• 한국구조물진단유지관리공학회 논문집
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• 제25권5호
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• pp.48-59
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• 2021

본 연구에서는 다른 재료특성을 갖는 강섬유 또는 탄소섬유만을 사용한 단일 섬유보강 모르타르(fiber-reinforced mortar, FRM)와 강 및 탄소 섬유를 혼합사용한 하이브리드 FRM의 압축·휨성능을 조사하기 위해 실험을 수행하였다. 모르타르 시편은 총 섬유혼입률 1.0%에서 부피에 의한 1+0%, 0.75+0.25%, 0.5+0.5%, 0.25+0.75% 및 0+1%의 혼합비율로 강섬유와 탄소섬유를 혼입하였다. 이들의 역학적 성능을 재령 28일에서 섬유가 없는 플레인 모르타르와 비교, 검토하였다. 모르타르의 실험결과는 강섬유 0.75% + 탄소섬유 0.25%를 혼합사용한 하이브리드 FRM가 가장 높은 압축강도와 휨강도를 나타내, 하이브리드 FRM의 시너지 보강효과를 확인할 수 있었다. 반면, 강섬유 0.5% + 탄소섬유 0.5%를 혼합사용한 하이브리드 FRM의 경우 가장 높은 휨인성을 얻었으며, 본 실험결과를 토대로 강도와 휨인성을 동시에 개선하기 위한 하이브리드 FRM의 최적의 섬유 혼합비율을 제시하였다. 게다가, FRM 시편의 이미지 분석을 위해 주사전자현미경(scanning electron microscope, SEM)을 통해 파단면을 관찰하였다. 이들 결과는 시멘트 매트릭스 내에서 하이브리드 보강섬유의 이미지 분석을 하는 데 큰 도움이 되었다.

• 콘크리트학회논문집
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• 제25권3호
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• pp.313-320
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• 2013

이 연구에서는 환경을 고려한 고성능 보수 보강재료 개발을 위하여 섬유를 보강한 폴리머 시멘트 모르타르의 특성을 연구하였다. 친환경 수지인 UM 수지를 일반 시멘트 모르타르와 일정 비율로 혼합하였다. 강도 증진의 영향을 확인하기 위해서 PVA 섬유, 강섬유 그리고 PVA섬유와 강섬유를 일정한 비율로 혼합한 하이브리드 섬유를 일정한 비율로 첨가하였다. 강도특성을 파악하기 위하여 섬유를 보강한 폴리머 시멘트 모르타르에 대하여 압축강도, 쪼갬 인장강도, 휨강도 실험을 수행하였다. 내구성을 파악하기 위하여 폴리머 시멘트 모르타르에 대하여 흡수율 실험, 내약품성 실험을 수행하였다. 실험 결과 UM 수지 폴리머 시멘트 모르타르는 내구성능이 개선되었고, 이러한 폴리머 시멘트 모르타르에 섬유를 보강하면 콘크리트 및 모르타르의 취약점인 인장강도와 휨강도가 증가하였다. 향후 외부 노출된 콘크리트 구조물의 내구성 향상을 위한 보수보강재료로 사용성을 확인하였다.

• Advances in materials Research
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• 제11권3호
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• pp.211-224
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• 2022

The shrinkage and the mechanical properties of polypropylene hybrid fiber reinforced mortar PHFRM were investigated in this study. Mortars were prepared with limestone crushing sand, Portland cement and polypropylene hybrid fibers PHF. Two types of virgin fibers, having the same length (30 mm) were used for reinforcing test mortars, fibers in diameter of 0.45 mm, used by PLAST BROS factory of Bordj Bou Arreridj (Algeria) for the fabrication of brooms (for household cleaning) and fibers in diameter of 0.25 mm, available on the market, having multiple applications. In this investigation, it was aimed to study the total and autogenous shrinkage, the flexural and compressive strength of mortars based on hybrid fibers. As a result, PHF have negatively affected the mortar workability. However, shrinkage risk was reduced and coarser fibers (PF45) were most effective for reducing shrinkage risk. The mechanical performances and the ductility of PHFRM were also enhanced.

• 한국건설순환자원학회논문집
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• 제9권3호
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• pp.311-321
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• 2021

콘크리트의 낮은 인장강도와 취성적인 특성 등의 약한 재료 특성을 개선하기 위하여 수년간 하이브리드 섬유보강 콘크리트에 관한 많은 연구가 진행되어 왔다. 그러나 비정질 강섬유와 유기섬유를 이용한 하이브리드 섬유보강 콘크리트의 특성에 관한 연구는 미진한 실정이다. 본 논문의 목적은 비정질 강섬유와 폴리아미드 섬유를 이용한 고성능 하이브리드 섬유보강 콘크리트의 압축 및 인장 거동을 평가한 후 이들에 대한 재료모델을 제안하는 것이다. 이를 위하여 목표 압축강도 40MPa 및 60MPa 각각에 대해서 비정질 강섬유와 폴리아미드 섬유를 총 부피비 1.0%로 설정하여 섬유 조합별로 고성능 하이브리드 섬유보강 콘크리트를 제작한 후, 압축 거동 및 인장 거동을 평가하였다. 고성능 하이브리드 섬유보강 콘크리트의 실험결과를 바탕으로 압축 및 인장거동에 대한 재료모델을 제안하였으며, 제안한 모델은 실험결과와 비교적 잘 일치하는 것으로 나타났다.

