• Computers and Concrete
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• 제18권3호
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• pp.367-388
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• 2016

In this paper, a simple practical method is introduced in which a simple weight measurement of concrete and finite element numerical analysis are used to determine the moisture transfer coefficient of concrete with a satisfactory accuracy. Six concrete mixtures with different water-to-cementitious material (w/cm) ratios and two pozzolanic materials including silica fume and zeolite were examined to validate the proposed method. The comparison between the distribution of the moisture content obtained from the model and the one from the experimental data during both the wetting and drying process properly validated the performance of the method.With the proposed method, it was also shown that the concrete moisture transfer coefficient considerably depends on the pore water saturation degree. The use of pozzolanic materials and also lowering w/cm ratio increased the moisture transfer coefficient during the initial sorption, and then, it significantly decreased with an increase in the water saturation degree.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.699-702
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• 2005

This study evaluates the properties of porous concrete for pavement according to content of silica fume and steel fiber. The results of the test indicate that in every condition, the void ratio and the coefficient of water permeability of porous concrete for pavement satisfy both the domestic standards and proposition values. Among the properties of strength, the compressive strength satisfies the standards in the specification of KNHC as for every factor of mixture but in the case of the flexural strength, more than $0.6vol.\%$ of steel fiber satisfied the JCI proposition values. The case when silica fume and steel fiber are used simultaneously presents the strongest durability and Noise Reduction Coefficient is 0.48 to prove that it possesses almost $50\%$ sound absorption.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.777-780
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• 2005

The paper presents details of an investigation into the effect of sand content upon the strength and shrinkage of mortar. This strategy was to produces more durable strength mortar with less cement. Cement mortars containing $20\;wt.\;\%$ Class F fly ash, and/or $6\;wt.\;\%$ silica fume were prepared at a water/binder ratio of 0.45 and sand/binder ratios of 2.0, 2.5, 2.7, and 3.0. The increase in sand/binder ratio caused a decrease in the mortar flow. However, the sand/binder ratio did not affect the strength development. Drying shrinkage decreased with increasing the sand contents.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.577-580
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• 2006

As this study is to estimate resistance of cement mortars using crushed sand under chemical attacks. Besides tests have been carried out with cement mortars by river sand and crushed sand by fine sand, cement mortars mix various proportions of silica fume and fly ash(up to 15% and 50% by weight for cement) were prepared and immersed in pure water, sodium sulfate solution, magnesium sulfate solution, seawater for 28days, 60days, 90days and 180days. Test on the change in the weight and compressive strength of cement mortars according to the duration of immersion time and the content of silica fume and fly ash was performed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.775-780
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• 2003

The propose of this study is to discover concrete secondary products for proper mixing by lightweight concrete. The standard of water ratio 50% and weight substition 0%, 10%, 20% by Fly-ash. When produce manufactures, there use for maintain its form weight substition and addition among the viscosity agent each Silica-fume and Hydroxy propyl methyl cellulos. Testing method was to operate slump, air content, compressive strength test, rapid freezing and thawing test. The result of this study is appeared when substition Fly-ash generally it had better use Silica-fume.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.821-824
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• 2006

As this study is to estimate long term resistance of cement mortars using crushed sand under chemical attacks. Besides tests have been carried out with cement mortars by river sand and crushed sand by fine sand, cement mortars mix various proportions of silica fume and fly ash(up to 15% and 50% by weight for cement) were prepared and immersed in pure water, sodium sulfate solution, magnesium sulfate solution, seawater for 28days, 90days, 180days, 365days. Test on the change in the weight and compressive strength of cement mortars according to the duration of immersion time and the content of silica fume and fly ash was performed.

• 콘크리트학회논문집
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• 제27권2호
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• pp.127-136
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• 2015

본 연구는 고강도 고함량 고로슬래그 콘크리트의 특성에 미치는 석회석 미분말과 실리카퓸의 영향을 검토하기 위해 50%에서 최대 80%까지 고로슬래그를 다량 혼합하고, 석회석 미분말을 최대 20%, 실리카퓸을 최대 10%까지 혼합한 물-결합재비 20%의 고강도 시멘트 모르터의 유동성, 강도발현, 수화 및 포졸란 반응 특성, 공극율 및 공극 크기 분포 등을 분석하였다. 실험결과에 따르면 고함량 고로슬래그 배합은 포틀랜드 시멘트 배합에 비해 고로슬래그의 낮은 표면 마찰로 유동성이 크게 향상되고, 시멘트 수화에 필요한 자유수가 많아져 수화반응이 촉진되면서 초기강도가 증가하나, 너무 낮은 물-결합재비와 단위시멘트량으로 인해 수산화칼슘의 생성량이 부족하여 포졸란 반응이 충분히 활성화되지 못함에 따라 장기강도 발현이 억제된다. 석회석 미분말은 유동성에는 큰 영향을 주지 않고, 역시 시멘트의 초기 수화를 촉진하는 것으로 나타났으나, 수화를 가속하는 효과는 고로슬래그보다 높지 않고, 고로슬래그와 달리 수경성이 없기 때문에 오히려 석회석 미분말의 치환율이 높아질수록 압축강도가 낮아지는 것으로 나타났다. 또한 고분말의 고로슬래그를 사용하거나, 또는 실리카퓸으로 고로슬래그를 치환하는 경우 시멘트 수화에 필요한 자유수를 더 많이 흡착함으로써 유동성과 강도를 저하시키는 것으로 나타났다. 또한 고로슬래그를 사용한 배합의 공극율이 보통 포틀랜드 시멘트 배합보다 낮게 나타났으나, 석회석 미분말은 공극율에 뚜렷한 영향을 나타내지 않았고 실리카퓸은 낮은 시멘트 수화도로 인해 공극율을 오히려 증가시키는 것으로 나타났다. 반면 공극 크기 분포에 있어서는 고로슬래그와 실리카퓸를 혼합한 경우 미세공극이 증가하는 것으로 나타났다.

