• Advances in concrete construction
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• 제9권4호
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• pp.387-395
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• 2020

This study has been carried out in two-phases to develop Fiber Reinforced Self-Compacting Concrete (FRSCC) performance. In the first phase, the composition of the quaternary composite binder compromised CEM I 42.5N (58-70%), Rice Husk Ash (25-37%), quartz sand (2.5-7.5%) and limestone crushing waste (2.5-7.5%) were optimized. And in the second phase, the effect of two fiber types (steel brass-plated and basalt) was investigated on the SCC optimized with the optimum CB as disperse reinforcement at 6 different ratios of 1, 1.2, 1.4, 1.6, 1.8, and 2.0% by weight of mix for each type. In this study, the theoretical principles of the synthesis of self-compacting dispersion-reinforced concrete have been developed which consists of optimizing structure-formation processes through the use of a mineral modifier, together with ground crushed cement in a vario-planetary mill to a specific surface area of 550 m2 / kg. The amorphous silica in the modifier composition intensifies the binding of calcium hydroxide formed during the hydration of C3S, helps reduce the basicity of the cement-composite, while reducing the growth of portlandite crystals. Limestone particles contribute to the formation of calcium hydrocarbonate and, together with fine ground quartz sand; act as microfiller, clogging the pores of the cement. Furthermore, the results revealed that the effect of fiber addition improves the mechanical properties of FRSCC. It was found that the steel fiber performed better than basalt fiber on tensile strength and modulus of elasticity; however, both fibers have the same performance on the first crack strength and sample destruction of FRSCC. It also illustrates that there will be an optimum percentage of fiber addition.

• Advances in concrete construction
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• 제6권2호
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• pp.199-220
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• 2018

In this study, the effects of sulphuric acid on the mechanical performance and the durability of Engineered Cementitious Composites (ECC) specimens were investigated. The carbon fiber reinforced polymer (CFRP) and basalt fiber reinforced polymer (BFRP) fabrics were used to evaluate the performances of the confined and unconfined ECC specimens under static and cyclic loading in the acidic environment. In addition, the use of CFRP and BFRP fabrics as a rehabilitation technique was also studied for the specimens exposed to the sulphuric acid environment. The polyvinyl alcohol (PVA) fiber with a fraction of 2% was used in the research. Two different PVA-ECC concretes were produced using low lime fly ash (LCFA) and high lime fly ash (HCFA) with the fly ash-to-OPC ratio of 1.2. Unwrapped PVA-ECC specimens were also produced as a reference concrete and all concrete specimens were continuously immersed in 5% sulphuric acid solution ($H_2SO_4$). The mechanical performance and the durability of specimens were evaluated by means of the visual inspection, weight change, static and cyclic loading, and failure mode. In addition, microscopic changes of the PVA-ECC specimens due to sulphuric acid attack were also assessed using scanning electron microscopy (SEM) to understand the macroscale behavior of the specimens. Results indicated that PVA-ECC specimens produced with low lime fly ash (LCFA) showed superior performance than the specimens produced with high lime fly ash (HCFA) in the acidic environment. In addition, confinement of ECC specimens with BFRP and CFRP fabrics significantly improved compressive strength, ductility, and durability of the specimens. PVA-ECC specimens wrapped with carbon FRP fabric showed better mechanical performance and durability properties than the specimens wrapped with basalt FRP fabric. Both FRP materials can be used as a rehabilitation material in the acidic environment.

• 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.299-314
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• 2023

Long-gauge carbon fiber line (CFL) sensors have received considerable attention in the past decade. However, there is still a need for an in-depth investigation of their measuring accuracy. This study investigates the accuracy of carbon fiber line sensors to monitor and differentiate the flexural behavior of two beams, one reinforced with steel bars alone and the other reinforced with steel and basalt fiber-reinforced polymer bars. A distributed set of long-gauge carbon fiber line, Fiber Bragg Grating (FBG), and traditional strain gauge sensors was mounted on the tensile concrete surface of the studied beams to compare the results and assess the accuracies of the proposed sensors. The test beams were loaded monotonically under four-point bending loading until failure. Results indicated the importance of using long-gauge sensors in providing useful, accurate, and reliable information regarding global structural behavior, while point sensors are affected by local damage and strain concentrations. Furthermore, long-gauge carbon fiber line sensors demonstrated good agreement with the corresponding Fiber Bragg Grating sensors with acceptable accuracy, thereby exhibiting potential for application in monitoring the health of large-scale structures.

