• Economic and Environmental Geology
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• v.51 no.4
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• pp.359-370
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• 2018

The batch and column experiments were performed to overcome the limitation of the neutralization process using the $scCO_2$-water-recycled aggregate, reducing its treatment time to 3 hour. The waste cement mortar and two kinds of recycled aggregate were used for the experiment. In the extraction batch experiment, three different types of waste mortar were reacted with water and $scCO_2$ for 1 ~ 24 hour and the pH of extracted solution from the treated waste mortar was measured to determine the minimum reaction time maintaining below 9.8 of pH. The continuous column experiment was also performed to identify the pH reduction effect of the neutralization process for the massive recycled aggregate, considering the non-equilibrium reaction in the field. Thirty five gram of waste mortar was mixed with 70 mL of distilled water in a high pressurized stainless steel cell at 100 bar and $50^{\circ}C$ for 1 ~ 24 hour as the neutralization process. The dried waste mortar was mixed with water at 150 rpm for 10 min. and the pH of water was measured for 15 days. The XRD and TG/DTA analyses for the waste mortar before and after the reaction were performed to identify the mineralogical change during the neutralization process. The acryl column (16 cm in diameter, 1 m in length) was packed with 3 hour treated (or untreated) recycled aggregate and 220 liter of distilled water was flushed down into the column. The pH and $Ca^{2+}$ concentration of the effluent from the column were measured at the certain time interval. The pH of extracted water from 3 hour treated waste mortar (10 ~ 13 mm in diameter) maintained below 9.8 (the legal limit). From XRD and TG/DTA analyses, the amount of portlandite in the waste mortar decreased after the neutralization process but the calcite was created as the secondary mineral. From the column experiment, the pH of the effluent from the column packed with 3 hour treated recycled aggregate kept below 9.8 regardless of their sizes, identifying that the recycled aggregate with 3 hour $scCO_2$ treatment can be reused in real construction sites.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.3
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• pp.206-214
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• 2014

This study is to evaluate how different bearing surface angles of abutment screw affect the mechanical stability of the joint in the conical seal design implant system. Materials and Methods: Internal connection type regular implants, two-piece cemented type abutments and tungsten carbide/carbon-coated titanium alloy abutment screws were selected. Titanium alloy screws with conical ($45^{\circ}$) and flat ($90^{\circ}$) head designs which fit on to abutment were fabricated. The abutments were tightened to implants with 30 Ncm by digital torque gauge. The loading was applied once to the central axis of abutment. The mean axial displacement was measured using micrometer before and after the tightening and loading (n = 5). The abutment was tightened to implants with 30 Ncm and T-shape stainless steel crown was cemented. Then the change in the amount of reverse-torque was measured after the repeated loading to the central axis, and the place 5 mm away from the central axis. Compressive bending and fatigue strength were measured at the place 5 mm away from the central axis (n = 5). Results: Both groups showed the largest axial displacement when abutment screw tightening and total displacement was greater in the flat head group compared to conical head group (P < 0.05). However, there were no significant differences in reverse torque value, compressive bending and fatigue strength (P > 0.05). Conclusion: Within the limitations of this study, the abutment screw head design had no effect on two groups regarding the joint stability, however the conical head design affected the settlement of abutment resulting in the reduced total displacement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.136-144
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• 2013

In this study, in order to establish a plan that will enable safe use of renewable resources such as diverse industrial by-products and urban recycled materials, we conducted experiments that focused on flow, bleeding, compressive strength and environmental pollution evaluation to evaluate the material properties of low strength concrete using BFS and SS. In the case of low strength concrete using BFS and SS, blending of at least BFS 6000 within a 30% range regardless of the type of sand used was found to be the most effective approach for improving the workability by securing the minimum unit quantity of water, restraining the bleeding ratio and establishing compressive strength by taking account of the applicability at the work site. In particular, in view of the efficient use of SS, the optimal mixing condition was found to be the mixing of BFS 8000 with in the 30% range, not only for improving the workability restraining the bleeding ratio and establishing the compressive strength but also for application to the work site. Further, the results of tests on hazardous substance content and those of elution tests conducted on soil cement using SS indicated that all values satisfied the environmental standards without any harmful effects on the surrounding environment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.24-34
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• 2020

