• Advances in concrete construction
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• 제13권6호
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• pp.433-450
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• 2022

The conventional disposal methods of waste tires are harmful to the environment. Moreover, the recycling/reuse of waste tires in domestic and industrial applications is limited due to parent product's quality control and environmental concerns. Additionally, the recycling industry often prefers powdered rubber particles (<0.60 mm). However, the processing of waste tires yields both powdered and coarser (>0.60 mm) size fractions. Reprocessing of coarser rubber requires higher energy increasing the product cost. Therefore, the waste tire rubber (WTR) less favored by the recycling industry is encouraged for use in construction products as one of the environment-friendly disposal methods. In this study, WTR fiber >0.60 mm size fraction is collected from the industry and sorted into 0.60-1.18, 1.18-2.36-, and 2.36-4.75-mm sizes. The effects of different fiber size fractions are studied by incorporating it as fine aggregates at 10%, 20%, and 30% in the self-compacting rubberized concrete (SCRC). The experimental investigations are carried out by performing fresh and hardened state tests. As the fresh state tests, the slump-flow, T500, V-funnel, and L-box are performed. As the hardened state tests, the scanning electron microscope, compressive strength, flexural strength and split tensile strength tests are conducted. Also, the water absorption, porosity, and ultrasonic pulse velocity tests are performed to measure durability. Furthermore, SCRC's energy absorption capacity is evaluated using the falling weight impact test. The statistical significance of content and size fraction of WTR fiber on SCRC is evaluated using the analysis of variance (ANOVA). As the general conclusion, implementation of various size fraction WTR fiber as fine aggregate showed potential for producing concrete for construction applications. Thus, use of WTR fiber in concrete is suggested for safe, and feasible waste tire disposal.

• Advances in concrete construction
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• 제8권3호
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• pp.239-246
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• 2019

Substitution of natural fine aggregates with industrial by-products like precious slag balls (PS Balls) offers various advantages like technical, economic and environmental which are very important in the present era of sustainability in construction industry. PS balls are manufactured by subjecting steel slag to slag atomizing Technology (SAT) which imparts them the desirable characteristics of fine aggregates. The main objective of this research paper is to assess the feasibility of producing good quality concrete by using PS balls, to identify the potential benefits by their incorporation and to provide solution for increasing their utilization in concrete applications. The study investigates the effect of PS balls as partial replacement of fine aggregates in various percentages (20%, 40%, 60%, 80% and 100%) on mechanical properties of concrete such as compressive strength, splitting tensile strength, and flexural strength. The optimum mix was found to be at 40% replacement of PS balls with maximum strength of 62.89 MPa at 28 days curing. Permeability of concrete was performed and it resulted in a more durable concrete with replacement of PS balls at 40% and 100% as fine aggregates. These two specific values were considered as optimum replacement is 40% and also the maximum possible replacement is 100%. Scanning electron microscope (SEM) analysis was done and it was found that the PS balls in concrete were unaffected and with optimum percentage of PS balls as fine aggregates in concrete resulted in good strength and less cracks. Hence, it is possible to produce good workable concrete with low water to cement ratio and higher strength concrete by incorporating PS balls.

• Advances in concrete construction
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• 제17권3호
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• pp.135-150
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• 2024

Nano-silica's growing use in construction, known for enhancing strength and durability by reducing porosity, drives this research's significance, especially considering Ecuador's reliance on cement in construction. A comprehensive comparative study on mortars made with General Use cement and aggregates from Pifo and San Antonio quarries has been studied. It explores the impact of incorporating nano-silica in varying proportions (0.75%, 1.00%, 1.25%) on mortar properties, contrasting them with conventional and prefabricated mortars. laboratory Testing is conducted according to standards to assess both fresh and hardened state properties, and microscopic analysis reveals the optimal nano-silica proportion's effects on mortar characteristics. Results shows that Incorporating 0.75% nano-silica resulted in a 61% increase in compressive strength at 7 days and. For a nanosilica content of 1.25%, a 14% increase in compressive strength was observed at 28 days in relation to the conventional mortar and the permeability of the mortar decreased by 30% when adding 0.75% nanosilica. It discusses economic viability and provides insights through SEM and EDS analyses. Overall, it underscores nano-silica's potential to enhance mortar properties and its relevance in creating more efficient and durable construction materials.

