• Computers and Concrete
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• 제26권6호
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• pp.505-513
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• 2020

Grading of aggregate influences significantly almost all of the concrete performances. The purpose of this paper is to propose practicable equations that express the optimized total aggregate gradation, by weight or by number of particles in a concrete mix. The principle is based on the fractal feature of the grading of combined aggregate in a solid skeleton of concrete. Therefore, equations are derived based on the so-called fractal dimension of the grain size distribution of aggregates. Obtained model was then applied in such a way a correlation between some properties of the dry concrete mix and the fractal dimension of the aggregate gradation has been built. This demonstrates that the parameter fractal dimension is an efficacious tool to establish a unified model to study the solid phase of concrete in order to design aggregate gradation to meet certain requirements or even to predict some characteristics of the dry concrete mixture.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.76-79
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• 2001

In Japan in of today, there is no aspect in which the quantity of waste glass bottle discharged from ordinary homes decreases. Moreover, the kind of shape and color of the waste glass bottles are increasing little by little. In the recycling of the glass bottle, it becomes a problem that many kind of the color is abounding. It is possible to use the transparent glass bottle as raw material of the glassware. Since the reproduction of the color is difficult, the colored glass bottle is not possible to use as a raw material. Therefore, the processing of these glass bottles entirely depends on the reclamation. In Japan, the security of the new reclaimed land is very difficult for the reason of the environmental damage. Moreover, the life expectancy in many reclaimed lands is anticipated with within two years. Therefore, the development of the processing method of glass bottle other than reclamation becomes a rapid problem. At present it is examined that it is used of an aggregate of the colored pavement, as one of the application methods of colored glass bottle. The particle size of produced glass aggregate is also 5mm or less, because the thickness is 5mm or less on almost glass bottles. And almost glass particles have the sharp tip. The application as the aggregate is limited for this sharpness of the particle. This study was carried out for the purpose of the establishment of sharpness measuring method of the glass aggregate particle. It is possible that the injury degree to human in the handling is known, if showing the sharpness of the aggregate particle at the objective numerical value is possible. And the application of the glass aggregate is spread. In this research, the balloon fracture method was used for the sharpness measurement of the glass particle. This method is based on the completely new idea, and it is possible to express completely the possibility of injury to the human. It is reported with the detailed result in full paper, because this study is continuous in order to get the JIS which is industrial standard of Japan.

• 한국철도학회논문집
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• 제12권4호
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• pp.481-487
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• 2009

포장궤도에서는 프리팩 콘크리트방식으로 도상자갈을 충전층의 골재로 활용한다. 골재의 조건은 강도가 확보되어야 하고, 주입성 확보를 위한 입도가 확보되어야 하며, 모르터의 부착강도를 높이기 위하여 골재 표면의 불순물이 제거되어야 한다. 골재의 원활한 공급 측면에서 기존 도상자갈을 재활용하는 것이 유리하며 재활용성을 높이기 위하여 기존의 철도도상규격을 크게 벗어나지 않는 기준을 적용하는 것이 필요하다. 따라서 본 연구에서는 포장궤도에서의 도상자갈 재활용성을 확보 할 수 있는 판단 기준을 마련하기 위하여 재활용 도상자갈의 재료 및 물리적 특성, 입도별 지지력 특성, 충전성, 강도특성 등을 검토하였으며, 그 결과를 바탕으로 골재 사용기준을 제안하고자 하였다.

• 대한기계학회논문집B
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• 제27권12호
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• pp.1734-1743
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• 2003

Aerosol generator using an electrically heated tube furnace is a stable apparatus to supply nanometer sized aerosols by using the evaporation and condensation processes. Using this method, we can generate highly concentrated polydisperse aerosols with relatively narrow size distribution. In this work, characteristics of particle size distribution, generated from a tube furnace, were experimentally investigated. We evaluated effects of several operation parameters on particle generation: temperature in the tube furnace, air flow rates through the tube, size of boat containing solid sodium chloride(NaCl). As the temperature increased, the geometric mean diameter increased and the total number concentration also increased. Dilution with air affected the size distribution of the particles due to coagulation. A smaller sized boat, which has small surface area to contact with air, brings smaller particles of narrow size distribution in comparison of that of a larger boat. Finally, we changed the electrical mobility diameter of aggregate sodium chloride particles by varying relative humidity of dilution air, and obtained non-aggregate sodium chloride particles, which are easy to generate exact monodisperse particles.

