고 Mn 강의 크리프파단특성에 미치는 P 첨가 및 이단용체화처리의 효과

류재석,최형섭,최주 대한금속재료학회(대한금속학회) 1979 대한금속·재료학회지 Vol.17 No.6

Ni을 節約한 高Mn 오스테나이트鋼을 새로이 合金設計하여 粒內强化를 위한 P 添加와 粒界强化를 위한 二段溶體化處理로써 크립破斷特性을 改善코자 하였다. 微量의 P를 添加하면 結晶粒內에 微細한 炭化物이 均一하게 析出되었으며 또한 粒界에 따른 析出物缺乏區域도 크게 減少되었다. 溶體化處理를 두 번 하면 粒界가 톱니꼴로 되어 粒界에서의 크랙의 生成 및 成長을 抑制하였다. 結晶粒度와 크립破斷壽命間에는 密接한 關係가 있어서 어느 適當한 粒度에 있어서 壽命이 가장 길었다. 粒界의 톱니化 및 P의 添加에 따른 效果로서 600℃, 26㎏/㎟에서의 크립破斷壽命이 約 10倍나 크게 改善되었다. An austenitic high manganese heat resisting alloy was newly designed. Effects of phosphorus addition and two step solution treatment on the microstructure of the alloy were investigated in order to improve creep rupture properties. A small addition of phosphorus resulted in the uniform dispersion of fine carbide precipitates in the matrix and the narrowing the width of the precipitate free zone along grain boundaries. Two step heat treatment brought out the serration of grain bourdary which was very effective in the prevention of the formation and the growth of cracks or cavities at the grain boundaries. It was found that the grain size was closely related to the rupture life, i. e., the maximum rupture life was achieved at the optimum grain size. As the result of combined effects of phosphorus addition and grain boundary strengthening by the serration, the rupture life was improved remarkably up to ten times at 600℃ and 26 ㎏/㎟.

폴리비닐아세테이트(PVAc)를 이용한 복합공법의 수밀성능 향상에 관한 연구

류재석,송일현,이용수 한국구조물진단유지관리공학회 2012 한국구조물진단유지관리공학회 논문집 Vol.16 No.4

본 연구에서는 시멘트에 작용하는 아크릴 코폴리머의 화학반응을 통해 강한 점착성과 유연성을 가지는 친환경적인 폴리비닐아세테이트(PVAc)를 이용하여 수밀성을 향상시키는 복합공법의 가능성을 알아보고자 하였으며, 이를 위한 실험 방법으로 1차로 실리케아트계 침투성 방수제를 도포 한 후, 2차로 PVAc를 혼입한 모르타를 도포한 후에 부착강도 및 흡수량에 대한 특성을 검토하였다. 이 실험 결과를 토대로 하여 현장 적용을 위한 Mock-up 부재를 제작하였고, 이 시험 부재에 대하여 복합공법을 적용한 후 실내 시험과 동일한 성능을 검토하였다. 또한, 탄산화 및 염소 이온 침투저항성 평가를 실시하여 내구성이 취약한 환경에 적합한지 여부를 검토 하였다. 그 결과 PVAc를 이용한 복합공밥을 적용한 시험체가 수밀성능이 가장 우수하였으며, 부착강도 또한 우수한 성능을 나타내었다. 또한, 간이 Mock-up 부재에 대한 성능평가에서 실내 시험과 동일한 경향을 보였으며, 압축강도 시험결과 보강 효과를 발휘함을 알 수 있었다. 탄산화 및 염소 이온 침투저항성 내구 성능 평가에서 가장 우수한 결과를 나타내어 지하구조물 및 해양구조물 등과 같은 취약한 지역에 적용이 가능함을 확인 할 수 있었다. In this study, hybrid method using polyvinyl acetate (PVAc) which has a strong adhesion and flexibility in which acrylic copolymer chemical-reaction reacts with cement, and is eco-friendly, is to improve the watertightness. The hybrid method is applied applied primarily waterproof stuff comprising silicate system and secondary mortar mixed with PVAc on the concrete surface. And then, in order to evaluate the performance, the properties of bond strength and amount of water absorption were measured. Based on the above experiments, mock-up specimens for field application were fabricated, and then the properties were evaluated as laboratory experiments. As the results, specimens cast from hybrid method using PVAc showed the best results on watertightness and bond strength. And also, with respect to experiment of mock-up specimens, the properties were in agreement with laboratory results. Especially, it could know that PVAc has strengthening effect from the results of the compressive strength. Due to outstanding results of carbonation depth and resistance to chloride ion penetration, it may be applied in weak areas such as underground and marine structures.

