• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.469-472
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• 2008

As a general rule, concrete has higher compression strength than bending and toughness. but Ductile fiber reinforced cementitious composite has high toughness property owing to adding a large volume fiber. Therefore uniaxial tensile strength test is imperative to evaluate high toughness property of ductile fiber reinforced cementitious composite in comparison with general concrete test. but in testing compression strength, Result is different by factor of thickness, shape and edge condition. Uniaxial tensile strength test is affected by fiber's length and section area because of cementitious composite property and factor of fiber arrangement. This study evaluates toughness property of ductile fiber reinforced cementitious composite according to thickness and edge condition. The more thickness is thin, the more high performance by fiber arrangement

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.367-370
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• 2002

PET, 나일론 등과 같이 타이어코드용으로 사용되는 섬유는 타이어 내에서 계속적인 신장, 굽힘 및 압축변형을 받기 때문에 이들로 인하여 내피로성이 아주 중요한 의미를 가진다. 일반적으로 타이어는 Tread, Bead, Carcass, Sidewall, Belt 등으로 구성되어 있는데, 여기에서 타이어 코드용 섬유는 타이어의 뼈대를 이루는 것으로 타이어의 성능과 수명을 좌우하는 아주 중요한 소재인 것이다[1-2]. (중략)

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.307-315
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• 2012

Recently, ultra high performance fiber reinforced concrete (UHPFRC) having over 180 MPa compressive strength and 10 MPa tensile strength has been developed in Korea. However, UHPFRC represents different material properties with normal concrete (NC) and conventional high performance concrete (HPC) such as a high early age autogenous shrinkage and a rapid dry on the surface, because it has a low water-binder ratio and high fineness admixtures without coarse aggregate. In this study, therefore, to propose suitable experimental methods and regulations, and to evaluate mechanical properties at a very early age for UHPFRC, setting, shrinkage and tensile tests were performed. From the setting test results, paraffin oil was an appropriate material to prevent drying effect on the surface, because if paraffin oil is applied on the surface, it can efficiently prevent the drying effect and does not disturb or catalyze the hydration of cement. From the ring-test results, it was defined that the shrinkage stress is generated at the time when the graph tendency of temperature and strain of inner steel ring is changed. By comparing with setting test result, the shrinkage stress was firstly occurred as the penetration resistance of 1.5 MPa was obtained, and it was about 0.6 and 2.1 hour faster than those of initial and final sets. So, the starting time of autogenous shrinkage measurement (time-zero) of UHPFRC was determined when the penetration resistance of 1.5 MPa was obtained. Finally, the tensile strength and elastic modulus of UHPFRC were measured from near initial setting time by using a very early age tensile test apparatus, and the prediction models for tensile strength and elastic modulus were proposed.

• Magazine of the Korea Concrete Institute
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• v.4 no.3
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• pp.147-155
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• 1992

최근들어 성능이 우수하고 품질이 높은 새로운 건설소재를 개발하려는 노력이 계속되고 있다. 본 논문에서는 고강도화 및 연성확보를 위하여 폴리머 콘크리트에 섬유를 혼입한 섬유보강 폴리머 콘크리트를 제조하여 강도 및 역학적 특성을 규명하고자 하였다. 이를 위하여 포괄적인 실험연구를 수행하였으며 주요실험변수로는 강섬유의 혼입량과 채움재(filler)의 혼입량, 그리고 양생온도를 주요변수로 선정하였다. 강섬유의 혼입량은 체적비로 0%, 1%, 2%로 변화시켰으며, 채움재와 수지의 비는 1.0과 1.5로 하였다. 본 연구결과 섬유의 혼입으로 인하여 압축강도, 휨강도, 인장강도 모두 증가하였으며, 특히 인장강도의 증가가 더 크게 나타났다. 양생온도가 증가한 경우 폴리머의 중합반응이 좋아져 강도가 증가하였다. 또한 본 논문에서는 섬유보강 폴리머 콘크리트의 응력-변형도 관계곡선을 도축하였으며, 이것은 구조설계시 중요한 기초가 될 것으로 사료된다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.305-312
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• 2017

