• Journal of the Mineralogical Society of Korea
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• v.23 no.4
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• pp.395-402
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• 2010

Mineralogical characterization was performed for the mineral assemblages precipitated at the boundary between limestone bedrock and bat guano deposits in the Gossi Cave, Korea. Francoanellite, taranakite, ardealite, brushite and monetite are observed as phosphate minerals and gypsum and a small amount of barite as sulfate minerals in the guano deposits. With the increase of depth, phosphates are changed as following sequence: taranakite ${\rightarrow}$ francoanellite ${\rightarrow}$ ardealite ${\rightarrow}$ brushite ${\rightarrow}$ monetite. This sequence indicates that the major parameters controlling the physico-chemical conditions under which these mineral assemblages were deposited are pH and relative humidity.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.219-228
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• 2010

It has been well known that concrete structures exposed to acid and sulfate environments such as sewer, sewage and wastewater, soil, groundwater, and seawater 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 concrete matrix by forming expansive hydration products due to the reaction between portland cement hydration products and acid and sulfate ions. Objectives of this experimental research are to investigate the effect of mineral admixtures on the resistance to acid and sulfate attack in concrete and to suggest high-resistance concrete mix against acid and sulfate attack. For this purpose, concretes specimens with three types of cement (ordinary portland cement (OPC), binary blended cement (BBC), and ternary blended cement (TBC) composed of different types and proportions of admixtures) were prepared at water-biner ratios of 32% and 43%. The concrete specimens were immersed in fresh water, 5% sulfuric acid, 10% sodium sulfate, and 10% magnesium sulfate solutions for 28, 56, 91, 182, and 365 days, respectively. To evaluate the resistance to acid and sulfate for concrete specimens, visual appearance changes were observed and compressive strength ratios and mass change ratios were measured. It was observed from the test results that the resistance against sulfuric acid and sodium sulfate solutions of the concretes containing mineral admixtures were much better than that of OPC concrete, but in the case of magnesium sulfate solution the concretes containing mineral admixtures was less resistant than OPC concrete due to formation of magnesium silicate hydrate (M-S-H) which is non-cementitious.

• Proceedings of the KSEEG Conference
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• 2003.04a
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• pp.53-56
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• 2003

폐광석에 함유되어 있는 중금속 원소는 물리ㆍ화학적 환경의 변화에 따라서 안정화 되어 자연적으로 정화가 진행되거나 혹은 재 용출될 수 있어 중요한 오염원으로 작용할 수 있다. 따라서 폐광석에 함유된 중금속이 흡착된 상태로 존재하는지, 광물형태(탄산염광물, 산화광물, 황산염광물 및 황화광물)로 존재하는지, 산화환경 혹은 환원환경에서 안정한 다른 광물의 결정 내에 치환된 형태로 존재하는 지를 규명하는 것은 물리화학적 환경변화에 따른 중금속의 거동(흡착반응, 탈착반응, 용해반응, 침전반응)을 예측할 수 있는 매우 유용한 평가 방법이라고 할 수 있다. (중략)

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.281-282
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• 2009

The purpose of this experimental research is to investigate the influence of mineral admixtures on the resistance to acid and sulfate. For this purpose, concrete specimens with types of mineral admixtures such as ground granulated blast-furnace slag, fly ash, and silica fume were made for water-binder ratios of 32% and 43%. It was observed from the test result that the resistance against acid and sulfate of the concretes containing mineral admixtures were much better than the case of plain concrete from immersion tests of 182 days.

• Journal of the Mineralogical Society of Korea
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• v.13 no.1
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• pp.1-14
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• 2000

알루나이트는 포항지역의 제3기 연일층군의 이암 층내의 탄산염 결핵체 주변에서 할로이사이트와 함께 극미립 변질물 (1-2 $\mu\textrm{m}$)로서 산출된다. 알루나이트는 정육면체와 유사한 능면체 결정형을 이루고 침상 내지 단주상의 할로이사이트와 밀접한 공생관계를 이룬다. X-선회절 분석에 의해서 이 알루나이트는 a=6.9897(1) $\AA$, c=17.2327(4)$\AA$, V=728.75(3) $\AA$3의 격자상수값을 갖는 것으로 밝혀졌다. X-선형광된 이 알루나이트의 화학식은 (K0.94N0.06)(Al2.55Fe3+0.45)(SO4)2(OH)6 으로서, 나트로알루나이트 단성분을 6-7 mole%정도 함유하는 것으로 분석되었다. 또한 시차열분석 (TG-DTG-DTA)을 통해서 알루나이트의 승화성 성분들 (H2O와 SO3)의 존재와 함유 정도를 조사하였고, 고온X-선회절분석을 병행하여 이 광물의 OH기의 이탈 반응 (52$0^{\circ}C$)과 고온상으로의 전이 반응 ($600^{\circ}C$ 및 $700^{\circ}C$)을 감정 하였다. K/Ar 법으로 측정된 알루나이트의 생성 연대 ($0.342\pm$0.008 Ma)와 안정동위원소들의 분석 결과 ($\delta$18Oso4=-1.7, $\delta$DSMOW=-31, $\delta$34S=-10.8)는 이 알루미늄 황산염 광물이 연일충군의 융기 이후에 야기된 민물의 유입에 의한 표성기원의 변질작용의 결과로 생성되었음을 지시한다. 알루나이트+할로이사이트 공생군의 침전은 이암 내에서 조성된 강산성 (pH=2-3)의 알루미늄 황산염 용액이 탄산염 결핵체를 만나 반응하여 pH가 국지적으로 증가되어 (pH=4) 과포화되는 과정에 의해서 야기되었다. 컴퓨터를 이용한 Al3+의 포화지수에 관한 화학적 평형 모델링 실험 결과, 알루미늄 황산염 용액으로부터의 알루나이트와 할로이사이트의 침전은 pH=4 및 \ulcornerSO42-=10-4M 조건에서 K+과 Si(OH)4의 농도가 10-4M 이상 유지되어야 가능한 것으로 밝혀졌다.

