• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.253-259
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• 2021

Plastic wastes generated from household waste are separated by mixed discharge with foreign substances, and recycling is relatively low. In this study, the effect of the ratio and content of mixed plastic waste coarse aggregate(MPWCA)s and mixed plastic waste fine aggregate(MPWFA)s filled with blast furnace slag fine powder on the slump and compressive strength of concrete was evaluated experimentally. The MPWCAs were found to have a similar fineness modulus, but have a single particle size distribution with a smaller particle size compared to coarse aggregates. However, the MPWFAs were found to have a single particle size distribution with a larger fineness modulus and particle size compared to fine aggregates. Meanwhile, the effect of improving the density and filling pores by the blast furnace slag fine power was found to be greater in the MPWFA compared to the MPWCA. As the amount of the mixed plastic waste aggregate(MPWA)s increased, the slump and compressive strength of concrete decreased. In particular, the lower the slump and compressive strength of concrete was found to decrease the greater the amount of MPWFA than MPWCA when the amount of MPWA was the same. This is because of the entrapped air and voids formed under the angular- and ROD-shaped aggregates among the MPWFAs. On the other hand, the addition of the admixture and the increase in the unit amount of cement were found to be effective in improving the compressive strength of the concrete with MPWAs.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.1
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• pp.48-53
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• 2009

The effect of bloating and fluxing agent on the microstructure and physical properties were studied in manufacturing the artificial lightweight aggregates of bulk density below] using clay and stone sludge. In case of the aggregates added only with bloating agent, the bulk density and water absorption were $0.5{\sim}1.0$ and $41{\sim}110%$ respectively but the microstucture was not uniform with a rough appearance. For the aggregates added with a fluxing agent and one bloating agent, a part of shell was lost due to explosion of specimen caused by over-bloating during a sintering. The mixed addition of bloating agents with vacuum oil, carbon and ${Fe_2}{O_3}$ made the microstructure homogeneous by generating an uniform black core and shell structure. The aggregates added with mixed agents and sintered at $1200^{\circ}C$ showed the bulk density 67 % lower and water absorption 48 times higher than those of the specimen with no additives. ]n this study, the artificial lightweight aggregates showing the bulk density of $0.5{\sim}1.0$ and water absorption of $50{\sim}125%$ could be fabricated to apply to various fields.

• 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.

• 한국해양학회지
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• v.12 no.2
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• pp.75-81
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• 1977

Distribution of drifting larvae of Anadara broughtnoii SCHRENCK was studied based on the planktonic sampling which has been collected in fifteen sampling areas of southern coast of Korea and Ulsan Bay during summer season from 1973 to 1977. Vertical and horizontal occurrence was analyzed related to the environmental factors such as surface water temperature, current velocity and depth of water column. High density of the larvae was observed in the Chinhae Bay which included the sampling areas Rampo, Sockcheon, Majeon, Changpo, Dangdong, Bedun, Changchoa, and Wonmun. Maximum occurrence of the farvae was accompanied with the highest water temperature of the summer season, and it was usually August when the water temperature was over 27$^{\circ}C$. In August, 1975, the highest density of the farvae was observed, when the mean surface water temperature was the highest compared to those of other years. The first appearence of the drifting larvae was also related to the surface water temperature. Each year the larae begin to appear from the late July and the ready-to-fall larvae appear in abundance from the mid-August. Vertical distribution patterns of the larvae are closely related to the depth of the water column as well as to the current velocity. In shallow water the larvae tend to aggregate in the bottom layer, while they are diffused to some extent in deep water. In shallow water column ( 8m) more or less 75% of the total larvae individuals was observed in the lower 4m layer and in deep water column ( 16m) only 45% of those was found in the lower 4m layer. In the water of lower velocity a large fraction of the larvae population is distributed in the lower depth layer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.715-723
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• 2017

This study investigates the properties of a high-performance cementitious composite with partial substitution of stone dust for fine aggregate. The relationship between the properties and particle size distribution was analyzed using several analytical models. Experiments were carried out to examine the flowability, rheology, and strength of cement mortars with different stone-dust replacement ratios of 0-30 wt.%. The results showed improved flowability, lower rheological parameters (yield stress and plastic viscosity), and improved strength as the amount of stone dust increased. These results are closely related to the packing density of the solid particles in the mortar. The effect was therefore estimated by introducing an optimum particle size distribution (PSD) model for maximum packing density. The PSD with a higher amount of stone dust was closer to the optimum PSD, and the optimization was quantified using RMSE. The improvement in the PSD by the stone dust was proven to affect the flowability, strength, and plastic viscosity based on several relevant analytical models. The reduction in yield stress is related to the increase of the average particle diameter when using stone dust.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2229-2233
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• 2015

