• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.118-125
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• 2011

The size and distribution of concrete void was one among the factor determining durability of concrete. Recently, there was a lot of researches related to the High-Fludity Concrete(HFC) with field applications. However, the research about the void structure having an effect on durability of concrete is insufficient. Therefore, in this research, Conventional Concrete(CC) and HFC using lime stone powder and fly-ash of 30 MPa range was manufactured and observed the void structure of CC and HFC. Experimental results showed that average pore diameter in the case of the 30 MPa range HFC was to be lower than CC and SEM analyzed result, HFC was firmer inner structure than CC.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.4
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• pp.251-257
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• 2011

In the present study, a 3-dimensional (3D) numerical model was developed to mimic the micro porous structure of a geological $CO_2$ storage reservoir. Especially, 3D modeling technique assigning random pore size to a 3D micro porous structure was devised. Numerical method using CFD (computational fluid dynamics) was applied for the 3D micro porous structure to calculate supercritical $CO_2$ flow field. The three different configurations of 3D micro porous model were designed and their flow fields were calculated. For the physical conditions of $CO_2$ flow, temperature and pressure were set up equivalent to geological underground condition where $CO_2$ fluid was stored. From the results, the characteristics of the supercritical $CO_2$ flow fields were scrutinized and the influence of the micro pore configuration on the flow field was investigated. In particular, the pressure difference and consequent $CO_2$ permeability were calculated and compared with increasing $CO_2$ flow rate.

• KSBB Journal
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• v.18 no.6
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• pp.448-454
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• 2003

We studied on the removal of toluene vapors in a lab-scale biofilter. There are three biofilters packed with reticulated polyurethane foams of different porosities of 15, 25, 45 PPI (Pore Per Inch) as media. A toluene-degrading strain (Pseudomonas Putida KCCM 11348, ATCC 12633) was naturally immobilized on the filter media by circulating the culture media. Three biofilters were operated under different sets of continuous experiments, varying both the design and operation parameters such as the inlet toluene concentration and the flow rate. Maximum elimination capacity of 115.5g/㎥hr of biofilter packed with foams of 25 PPI was obtained for toluene degradation. The effect of operating conditions such as flow rate, inlet toluene concentration and porosity on the performance of the biofilter was investigated.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.79-88
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• 2023

In this study, a development of the rust formation arising from steel corrosion was modelled to quantify the structural impact in steel reinforced concrete. The interfacial gap, cover depth and diameter of steel rebar were taken for variables in modelling. It was found that the interfacial gap was the most influencing on the structural limit at steel corrosion, followed by steel diameter and cover depth. At 75 mm of cover depth with 20 mm of the steel diameter, the rust amount to reach cracking accounted for 16.95-27.69 ㎛ to 1-10 ㎛ of the interfacial gap. It was found that there was no risk of cracking and structural limit until the rust was formed within the interfacial gap. With a further formation of rust, the concrete section was successively behaved to yielding, cracking and failure. Additionally, the interfacial gap was the most dominant parameter for the rust amount to reach the cracking of concrete at the interfacial zone, whilst the cover depth had a marginal effect on cracking but had a crucial influence on the rust to failure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.573-580
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• 2008

In this paper, we estimated the effect of the siliceous filler's particle size on the performance of Ultra High Performance Concrete (UHPC). Filler's particle diameters considered in this paper were about 2, 4, 8, 14, $26{\mu}m$ and the performance was evaluated by testing fluidity in fresh concrete, compressive strength, ultimate strain, elastic modulus and flexural strength in hardened concrete. We also carried out XRD and MIP tests to analyze the relationship between the mechanical properties and microstructure. Test results showed that the smaller filler's particle size improves flowability and strength properties. MIP results revealed that the smaller size of filler decreased the porosity and thus increased the strength of UHPC. From XRD analysis, we could find out there were little influence of filler's particle size on chemical reactivity in UHPC.

