• Computers and Concrete
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• 제14권3호
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• pp.299-313
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• 2014

Effects of polypropylene (PP) fibers, steel fibers (SF) and hybrid on the properties of highstrength fiber reinforced self-consolidating concrete (HSFR-SCC) under different volume contents are investigated in this study. Comprehensive laboratory tests were conducted in order to evaluate both fresh and hardened properties of HSFR-SCC. Test results indicated that the fiber types and fiber contents greatly influenced concrete workability but it is possible to achieve self consolidating properties while adding the fiber types in concrete mixtures. Compressive strength, dynamic modulus of elasticity, and rigidity of concrete were affected by the addition as well as volume fraction of PP fibers. However, the properties of concrete were improved by the incorporation of SF. Splitting tensile and flexural strengths of concrete became increasingly less influenced by the inclusion of PP fibers and increasingly more influenced by the addition of SF. Besides, the inclusion of PP fibers resulted in the better efficiency in the improvement of toughness than SF. Furthermore, the inclusion of fibers did not have significant effect on the durability of the concrete. Results of electrical resistivity, chloride ion penetration and ultrasonic pulse velocity tests confirmed that HSFR-SCC had enough endurance against deterioration, lower chloride ion penetrability and minimum reinforcement corrosion rate.

• 한국건축시공학회지
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• 제20권4호
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• pp.347-355
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• 2020

베트남의 경제 성장률과 도시인구는 꾸준히 증가함에 따라 베트남의 인프라 개발 건설 시장 규모는 더욱 커질 전망이다. 그러나 인프라 개발을 위한 베트남 정부는 재정 및 행정 능력의 한계로 이러한 문제를 해결하기 위한 방안으로 PPP를 채택하고 있다. PPP는 10년 이상 지속되는 장기 사업으로 사업 실패 시 장기적 큰 피해가 될 수 있어 위험관리가 매우 중요하다. 본 연구에서는 리스크 관리에 대한 리스크 요인의 영향과 관리정도 분석에 SOM분석을 제안한다. SOM분석 방법은 시각화 분석으로, 각 리스크 요인의 색상 패턴을 통해 상관 분석이 가능하다. 본 연구는 SOM을 활용하여 베트남 PPP 사업의 위험요인의 우선순위를 결정하고자 한다.

• 한국건설순환자원학회논문집
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• 제9권3호
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• pp.359-366
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• 2021

본 연구에서는 자기 치유 콘크리트의 주요 손상인 균열을 측정하고 이를 DB화 하기 위한 이미지 처리 기법 기반의 균열 모니터링 자동화 시스템 개발의 일환으로 균열 촬영 장비를 제작하고 균열 검출 및 분석이 가능한 프로그램을 개발하였다. 본 시스템은 기존의 육안으로 균열을 점검하는 외관조사를 대체하여 객관적이고 정량적인 데이터를 제공한다. 개발 시스템의 검증은 가상균열을 이용한 실내시험을 통해 균열 검출 알고리즘을 검증하였으며 자기치유 보수 모르타르 시공 현장에 적용하여 균열 검출 및 균열폭의 변화량을 모니터링하였다. 이미지 분석을 통해 검출된 균열폭의 경우 실측 균열폭과의 차이가 최대 0.0334mm로 나타났으며, 현장적용 결과 0.1mm 이하의 미세 균열 검출까지 가능하였으며 자기치유 보수 모르타르의 시간 경과에 따른 균열치유 효과를 균열폭 감소를 통해 확인할 수 있었다.

• 한국건설순환자원학회논문집
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• 제10권4호
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• pp.593-599
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• 2022

본 연구에서는 콘크리트 구조물의 주요 손상인 균열에 대한 효과적인 점검을 위하여 이미지 처리 기법을 이용한 균열 검출이 가능한 균열 모니터링 자동화 시스템 개발의 일환으로 머신비전을 이용하여 균열 촬영 장비를 제작하고 균열 이미지 촬영 및 분석이 가능한 프로그램을 개발하였다. 본 시스템은 기존의 육안으로 균열을 점검하는 외관조사를 대체하여 객관적이고 정량적인 데이터를 제공한다. 개발 시스템의 검증은 자기치유 콘크리트 수조 시공 현장에 적용하여 균열 검출 및 재령에 따른 균열폭의 변화량을 모니터링하였다. 이미지 분석을 통해 검출된 균열폭의 경우 디지털 현미경을 이용한 실측값과 차이가 최대 0.036 mm로 나타났으며, 자기치유 콘크리트의 재령 경과에 따른 균열 치유 효과를 균열폭 감소를 통해 확인할 수 있었다.

