• Journal of the Korean Ceramic Society
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• v.44 no.9
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• pp.502-509
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• 2007

This paper investigated how Fine Fly Ash (FFA) with $14,000\;cm^2/g$ of Fineness affects the micro structure and material properties of High-Performance Concrete (HPC) before and after hardening from Material Test of HPC and Cement Paste. FFA is applied as a substitute of Silica Fume which is used necessarily in producing HPC. As a Material Test results, 5% FFA series specimen shows the lower fluidity than SF series specimen. When, however, the Fluidity of 10% FFA series specimen is increased reversely to the similar value of SF series specimen. The Porosity of FFA series specimen of 3 day age is displayed to $21{\sim}24%$, which is higher than $19{\sim}20%$ porosity of SF series specimen, while that of 28 day age is reached to $8{\sim}9%$, which is improved compared with 10% fo SF series specimen. It can be thought that FFA has better influence on the porosity of HPC in case of long term age. The Compressive strength of FFA series specimen shows the similar result with the property of porosity. The compressive strength of 28 day age FFA series specimen is $98{\sim}106%$ of SF series specimen and 107% of plain specimen to reveal better strength development.

• Advances in concrete construction
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• v.6 no.4
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• pp.363-373
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• 2018

Portland cement pervious concrete (PCPC) is an effective pavement material to solve or reduce the urban waterlogging problems. The Mechanical properties, the permeability, the abrasion resistance and the frost resistance of PCPC without fine aggregate were investigated. The increase of porosity was achieved by fixing the dosage of coarse aggregate and reducing the amount of cement paste. The results show that the compressive strength and the flexural strength of PCPC decrease with the increase of porosity. The permeability coefficient and the wear loss of PCPC increase with the increase of the porosity. The compressive strength and the flexural strength of PCPC subjected to 25 freeze-thaw cycles are reduced by 13.7%-17.8% and 10.6%-18.3%, respectively. For PCPC subjected to the same freeze-thaw cycles, the mass loss firstly increases and then decreases with the increase of the porosity. The relative dynamic modulus elasticity decreases with the increase of freeze-thaw cycles. And the lower the PCPC porosity is, the more obvious the dynamic modulus elasticity decreases.

• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.2
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• pp.47-57
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• 2023

The increase of impermeable area ratio is causing hydrologic cycle problems in urban areas and groundwater depletion in rural areas, permeable pavements are getting attention to expand permeable areas. The performance of the permeable concrete block pavement, which is part of the permeable pavement, is greatly affected by the porosity. In addition, the permeability coefficient is a major factor when designing permeable concrete block pavement. Existing porosity and permeability test methods have problems such as uneconomical or poor field applicability. The object of this study was to develop a methodology for evaluating porosity and permeability coefficient using a surface image of a permeable concrete block. Specimens are manufactured with various porosity ranges and porosity and permeability tests are performed. After surface image preprocessing, normalization and binarization methods were compared. Through this, the method with the highest correlation with the lab test result was determined. From the results, the PDR (pore determined ratio) was obtained. Simple linear regression analysis is performed with PDR and lab test results. The results showed a high correlation of R² more than 0.8, and the errors were also low.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.12 no.3
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• pp.106-115
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• 2009

Knowledge about how to stabilize soil structure is essential to conserve soil systems and maintain various biogeochemical processes through soil. In urban area, soil structural systems are degraded with inappropriate management and land use and become vulnerable to erosion. We analyzed the structural changes of surface soils with different land uses, i.e., forests, parks, roadside green area, riparian area, and farmlands (soybean fields), in the Anyang Stream Watershed in order to find the factors influencing the stability of soil structure and the implication for better management of surface soil. Soil organic matter contents of other land use soils were only 18~52% of that in forest soils. Soil organic matter increased the stability of soil aggregates in the order of soybean fields < roadsides < riparian < parks < forests and also reduced soil bulk density (increased porosity). The lowest stability of soybean field soils was attributed to the often disturbance like tillage and it was considered that higher stability of park soils comparing to other land use soils except forests was owing to the covering of soil surface with grass. These results suggest that supply of soil organic matter and protection of soil surface with covering materials are very important to increase porosity and stability of soil structure.

• Wind and Structures
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• v.31 no.1
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• pp.43-57
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• 2020

Considering the wind barriers induced aerodynamic characteristic variations of both bridge deck and trains, this paper studies the effects of wind barriers on the safety and stability of trains as they run through an urban rail transit cable-stayed bridge which tends to be more vulnerable to wind due to its relatively low stiffness and lightweight. For the bridge equipped with wind barriers of different characteristics, the aerodynamic coefficients of trains and bridge decks are obtained from wind tunnel test firstly. And then, the space vibration equations of the wind-train-bridge system are established using the experimentally obtained aerodynamic coefficients. Through solving the dynamic equations, one can calculate the dynamic responses both the trains and bridge. The results indicate that setting wind barriers can effectively reduce the dynamic responses of both the trains and bridge, even though more wind forces acting on the bridge are caused by wind barriers. In addition, for urban rail transit cable-stayed bridges located in strong wind environment, the wind barriers are recommended to be set with 20% porosity and 2.5 m height according to the calculation results of cases with wind barriers porosity and height varying in two wide ranges, i.e., 10% - 40% and 2.0 m to 4.0 m, respectively.

