• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2005년도 춘계 학술기술논문발표대회 논문집
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• pp.211-214
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• 2005

Recently, Deterioration of the concrete sewer concrete structures by biochemical corrosion has been issued and a development of the inhibition system of corrosion that has been demanded. The sulfuric acid may react with the hardened cement paste and originate expansive products which can induce swelling and breakless of concrete. Also, a sulphuric acid reacts with calcium hydroxide to from $CaSO_4\;\cdot\;2H_2O$. This reaction accounts for consumption of the calcium hydroxide present in hardened cement paste. In this study, To present from biochemical corrosion of the sewer repair mortar that was spread with liquefied antibiotic and then its experimental properties were experimentally investigated and to estimate the effect of absorbed condition of restorative mortar, the number of coating times and coating contents with antibiotic on the durability properties of restorative mortar spread with antibiotics. Also, testing items such as carbonation depth, choloride ion penetration depth and chemical resistance was tested to estimate the durability properties in third study. In results, the novellus bacillus inhabiting in sewer concrete structures was restrained by antibiotics developed in this study. And carbonation depth, choloride ion penetration depth and chemical resistance of restorative mortar spread with antibiotics was superior to that of plain mortar.

• Corrosion Science and Technology
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• 제8권3호
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• pp.110-115
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• 2009

At the onset of corrosion of steel in concrete, hydrogen ions usually evolve in the process of electrochemical reaction, thereby decreasing the pH of the pore solution, which can be buffered by cement hydration products, as being representatively illustrated by calcium hydroxide. Hence, a fall in the pH is dependent on properties of cement hydration (i.e. hydration products and degree of hydration). The present study tested acid neutralization capacity (ANC) of cementitious binders of OPC(Ordinary Portland Cement), 30% PFA(Pulverized Fuel Ash), 60% GGBS(Ground Granulated Blast Furnace Slag), 10% SF(Silica Fume) to quantify the resistance of cement matrix to a pH fall. Cement pastes were cast at 0.4 of a free W/C ratio with 1.5% chlorides by weight of binder in cast. Powder samples obtained crushed and ground specimen after 200 days of curing were diluted in still water combined with different levels of 1M nitric acid solution, ranging from 0.5 to 20 mol/kg. Then, the pH of diluted solution was monitored until any further change in the pH did not take place. It was seen that the pH of the diluted solution gradually decreased as the molar amount of nitric acid increased. At some particular values of the pH, however, a decrease in the pH was marginal, which can be expressed in the peak resistances to a pH fall in the ANC curve. The peaks occurred at the variations in the pH, depending on binder type, but commonly at about 12.5 in the pH, indicate a resistance of precipitated calcium hydroxide. The measurement of water soluble chloride at the end of test showed that the amount of free chloride was significantly increased at the pH corresponding to the peaks in the ANC curve, which may reflect the adsorption of hydration products to chlorides.

• 한국구조물진단유지관리공학회 논문집
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• 제19권6호
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• pp.80-87
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• 2015

본 연구에서는 칼슘알루미네이트 시멘트(CAC) 모르타르의 수화생성물, 강도, 흡수율, 표면전기 저항성 및 염소이온 침투저항성을 실험적으로 고찰하였다. CAC 모르타르의 성능은 보통포틀랜드 시멘트(OPC) 모르타르의 성능과 상호 비교되었다. 실험 결과에 따르면, CAC 모르타르의 주요 수화생성물은 $C_2AH_8$ 및 $CAH_{10}$으로 조사되었으며, 압축 및 부착강도는 OPC 모르타르에 비하여 우수하게 나타났다. 뿐만 아니라, 표면전기 저항성 및 염소이온 침투저항성도 대체적으로 좋은 결과를 나타냄으로서, CAC의 우수한 성능도 확인하였다. 그러나, CAC 모르타르의 흡수율은 초기재령부터 OPC 모르타르에 비하여 다소 크게 나타남으로써, CAC 경화체의 표면흡수 성능을 개선하기 위한 연구가 더 필요할 것으로 판단된다. 반면, CAC 및 OPC 혼용배합 모르타르의 역학적 성능은 CAC 모르타르에 비하여 대체적으로 다소 떨어지는 것으로 조사됨으로써, CAC계 경화체 제조시 주의가 요구된다.

