• Computers and Concrete
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• 제10권1호
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• pp.35-47
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• 2012

The ideal gradating curve is used in this study to estimate densified aggregate blended ratio and total surface area of aggregate, there by under assigned paste amount of concrete, and coating paste thickness can then be deduced. Four groups of concrete mixtures were prepared and the corresponding concrete properties, such as workability, compression strength, ultrasonic velocity, surface resistivity and chloride ion penetration, were measured and finally the results are interpreted in terms of "coating thickness". The result shows as the coating thickness of the concrete is higher than critical one, the coating thickness on aggregate does affect the workability, and whatever workability is required the superplasticizer can be adjusted to achieve the demand workability. Under a fixed paste quality at the same age, coating paste thickness is inversely proportional to the concrete properties, especially as the coating thickness gets thinner.

• 국제학술발표논문집
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• The 2th International Conference on Construction Engineering and Project Management
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• pp.433-439
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• 2007

A ubiquitous environment in construction requires integrating hardware and software systems. Currently the Construction System Integration Lab (CSIL) at Pusan National University is currently studying the application of ubiquitous technology for better communication in the construction process. In this paper, a pilot of Ubiquitous Concrete Pour System (u-CPS) has been presented to demonstrate the effectiveness of data exchange in the concrete pour process. The u-CPS environment takes advantage of the RFID technology for collecting construction data. The pilot can automatically generate the data for concrete pour work such as departure time, arrival time, concrete pour time. Construction managers can keep track of the progress of concrete pour work using the information. A case study was done for a building construction using the pilot system, the result of which demonstrated that the RFID-base system can help improve the effectiveness of data communication during the concrete pour process.

• Computers and Concrete
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• 제4권5호
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• pp.347-362
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• 2007

Due to heterogeneities at all scales, concrete exhibits significant variability in mechanical behavior from sample to sample. An understanding of the fundamental mechanical performance of concrete must therefore be embedded in a stochastic framework. The current work attempts to address the connection between a two-dimensional concrete mesostructure and the random local material properties associated within that mesostructure. This work builds on previous work that has focused on the random configuration of concrete mesostructures. This was accomplished by developing an understanding of the effects of variations in the mortar strength and the mortar-aggregate interfacial strength in given deterministic mesostructural configurations. The results are assessed through direct tension tests that are validated by comparing experimental results of two different, pre-arranged mesostructures, with the intent of isolating the effect of local variations in strength. Agreement is shown both in mechanical property values as well as the qualitative nature of crack initiation and propagation.

• Structural Engineering and Mechanics
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• 제61권1호
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• pp.125-142
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• 2017

Extensive research work has been performed on shear strengthening of reinforced concrete (RC) beams retrofitted with externally bonded carbon fiber reinforced polymer (CFRP) in form of strips. However, most of this research work is experimental and very scarce studies are available on numerical modelling of such beams due to truly challenging nature of modelling concrete shear cracking and interfacial interaction between components of such beams. This paper presents an appropriate model for RC beam and to simulate its cracking without numerical computational difficulties, convergence and solution degradation problems. Modelling of steel and CFRP and their interfacial interaction with concrete are discussed. Finally, commercially available non-linear finite element software ABAQUS is used to validate the developed finite element model with key tests performed on full scale T-beams with and without CFRP retrofitting, taken from previous extensive research work. The modelling parameters for bonding behavior of CFRP with special anchors are also proposed. The results presented in this research work illustrate that appropriate modelling of bond behavior of all the three types of interfaces is important in order to correctly simulate the shear behavior of RC beams strengthened with CFRP.

• 콘크리트학회지
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• 제11권2호
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• pp.10-27
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• 1999

• 콘크리트학회지
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• 제11권2호
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• pp.5-9
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• 1999

• 콘크리트학회지
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• 제9권4호
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• pp.49-56
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• 1997

• 콘크리트학회지
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• 제8권3호
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• pp.5-18
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• 1996

• 한국건설관리학회논문집
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• 제15권4호
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• pp.49-57
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• 2014

최근 건설 구조물의 다양화, 대형화, 고층화 및 장지간화 되면서 콘크리트 구조재료에 관한 고성능화가 요구되고 있으며, 특히 콘크리트의 고강도 및 고성능화가 대두되고 있다. 콘크리트의 고성능화 및 재료 특성을 개선하는 방법으로 주로 첨단소재 기술에 의해 개발된 첨단 섬유를 적용하는 방법이 사용되어 왔으며, 고성능 섬유시멘트 복합체(이하 HPFC)를 적용한 콘크리트 기둥 공법이 그 중 하나이다. 본 연구는 시뮬레이션 기법을 활용해, 일반 RC 기둥 대비 프리캐스트 기법이 적용된 HPFC 기둥 공법 공정에 대한 작업프로세스를 분석함과 동시에, 수집한 작업데이터를 통해 HPFC 기둥 공법의 공정계획상 이슈를 도출하였다. 그 결과 생산성에 가장 영향이 큰 작업(노드)로 '콘크리트 작업조', '형틀 작업조'로 도출되었으며, 특히 '콘크리트 작업조'가 공정계획상 가장 중요한 요소로 작용함을 확인할 수 있었다. 해당 작업(노드)에 투입되는 작업조 수 변화를 통한 생산성 향상을 확인하였으며 본 연구를 바탕으로 HPFC 기둥 공법의 실용화 단계에 도움이 될 것으로 예상된다.

• 콘크리트학회논문집
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• 제12권5호
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• pp.25-34
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• 2000

When concrete is placed underwater, it is diluted with separating cementitious material and as a result the quality of concrete becomes poor. To solve this problem, antiwashout underwater concrete is increasingly used for the construction and repair of the concrete structure underwater. The objective of this study is to investigate the characteristics of antiwashout underwater concrete as to the mix proportion, casting and curing water through experimental researches. The unit weight of water and cement, water-cement ratio, fine aggregate ratio, unit weight of antiwashout underwater agent and superplasticizer, and casting and curing water were chosen to measure the suspended solids, pH, air contents, slump flow, unit weight of hardened concrete, and compressive strength. From this study, the incremental modulus at mix proportion design and unit weight of antiwashout underwater agent were increased more than fresh water, and it is a optimum mix proportion that the unit weight of water(and cement) is 230kg/$\textrm{m}^3$(460kg/$\textrm{m}^3$), waterOcement ratio is 50%, fine aggregate ratio is 40%, unit weight of antiwashout underwater agent is 1.2% of water contents per unit weight of concrete, and unit weight of supeplasticizer is 2.5% of cement contents per unit weight of concrete when the antiwashout underwater concrete is used for the underwater work of ocean.