The permeability of HMA(hot mixed asphalt) is a major influencing factor for long-term performance of the pavement. Especially, the lift thickness of the pavement during construction causes a wide range of physical properties of HMA. This study investigates the correlationship between the lift thickness and the physical properties of HMA through a series of laboratory experiments. The specimens were cored from a construction site of the dense graded asphalt pavement. The cored samples have various lift thickness and the number of compaction for the study. The results of the study show that the permeability of the sample decreases with the apperant density and t/NMAS, and the air void ratio. Therefore, the commonly used construction method as a constant lift thickness regardless of conditions needs to be reconsidered.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.785-788
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• 2008

This study is focused on applying heavyweight concrete to ballast used to have stability of a ship. Generally, heavyweight concrete is made from a high density aggregate like magnetite or limonite. However, these materials are hard to obtain them from relevant companies and so expensive. Therefore, this study plans to product heavyweight ballast concrete which is easy to obtain by recycled iron slag. Heavyweight ballast concrete isn't required to meet some compressive strength in use, but it is required to have high flowable and 2.7t/m3 of bulk density to fill the ballast tank densely. The designed field mix proportion of concrete based on the results of pre-experiment shows it can control the temperature crack and has superior chloride corrosion resistance after conducting chloride corrosion experiment. Also, it is prefer that before airtightness voltile corrosion inhibiter(VCI) is added in airtight space of shipyard.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.583-589
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• 2010

In this paper, the properties of reclaimed ash(RA) from various domestic thermal power plants(S, D and H) were analyzed, and the possibility of fabricating the artificial lightweight aggregate(ALA) using RA was studied. The chemical compositions of RA are similar to the clay, but it had higher concentrations of alkali earth metal oxides(CaO, MgO) and unburned-carbon. The TCLP(Toxicity Characteristic Leaching Procedure) results showed that the dissolution concentrations of heavy metal ions of RA were below the limitation defined by the enforcement regulation of wastes management law in Korea. The results of IC analysis showed that leaching concentration of $Cl^-$ ion was 124 ppm for RA of HN and ${SO_4}^{2-}$ ion was leached a few hundreds ppm for all RA in this study. The ALAs with various mass ratio of clay to reclaimed ash(RA:Clay = 7:3, 6:4, 5:5, 4:6, 3:7) were sintered with a electric muffle furnace at the temperature of $1050{\sim}1200^{\circ}C$. The specific gravity and water absorption(%) of the sintered ALAs were 1.1~1.8 and 10~30% respectively. The ALA sintered in the rotary kiln at $1125^{\circ}C$ showed a bulk density of 1.7 and water absorption of 15.2%.

• Journal of the Korean Ceramic Society
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• v.13 no.1
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• pp.11-19
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• 1976

This study was focused on the improvement of production techniques of small crucibles in relation with the appropriate selection of raw materials, various batch compositions and physical and chemical characteristics of the crucibles. Various tests gave the optimum batch composition for the carbon bond graphite cructble as follows: Pyontaek graphite flake (refractory aggregate) : 40Part Silicon carbide: 15Part Tar pitch (binder) : 11Part Inorganic additives (to improve the oxidation resistance) : 15 Part Cryolite : 3 Part Ferro manganese : 2 Part Ferrosilicon : 25 Part Crucibles pressed with 400kg/$\textrm{cm}^2$ at 12$0^{\circ}C$. and fired in reducing atmosphere at 120$0^{\circ}C$ brought the most favorable results as follows: Bulk density : 2.31 Apparent density : 2.58 Porosity : 15.2% Oxidation loss at 1, 50$0^{\circ}C$. for 3 hrs : below 3.77% Water absorption : 6.01% Compressive strength : 438kg/$\textrm{cm}^2$ Tensile strength : 256kg/$\textrm{cm}^2$.

• Development and Reproduction
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• v.18 no.4
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• pp.213-224
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• 2014

Previously we have shown that human abdominal adipose derived-stem cells (ADSCs) could aggregate during the high-density culture in the presence of human serum (HS). In the present study, we observed that human cord blood serum (CBS) and follicular fluid (HFF) also induced aggregation. Similarly, porcine serum could induce aggregation whereas bovine and sheep sera induced little aggregation. qRT-PCR analyses demonstrated that, compared to FBS-cultured ADSCs, HS-cultured cells exhibited higher level of mRNA expression of CLDN3, -6, -7, -15, and -16 genes among the tight junction proteins. ADSCs examined at the time of aggregation by culture with HS, BSA, HFF, CBS, or porcine serum showed significantly higher level of mRNA expression of JAM2 among JAM family members. In contrast, cells cultured in FBS, bovine serum or sheep serum, showed lower level of JAM2 expression. Immunocytochemical analyses demonstrated that the aggregates of HS-cultured cells (HS-Agg) showed intense staining against the anti-JAM2 antibody whereas neither non-aggregated cells (HS-Ex) nor FBS-cultured cells exhibited weak staining. Western blot results showed that HS-Agg expressed JAM2 protein more prominently than HS-Ex and FBS-cultured cells, both of latter reveled weaker intensity. These results suggest that the aggregation property of ADSCs during high-density culture would be dependent on the specific components of serum, and that JAM2 molecule could play a role in the animal sera-induced aggregation in vitro.