• 한국건설순환자원학회논문집
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• 제7권3호
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• pp.262-270
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• 2019

본 논문에서는 페로니켈슬래그 미분말 및 혼화재의 복합사용에 따른 모르타르의 강도 및 내구성 평가를 실시하였다. 페로니켈슬래그 및 생석회, 석고, 염화칼슘을 OPC 대비 20%로 치환하여 복합사용 하였으며, 휨강도 및 압축강도, SEM분석을 통한 모르타르의 강도 평가를 실시하였다. 석고를 혼화재로 사용하였을 때 초기강도 발현은 보이지만, 페로니켈슬래그 및 생석회, 염화칼슘을 혼화재로 복합사용 하였을 때 강도발현과 강도증진효과가 극대화 되었으며, 혼화재의 적절한 복합사용이 미세한 공극 채움과 밀도개선효과로 인해 강도와 내구성 개선에 영향을 주는 것으로 판단된다. 또한 화학적침식저항성 및 XRD 분석을 통해 혼화재의 적절한 복합사용은 수화 생성물인 Muscovite의 함량에 따라 강도가 증가하는 경향을 보였고, 규산염은 산 알칼리에는 용해되지 않으므로 화학적 침식 저항 성능이 OPC에 비하여 우수한 것으로 사료된다.

• 한국재료학회지
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• 제29권11호
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• pp.690-696
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• 2019

Geopolymer is an alumina silicate-based ceramic material that has good heat-resistance and fire-resistance; it can be cured at room temperature, and thus its manufacturing process is simple. Geopolymer can be used as a reinforcement or floor finish for high-speed curing applications. In this manuscript, we investigate a high-speed curing geopolymer achieved by adding calcium to augment the curing rate. Metakaolin is used as the main raw material, and aqueous solutions of KOH and $K_2SiO_3$ are used as the activators. As a result of optimizing the high bending strength as a target factor for geopolymers with $SiO_2/Al_2O_3$ ratio of 4.1 ~ 4.8, the optimum ranges of the active agent are found to be $0.1{\leq}K_2O/SiO_2{\leq}0.4$ and $10{\leq}H_2O/K_2O{\leq}32.5$, and the optimum range of the curing accelerator is found to be $$0.82{\leq_-}Ca(OH)_2/Al_2O_3{\leq_-}2.87$$. The maximum flexural strength is found to be 1.35 MPa at $Ca(OH)_2/Al_2O_3=2.82$, $K_2O/SiO_2=0.3$, and $H_2O/K_2O=11.3$. The physical and thermal properties are analyzed to validate the applicability of these materials as industrial insulating parts or repairing finishing materials in construction.

• 대한토목학회논문집
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• 제8권1호
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• pp.103-112
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• 1988

국산 플라이애쉬를 혼합(混合)한 시멘트경화체(硬化體)가 황산이나 염화칼슘침식에 대한 저항성이 포틀랜드 시멘트를 사용한 시멘트경화체(硬化體)보다 좋은 이유는 다음과 같다. 먼저 황산침식에 대한 저항성은 플라이애쉬가 석고생성(石膏生成)을 억제시키므로써 $C_3A$ 계(系) 수화물(水和物)이 ettringite로 전화(轉化)하는 것을 억제한 탓으로 생각된다. 한편 염화칼슘용액에 침지시킨 시멘트경화체(硬化體)의 경우, 염화칼슘의 이온전리작용(電離作用)에 의해 표면(表面)과 내부조직(內部組織)에 미세균열발생(微細龜裂發生)으로 열화현상(劣化現象)이 생기는 것을 플라이애쉬를 사용하므로서 억제하는데 유효하였다.