순환잔골재를 혼입한 자기충전 콘크리트의 현장적용을 위한 실험적 연구

류재석,송일현 한국구조물진단유지관리공학회 2011 한국구조물진단유지관리공학회 논문집 Vol.15 No.4

본 연구에서는 폐콘크리트에서 발생하는 순환잔골재가 구조용 재료로서 많은 문제점이 있음을 인지하고 순환잔골재가 포함하고 있는 미분말이 강도증진 효과와 유동성을 증가 시킬 수 있다는 특성을 이용하여 자기충전 콘크리트(Self-Compacting Concrete, 이하 SCC로 표기)에 활용하게 되었다. 즉 순환잔골재가 갖는 미분말이 자기충전 콘크리트 특성인 고강도(40 MPa 이상)와 높은 유동성(JSCE 2등급)을 발현하기에 적당하여 폐콘크리트에서 발생하는 순환잔골재를 일반잔골재 대비 순환잔골재의 혼입률을 25%씩 증가시켜, 총 5수준으로 달리하여 자기충전 콘크리트에 적용하였으며, 이에 따라 굳지 않은 콘크리트의 물리적 특성, 경화한 콘크리트의 역학적 및 내구 특성을 검토하여 순환잔골재를 자기충전 콘크리트 재료로서 활용 가능성을 검토하고자 한다. 그 결과 물리적, 역학적 및 내구특성의 5수준 배합비율 중 일반잔골재 대비 순환잔골재는 50% 혼입률까지 적용 가능하다는 결론을 얻었으며, 그 이상의 혼입률에서는 오히려 성능저하가 발생한다는 것을 알 수 있었다. 또한 실생활에서의 적용 가능성을 알아보기 위한 실구조물의 적용성이 차후 검토 되어야 할 것으로 판단된다. The purpose of this study, looking to which the recycled fine aggregates from waste concrete have a lot of problems as a material for structure purpose, is applying the recycled fine aggregate to Self-Compacting Concrete(In the reminder of this paper, it often referred to as SCC) by using the characteristic which the powder containing the recycled fine aggregates can increase strength and liquidity. In this study, that is, the recycled fine aggregate powder is appropriate for developing high strength(over 40 MPa) and liquidity(JSCE 2 grade), the characteristic of the SCC and it was increased the ratio of mixing the recycled fine aggregates emerging from waste concrete and the normal fine aggregates by 25%, making differential in total 5 levels and applied to SCC. After all, this study was reviewed the physical properties of the fresh concrete, analyzed the mechanical properties and durability of the hardening concrete and tried to ensure the possibility of utilizing the recycled fine aggregates as a material for SCC. As a result, this study reached a conclusion that among the 5-level replacement ratios of the physical, mechanical analysis and the durability characteristics, the normal fine aggregates could be applied up to a replacement ratio of 50% more than the recycled fine aggregates and resulted in a deterioration in performance the replacement ratio larger than 50%. It is judged that the applicability of the real structures should be followed up in order to check the possibility of applying the recycled fine aggregates to real life.