• Steel and Composite Structures
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• 제49권4호
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• pp.457-471
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• 2023

To make up for the performance weaknesses of recycled aggregate concrete (RAC), expand the application range of RAC, and alleviate the environmental problems caused by excessive exploitation of natural coarse aggregates (NCA), this study proposes a basalt fiber-reinforced recycled aggregate concrete (BFRRAC)-filled square steel tubular columns that combines two modification methods of steel tube and fiber, which may greatly enhance the mechanical properties of RAC. The axial compression performance for BFRRAC-filled square steel tubular columns was reported during this study. Seven specimens with different replacement ratios of recycled coarse aggregate (RCA), length-diameter ratios, along with basalt fiber (BF) contents were designed as well as fabricated for performing axial compression test. For each specimen, the whole failure process as well as mode of specimen were discovered, subsequently the load-axial displacement curve has obtained, after which the mechanical properties was explained. A finite element analysis model for specimens under axial compression was then established. Subsequently, based on this model, the factors affecting axial compression performance for BFRRAC-filled square steel tubes were extended and analyzed, after which the corresponding design suggestion was proposed. The results show that in the columns with length-diameter ratios of 5 and 8, bulging failure was presented, and the RAC was severely crushed at the bulging area of the specimen. The replacement ratio of RCA as well as BF content little affected specimen's peak load (less than 5%). As the content of BF enhanced from 0 kg/m³ to 4 kg/m³, the dissipation factor and ductility coefficients increased by 10.2% and 5.6%, respectively, with a wide range.

• 한국구조물진단유지관리공학회 논문집
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• 제24권6호
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• pp.153-160
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• 2020

지진동 하의 구조 시스템에서 기둥은 가장 중요한 구조 요소 중 하나이다. 이러한 관계로, 철근콘크리트(RC) 기둥의 내진 성능에 FRP 보강이 미치는 영행을 평가하기 위하여 광범위한 실험 연구가 이루어졌다. 이 중 상당수는 CFRP 또는 GFRP로 보강된 원형 단면 또는 정사각형 단면의 RC 기둥의 지진 거동에 집중하였다. 단면의 형태가 FRP 보강으로 인한 구속 효과에 영향을 미치기 때문에, 보강 효과와 최종 파괴 패턴이 형상에 따라 상이할 수 있다. 본 연구에서는 현무암 섬유를 함유한 BFRP 시트와 복합섬유 패널로 보강한 직사각형 단면을 가진 RC 기둥의 지진 거동을 살펴보기 위하여 반복하중 실험을 수행하였다. 실험 결과는 보강 효과가 크지 않았음을 보여주는데, BFRP 시트와 복합섬유 패널에 의한 구속 효과의 증가가 미미했음을 의미하며, 이는 기둥 단면 형상에 일부 기인하는 것으로 판단된다.

• 한국구조물진단유지관리공학회 논문집
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• 제27권6호
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• pp.47-54
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• 2023

본 연구에서는 GFRP, BFRP와 CFRP 보강근으로 보강된 콘크리트 시험체의 인장 거동 특성을 실험적으로 분석하였다. FRP 보강근의 인장강도는 설계강도와 유사하게 나타났으나, 탄성계수는 다소 낮게 측정되었다. 또한 인장강화 시험체는 OPC와 SFRC를 사용하여 150(W)×150(B)×1000(H) mm의 크기로 제작하였다. 균열간격은 탄성계수가 낮고 표면이 보다 매끄러운 GFRP 보강근이 가장 크게 나타났으며, 표면이 다소 거친 BFRP와 탄성계수가 높은 CFRP 보강근의 균열간격은 비슷하게 분석되었다. 하중-변형률관계에서도 GFRP보강근은 균열후 다소 급격한 거동을 보인것에 반하여 BFRP와 CFRP 보강근은 균열발생시 다소 안정적인 거동후 일정수준은 인장강화 효과를 유지하였다. 인장강화지수의 경우 직경이 증가할수록 인장강화지수는 다소 작게 분석되었으며, BFRP보다 GFRP의 경우가 인장강화지수는 높게 분석되었다.

