• Structural Engineering and Mechanics
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• v.90 no.5
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• pp.467-480
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• 2024

The mechanical properties and durability of concrete pavements may be degraded in extreme situations, resulting in the need for partial repair or total replacement. During the past few decades, there has been a growing body of research on substituting a portion of Portland cement with alternative cementitious materials for improving concrete properties. In this study, two different configurations of powdered and granulated blast furnace slag were implemented, replacing fine aggregates (by 12 wt.%) and Portland cement (by 0, 20, 40, and 60 wt.%) in the making of roller-compacted concrete (RCC) mixes. The specimens were fabricated to investigate the mechanical properties and durability specifications, involving freeze-thaw, salt-scaling, and water absorption resistance. The experimental results indicated that the optimum mechanical properties of RCC mixes could be achieved when 20-40 wt.% of powdered slag was added to concrete mixes containing slag aggregates. Accordingly, the increases in compressive, tensile, and flexural strengths were 45, 50, and 28%, in comparison to the control specimen at the age of 90 days. Also, incorporating 60 wt.% of powdered slag gave rise to the optimum mix plan in terms of freeze-thaw resistance such that a negligible strength degradation was experienced after 300 cycles. In addition, the optimal moisture content of the proposed RCC mixtures was measured to be in the range of 5 to 6.56%. Furthermore, the partial addition of granulated slag was found to be more advantageous than using entirely natural sand in the improvement of the mechanical and durability characteristics of all mixture plans.

• Advances in materials Research
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• v.13 no.3
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• pp.233-241
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• 2024

Quantitative analysis of the Zingiber Officinale sample using subcritical water extraction (SWE) was developed employing High-Performance Liquid Chromatography (HPLC) to bolster the advancement of this innovative green extraction process. This research focuses on three principal ginger bioactive compounds: 6-gingerol, 6-shagoal, and 10-gingerol. Various stages were undertaken to establish the quantitative analysis method, encompassing the optimisation of HPLC operating conditions and the formulation of standard calibration curves, yielding individual compound equations. A robust correlation within the calibration curve was achieved, exhibiting an r² value of 0.9814 and an RSD of 5.00%. A simultaneous, swift, and dependable method was established with an injection time of 20 minutes and an 8-minute delay between injections, in contrast to the previous HPLC analysis requiring a 45-minute injection time for detecting and quantifying all components. Notably, no post-treatment was applied after the SWE process. This advancement allows for potential future online measurement of Zingiber Officinale bioactive compounds extracted using subcritical water extraction through this technology.

• Advances in materials Research
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• v.13 no.3
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• pp.243-251
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• 2024

The asymmetric polylactic acid (PLA) membrane was prepared via phase inversion method using non-solvent induced separation (NIPS) technique. This study aims to synthesized as well as to characterize the PLA membrane and evaluating the membrane performance on water flux and permeability. In addition, this research also studied the removal performance of methylene blue dye. The polymer solution has been prepared using 12 wt.% of PLA and dissolved in 88 wt.% of Dimethylacetamide (DMAc) as a solvent. Then, the cast film was immersed in different ratio of coagulant bath medium (distilled water: methanol: ethanol) ranging from 100:0:0, 75:25:0, 75:0:25 and 75:12.5:12.5, respectively). Several characterizations were performed which include, membrane contact angle and membrane porosity. Performance PLA membranes were determined in terms of water flux and permeability at 1 bar transmembrane pressure using dead-end permeation cell. Finally, methylene blue (MB) removal efficiency was tested at the same transmembrane pressure. The findings revealed that the increase of alcohol concentration in coagulant bath resulted in higher porosity and lower contact angle. In short, MB dye rejection efficiency is also closely related to the amount of alcohol ratio used in coagulant baths. Increases in concentration of methanol and ethanol in coagulant bath medium increases the membrane porosity thus increased in efficiency of methylene blue rejection.

• Advances in materials Research
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• v.13 no.3
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• pp.153-160
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• 2024

This study investigates the application of alternating current (AC) and direct current (DC) anodization techniques on stainless steel 304L (SS304L) in an ethylene glycol and ammonium fluoride (NH4F) electrolyte solution to produce a nano-porous oxide layer. With limited research on AC anodizing of stainless steel, this study focuses on comparing AC and DC anodization in terms of current density versus time response, phase analysis using X-ray diffraction (XRD), and corrosion rate determined by linear polarization. Both AC and DC anodization were performed for 60 minutes at 50 V in an electrolyte solution containing 0.5% NH4F and 3% H₂O in ethylene glycol. The results show that AC anodization exhibited higher current density compared to DC anodization. XRD analysis revealed the presence of ferrite (α-Fe) and austenite (γ-Fe) phases in the as-received specimen, while both AC and DC anodized specimens exhibited only the γ-Fe phase. The corrosion rate of the AC-anodized specimen was measured at 0.00083 mm/year, lower than the corrosion rate of the DC-anodized specimen at 0.00197 mm/year. These findings indicate that AC anodization on stainless steel offers advantages in terms of higher current density, phase transformation, and lower corrosion rate compared to DC anodization. These results highlight the need for further investigation and exploration of AC anodization as a promising technique for enhancing the electrochemical properties of stainless steel.