서중 콘크리트에서 응결 지연형 혼화제의 정제화에 관한 연구

류재석,송일현,이용수,양능원,이준석 한국구조물진단유지관리학회 2012 한국구조물진단학회 학술발표회논문집 Vol.2012 No.1

Be constructed in the Middle East, recent overseas plant business mainly due to an increase in the amount of concrete in the construction sector is growing. When using plain concrete and concrete development of the initial expansion of the initial hydration, due to thermal stress that causes cracks in the concrete problems, and prevention of this by the use of the delay is expected to increase. In addition to the increase in domestic traffic produced in ready-mixed concrete plants and concrete due to high temperature during transportation upon arrival at the scene quickly if condensation begins to degrade due to the slump loss and workability after curing of cold joint and cause filling defects and the need for the measures. In the case of the powder that is currently on the market in order to obtain a uniform delay effects can be mixed, may be added, such as, wet, etc. Keep a less efficient storage, even if the delay has to be taken. This powder improves the delay and store it in a tablet, a delay effect to encourage the development of tablet, and the delay for compliance with basic properties was investigated.

재생골재의 표면처리에 의한 성능 향상

류재석,이용수,Ryou, Jae-Suk,Lee, Yong-Soo 한국건설순환자원학회 2013 한국건설순환자원학회지 Vol.8 No.4

친환경 콘크리트 개발을 위한 고분자 화합물의 적용에 관한 연구

류재석,이용수,송일현 대한토목학회 2012 대한토목학회논문집 A Vol.32 No.5A

본 연구는 수용성 폴리머의 일종인 폴리비닐아세테이트(Polyvinyl Acetate, 이하 PVAc)를 사용한 폴리머 시멘트 모르타르와 콘크리트의 특성에 관한 평가를 통하여 친환경 콘크리트 개발을 위한 기초자료를 획득하는 것이다. 이를 위해 PVAc를 혼입하지 않은 시멘트 모르타르 및 콘크리트와 결합재 대비 3%, 6%, 9% 12%의 PVAc를 각각 혼입한 폴리머 시멘트 모르타르 및 콘크리트와의 비교분석을 통한 물리적 특성을 평가하였으며, 폴리머 혼입에 따라 늘어나는 공기량을 제어하기 위해 소포제를 첨가하여 PVAc 콘크리트의 특성을 평가하였다. 그 결과 PVAc가 혼입된 폴리머 시멘트 모르타르의 경우 압축 강도는 낮아지나 휨강도와 건조수축의 성능이 향상되는 것으로 나타났으며, 콘크리트의 경우 혼입률이 6%일 때가 압축강도, 인장강도, 휨강도 및 탄성계수가 높아지는 것을 확인할 수 있었다. The objective of this paper is to obtain the basic data in order to develop an eco-friendly concrete through evaluation on the properties of polymer cement mortar and concrete using PVAc (Polyvinyl Acetate), as a kind of water-soluble polymer, For this purpose, the physical properties of cement mortar and concrete which does not contain the PVAc as the control batch were compared and analyzed with those using the PVAc. And then, the replacement amount of the PVAc was 3%, 6%, 9% and 12% by binder, respectively. And also, the properties of concrete using the PVAc were evaluated, by adding an antifoaming agent in order to control the air contents increasing with an increase of amount of polymer usage. As a result, in the case of polymer cement mortar using the PVAc, it presented that the compressive strength reduced, while the performance of flexural strength and drying shrinkage increased. When the replacement of the PVAc was 6% within concrete, the compressive, tensile, flexural strength and elastic modulus were increased.