• Journal of the Korean Society for Railway
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• v.18 no.6
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• pp.543-551
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• 2015

Quick-hardening track (QHT) is a construction method which is used to change from old ballast track to concrete track. Sufficient time for construction is important, as the construction should be done during operational breaks at night. Most of the time is spent on exchanging the ballast layer. If it is possible to apply the ballast non-exchange type of quick-hardening track, it would be more effective to reduce the construction time and costs. In this paper, pouring materials with high permeability are suggested and a construction method involving a layer separation pouring process considering the void condition is introduced in order to develop ballast non-exchange type of QHT. The separate pouring method can secure the required strength because optimized materials are poured into the upper layer and the lower layer for each void ratio condition. To ensure this process, a rheology analysis was conducted on the design of the pouring materials according to aggregate size, the aggregate distribution, the void ratio, the void size, the tortuosity and the permeability. A polymer series was used as the pouring material of the lower layer to secure the void filling capacity and for adhesion to the fine-grained layer. In addition, magnesium-phosphate ceramic (MPC) was used as the pouring material of the upper layer to secure the void-filling capacity and for adhesion of the coarse-grained layer. As a result of a mechanics test of the materials, satisfactory performance corresponding to existing quick-hardening track was noted.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.195-203
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• 2022

In this paper, the effects of the bottom ash aggregate sizes and compaction levels on the thermal conductivity of porous concrete were investigated. In this experimental study, bottom ash was used as aggregates after identifying the aggregate characteristics. SA mixtures included hybrid aggregates, and DA contained only one particle size. The water-binder ratio was fixed at 0.30, and the compaction levels were applied to the concrete specimens at 0.5, 1.5, and 3.0 MPa. Unit weight, total void ratio, and thermal conductivity were measured and analyzed. As the compaction level increased, the unit weight and thermal conductivity increased in the SA mixtures, but the total void ratio decreased. In addition, the thermal conductivity of the specimens under oven-dried condition were lower than that of the specimens under air-dried condition. The correlation between the unit weight, total porosity, and thermal conductivity of porous concrete was analyzed. The thermal conductivity-unit weight correlation was proportional, while the thermal conductivity-total void ratio correlation was inversely proportional.

• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.741-750
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• 2004

Air voids in hardened concrete have an important influence on concrete durability such as freeze-thaw resistance, surface scaling resistance, and water permeability, and they have been characterized by spacing factor Linear traverse and point count methods in ASTM standard have been used in estimating an air void system in hardened concrete. However, these methods require lots of time and efforts, further they are not repeatable. Image analysis method could be utilized In estimating an air void systems in hardened concrete with a developments of microscope, digital camera and computer program. The purpose of this study was to develope image analysis method and provide a guideline by comparing the results from ASTM method and image analysis method. The concerns were at air void content and diameter distribution, air voids system as well as spacing factors. The experimental variables included air content by air entrained agent (0, 0.01, $0.03\%$) and depth of specimen (top, middle, bottom). The result showed that it was possible to calculate spacing factor using image analysis technique, as well as air content, air diameter distribution, and air structure. This study also contributed in developing an reasonable and repeatable image analysis method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1215-1225
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• 2014

Volcanic rocks formed from magma near the earth surface commonly show vesicular structures due to exsolution of gaseous phases in magma. The distinction and the amount of vesicles are greatly various, but there are few researches on the effect of volume percentage of vesicles on the mechanical properties. In this study, mechanical characteristics of volcanic rocks in relation to the porosity are investigated through experimental tests with Jeju basalt. Two methods (the buoyancy method and the caliper method) are adopted for measuring porosity. And unconfined compressive strength, elastic modulus, tensile strength, and elastic wave velocity are plotted against porosity in order to propose the empirical relations after the regression analysis. Also, unconfined compressive strength and the elastic modulus in relation to the elastic wave velocity are proposed with the analysis. In the case of vesicular rocks with more than 5% porosity, it is found that the buoyancy method provides more accurate estimation of porosity than the caliper method. The unconfined compressive strength, the elastic modulus, and the elastic wave velocity decrease curvilinearly with increasing in porosity. Also, the unconfined compressive strength and the elastic modulus increase linearly with increasing in elastic wave velocity.

• Proceedings of the KSEEG Conference
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• 2003.04a
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• pp.325-329
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• 2003

일반적으로 스멕타이트는 온도, 시간, 공극수 내 K 함량 등이 증가하면서 일라이트화 작용을 통하여 일라이트-스멕타이트 혼합층광물(I-S)로 전이된다. 따라서, 벤토나이트(주로 스멕타이트질 광물로 구성된 화산쇄설물의 변질산물)는 지질환경에 따라 스멕타이트 또는 다양한 혼합층비를 갖는 I-S를 함유하게 된다. 이러한 벤토나이트 내 스멕타이트와 일라이트의 혼합층비는 팽창성(expandability)으로 정량화할 수 있다. (중략)