• Journal of the Korean Wood Science and Technology
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• v.15 no.2
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• pp.99-104
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• 1987

Fiber mats were made at various density levels, using fibers from papermill sludge, ricestraw and various mixtures of the two. The paper mill sludges were collected from Moorim Papermill Co, and Jeonjoo Papermill Co. They were soaked in the liquid sulfur compounds, sulfur-tall oil and sulfurpolyester compounds, and made into fiber-reinforced, sulfur-based composition board. Under optimum conditions of fiber mat preparation and saturation with molten sulfur and modified sulfur, the Young's moduls of the manufactured tiber-reinforced composition board are superior to those of conventional wood-based composition boards. For example, the moduli of elasticity of the composition board made from papermill sludge, with a density of 0.40gm/$cm^3$, were greater than 1,400,000psi as compared 800,000psi for high density hardboard(1.28gm/$cm^3$). The modulus of rupture of the best reinforced composition board manufactured was over 9000psi, comparable to 6000psi of high density hardboard. The proposed Bryant and Lee's theory, "Modified Rule of Mixtures" can be applicable to the nonoriented and short fibrous composition board, when it was modified from "Rule of Mixtures" established by Paul an Jones, and supplemented by Smith and Cox's theory, In the Bryant and Lee's theory of $E_c=\frac{1}{3}aE_fV_f+bE_mV_m$, the constants "a" and "b" for the composition boards made from papermill sludge and the mixtures of ricestraw and the sludge were identified to be in the ranges of 3.29~3.54 and -2.47~-2.80 respectively.

• Geomechanics and Engineering
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• v.31 no.3
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• pp.291-304
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• 2022

Maximum shear modulus (G_max or G₀) is an important soil property useful for many engineering applications, such as the analysis of soil-structure interactions, soil stability, liquefaction evaluation, ground deformation and performance of seismic design. In the current study, bender element (BE) tests are used to evaluate the effect of the void ratio, effective confining pressure, grading characteristics (D₅₀, C_u and C_c), anisotropic consolidation and initial fabric anisotropy produced during specimen preparation on the G_max of sand-gravel mixtures. Based on the tests results, an empirical equation is proposed to predict G_max in granular soils, evaluated by the experimental data. The artificial neural network (ANN) and Adaptive Neuro Fuzzy Inference System (ANFIS) models were also applied. Coefficient of determination (R²) and Root Mean Square Error (RMSE) between predicted and measured values of G_max were calculated for the empirical equation, ANN and ANFIS. The results indicate that all methods accuracy is high; however, ANFIS achieves the highest accuracy amongst the presented methods.

• International Journal of Highway Engineering
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• v.3 no.3 s.9
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• pp.119-133
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• 2001

The stiffness of chemcrete modified asphalt mixtures increase rapidly with time in the presence f oxygen and high temperature, Sometimes the asphalt pavements that have chemcrete modified asphalt mixture applied on the surface none show premature cracking because of the excessive increase in the stiffness f the asphalt mixtures. To mitigate this premature cracking, the chemcrete modified mixtures have been used as a base course material. In this study, the performance of the chemcrete modified asphalt binder and mixtures are investigated through a course of various laboratory tests including dynamic shear rheometer and bending beam rheometer tests for binders and uniaxial tensile fatigue, wheel tracking, and moisture damage tests for the mixtures. And also the resilient modulus of the conventional and chemcrete modified mixtures are compared based on the test results conducted on the specimens obtained from various in-situ test sections. It can be concluded from the tests results that the chemcrete modified mixtures show better rutting resistance than conventional mixtures. The chemcrete modified mixtures may have low temperature cracking when it is applied in the cold region. The stiffness of chemcrete modified mixtures is approximately 50 percent higher than that of conventional mixtures more than two years after the chemcrete modified mixture was applied in the base course.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.35-46
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• 2017

Most of high carbon fly ashes (HCFA) are discarded in landfills with high costs due to low recycling rate. This study aims to explore the geotechnical behaviors of HCFA mixtures reinforced with fiber and sand. A series of compaction test, unconfined compressive strength test and modified 1D consolidation test with bender element were performed. Specimens were prepared at their optimal moisture contents based on the results of compaction tests. The results of this study demonstrate that the inclusion of fibers to the matrix of HCFA increases unconfined compressive strength (UCS), strain at UCS, and maximum shear modulus ($G_{max}$) at a given void ratio. Reinforcement with sand increases UCS of HCFA; while the strain at UCS is irrelevant with sand fractions. Sand particles may disrupt the direct contacts between HCFA particles at low sand content, resulting in a decrease in $G_{max}$. However, it can be expected that the mixtures with sand content larger than 20% are in dense state; thus, $G_{max}$ of HCFA reinforced with sand shows greater value than that of unreinforced HCFA compacted with the same energy. Regardless of types of reinforcement, the compression index ($C_c$) of both fiber and sand reinforced HCFA is mainly determined by initial void ratio.

