• 한국건축시공학회지
• /
• 제22권6호
• /
• pp.577-583
• /
• 2022

대형 현장의 경우 다수의 레미콘사에서 콘크리트를 납품받게 되는 경우가 많으나 동일 콘크리트 배합표를 사용하더라도 재료와 제조장비의 등의 차로 인해 품질에 편차가 있을 것으로 생각된다. 하지만 그러한 검토 실적은 미비한 실정에 본 연구에서는 부산 지역의 12개 레미콘사에서 납품 받은 콘크리트를 대상으로 굳기 전 콘크리트 물성 및 압축강도, 염소이온 확산계수를 측정하였다. 굳기 전 콘크리트 물성은 기준을 만족하였고 압축강도는 설계기준 압축강도 대비 128%를 나타내었다. 염소이온 확산계수의 경우도 큰 편차없이 설계기준 압축강도별 평균값을 도출할 수 있었다. 압축강도는 강도가 높을수록 편차가 컸으며 염소이온 확산계수는 강도가 낮을수록 편차가 큰 경향을 파악할 수 있었다.

• 콘크리트학회논문집
• /
• 제20권6호
• /
• pp.721-729
• /
• 2008

본 연구는 조기강도 발현용 콘크리트의 유동특성 및 강도특성을 비롯한 공학적 특성을 알아보기 위한 것으로서 실내배합시험에서 각 실험 요인 및 수준을 설정하여 검토한 결과 시멘트의 경우 OPC보다 CHC와 HESPC가 우수한 품질 성능을 나타냈으며, PNS계 혼화제보다 PC계 혼화제가 경시변화 및 조기강도 발현 측면에서 우수하게 나타났다. 또한, 양생 온도에 따라 많은 차이를 나타냈는데, 양생온도 $12^{\circ}C$ 이하의 온도에서는 조기강도 발현에 상당한 취약성을 나타냈으며 콘크리트 종결 직후의 양생온도에 의해 조기강도 발현에 상당한 차이가 있는 것으로 나타났다. 5 MPa/18 hr의 강도 요구조건을 만족하기 위해서 OPC는 최소 $17^{\circ}C$ 이상, CHC는 $14^{\circ}C$ 이상, HESPC는 $11^{\circ}C$ 이상의 양생온도가 필요한 것으로 나타났다. 한편, 물-시멘트비에 따른 강도특성은 물-시멘트비가 낮을수록 우수한 강도발현을 보였다. 본 연구의 결과를 바탕으로 건설현장에서 활용된다면 조기강도를 앞당김으로써 공사기간 단축에 의한 공사원가 절감으로 경제적인 시공이 가능할 것으로 사료된다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
• /
• pp.191-194
• /
• 1999

Recently in Korea, may workers have reported the effects of the granulated blast furnace slag[BFS] of high fineness on the strength development of slag cement. We have studied the effect of slag fineness on the strength development of mortar with curing conditions, in order to get the basic data of high strength concrete using BFS. In this paper, we discussed the effects of slag fineness and porosity of mortar and the reaction of slag in hardened slag cement.

• Carbon letters
• /
• 제17권1호
• /
• pp.33-38
• /
• 2016

In the present study, exfoliated graphite nanoplatelets (xGnP) with different particle sizes were coated onto polyacrylonitrile-based carbon fibers by a direct coating method. The flexural properties, interlaminar shear strength, and the morphology of the xGnP-coated carbon fiber/phenolic matrix composites were investigated in terms of their longitudinal flexural strength and modulus, interlaminar shear strength, and by optical and scanning electron microscopic observations. The results were compared with a phenolic matrix composite counterpart prepared without xGnP. The flexural properties and interlaminar shear strength of the xGnP-coated carbon fiber/phenolic matrix composites were found to be higher than those of the uncoated composite. The flexural and interlaminar shear strengths were affected by the particle size of the xGnP, while the particle size had no significant effect on the flexural modulus. It seems that the interfacial contacts between the xGnP-coated carbon fibers and the phenolic matrix play a role in enhancing the flexural strength as well as the interlaminar shear strength of the composites.

• 대한조선학회 특별논문집
• /
• 대한조선학회 2017년도 특별논문집
• /
• pp.38-45
• /
• 2017

FPSO is widely used to develop deep sea oil fields and HHI has constructed ten(10) FPSOs. During these constructions, relevant structural design criteria such as yielding, buckling, fatigue, collision and impact strength were applied to verify structural safety. To apply the buckling strength evaluation for structures, the critical buckling stresses and applied stresses of relevant panels should be calculated. The plate and stiffened panels are to be idealized, which are needed much time and efforts by designers. Therefore, program development is necessary in order to evaluate the buckling strength conveniently and accurately. In this study, the buckling strength assessment system by using offshore code, DNV-RP-C201 was developed under MSC/PATRAN, pre-post program of finite element method. Graphic user interface program is written in MSC/PATRAN PCL functions. Source program to evaluate the buckling strength is developed in FORTRAN programming languages. The developed program is verified by comparing with the results of the Nauticus Hull developed by DNV Classification Society, and applied to the marine construction project conducted by Hyundai Heavy Industries LTD.

