• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2003년도 학술.기술논문 발표회
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• pp.49-52
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• 2003

The objective of this study the mechanical characteristics of prefoamed lightweight foamed concrete using the mineral foam agent which has high lightness, and strength. The compressive strength of lightweight foamed concrete using mineral foam agent are about 2 times degree high those the of lightweight foamed concrete using vegetable foam agent. Lightweight foamed concrete was able to obtain the result of 50kg/㎠ or more compressive strength, when was unit weight 0.8t/㎡. In the case of the same unit weight of concrete, it is influenced by w/c of foam agent ratio. The paper present extensive data on characteristics of compressive strength of the concrete manufatured with the different factors in mix design and also present optimum mix proportion.

• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2003년도 학술.기술논문발표회
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• pp.49.1-52
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• 2003

The objective of this study the mechanical characteristics of preformed lightweight foamed concrete using the mineral foam agent which has high lightness, and strength. The compressive strength of lightweight foamed concrete using mineral foam agent are about 2 times degree high those the of lightweight foamed concrete using vegetable foam agent. Lightweight foamed concrete was able to obtain the result of 50kg/$\textrm{m}^3$ or more compressive strength, when was unit weight 0.8t/$\textrm{m}^3$. In the can of the same unit weight of concrete, it is influenced by w/c of loan agent ratio. The paper present extensive data on characteristics of compressive strength of the concrete manufactured with the different factors in mix design and also present optimum mix proportion.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 1991년도 가을 학술발표회 논문집
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• pp.140-145
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• 1991

Tests were conducted to get a mix proportioning of high strength concrete between σ28 and (C/W) using low quality materials easily purchased in situ. Superplasticizer was used as a chemical admixture to compensate low slump of base concrete keeping it up about 15±2㎝. General material properties such as modulus of elasticity, poisson's ratio, unit weight and stress-strain characteristic of high strength concrete were obtained. Test results show that mix proportioning of high strength concrete proposed in this paper have reasonable validity and these can be used as a design criteria in high strength concrete construction.

• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2019년도 춘계 학술논문 발표대회
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• pp.105-106
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• 2019

In this research, considering the practical conditions at field, thermal cracking method was suggested based on the comparative analysis between predicted value and actual value obtained from the actual structure member with optimum mix design. The optimum mix design was deduced from the various mix designs with various proportions of cementitious binder for upper and lower placement lifts of mat-foundation mass concrete. Therefore, it can be stated that applying low heat mix design and different heating technique between upper and lower placement lifts for mass concrete are efficient to control the thermal cracking. As future issues, based on the interpretation result value, we will select the optimal combination that is applied specifically to the actual site, and deeply analyze the correlation between the measured value and the analysis value through the combination and the test of the actual structure.

• Journal of the Korea Institute of Building Construction
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• 제9권5호
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• pp.127-133
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• 2009

It is important to increase the strength of binders in order to enhance the strength of concrete. However, when the mineral admixture used for high strength concrete is incorporated individually, its dispersibility decreases due to the phenomenon of compaction, which reduces its fluidity and results in insufficient strength being created. To solve this problem, we can pre-mix each binder in advance to disperse a mineral admixture among binders, which will strengthen the fluidity and strength of concrete. Therefore, this study analyzed the properties of high strength concrete depending on the mix method used, to determine the effect of pre-mix cements ranging from W/B 15 to 35%. It was found that the fluidity of pre-mix increased to a level higher than that of individual mix due to its dispersion and ball bearing effect. The air content was slightly decreased from the result of individual mix due to the micro filler effect, which causes fine particles of silica-fume to fill the voids among cement particles, while the setting time of pre-mix was shorter than that of individual mix, because enhanced dispersion of pre-mix affects hydration heat time. The compressive strength of pre-mix increased due to the phenomenon of compaction of gap structure, and the variation of coefficient decreased by 1.69% on average in strength variation.

