• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.183-184
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• 2009

본 연구는 최근 활발히 진행되고 있는 초고강도 강섬유보강 철근콘크리트의 인장강화 모델을 제시하고 이를 비선형해석에 적용하여 초고강도 강섬유보강 철근콘크리트(Ultra High Strngth Fiber Reinforced Concrete, UHSFRC) 보의 거동특성을 알아보는데 그 목적을 두었다.

• Structural Engineering and Mechanics
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• 제91권2호
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• pp.149-161
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• 2024

In the world, the construction science and technology industry has developed strongly thanks to the application of Ultra-High Performance Concrete (UHPC) technology, with a strength greater than 150 Mpa and unprecedented durability. compared to previous materials. However, this technology can build special structures but has limited use in construction because it is not commercially feasible to replace regular concrete in most structural types due to material costs. high, lack of availability, limited design standards, complex manufacturing and maintenance techniques. This article examines the composition of UHPC materials and their performance in composite structures with conventional concrete, a promising choice for promoting the development of UHPC technology in construction. It is based on the combined use of UHPC as a covering layer around normal concrete or as an inner core to increase the strength of normal concrete, create a slender structure and reduce the cost and repair of construction works. Construction and transport infrastructure are degraded. Manufacturing costs are expected to be reduced with composite construction due to the advantages of combined materials.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.647-650
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• 2005

This paper is to investigate the shrinkage properties of ultra high strength concrete(UHSC) incorporating $5\%$ of expansive additives(EA) along with $1\%$ of shrinkage reducing agent(SRA). UHSC subjected to steam curing and incorporated with steel fiber exhibited higher compressive strength than control UHSC by as much as50MPa at 7days, while at 28days, noticeable change in compressive strength was not observed between UHSC mixtures. Control UHSC subjected to steam curing had a $922{\times}10^6$ of autogenous shrinkage strain value, which was 6.7 times of drying shrinkage strain value at 42 days. The combination of EA and SRA resulted in a decrease in autogenous shrinkage by as much as half of control mixture. Steam curing contributed to the reduction of autogenous shrinkage by as much as $11\%$ compared with that of standard curing.

• Advances in concrete construction
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• 제11권4호
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• pp.335-345
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• 2021

It is known from the literature that there are relatively few studies on the engineering properties of ultra-high performance concrete (UHPC) in early age. In fact, in order to ensure the safety of UHPC during construction and sufficient durability and long-term performance, it is necessary to explore the early behavior of UHPC. The test parameters (test control factors) investigated included the percentage of cement replaced by silica fume (SF), the percentage of cement replaced by ultra-fine silica powder (SFP), the amount of steel fiber (volume percent), and the amount of polypropylene fiber (volume percentage). The engineering properties of UHPC in the fresh mixing stage and at the age of 7 days were investigated. These properties include freshly mixed properties (slump, slump flow, and unit weight) and hardened mechanical properties (compressive strength, elastic modulus, flexural strength, and splitting tensile strength). Moreover, the effects of the experimental factors on the performance of the tested UHPC were evaluated by range analysis and variance analysis. The experiment results showed that the compressive strength of the C8 mix at the age of 7 days was highest of 111.5 MPa, and the compressive strength of the C1 mix at the age of 28 days was the highest of 128.1 MPa. In addition, the 28-day compressive strength in each experimental group increased by 13%-34% compared to the 7-day compressive strength. In terms of hardened mechanical properties, the performance of each experimental group was superior to that of the control group (without fiber and without additional binder materials), with considerable improvement, and the experimental group did not produce explosive or brittle damage after the test. Further, the flexural test process found that all test specimens exhibited deflection-hardening behavior, resulting in continued to increase carrying capacity after the first crack.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.29-32
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• 2006

The techniques related to ultra-high strength concrete(UHSC) became the key issue in recent days since requirements of the high-rise building which story is over than 100 gradually increases. Therefore, for the development of 150MPa UHSC this research is generally categorized by 4 parts: development of pre-mixed binders, evaluation for the fire performance of coarse aggregate, optimization of the mixture proportion, and mock-up test. Finally, based on the optimized mixture and its laboratory tests, mock-up test for wall and column specimens were carried out to simulate and evaluate the UHSC in real situation. The mechanical properties of core specimens were compared with the cylinder specimens made in laboratory. For instance, it showed the reasonable the results that the strength at the age of 91 days is 183MPa.

