• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.195-198
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• 1999

Fly ash is the most common artificial pozzolan, which is a material precipitated electrostatically from the exhaust gases of coal-fired power stations. Fly ash can be used as the supplementary material as well as the material for high performance concrete and hence, the development of high-volume fly ash concrete is imperative. In this study, the characteristics of drying shrinkage of high volume fly ash concrete is investigated. It is found from test results that as the replaced amount of fly ash in concrete is increased, drying shrinkage of concrete is reduced.

• International Journal of Concrete Structures and Materials
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• v.2 no.2
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• pp.161-167
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• 2008

Optimization of concrete mixing system is very important for the production of quality mixture of concrete and requires very complicated, specialized knowledge as there are a variety of variables that influence the result. One of the methods of optimizing the concrete mixing system is to minimize the volume of cement paste which, in turn, means maximizing the volume of aggregate. The purpose of this study is to determine the minimum volume of cement paste used in the design of concrete mixture and to design the optimum concrete mixing system based on the fluidity of mortar and concrete. In determining the minimum volume of cement paste, experiments of mortar and concrete were performed based on their workability, material segregation and bleeding. Type of aggregate, granularity distribution and sand percentage were used as test parameters and measurements were taken of the distribution of granularity, usage of HRWRA, minimum volume of paste and drying shrinkage and compressive strength of concrete.

• Nuclear Engineering and Technology
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• v.42 no.2
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• pp.175-182
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• 2010

As part of a fundamental study on the volume reduction of contaminated concrete wastes, the separation characteristics of the aggregates and the distribution of the radioactivity in the aggregates were investigated. Radioisotope $^{60}Co$ was artificially used as a model contaminant for non-radioactive crushed concrete waste. Volume reduction for radioactively contaminated dismantled concrete wastes was carried out using activated heavy weight concrete taken from the Korea Research Reactor 2 (KRR-2) and light weight concrete from the Uranium Conversion Plant (UCP). The results showed that most of the $^{60}Co$ nuclide was easily separated from the contaminated dismantled concrete waste and was concentrated mainly in the porous fine cement paste. The heating temperature was found to be one of the effective parameters in the removal of the radionuclide from concrete waste. The volume reduction rate achieved was above 80% for the KRR-2 concrete wastes and above 75% for the UCP concrete wastes by thermal and mechanical treatment.

• KIEAE Journal
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• v.15 no.4
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• pp.45-52
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• 2015

Purpose: Foam concrete is the concrete that contains large amount of air voids inside. In general, the density of foam concrete depends on parameters like water/binder ratio, foam volume, aggregate and pozzolan content, etc. Method: In this study, the effect of foam volume and fly ash content on dry density is investigated intensively in order to find the relationship between each parameter and their abilities to counteract with each other. According to the above information, though there are quite a number of studies on the effect micro fiber on foam concrete at low volume fractions, there is still lack of information especially on the high fiber content side. The objective of the second study is to investigate further on the use of micro fiber at higher volume fraction and fill in the lacking information. Beside from this study, the investigation of the effect of micro-fiber (polypropylene) to enhance the properties of foam concrete is also carried out. Result: Of the two variables that are investigated in this study, the foam volume and the fly ash content, show significant effect on the properties of foam concrete. The foam volume tends to decrease the density and strength of foam concrete. In the second part of our study, a large fibre volume fraction is proved to be able to evidently increase the flexural strength of foam concrete up to about 40% due to the effect of fibre bridging over the crack and a significant number of fibres that intercepts the crack surfaces. However, the compressive strength is found to decrease severely due to the occurrence of large pores as the result of fibre being added into concrete mixture.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.203-206
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• 1999

An experimental study is carried out to investigate the characteristics of concrete containing high volume fly ash. The compressive and tensile strength of fly ash concrete is slightly lower than those of ordinary concrete between 7and 28 days, however, the long-term compressive strength is significantly higher at 180 days. In durability, the high volume fly ash concretes are generally higher resistance of freeze and thaw and lowe chloride penetration, however, the depth of carbonation is increased with increasing fly ash content.

• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.473-480
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• 2005

In this study, a mix design for self compacting concrete was based on Okamura's method and concrete incorporated just a ground granulated blast furnace slag. Replacement ratio of slag is in the range of $20-80\%$ of cement matrix by volume. For the optimal self compactability in mixture incorporating ground granulated blast furnace slag, the paste and mortar tests were first completed. Then the slump flow, elapsed time of 500mm slump flow, V funnel time and filling height by U type box were conducted in concrete. The volume of coarse aggregate in self compacting concrete was in the range of $50-60\%$ to the solid volume percentage of coarse aggregate. Finally, the compressive and splitting tensile strengths were determined in the hardened self compacting concrete incorporating ground granulated blast furnace slag. From the test results, it is desirable for self compacting concrete that the replacement of ground granulated blast furnace slag is in the range of $40-60\%$ of cement matrix by volume and the volume of coarse aggregate to the solid volume percentage of coarse aggregate with a limit of $55\%$.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.11a
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• pp.63-66
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• 2002

In this study, it does a high volume flyash substituted concrete experiments in two curing temperature circumstances - 35$^{\circ}C$, 2$0^{\circ}C$. High volume flyash concrete is tested in fresh concrete properties and hardeded concrete properties. In the fresh concrete test items, there is slump, air contents, concrete setting tests. 3, 7, and 28 days water curing compressive strength is measured in the hardened concrete test. The purpose of this study is to submit a various flyash concrete data for application to field. The result of this study is that the best strength is developed at the plain concrete cured 2$0^{\circ}C$ and Mixing F43 shows the best strength among specimens which cured at 35$^{\circ}C$

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.301-307
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• 1996

High flowing concrete has been made using a combination of much amount cementitious materials and addition of SP agents, so that it makes possible to high flowing properties of fresh concrete. In the fluid mechanical and rheological point of view, high flowing concrete is affected on the relation between cement paste and aggregate of volume. In this experimental study, it is measured high flowing concrete of slump-flow about 65$\pm$5cm according to 0.54~0.80 of volume ratio and to analysed the properties of high flowing concrete in fresh and hardened concrete. It is the aim of this study to consider the affection of high flowing properties accoring to cement paste to aggregate ratio of volume on the combination of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.275-280
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• 2002

To study of high volume fly -ash concrete replace cement and fine aggregate together. Proportion consideration economy cost and performance improve replacement high volume fly-ash. Experimentation study of high-strength which cement about fly-ash replacement maximum 50%Flash concrete tested slump, air contest, setting and Hardening concrete tested day of age 1, 3, 7, 28, 91 compression strength in underwater curing. Purpose of study is consultation materials in field that variety of fly ash replacement concrete mix proportion comparison and valuation.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.258-261
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• 1998

Aggregate is cheaper than cement and confers considerable technical advantages on concrete, which has a higher volume stability and better durability than hydrated cement paste alone. and coarse aggregate is the largest particle size out of concrete and is much affect on the fruidity, compaction and non-segregation ability of high flowing concrete. As the compaction, fillingability and shrinkage of high flowing concrete, the volume ratio of coarse aggregate is prescribed by Japanese Architectural Standard Specificateon (JASS 5) : from 0.500 to 0.500㎥/㎥. It is the aim of this study to compare and analysis the fruidity, fillingability and non-segregation of high flosing concrete according to the volume ratio of coarse aggregate of concrete(G/Glim).