• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 춘계 학술논문 발표대회
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• pp.82-83
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• 2015

Recently, the research on steel fiber reinforced concrete has been actively conducted to compensate the defect of brittle fracture of concrete and to enhance toughness. Therefore, the effect of the mixture rate of straight steel fiber on flexural behavior of high strength steel fiber reinforced concrete was evaluated in this research. As a result, when 2% of steel fiber was mixed with concrete volume ratio, it showed the best flexural capacity.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 춘계 학술논문 발표대회
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• pp.289-290
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• 2012

In this study, it was evaluated about shrinkage properties of high strength concrete according to poly mix fiber and moisture evaporation condition. As a results, When concrete was mixed with poly mix fiber of spalling control, it reduced effect of shrinkage independent of the evaporation conditions of unsealed and sealed.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.275-276
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• 2018

Ultra high performance concrete(UHPC) represents high early age autogenous shrinkage strain due to its low water-to-binder ratio(W/B) and high fineness admixture usage. It has been reported that fiber can control restrained tensile stress and crack. The purpose of the present study is, therefore, to investigate the autogenous shrinkage as well as mechanical properties including compressive strength, flexural strength and modulus of elasticity on the UHPC with fiber type and pre-mix of binder.

• Computers and Concrete
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• 제34권3호
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• pp.367-378
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• 2024

This study evaluates the direct tensile strength of ultra-high-performance concrete (UHPC) using tests. A total of 45 dogbone-shaped specimens are tested, with the test variables being the fiber volume fraction and notch length. The test results showed that the material properties of UHPC were largely dependent on the fiber volume fraction and compressive strength. When steel fibers with more than 1% fiber volume fraction are mixed in the manufacturing of UHPC, the tensile strength can be more than twice that of plain UHPC. In addition, the incorporation of steel fibers enabled the significant improvement of the initial cracking strength. However, the effect of the notch length on the tensile behavior was insignificant. An assessment of the direct tensile strength is conducted using machine-learning algorithms (ML). For evaluation of the direct tensile strength of UHPC using ML, a total of 98 test data, including 53 data from other research works and 45 data from this experimental program, were collected. In total, 67 data with a 70% confidence interval on a normal distribution curve were selected, with 47 data among 67 used for ML training and 20 data used for ML testing. As a result, the machine-learning algorithm with a steel fiber volume fraction predicted that the tensile strength has an average of 0.98 and the lowest values of regression evaluation metrics among analytical and ML-based models. It is considered that an ML-based model can help to predict a more accurate tensile strength of UHPC.

• 한국건축시공학회지
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• 제10권4호
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• pp.3-9
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• 2010

본 연구는 고강도콘크리트의 내화성능 증진에 효과적인 것으로 알려진 섬유(PP+NY) 혼입율 변화에 따른 60 MPa, 80 MPa 3성분계 고강도콘크리트의 유동성 및 강도특성을 검토하고 내화시험을 통해 폭렬현상을 확인하였다. 섬유(PP+NY) 혼입율을 0%, 0.05%, 0.1%, 0.2%로 산정하여 실험한 결과, 유동성 및 강도가 미세하지만 저하하는 것으로 나타났으나, 전반적으로 목표 범위를 만족하는 것으로 나타났다. 3시간 내화 후 폭렬특성으로 0%에서는 폭렬현상이 나타났지만, 0.05%이상에서는 표면에 미세한 균열만 발생하고 피복 탈락현상은 나타나지 않는 것으로 나타났다. 또한 폭렬이 발생되지 않은 공시체의 경우 잔존압축강도율이 5 ~ 6%로 나타났다. 이상 적은 양의 섬유(PP+NY)혼입율인 0.05%이상에서 폭렬현상이 방지되어 가장 양호한 것으로 판단된다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.119-120
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• 2011