• Earthquakes and Structures
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• 제7권4호
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• pp.527-552
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• 2014

The development of modern concrete technology makes it much easier to produce high-strength concrete (HSC) or ultra-high-strength concrete (UHSC) with high workability. However, the application of this concrete is limited in practical construction of traditional reinforced concrete (RC) structures due to low-ductility performance. To further push up the limit of the design concrete strength, concrete-filled-steel-tube (CFST) columns have been recommended considering its superior strength and ductility performance. However, the beneficial composite action cannot be fully developed at early elastic stage as steel dilates more than concrete and thereby reducing the elastic strength and stiffness of the CFST columns. To resolve this problem, external confinement in the form of steel rings is proposed in this study to restrict the lateral dilation of concrete and steel. In this paper, a total of 29 high-strength CFST (HSCFST) columns of various dimensions cast with concrete strength of 75 to 120 MPa concrete and installed with external steel rings were tested under uni-axial compression. From the results, it can be concluded that the proposed ring installation can further improve both strength and ductility of HSCFST columns by restricting the column dilation. Lastly, an analytical model calculating the uni-axial strength of ring-confined HSCFST columns is proposed and verified based on the Von-Mises and Mohr-Coulomb failure criteria for steel tube and in-filled concrete, respectively.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.295-300
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• 2001

In road pavements, it is known that cement concrete pavement has superior durability, safety in compared with asphalt concrete pavement. But in reparing pavement cement concrete pavement is not usually applied because of the length of time while the road is interrupted when using Ordinary and Rapid-hardening Portland Cement. And Super High Early Strength Cement and Ultra Super High Early Strength Cement are not favorable for ready mixied concrete because of rapid setting time, high slump loss and other restrictions. We aim to develope specific cement and concrete developing 1 day strength of over 300 kg/$cm^{2}$ to open the road within one day and workable time is maintained over 1 hour that can be used as ready mixed concrete. In this study, we Produced cement using rapid-hardening cement, Hauyne clinker, anhydride gypsum and accelerator and studied on its properties. The concrete strength was over 300 kg/$cm^{2}$ at 1 day and 550 kg/$cm^{2}$ at 28 day and workable time was maintained for over 1 hour.

• 한국산학기술학회논문지
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• 제16권7호
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• pp.5015-5020
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• 2015

기존에 제안된 Perfobond rib connector의 강도평가식은 압축강도가 약 50 MPa 이하의 콘크리트 강도 범위에 대한 Push-out test의 결과로 유도된 것으로서, 압축강도 80 MPa 이상의 초고성능 콘크리트에 대한 전단 연결재 성능 평가를 위하여 Perfobond rib 연결재의 전단강도를 파악하기 위한 Push-out test를 수행하였다. Perfobond rib connector의 제작변수는 관통홀의 지름 및 개수이며, 강섬유가 혼입된 180 MPa의 콘크리와 강섬유를 혼입하지 않은 압축강도 80 MPa의 콘크리트를 적용하여 콘크리트 강도 변화에 대한 전단강도 변화를 검토하였다. 실험결과, 콘크리트 강도와 홀의 개수가 증가함 따라 전단강도가 증가하며, 다웰 효과에 의한 전단강도 증가율도 큰 것으로 나타났다. 기존에 다른 연구자들이 제안한 강도식으로 계산된 예측치와 비교한 결과, 실험값은 Oguejiofor & Hosain[2]이 제안한 강도식에 근접한 결과를 보였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.163-164
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• 2010

초고성능 콘크리트(UHPC)는 상대적으로 혼합 콘크리트 혹은 복합 구조체 콘크리트에 비해 재료성능이 우월한 콘크리트로 개발 되어져왔다. 본 연구에서는 UHPC의 노치된 보 실험의 하중-처짐 관계로부터 역해석 기법을 이용한 UHPC의 인장응력-CMOD 관계를 계산하여 종국적으로 실험이 용이치 않은 직접 인장강도를 실험식으로 추정하는 연구를 수행하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.406-412
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• 1997

This paper presents the newly developed model for the stress-strain relationship of ultra high- strength concrete on the basis of the more refined statistical to analysis the various test results available in the literature to be more rigorous in accuracy and generalized scheme. Through the comprehensive analysis of the previously existing equations for each model, multiple curves equation has turned out to be most appropriate to simulate the linearly varying ascending branch and brittle type of descending one. The principal variables to model the stress-strain relationship such as the modulus of elasticity, ultimate strain and deformation characteristics due to stress softening phenomenon were extensively studied to be simplified in the function of the concrete compressive strength.