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• pp.79-85
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• 1991

This paper aims at experimentally investigating the relationship between tensile load and average strain in the tension zone of SFRC beam. Also, it is attempted to find post cracking tension behavior of SFRC under tensile loading condition. The tension stiffening test is conducted on the long prizm of SFRC which embeds reinforcing bar in both ends of member. From this study, an empirical equation which represents the tension stiffening effect(i.e.effect of increasing tensile-~3trengthening contnbuted by SFRC when the reinforcing bar embeded in the SFRC member is under tensile loading condition) as a function of the average strain is presented .

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1677-1685
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• 2014

Short discrete fibers compounded with concrete can enhance the tensile resistance and ductility of concrete. Recently, the effectiveness of the reinforcement has increased according to the increasing length of steel fiber. However, the lengthening of steel fiber requires reducing the ratio of the fiber content to remain the workability and quality of concrete. Thus, the present study evaluated the flexural performance of fiber reinforced concrete with less than l.0% fiber volume ratios of steel fiber, 30mm and 60mm long, and polypropylene fiber, being evaluated as a good reinforcing material with chemical stability, long-term durability, and cost effectiveness. Concrete with more than 0.25% steel and 0.5% polypropylene fibers improved the brittle failure of concrete after reaching cracking strength. Concrete reinforced with polypropylene exhibited deflection-softening behavior, but that with more than 0.5% polypropylene delayed stress reduction and recovered flexural strength by 60 to 80% after cracking strength. In conclusion, concrete reinforced with more than 0.75% polypropylene could improve structural flexural performance. In particular, energy absorption capacity of reinforced concrete with 1.0% polypropylene fiber was similar to that with 0.5% and 0.7% steel fibers.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.377-385
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• 2003

Flexural characteristics of the R.C beams strengthened with newly-developed grid-type carbon fiber plastics(CFRP-GRIDS) were investigated. The tests were conducted under the four-points load to the failure to investigate the strengthening effects of CFRP-GRIDS on the beams. Results showed that initial cracks appeared in the boundary layers of fibers embedded in the newly-placed mortar concrete slowly progressed to the direction of supports and showed fracture of fiber plastics and brittle failure of concrete in compression in sequence after the yielding of steel reinforcement. Accordingly, the appropriate area of Grid-type carbon-fiber plastics in the strengthening design of deteriorated RC structures should be limited and given based on the ultimate strength design method to avoid the brittle failure of concrete structures.