• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.657-660
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• 2008

In this study, quantitative analysis on effect of hydration heat and autogenous shrinkage of concrete using BFS was studied. Especially, it analyze section data statistically which hydration heat and autogenous shrinkage rise, and it appeared the correlation of hydration heat and autogenous shrinkage as well as quantitative coefficients of the main properties. As a result, the section which hydration heat and autogenous shrinkage of BFS-50 rise rapidly is delayed than OPC, but the slope of hydration heat and autogenous shrinkage in that section appeared similar shape in each mixing. Finally it will be possible to control the amount of autogenous shrinkage because hydration heating velocity and autogenous shrinking velocity are decreased by using BFS.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.549-556
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• 2003

Various researches on the application of polymer dispersions to the cement mortar and concrete have been practised in many countries like America, Japan and Germany and so on because of high performance and good modification effect of these. In this study, SBR, Polymer dispersion that widely used in situ is employed that the self-flowability may be induced in the cemen mortar. In order to comprehend and investigate the modification of cement mortar with self-flowability by SBR and properties and fracture mode of adhesive strength in tension of that, experimental parameter was set as SBR solid-Cement ratio(S/C) and Cement:Fine aggregate(C:F) and the experiments such as Unit weight, Flow, Consistency change, Crack resistance and Segregation that inform on the general properties have been done. In addition of that, Adhesion in tension is measured with a view to comprehending the properties and fracture mode in tensile load. Consistency change of cement mortar modified by SBR did grow better as the ratio of SBR solid-Cement increased and was much superior to that of resin based flooring such as polyurethane and epoxy which recorded the loss of consistency in 90min. after mixing. Adhesive strength in tension increased with continuity in the curing age and showed the maximum in case of C:F=1:1 and S/C=20%. As the increase of curing age, the fracture mainly happened in the concrete substrate and the interface between the specimen and concrete substrate.

• Polymer(Korea)
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• v.32 no.1
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• pp.26-30
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• 2008

This study was designed to investigate the effect of hybridization of synthetic/natural materials for annulus fibrosus (AF) tissue regeneration in vitro and in vivo. The synthetic/natural hybrid scaffolds were prepared using PLGA (poly (lactic-co-glycolic) acid), SIS (small intestinal submucosa) and DBP (demineralized bone particles). PLGA, PLGA/SIS(20%), PLGA/DBP(20%) and PLGA/SIS (10%)/DBP (10%) scaffold were manufactured by solvent casting/salt leaching method. Compressive strength was measured. Rabbit AF cells were isolated, cultured and seeded into experimental groups. Hydroxyproline production and DNA quantity of AP cells on each scaffold was measured at 2, 4 and 6 weeks after in vitro culture. Cell-scaffold composites were implanted subcutaneously into athymic mice. After 1,4 and 6 weeks postoperatively, specimens were taken and H&E, Safranin-O and type I collagen staining were carried out concerning formation of cartilagenous tissue. In vitro PLGA/SIS scaffold was evaluated for total collagen content (bydroryproline/DNA content) and PLGA scaffold was evaluated for compressive strength.

• Journal of the Korea Institute of Building Construction
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• v.20 no.5
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• pp.399-407
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• 2020

The aim of the research is to provide the boundary conditions for segregation of normal strength grade and high fluidity concrete mixture (so called mid-fluidity concrete) with rheology parameters. Since the normal strength grade concrete mixture has a relatively high water-to-cement ratio and no SCMs, it is easy to be segregated when superplasticizer is added. Hence, to achieve the mid-fluidity concrete of normal strength grade and high fluidity, preventing segregation of the mixture is inevitable. In this research, using two superplasticizers with different solid concentrations, the flow behaviors and rheological behaviors were assessed by increasing fluidity until the segregation happened. According to the experiment in this research, an unusual behavior in rheology parameters was observed when the concrete mixture started to be segregated. From this results and report, it is expected to contribute on the definition of segregation with rheological test methods.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.2
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• pp.143-153
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• 2002

