• 대한토목학회논문집
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• 제14권2호
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• pp.299-305
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• 1994

연속철근 콘크리트포장(CRCP)의 공용성 추적조사를 위한 시험포장이 판교-구리간 고속도로에 시공되어 지금까지 2년간의 초기 공용성 조사가 진행되었다. 본 고에서는 본 시험포장의 초기재령 거동 및 온도변화 특성을 분석하였고 그 결과를 미국 휴스턴에서 실시된 유사한 시험포장에 대한 결과와 비교하였다. 연구 결과 판교-구리 시험포장은 초기균열의 발생패턴 측면에서 휴스턴 시험포장보다 대체적으로 좋은 결과를 보여주었다. 또한 초기균열의 억제 측면에서 2종 시멘트가 1종에 비해, 그리고 오후 포설이 오전 포설보다 효과적인 것으로 보여진다.

• 한국건축시공학회지
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• 제12권6호
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• pp.566-574
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• 2012

To address the problem of global warming, consumption of cement, the main material of concrete, should be decreased. Unfortunately, when industrial by-products are used in large quantities as admixture, the early age strength of concrete will be decreased, reducing its viability for use in concrete structures. Therefore, in this study, the application of an ionization accelerator and alkaline activator as addition agent of superplasticizer were investigated to secure a similar early age strength to that of normal concrete, thus increasing the viability of low cement concrete. Through the investigation, it was found that specimens that used a combination of Alkaline-activator (Na2Sio3) and ionization accelerator (Amine) had the highest early and long-age compressive strength. From this, we can determine an appropriate range of application of superplasticizer to improve early-age compressive strength of low cement concrete.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.254-255
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• 2014

This study is a part of development to improve early-age compressive strength of concrete by using industrial by-products. It tried to investigate the characteristics of early-age compressive strength according to curing temperature and industrial by-product replacement ratio 10, 20, and 30 %. As a result, regardless of industrial by-product replacement ratio and age, early-age compressive strength of concrete was found to be high compared to Plain using 100 % cement.

• 대한가정학회지
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• 제36권5호
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• pp.17-27
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• 1998

The need for periodic investigation on human growth rate and somatotypes has been increased because the scientific development and environmental factors have effected a lot on them recently. This study aimed to investigate the changes of the 638 female somatotypes in the age of 18-54 obtained by direct and indirect measurement. The measurement data were divided into 4 groups early young women age group (18-54), late young women age group (25-34), early middle age group (35-44), late middle age group (45-54) and compared each other based on each group by age. The results obtained from this study were as follows: 1. According to Mollison Curve based on the early young women, items of depth decreased overall and pp.P. length & shoulder length increased as the age increased. The circumference, breadth and thickness tended to increase, especially waist girth and thickness of waist increased markedly. The data showed that the increase rate of thickness was higher than that of breadth. 2. Gradual somatotype changes were observed by overlapping projection drawings obtained by direct measurement. Compared with the young women, the middle aged showed lower should point depth and hip line & crotch depth line were lengthened significantly. No significant difference was observed in overlapping of the early young women and the late young women' figure, neither was in early middle aged and the late middle aged. 3. By overlapping the side view of the young women group (18-37) and middle aged group (35-54), no significant postural characteristics were found, while the back tended to bend forward and the abdomen and hip appeared to get fat.

• 산업기술연구
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• 제25권A호
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• pp.49-56
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• 2005

Recently, very-early strength latex-modified concrete(below ; VES-LMC) has been developed for repairing and overlaying the old concrete bridge deck. VES-LMC provides the advantage of very-early-strength, as well as high flexural strength, bond strength, durability, resistance to corrosion, reduced water permeability and resistance to damage from freeze-thaw cycles. The compressive and flexural strength of VES-LMC are 21 MPa and 4.5 MPa at 3 hours after concrete placing, respectively. However, VES-LMC would have a relatively large shrinkage at early-age because of reduced water-cement ratio, big water self-dissipation, and rapid hydration reaction. Therefore, the purpose of this study was to evaluate the early-age and restrained shrinkage of VES-LMC, having an experimental variables such as latex contents and cement types. The latex contents included 0%, 5%, 10%, 15% and 20%, and the cement types included ordinary portland cement and very-early strength cement.

