• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.35 no.9
• /
• pp.199-206
• /
• 2019

Experimental study on the durability characteristics to examine the feasibility of concrete with high water-tightness and self-healing performance to minimize maintenance of concrete for artificial ground is as follows. 1) When blending agent, swelling agents, and curing accelerator were added on the ternary system cement with blast-furnace slag fine particles and fly ash to give a self-healing property, higher blending strengths by 82% at design standard strength of 24MPa and by 74% at design strength of 30MPa, respectively could be obtained. 2) The permeability test for the specimens having high water-tightness and no shrinkage showed that the permeability was reduced at maximum of 98%. However, the permeability was decreased as the design strength was increased, showing the reduction rate of 87% at the design strength of 50MPa. 3) The depth of carbonation of blast-furnace slag and fly ash was increased in all the specimens compared with those of OPC only. However, as the material age was increased, carbonation penetration depth was decreased compared with the reference blend. 4) Compared with the reference blending using only OPC, the freeze-thaw resistance was higher in the case of blending with 40% of blast-furnace slag and 10% of fly ash at the design standard strength of 50MPa. In addition, the freeze-thaw resistance in general was superior in the design standard strength of 50MPa with the lower water-binder ratio (W/B) as compared with the design standard strength of 24MPa and 30MPa with the high water-binder ratios.

• Journal of the Korean Ceramic Society
• /
• v.53 no.3
• /
• pp.354-361
• /
• 2016

The purpose of this study was to prepare lightweight foamed concrete by mixing coal fly ash of circulating fluidized bed combustion(CFBC) with cement, and to develop uses for recycling by analyzing carbonation behavior resulting from a change in conditions for pressurized carbonation. For concrete, CFBC coal fly ash was mixed with Portland cement to the water-binder ratio of 0.5, and aging was applied at room temperature after 3 days of curing at $20^{\circ}C$, RH 60%. For carbonation, temperature was fixed at $60^{\circ}C$ and time at 1 h in the use of autoclave. Pressures were controlled to be $5kgf/cm^2$ and the supercritical condition of $80kgf/cm^2$, and gas compositions were employed as $CO_2$ 100% and $CO_2$ 15%+N2 85%. In the characteristics of produced lightweight concrete, the characteristics of lightweight foamed concrete resulting from carbonation reaction were affirmed through rate of weight change, carbonation depth test, air permeability, and processing analysis for the day 28 specimen. Based on these results, it is concluded that the present approach could provide a viable method for mass production of eco-friendly lightweight foamed concrete from CFBC coal fly ash stabilized by carbonation.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.53 no.10
• /
• pp.546-550
• /
• 2004

Two fabrication approaches are proposed to planarize the sacrificial layer over hollow structures. One is the photoresist filling method that makes use of photolithography, thermal curing and plasma ashing. The other is the lamination method that is applying pressure and temperature to the organic film over the hollow structures. The fabrication results are compared with those of CMP process. Trenches and cavities with various dimensions have been made for the porposed process. Upon measuring the planarization levels, they are dependent on planarization methods and the geometrical size of hollow structures. The photoresist filling method is so strongly dependent on the width and depth of trenches that we have problems to use it for large dimensional trenches. To the contrary, the flatness of sacrificial layer over the trenches was found to be almost independent of trench dimensions for the lamination method. A CMP process shows the most excellent results, but the fabrication is complicated and the access to it is not so easy. It is important to choose the proper planarization method by considering the required flatness levels, materials to be planarized, and connection between the planarization step and the previous or the following process of it.

