• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.583-586
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• 2005

Strength of concrete is very important factor in design and quality management and may represent overall quality of concrete. Such strength of concrete may differ depending on amount of cement mixed, water and fine aggregate ratio. Classic concrete products have been produced mainly with ordinary portland cement(hereinafter 'cement'), water and fine aggregate as shown above, but various additives and mixture materials have been used for concrete manufacturing, along with development of high functional concrete and diversification of structures. Various kinds of chemical mixtures agents and mixture materials have been used as it requires concretes with other features which cannot be solved with existing materials only, such as high strength, high flexibility and no-separation in the water. Such addition of various mixture agents may cause change in cement hydrate, affecting strength. Hydration of cement is the process of producing potassium hydroxide, C-S-H, C-A-H and Ettringite, while causing heat generation reaction after it is mixed with water, and generation amounts of such hydrates play lots of roles in condensation and hardening. This study aims to analyze its strength and features with hydrates by making specimen according to curing temperature, types of mixture agent, mixing ratio and ages and by analyzing such hydrates in order to analyze role of cement hydrate on early strength of concrete.

• 콘크리트학회지
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• 제26권5호
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• pp.16-22
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• 2014

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.113-114
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• 2022

The aim of the research is to evaluate the segregation resistivity of the mixture conditions by changing the PVA and borax solutions for thixotropic property on concrete mixture. Since the water addition caused by producing solutions of PVA and borax induces segregation of the concrete mixture, the unit water was reduced by replacing the water amount for PVA and borax solution. By replacing the water from PVA and borax solutions, the segregation was prevented with prefixed concrete mix design and thixotropic properties were also occurred.

• 콘크리트학회논문집
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• 제28권4호
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• pp.427-434
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• 2016

이 연구의 목적은 인공경량골재 콘크리트의 생산에서 $CO_2$ 배출량을 저감시킬 수 있는 천연모래 치환 기반의 배합설계 절차를 제시하는 것이다. 379개의 경량골재 콘크리트 배합 데이터를 사용하여 $CO_2$ 배출량과 콘크리트의 압축강도에 대한 천연모래의 치환율의 영향을 평가하였다. Yang et al.이 제시한 배합설계절차 및 데이터베이스를 이용한 비선형 회귀 분석에 기반하여 목표 성능(압축강도, 초기 슬럼프, 공기량 및 $CO_2$ 저감률)을 만족하기 위한 천연모래의 치환율 및 콘크리트 배합설계를 결정할 수 있는 간단한 모델식을 제시하였다. 뿐만 아니라, 제안된 모델식은 주어진 경량골재 콘크리트 배합표에서 $CO_2$ 배출량을 직접 계산하는데 효율적으로 이용될 수 있다.

• 콘크리트학회논문집
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• 제17권3호
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• pp.473-480
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• 2005

In this study, a mix design for self compacting concrete was based on Okamura's method and concrete incorporated just a ground granulated blast furnace slag. Replacement ratio of slag is in the range of $20-80\%$ of cement matrix by volume. For the optimal self compactability in mixture incorporating ground granulated blast furnace slag, the paste and mortar tests were first completed. Then the slump flow, elapsed time of 500mm slump flow, V funnel time and filling height by U type box were conducted in concrete. The volume of coarse aggregate in self compacting concrete was in the range of $50-60\%$ to the solid volume percentage of coarse aggregate. Finally, the compressive and splitting tensile strengths were determined in the hardened self compacting concrete incorporating ground granulated blast furnace slag. From the test results, it is desirable for self compacting concrete that the replacement of ground granulated blast furnace slag is in the range of $40-60\%$ of cement matrix by volume and the volume of coarse aggregate to the solid volume percentage of coarse aggregate with a limit of $55\%$.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.997-1002
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• 2003

Roller-compacted concrete(RCC) dam is a new type that combines advantages of earthfill dam and concrete dam in construction, This method save cost due to their rapid method of construction. RCC is, used in RCC dams, no-slump concrete so it is different that measure method of consistency and mixture properties compare with conventional mass concrete, There are existing two major design method, which one used in USA the other used in Japan. The results obtained in this study would be useful in establishing mixture proportions for dam concrete for RCC dams by apply method of compound their merit.

