• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.260-265
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• 1996

Polyproplyene Fibers have many advantages such as light weight, low cost, chemical stability and duragbility. It has been reported that polypropylene fiber can increase the toughness of concrete and the resistance to crack formation. This study has been performed to investigate the dirability related properties such as permeability and diffusivity of polypropylene fiber reinforced concrete. The permeability and diffusivity were measured with GWT, Poroscope, and electrical conductivity of concrete. From the test result, it is found that the addition of the polypropylene fiber improved the permeability and diffusivity of concrete, when the workability reduction was corrected by water reducer. The relationships between the permeability and diffusivity, and other properties of polypropylene fiber reinforced concrete showed that the tesst results are interrelated each other.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.315-322
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• 1997

This paper describes an experimental study on the seawater resistance of steel fiber reinforced concrete. The test method adopted for this study may be devided into long-term immersion test and accelerated test by wetting and drying. Test were carried out to evaluate the procedure in which reduction in dynamic modulus, length change and compressive strength to nine months were measured. Resistance indicators are the water - cement ratio, the content of steel fiber, the immersion water(artificial seawater or freshwater). The conditions of intervals of immersing in artificial seawater and drying, low water-cement ratio, and non-steel fiber became most deteriorated.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.341-348
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• 1997

Fibers have been used to improve the tensile strength or toughness of concrete. Therefore many different kinds of fibers have been developed and tested to reinforcing concrete. Basalt fiber is one of the recently developed materials for this purpose. Basalt fibers have the advantage which is the fiber itself is a same kind of material as concrete. In this study, fiber length change, orientation of fiber, the strength properties of fiber reinforced concrete have been tested. The test result show that as the amount of fiber increases, 1) workability of concrete has been reduced significantly, 2) the length of fiber reduced down to less than 4mm, 3) orientation factors are between 0.248 and 0.350, 4) compressive strength and elastic modulus have been increased significantly, however, the other strength have not increased significantly.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.669-675
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• 1997

This paper investigates the performances of GFRP bar and its possibility for using a substitute of steel bar. GFRO bar was made with introducing the glass fiber into GTR added UPE. We carried out the tensile test of GFRP and steel bar and out the three point bend test bond-test and fracture energy measurement on the GFRP bar and steel bar reinforced concrete. The GFRP bar was excellent as comparison with steel bar in the contribution to the energy absorption and the ductility of concrete. But its tensile, bond and bend strengthes were comparatively small. In order to improve these defects, we judged that glass fibers in GFRP bar must be completely adhesive one another by the impregnating glass fibers into UPE.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.137-145
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• 1999

The use of steel fiber reinforced to improve the strength and flexural toughness of concrete is well known, but reinforcement of polymer concrete with steel fibers has been hardly reported till now. Polymer concrete has high strength, durability and freeze-thaw resistance than that of cement concrete, but it has disadvantage such as low flexural toughness. In this paper, the strength characteristics and flexural toughness of steel fiber reinforced polymer concrete are investigated experimentally with various steel fiber aspect ratios($\ell$/d), and contents(vol.%). As the result, the flexural and splitting tensile strengths and flexural toughness were increased aspect ratio, and reach the maximums at a aspect ratio of 50. The relationship between the compressive, flexural and splitting tensile strength were high. And the relationship between flexural strength and strain energy was approximately linear.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.371-374
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• 2005

The research reported in this paper provides the test results of eleven reinforced concrete beams strengthened with FRP composites. Three parameters were considered in this investigation: the amount of FRP composites, the types of bonding schemes(continuous sheets or strips), and the material types of FRP composites (Carbon or Glass). The experimental results indicated that because the rupture strain of FRP composites was relatively higher that the yield strain of steel bars, the RC beams strengthened with FRP composites failed due to concrete crushing before the FRP composites arrived at its rupture strain. The compatibility-aided truss model showed reasonable agreement between the predicted and experimental shear stress-strain curves of the beams throughout the entire loading history.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.283-286
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• 2005

The effectiveness of shear strengthening with glass fiber sheets on normal or low strength RC beams have been investigated experimentally. A design compressive strength of concrete of 13.5MPa has been planned considering the degradation state of the existing structure to be strengthened in this study. Also, concrete surface reinforcing agent was applied to increase bond capacity between concrete and GFRP sheets in case of low strength RC beams. Comparing the test results of low and normal strength beams strengthened with GFRP sheets indicated that total shear capacity of beams was decreased with concrete strength decreased, but the shear strengthening capacity of GFRP sheets are hardly affected by concrete strength. In addition, shear strengthening effects of RC beams strengthened with GFRP sheets can be estimated by $\rho_w{\cdot}f_w$ based on the maximum effective strain of FRP sheet proposed by ACI 440.2R recommendation.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.333-336
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• 2005

This paper presents a comparative evaluation of eight different types of steel fibers used as reinforcing material in concrete beams. The fibers which used ultra-strength steel fiber reinforced concrete were fiber length of 30 to 60mm, aspect ratio of 43 to 86, W/B ratio 0.16 to 0.30, fiber types of both ends hooked and straight shape and fiber volume fraction of 1 to 5$\%$. As for the test results, it estimated the influence of fiber volume, length and aspect ratio on the mechanical properties of high toughness concrete, the mechanical properties improved according to increase fiber volume, to increase aspect ratio and to long fiber length. And the resonable fiber volume in high toughness concrete was analyzed 2$\%$ based on the results of mechanical properties.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.87-90
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• 2005

An experimental investigation on the strength and behaviour of reinforced concrete columns using high performance fiber reinforced cement composites has been carried out. The columns were subjected to monotonic axial compression until failure. The variables in this study are the combination ratio of steel cord(SC) and Polyethylene (PE), and the volumetric ratio of transverse reinforcement Test results showed that the fibers, when used in a hybrid form, could result in superior composite performance compared to their individual fiber reinforced cement composites.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.861-864
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• 2008

This study was performanced to investigate the fractural and fatigue behavior of ultra-strength steel fiber reinforcement concrete. The tension softening diagram can describe the post-cracking behavior of concrete in tension. In this paper, Three points bending tests with a notch have been carried out to investigate tensile properties of the steel fiber reinforced concrete(SFRC) according to variation of the height. Poly-linear approximation method combined with FEM analysis is applied to the steel fiber reinforced concrete to determine the tension softening diagrams and also to certify the validity of the method. The simulated load-CMOD curves using the determined softening diagrams though the poly-linear approximation method completely agree with the measured ones.