• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1117-1120
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• 2008

In order to develop an Ultra High Performance Concrete (UHPC) suited to the Korean conditions, KICT has carried out several parts of research in the field of UHPC from 2003. KICT developed UHPC which was a structural material exhibiting very remarkable mechanical performances with compressive strength, tensile strength and flexural strength rising up to 200MPa, 15MPa and 35MPa, respectively. In addition, this material presents exceptional durability regard to the very low diffusion and penetration speeds of noxious substances like chloride ions. This 200MPa strength concrete has been effectively adopted for the construction of bridges like Sherbrooke Bridge in Canada in 1997, Sunyu Bridge in Korea in 2002, Meata Bridge in Japan in 2003, Sheperds Guelly Creek Bridge, the first ultra-high strength concrete highway bridge in Australia in 2004 and, more recently in 2005, Mars Hill highway bridge in USA in 2005. The construction of structures using ultra high performance concrete is a worldwide development trend of concrete technology for the construction of advanced facilities in the 21st century.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.61-69
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• 2024

An ultra-high strength prestressed prismatic beam of 100 MPa in compressive strength was developed by increasing the water-tightness of concrete by utilizing centrifugal molding processes without adding expensive admixtures. The centrifugal prismatic PSC beam developed as the superstructure of the avalanche tunnel was constructed on a rahmen bridge in a small local river. In this study, the centrifugal prismatic beam was compared and analyzed based on the results of measurements made through static load tests and the results of numerical analysis of the target structure. The common load-carrying capacity and safety of the rahmen bridge were evaluated. The static·dynamic load tests and finite element analysis results of this bridge were similar, and it was confirmed that the behavior of the centrifugal prismatic beam was well simulated. All centrifugally formed square beams that make up the composite rahmen bridge were evaluated to secure sufficient load carrying capacity under the design live load, and structural reliability was proven by ensuring safety.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.227-230
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• 2003

열방성 액정고분자 (Thermotropic liquid crystal polymer, TLCP)는 초고강도 섬유로의 응용가능성을 갖고 있어 많은 관심이 집중되고 있으며, 액정고분자의 고강도와 고탄성, 우수한 내열성과 내화학성, 가공시 성형수축률 및 선팽창계수가 작기 때문에 고성능 섬유 및 엔지니어링 플라스틱, 그리고 고분자 복합재료 등 다양한 분야에 응용되고 있다 [1]. 또한 범용성 열가소성 수지와 TLCP와의 용융블렌드는 고분자 복합재료의 강도 및 탄성의 향상뿐만 아니라 우수한 가공성 및 고성능 발현이 가능하기 때문에 현재 많은 연구가 진행되고 있다 [2]. (중략)

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.235-236
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• 2009

In this Study, we examined the characteristic of compressive strength according to various curing methods in order to obtain higher strength of UHPC in th e range of 200MPa.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.56-62
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• 2012

The results presented in this paper form part of an investigation into the optimization of a ternary blended cementitious system based on ordinary Portland cement (OPC)/blast furnace slag(BFS)/fly ash(FA) for the development of ultra high strength concrete. Concrete covering a wide range of BFS/FA blending proportions were investigated. Compressive strength at the ages of 3, 7 and 28 days for concrete specimens containing 0%, 10%, 20% and 30%FA along with 0%, 30%, 40% and 50%BFS as partial cement replacement at a water-binder ratio of 0.18 were investigated. Tests on porosity and pore size distribution were conducted using mercury intrusion porosimetry. The results show that the combination of FA10 and BFS30 can improve both short- and long-term properties of concrete as results of reducing of pores larger than 50nm.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.46-53
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• 2023

In this paper, we evaluated the flexural performance of three types of reinforced concrete beams (SHCC-RB, SHCC-SB, SHCC-FRP) strengthened with ordinary steel rebar, very high strength (super strength) rebar, and FRP bars together with strain-hardening cement composite (SHCC). For this purpose, a series of beam specimens were manufactured and four-point load bending experiments were performed. As a result of the experiment, all specimens strengthened with SHCC exhibited tightly controlled flexural microcrakcs with the crack width of less than 100 ㎛. This is mostly due to the material properties of SHCC showing tensile strain hardening properties with multiple microcracks under uniaxial tension. The specimen SHCC-FRP showed lower initial cracking moment and yield flexural strength than SHCC-RB, whereas the maximum flexural strength of SHCC-FRP was superior to that of SHCC-RC. This is because the tensile strength of FRP bars is higher than that of ordinary steel reabr. The initial cracking moment of the beam specimen SHCC-SB was similar to that of SHCC-RB, but the yield flexural strength and maximum flexural strength of SHCC-SB were evaluated to be the highest.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.371-379
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• 2013