• 한국건축시공학회지
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• 제5권3호
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• pp.75-82
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• 2005

Sewage facilities are positively necessary for environment improvement such as rainwater removal, sewage disposal, preservation of the quality of water and health of the citizens in present-day. Meanwhile, a deterioration of the concrete sewer pipe is increasing rapidly due to the chemical and physical attack and especially biochemical attack that is to say biodeterioration. So, in advanced countries, prediction techniques and corrosion inhibition system for sewer concrete are developed and are being applied. Also, antibiotics were developed already but application of that is low because it is not economical and has no practical use. But, in domestic, countermeasures for the corrosion of sewage concrete are not sufficient and biochemical attack is not reflected in those essentially. In this study, to prevent biochemical corrosion of the sewer concrete, surface of the concrete was spread with liquefied inorganic antibiotics and then its engineering properties were experimentally investigated. As a result, compressive strength of the specimen spread with antibiotics were similar to those of non spread, Both bond strength and abrasion amount of the specimen spread with antibiotics were inferior to non spread. Properties of absorption and air permeability of the specimen spread with antibiotics were superior to non spread. Finally, carbonation depth, chloride ion penetration depth and weight change ration of the specimen spread with antibiotics were smaller than non spread.

• 한국재료학회지
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• 제21권5호
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• pp.283-287
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• 2011

As the performance of microelectronic devices is improved, the use of copper as a heat dissipation member is increasing due to its good thermal conductivity. The high thermal conductivity of copper, however, leads to difficulties in the joining process. Satisfactory bonding with copper is known to be difficult, especially if high shear and peel strengths are desired. The primary reason is that a copper oxide layer develops rapidly and is weakly attached to the base metal under typical conditions. Thus, when a clean copper substrate is bonded, the initial strength of the joint is high, but upon environmental exposure, an oxide layer may develop, which will reduce the durability of the joint. In this study, an epoxy adhesive formulation was investigated to improve the strength and reliability of a copper to copper joint. Epoxy hardeners such as anhydride, dihydrazide, and dicyandiamide and catalysts such as triphenylphosphine and imidazole were added to an epoxy resin mixture of DGEBA and DGEBF. Differential scanning calorimetry (DSC) analyses revealed that the curing temperatures were dependent on the type of hardener rather than on the catalyst, and higher heat of curing resulted in a higher Tg. The reliability of the copper joint against a high temperature and high humidity environment was found to be the lowest in the case of dihydrazide addition. This is attributed to its high water permeability, which led to the formation of a weak boundary layer of copper oxide. It was also found that dicyandiamide provided the highest initial joint strength and reliability while anhydride yielded intermediate performance between dicyandiamide and dihydrazide.

• Computers and Concrete
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• 제31권2호
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• pp.85-95
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• 2023

Natural pozzolans are used as additives in cement to develop more durable and high-performance concrete. Pozzolanic activity index (PAI) is important for assessing the performance of a pozzolan as a binding material and has an important effect on the compressive strength, permeability, and chemical durability of concrete mixtures. However, the determining of the 28 days (short term) and 90 days (long term) PAI of concrete mixtures is a time-consuming process. In this study, to reduce extensive experimental work, it is aimed to predict the short term and long term PAIs as a function of the chemical compositions of various natural pozzolans. For this purpose, the chemical compositions of various natural pozzolans from Central Anatolia were determined with X-ray fluorescence spectroscopy. The mortar samples were prepared with the natural pozzolans and then, the short term and the long term PAIs were calculated based on compressive strength method. The effect of the natural pozzolans' chemical compositions on the short term and the long term PAIs were evaluated and the PAIs were predicted by using multiple linear regression (MLR) and adaptive neuro-fuzzy inference system (ANFIS) model. The prediction model results show that both reactive SiO₂ and SiO₂+Al₂O₃+Fe₂O₃ contents are the most effective parameters on PAI. According to the performance of prediction models determined with metrics such as root mean squared error (RMSE) and coefficient of correlation (R²), ANFIS models are more feasible than the multiple regression model in predicting the 28 days and 90 days pozzolanic activity. Estimation of PAIs based on the chemical component of natural pozzolana with high-performance prediction models is going to make an important contribution to material engineering applications in terms of selection of favorable natural pozzolana and saving time from tedious test processes.

