• 제목/요약/키워드: Strength Development

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고강도 콘크리트 휨부재의 정착 및 겹침이음길이에 관한 실험적 연구 (Experimental Research on Development and Splices Length in High-Strength Concrete Flexural Members)

  • 이기열;김우;정기오
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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    • pp.865-871
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    • 2003
  • This paper presents the test results of 24 beam-end specimens to investigate the effect of concrete strength and cover thickness on the development resistance capacity in tensile lap splice length regions. The results showed that as higher strength concrete was employed, nor only development resistance capacity was influenced by cover thickness, but also more sufficient safety factor reserved shorter than the lap splice length provision in current design code. From experimental research results, high-strength concrete development length was not inverse ratio of ($\sqrt{f_{ck}}$) but directly inverse of $f_{ck}$, and it is also said that there is a certain limit length of the embedded steel over which the assumption of uniform bond stress distribution is valid specially for high-strength concrete not having a same embed length such as normal-strength concrete in current design criteria hypothesis.

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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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양생온도변화에 따른 고로슬래그 시멘트를 사용한 콘크리트의 강도증진 성상 (Strength Development of Concrete Using Blast-Furnace Slag Cement under Various Curing Temperatures)

  • 윤기원;유호범;한민철;한천구
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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    • pp.163-166
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    • 1999
  • In this paper, strength development of concrete using blast-furnace slag cement(BSC) and ordinary portland cement(OPC) are discussed under varius W/C and curing temperatures. According to the experimental results, strength development of BSC concrete is lower than that of OPC concrete in low temperature at early age and maturity. In high curing temperature, BSC concrete has higher strength development than that of low temperature regardless of the elapse of age and maturity. BSC has much effect on the strength development of concrete at the condition of mass concrete, hot weather concreting and the concrete products with the steam curing, which is influenced by high temperature.

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염소 고함유시멘트의 페이스트 유동성과 모르타르 강도발현성에 미치는 화학 혼화제의 영향 (Effects of Chemical Admixture on the Paste Fluidity and Mortar Strength Development of High Chloride Cement)

  • 정찬일;박수경;이의학;이경희
    • 한국세라믹학회지
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    • 제44권1호
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    • pp.23-31
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    • 2007
  • To examine the effects of chemical admixture on the fluidity and strength development of high chloride cement, experiments were conducted in which lignosulfonate (LS), naphthalenesulfonate (NS), and polycorboxylate (PC) were each added in standard and excessive amounts, and the results were as follows. 1. Because adding KCl to NS causes a decrease in flow, adding PC is better in maintaining high cement fluidity. 2. When cement contained much chloride comes in contact with water, hydration begins 4 h after contact and securing workability becomes difficult, but by adding PC, workability can be secured to 10 h. 3. The bound water ratio and compressive strength in aging 3 days occupy $70\sim80%$ of those in aging 28 days, and the early compressive strength increases not only by adding KCl, but also by chemical admixture. 4. Although compressive strength development is excellent in NS, PC, if NS is added excessively, hydration becomes slow and while the pore structures become slightly minute, the strength development decreases due to severe setting retardation.

Development of slag based Shirasu geopolymer

  • Katpady, Dhruva Narayana;Takewaka, Koji;Yamaguchi, Toshinobu
    • Computers and Concrete
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    • 제20권1호
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    • pp.77-84
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    • 2017
  • Shirasu, a pyroclastic flow deposit, showed considerable performance as aluminosilicate source in geopolymer, based on past research. However, the polymerization reactivity was somewhat lower compared to the traditional fly ash based geopolymer even though the long-term strength was fairly good. The present study concentrates on the development of higher initial strength performance of Shirasu based geopolymer by utilizing ground granulated blast furnace slag as an admixture. Mortars with various mix proportions were adopted to study the effect of parametric changes on strength development along with the addition of slag in different percentages. A combination of sodium hydroxide and sodium silicate was used as alkaline activators considering parameters like molar ratios of alkali to geopolymer water and silica to alkali molar ratio. The mortars were cured at elevated temperatures under different curing conditions to analyze the effect on strength development. Compressive strength test, mercury intrusion porosimetry and X-ray powder diffraction were carried out to assess the strength performance and microstructure of slag-Shirasu based geopolymer. Based on the experimental study, it was observed that the initial and long-term strength development of Slag-Shirasu geopolymer were improved by the addition of slag.

Concrete Strength Estimating at Early Ages by the Equivalent Age

  • Kim, Moo-Han;Nam, Jae-Hyun;Khil, Bae-Su
    • KCI Concrete Journal
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    • 제14권2호
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    • pp.81-85
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    • 2002
  • The strength development of concrete is influenced by temperature and cement type which greatly affect hydration degree of cement. There is not pertinent concrete strength management method in korea. There are several methods for estimating the in-place strength of concrete. One such method is the maturity concept. The maturity concept is based on the fact that concrete gains strength gradually as a result of chemical reactions between cement and water; and for a specific concrete mixture, strength at any age and at normal conditions is related to the degree of hydration. The rate of hydration and, therefore, strength development of a given concrete will be a function of its temperature. Thus, strength of concrete depends on its time-temperature history. The goals of the present study are to investigate a relationship between strength of high-strength concrete and maturity that is expressed as a function of an integral of the curing period and temperature and predict strength of concrete.

