• International Journal of Highway Engineering
• /
• v.8 no.2 s.28
• /
• pp.95-104
• /
• 2006

Hysteresis is a common feature exhibited in hydraulic properties of an unsaturated soil. This study focuses on hysteresis observed in a compacted weathered granite subgrade soils based on the pressure plate laboratory tests. It was found that the Soil-Water Characteristics Curve of a soil is hysteretic and unique. The results also show that the wetting and drying curves predicted using the Fredlund and Xing model is quite close to the laboratory-measured results. For a specific matric suction, water content or coefficient of permeability on a wetting curve is always lower than those found on a drying curve.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.754-757
• /
• 2008

To maintain the indoor air quality, many ventilation systems and technologies have been developed in the highly insulated and air tight buildings. In this study, a porous construction material, which is applicable to passive ventilation system, is developed and measured the performances of the permeability and the resistance of water vapor, and the dust collection efficiency. The average coefficient of water vapor permeability shows $3.6\;g/m^2{\cdot}h{\cdot}mmHg$, which is slightly higher than Hanji ($2.4{\sim}3.2\;g/m^2{\cdot}h{\cdot}mmHg$) and the average water vapor resistance factor shows $0.303\;g/m^2{\cdot}h{\cdot}mmHg/g$, which is slightly smaller than Hanji($0.309{\sim}0.315\;g/m^2{\cdot}h{\cdot}mmHg/g$). The pressure drop of the porous construction material is smaller than the HEPA filter and the minimum dust collection efficiency shows 82.8% in the range of $2{\sim}9\;cm/s$.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.3
• /
• pp.83-91
• /
• 2015

Porous concrete consists of cement, water and coarse aggregate and has been used for the purpose of decreasing the earth environmental load such as air and water permeability, sound absorption, etc. However, the physical and mechanical properties of porous concrete changes due to compaction load during construction. For such a reason, the purpose of this study is to investigate the physical and mechanical properties of porous concrete according to the kinds of binder, the ratio of water to binder and target void ratio. In particular, this study has been carried out to investigate the influence of compaction load on the void ratio, strength and coefficient of permeability. Aggregate used in this study are by-products generated during production of crushed gravel with a maximum size of 13mm. The results of this study showed that the target void ratio, the coefficient of permeability and compressive strength of porous concrete had a close relationship with the void ratio, and it will be possible that the void ratio is suggested by the mix design of porous concrete. The compressive strength of porous concrete was the highest at the content of the expansive admixture of 5% and compared to non-mixture, 10% mixture of silica fume improved compressive strength about 32%. And in the result of the study to change the compaction load, the compressive strength increased from the load of 15kN, the void ratio decreased from the load of 0.8kN, the coefficient of permeability decreased from the load 35kN, respectively.

• Bulletin of the Korean Chemical Society
• /
• v.6 no.3
• /
• pp.128-131
• /
• 1985

A series of copolymer membranes of 2-hydroxyethylmethacrylate (HEMA) with selected hydrophobic monomers were prepared without crosslinking agents. The equilibrium water content, the partition coefficient, and the permeability of the solutes such as urea, methylurea, 1,3-di-methylurea, and acetamide via these membranes were measured. The partition coefficient data show that as the hydrophobicity of solutes increased, the partition of solutes were dictated by hydrophobic interaction between solute and polymer matrix. Diffusion coefficients obtained in these experiments decrease as the water content of polymer membrane decreases. This decrease is blunt as the excess heat capacities, ${\phi}C^0_p$ (excess) in aqueous solution at infinite dilution of solute increases. To investigate the relationship between water content and diffusion coefficient, the results of the diffusion experiments were examined in light of a free-volume model of diffusive transport. The remarkable increase of urea mobility in the polymer network containing relatively larger bulk water can be considered as water structure breaking effect.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.49 no.4
• /
• pp.51-59
• /
• 2007

Recently, concrete has been made porous and used for sound absorption, water permeation, vegetation and water purification according to void characteristics. Many studies are carried out on the utilization of sewage sludge, fly ash and waste concrete to reduce the environmental load. This study was performed to evaluate the void, strength, relationship between void and strength, permeability and chemical resistance properties of porous polymer concrete for pavement with different fillers. An unsaturated polyester resin was used as a binder, crushed stone and natural sand were used as an aggregate and bottom ash, fly ash and blast furnace slag were used as fillers. The mix proportions were determined to satisfy the requirement for the permeability coefficient, $1{\times}10^{-2}$ cm/s for general permeable cement concrete pavement in Korea. The void ratios of porous polymer concrete with fillers were in the range of $18{\sim}23%$. The compressive strength and flexural load of porous polymer concrete with fillers were in the range of $19{\sim}22$ MPa and $18{\sim}24$ KN, respectively. The permeability coefficients of porous polymer concrete with fillers were in the range of $5.5{\times}10^{-1}{\sim}9.7{\times}10^{-2}$ cm/s. At the sulfuric acid resistance, the weight reduction ratios of porous polymer concrete immersed during 8-week in 5% $H_{2}SO_{4}$ were in the range of $1.08{\sim}3.56%$.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.185-188
• /
• 2006

