• Proceedings of the Korea Air Pollution Research Association Conference
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• 2005.11a
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• pp.136-137
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• 2005

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2004.05a
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• pp.127-128
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• 2004

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.173-182
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• 2003

Recently, the durability of concrete structures has received great attention as the number of sea-side structures, such as new airport, bridges, and nuclear power plants, increases continuously. In this regards, many studies have been done on the chloride attack in concrete structures. However, those studies were confined mostly to the single deterioration due to chloride only, although actual environment is rather of combined type. The purpose of the present study is, therefore, to explore the effects of combined deterioration due to chlorides and sulfates in concrete structures. To this end, comprehensive experimental program has been set up to observe the chloride penetration behavior for various test series. The test results indicate that the chloride penetration is more pronounced for the case of combined attack than the case of single chloride attack. The surface chloride content is found to increase with time and the diffusion coefficient for chloride is found to decrease with time. The prediction equations for surface chloride content and diffusion coefficient were proposed according to test results. The equations for chloride penetration considering the time-dependent diffusion coefficients and surface chlorides were also suggested. The present study allows more realistic assessment of durability for such concrete structures which are subjected to combined attacks of chlorides and high concentration sulfates but the future studies for combined environment will assure the precise assessment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.427-435
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• 2012

In order to evaluate the effects of exposure conditions on the resistance to sulfate attack of normal and blended cement mortars, several mechanical characteristics of the mortars such as expansion, strength and bulk density were regularly monitored for 52 cycles under sodium sulfate attack. The mortar specimens were exposed to 3 different types of exposure conditions; 1) continuous full immersion(Exposure A), continuous half-immersion(Exposure B) and cyclic wetting-drying(Exposure C). Experimental results indicated that the maximum deterioration was noted in OPC mortar specimens subjected to Exposure B, showing the wide cracks in the portions where attacking solution is adjacent to air. Additionally, the beneficial effect of ground granulated blast-furnace slag and silica fume was clearly observed showing a superior resistance against sodium sulfate attack, because of its lower permeability and densified structure. Thus, it is suggested that when concrete made with normal cement is exposed to sulfate environment, proper considerations on the exposure conditions should be taken.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.413-426
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• 2009

The study was conducted to investigate the effects of indigenous bacteria on geochemical behavior of toxic heavy metals in contaminated paddy soil near an abandoned mine. The effects of sulfate amendment to stimulate microbial sulfate reduction on heavy metal behaviors were also investigated. Batch-type experiments were performed with lactate or glucose as a carbon source to activate indigenous bacteria in the soil under anaerobic condition for 100 days. Sulfate (250 mg/L) was artificially injected at 60 days after the onset of the experiments. In the case of glucose supply, solution pH increased from 4.8 to 7.6 while pH was maintained at 7~8 in the lactate solution. The initial low pH in the case of glucose supply likely resulted in the enhanced extraction of Fe and most heavy metals at the initial experimental period. Lactate supply exerted no significant difference on the amounts of dissolved Zn, Pb, Ni and Cu between microbial and abiotic control slurries; however, lower Zn, Pb and Ni and higher Cu concentrations were observed in the microbial slurries than in the controls when glucose supplied. Sulfate amendment led to dramatic decrease in dissolved Cr and maintenance of dissolved As, both of which had gradually increased over time till the sulfate injection. Black precipitates formed in solution after sulfate amendment, and violarite($Fe^{+2}{Ni^{+3}}_2S_4$) was found with XRD analysis in the microbial precipitates. Conceivably the mineral might be formed after Fe(III) reduction and microbial sulfate reduction with coprecipitation of heavy metal. The results suggested that heavy metals which can be readily extracted from contaminated paddy soils may be stabilized in soil formation by microbial sulfate reduction.