• 산업기술연구
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• 제21권A호
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• pp.285-292
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• 2001

The amount used of aggregates for concrete is increasing rapidly since the mid-1980s in Korea. The natural gravels from river are already displaced with crushed stone, and use of crushed sand as a substitute of natural river sands, also, is getting increased day by day. This paper is presented for mixture of high strength concrete using crushed sands. Mixing design of concretes are various water-cement ratios(w/c) such as 25%, 40%, 55% and different replacement ratio of crushed sands to natural sands such as 0%, 20%, 40%, 60%. As a results, it has been shown that compressive strength of concretes with w/c lower than 40% and 25% is higher than $400kgf/cm^2$ and $600kgf/cm^2$ respectively.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.344-347
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• 2004

The amount of coal ash has been increasing and development of effective use is urgently needed. Various by-products and waste are expected to be used as resources from the point of reduction in environmental load. This is an experimental study to compare the properties of high volume coal ash concrete using the reclaimed coal ash. For this purpose, authors have started work to develop a production method of hardening coal ash concrete. Laboratory tests show that the optimum mixture of coal ash concrete can be determined from multiple regression analysis. According to test results, it was found that the compressive strength of the concrete can be determined by a single curve. And it is obtained from the analysis of the results tested for concrete with the ratio of total power to water and amount of land reclamation ash.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.94-95
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• 2020

This paper introduces the mix design and performance evaluation of Ultra-High Performance Concrete (UHPC). The concrete mixture is designed to achieve a densely compacted cementitious matrix via the modified Andreasen & Andersen particle packing model. The compressive strengths of UHPC designed by this method reached 154MPa. The relationship between packing theory and compressive strength of UHPC is discussed in this paper.

• 대한토목학회논문집
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• 제30권5A호
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• pp.433-442
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• 2010

콘크리트의 염화물 확산계수의 제어는 염해에 노출된 콘크리트 구조물의 내구수명 확보에 필수적이며, 이를 위해 많은 연구가 진행되어 왔다. 본 연구는 목표 내구수명을 만족하는 목표확산계수를 도출하고 유전자 알고리즘을 통하여, 최적배합을 도출하는데 있다. 이를 위하여, 동일한 골재 및 혼화재를 사용한 30개의 배합과 그에 따른 염화물 확산계수를 분석하였으며, 27개를 대상으로 확산계수 예측식을 도출하였다. 확산계수 예측식의 변수로는 물-결합재비, 단위 혼화재량(슬래그, 플라이 애쉬, 실리카퓸), 단위 시멘트량, 단위 잔골재 및 굵은 골재량을 포함하도록 하였으며 나머지 3개의 배합에 대하여 검증을 수행하였다. 최적 함수식은 27개의 배합에 대하여 평균 18.7%의 오차와 16.0%의 변동계수를 보이고 있었다. 주어진 3개의 확산계수에 대하여, 유전자 알고리즘을 통하여 도출된 배합은 0.3%~12.2%의 오차범위를 가지며 각각의 배합인자를 도출하였다. 최종적으로 서로 다른 내구성 설계변수(목표내구수명, 피복두께, 표면염화물량, 혼화재량)와 노출환경(온도 및 습도)을 가정하여 목표 확산계수를 도출하였으며, 이에 만족하는 최적화된 콘크리트 배합을 제안하였다. 본 연구에서는 유전자 알고리즘을 이용하여, 내구성 콘크리트 배합도출에 대한 적용성을 평가하였으며, 제안된 기법은 다양한 확산계수의 범위를 가지는 광범위한 자료구축을 통하여 개선될 것이다.