• Journal of the Mineralogical Society of Korea
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• v.16 no.1
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• pp.75-90
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• 2003

Ettringite and thaumasite were observed in some concrete. The morphology and occurrence of these minerals were closely examined by performing SEM/EDAX analyses. We also experimentally induced the concrete deterioration using $Na_2SO_4$ solution with application of various environmental conditions. The stability of these minerals and deterioration characteristics under applied experimental conditions were determined. Abundant ettringite formed by“through solution reaction”occurred in many open spaces, and some microscopic ettringite formed by "tophochemical replacement" of calcium aluminate also occurred in cement paste. Severe cracking of cement paste causing premature deterioration was often associated with ettringite location. Under specific condition, ettringite was transformed to thaumasite, tricthloroaluminate, or decomposed. Thaumasite occurred with association of ettrinsite in concrete containing carbonate aggregate being subject to dedolomitization or in some concrete being subject to carbonation. Thaumasite appears to be formed under the similar condition to the general ettringite forming condition, but it formed solid solution with ettringite by substituting pre-existing ettringite. Ettringite can also be transformed to trichloroaluminate in the presence of abundant chlorides, but trichloroaluminate changed back to ettringite in late sulfate attack. It is considered that the substitution reaction direction solely depend on the concentration of chloride and sulfate ion.

• Resources Recycling
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• v.22 no.1
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• pp.64-71
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• 2013

Mineral carbonation has been proposed as a possible way for $CO_2$ sequestration. The electric arc furnace slags consist of calcium, magnesium and aluminum silicates in various combinations. If they could be used instead of natural mineral silicates for carbonation, considerable energy savings and $CO_2$ emissions reductions could be achieved. Indirect aqueous carbonation of the slags consists of two steps, extraction of calcium and carbonation. Acetic acid leaching of electric arc furnace slags had been already studied to extract Ca in them, but it was reported that the carbonation of the extracted $Ca^{2+}$ in the leached solution would suffer from too slow kinetics, even at high pressure of $CO_2$. In this work, to develop more efficient extraction of the electric arc furnace slags, hydrochloric acid leaching to separate calcium from them was studied, and the results were compared with the acetic acid ones. The phase boundary between $Ca^{2+}$ and $CaCO_3$ in the solution with pH was determined by thermodynamic calculations. Hydrochloric acid was more effective than acetic acid for the extraction of Ca in electric arc furnace slag, and there is a possibility to recycle an unreacted hydrochloric acid in the leached solution by electrolysis or evaporation.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.3
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• pp.167-183
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• 2023

The Janggun Pb-Zn deposit consists of Mn orebody, Pb-Zn orebody and Fe orebody. The Mn orebody composed of manganese carbonate orebody and manganese oxide orebody on the basis of their mineralogy and genesis. The geology of this deposit consists of Precambrian Weonnam formation, Yulri group, Paleozoic Jangsan formation, Dueumri formation, Janggum limestone formation, Dongsugok formation, Jaesan formation and Mesozoic Dongwhachi formation and Chungyang granite. This manganese carbonate orebody is hydrothermal replacement orebody formed by reaction of lead and zinc-bearing hydrothermal fluid and Paleozoic Janggum limestone formation. The wallrock alteration that is remarkably recognized with Pb-Zn mineralization at this hydrothermal replacement orebody consists of mainly rhodochrositization with minor of dolomitization, pyritization, sericitization and chloritization. Carbonates formed during wallrock alteration on the basis of paragenetic sequence are as followed : Ca-dolomite (Co type, wallrock) → ankerite and Ferroan ankerite (C1 type, early stage) → ankerite (C2 type) → sideroplesite (C3 type) → sideroplesite and pistomesite (C4 type, late stage). This means that Fe and Mn elements were enriched during evolution of hydrothermal fluid. Therefore, The substitution of elements during wallrock alteration beween dolomitic marble (Mg, Ca) and lead and zinc-bearing hydrothermal fluid (Fe, Mn) with paragenetic sequence is as followed : 1)Fe ↔ Mn and Mn ↔ Mg, Ca, Fe elements substitution (ankerite and Ferroan ankerite, C1 type, early stage), 2)Fe ↔ Mn, Mn ↔ Mg, Ca and Mg ↔ Ca elements substitution (ankerite, C2 type), 3)Fe ↔ Mn, Fe ↔ Ca and Mn ↔ Mg, Ca elements substitution (sideroplesite, C3 type), and 4)Fe ↔ Mg, Fe ↔ Mn and Mn ↔ Mg, Ca elements substitution (sideroplesite and pistomesite, C4 type, late stage)

• 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.

• Cement Symposium
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• s.49
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• pp.21-22
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• 2022

The purpose of this study is to reduce carbon dioxide emissions in the cement industry and to collect carbon dioxide generated in industrial facilities such as cement factories and thermal power plants, store and utilize it, and convert high-value-added resources. While conventional Ordinary Portland Cement is characterized by hardening through hydration reactions, basic research is underway to develop cement that reacts with carbon dioxide and converts it into carbonate mineralization.