• 한국지반환경공학회 논문집
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• 제24권11호
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• pp.5-10
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• 2023

지하수 제어가 필요한 분야에서 다방면으로 활용되는 Slag-CB는 CB의 일종으로 CB에 혼합되는 시멘트의 일부를 GGBS 로 치환하여 사용하는 차수벽의 일종이다. 일반적으로 Slag-CB는 GGBS의 치환율이 증가함에 따라 압축강도, 차수성, 내구성 및 내화학성 등이 장기적으로 향상되는 장점이 있으나, 벽체의 유연성 및 변형에 대한 저항성이 저하되며 파괴 시 취성을 보이는 문제가 있다. 이러한 문제를 해결하기 위해 일부 품질기준에서는 Slag-CB를 저강도로 설계하도록 권장하고 있어 GGBS 치환율이 높은 고강도의 Slag-CB의 현장 적용에 다소 어려움이 있다. 이에 본 연구에서는 Slag-CB의 유연성 및 변형에 대한 저항성을 개선하여 취성파괴를 방지함으로 Slag-CB의 현장 활용성 및 적용성을 향상시키기 위해 나일론 섬유를 혼합한 Slag-CB 차수벽을 대상으로 압축거동 특성을 평가하고, 이를 비교·분석함으로 Slag-CB의 유연성 및 변형에 대한 저항성을 향상시킬 수 있는 방안을 제시하였다.

• 설비공학논문집
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• 제29권10호
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• pp.504-514
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• 2017

The insulation performance of aircaps has been recognized and various studies regarding the aircap as a solution to increased building energy consumption are being carried out. However, the aircap is not durable and therefore it cannot play the role of an independent finishing material. Accordingly, the purpose of this study is to suggest an aircap wall module with improved durability through the lamination of the aircap and verify its effectiveness by evaluating its energy saving performance for lighting and air conditioning through a full-scale testbed. The conclusions of this study are as follows. 1) The aircap wall module featuring a laminated aircap that is being proposed in this study can save lighting energy due to the permeability of the aircap in comparison to previous insulating materials. 2) The aircap wall module with a laminated aircap is effective in improving heating and air-conditioning energy saving when it is more than 15 cm-thick during summer and winter in comparison to a 5 cm-thick prefabricated panel. 3) The aircap wall module featuring a laminated aircap is effective in improving lighting and heating and air-conditioning energy saving when it is 10 cm- and 5 cm-thick during summer and winter, respectively, in comparison to a 5 cm-thick prefabricated panel.

• 한국가구학회지
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• 제22권1호
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• pp.63-71
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• 2011

Hanji has known for its high qualities for more than thousand years. Hanji is stronger, and has better durability, air permeability, flexibility, thermal insulation, soundproofs and UV absorbability. Therefore, developing industrial interior finishing materials using Hanji is replaced with the PVC (Poly-Vinyl Chloride) materials instead, it will be a new environment-friendly material and positively represents Korean brand marketing. The industrial inter-construction material is discomposed by heat or light because of material characteristics. As a result, it emits a lot of noxious substances. Hanji is essentially a neutral paper since it does not rely on any acidic chemicals of artificial bleaching methods. Hanji is also known as the living paper because of its close relation to nature. Therefore, I would like to suggest that Hanji made from alternative material as a chicken fiber. It will be a non-polluting interior finishing materials by making use of Hanji to a taste of Korean culture in the green industry around the world. Rather than PVC used commonly in construction material, kitchen and office furniture, interior materials in the subway, trains, or other vessels, credit cards, and ID cards, I created an interior construction material by using patented Hanji. This will be increased the value of usefulness in the environment-friendly green industry instead of PVC.

• Korean Chemical Engineering Research
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• 제56권4호
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• pp.469-473
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• 2018

개질가스를 일반적으로 사용하는 정치용 PEMFC에 순수 수소를 공급했을 때 그 특성을 차량용 막과 전극 합체(MEA)와 비교하였다. 수소 공급량을 변화시키며 anode에서 수소공급량이 전체 성능에 미치는 영향을 비교하였다. 수소를 1.0~1.7 과잉(stoi.)범위에서 공급량을 변화시켰을 때 정치용이나 차량용 모두 OCV에 미치는 영향은 거의 없었다. 0.7 V에서 정치용 MEA의 전류밀도는 차량용보다 약 16% 높았다. 그리고 상대습도를 변화시키며 I-V 성능, 임피던스, LSV를 측정하였다. 상대습도 증가에 따라 OCV와 전해질 막 저항이 모두 감소하였다. 정치용 MEA의 수소투과도가 차량용보다 더 낮아 정치용 MEA의 전해질 막의 내구성이 차량용보다 더 높을 수 있음을 보였다.