• Advances in materials Research
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• v.13 no.3
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• pp.161-171
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• 2024

This study aimed to investigate the effect of physicochemical properties and mix ratios of iron ore (oxide feed): coke (reductant) on the carbothermic reductions of iron ore. Coke size was fixed at ≤63 ㎛ while iron ore size varied between 150-63 ㎛ and ≤63 ㎛ respectively. Mix ratios were changed from 100:0 (reference) to 80:20 and 60:40 while the temperature, heating rate and soaking duration in muffle furnace were fixed at 1100 ℃, 10 ℃/min and 1 hour. Particle size analyzer, XRF, CHNS and XRD analyses were used for determination of raw feed characteristics. The occurrence of phase transformations from various forms of iron oxides to iron during the carbothermal reductions were identified through XRD profiles and supported with weight loss (%). XRF analysis proved that iron ore is of high grade with 93.4% of Fe₂O₃ content. Other oxides present in minor amounts are 2% Al₂O₃ and 1.8% SiO₂ with negligible amounts of other compounds such as MnO, K₂O and CuO. Composite pellet with finer size iron particles (≤63 ㎛) and higher carbon content of 60:40 exhibited 45.13% weight lost compared to 32.30% and 3.88% respectively for 80:20 and 100:0 ratios. It is evident that reduction reactions can only occur with the presence of coke, the carbon supply. The small weight loss of 3.88% at 100:0 ratio occurs due to the removal of moisture and volatiles and oxidations of iron ore. Higher carbon supply at 60:40 leads into better heat and mass transfer and diffusivity during carbothermic reductions. Overall, finer particle size and higher carbon supply improves reactivity and gas-solid interactions resulting in increased reductions and phase transformations.

• Advances in materials Research
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• v.13 no.3
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• pp.183-194
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• 2024

D3 tools steel and 440C stainless steel (SS) are normally being employed for application such as knife blade and cutting tools. These steels are iron alloys which have high carbon and high chromium content. In this study, lab work focused on the microstructural and corrosion behavior of D3 tools steel and 440C SS after went through heat treatment processes. Heat treatments for both steels were started with normalizing at 1020 ℃, continue with hardening at 1000 ℃followed by oil quenching. Cryogenic treatment was carried out in liquid nitrogen for 24 hours. The addition of cryogenic heat treatment is believed to increase the hardness and corrosion resistance for steels. Both samples were then tempered at two different tempering temperatures, 160 ℃ and 426 ℃. For corrosion test, the samples were immersed in NaCl solution for 30 days to study the corrosion behavior of D3 tool steel and 440C SS after heat treatment. The mechanical properties of these steels have been investigated using Rockwell hardness machine before heat treatment, after heat treatment (before corrosion) and after corrosion test. Microstructure observation of samples was carried out by scanning electron microscopy. The corrosion rate of these steels was calculated after the corrosion test completed. From the results, the highest hardness is observed for D3 tool steel which tempered at 160 ℃(54.1 HRC). In terms of microstructural analysis, primary carbide and pearlite in the as-received samples transform to tempered martensite and cementite after heat treatment process. From this research, for corrosion test, heat treated 440C SS sample tempered with 426 ℃possessed the excellent corrosion resistance with corrosion rate 0.2808 mm/year.

• Advances in materials Research
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• v.13 no.3
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• pp.211-220
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• 2024

Polylactic acid or polylactide (PLA) is a biodegradable thermoplastic that can be produced from renewable material to create various components for industrial purposes. In 3D printing technology, PLA is used due to its good mechanical, electrical, printing properties, environmentally friendly and non-toxic properties. However, the physical properties and excellent electrical insulation properties of PLA have limited its application. In this study, with the carbon black (CB) as filler added into PLA, the lattice spacing and morphology were investigated by using X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The physical properties of PLA-carbon composite were evaluated by using tensile test, shore D hardness test and density and voids measurement. Impedance test was conducted to investigate the electrical properties of PLA-Carbon composites. The results demonstrate that the inclusion of carbon black as filler enhances the physical properties of the PLA-carbon composites, including tensile properties, hardness, and density. The addition of carbon black also leads to improved electrical conductivity of the composites. Better enhancement toward the electrical properties of PLA-carbon composites is observed with 1wt% of carbon black in N774 grade. The N550 grade with 2wt% of carbon black shows better improvement in the physical properties of PLA-carbon composites, achieving 10.686 MPa in tensile testing, 43.330 in shore D hardness test, and a density of 1.200 g/cm3 in density measurement. The findings suggest that PLA-carbon composites have the potential for enhanced performance in various industrial applications, particularly in sectors requiring improved physical and electrical properties.

