• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.269-274
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• 1997

Recently, premature reinforcement corrosion in concrete structures exposed to chloride containing environments has an important problem. This is due to an increasing use of marine aggregate of chloride containing admixture a the mixing stage and due to an increase of concrete construction in marine environments. In this study, the behavior of chloride ions introduced into concrete from concrete surface by a marine environment was modeled. The physicochemcial processes including the diffusion of chloride ion in aqueous phase of pores, the adsorption and desorption of chloride ions to and from the surface of solid phase of concrete, and the chemical reaction of chloride ion with solid phase were analyzed by using the finite element method. The results of this study may be used to predict the onset of reinforcement corrosion, and identify the maximum limit of chloride ions contained in admixtures.

• Journal of the Korean Chemical Society
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• v.60 no.3
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• pp.177-180
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• 2016

The surface properties of carbon microfibers (CMFs) are modified by chemical deposition of carbon nanofibers via the so-called ethylene processing. CMFs and the modified CMFs (MCMFs) are investigated as reinforcement additives to fabricate polyethylene (PE) composites with enhanced mechanical characteristics. The mechanical properties of the PE-MCMF composites are found to be better and favorable for applications under harsh climatic conditions such as those in Siberia. Improved adhesive interaction between MCMFs and PE is responsible for these enhanced mechanical properties.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.5-16
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• 2004

This paper presents the modeling of geosynthetic-reinforced compacted soils and discusses the reinforcement effect arising from confining the dilatancy deformation of the soil by geosynthetics. A series of compressive shear tests for compacted sandy soil specimens wrapped by geosynthetics are carried out by quantitatively examining the geosynthetic-reinforcement effect, occurring from a confinement of the dilative deformation in compacted soils during shearing. In the test, the initial degree of compaction is changed for each series of sandy soil specimens so that each series has different degree of dilatancy characteristics. Herein, the axial forces working on the geosynthetics so as to prevent dilative deformation of compacted soils during shearing are measured. Furthermore, the elasto-plastic modeling of compacted soils and a rational determination procedure for input parameters needed in the elasto-plastic modeling are presented. And to describe the irreversible deformation characteristics of compacted soils during shearing, the subloading yielding surface (Hashiguchi (1989)) to the elasto-plastic modeling is introduced. Finally, the elasto-plastic finite element simulation is carried out and the geosynthetic-reinforcement effect is discussed.

• Journal of the Korean Geotechnical Society
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• v.20 no.2
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• pp.37-46
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• 2004

This paper presents the modeling of geosynthetic-reinforced soils and discusses the reinforcement effect arising from confining the dilatancy deformation of the soil by geosynthetics. A series of compressive shear tests for compacted sandy soil specimens wrapped by geosynthetics are carried out by quantitatively examining the geosynthetic-reinforcement effect, and it occurred from the confinement of the dilative deformation of compacted soils during shearing. In the test, the initial degree of compaction is changed for each series of sandy soil specimens so that each series has different degree of dilatancy characteristics. Herein, the axial forces working to the geosynthetics so as to prevent dilative deformation of compacted soils during shearing are measured. Furthermore, the elasto-plastic modeling of compacted soils and a rational determination procedure of input parameters needed in the elasto-plastic modeling are presented. In this paper, the subloading yielding surface(Hashiguchi(1989)) is introduced to the elasto-plastic modeling which could describe the irreversible deformation characteristics of compacted soils during shearing. Finally, the elasto-plastic finite element simulation is carried out and the geosynthetic-reinforcement effect is discussed.