This paper investigates the cracking and tension-stiffening behavior of 100 MPa shrinkage-compensated strain-hardening cement composite (SHCC) and conventional concrete tie elements in monotonic and cyclic tension. Strain and surface crack formation of tension ties were monitored with two strain displacement transducers and a photo microscope with a lens of magnification 50 times. Three different cement composites such as conventional concrete, shrinkage-compensated SHCC, and normal SHCC were used in the tie specimens to investigate the influence of the cement composite type on the tension stiffening and cracking behavior. Test results indicated that initial shrinkage of the ultra high-strength cement composites is greatly reduced as the 10% replacement of cement by the shrinkage-compensating admixture based on calcium sulfo-aluminate (CSA). The test results on the SHCC tension ties showed that the first cracking load decreases proportionally to the initial shrinkage strain. Reinforced ultra high-strength SHCC ties with the initial shrinkage compensation exhibited improved tension stiffening and smaller crack spacings, i.e. the reduction in crack width. Cyclic loading did not have a significant effect on tension stiffening and cracking behavior of tension ties with normal concrete and SHCC materials.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.282-289
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• 2017

The flexural behavior tests of UHPC segmental Box girder which has 160MPa compressive strength and 15.4m length were carried out. The test variables are area of prestressing wires, volume fraction of steel fibers and longitudinal reinforcing bars in upper flange and web. PS tendons which has 32 strands of 15.2mm diameter in lower flange, 24 strands and 14 strands in lower flange were arranged and volume fraction of 2%, 1.5% and 1.0% is used in box girder concrete. UHPFRC box girder which has 32 strands in lower flange showed the over reinforcement and brittle behavior. UHPFRC box girder which has 24 strands showed the similar peak load as 32 strands girder and ductile behavior as large deflection. UHPFRC box girder which has 14 strands showed half of the peak load of 24 strands box girder and ductile behavior. After the application of the formular for the reinforcement index to the behavior of the UHPFRC box girders, reinforcement index does not determine the characteristic of behavior of UHPFRC box girder exactly. So the index should consider the dimension precisely and modify the reference value corresponding to the 0.005 strain of the prestressing strands.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.173-183
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• 2012

Recently, experimental studies to prevent explosive spalling based on spalling mechanism and addition of Polypropylene fiber in high strength concrete (HSC) are performed actively. However, with respect to ultra high strength concrete (UHSC), its compact internal structure is more difficult release vapor pressure at rapid rising temperature compared to HSC. Therefore, in this study, an experiment was conducted to evaluate spalling properties of UHSC using ${\Box}$ $100mm{\times}100{\times}H200mm$ rectangular specimen according to ISO-834 standard fire curve. With respect melting point of fiber, three fiber types of Polyethylene, Polypropylene, and Nylon fibers with melting temperature of $110^{\circ}C$, $165^{\circ}C$, and $225^{\circ}C$, respectively, were considered. Mixed fiber of 0.15% and 0.25% of concrete volume was used to consider spalling properties based on water vapor pressure release. Then, TGDTA test on fiber and FEM analysis were performed. The results showed that it is difficult to prevent initial spalling without loss of fiber mass even if fiber melting temperature is low. Also, in preventing thermal spalling, fiber that melts to rapidly create porosity within 10 minutes of fire is more effective than that of low melting temperature property of fiber.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.202-213
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• 2003

Tower Palace III project is the highest residential and commercial high-rise complex building in Korea. In order to construct a high-rise building, advanced construction and engineering technology is required. Therefore, with more developed construction and engineering technology based upon accumulated knowledge, construction speed of 13.4 days per floor including finish work was achieved in this project. To achieve this project successfully, three main advanced construction technology were applied: 1) Construction methods for 3-day cycle of structural work and curtain wall, 2) Tact scheduling method for finish work, 3) Management system of material, labor, work, and information. Also, four main engineering technology were applied: 1) New material such as high -flowing concrete and high strength concrete of 800 kgf/cm2, 2) New method such as a pipe-cooling system of a cool water circulating type, 3) Mechanical system such as smart-fan controlling kitchen-ventilation system, 4) Electrical system such as false car system.