• 한국도로학회논문집
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• 제6권2호
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• pp.47-59
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• 2004

콘크리트포장에 초기균열을 일으키는 중요한 인자 중 하나는 콘크리트 내부의 초기온도이다. 따라서 콘크리트포장의 초기균열 발생원인을 연구하기 위해서는 초기온도를 계측하여 분석하는 일이 필요하다. 본 논문에서는 초기균열이 발생하는 슬래브 장소와 초기균열의 발생시간이 초기온도패턴에 어떤 영향을 받는지를 검증하였고 더불어, 줄눈부에서 발생하는 균열의 발생시점과 시공시간과의 관계도 알아보았다. 본 논문을 위해서 "중부내륙고속도로 여주-충주간 제 1공구 시험도로 건설공사구간 STATION 1+400$\sim$1+700" 지점에서 시험시공이 이루어졌으며, 시공 후 72시간 동안 i-Button(온도계측센서)을 이용하여 온도계측을 시행하였으며, 초기균열의 거동은 Demec gauge를 사용하였으며, 초기균열 및 줄눈부 균열은 육안으로 확인하였다. 초기온도패턴과 초기균열의 분석 결과, 콘크리트의 초기온도패턴은 슬래브에 초기균열이 발생하는 위치와 시각에 영향을 주는 것으로 나타났다 초기균열균열은 온도낙차폭이 가장 큰 슬래브에서 발생하였으며, 그 시각은 슬래브의 온도가 급강하하는 새벽이었다. 또한, 콘크리트 슬래브의 거동이 인근 줄눈부에 발생한 초기균열에 따라 영향을 받으며. 줄눈부에 발생한 균열의 발생시기가 서로 다를 경우에 균열의 거동이 달라질 수 있다는 가능성이 제시되었다. 그 외에도, 오전에 시공한 슬래브에서의 균열 발생률이 오후에 시공한것보다 더 큰 것으로 나타났으며, 균열의 발생 간격이 큰 균열이 그렇지 않은 균열보다 더 큰 균열틈을 보였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.411-414
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• 2007

The confinement-shear lattice(CSL) model for hardened concretes developed by Cusatis is extended for early age concretes. The uniaxial behaviors available in the literature for 3 to 28 days were simulated by the CSL model to identify the change of the model parameters for various ages. The change with respect to the age was interpolated based on the chemomechanics to develop the extended version of CSL model.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.657-660
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• 2006

Recently, very-early strength latex-modified concrete(below ; VES-LMC) has been developed for repairing and overlaying the old concrete bridge deck. Early-age defects in high-performance concrete due to thermal and autogenous deformation shorten the life cycle of concrete structures. Thus, it is necessary to examine the behavior of early-age concrete at the stages of design and construction. The purpose of this study was to evaluate the autogenous shrinkage of VES-LMC, having an experimental variables such as retarder and water-cement ratio. The greater the retarder content in VES-LMC, the greater the expansion at early-age. This recommend the small retarder content as possible. The effect of water-cement ratio on early-age behavior is very small, because of the wrapped specimen in order to prevent water evaporation.

• 콘크리트학회논문집
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• 제17권1호
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• pp.11-18
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• 2005

온도 및 수분의 변화로 인하여 초기재령 콘크리트에서 발생하는 응력을 합리적으로 예측하기 위해서는 초기재령 콘크리트의 경화특성을 실제적으로 표현할 수 있는 컴플라이언스 함수가 필요하다. 그러나, 기존의 컴플라이언스 함수는 경화된 콘크리트의 데이터로부터 도출되어 초기재령 콘크리트의 특성을 합리적으로 표현하지 있지 않다. 또한 탄성 컴플라이언스를 측정하는 기존의 실험에서는 하중도달시간이 존재하므로 탄성 컴플라이언스와 크리프 컴플라이언스의 구분이 모호해지며 탄성 컴플라이언스에 크리프의 영향이 존재하는 문제점이 있다. 본 연구에서는 먼저 순간 컴플라이언스 함수를 실제적으로 추정할 수 있는 실험적 방법론을 제시하였다. 제시된 실험적 방법론을 이용하여 다양한 하중도달시간과 재령에 대하여 준-순간 컴플라이언스를 실험적으로 측정하여 순간 컴플라이언스를 제시하였다. 또한 초기재령 콘크리트에 대하여 크리프 실험을 수행하였다. 이로부터 고체화 이론에 기초하여 콘크리트의 컴플라이언 함수를 표현하는 B3 모델을 초기재령 콘크리트에 합리적으로 적용될 수 있도록 수정하여 제시하였다. 따라서 본 연구에서 제안된 컴플라이언스 함수는 초기재령 콘크리트의 시간에 따른 응력을 합리적으로 평가하는데 유용하게 활용될 수 있을 것으로 사료된다.

• 한국구조물진단유지관리공학회 논문집
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• 제6권1호
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• pp.103-109
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• 2002

Reinforced concrete structure resist to external load caused by integration of steel bar and concrete and this integration is obtained from bond stress between steel bar and concrete. Researches of bond stress between steel bar and concrete have been performed by many researcher, but existent researches of bond stress are concerned with compression strength of well cured concrete and insufficient study of bond stress according to early material. The secure regular strength of concrete in early age is caused by rapid velocity of early hardening process, but questionable bond stress in early age is proportion to strength of that. So this study performed experiments to compare bond stress according to material age and compression strength. The result is showed that bonding strength in early material age compare the ratio of concrete compression strength with the ratio of maximum bond stress the later inferior on the former.