Convergence Confinement Method (CCM) makes a more simple judgement in a ground-support reaction than numerical method. Also this method is good for the applicability of construction feedback and the analysis of field measurement. However, there has been little research with respect to the application of CCM in tunnel construction. One of the problems in CCM is a decision of the time to support installation. To decide a reasonable supporting installation time, support characteristic curve and displacement characteristic curve considering construction stage are proposed. In addition, to predict displacement distribution ratio and load distribution ratio, the time dependent support reaction curve is used. Finally, through a comparison of the result between CCM and numerical analysis, the trust of this study is proved and the practical application is proposed to control resonable tunnel construction management.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.03a
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• pp.29-29
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• 2011

아라미드 섬유는 열에 강한 튼튼한 방향족 폴리아마이드 섬유이다. 아마이드는 "85%이상의 아미드(CO-NH)기가 두 개의 방향족 고리에 직접 연결된 합성 폴리아미드로부터 제조된 섬유"로 정의된다. 아라미드 섬유는 크게 파라계와 메타계로 대별되는데 본 연구에서 사용한 파라계 아라미드는 인장강도, 강인성, 내열성이 뛰어나며 고강력 고탄성률을 지니고 있다. 일반적인 유기 섬유와는 다른 우수한 성질을 바탕으로 부직포, UD laminatig, staple 등의 형태로 크게 섬유보강 고무 복합재료 등의 각종 복합재료, 로프, 케이블, 방탄방호용과 같은 산업자재의 용도로 자동차, 우주항공, 정보통신, 국방, 등 다양한 관련 산업분야에서 사용이 확대되고 있는 고부가 소재이며 가격대비 성능비가 우수하기 때문에 세계적으로 산업용 섬유 및 초고성능 섬유시장에서 비중이 증가될 것으로 예상되고 있다. 본 연구에서는 Para-Aramid 필라멘트를 이용하여 ATY를 생산할 때 제조공정조건에 따른 ATY 물성을 알아보고 고강도를 요구하는 방화복, 고무 보강용 섬유 등의 소재에 맞는 ATY 사가공 최적공정조건을 도출하여 체계화된 data-base를 구축하여 생산성 향상 및 품질개선과 함께 산업자재용 직물개발에 응용하고자 한다. 아라미드를 ATY로 제조할 경우, 표면에 생기는 loop로 인하여 타소재와 접착시, 접착제 담지 성능이 향상되어 접착력이 상승되는 반면, 아라미드 ATY가 기존의 아라미드의 물성보다 저하되는 약점을 가지고 있으므로 이를 보완하기 위해 본 연구에서는 ATY 제조공정에서 중요 공정인자인 사속, heater 온도, over feed ratio를 변화시켜 시료를 제조하여 이들의 물성을 분석하여 최적의 물성을 갖는 ATY 사가공 공정을 도출함으로써 물성이 저하되는 문제를 보완 가능할 것으로 기대된다. 물성분석은 강신도, 초기탄성률을 각각 측정하여 인장특성을 확인하였으며, 습열수축률과 건열수축률을 측정하여 시료의 열수축률에 대해 측정을 하였다. 표면의 루프 발현 정도를 보기 위하여 Crimp Rigidity(CR%), 형태 불안정성(instability)등을 측정하였으며, 영상 현미경 시스템을 사용하여 ${\times}40$ 배율로 표면특성을 측정하였다.

• Journal of the Korean Geosynthetics Society
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• v.11 no.2
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• pp.39-47
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• 2012

This paper describes large-scale pullout test results of geosynthetic strip, which can be applied in reinforced earth wall with block-type wall facing. The pullout tests are conducted to evaluate the strain distribution, the induced pullout force and the pullout strength. The maximum pullout force is appeared regardless of reinforcement width and normal stress when end displacement is less than 15 mm. The pullout behavior based on horizontal spacing of reinforcement was similar in relationship between pullout force and end displacement. The strain distribution and pullout force distribution of the geosynthetic strip are concentrated in the front part of reinforcement, and it appeared clearly in higher normal stress condition This means that the pullout behavior of geosynthetic strip is affected by the bond between soil and friction resistance reinforcement according normal stress. Therefore, the pullout resistance design is reasonable when pullout behavior of geosynthetic strip should be evaluated by effective length considering tensile characteristic.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.4
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• pp.1-9
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• 2020

