• Korean Chemical Engineering Research
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• v.44 no.3
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• pp.307-313
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• 2006

In order to improve the efficiency of methane steam reforming process, a part of the system which produces hydrogen from heavy hydrocarbon resources such as coal, we combined metal catalyst with CaO sorbent and fabricated catalyst/sorbent. To increase the porosity and the compressive strength of sorbent, carbon black and ${\alpha}-alumina$ were mixed with CaO powder during preparation. The effects of sorbent composition on the physical properties were investigated by SEM, TGA, BET, XRD, abrasion strength measuring device and adsorption-desorption instrument. Sorbent with 5 wt％ $Al_2O_3$ and 10 wt％ carbon black showed the best physical features with $7.61kg_f$ strength and 47％ $CO_2$ adsorption capability. Various metal catalysts such as Ni, Co and Fe were supported on the sorbent developed and 10 wt％ Ni/sorbent was selected for methane steam reforming process based on the result of reaction experiment. The reaction system using the catalyst/sorbent showed better $H_2$ productivity compared to the detached system with catalyst and sorbent, indicating the effectiveness of the system developed in this study.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.1-10
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• 2018

Although the soil nailing method is generally used as a gravity grouting, the development and application of pressurized grouting method has recently increased to address the problem of joint generation and filling due to grouting. Pressurized grouting of the soil nailing method is generally used in combination with ordinary portland cement and water. In the field, the cement is mixed with the rapid setting cement to reduce curing time because ordinary portland cement takes more than 10 days to satisfy the required strength. In this study, uniaxial compression tests and laboratory tests were carried out to confirm the efficiency of the grouting material according to the mixing ratio of rapid setting cement. The mixing ratio of 30% grouting satisfies the required strength within 7 days and satisfies the optimum gel time. As a result of the laboratory test with granite weathered soil, the reinforcing effect was confirmed to be 1.5 times as compared with the gravity type at an injection time of 10 seconds and a strain of 15%. The friction resistance increases linearly with the increase of the injection time, but it is confirmed that the friction resistance decreases due to the hydraulic fracturing effect at the injection time exceeding the limit injection pressure. Numerical analysis was performed to compare the stability of slopes not reinforced with slopes reinforced with gravity and pressurized soil nailing.

• Geomechanics and Engineering
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• v.17 no.4
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• pp.333-342
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• 2019

Geological dynamic hazards during coal mining can be caused by the failure of a composite system consisting of roof rock and coal layers, subject to different loading rates due to different advancing velocities in the working face. In this paper, the uniaxial compression test simulations on the composite rock-coal layers were performed using $PFC^{2D}$ software and especially the effects of loading rate on the stress-strain behavior, strength characteristics and crack nucleation, propagation and coalescence in a composite layer were analyzed. In addition, considering the composite layer, the mechanisms for the advanced bore decompression in coal to prevent the geological dynamic hazards at a rapid advancing velocity of working face were explored. The uniaxial compressive strength and peak strain are found to increase with the increase of loading rate. After post-peak point, the stress-strain curve shows a steep stepped drop at a low loading rate, while the stress-strain curve exhibits a slowly progressive decrease at a high loading rate. The cracking mainly occurs within coal, and no apparent cracking is observed for rock. While at a high loading rate, the rock near the bedding plane is damaged by rapid crack propagation in coal. The cracking pattern is not a single shear zone, but exhibits as two simultaneously propagating shear zones in a "X" shape. Following this, the coal breaks into many pieces and the fragment size and number increase with loading rate. Whereas a low loading rate promotes the development of tensile crack, the failure pattern shows a V-shaped hybrid shear and tensile failure. The shear failure becomes dominant with an increasing loading rate. Meanwhile, with the increase of loading rate, the width of the main shear failure zone increases. Moreover, the advanced bore decompression changes the physical property and energy accumulation conditions of the composite layer, which increases the strain energy dissipation, and the occurrence possibility of geological dynamic hazards is reduced at a rapid advancing velocity of working face.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.415-423
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• 2006

As the shortage of natural & good quality aggregate for concrete, it is needed development of alternative aggregate. At the present time, the crushed sand is widely used among the alternation aggregate, and the usage of crushed sand will be increased more and more. Generally, crushed sud is produced with wet process in domestic, but some manufacturing companies which are handicapped with local restrict are produced by dry process. In this study, analyzing the facilities of dry crushed sand, the quality properties of dry crushed sand was done by Korean Industrial Standards. Based on the quality results of dry crushed sand, the experiment of concrete with the dry crushed sand which is substitute for sea sand was done. As the results of basic qualities, the amount of 0.08 mm sieve passing ratio was over KS criteria, and the fineness modulus was higher than sea sand, and the other physical properties of dry crushed sand was similar to sea sand. The results of concrete experiment, according to the substitutive ratio of dry crushed sand is increased, the slump and air content of concrete was decreased by increase of fine particles of dry crushed sand, and the unit weight content, compressive & tensile strength of concrete were increased on the contrary. The physical properties of concrete used dry crushed sand were showed same tendency without relation to W/B. Consequently, if the fine particle contents of dry crushed sand was lower, it is judged that dry crushed sand is no problem to use for concrete aggregate and the amount of usage will be increased.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.1 s.53
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• pp.97-105
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• 2009