• 한국건설순환자원학회논문집
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• 제5권4호
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• pp.458-465
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• 2017

본 연구에서는 굴 패각을 원료(골재)로 활용하기 위한 물리적인 가공방법에 관한 것을 실험을 통해 검토하고자 하였다. 실험결과 굴 패각의 형상에 의해 분쇄된 굴 패각의 적정 입도는 10mm 보다 작아야 될 것으로 판단된다. 또한 가동시간과 회수율, 각 입도별 잔류율과 다양한 입도분포를 고려할 때 굴 패각의 분쇄에는 커터 밀이 적합한 것으로 나타났다. 커터 밀의 경우, 8mm의 내부 스크린을 적용할 때, 회수율은 97.3% 12mm를 적용할 때, 98.2%, 20mm일 때, 98.9%로 나타나 스크린 사이즈가 커짐에 따라 회수율은 다소 증가되는 것으로 나타났다. 커터 밀의 내부 스크린과 인버터의 속도 차이에 의한 실험결과 스크린의 크기가 작을수록, 인버터의 속도가 빠를수록 조립률은 낮아지는 것으로 나타났으며, 동일한 스크린에서 인버터 속도의 상승은 더욱 낮은 입도범위의 재료 회수가 가능한 것으로 나타났다.

• Computers and Concrete
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• 제17권5호
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• pp.613-628
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• 2016

In this study, the influence of coarse aggregate size and type on chloride penetration of concrete was investigated, and the grey correlation analysis was applied to find the key influencing factor. Furthermore, the proposed 6-10-1 artificial neural network (ANN) model was constructed, and performed under the MATLAB program. Training, testing and validation of the model stages were performed using 81 experiment data sets. The results show that the aggregate type has less effect on the concrete permeability, compared with the size effect. For concrete with a lower w/b, the coarse aggregate with a larger particle size should be chose, however, for concrete with a higher w/c, the aggregate with a grading of 5-20 mm is preferred, too large or too small aggregates are adverse to concrete chloride diffusivity. A new idea for the optimum selection of aggregate to prepare concrete with a low penetration is provided. Moreover, the ANN model predicted values are compared with actual test results, and the average relative error of prediction is found to be 5.62%. ANN procedure provides guidelines to select appropriate coarse aggregate for required chloride penetration of concrete and will reduce number of trial and error, save cost and time.

• Journal of Korean Dental Science
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• 제6권2호
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• pp.41-49
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• 2013

Purpose: This study sought to compare the elemental constitution, morphological characteristics, particle size distribution, biocompatibility, and mineralization potential of Ortho MTA (OMTA) and ProRoot MTA (PMTA). Materials and Methods: OMTA and PMTA were compared using energy-dispersive spectrometry, particle size analysis, and scanning electron microscopy. The biocompatibility and mineralization-related gene expression (osteonectin and osteopontin) of both MTAs were also compared using methylthiazol tetrazolium assay and reverse transcription-polymerization chain reaction analysis, respectively. The results were analyzed by Kruskal-Wallis test with Bonferroni correction. P-value of <0.05 was considered significant. Result: The morphology of OMTA powders was similar to that of PMTA. The constituent elements of both MTAs were calcium, silicon, and aluminum. The mean particle sizes of OMTA and PMTA were 4.60 and 3.34 mm, respectively. Both MTAs had equally favorable in vitro biocompatibility and affected the messenger RNA expression of osteonectin and osteopontin. Conclusion: Within the limitations of this study, OMTA could be a promising biomaterial in clinical endodontics.