• 한국건설순환자원학회지
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• 제16권1호
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• pp.26-29
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• 2021

• KIEAE Journal
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• 제10권5호
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• pp.131-137
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• 2010

The building industry must aim at high-durability and sustainability. A holistic life cycle based approach is recommended to reduce the environmental load. In recent years, technical innovations in the construction industry have advanced to a great extent, and caused the active research and development of high-performance and multifunctional construction materials. Nowadays, various polymer powders have been commercialized to manufacture construction materials in the form of prepackaged-type products, which have rapidly been developed for lack of skilled workmen in construction sites. Recently, terpolymer powders of improved quality have been developed and commercialized as cement modifiers. And, hydrocalumite is a material that can adsorb the chloride ions (Cl-) causing the corrosion of reinforcing bars and liberate the nitrite ions (NO2-) inhibiting the corrosion in reinforced concrete, and can provide a self-corrosion inhibition function to the reinforced concrete. The purpose of this study is to ascertain the self-corrosion inhibition function of polymer-modified mortars using redispersible powders with hydrocalumite. Polymer-modified mortars using VA/E/MMA and VAE redispersible powders are prepared with various calumite contents and polymer-binder ratios, and tested for chloride ion penetration depth, corrosion inhibition. As a result, regardless of the polymer-binder ratio, the replacement of ordinary portland cement with hydrocalumite has a marked effect on the corrosion-inhibiting property of the polymer-modified mortars. Anti-corrosion effect of polymer-modified mortars using VA/E/MMA terpolymer powder with hydrocalumite is higher than that of VAE copolymer powder.

• Advances in concrete construction
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• 제8권3호
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• pp.225-237
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• 2019

Although applying self-consolidating concrete (SCC) in many modern structures is an inevitable fact, the high consumption of cement in its mixing designs has led to increased production costs and adverse environmental effects. In order to find economically viable sources with environmentally friendly features, natural pozzolan pumice and blast furnace slag in 10-50% of replacement binary designs have been investigated for experiments on the properties of fresh concrete, mechanical properties, and durability. As a natural pozzolan, pumice does not require advanced equipment to prepare for consumption and only needs to be powdered. Pumice has been the main focus of this research because of simple preparation. Also to validate the results, in addition to the control specimens of each design, fly ash as a known powder has been evaluated. Moreover, ternary mixes of pumice and silica fume were investigated to enhance the obtained results of binary mixes. It was concluded that pumice and slag powders indicated favorable performance in the high percentage of replacement.

• 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.

• 산업경영시스템학회지
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• 제40권4호
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• pp.230-236
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• 2017

The recent domestic construction market is in a difficult situation due to reduction of the government's SOC budget and new orders from public-sector, and the deterioration of housing supply situation in the private sector etc. In addition, the number of disasters in the construction industry has increased in recent years with 26,570 people (up 5.7% from the previous year) in 2016, unlike other industries that are in a declining trend. As such, the construction industry has unique characteristics and problems such as high industrial accidents rate, abnormal subcontracting structure, excessive working hours and work intensity. As a result, the construction workers have a lot of job stresses. Job stress has been recognized as one of the major causes of industrial accidents and many researches have been conducted on that. However, most of the researches were about the factors that induce job stress and how these factors affect disaster occurrence, job satisfaction, job performance, turnover intentions, and job exhaustion. The purpose of this study is to investigate the effect of positive psychological capital on job stress, which is emerging as a new human resources development paradigm useful in corporate management in order to find ways to reduce job stress. To do this, 347 data collected from construction workers in Daejeon, Sejong, and Chungcheong provinces were analyzed using statistical package(IBM SPSS 22) for basic statistical analysis, reliability analysis, and regression analysis. As a result, positive psychological capital has shown an alleviate effect on job stress. In particular, the higher the optimism, hope, and resiliency of positive psychological capital, the lower the job stress. However, the higher the self - efficacy, the higher the job stress.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.424-431
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• 2003

This report was studied about the advanced transit system for operating in oversea country and state of construction in the domestic. And we suggested the improvement policy against the major problems due to delay to operation and construction of advanced transit system in each cities of local self Government.