• Journal of the Korea Concrete Institute
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• 제19권3호
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• pp.377-383
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• 2007

In recent years the field application of high performance concrete has been increased to improve the quality and reliability of concrete structures. The mix design of the high performance concrete includes the 2 set-off mixture theory of mortar and coarse aggregate and that of paste and aggregate. The 2 set-off mixture theory of mortar and coarse aggregate has a problem of having to determine its value through repeated experiments in applying the rheological characteristics of mortar. The 2 set-off mixture theory of paste and aggregate has never been applied to high performance concrete since it doesn't take into account the relationship between optimum fine aggregate ratio and unit volume of powder nor does it consider the critical aggregate volume ratio. As the mixture theory of these high performance concretes, unlike that of general concrete, focuses on flowability and charge-ability, it does not consider intensity features in mix design also, the unit quantity of the materials used is determined by trial and error method in the same way as general concrete. This study is designed to reduce the frequency of trial and error by accurately calculating the optimum fine aggregate ratio, which makes it possible to minimize the aperture of aggregate in use by introducing the maximum density theory to the mix design of high performance concrete. Also, it is intended to propose a simple and reasonable mix design for high performance concrete meeting the requirements for both intensity and flowability. The mix design proposed in this study may reduce trial and error and conveniently produce high performance concrete which has self-chargeability by using more than the minimum unit volume of powder and optimum fine aggregate with minimum porosity.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.58-63
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• 1996

The waste foundry sand might be recycled in concrete, resulting in energy saving and environmental protection. An half Factorial Exprements were performed with the variables of W/C ratio, S/A, Sand/Waste foundry sand ratio and Slump as a preliminary study for optimum mix design of concrete. The results show that the W/C ratio is the most important factor to the concrete strength. The substitute of waste foundry sand up to 30% has little influence, saying that it can substitute the fine aggregate without damaging the concrete properties.

• International Journal of Concrete Structures and Materials
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• 제6권4호
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• pp.239-246
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• 2012

Pervious concrete is a tailored-property concrete with high water permeability which allow the passage of water to flow through easily through the existing interconnected large pore structure. This paper reports the results of an experimental investigation into the development of pervious concrete with reduced cement content and recycled concrete aggregate for sustainable permeable pavement construction. High fineness ground granulated blast furnace slag was used to replace up to 70 % cement by weight. The properties of the pervious concrete were evaluated by determining the compressive strength at 7 and 28 days, void content and water permeability under falling head. The compressive strength of pervious concrete increased with a reduction in the maximum aggregate size from 20 to 13 mm. The relationship between 28-day compressive strength and porosity for pervious concrete was adversely affected by the use of recycled concrete aggregate instead of natural aggregate. However, the binder materials type, age, aggregate size and test specimen shape had marginal effect on the strength-porosity relationship. The results also showed that the water permeability of pervious concrete is primarily influenced by the porosity and not affected by the use of recycled concrete aggregate in place of natural aggregate. The empirical inter-relationships developed among porosity, compressive strength and water permeability could be used in the mix design of pervious concrete with either natural or recycled concrete aggregates to meet the specification requirements of compressive strength and water permeability.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.73-78
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• 2002

This study examines self-compacting of concrete using Ground Calcium Carbonate(GCC) gathering in limestone mine of Banyans district in order to make self-compacting concrete in the range of design strength 300kgf/cm$^2$ and the optimal mix proportion of self-compacting concrete that can use in field structure. The result shows that the optimal GCC replacement ratio is 45$\pm$5% in the normal strength of design strength 300kgf/cm$^2$ and that the volume ratio of the optimal fine aggregate used as the way satisfying both viscosity and compacting ability without separating materials is 46%. The optimal volume ratio of the coarse aggregate considering the economical aspect of concrete is 50%. It is desirable that the optimal mix proportion satisfying self-compacting for replacement of GCC is decided through mix design according to each replacement ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.235-240
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• 1995

A 36 stories high multi-use building was designed with the specified concrete strength range of 300~400kg/$\textrm{cm}^2$ On the ground of the concept of compressive strength, adequate mix designing for the concrete, which has the target strength range of 390-520kg/$\textrm{cm}^2$, was carried out to provide enough strength margin. And with due regard to the workability and transportation time, the slump and slump flow ranged 16~21cm and 30~45cm respectively, maintaining these properties up to 2-hours from the beginning of the mix. The high-range water reducer is incorporated into the mix as a admixture. The building construction is controlled satisfactorily, so far. The actual average 28-day compressive strength is 370kg/$\textrm{cm}^2$, the standard deviation is 28kg/$\textrm{cm}^2$ and the coefficient of variation is 7.6% for concrete of 300kg/$\textrm{cm}^2$ specified strength.