• 한국농공학회논문집
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• 제54권5호
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• pp.25-34
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• 2012

It has been well known that concrete structures exposed to acid and sulfate environments such as sewer etc. show significant decrease in their durability due to chemical attack. Such deleterious acid and sulfate attacks lead to expansion and cracking in concrete, and thus, eventually result in damage to cement mortar by forming expansive hydration products due to the reaction between cement hydration products and acid and sulfate ions. In this study, the effect of fly ash and blast furnace slag on the bond performances of structural synthetic fiber in latex modified cement mortar under sulfate environments. Fly ash and blast furnace slag contents ranging from 0 % to 20 % are used in the mix proportions. The latex modified cement mortar specimens were immersed in fresh water, 8 % sodium sulfate ($Na_2SO_4$) solutions for 28 and 50 days, respectively. Pullout tests are conducted to measure the bond performance of structural synthetic fiber from latex modified cement mortar after sulfate environments exposure. Test results are found that the incorporation of fly ash and blast furnace slag can effectively enhance the PVA fiber-latex modified cement mortar interfacial bond properties (bond behavior, bond strength and interface toughness) after sulfate environments exposure. The microstructural observation confirms the findings on the interface bond mechanism drawn from the fiber pullout test results under sulfate environments.

• 한국지하수토양환경학회지:지하수토양환경
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• 제19권1호
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• pp.54-62
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• 2014

To better understand dissimilatory iron and sulfate reduction (DIR and DSR) by subsurface microorganisms, we investigated the effects of sulfate and electron donors on the microbial goethite (${\alpha}$-FeOOH) reduction. Batch systems were created 1) with acetate or glucose (donor), 2) with goethite and sulfate (acceptor), and 3) with aquifer sediment (microbial source). With 0.2 mM sulfate, goethite reduction coupled with acetate oxidation was limited. However, with 10 mM sulfate, 8 mM goethite reduction occurred with complete sulfate reduction and x-ray absorption fine-structure analysis indicated the formation of iron sulfide. This suggests that goethite reduction was due to the sulfide species produced by DSR bacteria rather than direct microbial reaction by DIR bacteria. Both acetate and glucose promoted goethite reduction. The rate of goethite reduction was faster with glucose, while the extent of goethite reduction was higher with acetate. Sulfate reduction (10 mM) occurred only with acetate. The results suggest that glucose-fermenting bacteria rapidly stimulated goethite reduction, but acetate-oxidizing DSR bacteria reduced goethite indirectly by producing sulfides. This study suggests that the availability of specific electron donor and sulfate significantly influence microbial community activities as well as goethite transformation, which should be considered for the bioremediation of contaminated environments.

• Journal of Periodontal and Implant Science
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• 제28권2호
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• pp.235-247
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• 1998

Calcium sulfate has a long history of medical use as an implant material. The biocompatibiliry of the material has been clearly established. Bone ingrowth concomitant with resorption occurs rapidly with efficient conduction of bone from particle to particle. Calcium sulfate also has a potential for functioning as a good bamer membrane. The purpose of this study was to compare the biocompatibility of different types of calcium sulfate grafting materials including an expelimental calcium sulfate compound on periodontal ligament cells in vitro as a preliminary test towards the development of a more convenient and useful form of grafting material which could promote regeneration of periodontal tissue. Human periodontal ligament cells were collected from the premolar teeth extracted for orthodontic treatment. cells were cultured in a.MEM culture medium containing 20% FBS, at $37^{\circ}C$ and 100% humidity, in a 5% CO2 incubator. Cells were cultured into 96 well culture plate $1{\times}104$ cells per well with $\alpha$-MEM and incubated for 24 hours. After discarding the medium, those cells were cultured in $\alpha$-MEM contained with 10% FBS alone (control group), in medcal-grade calcium sulfate(MGCS group), in plaster(plaster group), experimental calcium sulfate paste(CS paste group) for 1, 2, 3 day respectively. And then each group was characterized by examining of the cell counting, MTI assay, collagen synthesis. The results \vere as follows. 1. In the analysis of cell proliferation by cell counting, both medical-grdde calcium sulfate group and plaster group showed no stastically significant difference at day 1, 2, 3 accept for plaster group at day 1 compared to control group, but there was stastically significant difference between CS paste group and all other groups at day 1, 2, 3(P<0.05). 2. In the analysis of cytotoxicity by MIT assay, both medical-grade calcium sJlfate group and plaster group showed no stastically significant difference compared to control group at day 1, 2, 3 but there was stastically significant difference between CS paste group and all other groups at day 1, 2, 3(P<0.OS). 3. In the analysis of collagen synthesis by immunoblotting assay, high level was detected for medical-grade calcium sulfate group and plaster group at day 1, 2, 3 compared to CS paste group. On the basis of these results, medical-grade calcium sulfate and plaster was shown to possess biocompatibility whereas the CS paste had unfavourable outcome. This observation shows a need for modification of the materials contained in calcium sulfate paste.