• Herbal Formula Science
• /
• v.9 no.1
• /
• pp.319-334
• /
• 2001

Objective: The present study has been undertaken to investigate the effects of Korean Carthami Semen and Estradiol-Carthami Semen co-treatment on osteoporosis in ovariectomized rats. Method: In this experiment, the rats were ovariectomized. Rats were administered 3 kinds of medicine, Korean Carthami Semen, Estradiol, and Estradiol-Carthami Semen, which were taken orally. The levels of bone mineral density, osteocalcin, estradiol, ALP, phosphorus, calcium in serum, deoxypyridinoline in urine, calcium, phosphorus, ash weight of bone, body weight and uterus weight were measured. Results: These experimetal results, it appears that the only Carthami Semen have more less efficacy on osteoporosis but $E_2$-Carthami Semen co-treated group showed more effective on osteoporosis. Conclusions: Further west-east medicine combination study should be conducted to illustrate in depth the curing osteoporosis.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2016.05a
• /
• pp.181-182
• /
• 2016

We developed eco-friendly lightweight concrete in order to apply eco-friendly lightweight concrete into structural wall or slab of shallow depth urban railway system. However, since lightweight aggregate has different structural feature of porous and it has been overvalued at current KS standard when applied, we did compare the characteristics of freezing and thawing of normal weight aggregate concrete by comparative test method(KS, ASTM). According to test method, there was a big difference of dynamic elastic modulus in lightweight concrete rather than in normal weight aggregate concrete. The big absorption factor in lightweight aggregate is main reason for that. For more detail, in KS law in which only 14 days water curing is carried out, the big amount of moisture in lightweight aggregate is frozen and high heaving pressure occurs and finally that lead to destruction of lightweight concrete. Therefore, it is considered that in case of lightweight concrete, resistibility against freezing and thawing has been undervalued in domestic KS law compared to ASTM law, which is overseas standard. So, a variety of examination about testing criteria and rule would be necessary for exact assessment of lightweight concrete.

• Restorative Dentistry and Endodontics
• /
• v.15 no.1
• /
• pp.67-80
• /
• 1990

This study was performed for elucidating the effects on surface polishing of composite resins. In this study, Silux(microfilled), Graft(hybrid), Bisfil- I (hybrid posterior) and Hi-pol(conventional) were used. Sixty specimens were made with 4 brands of composite resins and Optilux system in $2.0{\times}1.3{\times}1.0cm$ resin block which has a cavity with 0.5cm diameter and 0.5cm depth. Polishing was done with #600 sand paper and Soflex, Super-snap, Micron finishing system, or Composite polishing kit. Final polished surfaces were measured by roughness tester(Kasaka Lab. Ltd., Japan) and image analyser(Omnimet Image Analyser, Buehler, USA). The results were as follows, 1. The celluloid strip produced the smoothest surfaces. 2. Light curing microfilled composite resin, Silux, had smoother surface than any others. 3. The surfaces polished by Soflex were smoothest. 4. Aluminum oxide disk, Soflex and Super-Snap, made smoother surface than diamond bur, M.F.S., or silicon point, Composite polishing kit. 5. The roughness values of surface polished by M.F.S. composed of diamond burs, were less than those of Composite polishing kit made from silicone points.

• Advances in concrete construction
• /
• v.5 no.1
• /
• pp.31-48
• /
• 2017

Supplementary cementitious materials (SCM) have turned out to be a vital portion of extraordinary strength and performance concrete. Metakaolin (MK) is one of SCM material is acquired by calcinations of kaolinite. Universally utilised as pozzolanic material in concrete to enhance mechanical and durability properties. This study investigates the fresh and hardened properties of conventional concrete (CC) and self compacting concrete (SCC) by partially replacing cement with MK in diverse percentages. In CC and SCC, partial replacement of cement with MK varies from 5-20%. Fresh concrete properties of CC are conducted by slump test and compaction factor tests and for SCC, slump flow, T500, J-Ring, L-Box, V-Funnel and U-Box tests. Hardened concrete characteristics are investigated by compressive, split tensile and flexural strengths at age of 7, 28 and 90 days of curing under water. Carbonation depth, water absorption and density of MK based CC and SCC was also computed. Fresh concrete test results indicated that increase in MK replacement increases workability of concrete in a constant w/b ratio. Also, outcomes reveal that concrete integrating MK had greater compressive, flexural and split tensile strengths. Optimum replacement level of MK for cement was 10%, which increased mechanical properties and robustness properties of concrete.