• Advances in materials Research
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• v.13 no.3
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• pp.221-232
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• 2024

Waste tire management and recycling have grown to be significant issues because they bring up a global environmental concern. Thus, turning recycled waste tires into useful products may help tackle the environmental issue. This research aims to study and compare the effect of recycled carbon black (rCB) and commercial carbon black (CB) at certain 15 vol. % of filler loading on the mechanical, thermal, morphology and electrical properties of epoxy/CB composites. For this project, epoxy resin, diethyltoluenediamine (DETDA), recovered carbon black (rCB) and commercial carbon black (CB) graded N330, N550, N660 and N774 were mixed and compared accordingly to the formulation determined. The CB content was dispersed in the epoxy matrix using the mechanical mixing technique. The distribution and dispersion of CB in the epoxy matrix affect the characteristics of the conductive composites. rCB content at 15 vol% was selected at fixed content for comparison purposes due to the optimum value in electrical conductivity results. The flexural strength results followed the sequence of rCB>N774>N660>N550>N330. As for electrical conductivity results, epoxy/N330 exhibited the highest conductivity value, while the others achieved a magnitude of X10^-3 due to the highest external surface area of N330. In terms of thermal stability, epoxy/N330 and epoxy/N774 were slightly more stable than epoxy/rCB.

• Geomechanics and Engineering
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• v.37 no.5
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• pp.511-525
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• 2024

Micropiled raft has been used to support the existing and new structures or to provide the seismic reinforcement of foundation systems. Recently, research on micropile or micropiled raft has been actively conducted as the usage of micropile has increased, and the reinforcement effect of pile for the raft, the pile installation methods, and methods for calculating the bearing capacity of micropiled raft have been proposed. In addition, existing research results show that the behavior of this foundation system is different depending on the pile conditions and can be greatly influenced by the characteristics of the upper or lower ground depending on the conditions of pile. In other words, considering that the micropile is a friction pile, it can be predicted that the reinforcing effect of micropile for the raft and the bearing capacity of micropiled raft may depend on the cohesion of upper soil layer depending on the pile conditions. However, existing studies have limitations in that they were conducted without taking this into account. However, existing studies have limitations as they have been conducted without considering these characteristics. Accordingly, this study investigated the reinforcing effect of micropile and the bearing characteristics of micropiled raft by varying the cohesion of upper soil layer and the stiffness of pile which affect the behavior of micropiled raft. In this results, the reinforcing effect of micropile on the raft also increased as the cohesion of soil layer increased, but the reinforcing effect of pile was more effective in ground conditions with decreased the cohesion. In addition, the relationship between the axial stiffness of micropile and the bearing capacity of micropiled raft was found to be a logarithmic linear relationship. It was found that the reinforcing effect of micropile can increase the bearing capacity of raft by 1.33~ 3.72 times depending on the cohesion of soil layer and the rigidity of pile.

• Steel and Composite Structures
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• v.51 no.3
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• pp.271-288
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• 2024

The primary objective of this study is to investigate the production and performance characteristics of structural concrete incorporating varying proportions (0%, 25%, and 50% by volume) of pumice stone, as well as aluminum lathe as an additive at 0%, 1%, 2%, and 3%, under fire conditions. The experiment will be conducted over a period of up to 1 hour, at temperatures ranging from 24℃, 200℃, 400℃ and 600℃. For the purpose of this, a total of twelve test samples were manufactured, and then tests of compressive strength (CS), splitting tensile strength (STS), and flexural strength (FS) were performed on these samples.Next, a comparison was made between the obtained values and the influence of temperature. To achieve this objective, the manufactured samples were placed at temperatures of 200℃, 400℃, and 600℃ for a duration of 1 hour, and were subjected to the influence of temperature.These values at 24 ℃ were then contrasted with the CS results obtained from test samples that were subjected to the temperature effect for an hour at 200 ℃, 400 ℃, and 600 ℃. A comprehensive analysis of the test outcomes reveals that the incorporation of aluminum lathe wastes into a mixture results in a significant reduction in the compressive strength of the concrete. As a result of this adjustment, the CS values dropped by 32.93%, 45.70%, and 52.07%, respectively. Furthermore, It was shown that testing the ratios of pumice stone alone resulted in a decrease in CS outcomes. Additionally, it was found that the presence of higher temperatures is clearly the primary factor contributing to the decrease in the strength of concrete. Due to elevated temperatures, the CS values decreased by 19.88%, 28.27%, and 38.61% respectively.After this investigation, an equation that explains the connection between CS and STS was provided through the utilization of the data of the experiments that were carried out.