• 제목/요약/키워드: early strength

검색결과 1,648건 처리시간 0.038초

AN EXPERIMENTAL INVESTIGATION ON MINIMUM COMPRESSIVE STRENGTH OF EARLY AGE CONCRETE TO PREVENT FROST DAMAGE FOR NUCLEAR POWER PLANT STRUCTURES IN COLD CLIMATES

  • Koh, Kyung-Taek;Park, Chun-Jin;Ryu, Gum-Sung;Park, Jung-Jun;Kim, Do-Gyeum;Lee, Jang-Hwa
    • Nuclear Engineering and Technology
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    • 제45권3호
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    • pp.393-400
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    • 2013
  • Concrete undergoing early frost damage in cold weather will experience significant loss of not only strength, but also of permeability and durability. Accordingly, concrete codes like ACI-306R prescribe a minimum compressive strength and duration of curing to prevent frost damage at an early age and secure the quality of concrete. Such minimum compressive strength and duration of curing are mostly defined based on the strength development of concrete. However, concrete subjected to frost damage at early age may not show a consistent relationship between its strength and durability. Especially, since durability of concrete is of utmost importance in nuclear power plant structures, this relationship should be imperatively clarified. Therefore, this study verifies the feasibility of the minimum compressive strength specified in the codes like ACI-306R by evaluating the strength development and the durability preventing the frost damage of early age concrete for nuclear power plant. The results indicate that the value of 5 MPa specified by the concrete standards like ACI-306R as the minimum compressive strength to prevent the early frost damage is reasonable in terms of the strength development, but seems to be inappropriate in the viewpoint of the resistance to chloride ion penetration and freeze-thaw. Consequently, it is recommended to propose a minimum compressive strength preventing early frost damage in terms of not only the strength development, but also in terms of the durability to secure the quality of concrete for nuclear power plants in cold climates.

동절기 콘크리트 초기 강도저하 및 품질 개선을 위한 조강형 혼화재료 활용에 대한 연구 (A Study on the High Early Strength Admixture Material for Improving on Reduced Initial Strength and Quality of Concrete in Cold Weather)

  • 김세종
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2022년도 가을 학술논문 발표대회
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    • pp.25-26
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    • 2022
  • The purpose of this study is to prevent serious disasters in cold weather by presenting an optimal blending design for securing high early strength when placing concrete by analyzing the properties and compressive strength of concrete formulations using high early strength admixture materials.

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초기 재령 콘크리트의 종파 속도와 강도의 상관관계 (Correlation between Longitudinal Wave Velocity and Strength of Early-aged Concrete)

  • 이휘근;이광명;김동수
    • 콘크리트학회논문집
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    • 제12권6호
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    • pp.67-74
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    • 2000
  • The usage of nondestructive testing on early-aged concrete leads to enhacned safty and allows effective scheduling of construction, thus making it possible to maximize the time and cost efficiencies. In this study, a reliable nondestructive strength evaluation method for early-aged concrete using the longitudinal wave velocity is proposed. Compression tests were performed to examine factors influencing the velocity-strength relationship of concrete, such as water-cement (w/c) ratio, fine aggregate ratio, curing temperature, and curing condition. The test results show that a change in the w/c ratio and curing temperature has minor effect on the velocity-strength relationship/ However, curing condition significantly influences the velocity-strength relationship of early-aged concrete. Moreover, the longitudinal wave velocity increases with decreasing fine aggregate ratio. It is concluded from this study that the strength evaluation of early-age concrete can be achieved by a nonlinear equation which considers the effects of curing condition and fine aggregate ratio.

급결제를 이용한 EVA 분말수지 혼입 폴리머 시멘트 모르타르의 초기강도 특성 (Early Strength Properties of EVA Polymer Powder-Modified Mortars with Quick Setting Agent)

  • 조영철;최낙운;이철웅;양석우;소양섭
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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    • pp.309-312
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    • 2005
  • Admixture compounds for shortening setting time and accelerating early strength development of EVA polymer powder-modified mortars were made by mixing various quick setting agents. As a result, the quick setting agents contribute to strength development of the mortars in the early curing age of 168h or less. In the viewpoint of early strength development of EVA polymer powder-modified mortars, an quick setting agent content of 20$\%$ is recommended. Early strength of EVA polymer powder-modified mortars expresses the excellent strength with 5$\%$, 10$\%$ of rates of polymer mixing. The rate of polymer mixing was able to be adjusted and flexural strength which is a predeterminded initial strength was also able to satisfy 3MPa(s).

