• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.38-39
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• 2015

This study reviewed slump and air content as pre-hardening characteristics depending on B/P production of amorphous steel fiber-reinforced concrete and evaluated compressive strength, flexural strength and tensile strength as post-hardening characteristics depending on B/P production of amorphous steel fiber-reinforced concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.65-66
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• 2010

In this paper, an experimental investigation on three high-strength steel fiber reinforced concrete beams with 0.5%-1.0% steel fiber and the one without steel fiber, which led to shear failure, is reported to investigate the effectiveness of steel fibers as shear reinforcement. The test results showed that the shear strengths of high-strength concrete beams increased and had more ductile behavior as larger amount of steel fiber were included.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.3
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• pp.433-452
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• 2019

This study deals with shotcrete reinforcing performance according to the amount of synthetic fiber (PP fiber) and proper evaluation method. The shotcrete compressive strength, flexural strength and flexural toughness were tested by setting the mixing amounts of steel fiber ($37.0kg/m^3$) and synthetic fiber (PP fiber) as parameters ($5.0kg/m^3$, $7.0kg/m^3$ and $9.0kg/m^3$). Particularly, circular panel flexural toughness test (Road and Traffic Authority, RTA) was performed to evaluate the shotcrete energy absorption capacity. As a result, the compressive strength and the bending strength of the steel fiber reinforced shotcrete were large, but the flexural toughness of the synthetic fibe (PP fiber) reinforced shotcrete was large. Therefore, synthetic fiber (PP fiber) reinforced shotcrete is considered to have a reinforcing effect comparable to that of steel fiber reinforced shotcrete. Analysis of the relationship between the flexural toughness and the energy absorption capacity of synthetic fiber (PP fiber) reinforced shotcrete revealed that the energy absorbing ability is exhibited at a flexural toughness lower than the allowable standard (3.0 MPa). (Class A: 2.55 MPa = 202J, Class B: 2.72 MPa = 282J, Class C: 3.07 MPa = 403J). As a result of this study, it can be concluded that the actual shotcrete support performance can be evaluated by evaluating the support performance of the shotcrete measured at less than the allowable standard (3.0 MPa) at the actual tunnel site.

• 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 Korean Tunnelling and Underground Space Association
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• v.15 no.1
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• pp.1-11
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• 2013

Steel fiber-reinforced concrete (SFRC) is widely used for tunnel lining structure such as shot-crete in NATM tunnel and segment in TBM tunnel. In tunnel fire accidents, structural performance of a lining is very important because the lining is the structure that directly exposed to fire. In this study, the effects of high temperatures, mix ratios and types on failure pattern, DPT tensile strength and coefficient of variation were investigated through Double Punch Tests (DPT) of SFRC subjected to high temperatures. In the results, it is confirmed that the residual DPT tensile strength increases as for SFRC and this is more in SFRC with higher mix ratio. But, the equation for evaluation of DPT tensile strength does not involve the number of failure surfaces SFRC specimens subjected to high temperatures, therefore, it is required to investigate more fracture energy in DPT tests.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.48-59
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• 2021

In this study, experiments were conducted to investigate the compressive·flexural performances of single fiber-reinforced mortar (FRM) using only steel fiber or carbon fiber which has different material properties as well as hybrid FRM using a mixture of steel and carbon fibers. The mortar specimens incorporated steel and carbon fibers in the mix proportions of 1+0%, 0.75+0.25%, 0.5+0.5%, 0.25+0.75% and 0+1% by volume at a total volume fraction of 1.0%. Their mechanical performance was compared and examined with a plain mortar without fiber at 28 days of age. The experiments of mortar showed that the hybrid FRM using a mixture of 0.75% steel fibers + 0.25% carbon fibers had the highest compressive and flexural strength, confirming by thus the synergistic reinforcing effect of the hybrid FRM. On the contrast, in the case of hybrid FRM using a mixture of 0.5% steel fibers + 0.5% carbon fibers witnessed the highest flexural toughness, suggesting as a result the optimal fiber mixing ratio of hybrid FRM to improve the strength and flexural toughness at the same time. Moreover, the fracture surface was observed through a scanning electron microscope (SEM) for image analysis of the FRM specimen. These results were of great help for images analysis of hybrid reinforcing fibers in cement matrix.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.15-16
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• 2017

In this study, the flexural behavior of fiber-reinforced concrete by fiber type were evaluated. As a result, the flexural strength of the hooked steel fiber-reinforced concrete(HSFRC) was lower than that of the amorphous metallic fiber reinforced concrete(AFRC), however it was shown strain-softening behavior by the pull-out of fiber. The flexural strength and the equivalent flexural strength of polyamide fiber-reinforced concrete(PAFRC) were lower than other specimens, but the equivalent flexural strength ratio was similar to that of AFRC. The flexural behavior of the fiber-reinforced concrete was associated with the bonding and pull-out properties of the fiber and matrix depending on the fiber type.

• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.581-589
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• 2014

This paper presents the tension stiffening behavior from experimental results of each 6 amorphous steel fibers and normal steel fibers reinforced direct tensile specimens with the main variables such as cover thickness to bar diameter ratio. A tension stiffening effect for steel fiber reinforced RC tension members improve on the increase in cover thickness, and also amorphous steel fiber is usually superior to normal steel fiber. The reinforcement of steel fibers controlled the splitting cracks and led to significant increase in the tension stiffening effect. In particular, if cover thickness is more than twice the bar diameter, the amorphous steel fiber reinforced specimen is controlled the splitting crack and increased the tension stiffening effect. And, the tension stiffening effect of amorphous steel fiber reinforced concrete tension members is different to current structural design code provision.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.35-44
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• 2017

In this study, steel fiber-reinforced concrete beams with ordinary steel reinforcements, that are below minimum steel reinforcement amount specified in domestic concrete structure design code, were tested in flexure until failure. Steel reinforcement ratio considered were 44%, 66%, 78% and 100% of the minimum steel reinforcement. Considered steel fiber volume fractions were 0.25%, 0.50%, 0.75% and 1.00%. In results, it is confirmed that steel fibers greatly improve crack performance. Also, the steel fibers contributed to increment in yield load not in ultimate load. But the increment was not greater than the reduction by steel reinforcement reduction. The use of steel fibers in RC beams lightly reinforced below the minimum reinforcement ratio specified design code reduced ductility greatly. Consequently, steel reinforcement ratio in steel fiber-reinforced beams lightly reinforced below the minimum steel reinforcement should be increased in order to enhance proper ductility.

• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.690-695
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• 2004

In this study, inorganic (steel, asbestos and carbon) and organic (polyacryl and polyamide) fibers were used to investigate their reinforcing effects of the physical properties of Portland cement. From the load-displacement curve of each reinforced specimen, fracture strength, Young's module, fracture energy and fracture toughness were computed and compared with each other. In addition, the experiment of their impact toughness was carried out and compared with the fracture energy. For the improvement of fracture strength the inorganic (asbestos) fiber reinforcement was most effective, while the best reinforcing effect of impact toughness was achieved by organic (polyacryl) fiber. And steel fiber proved to be most adequate for improvement of both fracture strength and impact toughness. Steel fiber also showed the highest fracture energy and fracture toughness among all of the fibers.