• Title/Summary/Keyword: 시멘트 복합체

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Moisture Sensitivity and Aging Effects of Recycled Wastepaper fiber Cement Composites (폐지섬유보강 시멘트 복합체의 수분민감성 및 열화특성)

  • 원종필;배동인;박찬기;박종영
    • Journal of the Korea Concrete Institute
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    • v.14 no.2
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    • pp.148-155
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    • 2002
  • This research investigates the moisture and aging effects of wastepaper fiber-cement composites. Wastepaper fibers is obtained by a dry process. Wastepaper fiber-cement composites was manufactured by the hatscheck process. The effects of moisture and aging on the performance of wastepaper fiber-cement composites were investigated through accelerated laboratory tests simulating the effects of moisture sensitivity and wet-dry cycles as well as freeze-thaw cycles and long-term drying. They were shown to possess acceptable moisture and aging performance compared with virgin fiber cement composites.

A Study on the Improvement of Workability of High Strength Steed Fiber Reinforced Cementitious Composites (고강도 강섬유 보강 시멘트 복합체의 워커빌리티 향상에 관한 연구)

  • Koh, Kyung-Taeg;Kang, Su-Tae;Park, Jung-Jun;Ryu, Gum-Sung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.8 no.3
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    • pp.141-148
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    • 2004
  • This paper present the experimental research investigating the influence of material factors such as a type or amount of superplasticizer, velocity agent, mineral admixture and steel fiber on the workability of high strength steel fiber reinforced cementitious composites. As for the test results, it was found that the workability of high strength steel fiber reinforced cementitious composites can be improved when the material factors were matched properly in amount and composition. Furthermore, it was shown that the smaller value of the aspect ratio of steel fiber improved the workability of fiber reinforced cementitious composites. And the steel fiber reinforced cementitious composites with better workability showed the enhanced compressive strength and flexural strength.

Quantitative Damage Evaluation of Fiber-Reinforced Cement Composite Using Acoustic Emission Technique (음향방출 기법을 이용한 섬유보강 시멘트 복합체의 정량적 손상평가)

  • Lee, Young-Oh;Yun, Yeo-Jin;Yun, Hyun-Do
    • Journal of the Korea Concrete Institute
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    • v.21 no.4
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    • pp.457-464
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    • 2009
  • Fiber is an important ingredient in fiber-reinforced cement composite (FRCC) which can control fracture of cement composite by bridging action. In compliance with the action of the fiber and the aggregate size, it also showed a different failure mechanism. For practical application, it is needed to investigate the fracture behavior of the FRCC and to understand the micro-mechanism of cement matrix with reinforcing fiber. In order to evaluate a characteristics of fracture process in the FRCC, acoustic emission (AE) technique was used for the analysis and evaluation of FRCC damage by acoustic emission under flexural and cyclic compressive loadings. The AE signals were monitored by AMSY4 AE instrument during the entire loading period. The specimens are reinforced with 0, 1.0, 1.5 and 2.0% (by volume) Polyvinyl alcohol (PVA) fiber. The test results showed that the damage progress of the FRCC was characteristic for the fiber replacement ratio. As a result of analyzing the felicity ratio (FR) values, it is shown that this values can be used for evaluating the degree of FRCC damage. On the whole the felicity ratio values of FRCC are shown between 0.4 and 1.1. And, the AE kaiser effect was shown in the all FRCC specimen. In addition, the damage behavior and the microscopic fracture process of the FRCC are evaluated using the AE parameters, such as calm ratio, b-value and felicity ratio. The purpose of this reserch was to advance the state of knowledge regarding the applicability of acoustic emission as an evaluation method for FRCC.

Preliminary Study on Development of High Strength Cement Composites at 2,000kg/㎥ of Specific Weight (단위중량 2,000kg/㎥급 고강도 시멘트 복합체 개발을 위한 기초연구)

  • Jeong, Yeon-Ung;Lim, Gwi-Hwan;Kang, Yong-Hak;Jung, Sang-hwa;Kim, Joo-Hyung
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.4
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    • pp.562-570
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    • 2020
  • This study explores manufacturing technology and basic properties of high strength cement composites at 2,000kg/㎥ of specific weight. It is suggested that lightweight-high strength cement composites can be produced by substituting silica sand in ulta-high performance concrete mixture with lightweight materials such as solid bubbles and lightweight fine aggregates. The 28-day compressive strengths of cement composites with solid bubbles were from 116MPa to 141MPa at below 2.0g/㎤ of unit density while the cement composites with lightweight aggregates possessed lower compressive strength and higher unit density. The specific weight calculated from mixture proportions did not have significant difference with unit density of hardened cement composites, indicating that unit density of hardened cement composites can be estimated from the specific weight in mixture proportions.

