• Computers and Concrete
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• 제25권1호
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• pp.83-94
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• 2020

The use of fly ash in modern-day concrete technology aiming sustainable constructions is on rapid rise. Fly ash, a spinoff from coal calcined thermal power plants with pozzolanic properties is used for cement replacement in concrete. Fly ash concrete is cost effective, which modifies and improves the fresh and hardened properties of concrete and additionally addresses the disposal and storage issues of fly ash. Soft computing techniques have gained attention in the civil engineering field which addresses the drawbacks of classical experimental and computational methods of determining the concrete compressive strength with varying percentages of fly ash. In this study, models based on soft computing techniques employed for the prediction of the compressive strengths of fly ash concrete are collected from literature. They are classified in a categorical way of concrete strengths such as control concrete, high strength concrete, high performance concrete, self-compacting concrete, and other concretes pertaining to the soft computing techniques usage. The performance of models in terms of statistical measures such as mean square error, root mean square error, coefficient of correlation, etc. has shown that soft computing techniques have potential applications for predicting the fly ash concrete compressive strengths.

• Advances in concrete construction
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• 제9권1호
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• pp.55-70
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• 2020

In this research article, acid resistance, sulphate resistance and sorptivity of self compacted concrete (SCC) prepared from C&D waste have been discussed. To improve the above properties of self compacted recycled aggregate concrete (SCRAC) along with mechanical and durability properties, different two stage mixing approaches (TSMA and TSMAsfc) were followed. In the proposed two stage mixing approach (TSMAsfc), silica fume, a proportional amount of cement and a proportional amount of water were mixed in premix stage which fills the pores and cracks of recycled aggregate concrete (RAC). The concrete specimen prepared using above mixing approaches were immersed in 1% concentration of sulphuric acid (H2SO4) and magnesium sulphate (MgSO4) solution for 28, 90 and 180 days for evaluating the acid resistance of SCRAC. Experimental results concluded that the proposed two stage mixing approach (TSMAsfc) is most suitable for acid resistance and sulphate resistance in terms of weight loss and strength loss due to the elimination of pores and cracks in the interfacial transition zone (ITZ). In modified two stage mixing approach, the pores and cracks of recycled concrete aggregate (RCA) were filled up and make ITZs of SCRAC stronger. Microstructure analysis was carried out to justify the reason of improvement of ITZs by electron probe micro analyser (EPMA) analysis. X-ray mapping was also done to know the presence of strength contributing elements presents in the concrete sample. It was established that SCRAC with modified mixing approach have shown improved results in terms of acid resistance, sulphate resistance, sorptivity and mechanical properties.

• 한국지반환경공학회 논문집
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• 제10권5호
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• pp.11-18
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• 2009

지하매설관 설치시 매설관 아래의 베딩면 상부 되메움재는 적절한 다짐이 필요하다. 그러나 원형매설관 설치시 기존 시공법의 경우는 관 하부의 다짐이 어렵고, 또한 다짐효율이 떨어져서 지하매설관의 안정성을 저감시키며, 이로 인하여 매설관의 파손이 발생한다. 이러한 지하매설관 되메움시 발생하는 문제점을 해결할 수 있는 방법 중의 하나가 유동성 채움재(CLSM)를 이용하는 것이다. 유동성 채움재는 저강도 콘크리트 개념을 지반공학에 적용하여 만들어진 것이다. 이의 대표적인 특성은 자기수평화(self-leveling), 자기다짐(self-compacting), 유동성(flowablility), 인위적인 강도조절, 시공단계를 줄여 시공비 절감이 가능하다는 것이다. 따라서, 본 논문에서는 유한요소해석을 수행하여 동일한 조건에서 현장발생토, 일반모래, 유동성채움재를 되메움재로 사용하였을 경우의 거동을 비교 분석하였다. 그 결과 되메움재로 유동성채움재를 사용하는 경우가 현장발생토사나 일반모래를 사용한 경우보다 지표침하 및 매설관의 변위를 감소시키는 것으로 나타났다.

• Computers and Concrete
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• 제12권3호
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• pp.243-259
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• 2013

Recent developments in Artificial Intelligence (AI) and computational intelligence have made it viable in the construction industry and structural analysis. This study usesthe Adaptive Network-based Fuzzy Inference System (ANFIS) as a modelling tool to predict the strain in tie section for High Strength Self Compacting Concrete (HSSCC) deep beams. 3773 experimental data were collected. The input data andits corresponding strains in tie section as output data were recorded at all loading stages. Results from ANFIS are compared with the classical linear regression (LR). The comparison shows that the ANFIS's results are highly accurate, precise and satisfactory.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.349-352
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• 2008

본 연구는 보통강도(30MPa) 고유동 자기충전 콘크리트를 구조체에 적용하기 위하여 두개의 철근콘크리트 보(고유동 자기충전 콘크리트 실험체, 일반 콘크리트 실험체)를 제작하여 4점 재하실험을 수행하고, 고유동 자기충전 콘크리트와 일반 콘크리트의 휨 거동 특성을 비교 분석 하였다. 실험 결과 모든 실험체는 휨에 의해 연성적인 파괴양상을 보였다. 고유동 자기충전 콘크리트와 일반 콘크리트 실험체의 강성 및 연성은 유사한 거동을 보였으나, 고유동 자기충전 콘크리트가 일반 콘크리트에 비해 균열제어 효과가 뛰어난 것으로 나타났다. 이상의 결과로 고유동 자기충전 콘크리트는 현장 적용이 가능할 것으로 판단된다.

