• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.10 no.2
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• pp.164-169
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• 1999

Background and Objectives : The intracordal cysts are more increasingly diagnosed and treated due to advanced laryngeal stroboscopy and laryngeal microsurgical technique. The intracordal cysts are frequently misdiagnosed as vocal polyp or nodule The purpose of this study is to evaluate clinical features of intracordal cysts. Materials and Methods : In the present series, 83 cases of the intracordal cysts treated with laryngeal microsurgery are reported. The intracordal cysts are diagnosed preoperatively with indirect laryngoscopy, laryngeal endoscopy, laryngeal stroboscopy and confirmed with laryngeal microsurgical findings and biopsies. Results : Intracordal cysts are 83 of 1900 patients treated with laryngeal microsurgery(4.4%)-ductal cysts are 56 cases and epidermoid cysts are 27 cases. Intracordal cysts are more frequent in women, forties and the frequent site is an anterior third of the true vocal cord. With the indirect laryngoscopic examination, the ductal cysts are frequently misdiagnosed as vocal polyps or nodules but the epidermoid cysts are relatively easily diagnosed. The etiologic factors of the intracordal cysts are suspected as voice abuse and upper respiratory infection. The degree of postoperative voice satisfaction is similar to that of the vocal polyps. Conclusion : Intracordal cysts are frequently misdiagnosed as polyps or nodules, therefore preoperative stroboscopic findings and laryngeal microsurgical findings is important. An ideal treatment is to enucleate the cysts avoiding rupture of cyst and injury of lamina propria of the vocal cord.

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.67-72
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• 2011

CMDS (Coal Mine Drainage Sludge) is mainly generated from acid mine drainage during physicochemical treatment or electrical purification. CMDS is well worth considering on recycling possibilities in various areas. This research applies the liner and cover materials using waste disposal landfill generally to treat acid mine drainage sludge. In this Part I of the two parts paper, physico-chemical characteristics of CMDS, bentonite and cement to prepare the liner have been identified using XRD, XRF, FESEM. In addition, combining their physicochemical characteristics, the optimum mixing ratio has been determined to be 1: 0.5: 0.3 for CMDS: bentonite: cement by the batch tests. Initial permeability of CMDS was $7.10{\times}10^{-7}cm/s$. Through the leaching test, it was confirmed that its mixture was environmentally safe. In the Part 2, a large-scale Lysimeter was used to simulate the effects of the layer on the freeze/thaw for evaluation on field applicability and stability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.1
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• pp.9-20
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• 2023

For highway concrete structures, the deterioration of the structure is accelerated due to the increase in the use of deicing materials, and sectional repair work is being frequently carried out to restore performance. However, after the repair work, re-damage such as cracks, delamination, and poor bond performance is exhibited in the repaired sectional area. In this study, overseas repair material requirements were first analyzed, and present domestic requirements were improved repair material performance through field surveys of common concrete structures, laboratory experiments, and test construction on a disused concrete bridge. In addition, performancebased quality requirements were presented so that all materials that meet the required performance can be applied, and different test methods for each material were unified into concrete test methods for consistent test results analysis. The considered performance requirements were compression strength, bending strength, and bond strength for structural properties, and length change rate, crack resistance, thermal expansion coefficient, and elasticity coefficient were for dimensional behavior. For resistance to chloride penetration resistance and freeze-thaw resistance were presented as durability. The proposed requirements for concrete repair materials are expected to contribute to the improvement of the quality of concrete sectional repair work in Korea.

• Journal of the Korea Institute of Building Construction
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• v.13 no.3
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• pp.202-208
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• 2013

The method used to test lightweight aggregate concrete for its resistance to freezing and thawing is different in each country. In Korea, the method of KS F 2456 on normal concrete is adopted for lightweight aggregate concrete, while the testing method of ASTM C 330 lightweight aggregates for structural concrete is used in the majority of overseas countries. In this study, we identified differences between KS F 2456 and ASTM C 330 in terms of the testing method for freezing and thawing resistance, and we studied the influence of this on the freezing and thawing resistance of lightweight aggregate concrete. The results of this study were as follows: Blocked lightweight aggregates had a slight collapse of shape and lost weight by repeated freezing and thawing, but unblocked lightweight aggregates were badly collapsed. And while the freezing and thawing resistance tests of normal concrete showed similar results despite the difference in the KS and ASTM testing method, the results for lightweight aggregate concrete were very different. So the KS test method shows evaluation results that are much lower than the ASTM test method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.235-242
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• 2005

