• Composites Research
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• 제20권2호
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• pp.21-26
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• 2007

이 논문은 합성섬유를 이용하여 포틀랜드 시멘트 모르타르를 보강한 복합재료인 ECC(Engineered Cementitious Composite)의 설계 과정과 건설현장에 이 복합재료를 적용할 수 있도록 시공성을 부여한 연구 내용을 정리하였다. 이 연구에서는 다양한 시공성, 즉 자기충전(self·consolidating)과 스프레이 시공성을 갖는 ECC를 제작하기 위하여 단계적인 재료 개발 방법론을 채택하였다. 우선 마이크로역학(micromechanics)과 안정상태균열이론(steady-state cracking theory)을 이용하여 골재와 섬유를 선정한 후, 굳기 전 재료의 레올로지를 제어하는 방법으로 시공성을 구현하였다. 여기서, 굳기 전 재료의 레올로지를 제어하기 위하여 화학첨가제(chemical admixtures)와 광물첨가재(mineral admixtures)의 양을 소량으로 조절하는 방법을 사용하였다. 이러한 방법을 활용함으로써 굳기 전에는 다양한 시공성을 나타내면서, 굳은 후에는 높은 연성(인장변형경화 거동)을 나타내는 실용적인 ECC 복합재료를 개발하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.539-540
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• 2009

이 연구에서는 레올로지 제어를 이용하여 자기충전용 ECC(Engineered Cementitious Composite)를 개발하는데 그 목적을 두었으며, 레올로지 제어를 위하여 시멘트 페이스트에 대한 시멘트와 혼화제(감수제, 증점제)의 흡착정도를 평가하였고, 모르타르에 대하여 자기충전성과 유동특성을 평가하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.313-316
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• 2005

In the recent design of high ductile fiber-reinforced cementitious composite ECC, which exhibits tensile strain-hardening behavior in the hardened state, optimizing both processing mechanical properties for specific applications is critical. This study introduced a method to develop useful ECCs in field, which possess the different fluid properties to facilitate diverse types of processing (i.e., self-consolidating or spray processing). Control of rheological modulation was regarded as a key factor to allow the performance of the desired processing, while retaining the ductile material properties. To control the rheological properties of the composite, we first determined basic ECC compositon, which is based on micromechanics and steady-state cracking theory. The stability and consequent viscosity of suspensions were, then, mediated by optimizing dosages of chemical and mineral admixtures. The rheological properties altered by this approach were revealed to be effective in obtaining ECC hardened properties, allowing us to readily achieve the desired function of the fresh ECC.

• Advances in concrete construction
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• 제11권3호
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• pp.193-206
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• 2021

Extensive research has been conducted on the basic mechanical property and structural applications of engineered cementitious composites (ECC). Despite the high tensile ductility and high toughness of ECC, transverse steel reinforcement is still necessary to confine ECC for high performance. However, limited research has examined performance of ECC confined with practical amount of transverse reinforcement. This paper presents the results of axial compression tests on 14 square ECC columns and 4 conventional concrete columns (used as control specimens) with transverse reinforcement. The test variables were spacing, configuration (square ties or square and diamond shape ties), and yield strength of stirrups. The test showed that ECC columns confined with steel stirrup had good compressive ductility, and the stirrup spacing had the greatest effect on the compressive performance. The self-confinement effect of ECC results in a more uniform but slower expansion of the whole column compared with CC ones. The test results are then compared against the predictions from a number of existing models for conventional confined concrete. It is indicated that these models fail to predict the axial strains at peak axial stress and the trend of the stress-strain curve of steel stirrups-confined ECC with sufficient accuracy. Several new equations are then proposed for the compressive properties of steel-confined ECC based on test results and potential approaches for future studies are proposed.

• Computers and Concrete
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• 제30권5호
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• pp.339-355
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• 2022

The high cost of ultra-high-performance engineered cementitious composite (UHP-ECC) is currently a crucial issue, especially in terms of the polyethylene (PE) fibers use. In this paper, cheap calcium carbonate whiskers (CW) were evaluated on the feasibility of hybrid with PE fibers. Diverse combinations of PE fibers and CW were employed to investigate the multi-scale enhancement on the UHP-ECC performance. A probabilistic-based UHP-ECC tensile strain reliability analysis approach was utilized, which was in general agreement with the experimental results. Furthermore, a multi-dimensional integrated representation was conducted for the comprehensive assessment of UHP-ECC. Results illustrated that CW improved the compressive strength and energy dissipation capacity of UHP-ECC owing to the microscopic strengthening mechanism. CW and PE fiber further promoted the saturated cracking of composite by multi-scale crack arresting effect. In particular, PE1.75-CW0.5 specimen possessed the best overall performance. The ultimate cracking width of PE1.75-CW0.5 group had 98 ㎛, which was 46.18% lower compared to PE2-CW0 group, the 28d compressive strength were slightly improved, the tensile strain capacity was comparable to that of PE2-CW0 group. The results above demonstrated that combinations of PE fiber and CW could significantly enhance the comprehensive performance of UHP-ECC, which was beneficial for large-scale engineering applications.

