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Meta Kaolin 및 Silica Fume을 이용한 고성능 고강도 시멘트 모르타르 특성에 관한 연구
정민철 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.5
시멘트 수화시 생성되는 수산화칼슘은 시멘트 모르타르의 강도 및 내구성을 감소시킨다. 이에 포졸란물질인 meta kaolin 및 silica fume을 이용하여 이러한 결점을 해결하고자 하였다. Meta kailin 및 silica fume의 함량변화에 대한 수산화칼슘의 감소는 Fourier의 시차열분석에 의해 규명되었고, mela kaolin 및 silica fume을 무첨가(0%)에 비하여 10% 이상 첨가시 수산화칼슘양이 큰 폭으로 감소함을 나타내었다. 이는 meta kaolin 및 silica fume의 SiO2 성분과 시멘트의 CaO와의 포졸란반응에 의한 것으로 나타났다. Calcium hydroxide produced by cement hydration decreases the durability and the compressive strength of cement mortars. Pozzolanic property of meta kaolin and silica fume allows to avoid this drawback. Calcium hydroxide consumption according to pozzolanic raction is evaluated by Fourier differential thermal analysis. Particulary the properties of high performance and high strength of cement mortar containing above 10% meta kaolin and silica fume were resulted in the pozzolanic activity.
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정민철,남기웅,정윤중 한국세라믹학회 1994 한국세라믹학회지 Vol.31 No.9
An underwater grout on material resistance against segregation in water were studied by water soluble polymer (methyl cellulose and acrylic acid ester and styrene). The mechanical properties of the grout agents were investigated through the observation of the microstructure and application of fracture mechanic. When the soluble polymer MC+AAES added with 0.6 wt% to the underwater grout agents the compressive strength, flexural strength and Young's modulus were about 58 MPa, 10 MPa and 3.2 GPa respectively, and critical stress intensity was about 0.8 MNm-1.5. It can be considered that the strength improvement and fracture toughness increase may be due to the pore decrease and bonding force by material resistance against segregation in water.
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정민철,남기웅,정윤중 한국세라믹학회 1994 한국세라믹학회지 Vol.31 No.6
Investigation for the high strength grouts using ordinary cement mortar, melamine formaldehyde condensate (MFC) with various admixtures was carried out. The physical properties of the grouts were investigated through the observation of the microstructure and the application of fracture mechanics. When the lime stone and fly ash was added with 6 wt% to the grouts, the compressive strength was about 72 MPa, 69 MPa respectively, and the flexural strength was about 11.9 MPa, 11.4 MPa respectively, the Young's modulus was about 4.3 GPa, 3.9 GPa, and the critical stress intensity was about 7.3 ×10-1MNm-1.5, 6.8×10-1MNm-1.5 respectively. When the silica fume was added with 6 wt% to the grouts, the compressive strength and the flexural strength were 81 MPa, 12.3 MPa, Young's modulus was 4.8 GPa and the critical stress intensity was about 8.4×10-1MNm-1.5.
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Mg ( OEt ) 2 / THF / SiCl4 / TiCl4 촉매에 의한 에틸렌의 기상 중합 및 공중합
정민철,김일,김재하,최홍기,우성일 ( Min Chul Chung,Il Kim,Jae Ha Kim,Hong Ki Choi,Seong Ihl Woo ) 한국화학공학회 1994 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.32 No.6
Homo- and co-polymerization of ethylene were carried out in both gas and slurry phases over Mg(OEt)₂/THF/SiCl₄/TiCl₄-AlEt₃ catalysts in the range of temperature 20-70℃ and pressure 2-10 psig. In gas phase polymerization, maximum activity was measured at the Al/Ti mole ratio of 377, and reaction rate dependence on AlEt₃ concentration could be explained with the Langmuir-Hinshelwood adsorption model. Even though maximum activities were obtained at the same temperature, 60℃ in both gas and slurry phases, overall activation energy was higher for the slurry phase(13 ㎉/㏖) than for the gas phase(4.7 ㎉/㏖) polymerization. The molecular weight behavior has been examined by measuring intrinsic viscosity. The molecular weight was increased as the ethylene pressure increased, and as the temperature and the concentration of AlEt₃ and hydrogen decreased. Using two different comonomers(propylene and butene-1), the copolymerization of ethylene was carried out. The intrinsic viscosity and the melt index were decreased as comonomer concentration increased, and the maximum activity was observed when the concentration of comonomer is about 20 ㏖%.
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