• International Journal of Concrete Structures and Materials
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• 제9권2호
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• pp.185-206
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• 2015

This paper presents statistical models developed to study the influence of key mix design parameters on the properties of lightweight self-consolidating concrete (LWSCC) with expanded shale (ESH) aggregates. Twenty LWSCC mixtures are designed and tested, where responses (properties) are evaluated to analyze influence of mix design parameters and develop the models. Such responses included slump flow diameter, V-funnel flow time, J-ring flow diameter, J-ring height difference, L-box ratio, filling capacity, sieve segregation, unit weight and compressive strength. The developed models are valid for mixes with 0.30-0.40 water-to-binder ratio, high range water reducing admixture of 0.3-1.2 % (by total content of binder) and total binder content of $410-550kg/m^3$. The models are able to identify the influential mix design parameters and their interactions which can be useful to reduce the test protocol needed for proportioning of LWSCCs. Three industrial class ESH-LWSCC mixtures are developed using statistical models and their performance is validated through test results with good agreement. The developed ESH-LWSCC mixtures are able to satisfy the European EFNARC criteria for self-consolidating concrete.

• 한국건축시공학회지
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• 제10권3호
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• pp.113-120
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• 2010

본 연구에서는 실내 배합 실험을 통하여 150MPa 초고강도 콘크리트의 제반 물성을 평가한 후 150MPa 초고강도 콘크리트제조를 위한 최적 배합 조건을 제시하고자 하며 압축강도, 응력-변형률 관계, 탄성계수와 인장강도, 휨강도 등과 같은 기본적인 재료역학 특성을 평가하고자 한다. 이를 위하여 초고강도 콘크리트의 목표 물성으로 배합강도는 150MPa, 슬럼프 플로는 $700{\pm}50mm$를 목표로 정하여 57개의 배합을 실시하였으며, 각각의 배합조건에 따른 물성 및 역학특성을 검토하였다. 실험결과 초고강도 콘크리트는 보통의 고강도 콘크리트보다 매우 큰 점성을 가지므로 이러한 점성과 콘크리트 타설 및 작업성의 상관성을 고려하여 700~800mm 정도의 플로값을 확보하여야 할 것으로 판단되며, 재령 56일 압축강도를 100%로 할 때 3일은 64%, 7일은 70%, 28일은 약 95% 발현하였다. 150MPa 정도의 초고강도 콘크리트 제조를 위한 단위 시멘트량은 대략 1030~1150kg/$m^3$ 정도이며, 물-결합재비는 12~14%의 범위 내에서 적당하며, 잔골재율은 점성 및 작업성을 고려하여 30~35% 범위 내에서 결정될 수 있음을 확인하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.369-372
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• 2008

본 연구에서는 소요의 유동성능 및 공기량을 확보할 수 있는 병용계 보통강도 고유동 자기충전 콘크리트를 제조하기 위하여 증점제 및 소포제 첨가량를 변화시킨 병용계 고유동 자기충전 콘크리트의 유동 특성을 실험적으로 분석 고찰하였다. 실험결과 증점제를 첨가한 병용계 고유동 자기충전 콘크리트의 Slump flow는 증점제 첨가량이 0.2%(${\times}$W %)일 때 가장 증가하였으며 증점제 첨가량이 높아질 경우 JSCE 기준안(2등급)에서 제시한 V-funnel의 유하시간 규정값을 크게 벗어나는 결과가 나타났다. 또한 증점제, 소포제 및 AE제를 첨가한 배합을 제외한 모든 배합이 목표 공기량 $4.5{\pm}1.5%$를 만족하지 못하였으며, 소포제를 첨가한 병용계 고유동 자기충전 콘크리트 배합은 최초배합 후 시간의 경과에도 불구하고 공기량(A1=1.5%)이 다소 감소하는 결과가 나타났다. 이러한 결과를 통하여 병용계 고유동 자기충전 콘크리트 제조시 소요의 유동성능을 얻기 위한 최적의 혼화제량을 알 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.949-952
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• 2006

An understanding of rheological property on cement paste is one of the important factor to design concrete such as High-fluidity Concrete (HFC) for a specific application. The HFC is a specially proportioned hydraulic cement concrete that enables the fresh concrete to flow easily into the forms and around the reinforcement and prestressing steel without vibration and segregation. Use of this type of concrete for the concrete building construction, manufacture of precast, prestressed bridge elements provides the benefits of increased rate of production and safety, reduced labor needs, and lower noise levels. This paper presents the performance of rheological properties of cement paste incorporating domestic high-water-reduced-admixture (HWRA) for an Ultra-high-fluidity concrete (UHFC). Investigation was carried out on cement pastes with combinations of various dosages of HWRA and water/cement ratios.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.433-436
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• 2006