• 한국전산구조공학회논문집
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• 제22권6호
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• pp.597-605
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• 2009

본 연구에서는 철근 보강된 Engineered Cementitious Composite(ECC) 면내요소에 대한 2축응력 상태에서의 면내전단거동에 관한 예측 모델을 제시하였다. 기존의 철근콘크리트와 상이한 특성, 즉 ECC 요소의 복수미세균열 현상에 의한 높은 연성의 인장 거동, 일반 콘크리트에 비하여 연성적인 압축 연화 거동, 그리고 ECC 균열면에서의 전단전달 거동 특성 등을 모델에 반영하였다. 면내 순수전단거동에 대한 실험 및 해석결과를 통하여 개발된 R-ECC-MCFT 모델은 ECC 면내전단거동 예측에 효과적인 것으로 평가되었다. 또한 철근 보강된 ECC 면내요소는 철근콘크리트 면내요소에 비하여 최대전단강도 및 전단변형률이 증가하기 때문에 면내전단변형에서 높은 연성을 확보하는 것으로 평가되었다.

• 한국농공학회논문집
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• 제47권5호
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• pp.27-39
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• 2005

In the recent design of high ductile fiber-reinforced ECC (engineered cementitious composite), optimizing both processing and mechanical properties for specific applications is critical. This study presents an innovative method to develop new class ECCs, which possess the different fluid properties to facilitate diverse types of processing (i.e., self-consolidating or shotcrete processing) while maintaining ductile hardened properties. In the material design concept, we employ a parallel control of fresh and hardened properties by using micromechanics and cement rheology. Control of colloidal interaction between the particles is regarded as a key factor to allow the performance of the specific processing. To determine how to control the particle interactions and the viscosity of cement suspension, we first introduce two chemical admixtures including a highly charged polyelectrolyte and a non-ionic polymer. Optimized mixing steps and dosages we, then, obtained within the solid concentration predetermined based on micromechanical principle. Test results indicate that the rheological properties altered by this approach were revealed to be highly effective in obtaining the desired function of the fresh ECC, allowing us to readily achieve hardened properties, represented by pseudo strain-hardening behavior in uniaxial tension.

• Earthquakes and Structures
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• 제7권5호
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• pp.691-704
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• 2014

Reinforced concrete (RC) shear walls are commonly used for building structures to resist seismic loading. While the RC shear walls can have a high load-carrying capacity, they tend to fail in a brittle mode under shear, accompanied by forming large diagonal cracks and bond splitting between concrete and steel reinforcement. Improving seismic performance of shear walls has remained a challenge for researchers all over the world. Engineered Cementitious Composite (ECC), featuring incredible ductility under tension, can be a promising material to replace concrete in shear walls with improved performance. Currently, the application of ECC to large structures is limited due to the lack of the proper constitutive models especially under shear. In this paper, a new Cyclic Softening Membrane Model for reinforced ECC is proposed. The model was built upon the Cyclic Softening Membrane Model for reinforced concrete by (Hsu and Mo 2010). The model was then implemented in the OpenSees program to perform analysis on several cases of shear walls under seismic loading. The seismic response of reinforced ECC compared with RC shear walls under monotonic and cyclic loading, their difference in pinching effect and energy dissipation capacity were studied. The modeling results revealed that reinforced ECC shear walls can have superior seismic performance to traditional RC shear walls.

• 한국공간구조학회논문집
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• 제12권1호
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• pp.51-58
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• 2012

압출성형 ECC 패널을 활용한 철근콘크리트 복합 슬래브 구조에 대한 비선형 휨 해석 모델을 새롭게 제시하였다. ECC 패널은 직접인장시험 결과로부터 균열 이후에 고인성 인장거동을 하는 재료로 모델링하였다. 개발 모델을 기존 철근콘크리트 슬래브 및 ECC 패널 철근콘크리트 복합슬래브 실험체의 휨 실험결과와 비교하였다. 예측결과는 실험결과와 잘 일치하였으며, ECC 패널 적용 철근콘크리트 복합슬래브는 균열제어, 휨내력 및 휨변형능력 개선에 장점이 있는 것으로 판단되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.933-936
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• 2008

모르타르에 2 %이내의 합성섬유를 혼입함으로써 콘크리트의 수십, 수백 배에 달하는 인장변형률 경화거동을 보이는 ECC가 기존 연구에 의해 개발되었으며, ECC를 구조부재에 사용할 경우, 구조물의 성능개선이 매우 커질 것으로 판단된다. 그러나 ECC를 사용한 구조물을 설계할 때 중요한 요인인 ECC의 인장거동 관계 예측에 대해서는 많은 연구가 이루어지지 않았으며, 특히 보다 실제적인 인장거동 관계를 예측하기 위해서는 섬유분산성 등 실제의 균열면응력-변위 곡선을 고려한 연구가 필요하다. 따라서, 이 연구에서는 ECC의 인장거동 관계를 예측할 수 있는 기법을 제시하였다. ECC의 인장거동 예측방법은 초기균열강도, 인장강도, 인장변형률을 구하는 과정으로 구성되는데, 보다 합리적이고 실제적인 ECC의 인장거동 예측을 위하여 균열면응력에서 가교작용에 기여하는 유효섬유의 개수를 섬유의 기울어진 각도와 섬유사이의 간격에 따라 예측하였다. 또한 극한인장변형률 예측을 위하여 화상처리기법을 사용하였다. ECC의 인장실험결과와의 비교를 통하여 예측방법의 타당성을 평가하였다.