• Title/Summary/Keyword: shrinkage cracking

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Evaluation of Mechanical Properties and Crack Resistant Performance in Concrete with Steel Fiber Reinforcement and CSA Expansive Admixture (CSA 팽창재를 혼입한 강섬유 보강 콘크리트의 역학적 성능 및 균열 저항성능 평가)

  • Choi, Se-Jin;Park, Ki-Tae;Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.1
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    • pp.75-83
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    • 2014
  • In order to prevent brittle failure of concrete, steel fiber reinforcement is effective composite material. However ductility of steel fiber reinforced concrete may be limited due to shrinkage caused by large content of cement binder. Chemical prestressing for steel fiber reinforcement in cement matrix can be induced through expansive admixture and this can increase reinforcing effect of steel fiber. In this study, mechanical performances in concrete with CSA (Calcium sulfoaluminate) expansive admixture and steel fiber reinforcement are evaluated. For this work, steel fiber reinforcement of 1 and 2% of volume ratio and CSA expansive admixture of 10% weight ratio of cement are added in concrete. Mechanical and fracture properties are evaluated in concrete with steel fiber reinforcement and CSA expansive admixture. CSA concrete with steel fiber reinforcement shows increase in tensile strength, initial cracking load, and ductility performance like enlarged fracture energy after cracking. With appropriate using expansive admixture and optimum ratio of steel fiber reinforcement, their interactive action can effectively improve brittle behavior in concrete.

Strength Properties of Cement Mortar with Slurry-Typed Cellulous Fiber (슬러리형 셀룰로오즈 파이버를 혼입한 시멘트 모르타르의 강도 특성)

  • Ryu, Hwa-Sung;Shin, Sang-Heon;Kwon, Seung-Jun
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.7 no.3
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    • pp.210-215
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    • 2019
  • Concrete members with wide surface area are vulnerable to cracking due to material behavior such as hydration heat and drying shrinkage. Recently many researches have been performed on improvement of strength and cracking resistance through fiber reinforcement, which are mainly focused on enhancement of tensile strength against cracking due to material behavior. In this paper, CFs(Cellulous Fibers) are manufactured for slurry type, and the engineering properties in cement mortar incorporated with CFs are evaluated for flow-ability, compressive, and flexural strength. Through SEM analysis, a pull-off characteristics of CF in matrix are analyzed. With CF addition of $0.5kg/m^3{\sim}1.0kg/m^3$, flexural strength is much improved and enough toughness of pull-off is also observed unlike plastic fiber containing smooth surface.

Joint Behavior of Concrete Pavements Using Joint Crack Inducer (줄눈균열 유도장치를 사용한 콘크리트 포장의 줄눈거동)

  • Park, Moon Gil;Choi, Ki Hyo;Nam, Young Kug;Jeong, Jin Hoon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.1D
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    • pp.57-65
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    • 2008
  • Joint of concrete pavement contributes to improvement of pavement performance by preventing occurrence of random cracking due to drying shrinkage and temperature changes of concrete slabs at early age. However, saw-cutting operations performed prior to sufficient concrete hardening develop micro-cracking of the concrete near the joints, which may develop to long-term distresses due to repetitious traffic and environmental loadings. To reduce the distresses, the joint crack inducers with heights of 100 mm, 150 mm, and 220 mm and the joint cracking slots with various depth were installed at a test section to investigate occurrence of the joint cracks and their behaviors over 5 months. As the results, higher efficiency of the crack inducing and larger behavior of the joint cracks were observed for the taller joint crack inducer. Higher efficiency of the crack inducing and improvement of the joint performance are warranted by additional investigation and reformation of the joint crack inducer.

Mechanical behaviour between adjacent cracks in CFRP plate reinforced RC slabs

  • Yuan, Xin;Bai, Hongyu;Sun, Chen;Li, Qinqing;Song, Yanfeng
    • Structural Engineering and Mechanics
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    • v.84 no.3
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    • pp.375-391
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    • 2022
  • This paper discussed and analyzed the interfacial stress distribution characteristic of adjacent cracks in Carbon Fiber Reinforced Polymer (CFRP) plate strengthened concrete slabs. One un-strengthened concrete test beam and four CFRP plate-strengthened concrete test beams were designed to carry out four-point flexural tests. The test data shows that the interfacial shear stress between the interface of CFRP plate and concrete can effectively reduce the crack shrinkage of the tensile concrete and reduces the width of crack. The maximum main crack flexural height in pure bending section of the strengthened specimen is smaller than that of the un-strengthened specimen, the CFRP plate improves the rigidity of specimens without brittle failure. The average ultimate bearing capacity of the CFRP-strengthened specimens was increased by 64.3% compared to that without CFRP-strengthen. This indicites that CFRP enhancement measures can effectively improve the ultimate bearing capacity and delay the occurrence of debonding damage. Based on the derivation of mechanical analysis model, the calculation formula of interfacial shear stress between adjacent cracks is proposed. The distributions characteristics of interfacial shear stress between certain crack widths were given. In the intermediate cracking region of pure bending sections, the length of the interfacial softening near the mid-span cracking position gradually increases as the load increases. The CFRP-concrete interface debonding capacity with the larger adjacent crack spacing is lower than that with the smaller adjacent crack spacing. The theoretical calculation results of interfacial bonding shear stress between adjacent cracks have good agreement with the experimental results. The interfacial debonding failure between adjacent cracks in the intermediate cracking region was mainly caused by the root of the main crack. The larger the spacing between adjacent cracks exists, the easier the interfacial debonding failure occurs.

