• Title/Summary/Keyword: Splitting tensile test

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Improving the brittle behavior of high-strength shielding concrete blended with lead oxide, bismuth oxide, and tungsten oxide nanoparticles against gamma ray

  • Mohamed Amin;Ahmad A. Hakamy;Abdullah M. Zeyad;Bassam A. Tayeh;Ibrahim Saad Agwa
    • Structural Engineering and Mechanics
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    • v.85 no.1
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    • pp.29-53
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    • 2023
  • High-strength shielding concrete against gamma radiation is a priority for many medical and industrial facilities. This paper aimed to investigate the gamma-ray shielding properties of high-strength hematite concrete mixed with silica fume (SF) with nanoparticles of lead dioxide (PbO2), tungsten oxide (WO3), and bismuth oxide (Bi2O3). The effect of mixing steel fibres with the aforementioned binders was also investigated. The reference mixture was prepared for high-strength concrete (HSCC) containing 100% hematite coarse and fine aggregate. Thirteen mixtures containing 5% SF and nanoparticles of PbO2, WO3, and Bi2O3 (2%, 5%, and 7% of the cement mass, respectively) were prepared. Steel fibres were added at a volume ratio of 0.28% of the volume of concrete with 5% of nanoparticles. The slump test was conducted to workability of fresh concrete Unit weight water permeability, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity tests were conducted to assess concrete's engineering properties at 28 days. Gamma-ray radiation of 137Cs emits photons with an energy of 662 keV, and that of 60Co emits two photons with energies of 1173 and 1332 keV were applied on concrete specimens to assess radiation shielding properties. Nanoparticles partially replacing cement reduced slump in workability of fresh concrete. The compressive strength of mixtures, including nanoparticles was shown to be greater, achieving 94.5 MPa for the mixture consisting of 7.5 PbO2. In contrast, the mixture (5PbO2-F) containing steel fibres achieved the highest values for splitting tensile, flexural strength, and modulus of elasticity (11.71, 15.97, and 42,840 MPa, respectively). High-strength shielded concrete (7.5PbO2) showed the best radiation protection. It also showed the minimum concrete thickness required to prevent the transmission of radiation.

Field Application of Hydraulic Rock Splitting Technique to Biotite Granite (흑운모화강암 지역에 대한 수압암반절개기술의 현장 적용)

  • Park, Jongoh;Lee, Dal-Heui;Woo, Ik
    • Tunnel and Underground Space
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    • v.27 no.5
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    • pp.263-270
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    • 2017
  • Hydraulic rock splitting is a technique which leads to failure of rockmass by means of water injection with a pressure higher than the tensile strength of rockmass, using straddle packer installed in boreholes drilled from free surface. Field tests were conducted in this study for several slopes of biotite granite according to various designs for borehole layout and water injection. Test results showed that new cracks were generated to connect to adjacent holes or that pre-existed cracks were propagated by injection, finally leading to failure. In particular, this study suggests the possibility of controlling the direction of generated cracks with guide slot, since new cracks were generated parallel to the guide slots carved on a borehole wall before injection. Various types of borehole layout and injection methods should be further developed for the practical uses, considering the factors influencing on crack generation.

Effect of Iron Ore Tailings Replacing Porous Basalt on Properties of Cement Stabilized Macadam