This research is a study on the characteristics of OPC-slag cement using nano-silica solution (NSS) with water-weight substitution method. The new replacement method is a fundamental step to study the behavior of cement with higher NSS replacement rates than previous studies. NSS was replaced by 10%, 20%, 30%, 40%, and 50% of the mixing water weight. As a result, the mechanical and microstructural characteristics were improved. This can be summarized in two ways. First, when the NSS is replaced with mixing water, the homogeneous dispersion action of the nano-silica particles is improved. This promotes initial hydration. Second, substitution of NSS with higher density than mixing water reduces w / b. This forms a dense hydration reaction material. The new substitution method did not show any degradation of mechanical and microstructural properties as compared with the results using the powdered nano-silica particles revealed in the previous study. Therefore, it is considered that the method of weight substitution of NSS used in this study can be applied to the formulation of OPC-slag cement.

• The Journal of the Korean bone and joint tumor society
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• v.13 no.2
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• pp.96-104
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• 2007

Purpose: The authors investigated whether 35 flexible nail-rotating hinge composite reconstructions around knee joint minimize junctional osteolysis of host bone. Material and Method: The reconstructive technique was as follows: 1) en bloc tumor resection, 2) filling of the host bone marrow cavity with multiple Ender nails, 3) assembling the Ender nails and an Endo-Link type total knee component with wire and bone cement. Result: Mean follow-up was 53 months (ranged 30~79). At final follow-up, 29 patients retained a mobile joint. Resection of more than 40% of bone showed a positive relationship with junctional hypertrophy (p=0.028). Eight patients showed nail breakage and eight prostheses were removed due to early or late infection. The cumulative prosthetic survival rate was 33% at 6 year. Average functional score according to the MSTS criteria was 26.8. Conclusion: Mid-term evaluations showed that results were fair. The revision process was straightforward. Junctional hypertrophy observed appears to give some clues as to how to minimize osteolysis at the prosthesis-host junction after modular prosthesis fixation.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.2
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• pp.201-208
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• 2008

Statement of problem: A new implant impression technique which use abutments as impression coping, and use resin cement as a splinting material was described. Accuracy of this technique was compared with conventional closed tray and resin splinted open tray technique for a $15^{\circ}$ angled 3-implant model Material and methods: A dental stone master model with 3 linearly positioned implant analogue and a reference framework which was passively fitted to it were fabricated. The center analogue was perpendicular to the plane of model and the outer analogues had a $15^{\circ}$angulation forward or backward. 10 closed tray impressions, 10 resin splinted open tray impressions, 10 abutment-resin framework cementation impressions and 10 abutment-metal framework cementation impressions were made with additional silicone material and poured with dental stone. A light microscope with image processing was used to record the vertical gap dimension between reference framework and analogue of duplicated cast made with each 4 impression techniques. Statistical analysis used one-way ANOVA with post-hoc tests Tukey test of .05 level of significance Results: Significant difference in the vertical gap dimension was found between closed tray technique; 74.3 (${\pm}33.4$)${\mu}m$ and resin splinted open tray technique, and two other new technique. (P<.05) Abutment-metal framework cementation technique;42.5 (${\pm}11.9$)${\mu}m$ was significantly different from resin splinted open tray technique. (P<.05) Abutmentresin framework cementation technique;51.0 (${\pm}14.1$)${\mu}m$ did not differ significantly from resin splinted open tray technique;50.3 (${\pm}16.9$)${\mu}m$. (P>.05) Conclusion: Within limitations of this study, the accuracy of implant level impressions of resin splinted open tray technique was superior to that of closed tray technique. A new technique using abutment and metal framework cementation was more accurate than resin splinted open tray technique.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.166-170
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• 2006