This paper presents a laboratory investigation into the effects of fillers using industrial by-product such as coal ash, IGCC slag on properties of hot-mixed asphalt concrete variation with filler content. For comparison, existing mixture with lime and dust have also been considered. Marshall and flow test has been considered for the purpose of mix design as well as evaluation of mixture. Other performance tests such as indirect tensile strength test, tensile strength ratio(moisture susceptibility), dynamic stability have also been carried out variation with filler content. It is observed that the mixes with industrial by-product exhibit conform with quality standard. Therefore, it has been recommended to utilize industrial by-product based on fly ash wherever available, not only reducing the produce cost but also partly solve the industrial by-product utilization and disposal problem.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.203-209
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• 2010

The base asphalt mixtures that used the waste recycle asphalt correcting from the four different overlay construction sites in Seoul city were made using the foamed asphalt method. The sample mixtures were made in different ratio of the recycle asphalt and new asphalt material and the performance of the mixtures of the different ratio was investigated in the laboratory. The laboratory tests includes the Marshall test, the indirect tensile test, the resilient modulus test, the creep test and the wheel tracking test. The test of the recycle foamed asphalt mixtures(RFA) were compared with the those of the recycle hot mix asphalt(RHA) mixtures. The performance of the RFA is comparable to that of the RHA. On the other hand, the indirect tensile strength of the RFA in dry condition is lower than that of RHA and the indirect tensile strength of the RFA in wet condition is much lower than that of the RHA.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.200-207
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• 2021

The purpose of this study is to investigate experimentally the effects of type of superplasticizer on tensile behavior and cracking pattern of alkali-activated slag-based cementless composite. Three mixtures were prepared according to type of superplasticizer, and the compressive strength and tension tests were performed. Test results showed that differences of tensile strength, tensile strain capacity, and toughness of composites were up to 28.1%, 39.1%, and 66.2%, respectively, according to type of superplasticizer, although fiber balling or poor dispersion of fibers in fresh composites was not observed. It was also observed that the type of superplasticizer influenced number of cracks and maximum fiber bridging stress.

• Journal of the Korean Geotechnical Society
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• v.29 no.12
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• pp.95-104
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• 2013

Recently, application of CSG is increasing in various design construction projects. At the initial stage of cementation CSG materials show the same mechanical characteristics as soil, however, as the cementation process develops, CSG materials gradually reveal material characteristics of concrete. The hardened CSG manifests elastic behavior such as maximum strength at small strain range and rapid brittle failure. In this research, PVA fiber stiffeners were used in order to: (1) reduce such brittle behavioral characteristics; (2) improve the relatively weak tension performance of CSG materials. The binding strength between the bed materials and fiber prevents rapid brittle failure and increases tensional strength of fiber reinforced CSG materials.Test results show that fiber reinforcement alone could induce the stress-strain characteristics of CSG materials from brittle failure to ductile failure and also increase the residual strength.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.571-578
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• 2003

An effective seismic retrofit scheme for inverted V braced (or chevron type) steel frames was proposed by studying the redistribution of forces in the post-buckling range. The steel frames with chevron bracing are highly prone to soft story response once the compression brace buckles under earthquake loading. This paper shows that the seismic performance of such frames could be significantly improved by supplying tie bars to redistribute the inelastic deformation demand over the height of the building. A practical design method of the retrofit tie bars was also proposed by considering the sequence of buckling occurrence.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.91-100
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• 2008

A technique strengthened to the reinforced concrete members using the external post- tensioned method offers the advantages in speed and simplicity of installation over other, established, strengthening techniques. But this technique has many unreasonable facts. This paper are analyzed an unreasonable facts of the previous external post-tension technique. The purpose of this paper proposed Bow system as the new technique strengthened to the reinforced concrete members. The Bow system which is better technique than the previous technique was introduced with the experimental/analytical data.