• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.536-544
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• 2016

Recently, with the increase in the number of high rise and huge scaled buildings, ultra-high strength concrete with 80~100 MPa has been used increasingly to withstand excessive loads. Among the components of concrete, the effects of the kinds and properties of fine aggregates on the performance and economic advantages of ultra-high strength concrete need to be evaluated carefully. Therefore, this study examined the effects of the type of fine aggregates and mixing methods on the engineering properties of ultra-high strength concrete by varying the fine aggregates including limestone fine aggregate (LFA), electrical arc slag fine aggregate (EFA), washed sea sand (SFA), and granite fine aggregate (GFA) and their mixtures. Ultra-high strength concrete was fabricated with a 20 % water to binder ratio (W/B) and incorporated with 70 % of Ordinary Portland cement: 20 % of fly ash:10 % silica fume. The test results indicate that for a given superplasticizer dose, the use of LFA resulted in increases in slump flow and L-flow compared to the mixtures using other aggregates due to the improved particle shape and grading of LFA. In addition, the use of LFA and EFA led to enhanced compressive strength and a decrease in autogenous shrinkage due to the improved elastic properties of LFA and the presence of free-CaO in EFA, which resulted in the formation of C-S-H.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.547-548
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• 2009

Fiber reinforcement has been being widely used in concrete to enhance the mechanical properties and to reduce the micro-cracking caused by plastic and drying shrinkage. While researches has been focused on the benefits of fiber reinforcement, the properties of fiber reinforced concrete are strongly dependent on the type, shape and the amount of fibers in concrete.

• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.817-820
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• 2008

이 논문은 초고강도 섬유보강 I형 보의 거동을 Diana를 사용하여 3차원 유한요소해석을 수행하였다. 보통 또는 고강도 콘크리트의 구성방정식과 달리 초고강도 섬유보강 콘크리트의 재료적 특성 즉, 인장 변형률 강화를 고려한 탄-소성 파괴 역학적 모델을 제안하여 해석에 반영하였다. 인장영역에서는 인장 변형률 강화를 고려한 다차원 고정 균열 규준을 사용하였고, 압축영역에서는 associated flow rule을 고려한 Drucker-Prager Criterion을 채택하였다. UHPFRC(Ultra-High Performance Fiber Reinforced Concrete) I형 보의 하중변형관계, 최초 균열, 최초 대각 균열, 극한상태 등의 결과를 실험결과와 비교하여 해석법의 유용성을 입증하였다.

• Magazine of the Korea Concrete Institute
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• v.14 no.6
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• pp.88-95
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• 2002

최근 국내에 60층을 초과하는 초고층 구조물들이 많이 건설되고 있으며, 콘크리트 품질의 향상 특히 콘크리트의 고강도화에 힘입어 이를 이용한 철근 콘크리트 고층 구조물들이 증가하고 있다. 이에 따라 이들 초고층, 초대형 구조물을 지지할 수 있는 고축력, 고연성의 기둥에 대한 설계 및 시공이 요구되고 있으며, 이에 가장 적합한 구조요소라 할 수 있는 콘크리트 충전 강관기둥(Concrete Filled Steel Tube Columns : CFT Columns)의 설계 및 시공에 관심이 높아지고 있다. 이러한 콘크리트 충전 강관기둥은 콘크리트가 강관에 의해 둘러싸여지기 때문에 축하중 저항 능력이 증가되는 장점과 동일한 단면으로 H형강을 사용한 순수 철골조 H형강 기둥의 강축(strong axis)과 약축(weak axis) 문제해결과 동시에 강성 (stiffness)을 증가시킬 수 있으며, 내화 성능이 향상되고 거푸집 대체 재료로 사용되는 등 여러 가지 장점을 지니고 있다. 한편 충전 강관기둥에 작용하는 축하중은 대부분 콘크리트가 부담하게 되는데 이러한 충전강관 기둥의 장점을 극대화하기 위해서는 보통강도 콘크리트보다는 압축강도 및 탄성계수가 큰 고강도 콘크리트의 사용은 불가피하게 된다.(중략)

• Cement
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• s.153
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• pp.44-49
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• 2000

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.76-83
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• 2021

This study examines the bending behavior of lap-spliced ultra-high-strength fiber-reinforced concrete members and evaluates the safety of the design codes for ultra-high-strength fiber-reinforced concrete structures. An experiment on a total of six beams was performed. The main variables were the fiber-inclusion and the lap-spliced length at the center of the beams. The steel fibers in a volume fraction of 2% were used, and the lap-splice lengths were determined to be 8db and 16db. As a result of the test, the specimens not reinforced with fiber lost abrupt load-bearing capacity at the lap region and did not experience yielding of the reinforcing bar. In the case of fiber-reinforced concrete, if a lap-splice length of 16db is secured, the yielding of the main reinforcing bar can be experienced, and appropriate flexural strength can be expressed. Based on the experimental results of this study, as a result of reviewing the lap-splice length calculation formulas of the current design standards and the ultra-high-strength concrete structural design recommendations, it was found that all of them were evaluated conservatively.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.395-396
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• 2010

The purpose of this research is that development of fire-high resistance concrete for high-rise buildings is carried out with a test, which is for confirmation of fire-resistance capacity of 80MPa high-strength concrete. In this test, self-developed Polymix to confirm fire-resistance capacity of high-strength concrete in domestic high-rise buildings recently is applied.

• Fire Science and Engineering
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• v.23 no.4
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• pp.7-12
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• 2009

As the concrete strength increases the degree of damage caused by the spalling becomes more serious because of the permeability. It is reported that the polypropylene (PP) fiber has an important role in protecting concrete from spalling. However, the excessive usage of PP fiber would not useful in spalling control and would decrease the workability of ultra high strength concrete. The high-temperature behaviors of high-strength reinforced concrete columns with various dosage of PP fibers and three types of fire endurance fibers were observed this study. In results, the ratio of unstressed residual strength of columns, in case of concrete strength 60MPa, increases as the dosage of PP fiber increases from 0% to 0.2%, however, the effect of fiber dosage on residual strength of column barely changes above 0.2% and in case of concrete strength 120MPa, PVA fiber is the most suitable fire endurance fiber in accounting fire endurance performance and workability.

• Land and Housing Review
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• v.4 no.3
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• pp.295-301
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• 2013

In this study, cases of domestic tall residential buildings were investigated for the structural types, numbers of stories, total heights, type of lateral load resisting systems, and zoning of concrete strength. Based on these investigation data, the structural planning pattern of tall residential building was analyzed. SRC structure is main structural types of tall residential building at the initial stage of domestic tall residential building, but RC structure is substituted for main structural types since 2005. Retaining wall system is positioned at the core part of structural plan as a lateral load resisting system. Concrete strength zoning of vertical members like columns are divided by vertical heights of lower parts, middle parts, and upper parts. Basic data of structural planning of 40stories and 60 stories residential buildings was proposed based on case investigation.