본 연구에서는 폐광산 주변에 산재되어 있는 광미/광폐석을 처리하기 위하여 고형화 실증 실험을 수행하였다. 고형화 공정에서 흔히 사용하는 포틀랜드 시멘트와 MSG-E, MSG-N을 고화제로 사용하였으며 현장 광미 및 광폐석을 대상으로 고화체를 양생하고 고화체의 압축강도 및 중금속 용출 정도를 측정하였다. 고화체의 물리/화학적 특성을 비교하기 위해 광미/고화제 비율, 배합수/고화제 비율 그리고 고화체 양생기간을 실험인자로 설정하였다. 실험 결과 광미/고화제의 비율 1:1 만을 고려하더라도 중금속 용출의 급격한 감소가 이루어지는 것을 확인할 수 있었으며 광미/고화제의 비율을 3:1 이하로 유지시키는 경우, 고화체의 압축강도가 현행 폐기물 관리법(20조 관련)에서 규정하고 있는 차단형 매립시설 내부막의 압축강도 기준인 $0.21kgf/mm^2$ 보다 높은 것으로 나타났다. 다양한 pH를 갖는 수용액에 대하여 시간에 따른 고화체의 중금속 용출률을 측정한 결과, 수용액의 pH가 1과 13인 강산/강염기 용액에서 일부 중금속의 용출 농도가 지하수 생활용수 기준치를 초과하였으나, pH와 3 - 11인 경우에는 중금속 용출률이 급격히 감소하여 모두 기준치 이하를 나타내었다. 또한, pH가 1과 13인 수용액의 경우에도 고화체와 반응하는 시간이 증가할수록 고화체의 buffering 효과에 의해 수용액의 pH가 감소하였다. 이러한 결과는 현장에서 접촉수의 pH가 강산이나 강염기라 하여도, 고화체의 buffering 효과에 의해 시간이 지남에 따라 수용액의 pH가 낮아져 고화체로부터의 중금속 용출은 매우 감소할 것임을 의미한다.ss of an active application defined using the model. The technique is developed in a platform- and language-independent way, and it is algorithmic and can be automated by computer program. We give an example dealing with network auction to illustrate the use of the model and the verification technique.품으로 내부 온도분포를 측정하였으며, 유한차분법 프로그램으로 대류열전달계수를 결정하였다. 대류열전달계수는 792에서 2,107 W/m$^2$로 분석되었다. 대류열전달 계수는 액상식품과의 상대속도가 증가함에 따라서 증가하였고, 점도가 증가함에 따라서는 감소하였다.ce of precision/recall of 90.99%/92.52%, and 93.39%/93.41% respectively. 의한 변성에 부분적으로 보호 작용을 나타 낼 것으로 추정된다.경(製麴72時間頃)의 활성(活性)은 보리쌀국(麴), 밀가루국(麴), 찹쌀국(麴), 고구마국(麴)의 순이었다.험 결과 오전용 사료는 관행적인 산란계 배합사료에서 Ca공급제를 제외한 것을 급여하고, 오후용 사료는 Ca공급제를 3배 첨가한 T2처리로 15:00~16:00시에 교체급여를 하면 사료섭취량 감소와 사료비 절감면에서 바람직할 것으로 사료되며, 고에너지-고단백질-저Ca의 분말사료와 저에너지-저단백질-고Ca의 펠렛사료를 혼합급여하면 산란계의 사료

• Resources Recycling
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• v.30 no.6
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• pp.19-27
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• 2021

Electrically conductive mortar used in industrial carbon material byproducts was manufactured and analyzed in this study. The contents of the carbon material and mixed water were controlled, and the distance between electrodes was set to 0.42 m and 0.88 m. The carbon material was graphite with a layered structure. The carbon material was used as fine powder and aggregate substitutes according to particle size. The average particle sizes of each materials were 18.4㎛ and 546.1 ㎛ and the electrical conductivities were 62.3 S/m and 32.5 S/m, respectively. To maintain similar mortar flow in each sample, the water content was increased with increasing carbon material, and accordingly, the porosity showed an increasing trend. When electrode distance of the mortar (week 6) was 0.42 m, the voltage-current values were 342 V-1.48 A (S20) and 349 V-1.44 A (S30). For electrode distance of 0.88 m, these values were 513 V-0.98 A (S20) and 500 V-1.01 A (S30). The exothermic properties improved with increasing carbon material content and decreasing electrode distance.

