• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.336-341
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• 1998

A comparative study on the effects of mean particle diameter and substitutional ratio of II-anhydrite on the fluidity of cement paste has been conducted. Three different mean particle diameters(4, 14 and $35{\mu}m$) and four different substitution ratios(3, 5, 10, 15wt%) have been tested while the dosage of two superplasticizers - naphtalenic(NSF) and polycarboxylic(NT-2) - has been varied from 0 to 2.0wt%. To investigate the effects of those parameters, the variation in fluidity and apparent viscosity of the cement paste has been observed as a function of the elapsed time. The initial fluidity of the cement paste is more affected by the increase in substitution ratio than by the mean particle size of the II-anhydrite. When the substitution ratio of the II-anhydrite is fixed at 10wt%, addition of 1.0wt% NT-2 improves the fluidity of paste cement more than that for NSF. This case has showed the best improvement of the fluidity in the range of parameters investigated. At the addition of 1.0wt% NT-2, apparent viscosity of the cement paste has been noticeably decreased as substitutional ratio of II-anhydrite increases. It was found that it would be more effective to substitute II-anhydrite at a certain ratio to improve the fluidity of the cement paste, in addition to adding NT-2.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.789-795
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• 1999

In this study, carbon fiber reinforced cement composites(CFRCs) reinforced with short noncircular type carbon fibers were fabricated and properties(drying shrinkage, resistance to freezing and thawing, and fracture toughness) were compared with those of the CFRCs reinforced with circular type carbon fibers. It was found that these properties greatly depended on the shape and length of carbon fibers. The drying shrinkage of CFRCs reinforced with C-type carbon fiber was superior to other CFRCs. This effect was increased with a high aspect ratio of fiber. The resistance to freezing and thawing was increased with the fiber length and fiber volume percent, but there was on remarkable effect to fiber shape. Fracture toughness and resistance to crack propagation of CFRCs reinforced with C-CFs were improved compared with other CFRCs. It was believed that the more absorption of fracture energy into the larger interface caused an increase in fracture toughness and resistance to crack propagation.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.815-821
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• 2005

Three major commercially available organic chemical admixtures are modified lignosulfonates (LS), sulfonated naphthalene-formaldehyde resins (SNF) and sulfonated melamine-formaldehyde (SMF). In this study, various sulfonated melamine-formaldehyde (SMF) superplasticizers were synthesized via four synthetic steps including hydroxymethylation (Step 1), sulfonation (Step 2), polymerization (Step 3) and neutralization and stabilization (Step 4). In this synthesis, mole ratio of melamine to formaline and the amount of acid catalyst used were varied. The obtained SMF superplasticizers were applied to cement paste and mortar and their physical properties including workability, slump loss, compressive strength were investigated. Also their hydrate shapes were investigated by examining SEM images of the cured paste. It was found that the fluidity properties of cement were significantly influenced by the structure of SMF condensates.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.10a
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• pp.154-155
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• 1999

동해 지역은 험준한 태백산맥을 경계로 동해안 연안에 위치하고 있으며 공업항만의 발달로 지방 산업의 발전이 가속화되고 있다. 특히 다량의 연료를 사용하는 대기배출시설인 시멘트공장 3개소와 화력발전소 1개소가 밀집되어 대기질 악화가 우려되고 있으며, 주요 배출물질로는 먼지, 질소산화물, 일산화탄소 등이 있다.(중략)

• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.652-660
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• 2008

For the recycling of rapid-chilled steel slag, the mechanical strengths and physical properties of EVA-polymer modified mortars with the various replacement ratios of rapid-chilled steel slag were investigated. Twenty five specimens of polymer modified mortars were prepared with the five different amounts of EVA-polymer modifier (0, 5, 10, 15, 20 wt%) and rapid-chilled steel slag (0, 25, 50, 75, 100 wt%). For the investigation of the characteristics of polymer modified mortars, the measurements such as water-cement ratio, unit volume weight, air content for fresh mortar and compressive strength, flexural strength, water absorption, hot water resistance, porosity and SEM investigation for curing specimens were conducted. As a results, with an increase in the replacement ratio of rapid-chilled steel slag, water-cement ratios decreased but unit volume weight increased remarkably. With increasing EVA-polymer modifier and the replacement ratio of rapid-chilled steel slag, percent of water absorption decreased but compressive and flexural strengths increased remarkably. By the hot water resistance test, mechanical strengths decreased but total pore volume and porosity increased remarkably. In the SEM observation, the components of specimen were shown to stick to each other in the form of co-matrix phase before hot water resistance test, but polymer modifier of co-matrix phase was decomposed or deteriorated after hot water resistance test.

• Applied Chemistry for Engineering
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• v.20 no.1
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• pp.67-74
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• 2009

Nowadays, recycling of recycled aggregates from the waste concrete is seriously demanded for the protection of environment and the shortage of aggregates owing to the large scale construction project. In this study, for the development of polymer composite recycling recycled aggregates from the waste concrete, twenty five specimens of the polymer composite were prepared with the five levels of replacement ratios of recycled aggregates (0, 25, 50, 75, 100%) and polymer-cement ratios (0,5, 10, 15, 20%), respectively. For the evaluation of the performance of polymer composite specimens, various physical properties such as compressive and flexural strengths, water absorption, hot water resistance, total pore volume and porosity were investigated. As a result, physical properties of polymer composite were remarkably improved with an increase of polymer cement ratios, but greatly decreased with the replacement ratios of recycled aggregates.

