• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.383-386
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• 2005

This paper is to investigate the effect of W/B, blend ratio of crushed sand with sea sand on fluidity and strength properties of high strength concrete utilizing crushed sand. W/B set up 0.25, 0.30, 0.35 and the blend ratio of crushed sand with sea sand set up 0:100, 30:70, 50:50, 70:30, 100:0 The results of this study are summarized as the follows; 1) The increase of the blend rate of crushed sand, affected on the enhancement of flow, the increase of dosage of SP and water content, but the decrease S/a 2) Compressive strength is increased when crushed sand $30\~70\%$ was replaced with sea sand. 3) The optimal replacement percentage of crushed sand is $50\%$ with sea sand.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.473-476
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• 2006

As a part of efforts to obtain high quality and economical efficiency of concrete, blast-furnace slag has been utilized by means of cement replacement. Therefore superior performance can be ensured, environmental pollution can be prevented and economical advantage can be obtained with utilization by cement replacement. But the studies on the blast-furnace slag are not systematic and reasonable. So, it was planed that basic data in regard to technique of manufacturing and economic improvement of concrete is showed with experimental comparison and investigation of Fluidity and engineering properties of concrete utilizing blast-furnace, industry by-product, as cement replacement in this study.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.110-111
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• 2014

Amount of slag which is a recycled aggregate that be produced as a industrial by-product from steel production process is increasing. But there is few suggestions for usage of slag except for shaft furnace slag and studies for utilizing this are lacked. In this study, it reviews flow characteristics according to replacement ratio of rapid cooling steelmaking slag from the perspective of rheology. Replacement ratio of ps ball is used by replacing 40, 45, 50% for each binder mass.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.27-30
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• 2003

This study is investigated the various properties and drying shrinkage of concrete according to water content under the condition proper fluidity is adjusted, in order to suggest the method for reduction of crack by drying shrinkage. According to the results, though water content varies, slump and air content are satisfied to the planed values, but shear slump and separation happen at water content of 120 and 140kg/$m^3$ due to the overuse of superplasticizer(SP). As water content is diminished, setting time is retarded by an increase of the using amount of SP, and compressive and tensile strength increase in the range of 160-180kg/㎥ of water content, but decrease significantly at 120 and 140kg/$m^3$. Length change by drying shrinkage decrease with a decrease of water content. Therefore, considering not only drying shrinkage but also fluidity, setting time and strength, it proves that the most appropriate water content of concrete is 160kg/$m^3$ in the condition of this experiment.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.44-47
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• 2003

High flowing concrete has not spread whole in the normal concrete structure, because it requires special quality control technique. Recently owing to the lack of natural resources and reinforcement of environmental standard, the construction cost of cement is rapidly increased. Also ready mixed concrete industry has gone through various economical difficulty as the manufacture cost of concrete is increased. So, the purpose of this study is to evaluate the qualities of middle fluidity concrete using the fly-ash and portland blast-furnace slag cement in order to decrease the amount of cement and resolve the problem of the quality control of high flowing concrete and the manufacture cost. The results of this study show that it reduces the amount of addition of superplasticizer and develope properties of concrete to the use the fly-ash and portland blast-furnace slag cement.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.393-394
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• 2010

This paper was examined the plastic viscosity and yield stress of paste and mortar on the part of the research to develop low viscosity and high fluidity concrete for high pumpability. Through this study, we examined the suitable material properties of paste and mortar to low viscosity and high fluidity concrete for high pumpability.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.81-87
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• 2003

The purpose of this study is the development of a recycling process to recover the hydrated ability of cement hydrate which accounts for a large proportion of cementitious powder by concrete waste in order to recycle cementitious powder by concrete waste as recycle cement. Therefore, after having theoretical consideration based on the properties of high-heated concrete, we consider the properties of hydration of cementitious powder in hardened mortar under various temperature conditions. As a result of experiment, it is revealed that an effective development of recycling cement is possible since the cementitious powder by concrete waste recovers a hydraulic property during burning at $600^{\circ}C$ or $700^{\circ}C$. And it is shown that the fluidity of mortar decreases rapidly as the burning temperature of recycle cement increases. however, the improved effect of fluidity is predominant if adding the additive such as fly-ash or blast furnace slag.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.89-94
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• 2003

Recently, the study to reduce and recycle industrial waste is underway vigorously in the various fields of industry according to the conservation of environment and resources. In construction work, the disposal problem of its waste and environmental disruption have already been serious all over the world. However the recycle of waste concrete is still at an early stage, recycled aggregate from waste concrete have only used those as subsidiary road fillers. The research institute and the company make the study that it is about the properties of recycled aggregate and those structural capacity since 1990. Through the experimentation last year, we know that strength and fluidity of recycle cement are inferior to normal cement, and admixing aggregate powder deteriorates its strength. The purpose of this study is to search for appropriate heating time and to improve performance of the recycle cement while heating hardened cement which is crushed, we investigate separating aggregate from hardened cement by preheating and improvement of strength and fluidity inrecycle cement which contains admixture.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.921-924
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• 2000

The purpose of this paper is to investigate the effects of admixture such as AE water reducing agent and Flyash on properties of cement mortar for floor. As for the effects of AE water reducing agent kinds, fluidity and air content increase in order for melamine type, lignine type and naphtalene type. As Flyash contents increase, fluidity shows high, but air content shows decline tendency. compressive strength according to AE water reducing agent kinds increase in order for melamine type, lignine type and naphtalene type. As AE water reducing agent content increases, it shows to be decreased. As for the effects of Flyash, it retards at early age but at later age it gains high with increase of Flyash contents due to pozzanic reaction. Drying shrinkage shows to be docreased slightly with increase of AE water reducing agent.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.929-932
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• 2000

In this paper, physical properties of fresh and hardened mortar for floor using expansion agent are described under various grain shape, grading and chloride contents of aggregates. According to experimental results, as fineness modulous increase, fluidity show high it also shows high with cement mortar using riversand and continuous distribution of grading. We can not detect any difference in fluidity according to chloride contents. Air content shows to be decreased with crushed stone having large fineness modulous and continuous distribute on of grading. chloride content does not influence on the air content. compressive strength tends to increase when crushed sand with continuous distribution of grading is used and chloride contents decreases.