• Title, Summary, Keyword: Toughness and durability

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A Study on the Flexural Toughness of Steel Fiber Reinforced Recycled Concrete (강섬유 보강 재생 콘크리트의 휨인성에 관한 연구)

  • Koo, Bong-Kuen;Kim, Tae-Bong;Kim, Chang-Woon;Park, Jae-Seong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.4 no.4
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    • pp.161-169
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    • 2000
  • Recycled aggregates were generated when concrete structures were dismembered. However, in concrete structures, because of durability, strength and toughness, recycled aggregates don't use generally. This study was done to use recycled aggregate in concrete structures. Problems of durability, strength, and toughness were caused troubles, when recycled aggregates were used, were solved as steel fibers and additives were added. Of course, steel fiber length, steel fiber contents, additive substitution, and recycled aggregate substitution were variables of this study. After flexural specimens($15{\times}15{\times}70cm$) with notch(45mm) were fabricated, basic strength tests were done and toughness was estimated using fracture mechanics parameters. The results suggest that JIC is a promising fracture criterion for all of these, while KIC(or GIC) almost certainly are not.

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A Study on the construction method of reinforced shotcrete using structural synthetic fiber (터널 지보특성 개선을 위한 보강함성섬유 숏크리트공법 연구)

  • Han, Il-Yeong;Kim, Bang-Lae;Won, Jong-Pil
    • 한국터널공학회:학술대회논문집
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    • pp.259-261
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    • 2005
  • The needs of improving the performance of wet shotcrete has become one of the most important issues in the tunnel field. The aim of this paper is to research the construction method of reinforced shotcrete using structural polymer fiber which exhibits a high quality in toughness and durability for the support of tunnel.

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A Study on the Automobile Clutch Disc Spline Hub with High Toughness by Powder Metallurgy (분말 야금에 의한 고인성 자동차 Clutch Disc Spline Hub 개발에 관한 연구)

  • 허만대;장경복;강성수
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.2
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    • pp.28-34
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    • 1998
  • Powder metallurgy processes are able to form Net-Shape products and have been widely used in the production of automobile parts to improve its productivity. However, because of pores in powder products, the toughness of powder products are generally poor. Therefore, forged products are used in parts which suffer severe fatigue loads. In this paper, the choice of powder materials and production processes such as mixing, compaction, sintering, heat treatment to produce automobile spline hub are studied. Three type of materials are selected and processed and its microstructure and properties are investigated by tensile test, compression ring test, and impact test. Materials and processing methods are selected from the results. Finally, experimental spline hubs are manufactured by selected processes from selected powders and proved by torsional durability test.

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Study on the Strength Characteristics and Flexural Toughness of Steel Fiber Reinforced Polymer Concrete (강섬유 보강 폴리머 콘크리트의 강도특성 및 휨인성에 관한 연구)

  • 김기락;연규석;이윤수
    • Journal of the Korea Concrete Institute
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    • v.11 no.4
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    • pp.137-145
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    • 1999
  • The use of steel fiber reinforced to improve the strength and flexural toughness of concrete is well known, but reinforcement of polymer concrete with steel fibers has been hardly reported till now. Polymer concrete has high strength, durability and freeze-thaw resistance than that of cement concrete, but it has disadvantage such as low flexural toughness. In this paper, the strength characteristics and flexural toughness of steel fiber reinforced polymer concrete are investigated experimentally with various steel fiber aspect ratios($\ell$/d), and contents(vol.%). As the result, the flexural and splitting tensile strengths and flexural toughness were increased aspect ratio, and reach the maximums at a aspect ratio of 50. The relationship between the compressive, flexural and splitting tensile strength were high. And the relationship between flexural strength and strain energy was approximately linear.

An Experimental Study on the Mechanical Study and Durability of PFRC(Polypropylene Fiber Reinforced Concrete) (폴리프로필렌 섬유보강 콘크리트(PFRC)의 역학적 특성 및 내구성에 관한 실험적 연구)

  • 박승범;이봉춘;권혁준;윤준석
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.293-298
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    • 1998
  • The result of an experimental study on the mechanical properties and durability of polypropylene fiber reinforced concrete are presented in this paper. This study has been performed to obtain the properties of PFRC such as strength, toughness and durability. The test variables are fiber content, fiber types, W/C ratio. PFRC shows the highest strength when the polypropylene fiber contents were increased to 2.0 vol.%. Also, freeze-thaw resistance and carbonation were somewhat more improved than plain concrete.

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A Study on the Strength and Drying Shrinkage Crack Control Properties of Polypropyl (폴리프로필렌 합성섬유보강 콘크리트의 강도 특성 및 건조수축균열제어 특성에 관한 연구)

  • 오병환;백상현
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.146-152
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    • 1996
  • Polypropylene fiber reinforced mortar and concrete as civil material or architectural material have been used in America and British etc, and have been researched. Polypropylene fibers have many advantages in many points ; in economical costs, chemical stability and durability. It has been reported that polypropylene fiber can control restrained tensile stresses and cracks and increase toughness, resistance to impact, corrosion, fatigue and durability. This study has been performed to obtain the properties of polypropylene fiber reinforced concrete such as compressive strength, flexural strength, toughness, slump, drying shrinkage crack and drying shrinkage characteristics. The test variables are fiber contents, fiber length, fiber types, and so on. From the results of this study, we can expect the effects of the admixtures of polypropylene fiber about strength and drying shrinkage properties in concrete and mortar.