• Economic and Environmental Geology
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• v.49 no.1
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• pp.13-22
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• 2016

The objectives of this study were to recover silica and iron oxides and $CO_2$ sequestration using serpentine via various acid dissolution and pH swing processes. Serpentine collected from Guhang-myeon in S. Korea were mainly composed of antigorite and magnetite consisting of $SiO_2$ (45.3 wt.%), MgO (41.3 wt.%), $Fe_2O_3$ (12.2 wt.%). Serpentine pulverized ($${\leq_-}75{\mu}m$$) and then dissolved in 3 different acids, HCl, $H_2SO_4$, $HNO_3$. Residues treated with acidic solution were recovered from the solution (step 1). And then the residual solution containing dissolved serpentine was titrated using $NH_4OH$. And pH of the solution increased up to pH=8.6 to obtain reddish precipitates (step 2). After recovery of the precipitates, the residual solution reacted with $CO_2$ and then pH increased up to pH=9.5 to precipitate white materials (step 3). The mineralogical characteristics of the original sample and harvested precipitates were examined by XRD, and TEM-EDS analyses. ICP-AES analysis was also used to investigate solution chemistry. The dissolved ions were Mg, Si, and Fe. The antigorite became noncrystralline silica after acid treatment (step 1). The precipitate at pH=8.6 was mainly amorphous iron oxide, of which size ranged from 2 to 10 nm and mainly consisting of Fe, O, and Si (step 2). At pH=9.5, nesquehonite [$Mg(HCO_3)(OH){\cdot}2(H_2O)$] and lasfordite [$MgCO_3{\cdot}H_2O$] were formed after reaction with $CO_2$ (step 3). The size of carbonated minerals was ranged from 1 to $6{\mu}m$. These results indicated that the acid treatment of serpentine and pH swing processes for the serpentine can be used for synthesis of other materials such as silica, iron oxides and magnesium carbonate. Also, This process may be useful for the precursor synthesis and $CO_2$ sequestration via mineral carbonation.

• Economic and Environmental Geology
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• v.30 no.4
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• pp.289-301
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• 1997

The Boguk cobalt mine is located within the Cretaceous Gyeongsang Sedimentary Basin. Major ore minerals including cobalt-bearing minerals (loellingite, cobaltite, and glaucodot) and Co-bearing arsenopyrite occur together with base-metal sulfides (pyrrhotite, chalcopyrite, pyrite, sphalerite, etc.) and minor amounts of oxides (magnetite and hematite) within fracture-filling $quartz{\pm}actinolite{\pm}carbonate$ veins. These veins are developed within an epicrustal micrographic granite stock which intrudes the Konchonri Formation (mainly of shale). Radiometric date of the granite (85.98 Ma) indicates a Late Cretaceous age for granite emplacement and associated cobalt mineralization. The vein mineralogy is relatively complex and changes with time: cobalt-bearing minerals with actinolite, carbonates, and quartz gangues (stages I and II) ${\rightarrow}$ base-metal sulfides, gold, and Fe oxides with quartz gangues (stage III) ${\rightarrow}$ barren carbonates (stages IV and V). The common occurrence of high-temperature minerals (cobalt-bearing minerals, molybdenite and actinolite) with low-temperature minerals (base-metal sulfides, gold and carbonates) in veins indicates a xenothermal condition of the hydrothermal mineralization. High enrichment of Co in the granite (avg. 50.90 ppm) indicates the magmatic hydrothermal derivation of cobalt from this cooling granite stock, whereas higher amounts of Cu and Zn in the Konchonri Formation shale suggest their derivations largely from shale. The decrease in temperature of hydrothermal fluids with a concomitant increase in fugacity of oxygen with time (for cobalt deposition in stages I and II, $T=560^{\circ}C-390^{\circ}C$ and log $fO_2=$ >-32.7 to -30.7 atm at $350^{\circ}C$; for base-metal sulfide deposition in stage III, $T=380^{\circ}-345^{\circ}C$ and log $fO_2={\geq}-30.7$ atm at $350^{\circ}C$) indicates a transition of the hydrothermal system from a magmatic-water domination toward a less-evolved meteoric-water domination. Sulfur isotope data of stage II sulfide minerals evidence that early, Co-bearing hydrothermal fluids derived originally from an igneous source with a ${\delta}^{34}S_{{\Sigma}S}$ value near 3 to 5‰. The remarkable increase in ${\delta}^{34}S_{H2S}$ values of hydrothermal fluids with time from cobalt deposition in stage II (3-5‰) to base-metal sulfide deposition in stage III (up to about 20‰) also indicates the change of the hydrothermal system toward the meteoric water domination, which resulted in the leaching-out and concentration of isotopically heavier sulfur (sedimentary sulfates), base metals (Cu, Zn, etc.) and gold from surrounding sedimentary rocks during the huge, meteoric water circulation. We suggest that without the formation of the later, meteoric water circulation extensively through surrounding sedimentary rocks the Boguk cobalt deposits would be simple veins only with actinolite + quartz + cobalt-bearing minerals. Furthermore, the formation of the meteoric water circulation after the culmination of a magmatic hydrothermal system resulted in the common occurrence of high-temperature minerals with later, lower-temperature minerals, resulting in a xenothermal feature of the mineralization.

