• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.549-554
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• 2002

In Powder System, SCC demands high dosage of superplasticizer and a lage amout of powder for suitable fluidity and viscosity. Okamura's method of most representative mixing design method in SCC of Powder-System is unfavorable economically because of using a large amount of powder. In addition, many ready-mixed concrete plants do not use his mix design method and procedure due to complexity for practical application. Therefore, Nan Su proposed more simple mix design method than Okamura's. It had an advantage in simplicity in practical application and required a smaller amount of powders compared with Okamura's method. This paper proposed an optimal mixture proportion of SCC with consideration of Nan Su's method. The new and modified mix design method required a smaller amount of powder than that of Nan Su's. To check the properties of SCC, considered with the requirements specified by the Japanese Society of Civil Engineering.(JSCE)

• Proceedings of the Korean Institute of Building Construction Conference
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• 2004.05a
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• pp.51-55
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• 2004

Generally, aggregate may limit the strength of concrete, and aggregate with undesirable properties including strength, shape and grading etc. cannot produce good concrete. Also, the properties of aggregate greatly affect the durability and structural performance of concrete. Recently, it has increased the using of crushed aggregate for concrete due to the exhaustion of good natural aggregate. In case of Korea, the using ratio of crushed stone occupies about 97％ of whole coarse aggregate, and ratio of crushed sand occupies about 18.3％ of whole fine aggregate. This is an experimental study to compare and analyze the properties of crushed sand for concrete in capital region and concrete according to the replacement ratio of crushed sand to do suitable mix design and improve the concrete quality. According to results, it was found that nearly all the properties of crushed sand satisfied with the value recommended by KS.

• Journal of the Korea Institute of Building Construction
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• v.18 no.2
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• pp.133-140
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• 2018

The objective of this study is to propose a reliable mixing design procedure of concrete using artificial lightweight aggregate produced from expanded bottom ash and dredged soil. Based on test results obtained from 25 mixes, empirical equations to determine water-to-cement ratio, unit cement content, and replacement level of lightweight fine aggregates were formulated with regard to the targeted performance (compressive strength, dry density, initial slump, and air content) of lightweight aggregate concrete. From the proposed equations and absolute volume mixing concept, unit weight of each ingredient was calculated. The proposed mix design procedure limits the fine aggregate-to-total aggregate ratio by considering the replacement level of lightweight fine aggregates, different to previous approach for expanded fly ash and clay-based lightweight aggregate concrete. Thus, it is expected that the proposed procedure is effectively applied for determining the first trial mixing proportions for the designed requirements of concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.145-146
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• 2015

When using non KS aggregate muck pile in general, compared to when using KS aggregate, when obtaining an identical slump a high unit quantity of water was confirmed, and when designing the concrete mix the compressive strength of concrete decreased due to an increase in W/B. Therefore because the use of non KS aggregate decreases the liquidity, strength and durability etc. qualities of concrete from an overall performance point of view, there is a need for the used of KS aggregate and when using aggregate that does not adhere to KS standards, it is determined there is a need for appropriate concrete mix design and care.

• Journal of the Korea Institute of Building Construction
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• v.5 no.1 s.15
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• pp.63-68
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• 2005

Generally, aggregate may limit the workability, strength and durability of concrete, and good concrete cannot be made with aggregate of bad property including low strength, bad shape and grading. But recently, it has been insufficient in quantity to collect good natural aggregate because of exhaustion of aggregate resources. In case of Korea, the using ratio of crushed stone occupies about 97 percent of total coarse aggregate, and ratio of crushed sand occupies about 18.3 percent of total fine aggregate. This is an experimental study to compare and analyze the properties of crushed sand for concrete in capital region and concrete according to the replacement ratio of crushed sand to improve quality and mix design of concrete using crushed sand. According to test results, it was found that nearly all the properties of crushed sand satisfied with the value recommended by KS. And it is recommended that FM of crushed sand should be lowered by improvement of manufacture system or grading adjustment should be used because FM of crushed sand was a bit higher.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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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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• 1998.04b
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• pp.719-724
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• 1998