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A Study on the Strength and Drying Shrinkage Crack Control Characteristics of Polypropylene Fiber Reinforced Concrete (폴리프로필렌 섬유보강 콘크리트의 강도 및 건조수축균열 제어특성 연구)

  • 오병환;이명규;유성원;백상현
    • Magazine of the Korea Concrete Institute
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    • v.8 no.6
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    • pp.151-161
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    • 1996
  • Recently, polypropylene fiber reinforced mortar and concrete as civil and architectural materials have been used in major countries in the world. Polypropylene fiber reinforced concrete has many advantages in terms of economical aspect, chemical stability and durability. It has been reported that polypropylene fiber can control restrained tensile stresses and cracks and increase toughness, resistance to impact, corrosion, fatigue and durability. The purpose of the present study is, therefore, to investigate the strength as well as many mechanical characteristics including toughness and shrinkage control properties. A specially devjsed shrinkage test has been applied to measure the crack control characteristics of polypropylene fiber reinforced concrete. The present study indicates that the polypropylene fiber reinforced concrete curbs greatly the crack occurrence due to shrinkage and enhances toughness resistance. The present study provides a firm base for the efficient use of polypropylene fiber reinforced concrete in actual construction such as pavements and slab structures.

Interfacial Evaluation and Damage Sensing of Carbon Fiber/Epoxy-AT-PEI Composite using Electro-Micromechanical Techniques (Electro-micromechanical 시험법을 이용한 탄소섬유 강화 Epoxy-AT PEI 복합재료의 손상 감지능 및 계면물성 평가)

  • Kim, Dae-Sik;Kong, Jin-Woo;Park, Joung-Man;Kim, Minyoung;Kim, Wonho;Ahn, Byung-Hyun;Park, Jin-Ho
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.212-215
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    • 2002
  • Interfacial evaluation and damage sensing of the carbon fiber/epoxy-amine terminated (AT)-polyetherimide (PEI) composites were performed using micromechanical test and electrical resistance measurement. As AT-PEI content increased, the fracture toughness of epoxy-AT-PEI matrix increased, and thus their interfacial shear strength (IFSS) was improved due to the improved toughness. After curing process, the changes in electrical resistance (ΔR) with increasing AT-PEI contents increased gradually because of the changes in thermal expansion coefficient (TEC) and thermal shrinkage of matrix. Matrix fracture toughness was correlated to the IFSS, residual stress and electrical resistance. The results obtained from the electrical resistance measurement during curing process, reversible stress/strain, and durability test were consistent with modified matrix toughness properties.

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Selecting optimized mix proportion of bagasse ash blended high performance concrete using analytical hierarchy process (AHP)

  • Praveenkumar, S.;Sankarasubramanian, G.;Sindhu, S.
    • Computers and Concrete
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    • v.23 no.6
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    • pp.459-470
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    • 2019
  • Apart from strength properties, durability, toughness and workability are also important criteria in defining the performance of a concrete structure. Hence "High Performance Concrete (HPC)" is introduced. It is different from high strength concrete and can have various applications. In this paper, the properties (Mechanical and Durability) of High Performance Concrete blended with bagasse ash at 5%, 10%, 15% and 20% are studied. However, it is difficult to analyze the performance based on different properties obtained from different experiments. Hence it is necessary to combine all the criteria/properties into a single value to obtain a result by a technique called Analytical Hierarchy Process (AHP).It is an effective tool for dealing with complex decision making, and may aid the decision maker to set priorities and make the best decision. In addition, the AHP incorporates a useful technique for checking the consistency of the decision maker?s evaluations, thus reducing the bias in the decision making process.

Compressive resistance behavior of UHPFRC encased steel composite stub column

  • Huang, Zhenyu;Huang, Xinxiong;Li, Weiwen;Zhang, Jiasheng
    • Steel and Composite Structures
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    • v.37 no.2
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    • pp.211-227
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    • 2020
  • To explore the feasibility of eliminating the longitudinal rebars and stirrups by using ultra-high-performance fiber reinforcement concrete (UHPFRC) in concrete encased steel composite stub column, compressive behavior of UHPFRC encased steel stub column has been experimentally investigated. Effect of concrete types (normal strength concrete, high strength concrete and UHPFRC), fiber fractions, and transverse reinforcement ratio on failure mode, ductility behavior and axial compressive resistance of composite columns have been quantified through axial compression tests. The experimental results show that concrete encased composite columns with NSC and HSC exhibit concrete crushing and spalling failure, respectively, while composite columns using UHPFRC exhibit concrete spitting and no concrete spalling is observed after failure. The incorporation of steel fiber as micro reinforcement significantly improves the concrete toughness, restrains the crack propagation and thus avoids the concrete spalling. No evidence of local buckling of rebars or yielding of stirrups has been detected in composite columns using UHPFRC. Steel fibers improve the bond strength between the concrete and, rebars and core shaped steel which contribute to the improvement of confining pressure on concrete. Three prediction models in Eurocode 4, AISC 360 and JGJ 138 and a proposed toughness index (T.I.) are employed to evaluate the compressive resistance and post peak ductility of the composite columns. It is found that all these three models predict close the compressive resistance of UHPFRC encased composite columns with/without the transverse reinforcement. UHPFRC encased composite columns can achieve a comparable level of ductility with the reinforced concrete (RC) columns using normal strength concrete. In terms of compressive resistance behavior, the feasibility of UHPFRC encased steel composite stub columns with lesser longitudinal reinforcement and stirrups has been verified in this study.