• 한국구조물진단유지관리공학회 논문집
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• 제8권4호
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• pp.195-202
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• 2004

본 연구에서는 결합재인 시멘트 외에 플라이애쉬, 고로슬래그 및 석회석 미분말을 사용하고 고성능감수제 등의 혼화제를 사용하여 고유동 무다짐이면서도 수화열을 적게 발생하는 콘크리트의 최적배합을 도출하였다. 이와 같이 선정된 배합으로 제조한 콘크리트의 장 단기거동을 기존 원전 콘크리트의 거동과 비교 검토하는 실험을 실시하였다. 연구결과 석회석이 혼합된 다성분계 고유동 콘크리트가 기존 원전용 콘크리트 보다는 시공성과 내구성이 향상되었음을 확인할 수가 있었다.

• Computers and Concrete
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• 제33권1호
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• pp.41-53
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• 2024

Under constant and cyclic axial compression, square composite short columns reinforced with Self Compacting Concrete (SCC) added with scrap rubber infilled inside steel tubes and with different types of concrete were cast and tested. The test is carried out to find the effectiveness of utilizing an aggregate manufactured from industrial waste and to address the problems associated with the need for alternative reinforcements along with waste management. The main testing parameters are the type of concrete, the effect of fiber inclusion, and the significance of rubber-infilled steel tubes. The failure modes of the columns and axial load-displacement curves of the steel tube-reinforced columns were all thoroughly investigated. According to the test results, all specimens failed due to compression failure with a longitudinal crack along the loading axis. The fiber-reinforced column specimens demonstrated improved ductility and energy absorption. In comparison to the normal-weight concrete columns, the lightweight concrete columns significantly improved the axial load-carrying capacity. The addition of basalt fiber to the columns significantly increased the yield stress and ultimate stress to 9.21%. The corresponding displacement at yield load and ultimate load was reduced to 10.36% and 28.79%, respectively. The precision of volumetric information regarding the obtained crack quantification, aggregates, and the fiber in concrete is studied in detail through image processing using MATLAB environment.

• Structural Monitoring and Maintenance
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• 제10권4호
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• pp.283-297
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• 2023

This research aims to simulate and investigate the efficiency of strengthening damaged concrete columns using concrete jacketing.The numerical program included unjacketed reference column made of ordinary RC concrete had a cross-sectional dimension of (100×100) mm and 560 mm long reinforced concrete. These cores were damaged by loading them with approximately 60% of their actual ultimate load capacities as a service load. Then, column specimens were strengthened by applying two types of self-compacting concrete SCC jacketing, which were 25 and 30 mm thick, on all four sides. Exposed to external loads at different directions vertically and horizontally simulate to the seismic load. The 3D Finite Element (FE) simulation is used to predict of three structural criteria that were selected and evaluated (deflection, stress, cracks). The results show that the failure of the strengthening columns is interesting and corresponds to the characteristics of the cracks formed in the concrete section,which was documented numerically using 3D Finite Element (FE). A significant improvement of deflection has been noted at the values at the top SECTION of columns compared to the reference sample reaching an average of up to 36.6% when using a 25 mm thick SCC-3500 jacket.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.429-430
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• 2010

본 연구에서는 플라이애쉬가 다량 치환된 고유동 HVFAC 콘크리트의 실리카흄 사용량에 따른 콘크리트 특성에 대한 연구결과를 보고하고자 한다. 결과로서, 실리카흄 사용량이 $10{\sim}20kg/m^3$일 때, 콘크리트의 유동성과 충전성능이 가장 좋은 것으로 나타났다. 그리고 실리카흄 사용량이 증가할 수록 탄산화계수는 기하급수적으로 증가하는 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.153-156
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• 2005

Surface dry condition examination method on the KS F 2504(Testing method for specific gravity and absorption of fine aggregate) has dim detail prescriptions which can cause different ways of understanding based on one's convinence, not on correct means of rule. So we investigate the problems about the inconsistency on decisioing surface dry condition at management examination in the lab and scene. In conclusion, free-falling method is easier and faster than self-weight method. And we also found that the most important face on decisioning surface dry is compacting factor of tamping rod.