Al - Zn - MgCu 합금의 시효처리와 가공열처리가 내피로특성 , 내응력부식성 및 강도에 미치는 영향

류재석,김인섭 대한금속재료학회 1980 대한금속재료학회 학술대회 개요집 Vol.1980 No.0

EP 나일론섬유를 혼입한 자기충전콘크리트(SCC)에 관한 실험적 연구

류재석,이용수,전중규,전찬기 한국구조물진단유지관리공학회 2011 한국구조물진단유지관리공학회 논문집 Vol.15 No.1

본 연구에서는 분산제 코팅을 통해 성능 개선된(EP) 나일론 섬유를 혼입한 자기충전 콘크리트의 가능성을 알아보고자 하였으며, 이를 위한 실험 방법으로 나일론 섬유 길이와 다른 유기계 섬유(폴리프로필렌, 셀룰로오스)를 혼입한 경우 그리고 광물질혼화재(고로슬래그 미분말, 플라이애쉬)의 종류를 달리 혼합한 2성분계 및 3성분계의 경우를 가지고 자기충전 콘크리트의 특성을 검토하였다. 이 실험 결과를 토대로 하여 실구조물 적용을 위한 Mock-up Test를 성능 개선된 나일론 섬유를 혼입한 자기충전콘크리트 와 일반콘크리트를 비교하여 실구조물 활용 가능성을 검토 하였다. 그 결과 굳지 않은 자기충전 콘크리트의 특성, 경화된 자기충전 콘크리트의 특성 및 내구특성을 종합해 볼 때 성능 개선된(EP) 나일론 섬유가 우수함을 알 수 있었고,성능 개선된 나일론 섬유에 따른 광물질 혼화재 사용에서는 플라이애쉬 보다 고로슬래그 미분말이 우수함을 알 수 있었다. In this study, we find out the feasibility of self-consolidating concrete with EP nylon fiber. Three kinds of method were used; when length of nylon fiber is differed for the experiment to investigate usability of nylon fiber with enhanced performance by dispersing-agent coating in self-consolidating concrete, when mixing in other organic fibers (polypropylene, cellulose) and in case of Binary Blended and Ternary Blended concrete mixed with different types of mineral admixtures (blast-furnace slag and fly ash). Based on the results of the experiment described above, comparison was made on the basic properties and dynamic characteristics of general fiber reinforced concrete mixed with enhanced performance nylon fiber and SCC mixed with enhanced performance nylon fiber as a Mock-up test prior to the experiment of application to the actual structure. Considering characteristics and durability of the fresh and hardened self-compacting concrete, dynamic characteristics and durability were found to be more outstanding when using nylon fiber for the mineral admixtures used, dynamic characteristics and durability were found to be more outstanding when using blast-furnace slag.

7075 알루미늄 합금의 내피로 내응력부식성에 미치는 이단시효처리의 영향

류재석,김인섭 대한금속재료학회(대한금속학회) 1981 대한금속·재료학회지 Vol.19 No.4

The effect of two step ageing (TAA) on the microstructure, fatigue and stress corrosion resistance was investigated on the 7075 aluminium alloy. The width of precipitate free zone (PFZ) and the size of precipitates along grain boundries were decreased with the TAA treatment without substantial loss of mechanical strength. Specimens which were failed by fatigue, showed various fracture modes depending on applied stress and heat treatment. The variation of fatigue fracture modes was caused by the initiation conditions of the fatigue cracks. The propagation of the stress corrosion cracks was controlled by the microstructure near the grain boundaries and by the deformation characteristics of the matrix. The fatigue limit at 10^7 cycles was improved up to 10% due to the possible introduction of matrix precipitate incoherency. The narrow PFZ and the small size of grain boundary precipitates have reduced the depth of stress corrosion cracks from 170㎛ to 110㎛.

열연 복합조직강의 제조를 위한 제어압연에 관한 연구

류재석,김인섭 대한금속재료학회(대한금속학회) 1982 대한금속·재료학회지 Vol.20 No.9

As-rolled dual phase steels were produced in a laboratory scale by a controlled rolling process. The relationship between mechanical properties and microstructures were investigated on the tensile specimens which were produced by varying finish-rolling temperatures, cooling methods and coiling temperatures. The Fe, 0.036-0.06% C, 1.1-1.7% Si, 1.3-1.7% Mn compositions showed the ferrite-martensite dual phase structures and the tensile properties of strength 55-80㎏/㎟, total elongation 25-39% and yield ratio 553% after finish rolling 30% at 780-840℃ followed by oil quenching. Air cooling down to A₁temperature (720℃) before oil quenching was found to decrease the optimum finish rolling temperatures by 30-50℃ through annihilation of hot-worked microstructures. Addition of 0.4% Cr could raise the coiling temperature to 350℃ without deteriorating the dual phase steel properties.