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질산칼슘 혼화재를 사용한 신속개방형 포장 콘크리트의 적정배합비 도출 (Mix Proportions of Early-Strength Pavement Concrete Using Calcium Nitrate)

  • 원종필;이시원;이상우;박해균
    • 대한토목학회논문집
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    • 제29권1A호
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    • pp.95-100
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    • 2009
  • 본 연구에서는 신속개방형 포장 콘크리트의 적정배합비를 도출하기 위한 실험을 실시하였다. 콘크리트 타설 후 8시간 후 교통개방을 하기 위해 조강제 및 조강시멘트를 사용하였으며 조강제의 적정 혼입량을 결정하기 위해 예비실험을 실시하였다. 이를 바탕으로 시멘트 및 잔골재율을 변수로 공기량, 슬럼프 경시변화, 응결시험, 압축강도, 휨강도 시험을 실시하였다. 실험 결과 8시간 목표 압축강도 21 MPa, 휨강도 3.8 MPa를 만족하는 신속개방형 교통개방 포장 콘크리트의 적정배합비를 도출하였다.

초기재령 콘크리트 슬래브의 처짐 예측 (Mechanical Properties of Reinforced Concrete Slabs at Early Ages)

  • 신성우;유석형;오성진;황동규;박기홍
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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    • pp.397-400
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    • 2002
  • The mechanical properties of concrete such as modulus of elasticity, bond strength and shear strength are proportional to square root of compressive strength. And compressive strength of concrete is developed rapidly at early ages. Thus the relationship between compressive strength and its mechanical properties should be verified because the mechanical properties of early age concrete and hardened concrete are different. In this study, to predict the concrete slab deflection at early ages, modulus of elasticity and effective moment of inertia(Ie) are observed and compared with experimental results.

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미세구조 특성을 고려한 초기재령 콘크리트의 강도예측모델 (Strength Estimation Model for Early-Age Concrete Considering Microstructural Characteristics)

  • 황수덕;김의태;이광명
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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    • pp.397-402
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    • 2001
  • Microstructural characteristics such as hydrates and porosity greatly influence the development of concrete strength. In this study, a strength estimation model for early-age concrete considerig, the microstructural characteristics was proposed, which considers the effects of both an increment of degree of hydration and capillary porosity on a strength increment. Hydration modeling and compressive strength test with curing temperature and curing ages were carried out. By comparing test results with estimated strength, it is found that the strength estimation model can estimate compressive strength of early-age concrete with curing ages and curing temperature within a margin of error.

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Early-Age Properties of Polymer Fiber-Reinforced Concrete

  • Myers, Daniel;Kang, Thomas H.K.;Ramseyer, Chris
    • International Journal of Concrete Structures and Materials
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    • 제2권1호
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    • pp.9-14
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    • 2008
  • The cracking problem in concrete is widespread and complex. This paper reviews the problem and focuses on those parts of the problem that are more readily solved. Polymer fibers are shown to have promise in several important areas of the cracking problem. To investigate one of these areas of the cracking problem more completely, an experimental research program focusing on the early-age properties of fibers was carried out. This study researched the properties of four polymer fibers; two of the fibers were macrofibers, and two were microfibers. Each fiber was tested at several dosage rates to identify optimum dosage levels. Early-age shrinkage, long-term shrinkage, compressive strength, and tensile strength were investigated. Long-term shrinkage and strength impacts from the polymer fibers were minimal; however, the polymer fibers were shown to have a great impact on early-age shrinkage and a moderate impact on early-age strength.

산업부산물을 활용한 조강형 결합재의 치환율에 따른 조기강도 특성에 관한 연구 (A Study on the Properties of Early Strength with the Replacement Ratio of Early Strength Type Binder Using Industrial By-product)

  • 전우철;권해원;서휘완;이재삼
    • 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.

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연약지반 표층혼합처리를 위한 조기강도 발현형 고화재의 개발 (Development of early strength type hardening Agent for Surface Soil Stabilization Method)

  • 기태경;김기훈;이병기;권오봉;김경민;박상준
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2013년도 추계 학술논문 발표대회
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    • pp.80-81
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    • 2013
  • There is the increasing number of constructing soil or structure on the soft ground during public works. Usually cement or slag cement has been the traditional material for surface soil stabilization method. Recently, early strength development properties of hardening agent is required for driving abilities of execution equipment and shortening of the construction time. Therefore, the purpose of this study is to develop the early compressive strength hardening agent for surface soil stabilization. The study was confirmed performance and availability of hardening agent using early strength type cement and industrial by-product minerals through early strength development properties in accordance with water cement ratio, content of hardening agent for soft soil.

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