The trends of research for concrete in recent days are the high performance, high flow, ultra high strength and high durability. These are being researched with a construction company and a materials company. Anyone have to use the good quality sand, gravel, high quality chemical compound and silica fume for ultra high strength concrete as yet. This paper was researched with the domestic materials, not use the high price silica fume for the development 100MPa ultra high strength concrete with laboratory tests and mock-up test.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
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• pp.157-160
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• 1994

Recently, many studies on the ultra high strength concrete are performed in our country. so, this study is aimed for analyzing the effects for replacement of silica fume and fly ash. As results, slump, slump flow and compressive strength is showed the high values in replacement silica fume. Tensile strength ratio is 1/17 and bending strength ratio is 1/6 for compressive, there are results of the test.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.388-391
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• 2004

This research investigates how the fineness modulus of fine aggregates and the grain shape of coarse aggregates affects flow characteristics, packing characteristics and compressive strength characteristic. The experimental results, show that increase of the fine aggregate's fineness modulus improved concrete flow, but filling ability was high at over KS regulation extent due to segregation phenomena. It is considered that the improvement of 0.1 spherical rate was effective to concrete fluidity elevation by reducing about $6\%$ of fine aggregate ratio displays which the smallest gap rate of aggregate. Compressive strength was increased to about 0.6MPa everytime F.M. 0.1 of fine aggregate fineness is increased. However, it was decreased to about 9MPa at F.M. 3.5 compared to F.M. 3.0.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.277-280
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• 2004

Recently, as structure is more higher and bigger, we need high strength and high performance concrete. Therefore it is necessary superplasticizer for high strength and high performance concrete. In this study, it is examined the properties of flow, air content and strength of concrete with polycarboxylate superplasticizer in comparison with existing superplasticizer. First, The slump loss of concrete used polycarboxylate superplasticizer showed 2cm until 120 minutes. Second, The air content loss of concrete used polycarboxylate superplasticizer showed $1\%$ until 120 minutes. Third, It is possible to manufacture $1000kgf/cm^2$ strength concrete using polycarboxylate superplasticizer with $806kg/m^3$ cement content, $18\%$ water-binder ratio, $15\%$ silica fume, $10\%$ fly-ash content.

• Advances in concrete construction
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• 제8권1호
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• pp.21-31
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• 2019

The rich recipe of ultra high performance concrete (UHPC) offers the higher mechanical, durability and dense microstructure property. The variable like cement/sand ratio, amount of supplementary cementitious material, water/binder ratio, amount of fiber etc. alters the UHPC hardened properties to any extent. Therefore, to understand the effects of these variables on the performance of UHPC, inevitably a stage-wise development is required. In the present experimental study, the effect of sand/cement ratio, the addition of finer material (fly ash and quartz powder) and, hybrid fiber on the fresh, compressive and microstructural property of UHPC is evaluated. The experiment is conducted in three phases; the first phase evaluates the flow value and strength attainment of ingredients, the second phase evaluates the efficiency of finer materials (fly ash and quartz powder) to develop the UHPC and the third phase evaluate the effect of hybrid fiber on the flow value and strength of ultra high performance hybrid fiber reinforced concrete (UHP-HFRC). It has been seen that the addition of fly ash improves the flow value and compressive strength of UHPC as compared to quartz powder. Further, the usage of hybrid fiber in fly ash contained matrix decreases the flow value and improves the strength of the UHP-HFRC matrix. The dense interface between matrix and fiber and, a higher amount of calcium silicate hydrate (CSH) in fly ash contained UHP-HFRC is revealed by SEM and XRD respectively. The dense interface (bond between the fiber and the UHPC matrix) and the higher CSH formation are the reason for the improvement in the compressive strength of fly ash based UHP-HFRC. The differential thermal analysis (DTA/TGA) shows the similar type of mass loss pattern, however, the amount of mass loss differs in fly ash and quartz powder contained UHP-HFRC.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.561-564
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• 2003

One of the most important reasons that CFT is used in many conditions is by using that we can achieve the effect, which reduce the section of the member. This research purpose to find the most ideal composition, which is achieved by the investigation in the concrete's property of matter like ability of Slump, Slump Flow, Air content, Bleeding, and Settlement when the high strength of concrete which is over 80㎫ is used in the CFT column.