• 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.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.540-548
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• 2002

The purpose of this study is to analyze the application of oyster shells (OS) as aggregates for concrete. For this purpose, five reference mixes with W/C ratios of 0.4 ∼0.6 at intervals of 0.05 were used. The replacement proportion of OS was varied with ratios of 0, 10, 30, 50 and 100％ by volume of fine or coarse aggregate in the reference mixes. OS was washed and crushed for using as aggregates. New chemical reaction between crushed OS aggregate and cement paste was tested through XRD and SEM analysis. Two strength properties (compressive and flexural) were considered. Strength tests were carried out at the ages of 1, 3, 7, 14 and 28 days. The variations of workability, air content and density, drying shrinkage of the specimens with different proportions of OS were also studied. Finally, the hollow concrete block using OS as a substitute material for fine aggregate was made for testing the application of OS. Experimental results showed that my new chemical reaction did not occur due to mixing OS in concrete. The workability and strengths decreased with increase in proportion of OS. The same trend was observed in density and unit weight, but air content increased due to the inherent pores in OS, which showed a possibility to produce light weight concrete with low strength by using OS as coarse aggregates for concrete. Tests on hollow concrete block showed that the compressive strength and absorption ratio were satisfied with quality requirements when the fine aggregate was substituted with OS up to 50％ in volume.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.6
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• pp.258-263
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• 2008

The fine aggregates of below 2 mm size was fabricated using by the vertical furnace in which the aggregates could be sintered at floating state and its physical properties were analyzed. The liquid formed at the surface of specimens sintered at $1200{\sim}l300^{\circ}C$ induced a gas in core to expand so the denser shell and porous core could be produced. The C series specimen fabricated by crushing an extruded body had an irregular shape and sharp edges but those became spheroidized by bloating due to gas expansion inside. The fine aggregates fabricated in this study was as light as floating in the water and had an apparent density of $0.68{\sim}1.08$. The absorption rate was proportioned to a porosity showing that the pores in core was not closed completely. The properties of fine aggregates fabricated in vertical furnace were similar with those of in an electric muffle furnace but the sticking-together phenomenon by surface fusion was not occurred in the vertical furnace. The aggregates fabricated in this study had a little lower impact resistance than that of natural aggregate but satisfied the unit volume weight standard specified in KS.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.283-290
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• 2009

Differently from fly ash, the bottom ash produced from thermoelectric power plant has been treated as an industrial waste matter, and almost reclaimed a tract from the sea. If this waste material is applicable to foam concrete as an aggregate owing to its light-weight, however, it may be worthy of environmental preservation by recycling of waste material as well as reducing self-weight of high-rising structure and horizontal forces and deformations of retaining wall subject to soil pressure. This study has an objective of evaluating the effects of application of bottom ash on the mechanical properties of foam concrete. Thus, the ratio of bottom ash to cement was selected as a variable for experiment and the effect was measured in terms of unit weight of concrete, air content, water-cement ratio and compressive strength. It can be observed from experiments that the application ratios have different effects on the material parameters considered in this experiment, thus major relationships between application ratio and each material parameter were finally introduced. The result of this study can be applied to decide a mix design proportion of foam concrete while bottom ash is used as an aggregate of the concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.152-153
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• 2013

Based on the Fire Service Act of mandatory provision, new buildings are strictly forced to use fire protection materials. Flame resistant EPS is one of those materials. Unlike conventional EPS that can be fused to make EPS ingot and be recycled for various purposes, flame resistant EPS waste cannot be recycled due to the presence of protective coating that is applied to increase the fire protection properties of EPS. A suitable alternative that can process large amount of flame resistant EPS wastes needs to be developed, and one of the possible alternative is to use them as construction materials. In this research, experiments were designed to observe whether the flame resistant EPS wastes can be utilized as partial replacements of fine aggregates in cement mortar. The replacement ratio of waste EPS was varied, and its effect on compressive strength and absorption capacity was investigated. According to the experimental results, both compressive strength and absorption capacity met the Korean Standard specification for cement bricks and blocks, indicating that flame resistant EPS wastes can be used for construction purposes.