Development and use of blended cement concrete is gaining more importance in the construction industry with reference to durability mainly due to the pore refinement and reduction in permeability. Cracks play a major role on important parameters like permeability, rate of chloride ingress, compressive strength and thus affect the reinforcement corrosion protection. Furthermore, when a crack occurs in the cover concrete, the corrosion of the steel reinforcement may be accelerated because the deterioration causing factors can pass through the crack. In recent years the effect of cracking on the penetration of concrete has been the subject of numerous investigations. Therefore assessing the service life using blended concrete becomes obviously in considering the durability. In the present study, the corrosion assessment of composite concrete beams with and without crack with of 0.3mm using OPC, 30% PFA, 60% GGBS, 10% SF was performed using half cell potential measurement, galvanic potential measurement, mass loss of steel over a period of 60days under marine environmental conditions and the results were discussed in detail.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.155-162
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• 2005

This paper presents an invetigation into the cause of deterioration of wet surrounding RC structures subjected to checmical attacks such as sewage. The antibacterial-reforming agent is developed after determining the permeability of the RC structure. After application of the anitbacterial-reforming agent through SEM, the permeability, compressive strength properties and the micro-structure of the concrete were evaluated for durability. In addition, the antibacterial-reforming agent was combined with a protective coating for the wet surrounding RC structure and evaluated for durability. The combined effect of the antibacterial-reforming agent and the protective coating were evaluated in field tests in both sewer system and tunnel sites.

• Journal of the Korean Geotechnical Society
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• v.31 no.11
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• pp.33-40
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• 2015

Volcanic rocks in Jeju Island indicate the differences in geological and mechanical characteristics from region to region, and have vesicular structure caused by various environmental factors. In this study, triaxial compressive strength tests were conducted for intact rocks sampled in northeastern onshore and offshore, southeastern offshore and northwestern offshore of Jeju Island. The estimated cohesion and internal friction angle from the results of triaxial compression tests were compared and analyzed with absorption, a parameter representing the vesicular properties of basalts in Jeju Island. As a result, it was found that the relationship between cohesion and absorption could be classified clearly, considering two different linear relationships in bulk specific gravity and absorption. As the absorption increases, the cohesion decreases exponentially. In addition, the internal friction angle decreases almost linearly with increasing in the absorption, regardless of the relationships in bulk specific gravity and absorption.

• Journal of the Korean Geotechnical Society
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• v.21 no.4
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• pp.21-29
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• 2005

Lightweight Foamed Soil (LWFS) could be the substitute of normal soils used in backfill to earth structures and embankment materials far soft ground improvement in port and harbor project because of its effectiveness in settlement reduction and earth pressure decrease due to its lightness. A series of triaxial and unconfined compression tests were performed to investigate behaviors of LWFS composed of dredged soils, cement and air foam, and cured at underwater conditions. The density of LWFS will increase if LWFS is cured at underwater conditions because high water pressure makes air foam disappear or demolish during the curing compared with LWFS cured at normal air conditions. This paper is to find the mechanical behaviors of LWFS cured at seawater depth of 5.0 m and 10.0 m, respectively, which simulates underwater curing conditions by underwater pressure simulator chamber developed during this study. In addition, new normalized factor formula, which takes account of mixing design conditions determining compressive strength of LWFS, was proposed to consider mixing design factor fur LWFS.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.316-321
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• 2016

This study developed an eco-block for grass growth using the expanded vermiculites that absorb bacteria selected considering for the high pH and dry environments and plant growth. For the developed eco-block, a fundamental properties including compressive strength gain and water absorption and ecology characteristics were tested. The selected bacteria was Bacillus alcalophilus a nd Rhodoblastus acidophilus and had high concentration of $10^9cell/mL$. The expanded vermiculite that was used for shelter of bacteria was added by 7.5% and 10% replacement of the natural aggregates by volume. The developed eco-block achieved the minimum requirements specified in SPS provision and significantly effective in reducing chemical Chemical Oxygen Demand(COD) concentration and enhancing the growth of fish and plant.

• Journal of the Korea Institute of Building Construction
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• v.16 no.3
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• pp.247-255
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• 2016

The exothermic property of electrical conductivity concrete would allow the heating system of house or snow melting system of tunnel, road or bridge deck. This study was performed on electric resistance, exothermic property and mechanical property of the mortar with graphite of carbon-based conductive material as a fundamental research for the heat conductive concrete development. As the results of this experiment, the increasement on the amorphous graphite substitution rate was found to decrease in the compressive strength, however, the electric resistance was found to be significantly lower. And, in order to demonstrate the exothermic property, the graphite was found to be included more than 15% of the total mortar volume. When low electric resistance obtained with a certain level of the graphite inclusion, exothermic value and applied voltage has a higher correlation, and the exothermic value and the square of the voltage appeared to be in a proportional relationship.