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플라이애시 및 고로슬래그 미분말을 사용한 콘크리트의 강도 발현 예측 모델식 연구 (A Study on Estimation Model of Strength Development of Concrete Using Fly Ash and Ground Granulated Blast-Furnace Slag)

  • 최연왕;박만석;정재권;최병걸;김경환
    • 한국구조물진단유지관리공학회 논문집
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    • 제17권5호
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    • pp.87-93
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    • 2013
  • 최근 콘크리트 산업은 $CO_2$ 가스 배출 저감을 목적으로 플라이애시 및 고로슬래그 미분말 등의 혼화재 사용량이 증가되고 있다. 그러나 국내의 경우 구조설계기준에서 사용되고 있는 강도 발현 예측 모델은 시멘트 종류 및 양생방법에 따른 상수값 ${\beta}_{sc}$를 포틀랜드시멘트에 관해서만 규정함에 따라 플라이애시 및 고로슬래그 미분말을 혼합 사용한 콘크리트의 시간에 따른 강도 발현 특성을 반영하지 못하는 실정이다. 따라서 본 논문에서는 플라이애시 및 고로스래그 미분말을 혼합한 보통강도 및 고강도 영역의 콘크리트의 시간에 따른 강도를 평가하였으며, 혼화재 종류 및 혼합률에 따른 콘크리트 강도발현 상수 ${\beta}_{sc}$ 값을 제안하였다.

조기강도 발현형 AE감수제를 사용한 콘크리트의 혼화재 치환방법 변화에 따른 초기 강도발현 특성 (Properties of Early Strength Development according to the Replacing Method of Admixture of Concrete Using AE Water Reducing Agent of Early-Strength Type)

  • 황인성;우종완;김규동;이승훈;한천구
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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    • pp.269-272
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    • 2003
  • This study is intended to investigate the properties of concrete using AE Water Reducing Agent of Early-Strength Type. According to the results, as for the replacing method of mineral admixture, setting time is shortened faster in order of replacement for fine aggregate, combination and replacement for cement, and when AE Water Reducing Agent of Early-Strength Type is used, it is shortened by about 4 hours, compared with normal AE Water Reducing Agent Compressive strength is lower in the case of replacement for fine aggregate, but higher in the other case than that of plain concrete. And When AE Water Reducing Agent of Early-Strength Type is used, early compressive strength is very high in comparison to normal AE Water Reducing Agent. Early strength development is very favorable by the use of AE Water Reducing Agent of Early-Strength Type regardless of the replacing method of mineral admixture at $20^{\circ}C$, but at $l0^{\circ}C$, it is effective for Early strength development that W/B is lowered to below 45%, BS of 20% is replaced for fine aggregate, and AE Water Reducing Agent of Early-Strength Type is used.

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초기 고온이력이 시멘트 모르터의 강도발현에 미치는 영향에 관한 연구 (An Experimental Study on the Characteristics of Compressive Strength in Cement Mortar under High Temperature conditions in an Early Age)

  • 김영주;최맹기;공민호;박희곤;김광기;정상진
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2005년도 춘계 학술기술논문발표대회 논문집
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    • pp.45-48
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    • 2005
  • This study is basic experiment for estimating influence of strength by curing temperature of concrete's heat of hydration and estimate relationship of compressive strength development by initial curing temperature factor, and then asume temperature factor which influence compressive strength development and for showing basic document of qualify control. According to the result of cement mortar by the curing temperature factor high-curing temperature shows high strength on 3 day compare with low curing-temperature, shows higher strength than the piece of high curing temperature.

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초기 재령에서 비소성 황토 혼입율에 따른 콘크리트의 강도 발현 분석 (Analyzing the Strength Development of Concrete with Function of Non-Sintered Hwangto Admixture Ratio at Early Ages )

  • 김태형;김원창;최형길;최희용;이태규
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2023년도 봄 학술논문 발표대회
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    • pp.39-40
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    • 2023
  • In this study, the compressive strength development was analyzed at early ages of concrete specimens admixed with non-sintered hwangto to reduce the CO2 emissions generated during cement production. The W/B of the specimens was set at 0.41, the percentage of non-sintered hwangto admixture was set at three levels of 15, 30, and 45%, and the compressive strength were measured at 1, 3, 7, and 28 days. The results showed that the compressive strength decreases as the percentage of non-sintered hwangto increases, but the strength development rate increases, and the NHTC41-15 test specimen developed a compressive strength close to NC41 at 28 days.

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