• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.513-520
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• 1999

20 million tons of coal ash has been produced in Korea annually. This causes the environmental problems and the cost of land for ash pond. However the amount of coal ash for recycling is small because of the low level of recycling technology and the ignorance. As the coal ash has the significant engineering properties, it can be utilized as soft ground stabilizer, backfill materials and so forth. The purpose of this paper is to summarize some of the recycling methods of coal ash. One is structural backfill materials, the other is flowable fill. Optimal mixture ratio(fly ash : bottom ash) is determined for structural backfill materials and the model test is performed. The model test accompanied with physical tests were executed for identifying that the flowable fly ash can be used as fill materials such as trench back filling.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.4
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• pp.365-373
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• 2016

Composites are the most useful restorative material. However, composites have some disadvantages such as polymerization shrinkage, long working time, and susceptibility to water and contamination, which are stood out more especially when treating children. To solve these problems, bulk-fill composites have been developed. The aim of this study is to compare mechanical properties of bulk-fill and conventional composites. Bulk-fill composites (SureFil SDR flow (SDR), Tetric N-Ceram bulk fill (TBF)) and conventional composites (Filtek Z-350 (Z-350), Unifil Flow (UF), Unifil Loflo Plus (UL)) were used. The Vickers hardness tester was used to measure the microhardness of materials, and Fourier transform infrared spectroscopy was used to measure the degree of conversion. Polymerization shrinkage was measured by using a linometer. Flexural and compressive properties were measured by using the universal testing machine. Data were statistically analyzed by ANOVA and Scheffe's post hoc test. The level of significance was set to p < 0.05. Most conventional composites showed higher microhardness than bulk-fill composites. However, bulk-fill composites showed a higher top/bottom microhardness ratio than conventional composites. Bulk-fill composites showed a higher top/bottom degree of conversion ratio than conventional composites. The polymerization shrinkage was highest in UL and lowest in Z-350. The polymerization shrinkage of flowable composites was higher than that of non flowable composites. The compressive properties were highest in Z-350 and lowest in SDR and UL. In terms of flexural properties, Z-350 was the highest. However, none of the bulk-fill composites exhibited mechanical properties as good as those of conventional composites. Nonetheless, the ratio of microhardness and degree of conversion, which are important properties of bulk filling, were higher in bulk-fill composites. Therefore, the bulk-fill composites might be considered suitable restorative materials in pediatric dentistry.

• Restorative Dentistry and Endodontics
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• v.40 no.4
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• pp.262-269
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• 2015

Objectives: The aim of this study was to evaluate the mechanical and physical properties of a newly developed fiber reinforced dental composite. Materials and Methods: Fiber reinforced composite EverX Posterior (EXP, GC EUROPE), and other commercially available bulk fill composites, including Filtek Bulk Fill (FB, 3M ESPE), SonicFill (SF, Kerr Corp.), SureFil (SDR, Dentsply), Venus Bulk Fill (VB, HerausKultzer), Tetric evoceram bulk fill (TECB, Ivoclar Vivadent), and Xtra Base (XB, Voco) were characterized. Composite samples light-cured with a LED device were evaluated in terms of flexural strength, flexural modulus (ISO 4049, n = 6), fracture toughness (n = 6), and Vickers hardness (0, 2, and 4 mm in depth at 24 hr, n = 5). The EXP samples and the fracture surface were observed under a scanning electron microscopy. Data were statistically analyzed using one-way ANOVA and unpaired t-test. Results: EXP, FB, and VB had significantly higher fracture toughness value compared to all the other bulk composite types. SF, EXP, and XB were not statistically different, and had significantly higher flexural strength values compared to other tested composite materials. EXP had the highest flexural modulus, VB had the lowest values. Vickers hardness values revealed SF, EXP, TECB, and XB were not statistically different, and had significantly higher values compared to other tested composite materials. SEM observations show well dispersed fibers working as a reinforcing phase. Conclusions: The addition of fibers to methacrylate-based matrix results in composites with either comparable or superior mechanical properties compared to the other bulk fill materials tested.