• Journal of the Mineralogical Society of Korea
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• v.25 no.3
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• pp.155-162
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• 2012

We observed characteristic oxidation and dissolution phenomena induced by dissolved oxygen for mackinawite that is produced via sulfate-reducing bacteria (SRB) living in anaerobic environments such as soils and groundwater. We tried to recognize the role of the sulfide minerals that usually coexist with some stabilized radionuclides (e.g., reduced uranium), which can be reoxidized and redissolved by an oxygen-rich groundwater invaded into a contaminated area. The mackinawite produced by 'Desulfovibrio desulfuricans', a sulfate-reducing bacterium, was conducted to be dissolved for 2 weeks by some oxidants such as 'hydrogen peroxide' and 'sodium nitrite'. Although mineralogical oxidation and dissolution characteristics were different from each other according to the oxidants, the initially oxidized solution was early stabilized through the oxygen consumption by ${\mu}m$-sized sulfide particles and the resultant increase of sulfate in solution. From these results, we can anticipate that the large amount of sulfide minerals generated by SRB can not only repress the anoxic environment to be disturbed by the consumption of oxygen in groundwater, but also contribute to stabilize the reduced/precipitated radionuclides as a buffer material for a long time.

• 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.

• Journal of the Mineralogical Society of Korea
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• v.17 no.1
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• pp.37-47
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• 2004

Sulfates such as alunite and schwertmannite formed under oxidation condition play a important role in geochemical processes taken place at waste dumps and a creek from Dalseong mine, Daegu. Water chemistry shows pH decreases from upstream toward downstream creek, mainly due to formation of schwertmannite that is the most abundant phase along the creek. The removal of Al from the creek is preferentially attributed to formation of Al-bearing minerals and Al-sulphates. Among them, alunite is the most important Al-sink phase that occurs at higher pH than $pK_1$, Al hydrolysis constant. With high saturation index, alunite formed at the creek has a spherical form, commonly associated with schwertmannite. Secondary minerals formed on the surface of altered or weathered surfaces of heavy metals from the wasted dump that underwent severe oxidation, where alunite has characteristic habits which are spheric, radiating, and botrytis-like aggregates. Natroalunite occurs in association with alunite, or as mixtures of both of them. Because the pH decreases with distance due to formation of schwertmannite, although total contents of dissolved ions slowly lessen at least in the AMD, it is expected that the minerals precipitated at the creek can be exposed to subsequent dissolution, which may induce possible environmental problems.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.396-399
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• 2004

산화환경에 노출된 폐광석에 포함되어 있는 황화광물은 산소와 물과의 화학반응을 통해 산화작용을 받게 되고, 이로 인하여 Fe, Mn, Pb, Zn, Cu 및 As등의 원소의 용해반응이 발생할 것으로 예상된다. 그러나 이와 같이 용해된 금속이온은 pH등 환경의 변화에 따라 2차광물(산화광물 및 황산염광물)로 침전되거나 흡착되어 수용액으로부터 제거되어 자연적으로 고정화 될 수 있다. 이처럼 황화광물의 산화작용에 의해 형성된 2차광물에 대한 광물학적 연구는 광산복원을 결정하는데 직접적인 지구화학적 자료로 활용될 수 있다. 삼산제일광산에 방치된 폐광석을 대상으로 XRD, SEM/EDS을 이용하여 광물학적 연구를 수행한 결과 침전과 공침, 흡착 등의 화학반응을 통하여 현재 고정화되고 있는 것이 확인되었다.

• Economic and Environmental Geology
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• v.46 no.6
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• pp.535-544
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• 2013

Influence of sulfate on the early hydration in the solidification treatment of abandoned mine tailings was characterized. Solidified specimens using hydrated lime as a binder were prepared with various amounts of added $Na_2SO_4$ and different curing days. Unconfined compressive strength measurement, heavy metal leaching test, XRD analysis were performed after 7-, 14- and 28-days curing. According to curing days strength of solidified specimens using only distilled water increased but those with addition of $Na_2SO_4$ decreased. External cracks of specimens developed definitely with increasing $Na_2SO_4$ concentration and curing days. Concentrations of Cu, Cd, Zn, and As in the leached solutions from solidified specimens decreased significantly but Pb was leached readily in cases of hydrated lime dosage more than 10 wt%. Gypsum and $MgSO_4$ were identified in the cracked solidified specimens by XRD analysis, and pillar-shaped crystals of SEM image were identified as gypsum in reference with EDS analysis. Crystallization of sulfate in the process of lime-tailing solidification caused cracking, which should be supplemented for solidification treatment of highly sulfur-contained tailing.