• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.653-656
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• 2008

초고강도 콘크리트는 결합재의 다량 사용에 따라 건조수축보다 큰 자기수축 변형이 나타나며 이는 구조물의 품질을 저해하는 요인으로 작용하여 초고강도 콘크리트의 수축변형을 최소화시키기 위한 기술이 필요하다. 이에 본 연구에서는 설계기준강도 100MPa 이상을 갖는 초고강도 콘크리트를 제조하고 팽창제를 혼입한 초고강도 콘크리트에 대하여 자유수축시험체로 매립형게이지를 통한 수축변형을 측정하였다. 그 결과 팽창제의 혼입으로 초기상태의 콘크리트는 팽창율이 증가하나 장기적 측면에서의 수축율이 둔화되는 것으로 나타났으며, 이를 통한 팽창제를 통하여 수축저감에 관한 효과가 기대된다. 아울러팽창제의 혼입에 따른 압축강도에 미치는 영향은 미미한 것으로 나타났다.

• 콘크리트학회논문집
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• 제25권2호
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• pp.145-153
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• 2013

촉진 염화물 확산계수는 최근들어 염화물 거동 평가를 위하여 많이 사용되고 있다. 촉진 염화물 확산계수는 겉보기 확산계수와 마찬가지로 재령에 따라 감소하는데, 이 연구에서는 공극률을 이용하여 촉진확산계수의 감소를 구현하였다. DUCOM 프로그램을 이용하여 15 배합에 대한 공극률을 도출하였으며, 이를 회귀분석하여 재령 270일 동안 감소하는 염화물 확산계수를 모델링하였다. 또한 자유염화물과 구속염화물간의 관계인 비선형 구속능을 고려하여, 고성능 콘크리트내의 염화물 거동을 평가하였다. 기존의 실험자료인 180일간 염화물에 침지되어 있는 시편을 이용하여, 이 연구에서 제안한 기법의 검증을 수행하였다. 제안된 기법은 다양한 물-시멘트비 및 혼화재(고로슬래그 미분말 및 플라이애쉬)를 가진 고성능 콘크리트의 염화물 거동을 적절하게 평가하였다. 또한 혼화재료를 사용한 콘크리트의 경우, 확산계수의 시간의존성이 뚜렷하므로 염화물 거동 해석시 재령에 따른 염화물 확산계수의 감소를 반드시 구현해야 함을 알 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제14권3호
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• pp.144-151
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• 2010

본 연구에서는 고비용의 실리카흄의 대체재로서 인산부산석고와 카올린을 활용한 시멘트매트릭스의 화학적, 기계적 성질에 대하여 분석하였다. 실험을 위하여 인산부산석고는 이수석고 형태인 건조석고, 반수석고, III형 무수석고, II형 무수석고로 실험용시료를 제조하였으며, $900^{\circ}C$에서 소성된 카올린은 서냉과 급냉의 형태로 제조된 메타카올린의 형태로 제조하였다. 또한 이재료를 활용하여 혼합시멘트를 제조하였으며, 제조된 시멘트를 사용하여 실리카 흄을 혼입한 시멘트 매트릭스와 재료적 성능을 비교 평가하였다. 실험결과 급냉 제조된 메타카올린이 다른 재료에 비하여 성능이 우수한 것으로 분석되었다.

• Computers and Concrete
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• 제17권6호
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• pp.801-814
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• 2016

An alternative type of building system with masonry units is extensively used nowadays to reduce the emission of CO2 and embodied energy. Long-term performance of such structures has become essential for sustaining the building technology. This study aims to assess the strength and durability properties of concrete prepared with unprocessed bagasse ash (BA) and silica fume (SF). A mix proportion of 1:3:3 was used to cast concrete cubes of size $100mm{\times}100mm{\times}100mm$ with various replacement levels of cement and tested. The cubes were cast with zero slump normally adopted in the manufacturing of hollow blocks. The cubes were exposed to acid attack, alkaline attack and sulphate attack to evaluate their durability. The mass loss and damages to concrete for all cases of exposures were determined at 30, 60, and 90 days, respectively. Then, the residual compressive strength for all cases was determined at the end of 90 days of durability test. The results showed that there was slight difference in mass loss before and after exposure to chemical attack in all the cases. Though the appearance was slightly different than the normal concrete the residual weight was not affected. The compressive strength of 10% bagasse ash (BA) as a replacement for cement, with 10% SF as admixture resulted in better strength than the normal concrete. Hence concrete with 10% replacement with BA along with 10% SF as admixture was considered to be durable. Besides solid concrete cubes, hollow blocks using the same concrete were casted and tested simultaneously to explore the possibility of production of masonry units.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.781-786
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• 2001