• Restorative Dentistry and Endodontics
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• 제40권2호
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• pp.97-103
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• 2015

The first part of this study reviewed the characteristics of calcium hydroxide ($Ca(OH)_2$) and summarized the results of in vitro studies related to its antimicrobial effects. The second part of this review covers in vivo studies including human clinical studies and animal studies. The use of $Ca(OH)_2$ as an intracanal medicament represented better histological results in animal studies. However, human clinical studies showed limited antimicrobial effects that microorganisms were reduced but not eliminated through the treatment, and that some species had resistance to $Ca(OH)_2$. Most of clinical outcome studies supported that there is no improvement in healing of periapical lesions when $Ca(OH)_2$ was applied between appointments. Further studies are required for the antimicrobial effects of $Ca(OH)_2$, and search for the ideal material and technique to completely clean infected root canals should be continued.

• Computers and Concrete
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• 제23권5호
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• pp.351-359
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• 2019

In this study, the calcium hydroxide, an inherent product of cement hydration, was treated using biomimetic carbonation method of incorporating stearic acid to generate the hydrophobic calcium carbonate on concrete surface. Carbonation reaction was carried out at various $CO_2$ pressure and temperatures and utilizing the Scanning Electron Microscope (SEM), chloride-ion penetration test apparatus, and compression test machine to investigate the hydrophobicity, durability, and mechanical properties of the synthesized products. Experimental results indicate that the calcium stearate may change the surface property of concrete from hydrophilicity to hydrophobicity. Increasing reaction temperature can change the particles from irregular shapes to needle-rod structures with increased shear stress and thus favorable to hydrophobicity and microhardness. The contact angle against water for the concrete surface was found to increase with increasing $CO_2$ pressure and temperature, and reached to an optimum value at around $90^{\circ}C$. The maximum static water contact angle of 128.7 degree was obtained at the $CO_2$ pressure of 2 atm and temperature of $90^{\circ}C$. It was also found that biomimetic carbonation increased the permeability, acid resistance and chloride-ion permeability of the concrete material. These unique results demonstrate that the needle-rod structures of $CaCO_3$ synthetized on concrete surface could enhance hydrophobicity, durability, and mechanical properties of concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.371-374
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• 2005

In this study, calcium chloride($CaCl_2$), sodium chloride (NaCl), organic acids-containing deicer(NS 40, NS 100), mixed deicier($NaCl\;70\%\;+\;CaCl_{2}\;30\%,\;NS\;40\;70\%\;+\;CaCl_{2}\;30\%,\;NaCl\;70\%\;+\;NS\;40\;30\%,\;NS\;40\;70\%\;+\;NaCl\;30\%$) is investigated based on the laboratory test for deicing performance. Test items for deicing performance were ice melting and ice penetration, freezing point depressions and eutectic points, pH, thermal properties for selected deicing chemicals. As a test results, in case of the use chloride-containing deicier in area that concrete structures has subjected to freez-thaw reaction in winter season, it showed desirable method that use deicing chemicals mixed with optimum ratio rather than use one deicing chemicals when is consider to deicing performance and effects, corrosion of steel materials, freez-thaw resistance of concrete. When use various deicing chemicals mixed, NS40($70\%$)+Calcium chloride($30\%$) showed the best effective method.

• 콘크리트학회지
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• 제5권1호
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• pp.129-138
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• 1993

프리텐션 방식 원심력 고강도 콘크리트 말뚝[KS F 4306]제조에 관한 실험적 연구로써 고황산염시멘트를 이용한 800kg/$ extrm{cm}^2$이상의 고강도콘크리트 제조시 수화 특성검토와 콘크르트 조직내의 기공율과 압축강도간의 상관식을 도출하여 고강도 발현기구를 규명하였으며 콘크리트 압축 및 휨강도간의 상관식 유도와 내구성 측면에서의 내동해성, 건조수축, 화학저항성등을 보통 포틀랜드 시멘트와 비교 고찰한 결과, 고황상염시멘트의 내구성이 우수함을 확인하였다.