• Cement
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• s.124
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• pp.58-64
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• 1991

• 레미콘
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• s.75
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• pp.78-82
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• 2003

• Proceedings of the KSEG Conference
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• 2002.04a
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• pp.129-136
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• 2002

대전광역시의 도심하천인 갑천, 유등천, 대전천을 대상으로 하천수의 수리화학적 특성과 동위원소 특성을 분석하였다. 하천의 수리화학적 특성은 상류에서는 $Ca(Mg)-HCO_3$ 유형을 보이다가 도심권을 통과하면서 $Ca(Mg)-SO_4(Cl)$유형으로 전환되고 하류에서는 $Na(Ca)-HCO_3(Cl,{\;}SO_4)$ 유형으로 변화를 보였다. 이와 같은 화학적 유형의 변화는 자연적 영향보다는 인위적 오염물질의 유입에 의한 것으로 해석된다. 하천수의 전기전도도와 수리화학적 유형으로 보면 대전천보다는 유등천과 갑천이 비교적 좋은 수질특성을 보인다. 그러나 하수종말처리장에서 방류되는 방류가 합류되는 갑천하류부터는 수질이 급격하게 나빠진다. 하천수의 pH는 상류에서 중성을 보이다가 도심권을 지나면서 최고 pH 9.8정도의 알카리성을 보인다. 이는 아파트의 우수관을 통한세제 유입에 기인하는 것으로 보인다. 하천수의 ${\delta}^{13}l3C-HCO_3$ 관계에서 중탄산 함량의 증가에 따른 ${\delta}^{13}C$ 값의 증가는 하천수내 $CO_2$의 기원이 유기물에서 무기물의 영향이 커짐을 의미한다. ${\delta}^{34}S-SO_4$의 함량관계는 황산염의 농도가 증가함에 따라서 ${\delta}^{34}S$ 값은 낮아진다. 갑천, 유등천, 대전천의 순으로 황산염의 농도가 증가하고 ${\delta}^{34}S$ 값은 낮아지는 경향을 보인다. 이를 바탕으로 볼 때 갑천 중상류의 경우에는 황산염의 기원이 자연적 반응외 비료 등으로부터 유입된 것으로 보이며, 대전천의 경우에는 유기오염에 의한 황산염의 유입이 상당한 것으로 판단된다. 갑천하류는 하수종말처리장의 방류수의 영향이 큰 것으로 해석된다. 대전시 도심하천수의 수리화학적수질 개선을 위해서는 하수종말처리장의 방류수 기준의 강화, 아파트단지에서의 세제의 유입의 차단, 그리고 부분적인 오염물질의 유입을 차단하여야 할 것이다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.151-152
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• 2011

본 연구에서는 황산니켈, 아세트산니켈, 썰파민산니켈 등 니켈 염 종류에 따른 무전해 니켈 도금피막의 기계적 특성을 평가하고자 하였다. 동일한 두께로 도금피막을 형성하여 내절성 시험결과 황산니켈을 사용한 무전해 니켈 도금피막의 경우 97회, 아세트산니켈을 사용한 경우 259회, 썰파민산 니켈을 사용한 경우 467회의 굴곡 시험 후 도금 피막이 파괴되어 썰파민산니켈이 니켈염으로 사용될 경우 가장 우수한 피막을 나타내었다. 도금피막의 연신울 측정결과 니켈염으로 황산니켈을 사용할 경우 0.28%의 연신율을 나타내었고 아세트산니켈을 사용할 경우 0.32%의 연신율을 나타내었고 썰파민산니켈을 니켈염으로 사용한 결과 0.69%의 높은 연신율을 나타내었으며 개발한 도금액을 PCB 도금을 위한 Cu Pattern에 도금한 경우 Cu line에 선택적으로 도금이 가능하였다.

• Journal of the Korea Concrete Institute
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• v.27 no.6
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• pp.641-649
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• 2015

The purpose of this study was to assess the durability of high-strength concrete with high volume mineral admixture (HVMAC) derived from previous studies within ternary blended concrete (TBC) and normal concrete (NC). Four durability evaluation types such as chloride penetration resistance, freezing and thawing resistance, carbonation resistance in two pre-treatment conditions, and sulfuric acid and sulfate resistance using 5% sulfuric acid ($H_2SO_4$), 10% sodium sulfate ($Na_2SO_4$), and 10% magnesium sulfate ($MgSO_4$) solution were selected and performed in this study. HVMAC showed the excellent chloride penetration resistance in any age and the freezing and thawing durability close to 100%. In addition, HVMAC affected more reduction in carbonation resistance than TBC. When the curing time was increased, to create a concrete internal organization densely improved resistance to carbonation. HVMAC also showed the most superior in sulfuric acid and sulfate resistance. As the reduction of calcium hydroxide and $C_3A$ to apply a large amount of admixture reduced the swelling and cracking of concrete, the strength reduction and mass change of concrete was found to be small indicated.