  • Qifang Ren;Fan Bu;Qinglin Huang;Haijun Yin;Yuelei Zhu;Rui Ma;Yi Ding;Libing Zhang;Jingchun Li;Lin Ju;Yanyan Wang;Wei Xu;Haixia Ji;Won-Chun Oh
    • Korean Journal of Materials Research
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    • v.34 no.6
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    • pp.291-302
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    • 2024
  • In this paper, iron ore tailings (IOT) were separated from the tailings field and used to prepare cement stabilized macadam (CSM) with porous basalt aggregate. First, the basic properties of the raw materials were studied. Porous basalt was replaced by IOT at ratios of 0, 20 %, 40 %, 60 %, 80 %, and 100 % as fine aggregate to prepare CSM, and the effects of different cement dosage (4 %, 5 %, 6 %) on CSM performance were also investigated. CSM's durability and mechanical performance with ages of 7 d, 28 d, and 90 d were studied with the unconfined compression strength test, splitting tensile strength test, compressive modulus test and freeze-thaw test, respectively. The changes in Ca2+ content in CSM of different ages and different IOT ratios were analyzed by the ethylene diamine tetraacetic acid (EDTA) titration method, and the micro-morphology of CSM with different ages and different IOT replaced ratio were observed by scanning electron microscopy (SEM). It was found that with the same cement dosage, the strengths of the IOT-replaced CSM were weaker than that of the porous basalt aggregate at early stage, and the strength was highest at the replaced ratio of 60 %. With a cement dosage of 4 %, the unconfined compressive strength of CSM without IOT was increased by 6.78 % at ages from 28 d to 90 d, while the splitting tensile strength increased by 7.89 %. However, once the IOT replaced ratio reached 100 %, the values increased by about 76.24 % and 17.78 %, which was better than 0 % IOT. The CSM-IOT performed better than the porous basalt CSM at 90 d age. This means IOT can replace porous basalt fine aggregate as a pavement base.

An Experimental Study on the Mechanical Properties of No-Fines Concrete (No-Fines Concrete의 역학적 특성에 관한 실험적 연구)

  • 홍건호;정일영
    • Magazine of the Korea Concrete Institute
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    • v.6 no.3
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    • pp.190-200
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    • 1994
  • The purpose of this research is to examine experimentally the mechanical properties and economics of No-fines concrete for its application to the low-rise housing construction. Basic mechanical properties of No fines concrete are studied by measuring of compressive, tensile strength and stress-strain relationship, and economics of it is compared with other materials in unit cost and wall construction cost. From the test results, it can be concluded that No-fines concrete has advantages of good workability, light weight and lower construction cost, even though it has lower strength and modulus of elasticity than normal conc:rt:te does.

Fatigue Failure Characteristics of Steel Fiber Reinforced Concrete Considering Cumulative Damage (누적손상을 고려한 강섬유보강 콘크리트의 피로파괴 특성)

  • 김동호;홍창우;이주형;이봉학
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.44 no.2
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    • pp.117-126
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    • 2002
  • Concrete containing discontinuous discrete steel fiber in a normal concrete is called steel fiber reinforced concrete(SFRC). Tensile as well as flexural strengths of concrete could be substantially increased by introducing closely spaced fibers which delay the onset of tension cracks and increase the tension strength of cracks. However, many properties of SFRC have not been investigated, especially properties on repeated loadings. Thus, the purposes of this dissertation is to study the flexural fatigue characteristics of SFRC considering cumulative damage. A series of experimental tests such as compressive strength, splitting tensile strength, flexural strength, flexural fatigue, and two steps stress level fatigue were conducted to clarify the basic properties and fatigue-related properties of SFRC. The main experimental variables were steel fiber fraction (0, 0.4, 0.7, 1, 1.5%), aspect ratio (60, 83). The principal results obtained through this study are as follows: The results of flexural fatigue tests showed that the flexural fatigue life of SFRC is approxmately 65% of ultimate strength, while that of plain is less than 58%. Especially, the behavior of flexural fatigue life shows excellent performance at 1.0% of steel-fiber volume fraction. The cumulative damage test of high-low two stress levels is within the value of 0.6 ∼ 1.1, while that of low-high stress steps is within the value of 2.4 ∼ 4.0.

Evaluation of Fracture Strength of WA-Vitrified and Resinoid Bond Grinding Wheels by Acoustic Emission (AE에 의한 WA계 비트리파이드 및 레지노이드 結合劑硏削숫돌의 破壞强度評價)

  • 강명순;한응교;권동호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.2
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    • pp.241-251
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    • 1988
  • The purpose of this paper is to evaluate fracture strength of WA-vitrified and resinoid bond grinding wheels by means of acoustic emission. The paper conducts tension test, compression test, splitting tensile test and bending test with AE measuring system. These tests have been carried out in accordance with the grain sizes and grades of grinding wheels. The fracture strength of grinding wheels is evaluated by the clarification of biaxal fracture criterion of Babel and Sines. It clarifies the influence of factors of grinding wheel upon AE characteristics and evaluates the predictability of life of grinding wheels and the perception of fracture.