• Economic and Environmental Geology
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• v.56 no.1
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• pp.103-114
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• 2023

The Christian Museum of Gongju Jeil Church was first built in 1931 and was largely damaged during the Korean War, but the walls and chimneys have been preserved. This building has a high architectural values in that the chapel was reconstructed in 1956, and maintains its original form through repair of damaged parts rather than new construction. The stained glass windows were as installed in 1979 and has a great significance in the Dalle de Verre method using lump glass. However, some of the stained glass damaged partially, such as various cracks and splits, and vertical and horizontal cracks in the joint fillers of supporting the colored glass. As the structural materials of the stained glass window, an iron frame and cement mortar filled with it were used, and corrosion of iron, cracking of mortar and granular decomposition appear partially due to weathering. In the joint fillers, the content of Ca and S is very high, indicating that gypsum were used as admixtures, and the gypsums grow in a rhombohedral and forms a bundle, which is investigated to have undergone recrystallization. As a result of modeling the ultrasonic velocity at the joint fillers, the left and right windows at the entrance show relatively weak in the range of 800 to 1,600m/s, and the lower right corner of the altar window and the upper left corner of the center window were also 1,000 to 1,800m/s, showing relatively low physical properties. And gypsums produced during the neutralization of lime mortar were detected in the joint fillers and contaminants on the surface. Such salts may cause damage to the joint material due to freezing and thawing, so appropriate preventive conservation is required. Also, since various damage types are complexly appearing in stained glass window and joint filler, customized conservation treatment should be reviewed through clinical tests.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.627-635
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• 2019

Cement-asbestos slate is the main asbestos containing material. It is a product made by combining 10~20% of asbestos and cement components. Man- and weathering-induced degradation of the cement-asbestos slates makes them a source of dispersion of asbestos fibres and represents a priority cause of concern. When the asbestos enters the human body, it causes cellular damage or deformation, and is not discharged well in vitro, and has been proven to cause diseases such as lung cancer, asbestos, malignant mesothelioma and pleural thickening. The International Agency for Research on Cancer (IARC) has designated asbestos as a group 1 carcinogen. Currently, most of these slats are disposed in a designated landfill, but the landfill capacity is approaching its limit, and there is a potential risk of exposure to the external environment even if it is land-filled. Therefore, this study aimed to exam the possibility of detoxification of asbestos-containing slate by using exothermic reaction and heat treatment. Cement-asbestos slate from the asbestos removal site was used for this experiment. Exothermic catalysts such as calcium chloride(CaCl₂), magnesium chloride(MgCl₂), sodium hydroxide(NaOH), sodium silicate(Na₂SiO₃), kaolin[Al₂Si₂O₅(OH)₄)], and talc[Mg₃Si₄O₁₀(OH)₂] were used. Six catalysts were applied to the cement-asbestos slate, respectively and then analyzed using TG-DTA. Based on the TG-DTA results, the heat treatment temperature for cement-asbestos slate transformation was determined at 750℃. XRD, SEM-EDS and TEM-EDS analyses were performed on the samples after the six catalysts applied to the slate and heat-treated at 750℃ for 2 hours. It was confirmed that chrysotile[Mg₃Si₂O₅(OH₅)] in the cement-asbestos slate was transformed into forsterite (Mg₂SiO₄) by catalysts and heat treatment. In addition, the change in the shape of minerals was observed by applying a physical force to the slate and the heat treated slate after coating catalysts. As a result, the chrysotile in the cement-asbestos slate maintained fibrous form, but the cement-asbestos slate after heat treatment of applying catalyst was broken into non-fibrous form. Therefore, this study shows the possibility to safely verify the complete transformation of asbestos minerals in this catalyst- and temperature-induced process.