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압축강도에 따른 수중불분리 콘크리트의 배합설계에 관한 연구
조영국,Jo, Young-Kug 한국건축시공학회 2003 한국건축시공학회지 Vol.3 No.3
At present, the antiwashout underwater concretes are used as popular construction materials in European countries, the United States and Japan. The water-soluble polymers in the antiwashout underwater concretes provide excellent segregation or washout resistance, self-compaction and self-leveling property to the concretes. The purpose of this study is to recommend to optimum mix proportions of antiwashout underwater concretes according to compressive strength of 300kgf/$\textrm{cm}^2$ to 500kgf/$\textrm{cm}^2$. The antiwashout underwater concretes are prepared with various unit cement content, unit water content, sand-aggregate ratio, unit antiwashout agent and superplasticizer content. And they are tested for flowability, and compressive strength. From the test results, it is possible to recommend the optimum mix proportions of antiwashout underwater concretes according to compressive strengths within the range of 300kgf/$\textrm{cm}^2$ to 500kgf/$\textrm{cm}^2$.
St/BA를 사용한 폴리머 시멘트 슬러리 도장재의 내부식성과 부착성
조영국 청운대학교 건설환경연구소 2015 청운대학교 건설환경연구소 논문집 Vol.10 No.1
The purpose of this study is to evaluate the adhesion to steel plate, anti-corrosion and bond performance of polymer(St/BA) cement slurry(PCS)-coated steels such as rebar and steel plate. From the test results, PCS-coated rebar using St/BA has a high adhesion ratio of 92%, and anti-corrosion of PCS-coated rebar using St/BA is improved to a great extent compared to that of un-coated rebar. The bond performance of coated rebar is considerably improved by using St/BA-cement slurry at surface of steel compared with that of un-coated rebar and epoxy coated rebar. In general, the bond strength of PCS-coated rebar with St/BA is better than that of un-coated rebar and epoxy coated rebar. The maximum bond strength of PCS-coated rebar at coating thickness of 100 µm and curing age of 7days is 1.32 and 1.38 times respectively, the strength of un-coated rebar and epoxy-coated rebar. In this study, it is recommended that optimum conditions for PCS are St/BA as binder, 100µm as coating thickness and 7day as curing age using St/BA as a cement modifier. 본 연구는 폴리머 디스퍼션으로 St/BA를 사용한 폴리머 시멘트 슬러리(PCS)를 제작하여 연강판과 이형철근에 도장하여 도장두께와 도장 후 양생재령에 따른 연강판에 대한 접착성, 시멘트 모르타르 및 콘크리트 속에 매립된 도장철근의 내부식성 및 부착성을 실험평가하였다. 본 연구결과, PCS 도장 연강판의 접착성은 92%의 우수한 접착성을 나타냈으며, PCS 도장철근의 시멘트 모르타르 속에서의 내부식성은 도장하지 않은 보통철근에 비해 크게 뛰어났다. 또한 PCS 도장철근의 부착강도는 도장두께와 양생재령에 따라 큰 영향을 받았는데, 최대부착강도는 보통철근과 에폭시철근에 비해 각각 1.32배 및 1.38배 크게 나타났다. 본 연구에서 부착강도는 양생재령과 도장두께가 크게 영향 받았으며 St/BA의 P/C 100%에서, 도장두께 100㎛와 양생재령 7일이 최적배합으로 제안할 수 있었다.
양생조건에 따른 폴리머 시멘트 모르터의 내마모성에 관한 연구
조영국,소승영,Jo, Young-Kug,So, Seoung-Young 한국건축시공학회 2005 한국건축시공학회지 Vol.5 No.4
In recent years, polymer-modified mortars using polymer dispersions have been widely used as finish and repair materials in the construction industry because of their excellent properties compares to those of ordinary cement mortar. Especially, the adhesion improvement of ordinary cement mortar and concrete has attracted a great deal of attention from researchers, and several unique and simply applicable techniques for the adhesion improvement have been developed. The purpose of this study is to evaluate the abrasion resistance of polymer-modified mortar according various curing methods. The polymer-modified mortar are prepared with various polymer-cement ratios, and are subjected to three curing methods such as dry rure, standard cure and freezing and thawing cure after two curing methods, and then tested for abrasion. From the test results, the polymer-modified mortars with various polymer-cement ratios have some superior abrasion resistance compared with plain mortar. The abrasion resistance of polymer-modified mortars increase with an increase in the polymer-cement ratio, and is better under water cure than any other curing methods. It is concluded that the abrasion resistance of cement mortar is markedly improved by modifying of polymer dispersion.
원료분체 $Nb_20_5$의 응집상태가 $Pb(MG_{1/3}Nb_{2/3})O_3$소결, 유전특성에 미치는 영향
조영국,김진호,박병옥,조상희 한국결정성장학회 1992 韓國結晶成長學會誌 Vol.2 No.1
일차입경이 동일한 $Nb_20_5$분체의 응집 상태가 $Pb(Mg_{1/3}Nb_{2/3})O_3$의 생성 반응 및 소결에 미치는 영향을 조사하였다. 합성 방법으로는 고체 반응법과 용융염법으로 나누어 각각 실험하였다. 고체 반응법의 경우에는 perovskite 상의 생성 반응이 $Nb_20_5$의 응집도가 낮을수록 크게 영향을 받았으나, 용융법시에는 거의 영향을 받지 않았다. 그 이유는 고상 반응법시에는 perovskite 상의 생성이 중간생성물인 perovskite 상의 분포의 균일성, 즉 $Nb_20_5$의 응집도에 지배를 받게되나, 용해, 석출 과정에 의해 진행되는 용융염법에서는 반응물의 비표면적에 의존하므로, 응집도에는 그다지 영향을 받지않는 것으로 사료된다. Effect of agglomeration of $Nb_20_5$ of the same primary particle size on formation reaction and sintering of $Pb(Mg_{1/3}\;Nb_{2/3})O_3$ was examined. Both solid state reaction and molten salt synthesis were adopted. With decreasing agglomeration of $Nb_20_5$ increased the rate of formation reaction of perovskite PMN in solid state reaction, but had little influence in molten salt synthesis. It was concluded that the increase in the inhomogeneity of the dispersion state of intermediate pyrochlore with increasing agglomeration of $Nb_20_5$ retarded the formation reaction of perovskite PMN in solid state reaction, while had little influnce in molten salt synthesis due to its solution - precipitation mechanism -mainly depends on powder surface area.