This study conducted to understand effects of CA (CaAl₂O₄) and CA₂ (CaAl₄O₇) ratio on chloride binding ability and compressive strength and pore structure of cement mortar incorporating mixture of CA and CA₂. The Portland cement based specimens were mixed with the clinkers CA and CA₂, and these calcium aluminate clinker mixture were replaced 0, 5, 10% by weight of cement. After all the test specimens were cured for 28 days under water curing, they were immersed in the distilled water and NaCl solution. As a result, 28 days compressive strength of all specimens was similar, and As the replacement ratio of calcium aluminate clinker in the specimen increased, Friedel's salt production tended to increase. However, it was dependent on the amount of Al₂O₃ in the level of 5% replacement and CA ratio in the level of 10% replacement. Through equilibrium isotherm result, it was also indicated that as replacement ratio of calcium aluminate clinker in cement matrix increased, chloride binding capacity was improved, and chloride penetration was suppressed. In this study, the specimen replaced with 10% of the calcium aluminate clinker mixture (CA 39%, CA₂ 60%) was remarkable to control chloride attack. We figured out necessity to understand optimal CA/CA₂ ratio to effectively apply CA₂ as a sustainable building material by improving the chloride binding ability in Portland cement based system.

• Journal of the Korean Geosynthetics Society
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• v.17 no.2
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• pp.41-49
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• 2018

The purpose of this study is to fabricate a full scale road embankment using lightweight air foamed soil as a soil material on soft ground and to investigate its material characteristics and behavior in order to promote dredged soil utilization and minimize ground improvement. As a result of the laboratory test of the onsite mixed samples, the total unit weight of the specimens decreased almost linearly until curing 28 days. In particular, the total unit weight after 28 days of curing was reduced to about 81% of the slurry state before curing, which will be useful in the formulation of similar native soil materials in the future. The unconfined compressive strength began to decrease with the 14th day of curing as shown in the previous study. When the cement content is increased, the strength decreases sharply at a small strain change after the occurrence of the maximum compressive strength, and the maximum strength is exhibited in a range of a smaller axial strain than normal range. The settlement at the surface layer of the ground due to the lightweight embankment was about 1 / 2.75 of the soil embankment and was in agreement with the unit weight ratio (1 / 2.7) of the embankment materials. This indicates the cause and effect of the settlement due to the difference in self weight of the embankments. Also, the difference in settlement between soil and lightweight embankment increased with increasing depth. This shows that the difference in the point at which the settlement is terminated is clear. The ground horizontal displacement under the lightweight embankment was about 15~20% smaller than that of the soil embankment and the depth of occurrence was also 4.5~5.0m shallower in the lightweight embankment.

• Korean Journal of Plant Resources
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• v.15 no.2
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• pp.164-171
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• 2002

Morphological characteristics and growth pattern of 10 Polygonatum collections indigenous to Korea were examined to select the promising medicinal, edible resources and horticultural crops. Plant heights of I0 collections ranged from 15 to 102cm. Stem type was ascending or erect, and node numbers per a stem was 6.2 to 23.2. Phyllotaxis type was alternate or verticillate, and leaf shape was elliptical or linear. Leave numbers per a stem was 5.2 to 63.4, and bract types were classified into bracteate and nonbracteate. Flowers bloomed from May 7 to May 30, and flowering period was 5 to 13 days. Inflorescence types were classified into racemose, corymbose, and umbellate. Flower numbers per a stem was 1.5 to 125.2, and flower length was 13.1 to 30.2㎜. Perianth shapes were classified into tubular, constrict and urceolate. Surface colors of rhizome were pale yellow, pale brown, brown, and dark brown. As a result of this experiment, P. sibiricum, P. odoratum var. pluriflorum and P. odoratum var. thunbergii were thought to be useful as the medicinal and edible resources plants. On the other hand, P. odoratum var. pluriflorum 'Variegata', and P. odoratum var. maximowiczii, P. lasianthum. P. involucratum, P. desoulavyi, P. humile, and P. inflatum were thought to be useful as horticultural plants.