• Journal of the Korea Concrete Institute
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• v.12 no.1
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• pp.113-125
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• 2000

The purpose of this study was to examine the durability characteristics of controlled low strength material(flowable fill) with high volume fly ash content. Flowable fill refer to self-compacted, cementitious material used primarily as a backfill in lieu of compacted fill. The two primary advantages of flowable fill over traditional methods are its ease of placement and the elimination of settlement. Therefore, in difficult compaction areas or areas where settlement is a concern, flowable fill should be considered. The fly ash used in this study met the requirements of KS L 5405 and ASTM C 618 for Class F material. The mix proportions used for flowable fill are selected to obtain low-strength materials in the 10 to 15kgf/$\textrm{cm}^2$ range. The optimized flowable fill was consisted of 60kg f/$\textrm{m}^3$ cement content, 280kgf/$\textrm{m}^3$ fly ash content, 1400kgf/$\textrm{m}^3$ sand content, and 320kgf/$\textrm{m}^3$ water content. Subsequently, durability tests including permeability, warm water immersion, repeated wetting & drying, freezing & thawing for high volume fly ash-flowable fill are conducted. The results indicated that flowable fill has acceptable durability characteristics.

• Journal of the Korean Geosynthetics Society
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• v.12 no.2
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• pp.25-33
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• 2013

This study introduces strength characteristics of the anti-washout grouting material using viscous modifiers and its characteristics mixed with coarse materials. Especially, this study focused on the strength characteristics of the grouts mixed with sea water. It is found that the anti-washout grout mixed with sea water has enough strength and good resistance to segregation just like that with fresh water. Also, a small scale test was performed to evaluate the solidification characteristic of the anti-washout grout mixed with coarse fill materials. It is also found that the strength of anti-washout grout mixed with coarse fill materials is greater and better segregation resistance than those of conventional grout with fill materials.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.3
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• pp.47-54
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• 2012

As a large construction such as highway, dam, reclaimed land etc. increase in number more and more, large amount of fill materials are required. It is needed to utilize a gypsum which is a by-product yielded from chemical plants, as fill materials. Though some studies have been conducted to know a engineering characteristic of gypsum, it is not certain that water contents were checked at $45^{\circ}C$ dry oven. This study proposed that water contents must be measured at $45^{\circ}C$ dry condition because gypsum is changed to other types as a dry temperature. As the results obtained by compaction tests, it is found that moisture of gypsum in compaction must be within -5.0~2.5 % O.M.C (optimal moisture content).

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1452-1457
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• 2010

Recently, coal ash is used as resources to make controlled low-strength material (CLSM) which a self-compacted, cementitious material used primarily as a backfill in lieu of compacted fill. Pozzolanic reaction is strongly related with self-cementation of coal ashes. However, this reaction depends on pozzolanic content in fill materials and is disappeared in 2-3 days after placement of coal ash fill. Therefore, state of coal ash fill is commonly very loose and not appropriate for foundations of structures without special treatments. In this study, a coal ash placement device was developed to place coal ashes effectively to improve density of coal ash fills. The device consists of a ribbon type mixer to obtain homogeneous materials mixture and a piston type pump for density control of fill materials. Based on several laboratory test results, more stable coal ash fill state can be obtained with controlling placement pressure.

• Korean Journal of Materials Research
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• v.26 no.9
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• pp.455-459
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• 2016

The deposition process for the gap-filling of sub-micrometer trenches using DMDMOS, $(CH_3)_2Si(OCH_3)_2$, and $C_xH_yO_z$ by flowable chemical vapor deposition (F-CVD) is presented. We obtained low-k films that possess superior gap-filling properties on trench patterns without voids or delamination. The newly developed technique for the gap-filling of submicrometer features will have a great impact on IMD and STI for the next generation of microelectronic devices. Moreover, this bottom up gap-fill mode is expected to be universal in other chemical vapor deposition systems.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.818-823
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• 2006

In this study, the suitability of CFGD(concrete faced gravefill dam) was investigated by examining the strength and deformation characteristics of a gravelfill material, a CFGD main fill material, and comparing them with those of several rockfill dam materials. The gravelfill material exhibited similar strength and deformation properties to those of the main fill materials of existing stable large rockfill dams. Since not only CFGD has environmental and economic advantages over CFRD, but its main fill material compares favorably with those of the existing stable CFRDs, CFGD may be the best choice when natural gravel materials are abundant in the vicinity of the dam construction location.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.667-675
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• 2008

As a large construction such as highway, dam, reclaimed land etc. increase in number more and more, large amount of fill materials are required. However, it's difficult to obtain it because of environmental problems and economical efficiency. A alternative plan is to utilize a gypsum which is a by-product yielded from chemical plants and verify suitability to use gypsum as fill materials. Therefore, a characteristic of compaction for gypsum is analyzed and construction methods are given regard to this characteristic from construction of dike using gypsum. Based on the results obtained, it is found that moisture of gypsum in compaction should to be more dry side of O.M.C(optimal moisture content) because of sponge phenomenon. When gypsum is used to fill materials, standards of compaction should be decided from laboratory test.