• 자원환경지질
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• 제57권2호
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• pp.177-184
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• 2024

연구는 국내 골재 생산 과정에서 발생하는 케이크의 발생을 줄이는 방안을 찾고자 수행되었다. 8개 습식 골재 생산 업체의 케이크를 수집하여 입도를 분석하였다. A 골재 생산 현장에서 시료를 채취하고 입도 분석을 수행했다. 생산 공정을 모델링하여 모래 회수 장치 전후에서 물질 수지를 계산했다. 8개의 케이크 입도 분석 결과 하나의 시료에서 모래가 50% 포함된 사례도 있었고 나머지는 약 5~25% 포함하고 있었다. 케이크 내 다양한 모래가 포함하고 있다는 결과는 현장의 모래 회수 장치의 회수 효율이 다양함을 의미할 수 있다. A 업체 파쇄 공정에서 모래 입도는 2차 파쇄 때보다 3차 파쇄 때에 2.8배 증가했고 케이크 입자도 더 많이 발생했다. 모래 회수 공정을 모사한 결과 사이클론 및 탈수체의 분극점이 낮아질수록 모래 생산은 증가했고 케이크 발생은 적어지는 추세가 나타났다. 현장에서 케이크의 발생을 줄이기 위해서 골재생산 공정에서 특히 모래 회수 장치의 적정 운전이 필요할 것으로 판단되었다.

• 한국도로학회논문집
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• 제8권1호
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• pp.107-117
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• 2006

Recently, there has been a remarkable trend of using aggregates at sizes smaller than 13 mm for drainage asphalt pavement (DAP) in order to reduce the noise generated between vehicle tires and road surface. These DAPs have their performance and durability seriously worsen after several years in-service due to the clogging of void space and the abrasion. This paper proposes the use of large size aggregates in porous asphalt mixtures to overcome these defects. Results of laboratory and field experiments on asphalt mixtures with several aggregate gradations are investigated and compared. The study focuses on advantages of DAP using large size aggregate and on particle size combinations containing no fine aggregates of size 2.36 mm or less, which have not been considered in current engineering practice.

• 실천공학교육논문지
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• 제13권3호
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• pp.559-566
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• 2021

골재입도시험은 건설관련 전공교육에서 반드시 필요한 골재입도 시험결과에 대한 특정목적의 정확성을 평가하는 연구이다. 본 연구는 골재 함수비가 골재 입도 분석에 미치는 영향을 평가하기 위하여 수행되었다. 아스팔트 플랜트 콜드빈과 야적장에 저장된 골재의 함수비 변화를 1년간 모니터링하여, 그 결과를 기초로 함수비가 다른 골재 샘플을 제작하였다. 각 골재 샘플에 대한 입도 곡선을 분석하여 골재 함수비가 골재 입도 분석에 미치는 영향을 평가하였다. 입도평가결과, 함수비가 높아짐에 따라 오븐 건조 골재의 입도 분석에서 5 mm 이하의 입자에 대한 입자 크기의 오차가 증가하였으며, 이 오차는 입자 크기가 작아질수록 증가함을 확인하였다. 또한 5 mm 이상의 골재 입자에 대해서는 이러한 함수비 증가에 따른 입도 분석의 오차가 급격히 작아지는 것을 확인하였다. 이러한 비 절건 상태의 골재에 대한 입도분석의 오차가 아스팔트 플랜트 내 핫빈 골재 관리에 미치는 영향에 대한 분석을 수행하였다. 분석결과, 일반적인 아스팔트 플랜트에서 첫 번째 핫빈의 최소 골재 크기는 2.38 mm 이상이므로, 비 절건상태 골재로 인한 최대 입도 오차는 2% 미만인 것으로 조사되었다. 따라서 아스팔트 혼합물 생산품질관리를 위하여 콜드빈 비 절건상태 골재의 입도시험 결과를 사용하는 것은 가능해 보인다.