• Transactions of Materials Processing
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• v.15 no.5 s.86
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• pp.360-365
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• 2006

Carbon nanotubes (CNTs) have been the subject of intensive studies for applications in the fields of nano technologies in recent years due to their superior mechanical, electric, optical and electronic properties. Because of their exceptionally small diameters (${\appros}\;several\;nm$) as well as their high Young's modulus (${\appros}1\;TPa$), tensile strength (${\appros}\;200\;GPa$) and high elongation (10-30%) in addition to a high chemical stability, CNTs are attractive reinforcement materials for light weight and high strength metal matrix composites. Although extensive researches have been performed on the electrical, mechanical and functional properties of CNTs, there are not many successful results on the mechanical properties of CNT dispersed nanocomposites. In this paper, we applied equal channel angular pressing for consolidation of CNT/Cu powder mixtures. We also investigated the hardness and microstructures of CNT/Cu nanocomposites used experimental for metal matrix composites.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.41-48
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• 2011

Warm-Mix Asphalt(WMA) mixtures, which meet environmental protection and have high energy efficiency, are emerging as an alternative to hot-mix asphalt mixtures. The objective of this study is to evaluate WMA made with Aspha-min in the laboratory and to compare the design results accomplished by new Mechanistic-Empirical Pavement Design Guide(MEPDG) with control mixture. An asphalt mixture with a nominal maximum size of 12.5mm and PG64-28 binder was used. Resilient modulus tests for a control mixture and WMA with 0.3% and 0.5% of Aspha-min were conducted. The results obtained by MEPDG after inputting the test output into the design indicated that the predicted rut depth of WMA using Aspha-min was much lower than that of control mixture, and showed that WMA was more resistant to rutting than control mixture.

• Membrane Journal
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• v.11 no.2
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• pp.74-82
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• 2001

By using a phenomenological approach, model equations incorporating the resistance-in¬series concept were established to evaluate quantitatively concentration polarization in the boundary layer in feed adjacent to the membrane surface in the vapor permeation and separation of volatile organic compounds (VOCS)/$N_2$ mixture through po]y(dimethylsiloxane) (PDMS) membrane. The vapor permeations of various VOCS/$N_2$ mixtures through PDMS membrane were carried out at various feed flow rates. Chlorinated hydrocarbons, such as, methylene chloride, chlorofonn, 1,2-clichloroethane and 1,1,2-trichloroethane were used as organic vapor. By fitting the model equations to the experimental penneation data. the model parameters were detennined. respectively. Both the mass transfer coefficient of VOC across tbe boundary layer and concentration polarization modulus as a measure of the extent of concentration polarization were eitimated Quantitatively by the mooe1 equations with the determined model parameters. From the analysis on the detennined model parameters, the boundary layer resistance due to the concentration polarization of VOCs component was found to be more significant when the condensability of voe was greater. This study seeks to emphasize the importance of the boundary resistance on the vapor penneation of the vapor/gas mixtures with high permeability and high selectivity towards the minor component VOC.

• Journal of the Korean Geotechnical Society
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• v.27 no.3
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• pp.85-94
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• 2011

Mixtures of sand and rubber particles ($D_{sand}/D_{rubber}=1$) are investigated to explore their characteristics under different stain level. Mixtures are prepared with different volumetric sand fractions ($sf=V_{sand}/V_{total}$). Experimental data are gathered from a resonant column, an instrumented oedometer, and a direct shear tests. Results show that sand and rubber differently control the behavior of the whole mixture with strain level. Non-linear degradation of small strain stiffness is observed for the mixtures with $sf{\geq}0.4$, while the mixtures with low sand fraction ($sf{\leq}0.2$) show significantly high elastic threshold strain. Vertical stress-deformation increases dramatically when the rubber particle works as a member of force chain. The strength of the mixtures increases as the content of rubber particle decreases, and contractive behavior is observed in the mixtures with $sf{\leq}0.8$. Rubber particle plays different roles with strain level in the mixture: it increases a coordination number and controls a plasticity of the mixture in small strain; it prevents a buckling of force chain in intermediate strain; it leads a contractive behavior in large strain.

• Computers and Concrete
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• v.17 no.4
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• pp.553-566
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• 2016

Fracture energy is one of the key parameters reveal cracking resistance and fracture toughness of concrete. The main purpose of this study is to determine fracture behavior, mechanical properties and microstructural analysis of high strength basalt fiber reinforced concrete (HSFRC). For this purpose, three-point bending tests were performed on notched beams produced using HSFRCs with 12 mm and 24mm fiber length and 1, 2 and $3kg/m^3$ fiber content in order to determine the value of fracture energy. Fracture energies of the notched beam specimens were calculated by analyzing load versus crack mouth opining displacement curves by the help of RILEM proposal. The results show that the effects of basalt fiber content and fiber length on fracture energy are very significant. The splitting tensile and flexural strength of HSFRC increased with increasing fiber content whereas a slight drop in flexural strength was observed for the mixture with 24mm fiber length and $3kg/m^3$ fiber content. On the other hand, there was no significant effect of fiber addition on the compressive strength and modulus of elasticity of the mixtures. In addition, microstructural analysis of the three components; cement paste, aggregate and basalt fiber were performed based on the Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy examinations.

• International Journal of Highway Engineering
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• v.20 no.2
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• pp.27-34
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• 2018

PURPOSES : It is necessary to prevent premature failure of concrete pavements caused by durability problems. The purpose of this study was to find factors affecting the durability of concrete pavements, and suggest improvement methods for existing concrete mix design. METHODS : Factors influencing durability were derived from laboratory test data for common field failure conditions and main properties of concrete cores taken from the field. The improvement of concrete properties was investigated by evaluating the performance of existing and proposed mix proportion designs and curing methods. RESULTS : The compressive strength and the absorbing performance of the low Blaine cement and the high-strength mixture were better than those of the Type I cement. Wet curing showed better compressive strength, elastic modulus, coefficient of thermal expansion, and absorption performance than air curing or compound curing. As a result of comparing concrete cores collected in the field, the sections with good durability showed good performance in terms of resistance to chloride ion penetration, absorption, and initial absorption rate. CONCLUSIONS : The absorption performance was considered as a possible foactor affecting durability of cement concrete pavements as a result of field core tests. In order to improve the durability of the pavement concrete, it is necessary to improve the existing mixtures and curing methods.