• Computers and Concrete
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• 제17권2호
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• pp.271-280
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• 2016

This study examined the mechanical properties and adiabatic temperature rise of low-heat concrete developed based on ternary blended cement using ASTM type IV (LHC) cement, ground fly ash (GFA) and limestone powder (LSP). To enhance reactivity of fly ash, especially at an early age, the grassy membrane was scratched through the additional vibrator milling process. The targeted 28-day strength of concrete was selected to be 42 MPa for application to high-strength mass concrete including nuclear plant structures. The concrete mixes prepared were cured under the isothermal conditions of $5^{\circ}C$, $20^{\circ}C$, and $40^{\circ}C$. Most concrete specimens gained a relatively high strength exceeding 10 MPa at an early age, achieving the targeted 28-day strength. All concrete specimens had higher moduli of elasticity and rupture than the predictions using ACI 318-11 equations, regardless of the curing temperature. The peak temperature rise and the ascending rate of the adiabatic temperature curve measured from the prepared concrete mixes were lower by 12% and 32%, respectively, in average than those of the control specimen made using 80% ordinary Portland cement and 20% conventional fly ash.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.469-472
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• 2006

Amount used of admixture fare is increasing for concrete economic efficiency and ability security. Security of economic efficiency and ability can expect by use of this admixture fare but is displaying a lot of problems on early age strength hold by hydrate delay relatively. Specially, in the case of construction site, concrete strength can speak that interrelation is high with mold removal of forms time. Therefore, is economical and need examination of plan that can secure robber within 3 days using admixture fare such as fly ash and blast furnace slage differential speech to secure function. In this study, adding liquid admixture within 1% of a binding agent quantity to examine these problem with physical characteristic after hardening ago specially, strength change at standard and air dry curing of observed change in priority. Air dried and water curing total strength enhancement effects appeared by thing which is in case of add test result liquid admixture by below 1% and strength deputy by passage of age could know is not big.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.211-215
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• 1996

This paper presents comparisons of pullout load of concrete with compressive strength of cylinders and cores, pulse velocity, and rebound number. A pullout test, which is a relatively new nondestructive technique, measures with a special tension ram the force required to pullout a specially shaped steel rod whose enlarged end has been cast into a concrete block. In this study 3 concrete mixes(normal strength, high-strength & super-high-strength) were made. From each mix, one 100$\times$70$\times$20 concrete block, 24 cylinders$(\phi10mm)$were casted. Each tests were performed on the concrete blocks at 3, 7, 28, and 91days. The test data shows that the pullout test is superior to the rebond hammer and the pulse velocity measurements on the evaluation of concrete strength. The pullout test is satisfactory for estimating the strength of in situ concrete at both early and late age, and its results can be reproduced with an acceptable degree of accuracy.

• 한국건축시공학회지
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• 제7권1호
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• pp.71-77
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• 2007

This paper is to investigate the effect of the curing temperature on strength development of concrete incorporating cement kiln dust(CKD) and blast furnace slag (BS) quantitatively. Estimation of the compressive strength of the concrete was conducted using the equivalent age equation and the rate constant model proposed by Carino. Correction of Carino model was studied to secure the accuracy of strength development estimation by introducing correction factors regarding rate constant and age. An increasing curing temperature results in an increase in strength at early age, but with the elapse of age, strength development at high curing temperature decreases compared with that at low curing temperature. Especially, the use of BS has a remarkable strength development at early age and even at later age, high strength is maintained due to accelerated pozzolanic activity resulting from high temperature. Whereas, at low curing temperature, the use of BS leads to a decrease in compressive strength. Accordingly, much attention should be paid to prevent strength loss at low temperature. Based on the strength development estimation using equivalent age equation, good agreements between measured strength and calculated strength are obtained.