• Journal of Periodontal and Implant Science
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• 제28권2호
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• pp.219-237
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• 1998

Numerous bone graft materials have been used in Periodontics, in an attempt to reach the main goal of periodontal therapy, i.e. the regeneration of periodontal tissue lost due to destructive periodontal diseases. The present study investigates the effect of composite graft of DFDB and Calcium sulfate with and without Calcium sulfate barrier in Periodontal 1-wall intrabony defects in dogs. Following the initiation of general anesthesia by I.V. administration of 40mg/Kg of Pentobabital, second premolar was extracted and full thickness flap elevated. The crown portion of premolars was removed. Exposed root canals were sealed with Caviton and covered completely with flap. After the healing period of 8 weeks, the surgical sites were re-opened and 1-wall intrabony defects were created, and treated with flap operation alone(control group), with composit graft of 80% DFDB and 20% Calcium sulfate(Experimental group 1), with composite graft of DFDB and calcium sulfate with calcium sulfate membrane( Experimental group 2). Healing response was histologically observed after 8 weeks and the results were as follows : 1. New bone formation was 70 % in the control group, 93 % in the Experimental group I, 89 % in the Experimental group II. There was a no differences between Experimental groups. 2. New cementum formation was not significantly different between control and two Experimental groups. 3. The length of connective tissue adhesion was 30 % in the control, 7% in the Experimental group I and 11 % in the Experimental group II. 4. After 8weeks, calcium sulfate was completely resorbed, while DFDB particle remained. These results suggest that the use of composite graft of allogenic DFDB and Calcium sulfate with and without Calcium sulfate barrier in periodontal 1 wall intrabony defects have little effect on connective tissue adhesion, but has beneficial effect on new alveolar bone and new cementum formation, and prevent downgrowth of epithelium and connective tissue effectively.

• 한국환경과학회지
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• 제2권1호
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• pp.43-49
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• 1993

두개의 서로 다른 해양환경에서 수거된 토적물의 공극수로부터 황산염 농도와 황산염의 황 안정 동위원고값$({\delta}^{34}SO_4_){pw}$이 측정되었다. 한지역은 북동태평양 심해(ST-1)이었고, 다른 한 지역은 황해 경기만의 연안역(ST-2)이었다. 두 개의 시추 코아 공히 공극수 황산염의 농도가 김이세 따라 감소하는 것을 보였는데, 이것은 황산염 환원작용이 두 지역 퇴적환경에서 모두 일어나고 있음을 시사한다. 정점 ST-2에서 공극수 황산염의 감소가 더욱 현저한 것은 이곳에서 환산염 환원이 더욱 빠르게 일어나고 있음을 나타내는 것이며, 이것은 심해환경에 비해 연안환경에서 퇴적속도가 훨씬 빠르다는 사실을 고려할 때 예측된 결과이다. 공극수 황산염의 황 안정동위원소 측정값 $({\delta}^{34}SO_4_){pw}$ 들은 Rayleigh 동위원소 분화방정식이 예측한 값들과 매울 잘 일치하고 있다. 측정갑들은 정점 ST-2에서 26.7%~61.3%의 범위를 보이는데 이것은32.4%~97.8%의 분포를 보인 정점 ST-1에 비하면 적은 값들이다. 정점 ST-2에서 공극수 황산염의 농도변화가 훨씬 더 컷음에도 불구하고 동위원소값들은 적은 규모로 증가하였다. 황산염 농도변화와 동위원소값의 변화 사잉에 이와같은 역비례 관계는 다음과 같은 두가지 연속적인 요일들에 의해 설명될 수 있다. 황산염 환원이 진행됨에 따라 공극수에 남아있는 황산염내 황에는 무거운 $^{34}S$가 점차 농축되는 반응효과가 첫째 요인이며, 이러한 반응효과가 커지면 커질수록 최종값인 $({\delta}^{34}SO_4_){pw}$ 는 오히려 줄어들게 하는 Rayleigh 방정식 자체의 구조효과가 둘째 요인이다.

