• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.19-25
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• 2005

Recycling of waste materials in the construction Industry is a useful method that can cope with an environment restriction of every country. In this study, synthetic lightweight aggregates are manufactured with recycled plastic and fly ash with 12 percent carbon. Nominal maximum-size aggregates of 9.5 mm were produced with fly ash contents of 0, 35, and $80\%$ by the total mass of the aggregate. An expanded clay lightweight aggregate and a normal-weight aggregate were used as comparison. Gradation, density, and absorption capacity are reported for the aggregates. Five batches of concrete were made with the different coarse aggregate types. Mechanical properties of the concrete were determined including density, compressive strength, elastic modulus, splitting tensile strength, fracture toughness, and fracture energy. Salt-scaling resistance, a concrete durability property, was also examined. Compressive and tensile strengths were lower for the synthetic aggregates; however, comparable fracture properties were obtained. Relatively low compressive modulus of elasticity was found for concretes with the synthetic lightweight aggregate, although high ductility was also obtained. As nv ash content of the synthetic lightweight aggregate increased, all properties of the concrete were improved. Excellent salt-scaling resistance was obtained with the synthetic lightweight aggregate containing 80 percent fly ash.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.89-97
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• 1999

In this study, fifteen reinforced high-strength lightweight concrete(HLC)beams were tested to investigate shear behavior of specimens according to shear reinforcement ratio. Test variables are shear span to effective depth ratio(a/d=2.5, 3.5, 4.5) and shear reinforcement ratio(0~1.0${\rho}_{v,ACI}$). Concrete compressive strength and tensile steel reinforcement ratio are constantly 439kg/$cm^2$ and 0.0203, respectively. Test results for the HLC beams showed that ACI code equation underestimates the shear strength of concrete($V_c$), and overestimates the shear strength of shear reinforcements($V_s$). It is revealed that the effectivenesses of shear reinforcements of reinforced HLC beams are lower than those of normal weight concrete beams. Then, the shear strengths of shear reinforcements are increased in proportion not to first degree of shear reinforcement ration but to square root of them.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.3
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• pp.158-163
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• 2012

The purpose of this study is to improve recycling rate of the coal reject ash by investigating bloating mechanism for artificial lightweight aggregate of reject ash. In this study, we use reject ash (R/A) and dredged soil (D/S) as raw materials. The artificial lightweight aggregates were formed by plastic forming (${\phi}$ = 10 mm) and sintered by temperature raising method at different temperatures (between 1200 and $1275^{\circ}C$). The physical properties of the aggregates such as bulk specific gravity, adsorption and microstructure of surface and cross-section are investigated with the sintering temperature and rate of R/A-D/S contents. As the result of the bulk specific gravity graphs, we can found out the inflection point at content of R/A 80 wt.%. From the microstructure images, we considered the artificial lightweight aggregates content of R/A over 80 wt.% are distributed numerous uniform micro-pores by vitrification without Black Core and the artificial lightweight aggregates of R/A below 80wt.% are distributed macro-pores with Black Core.

• Composites Research
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• v.23 no.4
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• pp.35-43
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• 2010

The purpose of this paper is to develop a Hybrid Fiber-reinforced High Strength Lightweight Cementitious Composite (HFSLCC) incorporated with lightweight filler and hybrid fibers for lightness and high ductility. Optimal ingredients and mixture proportion were determined on the basis of the micromechanical analysis and the steady-state cracking theory considering the fracture characteristics of matrix and the interfacial properties between fibers and matrix. Then 4 mixture proportions were determined according to the type and amount of fibers and the experiment was performed to evaluate the mechanical performance of those. The HFSLCC showed 3% of tensile strain, 4.2MPa of ultimate tensile stress, 57MPa of compressive strength and $1,660kg/m^3$ of bulk density. The mechanical performance of HFSLCC incorporated with PVA fibers of 1.0 Vol.% and PE fibers of 0.5 Vol.% is similar to those of the HFSLCC incorporated with fibers of 2.0 Vol.%.

• Industry Promotion Research
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• v.6 no.4
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• pp.1-9
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• 2021

The purpose of this study is to manufacture lightweight aggregates for recycling water treatment sludge, to identify the physical properties of the aggregates, and present a method of utilizing the manufactured lightweight aggregates. The chemical composition and thermal properties were examined via a raw materials analysis. The aggregate examined here was fired by the rapid sintering method and the single-particle density and water absorption rate were measured. Water treatment sludge has high ignition loss and high fire resistance. When 30wt% of purified sludge was added, the single-particle density of the aggregates was in the range of 0.8~1.2g/cm³ at a temperature of 1,150~1,200℃. At temperatures of 1200℃ or higher, ultra-light aggregates having a single-particle density of 0.8 or less could be produced. When applied to concrete by replacing the general aggregate in the concrete, a specimen having strength values of 200 to 450 kgf/cm² on 28 days was obtained, and when applied as a filter material, the performance was equal to or higher than that of ordinary sand.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.1
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• pp.1-8
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• 2024

On-device AI technology, which can operate AI models at the edge devices to support real-time processing and privacy enhancement, is attracting attention. As intelligent IoT is applied to various industries, services utilizing the on-device AI technology are increasing significantly. However, general deep learning models require a lot of computational resources for inference and learning. Therefore, various lightweighting methods such as quantization and pruning have been suggested to operate deep learning models in embedded edge devices. Among the lightweighting methods, we analyze how to lightweight and apply deep learning models to edge computing devices, focusing on pruning technology in this paper. In particular, we utilize dynamic and static pruning techniques to evaluate the inference speed, accuracy, and memory usage of a lightweight AI vision model. The content analyzed in this paper can be used for intelligent video control systems or video security systems in autonomous vehicles, where real-time processing are highly required. In addition, it is expected that the content can be used more effectively in various IoT services and industries.