Tension-Stiffening and Cracking Behavior of 100 MPa Shrinkage-Compensated Ultra High-Strength Strain-Hardening Cement Composite (UHS-SHCC) Ties (100 MPa급 수축보상 초고강도 변형경화형 시멘트 복합체를 사용한 인장부재의 인장강성 및 균열특성)

  • Song, Young-Jae;Yun, Hyun-Do
    • Journal of the Korea Concrete Institute
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    • v.25 no.4
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    • pp.371-379
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    • 2013
  • This paper investigates the cracking and tension-stiffening behavior of 100 MPa shrinkage-compensated strain-hardening cement composite (SHCC) and conventional concrete tie elements in monotonic and cyclic tension. Strain and surface crack formation of tension ties were monitored with two strain displacement transducers and a photo microscope with a lens of magnification 50 times. Three different cement composites such as conventional concrete, shrinkage-compensated SHCC, and normal SHCC were used in the tie specimens to investigate the influence of the cement composite type on the tension stiffening and cracking behavior. Test results indicated that initial shrinkage of the ultra high-strength cement composites is greatly reduced as the 10% replacement of cement by the shrinkage-compensating admixture based on calcium sulfo-aluminate (CSA). The test results on the SHCC tension ties showed that the first cracking load decreases proportionally to the initial shrinkage strain. Reinforced ultra high-strength SHCC ties with the initial shrinkage compensation exhibited improved tension stiffening and smaller crack spacings, i.e. the reduction in crack width. Cyclic loading did not have a significant effect on tension stiffening and cracking behavior of tension ties with normal concrete and SHCC materials.

Effect of Nanocellulose on the Mechanical and Self-shrinkage Properties of Cement Composites (나노셀룰로오스가 시멘트복합체의 역학적 특성 및 자기수축 특성에 미치는 영향)

  • Kim, Sun-Woo;Yoon, Byung-Tae
    • Applied Chemistry for Engineering
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    • v.27 no.4
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    • pp.380-385
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    • 2016
  • Nanocelluloses, mainly cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC, i.e., defect-free, rod-like crystalline residues after acid hydrolysis of fibers), have been the subject of recent interest. Due to the presence of hydroxyl groups on the surface of nanocelluloses, their surfaces are reactive, making them suitable candidates for reinforcing materials for manufacturing polymer composites. In this study, CNF was used as a reinforcing material for manufacturing cement composites. CNF was prepared by TEMPO (2,2,6,6,-tetramethyl piperidine-1-oxyl radical) oxidation procedure combined with extensive homogenization and ultrasonication. Transmission electron microscopy (TEM) analysis of the suspension showed the width of CNF between 10 and 15 nm. The compressive strength of cement composites containing 0.5% CNF was comparable to that of conventional cement composites. On the other hand, the tensile and flexural strength were improved by 49.7% and 38.8%, respectively, compared to those of conventional cement composites. Also, at an ambient condition, the degree of self-shrinkage reduction reached to 18.9% in one day, followed by 5.9% in 28 days after molding.

A Study on the Flow Loss of Cement-Based Composites Using High Range Water Reducing Admixture (고성능감수제를 사용한 시멘트복합체의 유동성 손실에 대한 연구)

  • 문한영;김기형
    • Magazine of the Korea Concrete Institute
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    • v.4 no.2
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    • pp.119-126
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    • 1992
  • 고강도 시멘트 복합체의 유동성 손실을 감소시키기 위한 연구의 일환으로 시멘트계 입자에 대한 고성능감수제의 흡착특성, 현탄액 속에서의 응집특성을 관찰하여 시멘트풀과 모르터의 유동성과 관련시켜 고찰하였다. 본 연구결과 알루미네이트계 화합물이 많이 함유된 보통포틀랜드 시멘트의 흡착률이 가장 크며, 시멘트풀 및 모르처의 유동성 손실이 작았으며 나프탈린계 고성능 감수제가 유동성 손실면에서 얼마간 유리하였다.

An Experimental Study on the Mechanical Properties of Silica Fume and Fly Ash.Cement Composites (실리카흄 및 플라이애쉬.시멘트 복합체의 역학적 특성에 관한 실험적 연구)

  • 박승범;윤의식
    • Magazine of the Korea Concrete Institute
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    • v.6 no.5
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    • pp.158-170
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    • 1994
  • The results of an experimental study on the manufacture and the mechanical properties of carbon fiber rekforced silica fume . cement composites and light weight fly ash . cement composites are presented in this paper. 11s the test results show, the flexural strength, fracture toughness and ductility of CF reinforced silica fume . cement composites were remarkably increased by the increase of carbon fiber contents. And the workability of the fly ash . cement composites were improved, but the compressive and flexural strength and bulk specific gravity of them are decreased by increasing the ratio of fly ash to cement. And the compressive and flexural strength of the fly ash cement composites by cured under the hot water were improved than those by mositure cured. Also, the manufacturing process technology of lightweight fly ash . cement composites in replacement of general autoclaved lightweight concrete was developed and its optimum mix proportions were proposed.

Experimental Study on the Improvement of Workability of Cementitious Composites Using Nano-bubble Water (나노버블수를 활용한 시멘트 복합체의 작업성 증진에 대한 실험적 연구)

  • Lee, Nankyoung;Kang, Sung-Hoon;Moon, Juhyuk
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.6
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    • pp.27-32
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    • 2021
  • This study was conducted to improve the workability of cementitious composites using nano-bubble water. The used nano-bubble water contains 7% of nano-sized bubbles with an averaged bubble size of 750 nm. Various different types of cementitious composites including ultar-high performance concrete, lightweight cementitious composites, and high-strength mortar have been tested to identify the changes of material properties. From the use of nano-bubble water, it was confirmed that workability has been improved by 3-22%. On the other hand, other material characteristics such as compressive strength did not have noticeable changes. Therefore, it was proposed that the use of nano-bubble water can enhance workability of cementitious composites without having significant impact on other material properties.