• Cement
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• s.40
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• pp.4-11
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• 1971

최근 우리 나라에서도 경영합리화와 생산성향상의 문제가 활발하게 논의되고 있고, 또한 이와 동시에 기업을 경영하는데 있어서 계획 및 관리의 필요성이 강조되고 있다. 이와 같이 기업환경의 급속한 구조 변화에 대비하여 본론에서는 생산성향상을 위한 가장 중요한 경영관리 기법중의 하나인 I.E(Industrial Engineering)에 대하여 소개하고저 한다. 본래 I.E는 그 수법이나 대상에 있어서 자연과학이나 사회과학분야에서 활용되고 있었으나 미국의 F.W.Tayler 박사가 이를 최초로 경영학적 측면에 도입, 적용하였다. 1890년대에 미국은 공업생산국으로서 산업근대화에로의 발전과정에서 경영자측은 기술이나 방법에의 개선에 의한 산출량 증가로서 노동자의 임금절하를 기도하고 있는 노동자측은 태업으로 임금문제를 해결하려고 하였다. 따라서 F.W.Taylor 는 산업발전에 최대의 장벽인 임금문제의 기술적인 해결에 주력하여 노사간의 분쟁을 $\ulcorner$성과급임금제도$\lrcorner$로서 조정하기 위해 $\ulcorner$과학적 관리법$\lrcorner$(The Scientific Management)을 체계화시키기 위한 일련의 작업에 착수하였다. 이외에도 테일러는 임금문제에 관련된 생산성 향상 문제까지도 연구발전시켜 생산계획$\cdot$공장관리$\cdot$작업조직$\cdot$자재관리$\cdot$공정관리 등의 전반적인 공장관리 문제를 해결하기 위하여 $\ulcorner$공장관리$\lrcorner$(Shop management)를 발표하여 I.E의 체계를 확립시키는 계기를 마련하였다. 이와 같이 I.E는 미국을 중심으로 발생한 것이지만 그간 우리나라에서도 도입 적용되어 발전되고 있음을 감안할 때 한국양회공업협회가 본기법에 대하여 관심을 갖고 일련의 조사활동을 시작한 것은 매우 의의있는 일이라 할 수 있다.

• Applied Chemistry for Engineering
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• v.21 no.4
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• pp.463-468
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• 2010

The polycarboxylic (PC) type concrete superplasticizer was synthesized. The effects of ethylene oxide group number and its molecular weight on the properties of the polycarboxylic type concrete superplasticizer and the concrete motar properties were studied. To investigated of the interfacial properties of the premixed-concrete with the superplasticizer, the type and the amount of polyethylene glycol, meta acrylate added, and type of the initialization agent were studied. Also the interfacial properties of the superplasticizer aqueous phase, the wettability on the cement particle, the fluidity of the cement mortar, and the strength properties of the concrete were measured. For a high fluidity of the cement mortar and a high strength of concrete, a low value of the surface tension and contact angle were required for PC. To have a good performance for PC, the reaction condition of 1.3 mol ratio of MA against to MPEG was suitable with KSP initiator.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.391-396
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• 2006

When radioactive wastewater was solidified treatment by cement, the drying rate of cement and the volume reduction ratio was decreased because of boric acid component in the wastewater. In order to supplement the demerit, effects of paraffin wax investigated in this study. Paraffin wax has a hydrophobic properties and a low affinity with inorganic materials. When the radioactive wastewater was tested by a small of wax, the compressive strength of solidified waste are decreased Therefore boric acid in radioactive wastewater are first treated by alkali salt and coated by the stearic acid. During the solidification step, The amount of paraffin wax addition get the result that the compressive strength of solidification with cement was the same as that with paraffin wax. The leaching properties of radioactive waste solidified was the same CFL (cumulative fraction leached), PR (penetration rate), effective diffusivity if paraffin wax content in solidified waste was 20% or 25%.

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.34-38
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• 2019

A cement industrial by-product was used as a Ca source for the carbonation process. It was confirmed that the most of cement industrial by-products was composed of CaO and KCl through ICP and XRD analyses. The optimal extractant type and concentration was 1.5 M of hydrochloric acid, and the solid/liquid ratio was 0.1 g/mL. It was assumed that the cation extraction efficiency was dependent of the pair ions and their binding formation and also the solubility from extraction efficiency results by varing extractants. After extraction process, it was also confirmed that the cation could be selectively separated from the solution with respect to the kind of additives and the injection order. When NaOH was injected into the solution to control pH values ranging from 9.5 and 13, impurities and $Ca(OH)_2$ were precipitated, whereas the separated K ion was precipitated in the form of KCl under the injected $C_2H_5OH$.