Structural Behavior of Concrete Pavement Due to Temperature Variations (온도변화에 의한 콘크리트 포장도로의 구조 거동 연구)

  • 조병완
    • Computational Structural Engineering
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    • v.4 no.2
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    • pp.95-102
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    • 1991
  • Some sections of concrete highway pavements have been viewed with great concern by highway officials and engineers due to the severe cracking and failure problems. This is mainly due to the traffic loads in addition to temperature variations between top and bottom of concrete slab, which cause the concrete slab to curl up and down depending on the thermal gradient, respectively. Subsequently, a major consideration was given to the derivation of stiffness matrix and equivalent nodal loads due to the uniform gravity load, temperature and shrinkage of concrete. And the structural behavior of concrete highway pavement due to the temperature variations throughout the nations has been emphasized.

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A Study on the Properties of Cement Mortar with the Content of Expansive Additives Under Various Curing Method (팽창재량 및 양생방법에 따른 시멘트 모르터의 특성에 관한 연구)

  • 한성수;김정진;김효구;홍상희;한천구
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.04a
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    • pp.181-186
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    • 1999
  • When the expansive additives are used in concrete to reduce the shrinkage cracking, it shows variable properties with the curing method and curing temperature. Therefore, in this study, the experiments are perfomed to present the expansion of cement mortar by varying the unit additions of expansive additives and the curing method. According to the test results, the order of expansion by curing method, which is caused by hydration heat of cement, is follows ; curing at water > curing at air after curing at water for 7 days > curing at air. Cement mortar using expansive additives shows that high expansion is place with rise of temperature.

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Fire Resistance of Reinforced Polyamide Fiber Ultra High Strength(160MPa) Concrete (폴리아미드 섬유보강 초고강도(160MPa) 콘크리트의 내화성능)

  • Jeon, Joong-Kyu;Chan, Chan-Ki;Kim, Soo-Young;Kim, Bok-Kyu;Kim, Pil-Sung;Yun, Kyung-Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.547-548
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    • 2009
  • Fiber reinforcement has been being widely used in concrete to enhance the mechanical properties and to reduce the micro-cracking caused by plastic and drying shrinkage. While researches has been focused on the benefits of fiber reinforcement, the properties of fiber reinforced concrete are strongly dependent on the type, shape and the amount of fibers in concrete.

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Crack Resistance Properties of Fiber Reinforced Concrete with Recycled PET Fiber (재생 PET 섬유가 혼입된 섬유 보강 콘크리트의 균열저항특성)

  • Kim, Sung-Bae;Kim, Hyun-Young;Yi, Na-Hyun;Kim, Jang-Jay-Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.545-546
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    • 2009
  • This study was performed to prove the possibility of utilizing short plastic fibers made for recycled polyethylene terephthalate (RPET) as a structural material. To measure of crack control capacity, restrained drying shrinkage cracking test was performed. In order to verify the capacity of RPET fiber, it was compared with poly propylene (PP) fiber, most widely used short synthetic fiber, for fiber volume fraction of 0%, 0.5%, 0.75%, and 1.0%.

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Material Characteristics of High-Strength Concrete Incorporating High Replacement Level of Blast-Furnace Slag (고로슬래그를 다량 함유한 고강도 콘크리트의 재료적 특성)

  • Lee, Hoi-Keun;Jung, Jae-Hong;Kim, Han-Joon;Lee, Seung-Hoon
    • Proceedings of the Korea Concrete Institute Conference
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    • 2010.05a
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    • pp.291-292
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    • 2010
  • In this study, high-strength concrete mixtures were made with blast-furnace slag of 50% and 70% replacement level to evaluate material properties including compressive strength development, adiabatic temperature rise, autogenous shrinkage and chloride-ion migration coefficient. Test results showed that the use of high percentage blast-furnace slag in high-strength concrete can reduce heat of hydration and chloride-ion migration coefficient, result in control thermal cracking and improve durability performance especially under high corrosive environment.

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Correlation Analysis between Crack and TQI in RC Slab Track

  • Kwon, Se-Kon;Park, Mi-Yun;Kim, Doo-Kie;Sho, Byung-Choon;Park, Jae-Hak
    • International Journal of Railway
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    • v.7 no.1
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    • pp.8-15
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    • 2014
  • Recently, in the total railroad construction field, concrete slab tracks have been adapted in place of ballast tracks. Because ballast tracks need frequent maintenance and are difficult to handle due to increasing maintenance costs, eventually concrete slab tracks were selected as an alternative. However, owing to the hydration heat reactions and temperature-affected shrinkage of the concrete, a variety of studies to solve maintenance problems related to concrete slab tracks are underway. This study analyzed characteristics of TQI values evaluating track irregularity, investigated the relationship between crack progress and TQI, and then evaluated the correlation between the two values. Through our analysis, we found that there is a need to supplement the problems of the current method and develop a track evaluation index which takes cracking into account. We also concluded that TQI is the main decision-making tool in track maintenance.