균열 보수용 폴리머 시멘트 복합체의 휨접착강도에 관한 연구

조영국 한국건축시공학회 2024 한국건축시공학회지 Vol.24 No.1

This research aims to assess the flexural bonding efficacy of polymer-cement composites(PCCs) inmending cracks within reinforced concrete(RC) structures. The study involved infilling PCCs intocement mortar cracks of varying dimensions, followed by evaluations of enhancements in flexuraladhesion and strength. The findings indicate that the flexural bond performance of PCCs in crack repairis influenced by the cement type, polymer dispersion, and the polymer-to-binder ratio. Specifically, theuse of ultra-high early strength cement combined with silica fume resulted in an up to 19.0%improvement in flexural bond strength compared to the application of ordinary Portland cement withsilica fume. It was observed that the augmentation in flexural strength of cement mortar filled withPCCs was significantly more dependent on the depth of the crack rather than the width. Furthermore,PCCs not only acted as repair agents but also as reinforcement materials, enhancing the flexuralstrength to a certain extent. Consequently, this study concludes that PCCs formulated with ultra-highearly strength cement, various polymer dispersions, silica fume, and a high polymer-to-binder ratioranging from 60% to 80% are highly effective as maintenance materials for crack filling in practicalsettings.

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.

Secondary Subaortic Stenosis after Patch Closure of Subarterial Ventricular Septal Defect

조영국,오수민,마재숙 한국심초음파학회 2010 Journal of Cardiovascular Imaging (J Cardiovasc Im Vol.18 No.2

Subaortic stenosis usually occurs without a previous heart operation, however, it can occur after heart surgery as well, with a condition known as a secondary subaortic stenosis (SSS). SSS has been reported after surgical repair of several congenital heart defects. There are only a few recorded cases of SSS after repair of ventricular septal defect (VSD). Here we report a rare case of SSS that occurred 3 years after surgical repair of subarterial VSD. A follow-up echocardiogram is essential for detecting SSS caused by the newly developed subaortic membrane in patients who had cardiac surgery.

바이오벤처 M&A만이 살길이다

조영국 한국바이오벤처협회 2003 Bio news Vol.1 No.-

바이오벤처기업의 활로모색을 위하여 - '과감한 M&A로 발전방안 모색을'

조영국 한국바이오벤처협회 2003 Bio news Vol.2 No.-

미국만을 바라보는 우리 바이오 기업에게 유럽은 새로운 시작이다

조영국 한국바이오벤처협회 2003 Bio news Vol.3 No.-

시론 : 기회의 창(窓)

조영국 경남대학교 극동문제연구소 2005 NEWS Vol.72 No.-

시멘트 콘크리트의 배합조건에 따른 pH 저감에 관한 연구

조영국 한국건축시공학회 2008 한국건축시공학회지 Vol.8 No.4

The purpose of this study is to evaluate the mix design of pH reducing cement concrete which can be used for environment-friendly concrete. Cement pastes and concretes are prepared with water-binder ratios and various admixtures such as blast-furnace slag, fly ash and recycled cement, and tested for compressive strength and pH. pH is measured through pore solution expressed from hydrated cement paste by special apparatus. From the test results, regardless of water-binder ratio, The pH of expressed pore solution from hydrated cement paste which is made of ordinary portland cement with blast-furnace slag, fly ash is decreased with increasing of admixtures content, and compressive strength is also slightly improved. The compressive strength of cement paste made of recycled cement which is burnt at 1000℃, for 2 hours is considerably increased compared with that of none-burnt recycled cement due to restoration of hydraulic property, but pH is a little higher. Porous concrete with ordinary portland cement has high pH in the range of 12.22 to 12.59, however, that is reduced to the range of 8.95 to 10.39 by carbonation at the surface of porous concrete. The pH reduction of porous concrete is possible by various admixture addition, however their degrees are very slight. Therefore, to reduce the pH considerably, carbonation method of porous concrete is better in pH reduction methods for plant survival condition of pH of 9.0 or less. In this study, it is apparent that pH for the environment-friendly porous concrete products used in the construction field can be suppressed by this carbonation method and various admixtures addition.

발생중인 Chick Wingbud 에서 Transforming Growth Factor β 유전자의 발현

조영국,김원선 한국유전학회 1995 Genes & Genomics Vol.17 No.1

In the developing chick embryos, several kinds of growth factors are known to play some major roles in the process of pattern formation and tissue differentiation. The present study was performed to examine the expression profile of transforming growth factor β's (TGF-β) in the early phase of chick wing development. The level of TGF-β1 and TGF-β2 gene expression increased with the advancing stages of chick wing development even though the amount of increase was not profound. In the case of TGF-β3, the level of gene expression at 5 days post-incubation was somewhat lower than that at 4 days post-incubation while the level increased again at 6 days post-incubation. Among the three TGF-β's, the level of TGF-β2 expression was most strong while the level of TGF-β1 expression was most weak. Examination of spatial expression pattern of TGF-β2 in the developing wingbud revealed that the expression was high at the region of apical ectodermal ridge at 4-5 days post-incubation, and, in the anterior and posterior necrotic zones, the signal intensity became strong with advancing developmental stages. The results obtained in the present study suggest that TGF-β's play some role(s) in the wing pattern formation, especially during early phase of chick wing development.

RC 구조물의 균열 보수용 폴리머 시멘트 복합체의 접착특성에 관한 연구

조영국,홍대원,권우찬,김완기 한국건축시공학회 2022 한국건축시공학회지 Vol.22 No.1

The purpose of this study is to evaluate the adhesion properties of polymer cement composites forcrack repair of an RC structure. Polymer cement composites are manufactured from cement, threetypes of polymers and silica fume, and the mixture is designed by adjusting the water cement ratio andAE reducing agent so that the viscosity target of the polymer cement composites is 700mPa․s or less. According to the test results, the Type-A adhesion in tension of the polymer cement compositeexceeded the adhesion standard of 1.0MPa of the polymer finishing material, and furthermore,depending on the type of polymer, the adhesion in tension was highest for SAE, followed in descendingorder by EVA, and SBR. In addition, the adhesion in tension of Type-B is up to 1/4.5 lower than that ofType-A, but the incorporation of silica fume shows a significant improvement in terms of adhesion intension. Based on this study, the basic mixing design of the polymer cement composites required forviscosity and adhesive performance required for crack repair of the RC structure was completed. Itcould be proposed as an optimal mixing design under conditions for intermixing polymer type EVA,SAE, and P/C 80%-100%. 본 연구의 목적은 RC 구조물의 균열 보수용 폴리머 시멘트 복합체의 접착성능을 평가하기 위함이다. 폴리머 시멘트 복합체는 시멘트, 폴리머와 실리카흄으로 제조하였으며, 점도가 700mPa․s 이하가 되도록 물시멘트비와 AE 감수제의 혼입량을조정하였다. 연구결과, Type-A 인장접착강도는 폴리머계 마감 재료의 접착기준인 1.0MPa을 상회하였으며, 폴리머 종류에따라 SAE, EVA, SBR 순으로 높은 인장접착강도를 나타냈다. 또한 Type-B의 인장접착강도는 Type-A에 비해 최대 1/4.5의낮은 강도를 나타냈으나 실리카흄의 혼입에 따른 상당한 강도개선 효과를 보였다. RC 구조물의 균열 보수에 필요한 점도와접착성능을 위해 EVA와 SAE의 폴리머 시멘트비 80%~100% 범위에서 일정량의 실리카 흄을 혼입하는 조건을 최적배합설계로 제안할 수 있었다.