This study is on the evaluation of performance of polymer cement mortar which is used for pre-wetting spray method. Pre-wetting spray method is an epoch-making method to repair concrete structures damaged, which is added a small quantity water preciously to dry mortar to reduce dust and rebound and spray mortar mixed with fixed quantity water at nozzle before spray. The result showed that physical performance such like compressive, flexural and adhesive strength of polymer cement mortar, TS 100 used for pre-wetting spray method was superior to other repair mortar. Also durable performance such as resistance on permeability of chloride ion, carbonation, chemical and freezing-thawing was excellent.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.125-132
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• 2015

This paper presents an experimental investigation in order to evaluate fresh and hardened properties of LP (Limestone Powder) blended cement concrete. The cement contents of the mixtures are replaced by LP in the range of 10%, 15%, 25%, and 35%, while a control mixture is prepared with only OPC (Ordinary Portland Cement). The fresh concrete properties like slump and air content are similar to those of control mixture up to 35% of replacement ratio of LP, however a delay in setting time is evaluated. The hardened properties including compressive strength, flexural strength, and rapid freezing and thawing resistance shows similar results of control mixture up to 15% of replacement. Relatively lower strength development is evaluated over 25% replacement of LP. For accelerated carbonation test, resistance to carbonation rapidly decreases with increasing LP replacement ratio due to the limited amount of $Ca(OH)_2$. From the study, LP replacement under 15% can be adopted considering reduction of strength and resistance to carbonation.

• Economic and Environmental Geology
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• v.40 no.6
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• pp.771-784
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• 2007

This study shows the weathering characteristics of mica-schist affected by faulting and metamorphism through laboratory tests. Frozen-thaw test, which simulate the physical-chemical weathering processes in the laboratory, shows the important influence of foliation developed in mica-schist, resulting in $20{\sim}40%$ reduction of UCS according to weathering grade of rock. Slaking durability test was carried out for different weathering grade rock specimens and indicated that the specimens from fault area had a low durability index compared to other relatively fresh samples. XRD analysis allowed to estimate the dynamic evolution of mineral composition through wet-dry cycle in which the chlorite was the most important mineral leached out during slaking test. The creep test indicated that the main deformation produced along the foliation plane. The compacted clay minerals between discontinuity planes influence on the discontinuity shearing properties and result in a big difference between peak shear strength and residual strength. The results of laboratory tests on mica-schist show the possibility of a important deformation along the foliation plane or discontinuity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.39-45
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• 2017

In this study, permeable repair materials mainly composed of silicate - based inorganic materials(SIM), which are easily available domestically, were prepared as a basic study for the development of permeable repair materials using SIM. SIM were compared and examined for their performance as repair materials by selecting a product group which has many cases of use in foreign countries. The SIM used were mainly composed of sodium, potassium and lithium silicate. Performance evaluation of SIM was performed by absorption and penetration, compression and adhesion, rapid chloride ion penetration, rapid freezing and thawing, and chemical resistance test. According to the test results, SIM showed effective performance in all areas, mainly because SIM permeates into the interior of the capillary and has a dense internal microstructure. Therefore, it can be used variously to improve the durability of concrete based on the results of this experiment.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.165-182
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• 2006

In this study, field test was performed to investigate the strength-improvement effect of shotcrete mixed Micro-silica fume and shotcrete quality was estimated by EFNARC standard. Deterioration test combined the Freezing-thawing and Carbonation was also performed in order to investigate a long-term durability of high-strength shotcrete. As a result of test, the compressive strength of shotcrete using Micro-silica fume was 45.2~55.8MPa and flexible strength was 5.01~6.66MPa, so a promotion ratio of strength was 37~79%, 17~61% respectively. And the strength-improvement effect of strength by silica fume addition ratio of 7.5~10% for cement mass was more superior to the others. Due to relative dynamic modulus, mass decrease rate and carbonation progress of shotcrete mixed Micro-silica fume, it was especially realized that Micro-silica fume reduced deterioration caused by steel fiber and improved a long-term durability of shotcrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.22-29
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• 2015

In this study, we tested to develop and apply structural insulation performance improvement concrete to field, which had compressive strength in 24 MPa and thermal conductivity twice as much as normal concrete. After experiment about slump and air contents, combination product of Plain and calcined diatomite powder showed reduction of slump and air contents and combination product with micro foam cell admixture, we cannot find result of slump and air contents reduction. Unit weight of combination product with insulation performance improvement materials decreased more than that of Plain. In the test of compressive strength, compressive strength of insulation performance improvement concrete decreased more than that of Plain but was content with 24 MPa. thermal conductivity of insulation performance improvement concrete tended to decrease. Freezing and thawing resistance of insulation performance improvement concrete was similar to that of Plain. In carbonation resistance test, combination product with calcined diatomite powder showed the result which was similar to that of Plain. In carbonation resistance test, combination product with micro foam cell admixture showed a increase compared to that of Plain and length variation of combination product generally increased.