Tension Stiffening Effect Considering Cover Thickness in Reinforced Concrete Tension Members (피복두께를 고려한 철근콘크리트 인장부재의 인장증강효과)

  • Lee, Gi-Yeol;Kim, Min-Joong;Kim, Woo;Lee, Hwa-Min
    • Journal of the Korea Concrete Institute
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    • v.23 no.6
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    • pp.791-797
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    • 2011
  • This paper presents the test results of 12 direct tensile specimens to investigate the effect of cover thickness on the tension stiffening behavior in axially loaded reinforced concrete tensile members. Six concrete cover thickness ratios are selected as a main experimental parameter. The results showed that, as cover thickness became thinner, more extensive split cracking along the reinforcement occurred and transverse crack spacing became smaller, making the effective tensile stiffness of thin specimens at the stabilized cracking stage to be much smaller than that of thick specimens. This observation is not implemented in the current design provisions, in which the significant reduction of tension stiffening effect can be achieved by applying thinner cover thickness. Based on the present results, a modified tension stiffening factor is proposed to account for the effect of the cover thickness.

Investigation of Material Properties of the Steel Fiber Reinforced Concrete (강섬유 보강콘크리트의 재료적 성상에 관한 고찰)

  • 이현호;권영호;허무원;정현석
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.10a
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    • pp.733-736
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    • 2002
  • As composite materials, the addition of steel fiber in concrete significantly improves the engineering properties of structural members. The purpose of this study is to define the strengthening effect of steel fiber in a point of material usage. From tile material test. compression strength, tensile splitting strength and flexural strength were evaluated by steel fiber volume fraction ($V_f$) and aspect ratio (AR) of steel fiber. In case of AR 67, $V_f$ 2.0% could be achieved maximum steel fiber strengthening effect. And the AR 80 case, $V_f$ 1.0% could be achieved maximum effect than the effect of $V_f$ 1.5%.

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Strength Characteristics of No-Fine Concrete Containing Recycled Aggregates (재생골재를 함유한 무잔골재 콘크리트의 강도특성)

  • 김태근;이광명;김낙경;고용일
    • Proceedings of the Korea Concrete Institute Conference
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    • 1998.10c
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    • pp.1-6
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    • 1998
  • Recently, as to destruction and renovation of aged building, waste concretes have been reclaimed near foreshore and filled up underground. Recycling demolished concrete as aggregate helps to settle economic and environmental problems of obtaining superior aggregates from natural sources and to dispose waste concretes. An experimental study was carried out to investigate the strength characteristics of no-fine concrete containing recycled aggregates. The cement-aggregate weight ratios of 1: 5, 1: 6, 1: 7 and water-cement ratios of 30, 35, 40, 45% were chosen for the mix design of no-fine concretes. The compressive and splitting tensile strength at 7 and 28 days were measured for 12 different mixes. On the basis of test results, the optimum mix proportion of no-fine concrete containing recycled aggregates was determined and applied to the production of retaining wall block.

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Fundamental Tests for General Use of High-Strength Lightweight Concrete (고강도 경량콘크리트의 실용화를 위한 기초적 실험연구)

  • 김형태;김원근
    • Proceedings of the Korea Concrete Institute Conference
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    • 1990.04a
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    • pp.39-44
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    • 1990
  • This experimental study is performed by using artificial lightweight aggregate manufactured in laboratory, and the test results of it are compared with those using foreign materials in respect of design compressive strength, unit weight. The tests on strength characteristics such as bending, splitting tensile strength and on mechanical characteristics including σ-εcurve, elastic modulus, poisson's ratio are performed to provide the fundamental data required for the design. From this study, it is possible to obtain the high-strength concrete having compressive strength of 500 kg/㎠ and unit weight of 1.85-2.0 t/㎥. And also it is recommended that sandlightweight concrete having high specfic strength is more practical for general use.

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