• 자원리싸이클링
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• 제16권2호
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• pp.17-22
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• 2007

The report of an investigation into the performance of mortar specimens made with recycled fine aggregate (RA) exposed to sodium sulfate solution for 360 days is presented in this paper. Mechanical properties of mortar specimens such as visual examination, compressive strength, expansion and mass loss were periodically monitored. From the test results, it was found that mortar specimens with higher replacement levels of Rh exhibited poor performance in sodium sulfate solution. However, compared to mortar specimens without RA, those with lower replacement levels of RA (up to 50% by mass) was more resistant to sulfate attack. Through the x-ray diffraction analysis, it was confirmed that the main products causing sulfate deterioration in RA mortar specimens were the formation of gypsum and thaumasite.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2005년도 INTERNATIONAL SYMPOSIUM ON SOIL & GROUNDWATER ENVIRONMENT
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• pp.271-273
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• 2005

The ${\delta}^{15}N\;and\;{\delta}^{15}O$ data of nitrate indicates the sources of nitrate in oxic groundwater as a mixture of ammonia or urea-containing fertilizer and manure. The ${\delta}^{34}S_{sulfate}$ values indicate that sulfate Is mainly originated from fertilizers and soil S. In sub-oxic groundwater, the increased ${\delta}^{34}S_{sulfate}$ values evidently indicate that sulfate is gradually removed by microbial mediated sulfate reduction. However, iron reduction does not occur In this study area. Such a reversed redox sequence may occur In the presence of stable iron oxides such as hematite and goethite in alluvlal aquifer.

• 한국염색가공학회지
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• 제12권2호
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• pp.96-102
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• 2000

For the effective treatment of dyeing-complex wastewater, the most effective chemical coagulation method was studied. For the chemical coagulation of dyeing-complex wastewater, polyferric sulfate, $4Al_2(SO_4)_3$, PAC, ferrous sulfate, ferric sulfate, $FeCl_2$ and lime were used. It was investigated that polyferric sulfate was the most efficient coagulant. The optimal conditions and results for polyferric sulfate include the followings. When initial $COD_{Mn}$ concentration was 600mg/L, the optimal initial pH, dosage of coagulant, dosage of lime and PAA for $COD_{Mn}$ removal efficiency were 5, 1,200mg/L, 500mg/L and lmg/L, respectively. The optimal dosage of polyferric sulfate was increased proportionally to the influent $COD_{Mn}$ concentration.

• 환경위생공학
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• 제13권2호
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• pp.47-56
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• 1998

Effects of sulfate on the anaerobic substrate utilization were evaluated using UASB (Upflow Anaerobic Sludge Blanket) reactor. Effect of sulfate on the organic removal rate was dependent on the relative amount of microorganisms in the reactor, the operational condition, and the characteristics of sludge. When the sulfate shock was applied to 0.0 - 3.0g SO$_{4}$$^{2-}$/d, more than 95% of COD removal efficiency was achieved. Therefore, if F/M ratio was kept to low sufficiently with recirculation, it is shown that operation of the reactor was not affected significantly, though sulfate shock load was doubled compared to the normal operation. Provided that it is shocked by high strength of sulfate or temporary shock load is applied frequently the efficiency of reactor may be disadvantageous as well as the wash-out of sludge will be increased by decreasing the size to the accumulated frequency of granular sludge and the size with maximum frequency.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.277-280
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• 2006

This paper presents the findings on the sulfate resistance of mortar specimens with or without alkali-free accelerator exposed to sodium sulfate solution for 270 days. Test results confirms a negative effect of alkali-free accelerator on the sulfate deterioration. Additionally, the influences of exposure concentration and temperature of sulfate solution on expansion were investigated. Especially, at a high concentration of solution a significant expansion of mortar specimens with alkali-free accelerator was observed. Further, low temperature also promoted the deterioration of the cement system due to sulfate attack.