• 한국건설순환자원학회논문집
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• 제9권4호
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• pp.585-593
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• 2021

본 연구에서는 고강도 시멘트 복합체의 배합조건에 따른 압축강도 발현 특성을 분석하기 위해 물/결합재비, OPC 대비 실리카 흄의 함량 및 단위 결합재량을 변수로 총 64개의 배합조건과 2종류의 양생 조건으로 배합실험 및 압축강도 측정을 실시하였다. 일반적인 OPC 콘크리트와 유사하게 물/결합재비의 증가는 고강도 시멘트 복합체의 압축강도를 감소하는 것으로 나타났으며, 상온 양생 시편의 경우 재령일에 따른 압축강도 증가가 뚜렷하게 발생하는 것으로 조사되었다. 하지만 고온 양생을 실시하는 경우 재령일에 따른 압축강도 증가는 관찰되지 않았다. OPC 대비 실리카 흄의 함량이 25%에서 15%로 낮아지는 경우 강도 변화는 미미한 것으로 조사되었으나, 15%에서 0% 감소하는 경우 뚜렷한 강도 감소가 식별되며, 물/결합재비가 낮은 경우 이러한 현상은 더욱 두드러지는 것으로 조사되었다. 단위 결합재량의 840kg/m³인 경우 압축강도 발현이 가장 우수한 것으로 나타났으며, 실리카 흄 함량이 낮은 경우 단위 결합재량 감소에 따른 압축강도 저하가 뚜렷해지는 것으로 조사되었다.

• International Journal of Concrete Structures and Materials
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• 제7권3호
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• pp.239-249
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• 2013

In the present scenario to fulfill the demands of sustainable construction, concrete made with multi-blended cement system of OPC and different mineral admixtures, is the judicious choice for the construction industry. Silica fume (SF) and fly ash (FA) are the most commonly used mineral admixtures in ternary blend cement systems. Synergy between the contributions of both on the mechanical properties of the concrete is an important factor. This study reports the effect of replacement of OPC by fly ash (20, 30, 40 and 50 % replacement of OPC) and/or silica fume (7 and 10 %) on the mechanical properties of concrete like compressive strength and split tensile strength, with three different w/b ratio of 0.3, 0.4 and 0.45. The results indicate that, as the total replacement level of OPC in concrete using ternary blend of OPC + FA + SF increases, the strength with respect to control mix increases up to certain replacement level and thereafter decreases. If the cement content of control mixes at each w/b ratio is kept constant, then as w/b ratio decreases, higher percentage of OPC can be replaced with FA + SF to get 28 days strength comparable to the control mix. A new method was proposed to find the efficiency factor of SF and FA individually in ternary blend cement system, based on principle of modified Bolomey's equation for predicting compressive strength of concrete using binary blend cement system. Efficiency factor for SF and FA were always higher in ternary blend cement system than their respective binary blend cement system. Split tensile strength of concrete using binary and ternary cement system were higher than OPC for a given compressive strength level.

• International Journal of Concrete Structures and Materials
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• 제10권sup3호
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• pp.97-108
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• 2016

When the energy performance of concrete is substantially higher than that of normal type concrete, such concrete is regarded as energy efficient concrete (WBSCSD 2009). An experimental study was conducted to investigate mechanical properties of energy efficient concrete with binary, ternary and quaternary admixture at different curing ages. Slump test for workability and air content test were performed on fresh concretes. Compressive strength, splitting tensile strength were made on hardened concrete specimens. The mechanical properties of concrete were compared with predicted values by ACI 363R-84 Code, NZS 3101-95 Code, CSA A23.3-94 Code, CEB-FIP Model, EN 1991, EC 2-02, AIJ Code, JSCE Code, and KCI Code. The use of silica fume increased the compressive strengths, splitting tensile strengths, modulus of elasticities and Poisson's ratios. On the other hand, the compressive strength and splitting tensile strength decreased with increasing fly ash.