• 한국군사과학기술학회지
• /
• 제17권4호
• /
• pp.413-421
• /
• 2014

Since the structural temperature of a flight vehicle flying at high speed rises rapidly due to aerodynamic heating, it is necessary for optimum structural design to obtain proper material properties at high temperature by taking into account of its operational environment. For a special alloy, analysis data on strength change due to exposure time to high temperature are very limited, and most of them are for an exposure time longer than 30 minutes for long term operations. In this study, base and weld metal samples of Ti-6Al-4V alloy had been prepared and high temperature tensile tests with induction heating were performed, and then high temperature strength characteristics and strength recovery characteristics through cooling have been analyzed. Pre-tests to determine maximum heating rate were performed, and response characteristics for temperature control were confirmed. As a result, high temperature tensile strength appeared to be lower than that of room temperature, but it was higher than that of high temperature of 30 minite exposure listed in MMPDS. In strength recovery through cooling Ti-6Al-4V alloy has shown higher recovery rate compared with other alloys.

• Journal of Ceramic Processing Research
• /
• 제13권spc2호
• /
• pp.198-201
• /
• 2012

The electrolytes in thermal batteries are nonconductive solids at ambient temperature, which prevent the self-discharge and corrosion. To meet severe environmental requirements and guarantee acceptable handling yields, all the pellets in cells should have adequate strength, especially for the cathodes due to their poor binding properties among FeS2 particles. By modifying the surface microstructure of FeS2 through molten-salt heat treatment, the inter-particle binding strength is greatly increased, resulting in the enhanced pellet strength and yield. The addition of Li2O also promoted the soft salt coating coverage of hard FeS2 particles, which can be explained by the enhanced wettability of the molten salt.

• 콘크리트학회논문집
• /
• 제21권6호
• /
• pp.753-761
• /
• 2009

이 논문은 철근콘크리트 휨부재의 인장겹침이음 영역에서의 정착저항능력에 대한 콘크리트 강도와 피복두께의 영향을 알아보기 위하여 총 24개의 beam-end 실험체의 실험 결과를 정리 분석한 것이다. 콘크리트 강도가 증가할수록 부착응력이 커지고 전달길이가 줄어든다는 부착특성과 얇은 피복에서 쉽게 발생하는 쪼갬균열 및 취성적인 균열 진전과 같은 균열거동을 근거로 하여 현행 설계기준의 등분포부착응력 가정에 의한 정착길이 규정을 고강도 콘크리트에도 그대로 적용할 수 있는지 조사하였다. 그 결과 콘크리트 강도에 따른 정착저항능력은 피복두께의 영향을 크게 받고 있으며, 고강도 콘크리트에서는 현행 설계기준 규정보다 짧은 겹침이음길이를 갖더라도 충분한 안전율을 확보하는 것으로 나타났다. 이러한 실험 결과로부터 고강도 콘크리트의 정착길이는 제곱근 압축강도의 반비례가 아닌 압축강도에 직접적으로 반비례함을 확인하였으며, 현 설계기준에서 보통강도 콘크리트에 적용하는 동일 매입길이에 대한 등 분포부착응력 가정이 아닌 새로운 정착길이 계산식을 제안하였다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1989년도 가을 학술발표회 논문집
• /
• pp.35-38
• /
• 1989

The purpose of this report is to investigate and analyze development and achievement of flowing and high-strength concrete by reacy mixed concrete companies in Korea. For this purpose, the investigation was divided into three parts, i.e., superplasticizers, flowing concrete, high-strength concrete. And, they were asked to quality control manager in ready mixed concrete companies. Many researches have been carried out. And, flowing concrete is applied to field in a few case. In order to improve practical applicability of high-strength concrete and make concrete strength higher, to begin with, profound research for concrete ingredients will be needed along with presentation of methods for obtaining workability and quality assurance.

• 펄프종이기술
• /
• 제48권2호
• /
• pp.99-105
• /
• 2016

The increase of wet web solid content after wet press and dry compressive strength were observed in lab study by judicious application of wood flour and starch for the old corrugated container (OCC). Pearl starch was better than cationic starch in strength development, but cationic starch was better for drainage. Application of vacuum on the mixed solution of wood flour and starch helped strength development further without loss of other properties. The effect of wood flour addition on wet web solid content improved as the wet pressing pressure increased. The use of wood flour and starch mixture improved wet web solid contents further.