• Journal of the Korean Society for Railway
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• v.19 no.2
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• pp.135-144
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• 2016

It is essential to lighten the weight of switch girders in order to reduce their costs of manufacturing and make it easier to use them in construction. Lightening the weight of switch is also important to the Maglev 3-way switches system, however, the design variables should be considered very carefully if lightening is to be applied to the system, because these variables are vitally related to the levitation stability. Because Urban Maglev trains have a structure in which train bogie wraps around the guiderail, the adjustment of a girder's height is a possible way to reduce the weight. The safety of the application of this concept is ensured by repeated experiments in a test bed, however, due to a lack of space and budget limits, the design parametric study for the system model can substitute for actual application. The purpose of this paper is to study the design parameters that are concerned with levitation stability while a Maglev train is running on the Maglev 3-way system depending on the weight of the switch girders. In this study, switch girder weight is reduced by adjustment of girder height and girders are and modeled as a flexible body. The effect of the adjustment of girder height on the levitation stability can be analyzed by comparing the velocity of the train when it passes the switch girders, with the lateral gap, and the levitation gap which are obtained from the co-simulation of the Maglev train's dynamics model and flexible switching system. The results of this research will be used to design a Maglev switch.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.268-275
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• 2021

The three factors that determine the strength of concrete are the strength of cement paste, aggregate and ITZ(Interfacial Transition Zone) between aggregate and cement paste. Out of these, the strength of ITZ is the most vulnerable. ITZ is formed in 10~50㎛, the ratio of calcium hydroxide is high, and CSH appears low ratio. A high calcium hydroxide ratio causes a decrease in the bond strength of ITZ. ITZ is due to further weak area. The problem of ITZ appears as a more disadvantageous factor when it used lightweight aggregate. The previous study of ITZ properties have measured interfacial toughness, identified influencing factors ITZ, and it progressed SEM and XRD analysis on cement matrix without using coarse aggregates. also it was identified microstructure using EMPA-BSE equipment. However, in previous studies, it is difficult to understand the microstructure and mechanical properties. Therefore, in this study, a method of measuring electrical resistance using EIS(Electrochemical Impedance Spectroscopy) measuring equipment was adopted to identify the ITZ between natural aggregate and lightweight aggregate, and it was tested the change of ITZ by surface coating of lightweight aggregate with ground granulated blast furnace slag. As a result, the compressive strength of natural aggregate and lightweight aggregate appear high strength of natural aggregate with high density, surface coating lightweight aggregate appear strength higher than natural aggregate. The electrical resistivity of ITZ according to the aggregate appeared difference.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.2
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• pp.82-86
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• 2011

Lightweight aggregate which is composed of sintered polycrystalline materials usually has a certain portion of pores inside of it. Because of such a structural characteristics, it tends to that movement of water in aggregate shows an abnormal behavior against the change of outside environment. In general, water movement behavior is controlled by porosity, distribution of pore size; however, dense surface layer will also affect water movement behavior in case of artificially sintered aggregates. Factors affecting water movement behavior in the aggregate are pore distribution, pore shape, pre-wetting method, etc. In this study, absorption characteristics of aggregate under the pressure and absorption rate according to water dipping time are analyzed for the basis of pressure pumping of lightweight concrete. Two kinds of aggregates were used for the test: one is made by 'L' company in Germany and the other is of our own made at the pilot plant in Kyonggi University. Absorption rate of aggregate is measured according to water dipping time, vacuum pressure, and quenching condition. Absorption rate of aggregate with $300^{\circ}C$ quenching is higher than that of aggregate with 24 hr water dipping. Generally the more vacuum the higher water absorption rate. Water absorption rate of 'L' aggregate under -300 mmHg is 54 % higher than that of aggregate with 24 hr water dipping; however, only 2 % increase in water absorption was measured for the K622 and K73 which were of our own.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.669-677
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• 2009

Twenty-four beam specimens were tested to examine the effect of the maximum aggregate size on the shear behavior of lightweight concrete continuous beams. The maximum aggregate size varied from 4 mm to 19 mm and shear span-to-depth ratio was 2.5 and 0.6 in each all-lightweight, sand-lightweight and normal weight concrete groups. The ratio of the normalized shear capacity of lightweight concrete beams to that of the company normal weight concrete beams was also compared with the modification factor specified in ACI 318-05 for lightweight concrete. The microphotograph showed that some unsplitted aggregates were observed in the failure planes of lightweight concrete beams, which contributed to the enhancement of the shear capacity of lightweight concrete beams. As a result, the normalized shear capacity of lightweight concrete continuous beams increased with the increase of the maximum aggregate size, though the increasing rate was lower than that of normal weight concrete continuous beams. The modification factor specified in ACI 318-05 was generally unconservative in the continuous lightweight concrete beams, showing an increase of the unconservatism with the increase of the maximum aggregate size. In addition, the conservatism of the shear provisions of ACI 318-05 was lower in lightweight concrete beams than in normal weight concrete beams.