• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.43-50
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• 2019

Effects of tensile strength and aspect ratio of steel fiber on compressive and flexural behavior of steel fiber-reinforced concrete (SFRC) with high- and normal-strength were investigated. Also, this study explores compressive behavior of SFRC with different loading rate. For this purpose, four types of steel fiber were used for SFRC with specified compressive strength of 35 and 60 MPa, respectively. Cylindrical specimens with a diameter of 150 mm and height of 300 mm were made for compression test, and prismatic specimens with a $150{\times}150mm$ cross-section and 450 mm span length were made for flexural test. Test results from compression and flexural tests indicated that the toughness of concrete significant increased with steel fibers. Especially, using steel fiber with high tensile strength and aspect ratio can be lead to performance improvement of high-strength SFRC. In this study, equations are suggested to predict compressive toughness ratio of SFRC from flexural toughness ratio.

• Journal of the Korea Institute of Building Construction
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• v.17 no.5
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• pp.403-409
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• 2017

In this study, mix proportioning of porous concrete with compressive strength and porosity exceeding 3MPa and 30%, respectively, was examined and then load capacity and flexural toughness of the porous concrete block were evaluated according to the different arrangements of the GFRP bars. To achieve the designed requirements of porous concrete, it can be recommended that water-to-cement ratio and cement-to-coarse aggregate ratio are 25% and 20%, respectively, under the aggregate particle distribution of 15~20mm. The failure mode of porous concrete blocks reinforced with GFRP bars was governed by shear cracks. As a result, very few flexural resistance of the GFRP was expected. However, the enhanced shear strength of porous concrete due to the dowel action of the GFRP bars increased the load capacity and toughness of the blocks. The porous concrete blocks reinforced with one GFRP bar at each compressive and tensile regions had 2.1 times higher load capacity than the companion non-reinforced block and exhibited a high ductile behavior with the ultimate toughness index ($I_{30}$) of 43.4.

• 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.

• 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.

• Tunnel and Underground Space
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• v.24 no.1
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• pp.67-80
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• 2014

Long-term stability and delayed failure of granite were evaluated through the laboratory test based on Wilkins method and Brazilian disc test (BDT) which yields tensile strength, mode I fracture toughness and subcritical crack growth parameters. Then, the long-term strength of granite was estimated by using analytical models and long-term stability of compressed air-energy storage (CAES) pilot cavern pressurized up to 5 ~ 6 MPa was evaluated using numerical code, FRACOD with the determined subcritical crack growth parameters. The results of test and analyses showed that the subcritical crack growth index, n was determined as 29.39 and the inner pressure of 5 ~ 6 MPa had an insignificant effect on the long-term stability of pilot cavern. It was also found that the measurement and analysis of acoustic emission events can describe the accumulation of damage due to subcritical crack growth quantitatively. That is, AE monitoring can provide the current status of rock under loading if we make an identical installation condition in the field with that of the laboratory test.