• Geomechanics and Engineering
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• v.5 no.2
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• pp.87-97
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• 2013

In this paper, a novel fibrous material known as axially reinforced braided composite rods (BCRs) have been developed for reinforcement of soils. These innovative materials consist of an axial reinforcement system, comprised of longitudinally oriented core fibres, which is responsible for mechanical performance and, a braided cover, which gives a ribbed surface texture for better interfacial interactions with soils. BCRs were produced using both thermosetting (unsaturated polyester) and thermoplastic (polypropylene) matrices and synthetic (carbon, glass, HT polyethylene), as well as natural (sisal) core fibres. BCRs were characterized for tensile properties and the influence of core fibres was studied. Moreover, BCRs containing carbon fibre in the core composition were characterized for piezoresistivity and strain sensing properties under flexural deformation. According to the experimental results, the developed braided composites showed tailorable and wide range of mechanical properties, depending on the core fibres and exhibited very good strain sensing behavior.

• Geotechnical Engineering
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• v.13 no.3
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• pp.77-86
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• 1997

Laboratory model test results for the ultimate bearing capacity of a surface strip foundation supported by a near-saturated clayey soil reinforced with layers of geogrid have been presented. The optimum values for the width of the reinforcement layers, the depth of reinforcement, and the location of the first layer of geogrid for mobilization of maximum bearing capacity have been determined. Based on the model test results, an empirical procedure to estimate the ultimate bearing capacity has been developed.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.777-780
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• 2001

Corrosion products of reinforcement in the concrete exerts pressure to the adjacent concrete that the concrete is subject to tensile stress. If the tensile strength exceeds the tensile strength, cracks are initiated around steel and propagates through concrete cover. Cracking of the cover means that the lifetime of the structure is ended. So the amount of corrosion which introduces crack in the concrete cover is a crucial factor in the reinforcement corrosion problem. In this study, relation between internal pressure and amount of corrosion are pursued by way of corrosion experiment and finite element analysis.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.387-392
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• 2002

In many years, post-tensioning method has been used for structural reinforcement of RC structures due to easy installation and good quality control. This study presents practical application results for the effectiveness of structural post-tensioning reinforcement of the FCM bridge girders, cement silos and building girders. For the FCM bridges deflected excessively at the end of girders, for cement silos cracked vertically at silo surface and for building girders deflected due to heavy load from roof, the external post-tensioning method was used for uplifting deflected girders and closing cracks with increasing resisting capacity of the structures. It was demonstrated that all the items were rehabilitated nearly to the initial construction status according to the field test results.

• Journal of Integrative Natural Science
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• v.6 no.3
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• pp.151-157
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• 2013

The ion exchange resins were synthesized from 1-aza-18-crown-6 macrocyclic ligand attached to styrene (2th petroleum in 4th class hazardous material) divinylbenzene (DVB) copolymer with crosslinks of 1%, 6%, and 15% by substitution reaction. These synthetic resins were confirmed by chlorine content, elementary analysis, surface area, and IR-spectrum. The object of this study was to seperate the metal ion absorbed in reinforcement water fire extinguishing agent. As the results of the effects of pH, equilibrium arrival time, and crosslink of synthetic resin on metal ion adsorption for resin adsorbent, the metal ions were showed high adsorption at pH 3 or over and adsorption equilibrium of metal ions was about 2 hours. In addition, adsorption selectivity for the resin in water was the order of Al (III) > Ni (II) > Sm (III) ions, adsorbability of the metal ions was in the crosslinks order of 1%, 6%, and 15%.

• Advanced Composite Materials
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• v.16 no.4
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• pp.259-267
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• 2007

Mechanical reinforcement of an all-sustainable composite, composed of papyrus stem-milled particles as reinforcement and poly-L-lactic acid (PLLA) resin as matrix, was investigated. The papyrus particles (average diameter of $70{\mu}m$) could be well dispersed in PLLA resin up to 50 wt% without any surface modification. Young's modulus of the composite was 4.2 GPa at 50 wt% of the papyrus content. This is a two-fold increment in modulus as compared to that of the PLLA matrix. The tensile strength of the composite was almost constant around 48 MPa irrespective of the papyrus content. Temperature dependence of the storage modulus demonstrated that the incorporation of papyrus restricts the large drop in the modulus above the glass transition of PLLA.