• Economic and Environmental Geology
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• v.37 no.1
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• pp.1-19
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• 2004

Metallic deposits in Korea have a variety of genetic types such as hydrothermal veins, skarns, hydrothermal replacement and alaskite deposits and so on. Geological, mineralogical and geochemical features including host rock, wall-rock alteration, ore and gangue mineralogy, mineral texture and secondary mineralogy related to weathering process control the environmental signatures of mining areas. The environmental signatures of metallic deposits closed from early 1970s to late 1990s in Korea show complicate geochemistry and mineralogy due to step weathering of primary and secondary minerals such as oxidation-precipitation-remobilization. The potentiality of low pH and high heavy metal Concentration s from acid mine drainage is great in base-metal deposits associated with polymetallic mineralization, breccia-pipe type and Cretaceous hydrothermal Au veins with the amount of pyrite whereas skam, hydrothermal replacement, hydrothermal Cu and Au-Ag vein deposits are in low contamination possibility. The geoenvironmental models reflecting the various geologic features closely relate to disuibution of sulfides and carbonates and their ratios and finally effect on characteristics of environmental signatures such as heavy metal species and their concentrations in acid mine drainage.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.293-304
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• 2017

This study was performed in order to hydrogeological analysis of aquifer, which is a necessary part for evaluating the efficiency of the combined well and open-closed loops geothermal (CWG) systems. CWG systems have been proposed for the effective utilization of geothermal energy by combining open loop geothermal systems and closed loop geothermal systems. Small aperture CWG systems and large aperture CWG systems were installed at a green house land with water curtain facilities in Chungju City. Aquifer tests include pumping tests and step-drawdown tests were conducted to analyse hydrogeological characteristics of aquifer in the study area. The transmissivity was estimated in the range of $13.49{\sim}58.99cm^2/sec$, and the storativity was estimated in the range of $1.13{\times}10^{-5}{\sim}5.20{\times}10^{-3}$. The geochemical analysis showed $Ca^{2+}$ ion and ${HCO_3}^-$ ion were dominant in groundwater. The Langelier Saturation Index and the Ryznar Stability Index showed low scaling potential of groundwater. In the analysis of vertical water temperature change, the geothermal gradient was estimated as $2.1^{\circ}C/100m$, which indicated the aquifer was enough for geothermal systems. In conclusion, groundwater is rich, can stably use geothermal heat, and it is less likely to cause deterioration of thermal energy efficiency by precipitation of carbonate minerals in study area. Therefore, the study area is suitable for installation of the combined geothermal system.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.2
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• pp.111-123
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• 2022

Carbonate green rust (CGR) and sulfate green rust (SGR) commonly occur in nature. In this study, CGR and SGR were synthesized through co-precipitation, and their formation mechanisms and physicochemical properties were investigated. X-ray diffraction (XRD) and Rietveld refinement showed both CGR and SGR with layered double hydroxide structure were successfully synthesized without any secondary phases under each synthetic condition. Refined structural parameters (unit cell) for two green rusts were a (=b) = 3.17 Å and c = 22.52 Å for CGR and a (=b) = 5.50 Å and c = 10.97 Å for SGR with the crystallite size 57.8 nm in diameter from (003) reflection and 40.1 nm from (001) reflections, respectively. Scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) results showed that both CGR and SGR had typical hexagonal plate-like crystal morphologies but their chemical composition is different in the content of C and S. In addition, Fourier transform infrared (FT-IR) spectroscopy analysis revealed that carbonate (CO₃^2-) and sulfate (SO₄^2-) molecules were occupied as interlayer anions of CGR and SGR, respectively. These SEM/EDS and FT-IR results were in good agreement with XRD results. Changes in the solution chemistry (i.e., pH, Eh and residual iron concentrations (Fe(II):Fe(III)) of the mixed solution) were observed as a function of the injection time of hydroxyl ion (OH^-) into the iron solution. Three different stages were observed in the formation of both CGR and SGR; precursor, intermediator, and green rust in the formation of both CGR and SGR. This study provides co-precipitation methods for CGR and SGR in a way of the stable synthesis. In addition, our findings for the formation mechanisms of the two green rusts and their physicochemical properties will provide crucial information with researches and industrials in utilizing green rust.