• Steel and Composite Structures
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• 제29권2호
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• pp.201-218
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• 2018

In this study, the effects of magnesium sulfate on the mechanical performance and the durability of confined and unconfined geopolymer concrete (GPC) specimens were investigated. The carbon and basalt fiber reinforced polymer (FRP) fabrics with 1-layer and 3-layers were used to evaluate the performances of the specimens under static and cyclic loading in the ambient and magnesium sulfate environments. In addition, the use of FRP materials as a rehabilitation technique was also studied. For the geopolymerization process of GPC specimens, the alkaline activator has selected a mixture of sodium silicate solution ($Na_2SiO_3$) and sodium hydroxide solution (NaOH) with a ratio ($Na_2SiO_3/NaOH$) of 2.5. In addition to GPC specimens, an ordinary concrete (NC) specimens were also produced as a reference specimens and some of the GPC and NC specimens were immersed in 5% magnesium sulfate solutions. The mechanical performance and the durability of the specimens were evaluated by visual appearance, weight change, static and cyclic loading, and failure modes of the specimens under magnesium sulfate and ambient environments. In addition, the microscopic changes of the specimens due to sulfate attack were also assessed by scanning electron microscopy (SEM) to understand the macroscale behavior of the specimens. Results indicated that geopolymer specimens produced with nano-silica and fly ash showed superior performance than the NC specimens in the sulfate environment. In addition, confined specimens with FRP fabrics significantly improved the compressive strength, ductility and durability resistance of the specimens and the improvement was found higher with the increased number of FRP layers. Specimens wrapped with carbon FRP fabrics showed better mechanical performance and durability properties than the specimens wrapped with basalt FRP fabrics. Both FRP materials can be used as a rehabilitation material in the sulfate environment.

• 한국구조물진단유지관리공학회 논문집
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• 제19권4호
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• pp.49-56
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• 2015

초고성능 콘크리트는 높은 강도와 유동성을 갖는 우수한 재료 특성을 나타내는 콘크리트이다. 그러나 고연성 시멘트 복합체에 비하여 낮은 연성을 나타낸다. 이 연구에서는 강섬유와 마이크로섬유의 조합이 초고성능 콘크리트의 인장거동에 미치는 영향을 조사하였다. 이를 위하여 강섬유와 폴리에틸렌, 폴리비닐알코올, 현무암섬유 조합에 따라 4가지 초고성능 콘크리트 배합을 결정하였고, 인장거동을 평가하기 위하여 직접인장 실험을 수행하였다. 또한 마이크로섬유가 제조과정에서 의도하지 않은 과도한 기포를 생성하는지를 확인하기 위하여 밀도실험을 수행하였다. 실험결과 인장강도가 높은 폴리에틸렌섬유는 초고성능 콘크리트의 인장거동을 향상시키는데 효과적임을 확인하였고, 현무암섬유는 초고성능 콘크리트의 균열강도 및 인장강도를 증가시키는데 효과적임을 확인하였다. 또한 마이크로섬유가 의도하지 않은 기포를 생성하지 않는다는 것도 확인하였다.

• 대한토목학회논문집
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• 제42권5호
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• pp.607-616
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• 2022

전 세계적으로 이상 기후 및 자연재난 등으로 인하여 철근콘크리트 구조물의 부식 및 열화 현상이 빈번히 발생됨에 따라 구조물의 노후화가 가속화되고 있다. 건설 분야에서는 이러한 내하력 저하에 대응하기 위하여 최근 저 중량 고강도 재료 장점을 가진 유리섬유 복합재료(GFRP)를 활용하여 많은 노후 구조물에 대하여 보수·보강을 수행하고 있다. 본 연구에서는 유리섬유에 비하여 보다 경제적이고 친환경적인 바잘트 섬유 복합재료(BFRP)를 활용하여 콘크리트 압축부재의 내진보강을 위한 횡구속 효과를 더욱 효과적으로 제공할 수 있는 보강재를 개발하고 그 성능을 평가하였다. 실험 시 고려된 주요 변수로는 바잘트섬유 복합재료(BFRP) 시공 시 적용되는 함침 수지의 양생 온도와 대상 콘크리트 압축부재의 재료 특성을 고려하였다. 콘크리트 압축부재의 재료 특성에 따른 횡구속 보강효과를 조사하기 위하여 본 연구에서는 일반 콘크리트와 섬유 보강을 통하여 내구성능이 개선된 콘크리트 시험체를 각각 제작하여 성능을 평가하였다. 그 결과, 일반 콘크리트의 경우 3.15배, 섬유 보강 콘크리트의 경우 약 3.72배의 보강 효과가 나타났으며 압축부재 내구특성 개선에 따른 보강 효과의 차이는 크지 않음을 알 수 있었다. 마지막으로 GFRP 압축부재 보강재에 대한 선행연구 결과를 통하여 바잘트 보강 복합재료의 성능을 비교한 결과 BFRP 보강재의 횡구속 보강효과가 상대적으로 약 1.18배 GFRP 보강재에 비하여 성능이 우수한 것으로 나타났다.