The Salt attack is one of the primary factors that cause the deterioration of durability in steel reinforced concrete structure. And to depreciate the deterioration from the Salt attack in concrete structure, pozzolanic materials are used widely in recent years. In this study, experiments about the resistance of chloride infiltration of concrete according to the replacement rations of Activated Hwangtoh and various pozzolanic materials(silica fume, fly ash, blast furnace slag and non Activated/Activated Hwangtoh) are performed and the results of this study were shown as follows; 1) As the replacement ratios of Activated Hwangtoh were getting higher, the strength of concrete was increased and in case of various pozzolanic materials, strength of Activated Hwangtoh in specimen was better than that of fly ash, blast furnace slag and non Activated Hwangtoh. 2) As the replacement ratios of Activated Hwangtoh were getting higher, the resistance of chloride infiltration of concrete was increased and in case of various pozzolanic materials, silica fume is better than any other pozzolanic materials and Activated Hwangtoh was better than that of fly ash, blast furnace slag and non Activated Hwangtoh.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 추계 학술논문 발표대회
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• pp.46-47
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• 2018

High performance concrete with low water-to-cement ratio has been widely used with increased demand of high rising buildings and huge scaled structures. Additionally, for high performance concrete, various SCMs are replaced to improve its performance from fresh state to hardened state. With the drawback of increased viscosity of the concrete mixture for high performance concrete, low-viscosity typed high range water reducer is the relatively new admixture. Therefore, as a goal of the research, under using various SCMs with wide range of content, the performance of low-viscosity typed high range water reducer was evaluated. Especially, in this research, the influence of low-viscosity typed high range water reducer on rheological properties including plastic viscosity and yield stress were assessed. As a result of the research, it is expected to provide a fundamental information of low -viscosity typed high ranged water reducer on high performance concrete with various conditions of SCMs.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.425-430
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• 2002

The needs of the times, a cement plays an important roll in the materials field. So, in this research we would like to study on the properties of Photocatalytic Cement for waste gas reduction. The fundamental phenomena of the Photocatalytic Cement were observed by the NOx Analyzer, Bonding strength, SEM, Flow and Surface hardness(Pencil tester). As a result of this study, the Photocatalytic Cement used Photocatalytic powder, admixture and other materials can obtain its physical properties, also photocatalytic efficiency. If we have added a various experiment, we could have to develop the Photocatalytic Cement.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.245-250
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• 1998

The Elastic modulus depends on the elastic property of composition materials, the gravity of aggregate, the bond strength of binder, the usage and quantity of admixture, curing and measuring method, etc. Accordingly, the aim of this study, by manufacturing concrete of practical high strength range(600~ 1000kg/$\textrm{cm}^2$) with the specific cement and mineral admixtures, is to compare elastic modulus with the existing equations and also to estimate elastic property of use materials. As a result, it could be confirmed that the existing equations which were proposed by the ACI 363, CEB-FIP Code, and New-RC have a tendency to the overestimation in general. However, it could be confirmed that the KCI-96 and Norwegian NS 3473 equations are closed to measuring results, and that the elastic modulus property have a different tendency due to types of cements.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.707-714
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• 2001

This paper presents the fundamental study on rational manu(acture of Very High Strength(VHS) concrete using industrial by-products as like silica fume, slag and fly ash. In this study, we had tested various mixing cases to manufacture the VHS concrete(target compressive strength : over 1,000 kgf/$cm^{2}$) which is easily workable (target slump flow : 60$\pm$l0cm), The main variables studied are; 1) test variables to find the optimum replacement ratio of mineral admixture, 2) test variables to find a rational water-binder ratio, a proper binder content, 3) test variables to find the method for reduction of slump loss, 4) test variables to know the influence of air entrainment on frost resistance. From the test results, it is concluded that the rational mix design can be made by using 40% slag, 10% silica fume, and water reducing agent(slump loss reduction type). We found that it is unnecessary to entrain air for freeze-thawing resistance.

• 한국건축시공학회지
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• 제2권2호
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• pp.151-156
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• 2002

When fresh concrete is exposed to low temperature, the concrete may suffer frost damage due to freezing at early ages and strength development may be delayed. One of the solution methods for resolve these problems is to reduce freezing temperature of concrete by the use of chemical admixture called Accelerators for freezing resistance. In this study, we investigate the effect on strength development of cement mortar using accelerators for freezing resistance with the variance curing condition. As the result of this study, the mortar using accelerators for freezing resistance show that continuously strength development in curing condition of -5$^{\circ}C$. And compressive strength under the variance temperature condition was higher than constant temperature condition in same maturity.