• Computers and Concrete
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• 제20권4호
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• pp.449-459
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• 2017

Fresh and hardened behaviors of a new hybrid fiber (steel fiber, polyvinyl alcohol fiber and calcium carbonate whisker) reinforced cementitious composites (HyFRCC) with admixtures (fly ash, silica fume and water reducer) have been studied. Within the limitations of the equipment and testing program, it is illustrated that the rheological properties of the new HyFRCC conform to the modified Bingham model. The relations between flow spread and yield stress as well as flow rate and plastic viscosity both conform well with negative exponent correlation, justifying that slump flow and flow rate test can be applied to replace the other two as simple rheology measurement and control method in jobsite. In addition, for the new HyFRCC with fly ash and water reducer, the mathematical model between the rheological and mechanical properties conform well with the quadratic function, and these quadratic function curves are always concave upward. Based on mathematical analysis, an optimal range of rheology/ flowability can be identified to achieve ideal mechanical properties. In addition, this optimization method can be extended to PVA fiber reinforced cement-based composites.

• 한국건축시공학회지
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• 제16권3호
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• pp.279-288
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• 2016

The fundamental performance of any construction material should cover at least two phases: safety and serviceability. Safety commonly represents adequate strength, while serviceability encompasses the control of cracking and deflections at service loads. With respect to rapid hydraulic binders as a construction material, the above two phases should also be considered. Recent research on rapid cooling ladle furnace slag (RC-LFS) has drawn much attention, particularly given that it shows remarkable rapid hydraulic ability to pulverize to a fineness of $6,300cm^2/g$. This industrial byproduct could contribute to developing the sustainability of the rapidly hardening cementitious material system. This paper aims to expand upon the applicability of an RC-LFS-based binder that is composed of two parts. It also seeks to illustrate the engineering performance of an RC-LFS-based hybrid fiber-reinforced composite and to increase the strength of the RC-LFS-based composite. Each step of this experiment followed ASTM standards. The engineering performance, in both fresh state and hardening state, was tested and discussed in this paper. According to the experimental results for fresh concrete, the air content increased following the addition of polypropylene fiber. For hardened concrete, the toughness and strength improved following the addition of a hybrid fiber. The hybrid fiber mixture, which contains 0.75% of steel fiber and 0.25% of polypropylene fiber, shows even better engineering performance than other mixtures.

• 한국지진공학회논문집
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• 제25권5호
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• pp.213-221
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• 2021

Many Korean domestic masonry structures constructed since 1970 have been found to be vulnerable to earthquakes because they lack efficient lateral force resistance. Many studies have shown that the brick and mortar suddenly experience brittle fracture and out-of-plane collapse when they reach the inelastic range. This study evaluated the seismic retrofitting of non-reinforced masonry with Hybrid Super Coating (HSC) and Cast, manufactured using glass fiber. Four types of specimen original specimen (BR-OR), one layered HSC (BR-HS-O), two-layered HSC (BR-HS-B), one layered HSC, and Cast (BR-CT-HS-O) were constructed and analyzed using compression, flexural tensile, diagonal compression, and triplet tests. The specimen responses were presented and discussed in load-displacement curves, maximum strength, and crack propagation. The compressive strength of the retrofit specimens slightly increased, while the flexural tensile strength of the retrofit specimens increased significantly. In addition, the HSC and Cast also produced a considerable increase in the ductile response of specimens before failure. Diagonal compression test results showed that HSC delayed brittle cracks between the mortar and bricks and resulted in larger displacement before failure than the original brick. The triplet test results confirmed that the bonding strength of the retrofit specimens also increased. The application of HSC and Cast was found to restrain the occurrence of brittle failure effectively and delayed the collapse of masonry wall structures.

• Composites Research
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• 제18권4호
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• pp.66-74
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• 2005

This paper reports new repair and strengthening mathod using improved material. This mathod have two type according to covering thickness of reinforcement. One type is near surface mounted FRP rod. Anther type is overay. Fiber Reinforced Plastic (FRP) materials has become very popular in recent years. FRP material used to rehabilitate many types of structures with superior characteristics such as high strength and stiffness and corrosion resistance. This strengthening mathod were used FRP rod which have better bond and shear strangth than current FRP rod. Development of FRP rod due to 3-D winding system. In addition, Ductile hybrid FRP has a certain plastic deformation and an elongation greater than 3% at maximum load is usually required for steel reinforcement in concrete structures. Moerover this mathod can be effective repair of base concrete by sprayed polymer mortar.