• International Journal of High-Rise Buildings
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• v.4 no.2
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• pp.135-142
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• 2015

As the skyscraper matures as a building type, its role in actively connecting to, and reinforcing, major threads of urban fabric becomes increasingly more important. The creation of public spaces inside of and adjacent to tall buildings allows for significant additions to the public realm, facilitating better connections between varied uses, providing needed access to critical transportation functions. In this more integrated version of the tall building type, the density afforded by a vertical structure is complemented by strategically devised porosity of plan and section. This paper examines three major tower projects which exemplify a progressive approach to permeable design: the recently completed Jingan Kerry Centre in Shanghai, the Lotte Supertower in Seoul, now half completed, and the One Vanderbilt tower being proposed next to Grand Central Terminal in New York City. These projects suggest possibilities for innovative approaches to private development strategies, public planning processes, and architectural design.

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.597-604
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• 2004

This work involves quantitatively investigating the correlation between reductions in strength and variations in pore structure under high temperature that can be utilized as estimation for predicting the inner temperature of member damaged by fire. The experimental results were remarkedly affected by micro-filling effect of silica fume and the different water-binder ratios. The increase of the exposure temperature caused the increase of porosity, which resulted from the reason that evaporable water in gel pore or capillary pores as well as chemically bound water was eliminated from hardened cement paste due to the dehydration of C-S-H and $Ca(OH)_2$. Thermal shrinkage of hardened cement paste gives rise to micro-crack, which cause the increase of porosity. Based on the experimental result that the increase of porosity is in charge of exposure temperature, how porosity is distributed can predict temperature-time history and assess the performance of concrete damaged by fire.

• Advances in concrete construction
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• v.8 no.4
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• pp.305-309
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• 2019

Pervious concrete pavements are the need of the day to avoid urban flooding and to facilitate ground water recharge. However, the strength of pervious or porous concrete is considerably less compared to conventional concrete. In this experimental investigation, an effort is made to improve the strength of pervious concrete by adopting fibres and a small amount of fine aggregate. A porous concrete with cement to aggregate ratio of 1:5 and a water-powder ratio of 0.4 is adopted. 30% of the cement is replaced by cementitious material ground granulated blast furnace slag (GGBS) for better strength and workability. Recron fibres at a dosage of 0.5, 1.0 and 1.5% by weight of cement were included to improve the impact strength. Since concrete pavements are subjected to impact loads, the impact strength was also calculated by "Drop ball method" in addition to compressive strength. The effect of fine aggregate and recron fibres on workability, porosity, compressive and impact strength was studied. The investigations have shown that 20% inclusion of fine aggregate and 1.5% recron fibres by weight of cement give better strength with an acceptable range of porosity.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.11a
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• pp.53-56
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• 2007

Recently, waste concrete emission has been increased by acceleration of urban development and the rapid growth of redevelopment projects, so recycling of waste concrete is actively progressed, But the usage is limited to a lower value added such as the roadbed material etc. To produce the high quality recycled aggregate, breaking and washing process is added to the existing process and inevitably increases the occurrence of particle, because old mortal is included in the recycled aggregate. Therefore, this study purpose is analysis the properties of lightweight foamed concrete made by waste concrete sludge which is the by-product from produce the recycled aggregate. In result, possibility of manufacture of lightweight foamed concrete which gives equal performance compared with ALC was detect(scope of density : $0.5{\sim}0.6$, scope of compressive strength : $3.5{\sim}4.0MPa$). And scope of porosity is as follow ; total porosity : $27{\sim}30%$, open porosity : $1{\sim}5%$

• Journal of Environmental Impact Assessment
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• v.15 no.2
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• pp.111-119
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• 2006

In Korea, an environment-friendly concept of "rain re-cycling" was initially introduced in apartment complex planning and designs in the late 1990s. Although its application cases are extremely few, with the growing importance of rainwater utilization, introduction of rainwater management facilities in urban areas began to drawn keen attention. In urban areas also, plans to introduce rainwater management facilities in apartment complexes as infrastructure improving living environment, such as sewage treatment facilities are very urgently required. In order to introduce rainwater management facilities as infrastructure in an apartment complex, apartment complex cases that had introduced the facilities were reviewed first. In this study, a few applied rainwater management facilities in an apartment complex were surveyed(Infiltration barrel, Rubble porosity storage tank, Underground storage tank). As a result, problems in introducing rainwater management facilities in apartment complexes in Korea were identified.