During the carbonation process in concrete, the rate of carbonation depends on porosity and moisture content of the concrete. For underground reinforced concrete structures, the interior concrete surface may be exposed to carbonation and the exterior concrete surface exposed to moisture due to wet soil or underground water. In this study, the permeability coefficients in mortar partially carbonated is derived as a function of carbonation depth and porosity of mortar by applying the so-called micro pore structure formation model (MPSFM) which was developed for the modeling of early-aged concrete. The permeability coefficient obtained from the micro-level modeling of carbonated mortar is verified with the results of accelerated carbonation test and water penetration test in cement mortar.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.506-509
• /
• 2008

Mathematical models have been developed to calculate hydrodynamic characteristics of perforated-wall structures. Most of the models separate the fluid regions into front and back of the wall, assume the solution in each region, and calculate the solution by using the matching condition at the wall. The matching condition involves the permeability parameter, which can be calculated by the methods proposed by Mei et al. or Sollitt and Cross. In this study, we compare these two methods. The former is advantageous because all the related variables are known, but it gives wrong result in the limit of long waves, i.e. zero transmission and perfect reflection of very long waves. In deep water, the latter predicts smaller transmission and larger reflection than the former, and vice versa in shallow water. In the latter method, the friction coefficient decreases as the wall thickness or the porosity of the wall increases.

• Water for future
• /
• v.7 no.2
• /
• pp.83-91
• /
• 1974

On the constructions of fill type dams, usually the constructions materials is desired to be obtained in vicinity ofthe dam sitc to justify economical feasilblity of the project. In the stability analysis of the dams, core parts takesa small fraction of the slip circle and main function of core is to decrease dam permeability. This paper shows results of various tests as physical properties, compactions (using single, double triple and four times of the tandard compaction energy) and the permeability tests. Single decomposed granite and mixed materials with clay soils were used in this test. And conclusions of these tests are as follows; 1. Criteira of weathering ratio should be caleulated by density measarment. 2. Permeability coefficient maiuly depends on th #200 sieve passing, and also passing soil quantities depends on the weathering condition of the soil. 3. It was established that low weathered decomposed granite can not be used for the core materials of the fill type dams. On the other hand, moderately weathered decomposed granite soil with particles could pass through #200 sieve in a quantity over 10%, could chieve permeability in a magnitude of $1{\times}10^{-5} cm/see$. 4. With the decomposed granite soil it is possible to perform three times larger compaction energy than the standard energy without any problems.

• Journal of the Korean Professional Engineers Association
• /
• v.33 no.4
• /
• pp.77-83
• /
• 2000

In this study, engineering characteristics of permeable mortar using water-quenched blast furnace slag as fine aggregates were analyzed by laboratory experiments to examine its suitability for permeable concrete pavement techniques. Engineering characteristics of mortar were investigated by performing both the compressive, flexural strength tests together with the constant head permeability tests for twenty-six types of mixing samples having different percetage of slag, cement and water. After 28days of curing, every performance was tested to find optimum mixture. When the go coefficient of permeability was 10$\^$-2/cm / sec and flexural strength was 30kg/㎠, we conclusion that the best mix design in permeable mortar was made in the condition,60% of cement and 20% of water percentage of unit slag contents. From the present investigations, it is concluded that suitability for permeable concrete pavement techniques using water-quenched blast furnace slag as fine aggregates may possibly be used to achieve effects on strength together with drainage effects.

• Archives of Pharmacal Research
• /
• v.10 no.2
• /
• pp.88-93
• /
• 1987

Chitosan ($\beta$-D-glucosaminan) is chemically prepared from chitin (N-acetyl-$\beta$- D-glucosaminan) which is an unutilized natural resource. We now report on the suitability of the chitosan matrix for use as vehicles for the controlled release of drugs. Salicylic acid and aspirin were used as model drugs in this study. The permeation of salicylic acid in the chitosan membranes was determined in a glass diffusion cell with two compartments of equal volume. Drug release studies on the devices were conducted in a beaker containing 5% sodium hydroxide solution. Partition coefficient (Kd) value for acetate membrane (472) is much greater than that for fluoro-perchlorate chitosan membrane (282). Higher Kd value for acetate chitosan membrane appears to be inconsisstent with the bulk salicylic acid concentration. The permeability constants of fluoro-perchlorate and acetate chisotan membranes for salicylic acid were 3.139 ${\times}10^{-7}cm^2$ min up to 60 min and that of 30% aspirin in the devices was 4.739${\times}10^{-7}cm^2$sec upto 60 min. As the loading dose of aspirin in a chitosan device increased, water up-take of chitosan device increased, but in case of salicylic acid it decreased. The release rate increased with increase in the molecular volume of the drugs. Thses result suggest that the release mechanism may be controlled mainly by diffusion through pores.