It is proposed in this paper to develop the rational mix design system of High-strength concrete which is adjusted in the domestic circumstances. 1) Collect a lots of data in order to introduce the optimum mix design which has relation among material variables which compose High-strength concrete and run by using SAS (Statistical analysis system) which is one of multivariate statistical analysis method. 2) Select the important material variables for mix design of High-strength concrete by major component analysis and propose the standard range of each material variable along the target strengths. From the results of this study, it was proposed the range of proper material variables in domestic circumstance, which are W/C, S/A, air and admixture amounts, etc, at the target strengths for concrete kind. Also it was developed the optimum mix design program of High-strength concrete according to target strength and size of aggregate and made mix design ease in domestic construction site.

• Steel and Composite Structures
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• v.29 no.1
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• pp.67-75
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• 2018

High performance concrete (HPC) depends on various parameters such as the type of cement, aggregate and water reducer amount. Generally, the ready concrete company in various regions according to the requirements and costs, mix design of concrete as well as type of cement, aggregates, and, amount of other components will vary as a result of moment decisions or dynamic optimization, though the ideal conditions will be more applicable for the design of mix proportion of concrete. This study aimed to apply dynamic optimization for mix design of HPC; consequently, the objective function, decision variables, input and output variables and constraints are defined and also the proposed dynamic optimization model is validated by experimental results. Results indicate that dynamic optimization objective function can be defined in such a way that the compressive strength or performance of all constraints is simultaneously examined, so changing any of the variables at each step of the process input and output data changes the dynamic of the process which makes concrete mix design formidable.

• International Journal of Concrete Structures and Materials
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• v.9 no.1
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• pp.1-20
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• 2015

This work is devoted to the study of fresh and hardened properties of concrete containing recycled gravel. Four formulations were studied, the concrete of reference and three concretes containing recycled gravel with 30, 65 and 100 % replacement ratios. All materials were formulated on the basis of S4 class of flowability and a target C35 class of compressive strength according to the standard EN 206-1. The paper first presents the mix design method which was based on the optimization of cementitious paste and granular skeleton, then discusses experimental results. The results show that the elastic modulus and the tensile strength decrease while the peak strain in compression increases. Correlation with the water porosity is also established. The validity of analytical expressions proposed by Eurocode 2 is also discussed. The obtained results, together with results from the literature, show that these relationships do not predict adequately the mechanical properties as well as the stress-strain curve of tested materials. New expressions were established to predict the elastic modulus and the peak strain from the compressive strength of natural concrete. It was found that the proposed relationship E-$f_c$ is applicable for any type of concrete while the effect of substitution has to be introduced into the stress-strain (${\varepsilon}_{c1}-f_c$) relationship for recycled aggregate concrete. For the full stress-strain curve, the model of Carreira and Chu seems more adequate.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.567-572
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• 2002

This research investigates experimentally an effect on the quality performances of the high flowing concrete according to binder types. The purpose of this study is to determine the optimum mix proportion of the high flowing concrete having good flowability, viscosity and no-segregation. For this purpose, two types using belite cement＋lime stone powder(LSP) and furnace slag cement+lime stone powder are selected and tested by design factors including water cement ratio, fine and coarse aggregate volume ratio. As test results of this study, the optimum mix proportion for binder types is as followings. 1) One type based belite cement ; water cement ratio $51^{\circ}C$, fine aggregate volume ratio $43^{\circ}C$ and coarse aggregate volume ratio $53^{\circ}C$, replacement ratio of LSP $42.7^{\circ}C$. 2) Another type based slag cement : water cement ratio $41^{\circ}C$, fine aggregate volume ratio $47^{\circ}C$ and coarse aggregate volume ratio $53^{\circ}C$, replacement ratio of LSP $13.5^{\circ}C$.