Recently, the effects of high temperature and fiber content on the residual mechnical properties of high-strength concrete were experimentally investigated. In this paper, residual mechanical properties of concrete with water to cement (w/c) ratios of 55%, 42% and 32% exposed to high temperature are compared with those obtained in fiber reinforced concretes of similar characteristics with the ranging of 0,05% to 0,20% polypropylene (PP) fibers by volume of concrete, and considered factors include pre-load levels (20% and 40% of the maximum load at room temperature). Outbreak time and water contents were tested and were determined the compressive strength. In the result, it is showed that to prevent the explosive spalling of 50MPa grade concretes exposed to high temperature need more than 0.05Vol.% PP fibers. Also, the cross-sectional area of PP fiber can influence on the residual mechanical properties and the spalling tendency of fiber reinforced concrete exposed to high temperature. Especially, the external loading increases not only the residual mechanical properties of concrete but also the risk of spalling and the brittle tendency.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 춘계 학술논문 발표대회
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• pp.213-214
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• 2012

This paper presents basic study to develop high performance concrete for concrete filled tube with addition content of steel fiber. In this study, all mixtures was added to nylon fiber (1.5 kg/㎥) and steel fiber was mixed by 0, 20 and 40 kg/㎥ respectively. To evaluate the property of high performance concrete was used to various test methods which were slump flow, air content, U-box test, O-lot test and L-flow(to 300 mm, 500 mm). Also, compressive strength test was measured by ages.

• 토지주택연구
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• 제2권1호
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• pp.53-60
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• 2011

인장을 받는 고강도콘크리트 부재의 정착특성을 평가하고 KCI 2007 정착길이 산정기준의 적용가능성을 평가하기 위하여 콘크리트강도와 정착길이, 섬유혼입률을 변수로 한 정착실험을 수행하였다. 정착실험 수행 결과, 인장을 받는 80MPa의 고강도콘크리트 부재에서 KCI 2007의 최소정착길이의 적용이 가능할 것으로 기대된다. 고강도콘크리트의 내화성능을 확보하기 위하여 혼입되는 섬유(NY+PP)는 0.1%까지 혼입하여도 고강도콘크리트의 정착특성에 영향을 미치지 않는 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.57-60
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• 2005

The objective of this paper is to investigate and analyze the behaviour of prestressed I section structural members constructed with ultra high perfomance steel fiber reinforced cementitious concrete (SFR-UHPC). This material is known as reactive powder concrete (RPC) mixed with domestic materials and its compressive strength is over 150MP. The parameters of test specimens were span to depth ratio, prestressing force, prestressing wire placement and web width. Most influential parameter to determine the failure mode between shear and flexural action was proved to be shear span ratio. The characteristics of ultra high-strength concrete is basically brittle, but due to the steel fiber reinforcement behaviour of this structure member became ductile after the peak load. As a result of the test, the stress block of compressive zone should be redefined. The proposed analytical calculation of internal force capacity based by plastic analysis gave a good prediction for the shear and flexural strength of specimens. The numerical verification of the finite element model which constitutive law developed for Mode I fracture of fiber reinforced concrete correctly captured the overall behaviour of the specimens tested.

• 한국건축시공학회지
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• 제11권4호
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• pp.353-362
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• 2011

High Strength Concrete (HSC) has weakness that in a fire, it is spalled and brittles. The phenomenon of spalling is made by water vapor's being confined in watertight concrete. This study is aimed to evaluate explosive spalling properties of high strength concrete with ${\square}100{\times}100{\times}200$ mm specimen and ${\square}400{\times}400{\times}1500$ mm column. To prevent spalling of concrete, fireproof coating and PP fiber are used. As a result, ${\square}400{\times}400{\times}1500$ mm column was prevented spalling likes ${\times}100{\times}100{\times}200$ mm specimen. When concrete protected failure to explosive spalling, quantity heat ratio (which fireproof coating specimen to pp fiber mixed specimen) between ${\square}100{\times}100{\times}200$ mm and ${\square}400{\times}400{\times}1500$ mm was maximum value at 20 minute, but difference of quantity heat ratio decreased and quantity heat ratio of each specimen is almost same at 30 minute.