• Journal of the Korean Wood Science and Technology
• /
• v.50 no.4
• /
• pp.256-271
• /
• 2022

Activated carbon (AC) derived from coconut shells (CS-AC) was obtained through pyrolysis at 700℃ and subsequently activated with H₃PO₄. AC was ground in a Wiley mill several times to form powder particles at particle scales of 80, 100, and 200 meshes. The characterization of the AC was studied using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FT-IR), and surface area analysis (S_BET). The CS-AC-200 mesh resulted in a higher percentage of mesopores and surface area. This particle size had a larger surface area with angular, irregular, and crushed shapes in the SEM view. The smaller particles had smoother surfaces, less wear, and increased curing depth and ratio of the hardness of the resin composite. Based on the characterization results of the AC, it is evident that CS-AC with a 200 mesh particle size has the potential to be used as a filler in biocomposites.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.28 no.3
• /
• pp.471-479
• /
• 2001

The purpose of this study was to compare the effect of the high intensity halogen light $(850\sim1000mW/cm^2)$ with that of the conventional halogen light $(400mW/cm^2)$ on the hardness of composite resin. Three resin composites (Z-100, 3M, U.S.A. : Tetric Ceram, Vivadent, Liechtenstein; SureFil, Dentsply, U.S.A.) were filed in the stainless steel moulds which were 4mm in diameter and 2, 3, 4, and 5mm in depth, respectively. They were cured under the four different modes : (1) conventional mode, 40 seconds at $400mW/cm^2$; (2) 'ramp' mode, 10 seconds at 100 to $1000mW/cm^2$ plus 10 seconds at $1000mW/cm^2$; (3) 'boost' mode, 10 seconds at $1000mW/cm^2$; and (4) 'standard' mode, 20 seconds at $850mW/cm^2$. The surface hardnesses of the top and the bottom of the resin samples were measured with a microhardness tester (MXT70, Matsuzawa, Japan). The top surface hardness was not significantly different among the curing modes. The bottom surface hardness was generally the highest in the conventional mode and the lowest in the high intensity boost mode. There was no significant difference in the bottom surface hardness between the conventional mode and the high intensity standard mode in 2mm depth. The results suggest that the curing time of the high intensity halogen light $(850mW/cm^2)$ should be at least 20 seconds to produce the equal level of the bottom surface hardness of 2mm resin composite as compared to the hardness produced by the conventional halogen light $(400mW/cm^2)$.

• Journal of the Korea Concrete Institute
• /
• v.20 no.4
• /
• pp.423-430
• /
• 2008

VES-LMC (very-early strength latex-modified concrete) has been widely used as repair material for bridge deck overlay or rehabilitation, because the overlaid or repaired could be opened to the traffic after 3 hours of curing. Although the field performance of VES-LMC generally indicates that it has an excellent bonding to the substrate and shows a long term performance, little quantitative data or research results have been presented in the literature on structural studies. The purpose of this study was to investigate the flexural behavior, interfacial performance, crack propagation, and strengthen effect of RC beam overlaid or repaired by VES-LMC through the 4-point flexural loading test. Two different types of RC beam were fabricated for repair and rehabilitation types. The test result showed that the strengthen effect, in term of flexural stiffness, increases as the depth of repair or overlay increases. More than 40% of stiffness was improved when the depth of repair was up to steel position. However, there was a little difference between 80 mm and 120 mm repaired beam. This means the repair depth must be considered. The interfacial behavior data showed that the repaired or overlaid beams had a little relative displacement. This means that two materials behave comparatively acting together. However, there were two specimens which had large displacement at the interface, because of poor bond strength. This suggested that interface treatment is one of the most important jobs in composite beams.