• 자원리싸이클링
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• 제19권5호
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• pp.50-57
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• 2010

플라이애쉬와 고로슬래그를 첨가하여 만드는 3성분계 콘크리트는 산업부산물 이용에 따른 초기공사비 절감과, 환경친화적인 측면에서 매우 효과적이다. 3성분계 콘크리트는 장기강도의 안정적인 발현, 높은 작업성과 수화열 감소에도 매우 효과적인 것으로 알려져 있다. 그러나, 3성분계 콘크리트는 포졸란계 혼화재의 사용에 따른 초기강도 발현이 문제점이다. 이러한 문제는 시공성 및 경제성에 있어 3성분계 콘크리트 사용을 제약하는 요소로 작용하고 있다. 본 연구에서는 이러한 문제를 해결하기 위하여 플라이애쉬, 고로슬래그 미분말을 혼입한 콘크리트에 있어 조강시멘트를 사용하여 단기 및 장기강도 발현, 투수저항성 및 내화학약품성을 평가하였다. 플라이애쉬 혼입율은 10%로 고정하고 고로슬래그 미분말을 0, 10, 20, 및 30%로 혼입한 3성분계 조강콘크리트를 제작하였다. 실험결과, HE-TBC의 압축 및 휨강도의 우수한 초기강도발현 특성을 얻을 수 있었으며 특히, 플라이애쉬 10% 및 고로슬래그 30%가 혼입된 HE-TBC의 투수특성은 매우 낮은 투수성을 나타내어 새로운 3성분계 조강콘크리트의 활용이 가능할 것으로 판단되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.651-654
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• 2005

Fast-setting cement is usually used for emergency repair construction of roads, bridges, buildings and so on. In this study, we tried to develop fast-setting ultra early strength mortar for prepacked concrete and evaluated the properties of fresh and hardened concrete with it. The flowability of the mortar was high enough to be easily poured into coarse aggregates. It showed high early strength development which can make it possible to use newly constructed structures within $3\~4$ hours regardless of curing conditions such as curing temperature and curing environment. And it also showed good resistance to drying shrinkage and chemical attack.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.413-414
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• 2009

국내 레디믹스트콘크리트 제품의 최적화된 콘크리트 재료모델을 개발 구축하기 위하여 본 연구에서는 보통 및 고강도 영역에서 사용되는 콘크리트를 제조하였으며, 국내 및 국외의 조기강도 발현에 대한 수준을 비교 검토하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2005년도 추계 학술논문 발표대회
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• pp.75-78
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• 2005

This raper investigates the effect of curing temperature on strength development of concrete incorporating cement kiln dust(CKD) and blast furnace slag (BS) quantitatively. Estimation of compressive strength of concrete was conducted using equivalent age equation and rate constant model. An increasing curing temperature results in an increase in strength at early age, but with the elapse of age, strength development at high curing temperature decreases compared with that at low curing temperature. Especially, the use of 35 has a remarkable strength development at early age and even at later age, high strength is maintained due to accelerated pozzolanic activity resulting from high temperature. Whereas, at low curing temperature, the use of BS leads to a decrease in compressive strength. Accordingly, much attention should be paid to prevent strength loss at low temperature. Based on the strength development estimation using equivalent age equation, good agreements between measured strength and calculated strength are obtained.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.455-460
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• 2000

Fly ash can be used as cement replacement material and can also produce the durable concrete. According to the results, the compressive strength of concrete containing fly ash is slightly lower than that of normal concrete at early ages, however, the long-term compressive strength is significantly higher beyond 90 days, and it increases the durability of concrete as well.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 춘계 학술논문 발표대회 1부
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• pp.73-75
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• 2011

In this study, prediction of later-age compressive strength of ultra-high strength concrete, based on the accelerated strength of concrete cured in 50, 60℃ warm water was investigated. W/B of 32, 23.5, 19% 3 levels were examined. And the specimens were cured in 50, 60℃ warm water. The results showed reliable accuracy by regression relation between 28day strength cured by standard curing method and accelerated strength of the concrete cured in warm water. And the specimens cured in 50, 60℃ showed more high strength development. So 60℃ curing could be considered in order to reduce the measurement error. As a result, the feasibility of 50, 60℃ warm water curing method at high strength level was confirmed.